Antioxidants Inhibit Monocyte Adhesion by Suppressing Nuclear Factor-icB Mobilization and Induction of Vascular Cell Adhesion Molecule-1 in Endothelial Cells Stimulated to Generate Radicals

Cell adhesion to endothelial cells stimulated by tumor necrosis factor-a (TNF) is due to induction of surface receptors, such as vascular cell adhesion molecule-1 (VCAM-1). The antiaxidant pyrrolidine dithiocarbamate (PDTC) specifically inhibits activation of nuclear factor-KB (NF-KB). Since *B motifs are present in VCAM-1 and intercellular adhesion molecule-1 (ICAM-1) promoters, we used PDTC to study the regulatory mechanisms of VCAM-1 and ICAM-1 induction and subsequent monocyte adhesion in TNF-treated human umbilical vein endothelial cells (HUVECs). PDTC or JV-acetylcysteine dose dependently reduced TNF-induced VCAM-1 but not ICAM-1 surface protein (also in human umbilical arterial endothelial cells) and mRNA expression (by 70% at 100 junol/L PDTC) in HUVECs as assessed by flow cytometry and porymerase chain reaction. Gel-shift analysis in HUVECs demonstrated that PDTC prevented NF-KB mobilization by TNF, suggesting that only VCAM-1 induction was controlled by NF-KB. Since HUVECs released superoxide anions in response to TNF, and H2O2 Tumor necrosis factor-a (TNF) potently stimulates leukocyte adhesion to human umbilical vein endothelial cells (HUVECs) by inducing various adhesion molecules, which exert distinct functions in leukocyte recruitment. Vascular cell adhesion molecule-1 (VCAM-1), an endothelial receptor for lymphocytes, may be involved in monocyte adhesion by interacting with the ^-integrin very late activation antigen-4. TNF also increases expression of intercellular adhesion molecule-1 (ICAM-1), a ligand for ftintegrins, and endothelial leukocyte adhesion molecule-1 (ELAM-1). Whereas ELAM-1 may account for polymorphonuclear leukocyte rolling and ICAM-1 mediates subsequent attachment, spreading, and migration, VCAM-1 may preferentially contribute to monocyte adhesion. Two TNF receptor types, R55 and R75, are present on FfUVECs. TNF-induced adhesion is controlled by R55, correlating with a dominant role for Received February 8, 1994; revision accepted July 4, 1994. From the Institut fur Prophylaxe der Kreislaufkrankheiten and Institut fur Immunologie (M.S., H.W.L.Z.-H.), Ludwig-Maximilians-Universitat, MOnchen, Germany. Correspondence to Christian Weber, MD, Institut fur Prophylaxe der Kreislaufkrankheiten, Pettenkoferstr 9, D-80336 MOnchen, FRG. © 1994 American Heart Association, Inc. induces VCAM-1, PDTC may act as a radical scavenger. Although ICAM-1 induction was unaffected, inhibitors of NADPH oxidase (apocynin) or cytochrome P-450 (SKF525a) suppressed VCAM-1 induction by TNF, revealing that several radicalgenerating systems are involved in its regulation. PDTC, apocynin, or SKF525a decreased adhesion of monocytic U937 cells to TNF-treated HUVECs (by 75% at 100 /unol/L PDTC). Inhibition by anti-VCAM-1 monoclonal antibody 1G11 indicated that U937 adhesion was VCAM-1 dependent and suppression by antioxidants was due to reduced VCAM-1 induction. In conclusion, our data reflect a major contribution of NF-KB activation to the mediation of VCAM-1-dependent monocyte adhesion in stimulated HUVECs. Antioxidants may represent a new approach in the treatment of conditions related to increased VCAM-1 expression. (Arteriosder Thmmb. 1994;14:1665-1673.)