Sulfide Metabolism Research Articles

Effect of three-day Glutathione introduction on hydrogen sulfide metabolism in liver of rats under experimental nephropathy conditions

Topicality. Scientists are becoming more interested in the exchange of sulfur-containing amino acids and hydrogen sulfide (H 2 S) metabolism and glutathione. But the effect of tripeptide on the H 2 S metabolism by nephropathy is not studied enough. Aim. To study the effect of tree-day glutathione introduction on the system of H 2 S-producing enzymes, concentration and production in the liver of rats under conditions of experimental nephropathy. Materials and methods. The experiment was conducted on albino mature male rats. The animals in experimental group were administered a single intraperitoneal dose of folic acid (250 mg/kg). Glutathione was introduced intragastral (100 mg/kg) during 3 days after intoxication. Results and discussion. Under conditions of experimental nephropathy, there was a decrease in concentration of hydrogen sulfide by 37.92 % and the production of hydrogen sulfide by 34.84 % compared with the control group. The introduction of glutathione led to an increase in these indicators by 36.32 % and 48.4 % compared with the animals with nephropathy. The activity of cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS) and cysteinaminotransferase (CAT) in the liver of rats with nephropathy was reduced by 38.98 %, 33.73 % and 26.76 % compared with animal control group. Glutathione increased the activity of CSE and CBS by 31 % and 33.55 % compared with a group of animals with nephropathy. The activity of cystathionine aminotransferase in the conditions of tripeptide increased by 49.3 % introduction and exceeded the date of the control group. Conclusions. The activity of H 2 S-producing enzymes in experimental nephropathy in the liver of rats is decreased. The introduction of glutathione increased the content of hydrogen sulfide and promoted the growth of the activity of H 2 S-producing enzymes in the liver of rats with nephropathy. As reasons for this effect, the possibility of including tripeptide as a source of cysteine in the synthesis of hydrogen sulfide is considered.

Synthesis, Metabolism, and Signaling Mechanisms of Hydrogen Sulfide: An Overview.

In addition to nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H2S) has recently emerged as the novel gasotransmitter involved in the regulation of the nervous system, cardiovascular functions, inflammatory response, gastrointestinal system, and renal function. H2S is synthesized from L-cysteine and/or L-homocysteine by cystathionine β-synthase, cystathionine γ-lyase, and cysteine aminotransferase together with 3-mercaptopyruvate sulfurtransferase. In addition, H2S is enzymatically metabolized in mitochondria by sulfide:quinone oxidoreductase, persulfide dioxygenase, and sulfite oxidase to thiosulfate, sulfite, and sulfate which enables to regulate its level by factors such as oxygen pressure, mitochondria density, or efficacy of mitochondrial electron transport. H2S modifies protein structure and function through the so-called sulfuration or persulfidation, that is, conversion of cysteine thiol (-SH) to persulfide (-SSH) groups. This, as well as other signaling mechanisms, is partially mediated by more oxidized H2S-derived species, polysulfides (H2Sn). In addition, H2S is able to react with reactive oxygen and nitrogen species to form other signaling molecules such as thionitrous acid (HSNO), nitrosopersulfide (SSNO-), and nitroxyl (HNO). All H2S-synthesizing enzymes are expressed in the vascular wall, and H2S has been demonstrated to regulate vascular tone, endothelial barrier permeability, angiogenesis, vascular smooth muscle cell proliferation and apoptosis, and inflammatory reaction. H2S-modifying therapies are promising approach for diseases such as arterial hypertension, diabetic angiopathy, and atherosclerosis.

Metabolism of sulfur compounds in homocystinurias.

Homocystinurias are rare genetic defects characterized by altered fluxes of sulfur compounds including homocysteine and cysteine. We explored whether the severely perturbed sulfur amino acid metabolism in patients with homocystinurias affects the metabolism of hydrogen sulfide. We studied 10 treated patients with a block in the conversion of homocysteine to cysteine due to cystathionine β-synthase deficiency (CBSD) and six treated patients with remethylation defects (RMD) and an enhanced flux of sulfur metabolites via transsulfuration. Control groups for CBSD and RMD patients consisted of 22 patients with phenylketonuria on a low-protein diet and of 12 healthy controls respectively. Plasma and urine concentrations of selected sulfur compounds were analysed by HPLC and LC-MS/MS. Patients with CBSD exhibited plasma concentrations of monobromobimane-detected sulfide similar to appropriate controls. Urinary homolanthionine and thiosulfate in CBSD were increased significantly 1.9 and 3 times suggesting higher hydrogen sulfide synthesis by γ-cystathionase and detoxification respectively. Surprisingly, patients with RMD had significantly lower plasma sulfide levels (53 and 64% of controls) with lower sulfite concentrations, and higher taurine and thiosulfate levels suggesting enhanced cysteine oxidation and hydrogen sulfide catabolism respectively. The results from this study suggest that severe inherited defects in sulfur amino acid metabolism may be accompanied by only moderately perturbed hydrogen sulfide metabolism and lends support to the hypothesis that enzymes in the transsulfuration pathway may not be the major contributors to the endogenous hydrogen sulfide pool. 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.

Central Role of Adenosine 5'-Phosphosulfate Reductase in the Control of Plant Hydrogen Sulfide Metabolism.

Hydrogen sulfide (H2S) has been postulated to be the third gasotransmitter in both animals and plants after nitric oxide (NO) and carbon monoxide (CO). In this review, the physiological roles of H2S in plant growth, development and responses to biotic, and abiotic stresses are summarized. The enzymes which generate H2S are subjected to tight regulation to produce H2S when needed, contributing to delicate responses of H2S to environmental stimuli. H2S occupies a central position in plant sulfur metabolism as it is the link of inorganic sulfur to the first organic sulfur-containing compound cysteine which is the starting point for the synthesis of methionine, coenzyme A, vitamins, etc. In sulfur assimilation, adenosine 5′-phosphosulfate reductase (APR) is the rate-limiting enzyme with the greatest control over the pathway and probably the generation of H2S which is an essential component in this process. APR is an evolutionarily conserved protein among plants, and two conserved domains PAPS_reductase and Thioredoxin are found in APR. Sulfate reduction including the APR-catalyzing step is carried out in chloroplasts. APR, the key enzyme in sulfur assimilation, is mainly regulated at transcription level by transcription factors in response to sulfur availability and environmental stimuli. The cis-acting elements in the promoter region of all the three APR genes in Solanum lycopersicum suggest that multiple factors such as sulfur starvation, cytokinins, CO2, and pathogens may regulate the expression of SlAPRs. In conclusion, as a critical enzyme in regulating sulfur assimilation, APR is probably critical for H2S generation during plants’ response to diverse environmental factors.

A novel transcription factor Rwdd1 and its SUMOylation inhibit the expression of sqr, a key gene of mitochondrial sulfide metabolism in Urechis unicinctus

Sulfide-quinone oxidoreductase (SQR) is a key enzyme of sulfide metabolism in metazoans, and responsible for oxidizing sulfide into thiosulfate and transmitting the generated electrons to the ubiquinone. It has been revealed that the sqr mRNA level increases significantly in echiuran worm Urechis unicinctus exposed to sulfide, and HSF1, NF1 and Sp1 have been verified to participate in its transcriptional regulation. In this study, we obtained 23 potential transcription factors interacting possibly with the proximal region (−391 to +50) of sqr promoter, and focused on the RWD domain-containing 1 (Rwdd1), a protein with the maximum number of clones in yeast one-hybrid (Y1H) screening, to investigate its transcriptional regulation to U. unincitus sqr. The ChIP and EMSA assays identified that the Rwdd1 can bind directly to the promoter (+18/+36) of U. unicinctus sqr. The point mutation and transient transfection experiments discovered that TACG was the key sequence of the DNA element bound by the Rwdd1. Furthermore, the U. unicinctus Rwdd1 (UuRwdd1) was identified to be a transcription repressor inhibiting the sqr promoter activity, and the SUMOylation of UuRwdd1 at the lysine of 90th enhanced its inhibitory effect on sqr transcription further. Western blotting found Rwdd1 responded to sulfide in hindguts from U. unincitus, and the protein content showed a remarkable drop in hindgut nuclei in the early sulfide exposure, and then increased significantly both in the total protein and the nuclear protein extract. We suggested that the Rwdd1 is a novel transcription factor, and these data improve our understanding of the sqr transcriptional regulation and the mitochondrial sulfide metabolism.

P-376 - Crosstalk between gasotransmitters at the H2S-synthesizing human cystathionine β-synthase: heme-based regulation by CO and NO

Cystathionine β-synthase (CBS) plays a central role in hydrogen sulfide (H2S) metabolism in human (patho) physiology. Each CBS monomer is composed of a central catalytic domain containing a pyridoxal 5’-phosphate active site flanked by two regulatory domains: an N-terminal domain harboring a b-type heme, and a C-terminal S-adenosyl-L-methionine (AdoMet)-binding domain. CBS is intricately regulated at different levels, its function depending on the redox state and availability of exogenous ligands, such as AdoMet and the gasotransmitters nitric oxide (NO) and carbon monoxide (CO). Herein, we employed static and stopped-flow absorption spectroscopy to investigate the kinetics of CO and NO binding to the CBS heme. NO binds faster and with higher affinity than CO, each gasotransmitter initially binding to opposite sides of the heme plane. AdoMet surprisingly enhances CO inhibition of H2S production, as well as CO and NO binding. In the clinically relevant p.P49L CBS variant, we observed much higher CO affinity with respect to WT CBS, likely resulting from increased flexibility of the heme surroundings. Overall, the binding kinetics attest the in vivo relevance of CO and NO inhibition of CBS-catalyzed H2S production, an underlying mechanism in the crosstalk between gasotransmitters.

A robust and versatile mass spectrometry platform for comprehensive assessment of the thiol redox metabolome

Several diseases are associated with perturbations in redox signaling and aberrant hydrogen sulfide metabolism, and numerous analytical methods exist for the measurement of the sulfur-containing species affected. However, uncertainty remains about their concentrations and speciation in cells/biofluids, perhaps in part due to differences in sample processing and detection principles. Using ultrahigh-performance liquid chromatography in combination with electrospray-ionization tandem mass spectrometry we here outline a specific and sensitive platform for the simultaneous measurement of 12 analytes, including total and free thiols, their disulfides and sulfide in complex biological matrices such as blood, saliva and urine. Total assay run time is < 10 min, enabling high-throughput analysis. Enhanced sensitivity and avoidance of artifactual thiol oxidation is achieved by taking advantage of the rapid reaction of sulfhydryl groups with N-ethylmaleimide. We optimized the analytical procedure for detection and separation conditions, linearity and precision including three stable isotope labelled standards. Its versatility for future more comprehensive coverage of the thiol redox metabolome was demonstrated by implementing additional analytes such as methanethiol, N-acetylcysteine, and coenzyme A. Apparent plasma sulfide concentrations were found to vary substantially with sample pretreatment and nature of the alkylating agent. In addition to protein binding in the form of mixed disulfides (S-thiolation) a significant fraction of aminothiols and sulfide appears to be also non-covalently associated with proteins. Methodological accuracy was tested by comparing the plasma redox status of 10 healthy human volunteers to a well-established protocol optimized for reduced/oxidized glutathione. In a proof-of-principle study a deeper analysis of the thiol redox metabolome including free reduced/oxidized as well as bound thiols and sulfide was performed. Additional determination of acid-labile sulfide/thiols was demonstrated in human blood cells, urine and saliva. Using this simplified mass spectrometry-based workflow the thiol redox metabolome can be determined in samples from clinical and translational studies, providing a novel prognostic/diagnostic platform for patient stratification, drug monitoring, and identification of new therapeutic approaches in redox diseases.

Thiosulfate sulfurtransferase-like domain–containing 1 protein interacts with thioredoxin

Rhodanese domains are structural modules present in the sulfurtransferase superfamily. These domains can exist as single units, in tandem repeats, or fused to domains with other activities. Despite their prevalence across species, the specific physiological roles of most sulfurtransferases are not known. Mammalian rhodanese and mercaptopyruvate sulfurtransferase are perhaps the best-studied members of this protein superfamily and are involved in hydrogen sulfide metabolism. The relatively unstudied human thiosulfate sulfurtransferase-like domain-containing 1 (TSTD1) protein, a single-domain cytoplasmic sulfurtransferase, was also postulated to play a role in the sulfide oxidation pathway using thiosulfate to form glutathione persulfide, for subsequent processing in the mitochondrial matrix. Prior kinetic analysis of TSTD1 was performed at pH 9.2, raising questions about relevance and the proposed model for TSTD1 function. In this study, we report a 1.04 Å resolution crystal structure of human TSTD1, which displays an exposed active site that is distinct from that of rhodanese and mercaptopyruvate sulfurtransferase. Kinetic studies with a combination of sulfur donors and acceptors reveal that TSTD1 exhibits a low Km for thioredoxin as a sulfane sulfur acceptor and that it utilizes thiosulfate inefficiently as a sulfur donor. The active site exposure and its interaction with thioredoxin suggest that TSTD1 might play a role in sulfide-based signaling. The apical localization of TSTD1 in human colonic crypts, which interfaces with sulfide-releasing microbes, and the overexpression of TSTD1 in colon cancer provide potentially intriguing clues as to its role in sulfide metabolism.

Investigations on the role of hemoglobin in sulfide metabolism by intact human red blood cells

In addition to their role as oxygen transporters, red blood cells (RBCs) contribute to cardiovascular homeostasis by regulating nitric oxide (NO) metabolism via interaction of hemoglobin (Hb) with nitrite and NO itself. RBCs were proposed to also participate in sulfide metabolism. Although Hb is known to react with sulfide, sulfide metabolism by intact RBCs has not been characterized so far. Therefore we explored the role of Hb in sulfide metabolism in intact human RBCs. We find that upon exposure of washed RBCs to sulfide, no changes in oxy/deoxyhemoglobin (oxy/deoxyHb) are observed by UV-vis and EPR spectroscopy. However, sulfide reacts with methemoglobin (metHb), forming a methemoglobin-sulfide (metHb-SH) complex. Moreover, while metHb-SH is stable in cell-free systems even in the presence of biologically relevant thiols, it gradually decomposes to produce oxyHb, inorganic polysulfides and thiosulfate in intact cells, as detected by EPR and mass spectrometry. Taken together, our results demonstrate that under physiological conditions RBCs are able to metabolize sulfide via intermediate formation of a metHb-SH complex, which subsequently decomposes to oxyHb. We speculate that decomposition of metHb-SH is preceded by an inner-sphere electron transfer, forming reduced Hb (which binds oxygen to form oxyHb) and thiyl radical (a process we here define as “reductive sulfhydration”), which upon release, gives rise to the oxidized products, thiosulfate and polysulfides. Thus, not only is metHb an efficient scavenger and regulator of sulfide in blood, intracellular sulfide itself may play a role in keeping Hb in the reduced oxygen-binding form and, therefore, be involved in RBC physiology and function.

Hydrogen Sulfide Biochemistry and Interplay with Other Gaseous Mediators in Mammalian Physiology.

Hydrogen sulfide (H2S) has emerged as a relevant signaling molecule in physiology, taking its seat as a bona fide gasotransmitter akin to nitric oxide (NO) and carbon monoxide (CO). After being merely regarded as a toxic poisonous molecule, it is now recognized that mammalian cells are equipped with sophisticated enzymatic systems for H2S production and breakdown. The signaling role of H2S is mainly related to its ability to modify different protein targets, particularly by promoting persulfidation of protein cysteine residues and by interacting with metal centers, mostly hemes. H2S has been shown to regulate a myriad of cellular processes with multiple physiological consequences. As such, dysfunctional H2S metabolism is increasingly implicated in different pathologies, from cardiovascular and neurodegenerative diseases to cancer. As a highly diffusible reactive species, the intra- and extracellular levels of H2S have to be kept under tight control and, accordingly, regulation of H2S metabolism occurs at different levels. Interestingly, even though H2S, NO, and CO have similar modes of action and parallel regulatory targets or precisely because of that, there is increasing evidence of a crosstalk between the three gasotransmitters. Herein are reviewed the biochemistry, metabolism, and signaling function of hydrogen sulfide, as well as its interplay with the other gasotransmitters, NO and CO.

Role of reactive oxygen species and sulfide-quinone oxoreductase in hydrogen sulfide-induced contraction of rat pulmonary arteries.

Application of H2S (“sulfide”) elicits a complex contraction in rat pulmonary arteries (PAs) comprising a small transient contraction (phase 1; Ph1) followed by relaxation and then a second, larger, and more sustained contraction (phase 2; Ph2). We investigated the mechanisms causing this response using isometric myography in rat second-order PAs, with Na2S as a sulfide donor. Both phases of contraction to 1,000 μM Na2S were attenuated by the pan-PKC inhibitor Gö6983 (3 μM) and by 50 μM ryanodine; the Ca2+ channel blocker nifedipine (1 μM) was without effect. Ph2 was attenuated by the mitochondrial complex III blocker myxothiazol (1 μM), the NADPH oxidase (NOX) blocker VAS2870 (10 μM), and the antioxidant TEMPOL (3 mM) but was unaffected by the complex I blocker rotenone (1 μM). The bath sulfide concentration, measured using an amperometric sensor, decreased rapidly following Na2S application, and the peak of Ph2 occurred when this had fallen to ~50 μM. Sulfide caused a transient increase in NAD(P)H autofluorescence, the offset of which coincided with development of the Ph2 contraction. Sulfide also caused a brief mitochondrial hyperpolarization (assessed using tetramethylrhodamine ethyl ester), followed immediately by depolarization and then a second more prolonged hyperpolarization, the onset of which was temporally correlated with the Ph2 contraction. Sulfide application to cultured PA smooth muscle cells increased reactive oxygen species (ROS) production (recorded using L012); this was absent when the mitochondrial flavoprotein sulfide-quinone oxoreductase (SQR) was knocked down using small interfering RNA. We propose that the Ph2 contraction is largely caused by SQR-mediated sulfide metabolism, which, by donating electrons to ubiquinone, increases electron production by complex III and thereby ROS production.

Metabolism of hydrogen sulfide (H2S) and Production of Reactive Sulfur Species (RSS) by superoxide dismutase

Reactive sulfur species (RSS) such as H2S, HS•, H2Sn, (n = 2–7) and HS2•- are chemically similar to H2O and the reactive oxygen species (ROS) HO•, H2O2, O2•- and act on common biological effectors. RSS were present in evolution long before ROS, and because both are metabolized by catalase it has been suggested that “antioxidant” enzymes originally evolved to regulate RSS and may continue to do so today. Here we examined RSS metabolism by Cu/Zn superoxide dismutase (SOD) using amperometric electrodes for dissolved H2S, a polysulfide-specific fluorescent probe (SSP4), and mass spectrometry to identify specific polysulfides (H2S2-H2S5). H2S was concentration- and oxygen-dependently oxidized by 1μM SOD to polysulfides (mainly H2S2, and to a lesser extent H2S3 and H2S5) with an EC50 of approximately 380μM H2S. H2S concentrations > 750μM inhibited SOD oxidation (IC50 = 1.25mM) with complete inhibition when H2S > 1.75mM. Polysulfides were not metabolized by SOD. SOD oxidation preferred dissolved H2S over hydrosulfide anion (HS-), whereas HS- inhibited polysulfide production. In hypoxia, other possible electron donors such as nitrate, nitrite, sulfite, sulfate, thiosulfate and metabisulfite were ineffective. Manganese SOD also catalyzed H2S oxidation to form polysulfides, but did not metabolize polysulfides indicating common attributes of these SODs. These experiments suggest that, unlike the well-known SOD-mediated dismutation of two O2•- to form H2O2 and O2, SOD catalyzes a reaction using H2S and O2 to form persulfide. These can then combine in various ways to form polysulfides and sulfur oxides. It is also possible that H2S (or polysulfides) interact/react with SOD cysteines to affect catalytic activity or to directly contribute to sulfide metabolism. Our studies suggest that H2S metabolism by SOD may have been an ancient mechanism to detoxify sulfide or to regulate RSS and along with catalase may continue to do so in contemporary organisms.

Colonic hydrogen sulfide produces portal hypertension and systemic hypotension in rats

Hydrogen sulfide, a toxic gas, at low concentrations is also a biological mediator in animals. In the colon, hydrogen sulfide is produced by intestinal tissues and gut sulfur bacteria. Gut-derived molecules undergo liver metabolism. Portal hypertension is one of the most common complications contributing to the high mortality in liver cirrhosis. We hypothesized that the colon-derived hydrogen sulfide may affect portal blood pressure. Sprague-Dawley rats were maintained either on tap water (controls) or on water solution of thioacetamide to produce liver cirrhosis (CRH-R). Hemodynamics were measured after administration of either saline or Na2S, a hydrogen sulfide donor, into (1) the colon, (2) the portal vein, or (3) the femoral vein. Expression of enzymes involved in hydrogen sulfide metabolism was measured by RT-PCR. CRH-R showed a significantly higher portal blood pressure but a lower arterial blood pressure than controls. Saline did not affect hemodynamic parameters. In controls, intracolonic hydrogen sulfide decreased arterial blood pressure and portal blood flow but increased portal blood pressure. Similarly, hydrogen sulfide administered into the portal vein decreased arterial blood pressure but increased portal blood pressure. In contrast, hydrogen sulfide administered into the systemic vein decreased both arterial and portal blood pressures. CRH-R showed significantly greater responses to hydrogen sulfide than controls. CRH-R had a significantly higher liver concentration of hydrogen sulfide but lower expression of rhodanese, an enzyme converting hydrogen sulfide to sulfate. In conclusion, colon-administered hydrogen sulfide increases portal blood pressure while decreasing the systemic arterial blood pressure. The response to hydrogen sulfide is more pronounced in cirrhotic rats which show reduced hydrogen sulfide liver metabolism. Therefore, colon-derived hydrogen sulfide may be involved in the regulation of portal blood pressure, and may contribute to portal hypertension. Impact statement Accumulating evidence suggests that gut-derived molecules affect the control of the circulatory system. Mechanisms controlling liver circulation have been profoundly studied; however, the effects of gut bacteria-derived molecules on portal blood pressure have not been established. In the colon, hydrogen sulfide is produced by intestinal tissues and gut sulfur bacteria. We found that colon-administered hydrogen sulfide increases portal blood pressure while decreasing the systemic arterial blood pressure. The hemodynamic response to hydrogen sulfide was more pronounced in cirrhotic rats which showed reduced hydrogen sulfide liver metabolism, i.e. lower expression of rhodanese, an enzyme converting hydrogen sulfide to sulfate. We propose that colon-derived hydrogen sulfide may affect the regulation of portal and arterial blood pressures and may be involved in portal hypertension.

Association of cystathionine beta-synthase polymorphisms and aneurysmal subarachnoid hemorrhage

OBJECTIVE Cystathionine β-synthase (CBS) is involved in homocysteine and hydrogen sulfide (H2S) metabolism. Both products have been implicated in the pathophysiology of cerebrovascular diseases. The impact of CBS polymorphisms on aneurysmal subarachnoid hemorrhage (aSAH) and its clinical sequelae is poorly understood. METHODS Blood samples from all patients enrolled in the CARAS (Cerebral Aneurysm Renin Angiotensin System) study were used for genetic evaluation. The CARAS study prospectively enrolled aSAH patients at 2 academic institutions in the United States from 2012 to 2015. Common CBS polymorphisms were detected using 5'exonuclease genotyping assays. Analysis of associations between CBS polymorphisms and aSAH was performed. RESULTS Samples from 149 aSAH patients and 50 controls were available for analysis. In multivariate logistic regression analysis, the insertion allele of the 844ins68 CBS insertion polymorphism showed a dominant effect on aSAH. The GG genotype of the CBS G/A single nucleotide polymorphism (rs234706) was independently associated with unfavorable functional outcome (modified Rankin Scale Score 3-6) at discharge and last follow-up, but not clinical vasospasm or delayed cerebral ischemia (DCI). CONCLUSIONS The insertion allele of the 844ins68 CBS insertion polymorphism was independently associated with aSAH while the GG genotype of rs234706 was associated with an unfavorable outcome both at discharge and last follow-up. Increased CBS activity may exert its neuroprotective effects through alteration of H2S levels, and independent of clinical vasospasm and DCI.

Nanoporous gold-based microbial biosensor for direct determination of sulfide

Environmental pollution caused by sulfide compounds has become a major problem for public health. Hence, there is an urgent need to explore a sensitive, selective, and simple sulfide detection method for environmental monitoring and protection. Here, a novel microbial biosensor was developed using recombinant Escherichia coli BL21 (E. coli BL21) expressing sulfide:quinone oxidoreductase (SQR) for sulfide detection. As an important enzyme involved in the initial step of sulfide metabolism, SQR oxidizes sulfides to polysulfides and transfers electrons to the electron transport chain. Nanoporous gold (NPG) with its unique properties was selected for recombinant E. coli BL21 cells immobilization, and then glassy carbon electrode (GCE) was modified by the resulting E. coli/NPG biocomposites to construct an E. coli/NPG/GCE bioelectrode. Due to the catalytic oxidation properties of NPG for sulfide, the electrochemical reaction of the E. coli/NPG/GCE bioelectrode is attributed to the co-catalysis of SQR and NPG. For sulfide detection, the E. coli/NPG/GCE bioelectrode showed a good linear response ranging from 50μM to 5mM, with a high sensitivity of 18.35μAmM−1cm−2 and a low detection limit of 2.55μM. The anti-interference ability of the E. coli/NPG/GCE bioelectrode is better than that of enzyme-based inhibitive biosensors. Further, the E. coli/NPG/GCE bioelectrode was successfully applied to the detection of sulfide in wastewater. These unique properties potentially make the E. coli/NPG/GCE bioelectrode an excellent choice for reliable sulfide detection.

Beyond a Gasotransmitter: Hydrogen Sulfide and Polysulfide in Cardiovascular Health and Immune Response.

Hydrogen sulfide (H2S) metabolism leads to the formation of oxidized sulfide species, including polysulfide, persulfide, and others. Evidence is emerging that many biological effects of H2S may indeed be due to polysulfide and persulfide activation of signaling pathways and reactivity with discrete small molecules. Recent Advances: Exogenous oxidized sulfide species, including polysulfides, are more reactive than H2S with a wide range of molecules. Importantly, endogenous polysulfide and persulfide formation has been reported to occur via transsulfuration enzymes, cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS). In light of the recent understanding of oxidized sulfide metabolite formation and reactivity, comparatively few studies have been reported comparing cellular biological and in vivo effects of H2S donors versus polysulfide and persulfide donors. Likewise, it is equally unclear when, how, and to what extent persulfide and polysulfide formation occurs in vivo under pathophysiological conditions. Additional studies regarding persulfide and polysulfide formation and molecular reactions are needed in nearly all aspects of biology to better understand how sulfide metabolites contribute to key chemical biology reactions involved in cardiovascular health and immune responses. Antioxid. Redox Signal. 27, 634-653.

Edoxaban improves venous thrombosis via increasing hydrogen sulfide and homocysteine in rat model.

Anticoagulant therapy is prescribed to millions of patients worldwide for the prevention and treatment of venous thrombosis. Evidence has indicated that edoxaban is a potential drug of oral anticoagulant in the acute treatment of venous thromboembolism. Hydrogen sulfide and homocysteine plasma concentration are indicators of cardiovascular and neurovascular disease risk factors that have attracted considerable attention for regulation of vascular health and homeostasis. However, the molecular mechanism of edoxaban‑mediated differences of hydrogen sulfide and homocysteine has not been investigated in the progression of venous thrombosis. In the present study, the authors analyzed the phosphoinositide 3‑kinase (PI3K)/protein kinase B (AKT) signaling pathway in the vein endothelial cells and expression levels of hydrogen sulfide and homocysteine. Homocysteine‑hydrogen sulfide metabolism through transsulfuration and that transsulfuration capacity and hydrogen sulfide availability have been investigated both invitro and invivo following treatment with edoxaban. Matrix metalloproteinase (MMP) activation and cystathionine β‑synthase (CBS) and cystathionine γ‑lyase (CGL) levels were studied in a cell model and rat model of vein thrombosis prior and post treatment of edoxaban. The therapeutic effects of edoxaban for rats with vein thrombosis were determined by clinical diagnose scores. The results demonstrated that edoxaban increased expression levels of hydrogen sulfide and homocysteine in microvascular endothelial cells. It was observed that the transsulfuration enzymes, CBS and CGL levels were upregulated in murine microvascular endothelial cells. The MMP‑9 expression level and activity and homocysteine‑hydrogen sulfide metabolism were increased in murine microvascular endothelial cells following edoxaban treatment. In addition, CBS and CGL activities were upregulated in murine microvascular endothelial cells and a rat model of venous thrombosis following treatment with edoxaban. Furthermore, it was observed that edoxaban increased PI3K and AKT expression both invitro and invivo. In addition, edoxaban significantly improved endothelial injury and inhibited thrombosis factors expression in rat model of venous thrombosis. In conclusion, these findings suggested that edoxaban can improve venous thrombosis by decreasing hydrogen sulfide and homocysteine through the PI3K/AKT signaling pathway.

Гендерні особливості впливу гіпергомоцистеїнемії на метаболізм сірковмісних амінокислот та гідроген сульфіду в печінці

Introduction. Sulfur amino acid disorders are recognized as metabolic risk factors for cardiovascular pathology. However, the question of the involvement of sulfur amino acids in the formation of the gender-defined pathology of cardiovascular system remains unclear.The aim of the study – research the impact of thiolactone hyperhomocysteinemia (HHC) on blood levels of sulfur-containing metabolites and enzymes activity in metabolism of homocysteine, cysteine and hydrogen sulfide in the liver of rats of both sexes.Methods of the research. Experiments were conducted on 40 white laboratory rats of both sexes weighing 220–280 g. Hyperhomocysteinemia was modeled by long-term intragastric administration of thiolactone D,L-homocysteine, dosage 100 mg / kg, in 1 % starch solution once per day for 28 days. The research determines the content of homocysteine, cysteine and hydrogen sulfide in blood serum and activity of enzymes in the liver – cystathionine-γ-lyase, cystathionine-β-synthase, cysteine aminotransferase, methionine adenosyltransferase, cysteine dioxygenase and γ-glutamylcysteine ligase.Results and Discussion. Hyperhomocysteinemia initiates gender-defined changes in the content of sulfur-containing metabolites in the serum of rats: increase homocysteine and cysteine and reduction of hydrogen sulfide is 111; 59.2 and 59.4 % in males (females – 82.4, 38.0 and 47.5 %, p&lt;0.05) respectively compared to the control group.HHC in males has led to a more distinct decreased in liver enzyme activity of homocysteine methylation and transsulfuration (on 20.5–24.8 % in males and on 13.4–15.4 % in females, p &lt;0.05), enzymes of cysteine degradation in oxidative and conjugation ways (in 21.1–22.0 % in males and on 13.4–15.3 % in females, p&lt;0.05) and H2S-synthesizing enzymes (20.6–25.9 % in males and on 13.5–17.5 % in females, p&lt;0.05) compared to the control group.Conclusions. It was shown, thiolactone homocysteine administration is accompanied by the rise of homocysteine, cysteine and the reduced levels of hydrogen sulfide in blood in individuals of both sexes, but more significant changes were observed in males. In addition, gender defined changes in the metabolism of sulfur-containing compounds in the liver were registered: male rats showed significantly greater decrease in liver enzyme activity of homocysteine remethylation and transsulfuration, cysteine degradation enzymes and synthesis of hydrogen sulfide in the liver compared to female rats.

СТАТЕВІ ВІДМІННОСТІ ВПЛИВУ ГІПЕРГОМОЦИСТЕЇНЕМІЇ НА МЕТАБОЛІЗМ ГІДРОГЕН СУЛЬФІДУ В СЕРЦЕВО-СУДИННІЙ СИСТЕМІ

Гіпергомоцистеїнемія є відомим та незалежним фактором ризику патології серця та судин. Показано, що за цього патологічного стану зменшується рівень гідроген сульфіду – біологічноактивної речовини, що причетна до регуляції тонусу судин, скоротливості міокарда. Однак залишається невивченим існування статевих відмінностей впливу гіпергомоцистеїнемії на метаболізм гідроген сульфіду в серцево-судинній системі.Мета дослідження – вплив експериментальної гіпергомоцистеїнемії на вміст гідроген сульфіду та його обмін у міокарді та аорті щурів різної статі.Матеріали і методи. Досліди проведено на 40 білих лабораторних щурах обох статей масою 220–280 г. Модель тривалої гіпергомоцистеїнемії створювали шляхом введення тіолактону D, L-гомоцистеїну інтрагастрально в дозі 100 мг/кг маси на 1% розчині крохмалю 1 раз на добу протягом 28 діб. У роботі визначали вміст гідроген сульфіду в міокарді та аорті, швидкість утилізації гідроген сульфіду в міокарді, а також активність ферментів цистатіонін-γ-ліази, цистеїнамінотрансферази, тіосульфатдитіолсульфідтрансферази, сульфітоксидази в міокарді та аорті.Результати досліджень та їх обговорення. Гіпергомоцистеїнемія супроводжується стать-специфічними змінами вмісту гідроген сульфіду в міокарді та аорті щурів: зниження рівня гідроген сульфіду в самців та самок становить відповідно (31,4–43,3) % та (20,0-25,1) % (р&lt;0,05) порівняно з контролем. Тривале введення тіолактону гомоцистеїну викликає більш істотні порушення метаболізму гідроген сульфіду в міокарді та аорті в самців: збільшення швидкості утилізації гідроген сульфіду становить 36,5 % (проти 22,5 % у самок, р&lt;0,05), зменшення активності H2S-синтезуючих ензимів становить 28,3–49,8 % (проти 17,1–36,8 % у самок, р&lt;0,05) порівняно з контролем.Висновки. Ввведення тіолактону гомоцистеїну викликає стать-специфічні зміни метаболізму гідроген сульфіду в міокарді та аорті. Показано, що у самців реєструється більш виразне зменшення вмісту гідроген сульфіду, активності Н2S-синтезуючих ензимів та мітохондріальної сульфітоксидази, а також збільшення швидкості утилізації екзогенного гідроген сульфіду в серцево-судинній системі порівняно з контролем.

Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis

Sulfide was used as an electron donor early in the evolution of photosynthesis, with many extant photosynthetic bacteria still capable of using sulfur compounds such as hydrogen sulfide (H2S) as a photosynthetic electron donor. Although enzymes involved in H2S oxidation have been characterized, mechanisms of regulation of sulfide-dependent photosynthesis have not been elucidated. In this study, we have identified a sulfide-responsive transcriptional repressor, SqrR, that functions as a master regulator of sulfide-dependent gene expression in the purple photosynthetic bacterium Rhodobacter capsulatus SqrR has three cysteine residues, two of which, C41 and C107, are conserved in SqrR homologs from other bacteria. Analysis with liquid chromatography coupled with an electrospray-interface tandem-mass spectrometer reveals that SqrR forms an intramolecular tetrasulfide bond between C41 and C107 when incubated with the sulfur donor glutathione persulfide. SqrR is oxidized in sulfide-stressed cells, and tetrasulfide-cross-linked SqrR binds more weakly to a target promoter relative to unmodified SqrR. C41S and C107S R. capsulatus SqrRs lack the ability to respond to sulfide, and constitutively repress target gene expression in cells. These results establish that SqrR is a sensor of H2S-derived reactive sulfur species that maintain sulfide homeostasis in this photosynthetic bacterium and reveal the mechanism of sulfide-dependent transcriptional derepression of genes involved in sulfide metabolism.