The hepatitis B virus X protein induces paracrine... : Hepatology (original) (raw)

Viral Hepatitis

The hepatitis B virus X protein induces paracrine activation of human hepatic stellate cells

Martín-Vílchez, Samuel1,3; Sanz-Cameno, Paloma1,3; Rodríguez-Muñoz, Yolanda1,3; Majano, Pedro L.2,3; Molina-Jiménez, Francisca2,3; López-Cabrera, Manuel2,3,4; Moreno-Otero, Ricardo1,3*; Lara-Pezzi, Enrique5

1_Gastroenterology and Hepatology Service, Hospital Universitario La Princesa, Universidad Autónoma de Madrid, Madrid, Spain_

2_Molecular Biology Unit, Hospital Universitario La Princesa, Universidad Autónoma de Madrid, Madrid, Spain_

3_CIBERehd (Centro de Investigación Biomédica en Red en el área temática de Enfermedades Hepáticas y Digestivas), Instituto de Salud Carlos III, Madrid, Spain_

4_Centro de Biología Molecular Severo Ocha (CSIC-UAM), Madrid, Spain_

5_Harefield Heart Science Centre, Imperial College London, Middlesex, United Kingdom_

*Address reprint requests to: Servicio de Gastroenterología y Hepatología, Hospital Universitario de la Princesa, Planta 3a, Diego de León, 62. 28006 Madrid, Spain

Email:[email protected]

Received 18 February 2007; Accepted 27 January 2008

Published online in Wiley InterScience (www.interscience.wiley.com).

Grant sponsor: Instituto de Salud Carlos III; Grant Number: C03/02; Grant sponsor: CIBERehd; Grant sponsor: Ministerio de Educación y Ciencia; Grant Numbers: SAF 2004/07885 SAF 2004/07855; Grant sponsor: Instituto de Salud Carlos III fellowship; Grant Number: FI06/00269; Grant sponsor: Spanish Centro Nacional de Investigaciones Cardiovasculares (CNIC) 3+3 Award; Grant sponsor: Marie Curie fellowship programme; Grant sponsor: Instituto de Salud Carlos III; Grant Number: CP03/00020.

Potential conflict of interest: Nothing to report.

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Abstract

Chronic hepatitis B virus (HBV) infection is a major cause of liver fibrosis, eventually leading to cirrhosis and hepatocellular carcinoma. Although the involvement of the X protein of HBV (HBx) in viral replication and tumor development has been extensively studied, little is known about its possible role in the development of fibrosis. In this work we show that expression of HBx in hepatocytes results in paracrine activation and proliferation of hepatic stellate cells (HSCs), the main producers of extracellular matrix proteins in the fibrotic liver. Both human primary HSCs and rat HSCs exposed to conditioned medium from HBx-expressing hepatocytes showed increased expression of collagen I, connective tissue growth factor, α smooth muscle actin, matrix metalloproteinase-2, and transforming growth factor-β (TGF-β), together with an enhanced proliferation rate. We found that HBx induced TGF-β secretion in hepatocytes and that the activation of HSCs by conditioned medium from HBx-expressing hepatocytes was prevented by a neutralizing anti-TGF-β antibody, indicating the involvement of this profibrotic factor in the process. Conclusion: Our results propose a direct role for HBx in the development of liver fibrosis by the paracrine activation of stellate cells and reinforce the indication of antiviral treatment in patients with advanced HBV-related chronic liver disease and persistent liver replication.

Abbreviations: α-SMA, alpha-smooth muscle actin; AP-1, activating protein-1; CTGF, connective tissue growth factor; DDR-2, discoidin domain receptor 2; DMEM, Dulbecco's modified Eagle's medium; DX, dexamethasone; ECM, extracellular matrix; Egr, early growth response factor; ELISA, enzyme-linked immunoabsorbent assay; FBS, fetal bovine serum; HBV, hepatitis B virus; HBx, hepatitis B virus X protein; HCC, hepatocellular carcinoma; HSC, hepatic stellate cell; MMP, matrix metalloproteinase; mRNA, messenger RNA; MT1-MMP, membrane type matrix metalloproteinase 1; PCR, polymerase chain reaction; PDGF, platelet-derived growth factor; PI3K, phosphoinositide 3 kinase, RPB5, human RNA polymerase II subunit 5; RT, reverse transcriptase; SE, standard error; Smad, small mothers against decapentaplegic; TGF-β, transforming growth factor-beta; TIMP, tissue inhibitor of metalloproteinase; TNFα, tumor necrosis factor-alpha.