Prostaglandin E2 inhibits platelet-derived growth factor-stimulated cell proliferation through a prostaglandin E receptor EP2 subtype in rat hepatic stellate cells

Prostaglandin (PG) E-2 inhibits hepatic stellate cell (HSC) mitogenesis. PGE-specific receptors are divided into four subtypes that are coupled either to Ca2+ mobilization (EP1 and EP3) or to the stimulation of adenyl cyclase (EP2 and EP4). The aims of the current study were to identify PGE receptor subtypes in cultured rat HSC and to examine which PGE receptor subtype(s) mediates the inhibitory effect of PGE(2) on platelet-derived growth factor (PDGF)-stimulated proliferation. Reverse transcription-polymerase chain reaction analysis was performed to detect PGE receptor subtype mRNA expression. Cell proliferation was determined by measuring [H-3] thymidine incorporation, and intracellular cyclic AMP was measured by radioimmunoassay. Cultured rat HSC expressed mRNAs for all four subtypes of PGE receptor. PGE(2)- and EP2-selective agonist produced dose-dependent inhibitory effects on PDGF-stimulated proliferation. Neither EP1-, EP3-, nor EP4-selective agonists showed any inhibitory effect. An adenylate cyclase inhibitor strongly blunted the inhibition of DNA synthesis elicited by PGE(2) and the EP2 agonist. The EP2 agonist generated higher and more prolonged increases in intracellular cyclic AMP than the EP4 agonist. Activation of the PGE EP2 receptor has an antiproliferative effect in HSC that may be mediated by cyclic AMP-related signal transduction pathways.