Hypoglycemic neuronal death

描述(由申请人提供)： 低血糖脑损伤是胰岛素治疗的一个严重风险，而这种风险是糖尿病患者最佳血糖控制的主要障碍。低血糖引起的神经元死亡不是能量衰竭的必然结果，而是由低血糖和葡萄糖重新输注引发的一系列事件的结果。重要的是要更充分地了解这一细胞死亡途径中的事件顺序，以便确定下游点，在这些点上可以进行治疗干预，以改善神经元存活和最终的认知功能。最近在这方面取得了重大进展，但仍然缺乏关于这条道路的连贯图景。这一建议的研究基于最近的显著观察：a)在葡萄糖重新输注时神经元产生活性氧物种(ROS)(类似于缺血后再灌注期间ROS的产生)；b)ROS的形成导致DNA损伤和PARP-1激活；c)PARP-1激活是介导低血糖神经元死亡的主要因素；d)锌螯合阻止低血糖诱导的PARP-1激活和细胞死亡；以及e)非葡萄糖底物可以将细胞从PARP-1介导的细胞死亡中拯救出来。我们提出，在没有葡萄糖的情况下，没有NADH产生的底物，因此没有nNOS或NADPH氧化酶产生ROS的底物，也没有线粒体产生超氧化物的电子来源，这是一种只有在葡萄糖重新输注后才产生ROS的机制。当葡萄糖重新输注时，这些部位中的每一个都可能形成ROS。本文提出的研究将使用细胞培养和严重低血糖的体内模型来确定ROS形成的主要部位(S)以及导致低血糖神经元死亡的事件之间的时间和因果关系。拟议的研究还将检查这些最近观察到的治疗方法。这些研究的一个关键的、新颖的方面是对葡萄糖重新输注过程中启动的ROS产生的关注。葡萄糖输注治疗严重低血糖通常是由医疗保健提供者发起的，因此原则上应该可以同时给予旨在阻断ROS产生或其后果的辅助剂。我们的目标是为这种环境确定有效的干预措施。

DESCRIPTION (provided by applicant): Hypoglycemic brain injury is a serious risk of insulin therapy, and this risk is a major impediment to optimal glucose control in diabetic patients. Neuronal death resulting from hypoglycemia is not an inevitable consequence of energy failure, but results instead from a sequence of events initiated by hypoglycemia and glucose re-infusion. It is important to more fully understand the sequence of events in this cell death pathway in order to identify downstream points at which therapeutic interventions can be made to improve neuronal survival and ultimate cognitive function. There has recently been significant progress in this regard, but a cohesive picture of this pathway is still lacking. Studies in this proposal are based on recent salient observations: a) reactive oxygen species (ROS) are generated in neurons at the time of glucose re-infusion (similar to ROS production during reperfusion after ischemia); b) ROS formation leads to DNA damage and PARP-1 activation; c) PARP-1 activation is a major factor mediating hypoglycemic neuronal death; d) zinc chelation blocks hypoglycemia-induced PARP-1 activation and cell death; and e) non-glucose substrates can rescue cells from PARP-1 - mediated cell death. We propose, as a mechanism by which ROS are produced only after glucose re-infusion, that in the absence of glucose there is no substrate for NADH production and consequently no substrate for ROS production by nNOS or NADPH oxidase, and no electron source for the mitochondrial generation of superoxide. Upon glucose re-infusion, ROS formation from each of these sites may occur. The studies proposed here will use cell culture and in vivo models of severe hypoglycemia to identify the major site(s) of ROS formation and the temporal and cause-effect relationships between the events leading to hypoglycemic neuronal death. Proposed studies will also examine therapeutic approaches suggested by these recent observations. A key, novel aspect of these studies is a focus on ROS production initiated during glucose re-infusion. Glucose infusion for severe hypoglycemia is generally initiated by health care providers, and consequently it should in principle be possible to simultaneously administer of adjunctive agents aimed at blocking ROS production or its consequences. We aim to identify effective interventions for this setting.