Zhou Tengfei, Zhang Mengqian, Zhao Liang, Li Aiqin, Qin Xiaomei
Institute of Cardiovascular Science, Peking University Health Science Center, Beijing, China; and Key Laboratory of Molecular Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China.
Institute of Cardiovascular Science, Peking University Health Science Center, Beijing, China; and Key Laboratory of Molecular Cardiovascular Science of Ministry of Education, Peking University Health Science Center, Beijing, China
Am J Physiol Cell Physiol. 2016 Oct 1;311(4):C572-C582. doi: 10.1152/ajpcell.00093.2016. Epub 2016 Aug 3.
Oxidative stress and impaired antioxidant defense are believed to be contributors to the cardiovascular aging process. The transcription factor nuclear factor-E2-related factor 2 (Nrf2) plays a key role in orchestrating cellular antioxidant defenses and maintaining redox homeostasis. Our previous study showed that Exendin-4, a glucagon-like peptide-1 analog, alleviates angiotensin II (ANG II)-induced vascular smooth muscle cell (VSMC) senescence by inhibiting Rac1 activation via cAMP/PKA (Zhao L, Li AQ, Zhou TF, Zhang MQ, Qin XM. Am J Physiol Cell Physiol 307: C1130-C1141, 2014). The objective of this study is to investigate if Nrf2 mediates the antisenescent effect of Exendin-4 in ANG II-induced VSMCs. Here we report that Exendin-4 triggered Nrf2 nuclear translocation, a downstream target of cAMP-responsive element-binding protein (CREB) and expressions of antioxidant genes heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 (NQO-1) in a dose- and time-dependent manner. In addition, knock-down of Nrf2 attenuated the inhibitory effects of Exendin-4 on ANG II-induced superoxidant generation and VSMC senescence. PKA/CREB pathway participated in the upregulations of HO-1 and NQO-1 induced by Exendin-4. Notably, our study revealed that Exendin-4 dose-dependently increased the acetylation of Nrf2 and the recruitment of transcriptional coactivator CREB binding protein (CBP) to Nrf2. The Exendin-4-induced Nrf2 transactivation was diminished in the presence of CBP small interfering RNA. Microscope imaging of Nrf2, as well as immunoblotting for Nrf2, showed that the Exendin-4-evoked Nrf2 acetylation favored its nuclear retention. Importantly, CBP silencing attenuated the suppressing effects of Exendin-4 on ANG II-induced VSMC senescence and superoxidant production. In conclusion, these results provide a mechanistic insight into how Nrf2 signaling mediates the antisenescent and antioxidative effects induced by Exendin-4 in VSMCs.
氧化应激和抗氧化防御受损被认为是心血管衰老过程的促成因素。转录因子核因子E2相关因子2（Nrf2）在协调细胞抗氧化防御和维持氧化还原稳态方面发挥着关键作用。我们之前的研究表明，胰高血糖素样肽-1类似物艾塞那肽-4通过cAMP/PKA抑制Rac1激活，减轻血管紧张素II（ANG II）诱导的血管平滑肌细胞（VSMC）衰老（Zhao L, Li AQ, Zhou TF, Zhang MQ, Qin XM. Am J Physiol Cell Physiol 307: C1130-C1141, 2014）。本研究的目的是调查Nrf2是否介导艾塞那肽-4对ANG II诱导的VSMC的抗衰老作用。在此我们报告，艾塞那肽-4以剂量和时间依赖性方式触发Nrf2核转位，cAMP反应元件结合蛋白（CREB）的下游靶点以及抗氧化基因血红素加氧酶-1（HO-1）和NAD（P）H醌氧化还原酶-1（NQO-1）的表达。此外，敲低Nrf2减弱了艾塞那肽-4对ANG II诱导的超氧化物生成和VSMC衰老的抑制作用。PKA/CREB途径参与了艾塞那肽-4诱导的HO-1和NQO-1的上调。值得注意的是，我们的研究表明，艾塞那肽-4剂量依赖性地增加Nrf2的乙酰化以及转录共激活因子CREB结合蛋白（CBP）向Nrf2的募集。在存在CBP小干扰RNA的情况下，艾塞那肽-4诱导的Nrf2反式激活减弱。Nrf2的显微镜成像以及Nrf2的免疫印迹显示，艾塞那肽-4引起的Nrf2乙酰化有利于其核内保留。重要的是，CBP沉默减弱了艾塞那肽-4对ANG II诱导的VSMC衰老和超氧化物产生的抑制作用。总之，这些结果为Nrf2信号通路如何介导艾塞那肽-4在VSMC中诱导的抗衰老和抗氧化作用提供了机制性见解。
