P153 LOSS OF NEUTROPHIL EXTRACELLULAR TRAPS VIA PEPTIDYL ARGININE DEIMINASE-4 DEFICIENCY AGGRAVATES CITROBACTER RODENTIUM- INDUCED GUT INFLAMMATION

Abstract

Citrobacter rodentium (CR) is an attaching-effacing enteropathogen which infects mice and causes intestinal inflammation. The CR infection model is appropriate for investigating host-pathogen interactions in the gut and understanding the pathogenesis of human inflammatory bowel diseases. Peptidyl arginine deiminase-4 (PAD4) is an enzyme required for the generation of neutrophil extracellular traps (NETs), which can provide antimicrobial effects during the host innate immune response; however, the role of PAD4 against gastrointestinal (GI) infection is largely unknown. In this study, we challenged PAD4-deficient (Pad4-/-) mice and wild type (WT) littermates against CR, and investigated bacteria clearance and gut pathology. Luminal colonization of CR in Pad4-/- mice peaked between 11-14 days post-infection (p.i.), whereas WT mice suppressed the infection by 14 days. Loss of PAD4 substantially increased CR dissemination to the spleen and mesenteric lymph nodes, which prolonged and aggravated CR-associated inflammation as indicated by splenomegaly, colomegaly and elevated systemic and colonic pro-inflammatory markers (lipocalin 2 and serum amyloid A). Likewise, the colonic antimicrobial cytokines, IL-22 and IL-17A, were more upregulated in Pad4-/- than WT mice in response to infection. Histological analysis revealed that transmissible colonic hyperplasia and goblet cell depletion were more pronounced in Pad4-/- than WT mice. Using a bioluminescent strain of CR (ICC180), we observed that the transit of CR through the gastrointestinal tract occurs more rapidly in Pad4-/- mice. Treating WT mice with deoxyribonuclease I (DNase I; disrupts NETs generation), recapitulated the exacerbated CR infection and gut pathology as in PAD4 deficient mice. Administration of the PAD4 inhibitor, Cl-amidine, also aggravated CR infection, but to a lesser extent than those observed in either Pad4-/- or DNase I-treated mice. Taken together, our findings highlight the importance of PAD4 in the mucosal clearance of CR and in resolving the gut-associated inflammation and colitis. In light of the ongoing efforts to target PAD4 or NETs to treat other inflammatory disorders, our findings caution that their inhibition may not be favorable against GI infection.