Hydrogen Sulfide as a Potential Therapeutic Target in Fibrosis

Recent advances in the role of gasotransmitters in necroptosis

Necroptosis is a finely regulated programmed cell death process involving complex molecular mechanisms and signal transduction networks. Among them, receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein are the key molecules regulating this process. In recent years, gasotransmitters such as nitric oxide, carbon monoxide and hydrogen sulfide have been suggested to play a regulatory role in necroptosis. This paper reviews the evidence that these gasotransmitters are involved in the regulation of necroptosis by influencing the production of reactive oxygen species, regulating the modification of S subunits of RIPK1 and RIPK3, regulating inflammatory mediators, and signal transduction. In addition, this review explores the potential therapeutic applications of these gasotransmitters in pathological conditions such as cardiovascular disease and ischemia-reperfusion injury. Although some studies have revealed the important role of gasotransmitters in necroptosis, the specific mechanism of action is still not fully understood. Future research is needed to further elucidate the molecular mechanisms of gasotransmitters in precisely regulating necroptosis, which will help develop new therapeutic strategies to prevent and treat related diseases.

H2S Donor SPRC Ameliorates Cardiac Aging by Suppression of JMJD3, a Histone Demethylase

Aims: S-propargyl-cysteine (SPRC) is an endogenous hydrogen sulfide (H2S) donor obtained by modifying the structure of S-allyl cysteine in garlic. This study aims to investigate the effect of SPRC on mitigating cardiac aging and the involvement of jumonji domain-containing protein 3 (JMJD3), a histone demethylase, which represents the primary risk factor in major aging related diseases, in this process, elucidating the preliminary mechanism through which SPRC regulation of JMJD3 occurs. Results: In vitro, SPRC mitigated the elevated levels of reactive oxygen species, senescence-associated β-galactosidase, p53, and p21, reversing the decline in mitochondrial membrane potential, which represented a reduction in cellular senescence. In vivo, SPRC improved Dox-induced cardiac pathological structure and function. Overexpression of JMJD3 accelerated cardiomyocytes and cardiac senescence, whereas its knockdown in vitro reduced the senescence phenotype. The potential binding site of the upstream transcription factor of JMJD3, sheared X box binding protein 1 (XBP1s), was determined using online software. SPRC promoted the expression of cystathionine γ-lyase (CSE), which subsequently inhibited the IRE1α/XBP1s signaling pathway and decreased JMJD3 expression. Innovations: This study is the first to establish JMJD3 as a crucial regulator of cardiac aging. SPRC can alleviate cardiac aging by upregulating CSE and inhibiting endoplasmic reticulum stress pathways, which in turn suppress JMJD3 expression. Conclusions: JMJD3 plays an essential role in cardiac aging regulation, whereas SPRC can suppress the expression of JMJD3 by upregulating CSE, thus delaying cardiac aging, which suggests that SPRC may serve as an aging protective agent, and pharmacological targeting of JMJD3 may also be a promising therapeutic approach in age-related heart diseases. Antioxid. Redox Signal. 42, 301-320.

Inhalable Carbonyl Sulfide Donor-Hybridized Selective Phosphodiesterase 10A Inhibitor for Treating Idiopathic Pulmonary Fibrosis by Inhibiting Tumor Growth Factor-β Signaling and Activating the cAMP/Protein Kinase A/cAMP Response Element-Binding Protein (CREB)/p53 Axis

Idiopathic pulmonary fibrosis (IPF) is a debilitating, incurable, and life-threatening disease that lacks effective therapy. The overexpression of phosphodiesterase 10A (PDE10A) plays a vital role in pulmonary fibrosis (PF). However, the impact of selective PDE10A inhibitors on the tumor growth factor-β (TGF-β)/small mother against decapentaplegic (Smad) signaling pathway remains unclear. Herein, we have exploited a novel carbonyl sulfide (COS)/hydrogen sulfide (H2S)-donor hybrid PDE10A inhibitor called COS-2080 with a well-defined mechanism of H2S-releasing action. It exhibited highly potent inhibitory activity against PDE10A and excellent PDE subfamily selectivity. Moreover, COS-2080 demonstrated significant antifibrotic effects by inhibiting cell proliferation and mitigating fibroblast-to-myofibroblast transition (FMT). A dry powder inhalation formulation called COS-2080-DPI has been developed using the ultrasonic spray freeze drying (USFD) technique, demonstrating significant antifibrotic efficacy in mice with bleomycin-induced PF at a dosage approximately 600 times lower than pirfenidone. This remarkable antifibrotic efficacy of COS-2080 on TGF-β1-induced FMT could be primarily attributed to its inhibition of the Smad2/Smad3 phosphorylation. Moreover, COS-2080 effectively attenuated fibrosis in MRC-5 cells by activating the cAMP/protein kinase A (PKA)/CREB pathway and potentially increasing levels of p53 protein. Our findings suggest that effective inhibition of PDE10A potentially confers a protective effect on FMT in PF by impeding TGF-β signaling and activating the cAMP/PKA/CREB/p53 axis.

Hydrogen sulfide donor NaHS inhibits formaldehyde-induced epithelial-mesenchymal transition in human lung epithelial cells via activating TGF-β1/Smad2/3 and MAPKs signaling pathways

Formaldehyde (FA) long term exposure leads to abnormal pulmonary function and small airway obstruction of the patients. Hydrogen sulfide (H2S) is one of the recognized gaseous transmitters involved in a wide range of cellular functions. It is unknown the involvement of H2S in FA-induced lung injury. The purpose of this study is to investigate the therapeutic potential and mechanism of H2S on FA-induced epithelial-mesenchymal transition (EMT) of human lung epithelial cells. The cell viability of Beas2B and A549 cells after FA treatment were assessed using MTT assay. The endogenous H2S was visualized by fluorescence microscopy using of the 7-azido-4-methylcoumarin (AzMC). Cell morphology was observed under phase contrast microscope. The mRNAs and proteins level were evaluated by reverse transcription-polymerase chain reaction and western blotting assays. FA treatment downregulated the endogenous H2S levels and the mRNAs and proteins level of H2S synthesizing enzymes, such as cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST) in Beas2B and A549 cells. FA treatment changed the cell morphology of Beas2B cells from cuboid to a spindle-shape, while declined the protein level of E-cadherin and increased the protein level of Vimentin. Moreover, FA treatment increased the proteins level of transforming growth factor-β1 (TGF-β1), phosphorylated-Smad2 (p-Smad2), phosphorylated-Smad3 (p-Smad3), phosphorylated-extracellular signal-regulated kinase (p-ERK), phosphorylated-c-Jun N-terminal kinase (p-JNK), and phosphorylated-P38 (p-P38). Furthermore, the inhibitors of TGF-β receptor type 1 (TGFβRI) and mitogen-activated protein kinases (MAPKs) signaling pathways reversed FA-induced decrease in E-cadherin expression and increase in Vimentin expression in Beas2B cells. Sodium hydrogen sulfide (NaHS) increased the level of H2S, while reversed FA-induced the low expression of E-cadherin and the high expression of Vimentin, TGF-β1, p-Smad2, p-Smad3, p-ERK, p-JNK, and p-P38. These findings indicates FA treatment downregulating the endogenous H2S in human lung epithelial cells. NaHS may inhibit FA-induced EMT in human lung epithelial cells via modulating TGF-β1/Smad2/3 and MAPKs signaling pathways. Therefore, we demonstrated that supplementation of exogenous H2S may inhibit FA-induced lung injury.

Hydrogen sulfide inhibits gene expression associated with aortic valve degeneration by inducing NRF2-related pro-autophagy effect in human aortic valve interstitial cells

Aortic valve stenosis (AS) is the most common valvular heart disease but there are currently no effective medical treatments that can delay disease progression due to a lack of knowledge of the precise pathophysiology. The expression of sulfide: quinone oxidoreductase (SQOR) and nuclear factor erythroid 2-related factor 2 (NRF2) was decreased in the aortic valve of AS patients. However, the role of SQOR and NRF2 in the pathophysiology of AS has not been found. We investigated the effects of hydrogen sulfide (H2S)-releasing compounds on diseased aortic valve interstitial cells (AVICs) to explain the cellular mechanism of SQOR and elucidate the medical value of H2S for AS treatment. Sodium hydrosulfide (NaHS) treatment increased the expression of SQOR and NRF2 gene and consequently induced the NRF2 target genes, such as NAD(P)H quinone dehydrogenase 1 and cystathionine γ-lyase. In addition, NaHS dose-dependently decreased the expression level of fibrosis and inflammation-related genes (MMP9, TNF-α, IL6) and calcification-related genes (ALP, osteocalcin, RUNX2, COL1A1) in human AVICs. Furthermore, NaHS activated the AMPK-mTOR pathway and inhibited the PI3K-AKT pathway, resulting in a pro-autophagy effect in human AVICs. An NRF2 inhibitor, brusatol, attenuated NaHS-induced AMPK activation and decreased the autophagy markers Beclin-1 and LC3AB, suggesting that the mechanism of action of H2S is related to NRF2. In conclusion, H2S decreased gene expression levels related to aortic valve degeneration and activated AMPK-mTOR-mediated pro-autophagy function associated with NRF2 in human AVICs. Therefore, H2S could be a potential therapeutic target for the development of AS treatment.

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.

Elucidating the Molecular Pathways and Therapeutic Interventions of Gaseous Mediators in the Context of Fibrosis

Fibrosis, a pathological alteration of the repair response, involves continuous organ damage, scar formation, and eventual functional failure in various chronic inflammatory disorders. Unfortunately, clinical practice offers limited treatment strategies, leading to high mortality rates in chronic diseases. As part of investigations into gaseous mediators, or gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), numerous studies have confirmed their beneficial roles in attenuating fibrosis. Their therapeutic mechanisms, which involve inhibiting oxidative stress, inflammation, apoptosis, and proliferation, have been increasingly elucidated. Additionally, novel gasotransmitters like hydrogen (H2) and sulfur dioxide (SO2) have emerged as promising options for fibrosis treatment. In this review, we primarily demonstrate and summarize the protective and therapeutic effects of gaseous mediators in the process of fibrosis, with a focus on elucidating the underlying molecular mechanisms involved in combating fibrosis.

Evaluating the Effect of Hydrogen Sulfide in the Idiopathic Pulmonary Fibrosis Model with a Fluorescent Probe

Hydrogen sulfide (H₂S), a gaseous signaling molecule, is involved in a wide range of physiological and pathological processes. H₂S has been proven to play a beneficial role in lung diseases, and the relationship between perturbations in endogenous H₂S synthesis and degree with idiopathic pulmonary fibrosis (IPF) has attacted increasing attention. However, the changes in endogenous lung H₂S levels in the pathological progression of chronic pulmonary diseases remain unclear. To this end, we synthesized a fluorescent probe (Bcy-HS) for the selective imaging of H₂S in living cells and mice. This probe was mainly used for in situ in vivo and cellular imaging as well as a systematic assessment of intrapulmonary H₂S levels at different stages of IPF. In addition, we also discussed the potential of H₂S supplementation in the treatment of pulmonary fibrotic diseases. Our results confirmed the key role of H₂S in pulmonary fibrosis. In cellular and mice models of pulmonary fibrosis, intracellular H₂S levels are reduced. However, the severity of oxidative damage and pulmonary fibrosis decreased after NaSH (H₂S donor). Therefore, we concluded that increasing the H₂S content in vivo may be a novel strategy for IPF treatment.

H2S Prodrug, SG-1002, Protects against Myocardial Oxidative Damage and Hypertrophy In Vitro via Induction of Cystathionine β-Synthase and Antioxidant Proteins

Endogenously produced hydrogen sulfide (H₂S) is critical for cardiovascular homeostasis. Therapeutic strategies aimed at increasing H₂S levels have proven cardioprotective in models of acute myocardial infarction (MI) and heart failure (HF). The present study was undertaken to investigate the effects of a novel H₂S prodrug, SG-1002, on stress induced hypertrophic signaling in murine HL-1 cardiac muscle cells. Treatment of HL-1 cells with SG-1002 under serum starvation without or with H₂O₂ increased the levels of H₂S, H₂S producing enzyme, and cystathionine β-synthase (CBS), as well as antioxidant protein levels, such as super oxide dismutase1 (SOD1) and catalase, and additionally decreased oxidative stress. SG-1002 also decreased the expression of hypertrophic/HF protein markers such as atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), galectin-3, TIMP1, collagen type III, and TGF-β1 in stressed HL-1 cells. Treatment with SG-1002 caused a significant induction of cell viability and a marked reduction of cellular cytotoxicity in HL-1 cells under serum starvation incubated without or with H₂O₂. Experimental results of this study suggest that SG-1002 attenuates myocardial cellular oxidative damage and/or hypertrophic signaling via increasing H₂S levels or H₂S producing enzymes, CBS, and antioxidant proteins.

The roles of hydrogen sulfide in renal physiology and disease states

Hydrogen sulfide (H₂S), an endogenous gaseous signaling transmitter, has gained recognition for its physiological effects. In this review, we aim to summarize and discuss existing studies about the roles of H₂S in renal functions and renal disease as well as the underlying mechanisms. H₂S is mainly produced by four pathways, and the kidneys are major H₂S–producing organs. Previous studies have shown that H₂S can impact multiple signaling pathways via sulfhydration. In renal physiology, H₂S promotes kidney excretion, regulates renin release and increases ATP production as a sensor for oxygen. H₂S is also involved in the development of kidney disease. H₂S has been implicated in renal ischemia/reperfusion and cisplatin–and sepsis–induced kidney disease. In chronic kidney diseases, especially diabetic nephropathy, hypertensive nephropathy and obstructive kidney disease, H₂S attenuates disease progression by regulating oxidative stress, inflammation and the renin–angiotensin–aldosterone system. Despite accumulating evidence from experimental studies suggesting the potential roles of H₂S donors in the treatment of kidney disease, these results need further clinical translation. Therefore, expanding the understanding of H₂S can not only promote our further understanding of renal physiology but also lay a foundation for transforming H₂S into a target for specific kidney diseases.

Function of gaseous hydrogen sulfide in liver fibrosis

Over the past few years, hydrogen sulfide (H2S) has been shown to exert several biological functions in mammalian. The endogenous production of H2S is mainly mediated by cystathione β-synthase, cystathione γ-lyase and 3-mercaptopyruvate sulfur transferase. These enzymes are broadly expressed in liver tissue and regulates liver function by working on a variety of molecular targets. As an important regulator of liver function, H2S is critically involved in the pathogenesis of various liver diseases, such as non-alcoholic steatohepatitis and liver cancer. Targeting H2S-generating enzymes may be a therapeutic strategy for controlling liver diseases. This review described the function of H2S in liver disease and summarized recent characterized role of H2S in several cellular process of the liver. [BMB Reports 2022; 55(10): 481-487].

Protective effect of hydrogen sulfide against stress-induced lung injury: involvement of Nrf2, NFκB/iNOS, and HIF-1α signaling pathways

Stress is a common phenomenon that is attracting increasing attention. Hydrogen sulfide (H2S) is a gasotransmitter that plays an important role in many physiological and pathological events. Our study aimed to estimate the effect and the underlying mechanisms of the H2S donor, sodium hydrosulfide (NaHS), against immobilization stress (IS)-induced lung injury. Forty adult male rats were classified into control group, NaHS group, and IS groups with and without NaHS treatment. Serum was obtained to determine corticosterone (CORT), total antioxidant capacity (TAC), tumor necrosis factor-α (TNF-α), and interleukin-10 (IL-10) levels. Lung H2S, nitric oxide (NO), inducible nitric oxide synthase (iNOS), and malondialdehyde (MDA) levels were measured. Lung expressions of H2S synthesizing enzymes and Western blot analysis of nuclear factor erythroid 2-related factor 2 (Nrf2) and hypoxia-inducible factor 1 alpha (HIF 1α) were estimated. Histopathological changes and immunohistochemical assessment of nuclear factor kappa B (NF-κB) and caspase-3 were also done. Pretreatment with NaHS led to marked histological protection from lung damage seen in IS rats. Furthermore, pretreatment with NaHS before IS protected lung H2S levels and expressions of H2S-synthesizing enzymes. Similarly, the levels of CORT, TNF-α, IL-10, MDA, TAC, NO, iNOS, HIF-1 α, and nuclear Nrf2 and expressions of NF-kB and caspase 3 were all maintained at near control levels in contrast to that in the IS rats. In conclusion, NaHS is protective against stress-induced lung injury due to its antioxidant, anti-inflammatory, anti-fibrotic, and antiapoptotic effects. Thus, NaHS can be used to minimize stress complications on lung.

Hydrogen sulfide, a gaseous signaling molecule, elongates primary cilia on kidney tubular epithelial cells by activating extracellular signal-regulated kinase

Primary cilia on kidney tubular cells play crucial roles in maintaining structure and physiological function. Emerging evidence indicates that the absence of primary cilia, and their length, are associated with kidney diseases. The length of primary cilia in kidney tubular epithelial cells depends, at least in part, on oxidative stress and extracellular signal-regulated kinase 1/2 (ERK) activation. Hydrogen sulfide (H₂S) is involved in antioxidant systems and the ERK signaling pathway. Therefore, in this study, we investigated the role of H₂S in primary cilia elongation and the downstream pathway. In cultured Madin-Darby Canine Kidney cells, the length of primary cilia gradually increased up to 4 days after the cells were grown to confluent monolayers. In addition, the expression of H₂S-producing enzyme increased concomitantly with primary cilia length. Treatment with NaHS, an exogenous H₂S donor, accelerated the elongation of primary cilia whereas DL-propargylglycine (a cystathionine γ-lyase inhibitor) and hydroxylamine (a cystathionine-β-synthase inhibitor) delayed their elongation. NaHS treatment increased ERK activation and Sec10 and Arl13b protein expression, both of which are involved in cilia formation and elongation. Treatment with U0126, an ERK inhibitor, delayed elongation of primary cilia and blocked the effect of NaHS-mediated primary cilia elongation and Sec10 and Arl13b upregulation. Finally, we also found that H₂S accelerated primary cilia elongation after ischemic kidney injury. These results indicate that H₂S lengthens primary cilia through ERK activation and a consequent increase in Sec10 and Arl13b expression, suggesting that H₂S and its downstream targets could be novel molecular targets for regulating primary cilia.

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.

Gasotransmitters: Potential Therapeutic Molecules of Fibrotic Diseases

Fibrosis is defined as the pathological progress of excessive extracellular matrix (ECM), such as collagen, fibronectin, and elastin deposition, as the regenerative capacity of cells cannot satisfy the dynamic repair of chronic damage. The well-known features of tissue fibrosis are characterized as the presence of excessive activated and proliferated fibroblasts and the differentiation of fibroblasts into myofibroblasts, and epithelial cells undergo the epithelial-mesenchymal transition (EMT) to expand the number of fibroblasts and myofibroblasts thereby driving fibrogenesis. In terms of mechanism, during the process of fibrosis, the activations of the TGF-β signaling pathway, oxidative stress, cellular senescence, and inflammatory response play crucial roles in the activation and proliferation of fibroblasts to generate ECM. The deaths due to severe fibrosis account for almost half of the total deaths from various diseases, and few treatment strategies are available for the prevention of fibrosis as yet. Recently, numerous studies demonstrated that three well-defined bioactive gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), generally exhibited anti-inflammatory, antioxidative, antiapoptotic, and antiproliferative properties. Besides these effects, a number of studies have reported that low-dose exogenous and endogenous gasotransmitters can delay and interfere with the occurrence and development of fibrotic diseases, including myocardial fibrosis, idiopathic pulmonary fibrosis, liver fibrosis, renal fibrosis, diabetic diaphragm fibrosis, and peritoneal fibrosis. Furthermore, in animal and clinical experiments, the inhalation of low-dose exogenous gas and intraperitoneal injection of gaseous donors, such as SNAP, CINOD, CORM, SAC, and NaHS, showed a significant therapeutic effect on the inhibition of fibrosis through modulating the TGF-β signaling pathway, attenuating oxidative stress and inflammatory response, and delaying the cellular senescence, while promoting the process of autophagy. In this review, we first demonstrate and summarize the therapeutic effects of gasotransmitters on diverse fibrotic diseases and highlight their molecular mechanisms in the process and development of fibrosis.

Cellular senescence and the senescence-associated secretory phenotype: Potential therapeutic targets for renal fibrosis

Renal fibrosis plays a crucial role in the progression of chronic kidney disease and end-stage renal disease. However, because the aetiology of this pathological process is complex and remains unclear, there is still no effective treatment. Cellular senescence and the senescence-associated secretory phenotype (SASP) have been reported to lead to renal fibrosis. This review first discusses the relationships among cellular senescence, the SASP and renal fibrosis. Then, the key role of the SASP in irreversible renal fibrosis, including fibroblast activation and abnormal extracellular matrix accumulation, is discussed, with the results of studies having indicated that inhibiting cellular senescence and the SASP might be a potential preventive and therapeutic strategy for renal fibrosis. Finally, we summarize promising therapeutic strategies revealed by existing research on senescent cells and the SASP, including emerging interventions targeting the SASP, caloric restriction and mimetics, and novel regeneration therapies with stem cells.

The Role of Hydrogen Sulfide in Respiratory Diseases

Respiratory diseases are leading causes of death and disability around the globe, with a diverse range of health problems. Treatment of respiratory diseases and infections has been verified to be thought-provoking because of the increasing incidence and mortality rate. Hydrogen sulfide (H₂S) is one of the recognized gaseous transmitters involved in an extensive range of cellular functions, and physiological and pathological processes in a variety of diseases, including respiratory diseases. Recently, the therapeutic potential of H₂S for respiratory diseases has been widely investigated. H₂S plays a vital therapeutic role in obstructive respiratory disease, pulmonary fibrosis, emphysema, pancreatic inflammatory/respiratory lung injury, pulmonary inflammation, bronchial asthma and bronchiectasis. Although the therapeutic role of H₂S has been extensively studied in various respiratory diseases, a concrete literature review will have an extraordinary impact on future therapeutics. This review provides a comprehensive overview of the effective role of H₂S in respiratory diseases. Besides, we also summarized H₂S production in the lung and its metabolism processes in respiratory diseases.

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

Role of hydrogen sulfide in cardiovascular ageing

Cardiovascular diseases are the main cause of morbidity and mortality in the Western society and ageing is a relevant non-modifiable risk factor. Morphological and functional alterations at endothelial level represent first events of ageing, inevitably followed by vascular dysfunction and consequent atherosclerosis that deeply influences cardiovascular health. Indeed, myocardial hypertrophy and fibrosis typically occur and contribute to compromise overall cardiac output. As regards the intracellular molecular mechanisms involved in the cardiovascular ageing, an intricate network is emerging, revealing a role for many mediators, including SIRT1/AMPK/PCG1α pathway, anti-oxidants factors (i.e. Nrf-2 and FOXOs) and pro-inflammatory cytokines. Thus, the search for pharmacological and non-pharmacological strategies that can promote a "healthy ageing", in order to slow down age-related machinery, are currently an exciting challenge for the biomedical research. Interestingly, hydrogen sulfide (H₂S) has been recently recognized as a new player capable to influence intracellular machinery involved in ageing and then it is view as a potential target for preventing cardiovascular diseases. Therefore, this review is focused on the role of H₂S in cardiovascular ageing, and on the evidence of the relationship between progressive decline in endogenous H₂S levels and the onset of various cardiovascular age-related diseases.

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.

Implications of hydrogen sulfide in liver pathophysiology: Mechanistic insights and therapeutic potential

Background

Over the last several decades, hydrogen sulfide (H₂S) has been found to exert multiple physiological functions in mammal systems. The endogenous production of H₂S is primarily mediated by cystathione β-synthase (CBS), cystathione γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST). These enzymes are widely expressed in the liver tissues and regulate hepatic functions by acting on various molecular targets.

Aim of Review

In the present review, we will highlight the recent advancements in the cellular events triggered by H₂S under liver diseases. The therapeutic effects of H₂S donors on hepatic diseases will also be discussed.

Key Scientific Concepts of Review

As a critical regulator of liver functions, H₂S is critically involved in the etiology of various liver disorders, such as nonalcoholic steatohepatitis (NASH), hepatic fibrosis, hepatic ischemia/reperfusion (IR) injury, and liver cancer. Targeting H₂S-producing enzymes may be a promising strategy for managing hepatic disorders.

Organic Isothiocyanates as Hydrogen Sulfide Donors

Significance: Hydrogen sulfide (H₂S), the "new entry" in the series of endogenous gasotransmitters, plays a fundamental role in regulating the biological functions of various organs and systems. Consequently, the lack of adequate levels of H₂S may represent the etiopathogenetic factor of multiple pathological alterations. In these diseases, the use of H₂S donors represents a precious and innovative opportunity. Recent Advances: Natural isothiocyanates (ITCs), sulfur compounds typical of some botanical species, have long been investigated because of their intriguing pharmacological profile. Recently, the ITC moiety has been proposed as a new H₂S-donor chemotype (with a l-cysteine-mediated reaction). Based on this recent discovery, we can clearly observe that almost all the effects of natural ITCs can be explained by the H₂S release. Consistently, the ITC function was also used as an original H₂S-releasing moiety for the design of synthetic H₂S donors and original "pharmacological hybrids." Very recently, the chemical mechanism of H₂S release, resulting from the reaction between l-cysteine and some ITCs, has been elucidated. Critical Issues: Available literature gives convincing demonstration that H₂S is the real player in ITC pharmacology. Further, countless studies have been carried out on natural ITCs, but this versatile moiety has been used only rarely for the design of synthetic H₂S donors with optimal drug-like properties. Future Directions: The development of more ITC-based synthetic H₂S donors with optimal drug-like properties and selectivity toward specific tissues/pathologies seem to represent a stimulating and indispensable prospect of future experimental activities.

Hydrogen Sulfide: Recent Progression and Perspectives for the Treatment of Diabetic Nephropathy

Diabetic kidney disease develops in approximately 40% of diabetic patients and is a major cause of chronic kidney diseases (CKD) and end stage kidney disease (ESKD) worldwide. Hydrogen sulfide (H₂S), the third gasotransmitter after nitric oxide (NO) and carbon monoxide (CO), is synthesized in nearly all organs, including the kidney. Though studies on H₂S regulation of renal physiology and pathophysiology are still in its infancy, emerging evidence shows that H₂S production by renal cells is reduced under disease states and H₂S donors ameliorate kidney injury. Specifically, aberrant H₂S level is implicated in various renal pathological conditions including diabetic nephropathy. This review presents the roles of H₂S in diabetic renal disease and the underlying mechanisms for the protective effects of H₂S against diabetic renal damage. H₂S may serve as fundamental strategies to treat diabetic kidney disease. These H₂S treatment modalities include precursors for H₂S synthesis, H₂S donors, and natural plant-derived compounds. Despite accumulating evidence from experimental studies suggests the potential role of the H₂S signaling pathway in the treatment of diabetic nephropathy, these results need further clinical translation. Expanding understanding of H₂S in the kidney may be vital to translate H₂S to be a novel therapy for diabetic renal disease.

Exogenous Hydrogen Sulfide Supplement Attenuates Isoproterenol-Induced Myocardial Hypertrophy in a Sirtuin 3-Dependent Manner

Hydrogen sulfide (H₂S) is a gasotransmitter with a variety of cardiovascular protective effects. Sirtuin 3 (SIRT3) is closely related to mitochondrial function and oxidative stress. We found that NaHS increased SIRT3 expression in the preventive effect on isoproterenol- (ISO-) induced myocardial hypertrophy. We further investigated whether exogenous H₂S supplement improved ISO-induced myocardial hypertrophy in a SIRT3-dependent manner. 10-week-old male 129S1/SvImJ (WT) mice and SIRT3 knockout (KO) mice were intraperitoneally injected with NaHS (50 μmol/kg/d) for two weeks and then intraperitoneally injected with ISO (60 mg/kg/d) for another two weeks. In WT mice, NaHS significantly reduced the cardiac index of ISO-induced mice, decreased the cross-sectional area of cardiomyocytes, and inhibited the expressions of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) mRNA. The activity of total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) in the myocardium was increased, but the level of malondialdehyde (MDA) was decreased. The fluorescence intensity of dihydroethidium staining for superoxide anion was attenuated. Optic atrophy 1 (OPA1) expression was upregulated, while dynamin-related protein 1 (DRP1) expression was downregulated. ERK, but not P38 and JNK, phosphorylation was downregulated. However, all above protective effects were unavailable in ISO-induced SIRT3 KO mice. Our present study suggested that exogenous H₂S supplement inhibited ISO-induced cardiac hypertrophy depending on SIRT3, which might be associated with antioxidant stress.

Reversal of Sp1 transactivation and TGFβ1/SMAD1 signaling by H2S prevent nickel-induced fibroblast activation

Nickel as a heavy metal is known to bring threat to human health, and nickel exposure is associated with changes in fibroblast activation which may contribute to its fibrotic properties. H₂S has recently emerged as an important gasotransmitter involved in numerous cellular signal transduction and pathophysiological responses. Interaction of nickel and H₂S on fibroblast cell activation has not been studied so far. Here, we showed that a lower dose of nickel (200 μM) induced the activation of human fibroblast cells, as evidenced by increased cell growth, migration and higher expressions of α-smooth muscle actin (αSMA) and fibronectin, while high dose of nickel (1 mM) inhibited cell viability. Nickel reduced intracellular thiol contents and stimulated oxidative stress. Nickel also repressed the mRNA and protein expression of cystathionine gamma-lyase (CSE, a H₂S-generating gene) and blocked the endogenous production of H₂S. Exogenously applied NaHS (a H₂S donor) had no effect on nickel-induced cell viability but significantly attenuated nickel-stimulated cell migration and the expression of αSMA and fibronectin. In contrast, CSE deficiency worsened nickel-induced αSMA expression. Moreover, H₂S incubation reversed nickel-stimulated TGFβ1/SMAD1 signal and blocked TGFβ1-initiated expressions of αSMA and fibronectin. Nickel inhibited the interaction of Sp1 with CSE promoter but strengthened the binding of Sp1 with TGFβ1 promoter, which was reversed by exogenously applied NaHS. These data reveal that H₂S protects from nickel-stimulated fibroblast activation and CSE/H₂S system can be a potential target for the treatment of tissue fibrosis induced by nickel.

Long-term exercise restores hydrogen sulfide in the kidney and contributes to exercise benefits in 5/6 nephrectomized rats

Physical exercise is shown to have protective effects on chronic kidney disease (CKD). CKD itself is associated with a reduction in renal hydrogen sulfide (H2S) concentration. This study was designed to investigate whether protective effects of exercise in 5/6 nephrectomized (5/6 NX) rats is associated with H2S levels in the kidney? Twenty four male Wistar rats weighing 250-300 g were assigned into 4 groups: 1- Sham 2- Sham exercise 3-5/6 NX 4-5/6 NX+exercise. To induce CKD, 4 days after removing upper and lower one-third parts of the left kidney, total right nephrectomy was performed. In the Sham groups, anesthesia and surgery were performed like the other groups without removal of the kidney mass. Exercise was performed by treadmill at a speed of 18 m/min for 8 weeks. At the end of the twelfth week, blood and kidney samples were collected to measure renal function (levels of plasma urea and creatinine), oxidative stress markers (renal MDA level and SOD activity), and histological indices. Eight weeks exercise significantly improved serum creatinine, BUN, renal MDA level, SOD activity, renal sympathetic nerve activity (RSNA), hypertension, and renal histology in addition to renal H2S level compared to the 5/6 NX group. The results suggest that regular exercise improves renal oxidative status and ameliorates renal damage, hypertension, and RSNA in 5/6 nephrectomized rats. These improvements by exercise might be associated with the increase in renal H2S level.

Hydrogen sulfide-producing cystathionine γ-lyase is critical in the progression of kidney fibrosis

Cystathionine γ-lyase (CSE), the last key enzyme of the transsulfuration pathway, is involved in the production of hydrogen sulfide (H₂S) and glutathione (GSH), which regulate redox balance and act as important antioxidant molecules. Impairment of the H₂S- and GSH-mediated antioxidant system is associated with the progression of chronic kidney disease (CKD), characterized by kidney fibrosis and dysfunction. Here, we evaluated the role of CSE in the progression of kidney fibrosis after unilateral ureteral obstruction (UUO) using mice deficient in the Cse gene. UUO of wild-type mice reduced the expression of H₂S-producing enzymes, CSE, cystathionine β-synthase, and 3-mercaptopyruvate sulfurtransferase in the obstructed kidneys, resulting in decreased H₂S and GSH levels. Cse gene deletion lowered H₂S and GSH levels in the kidneys. Deleting the Cse gene exacerbated the decrease in H₂S and GSH levels and increase in superoxide formation and oxidative damage to proteins, lipids, and DNA in the kidneys after UUO, which were accompanied by greater kidney fibrosis, deposition of extracellular matrixes, expression of α-smooth muscle actin, tubular damage, and infiltration of inflammatory cells. Furthermore, Cse gene deletion exacerbated mitochondrial fragmentation and apoptosis of renal tubule cells after UUO. The data provided herein constitute in vivo evidence that Cse deficiency impairs renal the H₂S- and GSH-producing activity and exacerbates UUO-induced kidney fibrosis. These data propose a novel therapeutic approach against CKD by regulating CSE and the transsulfuration pathway.

Long-term effects of hydrogen sulfide on the anabolic-catabolic balance of articular cartilage in vitro

Healthy cartilage maintenance relies on an equilibrium among the anabolic and catabolic processes in chondrocytes. With the onset of osteoarthritis (OA), increased interleukin (IL)-1β levels induce an inhibition of the synthesis of extracellular matrix (ECM) proteins, as well as an increase in proteases. This eventually leads to a predominance of the catabolic phenotype and the progressive loss of articular cartilage. Hydrogen sulfide (H₂S) is a small gaseous molecule recognized as the third endogenous gasotransmitter. When administered exogenously, it has shown anti-inflammatory and anti-catabolic properties in several in vitro and in vivo models. Here, OA cartilage disks were co-cultured in vitro with IL-1β (5 ng/ml) and NaSH or GYY4137 (200 or 1000 μM) for 21 days. The ability of these two H₂S-producing compounds to avoid long term extracellular matrix (ECM) destruction was evaluated. We used a glycosaminoglycan (GAG) quantification kit histology and immunohistochemistry (IHC) to evaluate matrix proteins degradation and matrix metalloproteinases (MMP) abundance. Through the GAGs quantification assay, safranin O (S-O) and toluidine blue (TB) stains, and keratan/chondroitin sulfate (KS/ChS) IHCs it was shown that co-stimulation with H₂S-forming reagents effectively avoided GAGs destruction. Both Masson's trichrome (MT) stain and collagen (col) type II IHC, as well as aggrecan (agg) IHC demonstrated that not only were these proteins protected but even promoted, their abundance being higher than in the basal condition. Further, stains also demonstrated that positivity in the inter-territorial and intra-cellular for the different matrix components were rescued, suggesting that NaSH and GYY4137 might also have pro-anabolic effects. In addition, a clear protective effect against the increased MMPs levels was seen, since increased MMP3 and 13 levels were subsequently reduced with the co-stimulation with sulfide compounds. In general, GYY4137 was more effective than NaSH, and increasing the dose improved the results. This study demonstrates that H₂S anti-catabolic effects, which had been previously proven in short-term (24-48 h) in vitro cellular models, are maintained over time directly in OA cartilage tissue.

Loss of the Protein Cystathionine β-Synthase During Kidney Injury Promotes Renal Tubulointerstitial Fibrosis

BACKGROUND/AIMS

Renal tubulointerstitial fibrosis (TIF) is the common pathway of progressive chronic kidney disease. Inflammation has been widely accepted as the major driving force of TIF. Cystathionine β-synthase (CBS) is the first and rate-limiting enzyme in the transsulfuration pathway. CBS is considered to play protective role in liver and pulmonary fibrosis, but its role in TIF remains unknown. The purpose of this study was to investigate the potential role and mechanism of CBS in renal inflammation and TIF.

METHODS

Renal function, tubulointerstitium damage index score, extracellular matrix (ECM) deposition, and the expressions of collagen I, collagen III, fibronectin, CD3, CD68, IL-1β, TNF-α were measured in sham operation and unilateral ureteral obstruction (UUO) rats. Proteomics and gene array analysis were performed to screen differentially expressed molecules in the development of renal inflammation and TIF in UUO rats. The expression of CBS was detected in patients with obstructive nephropathy and UUO rats. We confirmed the expression of CBS using western blot and real-time PCR in HK-2 cells. Overexpression plasmid and siRNA were transfected specifically to study the possible function of CBS in HK-2 cells.

RESULTS

Abundant expression of CBS, localized in renal tubular epithelial cells, was revealed in human and rat renal tissue, which correlated negatively with the progression of fibrotic disease. Expression of CBS was dramatically decreased in the obstructed kidney from UUO rats as compared with the sham group (SHM). In addition, knocking down CBS exacerbated extracellular matrix (ECM) deposition, whereas CBS overexpression attenuated TGF-β1-induced ECM deposition in vitro. Inflammatory and chemotactic factors were also increased in CBS knockdown HK-2 cells stimulated by IL-1β.

CONCLUSIONS

These findings establish CBS as a novel inhibitor in renal fibrosis and as a new therapeutic target in patients with chronic kidney disease.

Cystathionine γ-Lyase Deficiency Exacerbates CCl4-Induced Acute Hepatitis and Fibrosis in the Mouse Liver

AIMS

The present study examined the role of cystathionine γ-lyase (CSE) in carbon tetrachloride (CCl₄)-induced liver damage.

RESULTS

A CSE gene knock-out and luciferase gene knock-in (KI) mouse model was constructed to study the function of CSE and to trace its expression in living status. CCl₄ or lipopolysaccharide markedly downregulated CSE expression in the liver of mice. CSE-deficient mice showed increased serum alanine aminotransferase and aspartate aminotransferase levels, and liver damage after CCl₄ challenge, whereas albumin and endogenous hydrogen sulfide (H₂S) levels decreased significantly. CSE knockout mice showed increased serum homocysteine levels, upregulation of inflammatory cytokines, and increased autophagy and IκB-α degradation in the liver in response to CCl₄ treatment. The increase in pro-inflammatory cytokines, including tumor necrosis factor-alpha in CSE-deficient mice after CCl₄ challenge, was accompanied by a significant increase in liver tissue hydroxyproline and α-smooth muscle actin and histopathologic changes in the liver. However, H₂S donor pretreatment effectively attenuated most of these imbalances.

INNOVATION

Here, a CSE knock-out and luciferase KI mouse model was established for the first time to study the transcriptional regulation of CSE expression in real time in a non-invasive manner, providing information on the effects and potential mechanisms of CSE on CCl₄-induced liver injury.

CONCLUSION

CSE deficiency increases pro-inflammatory cytokines in the liver and exacerbates acute hepatitis and liver fibrosis by reducing H₂S production from L-cysteine in the liver. The present data suggest the potential of an H₂S donor for the treatment of liver diseases such as toxic hepatitis and fibrosis. Antioxid. Redox Signal. 27, 133-149.

Hydrogen sulfide promotes autophagy of hepatocellular carcinoma cells through the PI3K/Akt/mTOR signaling pathway

Hydrogen sulfide (H2S), in its gaseous form, plays an important role in tumor carcinogenesis. This study investigated the effects of H2S on the cell biological functions of hepatocellular carcinoma (HCC). HCC cell lines, HepG2 and HLE, were treated with NaHS, a donor of H2S, and rapamycin, a classic autophagy inducer, for different lengths of time. Western blotting, immunofluorescence, transmission electron microscopy (TEM), scratch assay, CCK-8 and flow cytometric analysis were carried out to examine the effects of H2S on HCC autophagy, cell behavior and PI3K/Akt/mTOR signaling. Treatment with NaHS upregulated expression of LC3-II and Atg5, two autophagy-related proteins, in HepG2 and HLE cells. TEM revealed increased numbers of intracellular double-membrane vesicles in those cells treated with NaHS. Like rapamycin, NaHS also significantly inhibited expression of p-PI3K, p-Akt and mTOR proteins in HCC cells. Interestingly, the expression of LC3-II was further increased when the cells were treated with NaHS together with rapamycin. In addition, NaHS inhibited HCC cell migration, proliferation and cell division. These findings show that H2S can induce HCC cell apoptosis. The biological function of the gasotransmitter H2S in HCC cells was enhanced by the addition of rapamycin. Hydrogen sulfide influences multiple biological functions of HCC cells through inhibiting the PI3K/Akt/mTOR signaling pathway.

Broad-Range Antiviral Activity of Hydrogen Sulfide Against Highly Pathogenic RNA Viruses

Hydrogen sulfide is an important endogenous mediator that has been the focus of intense investigation in the past few years, leading to the discovery of its role in vasoactive, cytoprotective and anti-inflammatory responses. Recently, we made a critical observation that H₂S also has a protective role in paramyxovirus infection by modulating inflammatory responses and viral replication. In this study we tested the antiviral and anti-inflammatory activity of the H₂S slow-releasing donor GYY4137 on enveloped RNA viruses from Ortho-, Filo-, Flavi- and Bunyavirus families, for which there is no FDA-approved vaccine or therapeutic available, with the exception of influenza. We found that GYY4137 significantly reduced replication of all tested viruses. In a model of influenza infection, GYY4137 treatment was associated with decreased expression of viral proteins and mRNA, suggesting inhibition of an early step of replication. The antiviral activity coincided with the decrease of viral-induced pro-inflammatory mediators and viral-induced nuclear translocation of transcription factors from Nuclear Factor (NF)-kB and Interferon Regulatory Factor families. In conclusion, increasing cellular H₂S is associated with significant antiviral activity against a broad range of emerging enveloped RNA viruses, and should be further explored as potential therapeutic approach in relevant preclinical models of viral infections.