title: Adenosine acts as an endogenous activator of the cellular antioxidant defense system.
abstract: Oxygen free radicals have been implicated in the pathogenesis of ischemic cell injuries. These free radicals are normally scavenged by antioxidant enzymes. Adenosine is normally released during ischemia and protects against ischemic injuries by interacting with adenosine receptors (ARs). The mechanism underlying its cytoprotective action is unclear. In this report, we provide evidence that activation of a unique A3AR in rat basophilic leukemia cells (RBL-2H3) leads to a 2 to 3 fold increase in activity of superoxide dismutase, catalase and glutathione peroxidase and also increases in the activity of glutathione reductase. Similar increases in enzyme activity were elicited in bovine and human endothelial cells, rat cardiac myocytes and smooth muscle cells. Increases in enzyme activity were attenuated by theophylline (an antagonist of the A3AR) and by pertussis toxin, implicating a role of A3AR/Gi protein in the activation. Importantly, activation of the A3AR decreased the degree of lipid peroxidation in these cells. These data provide strong evidence that the cytoprotective action of adenosine during ischemic cell injuries is mediated, at least in part, via a novel mechanism-activation of the cellular antioxidant enzymes.
authors.affiliation: Department of Pharmacology, Southern Illinois University School of Medicine, Springfield 62794.
authors.forename: S B
authors.initials: SB
authors.lastname: Maggirwar
authors.forename: D N
authors.initials: DN
authors.lastname: Dhanraj
authors.forename: S M
authors.initials: SM
authors.lastname: Somani
authors.forename: V
authors.initials: V
authors.lastname: Ramkumar
mesh_terms: D000241:Adenosine / Q000502:physiology*; D000243:Adenosine Deaminase / Q000494:pharmacology*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002374:Catalase / Q000096:biosynthesis / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology; D004790:Enzyme Induction; D005979:Glutathione Peroxidase / Q000096:biosynthesis / Q000378:metabolism*; D005980:Glutathione Reductase / Q000096:biosynthesis / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D015471:Leukemia, Basophilic, Acute; D012515:Mast-Cell Sarcoma; D009206:Myocardium / Q000201:enzymology; D037342:Pertussis Toxin; D010660:Phenylisopropyladenosine / Q000494:pharmacology*; D051381:Rats; D018047:Receptors, Purinergic P1 / Q000187:drug effects / Q000502:physiology; D013482:Superoxide Dismutase / Q000378:metabolism*; D013806:Theophylline / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D018047:Receptors, Purinergic P1; D010566:Virulence Factors, Bordetella; D010660:Phenylisopropyladenosine; D013806:Theophylline; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D037342:Pertussis Toxin; D000243:Adenosine Deaminase; D000241:Adenosine