title: Exogenous hepatitis B virus envelope proteins induce endoplasmic reticulum stress: involvement of cannabinoid axis in liver cancer cells.
abstract: HBV represents the most common chronic viral infection and major cause of hepatocellular carcinoma (HCC), although its exact role in liver tumorigenesis is unclear. Massive storage of the small (SHBs), middle (MHBs) and large surface (LHBs) HBV envelope proteins leads to cell stress and sustained inflammatory responses. Cannabinoid (CB) system is involved in the pathogenesis of liver diseases, stimulating acute and chronic inflammation, liver damage and fibrogenesis; it triggers endoplasmic reticulum (ER) stress response. The aim of our work was to investigate the activation of ER stress pathway after ectopic HBV envelope proteins expression, in liver cancer cells, and the role exerted by CB receptors. PCR, immunofluorescence and western blotting showed that exogenous LHBs and MHBs induce a clear ER stress response in Huh-7 cells expressing CB1 receptor. Up-regulation of the chaperone BiP/GRP78 (Binding Immunoglobulin Protein/Glucose-Regulated Protein 78) and of the transcription factor CHOP/GADD153 (C/EBP Homologous Protein/Growth Arrest and DNA Damage inducible gene 153), phosphorylation of PERK (PKR-like ER Kinase) and eIF2α (Eukaryotic Initiation Factor 2α) and splicing of XBP1 (X-box binding protein 1) was observed. CB1-/- HepG2 cells did not show any ER stress activation. Inhibition of CB1 receptor counteracted BiP expression in transfected Huh-7 and in HBV+ PLC/PRF/5 cells; whereas no effect was observed in HBV- HLF cells. These results suggest that HBV envelope proteins are able to induce the ER stress pathway. CB1 expression is directly correlated with ER stress function. Further investigations are needed to clarify the involvement of cannabinoid in HCC progression after HBV infection.
authors.affiliation: Department of Visceral, Thoracic and Vascular Surgery, Philipps University of Marburg, Marburg, Germany.
authors.forename: Roberta
authors.initials: R
authors.lastname: Montalbano
authors.affiliation: Department of Visceral, Thoracic and Vascular Surgery, Philipps University of Marburg, Marburg, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Honrath
authors.affiliation: Division of Gastroenterology, Philipps University of Marburg, Marburg, Germany.
authors.forename: Thaddeus Till
authors.initials: TT
authors.lastname: Wissniowski
authors.affiliation: Department of Visceral, Thoracic and Vascular Surgery, Philipps University of Marburg, Marburg, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Elxnat
authors.affiliation: Department of Visceral, Thoracic and Vascular Surgery, Philipps University of Marburg, Marburg, Germany.
authors.forename: Silvia
authors.initials: S
authors.lastname: Roth
authors.affiliation: Institute for Surgical Research, Philipps University of Marburg, Marburg, Germany.|Present address: Department of Gastroenterology CBF, Charité University Medicine Berlin and Bayer Pharma AG, Experimental Medicine Oncology, Berlin, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Ocker
authors.affiliation: Institute for Surgical Research, Philipps University of Marburg, Marburg, Germany.
authors.forename: Karl
authors.initials: K
authors.lastname: Quint
authors.affiliation: Department of Gastroenterology, Justus Liebig University, Giessen, Germany.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Churin
authors.affiliation: Department of Gastroenterology, Justus Liebig University, Giessen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Roederfeld
authors.affiliation: Department of Gastroenterology, Justus Liebig University, Giessen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Schroeder
authors.affiliation: Institute of Medical Virology, National Reference Centre for Hepatitis B and D Viruses, Justus Liebig University, Giessen, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Glebe
authors.affiliation: Department of Gastroenterology, Justus Liebig University, Giessen, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Roeb
authors.affiliation: Department of Visceral, Thoracic and Vascular Surgery, Philipps University of Marburg, Marburg, Germany.
authors.forename: Pietro
authors.initials: P
authors.lastname: Di Fazio
mesh_terms: D017209:Apoptosis; D002186:Cannabinoids / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D049109:Cell Proliferation; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress; D006509:Hepatitis B / Q000150:complications / Q000821:virology; D006515:Hepatitis B virus / Q000502:physiology; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D010766:Phosphorylation; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014759:Viral Envelope Proteins / Q000378:metabolism*
chemical_list: D002186:Cannabinoids; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D043884:Receptor, Cannabinoid, CB1; D014759:Viral Envelope Proteins
keywords: endocannabinoid system; endoplasmic reticulum stress; hepatitis B virus