Anti-Inflammatory Role of Cilostazol in Vascular Smooth Muscle Cells In vitro and In vivo

Aim: Cilostazol is a selective inhibitor of phosphodiesterase 3, by which it increases intracellular cAMP and activates protein kinase A, thereby inhibiting platelet aggregation and inducing peripheral vasodilation. We investigated whether cilostazol might prevent nuclear factor (NF)-kappa B activation by activating AMP-activated protein kinase (AMPK) in vascular smooth muscle cells (VSMC). Methods and Results: Cilostazol was observed to activate AMPK, as well as its downstream target, acetyl-CoA carboxylase, in rat VSMC. Phosphorylation of AMPK with cilostazol was not affected by co-treatment with an adenylate cyclase inhibitor, SQ 22536. Furthermore, a cell-permeable cyclic AMP analog, pCTP-cAMP, did not influence cilostazol-induced AMPK phosphorylation. These findings suggest that cilostazol-induced AMPK activation occurs through a signalling pathway independent of cyclic AMP. Cilostazol dose-dependently inhibited LPS-induced NF-kappa B activation in the present study. It was also observed to inhibit LPS-induced iNOS gene promoter activity and iNOS gene expression, resulting in markedly reduced NO production. An AMPK inhibitor compound C or siRNA for AMPK attenuated the observed cilostazol-induced inhibition of NF-kappa B activation by LPS. Ingestion of cilostazol inhibited NF-kappa B activation, as well as the induction of iNOS mRNA and protein expression, within the aortas of LPS-treated rats. Conclusion: In light of these findings, we suggest that cilostazol might attenuate cytokine-induced expression of the iNOS gene by inhibiting NF-kappa B following AMPK activation in VSMC.