The objective of this study was to quantify, in vivo, constitutive and tumor necrosis factor a (TNF-α)-enhanced expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in different tissues from healthy wild- type mice (C57BL/6) as well as interleukin-10 (IL-10)-deficient mice with and without active colitis. Using the dual radiolabel monoclonal antibody technique, we found substantial constitutive expression of MAdCAM-1 in the intestine, colon, and mesenteric lymph nodes. MAdCAM-1 expression in these tissues was significantly enhanced, in a time-dependent manner, by systemic administration of TNF-α. Maximum surface expression was observed at 18 h after TNF-α administration and remained significantly elevated at 48 h post- TNF-α injection. No significant constitutive nor TNF-α-induced expression of MAdCAM-1 was detected in skeletal muscle, brain, or heart. In IL-10- deficient (IL-10 k/o) mice with no clinical or histological evidence of colitis, constitutive and TNF-α-induced expression of MAdCAM-1 in the intestine, cecum, and colon was not different from those values obtained with healthy wild-type controls. IL-10-deficient mice with active colitis exhibited a four- to fivefold greater expression of MAdCAM-1 in the cecum and colon compared with their healthy controls or to IL-10 k/o mice with no evidence of colitis. Taken together, these data demonstrate that TNF-α enhances surface expression of MAdCAM-1 in intestinal and colonic tissues to the same extent in both wild-type and IL-10 k/o mice with no colonic inflammation, whereas IL-10 k/o mice with active colitis exhibited a profound up-regulation of MAdCAM-1 in the colon.
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