Action of cAMP on expression and release of adhesion molecules in human endothelial cells

The expression of E-selectin induced by tumor necrosis factor (TNF) on the surface of human umbilical vein endothelial cells (HUVEC) was partially inhibited by an increase in the level of adenosine 3',5'-cyclic monophosphate (cAMP), produced by forskolin or cholera toxin combined with the type IV phosphodiesterase inhibitor rolipram and the protein kinase A agonist phosphorothioate analogue of cAMP SpcAMPS. The same agents had no significant effect on the constitutive and TNF-stimulated expression of intercellular adhesion molecule 1 (ICAM-1), whereas the effect on vascular cell adhesion molecule 1 (VCAM-1) expression was variable depending on cell culture conditions. The stimulatory effects of phorbol 12-myristate 13-acetate and bacterial lipopolysaccharide (LPS) on E-selectin expression were also downregulated by the forskolin-rolipram combination and by SpcAMPS. Inhibition of the surface expression of E-selectin was associated with a decrease of the total amount of the protein in the cell lysate and a reduced mRNA level, with no significant effect on mRNA stability. In anesthetized rats, the terbutaline-rolipram combination reduced the rolling of leukocytes induced by LPS in the mesenteric microcirculation. In addition to their partial inhibitory effect on the TNF-induced surface expression of E-selectin on HUVEC, the forskolin-rolipram combination and SpcAMPS strongly inhibited the release of soluble E-selectin from these cells; the release of soluble ICAM-1 and VCAM-1 was unaffected by these agents. Isoproterenol reduced the release of soluble E-selectin, whereas it had no significant effect on the cell surface expression of the protein. This study underscores the potential anti-inflammatory effect of a rise in the endothelial cAMP level.