Yunnan Lu1, Mingming Zhou2, Yun Li3, Yan Li3, Ye Hua4, Yi Fan5. 1. Department of Neurology, Xishan People's Hospital of Wuxi City, Wuxi, Jiangsu 214000, China. 2. School of Nursing, Taihu University of Wuxi, Wuxi, Jiangsu 214000, China. 3. Neuroprotective Drug Discovery Center of Nanjing Medical University, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu 211166, China. 4. Department of Neurology, Affiliated Wuxi Clinical College of Nantong University, Wuxi, Jiangsu 214000, China; Department of Neurology, The Affiliated Wuxi No. 2 People's Hospital of Nanjing Medical University, 68 Zhongshan Road, Wuxi, Jiangsu 214000, China. Electronic address: 77819869@qq.com. 5. Neuroprotective Drug Discovery Center of Nanjing Medical University, Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu 211166, China. Electronic address: yfan@njmu.edu.cn.
Abstract
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: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.
Authors: Ivó H Hernández; Mario Villa-González; Gerardo Martín; Manuel Soto; María José Pérez-Álvarez Journal: Cells Date: 2021-06-30 Impact factor: 6.600