NLRP3 inflammasome activation in neutrophils directs early inflammatory response in murine peritonitis
Saeko Fukui, Shoichi Fukui, Stijn Van Bruggen, Lai Shi, Casey E. Sheehy, Long Chu, Denisa D. Wagner
Abstract
Abstract NLR family pyrin domain containing 3 (NLRP3) inflammasome mediates caspase-1-dependent processing of inflammatory cytokines such as IL-1β, an essential endothelial activator, and contributes to the pathology of inflammatory diseases. To evaluate the role of NLRP3 in neutrophils in endothelial activation, which is still elusive, we used the thioglycollate-induced peritonitis model characterized by an early neutrophil influx, on Nlrp3 − / − and Nlrp3 +/+ mice. Nlrp3 −/− mice recruited fewer neutrophils than Nlrp3 +/+ into the peritoneum and showed lower IL-1β in peritoneal lavage fluid. The higher production of IL-1β in Nlrp3 +/+ was neutrophil-dependent as neutrophil depletion prevented the IL-1β production. The Nlrp3 +/+ neutrophils collected from the peritoneal fluid formed significantly more filaments (specks) than Nlrp3 − / − neutrophils of ASC (apoptosis-associated speck-like protein containing a caspase activating and recruitment domain), a readout for inflammasome activation. Intravital microscopy revealed that leukocytes rolled significantly slower in Nlrp3 +/+ venules than in Nlrp3 − / − . Nlrp3 − / − endothelial cells isolated from mesenteric vessels demonstrated a lower percentage of P-selectin-positive cells with lower intensity of surface P-selectin expression than the Nlrp3 +/+ endothelial cells evaluated by flow cytometry. We conclude that neutrophils orchestrate acute thioglycollate-induced peritonitis by producing IL-1β in an NLRP3-dependent manner. This increases endothelial P-selectin expression and leukocyte transmigration.