Prostaglandin E₂ inhibits the proliferation of human gingival fibroblasts via the EP₂ receptor and Epac

Abstract

Elevated levels of prostaglandins such as PGE(2) in inflamed gingiva play a significant role in the tissue destruction caused by periodontitis, partly by targeting local fibroblasts. Only very few studies have shown that PGE(2) inhibits the proliferation of a gingival fibroblast (GF) cell line, and we expanded this research by using primary human GFs (hGFs) and looking into the mechanisms of the PGE(2) effect. GFs derived from healthy human gingiva were treated with PGE(2) and proliferation was assessed by measuring cell number and DNA synthesis and potential signaling pathways were investigated using selective activators or inhibitors. PGE(2) inhibited the proliferation of hGFs dose-dependently. The effect was mimicked by forskolin (adenylate cyclase stimulator) and augmented by IBMX (a cAMP-breakdown inhibitor), pointing to involvement of cAMP. Indeed, PGE(2) and forskolin induced cAMP generation in these cells. Using selective EP receptor agonists we found that the anti-proliferative effect of PGE(2) is mediated via the EP(2) receptor (which is coupled to adenylate cyclase activation). We also found that the effect of PGE(2) involved activation of Epac (exchange protein directly activated by cAMP), an intracellular cAMP sensor, and not PKA. While serum increased the amount of phospho-ERK in hGFs by approximately 300%, PGE(2) decreased it by approximately 50%. Finally, the PGE(2) effect does not require endogenous production of prostaglandins since it was not abrogated by two COX-inhibitors. In conclusion, in human gingival fibroblasts PGE(2) activates the EP(2)-cAMP-Epac pathway, reducing ERK phosphorylation and inhibiting proliferation. This effect could hamper periodontal healing and provide further insights into the pathogenesis of inflammatory periodontal disease.

Prostaglandin E₂ Inhibits Proteinase-Activated Receptor 2-Signal Transduction through Regulation of Receptor Internalization

“…These results suggest that PGE 2 -mediated PAR2 internalization contributes to the inhibition of PAR2-signal transduction. PGE 2 increases cAMP levels in many cell types, and it has been reported that PGE 2 inhibits ERK phosphorylation in a cAMP-dependent manner [34]. In our experiments, both of PGE 2 and forskolin, increased intracellular cAMP levels (Fig.…”

Prostaglandin E2 and Pain-An Update

“…EP 2 and EP 4 receptors are coupled to G s protein, and the agonist stimulation of those receptors activates adenylyl cyclase, which generates cyclic AMP (cAMP), followed by activation of protein kinase A (PKA) and, perhaps, exchange protein activated by cAMP (Epac). [8][9][10][11][12][13] 16) and may play roles in peripheral and/or spinal nociceptive processing. 8) 4.…”

“…Activation of the Epac/Rap pathway by PGE 2 via EP 2 and EP 4 might also occur in synovial and gingival fibroblasts, playing a role in the pathologies of rheumatoid arthritis and inflammatory periodontal disease. 12,13) …”

Mast Cell-derived Prostaglandin D2 Controls Hyaluronan Synthesis in Human Orbital Fibroblasts via DP1 Activation

“…6B). We then treated the cells with PGD 2 or PGJ 2 together with IBMX, a nonselective phosphodiesterase inhibitor that boosts cAMP levels by preventing its degradation (41). IBMX, in conjunction with either PGD 2 or PGJ 2 , significantly enhanced the ability of PGD 2 or PGJ 2 to generate HA (Fig.…”