Nrf2信号通路在镉致大鼠生殖毒性中的作用

Role of Nrf2 Signaling Pathway in Cadmium-induced Reproductive Toxicity in Rats

目的探讨Nrf2信号通路在镉致大鼠生殖毒性中的作用。方法 SD大鼠随机分为4组,每组6只。第1组为对照组,第2～4组为氯化镉低、中、高剂量组。第1组给予腹腔注射0.9%生理盐水,第2～4组分别给予腹腔注射1.14、2.28、4.56mg/kg体重的CdCl_2溶液,48h后处死动物,解剖取出大鼠睾丸、卵巢组织测定超氧化物歧化酶(SOD)活力、谷胱甘肽过氧化物酶(GSH-Px)活力、脂质过氧化物丙二醛(MDA)含量,并用Real-time PCR和Western blot法分别测定核转录因子NF-E2相关因子2(Nrf2)、谷胱甘肽-S-转移酶P1亚基(GST-P1)、谷氨酸半胱氨酸连接酶催化亚基(GCLC)的mRNA和Nrf2蛋白的表达水平。结果在1.14、2.28、4.56mg/kg剂量条件下,大鼠睾丸和卵巢SOD、GSH-Px活性均明显低于对照组(均P<0.05),MDA含量有所升高(P<0.05)。2.28和4.56mg/kg组大鼠睾丸和卵巢Nrf2mRNA和蛋白的表达水平均显著高于对照组(均P<0.05),大鼠睾丸Nrf2mRNA和蛋白的表达与氯化镉染毒剂量均存在明显的剂量-效应关系(均P<0.05)。2.28和4.56mg/kg组大鼠睾丸GST-P1和GCLC mRNA表达均显著高于对照组(均P<0.05),大鼠卵巢GST-P1、GCLC mRNA在4.56mg/kg剂量条件下的表达显著升高(均P<0.05),但GST-P1和GCLC mRNA表达分别在1.14和2.28mg/kg剂量条件下出现显著的下降(均P<0.05)。结论在一定染毒剂量条件下,镉可引起大鼠睾丸和卵巢发生氧化应激,激活Nrf2介导的抗氧化机制,上调下游Ⅱ相解毒酶的转录表达。雌性大鼠卵巢可能比雄性大鼠睾丸更容易受到镉毒性作用的损害。

Objective To investigate the role of Nrf2 signaling pathway in cadmium(CdCl2)-induced reproductive toxicity in rats.Methods Sprague-Dawley(SD)rats were randomly divided into 4 groups by weight:control group,and low-dose,medium-dose and high-dose CdCl2 groups.The rats were intraperitoneally injected with 0.9%saline solution in control group and with 1.14,2.28 and 4.56 mg/kg CdCl2 solution in CdCl2 groups.Forty-eight hours later,the animals were sacrificed to obtain the testicles and ovaries.The activities of superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px)and the contents of malondialdehyde(MDA)were measured,the mRNA expression of Nrf2,glutathione S-transferase P1(GST-P1),catalytic subunit of glutamate-cysteine ligase(GCLC)was detected by real-time PCR and the protein expression of Nrf2 by Western blotting.Results The activities of SOD and GSH-Px were significantly decreased and the content of MDA was significantly increased in the testicles and ovaries of rats treated with CdCl2 at 1.14,2.28,4.56 mg/kg(P<0.05).Compared with the control group,the mRNA and protein expression of Nrf2 was significantly increased in the testicles and ovaries of rats in the 2.28,4.56 mg/kg CdCl2 groups(P<0.05).There was a significant dose-effect relationship between the dose of CdCl2 and the expression of Nrf2 mRNA or Nrf2 protein in the testicles of rats(P<0.05).The mRNA expression levels of GST-P1 and GCLC were significantly increased in the testicles of rats in the 2.28,4.56 mg/kg CdCl2 groups(P<0.05),while the mRNA expression of GST-P1 and GCLC was significantly increased in 4.56 mg/kg CdCl2 group in the ovaries of rats(P<0.05).The mRNA expression of GSTP1 in the 1.14 mg/kg CdCl2 group and GCLC in the 2.28 mg/kg CdCl2 group was significantly decreased in the ovaries of rats(P<0.05).Conclusion A certain exposure dose of cadmium can induce the oxidative stress in the testicles and ovaries of rats,activate Nrf2-mediated antioxidant mechanism,and up-regulate the expression of the downstream phaseⅡdetoxification enzymes.The ovaries of female rats may be more sensitive to cadmium toxicity than the testicles of male rats.