Effect of Statin on Inflammation and Chronic Liver Fibrosis In Vivo

Abstract

Background: Persistent hepatic inflammation is deleterious to the liver, as it promotes apoptosis of parenchymal cells and the accumulation of extracellular matrix proteins upon chronic injury. Macrophages, which consist of resident Kupffer cells and monocyte-derived macrophages, are key regulators of liver fibrosis progression and regression in chronic liver diseases. Statins are competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase. In addition to inhibiting cholesterol biosynthesis in the liver, statins decrease isoprenoid-dependent modifications of many proteins. They thus mediate pleiotropic beneficial effects such as antioxidant and anti-inflammatory effects. Aims: In this study, we aim to assess the effect of pitavastatin in liver fibrosis and resolution. We will determine whether pitavastatin has an antifibrotic effect and whether it accelerates the regression of liver fibrosis. We will also investigate if these effects are modulated through the inflammatory pathway. Methods: Chronic liver fibrosis was induced by injecting 0.6 ml-kg of carbon tetrachloride (CCl4) intraperitoneally (i.p.) twice a week for 4 or 6 weeks into 10-week-old C57BL-6 male mice. Pitavastatin (10 mg-kg, i.p.) was administered daily. Fibrosis was assessed by Sirius Red staining of collagen fibers, by alpha-smooth muscle actin detection, and gene expression of some fibrotic genes. Moreover, interleukin-6 was assessed at the gene and protein levels. Finally, flow cytometry of the intrahepatic leukocytes was performed. Results: After 2 weeks of pitavastatin, CCl4-injected mice exhibited less fibrosis, Sirius red staining decreased by 33percent (p0.001, Mann-Whitney U), and -SMA by 35percent (p0.05). Gene expression of fibrotic and inflammatory genes was also decreased compared to mineral oil-injected mice (mRNA levels of fibrotic genes, TGF-β 44percent, -SMA 37percent p0.05, and MMP-9 56percent, p=0.08; and inflammatory genes, IL-6 mRNA levels 59percent, p0.05). When assessing the effect of statins on fibrosis regression, pitavastatin decr