热应激对肝脏中Keap1-Nrf2信号通路及下游基因表达的影响

Effects of heat stress on Keap1-Nrf2-ARE signal pathway of liver in dairy cows

[目的]本试验旨在探讨热应激对泌乳期奶牛肝脏及抗氧化应激信号通路Keap1-Nrf2-ARE基因表达的影响。[方法]6头泌乳期荷斯坦奶牛饲养于南京地区夏季炎热季节,试验从6至8月持续5周,在第1周(平均气温26℃)和最后1周(平均气温32℃)采集颈静脉血液和肝脏组织样品。检测血液中相关生化指标和皮质醇及肝脏组织中MDA等的含量,并检测奶牛肝脏HSP70、Keap1-Nrf2通路及其下游HO1、GCLM、NQO1、GCLC等基因的表达。[结果]与常温时相比,热应激奶牛血液中皮质醇含量和AKP活性极显著升高(P<0.01);奶牛肝脏组织中MDA含量显著升高(P<0.05),CAT、SOD和GSH-Px活性有所升高;肝脏组织中HSP70基因表达极显著升高(P<0.01),Keap1和Nrf2基因表达显著升高(P<0.05),其下游4个基因中,HO1和NQO1表达显著提高(P<0.05),GCLM和GCLC表达有升高趋势(P>0.05)。[结论]高温致泌乳奶牛肝脏处于应激状态,肝脏中Keap1-Nrf2-ARE信号通路介导的Ⅱ相解毒酶[谷氨酰半胱氨酸合成酶催化亚单位(GCLC)、醌氧化还原酶1(NQO1)、谷氨酸-半胱氨酸连接酶修饰亚基(GCLM)]和抗氧化基因的转录通路被激活,提示Nrf2通路在抗热应激过程中可能发挥着重要作用。

[ Objectives ] The aim of this experiment was to investigate the liver function injury and the genes expression of Keapl- Nrf2-ARE signaling pathways during thermal stress of lactation cows. [ Methods ] The study lasted for 5 weeks （from June to August）. Six lactation cows were selected. Blood samples were collected from jugular vein on both the first and last week to analyze the related blood composition and cortisol content, and malondialdehyde （MDA）content in the liver. The liver tissue samples were also collected by living donor. The gene expression of Keapl-Nrf2 pathway and its downstream HO1, GCLM, NQO1 and GCLC protein were tested. [Results] During heat stress, the cortisol and AKP increased significantly （P〈0.01）, the MDA content increased significantly （P〈0.05） ,the activities of CAT, SOD and GSH-Px was increased in cows liver tissue. In liver, the gene expression of HSPTO increased significantly（P〈0.01 ）. The gene expression of Keapl and Nrf2 increased significantly（P〈0.05）. And among the four downstream genes, HO1 and NQO1 increased significantly （P 〈 0. 05 ）;GCLM and GCLC increased but with no significance. [ Conclusions] Hyperthermia caused hepatic stress in dairy cows. The Keapl-Nrf2-ARE signal pathway mediated phase Ⅱ detoxification enzyme（ GCLC,NQO1 and GCLM）and some antioxidant genes were motivated.