MITOCHONDRIA RELATED EVENTS IN TRAUMATIC BRAIN INJURY

创伤性脑损伤(TI)后的中心事件是电生理功能的一过性或持续性损害，表现为昏迷、脑震荡或神经功能障碍。静息膜电位的持续降低，以及随之而来的神经元膜和轴突膜的充分再极化的失败，是引起这些效应的最可能的机制。这一应用围绕着一个中心假设，即线粒体功能障碍和离子泵减少，导致生物能量衰竭，是决定脑外伤后神经元和轴突恢复的主要限制因素。在这个应用中，我们建立在我们以前的研究基础上，证明了脑外伤后大量的兴奋性神经递质释放，导致钙内流。这反过来又会损害线粒体、神经丝和第二信使介导的离子通道，以及许多其他事件。这些问题将在临床和实验室环境中进行探索。具体地说，在大鼠颅脑损伤模型中，我们将使用免疫组织化学、分子生物学、电生理学和行为测试来验证这样的假设，即钙介导的对抑制性GABA1通道的损伤会加剧神经元损伤，从而恶化预后，并且GABA激动剂可以改善预后。我们将直接测量细胞色素氧化酶的活性，以显示脑外伤后线粒体的功能受损，并假设环孢素A特异性阻断线粒体转换孔(MPT)将阻止这些变化，并改善预后。在重型颅脑损伤患者中，将在同一脑区同时放置微透析和新的同轴深度电极，以及组织氧/二氧化碳/pH传感器系统，以测试在神经化学和神经生理事件的相互作用下氧分压升高和环孢素A的效果。我们将使用AVDO2、AVD乳酸和AVD葡萄糖来评估整体治疗效果，并将它们与CBF和MRI参数相关联。最后，我们将使用MRI水成像、扩散加权成像和脑血流量成像来显示脑肿胀，几乎总是伴随着脑外伤，是由于细胞毒性水肿所致。这些方法还将检验环孢菌素A将改善细胞毒性水肿的假设，以及N-乙酰-天冬氨酸光谱学将构成人类脑外伤中线粒体和神经元损伤的“替代标记”的假设。因此，这些新技术，通过一系列紧密结合的实验室和临床研究，将产生新的机制见解，并特别评估环孢菌素A和其他几种推定的脑损伤新疗法。

The central event after traumatic brain injury (TI) is the transient, or ongoing impairment of electrophysiological function, manifest as coma, "concussion" or neurological deficit. Persistent reduction in the Resting Membrane Potential, and consequent failure to adequately re-polarize neuronal and axonal membranes, are the most likely mechanisms for eliciting these effects. This application revolves around the central hypothesis that mitochondrial dysfunction and reduced ionic pumping, leading bioenergetic failure, is the major limiting factor, determining neuronal and axonal recovery after TBI. In this application, we build upon our previous studies, demonstrating massive excitatory neurotransmitter release after TBI, leading to calcium influx. This in turn damages mitochondria, neurofilaments, and second-messenger mediated ion channels, among many other events. These issues will be explored in the clinic and laboratory settings. Specifically, in rat TBI models, we will use immunohistochemistry, molecular biology, electrophysiology, and behavioral testing to validate the hypothesis that calcium-mediated damage to inhibitory GABA Cl channels exacerbates neuronal damage, and thus worsens outcomes, and that GABA agonists improve outcome. We will directly measure cytochrome oxidase activity, to show that mitochondria are functionally impaired after TBI, and we will posit that specific blockade of the Mitochondria Transition Pore (MPT) with Cyclosporin A, will prevent these changes, and improve outcome. In severely head injured patients, simultaneous microdialysis, and a new coaxial depth electrode, together with a tissue oxygen/CO2/pH sensor system, will be placed in the same brain region to test the effect of increased oxygen tension, and Cyclosporin A under the interplay of neurochemical and neurophysiological events. We will use AVDO2, AVD lactate, and AVD glucose to assess global therapy effects, and relate them to CBF and MRI parameters. Finally, we will use MRI water mapping, Diffusion Weighted Imaging, and CBF mapping, to show that the brain swelling, which almost always follows TBI is due to cytotoxic edema. These methods will also test the hypothesis that Cyclosporin A will ameliorate cytotoxic edema, and that N Acetyl Aspartate spectroscopy will constitute a "surrogate marker" for mitochondrialy, and neuronal damage in human TBI. Thus, these novel techniques, through a tightly integrated set of laboratory and clinical studies, will yield new mechanistic insights, and specifically evaluate Cyclosporin A and several other putative new therapies in TBI.