title: NF-kappaB-mediated expression of iNOS promotes epithelial defense against infection by Cryptosporidium parvum in neonatal piglets.
abstract: Cryptosporidium sp. parasitizes intestinal epithelium, resulting in enterocyte loss, villous atrophy, and malabsorptive diarrhea. We have shown that mucosal expression of inducible nitric oxide (NO) synthase (iNOS) is increased in infected piglets and that inhibition of iNOS in vitro has no short-term effect on barrier function. NO exerts inhibitory effects on a variety of pathogens; nevertheless, the specific sites of iNOS expression, pathways of iNOS induction, and mechanism of NO action in cryptosporidiosis remain unclear. Using an in vivo model of Cryptosporidium parvum infection, we have examined the location, mechanism of induction, specificity, and consequence of iNOS expression in neonatal piglets. In acute C. parvum infection, iNOS expression predominated in the villous epithelium, was NF-kappaB dependent, and was not restricted to infected enterocytes. Ongoing treatment of infected piglets with a selective iNOS inhibitor resulted in significant increases in villous epithelial parasitism and oocyst excretion but was not detrimental to maintenance of mucosal barrier function. Intensified parasitism could not be attributed to attenuated fluid loss or changes in epithelial proliferation or replacement rate, inasmuch as iNOS inhibition did not alter severity of diarrhea, piglet hydration, Cl- secretion, or kinetics of bromodeoxyuridine-labeled enterocytes. These findings suggest that induction of iNOS represents a nonspecific response of the epithelium that mediates enterocyte defense against C. parvum infection. iNOS did not contribute to the pathogenic sequelae of C. parvum infection.
authors.affiliation: Department of Molecular Biomedical Sciences, North Carolina State University College of Veterinary Medicine, 4700 Hillsborough St., Raleigh, NC 27606, USA. Jody_Gookin@ncsu.edu
authors.forename: Jody L
authors.initials: JL
authors.lastname: Gookin
authors.forename: Sophia
authors.initials: S
authors.lastname: Chiang
authors.forename: Jessica
authors.initials: J
authors.lastname: Allen
authors.forename: Martha U
authors.initials: MU
authors.lastname: Armstrong
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Stauffer
authors.forename: Colleen
authors.initials: C
authors.lastname: Finnegan
authors.forename: Michael P
authors.initials: MP
authors.lastname: Murtaugh
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight; D002712:Chlorides / Q000378:metabolism; D003457:Cryptosporidiosis / Q000201:enzymology / Q000378:metabolism*; D016785:Cryptosporidium parvum / Q000276:immunology*; D004847:Epithelial Cells / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D007082:Ileum / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D013552:Swine; D013553:Swine Diseases / Q000201:enzymology / Q000378:metabolism* / Q000469:parasitology*
chemical_list: D002712:Chlorides; D016328:NF-kappa B; D052247:Nitric Oxide Synthase Type II