Abstract 1357: A Novel Prostaglandin E2 Receptor EP4-Selective Agonist Attenuates Inflammatory Activation of Macrophages in vitro and in vivo
Background: Prostaglandin E2 ( PGE2 ) exerts its biological functions mainly via four G protein-coupled seven transmembrane receptors ( EP1– 4 ). Several lines of evidence suggest that the EP4 receptor may participate in the anti-inflammatory action of endogenous PGE2 in human macrophages. The specific agonists for EP4 may have considerable and practical clinical impact on inflammatory diseases. Thus, we synthesized a novel EP4 selective agonist, EP4RAG, and examined the effect of the compound on inflammatory activation of macrophages in vitro and in vivo.
Methods and Results : EP4RAG, a novel structural analog of PGE2, was chemically synthesized. EP4RAG effectively competed with [3H]PGE2 binding to mouse EP4 with Ki values of 2.8 ±0.24 nM ( mean±s.d n=4), using the membrane of CHO cells expressing EP4. EP4RAG was at least 125-fold more selective for mouse EP4 than the mouse EP1, EP2, and EP3 subtypes. PGE2 elicited cAMP production in human macrophages (ED50=3nM ), while EP4RAG stimulated lower level of cAMP production ( ED50=1μM ). EP4RAG attenuated LPS-induced inflammatory protein expression including monocyte chemoattractant protein ( MCP )-1(22.7±17.3 nM, mean of IC50 ±s.d. of three independent donors), tumor necrosis factor (TNF)-α (1.0±0.7nM) and macrophage inflammatory protein -1β ( 5.7±1.7nM ) in human primary macrophages derived from peripheral blood. We then examined the effect of EP4RAG on D-galactosamine plus LPS-induced TNF-α expression in mouse. EP4RAG administration (3mg/kg subcutaneously) suppressed the increase in TNF-α production in serum by 75% ( 29.6 ±2.41 ng/ml for non-treatment versus 7.4 ±2.16 ng/ml for EP4RAG, mean of TNF-α level ± s.e., p<0.005, n=9 ). EP4RAG treatment also attenuated the level of MCP-1 protein in ischemic lesion of experimental myocardial ischemia / reperfusion injury rat in vivo.
Conclusions: The EP4RAG attenuates inflammatory activation in vitro and in vivo by suppression of cytokines and chemokines. This study raises the possibility that EP4 selective agonists might provide a new therapeutic strategy for vascular inflammatory diseases.