Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160, USA.
Toxicol Appl Pharmacol. 2012 Aug 15;263(1):14-20. doi: 10.1016/j.taap.2012.05.017. Epub 2012 Jun 4.
Oxidative stress plays an important role in cadmium-induced liver injury. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that up-regulates cytoprotective genes in response to oxidative stress. To investigate the role of Nrf2 in cadmium-induced hepatotoxicity, Nrf2-null mice, wild-type mice, kelch-like ECH-associated protein 1-knockdown (Keap1-KD) mice with enhanced Nrf2, and Keap1-hepatocyte knockout (Keap1-HKO) mice with maximum Nrf2 activation were treated with cadmium chloride (3.5mg Cd/kg, i.p.). Blood and liver samples were collected 8h thereafter. Cadmium increased serum alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) activities, and caused extensive hepatic hemorrhage and necrosis in the Nrf2-null mice. In contrast, Nrf2-enhanced mice had lower serum ALT and LDH activities and less morphological alternations in the livers than wild-type mice. H(2)DCFDA (2',7'-dichlorodihydrofluoresein diacetate) staining of primary hepatocytes isolated from the four genotypes of mice indicated that oxidative stress was higher in Nrf2-null cells, and lower in Nrf2-enhanced cells than in wild-type cells. To further investigate the mechanism of the protective effect of Nrf2, mRNA of metallothionein (MT) and other cytoprotective genes were determined. Cadmium markedly induced MT-1 and MT-2 in livers of all four genotypes of mice. In contrast, genes involved in glutathione synthesis and reducing reactive oxygen species, including glutamate-cysteine ligase (Gclc), glutathione peroxidase-2 (Gpx2), and sulfiredoxin-1 (Srxn-1) were only induced in Nrf2-enhanced mice, but not in Nrf2-null mice. In conclusion, the present study shows that Nrf2 activation prevents cadmium-induced oxidative stress and liver injury through induction of genes involved in antioxidant defense rather than genes that scavenge Cd.
氧化应激在镉诱导的肝损伤中起着重要作用。核因子红细胞 2 相关因子 2（Nrf2）是一种转录因子，可响应氧化应激上调细胞保护基因。为了研究 Nrf2 在镉诱导的肝毒性中的作用，使用氯化镉（3.5mg Cd/kg，ip）处理 Nrf2 敲除（Nrf2-null）小鼠、野生型（Wild-type）小鼠、Kelch 样 ECH 相关蛋白 1 敲低（Keap1-KD）增强 Nrf2 的小鼠和 Keap1 肝细胞敲除（Keap1-HKO）最大激活 Nrf2 的小鼠。8 小时后收集血液和肝脏样本。镉增加了血清丙氨酸氨基转移酶（ALT）和乳酸脱氢酶（LDH）的活性，并导致 Nrf2 敲除小鼠的肝脏广泛出血和坏死。相比之下，与野生型小鼠相比，Nrf2 增强型小鼠的血清 ALT 和 LDH 活性较低，肝脏形态改变较小。对从四种基因型的小鼠分离的原代肝细胞进行 H（2）DCFDA（2'，7'-二氯二氢荧光素二乙酸酯）染色表明，Nrf2 敲除细胞的氧化应激水平较高，Nrf2 增强细胞的氧化应激水平低于野生型细胞。为了进一步研究 Nrf2 的保护作用的机制，测定了四种基因型小鼠肝脏中金属硫蛋白（MT）和其他细胞保护基因的 mRNA。镉在四种基因型小鼠的肝脏中明显诱导了 MT-1 和 MT-2。相比之下，参与谷胱甘肽合成和减少活性氧的基因，包括谷氨酸半胱氨酸连接酶（Gclc）、谷胱甘肽过氧化物酶-2（Gpx2）和硫氧还蛋白-1（Srxn-1），仅在 Nrf2 增强型小鼠中诱导，而在 Nrf2 敲除型小鼠中未诱导。总之，本研究表明，Nrf2 激活通过诱导抗氧化防御相关基因而不是清除 Cd 的基因来防止镉诱导的氧化应激和肝损伤。
