title: Induction of regulator of G-protein signaling 2 expression by long-acting β2-adrenoceptor agonists and glucocorticoids in human airway epithelial cells.
abstract: In asthma and chronic obstructive pulmonary disease (COPD) multiple mediators act on Gαq-linked G-protein-coupled receptors (GPCRs) to cause bronchoconstriction. However, acting on the airway epithelium, such mediators may also elicit inflammatory responses. In human bronchial epithelial BEAS-2B cells (bronchial epithelium + adenovirus 12-SV40 hybrid), regulator of G-protein signaling (RGS) 2 mRNA and protein were synergistically induced in response to combinations of long-acting β2-adrenoceptor agonist (LABA) (salmeterol, formoterol) plus glucocorticoid (dexamethasone, fluticasone propionate, budesonide). Equivalent responses occurred in primary human bronchial epithelial cells. Concentrations of glucocorticoid plus LABA required to induce RGS2 expression in BEAS-2B cells were consistent with the levels achieved therapeutically in the lungs. As RGS2 is a GTPase-activating protein that switches off Gαq, intracellular free calcium ([Ca(2+)]i) flux was used as a surrogate of responses induced by histamine, methacholine, and the thromboxane receptor agonist U46619 [(Z)-7-[(1S,4R,5R,6S)-5-[(E,3S)-3-hydroxyoct-1-enyl]-3-oxabicyclo[2.2.1]heptan-6-yl]hept-5-enoic acid]. This was significantly attenuated by salmeterol plus dexamethasone pretreatment, or RGS2 overexpression, and the protective effect of salmeterol plus dexamethasone was abolished by RGS2 RNA silencing. Although methacholine and U46619 induced interleukin-8 (IL-8) release and this was inhibited by RGS2 overexpression, the repression of U46619-induced IL-8 release by salmeterol plus dexamethasone was unaffected by RGS2 knockdown. Given a role for Gαq-mediated pathways in inducing IL-8 release, we propose that RGS2 acts redundantly with other effector processes to repress IL-8 expression. Thus, RGS2 expression is a novel effector mechanism in the airway epithelium that is induced by glucocorticoid/LABA combinations. This could contribute to the efficacy of glucocorticoid/LABA combinations in asthma and COPD.
authors.affiliation: Airways Inflammation Research Group, Snyder Institute for Chronic Diseases, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada (N.S.H., T.G., C.F.R., A.C., S.S., M.K., R.L., M.A.G., R.N.); GlaxoSmithKline Research and Development, Uxbridge, Middlesex, United Kingdom (M.J.); and Department of Physiology and Pharmacology, School of Medicine, West Virginia University, Morgantown, West Virginia (D.P.S.).
authors.forename: Neil S
authors.initials: NS
authors.lastname: Holden
authors.forename: Tresa
authors.initials: T
authors.lastname: George
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Rider
authors.forename: Ambika
authors.initials: A
authors.lastname: Chandrasekhar
authors.forename: Suharsh
authors.initials: S
authors.lastname: Shah
authors.forename: Manminder
authors.initials: M
authors.lastname: Kaur
authors.forename: Malcolm
authors.initials: M
authors.lastname: Johnson
authors.forename: David P
authors.initials: DP
authors.lastname: Siderovski
authors.forename: Richard
authors.initials: R
authors.lastname: Leigh
authors.forename: Mark A
authors.initials: MA
authors.lastname: Giembycz
authors.forename: Robert
authors.initials: R
authors.lastname: Newton
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists / Q000008:administration & dosage*; D004338:Drug Combinations; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D005938:Glucocorticoids / Q000008:administration & dosage*; D006801:Humans; D020710:RGS Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D004338:Drug Combinations; D005938:Glucocorticoids; D020710:RGS Proteins; C087182:RGS2 protein, human