Prostanoid receptor expression by human airway smooth muscle cells and regulation of the secretion of granulocyte colony-stimulating factor

The prostanoid receptors on human airway smooth muscle cells (HASMC) that augment the release by IL-1beta of granulocyte colony-stimulating factor (G-CSF) have been characterized and the signaling pathway elucidated. PCR of HASM cDNA identified products corresponding to EP2, EP3, and EP4 receptor subtypes. These findings were corroborated at the protein level by immunocytochemistry. IL-1beta promoted the elaboration of G-CSF, which was augmented by PGE(2). Cicaprost (IP receptor agonist) was approximately equiactive with PGE(2), whereas PGD(2), PGF(2alpha), and U-46619 (TP receptor agonist) were over 10-fold less potent. Neither SQ 29,548 nor BW A868C (TP and DP1 receptor antagonists, respectively) attenuated the enhancement of G-CSF release evoking any of the prostanoids studied. With respect to PGE(2), the EP receptor agonists 16,16-dimethyl PGE(2) (nonselective), misoprostol (EP2/EP3 selective), 17-phenyl-omega-trinor PGE(2) (EP1 selective), ONO-AE1-259, and butaprost ( both EP2 selective) were full agonists at enhancing G-CSF release. AH 6809 (10 muM) and L-161,982 (2 muM), which can be used in HASMC as selective EP2 and EP4 receptor antagonists, respectively, failed to displace to the right the PGE2 concentration-response curve that described the augmented G-CSF release. In contrast, AH 6809 and L-161,982 in combination competitively antagonized PGE(2)-induced G-CSF release. Augmentation of G-CSF release by PGE(2) was mimicked by 8-BrcAMP and abolished in cells infected with an adenovirus vector encoding an inhibitor protein of cAMP-dependent protein kinase (PKA). These data demonstrate that PGE2 facilitates G-CSF secretion from HASMC through a PKA-dependent mechanism by acting through EP2 and EP4 prostanoid receptors and that effective antagonism is realized only when both subtypes are blocked concurrently.