MODULATION OF PYROGEN-INDUCED UP-REGULATION OF ENDOTHELIAL-CELL ADHESION MOLECULES (CAMS) BY INTERLEUKIN-4 - TRANSCRIPTIONAL MECHANISMS ANDCAM-SHEDDING

The pyrogens interleukin 1 (IL-1), tumor necrosis factor (TNF), and ba cterial lipopolysaccharides (LPS) are known to increase endothelial ce ll (EC) adhesiveness for leukocytes by stimulating surface expression of various adhesion molecules. IL-4, a product of activated T-cells, w as shown to affect pyrogen-mediated regulation of EC adhesion molecule surface expression. In the present study, we investigated the effect of IL-4 on pyrogen-induced upregulation of the cell adhesion molecules (CAMs) ICAM-1 (intercellular cell adhesion molecule-1), ELAM-1 (endot helial leucocyte adhesion molecule-1), and VCAM-1 (vascular cell adhes ion molecule-1) in cultured human umbilical vein EC (HUVEC). Surface e xpression of adhesion molecules was quantified by flow cytometry, HUVE C mRNA content was estimated by Northern blot analysis, and ICAM-1 ant igen in conditioned media was measured by ELISA. Incubation of HUVEC w ith IL-1 (100 U/ml), TNF (500 U/ml), and LPS (10 mu g/ml) caused signi ficant increases in ICAM-1, ELAM-1, and VCAM-1 surface expression: IL- 1 caused about an eightfold increase in ICAM-1 expression, about a 13- fold increase in ELAM-1 surface expression, and about a fourfold incre ase in VCAM-1 expression. Coincubation of pyrogens with IL-4 (500 U/ml ) differentially influenced their proadhesive effects on the HUVEC sur face. In the presence of IL-4, IL-1-induced ICAM-1 upregulation was re duced, ELAM-1 upregulation was not significantly influenced by IL-4, a nd induction of VCAM-1 was enhanced by IL-4. IL-4 alone had no effect on ICAM-1 and ELAM-1 EC surface expression, whereas this cytokine was found to increase VCAM-1 expression about twofold after 24 hr. Norther n blot analysis showed that the changes in ICAM-1, ELAM-1, and VCAM-1 mRNA content of HUVEC during incubation with pyrogens and IL-4 resembl ed the phenomena observed on the cell surface. Determination of ICAM-1 antigen in HUVEC conditioned medium revealed corresponding changes in surface expression and antigen concentration in the conditioned mediu m. We conclude from our results that 1) IL-4 differentially regulates pyrogen-induced upregulation of adhesion molecules in EC, 2) at least in the case of ICAM-1, changes in shedding are not of major importance for the effects of pyrogens and IL-4 on EC-CAM surface expression, an d 3) CAM expression on EC surface is mainly regulated at a transcripti onal level. (C) 1994 Wiley-Liss, Inc.