TNF-alpha rapidly antagonizes the beta-adrenergic responses of the chloride current in guinea-pig ventricular myocytes.
The purpose of this study was to test the hypothesis that tumor necrosis factor-alpha (TNF-alpha) rapidly antagonizes the beta-adrenergic responses of the chloride current and to clarify the intracellular mechanisms responsible for the anti-adrenergic action. The whole-cell patch-clamp technique was used to monitor the anti-adrenergic effects of TNF-alpha on the cAMP-dependent chloride current (I(Cl)) recorded from isolated guinea-pig ventricular myocytes. Ramp pulses (+/-120 mV; dv/dt = +/-0.4 V/s) were applied from the holding potential of -40 mV. TNF-alpha rapidly (<15 min) inhibited the isoproterenol (Iso, 0.1 micromol/L)-induced I(Cl) in a concentration-dependent manner (30-1,000 U/ml, IC (50) = 144 U/ml, n=30). The inhibitory action of TNF-alpha was also observed when I(Cl) had been previously stimulated by 1 micromol/L forskolin (n=5). Prior exposure of myocytes to 5 microg/ml pertussis toxin (PTX) hardly affected the anti-adrenergic action of TNF-alpha (n=4). However, when I(Cl) was induced by both 8-bromo-cAMP (100 micromol/L) and isobutylmethylxanthine (0.1 mmol/L), TNF-alpha (1,000 U/ml) failed to decrease I(Cl) amplitude (n=5). Prior exposure of myocytes to 5 mg/ml pertussis toxin (PTX) hardly affected the anti-adrenergic action of TNF-alpha (n=4). Furthermore, despite of the presence of nitro-L-arginine methyl ester (0.1 mmol/L), a nitric oxide synthase (NOS) inhibitor, TNF-alpha reversed the Iso-induced increase in I(Cl) (n=5). These results suggest that TNF-alpha rapidly antagonizes the beta-adrenergic responses of I(Cl) by reducing cAMP concentration. This anti-adrenergic action is mediated by neither the PTX-sensitive G proteins regulatory pathway nor constitutive NOS activation.
Iino
Kenji
K
The 2nd Department of Internal Medicine, Akita University School of Medicine, Japan.
Watanabe
Hiroyuki
H
Saito
Takashi
T
Kibira
Satoshi
S
Iijima
Toshihiko
T
Miura
Mamoru
M
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D018118:Chloride Channels / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D006352:Heart Ventricles; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage / Q000494:pharmacology*
D000318:Adrenergic beta-Agonists; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D011943:Receptors, Adrenergic, beta; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D037342:Pertussis Toxin; D007545:Isoproterenol; D019331:NG-Nitroarginine Methyl Ester