Hypoglycemic neuronal death

描述（由申请人提供）： 低血糖性脑损伤是胰岛素治疗的一个严重风险，这种风险是糖尿病患者最佳血糖控制的主要障碍。由低血糖引起的神经元死亡不是能量衰竭的不可避免的后果，而是由低血糖和葡萄糖再输注引发的一系列事件引起的。重要的是要更充分地了解这个细胞死亡途径中的事件顺序，以确定下游点，在这些点可以进行治疗干预，以改善神经元的存活和最终的认知功能。最近在这方面取得了重大进展，但仍然缺乏关于这一途径的连贯一致的描述。这项建议的研究是基于最近的显著观察：a）葡萄糖再输注时，神经元中产生活性氧（ROS）（类似于缺血后再灌注期间的ROS产生）; B）ROS形成导致DNA损伤和PARP-1活化; c）PARP-1活化是介导低血糖神经元死亡的主要因素; d）锌螯合阻断低血糖诱导的PARP-1活化和细胞死亡;和我们提出，作为一种机制，ROS产生后，只有葡萄糖再输注，在没有葡萄糖的情况下，没有底物的NADH生产，因此没有底物的ROS生产的nNOS或NADPH氧化酶，并没有电子源的线粒体产生的超氧化物。在葡萄糖再输注后，这些位点中的每一个都可能发生ROS形成。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活性氧形成的主要部位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结果所建议的治疗方法。这些研究的一个关键、新颖的方面是关注葡萄糖再输注期间启动的ROS产生。严重低血糖的葡萄糖输注通常由医疗保健提供者启动，因此原则上应该可以同时给予旨在阻断ROS产生或其后果的预防剂。我们的目标是为这种情况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.