title: Pivotal role of NOX-2-containing NADPH oxidase in early ischemic preconditioning.
abstract: Reactive oxygen species (ROS)-mediated signaling is implicated in early ischemic preconditioning (PC). A NOX-2-containing NADPH oxidase is a recognized major source of ROS in cardiac myocytes, whose activity is augmented by preconditioning mimetics, such as angiotensin II. We hypothesized that this oxidase is an essential source of ROS in PC. Hearts from wild-type (WT) and NOX-2 knockout (KO) mice were Langendorff perfused and subjected to 35 min ischemia/reperfusion with or without preceding PC or drug treatment. Infarct size was measured by triphenyl tetrazolium chloride staining, and NADPH oxidase activity by lucigenin chemiluminescence. PC significantly attenuated infarct size in WT (26+/-2% vs. control, 38+/-2%, P<0.05) yet was ineffective in KO hearts (33+/-3% vs. control, 34+/-3%). Concomitantly, PC significantly increased NADPH oxidase activity in WT (+41+/-13%; P<0.05), but not in KO (-5+/-18%, P=NS). The ROS scavenger MPG (N-2-mercaptopropionyl glycine, 300 micromol/L) abrogated PC in WT (39+/-2% vs. control, 33+/-1%). CCPA (2-chloro N6 cyclopentyl adenosine, 200 nmol/L), a putative ROS-independent PC trigger, significantly attenuated infarct size in WT, MPG-treated WT and KO hearts (24+/-2, 23+/-1, and 20+/-3%, respectively, P<0.05). Furthermore, CCPA did not augment NADPH oxidase activity over control (+22+/-11%, P=NS). Inhibition of protein kinase C (PKC) with chelerythrine (CHE, 2 micromol/L) completely abrogated both PC (38+/-2% vs. CHE alone, 35+/-2%) and associated increases in oxidase activity (+3+/-10%, P=NS). PKC-dependent activation of a NOX-2-containing NADPH oxidase is pivotally involved in early ischemic PC. However, adenosine receptor activation can trigger a ROS and NOX-2 independent PC pathway.
authors.affiliation: King's College London, Cardiac Physiology, Cardiovascular Division, The Rayne Institute, St. Thomas' Hospital, London. SE1 7EH, UK. Robert.m.bell@kcl.ac.uk
authors.forename: Robert M
authors.initials: RM
authors.lastname: Bell
authors.forename: Alison C
authors.initials: AC
authors.lastname: Cave
authors.forename: Sofian
authors.initials: S
authors.lastname: Johar
authors.forename: David J
authors.initials: DJ
authors.lastname: Hearse
authors.forename: Ajay M
authors.initials: AM
authors.lastname: Shah
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shattock
mesh_terms: D000166:Acridines / Q000737:chemistry; D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D004396:Coloring Agents / Q000494:pharmacology; D006321:Heart / Q000502:physiology; D007511:Ischemia / Q000473:pathology; D019157:Ischemic Preconditioning, Myocardial; D049449:Luminescence; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009203:Myocardial Infarction / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology; D032383:Myocytes, Cardiac / Q000378:metabolism; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D017382:Reactive Oxygen Species; D043682:Receptor, Adenosine A1 / Q000378:metabolism; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D015427:Reperfusion Injury; D013778:Tetrazolium Salts / Q000494:pharmacology; D008625:Tiopronin / Q000494:pharmacology
chemical_list: D000166:Acridines; D000470:Alkaloids; D053119:Benzophenanthridines; D004396:Coloring Agents; D008562:Membrane Glycoproteins; D010617:Phenanthridines; D017382:Reactive Oxygen Species; D043682:Receptor, Adenosine A1; D018047:Receptors, Purinergic P1; D013778:Tetrazolium Salts; C033472:10,10'-dimethyl-9,9'-biacridinium; C009591:triphenyltetrazolium; D008625:Tiopronin; C016299:chelerythrine; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D011493:Protein Kinase C