The NLRP3 inflammasome selectively drives IL-1β secretion byPseudomonas aeruginosainfected neutrophils and regulates bacterial killingin vivo

Abstract

Macrophages infected with Gram-negative bacteria expressing flagellin or Type III secretion system (T3SS) structural proteins are known to activate the NLRC4 inflammasome, resulting in caspase-1 and Gasdermin D (GSDMD) cleavage, IL-1β secretion and pyroptotic cell death. We examined the role of these mediators in IL-1β secretion by neutrophils infected with Pseudomonas aeruginosa strain PAO1 that expresses the Type III secretion system (T3SS) effectors ExoS and ExoT. We found that IL-1β secretion by neutrophils was dependent on expression of the T3SS needle and translocon proteins. Although pro-GSDMD and pro-GSDME were processed in PAO1 infected neutrophils, only GSDMD was required for IL-1β secretion. PAO1 induced IL-1β secretion by macrophages was NLRC4 dependent, IL-1β secretion by neutrophils utilized NLRC4 only in the absence of P. aeruginosa exoenzymes. Instead, PAO1 induced IL-1β secretion required NLRP3, which mediated by ExoS ADP ribosyl transferase activity. We also found no role for GSDMD in NETosis induced by bacteria or PMA. Overall, these findings reveal fundamental differences between neutrophils and macrophages in IL-1β secretion in response to pathogenic bacteria.

An essential role for the Hv1 voltage-gated proton channel inPseudomonas aeruginosacorneal infection

“…The corneal epithelium of C57BL/6 and Hvcn1 -/mice was abraded and infected topically with 5×10 4 P. aeruginosa strain PAO1 that expresses Green Fluorescent Protein as we recently 10 described [20,21]. After 24h, corneal opacity and GFP+ bacteria were quantified by image analysis, and CFU was used as a measure of bacterial viability.…”