title: Adenosine inhibits lipopolysaccharide-induced cardiac expression of tumor necrosis factor-alpha.
abstract: Tumor necrosis factor-alpha (TNF-alpha) is elevated in the failing heart. Very little is known about regulation of TNF-alpha in cardiomyocytes. TNF-alpha expression by macrophages is diminished by adenosine. Therefore, we hypothesized that a similar mechanism might occur in the heart. Neonatal rat myocytes were stimulated with lipopolysaccharide (LPS), and TNF-alpha was measured by ELISA. In the absence of LPS, myocytes did not release TNF-alpha in the medium. After exposure to LPS, TNF-alpha increased to 70.1+/-3.5 pg/mL at 6 hours. Immunofluorescent staining confirmed that TNF-alpha was expressed in myocytes. Adenosine decreased TNF-alpha in a dose-dependent manner (1 to 100 micromol/L, 37% to 65% decrease, P<.01). Adenosine also decreased TNF-alpha in cell homogenates by 78% (P<.0001). The effect of adenosine could be replicated by the A2 agonist PD-125944 (DPMA), by cAMP agonists 8-bromo-cAMP, forskolin, and Ro 20-1724, but not by A1 and A3 agonists. Conversely, the effect of adenosine could be suppressed by the adenylate cyclase inhibitor MDL-12,330. Adenosine also inhibited TNF-alpha in adult rat ventricular myocytes (-60%, P<.005) and rat papillary muscles (-55%, P<.05). In neonatal myocytes, adenosine normalized LPS-induced calcium changes and improved LPS-induced negative inotropic (P<.01) and negative lusitropic (P<.01) effects. Our results demonstrate that adenosine can significantly diminish TNF-alpha levels in the heart. The effect appears to be mediated by the A2 receptor and transduced through a G protein-adenylyl cyclase pathway. These results may explain some cardioprotective effects of adenosine and provide a novel pharmacological intervention in congestive heart failure.
authors.affiliation: Division of Cardiology, University of Pittsburgh Medical Center, PA 15213, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Wagner
authors.forename: A
authors.initials: A
authors.lastname: Combes
authors.forename: C
authors.initials: C
authors.lastname: McTiernan
authors.forename: V J
authors.initials: VJ
authors.lastname: Sanders
authors.forename: B
authors.initials: B
authors.lastname: Lemster
authors.forename: A M
authors.initials: AM
authors.lastname: Feldman
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002317:Cardiovascular Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002478:Cells, Cultured; D003600:Cytosol / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D004176:Dipyridamole / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010210:Papillary Muscles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000187:drug effects
chemical_list: D002317:Cardiovascular Agents; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D010975:Platelet Aggregation Inhibitors; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D014409:Tumor Necrosis Factor-alpha; D004176:Dipyridamole; D000241:Adenosine; D002118:Calcium