Mechanism of cytokine-induced modulation of beta-adrenoceptor responsiveness in airway smooth muscle.
To elucidate the role of specific proinflammatory cytokines in regulating airway responsiveness, we examined the effects and mechanisms of action of IL-1beta, TNF-alpha, and IL-2 on the beta-adrenoceptor- and postreceptor-coupled transmembrane signaling mechanisms regulating relaxation in isolated rabbit tracheal smooth muscle (TSM) segments. During half-maximal isometric contraction of the tissues with acetylcholine, relaxation responses to isoproterenol, PGE2, and forskolin were separately compared in control (untreated) TSM and tissues incubated for 18 h with IL-1beta (10 ng/ml), TNF-(alpha (100 ng/ml), or IL-2 (200 ng/ml). Relative to controls, IL-1beta- and TNF-alpha-treated TSM, but not IL-2-treated tissues, depicted significant attenuation of their maximal relaxation and sensitivity (i.e., -log dose producing 50% maximal relaxation) to isoproterenol (P < 0.001) and PGE2 (P < 0.05); whereas the relaxation responses to direct stimulation of adenylate cyclase with forskolin were similar in the control and cytokine-treated tissues. Further, the attenuated relaxation to isoproterenol and PGE2 was ablated in the IL-1beta-treated TSM that were pretreated with either the muscarinic M2-receptor antagonist, methoctramine (10(-6) M), or pertussis toxin (100 ng/ml). Moreover, Western immunoblot analysis demonstrated that: (a) Gi protein expression was significantly enhanced in membrane fractions isolated from IL-1beta-treated TSM; and (b) the latter was largely attributed to induced enhanced expression of the Gi alpha2 and Gi alpha3 subunits. Collectively, these observations provide new evidence demonstrating that IL-lbeta and TNF-alpha induce impaired receptor-coupled airway relaxation in naive TSM, and that the latter effect is associated with increased muscarinic M2-receptor/Gi protein-coupled expression and function.
Hakonarson
H
H
Division of Pulmonary Medicine, Joseph Stokes, Jr. Research Institute, The Children's Hospital of Philadelphia, Pennsylvania 19104, USA.
Herrick
D J
DJ
Serrano
P G
PG
Grunstein
M M
MM
D000109:Acetylcholine / Q000494:pharmacology; D037361:Adenylate Cyclase Toxin; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D016207:Cytokines / Q000494:pharmacology*; D003959:Diamines / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000096:biosynthesis; D015870:Gene Expression / Q000187:drug effects; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D010276:Parasympatholytics / Q000494:pharmacology; D037342:Pertussis Toxin; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction; D014132:Trachea / Q000187:drug effects / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D016207:Cytokines; D003959:Diamines; D007375:Interleukin-1; D007376:Interleukin-2; D010276:Parasympatholytics; D011943:Receptors, Adrenergic, beta; D014409:Tumor Necrosis Factor-alpha; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D015232:Dinoprostone; D007545:Isoproterenol; D000109:Acetylcholine; C054938:methoctramine