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Direct Stimulation of KATP Channels by Exogenous and Endogenous Hydrogen Sulfide in Vascular Smooth Muscle Cells
Abstract
ATP-sensitive K+ (K(ATP)) channels in vascular smooth muscle cells (VSMC) are important targets for endogenous metabolic regulation and exogenous drug therapy. H2S, as a novel gasotransmitter, has been shown to relax rat aortic tissues via opening of K(ATP) channels. However, interaction of H2S, exogenous-applied or endogenous-produced, with K(ATP) channels in resistance artery VSMC has not been delineated. In the present study, using the whole-cell and single-channel patch-clamp technique, we demonstrated that exogenous H2S activated K(ATP) channels and hyperpolarized cell membrane in rat mesenteric artery VSMC. H2S enhanced the amplitude of whole-cell K(ATP) currents with an EC50 value of 116 +/- 8.3 microM and increased the open probability of single K(ATP) channels. H2S hyperpolarized membrane potentials by -12 mV in nystatin-perforated VSMC. Furthermore, inhibition of endogenous H2S production with D,L-propargylglycine (PPG) reduced whole-cell K(ATP) currents. PPG alone had no effect on unitary K(ATP) channel currents in cell-free membrane patches. In addition, effects of H2S on K(ATP) channels and membrane potentials were independent of cGMP-mediated phosphorylation. This study demonstrated modulation of K(ATP) channel activity by exogenous and endogenous H2S in resistance artery VSMC, thus helping elucidate cardiovascular functions of this endogenous gas.
... The mechanism by which H 2 S induces uterine artery dilation is not fully understood. Previous research in mesenteric vascular beds has implicated the activation of ATP-sensitive potassium (K ATP ) channels and large conductance Ca 2+ -activated voltage-dependent potassium (BK Ca ) channels in mediating H 2 S-induced vasodilation [15][16][17]. However, the contribution of K ATP channels to uterine vasodilation associated with pregnancy seems limited [15]. ...
... Various mechanisms have been proposed to elucidate the vasodilatory effects of H 2 S, depending on the specific vascular preparations under investigation. Previous studies focusing on resistance arteries have identified the involvement of K ATP channels [16], BK Ca channels [18,35], and K V channels [29,36] in H 2 S-induced vasodilation. Patch-clamp studies have demonstrated that H 2 S activates K ATP channels in vascular smooth muscle from mesenteric arteries [16] and hyperpolarizes mesenteric arteries through an iberiotoxinsensitive mechanism, indicating the participation of BK Ca channels [18,35]. ...
... Previous studies focusing on resistance arteries have identified the involvement of K ATP channels [16], BK Ca channels [18,35], and K V channels [29,36] in H 2 S-induced vasodilation. Patch-clamp studies have demonstrated that H 2 S activates K ATP channels in vascular smooth muscle from mesenteric arteries [16] and hyperpolarizes mesenteric arteries through an iberiotoxinsensitive mechanism, indicating the participation of BK Ca channels [18,35]. In separate experiments, H 2 S was found to hyperpolarize rat aorta and directly activate K V channels in CHO cells [37]. ...
Hydrogen sulfide (H2S) is a cardiovascular signaling molecule that causes vasodilation in vascular smooth muscle cells, but its mechanism is unclear. We examined how H2S affects mesenteric and uterine arteries without endothelium in nonpregnant and pregnant rats and the underlying mechanisms. H2S donors GYY4137 and NaHS relaxed uterine arteries more than mesenteric arteries in both pregnant and nonpregnant rats. GYY4137 and NaHS caused greater relaxation in the uterine artery of pregnant versus nonpregnant rats. High extracellular K⁺ abolished NaHS relaxation in pregnant uterine arteries, indicating potassium channel involvement. NaHS relaxation was unaffected by voltage-gated potassium channel blockers, reduced by ATP-sensitive potassium channel blockers, and abolished by calcium-activated potassium (BKCa) channel blockers. Thiol-reductant dithiothreitol also prevented NaHS relaxation. Thus, H2S has region-specific and pregnancy-enhanced vasodilator effects in the uterine arteries, mainly mediated by BKCa channels and sulfhydration.
... In the HEK293 cells, hydrogen sulfide-mediated S-sulfhydration targets the Cys43 in the Kir6.1 subunit of the K ATP channel and subsequently activates the ion channel (Mustafa et al., 2011). Further, it was observed that hydrogen sulfide also affects the activities of other Kir channels, i.e., Kir2 and Kir3 (Ha et al. 2018;Tang et al. 2005). ...
... Increase in the K uptake in the maize crop was observed when the inoculants of G. intraradices and G. mosseae (species of arbuscular mycorrhizal fungi) were applied in soil on the weight basis (Wu et al. 2005). Some strains of potassiumsolubilizing fungi (KSF) such as Aspergillus niger and Aspergillus terreus were found in soil samples rich in K, and both the species also showed the highest available K level in liquid medium when two insoluble forms of K such as potassium aluminium silicate and feldspar were used, based on their morphological features and colonies . ...
... The most frequent agent of mineral K solubilization seems to be tartaric acid (Zarjani et al. 2013). The other organic acids which are identified as K solubilizers are propionic, malonic, succinic, acetic, lactic, citric, glycolic, oxalic and fumaric acids (Wu et al. 2005). ...
This book on potassium in abiotic stress tolerance deals with the ongoing trend in increasing abiotic stresses and interlinked issues food security. As mineral nutrient potassium holds an important place in agriculture and is involved in various physiological and biochemical processes. It takes part in protein synthesis, carbohydrate metabolism, enzyme activation, cation-anion balance, osmoregulation, water movement, energy transfer, and regulates stomata and photosynthesis. Potassium plays an important role as abiotic stress buster. This book will deal with potassium relevance to plant functions and adaptations, range of its biological functions, role of potassium in abiotic stress tolerance, analyses of mechanisms responsible for perception and signal transduction of potassium under abiotic stress, critical evaluation of and cross-talks on nutrients and phytohormones signaling pathways under optimal and stressful conditions, and interaction of potassium with other nutrients for abiotic stress tolerance. This book will be of interest to teachers, researchers, scientists working on abiotic stresses. Also, the book serves as additional reading material for undergraduate and graduate students of agriculture, forestry, ecology, and environmental sciences. National and international agricultural scientists, policymakers will also find this to be a useful read.
... 13-68 pS in 140 mM KCl [50,51] 20-80 pS in 140 (bath)/5.4-100 (pipette) mM KCl [52] 80 pS in 145 mM K + [53,54] 135 pS in 120 (bath)/60 (pipette) mM K + [55] From 10 to 100 pS in 150 mM KCl (see Table 2). ...
... Open probability: NPo~0.32 at −100 mV [51] ≈0.9 between −100 and 60 mV [54] Open probability: 0.74 at 40 mV [56] 0.57 at −50 mV [32] 0.24 at −60 mV [57] Open probability: 0.013 at 50 mV [58] Open probability: 0.5 at −60 mV to 0.75 at 60 mV [27] BK(Ca)~1 ...
... The conductance of KATP of the PM ranges from 33-35 pS for the channels composed of Kir6.1 to 67-80 pS for those constituted by Kir6.2, in symmetrical 140 mM KCl (for review see e.g., [18]). However, conductance as low as 13 pS (in 140 mM symmetrical KCl solution) was recorded in rat mesenteric artery vascular smooth muscle cells (VSMC) [51]. In this latter cell type, the diversity of molecular entities of KATP channels is illustrated by their single-channel conductance ranging from 13 to 135 pS, with distinct conductance values of 13, 20, 50, 111 and 135 pS, recorded under similar ionic conditions in various studies [51,95]. ...
Potassium ions can cross both the outer and inner mitochondrial membranes by means of multiple routes. A few potassium-permeable ion channels exist in the outer membrane, while in the inner membrane, a multitude of different potassium-selective and potassium-permeable channels mediate K+ uptake into energized mitochondria. In contrast, potassium is exported from the matrix thanks to an H+/K+ exchanger whose molecular identity is still debated. Among the K+ channels of the inner mitochondrial membrane, the most widely studied is the ATP-dependent potassium channel, whose pharmacological activation protects cells against ischemic damage and neuronal injury. In this review, we briefly summarize and compare the different hypotheses regarding the molecular identity of this patho-physiologically relevant channel, taking into account the electrophysiological characteristics of the proposed components. In addition, we discuss the characteristics of the other channels sharing localization to both the plasma membrane and mitochondria.
... In the late 1980's and 1990's, pioneering work by several research groups led to the discovery of H 2 S as an endogenous gasotransmitter with pharmacological and physiological roles in the mammalian cells [1][2][3]. Subsequent studies have also reported its roles in cytoprotection [4][5][6][7][8], neuroprotection [9,10], smooth muscle relaxation [11,12], vasorelaxation and regulation of blood pressure [12][13][14][15][16][17][18], anti-inflammation [5,[19][20][21][22][23][24], cellular respiration [25][26][27][28][29], etc. Owing to its critical role in mammalian pathophysiology, H 2 S has found applications in several conditions as a therapeutic molecule [30][31][32]. ...
... In the late 1980's and 1990's, pioneering work by several research groups led to the discovery of H 2 S as an endogenous gasotransmitter with pharmacological and physiological roles in the mammalian cells [1][2][3]. Subsequent studies have also reported its roles in cytoprotection [4][5][6][7][8], neuroprotection [9,10], smooth muscle relaxation [11,12], vasorelaxation and regulation of blood pressure [12][13][14][15][16][17][18], anti-inflammation [5,[19][20][21][22][23][24], cellular respiration [25][26][27][28][29], etc. Owing to its critical role in mammalian pathophysiology, H 2 S has found applications in several conditions as a therapeutic molecule [30][31][32]. ...
Hydrogen sulfide (H 2 S) is a multifaceted gasotransmitter molecule which has potential applications in many pathological conditions including in lowering intraocular pressure and providing retinal neuroprotection. However, its unique physicochemical properties pose several challenges for developing its efficient and safe delivery method system. This study aims to overcome challenges related to H 2 S toxicity, gaseous nature, and narrow therapeutic concentrations range by developing polymeric microparticles to sustain the release of H 2 S for an extended period. Various formulation parameters and their interactions are quantitatively identified using Quality-by-Design (QbD) approach to optimize the microparticle-based H 2 S donor (HSD) delivery system. Microparticles were prepared using a solvent-evaporation coacervation process by using polycaprolactone (PCL), soy lecithin, dichloromethane, Na 2 S.9H 2 O, and silicone oil as polymer, surfactant, solvent, HSD, and dispersion medium, respectively. The microparticles were characterized for size, size distribution, entrapment efficiency, and H 2 S release profile. A Main Effects Screening (MES) and a Response Surface Design (RSD) model-based Box-Behnken Design (BBD) was developed to establish the relationship between critical process parameters (CPPs) and critical quality attributes (CQAs) qualitatively and quantitatively. The MES model identified polymer to drug ratio and dispersion medium quantity as significant CPPs among others, while the RSD model established their quantitative relationship. Finally, the target product performance was validated by comparing predicted and experimental outcomes. The QbD approach helped in achieving overall desired microparticle characteristics with fewer trials and provided a mathematical relationship between the CPPs and the CQAs useful for further manipulation and optimization of release profile up to at least 30 days.
Graphical Abstract
... In CSE-KO mice, endothelial dysfunction, with consequent hypertension and atherosclerosis, has been observed [14,[20][21][22][23][24][25]. These values are comparable to eNOS-KO mice, and endothelium-mediated vasorelaxing activity was reduced by approximately 60% [26]. ...
... The vasorelaxing activity of H2S is attributed, in part, to the stimulation of ionic channels on vascular smooth muscle or the endothelium, such as through ATP-sensitive potassium channels (KATP); voltage-gated potassium channels such as 7.4 (Kv7.4); and TRPV4 channels [11,21,22,136]. ...
Irisin is a myokine secreted under the influence of physical activity and exposure to low temperatures and through different exogenous stimuli by the cleavage of its precursor, fibronectin type III domain-containing protein 5 (FNDC5). It is mainly known for maintaining of metabolic homeostasis, promoting the browning of white adipose tissue, the thermogenesis process, and glucose homeostasis. Growing experimental evidence suggests the possible central role of irisin in the regulation of cardiometabolic pathophysiological processes. On the other side, hydrogen sulfide (H2S) is well recognized as a pleiotropic gasotransmitter that regulates several homeostatic balances and physiological functions and takes part in the pathogenesis of cardiometabolic diseases. Through the S-persulfidation of cysteine protein residues, H2S is capable of interacting with crucial signaling pathways, exerting beneficial effects in regulating glucose and lipid homeostasis as well. H2S and irisin seem to be intertwined; indeed, recently, H2S was found to regulate irisin secretion by activating the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)/FNDC5/irisin signaling pathway, and they share several mechanisms of action. Their involvement in metabolic diseases is confirmed by the detection of their lower circulating levels in obese and diabetic subjects. Along with the importance of metabolic disorders, these modulators exert favorable effects against cardiovascular diseases, preventing incidents of hypertension, atherosclerosis, heart failure, myocardial infarction, and ischemia–reperfusion injury. This review, for the first time, aims to explore the role of H2S and irisin and their possible crosstalk in cardiovascular diseases, pointing out the main effects exerted through the common molecular pathways involved.
... Hydrogen sulfide (H 2 S) is reported to elicit several physiological and pharmacological functions in mammalian cells [1][2][3][4][5]. In addition to modulating neuronal messages in the brain [6,7], H 2 S also mediates critical processes such as neurotransmission [6,8], cytoprotection [9][10][11][12][13], neuroprotection [14,15], smooth muscle relaxation [16,17], vasorelaxation and regulation of blood pressure [7,[17][18][19][20][21][22], antiinflammation [10,[23][24][25][26][27][28] and cellular respiration [29][30][31][32][33]. ...
... Hydrogen sulfide (H 2 S) is reported to elicit several physiological and pharmacological functions in mammalian cells [1][2][3][4][5]. In addition to modulating neuronal messages in the brain [6,7], H 2 S also mediates critical processes such as neurotransmission [6,8], cytoprotection [9][10][11][12][13], neuroprotection [14,15], smooth muscle relaxation [16,17], vasorelaxation and regulation of blood pressure [7,[17][18][19][20][21][22], antiinflammation [10,[23][24][25][26][27][28] and cellular respiration [29][30][31][32][33]. ...
Background: Hydrogen sulfide (H 2 S), an endogenous gasotransmitter, has potential applications in several conditions. However, its quantification in simulated physiological solutions is a major challenge due to its gaseous nature and other physicochemical properties. Aim: This study was designed to compare four commonly used H 2 S detection and quantification methods in aqueous solutions. Methods: The four techniques compared were one colorimetric, one chromatographic and two electrochemical methods. Results: Colorimetric and chromatographic methods quantified H 2 S in millimolar and micromole ranges, respectively. The electrochemical methods quantified H 2 S in the nanomole and picomole ranges and were less time-consuming. Conclusion: The H 2 S quantification method should be selected based on the specific requirements of a research project in terms of sensitivity, response time and cost-effectiveness.
... Data about arterial vasoconstriction are scarce and lack solidity on mechanisms, including only a few studies on rat cerebral arteries [11], dual modulation of H 2 S on rat-isolated gastric arteries [12], and an oxygenrelated vasomotor role [13]. Most of the evidence points to a ubiquitous vasorelaxant action of both endogenous and exogenous (micromolar range) H 2 S with the mediation of smooth muscle potassium channels leading to hyperpolarization/relaxation [14]. Indeed, several ion channels are involved in the vascular signaling of H 2 S including ATP-sensitive K + (K ATP ) channels [14], voltage-gated K + channels [15], and 4-aminopyridine-sensitive voltage-gated potassium channels [16]. ...
... Most of the evidence points to a ubiquitous vasorelaxant action of both endogenous and exogenous (micromolar range) H 2 S with the mediation of smooth muscle potassium channels leading to hyperpolarization/relaxation [14]. Indeed, several ion channels are involved in the vascular signaling of H 2 S including ATP-sensitive K + (K ATP ) channels [14], voltage-gated K + channels [15], and 4-aminopyridine-sensitive voltage-gated potassium channels [16]. In 2014, Eberhardt et al. suggested that two gasotransmitters, NO and H 2 S, react to produce nitroxyl (HNO). ...
Ischemia is the underlying mechanism in a wide variety of acute and persistent pathologies. As such, understanding the fine intracellular events occurring during (and after) the restriction of blood supply is pivotal to improving the outcomes in clinical settings. Among others, gaseous signaling molecules constitutively produced by mammalian cells (gasotransmitters) have been shown to be of potential interest for clinical treatment of ischemia/reperfusion injury. Nitric oxide (NO and its sibling, HNO), hydrogen sulfide (H2S), and carbon monoxide (CO) have long been proven to be cytoprotective in basic science experiments, and they are now awaiting confirmation with clinical trials. The aim of this work is to review the literature and the clinical trials database to address the state of development of potential therapeutic applications for NO, H2S, and CO and the clinical scenarios where they are more promising.
... Due to its high reactivity toward ubiquitous chemical groups, H 2 S has a plethora of molecular targets (Kimura, 2015). Potassium channels, such as ATP-sensitive potassium channel (K ATP ) (Mustafa et al., 2011;Tang et al., 2005) and the large-conductance calciumactivated potassium (BK Ca ) channel (Sitdikova et al., 2010(Sitdikova et al., , 2014Telezhkin et al., 2009), are also targets for H 2 S. The BK Ca channel is a tetrameric protein composed of four poreforming a subunits. Each a subunit consists of a short N-terminus, seven transmembrane segments, and a large C-terminus containing two regulating conductance of K 1 (RCK) domains located in the cytoplasm (Lee and Cui, 2010;Yang et al., 2015). ...
... One limitation of this study is the use of relatively high NaHS concentrations of 500-1000 mM. These concentrations were selected according to literature data that described NaHS effects in electrophysiological recordings (Tang et al., 2005;Sun et al., 2008;Sitdikova et al., 2010;Sekiguchi et al., 2014;Kuksis and Ferguson, 2015). For instance, Sitdikova used NaHS in the range from 10 mM to 10 mM and found that the activity of BK Ca in the plasma membrane of GH3 pituitary cells was modulated with EC 50 of 167 and 2000 mM (Sitdikova et al., 2010). ...
Reperfusion together with the preceding ischemic period results in serious damage to brain and heart tissues. Activation of potassium channels from the inner mitochondrial membrane leads to cytoprotection during such events. The mitochondrial large-conductance calcium-activated potassium channel (mitoBKCa) is one of these cytoprotective channels. It was previously shown that BKCa channels are blocked by hemin, which is present in excess during hemorrhage. In the experiments described in this work, we checked whether NaHS, known as a donor of gasotransmitter hydrogen sulfide (H2S), which can play an important role in cytoprotection, interacts with mitoBKCa channels. Indeed, using the biotin-switch method, it was found that mitoBKCa channels undergo S-sulfhydration in the presence of NaHS. Although patch-clamp experiments showed that NaHS has negligible effects on the activity of mitoBKCa channels, NaHS has been shown to almost fully activate hemin-inhibited mitoBKCa channels. The effects of NaHS were mimicked by imidazole, suggesting a common mechanism of activation of mitoBKCa channels inhibited by heme/hemin by molecules able to coordinate the iron ion of porphyrin. A set of absorption spectroscopy experiments with the 23 amino acid model peptides containing the heme-binding motif CXXCH suggested previously unrecognized roles of cysteines in heme binding. Significance Statement The activity of mitochondrial channels including mitoBKCa seems to play a significant role in cytoprotection during ischemia/reperfusion. Hemin, which is present in excess during hemorrhage, can potentially bind to and inhibit mitoBKCa activity. We found that hydrogen sulfide does not affect mitoBKCa activity unless it is blocked by hemin. In this case, hydrogen sulfide activates hemin-inhibited mitoBKCa by binding to hemin iron. The hydrogen sulfide effect could be mimicked in patch-clamp experiments by imidazole probably acting by a similar mechanism.
... In vitro, H 2 S donor sodium hydrosulfide (NaHS), which is actively used in experimental practice, also caused relaxation of thoracic aorta, mesenteric, renal arteries and portal vein. The relaxing effect of H 2 S on smooth muscle cells is associated with effects on cGC, and, as we noted earlier, on K AT P channels [23,228,229]. ...
... Hydrogen sulfide reduces myocardial contractility both in vitro and in vivo [66,228,229]. This effect is partially related to the activation of K AT P channels in CM [230]. ...
Over past few years, there has been a dramatic increase in studying physiological mechanisms of the activity of various signaling low-molecular molecules that directly or indirectly initiate adaptive changes in the cardiovascular system cells (CVSC) to hypoxia. These molecules include biologically active endogenous gases or gasotransmitters (H2S, NO and CO) that influence on many cellular processes, including mitochondrial biogenesis, oxidative phosphorylation, K+/Ca2+ exchange, contractility of cardiomyocytes (CM) and vascular smooth muscle cells (VSMC) under conditions of oxygen deficiency. The present review focuses on the mechanistic role of the gasotransmitters (NO, H2S, CO) in cardioprotection. The structural components of these mechanisms involve mitochondrial enzyme complexes and redox signal proteins, K+ and Ca2+ channels, and mitochondrial permeability transition pore (MPTP) that have been considered as the final molecular targets of mechanisms underlying antioxidant and mild mitochondrial uncoupling effects, preconditioning, vasodilatation and adaptation to hypoxia. In this article, we have reviewed recent findings on the gasotransmitters and proposed a unifying model of mitochondrial mechanisms of cardioprotection.
... H 2 S has also been shown to support pro-apoptotic upregulation of ERK/p38 as well as caspase-3 activation [72,73]. Similar to ECs, SMCs are affected by H 2 S-induced vasodilation through activation of ATP-sensitive (K ATP ) and cell membrane hyperpolarization [74], increasing guanosine 3 ,5 -cyclic monophosphate (cGMP) through phosphodiesterase inhibition [75], and a possible reactivity with nitric oxide (NO) resulting in lower NO bioavailability [76]. Thus, the role of H 2 S in controlling important vascular processes is well established, but how it may exert differential effects in ECs and SMCs remains unclear. ...
... H2S has also been shown to support pro-apoptotic upregulation of ERK/p38 as well as caspase-3 activation [72,73]. Similar to ECs, SMCs are affected by H2S-induced vasodilation through activation of ATP-sensitive (KATP) and cell membrane hyperpolarization [74], increasing guanosine 3′,5′-cyclic monophosphate (cGMP) through phosphodiesterase inhibition [75], and a possible reactivity with nitric oxide (NO) resulting in lower NO bioavailability [76]. Thus, the role of H2S in controlling important vascular processes is well established, but how it may exert differential effects in ECs and SMCs remains unclear. ...
Hydrogen sulfide (H2S) is an endogenous signaling molecule which is important for cardiovascular health, but its mechanism of action remains poorly understood. Here, we report measurements of H2S as well as its oxidized metabolites, termed small oxoacids of sulfur (SOS = HSOH and HOSOH), in four human primary vascular cell lines: smooth muscle and endothelial cells derived from both human arterial and coronary tissues. We use a methodology that targets small molecular weight sulfur species; mass spectrometric analysis allows for species quantification to report cellular concentrations based on an H2S calibration curve. The production of H2S and SOS is orders of magnitude higher in smooth muscle (nanomolar) as compared to endothelial cell lines (picomolar). In all the primary lines measured, the distributions of these three species were HOSOH >H2S > HSOH, with much higher SOS than seen previously in non-vascular cell lines. H2S and SOS were effluxed from smooth muscle cells in higher concentrations than endothelial cells. Aortic smooth muscle cells were used to examine changes under hypoxic growth conditions. Hypoxia caused notable increases in HSOH and ROS, which we attribute to enhanced sulfide quinone oxidase activity that results in reverse electron transport.
... H 2 S acts as a vasodilator in VSMCs by opening the ATP-sensitive potassium channel (K ATP channel). Further studies revealed that H 2 S sulfhydrates Cys43 on Kir6.1, a component of the K ATP channel, leading to decreased affinity of Kir 6.1 for ATP and enhanced affinity for phosphatidylinositol (4,5)-bisphosphate (PIP2), ultimately leading to K ATP channel activation and relaxation of VSMCs (Tang et al. 2005;Mustafa et al. 2011). ...
Hydrogen sulfide (H2S) is recognized as the third gasotransmitter, after nitric oxide (NO) and carbon monoxide (CO). It is known for its cardioprotective properties, including the relaxation of blood vessels, promotion of angiogenesis, regulation of myocardial cell apoptosis, inhibition of vascular smooth muscle cell proliferation, and reduction of inflammation. Additionally, abnormal H2S generation has been linked to the development of cardiovascular diseases (CVD), such as pulmonary hypertension, hypertension, atherosclerosis, vascular calcification, and myocardial injury. MicroRNAs (miRNAs) are non-coding, conserved, and versatile molecules that primarily influence gene expression by repressing translation and have emerged as biomarkers for CVD diagnosis. Studies have demonstrated that H2S can ameliorate cardiac dysfunction by regulating specific miRNAs, and certain miRNAs can also regulate H2S synthesis. The crosstalk between miRNAs and H2S offers a novel perspective for investigating the pathophysiology, prevention, and treatment of CVD. The present analysis outlines the interactions between H2S and miRNAs and their influence on CVD, providing insights into their future potential and advancement.
... Opening of KATP channels leads to hyperpolarization, reducing calcium influx via L-type Ca 2+ channels and preventing Ca 2+ overload. Tang and coworkers have reported that NaHS (100 µM) opens KATP channels in vascular smooth muscle cells (37). Additionally, it may indirectly activate KATP channels by causing intracellular acidosis (38). ...
: Ischemia is a common condition in the population and has become one of the leading causes of mortality in recent years. It occurs due to a shortage of oxygen in the cell caused by inadequate blood flow, leading to the formation of free radicals. These free radicals can bind to the phospholipids in the cell membrane, resulting in proxy radicals and lipid hydroperoxidation. Malondialdehyde (MDA) is a cytotoxic byproduct of lipid peroxidation that causes cell damage and necrosis by rupturing the cell membrane. Subsequently, mitochondrial dysfunction related to fatty acid oxidation can develop, further exacerbating the damage caused by ischemia. Reactive oxygen species (ROS) produced in mitochondria have been shown to elevate oxidative phosphorylation disorder and disrupt the functioning of complexes I and IV. These enzyme activities can be restored to normal levels by activating antioxidant enzymes such as superoxide dismutase (Mn-SOD) and catalase, thereby strengthening the antioxidant defense system. Various antioxidants have been found to have protective effects. In this review, we compare the antioxidant effects of various plants and tannins that have been studied up to this point on myocardial ischemia. We also explain some of the cellular and molecular pathways that have been investigated to protect the myocardium against ischemia-reperfusion injury.
... Hydrogen sulfide (H 2 S) is a colorless, flammable, membranepermeable and foul-smelling gas that was first described by Bernardino Ramazzini in 1713 as a toxic gas and subsequently established in the toxicological literature as a fatal gas at high concentrations [1][2][3][4]. However, experimental evidence over the past two decades has established a rapid paradigm shift in which H 2 S functions as an endogenous signaling molecule that participates in cellular homeostasis and influences a myriad of physiological and pathological processes at low concentrations [5][6][7][8]. In addition, low physiological concentrations of H 2 S produce pharmacological effects, affirming the fact that H 2 S has successfully overcome its historic notorious label in the toxicological literature. ...
For over three centuries, hydrogen sulfide (H 2 S) has been known as a toxic and deadly gas at high concentrations, with a distinctive smell of rotten eggs. However, studies over the past two decades have shown that H 2 S has risen above its historically notorious label and has now received significant scientific attention as an endogenously produced gaseous signaling molecule that participates in cellular homeostasis and influences a myriad of physiological and pathological processes at low concentrations. Its endogenous production is enzymatically regulated, and when dysregulated, contributes to pathogenesis of renal diseases. In addition, exogenous H 2 S administration has been reported to exhibit important therapeutic characteristics that target multiple molecular pathways in common renal pathologies in which reduced levels of renal and plasma H 2 S were observed. This review highlights functional anatomy of the kidney and renal production of H 2 S. The review also discusses current understanding of H 2 S in renal physiology and seeks to lay the foundation as a new targeted therapeutic agent for renal pathologies such as hypertensive nephropathy, diabetic kidney disease and water balance disorders.
... This suggests a role of SSH in BK Ca channel activation in pregnancy-associated uterine vasodilation, although how SSH-BKα activates BK Ca channels needs to be further delineated. Activation of vascular smooth muscle K ATP channels is the first mechanism known to mediate the vasodilatory effects of H 2 S in systemic arteries (20,65), which is achieved through SSH of Kir6.1 at Cys43 (23) and SUR2B at Cys24 and Cys2455 (36). Unexpectedly, low-pH QTRP fails to dig out these proteins in human UA even after treated with exogenous H 2 S. ...
Uterine artery (UA) hydrogen sulfide (H2S) production is augmented in pregnancy and upon stimulation by systemic/local vasodilators, contributing to pregnancy-dependent uterine vasodilation; however, how H2S exploits this role is largely unknown. S-sulfhydration converts free thiols (-SH) to persulfides (-SSH) at reactive cysteine(s) on targeted proteins to affect the entire proteome post-translationally, representing the main route for H2S to elicit its function. Herein we used Tag-Switch to quantify changes in sulfhydrated (SSH-) proteins (i.e., sulfhydromes) in H2S-treated nonpregnant (NP) and pregnant (P) human UA. We further used the Low-pH quantitative thiol reactivity profiling (low-pH QTRP) platform by which paired sulfhydromes were subjected to LC-MS/MS based peptide sequencing to generate site (cysteine)-specific pregnancy-dependent H2S-responsive human UA sulfhydrome. Total levels of sulfhydrated proteins were significantly greater in P versus NP human UA and further stimulated by treatment with NaHS. We identified a total of 360 and 1,671 SSH-peptides from 480 and 1,186 SSH-proteins in untreated and NaHS-treated human UA, respectively. Bioinformatics analyses identified pregnancy-dependent H2S-responsive human UA SSH-peptides/proteins, which were categorized to various molecular functions, pathways, and biological processes, especially vascular smooth muscle contraction/relaxation. Pregnancy-dependent changes in these proteins were rectified by immunoblotting of the Tag-Switch labeled SSH-proteins. Low-pH QTRP failed to identify low abundance SSH-proteins such as KATP channels in human UA; however, immunoblotting of Tag-Switch labeled SSH-proteins identified pregnancy-dependent upregulation of SSH-KATP channels without altering their total proteins. Thus, comprehensive analyses of human UA sulfhydromes influenced by endogenous and exogenous H2S inform novel roles of protein sulfhydration in uterine hemodynamics regulation.
... As an endogenous gas transmitter, H 2 S also plays an pivotal role in many cell systems by regulating the activity of ion channels. H 2 S was the first opener of (ATP Sensitive K + ) KATP channel identified in vascular smooth muscle cells (Tang et al., 2005). Through activation of KATP channels, H 2 S lowers blood pressure, protects heart from ischaemia and reperfusion injury (Givvimani et al., 2011;J. ...
Atrial fibrosis, a symbol of atrial structural remodelling, is a complex process involved in the occurrence and maintenance of atrial fibrillation (AF). Atrial fibrosis is regulated by multiple factors. Sulfur containing amino acids and their metabolites, such as hydrogen sulfide (H2S) and taurine, can inhibit the process of atrial fibrosis and alleviate atrial remodeling. However, homocysteine can promote the activation of atrial fibroblasts and further promote atrial fibrosis. In this review, we will focus on the recent progress in atrial structural changes and molecular mechanisms of atrial fibrosis, as well as the regulatory roles and possible mechanisms of sulfur containing amino acids and their metabolites in atrial fibrosis. It is expected to provide new ideas for clarifying the mechanism of atrial fibrosis and finding targets to inhibit the progress of atrial fibrosis.
... Among these channels, the activation of KATP channel has been closely linked to the development of pathological vasodilation and the induction of hypotension in various forms of distributive shock [17]. Several mechanisms may account for the activation of KATP channel in VS associated with CPB, including NO release, vasopressin deficiency, hypoxia, acidosis and an increase in the generation of hydrogen sulfide (see below) [17,36,[42][43][44][45]. ...
Vasoplegic syndrome (VS) is a common complication following cardiovascular surgery with cardiopulmonary bypass (CPB), and its incidence varies from 5 to 44%. It is defined as a distributive form of shock due to a significant drop in vascular resistance after CPB. Risk factors of VS include heart failure with low ejection fraction, renal failure, pre-operative use of angiotensin-converting enzyme inhibitors, prolonged aortic cross-clamp and left ventricular assist device surgery. The pathophysiology of VS after CPB is multi-factorial. Surgical trauma, exposure to the elements of the CPB circuit and ischemia-reperfusion promote a systemic inflammatory response with the release of cytokines (IL-1β, IL-6, IL-8, and TNF-α) with vasodilating properties, both direct and indirect through the expression of inducible nitric oxide (NO) synthase. The resulting increase in NO production fosters a decrease in vascular resistance and a reduced responsiveness to vasopressor agents. Further mechanisms of vasodilation include the lowering of plasma vasopressin, the desensitization of adrenergic receptors, and the activation of ATP-dependent potassium (KATP) channels. Patients developing VS experience more complications and have increased mortality. Management includes primarily fluid resuscitation and conventional vasopressors (catecholamines and vasopressin), while alternative vasopressors (angiotensin 2, methylene blue, hydroxocobalamin) and anti-inflammatory strategies (corticosteroids) may be used as a rescue therapy in deteriorating patients, albeit with insufficient evidence to provide any strong recommendation. In this review, we present an update of the pathophysiological mechanisms of vasoplegic syndrome complicating CPB and discuss available therapeutic options.
... The K ATPmediated vasorelaxant effects of H 2 S were first demonstrated by Zhao and colleagues, who observed that vasorelaxation of rat isolated aortic rings promoted by H 2 S, as well as reductions in BP levels in rats, were significantly lowered in the presence of the selective K ATP blocker glibenclamide [38]. Importantly, inhibition of H 2 S biosynthesis with PAG reduced K ATP currents supporting a crucial role for K ATP channels in the regulation of BP by endogenous H 2 S [92]. The opening of K ATP channels by H 2 S was also confirmed by patch-clamp electrophysiology, which recorded a significant amplitude of K ATP currents in VSMCs from rat mesenteric arteries after incubation with exogenous H 2 S. Citi and colleagues described the H 2 S-mediated vascular effects of two thiourea derivatives, demonstrating that both hyperpolarization of HASMCs and vasorelaxation of rat endothelium-denuded aortic rings were significantly reduced in the presence of glibenclamide [8]. ...
Natural sulfur compounds are emerging as therapeutic options for the management of hypertension and prehypertension. They are mainly represented by polysulfides from Alliaceae (i.e., garlic) and isothiocyanates from Brassicaceae (or crucifers). The beneficial cardiovascular effects of these compounds, especially garlic polysulfides, are well known and widely reported both in preclinical and clinical studies. However, only a few authors have linked the ability of natural sulfur compounds to induce vasorelaxation and subsequent antihypertensive effects with their ability to release hydrogen sulfide (H2S) in biological tissue. H2S is an endogenous gasotransmitter involved in vascular tone regulation. Some cardiovascular diseases, such as hypertension, are associated with lower plasma H2S levels. Consequently, exogenous sources of H2S (H2S donors) have been designed and synthesized or identified among secondary plant metabolites as potential therapeutic options. In addition to antioxidant effects due to its chemical properties as a reducing agent, H2S induces vasorelaxation by interacting with a range of molecular targets. The mechanisms of action accounting for H2S-induced vasodilation include opening of vascular potassium channels (such as ATP-sensitive (KATP) and voltage-operated (Kv7) channels), inhibition of 5-phosphodiesterase (5-PDE), and activation of vascular endothelial growth factor receptor-2 (VEGFR-2). These effects may be attributed to H2S-induced S-persulfidation (or S-sulfhydration), which is a posttranslational modification of cysteine residues of many types of proteins resulting in structural and functional alterations (activation/inhibition). Thus, H2S donors, such as natural sulfur compounds, are promising antihypertensive agents with novel mechanisms of action.
... Kang et al. reported that exogenous H 2 S also can protect the heart through its anti-myocardial fibrotic activity [117]. In addition, H 2 S has effects on vasodilation, maintaining homeostasis in the cardiovascular system, and improving the sensitivity of vascular pressure reflex [118,119]. Besides the direct effect on the cardiovascular system, H 2 S can increase the NO production of ECs by activating eNOS [120]. ...
Cardiovascular disease (CVD) is the first leading cause of death globally. Nitric oxide (NO) is an important signaling molecule that mediates diverse processes in the cardiovascular system, thereby providing a fundamental basis for NO-based therapy of CVD. At present, numerous prodrugs have been developed to release NO in vivo. However, the clinical application of these prodrugs still faces many problems, including the low payloads, burst release, and non-controlled delivery. To address these, various biomaterial-based platforms have been developed as the carriers to deliver NO to the targeted tissues in a controlled and sustained manner. This review aims to summarize recent developments of various therapeutic platforms, engineered to release NO for the treatment of CVD. In addition, two potential strategies to improve the effectiveness of existing NO therapy are also discussed, including the combination of NO-releasing platforms and either hydrogen sulfide-based therapy or stem cell therapy. Hopefully, some NO-releasing platforms may provide important therapeutic benefits for CVD.
... H 2 S increased the whole-cell currents and the single channel open probability of K ATP channels. Inhibition of endogenous H 2 S production reduced whole-cell K ATP currents in mesenteric artery smooth muscle cells (Tang et al., 2005). Second, K ATP channel can be sulfhydrated by H 2 S. H 2 S-mediated sulfhydration and hyperpolarization are absent in cells overexpressing C43S mutant Kir 6.1. ...
Hydrogen sulfide (H2S) has been highlighted as an important gasotransmitter in mammals. A growing number of studies have indicated that H2S plays a key role in the pathophysiology of vascular diseases and physiological vascular homeostasis. Alteration in H2S biogenesis has been reported in a variety of vascular diseases and H2S supplementation exerts effects of vasodilation. Accumulating evidence has shown vascular potassium channels activation is involved in H2S-induced vasodilation. This review aimed to summarize and discuss the role of H2S in the regulation of vascular tone, especially by interaction with different vascular potassium channels and the underlying mechanisms.
... In the first study of H 2 S and the activation of KATP channels, the authors described a reverse journey from the in vivo demonstration that H 2 S-induced blood pressure lowering (inhibited by glibenclamide), the in vitro experimental models represented by dilation of rat aortic tissue, hyperpolarization of isolated vascular smooth muscle cells and expression of cystathionine γ-lyase (CSE, one of the most important H 2 S-generating enzymes at the cardiovascular level) in vascular smooth muscle cells [14]. After this first demonstration, other studies focused their attention on the interaction between H 2 S and KATP channels confirming their involvement in the induction of vascular smooth muscle hyperpolarization recorded by electrophysiological measurements [28] and exploring this mechanism of action on distinct vessels such as cerebral arterioles or the hepatic artery [29,30]. As H 2 S acts by inducing S-persulfidation of proteins, it is quite unlikely to lead to selective activation of just one subtype of potassium channel. ...
After the discovery of hydrogen sulfide (H2S) in the central nervous system by Abe and Kimura in 1996, the physiopathological role of H2S has been widely investigated in several systems such as the cardiovascular. In particular, H2S plays a pivotal role in the control of vascular tone, exhibiting mechanisms of action able to induce vasodilation: for instance, activation of potassium channels (KATP and Kv7) and inhibition of 5-phosphodiesterase (5-PDE). These findings paved the way for the research of natural and synthetic exogenous H2S-donors (i.e., molecules able to release H2S) in order to have new tools for the management of hypertension. In this scenario, some natural molecules derived from Alliaceae (i.e., garlic) and Brassicaceae (i.e., rocket or broccoli) botanical families show the profile of slow H2S-donors able to mimic the endogenous production of this gasotransmitter and therefore can be viewed as interesting potential tools for management of hypertension or pre-hypertension. In this article, the preclinical and clinical impacts of these natural H2S-donors on hypertension and vascular integrity have been reviewed in order to give a complete panorama of their potential use for the management of hypertension and related vascular diseases.
... In the first study of H 2 S and the activation of KATP channels, the authors described a reverse journey from the in vivo demonstration that H 2 S-induced blood pressure lowering (inhibited by glibenclamide), the in vitro experimental models represented by dilation of rat aortic tissue, hyperpolarization of isolated vascular smooth muscle cells and expression of cystathionine γ-lyase (CSE, one of the most important H 2 S-generating enzymes at the cardiovascular level) in vascular smooth muscle cells [14]. After this first demonstration, other studies focused their attention on the interaction between H 2 S and KATP channels confirming their involvement in the induction of vascular smooth muscle hyperpolarization recorded by electrophysiological measurements [28] and exploring this mechanism of action on distinct vessels such as cerebral arterioles or the hepatic artery [29,30]. As H 2 S acts by inducing S-persulfidation of proteins, it is quite unlikely to lead to selective activation of just one subtype of potassium channel. ...
Citation: Piragine, E.; Citi, V.; Lawson, K.; Calderone, V.; Martelli, A. Potential Effects of Natural H 2 S-Donors in Hypertension Management.
After the discovery of hydrogen sulfide (H2S) in the central nervous system by Abe and
Kimura in 1996, the physiopathological role of H2S has been widely investigated in several systems
such as the cardiovascular. In particular, H2S plays a pivotal role in the control of vascular tone,
exhibiting mechanisms of action able to induce vasodilation: for instance, activation of potassium
channels (KATP and Kv7) and inhibition of 5-phosphodiesterase (5-PDE). These findings paved the
way for the research of natural and synthetic exogenous H2S-donors (i.e., molecules able to release
H2S) in order to have new tools for the management of hypertension. In this scenario, some natural
molecules derived from Alliaceae (i.e., garlic) and Brassicaceae (i.e., rocket or broccoli) botanical families
show the profile of slow H2S-donors able to mimic the endogenous production of this gasotransmitter
and therefore can be viewed as interesting potential tools for management of hypertension or prehypertension. In this article, the preclinical and clinical impacts of these natural H2S-donors on
hypertension and vascular integrity have been reviewed in order to give a complete panorama of
their potential use for the management of hypertension and related vascular diseases.
... An early study using rat aortic cells has postulated that the mechanism through which H2S exerts its vasorelaxantfunctions is the opening of ATP-sensitive potassium channels (KATP) [18]. By doing so, H2S increases the flow of K + ions, which protect cells against excessive shrinkage, and lowers blood pressure by hyperpolarization [18,198]. ...
Hydrogen sulfide (H2S) is the third gasotransmitter described in mammals. Colourless and water-soluble, H2S is a highly effective inhibitor of mitochondrial cytochrome c oxidase when present at high concentrations. However, when present at low concentrations, H2S can act as an inorganic energetic substrate for mammalian mitochondria. To oxidize H2S, mitochondria need the sulfide oxidizing unit (SOU), a set of three specific enzymes: sulfide quinone reductase (SQR), dioxygenase (ETHE1) and thiosulfate sulfurtransferase (TST). Liver metabolism, finely regulated by hormones and nutrients, is central to energy homeostasis, and liver metabolic inflexibility is known to be associated with several metabolic diseases, such as Non-Alcoholic Fatty Liver Disease (NAFLD). The unique position of this organ makes it likely to be exposed to high levels of H2S coming from both exogenous (gastrointestinal tract) and endogenous (metabolism of sulfur-containing amino acids) sources. Recently, impaired liver H2S biosynthesis has been reported in animal models of NAFLD, and in vivo supplementation of H2S donors prevented the further escalation of the illness into steatohepatitis (NASH). Almost all studies exploring the hepatic pathological relevance of H2S are usually focused on H2S biosynthesis pathway and/or using exogenous donors. As intrahepatic H2S levels can also be controlled by its mitochondrial oxidation, the objectives of my PhD were to investigate the pathophysiological importance of this pathway in liver metabolism and in the development of NAFLD. First, we showed that, physiologically, the liver nutritional status regulates hepatic mitochondrial H2S oxidation capacity and SQR protein expression, both being downregulated by fasting while overnight refeeding abolished the fasting inhibitory effect. Adenovirus-mediated overexpression of human SQR in mouse liver clearly demonstrated that SQR is the key regulatory enzyme of mitochondrial H2S oxidation. Enhancing this pathway i) increased in vivo glucose tolerance and liver insulin signalling, ii) stimulated glucose metabolism in primary cultures of mouse hepatocytes (13C-glucose fluoxomics), and iii) decreased liver fatty acid oxidation capacity. Second, when exploring the context of NAFLD, we observed that liver mitochondrial H2S oxidation capacity was downregulated in mice fed high fat/high sucrose (HF/HS) diet (NAFL model) and surprisingly was upregulated in mice fed methionine-choline deficient (MCD) diet (NASH model). In vivo supplementation with sodium thiosulfate (STS), an H2S donor, abrogated the inhibitory effect of HF/HS diet while it had no impact in the NASH model. Additionally, STS supplementation had no effect on body weight, glucose tolerance and insulin sensitivity in the NAFL model, and on liver steatosis in both NAFL and NASH models. However, STS supplementation did have an impact in the composition of gut microbiota. Similarly to the NAFLD mouse models, in morbid obese patients with simple steatosis (NAFL), liver SQR protein expression was found decreased, while in individuals with NASH SQR expression was found increased. Altogether, these studies, which confirmed that SQR is the key rate-limiting enzyme for liver mitochondrial H2S oxidation, clearly demonstrated for the first time that this pathway is finely regulated by the nutritional status of the liver and is altered in animal models of NAFLD and obese NAFLD patients. The novel observation that increasing hepatic mitochondrial H2S oxidation capacity increases hepatic glucose metabolism opens a new door in the field of liver pathophysiology, with this pathway being a potential protective target against the development of liver insulin resistance.
... It is produced by the action of at least three enzymes, cystathionine beta synthase (CBS), cystathionine gamma lyase (CSE) and mercaptopyruvate-sulfur transferase (MST) (20,21) . Numerous physiological functions assigned to be exclusively or partly regulated by H 2 S, some of which are vasodilation (22) , and angiogenesis (23) via direct activation of K ATP channels (24) . ...
This study was designed to find out the vasorelaxant effects of hydrogen sulfide (H2S) on arteries feeding human colon cancer. In addition, it also included the study of the possible roles of potassium (K2) and calcium (Ca2+) channel types in H2S-induced relaxation in the isolated arteries. Sodium sulfide (Na2S) showed a potent dose-dependent relaxant effect on Norepinephrine (1X10-5 M) precontracted arteries. The use of different specific K+ channel blockers (BaCl2, 4-AP, GLIB, and TEA) individually indicated H2S-induced relaxation was affected by all K channel types participated to a various extent, except Kv channels. Both Kca2+ and Kir channels played a major role in the induced relaxation, while K ATP played a minor and non-significant role. On the other hand, Kv channel played no direct role, and the induced response curve was very close to that of the control. Possible combinations of K channel blockers showed that some produced synergistic effect to different extent, whereas others produced mild and non-significant effect except at the highest doses used on dose-response curves. Thus, combinations of (GLIB+4-AP), (GLIB+BaCl2) and (BaCl2+TEA) caused a highly significant blocking in the induced response curve, while (BaCl2 +4-AP) and (TEA+4-AP) produced a mild inhibition except at the highest doses used in which the inhibition was significant.
... IRI induced a loss of approximately 50% of the retinal ganglion cells (IRI: 1540 ± 78 vs. untreated: 2592 ± 54; Figure 1, Col. 1 and 2). Inhaled H 2 S was able to attenuate this effect at concentrations of 120 and 80 ppm at specific time points (Figure 1, Col 4,6,7). At a concentration of 120 ppm, only the inhalation administered at 1.5 h after IRI had a protective effect, as indicated by a significantly reduced cell death (IRI + 120 ppm H 2 S at 1.5 h: 2039 ± 99, p < 0.001). ...
Background:
The ischemia-reperfusion injury (IRI) of neuronal tissue, such as the brain and retina, leads to possible cell death and loss of function. Current treatment options are limited, but preliminary observations suggest a protective effect of hydrogen sulfide (H2S). However, the dosage, timing, and mechanism of inhaled H2S treatment after IRI requires further exploration.
Methods:
We investigated possible neuroprotective effects of inhaled H2S by inducing retinal ischemia-reperfusion injury in rats for the duration of 1 h (120 mmHg), followed by the administration of hydrogen sulfide (H2S) for 1 h at different time points (0, 1.5, and 3 h after the initiation of reperfusion) and at different H2S concentrations (120, 80, and 40 ppm). We quantified the H2S effect by conducting retinal ganglion cell counts in fluorogold-labeled animals 7 days after IRI. The retinal tissue was harvested after 24 h for molecular analysis, including qPCR and Western blotting. Apoptotic and inflammatory mediators, transcription factors, and markers for oxidative stress were investigated. Histological analyses of the retina and the detection of inflammatory cytokines in serum assays were also performed.
Results:
The effects of inhaled H2S were most evident at a concentration of 80 ppm administered 1.5 h after IRI. H2S treatment increased the expression of anti-apoptotic Bcl-2, decreased pro-apoptotic Bax expression, reduced the release of the inflammatory cytokines IL-1β and TNF-α, attenuated NF-κB p65, and enhanced Akt phosphorylation. H2S also downregulated NOX4 and cystathionine β-synthase. Histological analyses illustrated a reduction in TNF-α in retinal ganglion cells and lower serum levels of TNF-α in H2S-treated animals after IRI.
Conclusion:
After neuronal IRI, H2S mediates neuroprotection in a time- and dose-dependent manner. The H2S treatment modulated transcription factor NF-κB activation and reduced retinal inflammation.
... We showed that H 2 S suppressed early development of atherosclerosis [20] and the proliferation of vascular smooth muscle cells [2,21], but promoted angiogenesis and endothelial proliferation [22][23]. H 2 S relaxes vascular tissues by opening KATP channels in vascular smooth muscle cells [11,[24][25] or by functioning as an endothelium-derived hyperpolarizing factor (EDHF) to cause endothelium-dependent vasorelaxation [26][27]. ...
Eukaryotes and microbiota produce H2S, using the same substrates and enzymes which constitute the reverse-trans-sulfuration and transsulfuration pathways. The homeostasis of gut microbiota impacts on the structural and functional integrity of gut epithelial barrier. Microbiota also serve as signalling sources to inform the host of the metabolism and functional changes. Microbiota dysbiosis negatively affect human health, contributing to diseases like obesity, diabetes, inflammatory bowel diseases, and asthma. Not by coincidence, these pathological conditions are also closely related to the abnormal metabolism and function of H2S signalling.H2S serves as a bacterial signal to the host and the host-produced H2S impacts on the population and size of microbiota. These bi-directional interactions become especially important for the digestion and utilization of sulfur amino acid in diet. Dietary restriction of sulfur amino acid increases the endogenous production of H2S by the host and consequently offers many health benefits. It, on the other hand, decreases the nutritional supply to the microbiota, which could be remedied by the co-application of prebiotics and probiotics. It is strategically sound to target the expression of H2S-producing enzymes in different organs to slow aging processes in our body and promote better health.
... 20,21 Likewise, patch-clamp experiments showed an increase in K ATP channel current in rat aortic smooth muscle cells only at 300 μM H 2 S, much higher than can be achieved in vivo. 22 Thus, there is speculation that vasorelaxation and other cardiovascular effects are induced through ill-defined biotransformation, resulting in reactive sulfur species such as sulfenic acid (RSOH), persulfide (e.g., RSSH), 23 S-nitroso (RSNO), 24 or other modifications of protein thiols that can alter biochemical activity. 25 Metabolomic profiling of reactive sulfur species such as cysteine sulfenic acid (CysSOH) and hydropersulfide (CysSSH) have shown that appreciable amounts are endogenously found in both prokaryotic and eukaryotic organisms. ...
... 10 H 2 S is an important endogenous vasodilator and has been confirmed as a gas opener of the K ATP channel in VSM. 11 Studies have shown that H 2 S is a powerful pulmonary artery vasodilator that can significantly reduce PH. 12 Endogenous H 2 S was found to be involved in the occurrence of hypoxic, 13 high pulmonary blood flow 14 and monocrotaline-induced 15,16 animal models of PH, and exogenous H 2 S could alleviate PH and pulmonary vascular structural remodeling. The mechanism includes relaxation of pulmonary VSM, 12 inhibition of proliferation in VSM cells, 17 induction of apoptosis in VSM cells, 18 inhibition of abnormal accumulation of extracellular matrix in VSM cells, 19 and improvement of antioxidant capacity of lung tissue, 20 etc. H 2 S is a potential dilatator of the human pulmonary artery and is an important drug for lowering pulmonary artery pressure. ...
Objective
To explore the relationship between endogenous hydrogen sulfide (H2S) and high-resolution computed tomography (HRCT) indexes in pulmonary vascular remodeling.
Methods
A total of 94 stable chronic obstructive pulmonary disease (COPD) patients were recruited for the study．Plasma H2S levels were measured using fluorescence probe. Fluorescence quantitative polymerase chain reaction was used to measure H2S synthase cystathionine-γ-lyase (CSE) mRNA and cystathionine-β-synthesis enzyme (CBS) mRNA. The main pulmonary artery diameter (mPAD), axial diagonal mPAD, coronal mPAD, sagittal mPAD, right pulmonary artery diameter (RPAD), left pulmonary artery diameter (LPAD), and ascending aortic diameter (AAD) and the percentage of total cross-sectional area of vessels less than 5 mm² of total lung area (%CSA <5) on HRCT were measured. Pulmonary arterial systolic pressure (PASP) of echocardiography, blood gas analysis, and routine blood tests were performed. Correlation analysis and multivariate linear regression were performed using SPSS 22.0.
Results
H2S was negatively correlated with mPAD, axial diagonal mPAD, and sagittal mPAD (r = −0.25~−0.32) and positively correlated with PaO2 (r = 0.35). Relative expression of CSE mRNA was positively correlated with PASP, coronal mPAD, sagittal mPAD, white blood cell count (WBC), and neutrophil count (N) (r = 0.30~0.44). The relative expression of CBS mRNA was positively correlated with PASP, WBC, and N (r = 0.34~0.41). In separate models predicting pulmonary vascular indexes, a 1μmol/L increase in H2S predicted lower pulmonary artery diameter (for axial diagonal mPAD, 0.76mm lower; for mPAD/AAD, 0.68mm lower). All P values were less than 0.05.
Conclusion
Endogenous H2S may be involved in pulmonary vascular remodeling, providing a new method for the diagnosis and treatment of COPD. The generation of H2S may be inhibited by hypoxia, inflammation, etc.
... [22], ! [25, 31,32]. ...
We analysed the modern literature about the hydrogen sulfide role in evolution of atmosphere, phylogenesis and possibility the use of its vazodylyatation properties for treatment and rehabilitation in sanatorium-resort terms. The mechanisms of gumoral and reflex action of hydrogen sulfide and sulfides baths are considered, testimonies, relative and absolute contra-indications, are resulted. It was shown that at the correct dosage and account of the initial state of reactivity of patient hydrogen sulfide can be the substantial factor for the local blood stream improvement, the trophic and regeneration processes activating, the whole organism physiological state renewal.
... The vasodilatory effects of H 2 S have been shown to be mediated by the activation of the adenosine triphosphate (ATP)-sensitive K + -channel (K ATP ) and BK Ca channels, resulting in SM relaxation [331,351,354]. In rat aortas, endogenous H 2 S maintains whole-cell K ATP currents, while exogenous H 2 S activates K ATP channels by increasing the availability of single channels of this type [355]. In freshly prepared endothelium-intact and denuded rat mesentery artery rings, exogenous H 2 S from donors (100 µM NaSH) potently induces vascular relaxation, which is partially attenuated by the mixture of the endothelial small conductance K + channel (SK Ca ) inhibitor apamin, and intermediate conductance K + -channel (IK Ca ) inhibitor charybdotoxin, or the K ATP channel inhibitor glibenclamide [337]. ...
Normal pregnancy is associated with dramatic increases in uterine blood flow to facilitate the bidirectional maternal–fetal exchanges of respiratory gases and to provide sole nutrient support for fetal growth and survival. The mechanism(s) underlying pregnancy-associated uterine vasodilation remain incompletely understood, but this is associated with elevated estrogens, which stimulate specific estrogen receptor (ER)-dependent vasodilator production in the uterine artery (UA). The classical ERs (ER and ER) and the plasma membrane-bound G protein-coupled ER (GPR30/GPER) are expressed in UA endothelial cells and smooth muscle cells, mediating the vasodilatory effects of estrogens through genomic and/or nongenomic pathways that are likely epigenetically modified. This chapter aims to summarize the literature on UA ERs with a focus on their roles in mediating the local UA production of vasodilators by estrogens and pregnancy and to deliberate on the potential clinic implications of dysregulated ER-mediated estrogen signaling in hypertensive pregnancy complications. The activation of these three ERs by estrogens enhances the endothelial production of nitric oxide (NO), which has been shown to play a key role in uterine vasodilation during pregnancy. However, the local blockade of NO biosynthesis only partially attenuates estrogen-induced and pregnancy-associated uterine vasodilation, suggesting that mechanisms other than NO exist to mediate uterine vasodilation. We summarize here the literature on the role of NO in ER-mediated mechanisms controlling estrogen-induced and pregnancy-associated uterine vasodilation and our recent work on a “new” UA vasodilator hydrogen sulfide (H2S) that has dramatically changed our view of how estrogens regulate uterine vasodilation in pregnancy.
... cGMP increases endothelial Ca +2 concentration and contributes to the opening of localized Ca +2 -dependent K + channels (K Ca ) (15). In contrast, H 2 S exerts its effects on vasodilation (16) and angiogenesis (17) via the direct activation of K ATP channels (18). ...
Recent studies have focused on the role of gaso-transmitters in cancer progression and prevention. Therefore, the current study was designed to explore the vasodilator activity of NO and H 2 S in the human mesenteric arteries of patients with colorectal cancer (CRC) via the activation of K + channels. A total of two sets of experiments were established for the current investigation. Blood samples from patients with CRC were obtained to detect serum levels of endocan and malondialdehyde (MDA). The role of K + channels in mediating the vasodilation of the human mesenteric artery in response to sodium nitroprusside (SNP) and sodium disulfide (Na 2 S) was assessed. The level of serum endocan was indicated to be decreased in patients with CRC compared with healthy individuals, while the level of serum MDA remained unaltered between groups. The arterial rings pre-contracted with norepinephrine were first relaxed by the cumulative addition of increasing concentrations of either SNP (30 nM-30 µM) or (1-6 mM). Maximal relaxation rates were then calculated at 15 min intervals for 60 min. Pre-incubation of arterial rings for 20 min with individual K + channel blockers was indicated to significantly reduce SNP-and Na 2 S-induced relaxation at different time points. Pre-treatment of L-nitro-arginine methyl ester did not alter vasodilation that was induced by Na 2 S. Furthermore, vasodilation of the CRC mesenteric artery was not altered by the synergistic application of SNP and Na 2 S, while pre-incubation of arterial rings with D,L-propargylglycine significantly enhanced vasodilation induced by SNP. These results indicated that endothelial dysfunction and oxidative stress do not serve roles in the pathogenesis of CRC. The dilatory mechanisms of NO and H 2 S in mesenteric arteries of patients with CRC were K + channel-and time-dependent, and the activity of cystathionine γ-lyase enzyme inhibited the ability of exogenous NO in vasodilation processes.
Hydrogen sulfide (H2S) is a gaseous signaling molecule produced in the body by three enzymes: cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). H2S is crucial in various physiological processes associated with female mammalian reproduction. These include estrus cycle, oocyte maturation, oocyte aging, ovulation, embryo transport and early embryo development, the development of the placenta and fetal membranes, pregnancy, and the initiation of labor. Despite the confirmed presence of H2S-producing enzymes in all female reproductive tissues, as described in this review, the exact mechanisms of H2S action in these tissues remain in most cases unclear. Therefore, this review aims to summarize the knowledge about the presence and effects of H2S in these tissues and outline possible signaling pathways that mediate these effects. Understanding these pathways may lead to the development of new therapeutic strategies in the field of women’s health and perinatal medicine.
The scarcity of suitable high-throughput screening technology for H2S donors has hampered the discovery of H2S donors. In this study, a long-lived cyclometalated iridium complex was rationally designed as a mitochondria-targeted H2S probe to monitor the real-time dynamic change of H2S. By using time-resolved emission spectroscopy (TRES) technique, an anti-interference high-throughput screening system was developed to monitor H2S in living cells with decreased false negative results. As a proof-of-concept, three natural products were identified as potential H2S donors from a natural product library using the developed TRES probe. Notably, the discovery of allicin and diallyl trisulfide demonstrated the feasibility of this screening platform, while garlic derived allyl methyl sulfide was explored as a H2S donor candidate. The results were further validated by a commercial assay. We anticipate this high-throughput platform could facilitate the discovery of H2S donors by discriminating the endogenous interfering fluorescence from biological system.
3D hydrogel‐based cell cultures provide models for studying cell behavior and can efficiently replicate the physiologic environment. Hydrogels can be tailored to mimic mechanical and biochemical properties of specific tissues and allow to produce gel‐in‐gel models. In this system, microspheres encapsulating cells are embedded in an outer hydrogel matrix, where cells are able to migrate. To enhance the efficiency of such studies, a lab‐on‐a‐chip named 3D cell migration‐chip (3DCM‐chip) is designed, which offers substantial advantages over traditional methods. 3DCM‐chip facilitates the analysis of biochemical and physical stimuli effects on cell migration/invasion in different cell types, including stem, normal, and tumor cells. 3DCM‐chip provides a smart platform for developing more complex cell co‐cultures systems. Herein the impact of human fibroblasts on MDA‐MB 231 breast cancer cells’ invasiveness is investigated. Moreover, how the presence of different cellular lines, including mesenchymal stem cells, normal human dermal fibroblasts, and human umbilical vein endothelial cells, affects the invasive behavior of cancer cells is investigated using 3DCM‐chip. Therefore, predictive tumoroid models with a more complex network of interactions between cells and microenvironment are here produced. 3DCM‐chip moves closer to the creation of in vitro systems that can potentially replicate key aspects of the physiological tumor microenvironment.
Hydrogen sulfide (H2S), a gas with a characteristic rotten-egg smell, gained historic notoriety for its toxicity and death at high concentrations especially among industrial workers. This is due to its ability to reversibly inhibit the activity of cytochrome c oxidase, a terminal enzyme of the mitochondrial electron transport chain. Recently, however, H2S has risen above its notorious public image and is now seen by researchers as an endogenously produced gaseous signaling molecule that plays an important role in cellular homeostasis and influences several physiological and pathological processes at low physiological and non-toxic concentrations. Its production is catalyzed by two cytosolic enzymes, cystathionine β-synthase and cystathionine γ-lyase, a mitochondrial enzyme, 3-mecaptopyruvate sulfurtransferase, and a peroxisomal enzyme, d-amino acid oxidase. Several recent experimental studies have demonstrated that at low micromolar concentrations, H2S plays a complex and essential role in normal renal function, and dysregulation of its production has been implicated in various renal pathologies. In addition, exogenous H2S administration has been reported to exhibit important therapeutic characteristics that target multiple molecular pathways in common renal pathologies in which reduced levels of renal and plasma H2S were observed. This chapter presents current understanding of H2S in the physiology of the renal system, and lays the foundation for discussion on H2S as a novel pharmacological agent to modify organ transplantation protocol, which are discussed in the subsequent chapters of this book.
Gasotransmitters are a class of small endogenously produced gaseous signaling molecules. They are dissolved gases in blood and other body fluids, and play important roles in cellular homeostasis and impact physiological and pathophysiological conditions. Nitric oxide was the first gasotransmitter to be identified followed by carbon monoxide, while hydrogen sulfide was recently established as the third member of the gasotransmitter family. Although these gases gained historic notoriety for their toxicity and death, studies over the past few decades have shown that they have risen above their notorious tags and have now emerged as important intracellular mediators of cytoprotection in various pathological conditions such as ischemia-reperfusion injury in organ transplantation. This chapter introduces gasotransmitters as volatile intracellular messenger molecules, with complex interactions with one another in compensatory and reciprocal fashion when the level of one is depleted under pathological conditions. In addition, the chapter also summarizes various therapeutic properties of these gases such as antioxidant, anti-inflammatory, anti-apoptotic and vasodilatory properties, enabling them to mediate donor organ protection during pre-transplant, peri-operative and post-transplant periods, and ultimately contributing to improving organ graft quality and prolonging transplant recipient survival.
Gaseous signaling molecules (GSMs) including nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H 2 S) have presented excellent therapeutic efficacy such as anti‐inflammatory, anti‐microbial and anti‐cancer effects and multiple biomedical applications in recent years. As the three most vital signaling molecules in human physiology, these three GSMs show so intertwined and orchestrated interactions that the synergy of multiple gases may demonstrate a more complex therapeutic potential than single gas delivery. Consequently, researchers have been devoted to developing codelivery systems of GSMs by synthesizing a single molecule as a dual donor to maximize the gaseous therapeutic efficacy. In this minireview, we summarize the recent developments of molecules or materials enabling codelivery of GSMs for biomedical applications. It appears that compared with the abundant cases of codelivery of NO and H 2 S, research on codelivery of CO and the other two GSMs separately remains to be explored.
Hypertension is a major public health problem globally. It is the most common cause of cardiovascular morbidities and mortalities, with a negative impact on renal function. Uncontrolled hypertension causes chronic kidney disease, which progresses to end-stage renal disease and eventually loss of renal function. Unfortunately, the mechanism underlying the pathogenesis of hypertension and its associated nephropathy is still poorly understood. Also worrying is the fact that despite conventional antihypertensive therapies, achievement of blood pressure control and preservation of renal function still remain a worldwide public health challenge in a significant subpopulation of hypertensive patients. This suggests the need for novel pharmacotherapeutic approaches to curb the problem. Hydrogen sulfide (H2S), the third established member of the gasotransmitter family after nitric oxide and carbon monoxide, has been recognized and established to possess antihypertensive and renoprotective properties, which may represent an important therapeutic alternative for hypertensive nephropathy. In this chapter, recent findings from preclinical studies about the therapeutic effect of H2S against hypertensive nephropathy and its future clinical use are discussed. A section of the chapter also discusses recent developments about clinical and translational research on calcium-based nephrolithiasis as a risk factor for hypertensive nephropathy, with a further discussion on H2S as an emerging novel therapy to improve clinical outcome.
Hydrogen sulfide (H2S), a gas with a characteristic rotten-egg smell, gained historic notoriety for its toxicity and death at high concentrations especially among industrial workers. This is due to its ability to reversibly inhibit the activity of cytochrome c oxidase, a terminal enzyme of the mitochondrial electron transport chain. Recently, however, H2S has risen above its notorious public image and is now seen by researchers as an endogenously produced gaseous signaling molecule that plays an important role in cellular homeostasis and influences several physiological and pathological processes at low physiological and nontoxic concentrations. Its production is catalyzed by two cytosolic enzymes, cystathionine β-synthase and cystathionine γ-lyase, a mitochondrial enzyme, 3-mercaptopyruvate sulfurtransferase, and a peroxisomal enzyme, d-amino acid oxidase. Several recent experimental studies have demonstrated that at low micromolar concentrations, H2S plays a complex and essential role in normal renal function, and dysregulation of its production has been implicated in various renal pathologies. In addition, exogenous H2S administration has been reported to exhibit important therapeutic characteristics that target multiple molecular pathways in common renal pathologies in which reduced levels of renal and plasma H2S were observed. Interestingly, whereas the distribution of all four H2S-producing enzymes is subcellular and tissue specific, they are abundantly expressed by endothelial cells, mesangial cells, and podocytes within the glomeruli, as well as in the brush border and cytoplasm of epithelial cells of the renal proximal tubules, distal tubules, and peritubular capillaries. This makes the kidney a rich source of endogenous H2S production. This chapter presents current understanding of H2S in renal physiology and lays the foundation for discussion on H2S as a new therapeutic target for common renal pathologies in the subsequent chapters.
BACKGROUND. Chronic kidney disease (CKD) is accompanied by the development of endothelial dysfunction, leading to a decrease in arterial reactivity to vasoactive agents. Uremia causes a change in the dilatation of arteries in various vascular regions, incl. and arteries of the pial membrane of the brain. The action of hydrogen sulfide (H 2 S), which can induce relaxation of smooth muscle cells of blood vessels, is currently considered a possible route of vasoprotection in various diseases, particularly, in CKD. THE AIM. To evaluate the role of calcium-activated potassium channels of large (BKCa) and intermediate (IKCa) conductance in H2S-induced dilatation of pial arteries in nephrectomized (NE) rats.
MATERIAL AND METHODS. In Wistar rats nephrectomy (NE) was performed by resection of 5/6 of the renal tissue mass. Sham-operated (LO) animals served as control. The reaction of the pial arteries of the sensomotor cortex of NE and control SO rats to the application of H 2 S under physiological conditions and against the background of the use of BKCa channel blockers – tetraethylammonium (TEA) and IKCa – channels – TRAM-34.
RESULTS. 4 months after NE, the application of H2S led to the dilatation of a smaller number of pial arteries (1.4 – 1.7 times) compared with SO rats. The preliminary exposure to TEA led to a decrease in the number of pial arteries responding by dilatation to the action of H 2 S in NE and SO rats. Against the background of the action of TRAM-34, the number of dilated arteries decreased under the action of H 2 S in SO rats, while in NE rats it practically did not change.
CONCLUSION. Under physiological conditions, dilatation of the pial arteries in rats under the action of H 2 S is realized (at least in part) through the activation of the BKCa and IKCa channels of the membrane of endothelial and smooth muscle cells. Uremia, caused by nephrectomy, leads to impairment of the mechanism of dilatation of pial arteries, mediated by activation of calcium-activated potassium channels intermediate conductance apparently due to dysfunction of endothelial cells.
The ever‐increasing percentages and absolute numbers of the world population over age 65 necessitates novel and effective measures to slow, counteract, and even reverse aging‐related morbidities (ARMs). These interventions are traditionally disease specific and reactionary such as the use of chemotherapy for cancer and vasodilators for cardiovascular disease. Alternatively, momentum in the field has gained for proactive modalities that ultimately target the aging processes as a whole, thus slowing or eliminating the onset of all aging‐related disorders. However, the later approach requires molecular and temporal mechanistic understandings of the aging process to be successful. Causes of aging are numerous; however, a central dogma is that aberrant and sustained production and exposure to reactive oxygen species (ROS) and free radicals drives the aging process, termed the free radical theory of aging. While still widely accepted, the free radical theory of aging has been amended in recent years, nonetheless, loss of redox homeostasis leads to a downward spiral of oxidative damage to macromolecules including DNA, lipids, and proteins resulting in the seemingly irreversible and self‐perpetuating aspects of aging and senescence. Thus, investigating mechanisms to safely and effectively maintain redox homeostasis through (i) dampening the production of ROS and free radicals through modifying metabolic pathways, (ii) enhancing endogenous anti‐oxidant processes, and/or (iii) applying these protective molecules exogenously, can ultimately provide therapeutic interventions against aging and ARMs. Here, we provide select examples in which hydrogen sulfide (H 2 S) itself, donor molecules, or the stimulation of its endogenous production by way of geroscience interventions were used to maintain cellular and organismal redox balance to extend lifespan, promote healthspan, and counter aging‐related diseases. Additionally, we also provide examples in which enhanced endogenous H 2 S production and/or altered trans‐sulfuration were found in models of exceptional longevity across evolutionary boundaries in which H 2 S impacts their specific aging trajectories.
Nitric oxide, carbon monoxide and hydrogen sulfide are three endogenous gasotransmitters that serve a role in regulating normal and pathological cellular activities. They can stimulate or inhibit cancer cell proliferation and invasion, as well as interfere with cancer cell responses to drug treatments. Understanding the molecular pathways governing the interactions between these gases and the tumor microenvironment can be utilized for the identification of a novel technique to disrupt cancer cell interactions and may contribute to the conception of effective and safe cancer therapy strategies. The present review discusses the effects of these gases in modulating the action of chemotherapies, as well as prospective pharmacological and therapeutic interfering approaches. A deeper knowledge of the mechanisms that underpin the cellular and pharmacological effects, as well as interactions, of each of the three gases could pave the way for therapeutic treatments and translational research.
Carbon monoxide (CO) is an odorless gas and hydrogen sulfide (H 2 S) has a stench odor, contributing to the bad smell of flatus and rotten eggs. This chapter offers an integrated view on what happens when CO meets H 2 S. CO production in mammalian cells is mostly catalyzed by heme oxygenase (HO). Heme, or known as reduced hematin, is both the substrate of HO for CO production and an inducer of HO expression. Recent studies reveal that the carotid bodies sense changes in CO and H 2 S levels as part of the key elements of the oxygen‐sensing reflex arc. Oxygen sensing and reaction are critical for hypoxia‐induced increase in blood flow in vital organs and homeostatic regulation of breathing. In biological systems, CO is involved in protoporphyrin metabolism and H 2 S is a critical component of transsulfuration or reverse transsulfuration in microbiota or mammals.
H 2 S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H 2 S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H 2 S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H 2 S and oxidative posttranscriptional modification of proteins, the effect of H 2 S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H 2 S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H 2 S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H 2 S in various cell types and organ systems are overviewed. Finally, the role of H 2 S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H 2 S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H 2 S in the physiological regulation of all organ functions emerges from this review.
Hypertension is the most common cause of cardiovascular morbidities and mortalities, and a major risk factor for renal dysfunction. It is considered one of the causes of chronic kidney disease, which progresses into end-stage renal disease and eventually loss of renal function. Yet, the mechanism underlying the pathogenesis of hypertension and its associated kidney injury is still poorly understood. Moreover, despite existing antihypertensive therapies, achievement of blood pressure control and preservation of renal function still remain a worldwide public health challenge in a subset of hypertensive patients. Therefore, novel modes of intervention are in demand. Hydrogen sulfide (H 2 S), a gaseous signaling molecule, has been established to possess antihypertensive and renoprotective properties, which may represent an important therapeutic alternative for the treatment of hypertension and kidney injury. This review discusses recent findings about H 2 S in hypertension and kidney injury from both experimental and clinical studies. It also addresses future direction regarding therapeutic use of H 2 S.
Intracellular potassium (K⁺) homeostasis is an essential requirement for the optimum processing of plant metabolism and overall functioning of plants. It is regulated by K⁺ ion uptake, efflux, and intracellular and long-distance translocation, which is arbitrated by a great amount of K⁺-selective and nonselective channels and transporters placed at both plasma and vacuolar membranes. Various abiotic stresses like drought, salinity, water-logging stress, etc. led to drastic deterioration of intracellular potassium homeostasis. These stresses aggravate a K⁺ channel and transporter expression along with the posttranslational control of their actions and optimization of K⁺ absorption and consequently cause programmed cell death. Though there are certain specialized approaches which regulate the action of K⁺ channels and transporters by membrane potential, cytosolic Ca²⁺, reactive oxygen species, polyamines, plant growth regulators, and gasotransmitters are related to the adaptive plant responses to the unfavorable environment. Therefore, this chapter mainly provides an insight into the molecular strategies associated with the potassium uptake and homeostasis during different abiotic stress conditions.
In acute experiments on laboratory rats, intra-portal administration of L-cysteine (20 mg/kg), the precursor of hydrogen sulfide synthesis, stimulated oxygen consumption of liver by 38.6% and reduced oxygen tension by 37.1%. Activation of tissue respiration occurred due to the strengthening of oxygen-dependent synthetic processes in liver, in particular those associated with mitochondrial enzyme-catalysed bile acid biosynthesis through the acidic pathway. The concentrations of taurocholic acid and mixtures of taurodeoxycholic and taurohenodeoxycholic acids increased by 10.3 and 17.9%, respectively, compared to the initial levels. In addition, the level of free cholesterol was decreased by 33.9% and esterification processes were intensified, as indicated by an increase in the concentration of esterified cholesterol by 22.6% in the bile of rats. The latter was to some extent confirmed by a decrease in the level of free bile acids (by 15.8%) involved in the biosynthesis of cholesterol esters and intensification of tissue respiration in the liver. L-cysteine dilated intrahepatic vessels, resulting in a significant decrease of the systemic blood pressure and blood pressure in the portal vein by 17.6 and 24.5%, respectively. L-cysteine increased the rate of local blood flow in the liver and blood supply by 28.2 and 24.4%, respectively. Blockade of cystathionine-γ-lyase by DL-propargylglycine (11 mg/kg) significantly inhibited the L-cysteine-induced tissue respiration and bile acid biosynthesis in the liver. Administration of DL-propargylglycine resulted in constriction of blood vessels of the liver and, as a consequence, to an increased blood pressure and a decreased blood flow rate in tissue. Our data point to an involvement of hydrogen sulfide in the regulation of liver tissue respiration and bile secretory function.
Hydrogen sulfide (H2S) plays a vital role in human physiology and in the pathophysiology of several diseases. In addition, a substantial role of H2S in inflammation has emerged. This chapter will discuss the involvement of H2S in various inflammatory diseases. Furthermore, the contribution of reactive oxygen species (ROS), adhesion molecules, and leukocyte recruitment in H2S-mediated inflammation will be discussed. The interrelationship of H2S with other gasotransmitters in inflammation will also be examined. There is mixed literature on the contribution of H2S to inflammation due to studies reporting both pro- and anti-inflammatory actions. These apparent discrepancies in the literature could be resolved with further studies.
This chapter will mainly focus on the general assets and applications of sulfur- or H2S-bearing thermal mineral waters on a world scale. It deals with basic information on hydrogen sulfide properties, on biological effects, and on the therapies traditionally used in medical hydrology as treatment for skin, respiratory, and musculoskeletal disorders. The authors provide information on additional therapeutic benefits of sulfurous waters in diseases such as myalgia (muscle pain), rheumatic diseases (osteoarthritis, rheumatoid arthritis, fibromyalgia), respiratory diseases (upper and lower respiratory tracts), dermatological/skin diseases, cardiovascular diseases, and other diseases (cancer, wound healing in diabetic patients). Possible side effects or situations of diseases for which sulfurous thermal waters are contraindicated are reported too.
Hydrogen sulfide (H 2 S) is an important brain, lung, and nose toxicant. Inhibition of cytochrome oxidase is the primary biochemical effect associated with lethal H 2 S exposure. The objective of this study was to evaluate the relationship between the concentration of sulfide and cytochrome oxidase activity in target tissues following acute exposure to sublethal concentrations of inhaled H 2 S. Hindbrain, lung, liver, and nasal (olfactory and respiratory epithelial) cytochrome oxidase activity and sulfide concentrations were determined in adult male CD rats immediately after a 3-h exposure to H 2 S (10, 30, 80, 200, and 400 ppm). We also determined lung sulfide and sulfide metabolite concentrations at 0, 1.5, 3, 3.25, 3.5, 4, 5, and 7 h after the start of a 3-h H 2 S exposure to 400 ppm. Lung sulfide concentrations increased during H 2 S exposure and rapidly returned to endogenous levels within 15 min after the cessation of the 400-ppm exposure. Lung sulfide metabolite concentrations were transiently increased immediately after the end of the 3-h H 2 S exposure. Decreased cytochrome oxidase activity was observed in the olfactory epithelium following exposure to > 30 ppm H 2 S. Increased olfactory epithelial sulfide concentrations were observed following exposure to 400 ppm H 2 S. Hind-brain and nasal respiratory epithelial sulfide concentrations were unaffected by acute H 2 S exposure. Nasal respiratory epithelial cytochrome oxidase activity was reduced following acute exposure to > 30 ppm H 2 S. Liver sulfide concentrations were increased following exposure to > 200 ppm H 2 S and cytochrome oxidase activity was increased following inhalation exposure to > 10 ppm H 2 S. Our results suggest that cytochrome oxidase inhibition is a sensitive biomarker of H 2 S exposure in target tissues, and sulfide concentrations are unlikely to increase postexposure in the brain, lung, or nose following a single 3-h exposure to < 30 ppm H 2 S.
Hydrogen sulphide (H2S is the primary chemical hazard in natural gas production in ‘sour’ gas fields. It is also a hazard in sewage treatment and
manure-containment operations, construction in wetlands, pelt processing, certain types of pulp and paper production, and
any situation in which organic material decays or inorganic sulphides exist under reducing conditions. H2S dissociates into free sulphide in the circulation. Sulphide binds to many macromolecules, among them cytochrome oxidase.
Although this is undoubtedly an important mechanism of toxicity due to H2S, there may be others. H2S provides little opportunity for escape at high concentrations because of the olfactory paralysis it causes, the steep exposure-response
relationships, and the characteristically sudden loss of consciousness it can cause which is colloquially termed ‘knockdown.’
Other effects may include mucosal irritation, which is associated at lower concentrations with a keratoconjunctivitis called
‘gas eye’ and at higher concentrations with risk of pulmonary oedema. Chronic central nervous system sequelae may possibly
follow repeated knockdowns: this is controversial and the primary effects of H2S may be confounded by anoxia or head trauma. Treatment is currently empirical, with a combination of nitrite and hyperbaric
oxygen preferred. The treatment regimen is not ideal and carries some risk.
The properties and roles of ATP-sensitive (KATP) and inwardly rectifying (KIR) potassium channels are reviewed. Potassium channels regulate the membrane potential of smooth muscle, which controls calcium entry through voltage-dependent calcium channels, and thereby contractility through changes in intracellular calcium. The KATP channel is likely to be composed of members of the inward rectifier channel gene family (Kir6) and sulfonylurea receptor proteins. The KIR channels do not appear to be as widely distributed as KATP channels in smooth muscle and may provide a mechanism by which changes in extracellular K+ can alter smooth muscle membrane potential, and thereby arterial diameter. The KATP channels contribute to the resting membrane conductance of some types of smooth muscle and can open under situations of metabolic compromise. The KATP channels are targets of a wide variety of vasodilators and constrictors, which act, respectively, through adenosine 3',5'-cyclic monophosphate/protein kinase A and protein kinase C. The KATP channels are also activated by a number of synthetic vasodilators (e.g., diazoxide and pinacidil) and are inhibited by the oral hypoglycemic sulfonylurea drugs (e.g., glibenclamide). Together, KATP and KIR channels are important regulators of smooth muscle function and represent important therapeutic targets.
This review examines the properties and roles of the four types of K+ channels that have been identified in the cell membrane of arterial smooth muscle cells. 1) Voltage-dependent K+ (KV) channels increase their activity with membrane depolarization and are important regulators of smooth muscle membrane potential in response to depolarizing stimuli. 2) Ca(2+)-activated K+ (KCa) channels respond to changes in intracellular Ca2+ to regulate membrane potential and play an important role in the control of myogenic tone in small arteries. 3) Inward rectifier K+ (KIR) channels regulate membrane potential in smooth muscle cells from several types of resistance arteries and may be responsible for external K(+)-induced dilations. 4) ATP-sensitive K+ (KATP) channels respond to changes in cellular metabolism and are targets of a variety of vasodilating stimuli. The main conclusions of this review are: 1) regulation of arterial smooth muscle membrane potential through activation or inhibition of K+ channel activity provides an important mechanism to dilate or constrict arteries; 2) KV, KCa, KIR, and KATP channels serve unique functions in the regulation of arterial smooth muscle membrane potential; and 3) K+ channels integrate a variety of vasoactive signals to dilate or constrict arteries through regulation of the membrane potential in arterial smooth muscle.
ATP-sensitive K+ (K(ATP)) channels have been proposed to be the target for hyperpolarizing vasodilators. However, the existence of a whole cell K(ATP) current that can regulate membrane potential has not been demonstrated in vascular muscle. Using the patch-clamp technique, we have examined the effects of varying intracellular ATP on membrane potential and currents in isolated rabbit pulmonary arterial smooth muscle cells. With 1 mM ATP in the pipette, cells had a mean resting potential of -55 mV. When ATP was omitted, the resting potential became significantly more hyperpolarized (-70 mV) and the depolarizing response to the K(ATP)-channel blocker, glibenclamide, was potentiated. In contrast, the hyperpolarizing effect of lemakalim was reduced. These hyperpolarized resting potentials were associated with increased activity of a basal, glibenclamide-sensitive time-independent K+ current. Furthermore, flash photolysis of ATP, 3-O-[1(4,5-dimethoxy-2-nitrophenyl)ethyl] ester, disodium salt ("caged ATP") in ATP-depleted cells caused rapid depolarization (<1 s) and block of the background K+ current. Our results are consistent with the idea that intracellular ATP can directly modulate the resting potential by inhibition of K+ channels. We propose that this ATP-sensitive K+ current play an important role in the maintenance of the resting potential in arterial muscle.
ATP-sensitive K+ channels with a conductance of 30 pS in smooth muscle cells of porcine coronary artery were found to be highly active in the intact cell-attached patch configuration when the pipette contained a physiological concentration of Ca2+ (greater than 10(-4) M). In the inside-out configuration, these channels were activated by extracellular Ca2+ and blocked by cytosolic ATP and glibenclamide. Endothelin applied to the pipette specifically blocked these channels in a concentration-dependent manner in the cell-attached configuration (half-maximal inhibition, 1.3 x 10(-9) M). A K+ channel opener, nicorandil, activated these channels even in the presence of 10(-8) M endothelin. In the whole-cell current-clamp method, the cell membrane was depolarized by endothelin and then repolarized by nicorandil. The membrane depolarization is closely related to contraction of smooth muscle cells. These results suggest that the ATP-sensitive K+ channels are important in controlling the vascular tone of the coronary artery and that endothelin can increase vascular tone by blocking these channels.
Intercellular adhesion in lymphocytes is mediated in part by the interaction of the integrin lymphocyte function-associated antigen-1 (LFA-1) with intercellular adhesion molecule-1 (ICAM-1). The B lymphoblastoid line JY expresses both LFA-1 and ICAM-1, and intercellular adhesion is enhanced by treatment with the phorbol ester phorbol 12-myristate 13-acetate (PMA), which also induced capping of LFA-1, ICAM-1, and human leukocyte antigen. Capping of LFA-1 is likely to result from protein kinase C (PKC) activation because receptor-mediated stimulation of PKC also led to capping. Additionally, adhesion mediated by PMA or lipopolysaccharide was blocked by either of two PKC inhibitors, calphostin C and staurosporine. PMA induced the apparent condensation of cytoskeletal elements that colocalized with the membrane protein cap. Cytoskeletal condensation and capping occurred in the absence of intercellular adhesion. Alteration in the distribution of cytoskeletal components and membrane redistribution of LFA-1 were inhibited by cytochalasin D, which also abolished intercellular adhesion. Taken together, these data suggest that intercellular adhesion is the result of PKC-mediated membrane redistribution of LFA-1 and ICAM-1, which is in turn associated with modification of the actin-based cytoskeleton.
Significant progress has been made in determining the action of sulfide on the primary target organs. It is reasonably clear that sulfide causes both K(+)-channel-mediated hyperpolarization of neurons and potentiation of other inhibitory mechanisms. It is not clear whether these processes are similar to those that occur in anoxia. Changes in perinatal and adult brain neurotransmitter content and release may be related to clinical impairment of cognition. H2S exposures at concentrations below the current occupational limits cause physiological changes in pulmonary function, thus suggesting that asthmatics are at risk. Studies of fetal and neonatal brain tissue have shown an abnormal development, and the long-term consequences of these neuronal changes have not yet been assessed. Finally, new approaches to therapy are required, such as the use of agents that actively remove sulfide from its sites of action. This may prove more useful in preventing some of the long-term adverse sequelae than the use of nitrites and hyperbaric O2, although the latter should be used in cases of pulmonary edema.
1. Properties of the pinacidil-sensitive K+ channel in the smooth muscle of the rabbit portal vein were investigated using cell-attached and inside- and outside-out patch clamp techniques. 2. In the cell-attached patch configuration, a K+ channel with a unitary conductance of 150 pS could be recorded when physiological salt solution (PSS) was in the pipette and high-K+ solution was in the bath. Tetraethylammonium (TEA; less than 1 mM) and charybdotoxin (CTX; greater than 50 nM) inhibited the 150 pS K+ channel from the outside of the membrane. This channel was activated by an increase in the concentrations of intracellular Ca2+ but not by pinacidil (less than or equal to 500 microM). 3. In the cell-attached patch configuration, bath application of pinacidil (greater than 3 microM) activated a K+ channel (ATP-sensitive K+ channel) with a unitary conductance of 15 pS and the enhancing action of pinacidil was blocked by glibenclamide. However, in the cell-free patch configuration, pinacidil (100 microM) failed to open the 15 pS K+ channel. With pinacidil in the pipette, the 15 pS K+ channel was completely inactivated within 5 s of the excision of the membrane. Opening of the 15 pS K+ channel also disappeared after saponin treatment (50 micrograms/ml). 4. In the cell-free patch configuration, application of guanosine 5'-diphosphate (GDP; greater than 100 microM) re-activated the inactivated 15 pS K+ channel only when pinacidil was present either in the pipette or bath. GDP increased the mean open time and open probability of the 15 pS K+ channel in a concentration-dependent manner. Simultaneous application of MgCl2 (less than or equal to 1 mM) with GDP did not modify the GDP-induced activation. Neither GDP nor GTP (1 mM) had any effect on the 150 pS K+ channel. 5. Guanosine 5'-triphosphate (GTP; 1 mM) activated the 15 pS K+ channel to a lesser extent that did GDP. Other guanine nucleotides (guanosine 5'-monophosphate, GMP, 1 mM; guanosine 5'-O-(3-thiotriphosphate), GTP gamma S, 100 microM; and guanosine 5'-O-(2-thiodiphosphate), GDP beta S, 1 mM) failed to activate the 15 pS K+ channel. However, GDP beta S, but not GMP or GTP gamma S, inhibited this channel when it was activated by 1 mM-GDP. 6. In the presence of pinacidil, adenosine 5'-triphosphate (ATP; greater than or equal to 10 microM) inhibited the ATP-sensitive K+ channel when it was activated by 1 mM-GDP.(ABSTRACT TRUNCATED AT 400 WORDS)
The characteristics of carbon monoxide (CO)-induced, endothelium-independent relaxation of rabbit aorta were compared with those of nitric oxide (NO)-induced and light-induced relaxation and endothelium-dependent relaxation mediated by endothelium-dependent relaxing factor (EDRF). CO was less than one thousandth as potent as NO as a relaxant. Various findings, including an increase in cyclic GMP associated with CO-induced relaxation, led to the conclusion that CO - like NO, EDRF and light - produces relaxation as a result of its stimulation of guanylate cyclase. LY 83583, which generates superoxide, was a potent, fast-acting inhibitor of acetylcholine-induced endothelium-dependent relaxation and NO-induced relaxation, and a fairly potent, moderately fast-acting inhibitor of photorelaxation, but only a very weak inhibitor of CO-induced relaxation. The ability of LY 83583 as well as hemoglobin to inhibit photorelaxation is consistent with the hypothesis that on radiation a photo-induced relaxing factor is formed which can stimulate guanylate cyclase and which can be inactivated by superoxide and by hemoglobin.
Calcitonin gene-related peptide (CGRP) is a 37-amino-acid peptide produced by alternative processing of messenger RNA from the calcitonin gene. CGRP is one of the most potent vasodilators known. It occurs in and is released from perivascular nerves and has been detected in the blood stream, suggesting that it is important in the control of blood flow. The mechanism by which it dilates arteries is not known. Here, we report that arterial dilations in response to CGRP are partially reversed by blockers of the ATP-sensitive potassium channel (K(ATP)), glibenclamide and barium. We also show that CGRP hyperpolarizes arterial smooth muscle and that blockers of K(ATP) channels reverse this hyperpolarization. Finally, we show that CGRP opens single K+ channels in patches on single smooth muscle cells from the same arteries. We propose that activation of K(ATP) channels underlies a substantial part of the relaxation produced by CGRP.
Vasodilators are used clinically for the treatment of hypertension and heart failure. The effects of some vasodilators seem
to be mediated by membrane hyperpolarization. The molecular basis of this hyperpolarization has been investigated by examining
the properties of single K+ channels in arterial smooth muscle cells. The presence of adenosine triphosphate (ATP)-sensitive
K+ channels in these cells was demonstrated at the single channel level. These channels were opened by the hyperpolarizing
vasodilator cromakalim and inhibited by the ATP-sensitive K+ channel blocker glibenclamide. Furthermore, in arterial rings
the vasorelaxing actions of the drugs diazoxide, cromakalim, and pinacidil and the hyperpolarizing actions of vasoactive intestinal
polypeptide and acetylcholine were blocked by inhibitors of the ATP-sensitive K+ channels, suggesting that all these agents
may act through a common pathway in smooth muscle by opening ATP-sensitive K+ channels.
Article de synthese traitant de la pharmacologie de l'oxyde nitrique, du facteur EDRF et du GMP cyclique dans les vaisseaux sanguins et les thrombocytes, de l'isolation et de l'identification du facteur EDRF comme de l'oxyde nitrique, et de la formation, de la liberation et du metabolisme de l'endothelium derived NO (EDNO)
1. Hydrogen sulphide inhaled, or sulphide or H 2 S injected in solution into the circulation, is carried for a time in the plasma in the form of an equilibrium mixture of sulphide and H 2 S. It only slowly penetrates into the red cells, where it is destroyed in reactions in which oxyhaemoglobin is reduced. The lethal dose of H 2 S will therefore vary according to the rate and site of its administration.
2. The physiological effects of hydrogen sulphide and other sulphides are similar to those of hydrocyanic acid, probably for the reason that both fix the iron in cytochrome A 3 , so reducing the oxygen intake of cells, and especially of nerve cells.
3. The most conspicuous actions of sulphides are on the nerve centres, which are first stimulated and then paralysed. The actions are reversible.
4. Because of the slow penetration of the red cells by H 2 S, or by the HS ion, the removal of sulphides from the plasma and their subsequent destruction is relatively slow, so that injections into the blood stream at sites from which the nerve centres are soon reached are more potent than those made at more remote places.
5. The reduction of oxyhaemoglobin resulting from the action of sulphides is reversible, and this is probably true also for the cytochrome A 3 . The action is therefore reversible, and the main treatment indicated is the application of artificial respiration.
1. Nitric oxide (NO) relaxes vascular smooth muscle (VSM) by mechanisms which are not fully understood. One possibility is that NO hyperpolarizes membranes, thereby diminishing Ca2+ entry through voltage-dependent Ca2+ channels. In the current study, the effects of NO on membrane potential of rabbit mesenteric arteries were recorded using intracellular microelectrodes. 2. NO, released by 3-morpholinosydnonimine (SIN-1, 3 microM), reversibly hyperpolarized arteries by -9.5 +/- 4.0 mV (means +/- S.D., n = 97) from a resting membrane potential of -53.1 +/- 5.7 mV. The hyperpolarization was blocked by oxyhaemoglobin (20 microM), and only occurred in arteries pre-treated with N omega-nitro-L-arginine (100 microM) or denuded of endothelium. 3. The effect of SIN-1 was concentration dependent (EC50 approximately 0.4 microM) and its dose response was shifted to the left by zaprinast (100 microM), an inhibitor of cGMP-specific phosphodiesterases. 4. The hyperpolarization due to SIN-1 was modified by changes in extracellular K+ concentration, but not by changes in Ca2+, Na+ or Cl-. The hyperpolarization was blocked by glibenclamide (IC50 approximately 0.15 microM), but not by apamin (3-300 nM), barium (5-150 microM), tetraethylammonium (0.1-10 mM), or 4-aminopyridine (5-500 microM). The hyperpolarization due to lemakalim (0.03-3 microM), an activator of ATP-sensitive potassium channels (KATP), displayed the same sensitivities to these K+ channel blocking agents, whereas the endothelium-derived hyperpolarizing factor, triggered by the addition of acetylcholine (3 microM), caused a hyperpolarization (-15.3 +/- 6.2 mV) that was blocked by apamin, but not by any other agent. 5. These results suggest that NO hyperpolarizes VSM in rabbit mesenteric arteries by activating KATP channels, with the accumulation of cGMP as an intermediate step.
Single‐channel recordings were made from cell‐attached and isolated patches, and whole‐cell currents zwere recorded under voltage clamp from single smooth muscle cells obtained by enzymic digestion of a small branch of the rat mesenteric artery.
In single voltage‐clamped cells 1 m m uridine diphosphate (UDP) or guanidine diphosphate (GDP) added to the pipette solution, or pinacidil (100 μ m ) a K‐channel opener (KCO) applied in the bathing solution, evoked an outward current of up to 100pA which was blocked by glibenclamide (10 μ m ). In single cells from which recordings were made by the ‘perforated patch’ (nystatin pipette) technique, metabolic inhibition by 1 m m NaCN and 10 m m 2‐deoxy‐glucose also evoked a similar glibenclamide‐sensitive current.
Single K‐channel activity was observed in cell‐attached patches only infrequently unless the metabolism of the cell was inhibited, whereupon channel activity blocked by glibenclamide was seen; pinacidil applied to the cell evoked similar glibenclamide‐sensitive channel activity. If the patch was pulled off the cell to form an isolated inside‐out patch, similar glibenclamide‐sensitive single‐channel currents were observed in the presence of UDP and/or pinacidil to those seen in cell‐attached mode; channel conductance was 20 pS (60:130 K‐gradient) and openings showed no voltage‐dependence and noisy inward currents, typical of the nucleoside diphosphate (NDP) activated K‐channel (K NDP ) seen previously in rabbit portal vein.
Formation of an isolated inside‐out patch into an ATP‐free solution did not increase the probability of channel opening which declined with time even when some single‐channel activity had occurred in the cell‐attached mode before detachment. However, application of 1 m m UDP or GDP, but not ATP, to inside‐out patches evoked single‐channel activity. Application of ATP‐free solution to isolated patches, previously exposed to ATP and in which channel activity had been seen, did not evoke channel activity.
It is concluded that small conductance K‐channels (K NDP ) open in smooth muscle cells from this small artery in response to UDP or GDP acting from the inside, or pinacidil acting from the outside; the same channels open during inhibition of metabolism presumably mainly due to the rise in nucleoside diphosphates, but a fall in the ATP concentration on the inside of the channel did not by itself evoke channel activity. Failure to respond to a fall in ATP concentration upon formation of an inside‐out patch could not be due to dephosphorylation of the channel because sometimes it had been active previously during cell‐attached recording. NDPs, instead of ATP, are more important regulators of K NDP channels. It is suggested that the K NDP is the main target K‐channel for KCOs.
In freshly-dispersed cells from rat mesenteric artery, levcromakalim (1 and 10 μM) induced a non-inactivating potassium current (IKCO), an event which was associated with increased current noise. IKCO was fully inhibited in the presence of 10 μM glibenclamide. Stationary fluctuation analysis of the current noise associated with IKCO induced by levcromakalim at a holding potential of −10 mV indicated that the unitary conductance of the underlying K-channels was 10.2 pS at 0 mV under the quasi-physiological conditions of the experiment.
In isolated arterioles both levcromakalim (10 nM - 10 μM) and nifedipine (10 nM - 10 μM) each elicted full, concentration-dependent, parallel reductions of the increases in [Ca2+]i (assessed using fura-2) and tension induced by 10 μM noradrenaline. However, the effects of both drugs on KCl-induced increases in tension and in [Ca2+]i, did not follow a simple relationship. Levcromakalim relaxed KCl- and noradrenaline-induced sustained contractions with a similar potency. This was in contrast to nifedipine which was approximately 20 times more potent against KCl-induced contractions.
It is concluded that levcromakalim relaxes rat mesenteric arterioles primarily by the opening of a small conductance, glibenclamide-sensitive K-channel. An additional action of levcromakalim is suggested by its relative inability to suppress the increase in [Ca2+]i produced by 30 mM K+-PSS.
The effects of atrial natriuretic factor (ANF) and isosorbide dinitrate (ISDN), activators of particulate and soluble guanylate cyclase, respectively, on K+ currents were investigated in patch-clamp recordings of smooth muscle cells cultured from rat thoracic aorta. In the cell-attached patch configuration, ANF enhanced Ca(2+)-activated K+ (KCa) channel activities as reported previously. When KCa channels were blocked with 1 mmol/L tetraethylammonium or 10(-7) mol/L charybdotoxin, ANF and ISDN applied to the bathing solution activated ATP-sensitive K+ (KATP) channels without altering channel conductance. Pretreatment with methylene blue, a guanylate cyclase inhibitor, abolished the effects of ISDN on KATP channels, whereas 8-bromo-cGMP activated these channels, suggesting that the effects of ISDN on KATP channels were mediated by cGMP. Our results suggest that vasorelaxant agents that increase intracellular cGMP concentrations modulate the gating of two major potassium channels, ATP sensitive and Ca2+ activated, that might play an important role in controlling vascular tone by changing the membrane potential.
1. Whole-cell K+ currents activated by calcitonin gene-related peptide (CGRP) in smooth muscle cells enzymatically isolated from rabbit mesenteric arteries were measured in the conventional and perforated configurations of the patch clamp technique. The signal transduction pathway from CGRP receptors to activation of potassium currents was investigated. 2. CGRP (10 nM) activated a whole-cell current that was blocked by glibenclamide (10 microM), an inhibitor of ATP-sensitive K+ channels. Elevating intracellular ATP reduced glibenclamide-sensitive currents. CGRP increased the glibenclamide-sensitive currents by 3- to 6-fold in cells dialysed with 0.1 mM ATP, 3.0 mM ATP or in intact cells. The reversal potential of the glibenclamide-sensitive current in the presence of CGRP shifted with the potassium equilibrium potential, while its current-voltage relationship exhibited little voltage dependence. 3. Forskolin (10 microM), an adenylyl cyclase activator, Sp-cAMPS (500 microM) and the catalytic subunit of protein kinase A increased glibenclamide-sensitive K+ currents 2.1-, 3.3- and 8.2-fold, respectively. 4. Nitric oxide and nitroprusside did not activate glibenclamide-sensitive K+ currents. 5. Dialysis of the cell's interior with inhibitors of protein kinase A (synthetic peptide inhibitor, 4.6 microM or H-8, 100 microM) completely blocked activation of K+ currents by CGRP. 6. Our results suggest the following signal transduction scheme for activation of K+ currents by CGRP in arterial smooth muscle: (1) CGRP stimulates adenylyl cyclase, which leads to an elevation of cAMP; (2) cAMP activates protein kinase A, which opens ATP-sensitive K+ channels.
. Single‐channel recordings were made from single, enzymatically isolated smooth muscle cells of rat portal vein by the patch‐clamp technique.
. Unitary potassium currents were identified through two types of K‐channels with conductances in 60:130 mM K‐gradient of 50 and 22 pS; these are referred to as LK and MK channels respectively.
. The LK channels became extremely active if isolated patches were created into nucleotide‐free solution; activity was inhibited by ATP applied to the inner surface of the patch with a half maximal inhibition (K i ) of 11–23 μ m . Channel activity declined and disappeared with time and could be regenerated by a brief application of Mg‐ATP or a nucleoside diphosphate such as UDP (in the presence of Mg). LK channel activity was rarely stimulated by levcromakalim and not by pinacidil (K‐channel openers, KCOs) but was blocked by glibenclamide.
. Activity of MK channels declined if isolated patches were created into nucleotide free solution; activity reappeared if UDP or ATP alone (in the presence of Mg) was applied; pinacidil or levcromakalim in the presence of ATP or UDP further increased channel activity which was blocked by glibenclamide.
. The LK channel inhibited by ATP i is very similar in its conductance and other properties to the K ATP channel described in tissues other than smooth muscle, in its conductance and properties the MK channel resembles the K NDP channel we have previous described as present in other smooth muscles and opening in responses to KCOs.
Endothelium-dependent relaxations are achieved by a combination of endothelium-derived prostacyclin (PGI2), nitric oxide (NO), and endothelium-derived hyperpolarizing factor (EDHF). However, it remains to be fully clarified whether the relative contribution of these three mechanisms to endothelium-dependent relaxations varies as a function of the vessel size. This study was designed to clarify this point. Acetylcholine (ACh)-induced endothelium-dependent relaxations were examined in isolated blood vessels taken from the aorta and the proximal and distal mesenteric arteries of the rat. The contributions of PGI2, NO, and EDHF were evaluated by the inhibitory effects of indomethacin, N omega-nitro-L-arginine methyl ester (L-NAME) in the presence of indomethacin, and KCl in the presence of indomethacin and L-NAME, respectively. The membrane potentials were recorded with microelectrodes. The expression of endothelial No synthase (eNOS) was examined by both immunostaining and immunoblotting. The contribution of PGI2 was negligible in three different-sized blood vessels. The contribution of NO was most prominent in the aorta, whereas that of EDHF was most prominent in the distal mesenteric arteries. The resting membrane potential was significantly deeper and the ACh-induced hyperpolarization was greater in the distal mesenteric arteries than those in the aorta. The expression of eNOS was the highest in the aorta and the lowest in the distal mesenteric arteries. These results indicate that the importance of EDHF increases as the vessel size decreases in endothelium-dependent relaxations in the rat mesenteric circulation.
Carbon monoxide (CO) induced a concentration‐dependent relaxation of isolated rat tail artery tissues which were precontracted with phenylephrine or U‐46619. This vasorelaxing effect of CO was independent of the presence of the intact endothelium.
The CO‐induced vasorelaxation was partially inhibited by the blockade of either the cyclicGMP pathway or big‐conductance calcium‐activated K (K Ca ) channels. When both the cyclicGMP pathway and K Ca channels were blocked, the CO‐induced vasorelaxation was completely abolished.
Incubation of vascular tissues with hemin, in order to enhance the endogenous production of CO, suppressed the phenylephrine‐induced vasocontraction in a time‐ and concentration‐dependent manner. The hemin‐induced suppression of the vascular contractile response to phenylephrine was abolished after the vascular tissues were co‐incubated with either oxyhaemoglobin or zinc protoporphyrin‐IX, suggesting an induced endogenous generation of CO from vascular tissues.
The effect of hemin incubation on vascular contractility did not involve the endogenous generation of nitric oxide.
Our results suggest that CO may activate both a cyclicGMP signalling pathway and K Ca channels in the same vascular tissues, and that the endogenously generated CO may significantly affect the vascular contractile responses.
Hydrogen sulfide (H2S), which is well known as a toxic gas, is produced endogenously in mammalian tissues from L-cysteine mainly by two pyridoxal-5'-phosphate-dependent enzymes, cystathionine beta-synthetase and cystathionine gamma-lyase. Recently, we showed that cystathionine beta-synthetase in the brain produces H2S, and that H2S facilitates the induction of hippocampal long-term potentiation by enhancing NMDA receptor activity. Here we show that mRNA for another H2S producing enzyme, cystathionine gamma-lyase, is expressed in the ileum, portal vein, and thoracic aorta. The ileum also expresses cystathionine beta-synthetase mRNA. These tissues produce H2S, and this production is blocked by cystathionine beta-synthetase and cystathionine gamma-lyase specific inhibitors. Although exogenously applied H2S alone relaxed these smooth muscles, much lower concentrations of H2S greatly enhanced the smooth muscle relaxation induced by NO in the thoracic aorta. These observations suggest that the endogenous H2S may regulate smooth muscle tone in synergy with NO.
We used patch clamp to study whole‐cell K ⁺ currents activated by calcitonin gene‐related peptide (CGRP) in smooth muscle cells freshly dissociated from pig coronary arteries.
CGRP (50 n m ) activated an inward current at −60 mV in symmetrical 140 m m K ⁺ that was blocked by glibenclamide (10 μ m ), an inhibitor of ATP‐sensitive potassium (K ATP ) channels. CGRP‐induced currents were larger in cells dialysed with 0.1 m m ATP than with 3.0 m m ATP.
Forskolin (10 μ m ) activated a glibenclamide‐sensitive current, as did intracellular dialysis with cAMP (100 μ m ). The catalytic subunit of cAMP‐dependent protein kinase (protein kinase A, PKA), added to the pipette solution, activated equivalent currents in five out of twelve cells.
CGRP‐induced currents were reduced by the PKA inhibitors adenosine 3′,5′‐cyclic monophosphorothioate, R P ‐isomer, triethylammonium salt (Rp‐cAMPS; 100 μ m ) and N ‐[2‐(( p ‐bromocinnamyl)amino)ethyl]‐5‐isoquinolinesulphonamide dihydrochloride (H‐89; 1 μ m ), and abolished by inclusion of a PKA inhibitor peptide in the pipette solution.
The β‐adrenergic agonist isoprenaline (10 μ m ) also activated a glibenclamide‐sensitive K ⁺ current.
CGRP‐induced currents were unaffected by the inhibitor of cGMP‐dependent protein kinase (PKG) KT5823 (1 μ m ). Sodium nitroprusside (10 μ m ) did not activate a glibenclamide‐sensitive current in cells held at −60 mV, but did activate an outward current at +60 mV that was abolished by KT5823, or by 100 n m iberiotoxin (an inhibitor of BK Ca channels).
Our findings suggest that CGRP activates coronary K ATP channels through a pathway that involves adenylyl cyclase and PKA, but not PKG.
Carbon monoxide (CO) is an endogenously generated gas that may play an important physiological role in the regulation of vascular tone. The CO-induced vasorelaxation, as a result of a direct action on vascular smooth muscles, has been demonstrated in many cases. Three major cellular mechanisms are proposed to explain the vasorelaxing effect of CO. These include the activation of soluble guanylyl cyclase, stimulation of various types of K channels, and inhibition of the cytochrome P450 dependent monooxygenase system in vascular smooth muscle cells. An interaction between CO and nitric oxide may also significantly contribute to the fine tuning of vascular tone. Furthermore, alterations in either the endogenous production of CO or the vascular responsiveness to CO have been encountered in several pathophysiological situations. A better understanding of the vascular effects of CO and the underlying cellular and molecular mechanisms will pave the way for the establishment of the role played by CO in vascular physiology and pathophysiology.
We used whole‐cell patch clamp to investigate the currents activated by nicorandil in smooth muscle cells isolated from rat small mesenteric arteries, and studied the relaxant effect of nicorandil using myography.
Nicorandil (300 μ M ) activated currents with near‐linear current‐voltage relationships and reversal potentials near to the equilibrium potential for K ⁺ .
The nicorandil‐activated current was blocked by glibenclamide (10 μ M ), but unaffected by iberiotoxin (100 n M ) and the guanylyl cyclase inhibitor LY 83583 (1 μ M ). During current activation by nicorandil, openings of channels with a unitary conductance of 31 pS were detected.
One hundred μ M nicorandil had no effect on currents through Ca ²⁺ channels recorded in response to depolarizing voltage steps using 10 m M Ba ²⁺ as a charge carrier. A small reduction in current amplitude was seen in 300 μ M nicorandil, though this was not statistically significant.
In arterial rings contracted with 20 m M K ⁺ Krebs solution containing 200 n M BAYK 8644, nicorandil produced a concentration‐dependent relaxation with mean pD 2 =4.77±0.06. Glibenclamide (10 μ M ) shifted the curve to the right (pD 2 =4.32±0.05), as did 60 m M K ⁺ . LY 83583 caused a dose‐dependent inhibition of the relaxant effect of nicorandil, while LY 83583 and glibenclamide together produced greater inhibition than either alone.
Metabolic inhibition with carbonyl cyanide m‐chlorophenyl hydrazone (30 n M ), or by reduction of extracellular glucose to 0.5 m M , increased the potency of nicorandil.
We conclude that nicorandil activates K ATP channels in these vessels and also acts through guanylyl cyclase to cause vasorelaxation, and that the potency of nicorandil is increased during metabolic inhibition.
Shear stress is one of the most important stimulators for the release of endothelium-derived relaxing factors. Although shear stress-induced release of nitric oxide (NO) has been extensively investigated, it remains to be elucidated whether endothelium-derived hyperpolarizing factor (EDHF) contributes to the endothelium-dependent relaxations to shear stress. This study was designed to address this point in the isolated rat mesenteric artery. Large mesenteric arteries (400-500 microm) and resistance mesenteric arteries (150-250 microm) of the rat were precontracted with phenylephrine (at 80 mm Hg of perfusion pressure), and the changes in vessel diameter in response to variable flow (0-300 microl/min) were continuously examined. The relative contributions of vasodilator prostaglandins, NO, and EDHF were analyzed by the inhibitory effects of indomethacin (10(-5) M), N(G)-nitro-L-arginine (L-NNA, 10(-4) M), and KCl (40 mM), respectively. The shear stress-induced relaxations were totally endothelium dependent in both-sized blood vessels, and the contribution of NO was more prominent in large arteries than in resistance arteries, whereas that of EDHF was noted in both-sized blood vessels. Tetrabutylammonium (a nonselective inhibitor of K channels) almost abolished, whereas the combination of charybdotoxin (an inhibitor of both large- and intermediate-conductance Ca2+ -activated K channels) and apamin (an inhibitor of small-conductance Ca2+ -activated K channels) significantly inhibited the EDHF-mediated component of the shear stress-induced relaxations. These results indicate that EDHF plays an important role in shear stress-induced endothelium-dependent relaxations, where K channels, especially calcium-activated K channels, appear to be involved.
Hydrogen sulfide (H(2)S) is produced endogenously from l-cysteine in mammalian tissues, and may function as a neuromodulator in the brain as well as a tone regulator in smooth muscle. H(2)S is present at relatively high levels in the brain, and cystathionine beta-synthase (CBS), which is highly expressed in the hippocampus, is involved in the production of brain H(2)S. Physiological concentrations of H(2)S selectively enhance NMDA receptor-mediated currents and facilitate the induction of hippocampal long-term potentiation (LTP). The NMDA receptor subunits are directly phosphorylated at specific sites by protein kinase A (PKA), resulting in the activation of NMDA-receptor-mediated excitatory postsynaptic currents. PKA activation is also observed in the induction of LTP. Here we show that physiological concentrations of H(2)S increase the production of cAMP in primary cultures of brain cells, neuronal and glial cell lines, and Xenopus oocytes. NMDA receptors expressed on Xenopus oocyte membrane are modulated by H(2)S. This modulation by H(2)S is specifically inhibited by adenylyl cyclase-specific inhibitor MDL-12, 330A. The present findings provide a mechanism for the previous observation that H(2)S modulates NMDA receptors and enhances the induction of LTP.
ATP-sensitive K+ channels have been classified based on their inhibition by cytoplasmic ATP. Recent evidence in vascular smooth muscle has suggested that these channels show weak sensitivity to intracellular ATP. However, it is not known whether these channels regulate the resting K+ conductance in vascular smooth muscles. Therefore, the aim of the present investigation was to characterize this current in rat aorta myocytes and to examine whether it contributes to setting the membrane potential.
The conventional and nystatin-permeablised whole cell patch clamp techniques were used to characterize the effect of glibenclamide on membrane potential and K+ current in enzymatically dispersed rat aorta myocytes.
The mean resting potential measured in current clamp mode using the permeabilized patch approach was -54 +/- 5 mV (n = 8). Glibenclamide (10 microM) caused a reversible 24-mV depolarization in these cells. In symmetrical K+ (135 mM) solution an inward glibenclamide-sensitive (10 microM) current (-4.1 +/- 0.7 pA/pF; n = 5), hereafter termed Iglib, was observed at a membrane potential of -80 mV when cells held at -60 mV were ramped from -80 to +80 mV. In the absence of any nucleotide in the pipette solution, Iglib measured by the conventional whole-cell method was -23.69 +/- 4.65 pA/pF (n = 9). With 1 and 3 mM ATP in the pipette, the average current density was -25 +/- 6.3 pA/pF (n = 8), and -9.4 +/- 2.7 pA/pF (n = 9), respectively. In the absence of ATP, 1 mM GDP significantly (P < 0.01) increased Iglib (-44.8 +/- 8.4 pA/pF; n = 13). Inclusion of 1 mM ATP in the GDP-containing pipette solution had no significant effect on the current amplitude (-56.4 +/- 10.7 pA/pF; n = 7). Iglib fell to -11.0 +/- 2.9 pA/pF (n = 10) if 1 mM GDP and 3 mM ATP were present. In symmetrical K+, the Iglib observed in the presence of 1 mM ATP in the pipette was increased by more than two-fold in the presence of 10 microM levcromakalim. In PSS containing 5 mM K+, a significant glibenclamide-sensitive current was observed at -45 mV membrane potential when cells dialyzed with 1 mM ATP were ramped between -80 to 30 mV.
These results demonstrate that Iglib channels in rat aorta myocytes differ from classical KATP channels, being relatively insensitive to intracellular ATP. Iglib therefore appears to have an important role in contributing to the maintenance of the resting potential in rat aortic smooth muscle.
Hydrogen sulphide is produced in the human large intestine by the bacterial reduction of dietary inorganic sulphate and sulphite and by fermentation of sulphur amino acids. Sulphide may damage the colonic epithelium and has been implicated in the pathogenesis of ulcerative colitis. The accurate measurement of sulphide in biological samples, particularly in gut contents is difficult due to the volatile nature of the compound, and the viscosity and turbidity of the samples. Here we describe a method for the determination of sulphide in gut contents and whole blood which overcomes these problems. Initially, samples are treated with zinc acetate to trap sulphide. A microdistillation pretreatment is then used, which releases sulphide from its stable, stored state, coupled to ion chromatography with electrochemical detection. The limit of detection of the method was determined as 2.5 micromol/l, which enabled sulphide levels in gut contents and whole blood samples obtained from humans to be accurately determined. A preliminary investigation in healthy human subjects showed blood sulphide ranged from 10 to 100 micromol/l. Whole blood sulphide did not change significantly when increasing amounts of protein from meat were fed. However, faecal sulphide did show a significant increase from 164 to 754 nmol/g in four subjects fed diets which contained 60 and 420 g meat.
Voltage-dependent K+ (Kv) channels were studied in smooth muscle cells (SMCs) freshly isolated from rat mesenteric arteries. A delayed outward rectifier Kv current (I
K) with a weak voltage dependence was identified. The amplitude of I
K, but not its inactivation kinetics, was inhibited by 4-aminopyridine (4-AP) (IC50, 5.1 ± 0.9 mm). The inhibitory effect of 4-AP was not use-dependent, and the unbinding of 4-AP from I
K channels was complete in the absence of depolarization stimuli, suggesting the binding of 4-AP to the closed state of Kv channels. There was no change in the steady-state inactivation, but the steady-state activation curve of I
K was shifted in the presence of 4-AP by +6 mV. Including 4-AP in pipette solution instantly inhibited I
K upon the rupture of cell membrane, indicating that 4-AP bound to the inner mouth of Kv channel pores. Several Kv channel proteins encoding the native I
K-type Kv channels, but not the transient outward A-type Kv channels, were identified. Among the identified I
K-encoding gene transcripts, the expression of Kv1.5 was the most abundant. Our results elucidate the modulating mechanisms for the 4-AP-induced I
K inhibition in rat mesenteric artery SMCs and suggest that the unique properties of Kv channels in these cells might be related to the heteromeric expression of the I
K-encoding genes with Kv1.5 subunit playing an important role.
Voltage-dependent delayed rectifier K+ (KV) channels and Ca(2+)-activated K+ (KCa) channels both play important roles in the regulation of the membrane potential and contractility of vascular smooth muscle cells (SMCs). The expression and function of these K+ channels in cultured vascular SMCs have been extensively studied. The long-term in vitro cell culture would change the properties of K+ channels in SMCs. However, whether the short-term culture could differentially affect the expression and function of KV and KCa channels was not clear. In the present study, both KV and KCa channel currents were identified in freshly dissociated SMCs and in 1-day-cultured SMCs from rat tail arteries. KCa currents were inhibited by iberiotoxin or tetraethylammonium (TEA), and amplified by the calcium ionophore A-23187. Kv currents were inhibited by 4-aminopyridine or beta-dendrotoxin. By using different pharmacological agents and manipulating the calcium concentrations in the recording solutions, it was revealed that in freshly dissociated SMCs the predominant component of total outward K+ currents is KCa current, and KV current a minor component. In contrast, KV current was found to be the predominant component of total outward K+ currents in SMCs primarily cultured with 10% fetal bovine serum at 37 degrees C for 24 h. Differential expression of KV and KCa channels in 1-day-cultured SMCs was thus demonstrated under our experimental conditions. Our results are important for interpreting the electrophysiological properties of vascular SMCs under different cell culture conditions and for understanding the relative contributions of KV and KCa channels to different cellular functions.
Hydrogen sulfide (H(2)S) has been traditionally viewed as a toxic gas. It is also, however, endogenously generated from cysteine metabolism. We attempted to assess the physiological role of H(2)S in the regulation of vascular contractility, the modulation of H(2)S production in vascular tissues, and the underlying mechanisms. Intravenous bolus injection of H(2)S transiently decreased blood pressure of rats by 12- 30 mmHg, which was antagonized by prior blockade of K(ATP) channels. H(2)S relaxed rat aortic tissues in vitro in a K(ATP) channel-dependent manner. In isolated vascular smooth muscle cells (SMCs), H(2)S directly increased K(ATP) channel currents and hyperpolarized membrane. The expression of H(2)S-generating enzyme was identified in vascular SMCs, but not in endothelium. The endogenous production of H(2)S from different vascular tissues was also directly measured with the abundant level in the order of tail artery, aorta and mesenteric artery. Most importantly, H(2)S production from vascular tissues was enhanced by nitric oxide. Our results demonstrate that H(2)S is an important endogenous vasoactive factor and the first identified gaseous opener of K(ATP) channels in vascular SMCs.
OBJECTIVE: To elucidate the mechanism of vascular hyporeactivity following severe hemorrhagic shock (HS) by studying the changes of ATP-sensitive potassium channels' (K(ATP)) properties and membrane potential of mesenteric arteriolar smooth muscle cells. METHODS: Single channel currents were studied on cell-attached and inside-out patches of enzymatically isolated mesenteric arteriolar smooth muscle cells (ASMCs). Membrane potentials of arteriolar strips and ASMCs were recorded by intracellular membrane potential recording method and confocal microscopy, respectively. RESULTS: K(ATP) channels in ASMCs were activated, which induced smooth muscle hyperpolarization following vascular hyporeactivity in HS. CONCLUSIONS: Hyperpolarizing effect of K(ATP) channel activation plays an important role in low vasoreactivity during severe hemorrhagic shock.
H(2)S is endogenously generated in vascular smooth muscle cells. The signal transduction pathways involved in the vascular effects of H(2)S have been unclear and were investigated in the present study. H(2)S induced a concentration-dependent relaxation of rat aortic tissues that was not affected by vascular denervation. The vasorelaxant potency of H(2)S was attenuated by the removal of the endothelium. Similarly, the blockade of nitric oxide synthase or the coapplication of the Ca(2+)-dependent K(+) channel blockers apamin and charybdotoxin reduced the H(2)S-induced relaxation of the endothelium-intact aortic tissues. Sodium nitroprusside (SNP)-induced relaxation was completely abolished by either 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ) or NS- 2028, two soluble guanylate cyclase inhibitors. Instead of inhibition, ODQ and NS-2028 potentiated the H(2)S-induced vasorelaxation, which was suppressed by superoxide dismutase. The vasorelaxant effect of H(2)S was also significantly attenuated when Ca(2+)-free bath solution was used. Finally, pretreatment of aortic tissues with H(2)S reduced the relaxant response of vascular tissues to SNP. Our results demonstrate that the vascular effect of H(2)S is partially mediated by a functional endothelium and dependent on the extracellular calcium entry but independent of the activation of the cGMP pathway.
ATP-sensitive K+ (K(ATP)) channels couple metabolic changes to membrane excitability in vascular smooth muscle cells (SMCs). While the electrophysiological properties of K(ATP) channels have been examined, little is known about the molecular basis of K(ATP) complex in vascular SMCs. We identified and cloned four K(ATP) subunit genes from rat mesenteric artery, namely rvKir6.1, rvKir6.2, rvKirSUR1, and rvSUR2B. These clones showed over 99.6% amino acid sequence identity with other previously reported isoforms. The mRNA expression patterns of the K(ATP) subunits varied among rat aorta, mesenteric artery, pulmonary artery, tail artery, hepatic artery, and portal vein. Heterologous co-expression of rvKir6.1 and rvSUR2B yielded functional K(ATP) channels that were inhibited by glibenclamide, and opened by pinacidil. Our results for the first time reported the expression of four K(ATP) subunits in same vascular tissues, unmasking the diversity of native K(ATP) channels in vascular SMCs.
The molecular mechanisms underlying the effects of nitric oxide (NO) and carbon monoxide (CO), individually and collectively, on large-conductance calcium-activated K(+) (K(Ca)) channels were investigated in rat vascular smooth muscle cells (SMCs). Both NO and CO increased the activity of native K(Ca) channels. Dehydrosoyasaponin-I, a specific agonist for beta subunit of K(Ca) channels, increased the open probability of native K(Ca) channels only when it was delivered to the cytoplasmic surface of membrane. CO, but not NO, further increased the activity of native K(Ca) channels that had been maximally stimulated by dehydrosoyasaponin-I. After treatment of SMCs with anti-K(Ca),beta subunit antisense oligodeoxynucleotides, the stimulatory effect of NO, but not of CO, on K(Ca) channels was nullified. CO, but not NO, enhanced the K(Ca) current densities of heterologously expressed cloned K(Ca),alpha subunit, showing that the presence of K(Ca),beta subunit is not a necessity for the effect of CO but essential for that of NO. Finally, pretreatment of SMCs with NO abolished the effects of subsequently applied CO or diethyl pyrocarbonate on K(Ca) channels. In summary, the stimulatory effects of CO and NO on K(Ca) channels rely on the specific interactions of these gases with K(Ca),alpha and K(Ca),beta subunits.
To study the changes of endogenous H2S and the effect of exogenously applied H2S on hypoxic pulmonary hypertension (HPH).
Male Wistar rats were randomly divided into control group (n = 6), hypoxia group (n = 7) and hypoxia + NaHS group (n = 6). The rats that received hypoxia were put into a normobaric hypoxic chamber to respire hypoxic gas containing 10% (volume fraction) O2 for 6 hours everyday. NaHS solution was injected to rats of hypoxia + NaHS group at a dosage of 0.78 mg.kg-1 before hypoxic challenge. After 21 days of hypoxia, the mean pulmonary artery pressure (mPAP) was measured. The weight ratio of right ventricle vs left ventricle and septum [RV/(LV + SP)] was measured. The microstructure and ultrastructure changes in pulmonary small arteries were examined using elastin staining and transparent electron microscope respectively. And the activity of H2S generating enzymes in homogenates of the lung tissue and pulmonary artery was measured. The cystathionine gamma--lyase (CSE) mRNA in lung tissue was also measured using quantitative RT-PCR.
Compared with rats in the control group, the mPAP increased 45.6% (P < 0.01) and the RV/(LV + SP) ratio increased 41% (P < 0.01) in rats of hypoxia group respectively. The relative medium thickness (RMT) and relative medium areas (RMA) increased 41% and 49% respectively (P all < 0.01) under optical microscope. The ultrastructure of the pulmonary small arteries also changed significantly. The H2S generating enzyme activity in lung tissue and in pulmonary artery decreased 52% and 54% respectively (P < 0.01). There were obviously negative correlations between the mPAP and H2S generating enzymes ativity. Relative CSE mRNA amount in lung tissue also decreased 53% (P < 0.01) in rats of hypoxia group compared with that of control group. The mPAP, and the RV/(LV + SP) ratio of rats in hypoxia + NaHS group decreased 31.2%, and 24% respectively compard with that of hypoxia group (P < 0.01). The RMT and RMA in rats of hypoxia + NaHS group also decreased 36% and 31% respectively (P < 0.01). In hypoxia + NaHS group, the H2S generating enzymes activity and relative CSE mRNA amount in the lung tissue increased 67.7% and 110% respectively compared with those in hypoxia group (P all < 0.01).
Endogenous H2S was involved in the pathogenesis of rat's HPH. Exogenously applied H2s could exert protective effect during HPH.
H2S is an important gasotransmitter with a vasorelaxant property. The modulation of endogenous H2S generation from different tissues and the functional consequence of this modulation are not clear. In the present study, the production of H2S from vascular tissues as well as the liver and ileum of rats was measured. The H2S production rate was significantly greater in rat liver than rat vascular tissues. H2S production in rat aortae, ileum, and liver tissues was upregulated by sodium nitroprusside in a cGMP-dependent fashion. Amino-oxyacetate (AOA) (1 mM) abolished H2S production in liver tissues and partially inhibited H2S production in the ileum, while D,L-propargylglycine (PPG) at a similar concentration only slightly inhibited H2S production in liver. Intraperitoneal injection PPG, but not AOA, significantly suppressed H2S production in liver, aorta, and ileum tissues. The systolic blood pressure of rats was significantly increased 2-3 weeks after i.p. injection of PPG. It is concluded that the endogenous production of H2S could be modulated by NO. AOA and PPG have different capacities in regulating the endogenous production of H2S in different types of tissues.
Bearing the public image of a deadly "gas of rotten eggs," hydrogen sulfide (H2S) can be generated in many types of mammalian cells. Functionally, H2S has been implicated in the induction of hippocampal long-term potentiation, brain development, and blood pressure regulation. By acting specifically on KATP channels, H2S can hyperpolarize cell membranes, relax smooth muscle cells, or decrease neuronal excitability. The endogenous metabolism and physiological functions of H2S position this gas well in the novel family of endogenous gaseous transmitters, termed "gasotransmitters." It is hypothesized that H2S is the third endogenous signaling gasotransmitter, besides nitric oxide and carbon monoxide. This positioning of H2S will open an exciting field-H2S physiology-encompassing realization of the interaction of H2S and other gasotransmitters, sulfurating modification of proteins, and the functional role of H2S in multiple systems. It may shed light on the pathogenesis of many diseases related to the abnormal metabolism of H2S.
Hydrogen sulfide (H2S) has been shown recently to function as an important gasotransmitter. The present study investigated the vascular effects of H2S, both exogenously applied and endogenously generated, on resistance mesenteric arteries of rats and the underlying mechanisms. Both H2S and NaHS evoked concentration-dependent relaxation of in vitro perfused rat mesenteric artery beds (MAB). The sensitivity of MAB to H2S (EC50, 25.2 +/- 3.6 microM) was about fivefold higher than that of rat aortic tissues. Removal of endothelium or coapplication of charybdotoxin and apamin to endothelium-intact MAB significantly reduced the vasorelaxation effects of H2S. The H2S-induced relaxation of MAB was partially mediated by ATP-sensitive K+ (KATP) channel activity in vascular smooth muscle cells. Pinacidil (EC50, 1.7 +/- 0.1 microM, n=6) mimicked, but glibenclamide (10 microM, n=6) suppressed, the vasorelaxant effect of H2S. KATP channel currents in isolated mesenteric artery smooth muscle cells were significantly augmented by H2S. L-cysteine, a substrate of cystathionine-gamma-lyase (CSE), at 1 mM increased endogenous H2S production by sixfold in rat mesenteric artery tissues and decreased contractility of MAB. DL-propargylglycine (a blocker of CSE) at 10 microM abolished L-cysteine-dependent increase in H2S production and relaxation of MAB. Our results demonstrated a tissue-specific relaxant response of resistance arteries to H2S. The stimulation of KATP channels in vascular smooth muscle cells and charybdotoxin/apamin-sensitive K+ channels in vascular endothelium by H2S represents important cellular mechanisms for H2S effect on MAB. Our study also demonstrated that endogenous CSE can generate sufficient H2S from exogenous L-cysteine to cause vasodilation. Future studies are merited to investigate direct contribution of endogenous H2S to regulation of vascular tone.
ATP-sensitive K+ channels (KATP) couple intermediary metabolism to cellular activity, and may play a role in the autoregulation of vascular tones. Such a regulation requires cellular mechanisms for sensing O2, CO2, and pH. Our recent studies have shown that the pancreatic KATP isoform (Kir6.2/SUR1) is regulated by CO2/pH. To identify the vascular KATP isoform(s) and elucidate its response to hypercapnic acidosis, we performed these studies on vascular smooth myocytes (VSMs). Whole-cell and single-channel currents were studied on VSMs acutely dissociated from mesenteric arteries and HEK293 cells expressing Kir6.1/SUR2B. Hypercapnic acidosis activated an inward rectifier current that was K+-selective and sensitive to levcromakalim and glibenclamide with unitary conductance of approximately 35pS. The maximal activation occurred at pH 6.5 to 6.8, and the current was inhibited at pH 6.2 to 5.9. The cloned Kir6.1/SUR2B channel responded to hypercapnia and intracellular acidification in an almost identical pattern to the VSM current. In situ hybridization histochemistry revealed expression of Kir6.1/SUR2B mRNAs in mesenteric arteries. Hypercapnia produced vasodilation of the isolated and perfused mesenteric arteries. Pharmacological interference of the KATP channels greatly eliminated the hypercapnic vasodilation. These results thus indicate that the Kir6.1/SUR2B channel is a critical player in the regulation of vascular tones during hypercapnic acidosis.
Hyperpolarizing vasodilators activate ATP-sensitive K channels in arterial smooth muscle
- Nb Standen
- Jm Quayle
- Nw Davies
- Je Brayden
- Y Huang
- Mt Nelson
Standen NB, Quayle JM, Davies NW, Brayden JE, Huang Y, and Nelson MT (1989)
Hyperpolarizing vasodilators activate ATP-sensitive K channels in arterial
smooth muscle. Science (Wash DC) 245:177–180.
Hyperpolarizing vasodilators activate ATP-sensitive K ϩ channels in arterial smooth muscle
- N B Standen
- J M Quayle
- N W Davies
- J E Brayden
- Y Huang
- Nelson Mt
Standen NB, Quayle JM, Davies NW, Brayden JE, Huang Y, and Nelson MT (1989)
Hyperpolarizing vasodilators activate ATP-sensitive K ϩ channels in arterial
smooth muscle. Science (Wash DC) 245:177-180.