title: E-ring 8-isoprostanes are agonists at EP2- and EP4-prostanoid receptors on human airway smooth muscle cells and regulate the release of colony-stimulating factors by activating cAMP-dependent protein kinase.
abstract: 8-Isoprostanes are bioactive lipid mediators formed via the nonenzymatic peroxidation of arachidonic acid by free radicals and reactive oxygen species. However, their cognate receptors, biological actions, and signaling pathways are poorly studied. Here, we report the effect of a variety of E- and Falpha-ring 8-isoprostanes on the release of granulocyte/macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) from human airway smooth muscle (HASM) cells stimulated with interleukin-1beta (IL-1beta). The elaboration of GM-CSF and G-CSF by IL-1beta was inhibited and augmented, respectively, in a concentration-dependent manner by 8-iso-prostaglandin (PG) E(1) and 8-iso-PGE(2), but not by 8-iso-PGF(1alpha), 8-iso-PGF(2alpha), and 8-iso-PGF(3)alpha. AH 6809 (6-isopropoxy-9-oxoxanthine-2-carboxylic acid), an EP(1)-/EP(2)-/DP-receptor blocking drug, antagonized the inhibitory effect of 8-iso-PGE(1) and 8-iso-PGE(2) on GM-CSF output with an affinity consistent with an interaction at prostanoid receptors of the EP(2)-subtype. In contrast, the facilitation by 8-iso-PGE(1) and 8-iso-PGE(2) of G-CSF release was unaffected by AH 6809 and the selective EP(4)-receptor antagonist L-161,982 [4'-[3-butyl-5-oxo-1-(2-trifluoromethyl-phenyl)-1,5-dihydro-[1,2,4]triazol-4-ylmethyl]-biphenyl-2-sulfonic acid (3-methyl-thiophene-2-carbonyl)-amide]. However, when used in combination, AH 6809 and L-161,982 displaced 5-fold to the right the 8-iso-PGE and 8-iso-PGE concentration-response curves. The opposing (1)effect of E-ring (2)8-isoprostanes on GM-CSF and G-CSF release was mimicked by 8-bromo-cAMP and abolished in cells infected with an adenovirus vector encoding an inhibitor protein of cAMP-dependent protein kinase (PKA). Together, these data demonstrate that E-ring 8-isoprostanes regulate the secretion of GM-CSF and G-CSF from HASM cells by a cAMP- and PKA-dependent mechanism. Moreover, antagonist studies revealed that 8-iso-PGE(1) and 8-iso-PGE(2) act solely via EP(2) -receptors to inhibit GM-CSF release, whereas both EP(2)- and EP(4)-receptor subtypes positively regulate G-CSF output.
authors.affiliation: Thoraic Medicine, National Heart and Lung Institute, Imperial College London, London, UK.
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Clarke
authors.forename: Maria G
authors.initials: MG
authors.lastname: Belvisi
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hardaker
authors.forename: Robert
authors.initials: R
authors.lastname: Newton
authors.forename: Mark A
authors.initials: MA
authors.lastname: Giembycz
mesh_terms: D000293:Adolescent; D000328:Adult; D002478:Cells, Cultured; D003115:Colony-Stimulating Factors / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism*; D018078:Receptors, Prostaglandin E / Q000819:agonists* / Q000378:metabolism / Q000502:physiology; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D014132:Trachea / Q000187:drug effects / Q000378:metabolism
chemical_list: D003115:Colony-Stimulating Factors; C545644:PTGER2 protein, human; C545650:PTGER4 protein, human; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; C075750:8-epi-prostaglandin F2alpha; D015237:Dinoprost; D017868:Cyclic AMP-Dependent Protein Kinases