RÉSUMÉ
BACKGROUND:Ischemic postconditioning is one of the effective ways to reduce ischemia-reperfusion injury and has been more and more widely used in clinical practice in recent years,but its specific molecular mechanism has yet to be studied. OBJECTIVE:To investigate the role and mechanism of piRNA-005854 in the aging cardiomyocytes caused by hypoxic postconditioning. METHODS:In vitro,cardiomyocytes were administered 8 mg/mL D-galactose for 9 days to induce their aging.β-Galactosidase staining was used to observe the aging of cardiomyocytes.Senescent cells were treated with hypoxia/reoxygenation and hypoxic postconditioning.ELISA was utilized to detect changes in myocardial injury markers creatine kinase isoenzyme MB and lactate dehydrogenase levels.Western blot assay was applied to detect the expression changes of autophagy-related proteins LC3II,p62,ULK1 and phosphorylated ULK1 in aging cardiomyocytes.qRT-PCR was employed to determine the expression level of piRNA-005854.piRNA-005854 inhibitor and piRNA-005854 mimics were transferred into aging cardiomyocytes and followed with hypoxic postconditioning.Western blot assay was used to examine the expression of LC3II,p62,ULK1 and phosphorylated ULK1. RESULTS AND CONCLUSION:(1)D-galactose induced obvious senescence of cardiomyocytes 9 days later.(2)Compared with the normoxia group,creatine kinase isoenzyme MB and lactate dehydrogenase levels increased in the hypoxia/reoxygenation group(P<0.01);LC3 II/I expression was increased;p62 expression was decreased;ULK1 phosphorylation level was increased,and piRNA-005854 expression was increased(P<0.01).(3)Compared with the hypoxia/reoxygenation group,creatine kinase isoenzyme MB and lactate dehydrogenase levels significantly reduced in the hypoxic postconditioning group(P<0.01);LC3 II/I expression significantly decreased(P<0.05);p62 expression increased(P<0.01);ULK1 phosphorylation level decreased(P<0.05),and piRNA-005854 expression decreased(P<0.01).(4)After transfection of piRNA-005854 inhibitor,LC3II/I expression was decreased(P<0.01);the expression of p62 was increased significantly(P<0.05);the phosphorylation level of ULK1 was decreased significantly(P<0.01).After transfection of piRNA-005854 mimics,LC3II/I expression was increased significantly;the expression of p62 was decreased,and the phosphorylation level of ULK1 was increased significantly(P<0.01).(5)The results show that piRNA-005854-mediated reduction of ULK1-dependent autophagy level is a possible mechanism that hypoxic postconditioning exerts its protective effect on aging cardiomyocytes.
RÉSUMÉ
BACKGROUND:Hyperhomocysteinemia is closely related to the function of islet β cells,but its specific molecular mechanism is not fully understood. OBJECTIVE:To investigate the role of N6 methyltransferase-like 3(METTL3)in homocysteine(Hcy)-induced autophagy of mouse islet β cells. METHODS:The 3rd and 4th generation mouse islet β cells were taken for the experiment.(1)Cell modeling and grouping:cells in control group were not treated with Hcy,while those in homocysteine group were treated with 100 μmol/L Hcy for 48 hours.(2)The mouse islet β-cells were transfected with the plasmids overexpressing Ad-METTL3 and si-METTL3 according to the instructions of LipofectamineTM 2000.Three different interfering fragments were designed,and the one with the best interfering efficiency was verified and screened by PCR.(3)After transfection,the cells were divided into control group,Hcy group,Ad-NC(negative control)+Hcy group,Ad-METTL3+Hcy group,si-NC(negative control)+Hcy group and si-METTL3+Hcy group.(4)qRT-PCR and western blot were used to detect the expression levels of METTL3 and autophagy-related proteins LC3Ⅱ/Ⅰ and p62 in cells.Insulin level was determined by ELISA to evaluate insulin secretion capacity of islet cells.Autophagy-related proteins and insulin level were detected after overexpression and interference with METTL3. RESULTS AND CONCLUSION:Compared with the control group,the expression level of LC3Ⅱ/Ⅰ was increased(P＜0.05),the expression of p62 was significantly reduced(P＜0.05),and the insulin secretion capacity was significantly decreased(P＜0.05)in the Hcy group.Compared with the control group,the protein and mRNA levels of METTL3 were reduced in the Hcy group(P＜0.05).After METTL3 silencing in islet β cells,Hcy further upregulated the expression of LC3Ⅱ/Ⅰ(P＜0.05),significantly dowregulated the expression of p62(P＜0.05),and increased the insulin level(P＜0.05).After overexpression of METTL3,Hcy significantly decreased the LC3Ⅱ/Ⅰ expression and increased the p62 expression in islet β cells(P＜0.05).To conclude,METTL3 is involved in the Hcy-induced autophagy regulation of islet β cells and plays a role in the regulation of insulin secretion.