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Abstract
Prostaglandins are synthesized by cyclooxygenases (COX)-1 and -2. The expression and
cellular localization of COX-1 and COX-2 in normal human colon and inflammatory bowel
disease (IBD) surgical resections were studied.
COX-1 and COX-2 protein expression and cellular localization were assessed by Western
blotting and immunohistochemistry.
COX-1 protein was expressed at equal levels in normal, Crohn's disease, and ulcerative
colitis colonic epithelial cells. COX-2 protein was not detected in normal epithelial
cells but was detected in Crohn's disease and ulcerative colitis epithelial cells.
Immunohistochemistry of normal, Crohn's colitis, and ulcerative colitis tissue showed
equivalent COX-1 expression in epithelial cells in the lower half of the colonic crypts.
COX-2 expression was absent from normal colon, whereas in Crohn's colitis and ulcerative
colitis, COX-2 was observed in apical epithelial cells and in lamina propria mononuclear
cells. In Crohn's ileitis, COX-2 was present in the villus epithelial cells. In ulcerative
colitis, colonic epithelial cells expressing COX-2 also expressed inducible nitric
oxide synthase.
COX-1 was localized in the crypt epithelium of the normal ileum and colon, and its
expression was unchanged in IBD. COX-2 was undetectable in normal ileum or colon,
but it was induced in apical epithelial cells of inflamed foci in IBD.