Hydrogen sulfide contributes to cardioprotection during ischemia-reperfusion injury by opening K ATP channels

Hydrogen sulfide in signaling pathways

For a long time hydrogen sulfide (H₂S) was considered a toxic compound, but recently H₂S (at low concentrations) has been found to play an important function in physiological processes. Hydrogen sulfide, like other well-known compounds - nitric oxide (NO) and carbon monoxide (CO) is a gaseous intracellular signal transducer. It regulates the cell cycle, apoptosis and the oxidative stress. Moreover, its functions include neuromodulation, regulation of cardiovascular system and inflammation. In this review, I focus on the metabolism of hydrogen sulfide (including enzymatic pathways of H₂S synthesis from l- and d-cysteine) and its signaling pathways in the cardiovascular system and the nervous system. I also describe how hydrogen sulfide may be used as therapeutic agent, i.e. in the cardiovascular diseases.

GYY4137 protects against myocardial ischemia and reperfusion injury by attenuating oxidative stress and apoptosis in rats

Hydrogen sulfide (H₂S) is a gasotransmitter that regulates cardiovascular functions. The present study aimed to determine the protective effect of slow-releasing H₂S donor GYY4137 on myocardial ischemia and reperfusion (I/R) injury and to investigate the possible signaling mechanisms involved. Male Sprague-Dawley rats were treated with GYY4137 at 12.5 mg/(kg·day), 25 mg/(kg·day) or 50 mg/(kg·day) intraperitoneally for 7 days. Then, rats were subjected to 30 minutes of left anterior descending coronary artery occlusion followed by reperfusion for 24 hours. We found that GYY4137 increased the cardiac ejection fraction and fractional shortening, reduced the ischemia area, alleviated histological injury and decreased plasma creatine kinase after myocardial I/R. Both H₂S concentration in plasma and cystathionine-γ-lyase (CSE) activity in the myocardium were enhanced in the GYY4137 treated groups. GYY4137 also decreased malondialdehyde and myeloperoxidase levels in serum, attenuated superoxide anion level and suppressed phosphorylation of mitogen activated protein kinases in the myocardium after I/R. Meanwhile, GYY4137 increased the expression of Bcl-2 but decreased the expression of Bax, caspase-3 activity and apoptosis in the myocardium. The data suggest that GYY4137 protects against myocardial ischemia and reperfusion injury by attenuating oxidative stress and apoptosis.

The role of gasotransmitters NO, H2S and CO in myocardial ischaemia/reperfusion injury and cardioprotection by preconditioning, postconditioning and remote conditioning

Ischaemic heart disease is one of the leading causes of morbidity and mortality worldwide. The development of cardioprotective therapeutic agents remains a partly unmet need and a challenge for both medicine and industry, with significant financial and social implications. Protection of the myocardium can be achieved by mechanical vascular occlusions such as preconditioning (PC), when brief episodes of ischaemia/reperfusion (I/R) are experienced prior to ischaemia; postconditioning (PostC), when the brief episodes are experienced at the immediate onset of reperfusion; and remote conditioning (RC), when the brief episodes are experienced in another vascular territory. The elucidation of the signalling pathways, which underlie the protective effects of PC, PostC and RC, would be expected to reveal novel molecular targets for cardioprotection that could be modulated by pharmacological agents to prevent reperfusion injury. Gasotransmitters including NO, hydrogen sulphide (H2S) and carbon monoxide (CO) are a growing family of regulatory molecules that affect physiological and pathological functions. NO, H2S and CO share several common properties; they are beneficial at low concentrations but hazardous in higher amounts; they relax smooth muscle cells, inhibit apoptosis and exert anti-inflammatory effects. In the cardiovascular system, NO, H2S and CO induce vasorelaxation and promote cardioprotection. In this review article, we summarize current knowledge on the role of the gasotransmitters NO, H2S and CO in myocardial I/R injury and cardioprotection provided by conditioning strategies and highlight future perspectives in cardioprotection by NO, H2S, CO, as well as their donor molecules.

KV 7 channels are involved in hypoxia-induced vasodilatation of porcine coronary arteries

BACKGROUND AND PURPOSE

Hypoxia causes vasodilatation of coronary arteries, but the underlying mechanisms are poorly understood. We hypothesized that hypoxia reduces intracellular Ca(2+) concentration ([Ca(2+)](i)) by opening of K channels and release of H₂S.

EXPERIMENTAL APPROACH

Porcine coronary arteries without endothelium were mounted for measurement of isometric tension and [Ca(2+)](i), and the expression of voltage-gated K channels K(V)7 channels (encoded by KCNQ genes) and large-conductance calcium-activated K channels (K(Ca)1.1) was examined. Voltage clamp assessed the role of K(V)7 channels in hypoxia.

KEY RESULTS

Gradual reduction of oxygen concentration from 95 to 1% dilated the precontracted coronary arteries and this was associated with reduced [Ca(2+)](i) in PGF(2α) (10 μM)-contracted arteries whereas no fall in [Ca(2+)](i) was observed in 30 mM K-contracted arteries. Blockers of ATP-sensitive voltage-gated potassium channels and K(Ca)1.1 inhibited hypoxia-induced dilatation in PGF2α -contracted arteries; this inhibition was more marked in the presence of the K(v)7 channel blockers, XE991 and linopirdine, while a K(V)7.1 blocker, failed to change hypoxic vasodilatation. XE991 also inhibited H₂S- and adenosine-induced vasodilatation. PCR revealed the expression of K(V)7.1, K(V)7.4, K(V)7.5 and K(Ca)1.1 channels, and K(Ca)1.1, K(V)7.4 and K(V)7.5 were also identified by immunoblotting. Voltage clamp studies showed the XE991-sensitive current was more marked in hypoxic conditions.

CONCLUSION

The K(V)7.4 and K(V)7.5 channels, which we identified in the coronary arteries, appear to have a major role in hypoxia-induced vasodilatation. The voltage clamp results further support the involvement of K(V)7 channels in this vasodilatation. Activation of these K(V)7 channels may be induced by H₂S and adenosine.

H2S and its role in redox signaling

Hydrogen sulfide (H2S) has emerged as an important gaseous signaling molecule that is produced endogenously by enzymes in the sulfur metabolic network. H2S exerts its effects on multiple physiological processes important under both normal and pathological conditions. These functions include neuromodulation, regulation of blood pressure and cardiac function, inflammation, cellular energetics and apoptosis. Despite the recognition of its biological importance and its beneficial effects, the mechanism of H2S action and the regulation of its tissue levels remain unclear in part owing to its chemical and physical properties that render handling and analysis challenging. Furthermore, the multitude of potential H2S effects has made it difficult to dissect its signaling mechanism and to identify specific targets. In this review, we focus on H2S metabolism and provide an overview of the recent literature that sheds some light on its mechanism of action in cellular redox signaling in health and disease. This article is part of a Special Issue entitled: Thiol-Based Redox Processes.

Hydrogen sulfide reduces regional myocardial ischemia injury through protection of mitochondrial function

Hydrogen sulfide (H2S) is a signaling gasotransmitter, involved in various physiological and pathological processes. H2S-donating drugs have been tested to conjugate the beneficial effects of H2S with other pharmaceutical properties. It has been shown that the endogenous cystathionine-γ-lyase (CSE)/H2S pathway participates in myocardial ischemia injury in isolated hearts in rats. The present study aimed to investigate the cytoprotective action of H2S against acute myocardial ischemia injury in rats. Isolated rat hearts were perfused and subjected to ischemic conditions for 4 h. The hearts were assigned to five groups: Sham, model, infarct plus low-dose (5 µmol/l) NaHS, infarct plus middle-dose (10 µmol/l) NaHS and infarct plus high-dose (20 µmol/l) NaHS. The administration of NaHS enhanced the activity of CSE, increased the content of H2S and reduced infarct volumes following myocardial ischemia injury. Furthermore, the administration of NaHS attenuated the injury to organelles (including the mitochondria, nucleus and myofilaments) by reducing lactate dehydrogenase activity, decreasing the level of mitochondrial malondialdehyde and increasing the activities of superoxide dismutase and glutathione peroxidase in the ischemic myocardial mitochondria. These protective effects of H2S against myocardial ischemia injury appeared to be mediated by its antioxidant activities and the preservation of mitochondrial function.

Alpha lipoic acid protects the heart against myocardial post ischemia-reperfusion arrhythmias via KATP channel activation in isolated rat hearts

The cardiovascular effects of alpha lipoic acid were evaluated in isolated rat hearts exposed to ischemia-reperfusion injury in vitro. Alpha-lipoic acid raised the level of sulfane sulfur playing an important role in the release of hydrogen sulfide. H2S was shown to prevent the post-reperfusion arrhythmias and to protect the cardiomyocytes from death caused by hypoxia. The activation of potassium ATP-sensitive channels (K(ATP) channels) is one of the most important mechanisms of action of hydrogen sulfide in the cardiovascular system. The aim of this study was to investigate whether alpha lipoic acid can prevent the occurrence of post-reperfusion arrhythmias in vitro using a Langendorff model of ischemia-reperfusion in rats affecting the K(ATP) channels. Alpha lipoic acid significantly improved post-reperfusion cardiac function (reducing incidence of arrhythmias), especially in a dose of 10(-7)M. These cardiovascular effects of this compound on the measured parameters were reversed by glibenclamide, a selective K(ATP) blocker. Alpha lipoic acid increased the level of sulfane sulfur in the hearts. This may suggest that the positive effects caused by alpha lipoic acid in the cardiovascular system are not only related to its strong antioxidant activity, and the influence on the activity of such enzymes as aldehyde dehydrogenase 2, as previously suggested, but this compound can affect K(ATP) channels. It is possible that this indirect effect of alpha lipoic acid is connected with changes in the release of sulfane sulfur and hydrogen sulfide.

Hydrogen sulfide alleviates cardiac contractile dysfunction in an Akt2-knockout murine model of insulin resistance: role of mitochondrial injury and apoptosis

Hydrogen sulfide (H2S) is a toxic gas now being recognized as an endogenous signaling molecule in multiple organ systems, in particular, the cardiovascular system. H2S is known to regulate cardiac function and protect against ischemic injury. However, little information is available regarding the effect of H2S on cardiac function in insulin resistance. This study was designed to examine the impact of H2S supplementation on cardiac function using an Akt2 knockout model of insulin resistance. Wild-type and Akt2 knockout mice were treated with NaHS (50 μM·kg(-1)·day(-1) ip for 10 days) prior to evaluation of echocardiographic, cardiomyocyte contractile, and intracellular Ca(2+) properties, apoptosis, and mitochondrial damage. Our results revealed that Akt2 ablation led to overtly enlarged ventricular end-systolic diameter, reduced myocardial and cardiomyocyte contractile function, and disrupted intracellular Ca(2+) homeostasis and apoptosis, the effects of which were ameliorated by H2S. Furthermore, Akt2 knockout displayed upregulated apoptotic protein markers (Bax, caspase-3, caspase-9, and caspace-12) and mitochondrial damage (reduced aconitase activity and NAD(+), elevated cytochrome-c release from mitochondria) along with reduced phosphorylation of PTEN, Akt, and GSK3β in the absence of changes in pan protein expression, the effects of which were abolished or significantly ameliorated by H2S treatment. In vitro data revealed that H2S-induced beneficial effect against Akt2 ablation was obliterated by mitochondrial uncoupling. Taken together, our findings suggest the H2S may reconcile Akt2 knockout-induced myocardial contractile defect and intracellular Ca(2+) mishandling, possibly via attenuation of mitochondrial injury and apoptosis.

Effects of post-resuscitation administration with sodium hydrosulfide on cardiac recovery in hypoxia-reoxygenated newborn piglets

Hydrogen sulfide may protect multiple organ systems against ischemic-reperfusion injuries. It is unknown if treatment with sodium hydrosulfide (NaHS, a hydrogen sulfide donor) will improve myocardial function and minimize oxidative stress in hypoxic-reoxygenated newborn piglets. Mixed breed piglets (1-5 day, 1.5-2.5 kg) were anesthetized and acutely instrumented for the measurement of systemic, pulmonary and regional (carotid, superior mesenteric and renal) hemodynamics and blood gas parameters. The piglets were induced with normocapnic alveolar hypoxia (10-15% oxygen, 2h) followed by reoxygenation with 100% (1h) then 21% oxygen (3h). At 10 min of reoxygenation, either NaHS (10mg/kg, 5 ml) or saline (5 ml) was administered intravenously for 30 min (5 min bolus followed by 25 min of continuous infusion) in a blinded, block-randomized fashion (n = 7/group). Plasma lactate and troponin I levels and tissue markers of myocardial oxidative stress were also determined. Two hours hypoxia caused cardiogenic shock (45 ± 3% of respective normoxic baseline), reduced regional perfusion with metabolic acidosis (pH 6.94 ± 0.02). NaHS infusion significantly improved recovery of cardiac index (84 ± 3% vs. 72 ± 5% in controls), systemic oxygen delivery (84 ± 3% vs. 72 ± 5% in controls) and systemic oxygen consumption (102 ± 5% vs. 84 ± 6% in controls) at 4h of reoxygenation. NaHS had no significant effect on systemic and pulmonary blood pressures, regional blood flows, plasma lactate and troponin I levels. The myocardial glutathionine ratio was reduced in piglets treated with NaHS (vs. controls, P<0.05). Post-resuscitation administration of NaHS improves cardiac function and systemic perfusion and attenuates myocardial oxidative stress in newborn piglets following hypoxia-reoxygenation.

Hydrogen sulfide chemical biology: pathophysiological roles and detection

Hydrogen sulfide (H2S) is the most recent endogenous gasotransmitter that has been reported to serve many physiological and pathological functions in different tissues. Studies over the past decade have revealed that H2S can be synthesized through numerous pathways and its bioavailability regulated through its conversion into different biochemical forms. H2S exerts its biological effects in various manners including redox regulation of protein and small molecular weight thiols, polysulfides, thiosulfate/sulfite, iron-sulfur cluster proteins, and anti-oxidant properties that affect multiple cellular and molecular responses. However, precise measurement of H2S bioavailability and its associated biochemical and pathophysiological roles remains less well understood. In this review, we discuss recent understanding of H2S chemical biology, its relationship to tissue pathophysiological responses and possible therapeutic uses.

Akt/eNOS signaling and PLN S-sulfhydration are involved in H₂S-dependent cardiac effects in frog and rat

Hydrogen sulfide (H₂S) has recently emerged as an important mediator of mammalian cardiovascular homeostasis. In nonmammalian vertebrates, little is known about the cardiac effects of H₂S. This study aimed to evaluate, in the avascular heart of the frog, Rana esculenta, whether and to what extent H₂S affects the cardiac performance, and what is the mechanism of action responsible for the observed effects. Results were analyzed in relation to those obtained in the rat heart, used as the mammalian model. Isolated and perfused (working and Langendorff) hearts, Western blot analysis, and modified biotin switch (S-sulfhydration) assay were used. In the frog heart, NaHS (used as H₂S donor, 10⁻¹²/10⁻⁷ M) dose-dependently decreased inotropism. This effect was reduced by glibenclamide (KATP channels blocker), NG-monomethyl-L-arginine (NOS inhibitor), 1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (guanylyl cyclase inhibitor), KT₅₈₂₃ (PKG inhibitor), and it was blocked by Akt1/2 (Akt inhibitor) and by detergent Triton X-100. In the rat, in addition to the classic negative inotropic effect, NaHS (10⁻¹²/10⁻⁷ M) exhibited negative lusitropism. In both frog and rat hearts, NaHS treatment induced Akt and eNOS phosphorylation and an increased cardiac protein S-sulfhydration that, in the rat heart, includes phospholamban. Our data suggest that H₂S represents a phylogenetically conserved cardioactive molecule. Results obtained on the rat heart extend the role of H₂S also to cardiac relaxation. H₂S effects involve KATP channels, the Akt/NOS-cGMP/PKG pathway, and S-sulfhydration of cardiac proteins.

H2S: a "double face" molecule in health and disease

H2S is a colorless, poisonous, and flammable gas with the characteristic foul odor of rotten eggs. H2S is present in effluent from hydrothermal vents and sulfur springs, which have been proposed to act as "pores" in the Earth surface, providing a source of energy in the form of reducing equivalents and of iron-sulfur centers. Remarkably, H2S-producing machineries or H2S-utilization capacity remain within a great diversity of microorganisms. In particular, two classes of bacteria have been identified, that is, sulfate- and sulfur-reducing and sulfur-oxidizing bacteria, both contributing to the balance of the H2S level. The human body produces H2S and uses it as a signaling molecule in several physiological processes. However, many diseases, including neurological diseases, cardiovascular diseases, inflammation, and metabolic disorders, have been linked to abnormal endogenous H2S functions and metabolism. Remarkably, in recent years, the therapeutic administration of H2S(-donors) appears relevant in the treatment of some diseases. Here, H2S metabolism, as well as its physiological and pathological roles in humans is reviewed. Furthermore, the therapeutic use of H2S is discussed.

Protective effect of endogenous hydrogen sulfide against oxidative stress in gastric ischemia-reperfusion injury

Hydrogen sulfide (H₂S) is a gaseous signaling molecule, which plays a critical role in a number of physiological and pathological progresses. In order to determine the effect of endogenous H₂S on gastric ischemia-reperfusion (GI-R), we evaluated the gastric mucosal damage in rats intraperitoneally injected with DL-propargylglycine (PAG, 50 mg/kg/day) or L-cysteine (L-cys, 50 mg/kg/day) for 7 days before GI-R. GI-R injury was achieved by clamping the celiac artery for 30 min, followed by reperfusion for 60 min. Gastric mucosal damage was macroscopically assessed in the area of injury and deep damage was assessed by histopathological scoring. PAG increased the area of gastric mucosal injury and deep damage compared with that in untreated GI-R rats (P<0.05). While PAG decreased the H₂S concentration and cystathionine γ-lyase (CSE) expression in the gastric mucosa, L-cys significantly attenuated the effects of GI-R. Western blot analysis revealed that the increases of malondialdehyde (MDA) and xanthine oxidase (XOD), and decreases of glutathione (GSH), superoxide dismutase (SOD) and the restriction of superoxide (O₂⁻) production in the PAG group were inhibited by L-cys (P<0.05). Endogenous H₂S has a protective effect against GI-R in rats by inhibiting oxygen free radical overproduction.

Physiological implications of hydrogen sulfide: a whiff exploration that blossomed

The important life-supporting role of hydrogen sulfide (H(2)S) has evolved from bacteria to plants, invertebrates, vertebrates, and finally to mammals. Over the centuries, however, H(2)S had only been known for its toxicity and environmental hazard. Physiological importance of H(2)S has been appreciated for about a decade. It started by the discovery of endogenous H(2)S production in mammalian cells and gained momentum by typifying this gasotransmitter with a variety of physiological functions. The H(2)S-catalyzing enzymes are differentially expressed in cardiovascular, neuronal, immune, renal, respiratory, gastrointestinal, reproductive, liver, and endocrine systems and affect the functions of these systems through the production of H(2)S. The physiological functions of H(2)S are mediated by different molecular targets, such as different ion channels and signaling proteins. Alternations of H(2)S metabolism lead to an array of pathological disturbances in the form of hypertension, atherosclerosis, heart failure, diabetes, cirrhosis, inflammation, sepsis, neurodegenerative disease, erectile dysfunction, and asthma, to name a few. Many new technologies have been developed to detect endogenous H(2)S production, and novel H(2)S-delivery compounds have been invented to aid therapeutic intervention of diseases related to abnormal H(2)S metabolism. While acknowledging the challenges ahead, research on H(2)S physiology and medicine is entering an exponential exploration era.

Hydrogen sulfide in the mammalian cardiovascular system

For more than a century, hydrogen sulfide (H(2)S) has been regarded as a toxic gas. This review surveys the growing recognition of the role of H(2)S as an endogenous signaling molecule in mammals, with emphasis on its physiological and pathological pathways in the cardiovascular system. In biological fluids, H(2)S gas is a weak acid that exists as about 15% H(2)S, 85% HS(-), and a trace of S(2-). Here, we use "H(2)S" to refer to this mixture. H(2)S has been found to influence heart contractile functions and may serve as a cardioprotectant for treating ischemic heart diseases and heart failure. Alterations of the endogenous H(2)S level have been found in animal models with various pathological conditions such as myocardial ischemia, spontaneous hypertension, and hypoxic pulmonary hypertension. In the vascular system, H(2)S exerts biphasic regulation of a vascular tone with varying effects based on its concentration and in the presence of nitric oxide. Over the past decade, several H(2)S-releasing compounds (NaHS, Na(2)S, GYY4137, etc.) have been utilized to test the effect of exogenous H(2)S under different physiological and pathological situations in vivo and in vitro. H(2)S has been found to promote angiogenesis and to protect against atherosclerosis and hypertension, while excess H(2)S may promote inflammation in septic or hemorrhagic shock. H(2)S-releasing compounds and inhibitors of H(2)S synthesis hold promise in alleviating specific disease conditions. This comprehensive review covers in detail the effects of H(2)S on the cardiovascular system, especially in disease situations, and also the various underlying mechanisms.

Total plasma sulfide as a marker of shock severity in nonsurgical adult patients

Previous animal and human studies have suggested that total plasma sulfide plays a role in the pathophysiology of shock. This study's aim was to determine the value of total plasma sulfide as a marker of shock severity in nonsurgical adult patients admitted to the ICU. Forty-one patients, with various types of shock (septic, cardiogenic, obstructive, and hypovolemic), were included in the study, with an average total plasma sulfide concentration of 23.2 ± 26.3 µM. Survivors (of shock) had lower total plasma sulfide concentrations than nonsurvivors (13.0 ± 26.3 vs. 31.9 ± 31.5 µM; P = 0.02). Total plasma sulfide correlated with dose of administered norepinephrine (R linear = 0.829; P = 0.001) and with Acute Physiology and Chronic Health Evaluation II (APACHE II) score (R cubic = 0.767; P = 0.001). Area under the receiver operating characteristic for total plasma sulfide as a predictor of ICU mortality was 0.739 (confidence interval, 0.587-0.892; P = 0.009). Even after correcting for APACHE II score and lactate values, total plasma sulfide correlated with mortality (odds ratio, 1.058; 95% confidence interval, 1.001-1.118; P = 0.045). The study provides evidence that, in nonsurgical adult ICU patients admitted because of any type of shock, total plasma sulfide correlates with administered norepinephrine dose at admission, severity of disease (APACHE II score ≥30 points), and survival outcome.

Hydrogen sulfide decreases the levels of ROS by inhibiting mitochondrial complex IV and increasing SOD activities in cardiomyocytes under ischemia/reperfusion

Inhibition of oxidative stress has been reported to be involved in the cardioprotective effects of hydrogen sulfide (H(2)S) during ischemia/reperfusion (I/R). However, the mechanism whereby H(2)S regulates the level of cardiac reactive oxygen species (ROS) during I/R remains unclear. Therefore, we investigated the effects of H(2)S on pathways that generate and scavenge ROS. Our results show that pretreating rat neonatal cardiomyocytes with NaHS, a H(2)S donor, reduced the levels of ROS during the hypoxia/reoxygenation (H/R) condition. We found that H(2)S inhibited mitochondrial complex IV activity and increased the activities of superoxide dismutases (SODs), including Mn-SOD and CuZn-SOD. Further studies indicated that H(2)S up-regulated the expression of Mn-SOD but not CuZn-SOD. Using a cell-free system, we showed that H(2)S activates CuZn-SOD. An isothermal titration calorimetry (ITC) analysis indicated that H(2)S directly interacts with CuZn-SOD. Taken together, H(2)S inhibits mitochondrial complex IV and activates SOD to decrease the levels of ROS in cardiomyocytes during I/R.

Hydrogen sulfide mitigates cardiac remodeling during myocardial infarction via improvement of angiogenesis

Exogenous hydrogen sulfide (H2S) leads to down-regulation of inflammatory responses and provides myocardial protection during acute ischemia/reperfusion injury; however its role during chronic heart failure (CHF) due to myocardial infarction (MI) is yet to be unveiled. We previously reported that H2S inhibits antiangiogenic factors such, as endostatin and angiostatin, but a little is known about its effect on parstatin (a fragment of proteinase-activated receptor-1, PAR-1). We hypothesize that H2S inhibits parstatin formation and promotes VEGF activation, thus promoting angiogenesis and significantly limiting the extent of MI injury. To verify this hypothesis MI was created in 12 week-old male mice by ligation of left anterior descending artery (LAD). Sham surgery was performed except LAD ligation. After the surgery mice were treated with sodium hydrogen sulfide (30 μmol/l NaHS, a donor for H2S, in drinking water) for 4 weeks. The LV tissue was analyzed for VEGF, flk-1 and flt-1, endostatin, angiostatin and parstatin. The expression of VEGF, flk-1 and flt-1 were significantly increased in treated mice while the level of endostatin, angiostatin and parstatin were decreased compared to in untreated mice. The echocardiography in mice treated with H2S showed the improvement of heart function compared to in untreated mice. The X-ray and Doppler blood flow measurements showed enhancement of cardiac-angiogenesis in mice treated with H2S. This observed cytoprotection was associated with an inhibition of anti-angiogenic proteins and stimulation of angiogenic factors. We established that administration of H2S at the time of MI ameliorated infarct size and preserved LV function during development of MI in mice. These results suggest that H2S is cytoprotective and angioprotective during evolution of MI.

Hydrogen Sulfide-a potent multichannel anti-arrhythmic drug

—Arrhythmia is a big headache for cardiologist for a long time. A new antiarrythmic drug with good effects and few side effects should be explored. Hydrogen sulfide, a newly found gaseous transmitter, was found to have multi-effects on a variety of ion channels. It may be a promising antiarrythmic drug. This article reviews the different effects of hydrogen sulfide on different ion channels.

Hydrogen sulfide is a partially redox-independent activator of the human jejunum Na+ channel, Nav1.5

Hydrogen sulfide (H(2)S) is produced endogenously by L-cysteine metabolism. H(2)S modulates several ion channels with an unclear mechanism of action. A possible mechanism is through reduction-oxidation reactions attributable to the redox potential of the sulfur moiety. The aims of this study were to determine the effects of the H(2)S donor NaHS on Na(V)1.5, a voltage-dependent sodium channel expressed in the gastrointestinal tract in human jejunum smooth muscle cells and interstitial cells of Cajal, and to elucidate whether H(2)S acts on Na(V)1.5 by redox reactions. Whole cell Na(+) currents were recorded in freshly dissociated human jejunum circular myocytes and Na(V)1.5-transfected human embryonic kidney-293 cells. RT-PCR amplified mRNA for H(2)S enzymes cystathionine β-synthase and cystathionine γ-lyase from the human jejunum. NaHS increased native Na(+) peak currents and shifted the half-point (V(1/2)) of steady-state activation and inactivation by +21 ± 2 mV and +15 ± 3 mV, respectively. Similar effects were seen on the heterologously expressed Na(V)1.5 α subunit with EC(50)s in the 10(-4) to 10(-3) M range. The reducing agent dithiothreitol (DTT) mimicked in part the effects of NaHS by increasing peak current and positively shifting steady-state activation. DTT together with NaHS had an additive effect on steady-state activation but not on peak current, suggesting that the latter may be altered via reduction. Pretreatment with the Hg(2+)-conjugated oxidizer thimerosal or the alkylating agent N-ethylmaleimide inhibited or decreased NaHS induction of Na(V)1.5 peak current. These studies show that H(2)S activates the gastrointestinal Na(+) channel, and the mechanism of action of H(2)S is partially redox independent.

Hydrogen sulfide and cell signaling

Hydrogen sulfide (H₂S) is a gaseous mediator synthesized from cysteine by cystathionine γ lyase (CSE) and other naturally occurring enzymes. Pharmacological experiments using H₂S donors and genetic experiments using CSE knockout mice suggest important roles for this vasodilator gas in the regulation of blood vessel caliber, cardiac response to ischemia/reperfusion injury, and inflammation. That H₂S inhibits cytochrome c oxidase and reduces cell energy production has been known for many decades, but more recently, a number of additional pharmacological targets for this gas have been identified. H₂S activates K(ATP) and transient receptor potential (TRP) channels but usually inhibits big conductance Ca²(+)-sensitive K(+) (BK(Ca)) channels, T-type calcium channels, and M-type calcium channels. H₂S may inhibit or activate NF-κB nuclear translocation while affecting the activity of numerous kinases including p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and Akt. These disparate effects may be secondary to the well-known reducing activity of H₂S and/or its ability to promote sulfhydration of protein cysteine moieties within the cell.

The protective role of hydrogen sulfide in myocardial ischemia-reperfusion-induced injury in diabetic rats

BACKGROUND

Hydrogen sulfide (H(2)S) displays anti-inflammatory and cytoprotective activities to attenuate myocardial ischemia-reperfusion (MIR)-induced injury, but its role in MIR in diabetics is not known. This study was undertaken to investigate whether H(2)S plays a protective role in MIR in diabetic rats.

METHODS

Diabetes was induced by streptozocin in Wistar rats, which were subjected to myocardial ischemia by blocking the left circumflex artery for 30 min, followed by 2h reperfusion. dl-propargylglycine (PAG) and sodium hydrosulfide (NaHS) were administered to the rats to investigate their effects on severity of MIR-induced injury.

RESULTS

Diabetic rats had smaller myocardial infarct sizes and higher serum levels of H(2)S (both P < 0.05) than non-diabetics when they underwent MIR. MIR significantly increased the serum level of H(2)S (49.5 ± 7.1 μM), H(2)S-synthesizing activity (7.4 ± 1.6 nmol/mg) and the myocardial infarct size (44.0 ± 7.2%), compared with sham-operated diabetic rats (21.7 ± 2.1 μM, 0.15 ± 0.4 nmol/mg and 1.2 ± 0.4%, respectively). Administration of NaHS increased the H(2)S level (65.8 ± 6.9 μM) and had little effect on H(2)S production activity (6.5 ± 2.2 nmol/mg), while PAG reduced both the H(2)S level (29.2 ± 5.0 μM) and H(2)S-synthesizing activity (2.2 ± 1.8 nmol/mg). NaHS significantly reduced the myocardial infarct size (31.2 ± 4.7%), inhibited the production of lipid peroxidation, MPO activity, and cell apoptosis, and downregulated expression of caspase-3, Fas, FasL, and TNF-α, which had been elevated by MIR, while PAG further increased the myocardial infarct size (58.3 ± 5.9%), and displayed opposite effects.

CONCLUSIONS

The study indicates that H(2)S may play a protective role in MIR-induced myocardial injury in diabetics by its anti-apoptotic, anti-oxidative and anti-inflammatory activities.

Hydrogen sulfide mitigates transition from compensatory hypertrophy to heart failure

We reported previously that although there is disruption of coordinated cardiac hypertrophy and angiogenesis in transition to heart failure, matrix metalloproteinase (MMP)-9 induced antiangiogenic factors play a vital role in this process. Previous studies have shown the cardioprotective role of hydrogen sulfide (H₂S) in various cardiac diseases, but its role during transition from compensatory hypertrophy to heart failure is yet to be unveiled. We hypothesize that H₂S induces MMP-2 activation and inhibits MMP-9 activation, thus promoting angiogenesis, and mitigates transition from compensatory cardiac hypertrophy to heart failure. To verify this, aortic banding (AB) was created to mimic pressure overload in wild-type (WT) mice, which were treated with sodium hydrosulfide (NaHS, H₂S donor) in drinking water and compared with untreated control mice. Mice were studied at 3 and 8 wk. In the NaHS-treated AB 8 wk group, the expression of MMP-2, CD31, and VEGF was increased while the expression of MMP-9, endostatin, angiostatin, and tissue inhibitor of matrix metalloproteinase (TIMP)-3 was decreased compared with untreated control mice. There was significant reduction in fibrosis in NaHS-treated groups. Echocardiograph and pressure-volume data revealed improvement of cardiac function in NaHS-treated groups over untreated controls. These results show that H₂S by inducing MMP-2 promotes VEGF synthesis and angiogenesis while it suppresses MMP-9 and TIMP-3 levels, inhibits antiangiogenic factors, reduces intracardiac fibrosis, and mitigates transition from compensatory hypertrophy to heart failure.

Hydrogen sulfide-mediated cardioprotection: mechanisms and therapeutic potential

H2S (hydrogen sulfide), viewed with dread for more than 300 years, is rapidly becoming a ubiquitously present and physiologically relevant signalling molecule. Knowledge of the production and metabolism of H2S has spurred interest in delineating its functions both in physiology and pathophysiology of disease. Although its role in blood pressure regulation and interaction with NO is controversial, H2S, through its anti-apoptotic, anti-inflammatory and antioxidant effects, has demonstrated significant cardioprotection. As a result, a number of sulfide-donor drugs, including garlic-derived polysulfides, are currently being designed and investigated for the treatment of cardiovascular conditions, specifically myocardial ischaemic disease. However, huge gaps remain in our knowledge about this gasotransmitter. Only by additional studies will we understand more about the role of this intriguing molecule in the treatment of cardiovascular disease.

Cardioprotective effects of hydrogen sulfide

The gaseous mediator hydrogen sulfide (H(2)S) is synthesized mainly by cystathionine γ-lyase in the heart and plays a role in the regulation of cardiovascular homeostasis. Here we first overview the state of the art in the literature on the cardioprotective effects of H(2)S in various models of cardiac injury. Subsequently, we present original data showing the beneficial effects of parenteral administration of a donor of H(2)S on myocardial and endothelial function during reperfusion in a canine experimental model of cardiopulmonary bypass. Overview of the literature demonstrates that various formulations of H(2)S exert cardioprotective effects in cultured cells, isolated hearts and various rodent and large animal models of regional or global myocardial ischemia and heart failure. In addition, the production of H(2)S plays a role in myocardial pre- and post-conditioning responses. The pathways implicated in the cardioprotective action of H(2)S are multiple and involve K(ATP) channels, regulation of mitochondrial respiration, and regulation of cytoprotective genes such as Nrf-2. In the experimental part of the current article, we demonstrate the cardioprotective effects of H(2)S in a canine model of cardiopulmonary bypass surgery. Anesthetized dogs were subjected hypothermic cardiopulmonary bypass with 60 min of hypothermic cardiac arrest in the presence of either saline (control, n=8), or H(2)S infusion (1 mg/kg/h for 2 h). Left ventricular hemodynamic variables (via combined pressure-volume-conductance catheter) as well as coronary blood flow, endothelium-dependent vasodilatation to acetylcholine and endothelium-independent vasodilatation to sodium nitroprusside were measured at baseline and after 60 min of reperfusion. Ex vivo vascular function and high-energy phosphate contents were also measured. H(2)S led to a significantly better recovery of preload recruitable stroke work (p<0.05) after 60 min of reperfusion. Coronary blood flow was also significantly higher in the H(2)S group (p<0.05). While the vasodilatory response to sodium nitroprusside was similar in both groups, acetylcholine resulted in a significantly higher increase in coronary blood flow in the H(2)S-treated group (p<0.05) both in vivo and ex vivo. Furthermore, high-energy phosphate contents were better preserved in the H(2)S group. Additionally, the cytoprotective effects of H(2)S were confirmed also using in vitro cell culture experiments in H9c2 cardiac myocytes exposed to hypoxia and reoxygenation or to the cytotoxic oxidant hydrogen peroxide. Thus, therapeutic administration of H(2)S exerts cardioprotective effects in a variety of experimental models, including a significant improvement of the recovery of myocardial and endothelial function in a canine model of cardiopulmonary bypass with hypothermic cardiac arrest.

Interaction of hydrogen sulfide with ion channels

1. Hydrogen sulfide (H(2)S) is a signalling gasotransmitter. It targets different ion channels and receptors, and fulfils its various roles in modulating the functions of different systems. However, the interaction of H(2)S with different types of ion channels and underlying molecular mechanisms has not been reviewed systematically. 2. H(2)S is the first identified endogenous gaseous opener of ATP-sensitive K(+) channels in vascular smooth muscle cells. Through the activation of ATP-sensitive K(+) channels, H(2)S lowers blood pressure, protects the heart from ischemia and reperfusion injury, inhibits insulin secretion in pancreatic beta cells, and exerts anti-inflammatory, anti-nociceptive and anti-apoptotic effects. 3. H(2)S inhibited L-type Ca(2+) channels in cardiomyocytes but stimulated the same channels in neurons, thus regulating intracellular Ca(2+) levels. H(2)S activated small and medium conductance K(Ca) channels but its effect on BK(Ca) channels has not been consistent. 4. H(2)S-induced hyperalgesia and pro-nociception seems to be related to the sensitization of both T-type Ca(2+) channels and TRPV(1) channels. The activation of TRPV(1) and TRPA(1) by H(2)S is believed to result in contraction of nonvascular smooth muscles and increased colonic mucosal Cl(-) secretion. 5. The activation of Cl(-) channel by H(2)S has been shown as a protective mechanism for neurons from oxytosis. H(2)S also potentiates N-methyl-d-aspartic acid receptor-mediated currents that are involved in regulating synaptic plasticity for learning and memory. 6. Given the important modulatory effects of H(2)S on different ion channels, many cellular functions and disease conditions related to homeostatic control of ion fluxes across cell membrane should be re-evaluated.

Novel insights into hydrogen sulfide--mediated cytoprotection

Hydrogen sulfide (H(2)S) is a colorless, water soluble, flammable gas that has the characteristic smell of rotten eggs. Like other members of the gasotransmitter family (nitric oxide and carbon monoxide), H(2)S has traditionally been considered to be a highly toxic gas and environmental hazard. However, much like for nitric oxide and carbon monoxide, the initial negative perception of H(2)S has evolved with the discovery that H(2)S is produced enzymatically in mammals under normal conditions. As a result of this discovery, there has been a great deal of work to elucidate the physiological role of H(2)S. H(2)S is now recognized to be cytoprotective in various models of cellular injury. Specifically, it has been demonstrated that the acute administration of H(2)S, either prior to ischemia or at reperfusion, significantly ameliorates in vitro or in vivo myocardial and hepatic ischemia-reperfusion injury. These studies have also demonstrated a cardioprotective role for endogenous H(2)S. This review article summarizes the current body of evidence demonstrating the cytoprotective effects of H(2)S with an emphasis on the cardioprotective effects. This review also provides a detailed description of the current signaling mechanisms shown to be responsible for these cardioprotective actions.

Regulation of cardiovascular cell function by hydrogen sulfide (H(2)S)

Since the discovery of endogenously-produced hydrogen sulfide (H(2)S) in various tissues, there has been an explosion of interest in H(2)S as a biological mediator alongside other gaseous mediators, nitric oxide and carbon monoxide. The identification of enzyme-regulated H(2)S synthetic pathways in the cardiovascular system has led to a number of studies examining specific regulatory actions of H(2)S. We review evidence showing that endogenously-generated and exogenously-administered H(2)S exerts a wide range of actions in vascular and myocardial cells including vasodilator/vasoconstrictor effects via modification of the smooth muscle tone, induction of apoptosis and anti-proliferative responses in the smooth muscle cells, angiogenic actions, effects relevant to inflammation and shock, and cytoprotection in models of myocardial ischemia-reperfusion injury. Several molecular mechanisms of action of H(2)S have been described. These include interactions of H(2)S with NO, redox regulation of multiple signaling proteins and regulation of K(ATP) channel opening. The gaps in our current understanding of precise mechanisms, the absence of selective pharmacological tools and the limited availability of H(2)S measurement techniques for living tissues, leave many questions about physiological and pathophysiological roles of H(2)S unanswered at present. Nevertheless, this area of investigation is advancing rapidly. We believe H(2)S holds promise as an endogenous mediator controlling a wide range of cardiovascular cell functions and integrated responses under both physiological and pathological conditions and may be amenable to therapeutic manipulation.

Butyrate-stimulated H2S production in colon cancer cells

Butyrate is a short-chain fatty acid that arrests growth of various types of cells. H(2)S can be endogenously produced by cystathionine gamma-lyase (CSE) or cystathionine beta-synthase (CBS) or both in colonic tissues. In this study, we observed endogenous H(2)S production in a colon cancer cell line (WiDr) and colonic tissues through the activity of both CSE and CBS. After 24 h of incubation of WiDr cells, butyrate increased cell production of H(2)S and upregulated CBS and CSE expressions. Both butyrate and NaHS (a H(2)S donor) decreased cell viability in a dose-dependent manner. Blockade of CBS, but not CSE, decreased butyrate-stimulated H(2)S production and reversed butyrate-inhibited cell viability. In addition, NaHS treatment stimulated the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK), but not c-Jun N-terminal kinase (JNK). Inhibition of the phosphorylation of either p38 MAPK or ERK did not abolish NaHS-induced cell death. Butyrate treatment increased the phosphorylation of ERK, not p38 MAPK and JNK, but inhibition of ERK and p38 MAPK phosphorylation did not inhibit butyrate-reduced cell viability. In conclusion, butyrate regulates endogenous H(2)S production by stimulating CBS expression in colon cancer cells, but butyrate and H(2)S inhibit cancer cell growth through different mechanisms.

4-aminopyridine-sensitive K+ channels contributes to NaHS-induced membrane hyperpolarization and relaxation in the rat coronary artery

The present study aimed at examining the role of potassium channels and endothelium in relaxations induced by sodium hydrogen sulphide (NaHS), which is the donor of gaseous hydrogen sulphide (H(2)S) and the effect of NaHS on endothelium-dependent relaxations in rat coronary arteries. Rat coronary arteries were suspended in a myograph for force measurement and changes of the membrane potential in arteries were determined by membrane potential-sensitive fluorescence dye. NaHS relaxed coronary arteries pre-contracted by U46619 and the relaxation was significantly less in high KCl-contracted rings. NaHS-induced relaxations were reduced by 4-aminopyridine (4-AP) but unaffected by glibenclamide, iberiotoxin, N(G)-nitro-L-arginine methyl ester, ODQ, indomethacin or by endothelium removal. The inhibitory effect of 4-AP was absent in NaHS-induced relaxations in high KCl-contracted rings. Addition of NaHS caused membrane hyperpolarization and this effect was inhibited by 4-AP but not by glibenclamide. NaHS causes endothelium-independent relaxations in rat coronary arteries partially through activation of 4-AP-sensitive potassium channel and ensuring hyperpolarization. Other potassium channels, Na(+)-K(+) pump or endothelium-derived relaxing factors play little role.

Effect of hydrogen sulfide on myocardial protection in the setting of cardioplegia and cardiopulmonary bypass

We investigated the impact of hydrogen sulfide (H(2)S) on myocardium in the setting of cold crystalloid cardioplegia and cardiopulmonary bypass (CP/CPB). Eighteen male Yorkshire pigs underwent 1 h CP/CPB followed by 2 h of reperfusion. Pigs received either: placebo (control, n=9), or H(2)S (as NaHS) as a bolus/infusion (bolus/infusion, n=6), or as an infusion (infusion, n=6). The expression pattern of various myocardial effector pathways was investigated. Coronary microvascular relaxation to endothelium-dependent and -independent agonists was assessed. No differences in cardiac function were observed among groups. Endothelium-dependent microvascular relaxation to adenosine diphosphate was improved in the H(2)S bolus/infusion group only (P<0.05). The expression of hemeoxygenase-1, phospho-heat shock proteins27 and phospho-p44/42 MAPK extracellular signal-regulated kinase were higher in H(2)S-treated groups (P<0.05). Phospho-endothelial nitric oxide synthase (P=0.08), phospho-B-cell lymphoma 2 (P=0.09), and phospho-Bad (P=0.06) all displayed a trend to be higher with H(2)S treatment. The expressions of apoptosis inducing factor and Bcl 2/adenovirus E1B 19 kDa-interacting protein were lower in H(2)S treated groups (P<0.05). The microtubule-associated protein 1 light chain 3 ratio was lower in the infusion group vs. control animals (P<0.05). There was a trend for lower phospho-mammalian target of rapamycin expression in the infusion group (P=0.07), whereas phosphorylation of p70S6K1 was higher with H(2)S-treatment (P=0.09). This study demonstrates that H(2)S-treatment may offer biochemical myocardial protection via attenuation of caspase-independent apoptosis and autophagy in the setting of CP/CPB.

Hydrogen sulfide protects against vascular remodeling from endothelial damage

Remodeling by its very nature implied synthesis and degradation of extracellular matrix (ECM) proteins. Although oxidative stress, matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) have been implicated in vascular remodeling, the differential role of MMPs versus TIMPs and oxidative stress in vascular remodeling was unclear. TIMP-3 induced vascular cell apoptosis, therefore, we hypothesized that during vascular injury TIMP-3, MMP-9 and -12 (elastin-degrading MMP) were increased, whereas MMP-2 (constitutive MMP) and TIMP-4 (cardioprotective TIMP) decreased. Because of the potent anti-oxidant, vasorelaxing, anti-hypertensive agent, hydrogen sulfide (H2S) was used to mitigate the vascular remodeling due to the differential expression of MMP and TIMP. Carotid artery injury was created by inserting a PE-10 catheter and rotating several times before pulling out. The insertion hole was sealed. Mice were grouped: wild type (WT), wild-type damaged artery (WTD), WT+NaHS (sodium hydrogen sulfide, precursor of H2S) treatment (30 µmol/L in drinking water/6 weeks) and WTD+NaHS treatment. Carotid arteries were analyzed for oxidative stress and remodeling, by measuring super oxide dismutase-1 (SOD1), p47 (NADPH oxidase subunit), nitrotyrosine, MMPs and TIMPs by in situ immunolabeling and by Western blot analyses. The results suggested robust increase in p47, nitrotyrosine, MMP-9, MMP-12, TIMP-3 and decrease in SOD1 and MMP-2 levels in the injured arteries. The treatment with H2S ameliorated these effects. We concluded that p47, TIMP-3, MMP-9 and -12 were increased where as SOD-1, MMP-2 and TIMP-4 were decreased in the injured arteries. The treatment with H2S mitigated the vascular remodeling by normalizing the levels of redox stress, MMPs and TIMPs.

Hydrogen sulphide ameliorates ischaemia-reperfusion injury in an experimental model of non-heart-beating donor kidney transplantation

BACKGROUND

: Therapies to alleviate ischaemia-reperfusion (IR) injury have an important role in kidney transplantation. This study used a porcine model of non-heart-beating (NHB) donor kidneys to investigate the effects of hydrogen sulphide on IR injury.

METHODS

: Porcine kidneys were subjected to 25 min of warm ischaemia and 18 h of cold storage. They were reperfused ex vivo with autologous oxygenated blood to assess renal function. A group treated with hydrogen sulphide (0.5 mmol/l) infused 10 min before and after reperfusion (n = 6) was compared with an untreated control group (n = 7).

RESULTS

: Hydrogen sulphide significantly improved renal blood flow compared with control values (mean(s.d.) area under the curve (AUC) 614.9(165.5) versus 270.3(86.7) ml per min per 100 g.h; P = 0.001) and renal function (AUC creatinine: 1640(248) versus 2328(154) micromol/l.h; P = 0.001; AUC creatinine clearance: 6.94(5.03) versus 0.96(0.32) ml per min per 100 g.h; P = 0.004). Oxidative damage was also reduced by hydrogen sulphide (urinary 8-isoprostane at 1 h of reperfusion: 478.9(237.1) versus 1605.6(632.7) pg/ml per mmol/l creatinine; P = 0.032).

CONCLUSION

: Hydrogen sulphide ameliorated the renal dysfunction associated with ischaemic damage, and has potential as a therapy against IR injury in NHB donor kidney transplantation.

H2S ameliorates oxidative and proteolytic stresses and protects the heart against adverse remodeling in chronic heart failure

Reactive oxygen and nitrogen species (ROS and RNS, respectively) generate nitrotyrosine and activate latent resident myocardial matrix metalloproteinases (MMPs). Although in chronic heart failure (CHF) there is robust increase in ROS, RNS, and MMP activation, recent data suggest that hydrogen sulfide (H(2)S, a strong antioxidant gas) is cardioprotective. However, the role of H(2)S in mitigating oxidative and proteolytic stresses in cardiac remodeling/apoptosis in CHF was unclear. To test the hypothesis that H(2)S ameliorated cardiac apoptosis and fibrosis by decreasing oxidative and proteolytic stresses, arteriovenous fistula (AVF) was created in wild-type (C57BL/6J) mice. The hearts were analyzed at 0, 2, and 6 wk after AVF. To reverse the remodeling, AVF mice were treated with NaHS (an H(2)S donor, 30 micromol/l in drinking water) at 8 and 10 wk. The levels of MMPs were measured by gelatin-gel zymography. The levels of nitrotyrosine, tissue inhibitors of metalloproteinase (TIMPs), beta(1)-integrin, and a disintegrin and metalloproteinase-12 (ADAM-12) were analyzed by Western blots. The levels of pericapillary and interstitial fibrosis were identified by Masson trichrome stains. The levels of apoptosis were measured by identifying the TdT-mediated dUTP nick end labeling (TUNEL)-positive cells and caspase-3 levels. The results suggested robust nitrotyrosine and MMP activation at 2 and 6 wk of AVF. The treatment with H(2)S donor mitigated nitrotyrosine generation and MMP activation (i.e., oxidative and proteolytic stresses). The levels of TIMP-1 and TIMP-3 were increased and TIMP-4 decreased in AVF hearts. The treatment with H(2)S donor reversed this change in TIMPs levels. The levels of ADAM-12, apoptosis, and fibrosis were robust and integrin were decreased in AVF hearts. The treatment with H(2)S donor attenuated the fibrosis, apoptosis, and decrease in integrin.

Effect of hydrogen sulfide in a porcine model of myocardial ischemia-reperfusion: comparison of different administration regimens and characterization of the cellular mechanisms of protection

OBJECTIVE

We investigate the impact of different regimens of parenteral hydrogen sulfide (H2S) administration on myocardium during ischemia-reperfusion (IR) and the molecular pathways involved in its cytoprotective effects.

METHODS

Eighteen male Yorkshire pigs underwent 60 minutes of mid-left anterior descending coronary artery occlusion followed by 120 minutes of reperfusion. Pigs received either placebo (control, n = 6) or H2S as a bolus (bolus group, n = 6, 0.2 mg/kg over 10 seconds at the start of reperfusion) or as an infusion (infusion group, n = 6, 2 mg.kg.h initiated at the onset of ischemia and continued into the reperfusion period). Myocardial function was monitored throughout the experiment. The area at risk and myocardial necrosis was determined by Monastral blue/triphenyl tetrazolium chloride staining. Apoptosis and the expression pattern of various intracellular effector pathways were investigated in the ischemic territory. Coronary microvascular reactivity to endothelium-dependent and endothelium-independent factors was measured.

RESULTS

H2S infusion but not bolus administration markedly reduce myocardial infarct size (P < 0.05) and improve regional left ventricular function, as well as endothelium-dependent and endothelium-independent microvascular reactivity (P < 0.05). The expression of B-cell lymphoma 2 (P = 0.059), heat shock protein 27 and alphaB-crystallin (P < 0.05) were lower in H2S-treated groups. Infusion of H2S caused higher expression of phospho-glycogen synthase kinase-3 beta isoform(P < 0.05) and lower expression of mammalian target of rapamycin and apoptosis-inducing factor (P < 0.05). Bolus of H2S caused higher expression of phospho-p44/42 MAPK extracellular signal-regulated kinase and lower expression of Beclin-1 (P < 0.05). The expression of caspase 3 and cleaved caspase 3 were lower (P < 0.05), whereas the expression of phospho-Bad(Ser136) was higher in the bolus group versus control and infusion groups (P < 0.05). The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cell count was lower in both H2S-treated groups compared with the control (P < 0.05).

CONCLUSIONS

This study demonstrates that infusion of H2S is superior to a bolus alone in reducing myocardial necrosis after IR injury, even though some markers of apoptosis and autophagy were affected in both H2S-treated groups. Thus, the current results indicate that infusion of H2S throughout IR may offer better myocardial protection from IR injury.

Anti-apoptotic action of hydrogen sulfide is associated with early JNK inhibition

The mechanism of action of Hydrogen sulfide (H(2)S) as a novel endogenous gaseous messenger and potential cardioprotectant is not fully understood. We therefore investigated the prevention of cardiomyocyte apoptosis by exogenous H(2)S and the signaling pathways leading to cardioprotection. Using a simulated ischemia-reperfusion (I/Re) model with primary cultured rat neonatal cardiomyocytes, I/Re induced a rapid, time-dependent phosphorylation of c-Jun N-terminal kinase (JNK), with significant elevation at 0.25 h and a peak at 0.5h during reperfusion. NaHS (H(2)S donor) significantly inhibited the early phosphorylation of JNK, especially at 0.5h. Both NaHS and SP600125 (specific JNK inhibitor) decreased the number of apoptotic cells, lowered cytochrome C release and enhanced Bcl-2 expression. When NaHS application was delayed 1h after reperfusion, the inhibition of apoptosis by H(2)S was negated. In conclusion, this is novel evidence that early JNK inhibition during reperfusion is associated with H(2)S-mediated protection against cardiomyocyte apoptosis.

Hypothermic organ preservation by static storage methods: Current status and a view to the future

The donor organ shortage is the largest problem in transplantation today and is one where organ preservation technology has an important role to play. Static storage of solid organs, especially of the kidney, continues to be the most common method employed for storage and transport of organs from deceased donors. However, the increase in organs obtained from expanded criteria donors and donors with cardiac death provide new challenges in crafting effective preservation methods for the future. This article reviews the current status of static hypothermic storage methods and discusses potential avenues for future exploitation of this technology as the available organ pool is expanded into the more marginal donor categories.

Oxytocin exerts protective effects on in vitro myocardial injury induced by ischemia and reperfusion

Among the cardiovascular pathologies, ischemic heart disease is a serious medical problem that can result in cardiac injury and (or) heart failure. The aim of the present study was to test the hypothesis that neuropeptide oxytocin induces cardioprotective effects on ischemia-reperfusion-induced myocardial damage. The functional parameters of isolated Langendorff-perfused rat hearts were recorded before and after global 25 min ischemia and subsequent reperfusion. The infarct size was determined by a computerized planimetric method. The results showed that oxytocin produced negative chronotropic effect even at low concentrations (90-125 nmol/L). Perfusion with oxytocin before ischemia resulted in significant reduction of the infarct size (p<0.01), which was about 66% smaller than that in the control group. To evaluate the functional mechanisms involved, further experiments were performed under conditions of constant heart rate. The lower dose of oxytocin (90 nmol/L), which was ineffective in spontaneously beating hearts, induced a significant decrease of contractility. Elimination of the negative chronotropic effect of oxytocin prevented its cardioprotective action. In conclusion, our results demonstrated an attenuation of the infarct size in oxytocin-treated hearts, indicating a cardioprotective effect of oxytocin. The data suggest that the negative chronotropic action of oxytocin participates in its protective effects on ischemia-reperfusion-induced myocardial injury.

Bench-to-bedside review: Hydrogen sulfide--the third gaseous transmitter: applications for critical care

Hydrogen sulfide (H2S), a gas with the characteristic odor of rotten eggs, is known for its toxicity and as an environmental hazard, inhibition of mitochondrial respiration resulting from blockade of cytochrome c oxidase being the main toxic mechanism. Recently, however, H2S has been recognized as a signaling molecule of the cardiovascular, inflammatory and nervous systems, and therefore, alongside nitric oxide and carbon monoxide, is referred to as the third endogenous gaseous transmitter. Inhalation of gaseous H2S as well as administration of inhibitors of its endogenous production and compounds that donate H2S have been studied in various models of shock. Based on the concept that multiorgan failure secondary to shock, inflammation and sepsis may represent an adaptive hypometabolic response to preserve ATP homoeostasis, particular interest has focused on the induction of a hibernation-like suspended animation with H2S. It must be underscored that currently only a limited number of data are available from clinically relevant large animal models. Moreover, several crucial issues warrant further investigation before the clinical application of this concept. First, the impact of hypothermia for any H2S-related organ protection remains a matter of debate. Second, similar to the friend and foe character of nitric oxide, no definitive conclusions can be made as to whether H2S exerts proinflammatory or anti-inflammatory properties. Finally, in addition to the question of dosing and timing (for example, bolus administration versus continuous intravenous infusion), the preferred route of H2S administration remains to be settled--that is, inhaling gaseous H2S versus intra-venous administration of injectable H2S preparations or H2S donors. To date, therefore, while H2S-induced suspended animation in humans may still be referred to as science fiction, there is ample promising preclinical data that this approach is a fascinating new therapeutic perspective for the management of shock states that merits further investigation.

Cardioprotective signaling to mitochondria

Mitochondria are central players in the pathophysiology of ischemia-reperfusion. Activation of plasma membrane G-coupled receptors or the Na,K-ATPase triggers cytosolic signaling pathways that result in cardioprotection. Our working hypothesis is that the occupied receptors migrate to caveolae, where signaling enzymes are scaffolded into signalosomes that bud off the plasma membrane and migrate to mitochondria. The signalosome-mitochondria interaction then initiates intramitochondrial signaling by opening the mitochondrial ATP-sensitive K(+) channel (mitoK(ATP)). MitoK(ATP) opening causes an increase in ROS production, which activates mitochondrial protein kinase C epsilon (PKCvarepsilon), which inhibits the mitochondrial permeability transition (MPT), thus decreasing cell death. We review the experimental findings that bear on these hypotheses and other modes of protection involving mitochondria.

Leukocyte trafficking and pain behavioral responses to a hydrogen sulfide donor in acute monoarthritis

Hydrogen sulfide (H(2)S) is an endogenous gaseous mediator with the ability to modulate tissue inflammation and pain. The aim of this study was to determine the effect of an H(2)S donor (Na(2)S) on leukocyte-endothelium interactions, blood flow, and pain sensation in acutely inflamed knee joints. Acute arthritis was induced in urethane anesthetized C57bl/6 mice by intra-articular injection of kaolin/carrageenan (24-h recovery), and the effect of local administration of Na(2)S on leukocyte trafficking was measured by intravital microscopy. Synovial blood flow was measured in inflamed knees by laser Doppler perfusion imaging. Finally, the effect of an intra-articular injection of Na(2)S on joint pain in control and inflamed rats was determined by hindlimb incapacitance and von Frey hair algesiometry. Local administration of an H(2)S donor to inflamed knees caused a dose-dependent reduction in leukocyte adherence and an increase in leukocyte velocity. These effects could be inhibited by coadministration of the ATP-sensitive K(+) channel blocker glibenclamide. Local administration of Na(2)S to inflamed joints caused a pronounced vasoconstrictor response; however, there was no observable effect of Na(2)S on joint pain. These findings establish H(2)S as a novel signaling molecule in rodent knee joints. H(2)S exhibits potent anti-inflammatory properties, but with no detectable effect on joint pain.

Hydrogen sulfide attenuates hepatic ischemia-reperfusion injury: role of antioxidant and antiapoptotic signaling

Hydrogen sulfide (H(2)S) is an endogenously produced gaseous signaling molecule with diverse physiological activity. The potential protective effects of H(2)S have not been evaluated in the liver. The purpose of the current study was to investigate if H(2)S could afford hepatoprotection in a murine model of hepatic ischemia-reperfusion (I/R) injury. Hepatic injury was achieved by subjecting mice to 60 min of ischemia followed by 5 h of reperfusion. H(2)S donor (IK1001) or vehicle were administered 5 min before reperfusion. H(2)S attenuated the elevation in serum alanine aminotransferase (ALT) by 68.6% and aspartate aminotransferase (AST) by 70.8% compared with vehicle group. H(2)S-mediated cytoprotection was associated with an improved balance between reduced glutathione (GSH) vs. oxidized glutathione (GSSG), an attenuated formation of lipid hydroperoxides, and an increased expression of thioredoxin-1 (Trx-1). Furthermore, H(2)S inhibited the progression of apoptosis after I/R injury by increasing the protein expression of heat shock protein (HSP-90) and Bcl-2. These results indicate that H(2)S protects the murine liver against I/R injury through an upregulation of intracellular antioxidant and antiapoptotic signaling pathways.