Study the Roles of Npc2 in the Regulation of Hepatic Stellate Cells Activation and Liver Fibrosis

In chronic liver diseases, regardless of their etiologies (such as viral infection, alcohol abuse, non-alcoholic fatty liver), the development of fibrosis is the first step toward the progression to cirrhosis, portal hypertension and hepatocellular carcinoma (HCC). Until now, there are no FDA-approved drugs for the treatment of liver cirrhosis; therefore, it is urgent to clarify the mechanisms of liver fibrosis and develop effective agents with fewer adverse side effects. Niemann-Pick Type C2 (NPC2) plays an important role in regulating intracellular free cholesterol trafficking and homeostasis through direct binding with free cholesterol. Loss of NPC2 results in free cholesterol accumulation in the cells. Previously, we reported that the patients with NPC2 down-regulation expressed much higher α-fetoprotein, multiple tumor type, vascular invasion, later pathological stage and shorter survival rate. In-vitro and in-vivo xenografts data demonstrated that the expression of NPC2 regulates cell proliferation, migration and tumorigenesis through regulates ERK1/2 activation. However, the roles of NPC2 in hepatic stellate cell (HSCs) activation and liver fibrosis are not fully understood. According to the MOST (Ministry of Science and Technology, Taiwan) reviewers’ comments in 2015, we recently reported that NPC2 is decreased in both mouse and human liver fibrosis tissues. Knockdown NPC2 in HSCs marked increased TGF-β1-induced collagen type 1 alpha 1 (Col1a1) and α-SMA expression. In contrast, NPC2 overexpression decreased TGF-β1-induced HSCs activation. Since high-cholesterol diet exacerbates liver fibrosis progression in rodents and human and accumulates free cholesterol in HSCs, we propose that NPC2 down regulation accumulates free cholesterol in HSCs and increases the sensitization of HSCs to different stimulations’ (such as TGF-β1, PDGF-BB or LPS) induced fibrogenesis, proliferation and inflammation. The goals of this project are: a) to extend our study to further investigate the regulatory mechanisms of NPC2 in different stimulations-induced hepatic stellate cells activation; b) to clarify the effects of NPC2 mediated free cholesterol accumulation in HSCs activation; c) to identify novel pathways that related to NPC2 down regulation in HSCs using integrated microarray, proteome and IPA analyses; and d) to establish in-vivo hepatic NPC2 overexpression and knockdown mouse models and verify the effects of NPC2 expression in mouse liver fibrosis progression. e) to identify novel agents that induce NPC2 expression to treat liver fibrosis. This study will clarify the roles of NPC2 in liver fibrosis and may shed light on the treatment modality for liver fibrosis in the future.