A role for the complement system in seizure induced neuronal and dendritic injury

项目摘要 癫痫是一种癫痫，通常与认知障碍并存。长时间持续发作 (癫痫持续状态；SE)通过重构增加发生颞叶癫痫(TLE)的风险 在脆弱的神经元网络中的突触连接，例如海马区的那些。广泛的证据 谷氨酸支持SE诱导的海马区突触树突起重构 兴奋性毒性、细胞凋亡和一些细胞内信号级联反应的异常激活与 常导致癫痫发作的神经细胞过度兴奋。尽管有这些发现，但 直接影响神经的兴奋性仍然难以捉摸。SE和SE组织病理学上的一个显著特征 癫痫是小胶质细胞的激活，它介导神经炎性和吞噬反应。这很好 已知小胶质细胞介导的神经炎症机制有助于癫痫发作；然而，差距仍然存在 关于它们的吞噬反应的潜在作用。SE期间和术后小胶质细胞进行多项物理治疗 与皮质和海马树突接触，这是我们最近在人类难治性疾病中发现的现象 癫痫。这些接触可能导致树突状结构的吞噬，从而修饰 神经元连接。最近的研究发现，来自免疫补体的C1q和C3蛋白 系统发出“Eat-Me”信号，引导正常小胶质细胞吞噬瘤外突触 发育中的大脑。此外，C1q和C3与海马区的病理性移除有关 神经退行性疾病模型中的突触结构。我们和其他人发现C1q-C3增加 难治性人类癫痫和实验性癫痫发作后的mRNA和蛋白水平。因此，我们 癫痫诱导的免疫补体系统激活对海马区有贡献的假设 突触-树突修饰，促进神经元/网络的过度兴奋、癫痫发作和记忆缺陷。 我们将追求以下目标，Aim1：表征补体激活和相关的反应 SE和TLE小鼠模型的建立；AIM2：确定SE诱导的C3激活对神经元的贡献 以及TLE小鼠模型中海马区突触树突的变化；目的：确定 SE诱导的C3激活在小鼠癫痫发作和海马区依赖记忆障碍中的作用 TLE模型。这项研究将为理解先天的吞噬作用提供一个强有力的框架。 免疫补体系统和小胶质细胞在SE诱导的癫痫环路产生中的作用我们的科学研究 这些发现很可能为直接调节血管紧张素转换酶的潜在治疗价值提供证据 补体级联以减轻癫痫发作和认知共病。重要的是，因为FDA- 经批准的补体抑制剂目前正用于人类的免疫疾病，我们的研究 可能为快速追踪这些药物的再用途以用于癫痫提供证据。 1

Project Summary Epilepsy is a seizure disorder that is often comorbid with cognitive disabilities. Prolonged-continuous seizures (status epilepticus; SE) increase the risk for the development of temporal lobe epilepsy (TLE) by remodeling synaptic connectivity in vulnerable neuronal networks such as those of the hippocampus. Extensive evidence supports that SE-induced hippocampal synaptodendritic remodeling orchestrated through glutamate excitotoxicity, apoptosis, and aberrant activation from a number of intracellular signaling cascades is linked to the neuronal hyperexcitability that often results in seizures. Despite these findings, the mechanisms that directly impact neural hyperexcitability remain elusive. A prominent hallmark in the histopathology of SE and epilepsy is activation of microglia, which mediate neuroinflammatory and phagocytic responses. It is well known that microglia-mediated neuroinflammatory mechanisms contribute to seizures; however, a gap remains on the potential role of their phagocytic responses. During and after SE microglia make multiple physical contacts with cortical and hippocampal dendrites, a phenomenon that we recently found in human refractory epilepsy. These contacts may result in the phagocytosis of dendritic structures and thereby modification of neuronal connectivity. Recent studies discovered that C1q and C3 proteins from the immune complement system send “eat-me” signals that guide microglia to phagocytose extranumerary synapses in the normal developing brain. In addition, C1q and C3 are associated with the pathological removal of hippocampal synaptic structures in models of neurodegenerative disorders. We and others found increases in C1q-C3 mRNA and protein levels in intractable human epilepsy and after SE in experimental models. Therefore, we hypothesized that seizure-induced activation of the immune complement system contributes to hippocampal synaptodendritic modifications that promote neuronal/network hyperexcitability, seizures, and memory deficits. We will pursue the following Aims, Aim1: To characterize complement activation and associated responses in a mouse model of SE and TLE; Aim2: To determine the contribution of SE-induced C3 activation to neuronal and synaptodendritic changes in the hippocampus in a mouse model of TLE; Aim3: To determine the contribution of SE-induced C3 activation to seizures and hippocampal-dependent memory deficits in a mouse model of TLE. This study will provide a strong framework for understanding the phagocytic role of the innate immune complement system and microglia in the SE-induced generation of epileptic circuits. Our scientific discoveries are likely to provide evidence for the potential therapeutic value of directly modulating the complement cascade to attenuate seizures and cognitive comorbidities in epilepsy. Importantly, because FDA- approved complement inhibitors are currently being used for immunological illnesses in humans, our study may provide evidence to fast track the repurposing of these drugs for their use in epilepsy. 1