新型突触后致密蛋白95（PSD95）结合肽CN2097抗脑缺血再灌注损伤的实验研究

Cerebral ischemia-reperfusion injury causes significant glutamate level increase in the synaptic cleft, which induces NR2B (NMDAR subunit)-PSD95 (postsynaptic density-95)-neuronal nitric oxide synthase (nNOS) coupling to mediate neuronal excitotoxicity. Our previous study demonstrates that PSD95 is also a TrkB-associated scaffold to activate downstream signals including calcium/calmodulin-dependent protein kinase II (CaMKII) and Akt (Cao et al., 2013, PLoS Biology). We have characterized a peptide mimic, namely CN2097, to target the PDZ domains of PSD95. Our preliminary results demonstrated that CN2097 specifically bound to PDZ domains of PSD95, and disrupted NMDA-induced NR2B-PSD95-nNOS association. Meanwhile, it promoted TrkB (the BDNF receptor)-PSD95-Gαi association and significantly enhanced BDNF-induced CaMKII and Akt activation. Furthermore, it facilitated long-term potentiation (LTP) induction in isolated hippocampal brain slices, and increased the number of synapses. Importantly, very preliminary results showed that tail vein administration of CN2097 improved neuromotor functions as well as learning and memory of ischemia-reperfusion injured mice. In the current study, we propose to exam CN2097’s effect on KA/NMDA-induced neuronal death and monitor the associated molecular changes. We will also exam the role of CN2097 during functional recovery of experimentally induced ischemia reperfusion stroke mice model. Meanwhile, we are set to elucidate the underlying mechanism of CN2097-mediated neuroprotective effects by focusing on PSD95 and related molecule. The results of this study will provide experimental basis for develop CN2097 as a peptide-based lead compound and a probable novel therapeutic against ischemic stroke.

脑缺血再灌注(IR)时突触间隙谷氨酸浓度升高，诱导突触后膜NR2B-PSD95-nNOS耦联，介导神经元兴奋性损伤。预实验结果显示我们研发的新型PSD95结合肽CN2097：1)阻断NMDA诱导的NR2B-PSD95-nNOS耦联，拮抗视网膜神经兴奋性损伤；2)增强PSD95-TrkB-Gαi信号传导及下游Akt和CaMKII活化；3)易化海马区LTP诱导，增加突触数目和强度；4)改善IR后小鼠的神经功能学评分及学习记忆功能。本项目将首先体外系统观察CN2097抗神经元兴奋性损伤的作用；全面评价尾静脉注射CN2097对脑IR后小鼠神经功能及认知的改善作用；阐明CN2097诱导上述作用的分子机制，解析调节PSD95在其中的作用。旨在明确CN2097对IR诱导神经损伤及认知功能障碍的干预作用及分子信号机制，为开发CN2097为缺血性脑卒中的先导肽类化合物提供实验依据。

脑缺血再灌注时突触间隙谷氨酸浓度升高，诱导突触后膜NR2B-PSD95-nNOS耦联，介导神经元兴奋性损伤。我们前期研究证实PSD95还是BDNF-TrkB通路的关键信号蛋白。本课题结果显示我们研发的新型PSD95结合肽CN2097阻断NMDA诱导的NR2B-PSD95-nNOS耦联，拮抗神经兴奋性损伤；CN2097还增强PSD95-TrkB-Gαi信号传导及下游Akt和CaMKII的活化，易化海马区LTP诱导，增加突触数目和强度；尾静脉注射CN2097对脑缺血再灌注后小鼠神经功能评分及认知的改善作用；我们研究还系统阐明了PSD95-Gαi轴在CN2097诱导的神经保护及改善认知中的分子机制。从而明确CN2097对脑缺血再灌注损伤诱导神经损伤及认知功能障碍的干预作用及分子机制，为开发CN2097为缺血性脑卒中先导靶向药物提供实验依据。

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