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AIM To assess the effects of hepatitis B virus(HBV) on the expression of host α-1,2-mannosidases and determine the underlying mechanisms.METHODS We measured the expression levels of MAN1A1, MAN1A2, MAN1B1, and MAN1C1 in cell lines HepG 2.2.15, HepN 10, HepA D38 and Hep G2 by Western blot. Viral antigens(HBs Ag and HBe Ag) in the culture medium were measured using the chemiluminescence method. HBV DNA quantification assays were performed using a commercial real-time PCR kit. Protein levels of human liver tissue α-1,2-mannosidases were also evaluated by Western blot. Plasmids containing seven individual viral genes of HBV(PTT22-HBx, PTT22-HBs, PTT22-pre S2, PTT22-pre S1, PTT22-HBc, PTT22-HBe, and PTT22-HBp) or control plasmids(PTT22-vector) were transfected into Hep G2 cells. MK886(PPARα) and GW9662(PPARγ) inhibitors were used to explore the effects of HBV on α-1,2-mannosidase expression after the PPARα and PPARγ pathways were blocked.RESULTS We showed that the expression of α-1,2-mannosidases was higher in stably transfected HBV cells than in controls. The expression levels of α-1,2-mannosidase were higher in AD38 cells than those in ND10 cells, which were in turn greater than those in G2.2.15 cells, and positively correlated with the expression of HBsA gin all the cell lines. Levels of α-1,2-mannosidase in nontumorous liver tissues of HBV-related HCC patients were also higher than in the tissues from non-HBVrelated HCC patients. Moreover, transfecting Hep G2 cells with a component of the HBV viral envelope also increased the expression of α-1,2-mannosidases. However, this envelope protein component could not induce MAN1C1 expression in the presence of a PPARα inhibitor, MK886. We also found that MK886 did not affect the expression of MAN1C1 in AD38 cells without tetracycline in the culture medium. This phenomenon was not observed in the case of GW9662.CONCLUSION Our results indicate that HBV increases the expression of α-mannosidases both in vitro and in vivo via activation of the PPARα pathway by its envelope protein.
AIM To assess the effects of hepatitis B virus (HBV) on the expression of host α-1,2-mannosidases and determine the underlying mechanisms. METHODS We measured the expression levels of MAN1A1, MAN1A2, MAN1B1, and MAN1C1 in cell lines HepG 2.2 .15, HepN 10, HepA D38 and Hep G2 by Western blot. Viral antigens (HBsAg and HBeAg) in the culture medium were measured using the chemiluminescence method. HBV DNA quantification assays were performed using a commercial real-time PCR kit. Protein levels of human liver tissue α-1,2-mannosidases were also evaluated by Western blot. Plasmids containing seven individual viral genes of HBV (PTT22-HBx, PTT22-HBs, PTT22-pre S2, PTT22-pre S1, PTT22-HBc , PTT22-HBe, and PTT22-HBp) or control plasmids (PTT22-vector) were transfected into Hep G2 cells. MK886 (PPARα) and GW9662 (PPARγ) inhibitors were used to explore the effects of HBV on α-1,2- mannosidase expression after the PPARα and PPARγ pathways were blocked .RESULTS We showed that the expression of α-1, 2-mannosidases was higher in stably transfected HBV cells than in controls. The expression levels of α-1,2-mannosidase were higher in AD38 cells than those in ND10 cells, which were in turn greater than those in G2.2.15 cells, and positively correlated with the expression of HBsA gin all the cell lines. Levels of α-1,2-mannosidase in nontumorous liver tissues of HBV-related HCC patients were also higher than the tissues from non-HBVrelated HCC patients. G2 envelope with a component of the HBV viral envelope also increased the expression of α-1,2-mannosidases. However, this envelope protein component could not induce MAN1C1 expression in the presence of a PPARα inhibitor, MK 886. We also found that MK886 did not affect the expression of MAN1C1 in AD38 cells without tetracycline in the culture medium. This phenomenon was not observed in the case of GW9662.CONCLUSION Our results indicate that HBV increases the expression of α-mannosidases both in vitro and i n vivo via activation of the PPARα pathway by its envelope protein.