Beneficial Role of Nrf2 in Regulating NADPH Generation and Consumption
Beneficial Role of Nrf2 in Regulating NADPH Generation and Consumption
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DOI：
10.1093/toxsci/kfr183
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发表时间：
2011-10-01
影响因子：
3.8
通讯作者：
Klaassen, Curtis D.
中科院分区：
文献类型：
--
作者：
Wu, Kai Connie;Cui, Julia Yue;Klaassen, Curtis D.
核因子红细胞2相关因子2（Nrf 2）是一种转录因子，促进细胞保护基因的转录，以响应氧化和亲电应激。Nrf 2的大部分功能是通过研究Nrf 2缺陷的生物模型来确定的，然而，对Nrf 2的分级激活的影响知之甚少。在本研究中，通过微阵列分析的基因组基因表达谱的特征在于与“基因剂量-反应”模型在肝脏的Nrf 2-null小鼠，野生型小鼠，Kelch样ECH相关蛋白1（Keap 1）-敲低（Keap 1-KD）小鼠增强Nrf 2激活，和Keap 1-肝细胞敲除（Keap 1-HKO）小鼠与最大肝Nrf 2激活。肝核Nrf 2蛋白、谷胱甘肽浓度和已知Nrf 2靶基因以剂量依赖性方式增加。总共有115个基因被鉴定为组成型诱导，80个基因被分级Nrf 2激活抑制。编码戊糖磷酸途径中的酶和酶的基因的信使RNA在Nrf 2缺乏的情况下较低，而在Nrf 2激活的情况下较高，表明Nrf 2对NADPH产生很重要。NADPH是抑制氧化应激的主要还原源，包括再生谷胱甘肽和硫氧还蛋白，也用于合成代谢途径，包括脂质合成。高效液相色谱-紫外吸收分析证实，肝脏NADPH浓度在Nrf 2-null小鼠中最低，在Keap 1-HKO小鼠中最高。此外，参与脂肪酸合成和去饱和的基因随着Nrf 2激活而下调。总之，本研究表明，Nrf 2通过促进NADPH的产生来保护免受环境侵害，NADPH优先通过帮助清除氧化应激而不是脂肪酸合成和去饱和来消耗。
Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that promotes the transcription of cytoprotective genes in response to oxidative and electrophilic stresses. Most functions of Nrf2 were identified by studying biological models with Nrf2 deficiency, however, little is known about the effects of graded Nrf2 activation. In the present study, genomic gene expression profiles by microarray analysis were characterized with a "gene dose-response" model in livers of Nrf2-null mice, wild-type mice, Kelch-like ECH associating protein 1 (Keap1)-knockdown (Keap1-KD) mice with enhanced Nrf2 activation, and Keap1-hepatocyte knockout (Keap1-HKO) mice with maximum hepatic Nrf2 activation. Hepatic nuclear Nrf2 protein, glutathione concentrations, and known Nrf2 target genes were increased in a dose-dependent manner. In total, 115 genes were identified to be constitutively induced and 80 genes suppressed with graded Nrf2 activation. Messenger RNA of genes encoding enzymes in the pentose phosphate pathway and enzyme were low with Nrf2 deficiency and high with Nrf2 activation, indicating that Nrf2 is important for NADPH production. NADPH is the major reducing resource to scavenge oxidative stress, including regenerating glutathione and thioredoxin and is also used for anabolic pathways including lipid synthesis. High performance liquid chromatography-ultraviolet absorbance analysis confirmed that hepatic NADPH concentration was lowest in Nrf2-null mice and highest in Keap1-HKO mice. In addition, genes involved in fatty acid synthesis and desaturation were downregulated with graded Nrf2 activation. In conclusion, the present study suggests that Nrf2 protects against environmental insults by promoting the generation of NADPH, which is preferentially consumed by aiding scavenging of oxidative stress rather than fatty acid synthesis and desaturation.