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[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。
[Objective] The aim of this study was to investigate the effect of heat stress on the gene expression of Keap1-Nrf2-ARE in liver and antioxidant signaling pathway in lactating dairy cows. [Method] Six lactating Holstein cows were housed in the summer hot season in Nanjing. The experiment lasted for 5 weeks from June to August. The neck was harvested in the first week (average temperature 26 ℃) and the last week (average temperature 32 ℃) Venous blood and liver tissue samples. The related biochemical indexes in blood and MDA in liver and cortisol were detected. The expression of HSP70, Keap1-Nrf2 pathway and HO1, GCLM, NQO1, GCLC and other genes in liver were detected. [Result] Compared with normal temperature, the content of cortisol and AKP activity in heat-stressed dairy cows increased significantly (P <0.01), the content of MDA in dairy cows increased significantly (P <0.05) (P <0.01). The expression of Keap1 and Nrf2 in liver increased significantly (P <0.05), and the expression of HO1 and NQO1 in the four downstream genes (P <0.05), GCLM and GCLC expression increased (P> 0.05). [Conclusion] The liver of pyrogen-induced lactating dairy cow is in stress state. The phase Ⅱ detoxification enzyme [glutamylcysteine synthetase catalytic subunit (GCLC), quinone oxidoreductase 1 (NQO1), glutamate-cysteine ligase modified subunit (GCLM)] and antioxidant genes, suggesting that Nrf2 pathway may play an important role in anti-heat stress.