Lipocalin-2-mediated Astrocyte Pyroptosis promotes neuroinflammatory injury via NLRP3 Inflammasome Activation in Cerebral Ischemia/Reperfusion Injury

Background: Neuroinflammation has been recognized as vital pathophysiological process during ischemic stroke. Activated astrocytes play a major role in inflammatory response. Lipocalin-2 (LCN2), secreted from activated astrocytes, promotes neuroinflammation. Pyroptosis, a pro-inflammatory programmed cell death, is emerging as a new area of research on stroke. Nevertheless, the potential role of LCN2 in astrocyte pyroptosis remains unclear. Methods: : Ischemic stroke model was established by middle cerebral artery occlusion (MCAO) in vivo . In vitro , oxygen-glucose deprivation and reoxygenation (O/R) was applied to cultured astrocytes. 24p3R (the LCN2 receptor) was inhibited by astrocyte-specific adeno-associated virus (AAV-GFAP-24p3Ri). We used MCC950 and Nigericin sodium salt (Nig) to inhibit or promote the activation of NLRP3 inflammasome pharmacologically. Histologic and biochemical analysis was performed on the death of astrocytes and neurons both in vivo and in vitro . Besides, the neurological deficit of mice was evaluated. Results: : LCN2 expression was significantly induced in astrocytes 24 hours after stroke onset in mouse MCAO models. Lcn2 knockout ( Lcn2 -/- ) mice exhibited reduced infract volume and improved neurological and cognitive functions after MCAO. LCN2 and its receptor 24p3R were colocalized in astrocytes. Mechanistically, suppression of 24p3R by AAV-GFAP-24p3Ri alleviated pyroptosis pores formation and pro-inflammatory cytokines secretion induced by LCN2, which was then reversed by NLRP3 inflammasome activation inducer Nig. Astrocyte pyroptosis was exacerbated in Lcn2 -/- mice by intracerebroventricularly administration of recombinant LCN2 (rLCN2), while the aggravation was restricted by blocking 24p3R or inhibiting NLRP3 inflammasome activation by MCC950. Conclusion: LCN2/24p3R mediates astrocyte pyroptosis via NLRP3 inflammasome activation following cerebral ischemia/reperfusion injury.