Ursolic acid ameliorates hepatic fibrosis in the rat by specific induction of apoptosis in hepatic stellate cells

Background & Aims: Specific induction of cell death in activated hepatic stellate cells (HSCs) is a promising therapeutic strategy for hepatic fibrosis. In this study, we evaluated the cell-killing effect of ursolic acid (UA), a pentacyclic triterpenoid, in activated HSCs both in vitro and in vivo. Methods: Culture-activated rat HSCs were treated with UA (0-40 mu M), and the mechanisms of cell death were evaluated. The cell killing effect of UA on activated HSCs in rats chronically treated with thioacetamide (TAA) was detected by dual staining of TdT-mediated dUTP nick-end labeling (TUNEL) and smooth muscle alpha-actin (alpha SMA) immunohistochemistry, and resolution of hepatic fibrosis was evaluated. Further, the protective effects of UA on progression of hepatic fibrosis caused by TAA and bile duct ligation (BDL) were evaluated. Results: UA induced apoptotic cell death in culture-activated HSCs, but not: in isolated hepatocytes and quiescent HSCs. Mitochodrial permeability transition (MPT) preceded the cleavage of caspase-3 and -9 following UA treatment. UA also decreased phosphorylation levels of Akt, and diminished nuclear localization of NF kappa B in these cells. In rats pretreated with TAA for 6 weeks, a single injection of UA induced remarkable increases in TUNEL- and alpha SMA-dual-positive cells in 24 h, and significant regression of hepatic fibrosis within 48 h. Moreover, UA ameliorated hepatic fibrogenesis caused by both chronic TAA administration and BDL. Conclusions: UA ameliorated experimental hepatic fibrosis most likely through specific induction of apoptosis in activated HSCs. It is therefore postulated that UA is a potential therapeutic reagent for resolution of hepatic fibrosis. (C) 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.