TNF-alpha inhibits isoproterenol-stimulated adenylyl cyclase activity in cultured airway smooth muscle cells.
Inflammation, increased cytokine production, and decreased responsiveness of airway smooth muscle (ASM) to beta-adrenergic agonists are characteristics of asthma. We questioned whether the cytokine tumor necrosis factor-alpha (TNF-alpha) directly impaired beta-adrenergic signal transduction in cultured canine ASM cells. Confluent ASM cells exposed to TNF-alpha (0.1-10 ng/ml) for 72 h showed lower maximal levels of adenylyl cyclase activity in response to isoproterenol (10 ng/ml; 14 +/- 4.3 vs. 7.5 +/- 1.3 pmol adenosine 3',5'-cyclic monophosphate x well(-1) x 20 min(-1), control vs. treated, respectively), despite no changes in beta-adrenergic receptor numbers (maximum number of binding sites = 4.8 +/- 0.72 vs. 4.5 +/- 0.81 fmol/mg protein, control vs. treated, respectively). Adenylyl cyclase activities in response to prostaglandin E1, NaF, or forskolin were not different in treated and untreated cells. These results demonstrate that a cytokine known to be increased during exacerbation of asthmatic symptoms directly impairs beta-adrenergic function in ASM cells and suggests a mechanism by which inflammation impairs beta-adrenergic receptor signal transduction in asthma.
Emala
C W
CW
Department of Anesthesiology, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA.
Kuhl
J
J
Hungerford
C L
CL
Hirshman
C A
CA
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004285:Dogs; D019204:GTP-Binding Proteins / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D014132:Trachea / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000318:Adrenergic beta-Agonists; D014409:Tumor Necrosis Factor-alpha; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D007545:Isoproterenol