Dissecting molecular mechanisms underlying ferroptosis in human umbilical cord mesenchymal stem cells:Role of cystathionineγ-lyase/hydrogen sulfide pathway

BACKGROUND Ferroptosis can induce low retention and engraftment after mesenchymal stem cell(MSC)delivery,which is considered a major challenge to the effectiveness of MSC-based pulmonary arterial hypertension(PAH)therapy.Interestingly,the cystathionineγ-lyase(CSE)/hydrogen sulfide(H_(2)S)pathway may contribute to mediating ferroptosis.However,the influence of the CSE/H_(2)S pathway on ferroptosis in human umbilical cord MSCs(HUCMSCs)remains unclear.AIM To clarify whether the effect of HUCMSCs on vascular remodelling in PAH mice is affected by CSE/H_(2)S pathway-mediated ferroptosis,and to investigate the functions of the CSE/H_(2)S pathway in ferroptosis in HUCMSCs and the underlying mechanisms.METHODS Erastin and ferrostatin-1(Fer-1)were used to induce and inhibit ferroptosis,respectively.HUCMSCs were transfected with a vector to overexpress or inhibit expression of CSE.A PAH mouse model was established using 4-wk-old male BALB/c nude mice under hypoxic conditions,and pulmonary pressure and vascular remodelling were measured.The survival of HUCMSCs after delivery was observed by in vivo bioluminescence imaging.Cell viability,iron accumulation,reactive oxygen species production,cystine uptake,and lipid peroxidation in HUCMSCs were tested.Ferroptosis-related proteins and S-sulfhydrated Kelchlike ECH-associating protein 1(Keap1)were detected by western blot analysis.RESULTS In vivo,CSE overexpression improved cell survival after erastin-treated HUCMSC delivery in mice with hypoxiainduced PAH.In vitro,CSE overexpression improved H_(2)S production and ferroptosis-related indexes,such as cell viability,iron level,reactive oxygen species production,cystine uptake,lipid peroxidation,mitochondrial membrane density,and ferroptosis-related protein expression,in erastin-treated HUCMSCs.In contrast,in vivo,CSE inhibition decreased cell survival after Fer-1-treated HUCMSC delivery and aggravated vascular remodelling in PAH mice.In vitro,CSE inhibition decreased H_(2)S levels and restored ferroptosis in Fer-1-treated HUCMSCs.Interestingly,upregulation of the CSE/H_(2)S pathway induced Keap1 S-sulfhydration,which contributed to the inhibition of ferroptosis.CONCLUSION Regulation of the CSE/H_(2)S pathway in HUCMSCs contributes to the inhibition of ferroptosis and improves the suppressive effect on vascular remodelling in mice with hypoxia-induced PAH.Moreover,the protective effect of the CSE/H_(2)S pathway against ferroptosis in HUCMSCs is mediated via S-sulfhydrated Keap1/nuclear factor erythroid 2-related factor 2 signalling.The present study may provide a novel therapeutic avenue for improving the protective capacity of transplanted MSCs in PAH.

Relationship between cystathionine γ-lyase gene polymorphism and essential hypertension in Northern Chinese Han population

Background Hydrogen sulfide （H2S） plays an important role in the smooth muscle cell relaxation and thereby participates in the development of hypertension. Cystathionine γ-lyase is the key enzyme in the endogenous production of H2S. Up to now, the reports on the relationship between the polymorphisms of cystathionine γ-lyase gene （CTH） and essential hypertension （EH） are limited. This study was designed to assess their underlying relationship. Methods A total of 503 hypertensive patients and 490 age-, gender- and area-matched normotensive controls were enrolled in this study. Based on the FASTSNP, a web server to identify putative functional single nucleotide polymorphisms （SNPs） of genes, we selected two SNPs, rs482843 and rs1021737, in the CTH gene for genotyping. Genotyping was performed by the polymerase chain reaction and restriction fragment length polymorphism method （PCR-RFLP）. The frequencies of the alleles and genotypes between cases and controls were compared by the chi-square test. The program Haplo.stats was used to investigate the relationship between the haplotypes and EH. Results These two SNPs were in Hardy-Weinberg Equilibrium in both cases and controls. The genotype distribution and allele frequencies of them did not significantly differ between cases and controls （all P〉0.05）. In the stepwise logistic regression analysis we failed to observe their association with hypertension. In addition, none of the four estimated haplotypes or diplotypes significantly increased or decreased the risk of hypertension before or after adjustment for several known risk factors. Conclusions The present study suggests that the SNPs rs482843 and rs1021737 of the CTH gene were not associated with essential hypertension in the Northern Chinese Han population. However, replications in other populations and further functional studies are still necessary to clarify the role of the CTH gene in the pathogenesis of EH.

嗜热四膜虫胱硫醚γ-裂解酶Cgl1的表达、定位及功能分析

含硫氨基酸在不同的生物体中具有重要调节功能,转硫途径相关酶促进半胱氨酸的生成和硫化氢产生。本研究从嗜热四膜虫中鉴定一种胱硫醚γ-裂解酶(cystathionineγ-lyase 1,CGL1,TTHERM_00052400)基因。CGL1在营养生长期高水平表达,而在饥饿阶段和有性生殖期,维持在较低的表达水平。通过密码子优化,人工合成CGL1基因,构建重组表达质粒pGEX-CGL1,转化大肠杆菌BL21(DE3)。E.coli/pGEX-CGL1表达重组蛋白质GST-Cgl1,并通过亲和层析获得纯化。GST-Cgl1裂解胱硫醚产生半胱氨酸,也具有裂解半胱氨酸和同型半胱氨酸产生H_2S的活性。进一步构建重组质粒pNEO4-3HA-CGL1和pSMC1hpNEO-CGL1,转化四膜虫细胞,获得带有HA标签和干扰CGL1的突变体细胞株。免疫荧光定位表明,HA-Cgl1生长期定位在亲本大核,饥饿期定位在细胞质,有性生殖前期定位在亲本大核,而在后期定位在胞质中。CGL1干扰的突变体细胞株在有性生殖过程中不能形成合子核,发育中的小核异常降解,产生仅有大核的异常单细胞。结果表明,嗜热四膜虫含有进化中保守的胱硫醚γ-裂解酶Cgl1。Cgl1具有产生和裂解半胱氨酸的活性。Cgl1定位在细胞质和细胞核中,参与了有性生殖过程细胞核的发育。

Therapeutic importance of hydrogen sulfide in age-associated neurodegenerative diseases

Hydrogen sulfide(H2S)is a gasotransmitter that acts as an antioxidant and exhibits a wide variety of cytoprotective and physiological functions in age-associated diseases.One of the major causes of age-related diseases is oxidative stress.In recent years,the importance of H2S has become clear,although its antioxidant function has not yet been fully explored.The enzymes cystathionineβ-synthase,cystathionineγ-lya-se,and 3-mercaptopyruvate sulfurtransferase are involved in the enzymatic production of H2S.Previously,H2S was considered a neuromodulator,given its role in long-term hippocampal potentiation,but it is now also recognized as an antioxidant in age-related neurodegeneration.Due to aerobic metabolism,the central nervous system is vulnerable to oxidative stress in brain aging,resulting in age-associated degenerative diseases.H2S exerts its antioxidant effect by limiting free radical reactions through the activation of antioxidant enzymes,including superoxide dismutase,catalase,and glutathione peroxidase,which protect against the effects of aging by regulating apoptosis-related genes,including p53,Bax,and Bcl-2.This review explores the implications and mechanisms of H2S as an antioxidant in age-associated neurodegenerative diseases,including Alzheimer’s disease,Parkinson’s disease,Huntington’s disease,and Down syndrome.

Role of hydrogen sulfide in portal hypertension and esophagogastric junction vascular disease

AIM: To investigate the association between endogenous hydrogen sulfide (H2S) and portal hypertension as well as its effect on vascular smooth muscle cells.

Changes in Hydrogen Sulfide in Rats with Hepatic Cirrhosis in Different Stages

This study aimed to observe changes in the hydrogen sulfide（H_2S） system in the blood and liver tissue of rats with hepatic cirrhosis at different stages by studying the effect of H_2S on the course of hyperdynamic circulation in rats with hepatic cirrhosis. H_2S concentration in the blood from the portal vein and inferior vena cava of hepatic cirrhosis rat model induced with carbon tetrachloride was detected on the 15 th, 30 th, and 52 nd day. The expression of cystathionine β-synthase（CBS） and cystathionine γ-lyase（CSE） protein, and CBS and CSE mRNA in the liver was detected by immunohistochemistry and reverse transcriptase polymerase chain reaction（RT-PCR）, respectively. The results indicated that H_2S concentration in the blood from the portal vein and inferior vena cava of rats with hepatic cirrhosis was significantly lower than that in the control group. H_2S was gradually decreased with the development of the disease and significantly lower in the blood from portal vein than in the blood of inferior vena cava at the mid-stage and the late stage groups. The expression levels of CBS and CSE protein, and CBS and CSE mR NA in the livers with hepatic cirrhosis at different stages were all higher than those in the control group, and the expression gradually increased with the development of the disease. The expression of CBS was lower than CSE in the same stages. The results indicated that the CSE mRNA was expressed predominantly in the cirrhosis groups as compared with CBS mRNA. Among experimental rats, the H_2S system has an important effect on the occurrence and development of hyperdynamic circulation in rats with hepatic cirrhosis. This finding adds to the literature by demonstrating that H_2S protects vascular remodelling in the liver, and that CSE is indispensable in this process.

Electrophysiological effects of hydrogen sulfide on human atrial fibers

Background It has been reported that endogenous or exogenous hydrogen sulfide （H2S） exerts physiological effects in the vertebrate cardiovascular system. We have also demonstrated that H2S acts as an important regulator of electrophysiological properties in guinea pig papillary muscles and on pacemaker cells in sinoatrial nodes of rabbits. This study was to observe the electrophysiological effects of H2S on human atrial fibers. Methods Human atrial samples were collected during cardiac surgery. Parameters of action potential in human atrial specialized fibers were recorded using a standard intracellular microetectrode technique. Results NariS （H2S donor） （50, 100 and 200 pmol/L） decreased the amplitude of action potential （APA）, maximal rate of depolarization （Vmax）, velocity of diastolic （phase 4） depolarization （VDD） and rate of pacemaker firing （RPF）, and shortened the duration of 90% repolarization （APD90） in a concentration-dependent manner. ATP-sensitive K＋ （KATP） channel blocker glibenclamide （Gli, 20 μmol/L） partially blocked the effects of NariS （100 μmol/L） on human atrial fiber cells. The L-type Ca2＋ channel agonist Bay K8644 （0.5 μmol/L） also partially blocked the effects of NariS （100 μmol/L）. An inhibitor of cystathionine y-lyase （CSE）, DL-propargylglycine （PPG, 200 μmol/L）, increased APA, Vmax, VDD and RPF, and prolonged APDg0. Conclusions H2S exerts a negative chronotropic action and accelerates the repolarization of human atrial specialized fibers, possibly as a result of increases in potassium efflux through the opening of KATP channels and a concomitant decrease in calcium influx. Endogenous H2S may be generated by CSE and act as an important regulator of electrophysiological properties in human atrial fibers.