Hydrogen Sulfide and the Immune System.

Hydrogen sulfide (H2S) is the "third gasotransmitter" recognized alongside nitric oxide (NO) and carbon monoxide (CO). H2S exhibits an array of biological effects in mammalian cells as revealed by studies showing important roles in the cardiovascular system, in cell signalling processes, post-translational modifications and in the immune system. Regarding the latter, using pharmacological and genetic approaches scientists have shown this molecule to have both pro- and anti-inflammatory effects in mammalian systems. The anti-inflammatory effects of H2S appeared to be due to its inhibitory action on the nuclear factor kappa beta signalling pathway; NF-kB representing a transcription factor involved in the regulation pro-inflammatory mediators like nitric oxide, prostaglandins, and cytokines. In contrast, results from several animal model describe a more complicated picture and report on pro-inflammatory effects linked to exposure to this molecule; linked to dosage used and point of administration of this molecule. Overall, roles for H2S in several inflammatory diseases spanning arthritis, atherosclerosis, sepsis, and asthma have been described by researchers. In light this work fascinating research, this chapter will cover H2S biology and its many roles in the immune system.

Hydrogen Sulfide Treatment Improves Post-Infarct Remodeling and Long-Term Cardiac Function in CSE Knockout and Wild-Type Mice.

Hydrogen sulfide (H2S) is recognized as an endogenous gaseous signaling molecule generated by cystathionine γ-lyase (CSE) in cardiovascular tissues. H2S up-regulation has been shown to reduce ischemic injury, and H2S donors are cardioprotective in rodent models when administered concurrent with myocardial ischemia. We evaluated the potential utility of H2S therapy in ameliorating cardiac remodeling with administration delayed until 2 h post-infarction in mice with or without cystathionine γ-lyase gene deletion (CSE-/-). The slow-release H2S donor, GYY4137, was administered from 2 h after surgery and daily for 28 days following myocardial infarction (MI) induced by coronary artery ligation, comparing responses in CSE-/- with wild-type (WT) mice (n = 5-10/group/genotype). Measures of cardiac function and expression of key genes associated with cardiac hypertrophy, fibrosis, and apoptosis were documented in atria, ventricle, and kidney tissues. Post-MI GYY4137 administration reduced infarct area and restored cardiac function, accompanied by reduction of the elevated ventricular expression of genes mediating cardiac remodeling to near-normal levels. Few differences between WT and CSE-/- mice were observed, except CSE-/- mice had higher blood pressures, and higher atrial Mir21a expression across all treatment groups. These findings suggest endogenous CSE gene deletion does not substantially exacerbate the long-term response to MI. Moreover, the H2S donor GYY4137 administered after onset of MI preserves cardiac function and protects against adverse cardiac remodeling in both WT and CSE-deficient mice.

Induction of caveolin-3/eNOS complex by nitroxyl (HNO) ameliorates diabetic cardiomyopathy.

Nitroxyl (HNO), one-electron reduced and protonated sibling of nitric oxide (NO), is a potential regulator of cardiovascular functions. It produces positive inotropic, lusitropic, myocardial anti-hypertrophic and vasodilator properties. Despite of these favorable actions, the significance and the possible mechanisms of HNO in diabetic hearts have yet to be fully elucidated. H9c2 cells or primary neonatal mouse cardiomyocytes were incubated with normal glucose (NG) or high glucose (HG). Male C57BL/6 mice received intraperitoneal injection of streptozotocin (STZ) to induce diabetes. Here, we demonstrated that the baseline fluorescence signals of HNO in H9c2 cells were reinforced by both HNO donor Angeli's salt (AS), and the mixture of hydrogen sulfide (H2S) donor sodium hydrogen sulfide (NaHS) and NO donor sodium nitroprusside (SNP), but decreased by HG. Pretreatment with AS significantly reduced HG-induced cell vitality injury, apoptosis, reactive oxygen species (ROS) generation, and hypertrophy in H9c2 cells. This effect was mediated by induction of caveolin-3 (Cav-3)/endothelial nitric oxide (NO) synthase (eNOS) complex. Disruption of Cav-3/eNOS by pharmacological manipulation or small interfering RNA (siRNA) abolished the protective effects of AS in HG-incubated H9c2 cells. In STZ-induced diabetic mice, administration of AS ameliorated the development of diabetic cardiomyopathy, as evidenced by improved cardiac function and reduced cardiac hypertrophy, apoptosis, oxidative stress and myocardial fibrosis without affecting hyperglycemia. This study shed light on how interaction of NO and H2S regulates cardiac pathology and provide new route to treat diabetic cardiomyopathy with HNO.

Biological Effects of Morpholin-4-Ium 4 Methoxyphenyl (Morpholino) Phosphinodithioate and Other Phosphorothioate-Based Hydrogen Sulfide Donors.

Significance: Hydrogen sulfide (H2S) is regarded as the third gasotransmitter along with nitric oxide and carbon monoxide. Extensive studies have demonstrated a variety of biological roles for H2S in neurophysiology, cardiovascular disease, endocrine regulation, and other physiological and pathological processes. Recent Advances: Novel H2S donors have proved useful in understanding the biological functions of H2S, with morpholin-4-ium 4 methoxyphenyl (morpholino) phosphinodithioate (GYY4137) being one of the most common pharmacological tools used. One advantage of GYY4137 over sulfide salts is its ability to release H2S in a slow and sustained manner akin to endogenous H2S production, rather than the delivery of H2S as a single concentrated burst. Critical Issues: Here, we summarize recent progress made in the characterization of the biological activities and pharmacological effects of GYY4137 in a range of in vitro and in vivo systems. Recent developments in the structural modification of GYY4137 to generate new compounds and their biological effects are also discussed. Future Directions: Slow-releasing H2S donor, GYY4137, and other phosphorothioate-based H2S donors are potent tools to study the biological functions of H2S. Despite recent progress, more work needs to be performed on these new compounds to unravel the mechanisms behind H2S release and pace of its discharge, as well as to define the effects of by-products of donors after H2S liberation. This will not only lead to better in-depth understanding of the biological effects of H2S but will also shed light on the future development of a new class of therapeutic agents with potential to treat a wide range of human diseases.

Metabolic stress is a primary pathogenic event in transgenic Caenorhabditis elegans expressing pan-neuronal human amyloid beta.

Alzheimer's disease (AD) is the most common neurodegenerative disease affecting the elderly worldwide. Mitochondrial dysfunction has been proposed as a key event in the etiology of AD. We have previously modeled amyloid-beta (Aß)-induced mitochondrial dysfunction in a transgenic Caenorhabditis elegans strain by expressing human Aß peptide specifically in neurons (GRU102). Here, we focus on the deeper metabolic changes associated with this Aß-induced mitochondrial dysfunction. Integrating metabolomics, transcriptomics and computational modeling, we identify alterations in Tricarboxylic Acid (TCA) cycle metabolism following even low-level Aß expression. In particular, GRU102 showed reduced activity of a rate-limiting TCA cycle enzyme, alpha-ketoglutarate dehydrogenase. These defects were associated with elevation of protein carbonyl content specifically in mitochondria. Importantly, metabolic failure occurred before any significant increase in global protein aggregate was detectable. Treatment with an anti-diabetes drug, Metformin, reversed Aß-induced metabolic defects, reduced protein aggregation and normalized lifespan of GRU102. Our results point to metabolic dysfunction as an early and causative event in Aß-induced pathology and a promising target for intervention.

Protective Smell of Hydrogen Sulfide and Polysulfide in Cisplatin-Induced Nephrotoxicity.

Though historically known as a toxic gas, hydrogen sulfide (H2S) has displayed a new face as the third endogenous gaseous signaling molecule after nitric oxide (NO) and carbon monoxide (CO). Here in this review, we survey the role and therapeutic potential of H2S in cisplatin-induced nephrotoxicity. Specifically, reduction of H2S by cystathionine γ-lyase (CSE) downregulation upon cisplatin treatment may contribute to cisplatin-induced renal cell injury, possibly by augmentation of endogenous reactive oxygen species (ROS) production, while H2S donation may prevent subsequent renal dysfunction by inhibiting NADPH oxidase activation. Intriguingly, H2S slow-releasing compound GYY4137 seems to increase the anticancer activity of cisplatin, at least in several cancer cell lines, and this is probably due to its own anticancer effect. However, the efficacy of H2S donors in tumor-bearing animals remains to be tested in terms of renal protection and cancer inhibition after receiving cisplatin. Furthermore, accumulative evidence regarding usage of polysulfide, a novel H2S derived molecule, in the therapy of cisplatin-induced nephrotoxicity, was also summarized.

A Review of Hydrogen Sulfide Synthesis, Metabolism, and Measurement: Is Modulation of Hydrogen Sulfide a Novel Therapeutic for Cancer?

Significance: Hydrogen sulfide (H2S) has been recognized as the third gaseous transmitter alongside nitric oxide and carbon monoxide. In the past decade, numerous studies have demonstrated an active role of H2S in the context of cancer biology. Recent Advances: The three H2S-producing enzymes, namely cystathionine γ-lyase (CSE), cystathionine ß-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (3MST), have been found to be highly expressed in numerous types of cancer. Moreover, inhibition of CBS has shown anti-tumor activity, particularly in colon cancer, ovarian cancer, and breast cancer, whereas the consequence of CSE or 3MST inhibition remains largely unexplored in cancer cells. Intriguingly, H2S donation at high amounts or a long time duration has also been observed to induce cancer cell apoptosis in vitro and in vivo while sparing noncancerous fibroblast cells. Therefore, a bell-shaped model has been proposed to explain the role of H2S in cancer development. Specifically, endogenous H2S or a relatively low level of exogenous H2S may exhibit a pro-cancer effect, whereas exposure to H2S at a higher amount or for a long period may lead to cancer cell death. This indicates that inhibition of H2S biosynthesis and H2S supplementation serve as two distinct ways for cancer treatment. This paradoxical role of H2S has stimulated the enthusiasm for the development of novel CBS inhibitors, H2S donors, and H2S-releasing hybrids. Critical Issues: A clear relationship between H2S level and cancer progression remains lacking. The possibility that the altered levels of these byproducts have influenced the cell viability of cancer cells has not been excluded in previous studies when modulating H2S producing enzymes. Future Directions: The consequence of CSE or 3MST inhibition in cancer cells need to be examined in the future. Better portrayal of the crosstalk among these gaseous transmitters may not only lead to an in-depth understanding of cancer progression but also shed light on novel strategies for cancer therapy.

Cystathionine-γ-lyase ameliorates the histone demethylase JMJD3-mediated autoimmune response in rheumatoid arthritis.

Cystathionine-γ-lyase (CSE), an enzyme associated with hydrogen sulfide (H2S) production, is an important endogenous regulator of inflammation. Jumonji domain-containing protein 3 (JMJD3) is implicated in the immune response and inflammation. Here, we investigated the potential contribution of JMJD3 to endogenous CSE-mediated inflammation in rheumatoid arthritis (RA). Upregulated CSE and JMJD3 were identified in synovial fibroblasts (SFs) from RA patients as well as in the joints of arthritic mice. Knocking down CSE augmented inflammation in IL-1ß-induced SFs by increasing JMJD3 expression. In addition, CSE-/- mice with collagen-induced arthritis (CIA) developed severe joint inflammation and bone erosion. Conversely, overexpressing CSE inhibited JMJD3 expression by the transcription factor Sp-1 and was accompanied by reduced inflammation in IL-1ß-treated SFs. Furthermore, JMJD3 silencing or the administration of the JMJD3 inhibitor GSK-J4 significantly decreased the inflammatory response in IL-1ß-treated SFs, mainly by controlling the methylation status of H3K27me3 at the promoter of its target genes. GSK-J4 markedly attenuated the severity of arthritis in CIA mice. In conclusion, suppressing JMJD3 expression by the transcription factor Sp-1 is likely responsible for the ability of CSE to negatively modulate the inflammatory response and reduce the progression of RA.

Renal protective effect of polysulfide in cisplatin-induced nephrotoxicity.

Cisplatin is a major chemotherapeutic drug for solid tumors whereas it may lead to severe nephrotoxicity. Despite decades of efforts, effective therapies remain largely lacking for this disease. In the current research, we investigated the therapeutic effect of hydrogen polysulfide, a novel hydrogen sulfide (H2S) derived signaling molecule, in cisplatin nephrotoxicity and the mechanisms involved. Our results showed that polysulfide donor Na2S4 ameliorated cisplatin-caused renal toxicity in vitro and in vivo through suppressing intracellular reactive oxygen species (ROS) generation and downstream mitogen-activated protein kinases (MAPKs) activation. Additionally, polysulfide may inhibit ROS production by simultaneously lessening the activation of NADPH oxidase and inducing nucleus translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) in RPT cells. Interestingly, polysulfide possesses anti-cancer activity and is able to add on more anti-cancer effect to cisplatin in non-small cell lung cancer (NSCLC) cell lines. Moreover, we observed that the number of sulfur atoms in polysulfide well reflected the efficacy of these molecules not only in cell protection but also cancer inhibition which may serve as a guide for further development of polysulfide donors for pharmaceutical usage. Taken together, our study suggests that polysulfide may be a novel and promising therapeutic agent to prevent cisplatin-induced nephrotoxicity.

Renal Protective Effect of Hydrogen Sulfide in Cisplatin-Induced Nephrotoxicity.

AIMS: Cisplatin is a major therapeutic drug for solid tumors, but can cause severe nephrotoxicity. However, the role and therapeutic potential of hydrogen sulfide (H2S), an endogenous gasotransmitter, in cisplatin-induced nephrotoxicity remain to be defined. RESULTS: Cisplatin led to the impairment of H2S production in vitro and in vivo by downregulating the expression level of cystathionine γ-lyase (CSE), which may contribute to the subsequent renal proximal tubule (RPT) cell death and thereby renal toxicity. H2S donors NaHS and GYY4137, but not AP39, mitigated cisplatin-induced RPT cell death and nephrotoxicity. The mechanisms underlying the protective effect of H2S donors included the suppression of intracellular reactive oxygen species generation and downstream mitogen-activated protein kinases by inhibiting NADPH oxidase activity, which may be possibly through persulfidating the subunit p47phox. Importantly, GYY4137 not only ameliorated cisplatin-caused renal injury but also added on more anticancer effect to cisplatin in cancer cell lines. Innovation and Conclusion: Our study provides a comprehensive understanding of the role and therapeutic potential of H2S in cisplatin-induced nephrotoxicity. Our results indicate that H2S may be a novel and promising therapeutic target to prevent cisplatin-induced nephrotoxicity. Antioxid. Redox Signal. 29, 455-470.

Hydrogen Sulfide As a Potential Target in Preventing Spermatogenic Failure and Testicular Dysfunction.

AIMS: Testis and sperm are particularly susceptible to inflammation and oxidative stress. Although hydrogen sulfide (H2S) has been considered an important biological signaling molecule in inflammatory and oxidative stress processes, its role in the male reproductive system was poorly understood. The aim of this study was to investigate the role of H2S in the regulation of male reproductive system. RESULTS: We found that both subfertile and infertile patients, especially asthenospermic patients, exhibited decreased concentration of H2S in their seminal plasma and diminished expression of H2S-generating enzyme (cystathionine ß-synthase [CBS]) in sperm. Supplying exogenous H2S to semen improved sperm motility of these asthenospermic patients. Furthermore, decreased sperm motility was observed in animal models with a defective in H2S generation such as lipopolysaccharide-treated mice, diabetic mice, and CBS-deficient mice. Our research showed that stress-induced reductions of endogenous H2S production and CBS expression are correlated with impaired spermatogenesis and a defective blood-testis barrier. Supplying exogenous H2S or overexpressing CBS could relieve the spermatogenic failure. This occurred primarily through the combination of anti-inflammatory and antioxidative effects. INNOVATION: These results provide the first indication that H2S is important for maintaining male fertility and protecting testicular function. CONCLUSION: H2S plays an important role in spermatogenic failure and testicular dysfunction mainly by its anti-inflammatory and antioxidative effects. Antioxid. Redox Signal. 28, 1447-1462.

Intracellular Hyper-Acidification Potentiated by Hydrogen Sulfide Mediates Invasive and Therapy Resistant Cancer Cell Death.

Slow and continuous release of H2S by GYY4137 has previously been demonstrated to kill cancer cells by increasing glycolysis and impairing anion exchanger and sodium/proton exchanger activity. This action is specific for cancer cells. The resulting lactate overproduction and defective pH homeostasis bring about intracellular acidification-induced cancer cell death. The present study investigated the potency of H2S released by GYY4137 against invasive and radio- as well as chemo-resistant cancers, known to be glycolytically active. We characterized and utilized cancer cell line pairs of various organ origins, based on their aggressive behaviors, and assessed their response to GYY4137. We compared glycolytic activity, via lactate production, and intracellular pH of each cancer cell line pair after exposure to H2S. Invasive and therapy resistant cancers, collectively termed aggressive cancers, are receptive to H2S-mediated cytotoxicity, albeit at a higher concentration of GYY4137 donor. While lactate production was enhanced, intracellular pH of aggressive cancers was only modestly decreased. Inherently, the magnitude of intracellular pH decrease is a key determinant for cancer cell sensitivity to H2S. We demonstrated the utility of coupling GYY4137 with either simvastatin, known to inhibit monocarboxylate transporter 4 (MCT4), or metformin, to further boost glycolysis, in bringing about cell death for aggressive cancers. Simvastatin inhibiting lactate extrusion thence contained excess lactate induced by GYY4137 within intracellular compartment. In contrast, the combined exposure to both GYY4137 and metformin overwhelms cancer cells with lactate over-production exceeding its expulsion rate. Together, GYY4137 and simvastatin or metformin synergize to induce intracellular hyper-acidification-mediated cancer cell death.

Discovery of medium ring thiophosphorus based heterocycles as antiproliferative agents.

Hydrogen sulfide (H2S) has been investigated for its potential in therapy. Recently, we reported novel H2S donor molecules based on a thiophosphorus core, which slowly release H2S and have improved anti-proliferative activity in cancer cell lines compared to the most widely studied H2S donor GYY4137 (1). Herein, we have prepared new thiophosphorus organic H2S donors with different ring sizes and evaluated them in two solid tumor cell lines and one normal cell line. A seven membered ring compound, 17, was found to be the most potent with sub-micromolar IC50s in breast (0.76µM) and ovarian (0.76µM) cancer cell lines. No significant H2S release was detected in aqueous solution for this compound. However, confocal imaging showed that H2S was released from 17 inside cells at a similar level to the widely studied H2S donor GYY4137, which was shown to release 10µM H2S after 12h at a concentration of 400µM. Comparison of 17 with its non-sulfur oxygen analogue, 26, provided evidence that the sulfur atom is important for its potency. However, the significant potency observed for 26 (5.94-11.0µM) indicates that the high potency of 17 is not entirely due to release of H2S. Additional mechanism(s) appear to be responsible for the observed activity, hence more detailed studies are required to better understand the role of H2S in cancer with potent thiophosphorus agents.

Identification of a previously undetected metabolic defect in the Complex II Caenorhabditis elegans mev-1 mutant strain using respiratory control analysis.

Hypometabolism may play an important role in the pathogenesis of ageing and ageing-related diseases. The nematode Caenorhabditis elegans offers the opportunity to study "living mitochondria" in a small (~1 mm) animal replete with a highly stereotypical, yet complex, anatomy and physiology. Basal oxygen consumption rate is often employed as a proxy for energy metabolism in this context. This parameter is traditionally measured using single-chamber Clark electrodes without the addition of metabolic modulators. Recently, multi-well oxygen electrodes, facilitating addition of metabolic modulators and hence study of respiratory control during different mitochondrial respiration states, have been developed. However, only limited official protocols exist for C. elegans, and key limitations of these techniques are therefore unclear. Following modification and testing of some of the existing protocols, we used these methods to explore mitochondrial bioenergetics in live nematodes of an electron transfer chain Complex II mutant strain, mev-1, and identified a previously undetected metabolic defect. We find that mev-1 mutants cannot respond adequately to increased energy demands, suggesting that oxidative phosphorylation is more severely impaired in these animals than has previously been appreciated.

H2S biosynthesis and catabolism: new insights from molecular studies.

Hydrogen sulfide (H2S) has profound biological effects within living organisms and is now increasingly being considered alongside other gaseous signalling molecules, such as nitric oxide (NO) and carbon monoxide (CO). Conventional use of pharmacological and molecular approaches has spawned a rapidly growing research field that has identified H2S as playing a functional role in cell-signalling and post-translational modifications. Recently, a number of laboratories have reported the use of siRNA methodologies and genetic mouse models to mimic the loss of function of genes involved in the biosynthesis and degradation of H2S within tissues. Studies utilising these systems are revealing new insights into the biology of H2S within the cardiovascular system, inflammatory disease, and in cell signalling. In light of this work, the current review will describe recent advances in H2S research made possible by the use of molecular approaches and genetic mouse models with perturbed capacities to generate or detoxify physiological levels of H2S gas within tissues.

Hydrogen Sulfide Regulates Krüppel-Like Factor 5 Transcription Activity via Specificity Protein 1 S-Sulfhydration at Cys664 to Prevent Myocardial Hypertrophy.

BACKGROUND: Hydrogen sulfide (H2S) is a gasotransmitter that regulates multiple cardiovascular functions. Krüppel-like factor 5 (KLF5) exerts diverse functions in the cardiovascular system. Whether and how H2S regulates KLF5 in myocardial hypertrophy is unknown. METHODS AND RESULTS: In our study, hypertrophic myocardial samples in the clinic were collected and underwent histological and molecular biological analysis. Spontaneously hypertensive rats and neonatal rat cardiomyocytes were studied for functional and signaling responses to GYY4137, an H2S-releasing compound. Expression of cystathionine γ-lyase, a principal enzyme for H2S generation in heart, decreased in human hypertrophic myocardium, whereas KLF5 expression increased. After GYY4137 administration for 4 weeks, myocardial hypertrophy was inhibited in spontaneously hypertensive rats, as demonstrated by improvement in cardiac structural parameters, heart mass, size of cardiac myocytes, and expression of atrial natriuretic peptide. H2S diminished expression of KLF5 in myocardium of spontaneously hypertensive rats and in hypertrophic cardiomyocytes. H2S also inhibits platelet-derived growth factor A promoter activity, decreased recruitment of KLF5 to the platelet-derived growth factor A promoter, and reduced atrial natriuretic peptide expression in angiotensin II-stimulated cardiomyocytes, and these effects are suppressed by KLF5 knockdown. KLF5 promoter activity and KLF5 expression was also reversed by H2S. H2S increased the S-sulfhydration on specificity protein 1 in cardiomyocytes. Moreover, H2S decreased KLF5 promoter activity; reduced KLF5 mRNA expression; attenuated specificity protein 1 binding activity with KLF5 promoter; and inhibited hypertrophy after specificity protein 1 mutated at Cys659, Cys689, and Cys692 but not Cys664 overexpression. CONCLUSIONS: These findings suggest that H2S regulates KLF5 transcription activity via specificity protein 1 S-sulfhydration at Cys664 to prevent myocardial hypertrophy.

Hydrogen Sulfide Induces Keap1 S-sulfhydration and Suppresses Diabetes-Accelerated Atherosclerosis via Nrf2 Activation.

Hydrogen sulfide (H2S) has been shown to have powerful antioxidative and anti-inflammatory properties that can regulate multiple cardiovascular functions. However, its precise role in diabetes-accelerated atherosclerosis remains unclear. We report here that H2S reduced aortic atherosclerotic plaque formation with reduction in superoxide (O2 (-)) generation and the adhesion molecules in streptozotocin (STZ)-induced LDLr(-/-) mice but not in LDLr(-/-)Nrf2(-/-) mice. In vitro, H2S inhibited foam cell formation, decreased O2 (-) generation, and increased nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and consequently heme oxygenase 1 (HO-1) expression upregulation in high glucose (HG) plus oxidized LDL (ox-LDL)-treated primary peritoneal macrophages from wild-type but not Nrf2(-/-) mice. H2S also decreased O2 (-) and adhesion molecule levels and increased Nrf2 nuclear translocation and HO-1 expression, which were suppressed by Nrf2 knockdown in HG/ox-LDL-treated endothelial cells. H2S increased S-sulfhydration of Keap1, induced Nrf2 dissociation from Keap1, enhanced Nrf2 nuclear translocation, and inhibited O2 (-) generation, which were abrogated after Keap1 mutated at Cys151, but not Cys273, in endothelial cells. Collectively, H2S attenuates diabetes-accelerated atherosclerosis, which may be related to inhibition of oxidative stress via Keap1 sulfhydrylation at Cys151 to activate Nrf2 signaling. This may provide a novel therapeutic target to prevent atherosclerosis in the context of diabetes.

Hydrogen Sulfide Mitigates Myocardial Infarction via Promotion of Mitochondrial Biogenesis-Dependent M2 Polarization of Macrophages.

AIMS: Macrophages are of key importance for tissue repair after myocardial infarction (MI). Hydrogen sulfide (H2S) has been shown to exert cardioprotective effects in MI. However, the mechanisms by which H2S modulates cardiac remodeling and repair post-MI remain to be clarified. RESULTS: In our current study, we showed that H2S supplementation ameliorated pathological remodeling and dysfunction post-MI in wild-type (WT) and CSE KO mice, resulting in decreased infarct size and mortality, accompanied by an increase in the number of M2-polarized macrophages at the early stage of MI. Strikingly, adoptive transfer of NaHS-treated bone marrow-derived macrophages into WT and CSE KO mice with depleted macrophages also ameliorated MI-induced cardiac functional deterioration. Further mechanistic studies demonstrated that NaHS-induced M2 polarization was achieved by enhanced mitochondrial biogenesis and fatty acid oxidation. INNOVATION AND CONCLUSION: Our study shows (for the first time) that H2S may have the potential as a therapeutic agent for MI via promotion of M2 macrophage polarization. Rebound Track: This work was rejected during standard peer review and rescued by Rebound Peer Review (Antioxid Redox Signal 16:293-296, 2012) with the following serving as open reviewers: Hideo Kimura, Chaoshu Tang, Xiaoli Tian, and Kenneth Olson. Antioxid. Redox Signal. 25, 268-281.

SIRT3 Mediates the Antioxidant Effect of Hydrogen Sulfide in Endothelial Cells.

AIM: Oxidative stress is a key contributor to endothelial dysfunction and associated cardiovascular pathogenesis. Hydrogen sulfide (H2S) is an antioxidant gasotransmitter that protects endothelial cells against oxidative stress. Sirtuin3 (SIRT3), which belongs to the silent information regulator 2 (SIR2) family, is an important deacetylase under oxidative stress. H2S is able to regulate the activity of several sirtuins. The present study aims to investigate the role of SIRT3 in the antioxidant effect of H2S in endothelial cells. RESULTS: Cultured EA.hy926 endothelial cells were exposed to hydrogen peroxide (H2O2) as a model of oxidative stress-induced cell injury. GYY4137, a slow-releasing H2S donor, improved cell viability, reduced oxidative stress and apoptosis, and improved mitochondrial function following H2O2 treatment. H2S reversed the stimulation of MAPK phosphorylation, downregulation of SIRT3 mRNA and reduction of the superoxide dismutase 2 and isocitrate dehydrogenase 2 expression which were induced by H2O2. H2S also increased activator protein 1 (AP-1) binding activity with SIRT3 promoter and this effect was absent in the presence of the specific AP-1 inhibitor, SR11302 or curcumin. Paraquat administration to mice induced a defected endothelium-dependent aortic vasodilatation and increased oxidative stress in both mouse aorta and small mesenteric artery, which were alleviated by GYY4137 treatment. This vasoprotective effect of H2S was absent in SIRT3 knockout mice. INNOVATION: The present results highlight a novel role for SIRT3 in the protective effect of H2S against oxidant damage in the endothelium both in vitro and in vivo. CONCLUSION: H2S enhances AP-1 binding activity with the SIRT3 promoter, thereby upregulating SIRT3 expression and ultimately reducing oxidant-provoked vascular endothelial dysfunction. Antioxid. Redox Signal. 24, 329-343.

GYY4137 attenuates remodeling, preserves cardiac function and modulates the natriuretic peptide response to ischemia.

AIMS: Myocardial infarction followed by adverse left ventricular (LV) remodeling is the most frequent proximate cause of heart failure. Hydrogen sulfide (H2S) is an important endogenous modulator of diverse physiological and pathophysiological processes. Its role in post-ischemic ventricular remodeling and the associated neurohormonal responses has not been defined. Here, we aimed at evaluating whether the slow-releasing water-soluble H2S donor GYY4137 (GYY) exerts cardioprotective effects and modulates the neurohormonal response to cardiac ischemic injury. METHODS AND RESULTS: Treatment for 2 or 7 days with GYY (100 mg/Kg/48 h, IP) after acute myocardial infarction (MI) in rats preserved LV dimensions and function in vivo, compared to untreated infarcted (MI), placebo- and dl-propargylglycine- (PAG, an inhibitor of endogenous H2S synthesis) treated animals (n=9/group/time-point). LV dimensions and function in GYY-treated animals were comparable to healthy sham-operated rats. GYY-treated hearts had significantly less LV fibrosis than MI, placebo and PAG hearts. A higher density of blood vessels was found in the LV scar area of GYY-treated animals compared to all other infarcted groups. Despite preserved LV structure and function, treatment with GYY increased the levels of the natriuretic peptides ANP and BNP in association with enhanced cyclic GMP levels, paralleled by higher cGMP-dependent protein kinase type I (cGKI) protein levels. CONCLUSIONS: Our data suggest that the slow-releasing H2S donor, GYY4137, preserves cardiac function, attenuates adverse remodeling and may exert post-ischemic cardioprotective (pro-angiogenic, anti-apoptotic, anti-hypertrophic and anti-fibrotic) effects in part through enhanced early post-ischemic endogenous natriuretic peptide activation.