Guo Hongtao, Wei Junping, Inoue Yusuke, Gonzalez Frank J, Kuo Paul C
Duke University Medical Center, Durham, North Carolina 27710, USA.
Am J Physiol Cell Physiol. 2003 Apr;284(4):C1090-9. doi: 10.1152/ajpcell.00394.2002. Epub 2002 Dec 4.
Nitric oxide (NO), endogenously synthesized by inducible NO synthase (iNOS), serves antioxidant and antiapoptotic functions in settings characterized by oxidative stress and proinflammatory cytokines such as sepsis and shock. However, the redox-sensitive mechanisms regulating hepatocyte expression of iNOS are largely unknown. In interleukin-1beta (IL-1beta)-stimulated hepatocytes exposed to superoxide, we demonstrate that hepatocyte nuclear factor-4alpha (HNF-4alpha) acts as an activator of redox-associated hepatocyte iNOS expression at the level of protein, mRNA, and promoter activation. In the absence of HNF-4alpha, this redox-mediated enhancement is ablated. HNF-4alpha functional activity is associated with a unique serine/threonine kinase-mediated phosphorylation pattern. This suggests that a redox-sensitive kinase pathway targets HNF-4alpha to augment hepatocyte iNOS expression. Previous studies have not addressed a redox-dependent kinase signaling pathway that targets HNF-4alpha and enhances hepatocyte iNOS gene transcription. A unique pattern of phosphorylation determines HNF-4alpha activity as a trans-activator of IL-1beta-mediated hepatocyte iNOS expression in the presence of oxidative stress.
一氧化氮（NO）由诱导型一氧化氮合酶（iNOS）内源性合成，在以氧化应激和促炎细胞因子为特征的环境中发挥抗氧化和抗凋亡功能，如脓毒症和休克。然而，调节iNOS在肝细胞中表达的氧化还原敏感机制在很大程度上尚不清楚。在暴露于超氧化物的白细胞介素-1β（IL-1β）刺激的肝细胞中，我们证明肝细胞核因子-4α（HNF-4α）在蛋白质、mRNA和启动子激活水平上作为氧化还原相关的肝细胞iNOS表达的激活剂。在没有HNF-4α的情况下，这种氧化还原介导的增强作用被消除。HNF-4α的功能活性与独特的丝氨酸/苏氨酸激酶介导的磷酸化模式相关。这表明一种氧化还原敏感的激酶途径靶向HNF-4α以增强肝细胞iNOS表达。先前的研究尚未涉及靶向HNF-4α并增强肝细胞iNOS基因转录的氧化还原依赖性激酶信号通路。一种独特的磷酸化模式决定了HNF-4α在氧化应激存在下作为IL-1β介导的肝细胞iNOS表达的反式激活剂的活性。
