Post-conditioning induced cardioprotection requires signaling through a redox-sensitive mechanism, mitochondrial ATP-sensitive K+ channel and protein kinase C activation

• Published in: Basic research in cardiology 2006-03, Vol.101 (2), p.180-189
• Main Authors: Penna, Claudia, Rastaldo, Raffaella, Mancardi, Daniele, Raimondo, Stefania, Cappello, Sandra, Gattullo, Donatella, Losano, Gianni, Pagliaro, Pasquale
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Enzyme Activation - drug effects; Enzyme Activation - physiology; Free Radical Scavengers - pharmacology; Heart - drug effects; Heart - physiopathology; Male; Mitochondria - metabolism; Myocardial Ischemia - physiopathology; Myocardial Reperfusion Injury - prevention & control; Myocardium - pathology; Organ Culture Techniques; Oxidation-Reduction; Potassium Channel Blockers - pharmacology; Potassium Channels - metabolism; Protein Kinase C - metabolism; Protein Kinase Inhibitors - pharmacology; Rats; Reactive Oxygen Species - metabolism; Signal Transduction - drug effects; Signal Transduction - physiology
• ISSN: 0300-8428; 1435-1803
• DOI: 10.1007/s00395-006-0584-5

Post-conditioning (Post-C) induced cardioprotection involves activation of guanylyl-cyclase. In the ischemic preconditioning scenario, the downstream targets of cGMP include mitochondrial ATP-sensitive K(+) (mK(ATP)) channels and protein kinase C (PKC), which involve reactive oxygen species (ROS) production. This study tests the hypothesis that mK(ATP), PKC and ROS are also involved in the Post-C protection. Isolated rat hearts underwent 30 min global ischemia (I) and 120 min reperfusion (R) with or without Post-C (i.e., 5 cycles of 10 s R/I immediately after the 30 min ischemia). In 6 groups (3 with and 3 without Post-C) either mK(ATP) channel blocker, 5- hydroxydecanoate (5-HD), or PKC inhibitor, chelerythrine (CHE) or ROS scavenger, N-acetyl-cysteine (NAC), were given during the entire reperfusion (120 min). In other 6 groups (3 with and 3 without Post-C), 5-HD, CHE or NAC were infused for 117 min only starting after 3 min of reperfusion not to interfere with the early effects of Post-C and/or reperfusion. In an additional group NAC was given during Post-C maneuvers (i.e., 3 min only). Myocardial damage was evaluated using nitro-blue tetrazolium staining and lactate dehydrogenase (LDH) release. Post-C attenuated myocardial infarct size (21 +/- 3% vs. 64 +/- 5% in control; p < 0.01). Such an effect was abolished by 5-HD or CHE given during either the 120 or 117 min of reperfusion as well as by NAC given during the 120 min or the initial 3 min of reperfusion. However, delayed NAC (i.e., 117 min infusion) did not alter the protective effect of Post- C (infarct size 32 +/- 5%; p < 0.01 vs. control, NS vs. Post-C). CHE, 5-HD or NAC given in the absence of Post-C did not alter the effects of I/R. Similar results were obtained in terms of LDH release. Our data show that Post-C induced protection involves an early redox-sensitive mechanism as well as a persistent activation of mK(ATP) and PKC, suggesting that the mK(ATP)/ROS/PKC pathway is involved in post-conditioning.