Regulation of mediators of the mitochondrial pathway in apoptotic A549 cells by PCSK9 siRNA. (A and B) A549 cells were transfected with PCSK9 siRNA or control siRNA for 48 h and the levels of cyto c (A) in mitochondria (COXIV as loading control) and (B) cytosol (GAPDH as loading control) were measured by western blot analysis. (C) PCSK9 siRNA inhibited Bcl-2 expression and increased Bax expression as detected by western blot analysis. Representative western blot images are shown and bar graphs present quantified expression levels determined by densitometric analysis. Values are expressed as the mean ± standard deviation (n=3). The ratio of cyto c/COXIV (GAPDH) in control siRNA group was assigned as ‘1’ and the ratio of cyto c/COXIV (GAPDH) in PCSK9 siRNA group was assigned as proportion of control siRNA group compared with PCSK9 siRNA group. The GAPDH in C image was used to control the accounts for the samples when examining the Bax or Bcl-2 levels. *P<0.05 vs. control siRNA group. siRNA, small interfering RNA; PCSK9, proprotein convertase subtilisin/kexin type 9; Bcl-2, B-cell lymphoma 2; Bax, Bcl-2-associated X protein; cyto c, cytochrome c; COX, cyto c oxidase.