突触外NR2B亚型NMDA受体在艾滋性认知功能障碍发病机制中作用的研究

HIV-1-associated neurocognitive disorders(HAND) is an important AIDS complication. Recent studies have shown that HIV-1 virus enters the brain soon after infection, but HAND clinical appearance has no positive correlation with the absolute level of the HIV-1 in brain. The key for mechanism of HAND is that HIV-1-infected, immune activated mononuclear phagocytes secrete a variety of neurotoxins leading to neuronal dysfunction and death. Our previous studies found that: monocyte chemoattractant protein-1 (MCP-1) is one of the important pathogenic factors among these secretory substances. MCP-1 induce neuronal damage and change synaptic transmission in rat hippocampal Slices. And NR2B subtype of NMDA receptor plays a key role in this process. Recent observations have shown that the location of NMDAR makes the key difference; survival promoting signals derive from synaptic NMDARs, whereas a cell-death signal comes from extrasynaptic NMDAR, which contain mostly NR2BRs. So the extrasynaptic NR2BR could be a potential target for MCP-1 induced neuronal damage. To uncover the mechanisms for HAND pathogenesis and to identify potential therapeutic targets for HAND, we propose to investigate the role that extrasynaptic NR2BR might play in HIV associated neuropathology and its link to neuronal injury and cognitive decline. Based on our previous observations we intend to further characterize the effects of MCP-1 on NR2AR/NR2BR in Xenopus oocytes, AIDS encephalitis in mice, rat hippocampal brain slices, and cultured hippocampal neurons. Patch clamp, gene transcription, protein expression, [Ca2 +]i dynamic scanning, RealTime-PCR, and other technology may be used to further study the role that extrasynaptic NR2BR might play in MCP-1 induced HAND. By completion of the proposed studies, we will not only provide new insights into the mechanisms of HIV-1 neuropathogenesis, but also furnish new target for therapies in the prevention and treatment of HAND.

艾滋性认知功能障碍(HAND)是重要艾滋病并发症。近年研究发现HIV-1病毒感染后很快进入大脑,但HAND发病因素与脑部病毒绝对水平无正相关, HIV-1感染的单核细胞产生的分泌物才是诱发HAND的致病因子。我们的前期研究发现:单核细胞趋化蛋白-1(MCP-1)是其中的重要致病因子,MCP-1损伤大鼠海马CA1区神经元结构并改变突触传递功能,而包括NR2B亚型在内的NMDA受体在此过程中起关键作用。因突触不同部位NMDAR在生理、病理上功能截然不同，我们下一步拟以表达NR2AR/NR2BR的爪蟾卵母细胞、艾滋病脑炎小鼠、大鼠海马脑片、培养海马细胞为研究对象,运用膜片钳、基因转录及蛋白表达、[Ca2+]i动态扫描、RT-PCR等技术,进一步研究突触外分布NR2B亚型NMDAR的过度激活在MCP-1诱发HAND过程中引起中枢神经系统损伤和认知功能障碍的作用及机制,为HAND的防治提供新的思路。

艾滋性认知功能障碍(HAND)是重要艾滋病并发症。我们的前期研究发现:单核细胞趋化蛋白-1(MCP-1)是其中的 重要致病因子。本项目研究证实，MCP-1损伤大鼠海马CA1区神经元结构并改变突触传递功能,包括NR2B亚型在内的NMDA受体在此过程中起关键作用。我们成功建立了爪蟾卵母细胞对NR2A受体及NR2B受体的表达体系，数据显示MCP-1能显著增强爪蟾卵母细胞表达体系上NR2AR和NR2BR介导的电流，MCP-1对大鼠海马脑片CA1区EPSCNR2AR、EPSCNR2BR电流也有明显的易化作用，说明无论在哺乳动物体系或非哺乳动物的细胞体系中，MCP-1都能显著增强NR2AR、NR2BR的功能。MCP-1对NR2AR的作用主要与神经系统功能的生理性调节有关，MCP-1对NR2BR的作用主要与神经损伤有关。MCP-1明显增加海马CA1区兴奋性突触活动，这种增强作用与AMPA受体、 NMDA受体尤其是NMDA亚型受体NR2BR的介导有关，MCP-1在海马脑片CA1区影响突出传递的作用部位在突触前膜。我们的实验证明MCP-1对海马脑片神经元的损伤作用可以通过AMPA受体拮抗剂、尤其是NMDA受体和CCR2受体拮抗剂减弱，提示这些拮抗剂将提供HAND等HIV-1相关脑疾病的有价值的潜在治疗方法，因此NMDA受体和CCR2受体拮抗剂作为神经保护药物很可能有益于改善HAND患者的认知功能障碍。本课题组首次制作MCP-1双侧海马注射的大鼠HAND模型并取得成功，一方面，可供研究MCP-1在整体动物水平上对大鼠认知功能及学习记忆功能的影响，另一方面，为后续研究药物靶点和治疗效果提供前期研究基础和成功的整体动物模型。MCP-1能显著损伤大鼠的学习记忆功能，而ifenprodil能显著缩短大鼠的逃避潜伏期，表明阻断NR2B受体能显著提升大鼠的学习记忆功能。