Lin Sue-Jane, Shu Pei-Yun, Chang Chungming, Ng Ah-Kau, Hu Cheng-po
Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China.
J Immunol. 2003 Nov 1;171(9):4708-16. doi: 10.4049/jimmunol.171.9.4708.
IL-4 has been known as a Th2 cytokine and can act on B cells, T cells, and monocytes. In this study we demonstrate that IL-4Rs are expressed on human hepatocellular carcinoma (HCC) cells. We found that IL-4 suppresses hepatitis B surface Ag (HBsAg) mRNA and HBsAg production in the Hep3B cell line, which contains an integrated hepatitis B virus (HBV) genome and constitutively secretes HBsAg. When Hep3B cells are further transfected with the plasmid pHBV3.6 that contains >1 U of HBV genome, IL-4 could suppress the production of all HBV RNA and secreted HBsAg and hepatitis B virus e Ag. Furthermore, an endogenous DNA polymerase activity assay shows a decrease in HBV DNA after IL-4 treatment. Using luciferase reporter assays we have demonstrated that IL-4 could suppress the activity of the surface promoter II and the core promotor (CP). To delineate how IL-4 suppressed the transcription of HBV genes, we have examined the effect of IL-4 on the expression of transcription factors that are known to bind to the core upstream regulatory sequence, which colocalizes with enhancer II of the HBV genome. Our results demonstrate that IL-4 suppresses the expression of C/EBPalpha. Furthermore, overexpression of C/EBPalpha blocked 43 and 30% of the IL-4-mediated suppression of CP activity and IL-4-induced suppression of pregenomic RNA, respectively. Finally, we have demonstrated that mutations affecting the C/EBPalpha-binding sites on core upstream regulatory sequence/enhancer II completely abolish the IL-4-mediated suppression of CP activity. Thus, down-regulation of C/EBPalpha may be involved in the anti-HBV effect of IL-4 in Hep3B cells.
白细胞介素-4（IL-4）一直被认为是一种辅助性T细胞2（Th2）细胞因子，可作用于B细胞、T细胞和单核细胞。在本研究中，我们证明IL-4受体在人肝细胞癌（HCC）细胞上表达。我们发现，IL-4可抑制Hep3B细胞系中乙型肝炎表面抗原（HBsAg）的mRNA和HBsAg的产生，该细胞系含有整合的乙型肝炎病毒（HBV）基因组并持续分泌HBsAg。当Hep3B细胞进一步用含有>1单位HBV基因组的质粒pHBV3.6转染时，IL-4可抑制所有HBV RNA的产生以及分泌的HBsAg和乙型肝炎病毒e抗原。此外，内源性DNA聚合酶活性测定显示IL-4处理后HBV DNA减少。使用荧光素酶报告基因测定，我们证明IL-4可抑制表面启动子II和核心启动子（CP）的活性。为了阐明IL-4如何抑制HBV基因的转录，我们研究了IL-4对已知与核心上游调控序列结合的转录因子表达的影响，该序列与HBV基因组的增强子II共定位。我们的结果表明，IL-4可抑制C/EBPα的表达。此外，C/EBPα的过表达分别阻断了43%和30%的IL-4介导的CP活性抑制和IL-4诱导的前基因组RNA抑制。最后，我们证明影响核心上游调控序列/增强子II上C/EBPα结合位点的突变完全消除了IL-4介导的CP活性抑制。因此，C/EBPα的下调可能参与了IL-4对Hep3B细胞的抗HBV作用。
