State Key Laboratory of Infectious Disease Diagnosis and Treatment, First Affiliated Hospital, Zhejiang University College of Medicine, 79 Qingchun Road, Hangzhou, Zhejiang 310003, China.
Antiviral Res. 2010 Mar;85(3):463-9. doi: 10.1016/j.antiviral.2009.10.011. Epub 2009 Oct 24.
As a major therapy for hepatitis B virus (HBV) infection, Interferon alpha (IFN-alpha) triggers intracellular signal transduction including JAK-STAT pathway to produce various antiviral effector mechanisms. However, patients with chronic hepatitis B usually show low response to IFN-alpha treatment and the underlying mechanism remains unclear. In the present study, HepG2 and HepG2.2.15 cells were used to examine the Type I IFN receptors expression, phosphorylation and methylation of STAT1. STAT1-PIAS1 interaction in cells was tested by protein co-immunoprecipitation. The potential improvement of S-adenosylmethionine (SAM) in the antiviral effect of IFN-alpha was also investigated. Our data demonstrated that both chains of the Type I IFN receptors were expressed for a much higher extent in HepG2.2.15 cells than in HepG2 cells. HBV inhibited dramatically the methylation rather than the phosphorylation of STAT1, which was consistent with an increased STAT1-PIAS1 interaction. Combined with IFN-alpha, SAM treatment effectively improved STAT1 methylation and attenuated STAT1-PIAS1 binding, followed by increased PKR and 2',5'-OAS mRNA expression, thus significantly reducing the HBsAg, HBeAg protein levels and HBV DNA load in the supernatant of HepG2.2.15 cells. Less STAT1 methylation and subsequent increased STAT1-PIAS1 interaction are involved in the mechanism of the IFN-alpha-antagonistic activity of HBV. By improving STAT1 methylation, SAM can enhance the antiviral effect of IFN-alpha.
作为乙型肝炎病毒 (HBV) 感染的主要治疗方法，干扰素 alpha (IFN-alpha) 触发细胞内信号转导，包括 JAK-STAT 途径，以产生各种抗病毒效应机制。然而，慢性乙型肝炎患者通常对 IFN-alpha 治疗反应较低，其潜在机制尚不清楚。在本研究中，使用 HepG2 和 HepG2.2.15 细胞来检测 I 型干扰素受体的表达、STAT1 的磷酸化和甲基化。通过蛋白质共免疫沉淀检测细胞中 STAT1-PIAS1 相互作用。还研究了 S-腺苷甲硫氨酸 (SAM) 在 IFN-alpha 抗病毒作用中的潜在改善作用。我们的数据表明，I 型干扰素受体的两条链在 HepG2.2.15 细胞中的表达程度远高于 HepG2 细胞。HBV 显著抑制 STAT1 的甲基化而不是磷酸化，这与 STAT1-PIAS1 相互作用的增加一致。与 IFN-alpha 联合使用时，SAM 治疗可有效改善 STAT1 甲基化并减弱 STAT1-PIAS1 结合，随后增加 PKR 和 2',5'-OAS mRNA 表达，从而显著降低 HepG2.2.15 细胞上清液中的 HBsAg、HBeAg 蛋白水平和 HBV DNA 载量。HBV 对 IFN-alpha 拮抗活性的机制涉及 STAT1 甲基化程度降低和随后 STAT1-PIAS1 相互作用增加。通过改善 STAT1 甲基化，SAM 可以增强 IFN-alpha 的抗病毒作用。
