The mTOR pathway in neuronal death and epileptogenesis

描述(申请人提供)：NMDA受体(NMDAR)的过度激活会导致神经元死亡，这是太多神经疾病的核心过程，包括创伤性损伤、中风和癫痫。低剂量的NMDA治疗、亚致死性缺血或轻度癫痫等预条件措施可以有效地防止随后的严厉侮辱导致的神经元死亡，这表明温和的应激条件可能是有益的，并表明可能有治疗干预的利基。我们最近证实，NMDAR的激活调节哺乳动物的雷帕霉素靶标(MTOR)途径。这一途径以前被认为是对生长因子、营养物质和其他应激条件(包括氧化应激和缺氧)的反应，影响细胞生长，也可能调节细胞死亡。我们的初步研究发现，NMDA治疗引起的神经元死亡在亮氨酸饥饿后有所减轻，亮氨酸饥饿是一种已知抑制mTOR途径的应激条件。MTOR通路的几个组成部分似乎与癫痫有关。为了进一步阐明mTOR通路在神经元死亡中的分子机制及其在癫痫发生中的作用，我们将确定作用于mTOR上游和下游的促生存因子Akt是否介导了抑制mTOR所产生的神经保护(Aim I)。已知营养耗竭和mTOR抑制会激活自噬过程。我们将确定自噬是否参与神经保护(AIM II)。最后，我们将确定抑制mTOR通路是否可以防止癫痫动物模型中神经元的丢失和减轻自发性癫痫的发展(目标III)。完成这三个目标中提出的实验将有助于深入了解mTOR在神经元死亡和癫痫发生中的分子机制。雷帕霉素(西罗莫司)已被用作器官移植的免疫抑制剂，最近已用于结节性硬化症(TSC)患者的临床试验。此外，在目前的医疗环境下，亮氨酸饥饿的方法在临床上是可以控制的。由于癫痫是一种破坏性的神经疾病，几乎没有可用的预防方法，因此拟议研究的任何积极结果都可以很容易地转化为新的癫痫预防临床策略，想必没有传统治疗药物开发所遇到的许多障碍。我们研究的公共卫生相关性结果将提高我们对mTOR信号通路在癫痫以及其他神经疾病(如中风和创伤性脑损伤)中的作用的理解。它还可能导致对这些神经疾病进行新的药理和饮食干预。

DESCRIPTION (provided by applicant): Excessive activation of NMDA receptors (NMDAR) causes neuronal death, a process central too many neurological disorders, including traumatic injury, stroke, and seizure. Pre-conditional actions such as low-dose NMDA treatment, sub-lethal ischemia, or mild seizure can effectively prevent neuronal death caused by subsequent harsh insults, suggesting that mild stress conditions can be beneficial and indicating a possible niche for therapeutic intervention. We have recently established that NMDAR activation regulates the mammalian target of rapamycin (mTOR) pathway. This pathway, previously understood to influence cell growth in response to growth factors, nutrients, and other stress conditions, including oxidative stresses and hypoxia, may also regulate cell death. Our preliminary studies found that neuronal death elicited by NMDA treatment is attenuated upon leucine starvation, a stress condition that is known to inhibit the mTOR pathway. Several components of the mTOR pathway appear to be associated with epilepsy. To further elucidate the molecular mechanism of the mTOR pathway in neuronal death and its involvement in epileptogenesis, we will determine whether the pro- survival factor Akt, which acts both up- and downstream of mTOR, mediates the neuroprotection conferred by inhibition of mTOR (Aim I). Nutrient depletion and mTOR inhibition are known to activate the process of autophagy. We will determine whether autophagy is involved in neuroprotection (Aim II). Finally, we will determine whether inhibition of the mTOR pathway prevents neuronal loss in animal models of epilepsy and attenuates the development of spontaneous seizure (Aim III). Accomplishing the experiments proposed in these three aims will provide insight into the molecular mechanisms of mTOR in neuronal death and in epileptogenesis. Rapamycin (Sirolimus) has been used as immunosuppressant for organ transplantation and was recently put on clinical trial in patients with tuberous sclerosis complex (TSC). Furthermore, the leucine-starvation approach is clinically manageable in current medical settings. As epilepsy is a devastating neurological disorder with few preventive approaches available, any positive results from the proposed study could be readily translated into new clinical strategies for epilepsy prevention, presumably without many of the barriers normally encountered by traditional development of therapeutic drugs. PUBLIC HEALTH RELEVANCE Results from our studies will improve our understanding of the role of the mTOR signaling pathway in epilepsy as well as other neurological disorders such as stroke and traumatic brain injury. It may also lead to new pharmacological and diet interventions for those neurological disorders.