miR-30e对电压门控钠通道Nav1.3的调节及其在颅脑创伤中的神经保护作用

The secondary brain injury following traumatic brain injury (TBI) results in tremendous neuronal death and apoptosis and usually causes miserable outcomes. It was found that the voltage-gated sodium channels (VGSCs) are activated in the earliest phase after brain injury and trigger the influx of extracellular Na+. The excitotoxic effect induced by increased [Na+]i is one of the most important mechanisms of the secondary brain injury. Through the research granted by National Natural Science Foundation We previously reported that the expression of Nav1.3, one of the VGSCs which mainly located in central nervous system, upregulated significantly at the early stage post-TBI, and the alterations in expression of Nav1.3 were correlated with severity of TBI. Specifically downregulation of Nav1.3 improved outcomes after severe TBI. The results of further study suggested that miR-30e, which was reported significantly downregulated after TBI, targeted regions in the 3’ UTR of Nav1.3 and Nav1.3 modulation is possible with the manipulation of miR-30e. We assume that a decreased miR-30e expression following TBI may be associated with the upregulation of Nav1.3 and consequently takes part in the excitotoxic cascade post-TBI. It is reasonable to predict the neuroprotective effects via extrinsic upregulation of miR-30e. We designed this project to validate this hypothesis through a chain of in vitro and in vivo assays and explore the mechanism underlying the neuroprotective effects of miR-30 by deeply research. It will be much helpful for profoundly understanding the mechanism behind the secondary brain injury induced by abnormally activated VGSCs and to discover the means to conquer it. To accomplish this project will be beneficial for investigating a specific neuroprotective way to treat TBI.

颅脑创伤（TBI）后的继发性脑损伤是造成TBI患者预后不良的重要原因。钠通道激活发生于TBI后早期，导致钠离子内流，诱发细胞毒性水肿，是诱导兴奋性毒性作用的最重要分子之一。我们通过前一项国自然项目的研究发现TBI 后早期钠通道α亚单位Nav1.3 表达上调，并与TBI 伤情呈正相关，下调其表达可显著改善TBI 预后。后续的研究证明脑损伤后miR-30e表达显著降低，且miR-30e能与Nav1.3基因的3’UTR结合，并显著降低Nav1.3的表达水平。我们推测TBI后miR-30e表达下调与Nav1.3异常高表达有关，上调miR-30e表达可通过降低Nav1.3蛋白表达水平削弱甚至中断TBI后的兴奋毒性作用。本项目拟验证该假说，并进一步探索上调miR-30e表达在TBI后的神经保护作用。研究将有助于深入了解钠通道异常激活诱导TBI继发性脑损伤的机制及其解决之道，探索TBI的脑保护方法。

Nav1.3在颅脑创伤后的高表达是导致患者二次损伤的主要原因，课题组发现miR-30e的下调可能是Nav1.3高表达的的主要原因，因此，本课题旨在证明miR-30e通过下调Nav1.3的神经保护作用机制。课题通过体外模型和体内模型分别证明miR-30e创伤后表达下调，并与Nav1.3的表达呈反比；其次，课题通过基因过表达技术证明了miR-30e的神经保护作用；最后，课题通过补救实验证明miR-30e/Nav1.3通路轴在miR-30e神经保护中的重要角色。课题中miR-30e/Nav1.3通路轴机制的阐明提示miR-30e是抑制Nav1.3诱导的颅脑创伤后损伤的重要潜在手段。