INDUCIBLE NITRIC-OXIDE SYNTHASE AND GUINEA-PIG ILEITIS INDUCED BY ADJUVANT

WE sought to establish a model of inflammatory bowel disease by augmen ting the activity of the local immune system with Freund's complete ad juvant, and to determine if inducible nitric oxide synthase (iNOS) exp ression and peroxynitrite formation accompanied the inflammatory condi tion. In anaesthetized guinea-pigs, a loop of distal ileum received in traluminal 50% ethanol followed by Freund's complete adjuvant. Control animals were sham operated. When the animals were killed 7 or 14 days later, loop lavage fluid was examined for nitrite and PGE, levels; mu cosal levels of granulocyte and macrophages were estimated by myeloper oxidase (MPO) and N-acetyl-D-glucosamidase (NAG) activity, respectivel y. Cellular localization if iNOS and peroxynitrite formation were dete rmined by immunohistochemistry with polyclonal antibodies directed aga inst peptide epitopes of mouse iNOS and nitrotyrosine, respectfully. A djuvant administration resulted in a persistent ileitis, featuring gut thickening, crypt hyperplasia, villus tip swelling and disruption, an d cellular infiltration. Lavage levels of PGE(2) and nitrite were mark edly elevated by adjuvant treatment. Immunoreactive iNOS and nitrotyro sine bordered on detectability in normal animals but were markedly evi dent with adjuvant treatment at day 7 and particularly day 14. Immunoh istochemistry suggested that enteric neurons and epithelia were major sites of iNOS activity and peroxynitrite formation. We conclude that l ocal administration of adjuvant establishes a chronic ileitis. inducib le nitric oxide synthase may contribute to the inflammatory process.