Amelioration of atherosclerosis in apolipoprotein E-deficient mice by inhibition of lipoprotein-associated phospholipase A2.

PURPOSE Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is involved in the pathogenesis of atherosclerosis, especially in advanced plaques. In the present study, the abilities of darapladib, a selective Lp-PLA(2) inhibitor, and lentivirus-mediated Lp-PLA(2) silencing on inflammation and atherosclerosis in apolipoprotein E-deficient mice were compared. METHODS Apolipoprotein E-deficient mice were fed on a high-fat diet and a constrictive collar was placed around the left carotid artery to induce plaque formation. The mice were randomly divided into control, negative control (NC), darapladib and RNA interference (RNAi) groups. Eight weeks after surgery, lentivirus-mediated RNAi construct or darapladib were used to decrease the expression of Lp-PLA(2). Plaques were collected five weeks later for histological analysis. Inflammatory gene expression in the atherosclerotic lesions were then determined at the mRNA and protein level. RESULTS The expression of pro-inflammatory cytokines was significantly reduced in the treatment group, compared to nontreatment group, whereas the plasma concentration of anti-inflammatory cytokines increased markedly. Moreover, our results demonstrated a significant reduction in plaque lipid content, as well as a rise in collagen content following Lp-PLA(2) inhibition. Interestingly, when comparing the two methods of Lp-PLA(2) inhibition, animals treated with Lp-PLA(2) RNAi were found to exhibit lower plaque areas and enhanced improvement of plaque stability as compared with animals treated with darapladib. Darapladib had no attenuating effect on atherosclerotic plaque area. These therapeutic effects were independent of plasma lipoprotein levels. CONCLUSIONS Lp-PLA(2) inhibition by darapladib or lentivirus-mediated RNAi ameliorated inflammation and atherosclerosis in apolipoprotein E-deficient mice. The effect was more prominent in the RNAi group.