The suppression of pancreatic lipase-related protein 2 ameliorates experimental hepatic fibrosis in mice

Abstract

Quiescent hepatic stellate cells (HSCs) store vitamin A as lipid droplets in the cytoplasm. When activated, these cells lose vitamin A and exhibit an increased capacity for proliferation, mobility, contractility, and the synthesis of collagen and other components of the extracellular matrix. Our previous work demonstrated that the lipid hydrolytic gene pancreatic lipase-related protein 2 (mPlrp2) is involved in the hydrolysis of retinyl esters (REs) in the liver. Here, we showed that bile duct ligation (BDL)-induced liver injury triggered the conditional expression of mPlrp2 in livers and describe evidence of a strong relationship between the expression of mPlrp2 and Acta-2, a marker for activated HSCs. RNA interference targeting mPlrp2 inhibited HSC activation and ameliorated hepatic fibrosis induced by BDL in mice. Liver BDL markedly reduced the adenosine level and increased the ratio between S-adenosyl-L-methionine (SAM) and S-adenosyl-L-homocysteine (SAH). Chromatin immunoprecipitation (ChIP) analysis demonstrated an increase in trimethylated histone H3K4 at the mPlrp2 promoter in BDL mice, which was associated with the conditional expression of mPlrp2 in the liver. SAM, a well-known hepatoprotective substance, inhibited mPlrp2 expression and reduced RE hydrolysis in mice with hepatic fibrosis induced by chronic CCl4 treatment. Liver fibrosis induced by CCl4 or BDL was improved in Plrp2−/− mice. Our results reveal that mPlrp2 suppression is a potential approach for treating hepatic fibrosis.