PHLPP1信号通路在英脱利匹特抑制尿毒症心肌缺血复灌损伤中的作用及机制研究

Recent studies have demonstrated that intralipid confered myocardial protection against ischemia reperfusion injury in healthy subjects, however, chronic kidney disease is an important independent risk for the development of coronary artery disease in patients subjecting myocardial infarct. Therefore, it's translationally important to determine whether intralipid confer cardioprotection in uremic myocardium. Our previous study has demonstrated that intralipid improved left ventricular pump function, reduced myocardial infarct and apoptosis through the activation of PI3K-Akt and MEK-ERK1/2 signals. PHLPP1 determines myocardial death through the regulation of Akt activity. Therefore, the aim of present study is to determine whether intralipdi-induced myocardial protection is maintained in uremic myocardium, and the role of PHLPP1 in intralipid-induced cardioprotection. We test the hypothesis that PHLPP1-Akt/ERK1/2-GSK3β-MPTP（ROS）signals may play a pivotal role in intralipid-induced cardioprotection in uremic myocardium and PHLPP1 would be a more promising potential therapeutic target for uremic patients suffering from myocardial infarct.

英脱利匹特可以保护健康的个体减轻心肌缺血复灌损伤，然而在临床上经历心肌缺血的病人常合并慢性肾脏疾病甚至尿毒症等心血管疾病危险因素，因此研究英脱利匹特对尿毒症个体的心肌缺血复灌损伤的影响具有重要的转化医学意义。我们前期的研究表明英脱利匹特显著改善健康大鼠左心室血流动力学，降低心肌梗死面积和细胞凋亡，减轻心肌缺血复灌损伤，其主要机制涉及PI3K-Akt和MEK-ERK1/2信号通路的激活。蛋白磷酸酶PHLPP1在促进细胞存活中起重要作用，其促使Akt去磷酸化，从而调节心肌细胞坏死和凋亡。本项目组拟在前期研究的基础上，通过建立尿毒症大鼠模型，研究英脱利匹特对尿毒症大鼠心肌缺血复灌损伤的作用和PHLPP1在尿毒症心肌缺血复灌损伤中的作用，阐明PHLPP1-Akt/ERK1/2-GSK3β-MPTP（ROS）通路在英脱利匹特抑制尿毒症心肌损伤中的作用，为尿毒症患者心肌缺血复灌损伤防治提供新的思路。

尿毒症加重心肌缺血再灌注损伤的机制目前仍不明确并且缺少有效的治疗手段，本项目阐明了PHLPP1信号通路在尿毒症心肌缺血再灌注损伤中的关键作用，证明了尿毒症心肌对常规心肌保护策略的抵抗性。在正常小鼠，心肌缺血再灌注损伤激活PHLPP1信号，而英脱利匹特显著抑制PHLPP1的活化，慢病毒过表达PHLPP1取消了英脱利匹特的心肌保护作用，敲低心脏的PHLPP1蛋白显著降低心肌细胞坏死和凋亡。在尿毒症小鼠，其心肌PHLPP1表达显著增加，英脱利匹特不能显著降低心脏的PHLPP1蛋白表达，而慢病毒敲低PHLPP1蛋白的表达可以显著降低尿毒症小鼠心肌缺血复灌损伤，但是加用英脱利匹特并未获得更强的心肌保护作用，表明PHLPP1作为重要的信号开关调控心肌缺血复灌损伤，抑制PHLPP1信号可以减轻尿毒症心肌缺血复灌损伤，揭示了PHLPP1分子在尿毒症心肌缺血复灌损伤中重要作用和潜在治疗价值。此外还观察到4PBA抑制内质网应激有效的减轻尿毒症心肌缺血再灌注损伤。