title: β2-Adrenoceptor agonists are required for development of the asthma phenotype in a murine model.
abstract: β(2)-Adrenoceptor (β2AR) agonists are the most effective class of bronchodilators and a mainstay of asthma management. The first potent β2AR agonist discovered and widely used in reversing the airway constriction associated with asthma exacerbation was the endogenous activator of the β2AR, epinephrine. In this study, we demonstrate that activation of the β2AR by epinephrine is paradoxically required for development of the asthma phenotype. In an antigen-driven model, mice sensitized and challenged with ovalbumin showed marked elevations in three cardinal features of the asthma phenotype: inflammatory cells in their bronchoalveolar lavage fluid, mucin over production, and airway hyperresponsiveness. However, genetic depletion of epinephrine using mice lacking the enzyme to synthesize epinephrine, phenylethanolamine N-methyltransferase, or mice that had undergone pharmacological sympathectomy with reserpine to deplete epinephrine, had complete attenuation of these three cardinal features of the asthma phenotype. Furthermore, administration of the long-acting β2AR agonist, formoterol, a drug currently used in asthma treatment, to phenylethanolamine N-methyltransferase-null mice restored the asthma phenotype. We conclude that β2AR agonist-induced activation is needed for pathogenesis of the asthma phenotype. These findings also rule out constitutive signaling by the β2AR as sufficient to drive the asthma phenotype, and may help explain why chronic administration of β2AR agonists, such as formoterol, have been associated with adverse outcomes in asthma. These data further support the hypothesis that chronic asthma management may be better served by treatment with certain "β-blockers."
authors.affiliation: Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204-5037, USA.
authors.forename: Vaidehi J
authors.initials: VJ
authors.lastname: Thanawala
authors.forename: Gloria S
authors.initials: GS
authors.lastname: Forkuo
authors.forename: Nour
authors.initials: N
authors.lastname: Al-Sawalha
authors.forename: Zoulikha
authors.initials: Z
authors.lastname: Azzegagh
authors.forename: Long P
authors.initials: LP
authors.lastname: Nguyen
authors.forename: Jason L
authors.initials: JL
authors.lastname: Eriksen
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Tuvim
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Lowder
authors.forename: Burton F
authors.initials: BF
authors.lastname: Dickey
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Knoll
authors.forename: Julia K L
authors.initials: JK
authors.lastname: Walker
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bond
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists / Q000494:pharmacology*; D000818:Animals; D001249:Asthma / Q000139:chemically induced* / Q000503:physiopathology; D001980:Bronchi / Q000503:physiopathology; D001992:Bronchoalveolar Lavage Fluid; D002851:Chromatography, High Pressure Liquid; D004195:Disease Models, Animal; D004837:Epinephrine / Q000378:metabolism; D004983:Ethanolamines / Q000494:pharmacology*; D000068759:Formoterol Fumarate; D051379:Mice; D018345:Mice, Knockout; D009077:Mucins / Q000378:metabolism; D010641:Phenotype
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D004983:Ethanolamines; D009077:Mucins; D000068759:Formoterol Fumarate; D004837:Epinephrine