小胶质细胞源性IL-10在脑出血后白质损伤修复中的作用及其Gas6-Axl机制

Intracerebral hemorrhage (ICH) is the most lethal subtype of stroke but currently lacks effective treatment. White matter injury (WMI) post-ICH associates with high incidence of motor, mood and cognition dysfunctions. There are studies reported that the expression of Interlukin-10 (IL-10) was evaluated in the peripheral blood in ICH patient, but the function of IL-10 in ICH, especially in WMI post-ICH is still unclear. In our preliminary results, we show that the mRNA expression level of IL-10 was increased and peaked at 5-7 days post-ICH in mice, and IL-10 co-localized with Iba-1. Chemokine/cytokine array showed that IL-10 deficiency (IL-10-/-) mouse had lower expression level of Gas6 compared to that in wildtype (WT) mouse after ICH, and IL-10 induced Gas6 expression in WT mouse primary microglia. In addition, oligodendrocyte progenitor cells (OPC) in IL-10-/- mouse brain had lower expression level of Axl mRNA, and Axl is one of the highest affinity receptors for Gas6. Furthermore, deficiency of IL-10 decreased mouse survival rate and also diminished the protein expression levels of neurofiliment and myeline binding protein post-ICH in mice. Meanwhile, IL-10-/- mouse had increased demyelinated axons in ipsilateral striatum around the glial scar at 4 weeks after ICH by transmission electron microscopy (TEM). These results indicate that IL-10 may involve in the pathological progress of WMI post-ICH, and the underlying mechanism could be regulating OPC proliferation by manipulating expression/activity of Gas6-Axl axis. Thus, in this proposal, we will use collagenase- and autologous blood-injection ICH mouse models, and mouse primary cell cultures to investigate: (1) the expression levels and cell sources of IL-10, Gas6, and Axl in mouse ipsilateral hemisphere after ICH; (2) whether IL-10 regulates the expression level of Gas6 and Axl, and the activity of Gas6-Axl signaling pathway in OPC; (3) whether IL-10 modifies proliferation, differentiation, and apoptosis of OPC, and subsequently regulates axonal remyelination at ipsilateral striatum and corpus callosum; (4) whether IL-10 contributes to the pathological progress of motor, mood, and cognition dysfunctions at late stage of ICH. Especially, we will use different techniques including experiments using molecular biology, MRI imaging, TEM scanning, electrophysiology, and various behavior tests. The insights gained from this study will advance our knowledge of the regulation of post-ICH WMI, and will be essential for future preclinical studies.

脑出血后白质损伤与情绪和认知异常密切相关。白介素10(IL-10)在脑出血患者外周血中表达升高，但与白质损伤是否相关尚不清楚。本课题前期工作显示，小鼠脑出血后患侧脑区IL-10基因表达增高，且主要来源于小胶质细胞；与少突胶质前体细胞(OPC)增殖相关的Gas6和Axl表达水平，同IL-10含量呈正相关；IL-10基因敲除小鼠脑出血后生存率下降，存活轴突和髓鞘标志物表达降低，髓鞘再生延缓。本项目拟利用小鼠脑出血模型和原代细胞培养，借助多种技术手段，明确脑出血后IL-10、Gas6和Axl的表达变化和细胞源性，及IL-10对Gas6-Axl轴的调控；继而探究IL-10在OPC功能调节和白质损伤修复中的作用；最后，确定IL-10对脑出血小鼠运动功能、情绪和认知等长期预后的影响。研究成果将丰富人们对脑出血后白质损伤的病理机制的理解，并为脑出血的治疗提供新的靶点和方向。

脑出血（Intracerebral hemorrhage, ICH）是第二常见的中风类型，致死率和致残率较高。白介素10 (Interleukin-10, IL-10)促进血肿清除，但其与ICH后白质损伤是否相关尚不清楚。实验室前期成果表明，以脂质代谢紊乱和脂质过氧化积累为特征的铁依赖性细胞死亡—铁死亡，可在ICH后发生于神经元中。而少突胶质前体细胞（Oligodendrocyte progenitor cells, OPCs）铁含量最高，抗氧化剂（如谷胱甘肽过氧化物酶）的数量较少，谷胱甘肽还原酶活性也只有一半，少突胶质细胞谱系是最容易受到氧化应激伤害的细胞类别。OPCs是否会发生铁死亡，已经调节OPCs铁死亡的潜在分子机制仍不清楚。在本研究中，我们研究了IL-10在ICH过程中的功能。发现在脑出血模型的急性期，同侧纹状体处IL-10的表达显著升高。IL-10-/-小鼠的OPCs细胞死亡多，少突胶质细胞生成减弱，成熟少突胶质细胞数量减少，白质损伤（White matter injury, WMI）和相关行为缺陷加重。体外实验中，发现IL-10通过激活JAK-STAT3轴，进而抑制OPC细胞中脂质活性氧产生，防止细胞铁死亡。我们的研究首次证明IL-10可以对脑出血后WMI和神经功能缺损产生有益影响。该研究首次表明IL-10减轻OPCs铁死亡，并在ICH后的WMI中发挥保护作用。加深了对IL-10在ICH中功能的认识，表明其可通过抑制OPCs铁死亡缓解ICH疾病进程，为进一步探讨靶向IL-10和OPC铁死亡用于治疗ICH提供了理论基础。