Intermittent activation of bradykinin B2 receptors and mitochondrial KATP channels trigger cardiac postconditioning through redox signaling.
OBJECTIVE
Postconditioning (PostC) maneuvers allow post-ischemic accumulation of autacoids, which trigger protection. We tested if PostC-triggering includes bradykinin (BK) B2 receptor activation and its downstream pathway.


RESULTS
Isolated rat hearts underwent 30 min ischemia and 120 min reperfusion. Infarct size was evaluated using nitro-blue tetrazolium staining. In Control hearts infarct size was 61+/-5% of risk area. PostC (5 cycles of 10 s reperfusion/ischemia) reduced infarct size to 22+/-4% (p<0.01). PostC protection was abolished by B2 BK receptor-antagonists (HOE140 or WIN64338), nitric oxide synthase-inhibitor (L-nitro-arginine-methylester), protein kinase G (PKG)-blocker (8-bromoguanosine-3',5'-cyclic-monophosphorothioate), and mitochondrial K(ATP) (mK(ATP))-blocker (5-hydroxydecanoate) each given for 3 min only. Since 3 min of BK-infusion (100 nM) did not reproduce PostC protection, protocols with Intermittent-BK infusion were used to mimic PostC: a) 5 cycles of 10 s oxygenated-no-BK/oxygenated+BK buffer; b) 5 cycles of 10 s oxygenated-no-BK/hypoxic+BK buffer. Both protocols with Intermittent-BK attenuated infarct size (36+/-5% and 38+/-4%, respectively; p<0.05 vs Control and NS vs PostC for both; NS vs each other). Intermittent-BK protection was abolished by the same antagonists used to prevent PostC protection. Intermittence of re-oxygenation only (5 cycles of 10 s oxygenated/hypoxic buffer) did not reproduce PostC. Yet, cardioprotection was triggered by intermittent mK(ATP) activation with diazoxide, but not by intermittent reactive oxygen species (ROS) generation with purine/xanthine oxidase. ROS scavengers (N-acetyl-L-cysteine or 2-mercaptopropionylglycine), given for 3 min only, abolished PostC-, Intermittent BK-and diazoxide-induced protection.


CONCLUSIONS
Intermittent targeting of specific cellular sites (i.e. BK B2 receptors and mK(ATP) channels) during early reperfusion triggers PostC protection via ROS signaling. Since neither intermittent oxygenation nor exogenous ROS generators can trigger protection, it is likely that intermittent autacoid accumulation and ROS compartmentalization may play a pivotal role in PostC-triggering.
Penna
Claudia
C
Dipartimento di Scienze Cliniche e Biologiche, dell'Università di Torino, Italy.
Mancardi
Daniele
D
Rastaldo
Raffaella
R
Losano
Gianni
G
Pagliaro
Pasquale
P
D000111:Acetylcysteine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D065094:Bradykinin B2 Receptor Antagonists; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D003652:Decanoic Acids / Q000494:pharmacology; D006880:Hydroxy Acids / Q000494:pharmacology; D008929:Mitochondria, Heart / Q000378:metabolism*; D009203:Myocardial Infarction / Q000517:prevention & control*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010084:Oxidation-Reduction; D010477:Perfusion; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D043782:Receptor, Bradykinin B2 / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
C104224:8-bromo-beta-phenylethenoguanosine 3',5'-cyclic monophosphate; D065094:Bradykinin B2 Receptor Antagonists; D003652:Decanoic Acids; D006880:Hydroxy Acids; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D017382:Reactive Oxygen Species; D043782:Receptor, Bradykinin B2; C117780:mitochondrial K(ATP) channel; D009569:Nitric Oxide; C052853:5-hydroxydecanoic acid; C065679:icatibant; D000255:Adenosine Triphosphate; D019001:Nitric Oxide Synthase; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; D001920:Bradykinin; D019331:NG-Nitroarginine Methyl Ester; D000111:Acetylcysteine