Abstract
Cilostazol is a selective inhibitor of phosphodiesterase type III that inhibits platelet aggregation. The beneficial effects of cilostazol have been attributed not only to its antiplatelet functions but also to its actions on the endothelium. Whether cilostazol regulates endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) through mitogen-activated protein kinase (MAPK) remains undetermined. The aim of this study was to investigate the effects of cilostazol on ET-1 and eNOS expression in HUVECs, and to assess its relationship with MAPK activity. HUVECs were cultured in vitro, stimulated with TNF-α, and pretreated with different concentrations of cilostazol. ET-1 and eNOS levels in the supernatant were detected by ELISA. RT-qPCR was performed to detect the mRNA expression levels of ET-1 and eNOS. The phosphorylation levels of p38/MAPK and protein expression levels of ET-1 and eNOS were assessed using western blotting. A P38 inhibitor, SB203580, was utilized to further validate the involvement of p38/MAPK in the regulation. Expression of ET-1, which was upregulated by TNF-α, was significantly suppressed by cilostazol in a dose-dependent manner, meanwhile, with as the cilostazol concentration was increased, the expression of eNOS increased as well. In addition, cilostazol also decreased phosphorylation of p38, which was upregulated by TNF-α. The observed upregulation of eNOS and ET-1 levels were completely abolished upon p38 inhibitor treatment, indicating the involvement of the p38/MAPK pathway in cilostazol-induced regulation of eNOS and ET-1 in HUVECs. The results indicated that cilostazol regulates ET-1 and eNOS production by suppressing the p38/MAPK signaling pathway in TNF-α-stimulated HUVECs, and this may contribute to the protective effects of cilostazol on the endothelium.