Investigating the Role of Pioglitazone, mitoNEET and Mitochondria following TBI

描述(申请人提供)：创伤性脑损伤(TBI)会导致严重的并发症，每年约有170万美国人受伤。这促使人们将重点放在神经保护和促再生治疗药物的发现和开发上。一个潜在的神经保护靶点是由颅脑损伤引起的兴奋性毒性引起的线粒体功能障碍。这种兴奋性毒性是由过度的突触谷氨酸引起的，从而导致损伤部位神经元的过度兴奋，导致线粒体钙循环/钙超载的大幅增加。线粒体呼吸在损伤后的头3至48小时出现明显的线粒体呼吸下降，而钙超载则先于线粒体呼吸显著下降。线粒体呼吸减少，这是线粒体生物能(产生三磷酸腺苷的能力)降低的迹象，导致细胞死亡途径的启动。随着受损神经元的死亡，组织损伤的程度增加，功能(运动和认知)能力下降。我们认为线粒体功能障碍是脑损伤神经病理后遗症的关键组成部分，也是脑损伤药物发现研究的重要治疗靶点。我们实验室的总体目标是确定线粒体功能障碍的改善是否会减少与脑外伤相关的神经细胞死亡。我们实验室和其他实验室的研究结果表明，已知的PPAR-？激动剂具有神经保护作用，可促进脑外伤后的功能恢复。为了支持这一点和我们实验室的目标，吡格列酮不仅可以减少脑外伤后的线粒体功能障碍，还可以与一种新的线粒体膜蛋白mitoNEET结合。然而，mitoNEET在吡格列酮介导的神经保护中的作用尚不清楚。初步结果表明，在MitoNEET基因敲除小鼠中，吡格列酮介导的神经保护作用缺失，而一种特定的mitoNEET配体(NL-1)对脑损伤后的神经具有保护作用。综上所述，这些数据表明，mitoNEET是吡格列酮介导的神经保护的重要组成部分。因此，为了了解吡格列酮的作用机制，我将检验一种假设，即吡格列酮改善线粒体生物能量学，从而减少脑损伤后的组织丢失和改善功能恢复的能力，取决于与mitoNEET的结合。我进一步假设，吡格列酮的保护作用可以被外源性MITONEET配体NL-1复制。

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) causes severe complications to the estimated 1.7 million Americans who are injured annually. This has precipitated a major focus on the discovery and development of neuroprotective and pro-regenerative therapeutic agents. One potential neuroprotective target, which has been well supported in the literature, is mitochondrial dysfunction resulting from TBI induced excitotoxicity This excitotoxicity is caused by excessive synaptic glutamate and the consequent over-excitation of neurons at the site of injury leading to large increases in mitochondrial Ca2+ cycling/Ca2+ overload. Ca2+ overload precedes a notable decrease in mitochondrial respiration, which has been documented in the first 3 to 48 hours post-injury. This decreased mitochondrial respiration, which is an indication of decreased mitochondrial bioenergetics (ability to generate ATP), leads to the initiation of cell death pathways. As the injured neurons die, the extent of tissue damage increases and functional (motor and cognitive) abilities decrease. We believe mitochondrial dysfunction to be a pivotal component to the neuropathological sequelae of brain injury and an important therapeutic target for drug discovery research in TBI. An overall goal of our laboratory is to determine whether amelioration of mitochondrial dysfunction will decrease the neuronal cell death associated with TBI. Findings from our lab and others show that pioglitazone, a known PPAR-? agonist, is neuroprotective and increases functional recovery following TBI. In support of this and the goals of our lab, pioglitazone not only reduces mitochondrial dysfunction following TBI, but also binds to mitoNEET, a novel mitochondrial membrane protein. However, the contribution of mitoNEET to pioglitazone- mediated neuroprotection is unknown. Preliminary results indicate that pioglitazone-mediated neuroprotection is absent in mitoNEET knockout mice and a specific mitoNEET ligand (NL-1) is neuroprotective following TBI. Taken together, these data suggest that mitoNEET is an essential component of pioglitazone mediated neuroprotection. Therefore, in order to understand the mechanisms of pioglitazone, I will test the hypothesis that pioglitazone's ability to improve mitochondrial bioenergetics, thereby decreasing tissue loss and improving functional recovery following TBI, hinges on binding mitoNEET. I further hypothesize that the protective effects of pioglitazone can be reproduced by NL-1, an exogenous mitoNEET ligand.