beta-adrenergic stimulation of rat cardiac fibroblasts enhances induction of nitric-oxide synthase by interleukin-1beta via message stabilization.
We have investigated factors modulating expression of inducible NO synthase (iNOS) in isolated adult rat cardiac fibroblasts. Treatment of cardiac fibroblasts with interleukin-1beta (IL-1beta) promotes induction of iNOS mRNA and protein and production of NO. Simultaneous incubation of cells with isoproterenol enhances the response to IL-1beta, even though isoproterenol alone is without effect. N(G)-nitro-L-arginine methyl ester inhibits the effect of isoproterenol + IL-1beta on NO production. beta(2)-Adrenergic receptors appear to mediate this effect of isoproterenol. Reverse transcriptase-polymerase chain reaction analyses show that beta(2)-receptor mRNA is the predominant beta-receptor message; in pharmacologic studies, ICI-118,551 significantly antagonizes isoproterenol-stimulated cyclic AMP production whereas CGP20712A does not. Dibutyryl-cyclic AMP and forskolin mimic the synergistic effect of isoproterenol on IL-1beta-induced NO production; H-89, a cyclic AMP-dependent protein kinase (PKA) inhibitor, antagonizes the enhancing effect of isoproterenol. Nuclear run-off experiments indicate that enhancement of iNOS by isoproterenol does not occur at the level of transcription. Message stability studies demonstrate that isoproterenol increases the half-life of iNOS mRNA from 1.0 to 1.9 h; this change is sufficient to account for the observed augmentation of iNOS mRNA and protein. Thus, cardiac fibroblasts produce significant amounts of NO in response to IL-1beta via induction of iNOS; beta-adrenergic stimulation enhances the IL-1beta effect by stabilizing the iNOS message. These data suggest that cardiac fibroblasts could participate in a paracrine mechanism whereby the direct positive inotropic effect of beta(1)-adrenergic stimulation of myocytes is opposed by beta(2)-adrenergic enhancement of NO production, a negative inotropic event, in neighboring fibroblasts.
Gustafsson
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AB
Biomedical Sciences Graduate Program, Departments of Pharmacology and Medicine, University of California at San Diego, La Jolla, California 92093-0636, USA. agustafsson@ucsd.edu
Brunton
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LL
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D004790:Enzyme Induction; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D006207:Half-Life; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000378:metabolism* / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D007375:Interleukin-1; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D007545:Isoproterenol