白质损伤（WMI）在蛛网膜下腔出血（SAH）后早期即发生，并长期存在。我们前期研究证实APOE亚型可影响SAH患者预后，从炎症反应等方面阐释了其机制，并发现其短肽可通过抑制小胶质细胞过度活化减轻白质损伤。小胶质细胞极化是介导白质损伤不同走向的关键靶点，其在SAH中具体作用研究甚少。新近发现APOE各亚型蛋白可通过核转录效应调控下游基因，发挥神经生物作用，这将颠覆传统认知！据此我们提出，明确APOE亚型与SAH后WMI作用及机制的关键是在阐明APOE亚型与WMI相关性的基础上，通过SAH在体模型及离体胶质细胞模型，明确APOE亚型与小胶质细胞极化直接相关。并体外激活小胶质细胞，多角度阐释APOE亚型通过核转录效应调控小胶质极化介导的炎症反应对髓鞘的影响及具体通路。本课题是申请人前期工作的延续，不仅可揭示APOE亚型在SAH后WMI中的核心机制，且对其外源性短肽的临床转化具有重要意义。

Subarachnoid hemorrhage (SAH) is a devastating subtype of stroke. White matter injury (WMI) occurs in the early stage of SAH and continues for long-time. WMI was demonstrated to correlate with neurological dysfunctions of SAH patients. Our previous works have shown the association between apolipoprotein E (APOE=gene, apoE=protein) polymorphisms and outcomes of SAH patients. Suppression of neuroinflammation with apoE-derived mimetic peptide could relieve white matter regions edema after experimental SAH. Microglia polarization is the key target of neurological disorders that related to inflammatory response. The specific role of microglia polarization-mediated inflammation in SAH , however，remains poorly understood. Notably，recent finding revealed that the direct transcriptional effects of apoE protein subtypes could result in differential neurobiological effects. Based on our previous data, we hypothesize that different subtypes of apoE protein could modulate microglial cells polarization via direct transcriptional effects, then mediate neuroinflammation and, thereby affect WMI after SAH. The following experiments are designed: 1) to investigate the role of APOE allele on WMI in wild type, APOE-/- and APOE transgenic mouse SAH model, as well as to further identify the neuroprotective effects of apoE-mimetic peptide. 2) To evaluate the influences of APOE allele and apoE-mimetic peptide on microglial polarization via murine microglia primary culture and, subsequently evaluate the influences of microglia polarization conditioned medium on oligodendrocytes myelination. 3) Using techniques including ChIP-Seq, as well as a series of bioinformatics analysis to explore the differential transcriptional effects of APOE allele and apoE-mimetic peptide on microglial polarization. The current project aims to reveal the significant detailed role and mechanisms of APOE allele in WMI after SAH. It is the continuation of the applicant's preliminary studies that related to early brain injury after SAH. Furthermore, this study offers new mechanisms and ideas for efficient brain protective therapeutics development, which will make a great significance of precision medical and translational research.