Neonatal neutrophils exhibit reduced NLRP3 inflammasome activation

Newborns are at high risk to develop sepsis. This is linked to innate immune responses at birth which are not completely adapted to postnatal life. Neutrophils are key players of innate immunity and exhibit a marked ontogenetic regulation of their functionality. Here, we studied the NLRP3 inflammasome in neonatal neutrophils and found lower baseline expression of NLRP3, pro-caspase-1, and the K+-channel KV1.3 compared with adult neutrophils. Following stimulation with lipopolysaccharide/nigericin, apoptosis-related speck-like protein containing a caspase recruitment domain oligomerization, caspase-1 activation, and interleukin-1β (IL-1β) release were significantly reduced in neonatal compared with adult neutrophils. Similarly, stimulation of neonatal neutrophils with E-selectin led to reduced NLRP3 inflammasome activation accompanied by diminished release of the alarmin S100A8/A9. Taken together, our results strongly indicate diminished NLRP3 inflammasome activation in neonatal neutrophils leading to a significant reduction of released IL-1β and S100A8/A9. These findings identify reduced neutrophil NLRP3 inflammasome activation as a critical component contributing to the inherent susceptibility to infections in neonates.