Yaqian Huang

Hydrogen sulfide suppresses oxidized low-density lipoprotein (ox-LDL)-stimulated monocyte chemoattractant protein 1 generation from macrophages via the nuclear factor κB (NF-κB) pathway.

Background: The mechanisms by which H2S regulates inflammation remain unclear. Results: H2S inhibits NF-κB p65 phosphorylation, nuclear translocation, DNA binding activity, and recruitment to MCP-1 promoter in ox-LDL-treated macrophages by targeting the free sulfhydryl group on cysteine 38 in p65. Conclusion: H2S inhibits macrophage inflammation by suppressing NF-κB activation. Significance: These findings reveal mechanisms for regulation of NF-κB pathway by H2S. This study was designed to examine the role of hydrogen sulfide (H2S) in the generation of oxidized low-density lipoprotein (ox-LDL)-stimulated monocyte chemoattractant protein 1 (MCP-1) from macrophages and possible mechanisms. THP-1 cells and RAW macrophages were pretreated with sodium hydrosulfide (NaHS) and hexyl acrylate and then treated with ox-LDL. The results showed that ox-LDL treatment down-regulated the H2S/cystathionine-β-synthase pathway, with increased MCP-1 protein and mRNA expression in both THP-1 cells and RAW macrophages. Hexyl acrylate promoted ox-LDL-induced inflammation, whereas the H2S donor NaHS inhibited it. NaHS markedly suppressed NF-κB p65 phosphorylation, nuclear translocation, DNA binding activity, and recruitment to the MCP-1 promoter in ox-LDL-treated macrophages. Furthermore, NaHS decreased the ratio of free thiol groups in p65, whereas the thiol reductant DTT reversed the inhibiting effect of H2S on the p65 DNA binding activity. Most importantly, site-specific mutation of cysteine 38 to serine in p65 abolished the effect of H2S on the sulfhydration of NF-κB and ox-LDL-induced NF-κB activation. These results suggested that endogenous H2S inhibited ox-LDL-induced macrophage inflammation by suppressing NF-κB p65 phosphorylation, nuclear translocation, DNA binding activity, and recruitment to the MCP-1 promoter. The sulfhydration of free thiol group on cysteine 38 in p65 served as a molecular mechanism by which H2S inhibited NF-κB pathway activation in ox-LDL-induced macrophage inflammation.

Sulfur dioxide inhibits vascular smooth muscle cell proliferation via suppressing the Erk/MAP kinase pathway mediated by cAMP/PKA signaling

The present study was designed to investigate the role of endogenous sulfur dioxide (SO2) in vascular smooth muscle cell (VSMC) proliferation, and explore the possible role of cross-talk between cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) and extracellular signal-regulated kinase (Erk)/mitogen-activated protein kinase (MAPK) pathways in this action. By cell counting, growth curve depict, flow cytometry and bromodeoxyuridine (BrdU) labeling assays, we found that SO2 inhibited VSMC proliferation by preventing cell cycle progression from G1 to S phase and by reducing DNA synthesis. SO2 synthase aspartate aminotransferase (AAT1 and AAT2) overexpression significantly inhibited serum-induced proliferating cell nuclear antigen (PCNA) protein expression in VSMCs, demonstrated by western blot analysis. Moreover, overexpression of AAT1 or AAT2 markedly reduced incorporation of BrdU in serum-treated VSMCs. By contrast, either AAT1 or AAT2 knockdown significantly exacerbated serum-stimulated VSMC proliferation. Thus, both exogenous- and endogenous-derived SO2 suppressed serum-induced VSMC proliferation. However, annexin V-propidium iodide (PI) staining and cell cycle analysis demonstrated that SO2 did not influence VSMC apoptosis in the serum-induced proliferation model. In a platelet-derived growth factor (PDGF)-BB-stimulated VSMC proliferation model, SO2 dephosphorylated the active sites of Erk1/2, MAPK kinase 1/2 and RAF proto-oncogene serine/threonine-protein kinase (c-Raf) induced by PDGF-BB. However, the inactivation of the three kinases of the Erk/MAPK pathway was not due to the separate interferences on them by SO2 simultaneously, but a consequence of the influence on the upstream activity of the c-Raf molecule. Hence, we examined the cAMP/PKA pathway, which could inhibit Erk/MAPK transduction in VSMCs. The results showed that SO2 could stimulate the cAMP/PKA pathway to block c-Raf activation, whereas the Ser259 site on c-Raf had an important role in SO2-induced suppression of Erk/MAPK pathway. The present study firstly demonstrated that SO2 exerted a negative regulation of VSMC proliferation via suppressing the Erk/MAPK pathway mediated by cAMP/PKA signaling.

Endogenous Sulfur Dioxide: A New Member of Gasotransmitter Family in the Cardiovascular System

Sulfur dioxide (SO2) was previously regarded as a toxic gas in atmospheric pollutants. But it has been found to be endogenously generated from metabolism of sulfur-containing amino acids in mammals through transamination by aspartate aminotransferase (AAT). SO2 could be produced in cardiovascular tissues catalyzed by its synthase AAT. In recent years, studies revealed that SO2 had physiological effects on the cardiovascular system, including vasorelaxation and cardiac function regulation. In addition, the pathophysiological effects of SO2 were also determined. For example, SO2 ameliorated systemic hypertension and pulmonary hypertension, prevented the development of atherosclerosis, and protected against myocardial ischemia-reperfusion (I/R) injury and isoproterenol-induced myocardial injury. These findings suggested that endogenous SO2 was a novel gasotransmitter in the cardiovascular system and provided a new therapy target for cardiovascular diseases.

H2S-Induced Sulfhydration: Biological Function and Detection Methodology

At appropriate concentrations, hydrogen sulfide, a well-known gasotransmitter, plays important roles in both physiology and pathophysiology. Increasing evidence suggests that modifying thiol groups of specific cysteines in target proteins via sulfhydration or persulfidation is one of the important mechanisms responsible for the biological functions of hydrogen sulfide. A variety of key proteins of different cellular pathways in mammals have been reported to be sulfhydrated by hydrogen sulfide to participate and regulate the processes of cell survival/death, cell differentiation, cell proliferation/hypertrophy, cellular metabolism, mitochondrial bioenergetics/biogenesis, endoplasmic reticulum stress, vasorelaxtion, inflammation, oxidative stress, etc. Moreover, S-sulfhydration also exerts many biological functions through the cross-talk with other post-translational modifications including phosphorylation, S-nitrosylation and tyrosine nitration. This review summarizes recent studies of hydrogen sulfide-induced sulfhydration as a posttranslational modification, an important biological function of hydrogen sulfide, and sulfhydrated proteins are introduced. Additionally, we discuss the main methods of detecting sulfhydration of proteins.

Downregulation of Endogenous Hydrogen Sulfide Pathway Is Involved in Mitochondrion-Related Endothelial Cell Apoptosis Induced by High Salt

Background. The study aimed to investigate whether endogenous H2S pathway was involved in high-salt-stimulated mitochondria-related vascular endothelial cell (VEC) apoptosis. Methods. Cultured human umbilical vein endothelial cells (HUVECs) were used in the study. H2S content in the supernatant was detected. Western blot was used to detect expression of cystathionine gamma-lyase (CSE), cleaved-caspase-3, and mitochondrial and cytosolic cytochrome c (cytc). Fluorescent probes were used to quantitatively detect superoxide anion generation and measure the in situ superoxide anion generation in HUVEC. Mitochondrial membrane pore opening, mitochondrial membrane potential, and caspase-9 activities were measured. The cell apoptosis was detected by cell death ELISA and TdT-mediated dUTP nick end labeling (TUNEL) methods. Results. High-salt treatment downregulated the endogenous VEC H2S/CSE pathway, in association with increased generation of oxygen free radicals, decreased mitochondrial membrane potential, enhanced the opening of mitochondrial membrane permeability transition pore and leakage of mitochondrial cytc, activated cytoplasmic caspase-9 and caspase-3 and subsequently induced VEC apoptosis. However, supplementation of H2S donor markedly inhibited VEC oxidative stress and mitochondria-related VEC apoptosis induced by high salt. Conclusion. H2S/CSE pathway is an important endogenous defensive system in endothelial cells antagonizing high-salt insult. The protective mechanisms for VEC damage might involve inhibiting oxidative stress and protecting mitochondrial injury.

Hydrogen Sulfide Inhibits High-Salt Diet-Induced Renal Oxidative Stress and Kidney Injury in Dahl Rats.

Background. The study was designed to investigate if H2S could inhibit high-salt diet-induced renal excessive oxidative stress and kidney injury in Dahl rats. Methods. Male salt-sensitive Dahl and SD rats were used. Blood pressure (BP), serum creatinine, urea, creatinine clearance rate, and 24-hour urine protein were measured. Renal ultra- and microstructures were observed. Collagen-I and -III contents the oxidants and antioxidants levels in renal tissue were detected. Keap1/Nrf2 association and Keap1 s-sulfhydration were detected. Results. After 8 weeks of high-salt diet, BP was significantly increased, renal function and structure were impaired, and collagen deposition was abundant in renal tissues with increased renal MPO activity, H2O2, MDA, GSSG, and •OH contents, reduced renal T-AOC and GSH contents, CAT, GSH-PX and SOD activity, and SOD expressions in Dahl rats. Furthermore, endogenous H2S in renal tissues was decreased in Dahl rats. H2S donor, however, decreased BP, improved renal function and structure, and inhibited collagen excessive deposition in kidney, in association with increased antioxidative activity and reduced oxidative stress in renal tissues. H2S activated Nrf2 by inducing Keap1 s-sulfhydration and subsequent Keap1/Nrf2 disassociation. Conclusions. H2S protected against high-salt diet-induced renal injury associated with enhanced antioxidant capacity and inhibited renal oxidative stress.

A meta-analysis of re-treatment for intravenous immunoglobulin-resistant Kawasaki disease

OBJECTIVE To determine the optimal drug therapy for intravenous immunoglobulin-resistant Kawasaki disease. METHODS Studies regarding drug therapy for intravenous immunoglobulin-resistant Kawasaki disease were selected from medical electronic databases including PubMed, Medline, Elsevier, and Springer Link. The effectiveness in terms of temperature recovery and coronary artery damage was compared between a second intravenous immunoglobulin treatment and glucocorticosteroid treatment for children with intravenous immunoglobulin-resistant Kawasaki disease using meta-analysis with Review Manager 5.3 software. Indices to evaluate the effects were body temperature, biomarker levels, and coronary artery lesions detected by echocardiography. Results are reported as relative risks or odds ratio with a 95% confidence interval and p<0.05. RESULTS Meta-analysis included 52 patients in the second intravenous immunoglobulin treatment group and 75 patients in the glucocorticosteroid treatment control group from four studies that met our inclusion criteria. Temperatures of patients who received glucocorticosteroid treatment were effectively controlled compared with those who received a second intravenous immunoglobulin treatment (relative risk=0.73, 95% confidence interval: 0.58-0.92, p=0.007). There were no differences, however, in the incidence of coronary artery lesions between the two groups (odds ratio=1.55, 95% confidence interval: 0.57-4.20, p=0.39). CONCLUSIONS Glucocorticosteroids are more effective in controlling body temperature compared with intravenous immunoglobulin re-treatment in intravenous immunoglobulin-resistant Kawasaki disease children; however, glucocorticosteroids and intravenous immunoglobulin re-treatment showed no difference in the prevention of coronary artery lesions.

Mechanical stretching stimulates collagen synthesis via down-regulating SO2/AAT1 pathway

The aim of the study was to investigate the role of endogenous sulfur dioxide (SO2)/ aspartate aminotransferase 1 (AAT1) pathway in stretch-induced excessive collagen expression and its mechanism. The mechanical stretch downregulated SO2/AAT1 pathway and increased collagen I and III protein expression. Importantly, AAT1 overexpression blocked the increase in collagen I and III expression, transforming growth factor-β1 (TGF- β1) expression and phosphorylation of Smad2/3 induced by stretch, but AAT1 knockdown mimicked the increase in collagen I and III expression, TGF- β1 expression and phosphorylation of Smad2/3 induced by stretch. Mechanistically, SB431542, a TGF-β1/Smad2/3 inhibitor, eliminated excessive collagen I and III accumulation induced by AAT1 knockdown, stretch or stretch plus AAT1 knockdown. In a rat model of high pulmonary blood flow-induced pulmonary vascular collagen accumulation, AAT1 expression and SO2 content in lung tissues of rat were reduced in shunt rats with high pulmonary blood flow. Supplement of SO2 derivatives inhibited activation of TGF- β1/Smad2/3 pathway and alleviated the excessive collagen accumulation in lung tissues of shunt rats. The results suggested that deficiency of endogenous SO2/AAT1 pathway mediated mechanical stretch-stimulated abnormal collagen accumulation via TGF-β1/Smad2/3 pathway.

Sulfur Dioxide Protects Against Collagen Accumulation in Pulmonary Artery in Association With Downregulation of the Transforming Growth Factor β1/Smad Pathway in Pulmonary Hypertensive Rats

BACKGROUND We aimed to explore the role of endogenous sulfur dioxide (SO2) in pulmonary vascular collagen remodeling induced by monocrotaline and its mechanisms. METHODS AND RESULTS A rat model of monocrotaline-induced pulmonary vascular collagen remodeling was developed and administered with l-aspartate-β-hydroxamate or SO2 donor. The morphology of small pulmonary arteries and collagen metabolism were examined. Cultured pulmonary arterial fibroblasts stimulated by transforming growth factor β1 (TGF-β1) were used to explore the mechanism. The results showed that in monocrotaline-treated rats, mean pulmonary artery pressure increased markedly, small pulmonary arterial remodeling developed, and collagen deposition in lung tissue and pulmonary arteries increased significantly in association with elevated SO2 content, aspartate aminotransferase (AAT) activity, and expression of AAT1 compared with control rats. Interestingly, l-aspartate-β-hydroxamate, an inhibitor of SO2 generation, further aggravated pulmonary vascular collagen remodeling in monocrotaline-treated rats, and inhibition of SO2 in pulmonary artery smooth muscle cells activated collagen accumulation in pulmonary arterial fibroblasts. SO2 donor, however, alleviated pulmonary vascular collagen remodeling with inhibited collagen synthesis, augmented collagen degradation, and decreased TGF-β1 expression of pulmonary arteries. Mechanistically, overexpression of AAT1, a key enzyme of SO2 production, prevented the activation of the TGF-β/type I TGF-β receptor/Smad2/3 signaling pathway and abnormal collagen synthesis in pulmonary arterial fibroblasts. In contrast, knockdown of AAT1 exacerbated Smad2/3 phosphorylation and deposition of collagen types I and III in TGF-β1-treated pulmonary arterial fibroblasts. CONCLUSIONS Endogenous SO2 plays a protective role in pulmonary artery collagen accumulation induced by monocrotaline via inhibition of the TGF-β/type I TGF-β receptor/Smad2/3 pathway.

Downregulated endogenous sulfur dioxide/aspartate aminotransferase pathway is involved in angiotensin II-stimulated cardiomyocyte autophagy and myocardial hypertrophy in mice

BACKGROUND The study was designed to investigate if endogenous sulfur dioxide (SO2) was involved in cardiomyocyte autophagy and myocardial hypertrophy stimulated by angiotensin II (Ang II). METHODS Thirty-two C57 mice were randomly divided into control, SO2, Ang II and Ang II+SO2 groups. Human myocardial cell line H9c2 was divided into four groups including control, SO2, Ang II and Ang II+SO2 groups. Blood pressure and myocardial hypertrophy of the mice were measured two weeks after Ang II administration. LC3 II/I ratio, and Beclin1, Atg4B and p62 expressions were determined both in vivo and in vitro. Autophagosome was observed in H9c2 cells with confocal microscope. Endogenous SO2 generation and aspartate aminotransferase (AAT) expression were measured. RESULTS In animal studies, hypertension and myocardial hypertrophy developed two weeks after Ang II administration. LC3 II/I ratio and Beclin1 and Atg4B expressions were markedly elevated (P all <0.05), but p62 expression was lowered (P<0.05) both in vivo and in vitro. Compared with control group, endogenous SO2 levels, AAT activity and AAT2 expression were obviously down-regulated (P all <0.05). However, SO2 donor significantly reduced Ang II-induced myocardial hypertrophy in mice. LC3 II/I ratio and Beclin1 and Atg4B expressions were down-regulated (P all <0.05) but p62 expression was significantly increased (P<0.05) in the presence of SO2 both in vivo and in vitro. CONCLUSION Down-regulated endogenous SO2/AAT2 pathway might be involved in the pathogenesis of myocardial hypertrophy. SO2 prevented Ang II -induced myocardial hypertrophy accompanied by down-regulating cardiomyocyte autophagy.