Microglia Activation and Polarization After Intracerebral Hemorrhage in Mice: the Role of Protease-Activated Receptor-1
Polarized microglia play a dual (beneficial/detrimental) role in neurological diseases. However, the status and the factors that modulate microglia polarization in intracerebral hemorrhage (ICH) remain unclear. In the present study, we investigated the role of protease-activated receptor-1 (PAR-1, a thrombin receptor) in ICH-induced microglia polarization in mice. Male wild-type (WT) and PAR-1 knockout (PAR-1 KO) mice received an infusion of 30-μL autologous blood or saline into the right basal ganglia. Mice were euthanized at different time points and the brains were used for Western blotting and immunohistochemistry. Some mice had magnetic resonance imaging. We found that ICH induced microglia activation and polarization. M1 phenotypic markers were markedly increased and reached a peak as early as 4 h, remained high at 3 days and decreased 7 days after ICH. M2 phenotypic markers were upregulated later than M1 markers reaching a peak at day 1 and declining by day 7 after ICH. PAR-1 was upregulated after ICH and expressed in the neurons and microglia. ICH induced less brain swelling and neuronal death in PAR-1 KO mice, and this was associated with less M1 polarization and reduced proinflammatory cytokine levels in the brain. In conclusion, these results suggest that polarized microglia occur dynamically after ICH and that PAR-1 plays a role in the microglia activation and polarization.
KeywordsCerebral hemorrhage Microglia Mouse Protease-activated receptor-1
This study was supported by grants NS-073595, NS-079157, NS-084049, NS-090925, NS-091545 and NS-096917 from the National Institutes of Health (NIH), 973 Program-2014CB541600, and by grants 81371336, 81400942, 81400945 from National Natural Science Foundation of China (NSFC) and grants LY13H090005 from Natural Science Foundation of Zhejiang Province (ZJNSF). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH, NSFC, and ZJNSF.
Compliance with Ethical Standards
Conflicts of Interest
Shu Wan, Yingying Cheng, Hang Jin, Dewei Guo, Ya Hua, Richard F. Keep, and Guohua Xi declare that they have no conflict of interest.
Compliance with Ethics Requirements
All institutional and national guidelines for the care and use of laboratory animals were followed.
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