ROLE OF TYROSINE KINASE ENZYMES IN TNF-ALPHA AND IL-1 INDUCED EXPRESSION OF ICAM-1 AND VCAM-1 ON HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS

The aim of this study was to analyse the potential roles of protein ki nase enzymes in tumour necrosis factor-alpha (TNF-alpha) and interleuk in-1 (IL-1) induced expression of the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (V CAM-1) on human umbilical vein endothelial cells (HUVEC). The authors observed a marked increase in ICAM-1 and VCAM-1 expression on HUVEC st imulated for 24 h by TNF-alpha (10 ng/ml) or IL-1 (20 ng/ml). Pre-trea tment of HUVEC for 30 min with protein tyrosine kinase (PTK) inhibitor s genistein and herbimycin A (10 mu g/ml and 0.5 mu g/ml, respectively ) before stimulation with IL-1 did not affect the expression of these molecules. Similar results were observed with respect to VCAM-1 expres sion on HUVEC stimulated by TNF-alpha. In contrast, pre-incubation of HUVEC with PTK inhibitors prior to the addition of TNF-alpha significa ntly enhanced subsequent expression of ICAM-1, although spontaneous ex pression of ICAM-1 on unstimulated HUVEC was unaffected. Western blot analysis demonstrated a significant increase in phosphorylated tyrosin e protein levels in HUVEC stimulated by TNF-alpha, and significantly l ower levels of these proteins in TNF-alpha stimulated HUVEC pre-treate d with PTK inhibitors. These results demonstrate that IL-1 induced ICA M-1 and VCAM-1 expression does not result from activation of PTK-depen dent pathways. In the case of TNF-alpha induced responses, the selecti ve co-stimulatory effect of this cytokine in combination with PTK inhi bitors on ICAM-1 expression suggests a complicated intracellular pathw ay of TNF-alpha induced ICAM-1 expression, possibly involving down-mod ulation of increases in ICAM-1 by PTK enzymes.