Regulation and distribution of MAdCAM-1 in endothelial cells in vitro.

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is a 60-kDa endothelial cell adhesion glycoprotein that regulates lymphocyte trafficking to Peyer's patches and lymph nodes. Although it is widely agreed that MAdCAM-1 induction is involved in chronic gut inflammation, few studies have investigated regulation of MAdCAM-1 expression. We used two endothelial lines [bEND.3 (brain) and SVEC (high endothelium)] to study the signal paths that regulate MAdCAM-1 expression in response to tumor necrosis factor (TNF)-alpha using RT-PCR, blotting, adhesion, and immunofluorescence. TNF-alpha induced both MAdCAM-1 mRNA and protein in a dose- and time-dependent manner. This induction was tyrosine kinase (TK), p42/44, p38 mitogen-activated protein kinase (MAPK), and nuclear factor (NF)-kappa B/poly-ADP ribose polymerase (PARP) dependent. Because MAdCAM-1 is regulated via MAPKs, we examined mitogen/extracellular signal-regulated kinase (MEK)-1/2 activation in SVEC. We found that MEK-1/2 is activated by TNF-alpha within minutes and is dependent on TK and p42/44 MAPKs. Similarly, TNF-alpha activated NF-kappa B through TK, p42/44, p38 MAPKs, and PARP pathways in SVEC cells. MAdCAM-1 was also shown to be frequently distributed to endothelial junctions both in vitro and in vivo. Cytokines like TNF-alpha stimulate MAdCAM-1 in high endothelium via TK, p38, p42/22 MAPKs, and NF-kappa B/PARP. MAdCAM-1 expression requires NF-kappa B translocation through both direct p42/44 and indirect p38 MAPK pathways in high endothelial cells.