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.

Regression of atherosclerosis in apolipoprotein E-deficient mice by lentivirus-mediated gene silencing of lipoprotein-associated phospholipase A2.

Overexpression of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is implicated in atherosclerosis. We tested the hypothesis that lentivirus-mediated Lp-PLA(2) silencing could inhibit atherosclerosis in apolipoprotein E-deficient mice. Sixty eight apolipoprotein E-deficient mice were fed 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) and RNA interference (RNAi) groups. Lp-PLA(2) RNAi or scrambled NC lentivirus viral suspensions were constructed and transfected into the carotid plaques 8 weeks after surgery; the control group was administered saline. The carotid plaques were assessed 7 weeks later using hematoxylin and eosin, Masson's trichrome and oil red O staining; plasma and lesion inflammatory gene expression were examined using ELISAs and real-time PCR. Seven weeks after transfection, the serum concentration and plaque mRNA expression of Lp-PLA(2) was significantly lower in the RNAi group, and lead to reduced local and systemic inflammatory gene expression. Lp-PLA(2) RNAi also ameliorated plaque progression, reduced the plaque lipid content and increased the plaque collagen content. The effects of Lp-PLA(2) RNAi were independent of serum lipoprotein levels, as the triglyceride and total cholesterol levels of the control, NC and RNAi groups were not significantly different. These findings support the hypothesis that lentivirus-mediated Lp-PLA(2) gene silencing has therapeutic potential to inhibit atherosclerosis and increase plaque stability, without altering the plasma lipoprotein profile.

Lentiviral-mediated RNA interference of lipoprotein-associated phospholipase A2 ameliorates inflammation and atherosclerosis in apolipoprotein E-deficient mice.

Lipoprotein associated phospholipase A2 (Lp-PLA2) overexpression is implicated in athero-sclerosis. In the present study, we evaluated the effects of lentiviral-mediated RNA interference (RNAi) of Lp-PLA2 on inflammation and atherosclerosis in apolipoprotein E-deficient mice. Apolipoprotein E-deficient mice were randomly allocated to control and experimental groups, and constrictive collars were used to induce plaque formation. Eight weeks after surgery, the lentiviral-mediated RNAi construct was used to silence expression of Lp-PLA2. Control and experimental lentivirus was transfected directly into carotid plaques or administered systemically. Tissues were collected for analysis 7 weeks after transfection. Inflammatory gene expression in the plasma and atherosclerotic lesions was then determined at the mRNA and protein levels. We observed no differences in body weight and plasma lipid levels at the end of the investigation. However, the expression levels of Lp-PLA2 and pro-inflammatory cytokines were significantly reduced in the RNAi groups, compared to the controls, whereas the plasma concentration of anti-inflammatory cytokines was markedly increased. Moreover, our results demonstrated a significant reduction in plaque area and lipid content, as well as a rise in collagen content following RNAi treatment. Importantly, when comparing the two methods of viral delivery, we found that transluminal local transfection exhibited enhanced improvement of plaque stability as compared to systemic administration. Inhibition of Lp-PLA2 by lentiviral-mediated RNAi ameliorates inflammation and atherosclerosis in apolipoprotein E-deficient mice. In addition, transluminal local delivery of Lp-PLA2 shRNA is superior to systemic administration for stabilizing atherosclerotic plaques.