Li Xu, Meng Ying, Wu Pingsheng, Zhang Zhenshu, Yang Xishan
Department of Emergency, Nanfang Hospital, Southern Medical University, Guangzhou, 510515, China.
Regul Pept. 2007 Jan 10;138(1):15-25. doi: 10.1016/j.regpep.2006.07.011. Epub 2006 Sep 12.
BACKGROUND/AIMS: Intrahepatic renin-angiotensin-aldosterone system (RAAS) plays a key role in the fibrogenesis of liver. However, the signal transduction mechanism underlying effects of Angiotensin II (Ang II) and Aldosterone (Aldo) on Nuclear Factor-kappaB (NF-kappaB) and active protein-1 (AP-1) pathway in hepatic fibrogenesis remains to be fully elucidated. The present study aims to investigate the signal transduction mechanism underlying effects of Ang II and Aldo on NF-kappaB and AP-1 pathway during hepatic fibrogenesis.
To assess the effect of AECI and Angiotensin II type 1 receptor (AT-1 receptor) blocker on NF-kappaB activity in liver, a model of fibrosis was performed in rat. In vitro, hepatic stellate cells (HSCs)-T6 cells were preincubated for 1 h or not with U0126, a specific inhibitor of extracellular signal regulated kinase (ERK), irbesartan, and N-acetylcysteine prior to exposure to Ang II or Aldo for the indicated times. DNA binding activity of NF-kappaB and AP-1 were analyzed by Electrophoretic mobility shift assay (EMSA). Western blot was used to detect expression of IkappaBalpha and Phospho-P42/44. RT-PCR was used to detect the expressions of tumor necrosis factor alpha (TNFalpha) mRNA and alpha1 (I) procollagen mRNA.
AECI and AT-1 receptor blocker exert anti-fibrosis effect through inhibiting NF-kappaB activation in liver. Ang II and Aldo increase HSCs NF-kappaB activity and NF-kappaB target gene-TNFalpha expression by inhibiting IkappaBalpha expression in a redox-sensitive manner. Ang II and Aldo also markedly increase HSCs AP-1 activity and AP-1 target gene-alpha1 (I) procollagen mRNA expression via ERK1/2 pathway in a redox-sensitive manner.
These results show that stimulation of NF-kappaB and AP-1 pathway mediate hepatic fibrogenesis induced by intrahepatic RAAS.
背景/目的：肝内肾素-血管紧张素-醛固酮系统（RAAS）在肝纤维化形成过程中起关键作用。然而，血管紧张素II（Ang II）和醛固酮（Aldo）对肝纤维化中核因子-κB（NF-κB）和活化蛋白-1（AP-1）信号通路影响的信号转导机制仍有待充分阐明。本研究旨在探讨Ang II和Aldo在肝纤维化过程中对NF-κB和AP-1信号通路影响的信号转导机制。
为评估血管紧张素转换酶抑制剂（AECI）和血管紧张素II 1型受体（AT-1受体）阻滞剂对肝脏中NF-κB活性的影响，在大鼠中建立纤维化模型。在体外，肝星状细胞（HSCs）-T6细胞在暴露于Ang II或Aldo指定时间之前，先用细胞外信号调节激酶（ERK）的特异性抑制剂U0126、厄贝沙坦和N-乙酰半胱氨酸预孵育1小时或不预孵育。通过电泳迁移率变动分析（EMSA）分析NF-κB和AP-1的DNA结合活性。采用蛋白质免疫印迹法检测IκBα和磷酸化P42/44的表达。采用逆转录-聚合酶链反应（RT-PCR）检测肿瘤坏死因子α（TNFα）mRNA和α1（I）前胶原mRNA的表达。
AECI和AT-1受体阻滞剂通过抑制肝脏中NF-κB的活化发挥抗纤维化作用。Ang II和Aldo通过以氧化还原敏感的方式抑制IκBα表达，增加肝星状细胞NF-κB活性和NF-κB靶基因-TNFα表达。Ang II和Aldo还通过ERK1/2信号通路以氧化还原敏感的方式显著增加肝星状细胞AP-1活性和AP-1靶基因-α1（I）前胶原mRNA表达。
这些结果表明，NF-κB和AP-1信号通路的激活介导了肝内RAAS诱导的肝纤维化。
