Amelioration of atherosclerosis in apolipoprotein E-deficient mice by combined RNA interference of lipoprotein-associated phospholipase A(2) and YKL-40

To test the hypothesis that combined RNA interference (RNAi) of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) and YKL-40 is superior to RNAi of Lp-PLA(2) or YKL-40 alone in ameliorating atherosclerosis. A total of 120 apolipoprotein E-deficient mice (apoE(-/-) mice) were randomly divided into five groups, including the vehicle alone, scrambled RNAi, Lp-PLA(2) RNAi, YKL-40 RNAi, and combined Lp-PLA(2) and YKL-40 RNAi groups. Constrictive collars were used to induce plaque formation. Lp-PLA(2) RNAi and YKL-40 RNAi viral suspensions were transduced into carotid plaques of the mice. Carotid plaques were harvested for histological analysis four weeks after viral vector transduction. Inflammatory gene expression in the plasma and atherosclerotic plaques was determined by ELISA and real-time PCR. Four weeks after RNAi, the serum concentration and plaque mRNA expression of Lp-PLA(2) and YKL-40 were remarkably attenuated, leading to reduced inflammatory gene expression. Plaques from the Lp-PLA(2) or YKL-40 RNAi group showed lower lipid content, higher collagen content, increased fibrous cap thickness, and lower mRNA expressions of MCP-1 and MMP-8 than than those in the vehicle and scramble groups. When compared with the isolated Lp-PLA(2) or YKL-40 RNAi group, the combined Lp-PLA(2) and YKL-40 RNAi group exhibited higher collagen content and fibrous cap thickness, and lower lipid content and local inflammation. The beneficial effects of RNAi were independent of the plasma lipoprotein profile. Combined RNAi of Lp-PLA(2) and YKL-40 is superior to RNAi of Lp-PLA(2) or YKL-40 alone in ameliorating atherosclerosis.