Department of Neurosurgery, Affiliated Hospital of Shaanxi University of Chinese Medicine, Xianyang, 712000, China.
College of foreign languages, Shaanxi University of Chinese Medicine, Xianyang, 712046, China.
J Mol Neurosci. 2019 Feb;67(2):217-226. doi: 10.1007/s12031-018-1227-7. Epub 2018 Nov 27.
Microglia play an essential role during cerebral an ischemia/reperfusion (I/R)-related inflammatory process. Because the M2 phenotype of microglia exhibits anti-inflammation activity, it has become a promising target for anti-inflammatory therapy. Vagus nerve stimulation (VNS) reportedly has neuroprotective effects against cerebral I/R injuries via its anti-inflammatory action. The aim of this study was to investigate the ability of non-invasive VNS (nVNS) to alleviate cerebral I/R in mice by promoting microglial M2 polarization. Neurological scoring and cerebral infarct volume assessments were performed 72 h after a middle cerebral artery occlusion (MCAO)-induced stroke. M2 phenotype microglia were identified by immunohistochemistry staining using Arg-1 and Iba-1 antibodies. The protein expressions of Arg-1, IL-17A, IL-10, Bax, and Bcl-2 were detected by Western blot. Apoptotic cells were detected using TUNEL staining. According to our results, nVNS decreased infarct volume, improved neurological outcomes, reduced apoptotic neurons (TUNELNeuN cells), and promoted microglial M2 polarization as indicated by elevated Arg-1 protein expression and increased Arg-1 cells after MCAO. Moreover, nVNS attenuated the increased levels of IL-17A protein expression after MCAO. To test the possible involvement of IL-17A in nVNS-induced neuroprotection and microglial M2 polarization, 1-μg recombinant IL-17A (rIL-17A) was intranasally administered once daily for three consecutive days after reperfusion. We found that the intranasal administration of rIL-17A nullified the nVNS-induced promotion of microglial M2 polarization. Furthermore, rIL-17A administration abolished the neuroprotective effect of nVNS. In conclusion, our study identifies microglial M2 polarization as an important mechanism underlying the nVNS-mediated neuroprotection against cerebral I/R. This effect of nVNS could be attributed to the inhibition of IL-17A expression.
小胶质细胞在与脑缺血/再灌注（I/R）相关的炎症过程中发挥着重要作用。由于小胶质细胞的 M2 表型表现出抗炎活性，因此它已成为抗炎治疗的有前途的靶点。迷走神经刺激（VNS）通过其抗炎作用被报道具有对脑 I/R 损伤的神经保护作用。本研究旨在通过促进小胶质细胞 M2 极化来研究非侵入性 VNS（nVNS）减轻小鼠脑 I/R 的能力。在大脑中动脉闭塞（MCAO）诱导的中风后 72 小时进行神经功能评分和脑梗死体积评估。通过使用 Arg-1 和 Iba-1 抗体的免疫组织化学染色鉴定 M2 表型小胶质细胞。通过 Western blot 检测 Arg-1、IL-17A、IL-10、Bax 和 Bcl-2 的蛋白表达。通过 TUNEL 染色检测凋亡细胞。根据我们的结果，nVNS 减少梗死体积，改善神经功能，减少凋亡神经元（TUNELNeuN 细胞），并在 MCAO 后通过增加 Arg-1 蛋白表达和增加 Arg-1 细胞来促进小胶质细胞 M2 极化。此外，nVNS 减弱了 MCAO 后 IL-17A 蛋白表达的增加。为了测试 IL-17A 在 nVNS 诱导的神经保护和小胶质细胞 M2 极化中的可能参与，在再灌注后连续 3 天每天通过鼻腔给予 1μg 重组 IL-17A（rIL-17A）。我们发现，鼻腔给予 rIL-17A 消除了 nVNS 诱导的小胶质细胞 M2 极化的促进作用。此外，rIL-17A 给药消除了 nVNS 的神经保护作用。总之，本研究将小胶质细胞 M2 极化鉴定为 nVNS 介导的脑 I/R 神经保护的重要机制。nVNS 的这种作用可能归因于 IL-17A 表达的抑制。
