Specificity protein-1 as a critical regulator of human cystathionine gamma-lyase in smooth muscle cells

Hydrogen Sulfide Ameliorates Heart Aging by Downregulating Matrix Metalloproteinase-9

PURPOSE

Aging contributes significantly to cardiovascular diseases and cardiac dysfunction, leading to the upregulation of matrix metalloproteinase-9 (MMP-9) in the heart and a significant decrease in hydrogen sulfide (H2S) content, coupled with impaired cardiac diastolic function. This study explores whether supplementing exogenous hydrogen sulfide during aging ameliorates the decline in H2S concentration in the heart, suppresses MMP-9 expression, and improves the age-associated impairment in cardiac morphology and function.

METHODS

We collected plasma from healthy individuals of different ages to determine the relationship between aging and H2S and MMP-9 levels through Elisa detection and liquid chromatography-tandem mass spectrometry (LC/MC) detection of plasma H2S content. Three-month-old mice were selected as the young group, while 18-month-old mice were selected as the old group, and sodium hydrosulfide (NaHS) was injected intraperitoneally from 15 months old until 18 months old as the old + NaHS group. Plasma MMP-9 content was detected using Elisa, plasma H2S content, cardiac H2S content, and cystathionine gamma-lyase (CSE) activity were detected using LC/MC, and cardiac function was detected using echocardiography. Heart structure was assessed using hematoxylin and eosin staining, Masone staining was used to detect the degree of cardiac fibrosis, while western blot was used to detect the expression of MMP-9, CSE, and aging marker proteins. Knockdown of MMP-9 and CSE in H9c2 cells using small interfering RNA was carried out to determine the upstream-downstream relationship between MMP-9 and CSE.

RESULTS

H2S content in the plasma of healthy individuals decreases with escalating age, whereas MMP-9 level rises with age progression. Aging leads to a decrease in H2S levels in the heart and plasma of mice, severe impairment of cardiac diastolic function, interstitial relaxation, and fibrosis of the heart. Supplementing with exogenous H2S can improve these phenomena.

CONCLUSION

H2S maintains the structure and function of the heart by inhibiting the expression of MMP-9 during the aging process.

NOS3 and CTH gene mutations as new molecular markers for detection of lung adenocarcinoma

Gene mutations can contribute to lung adenocarcinoma (LUAD) development, metastasis, and therapy. This study aims to identify mutations in the endothelial nitric oxide synthase (eNOS or NOS3) and cystathionine γ-lyase (CSE or CTH) genes that are connected to LUAD symptoms. Two gene polymorphisms were identified using Sanger sequencing in 31 LUAD patients' formalin-fixed paraffin-embedded (FFPE) tissues. Epidermal growth factor receptor (EGFR) mutation and programmed death-ligand 1 (PD-L1) expression were examined in 110 LUAD patients using real-time polymerase chain reaction and immunohistochemistry. Mutations in the selected genes were retrieved from the gnomAD database for all cancer types and the Mutagene and COSMIC databases for LUAD patients. The GeneMANIA prediction server was used to predict the interaction between the studied genes. Poorly and moderately differentiated tumours predominated, with pT3 N2 Mx being the most prevalent stage. Polymorphism data showed 189 NOS3 gene mutations and 34 CTH gene mutations. In 110 LUAD patients, 14 (12.73%) were PD-L1 positive and expressed 50% or more protein. Eight (7.27%) samples included EGFR mutations, including two deletions and two point mutations in exon 19, four point mutations in exon 21. In gnomAD, 4012 NOS3 mutations and 1214 CTH mutations are present. In the Mutagene and COSMIC databases, the NOS3 gene had 295 and 93 mutations, whereas the CTH gene had 61 and 36. According to the GeneMANIA prediction server, 10 genes are related to NOS3, eight with CTH, 15 with EGFR, and 5 with PD-L1. This study is the first to identify several previously unknown mutations in LUAD patients' NOS3 and CTH genes, with potential therapeutic implications.

Hypoxia increases persulfide and polysulfide formation by AMP kinase dependent cystathionine gamma lyase phosphorylation

Hydropersulfide and hydropolysulfide metabolites are increasingly important reactive sulfur species (RSS) regulating numerous cellular redox dependent functions. Intracellular production of these species is known to occur through RSS interactions or through translational mechanisms involving cysteinyl t-RNA synthetases. However, regulation of these species under cell stress conditions, such as hypoxia, that are known to modulate RSS remain poorly understood. Here we define an important mechanism of increased persulfide and polysulfide production involving cystathionine gamma lyase (CSE) phosphorylation at serine 346 and threonine 355 in a substrate specific manner, under acute hypoxic conditions. Hypoxic phosphorylation of CSE occurs in an AMP kinase dependent manner increasing enzyme activity involving unique inter- and intramolecular interactions within the tetramer. Importantly, both cellular hypoxia and tissue ischemia result in AMP Kinase dependent CSE phosphorylation that regulates blood flow in ischemic tissues. Our findings reveal hypoxia molecular signaling pathways regulating CSE dependent persulfide and polysulfide production impacting tissue and cellular response to stress.

H2S regulation of iron homeostasis by IRP1 improves vascular smooth muscle cell functions

Either H2S or iron is essential for cellular processes. Abnormal metabolism of H2S and iron has increased risk for cardiovascular diseases. The aim of the present study is to examine the mutual interplay of iron and H2S signals in regulation of vascular smooth muscle cell (SMC) functions. Here we found that deficiency of cystathionine gamma-lyase (CSE, a major H2S-producing enzyme in vascular system) induced but NaHS (a H2S donor) administration attenuated iron accumulation in aortic tissues from angiotensin II-infused mice. In vitro, iron overload induced labile iron levels, promoted cell proliferation, disrupted F-actin filaments, and inhibited protein expressions of SMC-specific markers (αSMA and calponin) more significantly in SMCs from CSE knockout mice (KO-SMCs) than the cells from wild-type mice (WT-SMCs), which could be reversed by exogenously applied NaHS. In contrast, KO-SMCs were more vulnerable to iron starvation-induced cell death. Either iron overload or NaHS did not affect elastin level and gelatinolytic activity. We further found that H2S induced more aconitase activity of iron regulatory protein 1 (IRP1) but inhibited its RNA binding activity accompanied with increased protein levels of ferritin and ferriportin, which would contribute to the lower level of labile iron level inside the cells. In addition, iron was able to suppress CSE-derived H2S generation, while iron also non-enzymatically induced H2S release from cysteine. This study reveals the mutual interaction between iron and H2S signals in regulating SMC phenotypes and functions; CSE/H2S system would be a target for preventing iron metabolic disorder-related vascular diseases.

Targeting Homocysteine and Hydrogen Sulfide Balance as Future Therapeutics in Cancer Treatment

A high level of homocysteine (Hcy) is associated with oxidative/ER stress, apoptosis, and impairment of angiogenesis, whereas hydrogen sulfide (H2S) has been found to reverse this condition. Recent studies have shown that cancer cells need to produce a high level of endogenous H2S to maintain cell proliferation, growth, viability, and migration. However, any novel mechanism that targets this balance of Hcy and H2S production has yet to be discovered or exploited. Cells require homocysteine metabolism via the methionine cycle for nucleotide synthesis, methylation, and reductive metabolism, and this pathway supports the high proliferative rate of cancer cells. Although the methionine cycle favors cancer cells for their survival and growth, this metabolism produces a massive amount of toxic Hcy that somehow cancer cells handle very well. Recently, research showed specific pathways important for balancing the antioxidative defense through H2S production in cancer cells. This review discusses the relationship between Hcy metabolism and the antiapoptotic, antioxidative, anti-inflammatory, and angiogenic effects of H2S in different cancer types. It also summarizes the historical understanding of targeting antioxidative defense systems, angiogenesis, and other protective mechanisms of cancer cells and the role of H2S production in the genesis, progression, and metastasis of cancer. This review defines a nexus of diet and precision medicine in targeting the delicate antioxidative system of cancer and explores possible future therapeutics that could exploit the Hcy and H2S balance.

From Gasotransmitter to Immunomodulator: The Emerging Role of Hydrogen Sulfide in Macrophage Biology

Hydrogen sulfide (H₂S) has been increasingly recognized as a crucial inflammatory mediator in immune cells, particularly macrophages, due to its direct and indirect effects on cellular signaling, redox homeostasis, and energy metabolism. The intricate regulation of endogenous H₂S production and metabolism involves the coordination of transsulfuration pathway (TSP) enzymes and sulfide oxidizing enzymes, with TSP's role at the intersection of the methionine pathway and glutathione synthesis reactions. Additionally, H₂S oxidation mediated by sulfide quinone oxidoreductase (SQR) in mammalian cells may partially control cellular concentrations of this gasotransmitter to induce signaling. H₂S is hypothesized to signal through the posttranslational modification known as persulfidation, with recent research highlighting the significance of reactive polysulfides, a derivative of sulfide metabolism. Overall, sulfides have been identified as having promising therapeutic potential to alleviate proinflammatory macrophage phenotypes, which are linked to the exacerbation of disease outcomes in various inflammatory conditions. H₂S is now acknowledged to have a significant influence on cellular energy metabolism by affecting the redox environment, gene expression, and transcription factor activity, resulting in changes to both mitochondrial and cytosolic energy metabolism processes. This review covers recent discoveries pertaining to the involvement of H₂S in macrophage cellular energy metabolism and redox regulation, and the potential implications for the inflammatory response of these cells in the broader framework of inflammatory diseases.

Hydrogen sulfide prevents the vascular dysfunction induced by severe traumatic brain injury in rats by reducing reactive oxygen species and modulating eNOS and H2S-synthesizing enzyme expression

AIM

To assess the effects of subchronic administration with NaHS, an exogenous H₂S donor, on TBI-induced hypertension and vascular impairments.

MAIN METHODS

Animals underweministration does not prevent the body weight loss but slightly imnt a lateral fluid percussion injury, and the hemodynamic variables were measured in vivo by plethysmograph method. The vascular function in vitro, the ROS levels by the DCFH-DA method and the expression of H₂S-synthesizing enzymes and eNOS by Western blot were measured in isolated thoracic aortas at day 7 post-TBI. The effect of L-NAME on NaHS-induced effects in vascular function was evaluated. Brain water content was determined 7 days after trauma induction. Body weight was recorded throughout the experimental protocol, whereas the sensorimotor function was evaluated using the neuroscore test at days -1 (basal), 2, and 7 after the TBI induction.

KEY FINDINGS

TBI animals showed: 1) an increase in hemodynamic variables and ROS levels in aortas; 2) vascular dysfunction; 3) sensorimotor dysfunction; and 4) a decrease in body weight, the expression of H₂S-synthesizing enzymes, and eNOS phosphorylation. Interestingly, NaHS subchronic administration (3.1 mg/kg; i.p.; every 24 h for six days) prevented the development of hypertension, vascular dysfunction, and oxidative stress. L-NAME abolished NaHS-induced effects. Furthermore, NaHS treatment restored H₂S-synthesizing enzymes and eNOS phosphorylation with no effect on body weight, sensorimotor impairments, or brain water content.

SIGNIFICANCE

Taken together, these results demonstrate that H₂S prevents TBI-induced hypertension by restoring vascular function and modulating ROS levels, H₂S-synthesizing enzymes expression, and eNOS phosphorylation.

Overview on hydrogen sulfide-mediated suppression of vascular calcification and hemoglobin/heme-mediated vascular damage in atherosclerosis

Vulnerable atherosclerotic plaques with hemorrhage considerably contribute to cardiovascular morbidity and mortality. Calcification is the main characteristic of advanced atherosclerotic lesions and calcified aortic valve disease (CAVD). Lyses of red blood cells and hemoglobin (Hb) release occur in human hemorrhagic complicated lesions. During the interaction of cell-free Hb with plaque constituents, Hb is oxidized to ferric and ferryl states accompanied by oxidative changes of the globin moieties and heme release. Accumulation of both ferryl-Hb and metHb has been observed in atherosclerotic plaques. The oxidation hotspots in the globin chain are the cysteine and tyrosine amino acids associated with the generation of Hb dimers, tetramers and polymers. Moreover, fragmentation of Hb occurs leading to the formation of globin-derived peptides. A series of these pro-atherogenic cellular responses can be suppressed by hydrogen sulfide (H2S). Since H2S has been explored to exhibit a wide range of physiologic functions to maintain vascular homeostasis, it is not surprising that H2S may play beneficial effects in the progression of atherosclerosis. In the present review, we summarize the findings about the effects of H2S on atherosclerosis and CAVD with a special emphasis on the oxidation of Hb/heme in atherosclerotic plaque development and vascular calcification.

NRF2 Regulates Cystathionine Gamma-Lyase Expression and Activity in Primary Airway Epithelial Cells Infected with Respiratory Syncytial Virus

Cystathionine-y-lyase (CSE) is a critical enzyme for hydrogen sulfide (H2S) biosynthesis and plays a key role in respiratory syncytial virus (RSV) pathogenesis. The transcription factor NRF2 is the master regulator of cytoprotective and antioxidant gene expression, and is degraded during RSV infection. While some evidence supports the role of NRF2 in CSE gene transcription, its role in CSE expression in airway epithelial cells is not known. Here, we show that RSV infection decreased CSE expression and activity in primary small airway epithelial (SAE) cells, while treatment with tert-butylhydroquinone (tBHQ), an NRF2 inducer, led to an increase of both. Using reporter gene assays, we identified an NRF2 response element required for the NRF2 inducible expression of the CSE promoter. Electrophoretic mobility shift assays demonstrated inducible specific NRF2 binding to the DNA probe corresponding to the putative CSE promoter NRF2 binding sequence. Using chromatin immunoprecipitation assays, we found a 50% reduction in NRF2 binding to the endogenous CSE proximal promoter in SAE cells infected with RSV, and increased binding in cells stimulated with tBHQ. Our results support the hypothesis that NRF2 regulates CSE gene transcription in airway epithelial cells, and that RSV-induced NRF2 degradation likely accounts for the observed reduced CSE expression and activity.

Exogenous hydrogen sulfide restores CSE and CBS but no 3-MST protein expression in the hypothalamus and brainstem after severe traumatic brain injury

Hydrogen sulfide (H₂S) is a gasotransmitter endogenously synthesized by cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), and 3-mercaptopiruvate sulfurtransferase (3-MST) enzymes. H₂S exogenous administration prevents the development of hemodynamic impairments after traumatic brain injury (TBI). Since the hypothalamus and the brainstem highly regulate the cardiovascular system, this study aimed to evaluate the effect of NaHS subchronic treatment on the changes of H₂S-sythesizing enzymes in those brain areas after TBI and in physiological conditions. For that purpose, animals were submitted to a lateral fluid percussion injury, and the changes in CBS, CSE, and 3-MST protein expression were measured by western blot at days 1, 2, 3, 7, and 28 in the vehicle group, and 7 and 28 days after NaHS treatment. After severe TBI induction, we found a decrease in CBS and CSE protein expression in the hypothalamus and brainstem; meanwhile, 3-MST protein expression diminished only in the hypothalamus compared to the Sham group. Remarkably, i.p. daily injections of NaHS, an H₂S donor, (3.1 mg/kg) during seven days: (1) restored CBS and CSE but no 3-MST protein expression in the hypothalamus at day 28 post-TBI; (2) reestablished only CSE in brainstem 7 and 28 days after TBI; and (3) did not modify H₂S-sythesizing enzymes protein expression in uninjured animals. Mainly, our results show that the NaHS effect on CBS and CSE protein expression is observed in a time- and tissue-dependent manner with no effect on 3-MST expression, which may suggest a potential role of H₂S synthesis in hypothalamus and brainstem impairments observed after TBI.

Deficiency of cystathionine gamma-lyase promotes aortic elastolysis and medial degeneration in aged mice

Enzymatic degradation of elastin by matrix metalloproteinases (MMPs) leads to the permanent dilation of aortic wall and constitutes the most prominent characters of aortic aneurysm and aging-related medial degeneration. Hydrogen sulfide (H₂S) as a gasotransmitter exhibits a wide variety of cardio-protective functions through its anti-inflammatory and anti-oxidative actions. Cystathionine gamma-lyase (CSE) is a main H₂S-generating enzyme in cardiovascular system. The regulatory roles of CSE/H₂S system on elastin homeostasis and blood vessel degeneration have not yet been explored. Here we found that aged CSE knockout mice had severe aortic dilation and elastic degradation in abdominal aorta and were more sensitive to angiotensin II-induced aortic elastolysis and medial degeneration. Administration of NaHS would protect the mice from angiotensin II-induced inflammation, gelatinolytic activity, elastin fragmentation, and aortic dilation. In addition, human aortic aneurysm samples had higher inflammatory infiltration and lower expression of CSE. In cultured smooth muscle cells (SMCs), TNFα-induced MMP2/9 hyperactivity and elastolysis could be attenuated by exogenously applied NaHS or CSE overexpression while further deteriorated by complete knockout of CSE. It was further found that H₂S inhibited MMP2 transcription by posttranslational modification of Sp1 via S-sulfhydration. H₂S also directly suppressed MMP hyperactivity by S-sulfhydrating the cysteine switch motif. Taken together, this study revealed the involvement of CSE/H₂S system in the pathogenesis of aortic elastolysis and medial degeneration by maintaining the inactive form of MMPs, suggesting that CSE/H₂S system can be a target for the prevention of age-related medial degeneration and treatment of aortic aneurysm.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Uremic Toxin Indoxyl Sulfate Impairs Hydrogen Sulfide Formation in Renal Tubular Cells

Hydrogen sulfide (H₂S) was the third gasotransmitter to be recognized as a cytoprotectant. A recent study demonstrated that exogenous supplementation of H₂S ameliorates functional insufficiency in chronic kidney disease (CKD). However, how the H₂S system is impaired by CKD has not been elucidated. The uremic toxin indoxyl sulfate (IS) is known to accumulate in CKD patients and harm the renal tubular cells. This study therefore treated the proximal tubular cells, LLC-PK₁, with IS to see how IS affects H₂S formation. Our results showed that H₂S release from LLC-PK₁ cells was markedly attenuated by IS when compared with control cells. The H₂S donors NaHS and GYY-4137 significantly attenuated IS-induced tubular damage, indicating that IS impairs H₂S formation. Interestingly, IS downregulated the H₂S-producing enzymes cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST), and these effects could be reversed by inhibition of the IS receptor, aryl hydrocarbon receptor (AhR). As transcription factor specificity protein 1 (Sp1) regulates the gene expression of H₂S-producing enzymes, we further showed that IS significantly decreased the DNA binding activity of Sp1 but not its protein expression. Blockade of AhR reversed low Sp1 activity caused by IS. Moreover, exogenous H₂S supplementation attenuated IS-mediated superoxide formation and depletion of the cellular glutathione content. These results clearly indicate that IS activates AhR, which then attenuates Sp1 function through the regulation of H₂S-producing enzyme expression. The attenuation of H₂S formation contributes to the low antioxidant defense of glutathione in uremic toxin-mediated oxidative stress, causing tubular cell damage.

The Pathophysiology of H2S in Renal Glomerular Diseases

Renal glomerular diseases such as glomerulosclerosis and diabetic nephropathy often result in the loss of glomerular function and consequently end-stage renal disease. The glomerulus consists of endothelial cells, mesangial cells and glomerular epithelial cells also referred to as podocytes. A fine-tuned crosstalk between glomerular cells warrants control of growth factor synthesis and of matrix production and degradation, preserving glomerular structure and function. Hydrogen sulfide (H2S) belongs together with nitric oxide (NO) and carbon monoxide (CO) to the group of gasotransmitters. During the last three decades, these higher concentration toxic gases have been found to be produced in mammalian cells in a well-coordinated manner. Recently, it became evident that H2S and the other gasotransmitters share common targets as signalling devices that trigger mainly protective pathways. In several animal models, H2S has been demonstrated as a protective factor in the context of kidney disorders, in particular of diabetic nephropathy. Here, we focus on the synthesis and action of H2S in glomerular cells, its beneficial effects in the glomerulus and its action in the context of the other gaseous signalling molecules NO and CO.

The Expression and Activity of Rhodanese, 3-Mercaptopyruvate Sulfurtransferase, Cystathionine γ-Lyase in the Most Frequently Chosen Cellular Research Models

This paper provides information concerning the activity and expression levels of three sulfurtransferases (STRs): rhodanese (TST, EC: 2.8.1.1), 3-mercaptopyruvate sulfurtransferase (MPST, EC: 2.8.1.2) and cystathionine γ-lyase (CTH, EC: 4.4.1.1) in various cell lines. Since very limited data are available in the scientific literature on this subject, the available data are included in this paper. These shortages often force the researchers to carry out their own screening tests that allow them to choose an appropriate model for their further studies. This work supplements the existing deficiencies in this area and presents the activity and expression of STRs in the eight most frequently chosen cell lines: the mouse mammary gland cell line (NMuNG, ATCC: CRL-1636), mouse mammary gland tumor (4T1, ATCC: CRL-2539), mouse fibroblast (MEF, ATCC: SCRC-1008), mouse melanoma (B16-F1, ATCC: CRL-6323), human colorectal adenocarcinoma (Caco-2, ATCC: HTB-37), human embryonic kidney (HEK-293, ATCC: CRL-1573), human osteosarcoma (MG-63, ATCC: CRL-1427) and rat myocardium (H9c2, ATCC: CRL-1446). Changes in STRs activity are directly related to the bioavailability of cysteine and the sulfane sulfur level, and thus the present authors also measured these parameters, as well as the level of glutathione (its reduced (GSH) and oxidized (GSSG) form) and the [GSH]/[GSSG] ratio that determines the antioxidant capacity of the cells. STRs demonstrate diverse functionality and clinical relevance; therefore, we also performed an analysis of genetic variation of STRs genes that revealed a large number of polymorphisms. Although STRs still provide challenges in several fields, responding to them could not only improve the understanding of various diseases, but may also provide a way to treat them.

Hydrogen Sulfide Actions in the Vasculature

Hydrogen sulfide (H2 S) is a small, gaseous molecule with poor solubility in water that is generated by multiple pathways in many species including humans. It acts as a signaling molecule in many tissues with both beneficial and pathological effects. This article discusses its many actions in the vascular system and the growing evidence of its role to regulate vascular tone, angiogenesis, endothelial barrier function, redox, and inflammation. Alterations in some disease states are also discussed including potential roles in promoting tumor growth and contributions to the development of metabolic disease. © 2021 American Physiological Society. Compr Physiol 11:1-22, 2021.

Cystathionine gamma-lyase/H2 S signaling facilitates myogenesis under aging and injury condition

Hydrogen sulfide (H₂ S) can be endogenously produced and belongs to the class of signaling molecules known as gasotransmitters. Cystathionine gamma-lyase (CSE)-derived H₂ S is implicated in the regulation of cell differentiation and the aging process, but the involvements of the CSE/H₂ S system in myogenesis upon aging and injury have not been explored. In this study, we demonstrated that CSE acts as a major H₂ S-generating enzyme in skeletal muscles and is significantly down-regulated in aged skeletal muscles in mice. CSE deficiency exacerbated the age-dependent sarcopenia and cardiotoxin-induced injury/regeneration in mouse skeletal muscle, possibly attributed to inefficient myogenesis. In contrast, supplement of NaHS (an H₂ S donor) induced the expressions of myogenic genes and promoted muscle regeneration in mice. In vitro, incubation of myoblast cells (C2C12) with H₂ S promoted myogenesis, as evidenced by the inhibition of cell cycle progression and migration, altered expressions of myogenic markers, elongation of myoblasts, and formation of multinucleated myotubes. Myogenesis was also found to upregulate CSE expression, while blockage of CSE/H₂ S signaling resulted in a suppression of myogenesis. Mechanically, H₂ S significantly induced the heterodimer formation between MEF2c and MRF4 and promoted the binding of MEF2c/MRF4 to myogenin promoter. MEF2c was S-sulfhydrated at both cysteine 361 and 420 in the C-terminal transactivation domain, and blockage of MEF2c S-sulfhydration abolished the stimulatory role of H₂ S on MEF2c/MRF4 heterodimer formation. These findings support an essential role for H₂ S in maintaining myogenesis, presenting it as a potential candidate for the prevention of age-related sarcopenia and treatment of muscle injury.

The Hidden Role of Hydrogen Sulfide Metabolism in Cancer

Hydrogen Sulfide (H₂S), an endogenously produced gasotransmitter, is involved in various important physiological and disease conditions, including vasodilation, stimulation of cellular bioenergetics, anti-inflammation, and pro-angiogenesis. In cancer, aberrant up-regulation of H₂S-producing enzymes is frequently observed in different cancer types. The recognition that tumor-derived H₂S plays various roles during cancer development reveals opportunities to target H₂S-mediated signaling pathways in cancer therapy. In this review, we will focus on the mechanism of H₂S-mediated protein persulfidation and the detailed information about the dysregulation of H₂S-producing enzymes and metabolism in different cancer types. We will also provide an update on mechanisms of H₂S-mediated cancer progression and summarize current options to modulate H₂S production for cancer therapy.

Endothelium as a Source and Target of H2S to Improve Its Trophism and Function

The vascular endothelium consists of a single layer of squamous endothelial cells (ECs) lining the inner surface of blood vessels. Nowadays, it is no longer considered as a simple barrier between the blood and vessel wall, but a central hub to control blood flow homeostasis and fulfill tissue metabolic demands by furnishing oxygen and nutrients. The endothelium regulates the proper functioning of vessels and microcirculation, in terms of tone control, blood fluidity, and fine tuning of inflammatory and redox reactions within the vessel wall and in surrounding tissues. This multiplicity of effects is due to the ability of ECs to produce, process, and release key modulators. Among these, gasotransmitters such as nitric oxide (NO) and hydrogen sulfide (H₂S) are very active molecules constitutively produced by endotheliocytes for the maintenance and control of vascular physiological functions, while their impairment is responsible for endothelial dysfunction and cardiovascular disorders such as hypertension, atherosclerosis, and impaired wound healing and vascularization due to diabetes, infections, and ischemia. Upregulation of H₂S producing enzymes and administration of H₂S donors can be considered as innovative therapeutic approaches to improve EC biology and function, to revert endothelial dysfunction or to prevent cardiovascular disease progression. This review will focus on the beneficial autocrine/paracrine properties of H₂S on ECs and the state of the art on H₂S potentiating drugs and tools.

Gasotransmitter synthesis and signalling in the renal glomerulus. Implications for glomerular diseases

Glomerular injury is a hallmark of kidney diseases such as diabetic nephropathy, IgA nephropathy or other forms of glomerulonephritis. Glomerular endothelial cells, mesangial cells, glomerular epithelial cells (podocytes) and, in an inflammatory context, infiltrating immune cells crosstalk to mediate signalling processes in the glomerulus. Under physiological conditions, mesangial cells act by the control of extracellular matrix production and degradation, by the synthesis of growth factors and by preserving a well-defined crosstalk with glomerular podocytes and endothelial cells to regulate glomerular structure and function. It is well known that mesangial cells are able to amplify an inflammatory process by the formation of cytokines, reactive oxygen species (ROS) and nitric oxide (NO). This exaggerated reaction may result in a vicious cycle with subsequent damage of neighboured podocytes and endothelial cells, loss of the filtration barrier and, finally destruction of the whole glomerulus. Unfortunately, all efforts to develop new therapies for the treatment of glomerular diseases by controlling unbridled ROS or NO production directly had so far no success. However, on-going research on ROS and NO defined these autacoids more as important signalling molecules than as endogenously produced cytotoxic compounds. New findings on signalling activities of ROS, NO but also hydrogen sulfide (H₂S) and carbon monoxide (CO) supported this paradigm shift. Because of their similar chemical properties and their similar signal transduction capacities, NO, H₂S and CO are meanwhile designated as the group of gasotransmitters. In this review, we describe the current knowledge of the signalling properties of gasotransmitters with a focus on glomerular cells and their role in glomerular diseases.

Estrogen Receptors and Estrogen-Induced Uterine Vasodilation in Pregnancy

Normal pregnancy is associated with dramatic increases in uterine blood flow to facilitate the bidirectional maternal–fetal exchanges of respiratory gases and to provide sole nutrient support for fetal growth and survival. The mechanism(s) underlying pregnancy-associated uterine vasodilation remain incompletely understood, but this is associated with elevated estrogens, which stimulate specific estrogen receptor (ER)-dependent vasodilator production in the uterine artery (UA). The classical ERs (ERα and ERβ) and the plasma-bound G protein-coupled ER (GPR30/GPER) are expressed in UA endothelial cells and smooth muscle cells, mediating the vasodilatory effects of estrogens through genomic and/or nongenomic pathways that are likely epigenetically modified. The activation of these three ERs by estrogens enhances the endothelial production of nitric oxide (NO), which has been shown to play a key role in uterine vasodilation during pregnancy. However, the local blockade of NO biosynthesis only partially attenuates estrogen-induced and pregnancy-associated uterine vasodilation, suggesting that mechanisms other than NO exist to mediate uterine vasodilation. In this review, we summarize the literature on the role of NO in ER-mediated mechanisms controlling estrogen-induced and pregnancy-associated uterine vasodilation and our recent work on a “new” UA vasodilator hydrogen sulfide (H₂S) that has dramatically changed our view of how estrogens regulate uterine vasodilation in pregnancy.

E2β stimulates ovine uterine artery endothelial cell H2S production in vitro by estrogen receptor-dependent upregulation of cystathionine β-synthase and cystathionine γ-lyase expression†

Endogenous hydrogen sulfide (H2S) is a potent vasodilator and proangiogenic second messenger synthesized from L-cysteine by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CTH). Estrogens are potent vasodilators that stimulate H2S biosynthesis in uterine arteries (UA) in vivo; however, the underlying mechanisms are unknown. We hypothesized that estrogens stimulate H2S biosynthesis in UA endothelial cells (UAEC) via specific estrogen receptor (ER)-dependent mechanisms. In cultured primary UAEC, treatment with estradiol-17β (E2β) stimulated CBS and CTH mRNAs and proteins in a time- and concentration-dependent fashion. As little as 0.1 nM E2β was effective in increasing CBS and CTH expressions and these stimulatory effects maximized with 10-100 nM E2β at 48-72 h. E2β also activated CBS and CTH promoters in UAEC, leading to CBS and CTH expression. Treatment with E2β stimulated H2S production, which was blocked by specific inhibitors of either CBS or CTH and their combination and the ER antagonist ICI 182780. Treatment with either specific agonist of ERα or ERβ stimulated both CBS and CTH mRNA and protein expressions and H2S production to levels similar to that of E2β. Specific antagonist of either ERα or ERβ blocked E2β-stimulated CBS and CTH mRNA and protein expressions and H2S production. Combinations of either ERα or ERβ agonists or their antagonists had no additive effects. Thus, E2β stimulates H2S production by upregulating CBS and CTH mRNA and protein expressions through specific ERα or ERβ-dependent CBS and CTH transcription in UAEC in vitro.

Drug-Eluting Stent Targeting Sp-1-Attenuated Restenosis by Engaging YAP-Mediated Vascular Smooth Muscle Cell Phenotypic Modulation

Background

Activation of the YAP (Yes‐associated protein) pathway has been demonstrated to be related to smooth muscle cells (SMCs) phenotypic modulation and vessel restenosis. The aim of this study was to illustrate the molecular mechanisms that regulate the expression of YAP during the process of SMCs phenotypic switch. Whether the molecular basis identified in the study could be a potential therapeutic target for drug‐eluting stents is further tested.

Methods and Results

In cell culture and in rat carotid arterial injury models, Sp‐1 (specificity protein 1) expression was significantly induced, and correlated with SMCs proliferative phenotype. Overexpression of Sp‐1 promoted SMCs proliferation and migration. Conversely, siSp‐1 transfection or Sp‐1 inhibitor Mithramycin A treatment attenuates SMC proliferation and migration. Through gain‐ and loss‐function assays, we demonstrated that YAP was involved in Sp‐1‐mediated SMC phenotypic switch. Mechanistically, activated Sp‐1 regulated YAP transcriptional expression through binding to its promoter. Moreover, we fabricated a Sp‐1 inhibitor Mithramycin A‐eluting stent and further tested it. In the rabbit carotid model, Mithramycin A‐eluting stent inhibited YAP transcription and attenuated in‐stent restenosis through regulating YAP‐mediated SMC phenotypic switch.

Conclusions

Sp‐1 controls phenotypic modulation of SMC by regulating transcription factor YAP. Drug‐eluting stent targeting Sp‐1 might represent a novel therapeutic strategy to prevent in‐stent restenosis.

Hydrogen sulfide signaling in mitochondria and disease

Hydrogen sulfide can signal through 3 distinct mechanisms: 1) reduction and/or direct binding of metalloprotein heme centers, 2) serving as a potent antioxidant through reactive oxygen species/reactive nitrogen species scavenging, or 3) post-translational modification of proteins by addition of a thiol (-SH) group onto reactive cysteine residues: a process known as persulfidation. Below toxic levels, hydrogen sulfide promotes mitochondrial biogenesis and function, thereby conferring protection against cellular stress. For these reasons, increases in hydrogen sulfide and hydrogen sulfide-producing enzymes have been implicated in several human disease states. This review will first summarize our current understanding of hydrogen sulfide production and metabolism, as well as its signaling mechanisms; second, this work will detail the known mechanisms of hydrogen sulfide in the mitochondria and the implications of its mitochondrial-specific impacts in several pathologic conditions.-Murphy, B., Bhattacharya, R., Mukherjee, P. Hydrogen sulfide signaling in mitochondria and disease.

Induction of cystathionine gamma-lyase expression and metallothionein-1 S-sulfhydration alleviate cadmium-induced cell death in myoblast cells

Hydrogen sulfide (H₂S), a multifunctional gasotransmitter, participates in a wide range of cellular signal transduction and pathophysiological processes. Cystathionine gamma-lyase (CSE) acts as a major H₂S-generating enzyme in peripheral organs and tissues. As a cysteine-rich and heavy metal-binding protein, metallothionein-1 (MT-1) is known to protect cells from various environmental stresses. Here we demonstrated that exposure of cadmium (Cd) induced oxidative stress, depleted intracellular thiols, and stimulated apoptotic cell death in mouse myoblast cells. CSE expression and H₂S production were significantly enhanced by Cd treatment. NaHS, a well-known H₂S donor, at physiologically relevant concentration significantly alleviated Cd-induced damage in both myoblasts and mouse skeletal muscles. In contrast, down-regulation of CSE/H₂S system deteriorated Cd-stimulated oxidative stress and cell death. Exposure of the cells to Cd lead to increased expressions of metal regulatory transcription factor 1 and MT-1, while siRNA-mediated MT-1 knockdown alleviated Cd-induced CSE expression and caused more oxidative stress and cell death. In addition, H₂S post-translationally modified MT-1 by S-sulfhydration and stabilized zinc-protein complex. Taken together, these data suggest that CSE/H₂S system would protect myoblasts and skeletal muscles from Cd-induced damage by S-sufhydrating MT-1.

Estradiol-17β stimulates H2 S biosynthesis by ER-dependent CBS and CSE transcription in uterine artery smooth muscle cells in vitro

Endogenous hydrogen sulfide (H₂ S), synthesized by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), is a potent vasodilator that can be stimulated by estradiol-17β (E ₂ β) in uterine artery (UA) smooth muscle (UASMC) in vivo; however, the underlying mechanisms are unknown. This study tested a hypothesis that E ₂ β stimulates H ₂ S biosynthesis by upregulating CBS expression via specific estrogen receptor (ER). Treatment with E ₂ β stimulated time- and concentration- dependent CBS and CSE messenger RNA (mRNA) and protein expressions, and H ₂ S production in cultured primary UASMC isolated from late pregnant ewes, which were blocked by ICI 182,780. Treatment with specific ERα or ERβ agonist mimicked these E ₂ β-stimulated responses, which were blocked by specific ERα or ERβ antagonist. Moreover, E ₂ β activated both CBS and CSE promoters and ICI 182,780 blocked the E ₂ β-stimulated responses. Thus, E ₂ β stimulates H ₂ S production by upregulating CBS and CSE expression via specific ER-dependent transcription in UASMC in vitro.

Regulators of the transsulfuration pathway

The transsulfuration pathway is a metabolic pathway where transfer of sulfur from homocysteine to cysteine occurs. The pathway leads to the generation of several sulfur metabolites, which include cysteine, GSH and the gaseous signalling molecule hydrogen sulfide (H₂ S). Precise control of this pathway is critical for maintenance of optimal cellular function and, therefore, the key enzymes of the pathway, cystathionine β-synthase and cystathionine γ-lyase, are regulated at multiple levels. Disruption of the transsulfuration pathway contributes to the pathology of several conditions such as vascular dysfunction, Huntington's disease and during ageing. Treatment with donors of hydrogen sulfide and/or stimulation of this pathway have proved beneficial in several of these disorders. In this review, we focus on the regulation of the transsulfuration pathway pertaining to cysteine and H₂ S, which could be targeted to develop novel therapeutics. LINKED ARTICLES: This article is part of a themed section on Chemical Biology of Reactive Sulfur Species. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.4/issuetoc.

Mammalian Sulfur Amino Acid Metabolism: A Nexus Between Redox Regulation, Nutrition, Epigenetics, and Detoxification

SIGNIFICANCE

Transsulfuration allows conversion of methionine into cysteine using homocysteine (Hcy) as an intermediate. This pathway produces S-adenosylmethionine (AdoMet), a key metabolite for cell function, and provides 50% of the cysteine needed for hepatic glutathione synthesis. The route requires the intake of essential nutrients (e.g., methionine and vitamins) and is regulated by their availability. Transsulfuration presents multiple interconnections with epigenetics, adenosine triphosphate (ATP), and glutathione synthesis, polyol and pentose phosphate pathways, and detoxification that rely mostly in the exchange of substrates or products. Major hepatic diseases, rare diseases, and sensorineural disorders, among others that concur with oxidative stress, present impaired transsulfuration. Recent Advances: In contrast to the classical view, a nuclear branch of the pathway, potentiated under oxidative stress, is emerging. Several transsulfuration proteins regulate gene expression, suggesting moonlighting activities. In addition, abnormalities in Hcy metabolism link nutrition and hearing loss.

CRITICAL ISSUES

Knowledge about the crossregulation between pathways is mostly limited to the hepatic availability/removal of substrates and inhibitors. However, advances regarding protein-protein interactions involving oncogenes, identification of several post-translational modifications (PTMs), and putative moonlighting activities expand the potential impact of transsulfuration beyond methylations and Hcy.

FUTURE DIRECTIONS

Increasing the knowledge on transsulfuration outside the liver, understanding the protein-protein interaction networks involving these enzymes, the functional role of their PTMs, or the mechanisms controlling their nucleocytoplasmic shuttling may provide further insights into the pathophysiological implications of this pathway, allowing design of new therapeutic interventions. Antioxid. Redox Signal. 29, 408-452.

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.

Construction and Development of a Cardiac Tissue-Specific and Hypoxia-Inducible Expression Vector

Purpose: Cardiovascular gene therapy is a sophisticated approach, thanks to the safety of vectors, stable transgene expression, delivery method, and different layers of the heart. To date, numerous expression vectors have been introduced in biotechnology and biopharmacy industries in relation to genetic manipulation. Despite the rapid growth of these modalities, they must be intelligently designed, addressing the cardiac-specific transgene expression and less side effects. Herein, we conducted a pilot project aiming to design a cardiac-specific hypoxia-inducible expression cassette. Methods: We explored a new approach to design an expression cassette containing cardiac specific enhancer, hypoxia response elements (HRE), cardiac specific promoter, internal ribosome entry site (IRES), and beta globin poly A sequence to elicit specific and inducible expression of the gene of interest. Enhanced green fluorescent protein (eGFP) was sub-cloned by BglII and NotI into the cassette. The specificity and inducible expression of the cassette was determined in both mouse myoblast C2C12 and mammary glandular tumor 4T1 as 'twin' cells. eGFP expression was evaluated by immunofluorescence microscope and flow cytometry at 520 nm emission peak. Results: Our data revealed that the designed expression cassette provided tissue specific and hypoxia inducible (O₂<1%) transgene expression. Conclusion: It is suggested that cardiac-specific enhancer combined with cardiac-specific promoter are efficient for myoblast specific gene expression. As well, this is for the first time that HRE are derived from three well known hypoxia-regulated promoters. Therefore, there is no longer need to overlap PCR process for one repeated sequence just in one promoter.

The expression of cystathionine gamma-lyase is regulated by estrogen receptor alpha in human osteoblasts

Hydrogen sulfide (H2S), generated in the osteoblasts predominantly via cystathionine-γ-lyase (CSE), is bone protective. Previous studies suggested that the onset of bone loss due to estrogen deficiency is associated to decreased levels of H2S and blunted gene expression of CSE. However, there are still a lot of unknowns on how H2S levels influence bone cells function. The present study aims to explore the mechanisms by which estrogen may regulate CSE expression, in particular the role of estrogen receptor alpha (ERα) in human osteoblasts (hOBs). Vertebral lamina derived hOBs were characterized and then assessed for CSE expression by western blot analysis in the presence or absence of ERα overexpression. Bioinformatic analysis, luciferase reporter assay and ChIP assay were performed to investigate ERα recruitment and activity on hCSE gene promoter. Three putative half Estrogen Responsive Elements (EREs) were identified in the hCSE core promoter and were found to participate in the ERα - mediated positive regulation of CSE expression. All osteoblast samples responded to ERα over-expression increasing the levels of CSE protein in a comparable manner. Notably, the ERα recruitment on the regulatory regions of the CSE promoter occurred predominantly in female hOBs than in male hOBs. The obtained results suggest that CSE/H2S system is in relation with estrogen signaling in bone in a gender specific manner.

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.

Vascular smooth muscle cell glycocalyx mediates shear stress-induced contractile responses via a Rho kinase (ROCK)-myosin light chain phosphatase (MLCP) pathway

The vascular smooth muscle cells (VSMCs) are exposed to interstitial flow induced shear stress that may be sensed by the surface glycocalyx, a surface layer composed primarily of proteoglycans and glycoproteins, to mediate cell contraction during the myogenic response. We, therefore, attempted to elucidate the signal pathway of the glycocalyx mechanotransduction in shear stress regulated SMC contraction. Human umbilical vein SMCs (HUVSMCs) deprived of serum for 3–4 days were exposed to a step increase (0 to 20 dyn/cm²) in shear stress in a parallel plate flow chamber, and reduction in the cell area was quantified as contraction. The expressions of Rho kinase (ROCK) and its downstream signal molecules, the myosin-binding subunit of myosin phosphatase (MYPT) and the myosin light chain 2 (MLC2), were evaluated. Results showed that the exposure of HUVSMCs to shear stress for 30 min induced cell contraction significantly, which was accompanied by ROCK1 up-regulation, re-distribution, as well as MYPT1 and MLC activation. However, these shear induced phenomenon could be completely abolished by heparinase III or Y-27632 pre-treatment. These results indicate shear stress induced VSMC contraction was mediated by cell surface glycocalyx via a ROCK-MLC phosphatase (MLCP) pathway, providing evidence of the glycocalyx mechanotransduction in myogenic response.

Placental Stem Villus Arterial Remodeling Associated with Reduced Hydrogen Sulfide Synthesis Contributes to Human Fetal Growth Restriction

Intrauterine fetal growth restriction (IUGR) is often associated with compromised umbilical arterial flow, indicating increased placental vascular resistance. Oxidative stress is causatively implicated. Hydrogen sulfide maintains differentiated smooth muscle in vascular beds, and its synthetic enzyme cystathionine-γ-lyase (CSE) is down-regulated in growth-restricted placentas. We hypothesized that remodeling of resistance arteries in stem villi contributes to IUGR by compromising umbilical blood flow via oxidative stress, reducing hydrogen sulfide signaling. Stem villus arteries in human IUGR placentas displaying absent or reversed end-diastolic flow contained reduced myosin heavy chain, smooth muscle actin, and desmin, and increased markers of dedifferentiation, cellular retinol-binding protein 1, and matrix metalloproteinase 2, compared to term and preterm controls. Wall thickness/lumen ratio was increased, lumen diameter decreased, but wall thickness remained unchanged in IUGR placentas. CSE correlated positively with myosin heavy chain, smooth muscle actin, and desmin. Birth weight correlated positively with CSE, myosin heavy chain, smooth muscle actin, and desmin, and negatively with cellular retinol-binding protein 1 and matrix metalloproteinase 2. These findings could be recapitulated in vitro by subjecting stem villus artery explants to hypoxia-reoxygenation, or inhibiting CSE. Treatment with a hydrogen sulfide donor, diallyl trisulfide, prevented these changes. IUGR is associated with vascular remodeling of the stem villus arteries. Oxidative stress results in reduction of placental CSE activity, decreased hydrogen sulfide production, and smooth muscle cell dedifferentiation in vitro. This vascular remodeling is reversible, and hydrogen sulfide donors are likely to improve pregnancy outcomes.

Vascular biology of hydrogen sulfide

Hydrogen sulfide (H₂S) is a ubiquitous signaling molecule with important functions in many mammalian organs and systems. Observations in the 1990s ascribed physiological actions to H₂S in the nervous system, proposing that this gasotransmitter acts as a neuromodulator. Soon after that, the vasodilating properties of H₂S were demonstrated. In the past decade, H₂S was shown to exert a multitude of physiological effects in the vessel wall. H₂S is produced by vascular cells and exhibits antioxidant, antiapoptotic, anti-inflammatory, and vasoactive properties. In this concise review, we have focused on the impact of H₂S on vascular structure and function with an emphasis on angiogenesis, vascular tone, vascular permeability and atherosclerosis. H₂S reduces arterial blood pressure, limits atheromatous plaque formation, and promotes vascularization of ischemic tissues. Although the beneficial properties of H₂S are well established, mechanistic insights into the molecular pathways implicated in disease prevention and treatment remain largely unexplored. Unraveling the targets and downstream effectors of H₂S in the vessel wall in the context of disease will aid in translation of preclinical observations. In addition, acute regulation of H₂S production is still poorly understood and additional work delineating the pathways regulating the enzymes that produce H₂S will allow pharmacological manipulation of this pathway. As the field continues to grow, we expect that H₂S-related compounds will find their way into clinical trials for diseases affecting the blood vessels.

Dichotomous effects of isomeric secondary amines containing an aromatic nitrile and nitro group on human aortic smooth muscle cells via inhibition of cystathionine-γ-lyase

Excessive proliferation of vascular smooth muscle cells (SMC) is an important contributor to the progression of atherosclerosis. Inhibition of proliferation can be achieved by endogenously produced and exogenously supplied nitrogen monoxide, commonly known as nitric oxide (NO). We report herein the dichotomous effects of two isomeric families of secondary amines, precursors to the N-nitrosated NO-donors, on HASMC proliferation. The syntheses of these two families were carried out using two equivalents of homologous, aliphatic monoamines and 2,6-difluoro-3-nitrobenzonitrile (2,6-DFNBN, O family) or 2,4-difluoro-5-nitrobenzonitrile (2,4-DFNBN, P family). The secondary amines belonging to the P family inhibited HASMC proliferation at all concentrations, whereas the O family induced HASMC proliferation at low concentrations, and exhibited inhibitory properties at high concentrations. A probable explanation of these behaviors is proposed herein. l-homocysteine (HCY) is known to induce HASMC proliferation at low concentrations (<1 mM) and inhibit HASMC proliferation at higher concentrations (>2.5 mM). Our findings suggest that these two families of amines inhibit cystathionine-γ-lyase (CSE) to varying extents, which directly results in altered levels of intracellular HCY and consequent changes in HASMC proliferation.

Tumor-associated mesenchymal stem cells inhibit naïve T cell expansion by blocking cysteine export from dendritic cells

Mesenchymal stem cells (MSCs) represent an important cellular constituent of the tumor microenvironment, which along with tumor cells themselves, serve to regulate protective immune responses in support of progressive disease. We report that tumor MSCs prevent the ability of dendritic cells (DC) to promote naïve CD4(+) and CD8(+) T cell expansion, interferon gamma secretion and cytotoxicity against tumor cells, which are critical to immune-mediated tumor eradication. Notably, tumor MSCs fail to prevent DC-mediated early T cell activation events or the ability of responder T cells to produce IL-2. The immunoregulatory activity of tumor MSCs is IL-10- and STAT3-dependent, with STAT3 repressing DC expression of cystathionase, a critical enzyme that converts methionine-to-cysteine. Under cysteine-deficient priming conditions, naïve T cells exhibit defective cellular metabolism and proliferation. Bioinformatics analyses as well as in vitro observations suggest that STAT3 may directly bind to a GAS-like motif within the cystathionase promoter (-269 to -261) leading to IL-10-STAT3 mediated repression of cystathionase gene transcription. Our collective results provide evidence for a novel mechanism of tumor MSC-mediated T cell inhibition within tumor microenvironment.

Transcriptional control of amino acid homeostasis is disrupted in Huntington's disease

Disturbances in amino acid metabolism, which have been observed in Huntington's disease (HD), may account for the profound inanition of HD patients. HD is triggered by an expansion of polyglutamine repeats in the protein huntingtin (Htt), impacting diverse cellular processes, ranging from transcriptional regulation to cognitive and motor functions. We show here that the master regulator of amino acid homeostasis, activating transcription factor 4 (ATF4), is dysfunctional in HD because of oxidative stress contributed by aberrant cysteine biosynthesis and transport. Consistent with these observations, antioxidant supplementation reverses the disordered ATF4 response to nutrient stress. Our findings establish a molecular link between amino acid disposition and oxidative stress leading to cytotoxicity. This signaling cascade may be relevant to other diseases involving redox imbalance and deficits in amino acid metabolism.

Hydrogen sulfide inhibits development of atherosclerosis through up-regulating protein S-nitrosylation

Hydrogen sulfide (H₂S) is an important gaseous signaling molecule that serves many important regulatory roles in physiological and pathophysiological conditions. H₂S exerts an anti-atherosclerotic effect through mediating the biological functions of nitric oxide (NO). However, its mechanism of action is unclear. The purpose of this study is to explore the effect mechanism of H₂S on the development of atherosclerosis with regard to protein S-nitrosylation. A total of 45 male apoE^-/- mice were randomly divided into three groups. Atherosclerosis was induced by Western diet (21% fat and 0.15% cholesterol) with/without administration of a H₂S donor (NaHS) or an endogenous cystathionine γ-lyase inhibitor (d, l-propargylglycine) for 12 weeks. After 12 weeks, plasma lipid and plasma NO levels were measured. Aortic gross lesion area and histopathological features of aortic lesion were determined. Additionally, the level of S-nitrosylated proteins in vascular smooth muscle cells (VSMCs) was detected using immunofluorescence in aorta. Rat VSMCs were performed in an in vitro experiment. Inducible nitric oxide synthase (iNOS) protein expression, NO generation, protein S-nitrosylation, and cell proliferation and migration were measured. We found that H₂S significantly reduced the aortic atherosclerotic lesion area (P=0.006) and inhibited lipid and macrophage accumulation (P=0.004, P=0.002) and VSMC proliferation (P=0.019) in apoE^-/- mice. H₂S could up-regulate levels of plasma NO and protein S-nitrosylation in aorta VSMCs. However, d, l- propargylglycine had the opposite effect, increasing the lesion area and the content of lipids and macrophages in the lesions of apoE^-/- mice and down-regulating plasma NO levels and protein S-nitrosylation in aorta VSMCs. In vitro experiments, H₂S could significantly reverse the reduction of iNOS expression and NO generation induced by oxidized low-density lipoprotein in VSMCs. Moreover, H₂S could increase the protein S-nitrosylation level of VSMCs in a dose-dependent manner, and the effect could be inhibited by iNOS inhibitors. In addition, proliferation and migration of VSMCs could be inhibited by H₂S in a dose-dependent manner, which could be blocked by an iNOS inhibitor or protein S-nitrosylation removal agent. Our data suggest that H₂S could inhibit the development of atherosclerosis by up-regulating plasma NO and protein S-nitrosylation, thereby inhibiting the proliferation and migration of VSMCs.

Hydrogen sulphide in cardiovascular system: A cascade from interaction between sulphur atoms and signalling molecules

As a gasotransmitter, hydrogen sulphide exerts its extensive physiological and pathophysiological effects in mammals. The interaction between sulphur atoms and signalling molecules forms a cascade that modulates cellular functions and homeostasis. In this review, we focus on the signalling mechanism underlying the effect of hydrogen sulphide in the cardiovascular system and metabolism as well as the biological relevance to human diseases.

Hydrogen sulfide: physiological properties and therapeutic potential in ischaemia

Hydrogen sulfide (H2 S) has become a molecule of high interest in recent years, and it is now recognized as the third gasotransmitter in addition to nitric oxide and carbon monoxide. In this review, we discuss the recent literature on the physiology of endogenous and exogenous H2 S, focusing upon the protective effects of hydrogen sulfide in models of hypoxia and ischaemia.

Hydrogen sulfide mediates the cardioprotective effects of gene therapy with PKG-Iα

Cyclic GMP-dependent protein kinase (PKG) is a serine-threonine kinase that mediates the cardioprotective effect of ischemic and pharmacologic preconditioning. Since hydrogen sulfide (H2S) has been implicated in mediating the cardioprotective effects of the cGMP modulators tadalafil and cinaciguat, we tested the hypothesis that myocardial gene therapy with PKG exerts cardioprotection against ischemia/reperfusion (I/R) injury through a mechanism involving H2S. Adult rat cardiomyocytes were infected with adenoviral vector encoding PKGIα or inactive mutant PKGIαK390A (K390A) for 24 h. Necrosis and apoptosis (n = 6/group) were determined after 90 min of simulated ischemia and 1 or 18 h of reoxygenation, respectively. To study the effect of PKGIα in vivo, mice received intramyocardial injections of adenoviral PKGIα or K390A. Four days later, the hearts were subjected to 30 min of ischemia followed by reperfusion for 24 h. The inhibitor of H2S-producing enzyme, cystathionine-γ-lyase (CSE), dl-propargylglycine (PAG, 50 mg/kg, ip) was given 30 min before ischemia. PKGIα overexpression induced CSE expression, whereas cystathionine-β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase expression was not changed. PKGIα overexpression increased H2S in the heart and cardiomyocytes in relation to control and PKGIαK390A. Moreover, PAG abolished protection with PKGIα in vitro by increasing necrosis (35.2 ± 1.7%, P < 0.05) and apoptosis (23.5 ± 1.8 %, P < 0.05) as compared to PKGIα-overexpressing cells (necrosis: 17.2 ± 0.9% and apoptosis: 13.2 ± 0.8%). In vivo, PKGIα overexpression reduced infarct size and preserved left ventricular fractional shortening as compared with K390A (P < 0.05) and PAG abolished the cardioprotective effect of PKGIα. The protective effect of myocardial gene therapy with PKGIα against I/R injury is mediated through a mechanism involving H2S signaling.

Estrogen Replacement Therapy in Ovariectomized Nonpregnant Ewes Stimulates Uterine Artery Hydrogen Sulfide Biosynthesis by Selectively Up-Regulating Cystathionine β-Synthase Expression

Estrogens dramatically dilate numerous vascular beds with the greatest response in the uterus. Endogenous hydrogen sulfide (H2S) is a potent vasodilator and proangiogenic second messenger, which is synthesized from L-cysteine by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). We hypothesized that estrogen replacement therapy (ERT) selectively stimulates H2S biosynthesis in uterine artery (UA) and other systemic arteries. Intact and endothelium-denuded UA, mesenteric artery (MA), and carotid artery (CA) were obtained from ovariectomized nonpregnant ewes (n = 5/group) receiving vehicle or estradiol-17β replacement therapy (ERT). Total RNA and protein were extracted for measuring CBS and CSE, and H2S production was determined by the methylene blue assay. Paraffin-embedded UA rings were used to localize CBS and CSE proteins by immunofluorescence microscopy. ERT significantly stimulated CBS mRNA and protein without altering CSE mRNA or protein in intact and denuded UA. Quantitative immunofluorescence microscopic analyses showed CBS and CSE protein localization in endothelium and smooth muscle and confirmed that ERT stimulated CBS but not CSE protein expression in UA endothelium and smooth muscle. ERT also stimulated CBS, but not CSE, mRNA and protein expression in intact and denuded MA but not CA in ovariectomized ewes. Concomitantly, ERT stimulated UA and MA but not CA H2S production. ERT-stimulated UA H2S production was completely blocked by a specific CBS but not CSE inhibitor. Thus, ERT selectively stimulates UA and MA but not CA H2S biosynthesis by specifically up-regulating CBS expression, implicating a role of H2S in estrogen-induced vasodilation and postmenopausal women's health.

MiR-22/Sp-1 Links Estrogens With the Up-Regulation of Cystathionine γ-Lyase in Myocardium, Which Contributes to Estrogenic Cardioprotection Against Oxidative Stress

Hydrogen sulfide, generated in the myocardium predominantly via cystathionine-γ-lyase (CSE), is cardioprotective. Our previous study has shown that estrogens enhance CSE expression in myocardium of female rats. The present study aims to explore the mechanisms by which estrogens regulate CSE expression, in particular to clarify the role of estrogen receptor subtypes and the transcriptional factor responsible for the estrogenic effects. We found that either the CSE inhibitor or the CSE small interfering RNA attenuated the protective effect of 17β-estradiol (E2) against H2O2- and hypoxia/reoxygenation-induced injury in primary cultured neonatal cardiomyocytes. E2 stimulates CSE expression via estrogen receptor (ER)-α both in cultured cardiomyocytes in vitro and in the myocardium of female mice in vivo. A specificity protein-1 (Sp-1) consensus site was identified in the rat CSE promoter and was found to mediate the E2-induced CSE expression. E2 increases ERα and Sp-1 and inhibits microRNA (miR)-22 expression in myocardium of ovariectomized rats. In primary cardiomyocytes, E2 stimulates Sp-1 expression through the ERα-mediated down-regulation of miR-22. It was confirmed that both ERα and Sp-1 were targeted by miR-22. In the myocardium of ovariectomized rats, the level of miR-22 inversely correlated to CSE, ERα, Sp-1, and antioxidant biomarkers and positively correlated to oxidative biomarkers. In summary, this study demonstrates that estrogens stimulate Sp-1 through the ERα-mediated down-regulation of miR-22 in cardiomyocytes, leading to the up-regulation of CSE, which in turn results in an increase of antioxidative defense. Interaction of ERα, miR-22, and Sp-1 may play a critical role in the control of oxidative stress status in the myocardium of female rats.

Tadalafil Integrates Nitric Oxide-Hydrogen Sulfide Signaling to Inhibit High Glucose-induced Matrix Protein Synthesis in Podocytes

Diabetes-induced kidney cell injury involves an increase in matrix protein expression that is only partly alleviated by current treatment, prompting a search for new modalities. We have previously shown that hydrogen sulfide (H2S) inhibits high glucose-induced protein synthesis in kidney podocytes. We tested whether tadalafil, a phosphodiesterase 5 inhibitor used to treat erectile dysfunction, ameliorates high glucose stimulation of matrix proteins by generating H2S in podocytes. Tadalafil abrogated high glucose stimulation of global protein synthesis and matrix protein laminin γ1. Tadalafil inhibited high glucose-induced activation of mechanistic target of rapamycin complex 1 and laminin γ1 accumulation in an AMP-activated protein kinase (AMPK)-dependent manner. Tadalafil increased AMPK phosphorylation by stimulating calcium-calmodulin kinase kinase β. Tadalafil rapidly increased the expression and activity of the H2S-generating enzyme cystathionine γ-lyase (CSE) by promoting its translation. dl-Propargylglycine, a CSE inhibitor, and siRNA against CSE inhibited tadalafil-induced AMPK phosphorylation and abrogated the tadalafil effect on high glucose stimulation of laminin γ1. In tadalafil-treated podocytes, we examined the interaction between H2S and nitric oxide (NO). N(ω)-Nitro-L-arginine methyl ester and 1H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxalin-1-one, inhibitors of NO synthase (NOS) and soluble guanylyl cyclase, respectively, abolished tadalafil induction of H2S and AMPK phosphorylation. Tadalafil rapidly augmented inducible NOS (iNOS) expression by increasing its mRNA, and siRNA for iNOS and 1400W, an iNOS blocker, inhibited tadalafil stimulation of CSE expression and AMPK phosphorylation. We conclude that tadalafil amelioration of high glucose stimulation of synthesis of proteins including matrix proteins in podocytes requires integration of the NO-H2S-AMPK axis leading to the inhibition of high glucose-induced mechanistic target of rapamycin complex 1 activity and mRNA translation.

Hydrogen sulfide represses androgen receptor transactivation by targeting at the second zinc finger module

Androgen receptor (AR) signaling is indispensable for the development of prostate cancer from the initial androgen-dependent state to a later aggressive androgen-resistant state. This study examined the role of hydrogen sulfide (H(2)S), a novel gasotransmitter, in the regulation of AR signaling as well as its mediation in androgen-independent cell growth in prostate cancer cells. Here we found that H(2)S inhibits cell proliferation of both androgen-dependent (LNCaP) and antiandrogen-resistant prostate cancer cells (LNCaP-B), with more significance on the latter, which was established by long term treatment of parental LNCaP cells with bicalutamide. The expression of cystathionine γ-lyase (CSE), a major H(2)S producing enzyme in prostate tissue, was reduced in both human prostate cancer tissues and LNCaP-B cells. LNCaP-B cells were resistant to bicalutamide-induced cell growth inhibition, and CSE overexpression could rebuild the sensitivity of LNCaP-B cells to bicalutamide. H(2)S significantly repressed the expression of prostate-specific antigen (PSA) and TMPRSS2, two AR-targeted genes. In addition, H(2)S inhibited AR binding with PSA promoter and androgen-responsive element (ARE) luciferase activity. We further found that AR is post-translationally modified by H(2)S through S-sulfhydration. Mutation of cysteine 611 and cysteine 614 in the second zinc finger module of AR-DNA binding domain diminished the effects of H(2)S on AR S-sulfhydration and AR dimerization. These data suggest that reduced CSE/H2S signaling contributes to antiandrogen-resistant status, and sufficient level of H(2)S is able to inhibit AR transactivation and treat castration-resistant prostate cancer.

Signaling molecules: hydrogen sulfide and polysulfide

SIGNIFICANCE

Hydrogen sulfide (H2S) has been recognized as a signaling molecule as well as a cytoprotectant. It modulates neurotransmission, regulates vascular tone, and protects various tissues and organs, including neurons, the heart, and kidneys, from oxidative stress and ischemia-reperfusion injury. H2S is produced from l-cysteine by cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST) along with cysteine aminotransferase.

RECENT ADVANCES

In addition to these enzymes, we recently identified a novel pathway to produce H2S from d-cysteine, which involves d-amino acid oxidase (DAO) along with 3MST. These enzymes are localized in the cytoplasm, mitochondria, and peroxisomes. However, some enzymes translocate to organelles under specific conditions. Moreover, H2S-derived potential signaling molecules such as polysulfides and HSNO have been identified.

CRITICAL ISSUES

The physiological stimulations, which trigger the production of H2S and its derivatives and maintain their local levels, remain unclear.

FUTURE DIRECTIONS

Understanding the regulation of the H2S production and H2S-derived signaling molecules and the specific stimuli that induce their release will provide new insights into the biology of H2S and therapeutic development in diseases involving these substances.