酪氨酸相互作用蛋白51( PTPIP51)调控心脏缺血再灌注损伤的作用及作用机制

Cardiac ischemia-reperfusion (I/R) injury usually accompanies with coronary heart disease which is one of the leading causes of heart failure. A variety of mechanisms, including ischemia/reperfusion-triggered excess reactive oxygen species (ROS) production, intracellular calcium overload, dysfunction of cardiac contractile activity, and necrotic or apoptotic cell death, have been proposed to explain cardiac dysfunction and subsequently pathological processes after cardiac ischemia/reperfusion. Mitochondria, the energy supplying organelle also as an important component of intracellular calcium buffering system, the primary resource of ROS production, as well as the central determinant of cell survival and death, are gradually recognized as a pivotal player in the genesis of ischemia/reperfusion injury. As a metabolically active tissue, heart cells contain prominent mitochondrial networks, occupying up to 40% of cell volume and generating ATP in response to energy needs through oxidative phosphorylation (OXPHOS). Dysfunctions of mitochondria, such as decreased mitochondrial electron transport chain activity and mitochondrial ATP synthesis, increased ROS production, the opening of the mitochondrial permeability transition pore (MPT), subsequent release of cytochrome C from mitochondria to cytosol, and eventually cell death, are closely associated with cardiac ischemia/reperfusion. ..Protein tyrosine phosphatase interacting protein 51 (PTPIP51) localizes on mitochondria and participates in multiple cellular processes including proliferation, differentiation and apoptosis. Dysfunction of PTPIP51 is associated with diseases such as cancers and neurodegenerative disorders. However, the cardiac function of PTPIP51 is still unclear. Our preliminary data showed that PTPIP51 protein has been upregulated in mouse ischemia/reperfusion hearts and in H2O2 treated cardiomyocytes, and overexpressing PTPIP51 led to cardiomyocytes apoptosis, while knockdown of PTPIP51 ameliorated H2O2-mediated apoptosis, indicating a pivotal role of PTPIP51 in cardiac ischemia/reperfusion. In the present study, by gain- and loss-of function approaches, we will investigate whether PTPIP51 regulates cardiac function during ischemia/reperfusion both in vitro and in vivo, and if so, to reveal the underlying mechanisms.

缺血再灌注损伤常伴随冠心病的发病过程，冠心病则是心衰的主要致病因素。线粒体是细胞重要的细胞器，是机体能量供应站、ROS产生主要部位、细胞内钙缓冲部位，以及细胞生存和死亡信号的调控中枢。心肌细胞中线粒体含量达细胞体积的40%以上，线粒体功能障碍与心肌缺血再灌注损伤密切相关。酪氨酸相互作用蛋白51(PTPIP51)位于线粒体，参与细胞多种生物学功能，如细胞增殖、分化、凋亡等，其异常与多种肿瘤及神经退行性病变相关。PTPIP51蛋白的心脏功能目前尚未可知。我们预实验发现，缺血再灌注心肌PTPIP51表达量明显增加；过表达PTPIP51诱导心肌细胞凋亡，敲低PTPIP51则抑制过氧化氢所致的细胞凋亡，提示PTPIP51在心脏中具有重要功能。本项目拟在心肌细胞、心脏缺血再灌注及心脏敲低PTPIP51小鼠模型中，深入探讨PTPIP51在心肌及缺血再灌注损伤心脏中的作用及作用机制。

心脏是代谢活跃的器官，含有丰富的线粒体，线粒体除通过氧化磷酸化为心肌细胞收缩提供ATP外，还是ROS产生的主要部位、是细胞内钙缓冲重要部位，以及是细胞生存和死亡信号的调控中枢。线粒体功能障碍在缺血再灌注心肌损伤过程中发挥重要作用。酪氨酸磷酸酶相互作用蛋白51（protein tyrosine phosphatase interacting protein 51，PTPIP51）定位于线粒体，其心脏功能尚未知。我们发现，在冠脉左前降支结扎再通术建立的缺血再灌注小鼠模型损伤的心肌及H2O2诱导的凋亡心肌细胞中，PTPIP51蛋白水平显著升高；心肌细胞过表达PTPIP51导致细胞凋亡，而敲低PTPIP51则保护心肌细胞抵抗H2O2所致凋亡，提示PTPIP51参与缺血再灌注及氧化应激所致心肌细胞损伤过程。过表达PTPIP51的心肌细胞其线粒体/肌质网接触长度增加，线粒体钙摄取增加，线粒体内Ca2+浓度增高，而胞浆Ca2+浓度降低；敲低PTPIP51则线粒体/肌质网接触长度减少、间距加大，提示PTPIP51可能通过调节线粒体/肌质网间接触而调节线粒体钙含量。在小鼠心脏特异性敲低PTPIP51后，尽管心脏形态、心肌细胞大小及心脏功能无明显改变，线粒体/肌质网接触数量、有效接触长度均降低，且线粒体/肌质网间距离增加；缺血再灌注所致心肌损伤面积减少、凋亡心肌细胞数量降低，并且心脏功能改善。因此，本研究发现心肌缺血再灌注损伤时，PTPIP51蛋白上调，通过增加线粒体/肌质网接触面积，使线粒体内Ca2+超载，从而诱导心肌细胞凋亡；敲低PTPIP51则可以保护心脏抵抗心肌缺血再灌注引起的损伤并改善心功能。研究结果为临床氧化应激相关心脏疾病的治疗提供了可能的治疗靶点。