AimTo explore the effect of PCSK9 siRNA on Bax, Bcl-2 expression in THP-1 derived macrophages apoptosis induced by ox-LDL.MethodsCells were incubated with varied concentrations of ox-LDL for different time.Western blot were conducted to detect the expression of Bax and Bcl-2. The siRNAs for PCSK9 were designed and synthesized, then THP-1 macrophages were transfected with PCSK9 siRNA (30, 50, 80 nmol/L) for 24 h and then a high level of ox-LDL (80 μg/mL) for an additional 48-hr. Bax , Bcl-2 protein levels were measured by Western blot and apoptosis was measured with Hoechst 33258 staining.Resultsox-LDL (20, 40, 60, 80 μg/mL) increased Bax expression in a dose-dependent manner, but inversely decreased Bcl-2 expression. Furthermore, 80 μg/mL ox-LDL increased Bax expression in a time-dependent manner, but inversely decreased Bcl-2 expression. However, PCSK9 siRNA attenuated ox-LDL-induced up-regulation of Bax, down-regulation of Bcl-2, and THP-1 cell apoptosis in a dose-dependent manner.ConclusionThe effect of PCSK9-siRNA aganist ox-LDL-induced THP-1 cell apoptosis is associated with down-regulating of Bax and up-regulating of Bcl-2.