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Hydrogen sulphide is an inhibitor of L-type calcium channels and mechanical contraction in rat cardiomyocytes
Abstract
Hydrogen sulphide (H(2)S) is an endogenously generated gaseous transmitter that has recently been suggested to regulate cardiovascular functions. To date, there is no direct evidence for a potential role of H(2)S in regulating calcium channels in the heart. The present study aims to examine the hypothesis that H(2)S is a novel inhibitor of the L-type calcium channel current (I(Ca,L)).
Electrophysiological measurements were performed in cardiomyocytes isolated from Wistar-Kyoto and spontaneously hypertensive rats. Bath application of 100 microM NaHS (a H(2)S donor) significantly reduced the time required for the repolarization of the action potential. Inhibition of the peak I(Ca,L) by NaHS was determined to be concentration-dependent (25, 50, 100, 200, and 400 microM). NaHS inhibited the recovery from depolarization-induced inactivation. Electric field-induced [Ca(2+)]i transients and contraction of single cardiomyocytes and isolated papillary muscles were reduced by NaHS treatment. In contrast, caffeine induced an increase in [Ca(2+)]i that was not altered by NaHS. NaHS had no effect on the K(ATP) current or on the levels of cAMP and cGMP in the current study.
H(2)S is a novel inhibitor of L-type calcium channels in cardiomyocytes. Moreover, H(2)S-induced inhibition of [Ca(2+)]i appears to be a secondary effect owing to its initial action towards I(Ca,L). The inhibitory effect of H(2)S on I(Ca,L) requires further investigation, particularly in the exploration of new pathways involved in cardiac calcium homeostasis and disease pathology.
... In cardiac myocytes, the RyR2 receptor is responsible for mediating sarcoplasmic calcium release upon calcium influx via activated L-type calcium channels (calcium-induced calcium release). The C3635 residue in RyR1 is a conserved cysteine among all three RyR isoforms; in the case of RyR2, the corresponding cysteine residue is C3602 [145,146]. In contrast to RyR1 channel activation by NO via S-nitrosylation of C3635, NO-mediated S-nitrosylation of C3602 in RyR2 does not alter channel activity; however, nitrosylation by S-nitrosoglutathione (GSNO), another biological source of NO, enhances the open probability of the channel [145,146]. ...
... The C3635 residue in RyR1 is a conserved cysteine among all three RyR isoforms; in the case of RyR2, the corresponding cysteine residue is C3602 [145,146]. In contrast to RyR1 channel activation by NO via S-nitrosylation of C3635, NO-mediated S-nitrosylation of C3602 in RyR2 does not alter channel activity; however, nitrosylation by S-nitrosoglutathione (GSNO), another biological source of NO, enhances the open probability of the channel [145,146]. Although the specific sites of S-nitrosylation in RyR2 channels have yet to be elucidated, it has been shown in nNOS knockout mice that hyponitrosylation of the RyR2 channel leads to arrhythmogenesis causing sudden cardiac death in the mice [135]. ...
... H 2 S has been recognized to confer cardioprotective effects against oxidative stress, apoptosis, and necrosis [154]. In rat heart tissue, application of NaSH resulted in an inhibition of LTCC function and was found to induce negative inotropy in cardiomyocytes [145,146]. In a later study, dithiothreitol (DTT; a reducing agent that breaks disulfide bridges between cysteine residues into sulfhydryl groups) was found to reverse the inhibition of NaSH on LTCCs while diamide (DM; an oxidizing agent that creates sulfide bridges between cysteine groups) prevented alterations of NaSH on LTCC calcium currents [169]. ...
Our understanding of the gaseous signaling molecules that play important roles in diverse physiological processes keeps expanding. These gas molecules, also called gasotransmitters, include NO, H2S, 1O2, CO, and CO2 and are generated within the cell through enzymatic pathways and photochemical reactions. These molecules are chemically unstable and directly react with amino acids such as cysteine, histidine, and so on. Compared to well-characterized reactive oxygen species (ROS), including H2O2, ONOO-, O2-, and OH·, the gasotransmitters are in general less polar and show higher solubility in hydrophobic environments like the lipid membrane. Correspondingly, accumulating evidence has begun to unveil the broad impacts of these gaseous molecules on the function of membrane proteins, including ion channels. This review summarizes the major physicochemical characteristics of representative gasotransmitters and their regulation of ion channel functions.
... Although epidemiological research has shown association between ambient H 2 S and cardiovascular disease hospitalization and mortality (Godleski et al., 2000;Bates et al., 2002;Finnbjornsdottir et al., 2015Finnbjornsdottir et al., , 2016, how it affects the functions of the cardiovascular system is unclear. Recent studies at the cellular level suggested that NaHS (H 2 S donor) can significantly shorten the action potential duration (APD) of cardiomyocytes, possibly by affecting the ATP-sensitive K + channel (K-ATP) (Bian et al., 2006;Johansen et al., 2006;Zhang et al., 2007;Abramochkin et al., 2009;Chan et al., 2018) and the L-type Ca 2+ channel (Ca-L) (Sun et al., 2008;Zhang et al., 2012). Experiments on rats have characterized the dosedependent effects of NaHS on ionic currents of the two channels, I CaL and I K,ATP (Sun et al., 2008;Zhong et al., 2010), and suggested that low doses of NaHS (i.e., 100 and 150 µmol/L) abbreviated APD by either an enhanced I K,ATP (Zhong et al., 2010) or a reduced I CaL (Sun et al., 2008). ...
... Recent studies at the cellular level suggested that NaHS (H 2 S donor) can significantly shorten the action potential duration (APD) of cardiomyocytes, possibly by affecting the ATP-sensitive K + channel (K-ATP) (Bian et al., 2006;Johansen et al., 2006;Zhang et al., 2007;Abramochkin et al., 2009;Chan et al., 2018) and the L-type Ca 2+ channel (Ca-L) (Sun et al., 2008;Zhang et al., 2012). Experiments on rats have characterized the dosedependent effects of NaHS on ionic currents of the two channels, I CaL and I K,ATP (Sun et al., 2008;Zhong et al., 2010), and suggested that low doses of NaHS (i.e., 100 and 150 µmol/L) abbreviated APD by either an enhanced I K,ATP (Zhong et al., 2010) or a reduced I CaL (Sun et al., 2008). Although it is possible that other channel currents may be involved in their experiments owing to the use of a high concentration of intracellular ATP or channel blockers, it is unclear if the observed increase in I K,ATP or decrease in I CaL is sufficient to account for the abbreviation of the APD by NaHS. ...
... Recent studies at the cellular level suggested that NaHS (H 2 S donor) can significantly shorten the action potential duration (APD) of cardiomyocytes, possibly by affecting the ATP-sensitive K + channel (K-ATP) (Bian et al., 2006;Johansen et al., 2006;Zhang et al., 2007;Abramochkin et al., 2009;Chan et al., 2018) and the L-type Ca 2+ channel (Ca-L) (Sun et al., 2008;Zhang et al., 2012). Experiments on rats have characterized the dosedependent effects of NaHS on ionic currents of the two channels, I CaL and I K,ATP (Sun et al., 2008;Zhong et al., 2010), and suggested that low doses of NaHS (i.e., 100 and 150 µmol/L) abbreviated APD by either an enhanced I K,ATP (Zhong et al., 2010) or a reduced I CaL (Sun et al., 2008). Although it is possible that other channel currents may be involved in their experiments owing to the use of a high concentration of intracellular ATP or channel blockers, it is unclear if the observed increase in I K,ATP or decrease in I CaL is sufficient to account for the abbreviation of the APD by NaHS. ...
Hydrogen sulfide (H2S), an ambient air pollutant, has been reported to increase cardiac events in patients with cardiovascular diseases, but the underlying mechanisms remain not elucidated. This study investigated the pro-arrhythmic effects of H2S in healthy and ischemic conditions. Experimental data of H2S effects on ionic channels (including the L-type Ca²⁺ channel and ATP-sensitive K⁺ channel) were incorporated into a virtual heart model to evaluate their integral action on cardiac arrhythmogenesis. It was shown that H2S depressed cellular excitability, abbreviated action potential duration, and augmented tissue’s transmural dispersion of repolarization, resulting in an increase in tissue susceptibility to initiation and maintenance of reentry. The observed effects of H2S on cardiac excitation are more remarkable in the ischemic condition than in the healthy condition. This study provides mechanistic insights into the pro-arrhythmic effects of air pollution (H2S), especially in the case with extant ischemic conditions.
... The major finding of the present study is that H 2 S greatly affected the electrophysiology of isolated cardiomyocytes beyond the inhibition of L-type Ca 2+ currents (I Ca,L ) that we and others have previously reported [43,74,93]. A significant alteration of Na + /Ca 2+ exchange and depolarizationactivated K + currents was effected by toxic level of H 2 S, i.e., at concentrations that in vivo lead to lethal cardiogenic shock and several types of arrhythmias [73]. ...
... Typically, whenever solutions of H 2 S at concentrations ≥ 50 µM were used in isolated hearts or isolated cells, the effect was a measurable depression in cardiac contractility [43,74]. This depression is an obvious pathological and toxic change in the function at the level of both individual myocytes and the intact heart. ...
... The mechanisms by which most channels are affected at the same time remain undetermined. As recently proposed for Ca 2+ channels, H 2 S could react with cysteine residues not only in L-type Ca 2+ channels [74,93], but also in the sarcoplasmic reticulum ryanodine receptors (RyR), thereby altering the 3D configurations and function of the channels. Whether other cardiac channels can be affected through a similar mechanism remains unknown. ...
We have previously demonstrated that methylene blue (MB) counteracts the effects of hydrogen sulfide (H2S) cardiotoxicity by improving cardiomyocyte contractility and intracellular Ca²⁺ homeostasis disrupted by H2S poisoning. In vivo, MB restores cardiac contractility severely depressed by sulfide and protects against arrhythmias, ranging from bundle branch block to ventricular tachycardia or fibrillation. To dissect the cellular mechanisms by which MB reduces arrhythmogenesis and improves bioenergetics in myocytes intoxicated with H2S, we evaluated the effects of H2S on resting membrane potential (Em), action potential (AP), Na⁺/Ca²⁺ exchange current (INaCa), depolarization-activated K⁺ currents and ATP levels in adult mouse cardiac myocytes and determined whether MB could counteract the toxic effects of H2S on myocyte electrophysiology and ATP. Exposure to toxic concentrations of H2S (100 µM) significantly depolarized Em, reduced AP amplitude, prolonged AP duration at 90% repolarization (APD90), suppressed INaCa and depolarization-activated K⁺ currents, and reduced ATP levels in adult mouse cardiac myocytes. Treating cardiomyocytes with MB (20 µg/ml) 3 min after H2S exposure restored Em, APD90, INaCa, depolarization-activated K⁺ currents, and ATP levels toward normal. MB improved mitochondrial membrane potential (∆ψm) and oxygen consumption rate in myocytes in which Complex I was blocked by rotenone. We conclude that MB ameliorated H2S-induced cardiomyocyte toxicity at multiple levels: (1) reversing excitation–contraction coupling defects (Ca²⁺ homeostasis and L-type Ca²⁺ channels); (2) reducing risks of arrhythmias (Em, APD, INaCa and depolarization-activated K⁺ currents); and (3) improving cellular bioenergetics (ATP, ∆ψm).
... The state of the art in bioactive H 2 S donors is presented in recent reviews [1,14]. A series of proof-of-concept studies on the pharmacological effects of H 2 S in vitro and in vivo was performed using inorganic sulfide donors such as NaHS and Na 2 S [15][16][17][18][19][20][21][22]. These donors provide fast extracellular release of H 2 S and therefore have restricted therapeutic potential. ...
... Furthermore, NaHS and L-cysteine decreased the contractility of isolated mouse atrium, while it was partially restored by glibenclamide [42], the inhibitor of K(ATP) channels. In single cardiomyocytes isolated from rat ventricles, NaHS reduced Ca 2+ -transients and contractions as well as the action potential amplitude [17,21]. ...
Considering the important cytoprotective and signaling roles but relatively narrow therapeutic index of hydrogen sulfide (H2S), advanced H2S donors are required to achieve a therapeutic effect. In this study, we proposed glutathione dithiophosphates as new combination donors of H2S and glutathione. The kinetics of H2S formation in dithiophosphate solutions suggested a continuous H2S release by the donors, which was higher for the dithiophosphate of reduced glutathione than oxidized glutathione. The compounds, unlike NaHS, inhibited the proliferation of C2C12 myoblasts at submillimolar concentrations due to an efficient increase in intracellular H2S. The H2S donors more profoundly affected reactive oxygen species and reduced glutathione levels in C2C12 myocytes, in which these parameters were elevated compared to myoblasts. Oxidized glutathione dithiophosphate as well as control donors exerted antioxidant action toward myocytes, whereas the effect of reduced glutathione dithiophosphate at (sub-)micromolar concentrations was rather modulating. This dithiophosphate showed an enhanced negative inotropic effect mediated by H2S upon contraction of the atrial myocardium, furthermore, its activity was prolonged and reluctant for washing. These findings identify glutathione dithiophosphates as redox-modulating H2S donors with long-acting profile, which are of interest for further pharmacological investigation.
... Studies in animal models of MI, IRI and heart failure have revealed significant reductions in endogenous H 2 S production that contribute to disease progression 61 . H 2 S also protects against MI and IRI by opening K + ATP channels 23,29,[98][99][100][101] . Furthermore, H 2 S interacts with NO in a Cth −/− mouse model of heart failure 61 . ...
... Variants in L-type Ca 2+ channels are linked to a variety of arrhythmias, and sulfide donors are known to inhibit L-type Ca 2+ currents and reduce intracellular Ca 2+ concentrations 167,168 . A decrease in action potential duration (APD) was reported with sodium hydrosulfide, facilitated by the reduction in peak L-type Ca 2+ current and Ca 2+ transients 101 . Although sulfide donors are also known to modulate T-type Ca 2+ channels in the nervous system and gastrointestinal tract, no studies have been reported on the effects of H 2 S on T-type Ca 2+ currents in cardiomyocytes 114,169 . ...
Hydrogen sulfide (H2S) has emerged as a gaseous signalling molecule with crucial implications for cardiovascular health. H2S is involved in many biological functions, including interactions with nitric oxide, activation of molecular signalling cascades, post-translational modifications and redox regulation. Various preclinical and clinical studies have shown that H2S and its synthesizing enzymes - cystathionine γ-lyase, cystathionine β-synthase and 3-mercaptosulfotransferase - can protect against cardiovascular pathologies, including arrhythmias, atherosclerosis, heart failure, myocardial infarction and ischaemia-reperfusion injury. The bioavailability of H2S and its metabolites, such as hydropersulfides and polysulfides, is substantially reduced in cardiovascular disease and has been associated with single-nucleotide polymorphisms in H2S synthesis enzymes. In this Review, we highlight the role of H2S, its synthesizing enzymes and metabolites, their roles in the cardiovascular system, and their involvement in cardiovascular disease and associated pathologies. We also discuss the latest clinical findings from the field and outline areas for future study.
... Such mechanisms include the effects of H 2 S on cysteine residues of proteins, by direct "sulfhydration" (S-SH bonds) (Mustafa et al., 2009). This mechanism has been put forward to account for the extreme and early toxicity of H 2 S on Ca 2+ channels for instance (Sun et al., 2008;Zhang et al., 2012), including sarcoplasmic reticulum ryanodine receptors (RyR) rich in free cysteine residues. Various ion channels, including K + -ATP (Chen et al., 2012), Ca 2+ (Sun et al., 2008;Telezhkin et al., 2010;Zhang et al., 2012), are affected by hydrogen sulfide in the heart and in the central nervous system. ...
... This mechanism has been put forward to account for the extreme and early toxicity of H 2 S on Ca 2+ channels for instance (Sun et al., 2008;Zhang et al., 2012), including sarcoplasmic reticulum ryanodine receptors (RyR) rich in free cysteine residues. Various ion channels, including K + -ATP (Chen et al., 2012), Ca 2+ (Sun et al., 2008;Telezhkin et al., 2010;Zhang et al., 2012), are affected by hydrogen sulfide in the heart and in the central nervous system. Not all the mechanisms of sulfide toxicity require the mitochondrial activity to be critically altered, as shown for the medullary neurons for instance (Greer et al., 1995). ...
Hydrogen sulfide (H2S) remains a chemical hazard in the gas and farming industry. It is easy to manufacture from common chemicals and thus represents a potential threat for the civilian population. It is also employed as a method of suicide, for which incidence has recently increased in the US.
H2S is a mitochondrial poison and exerts its toxicity through mechanisms that are thought to result from its high affinity to various metallo-proteins (such as – but not exclusively- the mitochondrial cytochrome c oxidase) and interactions with cysteine residues of proteins. Ion channels with critical implications for the cardiac and the brain functions appear to be affected very early during and following H2S exposure, an effect which is rapidly reversible during a light intoxication. However, during severe H2S intoxication, a coma, associated with a reduction in cardiac contractility, develops within minutes or even seconds leading to death by complete electro-mechanical dissociation of the heart. If the level of intoxication is milder, a rapid and spontaneous recovery of the coma occurs as soon as the exposure stops. The risk, although probably very small, of developing long-term debilitating motor or cognitive deficits is present. One of the major challenges impeding our effort to offer an effective treatment against H2S intoxication after exposure is that the pool of free/soluble H2S almost immediately disappears from the body preventing agents trapping free H2S (cobalt or ferric compounds) to play their protective role.
This paper (1) presents and discusses the neurological symptoms and lesions observed in various animals models and in humans following an acute exposure to sub-lethal or lethal levels of H2S, (2) reviews the potential interest of methylene blue (MB), a potent cyclic redox dye – currently used for the treatment of methemoglobinemia – which has potential rescuing effects on the mitochondrial activity, as an antidote against sulfide intoxication.
... H 2 S modulates cardiovascular homeostasis and exerts cardioprotective effects in different models of in vitro, ex vivo and in vivo ischemia/reperfusion [135][136][137][138][139][140]. Indeed, whole patch clamp experiments in rat cardiomyocytes revealed that NaHS negatively modulates L-type Ca 2+ channels composed by the Ca V 1.2 subunits [141,142]. More specifically, NaHS (up to 1 mM) causes a dose dependent reduction in the Ca 2+ current peak. ...
... Accordingly, the shortening of single cardiomyocytes and contraction of isolated rat papillary muscles are depressed. Electric field-induced Ca i transients in single cardiomyocytes are also reduced by 100 M NaHS [141,142]. Consistently, H 2 S exerts a negative inotropic effect in isolated perfused rat and papillary muscles when NaHS is administrated at concentrations ranging from 1 µM up to 1 mM [36,144]. More recently, it has been reported its negative chronotropic action in human atrial fibers by blocking L-type Ca 2+ channels and an enhancement in the repolarization phase by opening KATP channels (50-200 M µNaHS) [145]. ...
In addition to nitric oxide and carbon monoxide, hydrogen sulfde (H2S) is the third gasotransmitter in mammals.
It is synthesized from L-cysteine by cystathionine β-synthase, cystathionine γ-lyase or by sequential action of alanine
aminotransferase and 3-mercaptopyruvate sulfur transferase. Although initially it was suggested that in the vascular
wall H
2S is synthesized only by smooth muscle cells and relaxes them by activating ATP-sensitive potassium channels,
more recent studies indicate that H
2S is synthesized in endothelial cells as well. The physiological functions of H2S
are mediated by different molecular targets, such as different ion channels and signaling proteins. Endogenous H2S is involved in the regulation of many physiological processes in the cardiovascular system including the regulation of vascular tone, blood pressure and inhibits atherogenesis. Many new technologies have been developed to detect endogenous H2S production, and novel H2S-delivery compounds have been invented to aid therapeutic intervention of diseases related to abnormal H2S metabolism. The primary purpose of this review was to provide an overview of the role of H2S in the blood vessel, methods of endogenous production detections and common ion channels used to produce its biological effect describe its benefcial effects.
... These symptoms occur when the concentration of H 2 S in blood exceeds 2-5 μM [32,33] . Several main potential effects and interactions between H 2 S and related molecules involved in cardiomyocytes hampers determination of the mechanism of the action about H 2 S upon the cardiotoxicity, including: (i) activation of L-type calcium ion (Ca 2 + ) channels; (ii) activation of K ATP channels [32,34] ; (iii) reconfiguration of proteins with cysteine residues [35] ; (iv) inhibition of ATP to affect actin-myosin interactions [29] ; (v) influence of reactive oxygen species (ROS) accumulation in mitochondria, and then affecting various key ion channels [36] ; (vi) interaction between H 2 S and nitric oxide to increase production of cyclic guanosine phosphate [37] , as well as depression of the cyclic adenosine monophosphate pathway [38] , both of which can lead to the cardiac depression. In summary, the interaction between H 2 S and the cardiac disease can cause cardiotoxic effects and sequelae in direct or indirect ways. ...
Hydrogen sulfide (H2S) is a toxic, essential gas used in various biological and physical processes and has been the subject of many targeted studies on its role as a new gas transmitter. These studies have mainly focused on the production and pharmacological side effects caused by H2S. Therefore, effective strategies to remove H2S has become a key research topic. Furthermore, the development of novel nanoplatforms has provided new tools for the targeted removal of H2S. This paper was performed to review the association between H2S and disease, related H2S inhibitory drugs, as well as H2S responsive nanoplatforms (HRNs). This review first analyzed the role of H2S in multiple tissues and conditions. Second, common drugs used to eliminate H2S, as well as their potential for combination with anticancer agents, were summarized. Not only the existing studies on HRNs, but also the inhibition H2S combined with different therapeutic methods were both sorted out in this review. Furthermore, this review provided in-depth analysis of the potential of HRNs about treatment or detection in detail. Finally, potential challenges of HRNs were proposed. This study demonstrates the excellent potential of HRNs for biomedical applications.
... Similarly, Orlov et al. showed that H2S would trigger vasoconstriction in rat aortic rings through the activation of Ca 2+ influx via L-type channels, while Sun et al. showed that H2S would inhibit Ltype Ca 2+ -channels in rat cardiomyocytes [212,213]. Furthermore, in the brain, H2S facilitates the induction of hippocampal long-term potentiation (LTP) [214]. For H2S this effect depends on the activation of N-methyl D-Aspartate (NMDA) receptors whereas for NO and CO this induction occurs independently of NMDA receptors [214]. ...
Hydrogen sulfide (H2S) is the third gasotransmitter described in mammals. Colourless and water-soluble, H2S is a highly effective inhibitor of mitochondrial cytochrome c oxidase when present at high concentrations. However, when present at low concentrations, H2S can act as an inorganic energetic substrate for mammalian mitochondria. To oxidize H2S, mitochondria need the sulfide oxidizing unit (SOU), a set of three specific enzymes: sulfide quinone reductase (SQR), dioxygenase (ETHE1) and thiosulfate sulfurtransferase (TST). Liver metabolism, finely regulated by hormones and nutrients, is central to energy homeostasis, and liver metabolic inflexibility is known to be associated with several metabolic diseases, such as Non-Alcoholic Fatty Liver Disease (NAFLD). The unique position of this organ makes it likely to be exposed to high levels of H2S coming from both exogenous (gastrointestinal tract) and endogenous (metabolism of sulfur-containing amino acids) sources. Recently, impaired liver H2S biosynthesis has been reported in animal models of NAFLD, and in vivo supplementation of H2S donors prevented the further escalation of the illness into steatohepatitis (NASH). Almost all studies exploring the hepatic pathological relevance of H2S are usually focused on H2S biosynthesis pathway and/or using exogenous donors. As intrahepatic H2S levels can also be controlled by its mitochondrial oxidation, the objectives of my PhD were to investigate the pathophysiological importance of this pathway in liver metabolism and in the development of NAFLD. First, we showed that, physiologically, the liver nutritional status regulates hepatic mitochondrial H2S oxidation capacity and SQR protein expression, both being downregulated by fasting while overnight refeeding abolished the fasting inhibitory effect. Adenovirus-mediated overexpression of human SQR in mouse liver clearly demonstrated that SQR is the key regulatory enzyme of mitochondrial H2S oxidation. Enhancing this pathway i) increased in vivo glucose tolerance and liver insulin signalling, ii) stimulated glucose metabolism in primary cultures of mouse hepatocytes (13C-glucose fluoxomics), and iii) decreased liver fatty acid oxidation capacity. Second, when exploring the context of NAFLD, we observed that liver mitochondrial H2S oxidation capacity was downregulated in mice fed high fat/high sucrose (HF/HS) diet (NAFL model) and surprisingly was upregulated in mice fed methionine-choline deficient (MCD) diet (NASH model). In vivo supplementation with sodium thiosulfate (STS), an H2S donor, abrogated the inhibitory effect of HF/HS diet while it had no impact in the NASH model. Additionally, STS supplementation had no effect on body weight, glucose tolerance and insulin sensitivity in the NAFL model, and on liver steatosis in both NAFL and NASH models. However, STS supplementation did have an impact in the composition of gut microbiota. Similarly to the NAFLD mouse models, in morbid obese patients with simple steatosis (NAFL), liver SQR protein expression was found decreased, while in individuals with NASH SQR expression was found increased. Altogether, these studies, which confirmed that SQR is the key rate-limiting enzyme for liver mitochondrial H2S oxidation, clearly demonstrated for the first time that this pathway is finely regulated by the nutritional status of the liver and is altered in animal models of NAFLD and obese NAFLD patients. The novel observation that increasing hepatic mitochondrial H2S oxidation capacity increases hepatic glucose metabolism opens a new door in the field of liver pathophysiology, with this pathway being a potential protective target against the development of liver insulin resistance.
... One limitation of this study is the use of relatively high NaHS concentrations of 500-1000 mM. These concentrations were selected according to literature data that described NaHS effects in electrophysiological recordings (Tang et al., 2005;Sun et al., 2008;Sitdikova et al., 2010;Sekiguchi et al., 2014;Kuksis and Ferguson, 2015). For instance, Sitdikova used NaHS in the range from 10 mM to 10 mM and found that the activity of BK Ca in the plasma membrane of GH3 pituitary cells was modulated with EC 50 of 167 and 2000 mM (Sitdikova et al., 2010). ...
Reperfusion together with the preceding ischemic period results in serious damage to brain and heart tissues. Activation of potassium channels from the inner mitochondrial membrane leads to cytoprotection during such events. The mitochondrial large-conductance calcium-activated potassium channel (mitoBKCa) is one of these cytoprotective channels. It was previously shown that BKCa channels are blocked by hemin, which is present in excess during hemorrhage. In the experiments described in this work, we checked whether NaHS, known as a donor of gasotransmitter hydrogen sulfide (H2S), which can play an important role in cytoprotection, interacts with mitoBKCa channels. Indeed, using the biotin-switch method, it was found that mitoBKCa channels undergo S-sulfhydration in the presence of NaHS. Although patch-clamp experiments showed that NaHS has negligible effects on the activity of mitoBKCa channels, NaHS has been shown to almost fully activate hemin-inhibited mitoBKCa channels. The effects of NaHS were mimicked by imidazole, suggesting a common mechanism of activation of mitoBKCa channels inhibited by heme/hemin by molecules able to coordinate the iron ion of porphyrin. A set of absorption spectroscopy experiments with the 23 amino acid model peptides containing the heme-binding motif CXXCH suggested previously unrecognized roles of cysteines in heme binding. Significance Statement The activity of mitochondrial channels including mitoBKCa seems to play a significant role in cytoprotection during ischemia/reperfusion. Hemin, which is present in excess during hemorrhage, can potentially bind to and inhibit mitoBKCa activity. We found that hydrogen sulfide does not affect mitoBKCa activity unless it is blocked by hemin. In this case, hydrogen sulfide activates hemin-inhibited mitoBKCa by binding to hemin iron. The hydrogen sulfide effect could be mimicked in patch-clamp experiments by imidazole probably acting by a similar mechanism.
... The activation of I KATP can be proarrhythmic as it accelerates the phase 3 repolarization and reduces APD and ERP, leading to shortened critical length for initiating reentry arrhythmias (141). H 2 S was also reported to inhibit the I CaL in a concentration-dependent manner (142,143), and the involvement of I CaL was further evidenced by the observation that blockage of I KATP did not completely eliminate the effect of H 2 S (144). In our previous simulation study, we investigated the proarrhythmic effects of H 2 S using a multi-scale virtual heart (43). ...
Cardiovascular disease is the leading cause of death worldwide and kills over 17 million people per year. In the recent decade, growing epidemiological evidence links air pollution and cardiac arrhythmias, suggesting a detrimental influence of air pollution on cardiac electrophysiological functionality. However, the proarrhythmic mechanisms underlying the air pollution-induced cardiac arrhythmias are not fully understood. The purpose of this work is to provide recent advances in air pollution-induced arrhythmias with a comprehensive review of the literature on the common air pollutants and arrhythmias. Six common air pollutants of widespread concern are discussed, namely particulate matter, carbon monoxide, hydrogen sulfide, sulfur dioxide, nitrogen dioxide, and ozone. The epidemiological and clinical reports in recent years are reviewed by pollutant type, and the recently identified mechanisms including both the general pathways and the direct influences of air pollutants on the cellular electrophysiology are summarized. Particularly, this review focuses on the impaired ion channel functionality underlying the air pollution-induced arrhythmias. Alterations of ionic currents directly by the air pollutants, as well as the alterations mediated by intracellular signaling or other more general pathways are reviewed in this work. Finally, areas for future research are suggested to address several remaining scientific questions.
... H 2 S inhibits the activity of β adrenoreceptor by inhibiting adenylyl cyclase. [48] The H 2 S has also been reported to inhibit the L-type Ca ++ channels in cardiomyocyte, which leads to a decrease in contractility, thereby revealing the Ca ++ channel-blocking mechanism of H 2 S. [49] In the same year, H 2 S has been found to have the ability to block the angiotensin-converting enzyme and responsible for additive vasorelaxant response leading to the inhibition of angiotensin II production, ultimately resulting in reduced degradation of bradykinin. ...
... H 2 S increases the S-sulfhydration of mitogen-activated protein kinase 1 (MEK1) in HUVEC, while mice lacking the CSE gene have lower sulfhydrated MEK1 [344]. Various ion channels are also target proteins that can be sulfhydrated by H 2 S, resulting in either increased activity, such as in voltage-activated Ca 2+ channels in neurons [345][346][347] and Cl − /HCO 3 − exchangers in vascular SMC [348], or decreased activity, such as in l-type Ca 2+ channels in SMC [349,350]. CSE-derived endogenous H 2 S is a physiological vasorelaxant, as global CSE knockout mice display pronounced hypertension and diminished endothelium-dependent vasorelaxation in association with markedly reduced H 2 S levels in the serum, heart, aorta, and other tissues [351]. H 2 S can relax freshly prepared blood vessel rings from many vascular beds, including in cerebral [314], mesentery [352], coronary [353], uterine [37], and placental [338] arteries. ...
Normal pregnancy is associated with dramatic increases in uterine blood flow to facilitate the bidirectional maternal–fetal exchanges of respiratory gases and to provide sole nutrient support for fetal growth and survival. The mechanism(s) underlying pregnancy-associated uterine vasodilation remain incompletely understood, but this is associated with elevated estrogens, which stimulate specific estrogen receptor (ER)-dependent vasodilator production in the uterine artery (UA). The classical ERs (ER and ER) and the plasma membrane-bound G protein-coupled ER (GPR30/GPER) are expressed in UA endothelial cells and smooth muscle cells, mediating the vasodilatory effects of estrogens through genomic and/or nongenomic pathways that are likely epigenetically modified. This chapter aims to summarize the literature on UA ERs with a focus on their roles in mediating the local UA production of vasodilators by estrogens and pregnancy and to deliberate on the potential clinic implications of dysregulated ER-mediated estrogen signaling in hypertensive pregnancy complications. The activation of these three ERs by estrogens enhances the endothelial production of nitric oxide (NO), which has been shown to play a key role in uterine vasodilation during pregnancy. However, the local blockade of NO biosynthesis only partially attenuates estrogen-induced and pregnancy-associated uterine vasodilation, suggesting that mechanisms other than NO exist to mediate uterine vasodilation. We summarize here the literature on the role of NO in ER-mediated mechanisms controlling estrogen-induced and pregnancy-associated uterine vasodilation and our recent work on a “new” UA vasodilator hydrogen sulfide (H2S) that has dramatically changed our view of how estrogens regulate uterine vasodilation in pregnancy.
... For example, H 2 S protects the heart from ischemia and reperfusion injury through activating ATP-sensitive K þ channels 46 . It contracts vascular smooth muscle by inhibiting T-type Ca 2þ channels 47 and exerts protective effects on oxidative neurons through actions on Clchannels 48 . Over the last decade, researchers have turned their attention to the antitumor effects of H 2 S 49e51 . ...
As one of the most lethal diseases, pancreatic cancer shows a dismal overall prognosis and high resistance to most treatment modalities. Furthermore, pancreatic cancer escapes early detection during the curable period because early symptoms rarely emerge and specific markers for this disease have not been found. Although combinations of new drugs, multimodal therapies, and adjuvants prolong survival, most patients still relapse after surgery and eventually die. Consequently, the search for more effective treatments for pancreatic cancer is highly relevant and justified. As a newly re-discovered mediator of gasotransmission, hydrogen sulfide (H2S) undertakes essential functions, encompassing various signaling complexes that occupy key processes in human biology. Accumulating evidence indicates that H2S exhibits bimodal modulation of cancer development. Thus, endogenous or low levels of exogenous H2S are thought to promote cancer, whereas high doses of exogenous H2S suppress tumor proliferation. Similarly, inhibition of endogenous H2S production also suppresses tumor proliferation. Accordingly, H2S biosynthesis inhibitors and H2S supplementation (H2S donors) are two distinct strategies for the treatment of cancer. Unfortunately, modulation of endogenous H2S on pancreatic cancer has not been studied so far. However, H2S donors and their derivatives have been extensively studied as potential therapeutic agents for pancreatic cancer therapy by inhibiting cell proliferation, inducing apoptosis, arresting cell cycle, and suppressing invasion and migration through exploiting multiple signaling pathways. As far as we know, there is no review of the effects of H2S donors on pancreatic cancer. Based on these concerns, the therapeutic effects of some H2S donors and NO–H2S dual donors on pancreatic cancer were summarized in this paper. Exogenous H2S donors may be promising compounds for pancreatic cancer treatment.
... Endogenous H2S plays modulatory roles in hypoxia-induced cardiovascular responses, inhibiting the cardiovascular in spontaneously hypertensive rats (SHR) [9]. The bath application of 100 μM exogenous H2S can reduce the time required for the repolarization of the action potential [10]. ...
Cystathionine gamma-lyase (CSE) is one of the essential H2S-producing enzymes, and it regulates diverse functions in connection with cardiovascular function. It is crucial how exogenous H2S regulates CSE expression of the vascular endothelial cell during hypoxia. We examined the transcription and expression of CSE in HUVECs regulated by exogenous H2S with 100 μM during hypoxia by Luciferase assay, Western blotting, and quantitative RT-qPCR. Exogenous H2S influenced on the promoter activity of CSE in HUVECs during hypoxia. The effects of 100 μM H2S on CSE mRNA expression in HUVECs is decreased compared with 0 μM H2S. The consequences of 100 μM H2S on the expression level of CSE protein in HUVECs at two h of hypoxia is reduced compared with 0 μM H2S. These findings suggest that vascular endothelial cells can respond to the signals of hypoxia in the blood, and can respond to changes in H2S concentration in the blood, thus affect the blood vessels themselves.
... Or l'influx de Ca ++ provenant du réticulum sarcoplasmique grâce aux canaux calcium de type L joue un rôle crucial dans le couplage excitation/contraction de la cellule musculaire. Des études menées sur des cardiomyocytes de rat ont d'ailleurs montré que l'ajout exogène d'H2S conduit à une inhibition de l'ouverture des canaux calcium de type L. Ce mécanisme empêche ainsi la sortie du Ca ++ du réticulum sarcoplasmique produisant ainsi la vasodilatation (Sun et al., 2008). ...
Les 3-mercaptopyruvate sulfurtransférases (3-MST) et les thiosulfate sulfurtransférases (TST) sont des enzymes ubiquitaires de la famille des thioltransférases à domaine rhodanèse qui catalysent le transfert d’un atome de soufre d’un substrat donneur vers un substrat accepteur via un intermédiaire Cys-persulfure. Les 3-MST sont impliquées dans la formation de sulfure d’hydrogène (H2S), un gazotransmetteur toxique à forte concentration, alors que les TST interviendraient dans son élimination. L’objectif de mon projet était de décrypter les mécanismes moléculaires impliquant ces thioltransférases afin de mieux comprendre leurs rôles physiologiques. Pour cela, le mécanisme catalytique et les spécificités de substrats des enzymes humaines (3-MST, TSTD1 et Rhodanèse) et d’Escherichia coli (3-MST et GlpE) ont été caractérisés grâce à la mise au point de méthodes spécifiques permettant l’étude de chacune des étapes du mécanisme (fluorescence, stopped-flow, sonde H2S) et par une étude des relations structure-fonction menée en collaboration pour les aspects chimie théorique et cristallographie RX. J’ai montré que le site actif de ces enzymes est adapté à la catalyse d’un transfert de S0 à partir de composés soufrés non activés. De plus, le mécanisme de formation de l’intermédiaire persulfure ne dépend pas de l’enzyme mais du substrat donneur. En effet, la rupture de la liaison C-S du 3-mercaptopyruvate requiert la déprotonation des fonctions thiols du substrat et de la Cys essentielle, fonction assurée par la boucle catalytique CysX5 qui constitue un véritable site de reconnaissance thiolate, et l’intervention concomitante d’une molécule d’eau comme catalyseur acide. En présence de thiosulfate, hormis l’activation de la Cys seule la neutralisation des charges négatives du substrat est indispensable à la réaction de transfert de soufre. Enfin, et de façon inattendue, la 3-MST humaine pourrait être impliquée dans l’élimination cytosolique du sulfite, un composé toxique pour les cellules. Quant aux deux TST mitochondriales humaines, elles pourraient intervenir à la fois dans la signalisation cellulaire H2S-dépendante, via la production d’espèces polysulfure, et dans l’élimination d’H2S
... mitochondria due to disruption of the structure of the mitochondrial apparatus [20]. At the same time, it has been shown experimentally and clinically in 2000 that hypertension decreases the level of H 2 S in blood plasma, and the introduction of an exogenous hydrogen sulfide donor can cause a significant therapeutic effect [7,27]. There is little data available today about the effect of H 2 S on the total number of mitochondria in cells. ...
One of the leading causes of arterial hypertension (AH) is mitochondrial dysfunction (MD) – moreover, disorders in regulation of blood pressure occur on the background of progressive energy deficiency. At the same time, the cardioprotective effect of H2S has been proven. In particular, the inhibition of mitochondrial pore opening by hydrogen sulfide plays an important role, and H2S should affect the structural component of MD, namely, the ultrastructure of mitochondria. However, at present, the question of structural changes in the mitochondrial apparatus in patients with hypertension is extremely insufficiently studied. For the study of MD in healthy people and patients with pathology, almost the only objects (in the absence of surgical intervention) are blood cells, in particular leukocytes. Based on the above, the aim of the study was to investigate the effect of a hydrogen sulfide donor on the ultrastructure of the mitochondrial apparatus of leukocytes in patients with arterial hypertension. The effect of a hydrogen sulfide donor on some ultrastructural characteristics of the leukocyte mitochondrial apparatus in patients with hypertension was studied. The examination involved patients (men) with arterial hypertension aged 30-60 years, who were divided into 2 age groups: 30-40 and 40-60 years. Control groups (healthy men without signs of hypertension) were randomized by age. An electron microscopic and morphometric assessment of the structure of mitochondria revealed that under hypertension it undergoes significant changes that depend on the age of the patients. It has been established that the addition of a hydrogen sulfide donor (Full Spectrum Garlic phytopreparation (Swanson Health Products, USA) at a dose of 400 mg per day) to the traditional therapy of hypertension leads to positive changes in the mitochondrial ultrastructure of the studied cells aimed at increasing the energy capacity of the mitochondrial apparatus – the quantity reduction of structurally damaged mitochondria, and with an increase in the duration of treatment – the increase their total number in people of the younger age group (by 57.5%), and in the older age group – by 53.7%. Thus, the indicated effect of H2S significantly depends both on the age of the patients (young people respond more intensively) and on the duration of the hydrogen sulfide donor using (long-term use is accompanied by a more pronounced positive dynamics of changes).
... NaHS significantly inhibited the ability of calcium to contract mouse mesenteric arteries, supporting the view that vasorelaxation induced by NaHS involved inhibition of voltage-gated Ca 2+ channels (VGCC). NaHS inhibition of L-type calcium channel conductance has also been demonstrated in rat cardiac myocytes (Sun et al. 2008). In the present study, the concentration of NaHS required to significantly block the calciuminduced constriction was at least 10-fold higher than that which produced maximum vasorelaxation. ...
H2S causes vasorelaxation however there is considerable heterogeneity in the reported pharmacological mechanism of this effect. This study examines the contribution of endogenously released H2S in the regulation of vascular tone and the mechanism of H2S-induced vasorelaxation in small resistance-like arteries. Mesenteric arteries from C57 and eNOS−/− mice were mounted in myographs to record isometric force. Vasorelaxation responses to NaHS were examined in the presence of various inhibitors of vasorelaxation pathways. Expression and activity of the H2S-producing enzyme, cystathionine-γ-lyase (CSE), were also examined. CSE was expressed in vascular smooth muscle and perivascular adipose cells from mouse mesenteric artery. The substrate for CSE, l-cysteine, caused a modest vasorelaxation (35%) in arteries from C57 mice and poor vasorelaxation (10%) in arteries from eNOS−/− mice that was sensitive to the CSE inhibitor dl-propargylglycine. The fast H2S donor, NaHS, elicited a full and biphasic vasorelaxation response in mesenteric arteries (EC50 (1) 8.7 μM, EC50 (2) 0.6 mM), which was significantly inhibited in eNOS−/− vessels (P < 0.05), unaffected by endothelial removal, or blockers at any point in the NO via soluble guanylate cyclase and cGMP (NO-sGC-cGMP) vasorelaxation pathway. Vasorelaxation to NaHS was significantly inhibited by blocking K⁺ channels of the KCa and KV subtypes and the Cl⁻/HCO3⁻ exchanger (P < 0.05). Further experiments showed that NaHS can significantly inhibit voltage-gated Ca²⁺ channel function (P < 0.05). The vasorelaxant effect of H2S in small resistance-like arteries is complex, involving eNOS, K⁺ channels, Cl⁻/HCO3⁻ exchanger, and voltage-gated Ca²⁺ channels. CSE is present in the smooth muscle and periadventitial adipose tissue of these resistance-like vessels and can be activated to cause modest vasorelaxation under these in vitro conditions.
... This vasorelaxant effect was confirmed by subsequent studies in which H 2 S effects were attributed to the opening of K ATP channels in vascular smooth muscle cells (38). In addition, H 2 S was shown to protect the myocardium against ischemia/reperfusion injury (2,36), inhibit L-type calcium channels in cardiomyocytes (29), and promote angiogenesis (4,24,33). However, the role of H 2 S in renal function and salt-sensitive hypertension remains unknown. ...
... Свій ефект гідроген сульфід проявляє практично у всіх вісцеральних системах, а з'ясування механізмів його впливу, зокрема, у серцево-судинній системі, є об'єктом сучасних досліджень у теоретичній та практичній медицині [3,4]. Так, доведеним є його дозозалежний ефект ангіо-та кардіопротекції [5][6][7]. Науковими дослідженнями встановлені антиоксидантні та антиапоптичні властивості сірководню, а також його нейропротекторні та гастроцитопротекторні ефекти [8][9][10][11]. Основними ензимами, що беруть участь у синтезі ендогенного сірководню, є: цистатіонін-β-синтаза (cystathionine β-synthase -CBS), цистатіонін-γ-ліаза (cystathionine γ-lyase -CSE) та 3-меркаптопіруватсульфуртрансфераза (3-mercaptopyruvate sulfurtransferase -3-MST), причому остання реалізовує свої ефекти впливу спільно із цистеїнамінотрасферазою (cysteine aminotransferase -CAT), що мають специфічність локалізації [12][13][14]. ...
... L-type VDCC, an important pancreatic β-cell channel involved in regulation of insulin secretion, is also known as another target for H 2 S-induced modulation of pancreatic insulin secretion. Inhibitory effect of H 2 S on L-type VDCC was shown for the first time in the isolated rat cardiomyocytes [100]. Inactivation of VDCC by H 2 S in β-cells had been initially attributed to K ATP channel-induced hyperpolarization of cell membrane [86,101]. ...
... [90] (v) Regulates Ca 2þ influx and intracellular concentrations of Ca 2þ [91] and (vi) activates K þ and Clchannels to stabilize membrane potentials. [92][93][94] 3.1.2. Increases in glutathione levels: prevention of oxidative stress H 2 S, in the concentration range of 100 mM, enhances cellular metabolism in neurons, without inhibiting cytochrome c oxidase. ...
H 2 S is considered as a lethal 'gas of rotten eggs,' and recognized for hundreds of years as a toxicant. The gas can be harmful even if present as low as 0.05 ppm. The increase in its concentration causes ocular and respiratory problems. Exposure to the concentration of 1000 ppm can result in death. It was in 1990 when a surprise presence of H 2 S in rat and human brain tissues was revealed. Since then, so many vistas have been opened of this context. This paper reviews the burgeoning literature realted to H 2 S with profound role in mammalian physiology and its pathophysiologicaly. Despite known to be toxic, but at tiny concentrations in human and cell biology the gas has been found to play key signaling and regulatory functions. Herein, we report conjoint physiological, patho-physiological, and therapeutic aspects of the target molecule. From the overall study, it is eminent that a vast field is yet to be explored with regard to the mechanism of its biological action. Developing molecular models feasible for both in vivo and in vitro experiments and some other key roles are the future quests of this molecue. Hence, the study is an emphasis to trigger a persuasion among researchers to bring forth the scientific revelation of this molecule in connection with changing its toxic nature to human beneficiary. GRAPHICAL ABSTRACT ARTICLE HISTORY
... 23 H 2 S reduces the electrical activity of SANs, which may modulate the arrhythmogenesis of PVs and increase the risk of AF genesis. 24 H 2 S plays a critical role in cell signalling 25 and attenuates ischaemia-reperfusion injury by activating the ATP-sensitive potassium channel (K ATP ). 26 The activation of the K ATP channel shortens the action potential duration (APD), which may increase the risk of AF by facilitating the genesis of re-entry circuits. ...
Hydrogen sulphide (H2S), one of the most common toxic air pollutants, is an important aetiology of atrial fibrillation (AF). Pulmonary veins (PVs) and left atrium (LA) are the most important AF trigger and substrate. We investigated whether H2S may modulate the arrhythmogenesis of PVs and atria. Conventional microelectrodes and whole‐cell patch clamp were performed in rabbit PV, sinoatrial node (SAN) or atrial cardiomyocytes before and after the perfusion of NaHS with or without chelerythrine (a selective PKC inhibitor), rottlerin (a specific PKC δ inhibitor) or KB‐R7943 (a NCX inhibitor). NaHS reduced spontaneous beating rates, but increased the occurrences of delayed afterdepolarizations and burst firing in PVs and SANs. NaHS (100 μmol/L) increased IKATP and INCX in PV and LA cardiomyocytes, which were attenuated by chelerythrine (3 μmol/L). Chelerythrine, rottlerin (10 μmol/L) or KB‐R7943 (10 μmol/L) attenuated the arrhythmogenic effects of NaHS on PVs or SANs. NaHS shortened the action potential duration in LA, but not in right atrium or in the presence of chelerythrine. NaHS increased PKC activity, but did not translocate PKC isoforms α, ε to membrane in LA. In conclusion, through protein kinase C signalling, H2S increases PV and atrial arrhythmogenesis, which may contribute to air pollution‐induced AF.
... Les béta-bloquants jouent ce rôle mais présentent des effets indésirables ou des contreindications nécessitant des précautions d'emploi et des suivis réguliers.Le sulfure d'hydrogène aurait cette capacité à réduire la contractilité du muscle cardiaque et présenterait donc un effet inotrope négatif lors d'expérimentations in vitro et in vivo chez le rat. Cet effet serait la conséquence de l'activation des canaux K + ATP(38) (40). Un autre problème de santé public pourrait trouver une thérapeutique favorable en s'appuyant sur le sulfure d'hydrogène : les maladies thrombotiques et notamment l'infarctus du myocarde. ...
Le sulfure d’hydrogène (H2S), connu pour sa toxicité, a été décrit comme le troisièmegazotransmetteur de l’organisme avec le monoxyde d’azote et le monoxyde de carbone. Sespropriétés physico-chimiques font de lui un messager intra-cellulaire avec de nombreusesactions physiologiques grâce à sa synthèse endogène et pharmacologiques grâce àl’administration de donneurs de H2S. Deux grands effets sont induits par le sulfured’hydrogène : l’ouverture des canaux potassiques sensibles à l’Adénosine TriPhosphate etl’inhibition de la cytochrome c oxydase. De plus, cette molécule apporte un espoir dans denombreux domaines thérapeutiques. En effet, traiter une hypertension artérielle, prévenir lesdommages liés à l’utilisation d’anti-inflammatoires non stéroïdiens ou encore freiner laneurodégénérescence des patients atteints de la maladie de Parkinson ou d’Alzheimer seraientpossibles avec H2S. Enfin, le domaine de la neuroprotection post-arrêt cardiorespiratoire(ACR), orphelin de thérapeutiques, trouverait en ce gazotransmetteur une molécule idéale.Son utilisation protégerait des lésions oxydatives, inflammatoires et apoptotiques dusyndrome d’ischémie-reperfusion. Il entrainerait même un état de « suspended animation »caractérisé par un ralentissement du métabolisme ; ce qui donnerait un délai aux réanimateurspour traiter la cause de l’ACR. Le sulfure d’hydrogène serait alors la première substanceneuroprotectrice utilisée pour traiter ces victimes.
... 102,103 L tipi kalsiyum kanallarını bloke ettiği de gösterilmiştir. 104 Kobay solunum yolu düz kasında ve sıçan mesanesinde Vaniloid tipi "geçici reseptör potansiyel" kanallarını aktive etmektedir. 105,106 Transkripsiyon faktörlerine etkisi değişken bulunmuştur. ...
... Unfortunately, the mechanisms involved in the cardiac effects remain elusive. In an effort to elucidate the mechanisms it has been shown that: (1) glibenclamide partially blocked the negative inotropism induced by NaHS, suggesting that K ATP could be involved in this effect ( Chen et al., 2012;Xu et al., 2008); (2) 10 −9 M NaHS increased phosphorylation of Akt (Ser-493) and eNOS (Ser-1177) in rat heart implying that activation of this pathway may be involved in the negative inotropic effect of NaHS ( Mazza et al., 2013); and (3) NaHS inhibited isoproterenol-induced calcium transient by L-type calcium channel ( Sun et al., 2008;Zhang et al., 2012) and Serca2 associated with phospholamban ( Chen et al., 2012). Consistent with the above, cystathionine-γ−lyase (CSE) mRNA was found in the rat heart ( Fu et al., 2012). ...
Hydrogen sulfide is a gasotransmitter that mediates cardiovascular responses and could protect the heart from ischemia-reperfusion damage. Furthermore, this gas mediates bradycardia although the mechanisms involved remain elusive. In this regard, the inhibition of the cardiac sympathetic outflow may be partially involved. Thus, this study was designed to determine the capability of NaHS to inhibit the tachycardic responses induced by preganglionic stimulation of the cardioaccelerator sympathetic outflow. Wistar rats were anaesthetized with isoflurane, cannulated and pithed. Then, animals received gallamine and the effect of i.v. infusion of NaHS (310 and 560 μg/kg·min) was evaluated on the tachycardic responses induced by (1) sympathetic stimulation (0.1-3.2Hz) at C7-T1 region of the vertebral column; or i.v. injections of (2) noradrenaline (0.03-3 μg/kg) and (3) isoproterenol (0.0003-0.1 μg/kg). Notably, NaHS significantly and dose-dependently inhibited the tachycardic responses induced by electrical stimulation of the preganglionic sympathetic outflow without significantly modify the tachycardic responses induced by either noradrenaline or isoproterenol. These results allow us to conclude that i.v. infusion of NaHS inhibited the tachycardic responses induced by stimulation of the cardioaccelerator sympathetic outflow by a prejunctional mechanism.
... K + -ATP channel opening by H 2 S also occurs in cardiomyocytes, neurons, b-cells of the islets of Langerhans in pancreas, and intestinal smooth muscle cells resulting in the regulation of cardiac contractility, neurotransmission, insulin release, and, intestinal motility, respectively [36]. H 2 S has tissue-specific effects on high voltage L-type Ca ++ channels involved in the regulation of intracellular Ca ++ concentration; it appears to stimulate their opening in neurons [38] but inhibits them in cardiomyocytes [39]. T type Ca ++ channels are involved in H 2 S-induced pain perception [36]. ...
Hydrogen sulfide (H2S) is synthesized in nearly all organ systems including the kidney. Recent findings have revealed that H2S functions as a gasotransmitter affecting a wide range of physiologic functions similar to other gasotransmitters nitric oxide (NO) and carbon monoxide (CO). Research on H2S regulation of kidney function is still in early stages. H2S increases glomerular filtration rate (GFR) and inhibits sodium absorption by the tubules. There is burgeoning evidence that H2S generation by kidney cells is reduced in acute and chronic disease states and that H2S donors ameliorate injury. However, there are hints that the gas could also mediate kidney injury in specific models suggesting that its participation in kidney pathology is context-dependent. Expanding investigation of H2S in kidney physiology and disease will not only help us understand its regulatory role but it may also give us a potential new target for therapeutic intervention.
... Moreover, several studies showed that H 2 S closed the L-type calcium channel (LTCC). Both in vivo and in vitro experiments proved that H 2 S had a negative inotropic effect on rat heart [ 5 ], through direct inhibition of LTCC in cardiomyocytes [ 7 ]. These effects of H 2 S on ion channels may explain its inhibitory effect on the heart rate presented in our study. ...
Hydrogen sulfide (H2S) is an endogenous gaseous messenger suggested to regulate
cardiovascular functions. This study evaluates the possible protective effect of H2S in aconitine and
barium chloride (BaCl2) models of arrhythmias in rats. The effects of sodium hydrosulphide (NaHS, i.v.)
on electrocardiograph (ECG) patterns, biochemical cardiac markers (creatine kinase-MB isozyme and
cardiac troponin I), cardiac histopathology and aconitine (30 µg/kg, i.v.) and BaCl2 (15 mg/kg, i.v.) -
induced arrhythmias were studied in rats. NaHS significantly decreased heart rate at doses of 3, 4, and
6, but not 0.8 and 1.2 mg/kg. Aconitine caused 100% ventricular tachycardia (VT), 80% ventricular
fibrillation (VF), and 60% mortality after 26±5 sec. NaHS (0.8 mg/kg, i.v.) pretreatment significantly
decreased the VT, VF and mortality to 62.5, 25, and 0% respectively and delayed the occurrence of VT
by 349±2 sec. Similarly, BaCl2 caused 75% VF and 37.5% mortality after 18 ± 8 sec. NaHS (0.8 mg/kg i.v.)
pretreatment significantly decreased VF to 50% without affecting mortality rate. Moreover, NaHS (0.8
mg/kg, i.p., daily for 3 days) had no significant effects on ECG patterns, cardiac biomarkers or
histopathology. Our results indicate that H2S has a protective role against arrhythmias without affecting
ECG patterns, cardiac biomarkers or histopathology.
... In addition to K ATP channels, H 2 S has also been shown to inhibit L-type Ca 2+ channels in the cardiomyocyte and to activate transient receptor potential vanilloid channels in both the urinary tract and airway smooth muscle. These effects and their biological significance warrant further investigation (142,145,155). ...
Hydrogen sulfide (H2S) was identified as the third gasotransmitter in 1996 following the discoveries of the biological importance of nitric oxide and carbon monoxide. Although H2S has long been considered a highly toxic gas, the discovery of its presence and enzymatic production in mammalian tissues supports a critical role for this physiological signaling molecule. H2S is synthesized endogenously by three enzymes: cystathionine β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. H2S plays a pivotal role in the regulation of cardiovascular function as H2S has been shown to modulate: vasodilation, angiogenesis, inflammation, oxidative stress, and apoptosis. Perturbation of endogenous production of H2S has been associated with many pathological conditions of the cardiovascular system such as diabetes, heart failure, and hypertension. As such, modulation of the endogenous H2S signaling pathway or administration of exogenous H2S has been shown to be cytoprotective. This review article will provide a summary of the current body of evidence on the role of H2S signaling in the setting of myocardial ischemia and heart failure.
... In addition, H 2 S was found to mediate I CaL channel inhibition in V-like CMs derived from H9 hESCs. This is consistent with previous report that H 2 S inhibited I CaL in rat Vlike cardiomyocytes [22]. In human CMs, the outwardly rectifying potassium current I Ks and I Kr contribute to phase 2 and 3 repolarization of AP in both V-and A-CMs [23]. ...
Hydrogen sulfide (H(2)S) is a promising cardioprotective agent and a potential modulator of cardiac ion currents. Yet its cardiac effects on humans are poorly understood due to lack of functional cardiomyocytes. This study investigates electrophysiological responses of human pluripotent stem cells (hPSCs) derived cardiomyocytes towards H(2)S.
Cardiomyocytes of ventricular, atrial and nodal subtypes differentiated from H9 embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) were electrophysiologically characterized. The effect of NaHS, a donor of H(2)S, on action potential (AP), outward rectifier potassium currents (I(Ks) and I(Kr)), L-type Ca(2+) currents (I(CaL)) and hyperpolarization-activated inward current (I(f)) were determined by patch-clamp electrophysiology and confocal calcium imaging. In a concentration-dependent manner, NaHS (100 to 300 µM) consistently altered the action potential properties including prolonging action potential duration (APD) and slowing down contracting rates of ventricular-and atrial-like cardiomyocytes derived from both hESCs and hiPSCs. Moreover, inhibitions of slow and rapid I(K) (I(Ks) and I(Kr)), I(CaL) and I(f) were found in NaHS treated cardiomyocytes and it could collectively contribute to the remodeling of AP properties.
This is the first demonstration of effects of H(2)S on cardiac electrophysiology of human ventricular-like, atrial-like and nodal-like cardiomyocytes. It reaffirmed the inhibitory effect of H(2)S on I(CaL) and revealed additional novel inhibitory effects on I(f), I(Ks) and I(Kr) currents in human cardiomyocytes.
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.
Neuropathic pain can appear as a direct or indirect nerve damage lesion or disease that affects the somatosensory nervous system. If the neurons are damaged or indirectly stimulated, immune cells contribute significantly to inflammatory and neuropathic pain. After nerve injury, peripheral macrophages/spinal microglia accumulate around damaged neurons, producing endogenous hydrogen sulfide (H 2 S) through the cystathionine-γ-lyase (CSE) enzyme. H 2 S has a pronociceptive modulation on the Ca v 3.2 subtype, the predominant Ca v 3 isoform involved in pain processes. The present review provides relevant information about H 2 S modulation on the Ca v 3.2 T-type channels in neuropathic pain conditions. We have discussed that the dual effect of H 2 S on T-type channels is concentration-dependent, that is, an inhibitory effect is seen at low concentrations of 10 µM and an augmentation effect on T-current at 100 µM. The modulation mechanism of the Ca v 3.2 channel by H 2 S involves the direct participation of the redox/Zn ²⁺ affinity site located in the His191 in the extracellular loop of domain I of the channel, involving a group of extracellular cysteines, comprising C114, C123, C128, and C1333, that can modify the local redox environment. The indirect interaction pathways involve the regulation of the Ca v 3.2 channel through cytokines, kinases, and post-translational regulators of channel expression. The findings conclude that the CSE/H 2 S/Ca v 3.2 pathway could be a promising therapeutic target for neuropathic pain disorders.
H 2 S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H 2 S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H 2 S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H 2 S and oxidative posttranscriptional modification of proteins, the effect of H 2 S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H 2 S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H 2 S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H 2 S in various cell types and organ systems are overviewed. Finally, the role of H 2 S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H 2 S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H 2 S in the physiological regulation of all organ functions emerges from this review.
Advances in nanotechnology have enabled the rapid development of stimuli‐responsive therapeutic nanomaterials for precision gas therapy. Hydrogen sulfide (H2S) is a significant gaseous signaling molecule with intrinsic biochemical properties, which exerts its various physiological effects under both normal and pathological conditions. Various nanomaterials with H2S‐responsive properties, as new‐generation therapeutic agents, are explored to guide therapeutic behaviors in biological milieu. The cross disciplinary of H2S is an emerging scientific hotspot that studies the chemical properties, biological mechanisms, and therapeutic effects of H2S. This review summarizes the state‐of‐art research on H2S‐related nanomedicines. In particular, recent advances in H2S therapeutics for cancer, such as H2S‐mediated gas therapy and H2S‐related synergistic therapies (combined with chemotherapy, photodynamic therapy, photothermal therapy, and chemodynamic therapy) are highlighted. Versatile imaging techniques for real‐time monitoring H2S during biological diagnosis are reviewed. Finally, the biosafety issues, current challenges, and potential possibilities in the evolution of H2S‐based therapy that facilitate clinical translation to patients are discussed.
Cardiovascular diseases are the most common complications of diabetes, and diabetic cardiomyopathy is a major cause of people death in diabetes. Molecular, transcriptional, animal, and clinical studies have discovered numerous therapeutic targets or drugs for diabetic cardiomyopathy. Within this, hydrogen sulfide (H2S), an endogenous gasotransmitter alongside with nitric oxide (NO) and carbon monoxide (CO), is found to play a critical role in diabetic cardiomyopathy. Recently, the protective roles of H2S in diabetic cardiomyopathy have attracted enormous attention. In addition, H2S donors confer favorable effects in myocardial infarction, ischaemia-reperfusion injury, and heart failure under diabetic conditions. Further studies have disclosed that multiplex molecular mechanisms are responsible for the protective effects of H2S against diabetes-elicited cardiac injury, such as anti-oxidative, anti-apoptotic, anti-inflammatory, and anti-necrotic properties. In this review, we will summarize the current findings on H2S biology and pharmacology, especially focusing on the novel mechanisms of H2S-based protection against diabetic cardiomyopathy. Also, the potential roles of H2S in diabetes-aggravated ischaemia-reperfusion injury are discussed.
Hydrogen sulfide (H2S), nitric oxide (NO), carbon monoxide (CO), and sulfur dioxide (SO2) were previously considered as toxic gases, but now they are found to be members of mammalian gasotransmitters family. Both H2S and SO2 are endogenously produced in sulfur-containing amino acid metabolic pathway in vivo. The enzymes catalyzing the formation of H2S are mainly CBS, CSE, and 3-MST, and the key enzymes for SO2 production are AAT1 and AAT2. Endogenous NO is produced from L-arginine under catalysis of three isoforms of NOS (eNOS, iNOS, and nNOS). HO-mediated heme catabolism is the main source of endogenous CO. These four gasotransmitters play important physiological and pathophysiological roles in mammalian cardiovascular, nervous, gastrointestinal, respiratory, and immune systems. The similarity among these four gasotransmitters can be seen from the same and/or shared signals. With many studies on the biological effects of gasotransmitters on multiple systems, the interaction among H2S and other gasotransmitters has been gradually explored. H2S not only interacts with NO to form nitroxyl (HNO), but also regulates the HO/CO and AAT/SO2 pathways. Here, we review the biosynthesis and metabolism of the gasotransmitters in mammals, as well as the known complicated interactions among H2S and other gasotransmitters (NO, CO, and SO2) and their effects on various aspects of cardiovascular physiology and pathophysiology, such as vascular tension, angiogenesis, heart contractility, and cardiac protection.
Hydrogen sulfide, a small molecule, produced by endogenous enzymes, such as CTH, CBS, and MPST using L-cysteine as substrates, has been reported to have numerous protective effects. However, the key problem that the target of H2S and how it can affect the structure and activity of biological molecules is still unknown. Till now, there are two main theories of its working mechanism. One is that H2S can modify the free thiol in cysteine to produce the persulfide state of the thiol and the sulfhydration of cysteine can significantly change the structure and activity of target proteins. The other theory is that H2S, as an antioxidant molecule, can directly break the disulfide bond in target proteins, and the persulfide state of thiol can be an intermediate product during the reaction. Both phenomena exit for no doubt since they are both supported by large amounts of experiments. Here, we will summarize both theories and try to discuss which one is the more effective or direct mechanism for H2S and what is the relationship between them. Therefore, we will discover more protein targets of H2S with the mechanism and understand more about the effect of this small molecule.
Hydrogen sulfide (H2S) represents the third and the youngest member of the gaseous transmitters family. The dominant effect of H2S on isolated vessels is vasodilation. As the mechanism of H2S‐induced relaxation in human vessels remains unclear, the present study aimed to investigate the effects of H2S donor, sodium hydrosulfide (NaHS), on isolated human saphenous vein (HSV) and to determine the mechanism of action.
Our results showed that NaHS (1 µM – 3 mM) induced a concentration‐dependent relaxation of endothelium‐intact HSV rings pre‐contracted by phenylephrine. Pre‐treatment with L‐NAME, ODQ and KT5823 significantly inhibited NaHS‐induced relaxation, while indomethacin induced partial inhibition. Among K⁺ channels blockers, the combination of apamin and TRAM‐34 significantly affected the relaxation produced by NaHS, while iberiotoxin and glibenclamide only reduced maximal relaxation of HSV. NaHS partially relaxed endothelium‐intact rings pre‐contracted by high K⁺, as well as phenylephrine‐contracted rings in the presence of nifedipine. Additionally, the incubation of HSV rings with NaHS increased NO production. These results demonstrate that NaHS produces the concentration‐ and endothelium‐dependent relaxation of isolated HSV. Vasorelaxation to NaHS probably involves activation of NO/cGMP/PKG pathway and partially prostacyclin. In addition, different K⁺ channels subtypes, especially SKCa and IKCa, as well as BKCa and KATP channels in high concentrations of NaHS, probably participate in the NaHS‐induced vasorelaxation.
A new alleged monastrol-H2S releasing hybrid, named MADTOH, was designed based on the structure of monastrol (M) and 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione (ADTOH) and synthesized in 7.8% of overall yield. MADTOH was shown to be an H2S donor at physiological conditions. In addition, the hybrid causes a decrease in global calcium transient in cardiomyocytes similarly to nifedipine (NIFE), taken as positive control. Whole-cell voltage-clamp showed that MADTOH decreases L-type Ca2+ current in isolated ventricular cardiomyocytes
Normal pregnancy is associated with dramatic increases in uterine blood flow to facilitate the bidirectional maternal-fetal exchanges of respiratory gases and to provide the sole nutrient support for fetal growth and survival. The mechanism(s) underlying pregnancy-associated uterine vasodilation remains incompletely understood, but this is associated with elevated estrogens that stimulate specific estrogen receptors (ER)-dependent vasodilator production in uterine artery (UA). The classical ERs (ERα and ERβ) and the plasma-bound G protein-coupled ER (GPR30/GPER) are expressed in UA endothelial cells and smooth muscle cells, mediating the vasodilatory effects of estrogens through genomic and/or nongenomic pathways that are likely epigenetically modified. Activation of these three ERs by estrogens enhances endothelial production of nitric oxide (NO) that has been shown to play a key role in uterine vasodilation during pregnancy. However, local blockade of NO biosynthesis only partially attenuate estrogen-induced and pregnancy-associated uterine vasodilation, suggesting mechanisms other than NO exist to mediate uterine vasodilation. In this review, we summarized the literature on the role of NO in ER-mediated mechanisms controlling estrogen-induced and pregnancy-associated uterine vasodilation and our recent work on a "new" UA vasodilator hydrogen sulfide (H2S) that has dramatically changed our view of how estrogens regulate uterine vasodilation in pregnancy.
Acid-sensing ion channels (ASICs) have been implicated in many physiological and patho-physiological processes like synaptic plasticity, inflammation, pain perception, stroke-induced brain damage and, drug-seeking behaviour. Although ASICs have been shown to be modulated by gasotransmitters like nitric oxide (NO), their regulation by hydrogen sulfide (H2S) is not known. Here, we present strong evidence that H2S potentiates ASICs-mediated currents. Low pH-induced current in Chinese hamster ovary (CHO) cells, expressing homomeric either ASIC1a, ASIC2a or ASIC3, increased significantly by an H2S donor NaHS. The effect was reversed by washing the cells with NaHS-free external solution of pH 7.4. MTSES, a membrane impermeable cysteine thiol-modifier failed to abrogate the effect of NaHS on ASIC1a, suggesting that the target cysteine residues are not in the extracellular region of the channel. The effect of NaHS is not mediated through NO, as the basal NO level in cells did not change following NaHS application. This previously unknown mechanism of ASICs-modulation by H2S adds a new dimension to the ASICs in health and disease.
Hydrogen sulfide (H2S) exerts different effects on the cardiovascular system by modulating ion channels. The present study was to ascertain whether H2S affects L-type calcium (Ca2+) channels in vascular smooth muscle cells (VSMCs) and the subsequent signaling pathways. Here, CaV1.2 L-type Ca2+ currents (ICa, L) were inhibited by sodium hydrosulfide (NaHS, an H2S donor) in A7r5 cell lines using the whole-cell patch-clamp technique. Then NaHS significantly reduced intracellular Ca2+ concentration ([Ca2+]i) in Bayk8644-stimulated CaV1.2-HEK293 cells by using flow cytometry. However, NaHS did not affect the ryanodine-induced elevation of [Ca2+]i by means of confocal microscopy, ruling out its influence on the intracellular Ca2+ release. In the following, the sulfhydration of L-type Ca2+ channels was determined by Ellman's Test. The results showed that NaHS decreased the number of free sulfhydryls, which was further strengthened by the oxidant sulfhydryl modifier diamide (DM) and significantly counteracted by the reductant sulfhydryl modifier dithiothreitol (DTT). DTT also partly reversed the NaHS-reduced [Ca2+]i in CaV1.2-HEK293 cells. Additionally, NaHS did not change CaV1.2 expression. Furthermore, NaHS increased phosphorylation of PKC and ERK in both a concentration- and a time-dependent manner in VSMCs. Isradipine, L-type Ca2+ channel specific blocker, further increased H2S-induced phosphorylation of PKC and ERK, showing an additive effect with H2S. Therefore, our results suggest that H2S reduced ICa, L & [Ca2+]i and hence influenced the downstream PKC/ERK pathway, which was likely through regulating the sulfhydration of L-type Ca2+ channels in VSMCs.
Hydrogen sulfide (H2S) is an endogenously synthesized gaseous transmitter that participates in the regulation of the cardiovascular system and has a cardioprotective effect under ischemia–reperfusion conditions. Here, we studied possible mechanisms of the interaction of H2S and muscarinic acetylcholine receptors in the regulation of mice atrium contractility in the isometric conditions. We show that sodium hydrosulfide (NaHS), an exogenous donor of H2S, caused dose-dependent and reversible depression of the contractile force in the concentration range from 1 μM to 5 mM. The negative inotropic effect of NaHS did not change after the activation of muscarinic acetylcholine receptors by carbachol. However, we observed that the negative inotropic effect of carbachol increased after preliminary application of NaHS. The application of the reducing agent dithiothreitol did not change the effects of carbachol, which indicated that the effects of NaHS was not related to a direct action on the disulfide bonds of the receptor’s protein subunits. The increased effects of carbachol after NaHS application were not prevented by the inhibition of intracellular signaling pathway that mediated activation of M-cholinergic receptors, including adenylate cyclase, guanylate cyclase, and NO-synthase. However, an increase in the carbachol negative inotropic effect was not observed when ATP-dependent potassium channels were inhibited by glibenclamide. In its turn, activation of ATPdependent potassium channels by diazoxide resulted in an increase in carbachol negative inotropic action in the atrial myocardium of mice similar to the effect of NaHS. Our data indicate that the enhanced negative inotropic effect of carbachol under the action of H2S in the mouse atrium was mediated by the activation of ATP-dependent potassium channels.
Gasotransmitters are gas molecules produced endogenously in prokaryotic and eukaryotic cells for signalling purposes. This book provides, for the first time, a comprehensive description and systematic look at all gasotransmitters, established or proposed, since their detection in 2002. The content and scope covers the production, metabolism, and signalling roles of gasotransmitters. Conceptual advances, scientific discoveries and newly developed techniques described in this book influence our understanding of fundamental molecular and cellular events in biology and medicine.
This book serves as the state-of-the-art book for undergraduate and graduate students as well as post-doctoral fellows in biomedical disciplines and toxicologists studying the toxic mechanisms of gasotransmitters in the environment. It will also be welcomed by researchers in university and research institutes, government agencies, pharmaceutical and medical instrument industry, and clinical practice.
Carbon monoxide (CO), hydrogen sulfide (H2S), and nitric oxide (NO) constitute endogenous gaseous molecules produced by specific enzymes. These gases are chemically simple, but exert multiple effects and act through shared molecular targets to control both physiology and pathophysiology in the cardiovascular system (CVS). The gases act via direct and/or indirect interactions with each other in proteins such as heme-containing enzymes, the mitochondrial respiratory complex, and ion channels, among others. Studies of the major impacts of CO, H2S, and NO on the CVS have revealed their involvement in controlling blood pressure and in reducing cardiac reperfusion injuries, although their functional roles are not limited to these conditions. In this review, the basic aspects of CO, H2S, and NO, including their production and effects on enzymes, mitochondrial respiration and biogenesis, and ion channels are briefly addressed to provide insight into their biology with respect to the CVS. Finally, potential therapeutic applications of CO, H2S, and NO with the CVS are addressed, based on the use of exogenous donors and different types of delivery systems.
The gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S), long considered only toxicant, are produced in vivo during the catabolism of common biological molecules, and are crucial for a large variety of physiological processes. Mounting evidence is emerging that in poikilotherm vertebrates, as in mammals, they modulate the basal performance of the heart and the response to stress challenges. In this review, we will focus on teleost fish and amphibians to highlight the evolutionary importance in vertebrates of the cardiac control elicited by NO, CO and H2S, and the conservation of the intracellular cascades they activate. Although many gaps are still present due to discontinuous information, we will use examples obtained by studies from our and other laboratories to illustrate the complexity of the mechanisms that, by involving gasotransmitters, allows beat-to-beat, short-, medium- and long-term cardiac homeostasis. By presenting the latest data, we will also provide a framework in which the peculiar morpho-functional arrangement of the teleost and amphibian heart can be considered as a reference tool to decipher cardiac regulatory networks which are difficult to explore by using more conventional vertebrates, such as mammals. This article is protected by copyright. All rights reserved
H2S has excitatory and inhibitory effects on Ca2+ signals via transient receptor potential ankyrin 1 (TRPA1) and ATP-sensitive K+ channels, respectively. H2S converts intracellularly to polysulfides, which are more potent agonists for TRPA1 than H2S. Under inflammatory conditions, changes in the expression and activity of these H2S target channels and/or the conversion of H2S to polysulfides may modulate H2S effects. Effects of proinflammatory cytokines on H2S-induced Ca2+ signals and polysulfide production in RIN14B cells were examined using fluorescence imaging with fura-2 and SSP4, respectively. Na2S, a H2S donor, induced 1) the inhibition of spontaneous Ca2+ signals, 2) inhibition followed by [Ca2+]i increase, and 3) rapid [Ca2+]i increase without inhibition in 50% (23/46), 22% (10/46), and 17% (8/46) of cells tested, respectively. IL-1β augmented H2S-induced [Ca2+]i increases, which were inhibited by TRPA1 and voltage-dependent L-type Ca2+ channel blockers. However, IL-1β treatment did not affect [Ca2+]i increases evoked by a TRPA1 agonist or high concentration of KCl. Na2S increased intracellular polysulfide levels, which were enhanced by IL-1β treatment. A NOS inhibitor suppressed the increased polysulfide production and [Ca2+]i increase in IL-1β-treated cells. These results suggest that IL-1β augments H2S-induced [Ca2+]i increases via the conversion of H2S to polysulfides through NO synthesis, but not via changes in the activity and expression of target channels. Polysulfides may play an important role in the effects of H2S during inflammation.
The actions of hydrogen sulfide (H2S) on the heart and vasculature have been extensively reported. However, the mechanisms underlying the effects of H2S are unclear in the anesthetized rat. The objective of the current study is to investigate the effect of H2S on the electrocardiogram and examine the relationship between H2S-induced changes in heart rate (HR), mean arterial pressure (MAP), and respiratory function. Intravenous (iv) administration of the H2S donor sodium sulfide (Na2S) in the anesthetized Sprague-Dawley (SD) rat decreased MAP and HR and produced changes in respiratory function. The administration of Na2S significantly increased the RR interval at some doses, but had no effect on the PR or QTc(n)-B intervals. In experiments where respiration was maintained with a mechanical ventilator, we observed that that Na2S-induced decreases in MAP and HR were independent of respiration. In experiments where respiration was maintained by mechanical ventilation and HR was maintained by cardiac pacing, Na2S induced changes in MAP were not significantly altered whereas changes in HR were abolished. Co-administration of glybenclamide significantly increased MAP and HR responses at some doses, but methylene blue, diltiazem, and ivabradine had no significant effect when compared to control. The decreases in MAP and HR in response to Na2S can be dissociated and are independent of changes in respiratory function, K(+)ATP channels, methylene blue-sensitive mechanism involving L-type voltage sensitive calcium channels, or hyperpolarization-activated cyclic nucleotide-gated channel (HCN) If channels. Cardiovascular responses observed in spontaneously hypertensive (SHR) rats were more robust than those in SD rats.
Sulfur-containing gaseous signal molecules including hydrogen sulphide and sulfur dioxide were previously recognized as toxic gases. However, extensive studies have revealed that they can be generated in the cardiovascular system via a sulfur-containing amino acid metabolic pathway, and have an important role in cardiovascular physiology and pathophysiology. Ion channels are pore-forming membrane proteins present in the membrane of all biological cells; their functions include the establishment of a resting membrane potential and the control of action potentials and other electrical signals by conducting ions across the cell membrane. Evidence has now accumulated suggesting that the sulfur-containing gaseous signal molecules are important regulators of ion channels and transporters. The aims of this review are (1) to discuss the recent experimental evidences in the cardiovascular system regarding the regulatory effects of sulfur-containing gaseous signal molecules on a variety of ion channels, including ATP-sensitive potassium, calcium-activated potassium, voltage-gated potassium, L- and T-type calcium, transient receptor potential and chloride and sodium channels, and (2) to understand how the gaseous signal molecules affect ion channels and cardiovascular diseases.
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This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.
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.
We used patch-clamp techniques to elucidate the regulatory mechanisms of ATP-sensitive K(+) (K(ATP)) channels by stimulation of P(2) purinoceptors in guinea pig ventricular myocytes. Extracellular ATP at 0.1 mM transiently inhibited by 90.5 +/- 5.0% the whole cell K(ATP) channel current evoked by a reduction in intracellular ATP concentration to 0.5 mM and exposure to 30 microM pinacidil. ADP and AMP (both 1 mM) also decreased the current by 42.8 +/- 9.3% and 9.4 +/- 4.8%, respectively, but adenosine did not, even at 10 mM. ATP-induced channel inhibition was hardly observed in the presence of 0.2 mM suramin, 0.2 mM guanosine 5'-O-(2-thiodiphosphate), or 0.1 mM compound 48/80, whereas it was not influenced by the presence of 0.1 microM staurosporine or 10 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid in the pipette. In the presence of 10 microM wortmannin or the absence of ATP in the cytosol, the ATP-induced channel inhibition was irreversible. Phosphatidylinositol 4,5-bisphosphate (PIP(2)) at 0.1 mM in the outside-out patch pipette prevented ATP-induced channel inhibition. The half-maximal internal ATP concentrations for inhibition of channel activity determined in inside-out membrane patches were 13.8 microM in the presence and 1.12 mM in the absence of 0.1 mM ATP at the external side. It is concluded that activity of K(ATP) channels is modulated by extracellular ATP by a mechanism involving P(2Y) purinoceptors coupled to GTP-binding proteins associated with reduction of the sarcolemmal PIP(2) concentration via stimulation of phospholipase C.
Hydrogen sulfide (H2S) is synthesized in the body from l‐cysteine by several enzymes including cystathionine‐γ‐lyase (CSE). To date, there is little information about the potential role of H2S in inflammation. We have now investigated the part played by H2S in endotoxin‐induced inflammation in the mouse. E. coli lipopolysaccharide (LPS) administration produced a dose (10 and 20 mg/kg ip)‐ and time (6 and 24 h)‐dependent increase in plasma H2S concentration. LPS (10 mg/kg ip, 6 h) increased plasma H2S concentration from 34.1 ± 0.7 µM to 40.9 ± 0.6 µM (n=6, P<0.05) while H2S formation from added l‐cysteine was increased in both liver and kidney. CSE gene expression was also increased in both liver (94.2±2.7%, n=6, P<0.05) and kidney (77.5±3.2%, n=6, P<0.05). LPS injection also elevated lung (148.2±2.6%, n=6, P<0.05) and kidney (78.8±8.2%, n=6, P<0.05) myeloperoxidase (MPO, a marker of tissue neutrophil infiltration) activity alongside histological evidence of lung, liver, and kidney tissue inflammatory damage. Plasma nitrate/nitrite (NOx) concentration was additionally elevated in a time‐ and dose‐dependent manner in LPS‐injected animals. To examine directly the possible proinflammatory effect of H2S, mice were administered sodium hydrosulfide (H2S donor drug, 14 µmol/kg ip) that resulted in marked histological signs of lung inflammation, increased lung and liver MPO activity, and raised plasma TNF‐α concentration (4.6±1.4 ng/ml, n=6). In contrast, dl‐propargylglycine (CSE inhibitor, 50 mg/kg ip), exhibited marked anti‐inflammatory activity as evidenced by reduced lung and liver MPO activity, and ameliorated lung and liver tissue damage. In separate experiments, we also detected significantly higher (150.5±43.7 µM c.f. 43.8±5.1 µM, n=5, P<0.05) plasma H2S levels in humans with septic shock. These findings suggest that H2S exhibits proinflammatory activity in endotoxic shock and suggest a new approach to the development of novel drugs for this condition.
Endogenous H(2)S is synthesized mainly by cystathionine gamma-lyase in the heart. The present study investigated the role of H(2)S in cardioprotection induced by ischemic preconditioning. We have examined the effect of endogenous H(2)S and exogenous application of NaHS (H(2)S donor) on cardiac rhythm in the isolated rat heart subjected to low-flow ischemia insults as well as cell viability and function in isolated myocytes exposed to simulated ischemia solution. Preconditioning with NaHS (SP) or ischemia (IP) for three cycles (3 min each cycle separated by 5 min of recovery) significantly decreased the duration and severity of ischemia/reperfusion-induced arrhythmias in the isolated heart while increasing cell viability and the amplitude of electrically induced calcium transients after ischemia/reperfusion in cardiac myocytes. Both IP and SP also significantly attenuated the decreased H(2)S production during ischemia. Moreover, decreasing endogenous H(2)S production significantly attenuated the protective effect of IP in both the isolated heart and isolated cardiac myocytes. Blockade of protein kinase C with chelerythrine or bisindolylmaleimide I as well as ATP-sensitive K(+) (K(ATP)) channel with glibenclamide (a nonselective K(ATP) blocker) and HMR-1098 (1-[[5-[2-(5-Chloro-o-anisamido)ethyl]-2-methoxyphenyl]sulfonyl]-3-methylthiourea) (a sarcolemmal K(ATP) channel blocker) reversed the cardioprotection induced by SP or IP. However, blockade of mitochondrial K(ATP) channels with 5-hydroxydecanoic acid had no effect on the cardioprotection of SP, suggesting that, unlike the mechanism involved in IP, mitochondrial K(ATP) channels most probably do not play a major role in the cardioprotection of SP. Our findings suggest that endogenous H(2)S contributes to cardioprotection induced by IP, which effect may involve protein kinase C and sarcolemmal K(ATP) channels.
The cardiac electrophysiological effects of hydrogen sulfide (H2S) were examined in guinea pig papillary muscles in vitro using intracellular microelectrode technique. The results obtained were as follows: (1) the duration of action potential (APD) in the normal papillary muscles was decreased by NaHS (H(2)S donor, 50, 100, 200 micromol/L) in a concentration-dependent manner; (2) in partially depolarized papillary muscles, 100 micromol/L NaHS not only reduced APD, but also decreased the amplitude of action potential (APA), overshoot (OS) and maximal velocity of depolarization at phase 0 (V(max)); (3) pretreatment with ATP-sensitive K(+) (K(ATP)) channel blocker glibenclamide (20 micromol/L) partially blocked the effects of NaHS (100 micromol/L); (4) pretreatment with L-type Ca(2+) channel agonist Bay K8644 (0.5 micromol/L) also partially blocked the effects of NaHS (100 micromol/L); (5) pretreatment with Ca(2+)-free Krebs-Henseleit solution containing glibenclamide (20 micromol/L) completely blocked the effects of NaHS (100 micromol/L); (6) APD in the normal papillary muscles was increased by DL-propargylglycine (PPG, an inhibitor of cystathionine gamma-lyase, 200 micromol/L). All these results suggest that the electrophysiological effects of H(2)S on papillary muscles in our study are due to an increase in potassium efflux through the opening of K(ATP) channels and a decrease in calcium influx. Endogenous H(2)S may act as an important regulator in electrophysiological characters in papillary muscles.
The purpose of the present study was to test the hypothesis that steps between the excitation of the cell membrane and contraction are altered in cardiac failure. Ca2+-currents and [Ca2+]-transients were measured in single ventricular myocytes isolated from explanted hearts of patients with terminal heart failure undergoing transplantation, or from donors whose organs could not be used for technical reasons.
Peak Ca2+-current densities were unchanged, as was the current-voltage relation. However, in myocytes isolated from severely failing hearts resting [Ca2+]i-levels were elevated, peak [Ca2+]i-transients were significantly smaller, and the diastolic decline of [Ca2+]i was markedly slowed.
As the trigger for the release of Ca2+ from the sarcoplasmic reticulum is unchanged and the systolic [Ca2+]i-transient is reduced, severe heart failure can be described as partial electromechanical uncoupling.
The calcium antagonist flunarizine suppresses pathologic accumulation of calcium intracellularly without affecting the fast sodium or the slow calcium channel. To establish its value in differentiating between mechanisms of arrhythmias in the canine heart, the effect of flunarizine was investigated on ventricular tachycardia (VT) induced by ouabain intoxication or occurring 16-24 hours after occlusion of the left anterior descending coronary artery. Four groups of dogs were studied. Group 1 consisted of 13 animals with VT induced by ouabain intoxication (triggered-activity group). Group 2 included nine dogs in whom VT developed 16-24 hours after occlusion of the left anterior descending coronary artery (abnormal automaticity group). Group 3 included six dogs with normally conducted sinus beats, whereas group 4 consisted of six animals having a ventricular escape rhythm. With the exception of group 3, all dogs had surgically induced complete atrioventricular block. All animals were studied while conscious and without premedication. In groups 1 and 2, 2-3 mg/kg flunarizine was given intravenously after VT had persisted for at least 20 minutes. In groups 3 and 4, 2 mg/kg flunarizine was given after the rhythm was registered for 20 minutes. The cycle lengths of the different rhythms were compared before and after flunarizine. In group 1, flunarizine increased the cycle length of the VT from 300 +/- 30 to 410 +/- 50 msec (p less than or equal to 0.001). Termination of VT was seen in 11 out of 13 animals. In group 2, flunarizine resulted in a nonsignificant shortening of the RR interval from 450 +/- 60 to 440 +/- 60 msec. Persistent termination was observed in only one of nine dogs.(ABSTRACT TRUNCATED AT 250 WORDS)
Hypertrophic cardiomyopathy is characterized by a nondilated, hypertrophied left ventricle in the absence of any overt cause. A possible role of adrenergic innervation or of cellular calcium regulation is suggested by the presence of hyperdynamic left ventricular function and by the clinical and symptomatic improvement seen in patients treated with beta-receptor antagonists or calcium antagonists. Therefore, we measured the density of calcium-antagonist receptors and beta-adrenoceptors in the atrial myocardium of 16 patients with hypertrophic cardiomyopathy and 19 patients with various other cardiac disorders. For comparison, we also measured the number of voltage-sensitive sodium channels. Calcium-antagonist binding sites, measured as the amount of dihydropyridine bound to atrial tissue, were increased by 33 percent in patients with hypertrophic cardiomyopathy (mean [+/- SD], 397 +/- 104 fmol per milligram of protein in patients with hypertrophic cardiomyopathy, as compared with 299 +/- 108 in patients with other cardiac disorders; P less than 0.01). The densities of saxitoxin-binding sites on voltage-sensitive sodium channels and beta-adrenoceptors were the same in the two groups, although the density of beta-adrenoceptors was higher in atrial samples from patients receiving beta-receptor antagonists (165 +/- 86 fmol per milligram of protein [patients receiving beta-blockers] vs. 85 +/- 60 [patients not receiving beta-blockers]; P less than 0.04). The increase in the number of calcium-antagonist receptors in hypertrophic cardiomyopathy suggests that abnormal calcium fluxes through voltage-sensitive calcium channels may play a pathophysiologic part in the disease.
The Syrian cardiomyopathic hamster has a hereditary disease in which a progressive myocardial necrosis mimics human forms of cardiac hypertrophy. Lesions are associated with calcium overload and can be prevented with the calcium antagonist verapamil. Numbers of receptor binding sites for calcium antagonists in heart, brain, skeletal muscle, and smooth muscle were markedly increased in cardiomyopathic hamsters. The uptake of calcium-45 into brain synaptosomes was also increased in cardiomyopathic hamsters. The increase in calcium antagonist receptors and related voltage-sensitive calcium channels may be involved in the pathogenesis of this cardiomyopathy.
Organic inhibitors of calcium influx prevent outward as well as inward current through cardiac calcium channels but do not slow current activation. Although block is antagonized by raising external calcium or barium concentrations, the competitive effect of permeant cations does not occur at the same cation binding site at which inorganic blockers act. Organic drugs show varying degrees of use-dependent block, due in part to blockade of open channels. Nitrendipine blockade of calcium currents requires doses greater than 100-fold higher than expected from radioligand binding to isolated membranes.
We studied the acute hemodynamic effects of nifedipine in 20 patients with angiographically proved coronary artery disease. Eight patients were studied during exercise-induced pain. There was an expected abnormal increase in pulmonary wedge pressure (28 +/- 8 mm Hg, mean +/- SD) accompanying chest pain (onset 179 seconds, duration 334 seconds) and ST-segment depression (2.2 +/- 0.9 mm) on the ECG. Pacing stress was used in six patients and increased left ventricular (LV) end-diastolic pressure (from 16 +/- 6 to 26 +/- 6 mm Hg), volumes (end-diastolic 63 +/- 20 to 81 +/- 22 ml/m2, end-systolic 26 +/- 15 to 47 +/- 16 ml/m2) and impaired ejection fraction (0.60 +/- 0.15 to 0.44 +/- 0.11) compared with control values. In both groups, nifedipine, 20 mg sublingually, significantly shortened duration of pain, reduced ST depression on the ECG (p less than 0.001) and reversed all hemodynamic abnormalities. In another group of six patients with recent (less than 4 months) acute myocardial infarction and moderately severe LV dysfunction at rest, nifedipine reduced LV end-diastolic pressure from 21 +/- 6 to 12 +/- 5 mm Hg and volumes (end-diastolic from 109 +/- 35 to 95 +/- 32 ml/m2, end-systolic from 41 +/- 15 to 31 +/- 7 ml/m2), while the ejection fraction improved significantly, from 0.43 +/- 0.08 to 0.58 +/- 0.11. Thus, the antianginal effect of nifedipine is associated with improved systolic emptying and reduced diastolic filling of the heart. Nifedipine appears to have no discernible adverse effects in patients with depressed LV function.
The number of dihydropyridine and ryanodine receptors (DHP-R and RyR) has been measured in control and hypertrophied ventricles from rats, guinea pigs and ferrets to determine whether these two channels contribute to the alterations in excitation-contraction coupling (ECC), and in Ca2+ transient during compensated cardiac hypertrophy. We found that ventricular hypertrophy did not change the density of DHP-R. Mild hypertrophy did not alter the density of RyR in the rat but decreased it in the guinea-pig and in the ferret (30% and 36%, respectively). Severe hypertrophy decreased the density of RyR by 20% in the rat and by 34% in the guinea-pig. Therefore, the decrease is greater in ferret and guinea-pig hearts than in rat heart. We conclude that the sarcoplasmic reticulum (SR) Ca2+ release channels but not the L-type Ca2+ channels could contribute to the slowing of intracellular Ca2+ movements and to the reduced velocity of shortening of the hypertrophied hearts. We suggest that, in the guinea pig and ferret hearts which express only the beta myosin heavy chain (MHC) isoform, the reduced velocity of shortening during hypertrophy is related to the decrease in RyR density, whereas in the rat, it is regulated primarily via a shift in the MHC isoform, except in severe hypertrophy in which the moderate decrease in RyR would also be involved.
Fibrosis is commonly found in association with cardiac hypertrophy and failure, but the relation of the connective tissue response to the development of impaired cardiac function remains unclear. We examined passive myocardial stiffness, active contractile function, and fibrosis in the spontaneously hypertensive rat (SHR), a model of chronic pressure overload in which impaired cardiac function follows a long period of stable hypertrophy.
We studied the passive and active mechanical properties of left ventricular (LV) papillary muscles isolated from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) at the ages of 12 months and 20 to 23 months. Seven of 15 SHR between 20 and 23 months of age had findings consistent with heart failure (SHR-F). In comparison to preparations from WKY rats and nonfailing SHR (SHR-NF), papillary muscles from the SHR-F group demonstrated increased passive stiffness (central segment exponential stiffness constant, kcs: SHR-F 95.6 +/- 19.8, SHR-NF 42.1 +/- 9.7, WKY rats 39.5 +/- 9.5 (mean +/- SD); SHR-F P < .01 versus SHR-NF, WKY rats). The increase in stiffness was associated with an increase in LV collagen concentration (SHR-F 8.71 +/- 3.14, SHR-NF 5.83 +/- 1.20, WKY rats 4.78 +/- 0.70 mg hydroxyproline/g dry LV wt; SHR-F P < .01 versus SHR-NF, WKY rats); an increase in interstitial fibrosis, as determined histologically (SHR-F 13.5 +/- 8.0%, SHR-NF 4.9 +/- 2.1%, WKY rats 3.6 +/- 0.8%; SHR-F P < .01 versus SHR-NF, WKY rats); and impaired tension development (SHR-F 3.18 +/- 1.27, SHR-NF 4.41 +/- 1.04, WKY rats 4.64 +/- 0.85 kdyne/mm2; SHR-F P < .05 versus SHR-NF; P < .01 versus WKY rats).
The development of heart failure in the aging SHR is associated with marked myocardial fibrosis, increased passive stiffness, and impaired contractile function relative to age-matched nonfailing SHR and nonhypertensive control animals. These data suggest that fibrosis or events underlying the connective tissue response are important in the transition from compensated hypertrophy to failure in the SHR.
Ketanserin (KT), an antihypertensive agent, has been shown to prolong action potential duration (APD) and QT interval and to induce torsade de pointes in some patients. We previously suggested that the prolongation of APD could be due to KT inhibition of the fast component of the delayed rectifier current (IKr) in guinea-pig myocytes. However, in other tissue such as human atrium, Purkinje fibers, epicardial cells, and rat ventricular myocytes, the transient outward potassium current (Ito) is one of the major repolarizing currents. We investigated the possibility that KT could also increase APD by blocking Ito. Action potentials and membrane currents were recorded from rat ventricular myocytes known to have a large Ito by using whole-cell patch-clamp techniques. We found that KT (50 mumol/L) significantly prolonged APD at 50% repolarization by 218% (P < .05) and APD at 90% repolarization by 256% (P < .05) with no significant effect on other action potential parameters. Time-dependent Ito and sustained current (ISus) were measured in the presence of 400 nmol/L nisoldipine during depolarizing pulses to 40 mV from a holding potential of -100 mV every 10 seconds. KT resulted in a concentration- and time-dependent inhibition of charge area of Ito evaluated by integration with an EC50 of 8.3 mumol/L. The inhibitory effect of KT (10 mumol/L) was seen at voltages from 0 to 80 mV without any shift of the current-voltage relation of peak Ito. KT did not significantly change activation, inactivation, and reactivating curves of Ito. Kinetic analysis of Ito showed a biexponential fit of inactivation in 80.5% of total tracings studied at voltages between -30 and 80 mV (n = 149, R = .99 +/- .01). The inhibitory effect of KT was more prominent on charge areas of the slow component (Qs) than the fast component (Qf) of Ito (Qf = 33.2 +/- 6.2 s.pA and Qs = 235.5 +/- 7.4 s.pA for the control condition; 12.4 +/- 4.3 and 59.6 +/- 17 s.pA for KT at 40 mV; n = 4). The binding association (k) and dissociation (l) constants at 40 mV were 9.0 +/- 0.9x10(6) M-1.s-1 and 86.6 +/- 0.3 s-1, respectively. KT also blocked ISus in a dose-dependent manner with an EC50 of 11.2 mumol/L and had no significant effect on both the inward rectifier potassium current and the L-type calcium current.(ABSTRACT TRUNCATED AT 400 WORDS)
We wished to assess the respective roles of the antihypertensive and blood pressure (BP)-independent effects of antihypertensive drugs on arterial hemodynamics and left ventricular hypertrophy (LVH) in end-stage renal disease (ESRD) patients.
In a double-blind study, 24 ESRD patients with LVH were randomized to 12 months' administration of either the angiotensin-converting enzyme (ACE) inhibitor perindopril (n = 14) or the calcium channel blocker nitrendipine (n = 10). Repeated measurements of the following parameters were performed: BP (mercury sphygmomanometry), left ventricular mass (LVM, echocardiography), cardiac output (aortic cross-section and velocity integral), total peripheral resistance (cardiac output and mean BP), aortic and large-artery compliance (pulse wave velocity, Doppler flowmeter), and arterial wave reflections (augmentation index, applanation tonometry). Radioimmunoassay was used to determine plasma renin activity, aldosterone, and plasma catecholamine levels. Two-way (time-treatment) ANOVA for repeated measures was used for statistical analysis. Perindopril and nitrendipine induced significant and similar decreases in BP, total peripheral resistance (P < .001), aortic and arterial pulse wave velocities (P < .001), and arterial wave reflections (P < .01). At baseline, the two groups had LVH mostly due to increased LV end-diastolic diameter (LVEDD) (perindopril, 54.3 +/- 1.4 and nitrendipine, 54.3 +/ 2.4 mm) with near-normal mean LV wall thickness (perindopril, 11.4 +/- 0.3 and nitrendipine, 11.2 +/- 0.4 mm). A decrease in LVM was observed only in patients receiving perindopril (from 317 +/- 18 to 247 +/- 21 g) (time-treatment interaction, P = .036). Nitrendipine had no significant effect on LVM (314 +/- 29 versus 286 +/- 32 g). The decrease in LVM observed with perindopril was associated with a reduction in LVEDD (49.9 +/- 1.6 versus 54.3 +/- 1.4 mm after 12 months) (time-treatment interaction, P = .04), while the mean LV wall thickness was unchanged (11.4 +/- 0.3 versus 10.5 +/- 0.5 mm). Cardiac alterations were not correlated with changes in BP or with alterations in plasma renin activity or aldosterone or catecholamine levels.
In ESRD patients with LVH, ACE inhibition decreases LVM independently of its antihypertensive effect and of associated alterations in arterial hemodynamics. The decrease in LVM was due primarily to a decrease in LV volume, which may have resulted in these patients from chronic volume overload.
The flux of calcium ions (Ca2+) into the cytosol, where they serve as intracellular messengers, is regulated by two distinct families of Ca2+ channel proteins. These are the intracellular Ca2+ release channels, which allow Ca2+ to enter the cytosol from intracellular stores, and the plasma membrane Ca2+ channels, which control Ca2+ entry from the extracellular space. Each of these two families of channel proteins contains several subgroups. The intracellular channels include the large Ca2+ channels ("ryanodine receptors") that participate in cardiac and skeletal muscle excitation-contraction coupling, and smaller inositol trisphosphate (InsP3)-activated Ca2+ channels. The latter serve several functions, including the pharmacomechanical coupling that activates smooth muscle contraction, and possibly regulation of diastolic tone in the heart. The InsP3-activated Ca2+ channels may also participate in signal transduction systems that regulate cell growth. The family of plasma membrane Ca2+ channels includes L-type channels, which respond to membrane depolarization by generating a signal that opens the intracellular Ca2+ release channels. Calcium ion entry through L-type Ca2+ channels in the sinoatrial (SA) node contributes to pacemaker activity, whereas L-type Ca2+ channels in the atrioventricular (AV) node are essential for AV conduction. The T-type Ca2+ channels, another member of the family of plasma membrane Ca2+ channels, participate in pharmacomechanical coupling in smooth muscle. Opening of these channels in response to membrane depolarization participates in SA node pacemaker currents, but their role in the working cells of the atria and ventricle is less clear. Like the InsP3-activated intracellular Ca2+ release channels, T-type plasma membrane channels may regulate cell growth. Because most of the familiar Ca2+ channel blocking agents currently used in cardiology, such as nifedipine, verapamil and diltiazem, are selective for L-type Ca2+ channels, the recent development of drugs that selectively block T-type Ca2+ channels offers promise of new approaches to cardiovascular therapy.
To elucidate possible mechanisms underlying the cardiotoxicity of terfenadine, the effect of this antihistamine on L-type Ca2+ channel current (ICa,L) was studied in adult rat ventricular myocytes using the whole-cell patch-clamp technique. Myocytes were held at -70 mV and internally dialyzed and externally perfused with Na(+)- and K(+)-free solutions; exposure to terfenadine (10(-9) to 5 x 10(-6) mol/L) resulted in a concentration-dependent inhibition of peak ICa,L with a half-maximum inhibition concentration (IC50) of 142 nmol/L. The terfenadine-induced inhibition of ICa,L was not mediated via effects on histamine H1 receptors, because 1 mumol/L triprolidine, a more selective and potent H1 antagonist, had no effect on ICa,L. In this study, we found that terfenadine (1) increased both the fast and slow time constants of ICa,L inactivation, (2) shifted the steady state inactivation of ICa,L to more negative potentials, and (3) elicited a tonic block and a use-dependent block of ICa,L. The terfenadine-induced tonic and use-dependent block and the steady state inhibition of ICa,L were voltage dependent. Both tonic and use-dependent blocks of ICa,L by terfenadine at -40 mV were greater than that at -70 mV, and blocks were partially released by applying a long hyperpolarizing prepulse to -90 mV. These results suggest that terfenadine binds to L-type Ca2+ channels in inactivated and rested states and inhibits ICa,L predominantly by interacting with the inactivated state with an apparent dissociation constant of 60 nmol/L. Open-state block could be observed only at high concentrations of terfenadine. The high-affinity interaction of terfenadine with the inactivated state of L-type Ca2+ channels may play an important role in its cardiotoxicity under pathophysiological conditions, such as ischemia.
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.
Ca(2+) sparks are spatially localized intracellular Ca(2+) release events that were first described in 1993. Sparks have been ascribed to sarcoplasmic reticulum Ca(2+) release channel (ryanodine receptor, RyR) opening induced by Ca(2+) influx via L-type Ca(2+) channels or by spontaneous RyR openings and have been thought to reflect Ca(2+) release from a cluster of RyR. Here we describe a pharmacological approach to study sparks by exposing ventricular myocytes to caffeine with a rapid solution-switcher device. Sparks under these conditions have properties similar to naturally occurring sparks in terms of size and intracellular Ca(2+) concentration ([Ca(2+)](i)) amplitude. However, after the diffusion of caffeine, sparks first appear close to the cell surface membrane before coalescing to produce a whole cell transient. Our results support the idea that a whole cell [Ca(2+)](i) transient consists of the summation of sparks and that Ca(2+) sparks consist of the opening of a cluster of RyR and confirm that characteristics of the cluster rather than the L-type Ca(2+) channel-RyR relation determine spark properties.
Through the use of microanatomic techniques, we investigated the effects of treatment with some dihydropyridine-type calcium antagonists (CAs) (ie, lercanidipine, manidipine, and nicardipine) and with the nondihydropyridine-type vasodilator hydralazine on hypertension-dependent glomerular injury and on the morphology of afferent and efferent arterioles in spontaneously hypertensive rats (SHR). Fourteen-week-old male SHR and age-matched normotensive Wistar-Kyoto rats were left untreated (control groups). Four additional groups of 14-week-old SHR were treated for 12 weeks with daily oral doses of 2.5 mg/kg lercanidipine, 5 mg/kg manidipine, 3 mg/kg nicardipine, or 10 mg/kg hydralazine. These treatments decreased systolic blood pressure values to a similar extent in SHR. Signs of glomerular injury, as characterized by glomerulosclerosis, hypertrophy, and an increased number of mesangial cells, were observed in control SHR. The treatment with CAs improved glomerular morphology and decreased the number of mesangial cells. Lercanidipine and manidipine were more effective than nicardipine in countering glomerular injury. In the SHR, both afferent and efferent arterioles revealed luminal narrowing, accompanied by increased wall thickness in efferent arterioles. The dihydropyridine-type derivatives that were tested decreased the luminal narrowing of afferent arterioles. Lercanidipine and manidipine countered the luminal narrowing of efferent arterioles. Hydralazine had no effect on hypertension-dependent glomerular injury or vascular changes. The present data indicate that lercanidipine and manidipine vasodilate afferent and efferent arterioles in SHR. A vasodilatory activity on efferent arteriole, which is not induced by the majority of CAs, may represent an useful property in the treatment of hypertension complicated by renal disease.
Caffeine has been used as a pharmacological tool to study the ryanodine receptor (RYR)-mediated Ca2+ release from caffeine-sensitive, inositol 1,4,5,-trisphosphate (IP3)-insensitive pools. In the present study, we demonstrate multiple effects of caffeine on Ca2+ homeostasis in human B lymphocytes. Although B cells express a functional RYR, which can be activated by 4-chloro-m-cresol following depletion of IP(3)-sensitive pools, caffeine does not activate RYR-mediated Ca2+ release. Instead, caffeine dose-dependently inhibited IP3 receptor (IP3R)-mediated Ca2+ release, RYR-mediated Ca2+ release and B cell receptor-initiated Ca2+ influx, while high concentrations of caffeine (> or = 25 mM) induced a Ca2+ influx. In contrast with its ability to suppress receptor-stimulated Ca2+ influx, caffeine had no significant effect on the store-operated Ca2+ (SOC) channel-dependent Ca2+ influx induced by thapsigargin. Thus, caffeine may act as an inhibitor on a single or multiple site(s) responsible for regulating the IP3R channel, RYR channel and presumably the receptor-mediated SOC channel. The present report may be the first demonstration of multiple effects of caffeine on Ca2+ mobilization in single cell type. Our results suggest the need for caution regarding use of caffeine simply as a RYR-activator to study Ca2+ homeostasis in eucaryotic cells.
Downregulation of the L-type Ca(2+) current (I(Ca)) is an important determinant of the electrical remodeling of diseased atria. Using a rat model of heart failure (HF) due to ischemic cardiopathy, we studied I(Ca) in isolated left atrial myocytes with the whole-cell patch-clamp technique and biochemical assays. I(Ca) density was markedly reduced (1.7+/-0.1 pA/pF) compared with sham-operated rats (S) (4.1+/-0.2 pA/pF), but its gating properties were unchanged. Calcium channel alpha(1C)-subunit quantities were not significantly different between S and HF. The beta-adrenergic agonist isoproterenol (1 micromol/L) had far greater stimulatory effects on I(Ca) in HF than in S (2.5- versus 1-fold), thereby suppressing the difference in current density. Dialyzing cells with 100 micromol/L cAMP or pretreating them with the phosphatase inhibitor okadaic acid also increased I(Ca) and suppressed the difference in density between S and HF. Intracellular cAMP content was reduced more in HF than in S. The phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine had a greater effect on I(Ca) in HF than in S (76.0+/-11.2% versus 15.8+/-21.2%), whereas the inhibitory effect of atrial natriuretic peptide on I(Ca) was more important in S than in HF (54.1+/-4.8% versus 24.3+/-8.8%). Cyclic GMP extruded from HF myocytes was enhanced compared with S (55.8+/-8.0 versus 6.2+/-4.0 pmol. mL(-1)). Thus, I(Ca) downregulation in atrial myocytes from rats with heart failure is caused by changes in basal cAMP-dependent regulation of the current and is associated with increased response to catecholamines.
Hydrogen sulfide (H(2)S) has been traditionally viewed as a toxic gas. It is also, however, endogenously generated from cysteine metabolism. We attempted to assess the physiological role of H(2)S in the regulation of vascular contractility, the modulation of H(2)S production in vascular tissues, and the underlying mechanisms. Intravenous bolus injection of H(2)S transiently decreased blood pressure of rats by 12- 30 mmHg, which was antagonized by prior blockade of K(ATP) channels. H(2)S relaxed rat aortic tissues in vitro in a K(ATP) channel-dependent manner. In isolated vascular smooth muscle cells (SMCs), H(2)S directly increased K(ATP) channel currents and hyperpolarized membrane. The expression of H(2)S-generating enzyme was identified in vascular SMCs, but not in endothelium. The endogenous production of H(2)S from different vascular tissues was also directly measured with the abundant level in the order of tail artery, aorta and mesenteric artery. Most importantly, H(2)S production from vascular tissues was enhanced by nitric oxide. Our results demonstrate that H(2)S is an important endogenous vasoactive factor and the first identified gaseous opener of K(ATP) channels in vascular SMCs.
Heme oxygenase (HO) and carbon monoxide (CO) participate in the homeostatic control of cardiovascular functions, including the regulation of blood pressure (BP). Upregulation of the HO/CO system has been shown to lower BP in young (8 weeks) but not in adult (20 weeks) spontaneously hypertensive rats (SHR). The underlying mechanism for this selective effect, however, has been unknown and was investigated in the present study. The administration of hemin resulted in a marked decrease in BP (from 148.6+/-3.2 to 125.8+/-2.6 mm Hg, P<0.01) in young but not in prehypertensive (4 weeks) or adult SHR or Wistar-Kyoto rats at all ages. The inhibition of HO with chromium mesoporphyrin abrogated the BP-lowering effect of hemin. Significantly lower expression levels of HO-1 and soluble gyanylyl cyclase (sGC) as well as reduced cGMP content were detected in 8-week SHR but not in adult SHR or Wistar-Kyoto rats of all ages. These deficiencies were all corrected by hemin treatment. The expression of HO-2 protein was not different among all animal groups tested and not affected by hemin treatment. Desensitization of the sGC/cGMP pathway in adult SHR was demonstrated by the reduced vasorelaxant potency of the sGC activator 3-(5' -hydroxymethyl-2-'furyl)-1-benzylindazole. Thus, in young and prehypertensive SHR, a defective HO/CO-sGC/cGMP system might constitute a pathogenic mechanism for the development of hypertension. The HO/CO-sGC/cGMP system appears normal in adult SHR, but desensitization of the downstream targets of the system to sGC/cGMP may endow SHR at this stage a persistent hypertension status.
Lysophosphatidic acid (LPA) is a phospholipid messenger, which is released from activated platelets and leukocytes. This study examined the effects of LPA on myocardial contractility and characterized the signal transduction pathway involved in these effects. Functional effects of LPA were determined in isolated, electrically driven human myocardial preparations and rat cardiac myocytes. In human atrial and ventricular myocardial preparations, LPA (100 micromol/l) decreased isoprenaline (0.03 micromol/l) enhanced force of contraction by 17 +/- 2% and 28 +/- 3%, respectively. The effect of LPA was attenuated by suramin (1 mmol/l). In isolated rat cardiomyocytes, LPA (1-100 micromol/l) concentration dependently abolished isoprenaline (0.03 micromol/l) induced increase in cell shortening. This antiadrenergic effect was blunted after pretreatment with pertussis toxin (5 microg/ml, 12 h). Forskolin (10 micromol/l) stimulated adenylyl cyclase activity was inhibited by LPA in human myocardial membranes. PCR analysis of human atrial and ventricular cDNAs revealed the expression of two cognate LPA receptors: EDG-2 and EDG-7. Our results suggest that LPA exerts antiadrenergic effects on force of contraction in human and rodent myocardium via a Galpha(i/o) protein-mediated mechanism, most probably by LPA binding to the mammalian LPA receptors EDG-2 and/or EDG-7. This newly discovered action of LPA might be of pathophysiological importance in conditions like myocardial ischemia or inflammatory disorders when LPA release is enhanced.
Nitric oxide (NO) is produced from virtually all cell types composing the myocardium and regulates cardiac function through both vascular-dependent and -independent effects. The former include regulation of coronary vessel tone, thrombogenicity, and proliferative and inflammatory properties as well as cellular cross-talk supporting angiogenesis. The latter comprise the direct effects of NO on several aspects of cardiomyocyte contractility, from the fine regulation of excitation-contraction coupling to modulation of (presynaptic and postsynaptic) autonomic signaling and mitochondrial respiration. This multifaceted involvement of NO in cardiac physiology is supported by a tight molecular regulation of the three NO synthases, from cellular spatial confinement to posttranslational allosteric modulation by specific interacting proteins, acting in concert to restrict the influence of NO to a particular intracellular target in a stimulus-specific manner. Loss of this specificity, such as produced on excessive NO delivery from inflammatory cells (or cytokine-stimulated cardiomyocytes themselves), may result in profound cellular disturbances leading to heart failure. Future therapeutic manipulations of cardiac NO synthesis will necessarily draw on additional characterization of the cellular and molecular determinants for the net effect of this versatile radical on the cardiomyocyte biology.
Gases such as nitric oxide and carbon monoxide play important roles both in normal physiology and in disease. In recent years, interest has been directed towards other naturally occurring gases, notably hydrogen sulfide (H(2)S), which is both a potent vasodilator and a mediator of long-term potentiation in the brain. This article focuses on recent work that suggests a role for H(2)S, and perhaps other gases, in the CNS and cardiovascular system.
Hydrogen sulfide (H(2)S) is a newly found modulator in vascular system. This work showed that gene expression of cystathionine gamma-lyase (CSE), a H(2)S generating enzyme, and the activity of CSE in thoracic aorta were suppressed in hypertension rats. The plasma level of H(2)S also decreased in those rats. Exogenous administration of H(2)S could increase the plasma level of H(2)S and enhance the CSE activity of aorta. Exogenous administration of H(2)S also attenuated the elevation of pressure and lessened the aorta structural remodeling during the development of hypertension. In WKY rats, the gene expression and activity of CSE also decreased when the endogenous production of H(2)S was deprived by administration of DL-propargylglycine (specific inhibitor of CSE), accompanying the elevated pressure and the development of vascular remodeling. The results showed that endogenous H(2)S system was involved in both the maintenance of basal blood pressure and the development of hypertension. Exogenous H(2)S could exert beneficial effect on the pathogenesis of spontaneous hypertension.
Hydrogen sulfide (H2S), which was considered as a novel gasotransmitter, is produced endogenously from L-cysteine in mammalian brain and vessels, and might be a physiological function regulator to these organs. Here, we showed that mRNA for H2S producing enzyme, cystathionine gamma-lyase, was expressed in myocardial tissues and H2S could endogenously be produced in myocardial tissues. Negative inotropic effect of H2S was proved in present study in vitro and in vivo experiments, and the effect could partly be blocked by glibenclamide, a KATP channel blocker. An intravenous bolus injection of NaHS provoked a decrease in central venous pressure. The present findings suggested that H2S could be endogenously produced by heart tissues, as a physiological cardiac function regulator, mediated by KATP channel pathway.
Phosphoinositide 3-kinase (PI3K) is a key component in regulating myocardial growth, survival and contractility. LY294002 and wortmannin are two PI3K inhibitors used widely to establish the role of PI3K. The goal of this study was to examine the effects of acute application of LY294002 and wortmannin on cardiac myocyte contractility and underlying mechanisms.
Patch-clamp, indo-1 epifluorescence and video-edge detection techniques were used to measure outward K(+) currents, action potentials (AP), Ca(2+) transients and shortening of myocytes isolated from mouse left ventricular free wall.
In field-stimulated myocytes, LY294002 (10 micromol/l) increased Ca(2+) transient amplitude by 23%, and cell shortening amplitude by 60% in the absence or presence of wortmannin, while wortmannin alone had no effect. LY294002 (but not wortmannin) prolonged AP duration by specifically inhibiting slowly inactivating K(+) currents (i.e., the 4-aminopyrydine-sensitive I(k,slow1) and the tetraethylammonium-sensitive I(k,slow2)), leading to an increase in sarcoplasmic reticular Ca(2+) levels. It appeared that the AP prolongation was responsible for elevated contractility since AP-clamp of myocytes with prolonged APs (recorded in LY294002-treated myocytes) induced a 29% increase in cell shortening compared with control APs, while LY294002 application did not increase contractility in voltage-clamp studies using either step or AP depolarizations.
The putative PI3K inhibitor LY294002 increases Ca(2+) release and myocyte contractility via direct inhibition of cardiac I(k,slow) and AP prolongation, thus limiting the usefulness of this agent in the analyses of the role of PI3K in heart function.
Although downregulation of L-type Ca2+ current (I(Ca,L)) in chronic atrial fibrillation (AF) is an important determinant of electrical remodeling, the molecular mechanisms are not fully understood. Here, we tested whether reduced I(Ca,L) in AF is associated with alterations in phosphorylation-dependent channel regulation.
We used whole-cell voltage-clamp technique and biochemical assays to study regulation and expression of I(Ca,L) in myocytes and atrial tissue from 148 patients with sinus rhythm (SR) and chronic AF. Basal I(Ca,L) at +10 mV was smaller in AF than in SR (-3.8+/-0.3 pA/pF, n=138/37 [myocytes/patients] and -7.6+/-0.4 pA/pF, n=276/86, respectively; P<0.001), though protein levels of the pore-forming alpha1c and regulatory beta2a channel subunits were not different. In both groups, norepinephrine (0.01 to 10 micromol/L) increased I(Ca,L) with a similar maximum effect and comparable potency. Selective blockers of kinases revealed that basal I(Ca,L) was enhanced by Ca2+/calmodulin-dependent protein kinase II in SR but not in AF. Norepinephrine-activated I(Ca,L) was larger with protein kinase C block in SR only, suggesting decreased channel phosphorylation in AF. The type 1 and type 2A phosphatase inhibitor okadaic acid increased basal I(Ca,L) more effectively in AF than in SR, which was compatible with increased type 2A phosphatase but not type 1 phosphatase protein expression and higher phosphatase activity in AF.
In AF, increased protein phosphatase activity contributes to impaired basal I(Ca,L). We propose that protein phosphatases may be potential therapeutic targets for AF treatment.
The role of hydrogen sulfide (H(2)S) in myocardial infarction (MI) has not been previously studied. We therefore investigated the effect of H(2)S in a rat model of MI in vivo. Animals were randomly divided into three groups (n = 80) and received either vehicle, 14 micromol/kg of sodium hydrosulfide (NaHS), or 50 mg/kg propargylglycine (PAG) everyday for 1 wk before surgery, and the treatment was continued for a further 2 days after MI when the animals were killed. The mortality was 35% in vehicle-treated, 40% in PAG-treated, and 27.5% in NaHS-treated (P < 0.05 vs. vehicle) groups. Infarct size was 52.9 +/- 3.5% in vehicle-treated, 62.9 +/- 7.6% in PAG-treated, and 43.4 +/- 2.8% in NaHS-treated (P < 0.05 vs. vehicle) groups. Plasma H(2)S concentration was significantly increased after MI (59.2 +/- 7.16 microM) compared with the baseline concentration (i.e., 38.2 +/- 2.07 microM before MI; P < 0.05). Elevated plasma H(2)S after MI was abolished by treatment of animals with PAG (39.2 +/- 5.02 microM). We further showed for the first time cystathionine-gamma-lyase protein localization in the myocardium of the infarct area by using immunohistochemical staining. In the hypoxic vascular smooth muscle cells, we found that cell death was increased under the stimuli of hypoxia but that the increased cell death was attenuated by the pretreatment of NaHS (71 +/- 1.2% cell viability in hypoxic vehicle vs. 95 +/- 2.3% in nonhypoxic control; P < 0.05). In conclusion, endogenous H(2)S was cardioprotective in the rat model of MI. PAG reduced endogenous H(2)S production after MI by inhibiting cystathionine-gamma-lyase. The results suggest that H(2)S might provide a novel approach to the treatment of MI.
Hydrogen sulfide (H(2)S) is a gasotransmitter that regulates cardiovascular functions. The present study aimed to examine the hypothesis that chronic treatment with sodium hydrosulfide (NaHS, an H(2)S donor) is able to prevent left-ventricular remodeling in spontaneously hypertensive rats (SHR). Four-week-old SHR were treated with NaHS (10, 30, and 90 micromol x kg(-1) x day(-1)), a combination of NaHS (30 micromol x kg(-1) x day(-1)) and glibenclamide (5 mg x kg(-1) x day(-1)), glibenclamide alone (5 mg x kg(-1) x day(-1)), hydralazine alone (10 mg x kg(-1) x day(-1)), and placebo for 3 mo. At the end of the treatment period, variables such as cardiac geometry and function, intramyocardial arterioles ranging in diameter from 25 to 100 microm, perivascular and interstitial collagen content, reactive oxygen species (ROS), thiol groups, conjugated dienes, and DNA base modification were examined. The novel finding of the present study is that chronic NaHS treatment prevented the hypertrophy of intramyocardial arterioles and ventricular fibrosis, as well as decreased myocardial ROS and conjugated diene levels. The cardioprotective effects were blunted by coadministration of glibenclamide, suggesting a role of ATP-sensitive potassium channels in mediating the action of NaHS. Hydralazine caused a comparable reduction of blood pressure compared with NaHS treatment; however, it exerted no effect on the remodeling process or on ROS and conjugated diene levels. Moreover, NaHS treatment caused an increase in myocardial thiol group levels, whereas DNA base modification was not altered by NaHS treatment. In conclusion, the superior cardioprotective effects of NaHS treatment are worthy to be further explored to develop novel therapeutic approaches for the treatment of cardiac remodeling in hypertension.
Hydrogen sulfide (H(2)S) has been reported to be a gasotransmitter which regulates cardiovascular homeostasis. The present study aims to examine the hypothesis that hydrogen sulfide is able to promote angiogenesis.
Angiogenesis was assessed using in vitro parameters (i.e. endothelial cell proliferation, adhesion, transwell migration assay, scratched wound healing and formation of tube-like structure) and in vivo by assessing neovascularization in mice. Phosphorylation of Akt was measured using Western blot analysis.
Exogenously administered NaHS (H(2)S donor) concentration-dependently (10-20 micromol/l) increased cell growth, migration, scratched wound healing and tube-like structure formation in cultured endothelial cells. These effects of NaHS on endothelial wound healing and tube-like structure formation were prevented by either the phosphatidylinositol 3-kinase (PI3K) inhibitor LY 294002 (5 micromol/l) or transfection of a dominant-negative mutant of Akt. NaHS increased Akt phosphorylation and this effect was also blocked by either LY 294002 or wortmannin (25 nmol/l). NaHS did not significantly alter the levels of vascular endothelial growth factor, mRNA expression of fibroblast growth factor and angiopoietin-1, or nitric oxide metabolites. NaHS treatment (10 and 50 micromol kg(-1) day(-1)) significantly promoted neovascularization in vivo in mice.
The present study reports a novel proangiogenic role of H(2)S which is dependent on activation of Akt.