Department of Neurology, Xishan People's Hospital of Wuxi City, Wuxi, Jiangsu 214000, China.
School of Nursing, Taihu University of Wuxi, Wuxi, Jiangsu 214000, China.
Biochem Pharmacol. 2021 Apr;186:114464. doi: 10.1016/j.bcp.2021.114464. Epub 2021 Feb 10.
Increasing evidence suggests that microglia experience two distinct phenotypes after acute ischemic stroke (AIS): a deleterious M1 phenotype and a neuroprotective M2 phenotype. Promoting the phenotype shift of M1 microglia to M2 microglia is thought to improve functional recovery after AIS. Minocycline, a tetracycline antibiotic, can improve functional recovery after cerebral ischemia in pre-clinical and clinical research. However, the role and mechanisms of minocycline in microglia polarization is unclear.
Using the transient middle cerebral artery occlusion - reperfusion (MCAO/R) model, we treated mice with saline or different minocycline concentration (10, 25, or 50 mg/kg, i.p., daily for 2 wk) at 24 h after reperfusion. Neurobehavioral evaluation, rotarod test, and corner turning test were carried out on day 14 after reperfusion. Then, neuronal injury, reactive gliosis, and microglia polarization were performed on day 7 following MCAO/R. Finally, we treated primary microglial cultures with LPS (Lipopolysaccharide; 100 ng/mL) plus IFN-γ (20 ng/mL) 24 h to induce M1 phenotype and observed the effects of minocycline on the M1/M2-related mRNAs and the STAT1/STAT6 pathway.
We found that a 14-day treatment with minocycline increased the survival rate and promoted functional outcomes evaluated with neurobehavioral evaluation, rotarod test, and corner turning test. Meanwhile, minocycline reduced the brain infarct volume, alleviated neuronal injury, and suppressed reactive gliosis on day 7 following MCAO/R. Moreover, we observed an additive effect of minocycline on microglia polarization to the M1 and M2 phenotypes in vivo and in vitro. In the primary microglia, we further found that minocycline prevented neurons from OGD/R-induced cell death in neuron-microglia co-cultures via regulating M1/M2 microglia polarization through the STAT1/STAT6 pathway.
Minocycline promoted microglial M2 polarization and inhibited M1 polarization, leading to neuronal survival and neurological functional recovery. The findings deepen our understanding of the mechanisms underlying minocycline-mediated neuroprotection in AIS.
越来越多的证据表明，小胶质细胞在急性缺血性脑卒中（AIS）后经历两种不同的表型：有害的 M1 表型和神经保护的 M2 表型。促进 M1 小胶质细胞向 M2 小胶质细胞的表型转变被认为可以改善 AIS 后的功能恢复。米诺环素是一种四环素类抗生素，在临床前和临床研究中都能改善脑缺血后的功能恢复。然而，米诺环素在小胶质细胞极化中的作用和机制尚不清楚。
我们使用短暂性大脑中动脉闭塞-再灌注（MCAO/R）模型，在再灌注后 24 小时用生理盐水或不同浓度的米诺环素（10、25 或 50mg/kg，腹腔注射，每天 1 次，持续 2 周）处理小鼠。在再灌注后 14 天进行神经行为学评估、转棒试验和转角试验。然后，在 MCAO/R 后第 7 天进行神经元损伤、反应性神经胶质增生和小胶质细胞极化。最后，我们用 LPS（脂多糖；100ng/ml）+IFN-γ（20ng/ml）处理原代小胶质细胞 24 小时诱导 M1 表型，并观察米诺环素对 M1/M2 相关 mRNAs 和 STAT1/STAT6 通路的影响。
我们发现，米诺环素治疗 14 天可提高生存率，并通过神经行为学评估、转棒试验和转角试验评估改善功能结局。同时，米诺环素降低了脑梗死体积，减轻了神经元损伤，并在 MCAO/R 后第 7 天抑制了反应性神经胶质增生。此外，我们观察到米诺环素在体内和体外对小胶质细胞向 M1 和 M2 表型的极化具有相加作用。在原代小胶质细胞中，我们进一步发现米诺环素通过调节 STAT1/STAT6 通路，在神经元-小胶质细胞共培养物中防止 OGD/R 诱导的神经元死亡，从而促进小胶质细胞 M2 极化，抑制 M1 极化，导致神经元存活和神经功能恢复。这些发现加深了我们对米诺环素介导的 AIS 神经保护机制的理解。
