Evidence from patients with
inflammatory bowel disease (IBD) and animal models suggests that
inflammation alters blood flow to the mucosa, which precipitates mucosal barrier dysfunction. Impaired purinergic sympathetic regulation of submucosal arterioles, the resistance vessels of the splanchnic vasculature, is one of the defects identified during IBD and in mouse models of IBD. We hypothesized that this may be a consequence of upregulated catabolism of
ATP during
colitis. In vivo and in vitro video microscopy techniques were employed to measure the effects of
purinergic agonists and inhibitors of CD39, an
enzyme responsible for extracellular
ATP catabolism, on the diameter of colonic submucosal arterioles from control mice and mice with
dextran sodium sulfate [DSS, 5% (wt/vol)]
colitis. Using a
luciferase-based
ATP assay, we examined the degradation of
ATP and utilized real-time PCR, Western blotting, and immunohistochemistry to examine the expression and localization of CD39 during
colitis. Arterioles from mice with DSS
colitis did not constrict in response to
ATP (10 microM) but did constrict in the presence of its nonhydrolyzable analog
alpha,beta-methylene ATP (1 microM).
alpha,beta-Methylene ADP (100 microM), an inhibitor of CD39, restored
ATP-induced vasoconstriction in arterioles from mice with DSS-induced
colitis. CD39
protein and
mRNA expression was markedly increased during
colitis. Immunohistochemical analysis demonstrated that, in addition to vascular CD39, F4/80-immunoreactive macrophages accounted for a large proportion of submucosal CD39 staining during
colitis. These data implicate upregulation of CD39 in impaired sympathetic regulation of gastrointestinal blood flow during
colitis.