Mechanism Of Hydrogen Sulfide Research Articles

Hydrogen sulfide alleviates cigarette smoke-induced COPD through inhibition of the TGF-β1/smad pathway.

Smoking has become a major cause of chronic obstructive pulmonary disease through weakening of the respiratory mucus-ciliary transport system, impairing cough reflex sensitivity, and inducing inflammation. Recent researches have indicated that hydrogen sulfide is essential in the development of various lung diseases. However, the effect and mechanism of hydrogen sulfide on cigarette smoke-induced chronic obstructive pulmonary disease have not been reported. In this study, rats were treated with cigarette smoke to create a chronic obstructive pulmonary disease model followed by treatment with a low concentration of hydrogen sulfide. Pulmonary function, histopathological appearance, lung edema, permeability, airway remodeling indicators, oxidative products/antioxidases levels, inflammatory factors in lung, cell classification in bronchoalveolar lavage fluid were measured to examine the effect of hydrogen sulfide on chronic obstructive pulmonary disease model. The results showed that hydrogen sulfide effectively improved pulmonary function and reduced histopathological changes, lung edema, and permeability. Airway remodeling, oxidative stress, and inflammation were also reduced by hydrogen sulfide treatment. To understand the mechanisms, we measured the expression of TGF-β1, TGF-βIand TGF-βII receptors and Smad7 and phosphorylation of Smad2/Smad3. The results indicated that the TGF-β1 and Smad were activated in cigarette smoke-induced chronic obstructive pulmonary disease model, but inhibited by hydrogen sulfide. In conclusion, this study showed that hydrogen sulfide treatment alleviated cigarette smoke-induced chronic obstructive pulmonary disease through inhibition of the TGF-β1/Smad pathway. Impact statement COPD has become a severe public health issue in the world and smoking has become a major cause of COPD. As a result, it is a demandingly needed to explore new potential therapy for cigarette smoke-associated COPD. The present study suggested that H2S treatment improved pulmonary function and reduced histopathological changes, lung edema, permeability, inflammation, airway remodeling and oxidative injury in a COPD model induced by cigarette smoke. Although additional studies are required to elucidate the pharmacodynamics, pharmacokinetics, and pharmacology of H2S in the cigarette smoke-associated COPD, our findings provide an experimental basis for the potential clinical application of H2S in COPD treatment.

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.

Hydrogen sulfide attenuates cigarette smoke-induced airway remodeling by upregulating SIRT1 signaling pathway

Airway remodeling is one of the characteristics for chronic obstructive pulmonary disease (COPD). The mechanism underlying airway remodeling is associated with epithelial-mesenchymal transition (EMT) in the small airways of smokers and patients with COPD. Sirtuin 1 (SIRT1) is able to reduce oxidative stress, and to modulate EMT. Here, we investigated the effects and mechanisms of hydrogen sulfide (H2S) on pulmonary EMT in vitro and in vivo. We found that H2S donor NaHS inhibited cigarette smoke (CS)-induced airway remodeling, EMT and collagen deposition in mouse lungs. In human bronchial epithelial 16HBE cells, NaHS treatment also reduced CS extract (CSE)-induced EMT, collagen deposition and oxidative stress. Mechanistically, NaHS upregulated SIRT1 expression, but inhibited activation of TGF-β1/Smad3 signaling in vivo and in vitro. SIRT1 inhibition by a specific inhibitor EX527 significantly attenuated or abolished the ability of NaHS to reverse the CSE-induced oxidative stress. SIRT1 inhibition also abolished the protection of NaHS against CSE-induced EMT. Moreover, SIRT1 activation attenuated CSE-induced EMT by modifying TGF-β1-mediated Smad3 transactivation. In conclusion, H2S prevented CS-induced airway remodeling in mice by reversing oxidative stress and EMT, which was partially ameliorated by SIRT1 activation. These findings suggest that H2S may have therapeutic potential for the prevention and treatment of COPD.

Mechanisms of Hydrogen Sulfide against the Progression of Severe Alzheimer’s Disease in Transgenic Mice at Different Ages

Backgroud: Alzheimer disease is an age-related severe neurodegenerative pathology. The level of the third endogenous gas, hydrogen sulfide (H₂S), is decreased in the brain of Alzheimer’s disease (AD) patients compared with the brain of the age-matched normal individuals; also, plasma H₂S levels are negatively correlated with the severity of AD. Recently, we have demonstrated that systemic H₂S injections are neuroprotective in an early phase of preclinical AD. Objectives: This study focuses on the possible neuroprotection of a chronic treatment with an H₂S donor and sulfurous water (rich of H₂S) in a severe transgenic 3×Tg-AD mice model. Method: 3×Tg-AD mice at 2 different ages (6 and 12 months) were daily treated intraperitoneally with an H₂S donor and sulfurous water (rich of H₂S) for 3 months consecutively. We investigated the cognitive ability, brain morphological alterations, amyloid/tau cascade, excitotoxic, inflammatory and apoptotic responses. Results: Three months of treatments with H₂S significantly protected against impairment in learning and memory in a severe 3×Tg-AD mice model, at both ages studied, and reduced the size of Amyloid β plaques with preservation of the morphological picture. This neuroprotection appeared mainly in the cortex and hippocampus, associated with reduction in activity of c-jun N-terminal kinases, extracellular signal-regulated kinases and p38, which have an established role not only in the phosphorylation of tau protein but also in the inflammatory and excitotoxic response. Conclusion: Our findings indicate that appropriate treatments with various sources of H₂S, might represent an innovative approach to counteract early and severe AD progression in humans.

Involvement of K+ATP and Ca2+ channels in hydrogen sulfide-suppressed ageing of porcine oocytes

BackgroundHydrogen sulfide has been shown to improve the quality of oocytes destined for in vitro fertilization. Although hydrogen sulfide is capable of modulating ion channel activity in somatic cells, the role of hydrogen sulfide in gametes and embryos remains unknown. Our observations confirmed the hypothesis that the KATP and L-type Ca2+ ion channels play roles in porcine oocyte ageing and revealed a plausible contribution of hydrogen sulfide to the modulation of ion channel activity.ResultsWe confirmed the benefits of the activation and suppression of the KATP and L-type Ca2+ ion channels, respectively, for the preservation of oocyte quality.ConclusionsOur experiments identified hydrogen sulfide as promoting the desired ion channel activity, with the capacity to protect porcine oocytes against cell death. Further experiments are needed to determine the exact mechanism of hydrogen sulfide in gametes and embryos.

Hydrogen sulfide upregulated lncRNA CasC7 to reduce neuronal cell apoptosis in spinal cord ischemia-reperfusion injury rat

Hydrogen sulfide has been recognized as an important neuroprotective agent in the nervous system. The present study aimed to study the effect and the underlying mechanisms of hydrogen sulfide on spinal cord ischemia-reperfusion injury (SCII). The gene mRNA and protein expression were examined by RT-PCR and western blot, respectively. Spinal cord infarct zone was analyzed by Triphenyltetrazolium chloride staining. Cell apoptosis was detected by MTT assay. The relationship between miR-30c and CasC7 was analyzed by RNA immunoprecipitation (RIP) and RNA pull-down. We observed that SCII rat model have a bigger spinal cord infarct zone than the control rat, but NaSH preprocessing could reduce spinal cord infarct zone in SCII rat. OGD/R induced cell apoptosis, and NaSH preprocessing reduced the OGD/R-induced SH5Y-SY cells apoptosis. CasC7 was decreased in SCII rat and OGD/R-induced SH5Y-SY cells, while miR-30c expression was increased. NaSH preprocessing upregulated CasC7 and downregulated miR-30c in OGD/R-induced SH5Y-SY cells. In OGD/R induced SH5Y-SY cells with NaSH preprocessing, knockdown of CasC7 could upregulate miR-30c expression, promote cell apoptosis and downregulate miR-30c's target gene expression. The RIP and RNA pull-down demonstrated that CasC7 functioned as a miR-30c decoy, and miR-30c inhibitor could reverse the effect of si-CasC7. Moreover, intrathecal injection of si-CasC7 upregulated miR-30c expression and increased spinal cord infarct zone in SCII rat with NaSH preprocessing. Hydrogen sulfide protects spinal cord by upregulating CasC7 expression in SCII rat model.

Protective effects and mechanisms of hydrogen sulfide on isoproterenol-induced cardiac hypertrophy in mice

Protective effects and mechanisms of hydrogen sulfide on isoproterenol-induced cardiac hypertrophy in mice

Toxic effects and possible mechanisms of hydrogen sulfide and/or ammonia on porcine oocyte maturation in vitro

Previous studies suggest that hydrogen sulfide (H2S) and ammonia (NH3) are two major air pollutants which can cause damage to porcine health. However, the mechanisms underlying toxic effects of these compounds on porcine oocyte maturation are not clear. To clarify the mechanism, we evaluated the oocyte quality by detecting some events during oocytes maturation. In our study, porcine oocytes were cultured with different concentrations of Na2S and/or NH4Cl in vitro and the rate of the first polar body extrusion decreased significantly. Also, actin filament was seriously disrupted to damage the cytoskeleton which resulted in reduced rate of oocyte maturation. We explored the reactive oxygen species (ROS) generation and found that the ROS level was increased significantly after Na2S treatment but not after NH4Cl treatment. Moreover, early stage apoptosis rate was significantly increased and autophagy protein LC3 B expression level was higher in oocytes treated with Na2S and/or NH4Cl, which might be caused by ROS elevation. Additionally, exposure to Na2S and/or NH4Cl also caused ROS generation and early apoptosis in cumulus cells, which might further affect oocyte maturation in vitro. In summary, our data suggested that exposure to H2S and/or NH3 decreased porcine oocyte maturation in vitro, which might be caused by actin disruption, ROS generation, early apoptosis and autophagy.

Role and mechanism of hydrogen sulfide in cigarette smoke induced chronic obstructive pulmonary disease related pulmonary vascular remodeling in rats

Objective: To investigate the role and mechanism of hydrogen sulfide (H2S) in rats with chronic obstructive pulmonary disease (COPD) related pulmonary vascular remodeling. Methods: Twenty four healthy male Sprague-Dawley rats were randomly divided into 4 groups: control group, cigarette smoke (CS) group, CS+ Sodium hydrosulfide (NaHS) group and CS+ DL-propargylglycine (PPG) group. Rats in control group were fed normally and breathed clear air, and for the rest groups, passive cigarette smoke inhalation method were adopted to establish COPD model. After 8 weeks, the rats in corresponding groups were treated by NaHS or PPG. After 16 weeks, the markers of pulmonary vascular remodeling in all groups were measured. Proliferation marker proliferative cell nuclear antigen (PCNA) and oxidative stress marker 3-neurotrophin (3-NT) in all groups were measured by immunohistochemistry (IHC). Results: Compared with control group, the airway resistance was increased (0.859±0.283 vs 0.578±0.088, P<0.05) and the pathological scores was much higher in CS group, which suggested that the COPD model was successful. The degree of small resistance pulmonary artery medial wall thickness and full vascular muscularization of CS group were much higher (0.54±0.20 vs 0.37±0.12, 0.39±0.08; 0.61±0.16 vs 0.20±0.12, 0.34±0.13, all P<0.01)than control group and CS+ NaHS group, there was no significant difference between CS+ PPG group and CS group. In accordance with the results of morphometric analysis, the proliferation marker PCNA was more in CS group when compared with control group and CS+ NaHS group (0.27±0.08 vs 0.12±0.06, 0.14±0.06, both P<0.05), there was no significant difference between CS+ PPG group and CS group. Furthermore, the IHC also showed that 3-NT significantly increased in CS group compared with control group and CS+ NaHS group (0.26±0.08 vs 0.18±0.04, 0.19±0.06, both P<0.01), there was no significant difference between CS+ PPG group and CS group as well. In addition, the small resistance pulmonary artery medial wall thickness had strong correlation with the expression level of oxidative stress marker 3-NT (r=0.906, P<0.001). Conclusion: H2S significantly attenuates cigarette smoke induced COPD related pulmonary vascular remodeling, which could be related to its ability to decrease oxidative stress.

An isotope study of the accumulation mechanisms of high-sulfur gas from the Sichuan Basin, southwestern China

The mechanism of hydrogen sulfide (H2S) generation plays a key role in the exploration and development of marine high-sulfur natural gas, of which the major targets are the composition and isotope characteristics of sulfur-containing compounds. Hydrocarbon source rocks, reservoir rocks, natural gases and water-soluble gases from Sichuan Basin have been analyzed with an online method for the content of H2S and isotopic composition of different sulfur-containing compounds. The results of comparative analysis show that the sulfur-containing compounds in the source rocks are mainly formed by bacterial sulfate reduction (BSR), and the sulfur compounds in natural gas, water and reservoir are mainly formed by thermal sulfate reduction (TSR). Moreover, it has been shown that the isotopically reversion for methane and ethane in high sulfur content gas is caused by TSR. The sulfur isotopic composition of H2S in natural gas is inherited from the gypsum or brine of the same or adjacent layer, indicating that the generation and accumulation of H2S have the characteristics of either a self-generated source or a near-source.

Formation and Transport Mechanism of Hydrogen Sulfide in Coal Seam

H2S gas would pose a threat to coal mine safety. This article from the biodegradation, microbial sulfate reduction, thermal decomposition chemistry, chemical sulfate reduction and magmatic 5 aspects to analyze the formation mechanism of hydrogen sulfide gas in coal mine, a coal mine combined with field data, analysis of hydrogen sulfide gas in the coal mining the transport mechanisms. Research for the comprehensive management of coal mine hydrogen sulfide gas has certain significance.

Exogenous hydrogen sulfide promotes cell proliferation and differentiation by modulating autophagy in human keratinocytes

The effects and the underlying mechanisms of hydrogen sulfide (H2S) on keratinocyte proliferation and differentiation are still less known. In the current study, we investigated the effects and the underlying mechanisms of exogenous H2S on keratinocyte proliferation and differentiation. Human keratinocytes (HaCaT cells) were treated with various concentrations (0.05, 0.25, 0.5 and 1mM) of sodium hydrosulfide (NaHS, a donor of H2S) for 24h. A CCK-8 assay was used to assess cell viability. Western blot analysis was performed to determine the expression levels of proteins associated with differentiation and autophagy. Transmission electron microscopy was performed to observe autophagic vacuoles, and flow cytometry was applied to evaluate apoptosis. NaHS promoted the viability, induced the differentiation, and enhanced autophagic activity in a dose-dependent manner in HaCaT cells but had no effect on cell apoptosis. Blockage of autophagy by ATG5 siRNA inhibited NaHS-induced cell proliferation and differentiation. The current study demonstrated that autophagy in response to exogenous H2S treatment promoted keratinocyte proliferation and differentiation. Our results provide additional insights into the potential role of autophagy in keratinocyte proliferation and differentiation.

Adsorption of hydrogen sulfide by biochars derived from pyrolysis of different agricultural/forestry wastes

ABSTRACTThe characteristics and mechanisms of hydrogen sulfide (H2S) adsorption on three different biochars derived from agricultural/forestry wastes through pyrolysis at various temperatures (100 to 500 ºC) were investigated. In this study, the H2S breakthrough capacity was measured using a laboratory-characterized using pH and Fourier transform infrared spectroscopy analysis. The results obtained demonstrate that all biochars were effective in H2S sorption. The sorption capacity of the biochar for H2S removal is related to the pyrolysis temperature and pH of the surface. Certain threshold ranges of the pyrolysis temperature (from 100 to 500 ºC) and pH of the surface are presented. It also concluded that the sorption capacity (for removing H2S) of rice hull-derived biochar is the largest in three biochars (camphor-derived biochar, rice hull-derived biochar, and bamboo-derived biochar). These observations will be helpful in designing biochar as engineered sorbents for the removal of H2S.Implications: This paper focuses on the adsorption of hydrogen sulfide (H2S) by biochars derived from wastes. The characteristics and mechanisms of hydrogen sulfide (H2S) adsorption on three different boichars derived from agricultural/forestry wastes through pyrolysis at various temperatures were investigated. In this study, the H2S breakthrough capacity was measured using laboratory characterization with pH and Fourier-transform infrared spectroscopy analysis. The results obtained demonstrate that all biochars were effective in H2S sorption. The sorption capacity of the biochar for H2S removal is related to the pyrolysis temperature and pH of the surface.

Mechanisms of hydrogen sulfide (H2S) action on synaptic transmission at the mouse neuromuscular junction.

Hydrogen sulfide (H2S) is a widespread gasotransmitter also known as a powerful neuroprotective agent in the central nervous system. However, the action of H2S in peripheral synapses is much less studied. In the current project we studied the modulatory effects of the H2S donor sodium hydrosulfide (NaHS) on synaptic transmission in the mouse neuromuscular junction using microelectrode technique. Using focal recordings of presynaptic response and evoked transmitter release we have shown that NaHS (300 μM) increased evoked end-plate currents (EPCs) without changes of presynaptic waveforms which indicated the absence of NaHS effects on sodium and potassium currents of motor nerve endings. Using intracellular recordings it was shown that NaHS increased the frequency of miniature end-plate potentials (MEPPs) without changing their amplitudes indicating a pure presynaptic effect. Furthermore, NaHS increased the amplitude of end-plate potentials (EPPs) without influencing the resting membrane potential of muscle fibers. L-cysteine, a substrate of H2S synthesis induced, similar to NaHS, an increase of EPC amplitudes whereas inhibitors of H2S synthesis (β-cyano-L-alanine and aminooxyacetic acid) had the opposite effect. Inhibition of adenylate cyclase using MDL 12,330A hydrochloride (MDL 12,330A) or elevation of cAMP level with 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (pCPT-cAMP) completely prevented the facilitatory action of NaHS indicating involvement of the cAMP signaling cascade. The facilitatory effect of NaHS was significantly diminished when intracellular calcium (Ca(2+)) was buffered by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis acetoxymethyl ester (BAPTA-AM) and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid acetoxymethyl ester (EGTA-AM). Activation of ryanodine receptors by caffeine or ryanodine increased acetylcholine release and prevented further action of NaHS on transmitter release, likely due to an occlusion effect. Inhibition of ryanodine receptors by ryanodine or dantrolene also reduced the action of NaHS on EPC amplitudes. Our results indicate that in mammalian neuromuscular synapses endogenously produced H2S increases spontaneously and evoked quantal transmitter release from motor nerve endings without changing the response of nerve endings. The presynaptic effect of H2S appears mediated by intracellular Ca(2+) and cAMP signaling and involves presynaptic ryanodine receptors.

P94 Hydrogen sulfide facilitates carotid sinus baroreceptor reflex and activity of renovascular hypertensive rats

To explore the role and possible mechanism of hydrogen sulfide (H 2 S) in modulating carotid sinus baroreceptor reflex and activity of renovascular hypertensive rats. Renovascular hypertension was induced in male Sprague–Dawley rats by placing renal artery clip (two-kidney, one-clip; 2K1C).The functional curve of the carotid sinus baroreflex was measured by recording changes in arterial pressure with perfused carotid sinus. The functional curve of carotid baroreceptor (FCCB) was constructed by recording sinus nerve afferent discharge with perfused isolated carotid sinus. The expression of SUR2B and Kir6.1 of carotid sinus was examined. The systolic blood pressure (SBP) was significantly increased in the 2K1C group (172 ± 6.32 mmHg) comparing with the NaHS-treated group (134 ± 5.74 mmHg) ( P < 0.01). The plasma H 2 S concentration was decreased in the 2K1C group comparing with other groups. Perfusing the left carotid sinus with K-H solution and elevating the ISP from 0 to 250 mmHg. The reflexly decreased extent of blood pressure was obviously decreased in 2K1C group compared with other groups. The 2K1C group induced obvious changes in baroreflex parameters, marked decrease in RD and PS, and increased in TP, EP and SP, shifting the functional curve of the baroreflex to the right and upward. At the same time, the 2K1C group induced obvious changes in carotid sinus baroreceptor parameters, decreased PIV and PS, and increased TP and SP, shifting FCCB to the right and downward. All of these results were changed after the treatment of NaHS. SUR2B protein expression was higher in carotid sinus of the 2K1C + NaHS group than that of the 2K1C group. These data suggested that exogenous H 2 S exerted a facilitatory role on isolated baroreceptor reflex and activity in renovascular hypertensive rats through opening K ATP channels in vascular smooth muscle cells.

ERK1/2 pathway mediates the protective effect of hydrogen sulfide against cisplatin-induced injury in human marrow mesenchymai stem cells

Objective To explore the protection and mechanism of hydrogen sulfide （H2S） preconditioning against injury induced by cisplatin in human marrow mesenchymal stem cells （HMMSCs）. Methods HMMSCs were treated by cisplatin at 0, 5, 10, 20, 40, 60, 80 mg/L concentrations for 24 h respectively and were exposed to eisplatin at 20 mg/L concentrations for 0, 6, 12, 24, 36, 48 h respectively. HMMSCs were pretreated with NariS at 0, 0.4, 0.6, 0.8, 1.0 mmol/L respectively for 30 min before ex- posed to cisplatin at 20 mg/L concentrations for 24 h. HMMSCs were treated by U0126 or combined with human epidermal growth factor （HEGF） together for 30 min before they were preconditioned with NariS for 30 min. The cell survival rate, cell apoptosis rate, the expression of p-ERK1/2 and t-ERK1/2 were recorded. Results The cell survival rate decreased to 71.72%±2.72%, 59.41%±5.44%, 50.37%±4.55%, 38.97%±2.92%, 30.11%±4.64% and 21.71%_±5.35% respectively after cells were treated with eisplatin at 5, 10, 20, 40, 60, 80 mg/L concentrations respectively, and the differences were statistically significant compared with 0 mg/L group. The cell viability fell to 70.30%_±6.20%, 61.63%±2.70%, 51.29%_±3.13%, 38.72%±3.66% and 27.57%_±2.32% af- ter HMMSCs were treated with cisplatin at 20 mg/L for 6, 12, 24, 36, 48 h respectively, and the differences were statistically signif- icant compared with 0 h group. The cell viability increased to 65.99%±2.67%, 72.93%_±5.44%, 75.10%±4.71% and 76.56%-± 5.25% when HMMSCs got pretreatment of NariS, and the differences had statistical significance compared with cisplatin group. The cell apoptotic rate decreased from 35.29%±2.77% to 18.62%±0.97% when HMMSCs were pretreated with Naris at 0.6 mmo/ L. Treatment of HMMSCs with cisplatin at 20 mg/L for 24 h reduced p-ERK1/2 expression. The pretreatment of Naris could inhib- it the inhibitory action to the expression of p-ERK1/2 induced by eisplatin. Pretreatment with U0126 or HEGF inhibited or promot- ed the protection and the upregulated expression of p-ERK1/2 caused by NariS pretreatment. Conclusion The preconditioning of H2S can protect cell damage caused by cisplatin via activating the ERKI/2 pathway of HMMSCs. Key words: MAP kinase signaling system; Hydrogen sulfide; Mesenchymal stem cells; Cisplatin; Cytoproteetion

Hydrogen sulfide alleviates myocardial collagen remodeling in association with inhibition of TGF-β/Smad signaling pathway in spontaneously hypertensive rats.

The study was designed to explore the role and possible mechanisms of hydrogen sulfide (H2S) in the regulation of myocardial collagen remodeling in spontaneously hypertensive rats (SHRs). We treated nine-week-old male SHRs and age- and sex-matched Wistar-Kyoto rats (WKYs) with NaHS (90 μmol/kg(-1)·day(-1)) for 9 wks. At 18 wks, plasma H2S, tail arterial pressure, morphology of the heart, myocardial ultrastructure and collagen volume fraction (CVF), myocardial expressions of collagen I and III protein and procollagen I and III mRNA, transforming growth factor-β1 (TGF-β1), TGF-β type I receptor (TβR-I), type II receptor (TβR-II), p-Smad2 and 3, matrix metalloproteinase (MMP)-13 and tissue inhibitors of MMP (TIMP)-1 proteins were determined. TGF-β1-stimulated cultured cardiac fibroblasts (CFs) were used to further study the mechanisms. The results showed that compared with WKYs, SHRs showed a reduced plasma H2S, elevated tail artery pressure and increased myocardial collagen, TGF-β1, TβR-II, p-Smad2 and p-Smad3 expressions. However, NaHS markedly decreased tail artery pressure and inhibited myocardial collagen, TGF-β1, TβR-II, p-Smad2 and p-Smad3 protein expressions, but H2S had no effect on the expressions of MMP-13 and TIMP-1. Hydralazine reduced blood pressure but had no effect on myocardial collagen, MMP-13 and TIMP-1 expressions and TGF-β1/Smad signaling pathway. H2S prevented activation of the TGF-β1/Smad signaling pathway and abnormal collagen synthesis in CFs. In conclusion, the results suggested that H2S could prevent myocardial collagen remodeling in SHR. The mechanism might be associated with inhibition of collagen synthesis via TGF-β1/Smad signaling pathway.

P01 Mechanisms of hydrogen sulfide mediated contraction in rat small pulmonary arteries

The gas H2S (hereafter ‘sulfide’) typically acts as an vasodilator in the systemic circulation, but in pulmonary arteries elicits a biphasic contraction via an unknown mechanism. This is potentially a physiologically important effect, since it has also been proposed that the concentration of sulfide increases in pulmonary arteries under hypoxic conditions, thereby acting as an oxygen sensor which is important for initiating (and possibly mediating) hypoxic pulmonary vasoconstriction. We therefore assessed the mechanism of the sulfide-induced contraction in rat 2nd order pulmonary arteries (PA), using NaHS as a source of sulfide. Techniques used included recording of isometric force development and mitochondrial membrane potential in PA rings mounted in a small vessel myograph and measurement of reactive oxygen species (ROS) levels in segments of PA using the luminescent ROS indicator LO12 (10 μM). NaHS (500 μM) evoked a complex PA contraction comprising a small contraction followed by a second and larger contraction which gradually relaxed. The contraction was abolished by the mitochondrial complex three blocker antimycin (10 μg/ml) and was greatly reduced by the anti-oxidant TEMPOL (3 mM), the RyR blocker dantrolene (50 μM,) or the Rho kinase blocker Y27632 (1 μM). On the othe hand, the sulfide contraction was little affected by treatment of arteries with the mitochondrial complex 1 blocker rotenone (1 μM) or by their incubation in Ca2+-free PSS containing 0.2 mM EGTA. Incubation of pulmonary arteries in NaHS also caused activation of the monomeric G protein RhoA (measured using a G-lisa assay) and also of its downstream effector rho kinase (as shown by an increase in MYPT phosphorylation). A 15 min incubation of control cultured pulmonary artery smooth muscle cells (PASMC) in 1 mM NaHS (1 mM), followed by a 10 min wash to remove NaHS from the solution, led to a significant increase in cellular ROS production recorded using LO12. This increase in ROS was not present in PASMC in which expression of the the mitochondrial membrane flavoprotein sulfide-quinone oxoreductase (SQR) had been knocked down using siRNA. Application of a range of concentrations (10–1000 μM) of NaHS to pulmonary arteries led to a transient depolarisation of the mitochondrial membrane potential (recorded using TMRE) which was variably preceded and/or followed by hyperpolarisation. In the presence of rotenone, which caused depolarisation of the mitochondrial potential, low concentrations of NaHS (10–100 μM) caused a transient repolarisation, whereas high concentrations caused a complex response consisting of a transient repolarisation followed by a depolarisation and a second long-lasting repolarisation. Based on these results, we conclude that sulfide causes contraction by causing Ca2+ sensitisation and the release of Ca2+ from the sarcoplasmic reticulum via ryanodine receptors. Furthermore, we speculate that these responses are mediated by ROS produced by complex 3 owing to an increased flow of electrons into the mitochondrial electron transport chain consequent upon the metabolism of sulfide by SQR.

Neuroprotective mechanism of hydrogen sulfide after cerebral ischemia-reperfusion in rats

To explore the neuroprotective mechanism of exogenous hydrogen sulfide after cerebral ischemia-reperfusion (I/R) in rats. A total of 240 male Sprague-Dawley rats were randomly divided into 4 groups of sham-operation group (I), I/R model group (II), low-dose sodium hydrosulfide (NaHS) group (III) and high-dose NaHS group (IV) (n = 60 each). Reversible middle cerebral artery occlusion (MCAO) model was established by intraluminal suture. However, the rats of group I were operated without a blockage of middle cerebral artery. The occlusions in other groups were removed after 2 h. And at 20 min pre-removal, normal saline, 50 µmol/kg NaHS, and 100 µmol/kg NaHS were injected into the abdomens of rats in groups II, III and IV respectively. At 6 h, 24 h, 48 h and 7 d post-reperfusion, behavioral test was performed to evaluate the neurological deficiency. And triphenyltetrazolium chloride (TTC) staining was used to observe the volume of cerebral infarction. In addition, the protein expressions of tumor necrosis factor-alpha (TNF-α) and heat shock protein 20 (HSP20) in ischemic cortex were measured by immunohistochemistry and Western blot. Compared with I/R group, the neurological deficiency scores and volume of cerebral infarction of groups III and IV significantly decreased. Furthermore, the protein expression of HSP20 was markedly up-regulated in the groups III and IV while there was a marked down-regulation of TNF-α after reperfusion. NaHS may exert anti-necrotic and anti-inflammatory function by inducing the expression of HSP20, inhibiting the expression of TNF-α and reducing the size of cerebral infarction so as to protect neurons after I/R injury.

Therapeutic applications of organosulfur compounds as novel hydrogen sulfide donors and/or mediators

Hydrogen sulfide, once considered as toxic gas, is now recognized as an important biological mediator. The deficiency of hydrogen sulfide could lead to various pathological changes, such as arterial and pulmonary hypertension, Alzheimer’s disease, gastric mucosal injury and liver cirrhosis. However, excessive production of hydrogen sulfide, by using inorganic hydrogen sulfide donors such as NaHS, may contribute to the pathogenesis of inflammatory diseases, septic shock, cerebral stroke and mental retardation in patients with Down syndrome. Therefore, an increasing interest in organic molecules that are capable of regulating the formation of hydrogen sulfide has extended in recent years. Allium vegetables are one natural source of organic sulfur-containing compounds and have been widely investigated regarding their therapeutic applications, and it has been proven that the ingredients of garlic, such as diallyl disulfide, diallyl trisulfide and S-ally cysteine act as hydrogen sulfide donors or mediators in pharmaceutical studies. In addition, S-propargyl cysteine (ZYZ-802) and S-propyl cysteine, two synthetic cysteine analogs, have been examined and could be used to treat ischemic heart disease via modulation of the hydrogen sulfide pathway. In addition, drugs containing hydrogen sulfide-releasing moieties have been synthesized and widely reported in recent years, such as S-nonsteroidal anti-inflammatory drugs and the derivative of Lawesson’s reagents, which exhibit varied biological effects in experiments. As cystathionine β-synthase and cystathionine γ-lyase are the enzymes that are able to catalyze the production of endogenous hydrogen sulfide from cysteine, their inhibitors, such as dl-propylargylglycine and β-cyanoalanine, have been frequently used in studies on the biological mechanism of hydrogen sulfide. All these hydrogen sulfide donors, mediators and inhibitors have provided useful tools in the research of a variety of biological effects and are promising drug candidates of hydrogen sulfide.