GROWTH-REGULATION OF PRIMARY HUMAN KERATINOCYTES BY PROSTAGLANDIN-E RECEPTOR EP2 AND EP3 SUBTYPES

We examined the contribution of specific EP receptors in regulating ce ll growth. By RT-PCR and northern hybridization, adult human keratinoc ytes express mRNA for three PGE(2) receptor subtypes associated with c AMP signaling (EP2, EP3, and small amounts of EP4). In actively growin g, non-confluent primary keratinocyte cultures, the EP2 and EP4 select ive agonists, 11-deoxy PGE(1) and 1-OH PGE(1), caused complete reversa l of indomethacin-induced growth inhibition. The EP3/EP2 agonist (miso prostol), and the EP1/EP2 agonist (17-phenyl trinor PGE(2)), showed le ss activity. Similar results were obtained with agonist-induced cAMP f ormation. The ability of exogenous dibutyryl cAMP to completely revers e indomethacin-induced growth inhibition support the conclusion that g rowth stimulation occurs via an EP2 and/or EP4 receptor-adenylyl cycla se coupled response, In contrast, activation of EP3 receptors by sulpr ostone, which is virtually devoid of agonist activity at EP2 or EP4 re ceptors, inhibited bromodeoxyuridine uptake in indomethacin-treated ce lls up to 30%. Although human EP3 receptor variants have been shown in other cell types to markedly inhibit cAMP formation via a pertussis t oxin sensitive mechanism, EP3 receptor activation and presumably growt h inhibition was independent of adenylylcyclase, suggesting activation of other signaling pathways. (C) 1998 Elsevier Science B.V.