HO-1 Induced by Cilostazol Protects Against TNF-<FONT FACE= HCI Tulip >&#1345;-associated Cytotoxicity via a PPAR-&#1347;-dependent Pathway in Human Endothelial Cells

HO-1 Induced by Cilostazol Protects Against TNF-<FONT FACE= HCI Tulip >&#1345;-associated Cytotoxicity via a PPAR-&#1347;-dependent Pathway in Human Endothelial Cells

A large body of evidence has indicated that induction of endogenous antioxidative proteins seems to be a reasonable strategy for delaying the progression of cell injury. In our previous study, cilostazol was found to increase the expression of the antioxidant enzyme heme oxygenase-1 (HO-1) in synovial cells. Thus, the present study was undertaken to examine whether cilostazol is able to counteract tumor necrosis factor-&#1345; (TNF-&#1345;)-induced cell death in endothelial cells via the induction of HO-1 expression. We exposed human umbilical vein endothelial cells (HUVECs) to TNF-&#1345; (50 ng/ml), with or without cilostazol (10&#1356;M). Pretreatment with cilostazol markedly reduced TNF-&#1345;-induced viability loss in the HUVECs, which was reversed by zinc protoporphyrine IX (ZnPP), an inhibitor of HO-1. Moreover, cilostazol increased HO-1 protein and mRNA expression. Cilostazol-induced HO-1 induction was markedly attenuated not only by ZnPP but also by copper-protoporphyrin IX (CuPP). In an assay measuring peroxisome proliferator-activated receptor-&#1347; (PPAR-&#1347;) transcription activity, cilostazol directly increased PPAR-&#1347; transcriptional activity which was completely abolished by HO-1 inhibitor. Furthermore, increased PPAR-&#1347; activity by cilostazol and rosiglitazone was completely abolished in cells transfected with HO-1 siRNA. Taken together, these results indicate that cilostazol up-regulates HO-1 and protects cells against TNF-&#1345;-induced endothelial cytotoxicity via a PPAR-&#1347;- dependent pathway.