Hongfang Jin

Role of Hydrogen Sulfide in the Development of Atherosclerotic Lesions in Apolipoprotein E Knockout Mice

Objective—We explored the effect of hydrogen sulfide (H2S) on atherosclerotic progression, particularly on intracellular adhesion molecule-1 (ICAM-1) in apolipoprotein-E knockout (apoE−/−) mice and human umbilical vein endothelial cells (HUVECs). Methods and Results—ApoE−/− mice were treated with sodium hydrosulfide (NaHS) or DL-propargylglycine (PPG); HUVECs were pretreated with NaHS. Compared with control mice, apoE−/− mice showed decreased plasma H2S level and aortic H2S production but increased plasma ICAM-1 and aortic ICAM-1 protein and mRNA. Compared with apoE−/− mice, apoE−/−+NaHS mice showed increased plasma H2S level, but decreased size of atherosclerotic plaque and plasma and aortic ICAM-1 levels, whereas apoE−/−+PPG mice showed decreased plasma H2S level but enlarged plaque size and increased plasma and aortic ICAM-1 levels. NaHS suppressed ICAM-1 expression in tumor necrosis factor (TNF)-&agr;–treated HUVECs. NaHS inhibited I&kgr;B degradation and NF-&kgr;B nuclear translocation in HUVECs treated with TNF-&agr;. Conclusions—The vascular CSE/H2S pathway was disturbed in apoE−/− mice. H2S exerted an antiatherogenic effect and inhibited ICAM-1 expression in apoE−/− mice. H2S inhibited ICAM-1 expression in TNF-&agr;-induced HUVECs via the NF-&kgr;B pathway.

Endogenously generated sulfur dioxide and its vasorelaxant effect in rats

AbstractAim:The present study was designed to explore the endogenous production and localization of the sulfur dioxide (SO2)/aspartate aminotransferase pathway in vascular tissues of rats and to examine its vasorelaxant effect on isolated aortic rings, as well as the possible mechanisms.Methods:The content of SO2 in the samples was determined by using high performance liquid chromatography with fluorescence detection. Aspartate aminotransferase activity and its gene expression were measured by an enzymatic method and quantitative RT–PCR, respectively. Aspartate aminotransferase mRNA location in aorta was detected by in situ hybridization. The vasorelaxant effect of SO2 on isolated aortic rings of the rats was investigated in vitro. L-type calcium channel blocker, nicardipine, and L-type calcium channel agonist, Bay K8644, were used to explore the mechanisms by which SO2 relaxed the aortic rings.Results:Aorta had the highest SO2 content among the vascular tissues tested (P<0.01). The aortic aspartate aminotransferase mRNA located in endothelia and vascular smooth muscle cells beneath the endothelial layer. Furthermore, a physiological dose of the SO2 derivatives (Na2SO3/NaHSO3) relaxed isolated artery rings slightly, whereas higher doses (1–12 mmol/L) relaxed rings in a concentration-dependent manner. Pretreatment with nicardipine eliminated the vasorelaxant response of the norepinephrine-contracted rings to SO2 completely. Incubation with nicardipine or SO2 derivatives successfully prevented vasoconstriction induced by Bay K8644.Conclusion:Endogenous SO2 and its derivatives have a vasorelaxant function, the mechanisms of which might involve the inhibition of the L-type calcium channel.

Regulatory effects of hydrogen sulfide on IL-6, IL-8 and IL-10 levels in the plasma and pulmonary tissue of rats with acute lung injury.

We examined the possible role of hydrogen sulfide (H2S) in the pathogenesis of oleic acid (OA)-induced acute lung injury (ALI) and its regulatory effects on the inflammatory response. Compared to control rats, the OA-treated rats had decreased partial pressure of oxygen in the arterial blood (PaO2) levels, an increased pulmonary wet/dry weight (W/D) ratio, increased index of quantitative assessment (IQA) score and increased frequency of polymorphonuclear (PMN) cells in the lung 2, 4 or 6 h after OA injection (0.1 ml/kg, intravenous injection). In addition, significantly increased IL-6, IL-8 and IL-10 levels together with decreased H2S levels were observed in the plasma and lung tissue of OA-treated rats compared to controls. Administration of the H2S donor sodium hydrosulfide (NaHS, 56 μmol/L, intraperitoneal injection) into OA-treated rats increased the PaO2 level, reduced the lung W/D ratio and infiltration of PMN cells, and alleviated the degree of ALI (measured by the IQA score). In addition, NaHS decreased IL-6 and IL-8 levels but increased IL-10 levels in the plasma and lung tissues, suggesting that H2S may regulate the inflammatory response during ALI via regulation of IL-6, IL-8 and IL-10. Thus, the down-regulation of endogenous H2S production might be involved in the pathogenesis of OA-induced ALI in rats.

Hydrogen sulfide regulates lung tissue-oxidized glutathione and total antioxidant capacity in hypoxic pulmonary hypertensive rats

AbstractAim:To investigate the modulatory effect of sudium hydrosulfide on lung tissue-oxidized glutathione and total antioxidant capacity in the development of hypoxic pulmonary hypertension (HPH).Methods:After 21 d of hypoxia, the mean pulmonary artery pressure was measured by cardiac catheterization. The plasma H2S level and production of H2S in the lung tissues were determined by using a spectrophotometer. The lung homogenates were assayed for total antioxidant capacity (T-AOC), superoxide dismutase (SOD), oxidized glutathione (GSSG), reduced glutathione and malonaldehyde by colorimetry. The mRNA level of SOD was analyzed by real-time PCR, and the SOD expression was detected by Western blotting.Results:In the hypoxia group, the plasma H2S concentration and H2S production in the lung was significantly decreased compared with the control group (187.2±13.1 vs 299.6±12.4 μmol/L; 0.138±0.013 vs 0.289±0.036 nmol·mg−1·min−1, P<0.01). The administration of sodium hydrosulfide could reduce the mean pulmonary artery pressure by 31.2% compared with the hypoxia group (P<0.01). Treatment with sodium hydrosulfide decreased GSSG, and the T-AOC level of the lung tissues was enhanced compared with the hypoxia group (P<0.05). There were no significant changes in the lung tissue SOD mRNA level, protein level, and its activity among the 3 groups.Conclusion:Oxidative stress occurred in the development of HPH and was accompanied by a decrease in the endogenous production of H2S in the lung tissues. H2S acted as an antioxidant during the oxidative stress of HPH partly as a result of the attenuated GSSG content.

Regulatory effect of hydrogen sulfide on vascular collagen content in spontaneously hypertensive rats.

The present study aimed to examine the regulatory effect of hydrogen sulfide (H2S) on vascular collagen remodeling in hypertensive rats. After 5 weeks of H2S donor treatment, tail blood pressure, the endogenous H2S production rate, levels of hydroxyproline and collagen type I, collagen type I protein expression in the thoracic aorta, [3H]thymidine ([3H]TdR) incorporation, [3H]proline incorporation, and [3H]hydroxyproline secretion in cultured vascular smooth muscle cells (VSMCs) were measured. We also examined the effects of NaHS on angiotensin II–induced mitogen-activated protein kinase (MAPK) activation and angiotensin II type 1 (AT1) receptor binding affinity. Vascular hydroxyproline and collagen type I levels were high, and collagen type I immunohistochemical staining in the thoracic aorta was strong in SHRs compared to Wistar Kyoto (WKY) rats. [3H]TdR and [3H]proline incorporation and [3H]hydroxyproline secretion were also higher in cultured VSMCs from SHR than those from WKY rats. However, vascular H2S production was lower in SHR compared with WKY rats. Treatment with NaHS increased vascular H2S production in SHRs, and partly reversed the changes in [3H]TdR and [3H]proline incorporation and [3H]hydroxyproline secretion. In cultured VSMCs, [3H]TdR and [3H]proline incorporation stimulated by angiotensin II was inhibited by incubation with NaHS. The inhibitory effect of NaHS on VSMC proliferation and collagen generation was stronger in the SHR than in the WKY group. Moreover, NaHS could dose-dependently decrease angiotensin II-induced MAPK activation. NaHS also decreased AT1 receptor binding as well as the binding affinity of the AT1 receptor. Thus, in SHRs, which demonstrated vascular remodeling and collagen accumulation, the endogenous H2S pathway is involved in the regulation of excess vascular collagen.

Hydrogen Sulfide Attenuates Hyperhomocysteinemia-Induced Cardiomyocytic Endoplasmic Reticulum Stress in Rats

The mechanisms responsible for the cardioprotective effect of hydrogen sulfide (H(2)S) are unclear. The present study was designed to examine whether H(2)S could regulate hyperhomocysteinemia (HHcy)-induced cardiomyocytic endoplasmic reticulum (ER) stress. A rat model of HHcy was produced, and H9c2 cells (rat embryonic heart-derived cell line) were cultured. The plasma homocysteine was measured by using HPLC. Plasma H(2)S concentration and myocardial H(2)S production were measured with a sulfide-sensitive electrode. Confocal immunofluorescent analysis for cardiomyocytic C/EBP homologous protein (CHOP) was performed. Glucose-regulated protein 78 (GRP78), CHOP, and caspase 12 expressions by myocardial tissues and cleaved caspase 12 and p-eIF2alpha expressions by H9c2 cells were detected with Western blotting. The results showed that methionine overload induced HHcy, resulting in a marked cardiomyocytic ER stress, whereas endogenous production of H(2)S was reduced in rats with HHcy. H(2)S supplementation, however, decreased expressions of ER stress-associated proteins, including GRP78, CHOP, and caspase 12, by myocardial tissues in vivo. The inhibition of endogenous H(2)S production further enhanced cardiomyocytic ER stress, but H(2)S supplementation effectively antagonized the H9c2 cell CHOP, cleaved caspase 12 and p-eIF2alpha expressions induced by Hcy, thapsigargin, or tunicamycin in vitro. The results suggest that H(2)S can attenuate cardiomyocytic ER stress in HHcy-induced cardiomyocytic injury.

The biological effect of endogenous sulfur dioxide in the cardiovascular system

Sulfur dioxide is considered a toxic gas in air pollution and detrimental to many organs, however, it can be generated endogenously in the cardiovascular system in vivo. Gaseous sulfur dioxide has an endothelium-dependent vasorelaxing effect at low concentrations, but is endothelium-independent at high concentrations and has a negative inotropic effect on cardiac function. This vasorelaxing effect is mediated by adenosine triphosphate-sensitive calcium channels and L-type calcium channels. Under pathophysiological conditions, sulfur dioxide increases anti-inflammatory response and antioxidant capacities in pulmonary hypertensive rats. Sulfur dioxide also attenuates increased blood pressure and vascular remodeling in spontaneously hypertensive and hypoxic pulmonary hypertensive rats. Recent studies suggest that endogenous sulfur dioxide is also involved in the process of myocardial ischemia-reperfusion injury and lipid metabolism. Therefore, the evidence suggests that endogenous sulfur dioxide may be a novel gasotransmitter in the cardiovascular system. The significance of sulfur dioxide on the cardiovascular system is intriguing and appealing.

Endogenous generation of sulfur dioxide in rat tissues

While sulfur dioxide (SO(2)) has been previously known for its toxicological effects, it is now known to be produced endogenously in mammals from sulfur-containing amino acid L-cysteine. L-cysteine is catalyzed by cysteine dioxygenase (CDO) to L-cysteinesulfinate, which converts to β-sulfinylpyruvate through transamination by aspartate aminotransferase (AAT), and finally spontaneously decomposes to pyruvate and SO(2). The present study explored endogenous SO(2) production, and AAT and CDO distribution in different rat tissue. SO(2) content was highest in stomach, followed by tissues in the right ventricle, left ventricle, cerebral gray matter, pancreas, lung, cerebral white matter, renal medulla, spleen, renal cortex and liver. AAT activity and AAT1 mRNA expression were highest in the left ventricle, while AAT1 protein expression was highest in the right ventricle. AAT2 and CDO mRNA expressions were both highest in liver tissue. AAT2 protein expression was highest in the renal medulla, but CDO protein expression was highest in liver tissue. In all tissues, AAT1 and AAT2 were mainly distributed in the cytoplasm rather than the nucleus. These observed differences among tissues endogenously generating SO(2) and associated enzymes are important in implicating the discovery of SO(2) as a novel endogenous signaling molecule.

Effects of endogenous sulfur dioxide on monocrotaline-induced pulmonary hypertension in rats

AbstractAim:The present study aimed to explore the protective effect of endogenous sulfur dioxide (SO2) in the development of monocrotaline (MCT)-induced pulmonary hypertension (PH) in rats.Methods:Forty Wistar rats were randomly divided into the MCT group receiving MCT treatment, the MCT+L-aspartate-β-hydroxamate (HDX) group receiving MCT plus HDX treatment, the MCT+SO2 group receiving MCT plus SO2 donor treatment, and the control group. Mean pulmonary artery pressure (mPAP) and structural changes in pulmonary arteries were evaluated. SO2 content, aspartate aminotransferase activity, and gene expression were measured. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), reduced glutathione (GSH), oxidized glutathione, and malondialdehyde (MDA) levels were assayed.Results:In the MCT-treated rats, mPAP and right ventricle/(left ventricle+septum) increased significantly (P<0.01), pulmonary vascular structural remodeling developed, and SOD, GSH-Px, CAT, GSH, and MDA levels of lung homogenates significantly increased (P<0.01) in association with the elevated SO2 content, aspartate aminotransferase activity, and gene expression, compared with the control rats. In the MCT+HDX-treated rats, lung tissues and plasma SO2 content and aspartate aminotransferase activities decreased significantly, whereas the mPAP and pulmonary vascular structural remodeling were markedly aggravated with the decreased SOD, CAT, and GSH levels of lung tissue homogenates compared with the MCT-treated rats (P<0.01). In contrast, with the use of a SO2 donor, the pulmonary vascular structural remodeling was obviously lessened with elevated lung tissue SOD, GSH-Px, and MDA content, and plasma SOD, GSH-Px, and CAT levels.Conclusion:Endogenous SO2 might play a protective role in the pathogenesis of MCT-induced PH and promote endogenous antioxidative capacities.

Effects of sulfur dioxide on hypoxic pulmonary vascular structural remodeling

Hypoxic pulmonary hypertension is a pathophysiological process important in the development of various cardiopulmonary diseases. Recently, we found that sulfur dioxide could be produced endogenously by pulmonary vessels, and that it showed vascular regulatory capabilities. In this paper, we examined the role of sulfur dioxide in hypoxic pulmonary vascular structural remodeling (HPVSR). A total of 48 Wistar rats were divided into six groups. Rats in the hypoxic group, hypoxic+sulfur dioxide group, and hypoxic+hydroxamate group were left under hypoxic conditions, whereas the control group, control+sulfur dioxide group, and control+hydroxamate group rats were left in room air. For each group, we measured the pulmonary arterial pressure, sulfur dioxide content in plasma and lung tissue, glutamate oxaloacetate transaminase 1 and 2 mRNAs, micro- and ultra-structural changes in pulmonary arteries, proliferation of pulmonary smooth muscle cells, vascular collagen metabolism, pulmonary endothelial cell inflammatory response, and pulmonary vascular endothelin-1 production in the rats. In hypoxic rats, the content of sulfur dioxide in plasma and lung tissue decreased significantly in comparison with those in the control groups, and significant pulmonary hypertension, pulmonary vascular structural remodeling, and increased vascular inflammatory response were also observed in hypoxic rats. Sulfur dioxide donor significantly downregulated Raf-1, mitogen-activated protein kinase kinase-1 (MEK-1) and p-ERK/ERK, and inhibited pulmonary vascular smooth muscle cell proliferation, collagen remodeling and pulmonary vascular endothelial cell nuclear factor-κB (NF-κB), and intercellular adhesion molecule 1 (ICAM-1) expressions. It also prevented pulmonary hypertension and pulmonary vascular structural remodeling in association with the upregulated sulfur dioxide/glutamate oxaloacetate transaminase pathway. Hydroxamate, however, advanced pulmonary hypertension, pulmonary vascular structural remodeling, and inflammatory response of the pulmonary artery in association with a downregulated sulfur dioxide/glutamate oxaloacetate transaminase pathway. The results suggested that sulfur dioxide markedly inhibited Raf-1, MEK-1, and the phosphorylation of extracellular signal-regulated kinase (ERK), and then inhibited pulmonary arterial smooth muscle cell (PASMC) proliferation induced by hypoxia. The downregulated sulfur dioxide/glutamate oxaloacetate transaminase pathway may be involved in the mechanisms responsible for pulmonary hypertension and pulmonary vascular structural remodeling.