NLRP3 Exacerbate NETosis-Associated Neuroinflammation in an LPS-Induced Inflamed Brain

Abstract

Neutrophil extracellular traps (NETs) exert a novel function of trapping pathogens. Released NETs can accumulate in inflamed tissues, be recognized by other immune cells for clearance, and lead to tissue toxicity. Therefore, the deleterious effect of NET is an etiological factor, causing several diseases directly or indirectly. NLR family pyrin domain containing 3 (NLRP3) in neutrophils is pivotal in signaling the innate immune response and is associated with several NET-related diseases. Despite these observations, the role of NLRP3 in NET formation in neuroinflammation remains elusive. Therefore, we aimed to explore NET formation promoted by NLRP3 in an LPS-induced inflamed brain. Wild-type and NLRP3 knockout mice were used to investigate the role of NLRP3 in NET formation. Brain inflammation was systemically induced by administering LPS. In such an environment, the NET formation was evaluated based on the expression of its characteristic indicators. DNA leakage and NET formation were analyzed in both mice through Western blot, flow cytometry, and in vitro live cell imaging as well as two-photon imaging. Our data revealed that NLRP3 promotes DNA leakage and facilitates NET formation accompanied by neutrophil death. Moreover, NLRP3 is not involved in neutrophil infiltration but is predisposed to boost NET formation, which is accompanied by neutrophil death in the LPS-induced inflamed brain. Furthermore, either NLRP3 deficiency or neutrophil depletion diminished pro-inflammatory cytokine, IL-1β, and alleviated blood-brain barrier damage. Overall, the results suggest that NLRP3 exacerbates NETosis in vitro and in the inflamed brain, aggravating neuroinflammation. These findings provide a clue that NLRP3 would be a potential therapeutic target to alleviate neuroinflammation.