Elevation of cyclic AMP levels in astrocytes antagonizes cytokine- induced adhesion molecule expression

Abstract

We have examined the effect of elevating cyclic AMP levers on cytokine- mediated enhancement of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) gene expression by astrocytes. Treatment of astrocytes with the cyclic AMP mimetic dibutyryl-cyclic AMP, or the agonists norepinephrine, forskolin, prostaglandin E2, and cholera toxin alone had no effect on ICAM-1 or VCAM-1 mRNA gene expression. However, elevating cyclic AMP levels within the cells by these agents suppressed interleukin-1β- and tumor necrosis factor-α-induced adhesion molecule expression at both the mRNA and protein levels. The phosphodiesterase type IV inhibitor, rolipram, was able to potentiate the inhibitory effect of forskolin on ICAM-1 and VCAM-1 gene expression. Inhibition of tumor necrosis factor-α-induced VCAM-1 mRNA levels by forskolin was partially due to enhanced degradation of VCAM-1 message, whereas the decay rates of tumor necrosis factorα-induced ICAM-1 message and interleukin-1β-induced ICAM- 1/VCAM-1 message were not affected by forskolin treatment. These results demonstrate that the pathways used by interleukin-1β and tumor necrosis factor-α to induce adhesion molecule expression are antagonized by cyclic AMP-dependent protein kinase-mediated signaling pathways.