Transcription profiling of mouse Nrf2 knockout caused by ROS-mediated insulin/IGF-1 resistance

The liver is frequently challenged by surgery-induced metabolic overload, viruses, or toxins, which induce the formation of reactive oxygen species. To determine the effect of oxidative stress on liver regeneration and to identify the underlying signalling pathways, we studied liver repair in mice lacking the Nrf2 transcription factor. In these animals, expression of several cytoprotective enzymes was reduced in hepatocytes, resulting in oxidative stress. As a consequence, tissue damage was aggravated, and liver regeneration after partial hepatectomy was delayed. Using in vitro and in vivo studies we identified oxidative stress-induced insulin/insulin-like growth factor resistance as the underlying mechanism. This deficiency impaired the activation of p38 mitogen-activated kinase, Akt kinase, and downstream targets after hepatectomy, resulting in enhanced death and delayed proliferation of hepatocytes. Our results reveal novel roles of Nrf2 in the regulation of growth factor signalling and in tissue repair. In addition, they provide new insight into the mechanisms underlying oxidative stress-induced defects in liver regeneration and thus offer new avenues to improve regeneration in patients with acute or chronic liver damage. Experiment Overall Design: Livers from Nrf2 k.o. and wt mice; 3 hybridizations per genotype: RNA samples were pooled from 3 individual animals肝脏常遭受手术诱导的代谢负荷、病毒或毒素的侵袭，此类因素可诱导活性氧（reactive oxygen species）的生成。为明确氧化应激对肝脏再生的影响并解析其潜在信号通路，我们对缺失Nrf2转录因子（Nrf2 transcription factor）的小鼠开展了肝脏修复相关研究。在该类小鼠体内，肝细胞中多种细胞保护酶的表达水平下调，进而引发氧化应激。由此加剧了组织损伤，并延缓了部分肝切除术后的肝脏再生过程。通过体外与体内实验，我们确定氧化应激诱导的胰岛素/胰岛素样生长因子抵抗是其潜在机制。该缺陷会削弱肝切除术后p38丝裂原活化蛋白激酶（p38 mitogen-activated kinase）、Akt激酶（Akt kinase）及其下游靶标的激活过程，最终导致肝细胞死亡加剧、增殖延迟。本研究结果揭示了Nrf2在生长因子信号通路调控及组织修复中的全新作用。此外，本研究还为解析氧化应激诱导的肝脏再生缺陷的潜在机制提供了新视角，并为改善急性或慢性肝损伤患者的肝脏再生提供了全新方向。实验整体设计：取材自Nrf2基因敲除（knock out, k.o.）与野生型（wild type, wt）小鼠的肝脏；每个基因型设置3次杂交实验：RNA样本取自3只个体小鼠的混合样品。