C2-ceramide inhibits the prostaglandin E2-induced accumulation of cAMP in human gingival fibroblasts

Abstract

Ceramide is generated by the hydrolysis of membrane sphingomyelin by sphingomyelinase and is implicated in multiple signaling pathways, including those regulating differentiation, inflammation and immune responses. Excess formation of prostaglandin E2 (PGE2) is thought to increase susceptibility to infection, rheumatoid arthritis and inflammation, including periodontal diseases. We investigated the inhibitory effect of C2-ceramide, a short-chain ceramide analog, on the PGE2-stimulated accumulation of cAMP in human gingival fibroblasts. In human gingival fibroblasts pre-treated with C2-ceramide for 18 h, the PGE2-stimulated accumulation of cAMP was reduced, but an inactive C2-ceramide analog had no such effect. The accumulation of cAMP induced by EP2 and EP4 receptor agonists (ONO-AE1-259 and ONO-AE1-329, respectively) was inhibited in cells treated with C2-ceramide. However, treatment with C2-ceramide had no effect on the expression of mRNAs encoding the EP2 and EP4 receptors. Accumulation of cAMP could be induced by cAMP-elevating agents (forskolin, isobutylmethylxanthine and mastparan) but was not reduced by treatment with C2-ceramide. These observations suggest that C2-ceramide attenuates PGE2 receptor function and consequently inhibits the accumulation of cAMP in human gingival fibroblasts.