Hydrogen sulfide facilitates carotid sinus baroreflex in anesthetized rats.
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AIM: To study effects of hydrogen sulfide (H2S) on the carotid sinus baroreflex (CSB). METHODS: The functional curve of the carotid sinus baroreflex was measured by recording changes in arterial pressure in anesthetized male rats with perfused carotid sinus. RESULTS: H2S (derived from sodium hydrosulfide) at concentrations of 25, 50, and 100 micromol/L facilitated the CSB, shifting the functional curve of the baroreflex downward and to the left. There was a marked increase in peak slope (PS) and reflex decrease in blood pressure (RD). Effects were concentration-dependent. Pretreatment with glibenclamide (20 micromol/L), a K(ATP) channel blocker, abolished the above effects of H2S on CSB. Pretreatment with Bay K8644 (an agonist of calcium channels; 500 nmol/L) eliminated the effect of H2S on CSB. An inhibitor of cystathionine gamma-lyase (CSE), DL-propargylglycine (PPG; 200 micromol/L), inhibited CSB in male rats and shifted the functional curve of the baroreflex upward and to the right. CONCLUSION: These data suggest that exogenous H2S exerts a facilitatory role on isolated CSB through opening K(ATP) channels and further closing the calcium channels in vascular smooth muscle. Endogenous H2S may activate the activity of the CSB in vivo. (+info)
Hydrogen sulfide ameliorates vascular calcification induced by vitamin D3 plus nicotine in rats.
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AIM: To investigate the role of the endogenous cystathionine gamma-synthase (CSE)/hydrogen sulfide (H2S) pathway in vascular calcification in vivo. METHODS: A rat vascular calcification model was established by administration of vitamin D3 plus nicotine (VDN). The amount of CSE and osteopontin (OPN) mRNA was determined by using semi-quantitative reverse-transcription polymerase chain reaction. The calcium content, 45Ca2+ accumulation and alkaline phosphatase (ALP) activity were measured. H2S production and CSE activity were measured. RESULTS: von Kossa staining produced strong positive black/brown staining in areas among the elastic fibers of the medial layer in the calcified aorta. The calcium content, 45Ca2+ accumulation and ALP activity in calcified arteries increased by 6.77-, 1.42-, and 1.87-fold, respectively, compared with controls. The expression of the OPN gene was upregulated (P<0.01). Expression of the CSE gene was downregulated. However, calcium content, 45Ca2+ uptake and ALP activity in the VDN plus NaHS group was lower than that in the VDN group. The content of calcium and 45Ca2+ accumulation and activity of ALP in the aorta were 34.8%, 40.75% and 63.5% lower in the low-dosage NaHS group than in the VDN group, respectively (P<0.01), and the calcium content and deposition of 45Ca2+ and activity of ALP was 83.9%, 37.8 % and 46.2% lower in the aorta in the high-dosage NaHS group than in the VDN group, respectively (P<0.01). The expression of the OPN gene was downregulated. CONCLUSION: The production of H2S, and CSE activity were decreased and CSE gene expression was downregulated in rats with vascular calcification. H2S can ameliorate vascular calcification, suggesting that the H2S/CSE pathway plays a regulatory role in the pathogenesis of vascular calcification. (+info)
Nitric oxide-releasing flurbiprofen reduces formation of proinflammatory hydrogen sulfide in lipopolysaccharide-treated rat.
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The biosynthesis of both nitric oxide (NO) and hydrogen sulfide (H2S) is increased in lipopolysaccharide (LPS)-injected mice and rats but their interaction in these models is not known. In this study we examined the effect of the NO donor, nitroflurbiprofen (and the parent molecule flurbiprofen) on NO and H2S metabolism in tissues from LPS-pretreated rats. Administration of LPS (10 mg kg(-1), i.p.; 6 h) resulted in an increase (P<0.05) in plasma TNF-alpha, IL-1beta and nitrate/nitrite (NO(x)) concentrations, liver H2S synthesis (from added cysteine), CSE mRNA, inducible nitric oxide synthase (iNOS), myeloperoxidase (MPO) activity (marker for neutrophil infiltration) and nuclear factor-kappa B (NF-kappaB) activation. Nitroflurbiprofen (3-30 mg kg(-1), i.p.) administration resulted in a dose-dependent inhibition of the LPS-mediated increase in plasma TNF-alpha, IL-1beta and NO(x) concentration, liver H2S synthesis (55.00+/-0.95 nmole mg protein(-1), c.f. 62.38+/-0.47 nmole mg protein(-1), n = 5, P<0.05), CSE mRNA, iNOS, MPO activity and NF-kappaB activation. Flurbiprofen (21 mg kg(-1), i.p.) was without effect. These results show for the first time that nitroflurbiprofen downregulates the biosynthesis of proinflammatory H2S and suggest that such an effect may contribute to the augmented anti-inflammatory activity of this compound. These data also highlight the existence of 'crosstalk' between NO and H2S in this model of endotoxic shock. (+info)
Pro-apoptotic effect of endogenous H2S on human aorta smooth muscle cells.
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Cystathionine gamma-lyase (CSE) is a key enzyme in the trans-sulfuration pathway, which uses L-cysteine to produce hydrogen sulfide (H2S). The CSE/H2S system has been shown to play an important role in regulating cellular functions in different systems. In the present study, we overexpressed CSE in human aorta smooth muscle cells (HASMCs) using a recombinant defective adenovirus containing CSE gene (Ad-CSE). Infection of HASMCs with Ad-CSE resulted in a significant increase in the expression of CSE protein and H2S production. Ad-CSE transfection inhibited cell growth and stimulated apoptosis, as evidenced by cell viability assay, Hoechst 33258 staining, TUNEL, and caspase 3 activation. CSE-mediated apoptosis was associated with an increased ERK and p38 MAPK activation, up-regulation of p21(Cip/WAK-1), and down-regulation of cyclin D1 expression. After inhibiting endogenous background CSE gene expression, direct administration of H2S at 100 microM induced apoptosis of HASMCs. The other two endproducts of CSE-catalyzed enzymatic reaction, ammonium and pyruvate, failed to do so. These results demonstrate that overexpression of CSE stimulates SMC apoptosis due to an increased endogenous production of H2S. Adenovirus-mediated transfer of CSE gene may provide a novel therapeutic approach in treating vascular diseases linked to abnormal cellular proliferation and vascular remodeling. (+info)
Hyperhomocysteinemia associated with decreased renal transsulfuration activity in Dahl S rats.
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Elevated plasma homocysteine (Hcys) has been reported to participate in the development of arterial and glomerular sclerosis in Dahl salt-sensitive hypertensive (SS) rats. The mechanism resulting in hyperhomocysteinemia in these animals remains unknown. Disposal of Hcys in the kidneys plays an important role in regulating the plasma Hcys level. We, therefore, examined the activities and expressions of the enzymes involved in the metabolism of Hcys in the kidneys of SS rats, compared with that of Brown Norway rats and SSBN13 rats, a consomic subcolony of SS rats that carries a substituted chromosome 13 from Brown Norway rats. High-performance liquid chromatography analysis demonstrated that plasma Hcys levels were significantly higher in SS rats. The conversion of S-adenosylhomocysteine into Hcys via S-adenosylhomocysteine hydrolase by renal tissue was not different among these 3 rat strains. However, the metabolic rate of Hcys into cysteine was markedly reduced in the SS rat kidneys. The mRNA and protein levels of cystathionine beta-synthase (CBS), one of the key enzymes in the transsulfuration pathway in the kidneys, were significantly lower in SS rats. In microdissected nephron segments, CBS mRNA was shown to be mainly present in renal proximal tubules (PTs). The mRNA levels of CBS in the PTs were also significantly decreased in SS rats, accompanied by a reduced CBS activity in PTs. We conclude that hyperhomocysteinemia is associated with a decreased activity and expression of CBS in renal PTs because of the defect of chromosome 13 in SS rats. (+info)
L-cysteine inhibits insulin release from the pancreatic beta-cell: possible involvement of metabolic production of hydrogen sulfide, a novel gasotransmitter.
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Hydrogen sulfide (H(2)S) was historically recognized as a toxic gas generated by natural resources. However, its enzymatic production from L-cysteine has recently been demonstrated in mammals. Cystathionine beta-synthase and cystathionine gamma-lyase, both of which can produce H(2)S, were expressed in mouse pancreatic islet cells and the beta-cell line, MIN6. L-cysteine and the H(2)S donor NaHS inhibited glucose-induced insulin release from islets and MIN6 cells. These inhibitory effects were reproduced when insulin release was stimulated by alpha-ketoisocaproate, tolbutamide, or high K+. L-cysteine and NaHS inhibited glucose-potentiated insulin release in the copresence of diazoxide and high K+. Real-time imaging of intracellular Ca2+ concentration ([Ca2+](i)) demonstrated that both L-cysteine and NaHS reversibly suppressed glucose-induced [Ca2+](i) oscillation in a single beta-cell without obvious changes in the mean value. These substances inhibited Ca2+ - or guanosine 5'-0-3-thiotriphosphate-induced insulin release from islets permeabilized with streptolysin-O. L-cysteine and NaHS reduced ATP production and attenuated glucose-induced hyperpolarization of the mitochondrial membrane potential. Finally, L-cysteine increased H(2)S content in MIN6 cells. We suggest here that L-cysteine inhibits insulin release via multiple actions on the insulin secretory process through H(2)S production. Because the activities of H(2)S-producing enzymes and the tissue H(2)S contents are known to increase under diabetic conditions, the inhibition may participate in the deterioration of insulin release in this disease. (+info)
Inborn errors of sulfur-containing amino acid metabolism.
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Two superimposed metabolic sequences, transsulfuration and the methionine/homocysteine cycle, form the pathway for methionine metabolism in mammalian liver. This combined pathway was formulated first to explain observations in subjects with homocystinuria caused by cystathionine synthase deficiency. Since that time additional inborn errors have been discovered, and currently we know of human subjects with isolated defects in all of the reactions of the combined pathway with only one exception: betaine homocysteine methyltransferase. Studies of these inborn errors have contributed significantly to our knowledge of human methionine metabolism and to the clinical consequences of impaired metabolism. Transsulfuration appears to function primarily for the metabolism of excess methionine, and each of the 5 defects in this pathway results in the accumulation of 1 or more of the normal metabolites. Thus, studies of these disorders may provide insight into both the potential pathological sequelae of nutritional methionine excess as well as whether laboratory testing allows the detection of excess. (+info)
Vitamin B-6 deficiency suppresses the hepatic transsulfuration pathway but increases glutathione concentration in rats fed AIN-76A or AIN-93G diets.
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The transsulfuration pathway, which aids in regulating homocysteine concentration and mediates cysteine synthesis, may be sensitive to vitamin B-6 status because cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CGL) require pyridoxal 5'-phosphate (PLP). To assess relations between vitamin B-6 and transsulfuration, we evaluated the effects of dietary pyridoxine (PN) on the hepatic concentration of relevant metabolites and in vitro activity of CBS and CGL. Growing rats were fed AIN-93G- or AIN-76A-based diets that ranged from adequate to deficient in vitamin B-6 (2, 1, 0.5, 0.1, or 0 mg of PN/kg diet, n = 5). This design allowed assessment of the effects of supplemental methionine (AIN-76A) vs. cysteine (AIN-93G) in common research diets over a range of vitamin B-6 levels. CBS activity, assayed in the presence or absence of added S-adenosylmethionine, was independent of diet type and PN level. CGL activity was independent of diet type but proportional to dietary PN. Rats fed deficient (0 and 0.1 mg PN/kg) diets exhibited only approximately 30% of the CGL activity of those fed the 2 mg PN/kg diets. Hepatic cystathionine increased from 20 to 30 nmol/g for the 1-2 mg PN/kg diets to approximately 85 nmol/g for the 0 mg PN/kg diet; however, cysteine was reduced only in B-6-deficient rats consuming the AIN-93G diet (means of 30-40 nmol/g for adequate to 11.6 nmol/g for 0 mg PN/kg AIN-76A diet). In spite of these effects, hepatic glutathione concentration increased in vitamin B-6 deficiency. These results suggest that vitamin B-6-dependent changes in transsulfuration do not limit hepatic glutathione production. (+info)