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The Possible Role of Hydrogen Sulfide as an Endogenous Smooth Muscle Relaxant in Synergy with Nitric Oxide
Abstract
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.
... Several other enzymes can also produce polysulfides, including su doreductase (SQR), myoglobin, neuroglobin, catalase, superoxide d myeloperoxidase, and cysteinyl tRNA synthetase (CARS) [17][18][19][20][21][22][23]. The tion of H2S with NO also produces polysulfides that have been predicted of synergistic effect of H2S and NO on vascular relaxation [6,[24][25][26][27][28][29][30][31][32]. ...
... Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), which catalyse a pathway to produce cysteine, also play a role in producing H 2 S [4][5][6]. Although CSE levels are very low in the brain, it plays an important role under pathological conditions such as Alzheimer's disease and Huntington's disease [7][8][9]. ...
... H 2 S relaxes vascular smooth muscle in synergy with NO [6], and a similar synergistic effect was observed in intestine [90]. H 2 S 2 and H 2 S 3 are produced from H 2 S and NO [31,32]. ...
Hydrogen sulfide (H2S) and polysulfides (H2Sn, n ≥ 2) produced by enzymes play a role as signalling molecules regulating neurotransmission, vascular tone, cytoprotection, inflammation, oxygen sensing, and energy formation. H2Sn, which have additional sulfur atoms to H2S, and other S-sulfurated molecules such as cysteine persulfide and S-sulfurated cysteine residues of proteins, are produced by enzymes including 3-mercaptopyruvate sulfurtransferase (3MST). H2Sn are also generated by the chemical interaction of H2S with NO, or to a lesser extent with H2O2. S-sulfuration (S-sulfhydration) has been proposed as a mode of action of H2S and H2Sn to regulate the activity of target molecules. Recently, we found that H2S/H2S2 regulate the release of neurotransmitters, such as GABA, glutamate, and D-serine, a co-agonist of N-methyl-D-aspartate (NMDA) receptors. H2S facilitates the induction of hippocampal long-term potentiation, a synaptic model of memory formation, by enhancing the activity of NMDA receptors, while H2S2 achieves this by activating transient receptor potential ankyrin 1 (TRPA1) channels in astrocytes, potentially leading to the activation of nearby neurons. The recent findings show the other aspects of TRPA1 channels—that is, the regulation of the levels of sulfur-containing molecules and their metabolizing enzymes. Disturbance of the signalling by H2S/H2Sn has been demonstrated to be involved in various diseases, including cognitive and psychiatric diseases. The physiological and pathophysiological roles of these molecules will be discussed.
... Although H 2 S and NO exert their effects via separate pathways, they act cooperatively to expedite angiogenesis, anti-inflammation, and vasodilatation [30]. H 2 S is known to enhance the ability of NO to relax smooth muscle [31]. NO can increase H 2 S endogenous production by elevating CSE and CBS expression in vascular smooth muscle cells [32]. Lee et al. reported that the co-release of NO and H 2 S accelerated tube formation by HUVECs as compared to the single NO or H 2 S-releasing groups in vitro [33]. ...
... Especially, H 2 S can contribute to angiogenesis and vasorelaxation as an enhancer of vascular NO signaling [68]. Hosoki et al. found that H 2 S induced much stronger vascular relaxation in the presence of NO [31]. Therefore, the synergistic effect of NO and H 2 S had great potential for vascular remolding. ...
Nitric oxide (NO) and hydrogen sulfide (H 2 S) gasotransmitters exhibit potential therapeutic effects in the car-diovascular system. Herein, biomimicking multilayer structures of biological blood vessels, bilayer small-diameter vascular grafts (SDVGs) with on-demand NO and H 2 S release capabilities, were designed and fabricated. The keratin-based H 2 S donor (KTC) with good biocompatibility and high stability was first synthesized and then electrospun with poly (L-lactide-co-caprolactone) (PLCL) to be used as the outer layer of grafts. The elec-trospun poly (ε-caprolactone) (PCL) mats were aminolyzed and further chelated with copper (II) ions to construct glutathione peroxidase (GPx)-like structural surfaces for the catalytic generation of NO, which acted as the inner layer of grafts. The on-demand release of NO and H 2 S selectively and synergistically promoted the proliferation and migration of human umbilical vein endothelial cells (HUVECs) while inhibiting the proliferation and migration of human umbilical artery smooth muscle cells (HUASMCs). Dual releases of NO and H 2 S gaso-transmitters could enhance their respective production, resulting in enhanced promotion of HUVECs and inhibition of HUASMCs owing to their combined actions. In addition, the bilayer grafts were conducive to forming endothelial cell layers under flow shear stress. In rat abdominal aorta replacement models, the grafts remained patency for 6 months. These grafts were capable of facilitating rapid endothelialization and alleviating neo-intimal hyperplasia without obvious injury, inflammation, or thrombosis. More importantly, the grafts were expected to avoid calcification with the degradation of the grafts. Taken together, these bilayer grafts will be greatly promising candidates for SDVGs with rapid endothelialization and anti-calcification properties.
... H 2 S is commonly known as a vasodilator [92]. One of the first reports came from Hosoki et al. in 1997, showing that H 2 S promoted NO-induced VSMC relaxation in rat thoracic aorta [93]. Then, numerous studies showed that H 2 S decreases blood pressure in spontaneously hypertensive rats (SHRs) [94][95][96] and salt-sensitive hypertension in Dahl rats [97]. ...
... H 2 S is commonly known as a vasodilator [92]. One of the first reports came from Hosoki et al. in 1997, showing that H 2 S promoted NO-induced VSMC relaxation in rat thoracic aorta [93]. Then, numerous studies showed that H 2 S decreases blood pressure in spontaneously hypertensive rats (SHRs) [94][95][96] and salt-sensitive hypertension in Dahl rats [97]. ...
Peripheral artery disease (PAD) affects more than 230 million people worldwide. PAD patients suffer from reduced quality of life and are at increased risk of vascular complications and all-cause mortality. Despite its prevalence, impact on quality of life and poor long-term clinical outcomes, PAD remains underdiagnosed and undertreated compared to myocardial infarction and stroke. PAD is due to a combination of macrovascular atherosclerosis and calcification, combined with microvascular rarefaction, leading to chronic peripheral ischemia. Novel therapies are needed to address the increasing incidence of PAD and its difficult long-term pharmacological and surgical management. The cysteine-derived gasotransmitter hydrogen sulfide (H2S) has interesting vasorelaxant, cytoprotective, antioxidant and anti-inflammatory properties. In this review, we describe the current understanding of PAD pathophysiology and the remarkable benefits of H2S against atherosclerosis, inflammation, vascular calcification, and other vasculo-protective effects.
... Since the thiosulfate: GSH sulfurtransferase activity of RHODs is strongly inhibited by the product GSSH [45], the reaction normally favors the reverse direction. The functional role of the human RHOD during H 2 S oxidation is to catalyze the reverse reaction for the production of thiosulfate, as the kcat/K m value for the reverse reaction is 217,000-fold faster than that of the forward reaction [54,66]. The forward reaction can be enhanced by removing GSSH. ...
... H 2 S has numerous physiological effects. It is a well-known vasorelaxant [66]. In humans with hypertension, H 2 S-generating enzymes including cystathionine γ-lyase are markedly decreased [67]. ...
Hydrogen sulfide (H2S) and its oxidation product zero-valent sulfur (S0) play important roles in animals, plants, and bacteria. Inside cells, S0 exists in various forms, including polysulfide and persulfide, which are collectively referred to as sulfane sulfur. Due to the known health benefits, the donors of H2S and sulfane sulfur have been developed and tested. Among them, thiosulfate is a known H2S and sulfane sulfur donor. We have previously reported that thiosulfate is an effective sulfane sulfur donor in Escherichia coli; however, it is unclear how it converts thiosulfate to cellular sulfane sulfur. In this study, we showed that one of the various rhodaneses, PspE, in E. coli was responsible for the conversion. After the thiosulfate addition, the ΔpspE mutant did not increase cellular sulfane sulfur, but the wild type and the complemented strain ΔpspE::pspE increased cellular sulfane sulfur from about 92 μM to 220 μM and 355 μM, respectively. LC-MS analysis revealed a significant increase in glutathione persulfide (GSSH) in the wild type and the ΔpspE::pspE strain. The kinetic analysis supported that PspE was the most effective rhodanese in E. coli in converting thiosulfate to glutathione persulfide. The increased cellular sulfane sulfur alleviated the toxicity of hydrogen peroxide during E. coli growth. Although cellular thiols might reduce the increased cellular sulfane sulfur to H2S, increased H2S was not detected in the wild type. The finding that rhodanese is required to convert thiosulfate to cellular sulfane sulfur in E. coli may guide the use of thiosulfate as the donor of H2S and sulfane sulfur in human and animal tests.
... Among S-sulfhydrated proteins belong ATP synthase, lactate dehydrogenase, ion channels, phosphodiesterase, and many others (23, 44,45,47). In ion channels, H 2 S is capable of opening ATP-sensitive potassium channels (K ATP ) in the smooth muscle of arteries (48), myocytes (49), and smooth muscle of the intestine (50) or eye (51). However, H 2 S also regulates other channels such as largeconductance calcium-activated potassium ion channels (BK Ca ) (52), L-type and T-type Ca 2+ channels (53,54), Cl − channels (55), and transient receptor potential vanilloid and ankyrin channels (TRPV and TRPA) (56,57). ...
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.
... 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
... NO increases cGMP levels by activating soluble guanylate cyclase (sGC); subsequently, cGMP acts as a second intracellular messenger to regulate calcium channels and contractile proteins involved in the relaxation of cavernous smooth muscle (58). As early as 1997, Hosoki et al. (59) proposed the possibility of synergism between H 2 S and NO. They found that 100-mM NaHS had a weak effect on relaxing thoracic aortic smooth muscle in rats; however, when administered in the presence of 10-nM sodium nitroprusside (SNP, an NO donor), NaHS strongly relaxed the smooth muscle. ...
As an important gas signaling molecule, hydrogen sulfide (H2S) affects multiple organ systems, including the nervous, cardiovascular, digestive, and genitourinary, reproductive systems. In particular, H2S not only regulates female reproductive function but also holds great promise in the treatment of male reproductive diseases and disorders, such as erectile dysfunction, prostate cancer, varicocele, and infertility. In this review, we summarize the relationship between H2S and male reproductive organs, including the penis, testis, prostate, vas deferens, and epididymis. As lower urinary tract symptoms have a significant impact on penile erection disorders, we also address the potential ameliorative effects of H2S in erectile dysfunction resulting from bladder disease. Additionally, we discuss the regulatory role of H2S in cavernous smooth muscle relaxation, which involves the NO/cGMP pathway, the RhoA/Rho-kinase pathway, and K⁺ channel activation. Recently, various compounds that can alleviate erectile dysfunction have been reported to be at least partly dependent on H2S. Therefore, understanding the role of H2S in the male reproductive system may help develop novel strategies for the clinical treatment of male reproductive system diseases.
... 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]. ...
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.
... Inducible NOS (i-NOS or NOS-II) in contrast, is stimulated by proinflammatory cytokines, and excessive synthesis of NO in this instance, is responsible for pathophysiological inflammation [11]. H 2 S causes relaxation of vascular smooth muscle cells by decreasing angiotensin II type1 (AT 1 ) receptor binding together with binding affinity opening of K-ATPase channels [12] and also by enhancement of NO effects [13]. eNOS conversely, depends upon calcium/calmodulin (CaM), and is activated by a stimulatory response of different Ca 2+ rallying cell surface receptors in the vascular endothelial layer [14]. ...
Aim
Hydrogen sulfide and nitricoxide possess cytoprotective activity and in vivo, they are generated from exogenous sodium hydrosulfide and L-arginine respectively. Cisplatin is a major chemotherapeutic agent used to treat cancer and has a high incidence of nephrotoxicity as a side effect. The study aim was to explore the effects of NaHS and L-arginine or their combination on cisplatin induced nephrotoxicity in rats.
Methods
Wistar Kyoto rats were given a single intraperitoneal dose of cisplatin (5 mg/kg) followed either by NaHS (56 μmol/kg, i. p.), L-arginine (1.25 g/L in drinking water) or their combination daily for 28-days. Post-mortem plasma, urine and kidney samples were collected for biochemical assays and histopathological analysis.
Results
Cisplatin decreased body weights and increased urinary output, while plasma creatinine and urea levels were elevated, but sodium and potassium concentrations were diminished. The renal function parameters, blood urea nitrogen and creatinine clearance, were raised and decreased respectively. Regarding markers of reactive oxygen species, plasma total superoxide dismutase was reduced, whereas malondiadehyde was augmented.
Cisplatin also diminished plasma and urinary H2S as well as plasma NO, while NaHS and L-arginine counteracted this activity on both redox-active molecules. Cisplatin cotreatment with NaHS, and/or L-arginine exhibited a reversal of all other measured parameters.
Conclusion
In current study, NaHS and L-arginine as monotherapy protected the rats from cisplatin-induced nephrotoxicity but the combination of both worked more effectively suggesting the augmented anti-inflammatory and antioxidative potential of test treatments when administered together.
... This process facilitates the initiation of long-term potentiation in the hippocampus by increasing the stimulation of NMDA receptors [128]. In 1997, the enzyme cystathionine gamma-lyase (CSE) was shown to be present in the thoracic aorta, portal vein, and ileum and to produce H 2 S [129]. H 2 S has also been shown to have the ability to relax these tissues. ...
The phrase “Let food be thy medicine…” means that food can be a form of medicine and medicine can be a form of food; in other words, that the diet we eat can have a significant impact on our health and well-being. Today, this phrase is gaining prominence as more and more scientific evi-dence suggests that one’s diet can help prevent and treat disease. A diet rich in fruits, vegetables, whole grains, and lean protein can help reduce the risk of heart disease, cancer, diabetes, and other health problems and, on the other hand, a diet rich in processed foods, added sugars, and satu-rated fats can increase the risk of the same diseases. Electrophilic compounds in the diet can have a significant impact on our health, and they are molecules that covalently modify cysteine residues present in the thiol-rich Keap1 protein. These compounds bind to Keap1 and activate NRF2, which promotes its translocation to the nucleus and its binding to DNA in the ARE region, triggering the antioxidant response and protecting against oxidative stress. These compounds include poly-phenols and flavonoids that are nucleophilic but are converted to electrophilic quinones by met-abolic enzymes such as polyphenol oxidases (PPOs) and sulfur compounds present in foods such as the Brassica genus (broccoli, cauliflower, cabbage, Brussel sprouts, etc.) and garlic. This review summarizes our current knowledge on this subject.
... Recent studies suggest that hydrogen sulfide (H 2 S) has increasingly being recognized as the third gaseous mediator in mammals [3,4]. Hydrogen sulfide can be produced endogenously in various mammalian tissues from L-cysteine metabolism mainly by either cystathionine beta-synthase (CBS) or cystathionine gamma-lyase (CSE), both using pyridoxal 5'-phosphate (vitamin B(6)) as a cofactor [5,6]. It appears to have more target molecules than NO or CO and play multiple roles in biological functions including neuroprotection [7,8], cardioprotection [9,10], antihypertension [11], and osteoblastic protection [12]. ...
A new Near-infrared fluorescent probe for hydrogen sulfide detection was synthesized by employing dicyanoisophorone based fluorescence dye as a fluorophore and methyl 3-(2-(carbonyl)phenyl)-2-cyanoacrylate group as the response unit. The Probe DCI-H2S showed a long emission wavelength (λem = 674 nm). Based on the H2S-induced addition–cyclization of deprotecting methyl 3-(2-(carbonyl)phenyl)-2-cyanoacrylate group, the probe DCI-H2S showed high selectivity, sensitivity and response speed toward hydrogen sulfide under room temperature. These numerous advantages of the probe DCI-H2S make it to potentially detect endogenous hydrogen sulfide in living organisms.
... CGL is predominantly located in liver [21,26], kidney [21]. This enzyme is also present in the vasculature [32][33][34][35][36]. ...
... 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.
... 17 In recent years, one popular method to alleviate salt stress is the application of exogenous substances. 18 As a gas signal molecule, 19 H 2 S plays an important role in plant growth and development as well as response to abiotic stresses. 20 Because H 2 S and NaHS can form a dynamic equilibrium in plants, NaHS is often used as a donor of H 2 S in biological research. ...
Salt stress is a prevailing abiotic stress in nature, with soil salinization becoming a pressing issue worldwide. High soil salinity severely hampers plant growth and leads to reduced crop yields. Hydrogen sulfide (H2S), a gas signal molecule, is known to be synthesized in plants exposed to abiotic stress, contributing to enhanced plant stress resistance. To investigate the impact of sodium hydrosulfide hydrate (NaHS, a H2S donor) on millet’s response to salt stress, millet seedlings were subjected to pretreatment with 200 μM NaHS, followed by 100 mM NaCl stress under soil culture conditions. The growth, osmotic adjustment substances, antioxidant characteristics, membrane damage, and expression levels of related genes in millet seedlings were detected and analyzed. The results showed that NaHS pretreatment alleviated the inhibition of salt stress on the growth of foxtail millet seedlings, increased the proline content and antioxidant enzyme activities, as well as the expression levels of SiASR4, SiRPLK35 and SiHAK23 genes under salt stress. These findings demonstrated that NaHS pretreatment can enhance salt tolerance in foxtail millet seedlings by regulating the content of osmotic adjustment substances and antioxidant enzyme activity, reducing electrolyte permeability, and activating the expression of salt-resistant genes.
... Overall, H2S is a gasotransmitter that plays a crucial role in regulating various physiological processes in the body. Its vasodilatory, anti-inflammatory, and cytoprotective effects make it a promising therapeutic target for the treatment of various diseases such as hypertension, inflammation, and oxidative stress-related disorders [21,22]. ...
Autonomic nervous system (ANS) regulates the physiologic process in the body and has essential role in the systems such as blood pressure regulation, respiration, heart rate, and sexual arousal. ANS is divided into the sympathetic nervous system and the parasympathetic nervous system and regulates whole organism functions in the body. Although the main neurotransmitters in the ANS are norephinephrine, epinephrine, and acetilcholine, many other different agents and chemicals play an important role of the neurotransmitters function. These molecules act on many different receptors and sides. This chapter provides a detailed evaluation of neurotransmitters, related molecules, their receptors and how they function to maintain autonomic functions in both the central and peripheral parts of the systems.
... Then the seedlings were cultured for another 6 days. Finally, the seedlings were treated with different concentrations (0, 100, 200, 500, and 1000 µM) of NaHS, a donor of H 2 S (purchased from Sigma, St Louis, MO, USA), with three replicates as depicted by Hosoki et al. (1997). All the seedlings grew in an environmentallycontrolled growth room (temperature of 22 -26°C, light intensity at 800 -1000 µmol m -2 s -1 , 14/10 h day/night photoperiod, and humidity of 50 -70%). ...
The effects of hydrogen sulfide (H2S), released from the donor sodium hydrosulfide (NaHS), on maize seedlings grown hydroponically for 6 days were investigated. Plant biomass, malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide (O2•−) content, and root exudates (organic acids) were measured. Results showed that 100 and 200 µM NaHS is the most appropriate and suitable concentration for the growth and development of maize seedlings, without affecting the MDA and H2O2 contents but altering the O2•−. In addition, high concentrations of 500 and 1000 µM NaHS adversely affected these parameters compared with the control (CK). The pH of the root exudates declined under NaHS treatments. The organic acids in the root exudates, including fumaric, acetic, formic, and malic acids exhibited higher contents at 100 µM NaHS treatment, the lactic and citric acids were higher at both 100 and 200 µM NaHS. In contrast, oxalic acid was reduced at all NaHS concentrations compared with the CK. Low contents of all the organic acids analyzed were found under 500 and 1000 µM NaHS treatment. In conclusion, all the above parameters were affected by the application of NaHS, while higher NaHS concentration was toxic for maize seedlings.
... H 2 S is now established among researchers as the third identified member of a family of gaseous signaling molecules (gasotransmitters) after nitric oxide and carbon monoxide [17][18][19]. In mammalian cells, H 2 S is enzymatically produced at low physiological and non-toxic concentrations using the sulfur-containing amino acid, L-cysteine as a substrate, and catalyzed by the cytosolic enzymes, cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CSE) [20] and the mitochondrial enzyme, 3-mercaptopyruvate sulfurtransferase (3-MST) [21]. Interestingly, a fourth enzymatic pathway involving the peroxisomal enzyme, D-amino acid oxidase (DAO) coupled with 3-MST, also produces H 2 S from D-cysteine, a naturally occurring enantiomer of L-cysteine [22] (Fig. 1). ...
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.
... Hydrogen sulfide was first identified as an endogenous neuromodulator and modulator of vascular tone and blood pressure (4,11), while further studies revealed much broader H2S functions, such as a role in angiogenesis, glucose metabolism, energy production, nociception, cardioprotection, inflammation, penile erectile function, anticancer effect, and many others (9,12). Studies from our group and a few others have demonstrated a direct vasorelaxant effect of H2S on isolated human blood vessels. ...
Hydrogen sulfide (H 2 S) is the youngest member of the gasotransmitters family consisting of nitric oxide (NO) and carbon monoxide (CO). This signalling molecule is implicated in the regulation of a wide range of processes, such as inflammation, pain, and tissue repair, and has an important role in signalling processes affecting cardiovascular health, either as an independent effector or as an enhancer of the NO system. With the discovery of the H 2 S role in the pathogenesis of many diseases, the development of new pharmaceuticals that could be useful in conditions with disturbed levels of endogenous H 2 S began. Today, the development of H 2 S-releasing drugs has reached the level of clinical studies. Drugs such as SG1002, aimed at the treatment of heart failure, and ATB-346, aimed at the treatment of arthritis, have been tested in Phase I/II clinical studies and have shown significant therapeutic potential. Additionally, it has been shown that some already known drugs, such as zofenopril, produce part of their beneficial effects by releasing H 2 S. Evidence from clinical studies presented in this paper encourages further clinical testing of H 2 S-based therapeutics and the possibility of their application in a wide range of diseases, such as hypertension, diabetes and chronic kidney disease.
... Over the last three decades, hydrogen sulfide (H 2 S) has overcome its past reputation as a toxic gas and gained much attention as a molecule of various biological roles spanning from neurotransmission, vasorelaxation [60], nociception [61,62], cytoprotection [63,64], cardiovascular modulation [65], atherosclerosis [66], and ischemia-reperfusion injuries [67] to diabetes complications [68,69]. In mammalian tissue, H 2 S is synthesized from L-cysteine by two cytosolic pyridoxal 5 -phosphate (PLP)-dependent enzymes, i.e., cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) [70][71][72]. A PLP-independent enzyme 3-mercaptopyruvate sulfurtransferase (3MST) has also recently been identified to produce H 2 S from 3-mercaptopyruvate [73,74] (Figure 1A). ...
Diabetic nephropathy (DN) remains the leading cause of vascular morbidity and mortality in diabetes patients. Despite the progress in understanding the diabetic disease process and advanced management of nephropathy, a number of patients still progress to end-stage renal disease (ESRD). The underlying mechanism still needs to be clarified. Gaseous signaling molecules, so-called gasotransmitters, such as nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), have been shown to play an essential role in the development, progression, and ramification of DN depending on their availability and physiological actions. Although the studies on gasotransmitter regulations of DN are still emerging, the evidence revealed an aberrant level of gasotransmitters in patients with diabetes. In studies, different gasotransmitter donors have been implicated in ameliorating diabetic renal dysfunction. In this perspective, we summarized an overview of the recent advances in the physiological relevance of the gaseous molecules and their multifaceted interaction with other potential factors, such as extracellular matrix (ECM), in the severity modulation of DN. Moreover, the perspective of the present review highlights the possible therapeutic interventions of gasotransmitters in ameliorating this dreaded disease.
... Soybean (Glycine max, Zhonghuang 13) seeds were surface sterilized for 30 s with 75% ethanol and then for 4 min with 50% sodium hypochlorite solution before being sown in sterilized polypropylene planting bags (17 cm × 33 cm × 0.05 mm, Xinglong brand, Baoding, China) containing 450 g growth substrate (river sand and perlite, v:v = 2:1) with a moderate N-free nutrient solution. The nutrition solution contained the following ingredients: 100 mg/L CaCl 2 ·2H 2 O, 100 mg/L KH 2 PO 4 , 5 mg/L FeC 6 NaHS was applied as an exogenous H 2 S donor [45]. After the first true leaves had fully developed, some plants were inoculated with rhizobia (Sinorhizobium fredii Q8 strain) by injecting a 10 mL rhizobia solution (OD 600 = 0.05) into each bag along the rhizome. ...
Hydrogen sulfide (H2S), a novel gas signaling molecule, plays a crucial role in plant growth and stress response. However, little attention has been devoted to the regulation of H2S on nutrient transport and utilization in legume–rhizobia symbiosis systems. Although we have previously proven that H2S synergized with rhizobia to considerably enhance nitrogen (N) metabolism and remobilization in N-deficient soybeans, it remains uncertain if changes in nutrient absorption, metabolism, and accumulation occur concurrently. Therefore, employing a synergistic treatment of H2S and rhizobia, we examined the dry matter biomass and carbon (C), N, phosphorous (P), and potassium (K) nutrient content in various organs of soybean from blooming to maturity. Firstly, H2S and rhizobia application obviously improved leaf and plant phenotypes and biomass accumulation in different organs during N-deficient soybean development. Second, from flowering to maturity, the contents and stoichiometric ratios of C, N, P, and K in various organs of soybean were changed to variable degrees by H2S and rhizobia. Furthermore, H2S collaborated with rhizobia to significantly affect grain nutrient harvest across soybean growth as well as overall plant nutrient accumulation. Consequently, H2S synergizes with rhizobia to optimize grain harvest quality and nutrient accumulation across the plant by managing the rational allocation and dynamic balance of nutrients in diverse organs, hence boosting soybean development and production.
This review summarises progress in the research of homocystinuria (HCU) in the past three decades. HCU due to cystathionine β‐synthase (CBS) was discovered in 1962, and Prof. Jan Peter Kraus summarised developments in the field in the first‐ever Komrower lecture in 1993. In the past three decades, significant advancements have been achieved in the biology of CBS, including gene organisation, tissue expression, 3D structures, and regulatory mechanisms. Renewed interest in CBS arose in the late 1990s when this enzyme was implicated in biogenesis of H 2 S. Advancements in genetic and biochemical techniques enabled the identification of several hundreds of pathogenic CBS variants and the misfolding of missense mutations as a common mechanism. Several cellular, invertebrate and murine HCU models allowed us to gain insights into functional and metabolic pathophysiology of the disease. Establishing the E‐HOD consortium and patient networks, HCU Network Australia and HCU Network America, offered new possibilities for acquiring clinical data in registries and data on patients´ quality of life. A recent analysis of data from the E‐HOD registry showed that the clinical variability of HCU is broad, extending from severe childhood disease to milder (late) adulthood forms, which typically respond to pyridoxine. Pyridoxine responsiveness appears to be the key factor determining the clinical course of HCU. Increased awareness about HCU played a role in developing novel therapies, such as gene therapy, correction of misfolding by chaperones, removal of methionine from the gut and enzyme therapies that decrease homocysteine or methionine in the circulation.
The transsulfuration pathway plays a key role in mammals for maintaining the balance between cysteine and homocysteine, whose concentrations are critical in several biochemical processes. Human cystathionine β-synthase is a heme-containing, pyridoxal 5'-phosphate (PLP)-dependent enzyme found in this pathway. The heme group does not participate directly in catalysis, but has a regulatory function, whereby CO or NO binding inhibits the PLP-dependent reactions. In this study, we explore the detailed structural changes responsible for inhibition using quantum chemical calculations to validate the experimentally observed bonding patterns associated with heme CO and NO binding and molecular dynamics simulations to explore the medium-range structural changes triggered by gas binding and propagating to the PLP active site, which is more than 20 Å distant from the heme group. Our results support a previously proposed mechanical signaling model, whereby the cysteine decoordination associated with gas ligand binding leads to breaking of a hydrogen bond with an arginine residue on a neighbouring helix. In turn, this leads to a shift in position of the helix, and hence also of the PLP cofactor, ultimately disrupting a key hydrogen bond that stabilizes the PLP in its catalytically active form.
The gasotransmitter hydrogen sulfide (H 2 S) is thought to be involved in the post‐translational modification of cysteine residues to produce reactive persulfides. A persulfide‐specific chemoselective proteomics approach with mammalian cells has identified a broad range of zinc finger (ZF) proteins as targets of persulfidation. Parallel studies with isolated ZFs show that persulfidation is mediated by Zn II , O 2 , and H 2 S, with intermediates involving oxygen‐ and sulfur‐based radicals detected by mass spectrometry and optical spectroscopies. A small molecule Zn II complex exhibits analogous reactivity with H 2 S and O 2 , giving a persulfidated product. These data show that Zn II is not just a biological structural element, but also plays a critical role in mediating H 2 S‐dependent persulfidation. ZF persulfidation appears to be a general post‐translational modification and a possible conduit for H 2 S signaling. This work has implications for our understanding of H 2 S‐mediated signaling and the regulation of ZFs in cellular physiology and development.
The gasotransmitter hydrogen sulfide (H2S) is thought to be involved in the post‐translational modification of cysteine residues to produce reactive persulfides. A persulfide‐specific chemoselective proteomics approach with mammalian cells has identified a broad range of zinc finger (ZF) proteins as targets of persulfidation. Parallel studies with isolated ZFs show that persulfidation is mediated by ZnII, O2, and H2S, with intermediates involving oxygen‐ and sulfur‐based radicals detected by mass spectrometry and optical spectroscopies. A small molecule ZnII complex exhibits analogous reactivity with H2S and O2, giving a persulfidated product. These data show that ZnII is not just a biological structural element, but also plays a critical role in mediating H2S‐dependent persulfidation. ZF persulfidation appears to be a general post‐translational modification and a possible conduit for H2S signaling. This work has implications for our understanding of H2S‐mediated signaling and the regulation of ZFs in cellular physiology and development.
A meta-analysis of 22 persulfide-specific proteomics datasets reveals widespread persulfidation of zinc finger proteins across various species, highlighting the role of persulfidation as an important post-translational modification.
Fibrosis, a pathological alteration of the repair response, involves continuous organ damage, scar formation, and eventual functional failure in various chronic inflammatory disorders. Unfortunately, clinical practice offers limited treatment strategies, leading to high mortality rates in chronic diseases. As part of investigations into gaseous mediators, or gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), numerous studies have confirmed their beneficial roles in attenuating fibrosis. Their therapeutic mechanisms, which involve inhibiting oxidative stress, inflammation, apoptosis, and proliferation, have been increasingly elucidated. Additionally, novel gasotransmitters like hydrogen (H2) and sulfur dioxide (SO2) have emerged as promising options for fibrosis treatment. In this review, we primarily demonstrate and summarize the protective and therapeutic effects of gaseous mediators in the process of fibrosis, with a focus on elucidating the underlying molecular mechanisms involved in combating fibrosis.
In this work, we analyzed the role of voltage-gated (KV), calcium-activated (KCa), and inward-rectifier potassium channels (Kir) in the effects of hydrogen sulphide (H2S) donor sodium hydrosulphide (NaHS) on the spontaneous contractile activity of the rat jejunum. Experiments were performed on jejunum segments under isometric contraction conditions. It was shown that NaHS reduced the basal tension of the segments, the amplitude, and the frequency of spontaneous contractions in a dose-dependent manner (10–500 μM); the half-effective concentration (EC50) of the inhibitory effect of NaHS on amplitude was 165 μM. The KV channel blocker 4-AP (200 µM) increased the amplitude of spontaneous contractions and subsequent application of NaHS (200 μM) suppressed the amplitude and frequency of spontaneous activity as well as in the control; the effect on tonic tension was less pronounced. TEA (3 mM), a non-specific blocker, and paxillin (1 µM), a specific blocker of large conductance KСа (ВK) channels, increased the amplitude of spontaneous contractions, while the inhibitory effect of NaHS was completely preserved. The selective blocker of small conductance KCa (SK) channels NS8593 (4 μM) did not affect the tension and the parameters of spontaneous contractions and did not prevent the effects of NaHS. Diazoxide (100 μM), the opener of КATP channels, caused a decrease in the basal tone, the amplitude and frequency of spontaneous contractions. Diazoxide and KATP channel blocker glibenclamide (50 μM) prevented the effects of NaHS on the basal tone. The Kir-channel blocker BaCl2 (30 µM) increased the amplitude of spontaneous contractions and eliminated the inhibitory effects of NaHS on the frequency and amplitude of spontaneous contractions, and the basal tension decrease was less pronounced compared to control. Thus, a decrease in the tonic tension of a rat jejunum preparation under the action of an H2S donor is associated with the activation of Kir, including КATP channels, while the effects of H2S on the amplitude and frequency of spontaneous contractions are mediated by an increase in Ba2+-sensitive conductance.
The intriguing chemistry of chalcogen (S, Se)-containing ligands and their capability to bridge multiple metal centres have resulted in a plethora of reports on transition metal complexes featuring hydrosulfide (HS-) and polychalcogenides (En2-, E = S, Se). While a large number of such molecules are strictly organometallic complexes, examples of non-organometallic complexes featuring HS- and En2- with N-/O-donor ligands are relatively rare. The general synthetic procedure for the transition metal-hydrosulfido complexes involves the reaction of the corresponding metal salts with HS-/H2S and this is prone to generate sulfido bridged oligomers in the absence of sterically demanding ligands. On the other hand, the synthetic methods for the preparation of transition metal-polychalcogenido complexes include the reaction of the corresponding metal salts with En2- or the two electron oxidation of low-valent metals with elemental chalcogen, often at an elevated temperature and/or for a long time. Recently, we have developed new synthetic methods for the preparation of two new classes of binuclear transition metal complexes featuring either HS-, or Sn2- and Sen2- ligands. The new method for the synthesis of transition metal-hydrosulfido complexes involved transition metal-mediated hydrolysis of thiolates at room temperature (RT), while the method for the synthesis of transition metal-polychalcogenido complexes involved redox reaction of coordinated thiolates and exogenous elemental chalcogens at RT. An overview of the synthetic aspects, structural properties and intriguing reactivity of these two new classes of transition metal complexes is presented.
This study was performed to explore the role of nitric oxide, intracellular and extracellular calcium in the effects of hydrogen sulfide on spontaneous and carbachol-induced contractions of a rat jejunum preparation during a isometric contraction. Application of H2S donor, sodium hydrosulfide, led to a decrease in tonic tension, the amplitude and frequency of spontaneous contractions, as well as in the amplitude induced by carbachol, a nonspecific acetylcholine receptor agonist. Inhibiting the production of endogenous NO synthesis by with L-NAME, the effect of H2S donor remained unchanged, while in the presence of SNAP, a NO donor, the effects of NaHS on the amplitude of spontaneous and carbachol-induced contractions were less pronounced. Dantrolene, a ryanodine receptor inhibitor was used to stop a decrease in tonic tension in the presence of NaHS. The calcium-free solution reduced the inhibitory effect of NaHS on carbachol-induced contractions. This suggests that the inhibitory effect of H2S is associated with the dynamics of the intracellular concentration of calcium ions, and the interaction between NO and H2S occurs at the level of common targets of two gases.
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.
Given that trace level H2S quantitation in biological samples currently requires expensive and time-consuming instrumental procedures, we herein developed an electrochemical Ag/C sensor for the detection of H2S in protein-containing neutral solutions. The detection principle was based on the increase in galvanic current that was elicited by the sulfidation of the Ag electrode and was linearly dependent on the concentration of H2S. This linear relationship enabled the quantitation of H2S in the concentration range of 0.037–6.7 µmol L⁻¹ in mock biological samples without any pretreatment, highlighting the potential of the Ag/C sensor for the analysis of water quality and food, blood, and other biological samples.
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Hydrogen sulfide (H2S) was recognized as a gaseous signaling molecule, similar to nitric oxide (-NO) and carbon monoxide (CO). The aim of this review is to provide an overview of the formation of hydrogen sulfide (H2S) in the human body. H2S is synthesized by enzymatic processes involving cysteine and several enzymes, including cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), cysteine aminotransferase (CAT), 3-mercaptopyruvate sulfurtransferase (3MST) and D-amino acid oxidase (DAO). The physiological and pathological effects of hydrogen sulfide (H2S) on various systems in the human body have led to extensive research efforts to develop appropriate methods to deliver H2S under conditions that mimic physiological settings and respond to various stimuli. These functions span a wide spectrum, ranging from effects on the endocrine system and cellular lifespan to protection of liver and kidney function. The exact physiological and hazardous thresholds of hydrogen sulfide (H2S) in the human body are currently not well understood and need to be researched in depth. This article provides an overview of the physiological significance of H2S in the human body. It highlights the various sources of H2S production in different situations and examines existing techniques for detecting this gas.
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.
Diabetic kidney disease (DKD) is a chronic renal pathology, which is currently the leading cause of end-stage renal disease. It accounts for 40% of morbidity and mortality among the diabetic population despite optimal management. Its clinical hallmark includes persistent hyperglycemia, hypercreatininemia, uremia, sustained albuminuria, renal hemodynamic changes, and elevated blood pressure. Histologically, DKD presents with excessive accumulation and deposition of extracellular matrix, leading to expansion of mesangial matrix, thickening of glomerular basement membrane, and tubulointerstitial fibrosis. At the molecular level, accumulating evidence suggests that hyperglycemia or high glucose mediates renal injury in DKD via multiple molecular mechanisms such as induction of oxidative stress, upregulation of renal transforming growth factor beta-1 expression, production of pro-inflammatory cytokines, activation of fibroblasts and renin-angiotensin-aldosterone system, and depletion of adenosine triphosphate. Moreover, existing therapies only retard the disease progression but do not prevent or reverse it. Therefore, novel modes of pharmacotherapeutic intervention are in demand to target additional disease mechanisms. A substantial body of experimental evidence demonstrates that hydrogen sulfide (H2S), a gas with a historic notorious label, has recently been established to possess important therapeutic properties that prevent and/or reverse DKD development and progression of DKD by targeting several important molecular pathways, and therefore could be considered a novel pharmacological agent for DKD treatment. The aim of this chapter is to discuss recent experimental findings on the molecular mechanisms underlying the pharmacotherapeutic effects of H2S against DKD development and progression, and its translation from bench to bedside, which could lay the foundation for its future clinical use. A section of the chapter also discusses focal segmental glomerulosclerosis as a mediator of DKD progression to end-stage renal disease, and H2S as a potential novel therapy.
Vascular ageing, characterized by structural and functional changes in blood vessels of which arterial stiffness and endothelial dysfunction are key components, is associated with increased risk of cardiovascular and other age-related diseases. As the global population continues to age, understanding the underlying mechanisms and developing effective therapeutic interventions to mitigate vascular ageing becomes crucial for improving cardiovascular health outcomes. Therefore, this review provides an overview of the current knowledge on pharmacological modulation of vascular ageing, highlighting key strategies and promising therapeutic targets. Several molecular pathways have been identified as central players in vascular ageing, including oxidative stress and inflammation, the renin-angiotensin-aldosterone system, cellular senescence, macroautophagy, extracellular matrix remodelling, calcification, and gasotransmitter-related signalling. Pharmacological and dietary interventions targeting these pathways have shown potential in ameliorating age-related vascular changes. Nevertheless, the development and application of drugs targeting vascular ageing is complicated by various inherent challenges and limitations, such as certain preclinical methodological considerations, interactions with exercise training and sex/gender-related differences, which should be taken into account. Overall, pharmacological modulation of endothelial dysfunction and arterial stiffness as hallmarks of vascular ageing, holds great promise for improving cardiovascular health in the ageing population. Nonetheless, further research is needed to fully elucidate the underlying mechanisms and optimize the efficacy and safety of these interventions for clinical translation.
Hydrogen sulfide (H2S) and polysulfides (H2Sn, n ≥ 2) are signaling molecules produced by 3-mercaptopyruvate sulfurtransferase (3MST) that play various physiological roles, including the induction of hippocampal long-term potentiation (LTP), a synaptic model of memory formation, by enhancing N-methyl-d-aspartate (NMDA) receptor activity. However, the presynaptic action of H2S/H2Sn on neurotransmitter release, regulation of LTP induction, and animal behavior are poorly understood. Here, we showed that H2S/H2S2 applied to the rat hippocampus by in vivo microdialysis induces the release of GABA, glutamate, and d-serine, a co-agonist of NMDA receptors. Animals with genetically knocked-out 3MST and the target of H2S2, transient receptor potential ankyrin 1 (TRPA1) channels, revealed that H2S/H2S2, 3MST, and TRPA1 activation play a critical role in LTP induction, and the lack of 3MST causes behavioral hypersensitivity to NMDA receptor antagonism, as in schizophrenia. H2S/H2Sn, 3MST, and TRPA1 channels have therapeutic potential for psychiatric diseases and cognitive deficits.
Hydrogen sulfide (H2S) is a significant physiologic inhibitory neurotransmitter. The main goal of this research was to examine the contribution of diverse potassium (K⁺) channels and nitric oxide (NO) in mediating the H2S effect on electrical field stimulation (EFS)-induced neurogenic contractile responses in the lower esophageal sphincter (LES). EFS-induced contractile responses of rabbit isolated LES strips were recorded using force transducers in organ baths that contain Krebs–Henseleit solutions (20 ml). Cumulative doses of NaHS, L-cysteine, PAG, and AOAA were evaluated in NO-dependent and NO-independent groups. The experiments were conducted again in the presence of K⁺ channel blockers. In both NO-dependent and NO-independent groups, NaHS, L-cysteine, PAG, and AOAA significantly reduced EFS-induced contractile responses. In the NO-dependent group, the effect of NaHS and L-cysteine decreased in the presence of 4-AP, and also the effect of NaHS decreased in the NO-dependent and independent group in the presence of TEA. In the NO-independent group, K⁺ channel blockers didn’t change L-cysteine-induced relaxations. K⁺ channel blockers had no impact on the effects of PAG and AOAA. In addition, NaHS significantly relaxed 80-mM KCl-induced contractions, whereas L-cysteine, PAG, and AOAA did not. In the present study, H2S decreased the amplitudes of EFS-induced contraction responses. These results suggest that Kv channels and NO significantly contribute to exogenous H2S and endogenous H2S precursor L-cysteine inhibitory effect on lower esophageal sphincter smooth muscle.
Hydrogen sulfide (H 2 S), as an endogenous gas signaling molecule, plays an important role in plant growth regulation and resistance to abiotic stress. This study aims to investigate the mechanism of exogenous H 2 S on the growth and development of Reaumuria soongorica seedlings under salt stress and to determine the optimal concentration for foliar application. To investigate the regulatory effects of exogenous H 2 S (donor sodium hydrosulfide, NaHS) at concentrations ranging from 0 to 1 mM on reactive oxygen species (ROS), antioxidant system, and osmoregulation in R. soongorica seedlings under 300 mM NaCl stress. The growth of R. soongorica seedlings was inhibited by salt stress, which resulted in a decrease in the leaf relative water content (LRWC), specific leaf area (SLA), and soluble sugar content in leaves, elevated activity levels of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); and accumulated superoxide anion (O 2 – ), proline, malondialdehyde (MDA), and soluble protein content in leaves; and increased L-cysteine desulfhydrase (LCD) activity and endogenous H 2 S content. This indicated that a high level of ROS was produced in the leaves of R. soongorica seedlings and seriously affected the growth and development of R. soongorica seedlings. The exogenous application of different concentrations of NaHS reduced the content of O 2 – , proline and MDA, increased the activity of antioxidant enzymes and the content of osmoregulators (soluble sugars and soluble proteins), while the LCD enzyme activity and the content of endogenous H 2 S were further increased with the continuous application of exogenous H 2 S. The inhibitory effects of salt stress on the growth rate of plant height and ground diameter, the LRWC, biomass, and SLA were effectively alleviated. A comprehensive analysis showed that the LRWC, POD, and proline could be used as the main indicators to evaluate the alleviating effect of exogenous H 2 S on R. soongorica seedlings under salt stress. The optimal concentration of exogenous H 2 S for R. soongorica seedlings under salt stress was 0.025 mM. This study provides an important theoretical foundation for understanding the salt tolerance mechanism of R. soongorica and for cultivating high-quality germplasm resources.
Hydrogen sulfide (H2 S) is an important gaseous signaling molecule known to be critically involved in regulating cellular redox homeostasis. As the beneficial and therapeutic effects of H2 S in pathophysiology, such as in cardiovascular and neurodegenerative diseases, have emerged, so too has the drive for the development of H2 S-releasing compounds (aka donors) and their therapeutic applications. Most reported donor compounds singularly release H2 S through biocompatible triggers. An emerging area in the field is the development of compounds that can co-deliver H2 S with other drugs or biologically relevant species, such as reactive oxygen and nitrogen species (ROS and RNS, respectively). These H2 S-based dual donors and hybrid drugs are expected to offset negative side effects from individual treatments or achieve synergistic effects rendering them more clinically effective. Additionally, considering that molecules exist and interact physiologically, dual donors may more accurately mimic biological systems as compared to single donors and allow for the elucidation of fundamental chemistry and biology. This review focuses on the recent advances in the development of H2 S-based dual donors and hybrid drugs along with their design principles and synergistic effects.
When histiocyte are ischemic for a certain time and blood supply is suddenly restored, the pathological condition of rapidly aggravated tissue damage is called ischemia reperfusion injury, which is mainly caused by a large amount of Ca2+ influx and oxygen free radicals attacking ischemic histiocyte. Ischemia reperfusion injury can increase the incidence rate and mortality of some diseases, such as acute myocardial infarction, ischemic stroke, acute renal injury, intestinal obstruction, hyperkalemia and multiple organ failure, and it also brings great challenges to surgery such as organ transplantation. However, the current treatment methods for ischemia-reperfusion are still very limited. Fortunately, increasing evidence suggests that reasonable concentrations of hydrogen sulfide may play a powerful organ protective role in ischemia-reperfusion injury, mainly through mechanisms such as anti apoptotic, antioxidant, stress reduction, regulation of autophagy, and inhibition of inflammation. Therefore, hydrogen sulfide has profound clinical conversion prospects in the treatment of I/R injury. This article systematically summarizes the generation and physiological effects of endogenous hydrogen sulfide, as well as its protective mechanisms in different systems such as the heart, brain, kidney, liver, retina, and testes. In addition, the clinical transformation prospects and current challenges of hydrogen sulfide in ischemia-reperfusion injury were discussed.
The purpose of this narrative review is to highlight the importance of microbial metabolites in the pathogenesis of periodontal diseases. These diseases, involving gingivitis and periodontitis are inflammatory conditions initiated and maintained by the polymicrobial dental plaque/biofilm. Gingivitis is a reversible inflammatory condition while periodontitis involves also irreversible destruction of the periodontal tissues including the alveolar bone. The inflammatory response of the host is a natural reaction to the formation of plaque and the continuous release of metabolic waste products. The microorganisms grow in a nutritious and shielded niche in the periodontal pocket, protected from natural cleaning forces such as saliva. It is a paradox that the consequences of the enhanced inflammatory reaction also enable more slow-growing, fastidious, anaerobic bacteria, with often complex metabolic pathways, to colonize and thrive. Based on complex food chains, nutrient networks and bacterial interactions, a diverse microbial community is formed and established in the gingival pocket. This microbiota is dominated by anaerobic, often motile, Gram-negatives with proteolytic metabolism. Although this alternation in bacterial composition often is considered pathologic, it is a natural development that is promoted by ecological factors and not necessarily a true “dysbiosis”. Normal commensals are adapting to the gingival crevice when tooth cleaning procedures are absent. The proteolytic metabolism is highly complex and involves a number of metabolic pathways with production of a cascade of metabolites in an unspecific manner. The metabolites involve short chain fatty acids (SCFAs; formic, acetic, propionic, butyric, and valeric acid), amines (indole, scatole, cadaverine, putrescine, spermine, spermidine) and gases (NH 3 , CO, NO, H 2 S, H 2 ). A homeostatic condition is often present between the colonizers and the host response, where continuous metabolic fluctuations are balanced by the inflammatory response. While it is well established that the effect of the dental biofilm on the host response and tissue repair is mediated by microbial metabolites, the mechanisms behind the tissue destruction (loss of clinical attachment and bone) are still poorly understood. Studies addressing the functions of the microbiota, the metabolites, and how they interplay with host tissues and cells, are therefore warranted.
Hydrogen sulfide (H2 S) performs a crucial role in plant development and abiotic stress responses by interacting with other signalling molecules. However, the synergistic involvement of H2 S and rhizobia in photosynthetic carbon (C) metabolism in soybean (Glycine max) under nitrogen (N) deficiency has been largely overlooked. Therefore, we scrutinised how H2 S drives photosynthetic C fixation, utilisation, and accumulation in soybean-rhizobia symbiotic systems. When soybeans encountered N deficiency, organ growth, grain output, and nodule N-fixation performance were considerably improved owing to H2 S and rhizobia. Furthermore, H2 S collaborated with rhizobia to actively govern assimilation product generation and transport, modulating C allocation, utilisation, and accumulation. Additionally, H2 S and rhizobia profoundly affected critical enzyme activities and coding gene expressions implicated in C fixation, transport, and metabolism. Furthermore, we observed substantial effects of H2 S and rhizobia on primary metabolism and C-N coupled metabolic networks in essential organs via C metabolic regulation. Consequently, H2 S synergy with rhizobia inspired complex primary metabolism and C-N coupled metabolic pathways by directing the expression of key enzymes and related coding genes involved in C metabolism, stimulating effective C fixation, transport, and distribution, and ultimately improving N fixation, growth, and grain yield in soybeans.
Cadmium (Cd) levels in agricultural soils are increasing because of industrial expansion and pesticide discharge. There are few plants that tolerate heavy metals particularly Cd. NaHS as hydrogen sulfide (H2S) donor plays a significant role in Cd tolerance by plants reducing its toxicity. The present research was oriented to evaluate the effect of NaHS in Cd and macro-/micronutrient uptake, as well as some physical and chemical parameters in Leucaena leucocephala plants exposed to this metal. Seedlings were grown in a hydroponic system and exposed to 5 ppm of Cd and NaHS at 1, 10, and 100 μM for 3 days. Inductively coupled plasma optical emission spectrometry (ICP/OES) was used to quantify Cd content and macro-/micronutrients in plant tissues. Results show a significant difference (Fisher’s LSD) in radicle length and chlorophyll but did not show effect on carotenoids content. Addition of NaHS to the media shows a significant increase in Cd uptake by root as NaHS concentration in media increased. The maximum Cd uptake (7670 ± 102 mg/kg) was found in the roots of plants exposed to 100 μM of NaHS. A significant reduction in catalase (CAT) activity was observed in the root system, which is due to Cd concentration inside tissues. Results suggested that NaHS helps to decrease the toxic effect of Cd on the growth and development of plants.Graphical abstract
Dietary methionine restriction (MR) increases longevity by improving health. In experimental models, MR is accompanied by decreased cystathionine β-synthase activity and increased cystathionine γ-lyase activity. These enzymes are parts of the transsulfuration pathway which produces cysteine and 2-oxobutanoate. Thus, the decrease in cystathionine β-synthase activity is likely to account for the loss of tissue cysteine observed in MR animals. Despite this decrease in cysteine levels, these tissues exhibit increased H2S production which is thought to be generated by β-elimination of the thiol moiety of cysteine, as catalyzed by cystathionine β-synthase or cystathionine γ-lyase. Another possibility for this H2S production is the cystathionine γ-lyase-catalyzed β-elimination of cysteine persulfide from cystine, which upon reduction yields H2S and cysteine. Here, we demonstrate that MR increases cystathionine γ-lyase production and activities in the liver and kidneys, and that cystine is a superior substrate for cystathionine γ-lyase catalyzed β-elimination as compared to cysteine. Moreover, cystine and cystathionine exhibit comparable Kcat/Km values (6000 M-1 s-1) as substrates for cystathionine γ-lyase-catalyzed β-elimination. By contrast, cysteine inhibits cystathionine γ-lyase in a non-competitive manner (Ki ~ 0.5 mM), which limits its ability to function as a substrate for β-elimination by this enzyme. Cysteine inhibits the enzyme by reacting with its pyridoxal 5'-phosphate cofactor to form a thiazolidine and in so doing prevents further catalysis. These enzymological observations are consistent with the notion that during MR cystathionine γ-lyase is repurposed to catabolize cystine and thereby form cysteine persulfide, which upon reduction produces cysteine.
We elucidated the structure and alternative splicing patterns of the rat cystathionine beta-synthase gene. The gene is 20-25 kilobase pairs long, and its coding region is divided into 17 exons. These are alternatively spliced, forming four distinct mRNAs (types I through IV). The predicted open reading frames encode proteins of 61.5, 39, 60, and 52.5 kDa, respectively. Exons 13 and 16 are used alternatively and mutually exclusively. Exon 13 includes a stop codon and encodes the unique carboxyl-terminal sequence found in types II and IV. Exon 16 is present only in type I. Types I and III, which differ by 42 nucleotides (exon 16), are the predominant synthase mRNA forms in rat liver. Seventeen arginine peptides from pure liver synthase matched the deduced amino acid sequences of types I and III. These two polypeptides are detectable in liver extracts; each exhibits enzymatic activity when expressed in transfected Chinese hamster cells. Synthase shows substantial sequence similarity with pyridoxal 5'-phosphate dependent enzymes from lower organisms. Similarity of synthase to Escherichia coli O-acetylserine (thiol)-lyase (cysK) is 52%; E. coli tryptophan synthase beta chain (trpB), 36%; yeast serine deaminase, 33%. Lysine 116 in synthase aligns with the established pyridoxyllysine residue of these enzymes suggesting that it is the pyridoxal 5'-phosphate binding residue.
Although long-term potentiation (LTP) in the CA1 region of the hippocampus is initiated postsynaptically by the influx of Ca2+ through N-methyl-D-aspartate receptor channels, the maintenance of LTP seems to be at least in part presynaptic. This suggests that the postsynaptic cell releases a retrograde messenger to activate the presynaptic terminals. It is likely that this messenger is membrane-permeant and reaches the presynaptic neuron by diffusion. We therefore have investigated two major membrane-permeant candidate retrograde messengers, arachidonic acid and nitric oxide (NO). Consistent with arachidonic acid or a lipoxygenase metabolite being a retrograde messenger, the phospholipase A2 and lipoxygenase inhibitor nordihydroguaiaretic acid blocked LTP in the guinea pig CA1 region in vitro. However, arachidonic acid (up to 100 microM) did not reliably produce activity-independent LTP, and activity-dependent potentiation by arachidonic acid was blocked by DL-aminophosphonovaleric acid. Since nordihydroguaiaretic acid also interferes with signal transduction involving NO, we next examined whether inhibitors of NO synthase block LTP. NG-Nitro-L-arginine blocked LTP when given in the bath, and this inhibition was partially overcome by high concentrations of L-arginine, suggesting that the inhibitor is specific to NO synthase. NG-Nitro-L-arginine and NG-methyl-L-arginine (but not NG-methyl-D-arginine) also blocked LTP when injected intracellularly, indicating that NO synthase is located in the postsynaptic cell. The NO, in turn, seems to be released into the extracellular space, since bathing the slice with hemoglobin, a protein that binds NO and is not taken up by cells, also blocked LTP. Moreover, NO enhances spontaneous presynaptic release of transmitter from hippocampal neurons in dissociated cell culture. These data favor the idea that NO might be a retrograde messenger in LTP.
Nitric oxide mediates vascular relaxing effects of endothelial cells, cytotoxic actions of macrophages and neutrophils, and influences of excitatory amino acids on cerebellar cyclic GMP. Its enzymatic formation from arginine by a soluble enzyme associated with stoichiometric production of citrulline requires NADPH and Ca2+. We show that nitric oxide synthetase activity requires calmodulin. Utilizing a 2',5'-ADP affinity column eluted with NADPH, we have purified nitric oxide synthetase 6000-fold to homogeneity from rat cerebellum. The purified enzyme migrates as a single 150-kDa band on SDS/PAGE, and the native enzyme appears to be a monomer.
Long-term potentiation (LTP) in the hippocampus is known to involve NMDA (N-methyl-D-aspartate) receptors. Since activation of NMDA receptors in the cerebellum results in the formation of nitric oxide (NO), we studied the possible involvement of this messenger in hippocampal synaptic plasticity. We report here that the NO-synthase inhibitor, L-N omega-nitro-arginine, blocks LTP and that sodium nitroprusside, which releases NO, produces a long-lasting enhancement in synaptic efficacy which is not additive with tetanus-induced LTP.
A cDNA clone for cystathionine gamma-lyase was isolated from a rat cDNA library in lambda gt11 by screening with a monospecific antiserum. The identity of this clone, containing 600 bp proximal to the 3'-end of the gene, was confirmed by positive hybridization selection. Northern-blot hybridization showed the expected higher abundance of the corresponding mRNA in liver than in brain. Two further cDNA clones from a plasmid pcD library were isolated by colony hybridization with the first clone and were found to contain inserts of 1600 and 1850 bp. One of these was confirmed as encoding cystathionine gamma-lyase by hybridization with two independent pools of oligodeoxynucleotides corresponding to partial amino acid sequence information for cystathionine gamma-lyase. The other clone (estimated to represent all but 8% of the 5'-end of the mRNA) was sequenced and its deduced amino acid sequence showed similarity to those of the Escherichia coli enzymes cystathionine beta-lyase and cystathionine gamma-synthase throughout its length, especially to that of the latter.
Carbon monoxide, an activator of guanylyl cyclase, is formed by the action of the enzyme heme oxygenase. By in situ hybridization in brain slices, discrete neuronal localization of messenger RNA for the constitutive form of heme oxygenase throughout the brain has been demonstrated. This localization is essentially the same as that for soluble guanylyl cyclase messenger RNA. In primary cultures of olfactory neurons, zinc protoporphyrin-9, a potent selective inhibitor of heme oxygenase, depletes endogenous guanosine 3',5'-monophosphate (cGMP). Thus, carbon monoxide, like nitric oxide, may be a physiologic regulator of cGMP. These findings, together with the neuronal localizations of heme oxygenase, suggest that carbon monoxide may function as a neurotransmitter.
Hydrogen sulfide (H2S), which is well known as a toxic gas, is produced endogenously from L-cysteine in mammalian tissues. H2S is present at relatively high levels in the brain, suggesting that it has a physiological function. Two other gases, nitric oxide and carbon monoxide, are also endogenously produced and have been proposed as neuronal messengers in the brain. In this work we show the following: (1) an H2S-producing enzyme, cystathionine beta-synthase (CBS), is highly expressed in the hippocampus; (2) CBS inhibitors hydroxylamine and amino-oxyacetate suppress the production of brain H2S; and (3) a CBS activator, S-adenosyl-L-methionine, enhances H2S production, indicating that CBS contributes to the production of endogenous H2S. We also show that physiological concentrations of H2S selectively enhance NMDA receptor-mediated responses and facilitate the induction of hippocampal long-term potentiation. These observations suggest that endogenous H2S functions as a neuromodulator in the brain.
Nitric oxide (NO) released by vascular endothelial cells accounts for the relaxation of strips of vascular tissue1 and for the inhibition of platelet aggregation2 and platelet adhesion3 attributed to endothelium-derived relaxing factor4. We now demonstrate that NO can be synthesized from L-arginine by porcine aortic endothelial cells in culture. Nitric oxide was detected by bioassay5, chemiluminescence1 or by mass spectrometry. Release of NO from the endothelial cells induced by bradykinin and the calcium ionophore A23187 was reversibly enhanced by infusions of L-arginine and L-citrulline, but not D-arginine or other close structural analogues. Mass spectrometry studies using 15N-labelled L-arginine indicated that this enhancement was due to the formation of NO from the terminal guanidino nitrogen atom(s) of L-arginine. The strict substrate specificity of this reaction suggests that L-arginine is the precursor for NO synthesis in vascular endothelial cells.
1. The catalytic properties of extensively purified preparations of chicken liver serine sulphhydrase (I; EC 4.2.1.22) and rat liver cystathionine β-synthase (II; EC 4.2.1.13) have been investigated in parallel. These two enzymes catalysed similar sets of reactions involving replacement of polar groups in l-serine, β-substituted analogues of serine, l-cysteine or its derivatives, on incubation with a variety of mercapto compounds, resulting in production of corresponding l-cysteine thioethers. Both enzymes failed to catalyse α,β-elimination reactions.
β-Cyanoalanine, the neurotoxin naturally present in various species of Vicia (vetch), is shown to be an effective inhibitor in vitro of rat liver cystathionase. Inhibition was reversible with increasing amounts of substrate, and no evidence of an inhibitor-pyridoxal phosphate interaction was found. Structure-activity studies suggest that the cyano group and the N-unsubstituted amino acid of l configuration are probably essential structural features of the inhibition.
Endothelium-derived relaxing factor (EDRF) is a labile humoral agent which mediates the action of some vasodilators. Nitrovasodilators, which may act by releasing nitric oxide (NO), mimic the effect of EDRF and it has recently been suggested by Furchgott that EDRF may be NO. We have examined this suggestion by studying the release of EDRF and NO from endothelial cells in culture. No was determined as the chemiluminescent product of its reaction with ozone. The biological activity of EDRF and of NO was measured by bioassay. The relaxation of the bioassay tissues induced by EDRF was indistinguishable from that induced by NO. Both substances were equally unstable. Bradykinin caused concentration-dependent release of NO from the cells in amounts sufficient to account for the biological activity of EDRF. The relaxations induced by EDRF and NO were inhibited by haemoglobin and enhanced by superoxide dismutase to a similar degree. Thus NO released from endothelial cells is indistinguishable from EDRF in terms of biological activity, stability, and susceptibility to an inhibitor and to a potentiator. We suggest that EDRF and NO are identical.
In an attempt at evaluating the therapeutic effects of cysteine depletion on the growth of cysteine-dependent L1210 leukemia, the effects in vivo of a cysteine- and cystine-degrading enzyme as well as the combined use of an inhibitor of cysteine biosynthesis with cystine-free diets, were measured in mice. The kinetic properties of rat liver γ-cystathionase (EC 4.2.1.13) and Enterobacter cloacae cysteine desulfhydrase (EC 4.4.1.1) toward the catabolism of cystine and cysteine, as well as the inhibitory properties of some possible physiological components, are described. A novel and sensitive assay for the detection of cysteine in biological fluids was used to measure the ability of these enzymes to deplete plasma cysteine levels when injected into normal mice. Cysteine desulfhydrase caused no alteration in mouse plasma cysteine concentrations, presumably due to rapid clearance ( less than 10 min) of the enzyme. γ-Cystathionase caused a 60 per cent drop in plasma cysteine concentrations which returned to normal with the clearance of the enzyme (). The properties and limitations of these enzymes are discussed within the context of their ability to deplete plasma cys(e)ine in vivo. When propargylglycine, an effective covalent inhibitor of γ-cystathionase, both in vitro (Ki = 0.1 mM, saturating ) and in vivo, was combined with diets lacking cystine, no reduction in plasma cysteine or increase in survival of mice bearing L1210 leukemia could be observed. The compound would induce a cystathioninemia and a cystathioninuria when given to mice and was not toxic in cell culture or in animals when tested with an adequate source of cystine, but was highly toxic in the absence of cystine.
Long-term potentiation is a long-lasting, use-dependent increase in the strength of synaptic connections. We investigated the role of nitric oxide (NO) in determining the duration of potentiation induced by high frequency stimulation of afferents in the CA1 region of the rat hippocampus. The calcium/calmodulin-dependent production of NO can be initiated by activation of excitatory amino acid receptors and results in increased levels of cGMP in target cells. Here we report that only a relatively short-term potentiation can be induced in the presence of nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor. The effects of L-NAME on the duration of potentiation are partially reversed by coadministration of L-arginine, a precursor of neuronal NO, and by dibutyryl cGMP. Hemoglobin, which binds extracellular NO, also shortens the duration of stimulus-induced potentiation. The results suggest a role for NO in the maintenance of activity-dependent synaptic enhancements, possibly via the generation of cGMP.
The reported relaxing effect of CO on various smooth muscle tissues could also be found in guinea pig ileal strips. The effect was pronounced after precontraction with 10-100 nM acetylcholine and rather small with KCl. Based on the photoreversibility of the CO-dependent relaxation, a photochemical action spectrum was established which showed a maximum at around 422 nm. This definitely rules out the participation of a cytochrome P450 dependent process as postulated for the CO induced relaxation of lamb ductus arteriosus. With regard to the potency of KCN and antimycin A to relax ileal smooth muscle, the involvement of respiratory chain inhibition was reinvestigated, but no indication for such a mechanism could be obtained. In analogy to the mechanism of CO-inhibition of platelet activation we found that CO about doubles cGMP levels in guinea pig ileal strips. This is similar to NO which also leads to effective relaxation. We propose that CO can be considered and experimentally used as a convenient activator of soluble G-cyclase in smooth muscle and platelets.
Long-term potentiation (LTP) of synaptic transmission is a widely studied model of neuronal plasticity. The induction of LTP is known to require processes in the postsynaptic neuron, while experimental evidence suggests that the expression of LTP may occur in the presynaptic terminal. This has led to speculation that a retrograde messenger travels from the post- to the presynaptic cell during induction of LTP. Extracellular application or postsynaptic injection of two inhibitors of nitric oxide synthase, N-nitro-L-arginine or NG-methyl-L-arginine, blocks LTP. Extracellular application of hemoglobin, which binds nitric oxide, also attenuates LTP. These findings suggest that nitric oxide liberated from postsynaptic neurons may travel back to presynaptic terminals to cause LTP expression.
Previous studies have established that nitrovasodilators potentiate the inhibition of platelet function by activators of adenylyl cyclase, but uncertainty exists as to whether a comparable effect is seen in vascular smooth muscle. We initially studied the effects of the nitrovasodilators, sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), on the relaxation by isoprenaline of rat aortic smooth muscle that had been precontracted by phenylephrine. Concentrations of SNP (0.25 nM) and SIN-1 (30 nM) that relaxed aortic smooth muscle less than 30% alone, caused significant (3-fold) decreases in the IC50 values for isoprenaline. The cAMP phosphodiesterase inhibitors, cilostamide (20 nM) and Ro 20-1724 (10 microM), caused comparable reductions in the IC50 values for isoprenaline. At these concentrations, each of the four compounds also increased the maximum relaxation achieved with isoprenaline. Even more marked synergistic interactions were observed between isoprenaline and either the nitrovasodilators or the cAMP phosphodiesterase inhibitors when these compounds were added simultaneously before contraction of aortic smooth muscle by phenylephrine. Thus, concentrations of SNP (5 nM), SIN-1 (1 microM), cilostamide (1 microM) and Ro 20-1724 (100 microM) that inhibited contraction by less than 30% decreased the IC50 values for isoprenaline by 8- to 10-fold. At the above concentrations, these compounds each caused a supra-additive inhibition of contraction when added with 100 nM isoprenaline. Thus, synergism between nitrovasodilators and isoprenaline, an activator of adenylyl cyclase, could be detected in vascular smooth muscle and was particularly marked when inhibition of contraction was studied. This action of nitrovasodilators resembled that of inhibitors of cAMP phosphodiesterase.
A sandwich preparation was obtained by placing a segment of the endothelium-free guinea pig coronary artery over the intact carotid artery with the objective being to determine whether the endothelium-dependent hyperpolarization by acetylcholine chloride (ACh) is mediated by a humoral factor. ACh hyperpolarized the sandwiched coronary smooth muscle membrane, the amplitude being larger than that of the carotid artery and smaller than that of the intact coronary artery. When spontaneously active smooth muscles (stomach antrum or portal vein) were used as the donor tissue, no electrical signal was transducted to the overlying coronary smooth muscles. In the sandwiched coronary artery, the ACh-induced hyperpolarization was not inhibited by ouabain, indomethacin, or nitroarginine. Pinacidil hyperpolarized the coronary smooth muscle membrane; the responses were inhibited by glybenclamide but not by tetraethylammonium chloride (TEA). The ACh-induced hyperpolarization was inhibited by TEA but not by glybenclamide. These results suggest that the ACh-induced hyperpolarization is mediated by an endothelium-derived humoral substance (endothelium-derived hyperpolarizing factor). Possible contribution of Ca-dependent K channels, but not ATP-sensitive K channels, to the endothelium-derived hyperpolarizing factor-induced hyperpolarization was considered.
Studies of cultured bovine aortic endothelial cells using quantitative chemiluminescence techniques have shown that the amount of nitric oxide released under basal conditions, or in response to either bradykinin or the calcium ionophore A23187 is insufficient to account for the vasorelaxant activities of the endothelium-derived relaxing factor (EDRF) derived from the same source. This observation contradicts previous suggestions that nitric oxide and EDRF are the same compound, but may be explained if EDRF is a compound that contains nitric oxide within its structure but is a much more potent vasodilator than nitric oxide. Such a molecule could be one of several nitrosothiols which may yield nitric oxide after a one-electron reduction. The present experiments were carried out to test the possibility that the biological activities of the endothelium-derived relaxing factor might more closely resemble those of one of these compounds, S-nitrosocysteine, than nitric oxide. Nitric oxide release from cultured bovine aortic endothelial cells was detected by chemiluminescence and bioassay experiments compared the vasodilator potencies of nitric oxide, S-nitrosocysteine, and EDRF. The results suggest that EDRF is much more likely to be a nitrosylated compound such as a nitrosothiol than authentic nitric oxide.
Experiments were designed to determine whether endothelium‐dependent relaxing factor(s) released by acetylcholine from the canine femoral artery influences the membrane potential of coronary arterial smooth muscle.
The membrane potential was recorded in small canine coronary arteries (internal diameter ≤ 500 μm; without endothelium) by means of intracellular microelectrodes. The organ bath also contained a strip of left descending coronary artery without endothelium in which isometric force was measured to bioassay relaxing factors(s) as well as segments of femoral artery with endothelium, which served as the source of endothelium‐derived relaxing factor(s).
Acetylcholine induced endothelium‐dependent, transient hyperpolarizations and relaxations that were not affected by indomethacin.
Inhibition of the sodium‐potassium pump by ouabain or potassium‐free solution did not inhibit the relaxation to acetylcholine but prevented the corresponding hyperpolarization.
Activation of the sodium‐potassium pump of the smooth muscle cells by readmission of potassium ions after incubation in potassium‐free solution caused relaxation and marked hyperpolarization.
These results suggest that endothelium‐derived relaxing factor(s) induces hyperpolarization of vascular smooth muscle of the canine coronary artery, possibly by activation of sodium‐potassium pumping, but that this effect on the cell membrane may only partially explain endothelium‐dependent relaxations evoked by acetylcholine.
In biological systems oxidation of heme is carried out by two isozymes of the microsomal heme oxygenase, HO-1 and HO-2. HO-1 is the commonly known heme oxygenase, the activity of which can be induced by up to 100-fold in response to a wide variety of stimuli (metals, heme, hormones, etc.). HO-2 was only recently discovered, and the isozyme appears to be uninducible. The two forms are products of two different genes and differ in their tissue expression. The primary structure of HO-1 and an HO-2 fragment of 91 amino acid residues show only 58% homology, but share a region with 100% secondary structure homology. This region is believed to be the catalytic site. Most likely, HO-1 gene is regulated in the same manner as metallothione in the gene. HO-1 has a heat shock regulatory element, and possibly many promoter elements, which bind to respective inducers and cause transcription of the gene. In vivo induction of HO-1 activity in the liver is accompanied by decreases in the total P-450 levels and, in a reconstituted system, cytochrome P-450b heme can be quantitatively converted to biliverdin by HO-1 and HO-2. The enzyme activity is inhibited in vivo for extended periods subsequent to binding of Zn- and Sn- protoporphyrins. This property appears useful for the suppression of bilirubin production. The metalloporphyrins, however, are not innocuous and cause major disruptions in cellular metabolism. In this review recent findings on heme oxygenase are highlighted.
This chapter briefly summarizes the mammalian metabolism of methionine and cysteine with emphasis on the chemical transformations of sulfur. Methionine and cysteine, the two sulfur-containing protein amino acids, are metabolized by a variety of reactions and pathways to at least two dozen intermediates and products. Some of these metabolites serve functions that are essential for survival of the organism. Methionine and cysteine have, in addition, important catalytic roles in the active sites of many enzymes. Several of these metabolic processes and catalytic functions exploit unique aspects of sulfur chemistry to accomplish biochemical transformations that would be difficult or impossible to effect in the absence of the sulfur amino acids. Methionine metabolism is initiated by the formation of S- adenosylmethionine (AdoMet), a sulfonium compound in which each of the carbons attached to sulfur is activated toward nucleophilic attack. Cysteine is synthesized by mammals. Cysteine sulfur is derived from methionine whereas the carbon and nitrogen of cysteine are derived from serine.
1. The interactions between endothelium-derived nitric oxide (NO) and prostacyclin as inhibitors of platelet aggregation were examined. 2. Porcine aortic endothelial cells treated with indomethacin and stimulated with bradykinin (10-100 nM) released NO in quantities sufficient to account for the inhibition of platelet aggregation attributed to endothelium-derived relaxing factor (EDRF). 3. In the absence of indomethacin, stimulation of the cells with bradykinin (1-3 nM) released small amounts of prostacyclin and EDRF which synergistically inhibited platelet aggregation. 4. EDRF and authentic NO also caused disaggregation of platelets aggregated either with collagen or with U46619. 5. A reciprocal potentiation of both the anti- and the dis-aggregating activity was also observed between low concentrations of prostacyclin and authentic NO or EDRF released from endothelial cells. 6. It is likely that interactions between prostacyclin and NO released by the endothelium play a role in the homeostatic regulation of platelet-vessel wall interactions.
Despite its very potent vasodilating action in vivo, acetylcholine (ACh) does not always produce relaxation of isolated preparations of blood vessels in vitro. For example, in the helical strip of the rabbit descending thoracic aorta, the only reported response to ACh has been graded contractions, occurring at concentrations above 0.1 muM and mediated by muscarinic receptors. Recently, we observed that in a ring preparation from the rabbit thoracic aorta, ACh produced marked relaxation at concentrations lower than those required to produce contraction (confirming an earlier report by Jelliffe). In investigating this apparent discrepancy, we discovered that the loss of relaxation of ACh in the case of the strip was the result of unintentional rubbing of its intimal surface against foreign surfaces during its preparation. If care was taken to avoid rubbing of the intimal surface during preparation, the tissue, whether ring, transverse strip or helical strip, always exhibited relaxation to ACh, and the possibility was considered that rubbing of the intimal surface had removed endothelial cells. We demonstrate here that relaxation of isolated preparations of rabbit thoracic aorta and other blood vessels by ACh requires the presence of endothelial cells, and that ACh, acting on muscarinic receptors of these cells, stimulates release of a substance(s) that causes relaxation of the vascular smooth muscle. We propose that this may be one of the principal mechanisms for ACh-induced vasodilation in vivo. Preliminary reports on some aspects of the work have been reported elsewhere.
The objective of this study was to examine the relationship between relaxation and cyclic GMP accumulation in bovine intrapulmonary artery in response to acetylcholine. Acetylcholine relaxed or contracted isolated arterial rings possessing an intact or damaged endothelial layer, respectively. Acetylcholine-elicited relaxation of phenylephrine-precontracted rings was accompanied by a time- and concentration-dependent accumulation of arterial cyclic GMP but not of cyclic AMP. Relaxation and cyclic GMP accumulation were both antagonized by atropine and methylene blue. Quinacrine, on the other hand, antagonized relaxation without altering the accumulation of cyclic GMP. Nitroglycerin and S-nitroso-N-acetylpenicillamine also relaxed intrapulmonary rings possessing an intact endothelium and caused a concomitant rise in cyclic GMP but not cyclic AMP levels. Both effects were antagonized by methylene blue but not by atropine or quinacrine. Arterial rings prepared with damaged endothelium contracted to acetylcholine but relaxed to nitroglycerin and S-nitroso-N-acetylpenicillamine. Acetylcholine-elicited contraction was markedly inhibited by atropine, partially inhibited by quinacrine and potentiated by methylene blue. Cyclic GMP levels were increased in endothelium-damaged rings contracted by acetylcholine and this was inhibited both by atropine and methylene blue but not by quinacrine. The effects of quinacrine on acetylcholine-elicited changes in tone appear to be nonspecific. These observations indicate that relaxation of bovine intrapulmonary artery by both acetylcholine and nitrogen oxide-containing vasodilators is closely associated with the accumulation of cyclic GMP. Moreover, there appears to be a clear dissociation between contraction and cyclic GMP accumulation elicited by acetylcholine.
The information available on the biological activity of hydrogen sulfide has been examined for present status of critical results pertaining to the toxicity of hydrogen sulfide. This review of the literature is intended as an evaluative report rather than an annotated bibliography of all the source material examined on hydrogen sulfide. The information was selected as it might relate to potential toxic effects of hydrogen sulfide to man and summarized, noting information gaps that may require further investigation. Several recommendations are listed for possible consideration for either toxicological research or additional short- and long-term tests. Two bibliographies have been provided to assist in locating references considered in this report: (1) literature examined but not cited and (2) reference citations. The majority of the references in the first bibliography were considered peripheral information and less appropriate for inclusion in this report.
The contribution of cystathionine gamma-lyase, cystathionine beta-synthase and cysteine aminotransferase coupled to 3-mercaptopyruvate sulphurtransferase to cysteine desulphhydration in rat liver and kidney was assessed with four different assay systems. Cystathionine gamma-lyase and cystathionine beta-synthase were active when homogenates were incubated with 280 mM-L-cysteine and 3 mM-pyridoxal 5'-phosphate at pH 7.8. Cysteine aminotransferase in combination with 3-mercaptopyruvate sulphurtransferase catalysed essentially all of the H2S production from cysteine at pH 9.7 with 160 mM-L-cysteine, 2 mM-pyridoxal 5'-phosphate, 3 mM-2-oxoglutarate and 3 mM-dithiothreitol. At more-physiological concentrations of cysteine (2 mM) cystathionine gamma-lyase and cystathionine beta-synthase both appeared to be active in cysteine desulphhydration, whereas the aminotransferase pathway did not. The effect of inhibition of cystathionine gamma-lyase by a suicide inactivator, propargylglycine, in the intact rat was also investigated; there was no significant effect of propargylglycine administration on the urinary excretion of total 35S, 35SO4(2-) or [35S]taurine formed from labelled dietary cysteine.
Nitric oxide (NO) and carbon monoxide (CO) may act as retrograde messages for long-term potentiation (LTP) in the hippocampus. Zinc protoporphyrin IX, an inhibitor of the enzyme that produces CO, blocked induction of LTP in the CA1 region of hippocampal slices. Application of either NO or CO to slices produced a rapid and long-lasting increase in the size of evoked synaptic potentials if, and only if, the application occurred at the same time as weak tetanic stimulation. This long-term enhancement was spatially restricted to synapses from active presynaptic fibers and appeared to involve mechanisms utilized by LTP, occluding the subsequent induction of LTP by strong tetanic stimulation. The enhancement by NO and CO was not blocked by an N-methyl-D-aspartate (NMDA) receptor blocker, suggesting that NO and CO act downstream from the NMDA receptor. Also, CO produced long-term enhancement when paired with low-frequency stimulation. These results are consistent with the hypothesis that NO and CO, either alone or in combination, serve as retrograde messages that produce activity-dependent presynaptic enhancement during LTP.
Evidence that carbon monoxide can serve as an intercellular messenger in brain, a role much like that demonstrated for nitric oxide in various tissue, prompted us to investigate whether carbon monoxide participates in long-term potentiation (LTP), the cellular mechanism that may underlie certain forms of learning and memory. Although LTP is triggered in the postsynaptic neuron, at least some fraction of LTP is expressed presynaptically as an increase in the quantity of neurotransmitter released. Thus, a retrograde signal must form the communication link between the postsynaptic site of induction and the presynaptic site of expression. To test whether carbon monoxide might act as a retrograde signal in LTP, we have investigated the effect on LTP of inhibitors of the enzyme haem oxygenase-2, which catalyses the production of carbon monoxide in the brain. We find that these inhibitors prevent the induction of LTP and have no effect on one form of long-term depression. Furthermore, they will reverse LTP that is already established.
Carbon monoxide (CO) is a low molecular weight oxide produced endogenously from fatty acids and heme protein. A physiological role for CO has been suggested for vascular smooth muscle, hemostasis, and olfactory neurons, but direct evidence is lacking. Heme oxygenase, which catalyzes the formation of CO from heme proteins, is present in small intestinal smooth muscle. The effect of 1% CO on whole cell currents in normal human jejunal circular muscle cells was studied with the use of a perforated patch-clamp technique. A 1% CO-containing Krebs solution caused an initial and transient increase in whole cell current in 20 of 22 cells tested (175 +/- 40%, mean +/- SE) and a transient hyperpolarization (15.6 +/- 3.6 mV, mean +/- SE) of the membrane potential. During prolonged recordings, 1% CO evoked ongoing cyclic increases and decreases in the whole cell current. Each current increase was accompanied by a sharp membrane hyperpolarization. These data suggest that CO may modulate whole cell potassium current and membrane potential.
The flow-induced relaxation of a branch of the rabbit middle cerebral artery was examined to determine if an endothelial-independent as well as -dependent component occurs in pial as well as systemic small arteries and the possible role of products of the cyclooxygenase and the L-arginine nitric oxide synthase pathways.
Intraluminal flow was achieved by the infusion of a tissue bath solution into isometrically mounted rabbit pial arteries in a resistance artery myograph through a small pipette.
Intraluminal flow caused relaxation of the artery segment precontracted with 10 microM histamine. Treatment of endothelium-intact vessels with the nitric oxide synthase inhibitors NG-nitro-L-arginine (L-NNA) (100 microM) or NG-nitro-L-arginine methyl ester (L-NAME) (0.3 mM) significantly reduced the relaxation at flow rates of 5-30 microliters/min. This effect was partially reversed by 1 mM L-arginine. These inhibitors had no effect on the flow-induced relaxation of endothelium-denuded vessels. L-NNA did not influence the relaxation to 1 and 3 microM papaverine. Exposure to 10 microM aspirin, 10 microM indomethacin, or 300 nM tetrodotoxin had no effect on the flow-induced relaxation of either endothelium-intact or -denuded vessels (n = 6). Flow-induced relaxation was attenuated, but not abolished, by removal of the cerebrovascular endothelium. This reduction was not statistically significant.
These results show that intraluminal flow caused relaxation of a branch of the rabbit middle cerebral artery, in part through a mechanism sensitive to inhibitors of nitric oxide synthase, most likely the generation of nitric oxide from the vascular endothelium. The major component of the relaxant response is independent of the endothelium and of nitric oxide synthesis through an L-NNA- or L-NAME-sensitive mechanism. The relaxation does not involve cyclooxygenase products nor neurogenic mediators. These results suggest that pial arteries, like those of the rabbit ear, exhibit a novel mechanism for the flow-induced relaxation of agonist-induced tone that is intrinsic to the tissues of the vascular wall subjacent to the endothelium.
Long-term potentiation of synaptic transmission in the hippocampus is the primary experimental model for investigating the synaptic basis of learning and memory in vertebrates. The best understood form of long-term potentiation is induced by the activation of the N-methyl-D-aspartate receptor complex. This subtype of glutamate receptor endows long-term potentiation with Hebbian characteristics, and allows electrical events at the postsynaptic membrane to be transduced into chemical signals which, in turn, are thought to activate both pre- and postsynaptic mechanisms to generate a persistent increase in synaptic strength.
Patch-clamp recordings from rabbit corneal epithelial cells have identified a large-conductance (167 pS in symmetrical 150 mM KCl) K channel that is the major contributor to the whole cell current (J. L. Rae and G. Farrugia. J. Membr. Biol. 129: 81-87, 1992). We report here on the regulation of this channel by changes in cellular osmolality and/or volume. Exchanging the bath solution with a hyposmotic (225 or 150 mosM) solution resulted in cellular swelling and selective activation of the K current (126 +/- 86 and 273 +/- 184% increase, respectively). Hyperosmotic solution changes (380 mosM) resulted in cell shrinkage and deactivation of the K current (44.2 +/- 21% decrease). Similar increases in the cell volume and whole cell current were observed on increasing (in perforated patch experiments) the chloride ion concentration (50 mM) in the pipette intracellular solution (127 +/- 63% increase). These changes were accompanied by marked shifts in the resting membrane voltage. We conclude that the K channels in these cells can respond to alteration in cellular osmolality or volume, resulting in changes in the whole cell current and resting voltage.
The incorporation of sulfide into methylene blue in the presence of acidic N,N-dimethyl-p-phenylenediamine and ferric chloride has been utilized to provide a direct determination for sulfide at concentrations of 2 to 80 mμmoles per milliliter. No distillation step is required. At concentrations of 10−3M, only slight interference by organic thiols was observed. Advantages in sensitivity, specificity, color stability, and convenience are offered over earlier methods.
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Y. Sagara, Y. Liu and Y. Kimura for reading this manuscript. This
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