title: Adenosine and TNF-alpha exert similar inotropic effect on heart cultures, suggesting a cardioprotective mechanism against hypoxia.
abstract: When cardiomyocytes were subjected to hypoxia, tumor necrosis factor-alpha (TNF-alpha; 3-50 ng/ml) or adenosine (1-100 microM), decreased hypoxic damage as was detected by lactate dehydrogenase (LDH) release, MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) absorbance, ROS (reactive oxygen species) measurement or desmin immunostaining. This cardioprotection was not prevented in TNF-alpha-treated cultures by 5-hydroxydecanoic acid (5-HD). Our aim was to elucidate whether adenosine and TNF-alpha mediate a similar protective mechanism against hypoxia in primary heart cultures and in H9c2 cardiomyocytes. Adenosine and TNF-alpha are known for their negative inotropic effects on the heart. We have suggested that deoxyglucose uptake reflects heart contractility in cell cultures; therefore, we assayed its accumulation under various conditions. Treatment for 20 min with adenosine, R-PIA [(-)-N(6)-phenylisopropyladenosine] (10 microM), or TNF-alpha reduced (3)H-deoxyglucose uptake in primary heart cultures and also in H9c2 cardiomyocytes by 30-50%. Isoproterenol accelerated (3)H-deoxyglucose uptake by 50%. Adenosine, R-PIA, or TNF-alpha attenuated the stimulatory effect of isoproterenol on (3)H-deoxyglucose uptake to control levels. Hypoxia reduced (3)H-deoxyglucose uptake by 50%, as in the treatment of the hypoxic cultures with TNF-alpha or adenosine. Glibenclamide (2 microM), 5-HD (300 microM), or diazoxide (50 microM) increased (3)H-deoxyglucose uptake by 50-80%. Adenosine (100 microM) and TNF-alpha (50 ng/ml) stimulated (86)Rb efflux. Glibenclamide attenuated this effect. We demonstrate that TNF-alpha, like adenosine, accelerated Ca(2+) uptake into the sarcoplasmic reticulum (SR) by 50-100% and therefore prevented cardiomyocyte Ca(2+) overload. Our findings further suggest that TNF-alpha, as well as adenosine, may mediate an adaptive effect in the heart by preventing Ca(2+) overload via activation of SR Ca-ATPase (SERCA(2)a).
authors.affiliation: The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
authors.forename: Dalia
authors.initials: D
authors.lastname: El-Ani
authors.forename: Reuven
authors.initials: R
authors.lastname: Zimlichman
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Mashiach
authors.forename: Asher
authors.initials: A
authors.lastname: Shainberg
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D003847:Deoxyglucose / Q000378:metabolism; D003981:Diazoxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004347:Drug Interactions; D005905:Glyburide / Q000494:pharmacology; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D018696:Neuroprotective Agents / Q000494:pharmacology; D051381:Rats; D012414:Rubidium Radioisotopes / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D000889:Anti-Arrhythmia Agents; D004338:Drug Combinations; D018696:Neuroprotective Agents; D012414:Rubidium Radioisotopes; D014409:Tumor Necrosis Factor-alpha; C047235:N-(1-methyl-2-phenylethyl)adenosine; D003847:Deoxyglucose; D000241:Adenosine; D007545:Isoproterenol; D003981:Diazoxide; D005905:Glyburide