title: Upregulation of microRNA-146a by hepatitis B virus X protein contributes to hepatitis development by downregulating complement factor H.
abstract: Hepatic injuries in hepatitis B virus (HBV) patients are caused by immune responses of the host. In our previous study, microRNA-146a (miR-146a), an innate immunity-related miRNA, and complement factor H (CFH), an important negative regulator of the alternative pathway of complement activation, were differentially expressed in HBV-expressing and HBV-free hepatocytes. Here, the roles of these factors in HBV-related liver inflammation were analyzed in detail. The expression levels of miR-146a and CFH in HBV-expressing hepatocytes were assessed via analyses of hepatocyte cell lines, transgenic mice, adenovirus-infected mice, and HBV-positive human liver samples. The expression level of miR-146a was upregulated in HBV-expressing Huh-7 hepatocytes, HBV-expressing mice, and patients with HBV infection. Further results demonstrated that the HBV X protein (HBx) was responsible for its effects on miR-146a expression through NF-κB-mediated enhancement of miR-146a promoter activity. HBV/HBx also downregulated the expression of CFH mRNA in hepatocyte cell lines and the livers of humans and transgenic mice. Furthermore, overexpression and inhibition of miR-146a in Huh-7 cells downregulated and upregulated CFH mRNA levels, respectively. Luciferase reporter assays demonstrated that miR-146a downregulated CFH mRNA expression in hepatocytes via 3'-untranslated-region (UTR) pairing. The overall effect of this process in vivo is to promote liver inflammation. These results demonstrate that the HBx-miR-146a-CFH-complement activation regulation pathway might play an important role in the immunopathogenesis of chronic HBV infection. These findings have important implications for understanding the immunopathogenesis of chronic hepatitis B and developing effective therapeutic interventions.
  
  
  OBJECTIVE
  Hepatitis B virus (HBV) remains an important pathogen and can cause severe liver diseases, including hepatitis, liver cirrhosis, and hepatocellular carcinoma. Although HBV was found in 1966, the molecular mechanisms of pathogenesis are still poorly understood. In the present study, we found that the HBV X protein (HBx) promoted the expression of miR-146a, an innate immunity-related miRNA, through the NF-κB signal pathway and that increasingly expressed miR-146a downregulated its target complement factor H (CFH), an important negative regulator of the complement alternative pathway, leading to the promotion of liver inflammation. We demonstrated that the HBx-miR-146a-CFH-complement activation regulation pathway is potentially an important mechanism of immunopathogenesis caused by chronic HBV infection. Our data provide a novel molecular mechanism of HBV pathogenesis and thus help to understand the correlations between the complement system, an important part of innate immunity, and HBV-associated disease. These findings will also be important to identify potential therapeutic targets for HBV infection.
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Jun-Feng
authors: JF
authors: Li
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Xiao-Peng
authors: XP
authors: Dai
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Wei
authors: W
authors: Zhang
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Shi-Hui
authors: SH
authors: Sun
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Yang
authors: Y
authors: Zeng
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Guang-Yu
authors: GY
authors: Zhao
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Zhi-Hua
authors: ZH
authors: Kou
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Yan
authors: Y
authors: Guo
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.
authors: Hong
authors: H
authors: Yu
authors: Laboratory of Viral Immunology, Lindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA.
authors: Lan-Ying
authors: LY
authors: Du
authors: Shi-Bo
authors: SB
authors: Jiang
authors: The State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China yszhou@bmi.ac.cn.
authors: Yu-Sen
authors: YS
authors: Zhou
mesh_terms: D000818:Animals; D002460:Cell Line; D017242:Complement Factor H / Q000037:antagonists & inhibitors*; D006509:Hepatitis B / Q000276:immunology* / Q000473:pathology*; D022781:Hepatocytes / Q000821:virology; D054884:Host-Pathogen Interactions; D006801:Humans; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000096:biosynthesis*; D015534:Trans-Activators / Q000378:metabolism*; D015854:Up-Regulation; D054334:Viral Regulatory and Accessory Proteins
chemical_list: C542542:MIRN146 microRNA, human; D035683:MicroRNAs; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D017242:Complement Factor H