Exogenous Administration Of H2S Research Articles

Hydrogen sulfide suppresses H2O2-induced proliferation and migration of HepG2 cells through Wnt/β-catenin signaling pathway.

Both H2S and H2O2 affect many cellular events, such as cell differentiation, cell proliferation and cell death. However, there is some controversy about the roles of H2S and H2O2, since the detailed mechanisms they are involved remain unclear. In this study, low concentration of H2O2 (40μM) increased the viability of hepatocellular carcinoma cells HepG2, while both H2S and high concentration of H2O2 decreased the cell viability in a dose-dependent manner. Wound healing assay indicated that 40μM H2O2 promoted migration of HepG2 cells, which was suppressed by exogenous H2S. Further analysis revealed that administration of exogenous H2S and H2O2 changed the redox status of Wnt3a in HepG2 cells. Altered expression of proteins including Cyclin D1, TCF-4, and MMP7, which are downstream of the Wnt3a/β-catenin signaling pathway, were found after treatment with exogenous H2S and H2O2. Compared with H2S, low concentration of H2O2 showed opposite effects on these protein expression levels in HepG2 cells. These results suggest that H2S suppressed H2O2-induced proliferation and migration of HepG2 through regulating Wnt3a/β-catenin signaling pathway.

GYY4137, a H2S donor, ameliorates kidney injuries in diabetic mice by modifying renal ROS-associated enzymes

Diabetic nephropathy (DN) is a common microvascular complication of both type 1 and type 2 diabetes mellitus and often advances to end-stage renal disease. Oxidative stress plays an important role in the pathogenesis and progress of DN. Hydrogen sulfide (H2S) is considered as a promising candidate for the management of DN. But the antioxidant effects of H2S in DN have not been fully studied. In mouse model induced by high-fat diet and streptozotocin, GYY4137, a H2S donor, ameliorated albuminuria at weeks 6 & 8 and decreased serum creatinine at week 8, but not hyperglycemia. Renal nitrotyrosine and urinary 8-isoprostane were reduced along with the suppressed levels of renal laminin and kidney-injury-molecule 1. Renal NADPH oxidase (NOX) 2 was lower but heme oxygenase (HO) 2, paraoxonase (PON) 1, PON2 were higher in DN+GYY than DN group. NOX1, NOX4, HO1, superoxide dismutases 1–3 were similar between groups. Except for a rise at HO2, all the affected enzymes were unchanged in mRNA levels. The affected reactive-oxygen-species (ROS) enzymes were mainly located in the renal sodium-hydrogen-exchanger positive proximal tubules with similar distribution but changed immunofluorence in GYY4137 treated DN mice. Kidney morphological alterations in DN mice under light and electrical-microscopes were also improved by GYY4137. Thus, exogenous H2S administration may improve the renal oxidative damage in DN by reducing ROS production and enhancing ROS cleavage in kidney via the affected enzymes. This study may shed a light on therapeutic applications in diabetic nephropathy with H2S donors in the future.

Hydrogen Sulfide Inhibited Sympathetic Activation in D-Galactose-Induced Aging Rats by Upregulating Klotho and Inhibiting Inflammation in the Paraventricular Nucleus

The present study aimed to explore the central relationship between cardiovascular conditions and aging. D-galactose (D-gal) was utilized to induce an accelerated aging model and to evaluate the effects of hydrogen sulfide (H2S) on aging-related cardiovascular risk factors and mechanisms. Eight-week-old Sprague Dawley rats were given an intraperitoneal injection of 250 mg/kg D-gal every day with or without H2S (56 μmol/kg) for 12 weeks. We found that D-gal treatment induced a noticeably aging-related increase in p16, p53 and p21 protein levels and senescence-associated beta-galactosidase staining. In addition, the level of noradrenalin was increased, accompanied by enhanced blood pressure and renal sympathetic nerve activity in aged rats. The greater sympathetic responses were related with the increased level of inflammation. The decreased level of klotho in the paraventricular nucleus neuron also contributed to sympathetic activation in D-gal-induced aged rats. However, the exogenous administration of H2S attenuated the sympathetic activity in aged rats, as evidenced by the decreased blood pressure, renal sympathetic nerve activity and noradrenalin level. The ameliorated cellular senescence, inflammation and heightened klotho in the paraventricular nucleus were attributed to the protective effects of H2S. The present study provides further evidence for the drug development of H2S for the prevention or treatment of the aging-associated cardiovascular diseases.

Hydrogen Sulfide Donor GYY4137 Rescues NRF2 Activation in Respiratory Syncytial Virus Infection.

Respiratory syncytial virus (RSV) can cause severe respiratory illness in infants, immunocompromised, and older adults. Despite its burden, no vaccine or specific treatment is available. RSV infection is associated with increased reactive oxygen species (ROS) production, degradation of the transcription factor nuclear factor erythroid 2-related factor 2 (NRF2), and decreased antioxidant enzymes (AOEs), leading to oxidative damage and lung injury. Hydrogen sulfide (H2S) is an endogenous gaseous molecule that plays a physiological role in numerous cellular processes and a protective role in multiple pathological conditions, displaying vasoactive, cytoprotective, anti-inflammatory, and antioxidant activities. H2S can promote NRF2 activation through the sulfhydration of Kelch-like ECH-associated protein 1, the cytoplasmic repressor of NRF2. Here we investigated whether increasing cellular H2S levels could rescue NRF2 and NRF2-dependent gene expression in RSV-infected primary airway epithelial cells. We found that treatment with the H2S donor GYY4137 significantly increased NRF2 levels and AOEs gene expression by decreasing KEAP1 levels, and by modulating pathways involved in RSV-induced NRF2 degradation, such as NRF2 ubiquitination, and promyelocytic leukemia (PML) protein levels. These results suggest that the administration of exogenous H2S can positively impact the altered redox balance associated with RSV infection, which represents an important determinant of RSV-induced lung disease.

Engineered Carbon Nanostructures for Preventing Alzheimer’s Disease

Alzheimer’s disease (AD) is an aging-associated devastating disease that affects over 5 million Americans and imposes an annual economic burden of $236 billion. Currently, all efforts to develop remedies to AD have failed. This unfortunate situation calls for the development of new research directions. One of the common pathological features of AD is the decline in endogenous production of hydrogen sulfide (H2S), a gaseous signaling molecule. H2S in the brain is historically believed to be solely derived via enzymatic production and deficiencies in H2S producing enzymes, such as cystathionine-γ-lyase (CGL) and cystathionine-β-synthase (CBS) are associated with neurodegenerative diseases. Exogenous administration of H2S and H2S donors have shown to attenuate Alzheimer’s and Parkinson’s disease phenotypes in rodent models. However, exogenous H2S gas and donor molecules are short-lived, highly reactive, and display acute toxicity at elevated levels, and delivery to the intended tissue may be challenging to achieve in the clinic. Thus, discovering new technologies that regulate and/or augment endogenous enzymatic H2S pose novel scientific and therapeutic avenues particularly for the treatment of neurodegenerative disorders such as Alzheimer’s disease.We are designing enzyme-mimicking carbon nanostructures (EMCNs) that can augment the production of H2S using biological substrates present in the body and compensate for the declining enzyme activity and prevent the progression of Alzheimer’s disease. Carbon nanostructures with sp2 carbons are composed of multiple electron-deficient double bonds, which can be systematically replaced with functional groups to create a heterogeneous surface that is fundamentally different from that originally present. Based on the sp2 site engineering concept, we selected and synthesized EMCNs capable of interacting with the sulfur-containing biomolecules, catalyzing their breakdown into H2S and other products, thus mimicking CGL and CBS enzymes.The ability of EMCNs to mimic enzymes was evaluated with lead acetate saturated paper-based assay. EMCNs break down cysteine to produce H2S, which reacts with lead acetate to form lead sulfide. The concentration of H2S generated is calculated by using sodium hydrosulfide as an equimolar H2S donor for calibration. The H2S generation from EMCNs can be matched with the CBS enzyme. Further, EMCNs are stable and demonstrate long-term activity. In a repeated exposure experiment, H2S production was constant over a 20 day period where the substrate was added every day without replenishing ECMNs. If EMCNs were a reactant, the H2S production should have decreased with repeated substrate addition until all the EMCN was consumed.The efficacy of EMCNs to produce H2S in vitro was demonstrated with murine neuronal cells. P3 multi-photon fluorescent probe was utilized to detect intracellular H2S levels. The fluorescence intensity of the neuronal cells exposed to EMCN increased in a concentration-dependent manner. Neither cells nor EMCN exhibited auto-fluorescence under multi-photon microscopy. Beta-amyloid (Aβ) plaques, a hallmark of brain pathology in Alzheimer's disease patients, is formed by aggregation of β-amyloid peptides. The role of EMCNs in the AD model was evaluated with β-amyloid toxicity assay using Aβ1-42, which is selectively toxic to neurons. Preliminary studies suggest that EMCNs protect neuronal cells against the toxicity induced by Aβ1-42 by 19%. The ability of EMCNs to produce H2S under physiological conditions thus offers potential for rescuing enzyme deficiencies in Alzheimer’s disease.

Brain Histology and Immunohistochemistry After Resuscitation From Hemorrhagic Shock in Swine With Pre-Existing Atherosclerosis and Sodium Thiosulfate (Na2S2O3) Treatment.

BackgroundThe hydrogen sulfide (H2S) and the oxytocin/oxytocin receptor (OT/OTR) systems interact in the central nervous and cardiovascular system. As a consequence of osmotic balance stress, H2S stimulates OT release from the paraventricular nuclei (PVN) in the hypothalamic regulation of blood volume and pressure. Hemorrhagic shock (HS) represents one of the most pronounced acute changes in blood volume, which, moreover, may cause at least transient brain tissue hypoxia. Atherosclerosis is associated with reduced vascular expression of the main endogenous H2S producing enzyme cystathionine-γ-lyase (CSE), and, hence, exogenous H2S administration could be beneficial in these patients, in particular after HS. However, so far cerebral effects of systemic H2S administration are poorly understood. Having previously shown lung-protective effects of therapeutic Na2S2O3 administration in a clinically relevant, long-term, porcine model of HS and resuscitation we evaluated if these protective effects were extended to the brain.MethodsIn this study, available unanalyzed paraffin embedded brain sections (Na2S2O3 N = 8 or vehicle N = 5) of our recently published HS study were analyzed via neuro-histopathology and immunohistochemistry for the endogenous H2S producing enzymes, OT, OTR, and markers for brain injury and oxidative stress (glial fibrillary acidic protein (GFAP) and nitrotyrosine).ResultsNeuro-histopathological analysis revealed uninjured brain tissue with minor white matter edema. Protein quantification in the hypothalamic PVN showed no significant inter-group differences between vehicle or Na2S2O3 treatment.ConclusionsThe endogenous H2S enzymes, OT/OTR co-localized in magnocellular neurons in the hypothalamus, which may reflect their interaction in response to HS-induced hypovolemia. The preserved blood brain barrier (BBB) may have resulted in impermeability for Na2S2O3 and no inter-group differences in the PVN. Nonetheless, our results do not preclude that Na2S2O3 could have a therapeutic benefit in the brain in an injury that disrupts the BBB, e.g., traumatic brain injury (TBI) or acute subdural hematoma (ASDH).

Physiological, Pathological and Pharmacological Interactions of Hydrogen Sulphide and Nitric Oxide in the Myocardium of Rats with Left Ventricular Hypertrophy.

Left ventricular hypertrophy (LVH) is characterized by increased myocardium thickness due to increased oxidative stress and downregulation of cystathione γ lyase (CSE) endothelial nitric oxide synthase (eNOS). Upregulation of CSE by hydrogen sulphide (H2S) and ENOS by L-arginine can arrest the progression of LVH individually. The present study explored the combined treatment of H2S and NO in the progression of LVH, and demonstrated that the response is due to H2S, NO or formation of either new molecule in physiological, pathological, and pharmacological in vivo settings of LVH. Exogenous administration H2S+NO in LVH significantly reduced (all p < 0.05) systolic blood pressure (SBP) and mean arterial pressure (MAP), LV index, heart index and oxidative stress when compared to the LVH group. There was downregulation of CSE mRNA and eNOS in the heart, and exogenous administration of H2S+NO groups upregulated eNOS MRNA while CSE MRNA remained downregulated in the hearts of the LVH group. Similar trends were observed with concentrations of H2S and NO in the plasma and tissue. It can be concluded that combined treatment of LVH with H2S and NO significantly ameliorate the progression of LVH by attenuating systemic hemodynamic and physical indices, and by decreasing oxidative stress. Molecular expression data in the myocardium of LVH depicts that combined treatment upregulated eNOS/NO while it downregulated CSE/H2S pathways in in vivo settings, and it is always eNOS/NO pathways which play a major role.

H2S as a Therapeutic Adjuvant Against COVID-19: Why and How?

H2S as a Therapeutic Adjuvant Against COVID-19: Why and How?

Hydrogen Sulfide-Evoked Intracellular Ca2+ Signals in Primary Cultures of Metastatic Colorectal Cancer Cells.

Simple SummaryColorectal cancer (CRC) is the most common type of gastrointestinal cancer and the third most predominant cancer in the world. CRC is potentially curable with surgical resection of the primary tumor. The clinical problem of colorectal cancer, however, is the spread and outgrowth of metastases, which are difficult to eradicate and lead to a patient’s death. The failure of conventional treatment to significantly improved outcomes in mCRC has prompted the search for alternative molecular targets with the goal of ameliorating the prognosis of these patients. The present investigation revealed that exogenous delivery of hydrogen sulfide (H2S) suppresses proliferation in metastatic colorectal cancer cells by inducing an increase in intracellular Ca2+ concentration. H2S was effective on metastatic, but not normal, cells. Therefore, we propose that exogenous administration of H2S to patients affected by metastatic colorectal carcinoma could represent a promising therapeutic alternative.Exogenous administration of hydrogen sulfide (H2S) is emerging as an alternative anticancer treatment. H2S-releasing compounds have been shown to exert a strong anticancer effect by suppressing proliferation and/or inducing apoptosis in several cancer cell types, including colorectal carcinoma (CRC). The mechanism whereby exogenous H2S affects CRC cell proliferation is yet to be clearly elucidated, but it could involve an increase in intracellular Ca2+ concentration ([Ca2+]i). Herein, we sought to assess for the first time whether (and how) sodium hydrosulfide (NaHS), one of the most widely employed H2S donors, induced intracellular Ca2+ signals in primary cultures of human metastatic CRC (mCRC) cells. We provided the evidence that NaHS induced extracellular Ca2+ entry in mCRC cells by activating the Ca2+-permeable channel Transient Receptor Potential Vanilloid 1 (TRPV1) followed by the Na+-dependent recruitment of the reverse-mode of the Na+/Ca2+ (NCX) exchanger. In agreement with these observations, TRPV1 protein was expressed and capsaicin, a selective TRPV1 agonist, induced Ca2+ influx by engaging both TRPV1 and NCX in mCRC cells. Finally, NaHS reduced mCRC cell proliferation, but did not promote apoptosis or aberrant mitochondrial depolarization. These data support the notion that exogenous administration of H2S may prevent mCRC cell proliferation through an increase in [Ca2+]i, which is triggered by TRPV1.

Hydrogen Sulfide Attenuated Angiotensin II-Induced Sympathetic Excitation in Offspring of Renovascular Hypertensive Rats.

ObjectiveNumerous findings have demonstrated a strong association between parental health during pregnancy and cardiovascular disease in adult offspring. This study investigated whether sensitivity to angiotensin II (Ang II) is enhanced in offspring of renovascular hypertensive animals and whether hydrogen sulfide (H2S) can attenuate the increased response to Ang II in offspring.MethodThe systolic blood pressure (SBP) was measured by non-invasive tail-cuff plethysmograpy every two weeks in all offspring from 8 to 16 weeks. After intracerebroventricular microinjection of Ang II in the offspring, blood pressure, heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded to test the response to Ang II in the offspring. Western blot analysis was used to examine the protein expression of AT1R, AT1R-associated protein (ATRAP), Nox2, p67phox, and nitrotyrosine in the nucleus tractus solitarii (NTS).ResultsThe SBP in the offspring of hypertensive rats were significantly higher than that in control group, and the above effects were significantly improved by prenatal or postnatal administration of H2S. Intralateroventricular microinjection of Ang II induced greater sympathetic responses in offspring of hypertensive rats than control group. The expression of AT1R and oxidative stress-related protein was increased, whereas that of ATRAP was decreased in the NTS in offspring of hypertensive rats. Exogenous administration of H2S prenatally or postnatally improved the above effects.ConclusionPrenatal or postnatal administration of H2S attenuated AngII-induced sympathetic excitation in offspring of hypertensive rats, which may occur by modulating the balance between AT1R and ATRAP and downregulating oxidative stress-related protein expression in the NTS.

Searching for novel hydrogen sulfide donors: The vascular effects of two thiourea derivatives

The gasotransmitter hydrogen sulfide (H2S) is involved in the regulation of the vascular tone and an impairment of its endogenous production may play a role in hypertension. Thus, the administration of exogenous H2S may be a possible novel and effective strategy to control blood pressure. Some natural and synthetic sulfur compounds are suitable H2S-donors, exhibiting long-lasting H2S release; however, novel H2S-releasing agents are needed to improve the pharmacological armamentarium for the treatment of cardiovascular diseases.For this purpose, N-phenylthiourea (PTU) and N,N’-diphenylthiourea (DPTU) compounds have been investigated as potential H2S-donors. The thioureas showed long-lasting H2S donation in cell free environment and in human aortic smooth muscle cells (HASMCs). In HASMCs, DPTU caused membrane hyperpolarization, mediated by activation of KATP and Kv7 potassium channels. The thiourea derivatives promoted vasodilation in rat aortic rings, which was abolished by KATP and Kv7 blockers. The vasorelaxing effects were also observed in angiotensin II-constricted coronary vessels.In conclusion, thiourea represents an original H2S-donor functional group, which releases H2S with slow and long lasting kinetic, and promotes typical H2S-mediated vascular effects. Such a moiety will be extremely useful for developing original cardiovascular drugs and new chemical tools for investigating the pharmacological roles of H2S.

H2S attenuates sepsis-induced cardiac dysfunction via a PI3K/Akt-dependent mechanism.

The heart is the most vulnerable target organ in sepsis, and it has been previously reported that hydrogen sulfide (H2S) has a protective role in heart dysfunction caused by sepsis. Additionally, studies have demonstrated that the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway has a protective function during sepsis. However, the potential association between H2S and PI3K/Akt in sepsis-induced cardiac dysfunction is unclear. Therefore, the PI3K inhibitor LY294002 was used to investigate the role of PI3K/Akt signaling in the protective effects of H2S during sepsis-induced myocardial injury. A rat sepsis model was established using cecal ligation and puncture (CLP) surgery. Sodium hydrosulfide, a H2S donor, was administered intraperitoneally (8.9 µmol/kg), and serum myocardial enzyme levels, inflammatory cytokine levels, cardiac histology and cardiomyocyte apoptosis were assessed to determine the extent of myocardial damage. The results demonstrated that exogenous H2S reduced serum myocardial enzyme levels, decreased the levels of the inflammatory factors tumor necrosis factor (TNF)-α and interleukin (IL)-6, and increased the level of anti-inflammatory IL-10 following CLP. Staining of histological sections demonstrated that myocardial damage and cardiomyocyte apoptosis were alleviated by the administration of exogenous H2S. Western blot analysis was used to detect phosphorylated and total PI3K and Akt levels, as well as NF-κB, B-cell lymphoma-2, Bcl-2-associated X protein (Bax) and caspase levels, and the results demonstrated that H2S significantly increased PI3K and Akt phosphorylation. This indicated that the PI3K/Akt signaling pathway was activated by H2S. Additionally, H2S reduced Bax and caspase expression, indicating that apoptosis was inhibited, and decreased NF-κB levels, indicating that inflammation was reduced. Furthermore, the PI3K inhibitor LY294002 eliminated the protective effects of H2S. In conclusion, the results of the current study suggest that exogenous H2S activates PI3K/Akt signaling to attenuate myocardial damage in sepsis.

Interaction of the hydrogen sulfide system with the oxytocin system in the injured mouse heart

BackgroundBoth the hydrogen sulfide/cystathionine-γ-lyase (H2S/CSE) and oxytocin/oxytocin receptor (OT/OTR) systems have been reported to be cardioprotective. H2S can stimulate OT release, thereby affecting blood volume and pressure regulation. Systemic hyper-inflammation after blunt chest trauma is enhanced in cigarette smoke (CS)-exposed CSE−/− mice compared to wildtype (WT). CS increases myometrial OTR expression, but to this point, no data are available on the effects CS exposure on the cardiac OT/OTR system. Since a contusion of the thorax (Txt) can cause myocardial injury, the aim of this post hoc study was to investigate the effects of CSE−/− and exogenous administration of GYY4137 (a slow release H2S releasing compound) on OTR expression in the heart, after acute on chronic disease, of CS exposed mice undergoing Txt.MethodsThis study is a post hoc analysis of material obtained in wild type (WT) homozygous CSE−/− mice after 2-3 weeks of CS exposure and subsequent anesthesia, blast wave-induced TxT, and surgical instrumentation for mechanical ventilation (MV) and hemodynamic monitoring. CSE−/− animals received a 50 μg/g GYY4137-bolus after TxT. After 4h of MV, animals were exsanguinated and organs were harvested. The heart was cut transversally, formalin-fixed, and paraffin-embedded. Immunohistochemistry for OTR, arginine-vasopressin-receptor (AVPR), and vascular endothelial growth factor (VEGF) was performed with naïve animals as native controls.ResultsCSE−/− was associated with hypertension and lower blood glucose levels, partially and significantly restored by GYY4137 treatment, respectively. Myocardial OTR expression was reduced upon injury, and this was aggravated in CSE−/−. Exogenous H2S administration restored myocardial protein expression to WT levels.ConclusionsThis study suggests that cardiac CSE regulates cardiac OTR expression, and this effect might play a role in the regulation of cardiovascular function.

Sulphur balneotherapy and patient’s immunity: H2S effects on human CD4+ T cell polarization to Th17 and Treg phenotype

H2S - known for decades as a toxic gas - is endogenously generated from cysteine and belongs to the family of gasotransmitters, such as nitric oxide (NO) and carbon monoxide (CO) (Szabo C, 2007). H2S-donors, sulfur balneotherapy and sulfur spa waters might be beneficial in the treatment of colitis, asthma, psoriasis and systemic lupus erythematosus (Fiorucci S, 2007; Zhang G, 2013; Han Y, 2013). However, the role of H2S in inflammation is still under debate and the molecular mechanisms of H2S in immune regulation remain largely unknown. H2S has been reported to exert both pro-inflammatory and anti-inflammatory effects. The inhibition of endogenous H2S production suppresses inflammatory response (Miller et al., 2012). On the other hand, administration of exogenous H2S has been shown to possess anti-inflammatory effects (Zanardo et al., 2006) i.e. down-regulation of pro-inflammatory cytokine expression (IL-1, TNF, IFN IL-12, IL-23) and increased expression of IL-10, a classical anti-inflammatory cytokine. We have previously demonstrated both in vitro and in vivo on primary psoriatic lesions that hydrogen sulfide not only reduce the basal expression and secretion of IL-8, but also interfere with IL-17- and IL-22-induced IL-8 production. Moreover, we showed that hydrogen sulfide dramatically decreased CD4 T cell proliferation in response to mitogens and reduced IL-2 production (Mirandola P et al., 2007). A fine balance between IL-17 producing CD4+ T cells (Th17) and Treg has recently emerged as a crucial point in inflammation associated with various autoimmune and immune-mediated diseases. The Th17 and Treg developmental pathways are reciprocally interconnected. Th17 cells represent a pro-inflammatory subset, that contributes to autoimmunity and tissue damage (Burkett PR, 2015). On the contrary, Treg cells have a suppressor activity important in the establishment and maintenance of self-tolerance. Recently, H2S has been suggested to be involved in T cells lineage polarization and T cell-associated immune homeostasis. Yang et al. demonstrated that H2S is required for FoxP3 stable expression and Treg differentiation in mouse models. Reduced levels of H2S were responsible for the impairment of CD4+Foxp3+ Treg cell differentiation and function and the onset of systemic autoimmune disease in mice (Yang R, 2015). Given the pivotal role of Th17/Treg cell ratio in the onset and clinical evolution of immune-mediated pathologies, we investigated the effects of exogenous H2S on human resting CD4 T cell polarization to Th17 and/or Treg phenotype. We differentiated ex-vivo human resting CD4+ (Th0) T cells to Th17 or Treg lineages treating cell cultures with the H2S-releasing donor NaHS. By RT-PCR, we observed that NaHS treatment increased Foxp3 mRNA levels in CD4+ T cells cultured under Treg-polarizing conditions. However, NaHS was also able to increase RORγT mRNA levels in CD4+ T cells under Th17 polarizing conditions, suggesting a role of sulfurs in the activation of both polarization pathways.

Gas signaling molecule hydrogen sulfide attenuates doxorubicin-induced dilated cardiomyopathy.

Increasing evidence has revealed that hydrogen sulfide (H2S) has beneficial effects in the treatment of various cardiovascular diseases. However, whether H2S can attenuate the development of dilated cardiomyopathy (DCM) remains unclear. In this study, we generated a rat model of DCM induced by doxorubicin and investigated the protective effects of H2S against DCM. Cardiac structure and function were analyzed by two-dimensional echocardiography. Oxidative stress was evaluated by measuring malondialdehyde, superoxide dismutase, glutathione peroxidase and reactive oxygen species. Cardiomyocyte apoptosis was assessed by flow cytometry following Annexin V/PI staining. Our results showed that exogenous administration of H2S could improve left ventricular structure and function in DCM rats. H2S was found to suppress doxorubicin-induced oxidative stress by activating the Nrf2 pathway and upregulating the expression of antioxidant proteins NQO1 and GCLM. Moreover, H2S was also found to inhibit doxorubicin-induced cardiomyocyte apoptosis by activating the PI3K/Akt signaling pathway. In conclusion, our study demonstrates that H2S protects against doxorubicin-induced DCM via attenuation of oxidative stress and apoptosis.

Phosphonothioate-Based Hydrogen Sulfide Releasing Reagents: Chemistry and Biological Applications

Hydrogen sulfide (H2S) is a newly recognized gasotransmitter. Studies have demonstrated that the production of endogenous H2S and the exogenous administration of H2S can regulate many physiological and/or pathological processes. Therefore, H2S releasing agents (also known as H2S donors) are important research tools in advancing our understanding of the biology and clinical potential of H2S. Among currently available donors, GYY4137 is probably the most well-known and has been used in many studies in the past 10 years. Recently, a number of GYY4137 derivatives (e.g., phosphonothioate-based compounds) have been developed as H2S donors. In this review, we summarize the development and application of these donors, which include Lawesson’s reagent, substituted phosphorodithioates, cyclic phosphorane analogs, and pH-controlled phosphonamidothioates (JK donors). These donors have advantages such as good water-solubility, slow and controllable H2S release capability, and a variety of reported biological activities. However, it should be noted that the detailed H2S release profiles and byproducts under real biological systems are still unclear for many of these donors. Only after we figure out these unknowns we will see better applications of these donors in H2S research and therapy.

Protective Actions of H2S in Acute Myocardial Infarction and Heart Failure.

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

H2S-Releasing Polymer Micelles for Studying Selective Cell Toxicity.

We report the preparation of S-aroylthiooxime (SATO) functionalized amphiphilic block copolymer micelles that release hydrogen sulfide (H2S), a gaseous signaling molecule of relevance to various physiological and pathological conditions. The micelles release H2S in response to cysteine with a half-life of 3.3 h, which is substantially slower than a related small molecule SATO. Exogenous administration of H2S impacts growth and proliferation of cancer cells; however, the limited control over H2S generation from inorganic sulfide sources results in conflicting reports. Therefore, we compare the cellular cytotoxicity of SATO-functionalized micelles, which release H2S in a sustained manner, to Na2S, which releases H2S in a single dose. Our results show that H2S-releasing micelles significantly reduce the survival of HCT116 colon cancer cells relative to Na2S, GYY4137, and a small molecule SATO, indicating that release kinetics may play an important role in determining toxicity of H2S toward cancer cells. Furthermore, H2S-releasing micelles are well tolerated by immortalized fibroblasts (NIH/3T3 cells), suggesting a selective toxicity of H2S toward cancer cells.

Exogenous H2S regulates endoplasmic reticulum-mitochondria cross-talk to inhibit apoptotic pathways in STZ-induced type I diabetes.

The upregulation of reactive oxygen species (ROS) is a primary cause of cardiomyocyte apoptosis in diabetes cardiomyopathy (DCM). Mitofusin-2 (Mfn-2) is a key protein that bridges the mitochondria and endoplasmic reticulum (ER). Hydrogen sulfide (H2S)-mediated cardioprotection is related to antioxidant effects. The present study demonstrated that H2S inhibited the interaction between the ER and mitochondrial apoptotic pathway. This study investigated cardiac function, ultrastructural changes in the ER and mitochondria, apoptotic rate using TUNEL, and the expression of ER stress-associated proteins and mitochondrial apoptotic proteins in cardiac tissues in STZ-induced type I diabetic rats treated with or without NaHS (donor of H2S). Mitochondria of cardiac tissues were isolated, and MPTP opening and cytochrome c (cyt C) and Mfn-2 expression were also detected. Our data showed that hyperglycemia decreased the cardiac function by ultrasound cardiogram, and the administration of exogenous H2S ameliorated these changes. We demonstrated that the expression of ER stress sensors and apoptotic rates were elevated in cardiac tissue of DCM and cultured H9C2 cells, but the expression of these proteins was reduced following exogenous H2S treatment. The expression of mitochondrial apoptotic proteins, cyt C, and mPTP opening was decreased following treatment with exogenous H2S. In our experiment, the expression and immunofluorescence of Mfn-2 were both decreased after transfection with Mfn-2-siRNA. Hyperglycemia stimulated ER interactions and mitochondrial apoptotic pathways, which were inhibited by exogenous H2S treatment through the regulation of Mfn-2 expression.

Up Regulation of cystathione γ lyase and Hydrogen Sulphide in the Myocardium Inhibits the Progression of Isoproterenol-Caffeine Induced Left Ventricular Hypertrophy in Wistar Kyoto Rats.

Hydrogen sulphide (H2S) is an emerging molecule in many cardiovascular complications but its role in left ventricular hypertrophy (LVH) is unknown. The present study explored the effect of exogenous H2S administration in the regression of LVH by modulating oxidative stress, arterial stiffness and expression of cystathione γ lyase (CSE) in the myocardium. Animals were divided into four groups: Control, LVH, Control-H2S and LVH-H2S. LVH was induced by administering isoprenaline (5mg/kg, every 72 hours, S/C) and caffeine in drinking water (62mg/L) for 2 weeks. Intraperitoneal NaHS, 56μM/kg/day for 5 weeks, was given as an H2S donor. Myocardial expression of Cystathione γ lyase (CSE) mRNA was quantified using real time polymerase chain reaction (qPCR).There was a 3 fold reduction in the expression of myocardial CSE mRNA in LVH but it was up regulated by 7 and 4 fold in the Control-H2S and LVH-H2S myocardium, respectively. Systolic blood pressure, mean arterial pressure, pulse wave velocity were reduced (all P<0.05) in LVH-H2S when compared to the LVH group. Heart, LV weight, myocardial thickness were reduced while LV internal diameter was increased (all P<0.05) in the LVH-H2S when compared to the LVH group. Exogenous administration of H2S in LVH increased superoxide dismutase, glutathione and total antioxidant capacity but significantly reduced (all P<0.05) plasma malanodialdehyde in the LVH-H2S compared to the LVH group. The renal cortical blood perfusion increased by 40% in LVH-H2S as compared to the LVH group. Exogenous administration of H2S suppressed the progression of LVH which was associated with an up regulation of myocardial CSE mRNA/ H2S and a reduction in pulse wave velocity with a blunting of systemic hemodynamic. This CSE/H2S pathway exhibits an antihypertrophic role by antagonizing the hypertrophic actions of angiotensin II(Ang II) and noradrenaline (NA) but attenuates oxidative stress and improves pulse wave velocity which helps to suppress LVH. Exogenous administration of H2S augmented the reduced renal cortical blood perfusion in the LVH state.