PAD4-dependent neutrophil extracellular traps dagame intestinal barrier integrity through histone protein components

Abstract Infiltrating neutrophils and neutrophil extracellular traps (NETs) accumulate in the inflamed epithelium to induce mucosal inflammation in patients with inflammatory bowel diseases. The formation of NETs is initiated by peptidyl arginine deiminase 4 (PAD4), which facilitates NET generation through chromatin decondensation. We recently demonstrated that NETs impair intestinal epithelium integrity, permeability, and viability in mice with colitis. In addition, disruption of NET formation by administering DNase I or PAD4 inhibitors attenuates intestinal inflammation in colitic mice. However, the effect of genetic loss on PAD4-mediated NET formation and intestinal inflammation has not been determined in chemical-induced colitis models. Moreover, the specific NET components responsible for the damage and impaired barrier integrity in the intestinal epithelium are also unknown. Here we demonstrated that mice lacking PAD4 failed to produce NETs in the intestine in response to dextran sulfate sodium (DSS)-induced colitis. This impairment in PAD4-deficient mice ameliorated intestinal inflammation, barrier function, and integrity. Mechanistically, NETs, particularly the histone components, altered the integrity of junctional proteins and induced cytotoxicity, resulting in increased gut epithelium permeability. In contrast, inhibition of histone activity in NETs restored the expression and localization of junctional proteins and cell viability, thus enhancing intestinal barrier functions. Collectively, our findings indicate that extracellular histones of NETs have a detrimental role in regulating intestinal barrier function inCaco-2 monolayers and in vivo.