Cyclophilin D as a Therapeutic Target following Traumatic Brain Injury

描述（由申请人提供）：本研究的目的是尽量减少创伤性脑损伤（TBI）后继发性细胞死亡和由此引起的发病率。改善脑外伤后预后的临床干预措施极为有限。线粒体功能障碍是创伤性脑损伤（TBI）神经病理后遗症的关键环节。tbi诱导的线粒体Ca2+循环/过载增加最终导致线粒体通透性过渡孔（mPTP）的打开。这个孔位于线粒体内膜上，在Ca2+和氧化应激升高时打开，并由线粒体蛋白亲环蛋白D （CypD）控制。当延长时，mPTP开放是灾难性的，因为线粒体膜电位的丧失，以及线粒体中钙和死亡相关蛋白的释放。本研究的目的是通过限制mPTP的开放来减少TBI后的继发性细胞死亡和由此引起的发病率。免疫抑制剂环孢素A （CsA）通过与CypD结合抑制mPTP开放。我们和其他人之前已经证明CsA可以减少实验性TBI后的组织损伤程度。不幸的是，由于CsA对钙调磷酸酶的抑制作用，它在高浓度时是有毒的。最近，我们已经证明，初级神经元中的CypD水平大约是星形胶质细胞中CypD水平的两倍，并且突触线粒体（神经元来源）中的CypD水平也显著高于非突触线粒体（主要是非神经元来源）。由于其高CypD含量，我们假设神经元线粒体更容易受到mPTP开放的影响，也需要更高的CsA水平来抑制mPTP的开放。为了验证这一假设，我们建议使用遗传和新的药理学方法来抑制神经元损伤后的CypD。具体来说，我们将使用CypD敲除小鼠和不结合或抑制钙调磷酸酶的CsA衍生物NIM811。具体目的是：1：评估假设，高CypD含量的神经元线粒体增加易感性mPTP开放后的损伤，导致细胞内Ca2+和氧化应激升高。2：评估CypD抑制剂NIM811水平保护神经元免受兴奋毒性损伤与其CypD含量成正比的假设。目的：探讨线粒体CypD水平调节小鼠脑外伤后神经病理和功能结局的假说。4：检验CypD抑制剂NIM811减轻TBI后组织损伤和改善功能结局的假设。基于这些研究结果，我们预计NIM811将显示出强大的潜力，作为TBI的新疗法。

DESCRIPTION (provided by applicant): The goal of this research is to minimize the secondary cell death and resultant morbidity following traumatic brain injury (TBI). Clinical interventions to improve outcome following TBI are extremely limited. Mitochondrial dysfunction is a pivotal link in the neuropathological sequalae of traumatic brain injury (TBI). TBI-induced increases in mitochondrial Ca2+ cycling/overload ultimately lead to opening of the mitochondrial permeability transition pore (mPTP). This pore, located on the inner mitochondrial membrane, opens in response to elevated Ca2+ and oxidative stress, and is gated by the mitochondrial protein cyclophilin D (CypD). When prolonged, mPTP opening is catastrophic as a result of the loss of mitochondrial membrane potential, and the release of calcium and death-related proteins from mitochondria. The goal of this research is to minimize the secondary cell death and resultant morbidity following TBI by limiting mPTP opening. The immunosuppressant Cyclosporin A (CsA) inhibits mPTP opening by binding to CypD. We and others previously demonstrated that CsA reduces the extent of tissue damage when administered following experimental TBI. Unfortunately, CsA is toxic at high concentrations, resulting from its inhibition of calcineurin. Recently we have demonstrated that CypD levels in primary neurons are approximately double the levels found in astrocytes and that CypD levels are also significantly higher in synaptic mitochondria (neuronal origin) compared to non-synaptic mitochondria (predominately non-neuronal origin). As a result of their high CypD content, we hypothesize that neuronal mitochondria are more vulnerable to mPTP opening and also require greater CsA levels to inhibit mPTP opening. To test this hypothesis we propose to use genetic and newer pharmacologic approaches to inhibit CypD following neuronal injury. Specifically, we will use CypD knockout mice and a CsA derivative, NIM811, which does not bind to or inhibit calcineurin. The specific aims are: 1: To evaluate the hypothesis that the high CypD content of neuronal mitochondria enhances vulnerability to mPTP opening following insults that result in elevated intracellular Ca2+ and oxidative stress. 2: To evaluate the hypothesis that the levels of the CypD inhibitor NIM811 required to protect neurons from excitotoxic insult is proportional to their CypD content. 3: To examine the hypothesis that mitochondrial CypD levels modulate the neuropathologic and functional outcome following TBI in mice. 4: To examine the hypothesis that CypD inhibitor NIM811 reduces tissue damage and improves functional outcome following TBI. Based on the results of these studies, we anticipate that NIM811 will exhibit strong potential as novel therapy for TBI.