[The effects of hepatitis C virus core protein on biological behaviors of human hepatocytes].

OBJECTIVE: To investigate the effects of hepatitis C virus (HCV) core protein on the biological behaviors of human hepatocytes and their underlying mechanism.

METHODS: A cell line expressing stably HCV core protein-QSG7701/core was constructed by transfecting the plasmid pcDNA3.1-core (expressing HCV core protein) into the human immortalized hepatocytes of the line QSG7701. The biological behaviors of these transfected cells were observed through plating-efficiency test, growth curve and flow cytometry (FCM). The association between HCV core protein and the expression of activated caspase-3 protein was evaluated by immunocytochemistry. The phosphorylation of mitogen-activate protein kinases (MAPKs) was detected with Western blotting. The activation of nuclear transcriptors AP-1, important effector molecule of MAPKs, and nuclear factor-kappa binding (NF-kappaB) were evaluated with luciferase assays and electrophoretic mobility shift assay (EMSA).

RESULTS: HCV core protein was expressed in the QSG7701/core cells and not in the QSG7701/pcDNA3.1 cells and untransfected QSG7701 cells. There were no significant differences in the expression levels of total P44/42(MAPK), p38(MAPK) and JNK among the QSG7701/core cells, QSG7701/pcDNA3.1 cells and untransfected QSG7701 cells. The expression levels of phophorylated P44/42(MAPK), p38(MAPK) and JNK in the QSG7701/core cells were significantly weaker than those in the QSG7701/pcDNA3.1 cells and untransfected QSG7701 cells. Plating efficiency test showed that the clone formation rate of the QSG7701/core cells was 32.25%, significantly lower than those of QSG7701/pcDNA3.1 and untransfected QSG7701 cells (47.5% and 42.5% respectively, both P < 0.01). The growth curve showed that the multiplication time of the QSG7701/core cells was 36 hours, significantly longer than those of the QSG7701/pcDNA3.1 and untransfected QSG7701 cells (27 and 28 hours respectively). FCM showed that the apoptotic rate of the QSG770/1core was 1.04%, lower than those of the QSG7701/pcDNA3.1 and untransfected QSG7701 cells (1.68% and 3.7% respectively), and that the percentage of theQSG770/1core cells at the G(0)/G(1) stage increased and those in the S stage decreased. Immunocytochemistry showed that the expression intensity of caspase-3 in the QSG7701/core cells was significantly weaker than those of the QSG7701/pcDNA3.1 cells and untransfected QSG7701 cells.

CONCLUSION: HCV core protein suppresses cell proliferation and apoptosis by downregmicrolating the phosphorylation of MAPKs and activating the transcriptors AP-1 and NF-kappaB, thus promoting the persistency of HCV infection which leads to chronic hepatitis C and hepatocellular cancer.