MK5 Regulates Microglial Activation and Neuroinflammation in Experimental Stroke Models.

OBJECTIVE: Microglial activation plays a crucial role in neuroinflammation following ischemic stroke. This study was conducted to investigate the role and potential mechanisms of MK5 within microglial cells in the inflammatory response following ischemic stroke in mice in vivo and in vitro. METHODS: Microglia-specific conditional MK5 knockout (MK5 cKO) mice and their control mice (MK5(f/f)) were subjected to middle cerebral artery occlusion (MCAO). BV2 cells (a mouse microglial cell line) were transfected with small interfering RNA (siRNA) to knock down MK5 levels and subsequently exposed to oxygen-glucose deprivation/reperfusion (OGD/R) to simulate ischemic conditions in vitro. Following MCAO, behavioral tests and infarct volume measurements were conducted. Levels of cytokines and microglial markers were evaluated using qPCR and Western blotting, while immunofluorescence was employed to observe microglial activation. Additionally, Western blotting was performed to assess the phosphorylation of HSP27 and NF-κB. RESULTS: Compared to the control group, the knockout of the MK5 gene in microglia significantly exacerbated neurological deficits and increased infarct volume in MCAO mice. The loss of the MK5 promoted inflammation by upregulating pro-inflammatory factors and downregulating anti-inflammatory factors, while also enhancing microglial activation in both MCAO mice and BV2 microglial cells subjected to OGD/R. Furthermore, the knockout of the MK5 gene in microglia reduced the phosphorylation levels of HSP27 and increased the phosphorylation levels of NF-κB in the aforementioned models. CONCLUSION: Microglial MK5 plays a critical role in the ischemic neuroinflammatory response by regulating the phosphorylation of HSP27 and NF-κB, positioning it as a potential target for stroke treatment.