title: Prolonged heterologous beta2-adrenoceptor desensitization promotes proasthmatic airway smooth muscle function via PKA/ERK1/2-mediated phosphodiesterase-4 induction.
abstract: Beta2-adrenergic receptor (beta2AR) agonists acutely relieve bronchoconstriction via cAMP-mediated relaxation of airway smooth muscle (ASM). Airway constrictor responsiveness may be significantly heightened, however, following protracted exposure to these agents, presumably reflecting the effects of beta2AR desensitization in ASM accompanying prolonged cAMP signaling. Because cAMP phosphodiesterase (PDE) activity can significantly modulate ASM contractility, we investigated the mechanism regulating PDE expression and its potential role in mediating changes in agonist-induced constrictor and relaxation responsiveness in ASM following its heterologous beta2AR desensitization by prolonged exposure to cAMP-elevating agents. Isolated rabbit ASM tissues and cultured human ASM cells treated for 24 h with the receptor- or nonreceptor-coupled cAMP-stimulating agent, prostaglandin E(2) (PGE(2)) or forskolin, respectively, exhibited constrictor hyperresponsiveness to acetylcholine and impaired beta2AR-mediated relaxation and cAMP accumulation. These proasthmatic-like changes in ASM function were associated with upregulated PDE4 activity, reflective of increased transcription of the PDE4D5 isoform, and were prevented by pretreatment of the ASM with a PDE4 inhibitor. Extended studies using gene silencing and pharmacological approaches to inhibit specific intracellular signaling molecules demonstrated that the mechanism underlying PGE(2)-induced transcriptional upregulation of PDE4D5 involves PKA-dependent activation of G(i) protein signaling via the betagamma-subunits, the latter eliciting downstream activation of ERK1/2 and its consequent induction of PDE4D5 transcription. Collectively, these findings identify that beta2AR desensitization in ASM following prolonged exposure to cAMP-elevating agents is associated with proasthmatic-like changes in ASM responsiveness that are mediated by upregulated PDE4 expression induced by activated cross talk between the PKA and ERK1/2 signaling pathways.
authors: The Joseph Stokes Jr. Research Institute, Division of Pulmonary Medicine, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors: Aihua
authors: A
authors: Hu
authors: Gustavo
authors: G
authors: Nino
authors: Judith S
authors: JS
authors: Grunstein
authors: Sumbul
authors: S
authors: Fatma
authors: Michael M
authors: MM
authors: Grunstein
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists; D000818:Animals; D001249:Asthma / Q000503:physiopathology; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000096:biosynthesis*; D015232:Dinoprostone / Q000502:physiology; D004790:Enzyme Induction; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009570:Nitriles / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D058988:Phosphodiesterase 4 Inhibitors; D011817:Rabbits; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D020889:Rolipram / Q000494:pharmacology; D015398:Signal Transduction; D013449:Sulfonamides / Q000494:pharmacology; D014132:Trachea / Q000502:physiology*
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D002070:Butadienes; D017362:Cyclic AMP Response Element-Binding Protein; D007546:Isoquinolines; D009570:Nitriles; D058988:Phosphodiesterase 4 Inhibitors; D043562:Receptors, G-Protein-Coupled; D013449:Sulfonamides; C113580:U 0126; D005576:Colforsin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D020889:Rolipram; D015232:Dinoprostone; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide