Entamoeba histolytica Alters ileal Paneth Cell Functions in Intact and Muc2 Mucin Deficiency.

Enteric α-defensins, termed cryptdins (Crps) in mice, and lysozymes secreted by Paneth cells contribute to innate host defense in the ileum. Antimicrobial factors including lysozymes and β-defensins are often embedded in luminal glycosylated colonic Muc2 mucin secreted by goblet cells that form the protective mucus layer critical in gut homeostasis and pathogen invasion. In this study we investigated ileal innate immunity against Entamoeba histolytica (Eh ), the causative agent of intestinal amebiasis, by inoculating parasites in closed ileal loops in Muc2+/+ and Muc2-/- littermates and quantifying Paneth cell localization (lysozyme expression) and function (Crps secretion). Relative to Muc2+/+ littermates, Muc2-/- showed disorganized mislocalization of Paneth cells that was diffusely distributed with elevated lysozyme secretion in the crypts and on villi in response to Eh Inhibiting Eh Gal-lectin binding with exogenous galactose and Eh CP5- Eh had no effect on parasite-induced erratic Paneth cell lysozyme synthesis. Although basal ileal expression of Crp genes was unaffected in Muc2-/- mice in response to Eh there was robust release of pro-inflammatory cytokines and Crp peptide secretions in luminal exudates that was also present in the colon. Interestingly, Eh secreted cysteine proteinases cleaved the pro-region of Crp 4 but not the active form. These findings define Muc2 mucin as an essential component of ileal barrier function that regulates localization and function of Paneth cells critical in host defense against microbes.