Activation of E-prostanoid4 and E-prostanoid2 receptors inhibits TNF-α release from human alveolar macrophages

Prostaglandin (PG)E-2 has been shown to inhibit mediator release from human alveolar macrophages (AMs), but the prostanoid receptor(s) mediating this response have not yet been documented. To investigate this, the present authors conducted a range of pharmacological and expression-based studies in monocyte-derived macrophages (MDMs) and AMs. MDMs were obtained by in vitro differentiation of monocytes from the peripheral blood of healthy human volunteers. Human AMs were obtained by perfusion of lung tissue from carcinoma resection patients. In MDMs, PGE(2) potently inhibited lipopolysaccharide-induced tumour necrosis factor (TNF)-alpha release (p[A](50) 8.51+/-0.11, maximum inhibition 95.9+/-4.8%). In human AMs, PGE(2) also inhibited TNF-alpha release but the observed concentration-effect curve was very flat and inhibition was incomplete. The shape of the PGE(2) curve in AMs suggested that its effects were mediated by activation of a heterogeneous receptor population. Expression studies combined with the use of various E-prostanoid (EP) receptor agonists and a selective EP4-receptor antagonist (Ono-AE2-227) confirmed that the inhibitory effects of PGE(2) in both AMs and MDMs were mediated by activation of EP4 and EP2 receptors. These data indicate that both E-prostanoid(4) and E-prostanoid(2) selective agonists may have anti-inflammatory properties in lung diseases where macrophages play a role.