星形胶质细胞Toll样受体4激活对幼年小鼠癫痫发生的影响及机制研究

The highest incidence of seizures occurs in early life, suggesting that seizure activities may be related to deficits in brain development. Plenty of predisposed risk factors during development, such as immune challenges, not only affect brain development, but also promote epileptogenesis, suggesting immune activation is one of the key factors linking epilepsy to abnormal brain development. Astrocytes regulate neuron development, and abnormal astrocyte development can lead to many serious neurodevelopmental disorders. Besides, astrocytes are involved in epileptogenensis by evoking immune responses in the brain. There is a rapidly growing body of evidence that supports the involvement of inflammation and immune responses in epileptogenesis. The pattern recognition receptor Toll-like receptor 4 (TLR4) has known to be involved in epileptogenesis, and is expressed in neurons and astrocytes, where they possibly initiate different signaling pathways after being activated by lipopolysaccharide (LPS). In addition, activation of TLR4-mediated signaling during postnatal development can lead to an increase in the astrocyte number and abnormal neuronal development and function. These lines of evidence indicate that astrocytic TLR4 may play important roles in early-life epilepsy. However, the detailed effects and mechanisms remain to be elucidated. In this study, we will explore the effects of astrocytic TLR4 activation during the critical period of postnatal development on seizure susceptibility in young mice, as well as the underlying signaling pathway of astrocytic TLR4 activation, to elucidate the critical molecular and cellular mechanisms of astrocytic TLR4-mediated immune response in early-life epileptic seizures.

儿童和青少年是癫痫高发人群，提示癫痫与脑发育相关。发育过程中许多环境致病因素，如免疫活性物质等不仅会影响脑发育，还可以诱发癫痫，提示免疫反应可能是癫痫与脑发育相关联的重要因素。星形胶质细胞(AS)发育和功能异常与多种神经发育疾病有关，并能通过介导免疫反应而参与癫痫发生。作为模式识别受体的Toll样受体4 (TLR4)与癫痫发生密切相关，并在神经元和胶质细胞中均有表达，但其介导的信号通路在神经元和AS中可能不同。发育期TLR4激活可引起海马AS数目增加和神经元发育异常。以上结果提示，AS-TLR4很可能在幼年癫痫发生中起重要作用，但具体机制尚不清楚。本项目以阐明发育过程中癫痫发病机制为目标，将利用TLR4通路工具小鼠结合行为、电生理和胚胎电转等技术，详细研究AS-TLR4功能及其信号通路在发育关键期内调控癫痫发生的分子细胞机制，为幼年癫痫发病的神经生物学机制提供科学依据，具有潜在的应用价值。

星形胶质细胞是中枢神经系统（CNS）内广泛分布的一类胶质细胞，参与多种生理和病理过程。在大脑发育过程中，星形胶质细胞通过调节轴突导向、突触形成、突触消除、突触功能、神经元存活等来协调脑内神经元环路的发育。已发现多种神经系统疾病的发生，如癫痫、自闭症谱系障碍（ASD）等，与星形胶质细胞的发育和功能异常相关。另外，作为脑内最主要的免疫应答细胞之一，星形胶质细胞中重要免疫信号的激活也对发育关键期内CNS的发育具有重要的调控作用。作为模式识别受体的Toll样受体4 (TLR4)与癫痫等神经发育疾病密切相关，并在神经元和胶质细胞中均有表达，但其介导的信号通路在神经元和星形胶质细胞中可能不同。前期研究报道发育关键期TLR4激活可引起海马星形胶质细胞数目增加和神经元发育的异常。这些结果提示我们，星形胶质细胞TLR4很可能在幼年癫痫发生中起重要作用，但具体机制尚不清楚。在这个课题中，我们利用了TLR4通路工具小鼠，结合行为学、电生理、免疫组化、原代神经元和星形胶质细胞培养以及子宫内胚胎电转等技术，详细研究了星形胶质细胞TLR4功能及其信号通路在不同发育关键期内调控神经发育相关疾病发生的分子细胞机制，为出生后早期和胚胎后期等发育关键期内免疫刺激对神经发育相关疾病发病（尤其是幼年癫痫和自闭症）的作用提供了科学依据，具有潜在的应用价值。