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 kinase enzymes in tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) induced expression of the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on human umbilical vein endothelial cells (HUVEC). The authors observed a marked increase in ICAM-1 and VCAM-1 expression on HUVEC stimulated for 24 h by TNF-alpha (10 ng/ml) or IL-1 (20 ng/ml). Pre-treatment of HUVEC for 30 min with protein tyrosine kinase (PTK) inhibitors 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 expression on HUVEC stimulated by TNF-alpha. In contrast, pre-incubation of HUVEC with PTK inhibitors prior to the addition of TNF-alpha significantly enhanced subsequent expression of ICAM-1, although spontaneous expression of ICAM-1 on unstimulated HUVEC was unaffected. Western blot analysis demonstrated a significant increase in phosphorylated tyrosine protein levels in HUVEC stimulated by TNF-alpha, and significantly lower levels of these proteins in TNF-alpha stimulated HUVEC pre-treated with PTK inhibitors. These results demonstrate that IL-1 induced ICAM-1 and VCAM-1 expression does not result from activation of PTK-dependent pathways. In the case of TNF-alpha induced responses, the selective co-stimulatory effect of this cytokine in combination with PTK inhibitors on ICAM-1 expression suggests a complicated intracellular pathway of TNF-alpha induced ICAM-1 expression, possibly involving down-modulation of increases in ICAM-1 by PTK enzymes.