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

Hydrogen sulfide upregulates hypoxia inducible factors and erythropoietin production in chronic kidney disease induced by 5/6 nephrectomized rats

INTRODUCTION

In end stage renal disease )ESRD(, reduced EPO production resulted in decreased oxygen diffusion that cause Hypoxia-inducible factors (HIFs) stabilization. The mechanism of beneficial effects of H2S in chronic kidney disease (CKD) is the aim of the present study to examine the effects of the H2S donor sodium hydrosulfide (NaHS) on renal function parameters, oxidative stress indices and expression levels of HIF-2α gene and erythropoietin protein in 5/6 nephrectomy-induced chronic renal failure in rats.

METHODS AND MATERIALS

Male rats were assigned into 3 groups (n = 8): Sham, CKD and NaHS groups. In the CKD group, 5/6 nephrectomy was performed. In the sham group, rats were anesthetized but 5/6 nephrectomy was not induced. In the NaHS group, 30 µmol/L of NaHS in drinking water for 8 weeks was adminstrated 4 weeks after 5/6 nephrectomy induction. At the end of the 12 week, blood and renal tissues were taken to evaluate renal function parameters, oxidative stress indices and expression levels of HIF-2α gene and erythropoietin protein.

RESULTS

The induction of 5/6 nephrectomy significantly caused renal dysfunction, oxidative stress, increased HIF-2α gene expression and decreased erythropoietin levels in renal tissue samples. NaHS administration resulted in a marked improvement in renal function and oxidative stress indicators, a marked reduction in HIF-2α gene expression as well as an increase in erythropoietin protein levels in comparison with the CKD group.

CONCLUSION

In this study, regional hypoxia and oxidative stress in CKD, may cause the stabilization of the HIFs complexes, although erythropoietin synthesis was not increased due to destructive effects of CKD on the kidney tissues. Administration of NaHS caused up-regulating HIF-erythropoietin signaling pathway.

The Influence of Balneotherapy Using Salty Sulfide-Hydrogen Sulfide Water on Selected Markers of the Cardiovascular System: A Prospective Study

Background: The sulfide-hydrogen sulfide brine balneotherapy (HSBB), including a combination of dissolved hydrogen sulfide (H2S) gas, inorganic sulfur ions (S2-), and hydrosulfide ions (HS-), is one of the most important and most effective forms of spa treatment in patients with osteoarticular disorders (OADs). Some cardiovascular diseases (CVDs) are often considered to be contraindications to HSBB since the presence of thiol groups may lead to an increased quantity of reactive oxygen species (ROS), which damage the vascular endothelium, and endothelial dysfunction is considered to be the main cause of atherosclerosis. However, there are a number of literature reports suggesting this theory to be false. H2S is a member of the endogenous gaseous transmitter family and, since it is a relatively recent addition, it has the least well-known biological properties. H2S-NO interactions play an important role in oxidative stress in CVDs. The general objective of this study was to assess the cardiovascular safety of HSBB and analyze the effect of HSBB on selected cardiovascular risk markers. Methods: A total of 100 patients at the age of 76.3 (±7.5) years from the Włókniarz Sanatorium in Busko-Zdrój were initially included in the study. The following parameters were assessed: age, sex, height, body weight, body surface area (BSA), body mass index (BMI), systolic (SBP) and diastolic blood pressure (DBP), heart rate, the diagnosis of OAD that was the indication for balneotherapy, creatinine (CREAT), glomerular filtration rate (GFR), lipid panel, C-reactive protein (CRP), uric acid (UA), and fibrinogen (FIBR) and cardiovascular markers: (cardiac troponin T (cTnT), N-terminal pro-B-type natriuretic peptide (NT-proBNP). Results: A significant decrease in DBP and a trend towards SBP reduction were observed over the course of the study. A significant decrease was observed in CRP levels decreasing from 2.7 (±3.6) mg/L to 2.06 (±1.91) mg/L, whereas FIBR rose significantly from 2.95 (±0.59) g/L to 3.23 (±1.23) g/L. LDL-C levels decreased slightly, statistically significant, from 129.36 (±40.67) mg/dL to 123.74 (±36.14) mg/dL. HSBB did not affect the levels of evaluated cardiovascular biomarkers, namely NT-proBNP (137.41 (±176.52) pg/mL vs. 142.89 (±182.82) pg/mL; p = 0.477) and cTnT (9.64 (±4.13) vs. 9.65 (±3.91) ng/L; p = 0.948). A multiple regression analysis of pre-balneotherapy and post-balneotherapy values showed cTnT levels to be independently correlated only with CREAT levels and GFR values. None of the assessed parameters independently correlated with the NT-proBNP level. Conclusions: HSBB resulted in a statistically significant improvement in a subclinical pro-inflammatory state. HSBB has a beneficial effect in modifying key cardiovascular risk factors by reducing LDL-C levels and DBP values. HSBB has a neutral effect on cardiovascular ischemia/injury. Despite slightly elevated baseline levels of the biochemical marker of HF (NT-proBNP), HSBB causes no further increase in this marker. The use of HSBB in patients with OAD has either a neutral effect or a potentially beneficial effect on the cardiovascular system, which may constitute grounds for further studies to verify the current cardiovascular contraindications for this form of therapy.

Prognostic value of a disintegrin and metalloproteinase Domain-8 in heart failure

Background

Heart failure (HF) is a severe disease threatening people's health. The aim of this study is to find a significant biomarker inducive to predicting the prognosis of HF.

Methods

GSE135055 and GSE161472 datasets were reanalyzed for exploring key genes related to HF. This single-center, prospective, observational cohort study enrolled 298 patients with or without HF from the Cardiology Department of Zhongda Hospital. Levels of ADAM8 were measured using ELISA kits. Major adverse cardiovascular events (MACEs) were defined as the composite end points of the first occurrence of rehospitalization because of HF or cardiac-related death during one-year follow-up.

Results

(1) Bioinformatics analysis showed that ADAM8 was a key gene in HF via mainly regulating the mechanisms of extracellular matrix (ECM) organization. (2) Levels of ADAM8 were significantly increased in the HF group, compared to the non-failing (NF) group (p < 0.001), especially in patients with HFrEF (p < 0.05), and HFmEF (p < 0.05). The prevalence of HF in the high ADAM8 group (≧472.916 pg/mL) was significantly higher than in the low ADAM8 group (<472.916 pg/mL) (41.95 % vs 30.54 %, p < 0.01). (3) Correlation analysis revealed that ADAM8 was negatively correlated to the left ventricular ejection fraction (LVEF) (r = -0.272, p < 0.001). ROC analysis showed that the AUC of ADAM8 in predicting HF and predicting the MACE were 0.701 (p < 0.0001) and 0.683 (p < 0.0001), respectively. (4) Logistic and Cox regression both indicated that high ADAM8 expression can predict adverse prognosis of HF.

Conclusions

ADAM8 may be a risk factor for HF, especially in cases of HFrEF and HFmEF. High ADAM8 expression in plasma was related to the decreased heart function, and can predict the adverse prognosis of HF.

Role of platelet factor 4 in arteriovenous fistula maturation failure: What do we know so far?

The rate of arteriovenous fistula (AVF) maturation failure remains unacceptably high despite continuous efforts on technique improvement and careful pre-surgery planning. In fact, half of all newly created AVFs are unable to be used for hemodialysis (HD) without a salvage procedure. While vascular stenosis in the venous limb of the access is the culprit, the underlying factors leading to vascular narrowing and AVF maturation failure are yet to be determined. We have recently demonstrated that AVF non-maturation is associated with post-operative medial fibrosis and fibrotic stenosis, and post-operative intimal hyperplasia (IH) exacerbates the situation. Multiple pathological processes and signaling pathways are underlying the stenotic remodeling of the AVF. Our group has recently indicated that a pro-inflammatory cytokine platelet factor 4 (PF4/CXCL4) is upregulated in veins that fail to mature after AVF creation. Platelet factor 4 is a fibrosis marker and can be detected in vascular stenosis tissue, suggesting that it may contribute to AVF maturation failure through stimulation of fibrosis and development of fibrotic stenosis. Here, we present an overview of the how PF4-mediated fibrosis determines AVF maturation failure.

Cardioprotective Effects of Hydrogen Sulfide and Its Potential Therapeutic Implications in the Amelioration of Duchenne Muscular Dystrophy Cardiomyopathy

Hydrogen sulfide (H2S) belongs to the family of gasotransmitters and can modulate a myriad of biological signaling pathways. Among others, its cardioprotective effects, through antioxidant, anti-inflammatory, anti-fibrotic, and proangiogenic activities, are well-documented in experimental studies. Cardiorespiratory failure, predominantly cardiomyopathy, is a life-threatening complication that is the number one cause of death in patients with Duchenne muscular dystrophy (DMD). Although recent data suggest the role of H2S in ameliorating muscle wasting in murine and Caenorhabditis elegans models of DMD, possible cardioprotective effects have not yet been addressed. In this review, we summarize the current understanding of the role of H2S in animal models of cardiac dysfunctions and cardiac cells. We highlight that DMD may be amenable to H2S supplementation, and we suggest H2S as a possible factor regulating DMD-associated cardiomyopathy.

Dissolving sodium hydrosulfide in drinking water is not a good source of hydrogen sulfide for animal studies

Hydrogen sulfide (H2S) has many physiological and pathological roles in the human body. Sodium hydrosulfide (NaHS) is widely used as a pharmacological tool for assessing H2S effects in biological experiments. Although H2S loss from NaHS solution is a matter of minutes, some animal studies use NaHS in solution as an H2S-donating compound in drinking water. This study addresses whether 30 μM NaHS in drinking water prepared in rat/mouse water bottles remains stable for at least 12-24 h, as presumed by some authors. NaHS solutions (30 μM) were prepared in drinking water and immediately transferred to rat/mice water bottles. Samples were obtained from the tip of water bottles and from inside of the bottles at 0, 1, 2, 3, 4, 5, 6, 12, and 24 h for sulfide measurement using the methylene blue method. Furthermore, NaHS (30 μM) was administered to male and female rats for two weeks, and serum sulfide concentrations were measured every other day in the first week and at the end of the second week. NaHS solution was unstable in the samples obtained from the tip of water bottles; it declined by 72% and 75% after 12 and 24 h, respectively. In the samples obtained from the inside of the water bottles, the decline in the NaHS was not significant until 2 h; however, it decreased by 47% and 72% after 12 and 24 h, respectively. NaHS administration did not affect serum sulfide levels in male and female rats. In conclusion, NaHS solution prepared in drinking water can not be used for H2S donation as the solution is unstable. This route of administration exposes animals to variable and lower-than-expected amounts of NaHS.

Protective Effects of H2S Donor Treatment in Experimental Colitis: A Focus on Antioxidants

Inflammatory bowel diseases (IBD) are chronic, inflammatory disorders of the gastrointestinal (GI) system, which have become a global disease over the past few decades. It has become increasingly clear that oxidative stress plays a role in the pathogenesis of IBD. Even though several effective therapies exist against IBD, these might have serious side effects. It has been proposed that hydrogen sulfide (H₂S), as a novel gasotransmitter, has several physiological and pathological effects on the body. Our present study aimed to investigate the effects of H₂S administration on antioxidant molecules in experimental rat colitis. As a model of IBD, 2,4,6-trinitrobenzenesulfonic acid (TNBS) was used intracolonically (i.c.) to induce colitis in male Wistar-Hannover rats. Animals were orally treated (2 times/day) with H₂S donor Lawesson's reagent (LR). Our results showed that H₂S administration significantly decreased the severity of inflammation in the colons. Furthermore, LR significantly suppressed the level of oxidative stress marker 3-nitrotyrosine (3-NT) and caused a significant elevation in the levels of antioxidant GSH, Prdx1, Prdx6, and the activity of SOD compared to TNBS. In conclusion, our results suggest that these antioxidants may offer potential therapeutic targets and H₂S treatment through the activation of antioxidant defense mechanisms and may provide a promising strategy against IBD.

The Biochemistry and Physiology of A Disintegrin and Metalloproteinases (ADAMs and ADAM-TSs) in Human Pathologies

Metalloproteinases are a group of proteinases that plays a substantial role in extracellular matrix remodeling and its molecular signaling. Among these metalloproteinases, ADAMs (a disintegrin and metalloproteinases) and ADAM-TSs (ADAMs with thrombospondin domains) have emerged as highly efficient contributors mediating proteolytic processing of various signaling molecules. ADAMs are transmembrane metalloenzymes that facilitate the extracellular domain shedding of membrane-anchored proteins, cytokines, growth factors, ligands, and their receptors and therefore modulate their biological functions. ADAM-TSs are secretory, and soluble extracellular proteinases that mediate the cleavage of non-fibrillar extracellular matrix proteins. ADAMs and ADAM-TSs possess pro-domain, metalloproteinase, disintegrin, and cysteine-rich domains in common, but ADAM-TSs have characteristic thrombospondin motifs instead of the transmembrane domain. Most ADAMs and ADAM-TSs are activated by cleavage of pro-domain via pro-protein convertases at their N-terminus, hence directing them to various signaling pathways. In this article, we are discussing not only the structure and regulation of ADAMs and ADAM-TSs, but also the importance of these metalloproteinases in various human pathophysiological conditions like cardiovascular diseases, colorectal cancer, autoinflammatory diseases (sepsis/rheumatoid arthritis), Alzheimer's disease, proliferative retinopathies, and infectious diseases. Therefore, based on the emerging role of ADAMs and ADAM-TSs in various human pathologies, as summarized in this review, these metalloproteases can be considered as critical therapeutic targets and diagnostic biomarkers.

An Alzheimer’s Disease Patient-Derived Olfactory Stem Cell Model Identifies Gene Expression Changes Associated with Cognition

An early symptom of Alzheimer’s disease (AD) is an impaired sense of smell, for which the molecular basis remains elusive. Here, we generated human olfactory neurosphere-derived (ONS) cells from people with AD and mild cognitive impairment (MCI), and performed global RNA sequencing to determine gene expression changes. ONS cells expressed markers of neuroglial differentiation, providing a unique cellular model to explore changes of early AD-associated pathways. Our transcriptomics data from ONS cells revealed differentially expressed genes (DEGs) associated with cognitive processes in AD cells compared to MCI, or matched healthy controls (HC). A-Kinase Anchoring Protein 6 (AKAP6) was the most significantly altered gene in AD compared to both MCI and HC, and has been linked to cognitive function. The greatest change in gene expression of all DEGs occurred between AD and MCI. Gene pathway analysis revealed defects in multiple cellular processes with aging, intellectual deficiency and alternative splicing being the most significantly dysregulated in AD ONS cells. Our results demonstrate that ONS cells can provide a cellular model for AD that recapitulates disease-associated differences. We have revealed potential novel genes, including AKAP6 that may have a role in AD, particularly MCI to AD transition, and should be further examined.

Hydrogen Sulfide Releasing Hydrogel for Alleviating Cardiac Inflammation and Protecting Against Myocardial Ischemia-Reperfusion Injury

Myocardial infarction is one of the leading causes of death worldwide. Thus, protection against myocardial ischemia-reperfusion injury is particularly important to improve the prognosis of myocardial infarction. Recently, hydrogen sulfide...

ADAM and ADAMTS disintegrin and metalloproteinases as major factors and molecular targets in vascular malfunction and disease

A Disintegrin and Metalloproteinase (ADAM) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) are two closely related families of proteolytic enzymes. ADAMs are largely membrane-bound enzymes that act as molecular scissors or sheddases of membrane-bound proteins, growth factors, cytokines, receptors and ligands, whereas ADAMTS are mainly secreted enzymes. ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and transmembrane domain. Similarly, ADAMTS family members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but instead of a transmembrane domain they have thrombospondin motifs. Most ADAMs and ADAMTS are activated by pro-protein convertases, and can be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C. Activated ADAMs and ADAMTS participate in numerous vascular processes including angiogenesis, vascular smooth muscle cell proliferation and migration, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs and ADAMTS also play a role in vascular malfunction and cardiovascular diseases such as hypertension, atherosclerosis, coronary artery disease, myocardial infarction, heart failure, peripheral artery disease, and vascular aneurysm. Decreased ADAMTS13 is involved in thrombotic thrombocytopenic purpura and microangiopathies. The activity of ADAMs and ADAMTS can be regulated by endogenous tissue inhibitors of metalloproteinases and other synthetic small molecule inhibitors. ADAMs and ADAMTS can be used as diagnostic biomarkers and molecular targets in cardiovascular disease, and modulators of ADAMs and ADAMTS activity may provide potential new approaches for the management of cardiovascular disorders.

H2S signaling and extracellular matrix remodeling in cardiovascular diseases: A tale of tense relationship

Extracellular matrix (ECM) is a non-cellular three-dimensional macromolecular network that not only provides mechanical support but also transduces essential molecular signals in organ functions. ECM is constantly remodeled to control tissue homeostasis, responsible for cell adhesion, cell migration, cell-to-cell communication, and cell differentiation, etc. The dysregulation of ECM components contributes to various diseases, including cardiovascular diseases, fibrosis, cancer, and neurodegenerative diseases, etc. Aberrant ECM remodeling is initiated by various stress, such as oxidative stress, inflammation, ischemia, and mechanical stress, etc. Hydrogen sulfide (H₂S) is a gasotransmitter that exhibits a wide variety of cytoprotective and physiological functions through its anti-oxidative and anti-inflammatory actions. Amounting research shows that H₂S can attenuate aberrant ECM remodeling. In this review, we discussed the implications and mechanisms of H₂S in the regulation of ECM remodeling in cardiovascular diseases, and highlighted the potential of H₂S in the prevention and treatment of cardiovascular diseases through attenuating adverse ECM remodeling.

Role of Hydrogen Sulfide in the Treatment of Fibrosis

Hydrogen sulfide (H₂S) is a biological gas, the abnormal metabolism of which has associations with the pathogenesis of fibrosis. The purpose of this paper was to determine the potential of H₂S in the prevention and treatment of fibrosis. The data is obtained mainly from articles found in the PubMed database using the keywords “fibrosis” and “hydrogen sulfide,” limiting the results to those published within the last 10 years. Some additional resources have also been used, such as books and articles within journals. Evidence of decreased H₂S enzyme levels in animal models with fibrotic diseases has been found. The protective role of H₂S has been validated by the administration of exogenous H₂S donors in animal models with fibrosis. It is also evident that H₂S is involved in complex signaling pathways and ion channels that inhibit fibrosis development. These findings support the role of H₂S in the treatment of a variety of fibrotic diseases. A randomized controlled trial in fibrosis patients comparing the efficacy of exogenous H₂S and placebo in addition to standard of care can be implemented to validate this further.

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 as a Potential Therapy for Heart Failure-Past, Present, and Future

Hydrogen sulfide (H2S) is an endogenous, gaseous signaling molecule that plays a critical role in cardiac and vascular biology. H2S regulates vascular tone and oxidant defenses and exerts cytoprotective effects in the heart and circulation. Recent studies indicate that H2S modulates various components of metabolic syndrome, including obesity and glucose metabolism. This review will discuss studies exhibiting H2S -derived cardioprotective signaling in heart failure with reduced ejection fraction (HFrEF). We will also discuss the role of H2S in metabolic syndrome and heart failure with preserved ejection fraction (HFpEF).

Harnessing the Benefits of Endogenous Hydrogen Sulfide to Reduce Cardiovascular Disease

Cardiovascular disease is the leading cause of death in the U.S. While various studies have shown the beneficial impact of exogenous hydrogen sulfide (H₂S)-releasing drugs, few have demonstrated the influence of endogenous H₂S production. Modulating the predominant enzymatic sources of H₂S-cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase-is an emerging and promising research area. This review frames the discussion of harnessing endogenous H₂S within the context of a non-ischemic form of cardiomyopathy, termed diabetic cardiomyopathy, and heart failure. Also, we examine the current literature around therapeutic interventions, such as intermittent fasting and exercise, that stimulate H₂S production.

Protective mechanisms of hydrogen sulfide in myocardial ischemia

Hydrogen sulfide (H₂ S), which has been identified as the third gaseous signaling molecule after nitric oxide (NO) and carbon monoxide (CO), plays an important role in maintaining homeostasis in the cardiovascular system. Endogenous H₂ S is produced mainly by three endogenous enzymes: cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfur transferase. Numerous studies have shown that H₂ S has a significant protective role in myocardial ischemia. The mechanisms by which H₂ S affords cardioprotection include the antifibrotic and antiapoptotic effects, regulation of ion channels, protection of mitochondria, reduction of oxidative stress and inflammatory response, regulation of microRNA expression, and promotion of angiogenesis. Amplification of NO- and CO-mediated signaling through crosstalk between H₂ S, NO, and CO may also contribute to the cardioprotective effect. Exogenous H₂ S donors are expected to become effective drugs for the treatment of cardiovascular diseases. This review article focuses on the protective mechanisms and potential therapeutic applications of H₂ S in myocardial ischemia.

Effect of gasotransmitters treatment on expression of hypertension, vascular and cardiac remodeling and hypertensive nephropathy genes in left ventricular hypertrophy

BACKGROUND

Cardiac and renal dysfunction are often co-morbid pathologies leading to worsening prognosis resulting in difficulty in therapy of left ventricular hypertrophy (LVH). The aim of the current study was to determine the changes in expression of human ortholog genes of hypertension, vascular and cardiac remodeling and hypertensive nephropathy phenotypes under normal, disease and upon treatment with gasotransmitter including H₂S (hydrogen sulphide), NO (nitric oxide) and combined (H₂S + NO).

METHODS

A total of 72 Wistar Kyoto rats (with equivalent male and female animals) were recruited in the present study where LVH rat models were treated with H₂S and NO individually as well as with both combined. Cardiac and renal physical indices were recorded and relative gene expression were quantified.

RESULTS

Both cardiac and renal physical indices were significantly modified with individual as well as combined H₂S + NO treatment in control and LVH rats. Expression analysis revealed, hypertension, vascular remodeling genes ACE, TNFα and IGF1, mRNAs to be significantly higher (P ≤ 0.05) in the myocardia and renal tissues of LVH rats, while individual and combined H₂S + NO treatment resulted in lowering the gene expression to normal/near to normal levels. The cardiac remodeling genes MYH7, TGFβ, SMAD4 and BRG1 expression were significantly up-regulated (P ≤ 0.05) in the myocardia of LVH where the combined H₂S + NO treatment resulted in normal/near to normal expression more effectively as compared to individual treatments. In addition individual as well as combined H₂S and NO treatment significantly decreased PKD1 expression in renal tissue, which was up-regulated in LVH rats (P ≤ 0.05).

CONCLUSIONS

The reduction in hemodynamic parameters and cardiac indices as well as alteration in gene expression on treatment of LVH rat model indicates important therapeutic potential of combined treatment with H₂S + NO gasotransmitters in hypertension and cardiac hypertrophy when present as co-morbidity with renal complications.

Hydrogen Sulfide as a Potential Alternative for the Treatment of Myocardial Fibrosis

Harmful, stressful conditions or events in the cardiovascular system result in cellular damage, inflammation, and fibrosis. Currently, there is no targeted therapy for myocardial fibrosis, which is highly associated with a large number of cardiovascular diseases and can lead to fatal heart failure. Hydrogen sulfide (H₂S) is an endogenous gasotransmitter similar to nitric oxide and carbon monoxide. H₂S is involved in the suppression of oxidative stress, inflammation, and cellular death in the cardiovascular system. The level of H₂S in the body can be boosted by stimulating its synthesis or supplying it exogenously with a simple H₂S donor with a rapid- or slow-releasing mode, an organosulfur compound, or a hybrid with known drugs (e.g., aspirin). Hypertension, myocardial infarction, and inflammation are exaggerated when H₂S is reduced. In addition, the exogenous delivery of H₂S mitigates myocardial fibrosis caused by various pathological conditions, such as a myocardial infarct, hypertension, diabetes, or excessive β-adrenergic stimulation, via its involvement in a variety of signaling pathways. Numerous experimental findings suggest that H₂S may work as a potential alternative for the management of myocardial fibrosis. In this review, the antifibrosis role of H₂S is briefly addressed in order to gain insight into the development of novel strategies for the treatment of myocardial fibrosis.

Dysregulation of 1-carbon metabolism and muscle atrophy: potential roles of forkhead box O proteins and PPARγ co-activator-1α

Homocysteine, a non-proteinogenic amino acid but an important metabolic intermediate is generated as an integral component for the “1-carbon metabolism” during normal physiology. It is catabolized to cysteine via the transulfuration pathway resulting in the generation of hydrogen sulfide, a naturally endogenous byproduct. Genetics or metabolic derangement can alter homocysteine concentration leading to hyperhomocysteinemia (HHcy), a physiologically unfavorable condition that causes serious medical conditions including muscle wasting. HHcy environment can derail physiological processes by targeting biomolecules such as Akt; however, not much is known regarding the effects of HHcy on regulation of transcription factors such as forkhead box O (FOXO) proteins. Recently, hydrogen sulfide has been shown to be highly effective in alleviating the effects of HHcy by serving as an antiapoptotic factor, but role of FOXO and its interaction with hydrogen sulfide are yet to be established. In this review, we discuss role(s) of HHcy in skeletal muscle atrophy and how HHcy interact with FOXO and peroxisome proliferator-activated receptor gamma coactivator 1-alpha expressions that are relevant in musculoskeletal atrophy. Further, therapeutic intervention with hydrogen sulfide for harnessing its beneficial effects might help mitigate the dysregulated 1-carbon metabolism that happens to be the hallmark of HHcy-induced pathologies such as muscle atrophy.

A Disintegrin and Metalloproteinase (ADAM) and ADAM with thrombospondin motifs (ADAMTS) family in vascular biology and disease

A Disintegrin and Metalloproteinase (ADAM) is a family of proteolytic enzymes that possess sheddase function and regulate shedding of membrane-bound proteins, growth factors, cytokines, ligands and receptors. Typically, ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and a characteristic transmembrane domain. Most ADAMs are activated by proprotein convertases, but can also be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C activators. A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) is a family of secreted enzymes closely related to ADAMs. Like ADAMs, ADAMTS members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but they lack a transmembrane domain and instead have characteristic thrombospondin motifs. Activated ADAMs perform several functions and participate in multiple cardiovascular processes including vascular smooth muscle cell proliferation and migration, angiogenesis, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs may also be involved in pathological conditions and cardiovascular diseases such as atherosclerosis, hypertension, aneurysm, coronary artery disease, myocardial infarction and heart failure. Like ADAMs, ADAMTS have a wide-spectrum role in vascular biology and cardiovascular pathophysiology. ADAMs and ADAMTS activity is naturally controlled by endogenous inhibitors such as tissue inhibitors of metalloproteinases (TIMPs), and their activity can also be suppressed by synthetic small molecule inhibitors. ADAMs and ADAMTS can serve as important diagnostic biomarkers and potential therapeutic targets for cardiovascular disorders. Natural and synthetic inhibitors of ADAMs and ADAMTS could be potential therapeutic tools for the management of cardiovascular diseases.

The biologic effect of hydrogen sulfide and its function in various diseases

INTRODUCTION

Hydrogen sulfide (H2S), a colorless, water soluble, flammable gas with a characteristic smell of rotten eggs, has been known as a highly toxic gas for several years. However, much like carbon monoxide (CO) and nitric oxide (NO), the initial negative perception of H2S has developed with the discovery that H2S is generated enzymatically in animals under normal conditions. With the result of this discovery, much more work is needed to elucidate the biologic effects of H2S. In recent years, its cytoprotective properties have been recognized in multiple organs and tissues. In particular, H2S plays important roles in combating oxidative species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) and protect the body from oxidative stress. Therefore, this review discusses the biologic effect of H2S and how it protects cells in various diseases by acting as an antioxidant that reduces excessive amounts of ROS and RNS.

ETHICS AND DISSEMINATION

Ethical approval and informed consent are not required, as the study will be a literature review and will not involve direct contact with patients or alterations to patient care.

CONCLUSION

H2S has been found to be cytoprotective in oxidative stress in a wide range of physiologic and pathologic conditions, an increasing number of therapeutic potentials of H2S also have been revealed. However, there is still much debate on the clear mechanism of action of H2S, so that the mechanisms of cell signaling that promote cellular survival and organ protection need to be further investigated to provide better H2S-based therapeutics.

Hydrogen Sulfide (H2S)-Releasing Compounds: Therapeutic Potential in Cardiovascular Diseases

Cardiovascular disease is the main cause of death worldwide, but its pathogenesis is not yet clear. Hydrogen sulfide (H₂S) is considered to be the third most important endogenous gasotransmitter in the organism after carbon monoxide and nitric oxide. It can be synthesized in mammalian tissues and can freely cross the cell membrane and exert many biological effects in various systems including cardiovascular system. More and more recent studies have supported the protective effects of endogenous H₂S and exogenous H₂S-releasing compounds (such as NaHS, Na₂S, and GYY4137) in cardiovascular diseases, such as cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and atherosclerosis. Here, we provided an up-to-date overview of the mechanistic actions of H₂S as well as the therapeutic potential of various classes of H₂S donors in treating cardiovascular diseases.

Novel H2S-NO hybrid molecule (ZYZ-803) promoted synergistic effects against heart failure

Therapeutic strategies that increase hydrogen sulfide (H₂S) or nitric oxide (NO) are cytoprotective in various models of cardiovascular injury. However, the nature of interaction between H₂S and NO in heart failure and the underlying mechanisms for the protective effects remain undefined. The present study tested the cardioprotective effect of ZYZ-803, a novel synthetic H₂S-NO hybrid molecule that decomposed to release H₂S and NO. ZYZ-803 dose dependently improved left ventricular remodeling and preserved left ventricular function in the setting of isoprenaline-induced heart failure. The cardioprotective effect of ZYZ-803 is significantly more potent than that of H₂S and/or NO donor alone. ZYZ-803 stimulated the expression of cystathionine γ-lyase (CSE) for H₂S generation and the activity of endothelial NO synthase (eNOS) for NO production. Blocking CSE and/or eNOS suppressed ZYZ-803-induced H₂S and NO production and cardioprotection. ZYZ-803 increased vascular endothelial growth factor (VEGF) concentration and cyclic guanosine 5′-monophosphate (cGMP) level. Moreover, ZYZ-803 upregulated the endogenous antioxidants, glutathione peroxidase (GPx) and heme oxygenase 1 (HO-1). These findings indicate that H₂S and NO cooperatively attenuates left ventricular remodeling and dysfunction during the development of heart failure through VEGF/cGMP pathway and ZYZ-803 provide expanding insight into strategies for treatment of heart failure.

H2S and homocysteine control a novel feedback regulation of cystathionine beta synthase and cystathionine gamma lyase in cardiomyocytes

Hydrogen sulfide (H₂S), a cardioprotective gas, is endogenously produced from homocysteine by cystathionine beta synthase (CBS) and cystathionine gamma lyase (CSE) enzymes. However, effect of H₂S or homocysteine on CBS and CSE expression, and cross-talk between CBS and CSE are unclear. We hypothesize that homocysteine and H₂S regulate CBS and CSE expressions in a dose dependent manner in cardiomyocytes, and CBS deficiency induces cardiac CSE expression. To test the hypothesis, we treated murine atrial HL1 cardiomyocytes with increasing doses of homocysteine or Na₂S/GYY4137, a H₂S donor, and measured the levels of CBS and CSE. We found that homocysteine upregulates CSE but downregulates CBS whereas Na₂S/GYY4137 downregulates CSE but upregulates CBS in a dose-dependent manner. Moreover, the Na₂S-treatment downregulates specificity protein-1 (SP1), an inducer for CSE, and upregulates miR-133a that targets SP1 and inhibits cardiomyocytes hypertrophy. Conversely, in the homocysteine-treated cardiomyocytes, CBS and miR-133a were downregulated and hypertrophy was induced. In vivo studies using CBS+/-, a model for hyperhomocysteinemia, and sibling CBS+/+ control mice revealed that deficiency of CBS upregulates cardiac CSE, plausibly by inducing SP1. In conclusion, we revealed a novel mechanism for H₂S-mediated regulation of homocysteine metabolism in cardiomyocytes, and a negative feedback regulation between CBS and CSE in the heart.

Cardioprotective effect of KR-33889, a novel PARP inhibitor, against oxidative stress-induced apoptosis in H9c2 cells and isolated rat hearts

Oxidative stress plays a critical role in cardiac injury during ischemia/reperfusion (I/R). Despite a potent cardioprotective activity of KR-33889, a novel poly (ADP-ribose) polymerase inhibitor, its underlying mechanism remains unresolved. This study was designed to investigate the protective effects of KR-33889 against oxidative stress-induced apoptosis in rat cardiomyocytes H9c2 cells and isolated rat hearts. H₂O₂ caused severe injury to H9c2 cells, mainly due to apoptosis, as revealed by TUNEL assay. However, KR-33889 pretreatment significantly attenuated H₂O₂-induced apoptosis of H9c2 cells, which was accompanied by decrease in expression of both cleaved caspase-3 and Bax and increase in Bcl-2 expression and the ratio of Bcl-2/Bax. KR-33889 also significantly enhanced the expression of anti-oxidant enzymes including heme oxygenase-1, Cu/Zn-superoxide dismutase (SOD), Mn-SOD, and catalase, thereby inhibiting production of intracellular ROS. Furthermore, KR-33889 reversed H₂O₂-induced decrease in phosphorylation of Akt, GSK-3β, ERK1/2, p38 MAPK, and SAPK/JNK during most H₂O₂ exposure time. In globally ischemic rat hearts, KR-33889 inhibited both I/R-induced decrease in cardiac contractility and apoptosis by increasing Bcl-2, decreasing both cleaved caspase-3 and Bax expression, and enhancing expression of anti-oxidant enzymes. Taken together, these results suggest that KR-33889 may have therapeutic potential to prevent I/R-induced heart injury in ischemic heart diseases mainly by reducing oxidative stress-mediated myocardial apoptosis.

Hydrogen Sulfide Inhibits High-Salt Diet-Induced Myocardial Oxidative Stress and Myocardial Hypertrophy in Dahl Rats

The study aimed to examine the protective effect of hydrogen sulfide (H₂S) on high-salt-induced oxidative stress and myocardial hypertrophy in salt-sensitive (Dahl) rats. Thirty male Dahl rats and 40 SD rats were included in the study. They were randomly divided into Dahl control (Dahl + NS), Dahl high salt (Dahl + HS), Dahl + HS + NaHS, SD + NS, SD + HS, SD + HS + NaHS, and SD + HS + hydroxylamine (HA). Rats in Dahl + NS and SD + NS groups were given chow with 0.5% NaCl and 0.9% normal saline intraperitoneally daily. Myocardial structure, α-myosin heavy chain (α-MHC) and β-myosin heavy chain (β-MHC) expressions were determined. Endogenous myocardial H₂S pathway and oxidative stress in myocardial tissues were tested. Myocardial H₂S pathway was downregulated with myocardial hypertrophy featured by increased heart weight/body weight and cardiomyocytes cross-sectional area, decreased α-MHC and increased β-MHC expressions in Dahl rats with high-salt diet (all P < 0.01), and oxidative stress in myocardial tissues was significantly activated, demonstrated by the increased contents of hydroxyl radical, malondialdehyde and oxidized glutathione and decreased total antioxidant capacity, carbon monoxide, catalase, glutathione, glutathione peroxidase, superoxide dismutase (SOD) activities and decreased SOD1 and SOD2 protein expressions (P < 0.05, P < 0.01). However, H₂S reduced myocardial hypertrophy with decreased heart weight/body weight and cardiomyocytes cross-sectional area, increased α-MHC, decreased β-MHC expressions and inhibited oxidative stress in myocardial tissues of Dahl rats with high-salt diet. However, no significant difference was found in H₂S pathway, myocardial structure, α-MHC and β-MHC protein and oxidative status in myocardial tissues among SD + NS, SD + HS, and SD + HS + NaHS groups. HA, an inhibitor of cystathionine β-synthase, inhibited myocardial H₂S pathway (P < 0.01), and stimulated myocardial hypertrophy and oxidative stress in SD rats with high-salt diet. Hence, H₂S inhibited myocardial hypertrophy in high salt-stimulated Dahl rats in association with the enhancement of antioxidant capacity, thereby inhibiting oxidative stress in myocardial tissues.

Protective Actions of H2S in Acute Myocardial Infarction and Heart Failure

Hydrogen sulfide (H2S) was identified as the third gasotransmitter in 1996 following the discoveries of the biological importance of nitric oxide and carbon monoxide. Although H2S has long been considered a highly toxic gas, the discovery of its presence and enzymatic production in mammalian tissues supports a critical role for this physiological signaling molecule. H2S is synthesized endogenously by three enzymes: cystathionine β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. H2S plays a pivotal role in the regulation of cardiovascular function as H2S has been shown to modulate: vasodilation, angiogenesis, inflammation, oxidative stress, and apoptosis. Perturbation of endogenous production of H2S has been associated with many pathological conditions of the cardiovascular system such as diabetes, heart failure, and hypertension. As such, modulation of the endogenous H2S signaling pathway or administration of exogenous H2S has been shown to be cytoprotective. This review article will provide a summary of the current body of evidence on the role of H2S signaling in the setting of myocardial ischemia and heart failure. © 2017 American Physiological Society. Compr Physiol 7:583-602, 2017.

Hydrogen Sulfide Reduces Recruitment of CD11b+Gr-1+ Cells in Mice With Myocardial Infarction

The present study aimed to elucidate the mechanisms by which hydrogen sulfide (H2S) attenuates left ventricular remodeling after myocardial infarction (MI). MI was created in mice by left coronary artery ligation. One group of mice received injections of the H2S donor sodium hydrosulfide (NaHS) immediately before and 1 h after ligation, while the control group received saline alone. During both the subacute and chronic stages (1 and 4 weeks postinfarction, respectively), NaHS-treated mice demonstrated attenuation of cardiac dilation in the infarcted myocardium. Furthermore, fewer CD11b+Gr-1+ myeloid cells were detected in the infarct myocardium and peripheral blood from NaHS-treated mice, while more CD11b+Gr-1+ cells remained in the spleen and bone marrow in these animals. NaHS-treated mice also exhibited reduction in cardiomyocyte apoptosis, interstitial fibrosis, cardiac hypertrophy, and pulmonary edema, as well as overall better survival rates, when compared to controls. Thus, exogenous H2S has favorable effects on cardiac remodeling after MI. These observations further support the emerging concept that H2S treatment might have therapeutic benefits in the setting of ischemia-induced heart failure.

Hydrogen Sulfide Improves Myocardial Remodeling via Downregulated Angiotensin Ⅱ/AT1R Pathway in Renovascular Hypertensive Rats

BACKGROUND

Hydrogen sulfide (H₂S) is an important endogenous gaseous transmitter in many physiological functions. Plasma H₂S decreased, and angiotensin II (Ang II) type 1 receptor (AT1R) increased in the myocardial tissues in 2-kidney 1-clip (2K1C) rats than in normotensive rats. Accumulating evidences suggest that H₂S inhibited Ang II/AT1R pathway to regulate cardiovascular function. Therefore, we hypothesized that H₂S may exert beneficial effects on myocardial remodeling in 2K1C rat models of renovascular hypertension.

METHODS AND RESULTS

Sodium hydrosulfide (NaHS, 56 µmol/kg/day) was administered intraperitoneally to the rats from the 7th day after 2K1C operation. Systolic blood pressure was significantly increased from the first week after the operation and was lowered after NaHS treatment for 4 weeks. H₂S could also inhibit the ratio of left ventricle and septum weight to body weight, improve cross-sectional area, and ameliorate ventricular dysfunction. Additionally, the protein expression of AT1R and Ang II serum content were downregulated, whereas superoxide dismutase (SOD) protein was upregulated in 2K1C rats by NaHS treatment for 4 weeks. Furthermore, the reactive oxygen species level and AT1R protein were increased, whereas SOD protein was decreased in cardiomyocytes treated with Ang II compared with the control group. NaHS could reverse these changes. Losartan and N-acetylcysteine could also reverse Ang II-induced changes.

CONCLUSIONS

The protective effect of H₂S is attributable to the suppression of oxidative stress. This process involves the inhibition of the Ang II/AT1R pathway and upregulation of antioxidant enzymes in 2K1C rats.

Hydrogen (H2) Inhibits Isoproterenol-Induced Cardiac Hypertrophy via Antioxidative Pathways

Background and Purpose: Hydrogen (H₂) has been shown to have a strong antioxidant effect on preventing oxidative stress-related diseases. The goal of the present study is to determine the pharmacodynamics of H₂ in a model of isoproterenol (ISO)-induced cardiac hypertrophy.

Methods: Mice (C57BL/6J; 8–10 weeks of age) were randomly assigned to four groups: Control group (n = 10), ISO group (n = 12), ISO plus H₂ group (n = 12), and H₂ group (n = 12). Mice received H₂ (1 ml/100g/day, intraperitoneal injection) for 7 days before ISO (0.5 mg/100g/day, subcutaneous injection) infusion, and then received ISO with or without H₂ for another 7 days. Then, cardiac function was evaluated by echocardiography. Cardiac hypertrophy was reflected by heart weight/body weight, gross morphology of hearts, and heart sections stained with hematoxylin and eosin, and relative atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) mRNA levels. Cardiac reactive oxygen species (ROS), 3-nitrotyrosine and p67 (phox) levels were analyzed by dihydroethidium staining, immunohistochemistry and Western blotting, respectively. For in vitro study, H9c2 cardiomyocytes were pretreated with H₂-rich medium for 30 min, and then treated with ISO (10 μM) for the indicated time. The medium and ISO were re-changed every 24 h. Cardiomyocyte surface areas, relative ANP and BNP mRNA levels, the expression of 3-nitrotyrosine, and the dissipation of mitochondrial membrane potential (MMP) were examined. Moreover, the expression of extracellular signal-regulated kinase1/2 (ERK1/2), p-ERK1/2, p38, p-p38, c-Jun NH2-terminal kinase (JNK), and p-JNK were measured by Western blotting both in vivo and in vitro.

Results: Intraperitoneal injection of H₂ prevented cardiac hypertrophy and improved cardiac function in ISO-infused mice. H₂-rich medium blocked ISO-mediated cardiomyocytes hypertrophy in vitro. H₂ blocked the excessive expression of NADPH oxidase and the accumulation of ROS, attenuated the decrease of MMP, and inhibited ROS-sensitive ERK1/2, p38, and JNK signaling pathways.

Conclusion: H₂ inhibits ISO-induced cardiac/cardiomyocytes hypertrophy both in vivo and in vitro, and improves the impaired left ventricular function. H₂ exerts its protective effects partially through blocking ROS-sensitive ERK1/2, p38, and JNK signaling pathways.

Sodium Sulfide Attenuates Ischemic-Induced Heart Failure by Enhancing Proteasomal Function in an Nrf2-Dependent Manner

BACKGROUND

Therapeutic strategies aimed at increasing hydrogen sulfide (H2S) levels exert cytoprotective effects in various models of cardiovascular injury. However, the underlying mechanism(s) responsible for this protection remain to be fully elucidated. Nuclear factor E2-related factor 2 (Nrf2) is a cellular target of H2S and facilitator of H2S-mediated cardioprotection after acute myocardial infarction. Here, we tested the hypothesis that Nrf2 mediates the cardioprotective effects of H2S therapy in the setting of heart failure.

METHODS AND RESULTS

Mice (12 weeks of age) deficient in Nrf2 (Nrf2 KO; C57BL/6J background) and wild-type littermates were subjected to ischemic-induced heart failure. Wild-type mice treated with H2S in the form of sodium sulfide (Na2S) displayed enhanced Nrf2 signaling, improved left ventricular function, and less cardiac hypertrophy after the induction of heart failure. In contrast, Na2S therapy failed to provide protection against heart failure in Nrf2 KO mice. Studies aimed at evaluating the underlying cardioprotective mechanisms found that Na2S increased the expression of proteasome subunits, resulting in an increased proteasome activity and a reduction in the accumulation of damaged proteins. In contrast, Na2S therapy failed to enhance the proteasome and failed to attenuate the accumulation of damaged proteins in Nrf2 KO mice. Additionally, Na2S failed to improve cardiac function when the proteasome was inhibited.

CONCLUSIONS

These findings indicate that Na2S therapy enhances proteasomal activity and function during the development of heart failure in an Nrf2-dependent manner and that this enhancement leads to attenuation in cardiac dysfunction.

Characterization of cytoprotective and toxic properties of iron chelator SIH, prochelator BSIH and their degradation products

Free cellular iron catalyzes the formation of toxic hydroxyl radicals and therefore chelation of iron could be a promising therapeutic approach in pathological states associated with oxidative stress. Salicylaldehyde isonicotinoyl hydrazone (SIH) is a strong intracellular iron chelator with well documented potential to protect against oxidative damage both in vitro and in vivo. Due to the short biological half-life of SIH and risk of toxicity due to iron depletion, boronate prochelator BSIH has been designed. BSIH cannot bind iron until it is activated by certain reactive oxygen species to active chelator SIH. The aim of this study was to examine the toxicity and cytoprotective potential of BSIH, SIH, and their decomposition products against hydrogen peroxide-induced injury of H9c2 cardiomyoblast cells. Using HPLC, we observed that salicylaldehyde was the main decomposition products of SIH and BSIH, although a small amount of salicylic acid was also detected. In the case of BSIH, the concentration of formed salicylaldehyde consistently exceeded that of SIH. Isoniazid and salicylic acid were not toxic nor did they provide any antioxidant protective effect in H9c2 cells. In contrast, salicylaldehyde was able to chelate intracellular iron and significantly preserve cellular viability and mitochondrial inner membrane potential induced by hydrogen peroxide. However it was consistently less effective than SIH. The inherent toxicities of salicylaldehyde and SIH were similar. Hence, although SIH - the active chelating agent formed following the BSIH activation - undergoes rapid hydrolysis, its principal decomposition product salicylaldehyde accounts markedly for both cytoprotective and toxic properties.

Hydrogen Sulfide and Cellular Redox Homeostasis

Intracellular redox imbalance is mainly caused by overproduction of reactive oxygen species (ROS) or weakness of the natural antioxidant defense system. It is involved in the pathophysiology of a wide array of human diseases. Hydrogen sulfide (H₂S) is now recognized as the third “gasotransmitters” and proved to exert a wide range of physiological and cytoprotective functions in the biological systems. Among these functions, the role of H₂S in oxidative stress has been one of the main focuses over years. However, the underlying mechanisms for the antioxidant effect of H₂S are still poorly comprehended. This review presents an overview of the current understanding of H₂S specially focusing on the new understanding and mechanisms of the antioxidant effects of H₂S based on recent reports. Both inhibition of ROS generation and stimulation of antioxidants are discussed. H₂S-induced S-sulfhydration of key proteins (e.g., p66Shc and Keap1) is also one of the focuses of this review.

Long-term release of a thiobenzamide from a backbone functionalized poly(lactic acid)

Hydrogen sulfide is emerging as a critically important molecule in medicine, yet there are few methods for the long-term delivery of molecules that degrade to release H2S. In this paper the first long-term release of a thiobenzamide that degrades to release H2S is described. A series of polymers were synthesized by the copolymerization of L-lactide and a lactide functionalized with 4-hydroxythiobenzamide. A new method to attach functional groups to a derivative of L-lactide is described based on the addition of a thiol to an α,β-unsaturated lactide using catalytic I2. This reaction proceeded under mild conditions and did not ring-open the lactone. The copolymers had molecular weights from 8 to 88 kg mol-1 with PDIs below 1.50. Two sets of microparticles were fabricated from a copolymer; the average diameters of the microparticles were 0.53 and 12 μm. The degradation of the smaller microparticles was investigated in buffered water to demonstrate the slow release of thiobenzamide over 4 weeks. Based on the ability to synthesize polymers with different loadings of thiobenzamide and that thiobenzamide is a known precursor to H2S, these particles provide a polymer-based method to deliver H2S over days to weeks.

Urotensin II Protects Cardiomyocytes from Apoptosis Induced by Oxidative Stress through the CSE/H2S Pathway

Plasma urotensin II (UII) has been observed to be raised in patients with acute myocardial infarction; suggesting a possible cardiac protective role for this peptide. However, the molecular mechanism is unclear. Here, we treated cultured cardiomyocytes with H₂O₂ to induce oxidative stress; observed the effect of UII on H₂O₂-induced apoptosis and explored potential mechanisms. UII pretreatment significantly reduced the number of apoptotic cardiomyocytes induced by H₂O₂; and it partly abolished the increase of pro-apoptotic protein Bax and the decrease of anti-apoptotic protein Bcl-2 in cardiomyocytes induced by H₂O₂. SiRNA targeted to the urotensin II receptor (UT) greatly inhibited these effects. Further analysis revealed that UII increased the production of hydrogen sulfide (H₂S) and the level of cystathionine-γ-lyase (CSE) by activating the ERK signaling in H₂O₂-treated-cardiomyocytes. Si-CSE or ERK inhibitor not only greatly inhibited the increase in CSE level or the phosphorylation of ERK induced by UII but also reversed anti-apoptosis of UII in H₂O₂-treated-cadiomyocytes. In conclusion, UII rapidly promoted the phosphorylation of ERK and upregulated CSE level and H₂S production, which in turn activated ERK signaling to protect cardiomyocytes from apoptosis under oxidative stress. These results suggest that increased plasma UII level may protect cardiomyocytes at the early-phase of acute myocardial infarction in patients.

Hydrogen Sulfide Donor GYY4137 Protects against Myocardial Fibrosis

Hydrogen sulfide (H₂S) is a gasotransmitter which regulates multiple cardiovascular functions. However, the precise roles of H₂S in modulating myocardial fibrosis in vivo and cardiac fibroblast proliferation in vitro remain unclear. We investigated the effect of GYY4137, a slow-releasing H₂S donor, on myocardial fibrosis. Spontaneously hypertensive rats (SHR) were administrated with GYY4137 by intraperitoneal injection daily for 4 weeks. GYY4137 decreased systolic blood pressure and inhibited myocardial fibrosis in SHR as evidenced by improved cardiac collagen volume fraction (CVF) in the left ventricle (LV), ratio of perivascular collagen area (PVCA) to lumen area (LA) in perivascular regions, reduced hydroxyproline concentration, collagen I and III mRNA expression, and cross-linked collagen. GYY4137 also inhibited angiotensin II- (Ang II-) induced neonatal rat cardiac fibroblast proliferation, reduced the number of fibroblasts in S phase, decreased collagen I and III mRNA expression and protein synthesis, attenuated oxidative stress, and suppressed α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1) expression as well as Smad2 phosphorylation. These results indicate that GYY4137 improves myocardial fibrosis perhaps by a mechanism involving inhibition of oxidative stress, blockade of the TGF-β1/Smad2 signaling pathway, and decrease in α-SMA expression in cardiac fibroblasts.

Hydrogen Sulfide as a Potential Therapeutic Target in Fibrosis

Hydrogen sulfide (H₂S), produced endogenously by the activation of two major H₂S-generating enzymes (cystathionine β-synthase and cystathionine γ-lyase), plays important regulatory roles in different physiologic and pathologic conditions. The abnormal metabolism of H₂S is associated with fibrosis pathogenesis, causing damage in structure and function of different organs. A number of in vivo and in vitro studies have shown that both endogenous H₂S level and the expressions of H₂S-generating enzymes in plasma and tissues are significantly downregulated during fibrosis. Supplement with exogenous H₂S mitigates the severity of fibrosis in various experimental animal models. The protective role of H₂S in the development of fibrosis is primarily attributed to its antioxidation, antiapoptosis, anti-inflammation, proangiogenesis, and inhibition of fibroblasts activities. Future studies might focus on the potential to intervene fibrosis by targeting the pathway of endogenous H₂S-producing enzymes and H₂S itself.

The Cardioprotective Effects of Hydrogen Sulfide in Heart Diseases: From Molecular Mechanisms to Therapeutic Potential

Hydrogen sulfide (H₂S) is now recognized as a third gaseous mediator along with nitric oxide (NO) and carbon monoxide (CO), though it was originally considered as a malodorous and toxic gas. H₂S is produced endogenously from cysteine by three enzymes in mammalian tissues. An increasing body of evidence suggests the involvement of H₂S in different physiological and pathological processes. Recent studies have shown that H₂S has the potential to protect the heart against myocardial infarction, arrhythmia, hypertrophy, fibrosis, ischemia-reperfusion injury, and heart failure. Some mechanisms, such as antioxidative action, preservation of mitochondrial function, reduction of apoptosis, anti-inflammatory responses, angiogenic actions, regulation of ion channel, and interaction with NO, could be responsible for the cardioprotective effect of H₂S. Although several mechanisms have been identified, there is a need for further research to identify the specific molecular mechanism of cardioprotection in different cardiac diseases. Therefore, insight into the molecular mechanisms underlying H₂S action in the heart may promote the understanding of pathophysiology of cardiac diseases and lead to new therapeutic targets based on modulation of H₂S production.

Overexpression of TFAM or twinkle increases mtDNA copy number and facilitates cardioprotection associated with limited mitochondrial oxidative stress

Background

Mitochondrial DNA (mtDNA) copy number decreases in animal and human heart failure (HF), yet its role in cardiomyocytes remains to be elucidated. Thus, we investigated the cardioprotective function of increased mtDNA copy number resulting from the overexpression of human transcription factor A of mitochondria (TFAM) or Twinkle helicase in volume overload (VO)-induced HF.

Methods and Results

Two strains of transgenic (TG) mice, one overexpressing TFAM and the other overexpressing Twinkle helicase, exhibit an approximately 2-fold equivalent increase in mtDNA copy number in heart. These TG mice display similar attenuations in eccentric hypertrophy and improved cardiac function compared to wild-type (WT) mice without any deterioration of mitochondrial enzymatic activities in response to VO, which was accompanied by a reduction in matrix-metalloproteinase (MMP) activity and reactive oxygen species after 8 weeks of VO. Moreover, acute VO-induced MMP-2 and MMP-9 upregulation was also suppressed at 24 h in both TG mice. In isolated rat cardiomyocytes, mitochondrial reactive oxygen species (mitoROS) upregulated MMP-2 and MMP-9 expression, and human TFAM (hTFAM) overexpression suppressed mitoROS and their upregulation. Additionally, mitoROS were equally suppressed in H9c2 rat cardiomyoblasts that overexpress hTFAM or rat Twinkle, both of which exhibit increased mtDNA copy number. Furthermore, mitoROS and mitochondrial protein oxidation from both TG mice were suppressed compared to WT mice.

Conclusions

The overexpression of TFAM or Twinkle results in increased mtDNA copy number and facilitates cardioprotection associated with limited mitochondrial oxidative stress. Our findings suggest that increasing mtDNA copy number could be a useful therapeutic strategy to target mitoROS in HF.

Role of hydrogen sulfide in brain synaptic remodeling

Synapses are the functional connection between neurons which are necessary for the transfer of electric activity or chemical activity from one cell to another. Synapses are formed by the pre- and postsynaptic membrane which communicates between pre- and postneurons while a neurochemical modulator is operated in this process. H2S has been known as a toxic gas with rotten eggs smell. However, increasing number of researches show that it regulate a variety of physiological and pathological processes in mammals. Hence, H2S is a physiologically important molecule and has been referred to as the third gaseous molecule alongside carbon monoxide and nitric oxide. The previous era has made an exponential development in the physiological and pathological significance of H2S. Specifically, in the central nervous system, H2S facilitates long-term potentiation and regulates intracellular calcium concentration in brain cells. We as well as others have also shown that H2S has antioxidant, antiapoptotic, and anti-inflammatory properties against various neurodegenerative disorders such as stroke, Alzheimer's disease, and vascular dementia. In this chapter, we highlight the current knowledge of H2S and its neuroprotective effects with a special emphasis on synaptic remodeling.

Hydrogen sulfide attenuates high fat diet-induced cardiac dysfunction via the suppression of endoplasmic reticulum stress

Diabetic cardiomyopathy is a significant contributor to the morbidity and mortality associated with diabetes and metabolic syndrome. However, the underlying molecular mechanisms that lead to its development have not been fully elucidated. Hydrogen sulfide (H2S) is an endogenously produced signaling molecule that is critical for the regulation of cardiovascular homeostasis. Recently, therapeutic strategies aimed at increasing its levels have proven cardioprotective in models of acute myocardial ischemia-reperfusion injury and heart failure. The precise role of H2S in the pathogenesis of diabetic cardiomyopathy has not yet been established. Therefore, the goal of the present study was to evaluate circulating and cardiac H2S levels in a murine model of high fat diet (HFD)-induced cardiomyopathy. Diabetic cardiomyopathy was produced by feeding mice HFD (60% fat) chow for 24 weeks. HFD feeding reduced both circulating and cardiac H2S and induced hallmark features of type-2 diabetes. We also observed marked cardiac dysfunction, evidence of cardiac enlargement, cardiac hypertrophy, and fibrosis. H2S therapy (SG-1002, an orally active H2S donor) restored sulfide levels, improved some of the metabolic perturbations stemming from HFD feeding, and attenuated HFD-induced cardiac dysfunction. Additional analysis revealed that H2S therapy restored adiponectin levels and suppressed cardiac ER stress stemming from HFD feeding. These results suggest that diminished circulating and cardiac H2S levels play a role in the pathophysiology of HFD-induced cardiomyopathy. Additionally, these results suggest that H2S therapy may be of clinical importance in the treatment of cardiovascular complications stemming from diabetes.

Hydrogen sulfide provides cardioprotection against myocardial/ischemia reperfusion injury in the diabetic state through the activation of the RISK pathway

Background

Coronary artery disease remains the principal cause of death in patients with diabetes mellitus. Diabetic mice display exacerbated injury following myocardial ischemia-reperfusion (MI/R) and are resistant to most therapeutic interventions. We have reported that sodium sulfide (Na₂S) therapy confers cardioprotection during MI/R in non-diabetic mice. Here we tested the hypothesis that Na₂S therapy would limit the extent of myocardial injury following MI/R when administered at the time of reperfusion.

Methods and results

Diabetic mice (db/db, 12 weeks of age) were subjected to transient myocardial ischemia for a period of 30 minutes followed by reperfusion up to 24 hours. Na₂S (0.05 to 1 mg/kg) or saline (vehicle) was administered into the left ventricular lumen at the time of reperfusion. Na₂S therapy significantly decreased myocardial injury in the db/db diabetic mouse, as evidenced by a reduction in infarct size and circulating troponin-I levels. The reduction in myocardial injury was also associated with a reduction in oxidative stress and a decrease in cleaved caspase-3 expression. In an effort to evaluate the signaling mechanism responsible for the observed cardioprotection, additional groups of mice were sacrificed during early reperfusion. Hearts were excised and processed for Western blot analysis. These studies revealed that Na₂S therapy activated the Erk1/2 arm of the Reperfusion Injury Salvage Kinase (RISK) pathway.

Conclusion

These findings provide important information that myocardial Erk1/2 activation by Na₂S therapy following MI/R sets into motion events, which ultimately lead to cardioprotection in the setting of diabetes.

Comparison of various iron chelators and prochelators as protective agents against cardiomyocyte oxidative injury

Oxidative stress is a common denominator of numerous cardiovascular disorders. Free cellular iron catalyzes the formation of highly toxic hydroxyl radicals, and iron chelation may thus be an effective therapeutic approach. However, using classical iron chelators in diseases without iron overload poses risks that necessitate more advanced approaches, such as prochelators that are activated to chelate iron only under disease-specific oxidative stress conditions. In this study, three cell-membrane-permeable iron chelators (clinically used deferasirox and experimental SIH and HAPI) and five boronate-masked prochelator analogs were evaluated for their ability to protect cardiac cells against oxidative injury induced by hydrogen peroxide. Whereas the deferasirox-derived agents TIP and TRA-IMM displayed negligible protection and even considerable toxicity, the aroylhydrazone prochelators BHAPI and BSIH-PD provided significant cytoprotection and displayed lower toxicity after prolonged cellular exposure compared to their parent chelators HAPI and SIH, respectively. Overall, the most favorable properties in terms of protective efficiency and low inherent cytotoxicity were observed with the aroylhydrazone prochelator BSIH. BSIH efficiently protected both H9c2 rat cardiomyoblast-derived cells and isolated primary rat cardiomyocytes against hydrogen peroxide-induced mitochondrial and lysosomal dysregulation and cell death. At the same time, BSIH was nontoxic at concentrations up to its solubility limit (600 μM) and in 72-h incubation. Hence, BSIH merits further investigation for prevention and/or treatment of cardiovascular disorders associated with a known (or presumed) component of oxidative stress.

Estrogens increase cystathionine-γ-lyase expression and decrease inflammation and oxidative stress in the myocardium of ovariectomized rats

OBJECTIVE

Hydrogen sulfide (H2S), generated in the myocardium predominantly via cystathionine-γ-lyase (CSE), is cardioprotective. The objectives of the present study were to investigate the effects of estrogens on CSE expression and H2S generation in the myocardium and to examine whether serum 17β-estradiol (E2) level is associated with CSE activity and H2S generation and whether H2S or E2 level is associated with proinflammatory cytokines and oxidative stress status.

METHODS

Ovariectomized Sprague-Dawley rats received subcutaneous E2 (30 μg/kg/d) or vehicle for 12 weeks. At the end of the 12-week treatment, CSE expression, H2S generation, reduced glutathione/oxidized glutathione (GSH/GSSG) ratio, total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, catalase (CAT) activity, interleukin (IL)-6 concentration, and tumor necrosis factor-α (TNF-α) concentration in the left ventricle were determined.

RESULTS

E2 increased CSE expression and H2S generation in the myocardium of ovariectomized rats. H2S production rate and serum E2 were positively correlated. E2 increased GSH/GSSG ratio, T-AOC, CAT, and SOD activity but decreased IL-6 and TNF-α levels. Serum E2 level was positively correlated with GSH/GSSG ratio, T-AOC, CAT, and SOD activity, and inversely correlated with IL-6 and TNF-α levels. H2S generation rate was positively correlated with T-AOC and GSH/GSSG ratio, and inversely correlated with IL-6 and TNF-α levels.

CONCLUSIONS

E2 increases CSE expression and endogenous H2S generation in the myocardium. The effects of E2 are associated with decreased oxidative stress and inflammatory status. Our data suggest that estrogens might exert cardioprotective effects through up-regulation of CSE expression and H2S generation.

Cardioprotection of H2S by downregulating iNOS and upregulating HO-1 expression in mice with CVB3-induced myocarditis

AIMS

To explore the effects and potential mechanisms of hydrogen sulfide (H2S) in CVB3-induced mice with myocarditis.

MAIN METHODS

A total of 75 six-week-old inbred male Balb/c mice were divided randomly into four groups (N, C, P and S). Group N was the negative control. The others were inoculated intraperitoneally (i.p.) with CVB3. Subsequently, groups P and S were injected i.p. once a day with DL-Proparglygylcine (PAG) and NaHS respectively. Group C was the positive control. Inducible nitric oxide synthase (iNOS) and heme oxygenase-1(HO-1) expression on cardiac tissues were evaluated by histopathological examination, immunohistochemistry, RT-PCR and Western blot.

KEY FINDINGS

The heart-weight to body-weight (HW/BW) ratio, the histologic scores and the iNOS mRNA and protein expression levels were higher, and the HO-1 mRNA and protein expression levels were lower in mice treated with PAG than those mice solely inoculated with CVB3. Mice in group S had a significant decreased in the HW/BW ratio, the histologic scores and the iNOS mRNA and protein expression levels, and had a significant increased in the HO-1 mRNA and protein expression levels compared to the mice in group C. H2S can attenuate inflammatory cell infiltration, alleviate cardiac edema, and limit myocardial lesions.

SIGNIFICANCE

Our data support that H2S can inhibit iNOS overexpression and induce HO-1 expression, both of which contribute to the cardioprotection of H2S in CVB3-induced mice myocarditis.

Hydrogen sulfide suppresses the expression of MMP-8, MMP-13, and TIMP-1 in left ventricles of rats with cardiac volume overload

AIM

To study the effects of hydrogen sulfide (H2S) on the left ventricular expression of MMP-8, MMP-13, and TIMP-1 in a rat model of congenital heart disease.

METHODS

Male SD rats underwent abdominal aorta-inferior vena cava shunt operation. H2S donor NaHS (56 μmol·kg(-1)·d(-1), ip) was injected from the next day for 8 weeks. At 8 weeks, the hemodynamic parameters, including the left ventricular systolic pressure (LVSP), the left ventricular peak rate of contraction and relaxation (LV ± dp/dtmax) and the left ventricular end diastolic pressure (LVEDP) were measured. The left ventricular tissues were dissected out, and hydroxyproline and collagen I contents were detected with ELISA. The expression of MMP-8, MMP-13, and a tissue inhibitor of metalloproteinase-1 (TIMP-1) in the tissues was measured using real-time PCR, Western blotting, and immunohistochemistry, respectively.

RESULTS

The shunt operation markedly reduced LVSP and LV ± dp/dtmax, increased LVEDP, hydroxyproline and collagen I contents, as well as the mRNA and protein levels of MMP-8, MMP-13, and TIMP-1 in the left ventricles. Chronic treatment of the shunt operation rats with NaHS effectively prevented the abnormalities in the hemodynamic parameters, hydroxyproline and collagen I contents, and the mRNA and protein levels of MMP-13 and TIMP-1 in the left ventricles. NaHS also prevented the increase of MMP-8 protein expression, but did not affect the increase of mRNA level of MMP-8 in the shunt operation rats.

CONCLUSION

H2S suppresses protein and mRNA expression of MMP-8, MMP-13, and TIMP-1 in rats with cardiac volume overload, which may be contributed to the amelioration of ventricular structural remodeling and cardiac function.