Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
Department of Neurosurgery, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Third Hospital of Shanxi Medical University, Taiyuan, 030032, China.
J Neuroinflammation. 2022 Dec 14;19(1):301. doi: 10.1186/s12974-022-02665-x.
Microglia-induced excessive neuroinflammation plays a crucial role in the pathophysiology of multiple neurological diseases, such as ischaemic stroke. Controlling inflammatory responses is considered a promising therapeutic approach. Sirtuin 5 (SIRT5) mediates lysine desuccinylation, which is involved in various critical biological processes, but its role in ischaemic stroke remains poorly understood. This research systematically explored the function and potential mechanism of SIRT5 in microglia-induced neuroinflammation in ischaemic stroke.
Mice subjected to middle cerebral artery occlusion were established as the animal model, and primary cultured microglia treated with oxygen-glucose deprivation and reperfusion were established as the cell model of ischaemic stroke. SIRT5 short hairpin RNA, adenovirus and adeno-associated virus techniques were employed to modulate SIRT5 expression in microglia both in vitro and in vivo. Coimmunoprecipitation, western blot and quantitative real-time PCR assays were performed to reveal the molecular mechanism.
In the current study, we showed that SIRT5 expression in microglia was increased in the early phase of ischaemic stroke. SIRT5 interacts with and desuccinylates Annexin A1 (ANXA1) at K166, which in turn decreases its SUMOylation level. Notably, the desuccinylation of ANXA1 blocks its membrane recruitment and extracellular secretion, resulting in the hyperactivation of microglia and excessive expression of proinflammatory cytokines and chemokines, ultimately leading to neuronal cell damage after ischaemic stroke. Further investigation showed that microglia-specific forced overexpression of SIRT5 worsened ischaemic brain injury, whereas downregulation of SIRT5 exhibited neuroprotective and cognitive-preserving effects against ischaemic brain injury, as proven by the decreased infarct area, reduced neurological deficit scores, and improved cognitive function.
Collectively, these data identify SIRT5 as a novel regulator of microglia-induced neuroinflammation and neuronal damage after cerebral ischaemia. Interventions targeting SIRT5 expression may represent a potential therapeutic target for ischaemic stroke.
小胶质细胞诱导的过度神经炎症在多种神经疾病的病理生理学中起着关键作用，如缺血性中风。控制炎症反应被认为是一种有前途的治疗方法。Sirtuin 5（SIRT5）介导赖氨酸脱琥珀酰化，这涉及到各种关键的生物学过程，但它在缺血性中风中的作用仍知之甚少。本研究系统地探讨了 SIRT5 在缺血性中风中小胶质细胞诱导的神经炎症中的功能和潜在机制。
建立大脑中动脉闭塞的小鼠作为动物模型，建立氧葡萄糖剥夺和再灌注的原代培养小胶质细胞作为缺血性中风的细胞模型。采用 SIRT5 短发夹 RNA、腺病毒和腺相关病毒技术，在体外和体内调节小胶质细胞中的 SIRT5 表达。采用免疫共沉淀、western blot 和实时定量 PCR 检测揭示分子机制。
在本研究中，我们表明 SIRT5 在缺血性中风的早期阶段在小胶质细胞中表达增加。SIRT5 与膜联蛋白 A1（ANXA1）相互作用并在 K166 处脱琥珀酰化，从而降低其 SUMO 化水平。值得注意的是，ANXA1 的脱琥珀酰化阻止其膜募集和细胞外分泌，导致小胶质细胞过度激活和促炎细胞因子和趋化因子的过度表达，最终导致缺血性中风后的神经元细胞损伤。进一步的研究表明，小胶质细胞特异性过表达 SIRT5 加重缺血性脑损伤，而 SIRT5 的下调对缺血性脑损伤具有神经保护和认知保存作用，如梗死面积减少、神经功能缺损评分降低和认知功能改善。
总之，这些数据表明 SIRT5 是小胶质细胞诱导的神经炎症和缺血性脑损伤后神经元损伤的新型调节因子。靶向 SIRT5 表达的干预可能代表缺血性中风的潜在治疗靶点。
