Super-low Dose Endotoxin Pre-conditioning Exacerbates Sepsis Mortality

Sepsis mortality varies dramatically in individuals of variable immune conditions, with poorly defined mechanisms. This phenomenon complements the hypothesis that innate immunity may adopt rudimentary memory, as demonstrated in vitro with endotoxin priming and tolerance in cultured monocytes. However, previous in vivo studies only examined the protective effect of endotoxin tolerance in the context of sepsis. In sharp contrast, we report herein that pre-conditioning with super-low or low dose endotoxin lipopolysaccharide (LPS) cause strikingly opposite survival outcomes. Mice pre-conditioned with super-low dose LPS experienced severe tissue damage, inflammation, increased bacterial load in circulation, and elevatedmortalitywhen theywere subjected to cecal-ligation and puncture (CLP). This is in contrast to thewell-reported protective phenomenon with CLPmice pre-conditioned with lowdose LPS.Mechanistically,we demonstrated that super-lowand lowdose LPS differentially modulate the formation of neutrophil extracellular trap (NET) in neutrophils. Instead of increased ERK activation and NET formation in neutrophils pre-conditioned with low dose LPS, we observed significantly reduced ERK activation and compromised NET generation in neutrophils pre-conditioned with super-low dose LPS. Collectively, our findings reveal amechanismpotentially responsible for the dynamic programming of innate immunity in vivo as it relates to sepsis risks.