Interleukin-1 activates nuclear factor kappa-B and induces manganese superoxide dismutase in human hepatoma cells

我们用原代大鼠肝细胞和培养的人肝癌细胞株(Huh-6)研究了炎性细胞因子诱导Mn-SOD基因表达的机制。在炎性细胞因子中，白介素1(IL-1)可诱导原代大鼠肝细胞和Huh-6细胞表达Mn-SOD。转录抑制剂放线菌素D不影响IL-1诱导的Mn-SODmRNA量，蛋白质合成抑制剂放线菌亚胺抑制IL-1诱导的MnSODmRNA量。这些结果表明，MnSODmRNA量的增加是在转录水平上控制的，可能与新蛋白质的合成有关。我们研究了IL-1介导的信号通路导致使用Huh-6诱导Mn-SOD mRNA的表达。磷脂酰胆碱-磷脂酶C可能是信号转导途径的候选者。加入IL-1后，检测C/EBP和NFkB的DNA结合活性，C/EBP活性不变，而NFkB活性增加。NFkB的抑制剂TPCK可抑制IL-1诱导的Mn-SOD mRNA表达，而IL-1可促进构成NFkB的p65mRNA的表达。

We examined the mechanism of Mn-SOD mRNA induction by inflammatory cytokines using primary rat hepatocytes and cultured human hepatoma cell line (Huh-6). Among inflammatory cytokines, Interleukin-1 (IL-1) induced the expression of Mn-SOD mRNA both in primary rat hepatocytes and Huh-6. Actinomycin D,an inhibitor of transcription, did not affect the IL-1-mediated induction of Mn-SOD mRNA.Cycloheximide, an inhibitor of protein synthesis, inhibited the IL-1-mediated induction of Mn-SOD mRNA.These results suggest that the increased expression of Mn-SOD mRNA is controlled at the transcriptional level and that it is due to synthesis of new protein. We examine the IL-1-mediated signal pathways leading to the induction of Mn-SOD mRNA using Huh-6. Phosphatidylcholine-phospholipase C might be a candidate responsible for the signal pathways. We next examined the DNA bindingactivity of C/EBP and NFkB after addition of IL-1 into the cultured medium.The activity of C/EBP did not change, but the activity of NFkB increased. TPCK,an inhibitor of NFkB,decreased the induction of Mn-SOD mRNA expression by IL-1.Furthermore, IL-1 enhanced the expression of p65 mRNA,which constitutes NFkB.We concluded that NFkB is essential for the increased expression of IL-1-mediated Mn-SOD mRNA.