A protective role of ciglitazone in ox‐LDL‐induced rat microvascular endothelial cells via modulating PPARγ‐dependent AMPK/eNOS pathway

Abstract

Abstract Thiazolidinediones, the antidiabetic agents such as ciglitazone, has been proved to be effective in limiting atherosclerotic events. However, the underlying mechanism remains elucidative. Ox‐ LDL receptor‐1 ( LOX ‐1) plays a central role in ox‐ LDL ‐mediated atherosclerosis via endothelial nitric oxide synthase ( eNOS ) uncoupling and nitric oxide reduction. Therefore, we tested the hypothesis that ciglitazone, the PPAR γ agonist, protected endothelial cells against ox‐ LDL through regulating eNOS activity and LOX ‐1 signalling. In the present study, rat microvascular endothelial cells ( RMVEC s) were stimulated by ox‐ LDL . The impact of ciglitazone on cell apoptosis and angiogenesis, eNOS expression and phosphorylation, nitric oxide synthesis and related AMPK , Akt and VEGF signalling pathway were observed. Our data showed that both eNOS and Akt phosphorylation, VEGF expression and nitric oxide production were significantly decreased, RMVEC s ageing and apoptosis increased after ox‐ LDL induction for 24 hrs, all of which were effectively reversed by ciglitazone pre‐treatment. Meanwhile, phosphorylation of AMP ‐activated protein kinase ( AMPK ) was suppressed by ox‐ LDL , which was also prevented by ciglitazone. Of interest, AMPK inhibition abolished ciglitazone‐mediated eNOS function, nitric oxide synthesis and angiogenesis, and increased RMVEC s ageing and apoptosis. Further experiments showed that inhibition of PPAR γ significantly suppressed AMPK phosphorylation, eNOS expression and nitric oxide production. Ciglitazone‐mediated angiogenesis and reduced cell ageing and apoptosis were reversed. Furthermore, LOX ‐1 protein expression in RMVEC s was suppressed by ciglitazone, but re‐enhanced by blocking PPAR γ or AMPK . Ox‐ LDL ‐induced suppression of eNOS and nitric oxide synthesis were largely prevented by silencing LOX ‐1. Collectively, these data demonstrate that ciglitazone‐mediated PPAR γ activation suppresses LOX ‐1 and moderates AMPK / eNOS pathway, which contributes to endothelial cell survival and function preservation.