Immune responses in traumatic RGC death

 描述(由申请人提供)： 神经系统创伤性损伤，如创伤性脑损伤(TBI)、脊髓损伤(SCI)和创伤性视神经病变(TON)，在美国是导致死亡和残疾的主要原因，也是退伍军人医疗保健的主要挑战。除原发损伤外，发生在原发损伤后的继发性损伤会显著加重损伤，并导致约40%的创伤性脑损伤死亡。由于原发损伤几乎无法逆转，因此治疗的主要目的是防止继发性损伤所致的神经元死亡。谷氨酸兴奋性毒性是颅脑损伤、脊髓损伤和TON的主要继发性损伤之一，谷氨酸受体的过度刺激导致神经元损伤，最终导致神经元死亡的病理过程。因此，有效地减少或预防谷氨酸的兴奋性毒性将减少对神经元的继发性损伤。此外，谷氨酸的兴奋性毒性也在许多其他神经退行性疾病中发挥关键作用，如青光眼，这是世界上包括退伍军人在内的主要致盲原因。TON和青光眼都会特别损伤视网膜神经节细胞(RGC)。由于RGCs是唯一将视觉信号从眼睛传递到大脑的细胞，RGCs的丧失将导致不可逆转的视力丧失，目前还没有有效的治疗方法。因此，防止视网膜神经节细胞在TON和青光眼中死亡对于保护视力至关重要。了解RGC对谷氨酸兴奋性毒性、TON或青光眼易感性的控制机制，将有助于我们制定治疗策略，以防止RGC在这些疾病中死亡。最近的研究表明，免疫分子在中枢神经系统疾病的神经元修复和细胞死亡中发挥着重要作用。在视网膜中，主要组织相容性复合体(MHC)I类分子的受体、T细胞受体(TCR)及其相关蛋白由RGC表达。这些分子的突变损害了RGC的树突和轴突结构，增加了RGC对谷氨酸兴奋性毒性的易感性，同时上调运动神经元MHCI的表达，显着促进了脊髓损伤后运动能力的恢复。这些发现有力地支持了MHCI/TCR可以保护RGC免于死亡的可能性。在本研究中，我们计划研究视网膜节细胞对谷氨酸兴奋毒性和视神经挤压(ONC)的易感性，探讨TCR在调节RGC易损性中的作用，并确定激活TCR预防RGC死亡的治疗潜力。本研究的第一个目标是确定TcR的关键分子CD3在RGC易损性中的作用。我们的初步结果表明，不同亚型的视网膜节细胞对谷氨酸兴奋毒性的易感性不同，在CD3-/-小鼠中，视网膜节细胞对谷氨酸兴奋性毒性的易感性显着增加。我们将进一步研究四种亚型视网膜节细胞对谷氨酸兴奋毒性和视网膜节细胞的易感性，以及CD3在视网膜节细胞易感性中的作用。第二个目标是确定过表达CD3以保护视网膜节细胞的治疗潜力。我们的初步结果表明，在CD3-/-视网膜的视网膜节细胞中表达CD3可以修复视网膜节细胞树突状缺陷，提示CD3对视网膜节细胞的作用是可逆的。我们计划进一步确定是否可以通过过度表达编码CD3的基因来增强视网膜节细胞的抵抗力。本研究的第三个目标是确定CD3CD3激活分子保护视网膜节细胞的治疗潜力。已有研究表明，外源性CD3激活分子可在体外激活CD3。我们将进一步确定外源性CD3激活分子是否与CD3的过度表达协同作用来保护视网膜节细胞。总之，这项研究将确定MHCI-TCR在调节RGC对病理性侮辱的脆弱性中的作用，并测试使用MHCI-TCR的潜力 MHCI/TCR介导的保护RGC免受疾病死亡的机制。虽然RGCs在本研究中被用作模型，但该结果可能为研究CNS其他区域的神经元死亡提供重要的见解，因此，对于CNS创伤后的神经元保护具有重要意义。

 DESCRIPTION (provided by applicant): Traumatic injuries of the nervous system, such as traumatic brain injury (TBI), spinal cord injury (SCI) and traumatic optic neuropathy (TON), are major causes of death and disability in the USA and major challenges for the healthcare of veterans. In addition to the primary injury, secondary injuries, which occur after the primary injury dramatically worsens the damage and cause about 40% of TBI deaths. Because little can be done to reverse the primary injury, the primary aim of the treatment is to prevent secondary injury induced neuronal death. One of the major secondary injuries of TBI, SCI and TON is glutamate excitotoxicity, the pathological process by which neurons are damaged and eventually killed by excessive stimulation of glutamate receptors. Therefore, effectively minimizing or preventing glutamate excitotoxicity will reduce the secondary injury to neurons. In addition, glutamate excitotoxicity also plays critical roles in many other neurodegenerative diseases, such as glaucoma, the leading cause of blindness in the world, including veteran population. Both TON and glaucoma specifically injure retinal ganglion cells (RGCs). Because RGCs are the only cells relaying the visual signals from the eyes to the brain, loss of RGCs will result in an irreversible loss of vision and no effective treatments are currently available. Therefore, preventing RGCs from death in TON and glaucoma is crucial to preserve vision. Understanding the mechanisms which control the vulnerability of RGCs to glutamate excitotoxicity, TON or glaucoma will help us to develop treatment strategies to prevent RGC death in these diseases. Recent studies have shown that immune molecules play important roles in neuron repair and cell death in CNS diseases. In the retina, the receptors of major histocompatibility complex (MHC) class I molecules, T-cell receptor, (TCR) and their associated proteins are expressed by RGCs. Mutation of these molecules compromised RGC dendrite and axon structure and increased the vulnerability of RGCs to glutamate excitotoxicity while up-regulated MHCI expression in motor neurons significantly promoted the recovery of locomotor abilities after SCI. These findings strongly support the possibility that MHCI/TCR could protect RGCs from death. In this study, we plan to characterize the vulnerability of RGCs to glutamate excitotoxicity and optic nerve crush (ONC), investigate the roles of TCR in the regulation of RGC vulnerability, and determine the therapeutic potential of activation of TCR for the prevention of RGC death. The first goal of this study is to determine the contribution of a key molecule of TCR, CD3, to the vulnerability of RGCs. Our preliminary results showed that different subtypes of RGCs have different vulnerability to glutamate excitotoxicity and RGC vulnerability to glutamate excitotoxicity is dramatically increased in CD3-/- mice. We will further characterize the vulnerability of four subtypes of RGCs to glutamate excitotoxicity and ONC, and the contribution of CD3to RGC vulnerability. The second goal is to determine the therapeutic potential of overexpressing CD3 to protect RGCs. Our preliminary results demonstrated that expressing CD3 in RGCs of CD3-/- retinas restored the RGC dendritic defects, suggesting the reversibility of CD3-mediated effects on RGCs. We plan to further determine whether the resistance of RGCs can be enhanced by over-expressing the gene encoding CD3. The third goal of this study is to determine the therapeutic potentials of CD3 activating molecules to protect RGCs. It has been demonstrated that CD3 could be activated by exogenous CD3 activating molecules in vitro. We will further determine if the exogenous CD3activating molecules work synergistically with the over-expression of CD3 to protect RGCs. Overall, this study will identify the role of MHCI-TCR in the regulation of the vulnerability of RGCs to pathological insults, and test the potential of using MHCI/TCR mediated mechanisms to protect RGCs from death in diseases. Although RGCs are used as a model in this study, the results could provide important insights into the neuronal death of other areas of CNS and, therefore, have important implications in neuronal protection following traumatic injuries in the CNS.