P2X7受体介导小胶质细胞活化在高原缺氧所致记忆损伤中的作用及机制研究

Hypobaric hypoxia, resembling high altitude hypoxia severely affects the CNS including memory impairments. Synaptic plasticity in hippocampus is closely associated with learning and memory. Recently researches show that microglia are essential for the establishment, function, modification of synaptic connections and paticipate in memory modulation. Accumulated evidence indicates that microglia was activated during hypoxia, but the mechanism of hypoxia induced microglia activation is unclear. The P2X7receptor (P2X7R)is a unique member of the P2X receptor family,which was mainly expressed on microglia and plays an important roles in cognitive function. Considerable researches suggested that P2X7 receptor was activated by hypoxia, which are associated with many pathological process. Our previous research showed that P2X7 receptor mediates microglia activation, but during hypoxia exposure whether P2X7 receptor is an capital factor that contribute to hypoxia-induced microglia activation is still unclear, and and the following mechanism of microglia activated by P2X7R in hypoxia-induced memory impairments needs to be further study. This study will use acute hypobaric hypoxia(HH) rat model, combine in vivo and in vitro experiment and apply some methods include morphology, molecular biologyand [Ca2+]i image and patch clamp, to observe the expression of P2X7 receptor in hippocampus in HH rats, to explore the relationship of expression of P2X7 receptor with hippocampus microglia activation and with memory impairments induced by hypoxia; to speculate the effects of P2X7 receptors activation on the glycine release from microlgia after hypoxia and its signal transduction pathways; and to investigate whether glycine release from microlgia is mainly mechanism of hypoxia Hypoxia induces Plasticity in hippocampus Synaptic. This study will lead to a better understanding of the molecular mechanisms of hypoxia induced memory impairment and provide clues for the development of new therapeutic drugs.

高原缺氧可导致严重的记忆损伤，但机制不明。缺氧引起小胶质细胞活化，调控神经元突触可塑性，是导致记忆损伤的重要环节，但缺氧导致小胶质细胞活化的机制尚不清楚。嘌呤受体P2X7主要表达于小胶质细胞，在记忆的调控中具有重要作用。缺氧导致P2X7受体激活参与多种病理过程，我们前期研究发现P2X7介导小胶质细胞活化，但P2X7受体是否是缺氧引起小胶质细胞活化的关键因素，通过何种信号机制参与记忆损伤过程尚待探讨。本项目拟采用急性缺氧小鼠，结合在体及离体实验，综合应用形态学、分子生物学及电生理学等方法，①观察缺氧小鼠海马P2X7受体表达及激活与小胶质细胞活化的关系，探讨P2X7受体在缺氧所致记忆损伤中的作用；②研究缺氧激活P2X7受体对小胶质细胞甘氨酸释放的影响及其胞内机制；③阐明P2X7受体介导小胶质细胞激活释放的甘氨酸是海马神经元突触可塑性改变的主要机制。该研究对阐明缺氧导致记忆损伤机制意义重大。

高原缺氧可导致严重的记忆损伤.研究表明，缺氧引起小胶质细胞活化，调控神经元突触可塑性，是导致记忆损伤的重要环节。exATP-P7X7受体途径是介导小胶质细胞活化的重要机制。缺氧条件下，P2X7受体激活引起小胶质细胞活化，从而调控突触可塑性参与记忆损伤过程。本项目采用急性缺氧小鼠，结合在体及离体实验，综合应用形态学、分子生物学及电生理学等方法，观察了急性低压缺氧小鼠海马小胶质细胞活化与P2X7受体表达变化的规律和关系，阐明了P2X7受体在缺氧所致记忆损伤中的作用；以小胶质细胞释放甘氨酸为切入点，探讨了P2X7受体介导小胶质细胞活化的调节机制，及其在海马神经元兴奋性突触后电流的作用。该研究对阐明缺氧导致记忆损伤机制意义重大。研究发现，①小鼠海马CA1-CA3区的P2X7受体主要表达于小胶质细胞，其表达量在缺氧2d后显著增加。②缺氧引起小鼠海马组织小胶质细胞活化标记物CD11b增加，抑制P2X7受体激活，可以抑制小胶质细胞活化，并且改善缺氧诱导小鼠的空间记忆损伤，但对缺氧导致的小鼠自发活动减少没有影响。③离体培养的BV-2小胶质细胞的表达有P2X7受体，缺氧促进BV-2小胶质细胞CD11b表达，P2X7受体拮抗剂BBG可以抑制该效应。③P2X7受体激活可以促进小胶质细胞内Ca2+浓度增加，此效应可能与细胞外Ca2+大量内流有关。④缺氧引起小胶质细胞gly释放增加，这一过程受到P2X7受体的调控。⑤缺氧导致小鼠海马 CA1 区锥体细胞的自发性兴奋性突触后电（sEPSCs）发放频率显著增加，该效应可被BBG所阻断，表明P2X7受体参与缺氧对小鼠海马神经元兴奋性的调控，从而影响缺氧所致小鼠记忆功能损伤。