Neuroinflammation contributes to the pathogenesis of early brain injury induced by subarachnoid hemorrhage (SAH). Previous reports have demonstrated that triggering receptor expressed on myeloid cells 1 (TREM-1) regulates inflammatory response caused by ischemic stroke or myocardial infarction. However, whether TREM-1 could modulate neuroinflammation after SAH remains largely unknown. Here, using a mouse model of SAH, we found that the expression of TREM-1 was mainly located in microglia cells and increased to peak at 24 h following SAH. Then, TREM-1 antagonist or mimic was intranasally administrated to investigate its effect on SAH. TREM-1 inhibition with LP17 improved neurological deficits, mitigated brain water content, and preserved brain-blood barrier integrity 24 h after SAH, whereas recombinant TREM-1, a mimic of TREM-1, deteriorated these outcomes. In addition, LP17 administration restored long-term sensorimotor coordination and cognitive deficits. Pharmacological blockade of TREM-1 reduced TUNEL-positive and FJC-positive neurons, and CD68-stained microglia in ipsilateral cerebral cortex. Neutrophil invasion was inhibited as protein level of myeloperoxidase (MPO), and MPO-positive cells were both decreased. Moreover, we found that LP17 treatment ameliorated microglial pyroptosis by diminishing levels of N-terminal fragment of GSDMD (GSDMD-N) and IL-1β production. Mechanistically, both in vivo and in vitro, we depicted that TREM-1 can trigger microglial pyroptosis via activating NLRP3 inflammasome. In conclusion, our results revealed the critical role of TREM-1 in neuroinflammation following SAH, suggesting that TREM-1 inhibition might be a potential therapeutic approach for SAH.
Keywords: Microglia; NLRP3 inflammasome; Pyroptosis; Subarachnoid hemorrhage; TREM-1.