NDRG2在创伤性脑缺血诱导星形胶质细胞程序性坏死中的作用和机制研究

Craniocerebral trauma is the most serious kind of trauma. The ischemia in brain tissue is the main reason for the secondary damage via craniocerebral trauma. Astrocytes play a key role in the restoration of brain tissue damage. Thus, it is urgent to investigate the underlying mechanism of astrocyte activation and the inhibition of cell death. Our group has been engaging in the study of brain damage and protection for a couple of years. Previous study showed that cerebral ischemia aggravated the brain damage via the induction of astrocyte necroptosis, Recently, we found that NDRG2, which is a gene highly expressed in astrocytes, can inhibit astrocyte necroptosis through the repression of RIP1 and RIP3 complex activation, which blocked process of astrocyte necroptosis in advance. It suggests that NDRG2 might be play key roles in the suppression of ischemia induced astrocyte necroptosis and the promotion of brain recovery. In the current project, we are planning to start with establishment of ischemic model in NDRG2 knockout mice, and determine the association and function of NDRG2, RIP1 and RIP3 in the process of astrocyte necroptosis. Second, we will elucidate the role the NDRG2 in the cell biological behavior alterations during necroptosis. Finally, we are going to explore the underlying mechanism of NDRG2 in regulation of RIP1/RIP3 necrosome complex in astrocytes. This project is critical for the significance of both the prevention and treatment of craniocerebral trauma and extending the value of NDRG2 in clinical application.

颅脑创伤是外伤中最严重的一类，而脑组织缺血缺氧是创伤后脑继发性损害的重要原因。星形胶质细胞在脑组织损伤修复中地位重要，如何促进其活化、抑制其死亡是目前研究的热点和难点。课题组多年从事脑损伤与保护的研究，前期研究显示，脑缺血通过诱导星形胶质细胞发生程序性坏死，加重脑组织损伤。我们近期发现，星形胶质细胞中高表达的分子NDRG2，可以通过抑制坏死复合体中RIP1和RIP3的活化，阻断程序性坏死进程，提示了NDRG2在抑制缺血诱发的星形胶质细胞坏死和促进脑修复过程具有重要作用。本项目拟利用NDRG2基因敲除鼠建立脑缺血模型，明确NDRG2、RIP1/RIP3等分子与星形胶质细胞坏死的关系和作用；从细胞水平分析星形胶质细胞坏死的方式和原因；从分子水平阐明NDRG2调控RIP1/RIP3坏死复合体的具体机制和功能结构域。本研究对创伤性脑缺血疾病的早期治疗、扩展NDRG2临床应用价值均具有重要意义。

本项目研究发现NDRG2可以通过抑制RIPK1来抑制细胞程序性坏死从而减少缺血性损伤引起的星形胶质细胞死亡。通过建立动物脑缺血损伤(MCAO)模型和在体外用OGD诱导模拟缺血损伤的细胞，我们证实了在缺血损伤情况下星形胶质细胞通过RIPK1发生细胞程序性坏死，表现为GFAP蛋白和mRNA水平下降，RIPK1蛋白和mRNA水平升高，细胞的存活率下降，乳酸脱氢酶LDH的泄漏率升高；NDRG2基因的敲除可以显著加重细胞程序性坏死，表现为NDRG2敲除的MCAO小鼠和OGD处理的星形胶质细胞相比NDRG2未敲除MCAO小鼠和OGD处理的星形胶质细胞GFAP蛋白和mRNA水平下降，RIPK1蛋白和mRNA水平升高，细胞的存活率下降，乳酸脱氢酶LDH的泄漏率升高，而过表达NDRG2可以减缓这一过程，同时细胞程序性坏死抑制剂Nec-1可以恢复NDRG2基因的敲除引起的细胞程序性坏死被加重的现象，Nec-1通过抑制RIPK1来抑制细胞程序性坏死。星形胶质细胞是在神经系统中分布最广的神经胶质细胞，不仅为神经元提供代谢和营养支持，而且在保护神经元存活、调节突触功能以及神经再生和神经修复中起至关重要的作用。因此，本项目为通过活化星形胶质细胞，抑制细胞凋亡、坏死的发生来治疗缺血诱发的脑组织损伤提供了重要依据。