BackgroundIntracerebral hemorrhage (ICH) induces microglial activation and the release of inflammatory cytokines, leading to inflammation in the brain. IRAK4, an essential component of the MyD88-dependent pathway, activates subsets of divergent signaling pathways in inflammation.MethodsIn the experiment, microglia were stimulated with erythrocyte lysates, and then miR-367, IRAK4, NF-ĸB activation and downstream proinflammatory mediator production were analyzed. In addition, inflammation, brain edema, and neurological functions in ICH mice were also assessed.ResultsHere, we report that ICH downregulated miR-367 expression but upregulated IRAK4 expression in primary microglia. We also demonstrate that miR-367 suppressed IRAK4 expression by directly binding its 3′-untranslated region. MiR-367 inhibited NF-ĸB activation and downstream proinflammatory mediator production. Knocking down IRAK4 in microglia significantly decreased the IRAK4 expression and inhibited the NF-ĸB activation and the downstream production of proinflammatory mediators. In addition, our results indicate that miR-367 could inhibit expression of proinflammatory cytokines, reduce brain edema, and improve neurological functions in ICH mice.ConclusionsIn conclusion, our study demonstrates that miR-367/IRAK4 pathway plays an important role in microglial activation and neuroinflammation in ICH. Our finding also suggests that miR-367 might represent a potential therapeutic target for ICH.

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Previous study demonstrates that intracerebral hemorrhage (ICH) promotes microglia activation and inflammation. However, the exact mechanism of microglia activation induced by ICH is not clear. In this experiment, microglia autophagy was examined using electron microscopy, conversion of light chain 3(LC3), and monodansylcadaverine (MDC) staining to detect autophagic vacuoles. We found that ICH induced microglia autophagy and activation. The suppression of autophagy using either pharmacologic inhibitors (3-methyladenine, bafilomycin A1) or RNA interference in essential autophagy genes (BECN1 and ATG5) decreased the microglia activation and inflammation in ICH. Moreover, autophagy inhibitors reduced brain damage in ICH. In conclusion, these data indicate that ICH contributes to microglia autophagic activation through BECN1 and ATG5 and provide the therapeutical strategy for ICH.

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