氧化低密度脂蛋白及其受体在高血压导致心肌线粒体损伤中的作用机制和干预研究

Hypertension is often accompanied by metabolism disorders, which enhance myocardial injury. Ox-LDL is one of the most important factors among these disorders. We and others have shown that mechanical stress produced by hypertension may induce cardiac hypertrophy through direct activation of the AT1 receptor. Recently, we observed that under the state of mechanical stress ox-LDL might induce cardiac mitochondrial injury through binding of its receptor LOX-1 with AT1 receptor and that the nucleosome assembly protein Nap1l1 was associated with the mitochondrial dysfunction. On the basis of these results, we suppose that underlying pressure overload ox-LDL induces binding and activation of LOX-1 and AT1 receptor, downregulation of Nap1l1 and impairment of the function of mitochondrial protein Drp1, leading to the myocardial mitochondria dysfunction and cardiac injuries. In the present study, we will prove our hypothesis by examination of mitochondia and cardiomyocyte injuries after infusion of ox-LDL in mechanical stress models produced in inducible cardiac-specific LOX-1, AT1 or Nap1l1 knockout mice and cardiac-specific Nap1l1 overexpression mice, and in cultured cardiomyocytes preteated with Drp1 specific inhibitor mdivi-1 and inhibitors of other molecules. The study will provide novel sight for molecular mechanisms underlying cardiac injury induced by ox-LDL in the hypertensive.

高血压常伴有代谢紊乱，加重心肌损伤，而氧化低密度脂蛋白（ox-LDL）升高是其重要原因，尚缺少有效干预手段。机械应力可直接通过AT1受体导致心肌肥厚，而我们最近工作显示，机械应力状态下Ox-LDL通过其受体LOX-1激活AT1受体导致心肌线粒体损伤；也观察到核小体组装蛋白Nap1l1参与调控ox-LDL导致的心肌线粒体损伤，其机制尚未见报道。我们推测，高血压时ox-LDL激活LOX-1并与AT受体结合使Nap1l1水平降低，进而引起线粒体蛋白Drp1功能失调导致线粒体和心肌损伤。本项目拟在AT受体、LOX-1、Nap1l1心肌特异性基因敲除鼠中建立压力超负荷模型并在心肌细胞中建立机械牵张模型，通过ox-LDL和相应药物或基因手段干预LOX-1、AT1受体、Nap1l1、Drp1，观察心肌线粒体和心肌变化，阐明高血压机械应力下ox-LDL通过LOX-1导致心肌线粒体损伤的分子机制。

高血压常伴有代谢紊乱，加重心肌损伤，而氧化低密度脂蛋白（ox-LDL）升高是其重要原因，尚缺少有效干预手段。我们在本项目的研究中观察到ox-LDL能够加重压力超负荷诱导的心肌肥厚及心力衰竭，在此过程中核小体组装蛋白1样蛋白1（NAP1L1）表达增加；NAP1L1下调能够减轻ox-LDL及压力超负荷诱导的心肌重构和心力衰竭，NAP1L1过表达能够加重ox-LDL及压力超负荷诱导的心肌重构和心力衰竭。通过体内体外实验，我们进一步检测和确定了NAP1L1在ox-LDL及压力超负荷诱导的心肌损伤中对线粒体功能的调控作用。并发现NAP1L1能够调控ox-LDL及压力超负荷诱导的心肌损伤中DRP1 S616位点的磷酸化。通过构建DRP1拟磷突变过表达腺相关病毒（AAV9-DRP1 S616D），发现DRP1 S616位点磷酸化的增加削弱Nap1l1敲除对心功能的保护作用。体外使用Mdivi-1抑制DRP1活性，可以减轻心肌细胞的线粒体损伤和活力下降。本课题研究表明组蛋白伴侣NAP1L1参与了ox-LDL加重压力超负荷诱导的心力衰竭。在此过程中，NAP1L1通过调控DRP1 S616位点的磷酸化，从而调控线粒体损伤和心力衰竭。本研究为有效防治心力衰竭的发生发展提供了新的思路。