Sirolimus and Everolimus Induce Endothelial Cellular Senescence Via Sirtuin 1 Down-Regulation : Therapeutic Implication of Cilostazol After Drug-Eluting Stent Implantation

ObjectivesThe aim of this study was to compare the effects of paclitaxel, sirolimus, and everolimus on the senescent phenotype in human endothelial cells, and to further investigate possible involvement of mammalian sirtuin 1 (Sirt1) down-regulation as a mechanism.BackgroundEndothelial cell senescence may play a role in impaired re-endothelialization after drug-eluting stent (DES) implantation. Recently, the down-regulation of Sirt1 has been shown to mediate oxidative stress-induced endothelial senescence.MethodsSenescent human umbilical vein endothelial cells (HUVEC) were judged by senescence-associated β-galactosidase assay (SA-βgal), morphological appearance, and plasminogen activator inhibitor (PAI)-1.ResultsTreatment with paclitaxel, sirolimus, and everolimus significantly caused a senescent phenotype and PAI-1 up-regulation, associated with a decrease in endothelial nitric oxide synthase (eNOS) and Sirt1 expression. Overexpression of Sirt1 or Sirt1 activation reversed the sirolimus- or everolimus-induced senescent phenotype. Interestingly, paclitaxel-induced senescence was not suppressed by Sirt1 overexpression, suggesting the existence of a different mechanism. Cilostazol markedly inhibited the sirolimus- or everolimus-induced senescent phenotype (sirolimus or everolimus [2.5 nmol/l]; 49.2% or 53.0% SA-βgal positive vs. only 13.6% or 14.6% with cilostazol [100 μmol/l]) and PAI-1 up-regulation, but had no influence on the effects of paclitaxel. Finally, aspirin significantly blunted sirolimus- or everolimus-induced senescence, but neither ticlopidine nor clopidogrel had any effects.ConclusionsSirolimus and everolimus induce endothelial senescence involving down-regulation of Sirt1. In contrast, the development of endothelial senescence by paclitaxel involves a Sirt1-independent pathway. Because sirolimus and everolimus are involved in Sirt1 modulation, cilostazol rescues HUVEC from sirolimus- or everolimus-induced senescence. These results may have therapeutic implications in the clinical sequelae after DES implantation.