title: Pro-asthmatic cytokines regulate unliganded and ligand-dependent glucocorticoid receptor signaling in airway smooth muscle.
abstract: To elucidate the regulation of glucocorticoid receptor (GR) signaling under pro-asthmatic conditions, cultured human airway smooth muscle (HASM) cells were treated with proinflammatory cytokines or GR ligands alone and in combination, and then examined for induced changes in ligand-dependent and -independent GR activation and downstream signaling events. Ligand stimulation with either cortisone or dexamethsone (DEX) acutely elicited GR translocation to the nucleus and, comparably, ligand-independent stimulation either with the Th2 cytokine, IL-13, or the pleiotropic cytokine combination, IL-1β/TNFα, also acutely evoked GR translocation. The latter response was potentiated by combined exposure of cells to GR ligand and cytokine. Similarly, treatment with either DEX or IL-13 alone induced GR phosphorylation at its serine-211 residue (GR(Ser211)), denoting its activated state, and combined treatment with DEX+IL-13 elicited heightened and sustained GR(Ser211) phosphorylation. Interestingly, the above ligand-independent GR responses to IL-13 alone were not associated with downstream GR binding to its consensus DNA sequence or GR transactivation, whereas both DEX-induced GR:DNA binding and transcriptional activity were significantly heightened in the presence of IL-13, coupled to increased recruitment of the transcriptional co-factor, MED14. The stimulated GR signaling responses to DEX were prevented in IL-13-exposed cells wherein GR(Ser211) phosphorylation was suppressed either by transfection with specific serine phosphorylation-deficient mutant GRs or treatment with inhibitors of the MAPKs, ERK1/2 and JNK. Collectively, these novel data highlight a heretofore-unidentified homeostatic mechanism in HASM cells that involves pro-asthmatic cytokine-driven, MAPK-mediated, non-ligand-dependent GR activation that confers heightened glucocorticoid ligand-stimulated GR signaling. These findings raise the consideration that perturbations in this homeostatic cytokine-driven GR signaling mechanism may be responsible, at least in part, for the insensirtivity to glucocorticoid therapy that is commonly seen in individuals with severe asthma.
authors.affiliation: Division of Pulmonary Medicine, Children's Hospital of Philadelphia Research Institute, University of Pennsylvania Perlman School of Medicine, Philadelphia, Pennsylvania, United States of America.
authors.forename: Aihua
authors.initials: A
authors.lastname: Hu
authors.forename: Maureen B
authors.initials: MB
authors.lastname: Josephson
authors.forename: Barry L
authors.initials: BL
authors.lastname: Diener
authors.forename: Gustavo
authors.initials: G
authors.lastname: Nino
authors.forename: Shuyun
authors.initials: S
authors.lastname: Xu
authors.forename: Chinmay
authors.initials: C
authors.lastname: Paranjape
authors.forename: Jordan S
authors.initials: JS
authors.lastname: Orange
authors.forename: Michael M
authors.initials: MM
authors.lastname: Grunstein
mesh_terms: D001249:Asthma / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008024:Ligands; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D021381:Protein Transport / Q000187:drug effects; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*; D012137:Respiratory System / Q000187:drug effects* / Q000378:metabolism*; D020218:Response Elements; D015398:Signal Transduction / Q000187:drug effects*; D015533:Transcriptional Activation
chemical_list: D016207:Cytokines; D008024:Ligands; D011965:Receptors, Glucocorticoid; D020928:Mitogen-Activated Protein Kinases