解偶联蛋白UCP2在环氧二十碳三烯酸改善高血压肾动脉内皮功能障碍中的作用

Epoxyeicosatrienoic acids (EETs) have strong effects on the regulation of blood pressure in the kidney. Conversion of EETs to their corresponding diols by soluble epoxide hydrolase (sEH) is responsible for decreasing EET levels and thereby diminishing their beneficial cardiovascular properties. The mitochondrial uncoupling protein 2 (UCP2) is one of mitochondrial inner membrane transporters, which dissipates the proton gradient and then mitigates mitochondrial reactive oxygen species (ROS) production. UCP2 has been shown as a new target for the prevention and treatment of hypertension. However, whether EETs could ameliorate endothelial dysfunction via UCP2 activation in hypertensive renal arteries and thus play an anti-hypertensive effect has not been reported. Preliminary data in this study demonstrated that the endothelium-dependent relaxation was impaired, ROS production was elevated, and UCP2 expression was reduced in renal arteries from spontaneously hypertensive rats (SHR) compared with those from WKY rats. Incubation with sEH inhibitor t-AUCB improved the impaired relaxation, increased AMPK and eNOS phosphorylations, and up-regulated UCP2 expression in SHR renal arteries. Based on these observations, we speculated that t-AUCB scavenged ROS and increased nitric oxide (NO) production through the activation of AMPK/UCP2/eNOS pathway by evevating EETs level, thus restoring NO bilavailability and improving endothelial dysfunction in hypertension. Using SHR, UCP2 knockout mice, eNOS knockout mice, and primary cultured endothelial cells, the present study aimed to elucidate the role of UCP2 in the improved endothelial function by EETs in hypertensive renal arteries. This study contributes to provide valuable information regarding the treatment of hypertension-related vascular events.

环氧二十碳三烯酸(EETs)在肾脏具有很强的调控血压的效应，经可溶性环氧化合物水解酶(sEH)代谢迅速降解。UCP2是线粒体内膜上的解偶联蛋白，可减少线粒体源性ROS的产生，在高血压的防治中逐渐受到关注。但是，关于EETs是否能够通过UCP2改善高血压肾内动脉内皮功能、从而降血压尚未见报道。申请人预实验结果显示：与WKY大鼠相比，SHR大鼠肾动脉内皮依赖性舒张功能降低，ROS产生增多，UCP2表达降低；sEH抑制剂t-AUCB能够改善其受损的舒张功能、增加AMPK和eNOS磷酸化、上调UCP2表达。据此提出科学设想：EETs通过AMPK/UCP2/eNOS系列激活，促进NO生成，减少ROS，从而改善高血压内皮功能。本研究拟利用SHR大鼠、UCP2和eNOS基因敲除小鼠以及原代内皮细胞，深入研究UCP2在EETs改善高血压肾动脉内皮功能中的重要作用，为高血压相关心血管疾病的治疗提供新的依据。

血管内皮功能障碍由一氧化氮（NO）产生与释放量减少、活性氧（ROS）增加、NO生物利用度降低所导致。在糖尿病、肥胖及高血压等疾病中，除发生血管内皮功能障碍外，我们的研究发现在肥胖小鼠中苯肾上腺素诱导的主动脉收缩功能降低，而蛋白激酶Cδ（PKCδ）是维持这种收缩功能的主要因素。. 胰高血糖素样肽-1（GLP-1）是一种主要由肠道L型细胞分泌的多肽，除降血糖作用外，GLP-1在心血管系统也发挥了重要作用，如在高血压中通过促进NO的生成与释放改善血管的舒张功能。然而，GLP-1在循环中迅速被二肽基肽酶-4（DPP-4）降解失活，因此，临床上使用DPP-4抑制剂或GLP-1类似物来增加活性GLP-1水平。GLP-1通过其受体发挥其生物学活性，我们的研究发现在自发性高血压大鼠（SHR）肾内动脉中GLP-1受体（GLP-1R）表达减少，其可能由PKCβ介导的。而DPP-4高选择性抑制剂sitagliptin能够增加SHR大鼠血浆中活性GLP-1含量，上调SHR大鼠肾内动脉GLP-1R的表达；我们还发现SHR大鼠肾内动脉的内皮依赖性收缩功能增强，而GLP-1激活SHR大鼠肾内动脉中AMPK后，上调解偶联蛋白2（UCP2）的表达，通过清除线粒体源性ROS、降低环氧合酶2（COX-2）的表达，从而降低内皮依赖性收缩功能，发挥降低血压的作用。. 我们发现黄连提取物黄连素（berberine）在SHR大鼠颈总动脉中通过抑制内质网应激，降低ROS/COX-2水平，减弱其内皮依赖性收缩功能。此外，berberine在大鼠胰岛瘤INS-1E细胞系和糖尿病小鼠胰岛中通过激活AMPK/UCP2信号通路，降低氧化应激、促进胰岛素分泌。. 综上所述：1）本研究通过探讨肥胖中引起血管收缩功能减弱的原因，为阐明肥胖血管功能障碍提供新的思路，为改善肥胖血管功能障碍提供新的靶点和措施；2）PKCβ有望成为调节GLP-1R表达、进而使GLP-1有效发挥其活性的新靶点；3）UCP2信号分子可能成为治疗高血压相关的心血管疾病以及2型糖尿病治疗中恢复胰岛素分泌的关键信号分子。