title: Post-conditioning induced cardioprotection requires signaling through a redox-sensitive mechanism, mitochondrial ATP-sensitive K+ channel and protein kinase C activation.
abstract: 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.
authors.affiliation: Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Ospedale S. Luigi, Regione Gonzole, 10043, Orbassano, TO, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Penna
authors.forename: Raffaella
authors.initials: R
authors.lastname: Rastaldo
authors.forename: Daniele
authors.initials: D
authors.lastname: Mancardi
authors.forename: Stefania
authors.initials: S
authors.lastname: Raimondo
authors.forename: Sandra
authors.initials: S
authors.lastname: Cappello
authors.forename: Donatella
authors.initials: D
authors.lastname: Gattullo
authors.forename: Gianni
authors.initials: G
authors.lastname: Losano
authors.forename: Pasquale
authors.initials: P
authors.lastname: Pagliaro
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D017202:Myocardial Ischemia / Q000503:physiopathology*; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D009924:Organ Culture Techniques; D010084:Oxidation-Reduction; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D016166:Free Radical Scavengers; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D011493:Protein Kinase C