Kallistatin attenuates endothelial senescence by modulating Let‐7g‐mediated miR‐34a‐SIRT1‐eNOSpathway

AbstractKallistatin, a plasma protein, protects against vascular and organ injury. This study is aimed to investigate the role and mechanism of kallistatin in endothelial senescence. Kallistatin inhibited H2O2‐induced senescence in human endothelial cells, as indicated by reduced senescence‐associated‐β‐galactosidase activity, p16INK4aand plasminogen activator inhibitor‐1 expression, and elevated telomerase activity. Kallistatin blocked H2O2‐induced superoxide formation,NADPHoxidase levels andVCAM‐1,ICAM‐1,IL‐6 and miR‐34a synthesis. Kallistatin reversed H2O2‐mediated inhibition of endothelial nitric oxide synthase (eNOS),SIRT1, catalase and superoxide dismutase (SOD)‐2 expression, and kallistatin alone stimulated the synthesis of these antioxidant enzymes. Moreover, kallistatin's anti‐senescence and anti‐oxidant effects were attributed toSIRT1‐mediatedeNOSpathway. Kallistatin, via interaction with tyrosine kinase, up‐regulated Let‐7g, whereas Let‐7g inhibitor abolished kallistatin's effects on miR‐34a andSIRT1/eNOSsynthesis, leading to inhibition of senescence, oxidative stress and inflammation. Furthermore, lung endothelial cells isolated from endothelium‐specific kallistatin knockout mice displayed marked reduction in mouse kallistatin levels. Kallistatin deficiency in mouse endothelial cells exacerbated senescence, oxidative stress and inflammation compared to wild‐type mouse endothelial cells, and H2O2treatment further magnified these effects. Kallistatin deficiency caused marked reduction in Let‐7g,SIRT1,eNOS, catalase andSOD‐1mRNAlevels, and elevated miR‐34a synthesis in mouse endothelial cells. These findings indicate that endogenous kallistatin through novel mechanisms protects against endothelial senescence by modulating Let‐7g‐mediated miR‐34a‐SIRT1‐eNOSpathway.