Hepatitis B virus X gene inhibits hepatocyte apoptosis in mice via Akt/mTOR pathway

Abstract

Objective To investigate the effect of hepatitis B virus X (HBx) on apoptosis and cell cycle of hepatocytes in mice with normal immune functions and explore the underlying mechanisms. Methods We transduced HBx gene in cultured mouse hepatic progenitor cells (HPCs) via lentiviral vectors to obtain HBx-expressing mouse HPCs (HBx-EGFP-14-19 cells), and the expression of HBx at both mRNA and protein levels in the cells were examined using qRT-PCR and Western blotting. HBx-EGFP-14-19 cells were then injected into the hepatic portal vein of KM mice, and 120 d after the injection, the liver tissues of the mice were collected to examine the expression of HBx using qRT-PCR, Western blotting and immunohistochemistry. The apoptotic index of the hepatocytes of the mice was investigated using TUNEL-FITC/DAPI method, and the expression levels of apoptosis-related and cell cycle-related factors were detected using qRT-PCR and Western blotting. We also detected the changes in the expression levels of the molecules associated with Akt/mTOR signaling in response to an Akt inhibitor in the mice with HBx-EGFP-14-19 cell injection. Results We successfully obtained HBx-EGFP-14-19 cells that expressed HBx mRNA and protein. At 120 d after injection of HBx-EGFP-14-19 cells, the hepatocytes of the mice showed a decreased apoptotic index, lowered expression of the pro-apoptotic factors caspase-9 and Bad, and increased mRNA expression of CDK2 and cyclin D1 and protein expression of CDK2, cyclin D1, p-Akt and p-mTOR. Treatment of the mice with the Akt inhibitor MK2206 obviously abolished these changes induced by HBx overexpression. Conclusion HBx suppresses apoptosis and accelerates cell cycle progression of the hepatocytes in mice by activating Akt/mTOR signaling pathway.

Keywords

• hepatitis b virus x
• animal model
• apoptosis
• akt/mtor