INHIBITION OF E-SELECTIN GENE-TRANSCRIPTION THROUGH A CAMP-DEPENDENT PROTEIN-KINASE PATHWAY

Cytokines induce the expression of E-selectin, VCAM-1, and ICAM-1 on h uman umbilical vein endothelial cells (HUVECs). We show that expressio n of these surface proteins is differently affected by cAMP. Increased cAMP levels decrease E-selectin and VCAM-1 but increase ICAM-1 expres sion. We demonstrate by mRNA half-life analysis and nuclear run-on ass ays that the cAMP repression of E-selectin occurs at the transcription level. This effect is abolished by protein kinase A inhibition, sugge sting that repression is mediated by protein kinase A-driven phosphory lation. We found that a minimal E-selectin promoter sequence necessary to confer cytokine inducibility is also sufficient to mimic the cAMP effect in transfected HUVECs. Previously we characterized two regions (NF-kappa B and NF-ELAM1) of the minimal promoter that bind transcript ion factors necessary for E-selectin induction. Increased cAMP did not alter the binding of the complexes formed on either the NF-kappa B or NF-ELAM1 site. In contrast, in interleukin-1-treated HUVECs transacti vity due to an NF-kappa B site is reduced by elevated cAMP. Increased cAMP in HUVECs appears to induce a protein kinase activity that reduce s the cytokine signal for E-selectin and VCAM-1 expression. The reduct ion in signal may occur through an inhibitory phosphorylation of one o r more of the factors responsible for regulating E-selectin expression .