Department of Neurosurgery, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Zhongshan Road 321, Nanjing 210008, Jiangsu Province, PR China.
Department of Neurosurgery, Nanjing Drum Tower Hospital, Clinical College of Nanjing Medical University, Zhongshan Road 321, Nanjing 210008, Jiangsu Province, PR China.
Exp Neurol. 2021 Feb;336:113532. doi: 10.1016/j.expneurol.2020.113532. Epub 2020 Nov 24.
Increasing evidence suggests that microglial polarization plays an important role in the pathological processes of neuroinflammation following subarachnoid hemorrhage (SAH). Previous studies indicated that milk fat globule-epidermal growth factor-8 (MFG-E8) has potential anti-apoptotic and anti-inflammatory effects in cerebral ischemia. However, the effects of MFG-E8 on microglial polarization have not been evaluated after SAH. Therefore, the aim of this study was to explore the role of MFG-E8 in anti-inflammation, and its effects on microglial polarization following SAH. We established the SAH model via prechiasmatic cistern blood injection in mice. Double-immunofluorescence staining, western blotting and quantitative real-time polymerase chain reaction (q-PCR) were performed to investigate the expression and cellular distribution of MFG-E8. Two different dosages (1 and 5 μg) of recombinant human MFG-E8 (rhMFG-E8) were injected intracerebroventricularly (i.c.v.) at 1 h after SAH. Brain water content, neurological scores, beam-walking score, Fluoro-Jade C (FJC), and terminal deoxynucleotidyl transferase dUTP nick endlabeling staining (TUNEL) were measured at 24 h. Suppression of MFG-E8, integrin β3 and phosphorylation of STAT3 were achieved by specific siRNAs (500 pmol/5 μl) and the STAT3 inhibitor Stattic (5 μM). The potential signaling pathways and microglial polarization were measured by immunofluorescence labeling and western blotting. SAH induction increased the levels of inflammatory mediators and the proportion of M1 cells, and caused neuronal apoptosis in mice at 24 h. Treatment with rhMFG-E8 (5 μg) remarkably decreased brain edema, improved neurological functions, reduced the levels of proinflammatory factors, and promoted the microglial to shift to M2 phenotype. However, knockdown of MFG-E8 and integrin β3 via siRNA abolished the effects of MFG-E8 on anti-inflammation and M2 phenotype polarization. The STAT3 inhibitor Stattic further clarified the role of rhMFG-E8 in microglial polarization by regulating the protein levels of the integrin β3/SOCS3/STAT3 pathway. rhMFG-E8 inhibits neuronal inflammation by transformation the microglial phenotype toward M2 and its direct protective effect on neurons after SAH, which may be mediated by modulation of the integrin β3/SOCS3/STAT3 signaling pathway, highlighting rhMFG-E8 as a potential therapeutic target for the treatment of SAH patients.
越来越多的证据表明,小胶质细胞极化在蛛网膜下腔出血(SAH)后的神经炎症病理过程中起着重要作用。先前的研究表明,牛奶脂肪球表皮生长因子 8(MFG-E8)在脑缺血中具有潜在的抗凋亡和抗炎作用。然而,MFG-E8 对 SAH 后小胶质细胞极化的影响尚未得到评估。因此,本研究旨在探讨 MFG-E8 在抗炎中的作用及其对 SAH 后小胶质细胞极化的影响。我们通过前颅窝底池血注入法建立了 SAH 模型。通过双重免疫荧光染色、Western blot 和实时定量聚合酶链反应(q-PCR)来研究 MFG-E8 的表达和细胞分布。在 SAH 后 1 小时,通过脑室内注射两种不同剂量(1 和 5μg)的重组人 MFG-E8(rhMFG-E8)。在 24 小时测量脑水含量、神经评分、束走评分、氟罗-杰德 C(FJC)和末端脱氧核苷酸转移酶 dUTP 缺口末端标记染色(TUNEL)。通过特异性 siRNA(500pmol/5μl)和 STAT3 抑制剂 Stattic(5μM)抑制 MFG-E8、整合素β3 和 STAT3 的磷酸化。通过免疫荧光标记和 Western blot 测量潜在的信号通路和小胶质细胞极化。SAH 诱导可在 24 小时内增加炎症介质水平和 M1 细胞比例,并导致神经元凋亡。rhMFG-E8(5μg)治疗可显著减轻脑水肿,改善神经功能,降低促炎因子水平,并促进小胶质细胞向 M2 表型转化。然而,通过 siRNA 敲低 MFG-E8 和整合素β3 可消除 MFG-E8 对抗炎和 M2 表型极化的影响。STAT3 抑制剂 Stattic 通过调节整合素β3/SOCS3/STAT3 通路的蛋白水平,进一步阐明了 rhMFG-E8 在小胶质细胞极化中的作用。rhMFG-E8 通过将小胶质细胞表型转化为 M2 来抑制神经元炎症,并且对 SAH 后神经元有直接的保护作用,这可能是通过调节整合素β3/SOCS3/STAT3 信号通路介导的,凸显了 rhMFG-E8 作为治疗 SAH 患者的潜在治疗靶点。