Simvastatin reduces atherogenesis and promotes the expression of hepatic genes associated with reverse cholesterol transport in apoE-knockout mice fed high-fat diet

Abstract

Background: Statins are first-line pharmacotherapeutic agents for hypercholesterolemia treatment in humans. However the effects of statins on atherosclerosis in mouse models are very paradoxical. In this work, we wanted to evaluate the effects of simvastatin on serum cholesterol, atherogenesis, and the expression of several factors playing important roles in reverse cholesterol transport (RCT) in apoE-/- mice fed a high-fat diet.

Results: The atherosclerotic lesion formation displayed by oil red O staining positive area was reduced significantly by 35% or 47% in either aortic root section or aortic arch en face in simvastatin administrated apoE-/- mice compared to the control. Plasma analysis by enzymatic method or ELISA showed that high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein A-I (apoA-I) contents were remarkably increased by treatment with simvastatin. And plasma lecithin-cholesterol acyltransferase (LCAT) activity was markedly increased by simvastatin treatment. Real-time PCR detection disclosed that the expression of several transporters involved in reverse cholesterol transport, including macrophage scavenger receptor class B type I, hepatic ATP-binding cassette (ABC) transporters ABCG5, and ABCB4 were induced by simvastatin treatment, the expression of hepatic ABCA1 and apoA-I, which play roles in the maturation of HDL-C, were also elevated in simvastatin treated groups.

Conclusions: We demonstrated the anti-atherogenesis effects of simvastatin in apoE-/- mice fed a high-fat diet. We confirmed here for the first time simvastatin increased the expression of hepatic ABCB4 and ABCG5, which involved in secretion of cholesterol and bile acids into the bile, besides upregulated ABCA1 and apoA-I. The elevated HDL-C level, increased LCAT activity and the stimulation of several transporters involved in RCT may all contribute to the anti-atherosclerotic effect of simvastatin.

Figure 1

Simvastatin inhibits atherosclerotic lesion formation in apoE-/- mice fed a high-fat diet. A, Representative of Oil Red O-stained aortic sections (10× magnification). B, Quantitation of lesion areas in Oil Red O-stained aortic sections by Image-Pro Plus software. C, Quantification of atherosclerotic lesions in the en-face of the aortic arch. ** P < 0.01 versus model group.

Figure 2

Effect of simvastatin on endogenous LCAT activity in plasma. LCAT activity was measured as the utilization rate of FC in native plasma. LCAT activity was expressed as nanomoles FC consumed per hr per ml plasma. Data are expressed as means ± SD (n = 10). * P < 0.05 versus model group.

Figure 3

Effect of simvastatin on the expression of hepatic genes which play roles in cholesterol transport. A, Effect of simvastatin on the mRNA expression of hepatic genes by real-time PCR. Expression levels of mRNA are indicated as fold differences compared with model mice. B, Effect of simvastatin on the protein expression of hepatic genes by western blots. C, Densitometric quantitation of western blot data (n = 5) by Quantity One software. * P < 0.05, ** P < 0.01 versus model group.

Figure 4

Effect of simvastatin on the expression of transporter genes involved in cholesterol efflux in peritoneal macrophages. A, Effect of simvastatin on the mRNA expression of macrophage transporter genes by real-time PCR. Expression levels of mRNA are indicated as fold differences compared with model mice. B, Effect of simvastatin on the protein expression of macrophage transporter genes by western blots. C, Densitometric quantitation of western blot data (n = 5) by Quantity One software. * P < 0.05 versus model group