Reactive oxygen species trigger ischemic and pharmacological postconditioning: In vivo and in vitro characterization

Abstract

Reactive oxygen species (ROS) generated by ischemic and pharmacological preconditioning are known to act as triggers of cardiac protection; however, the involvement of ROS in ischemic and pharmacological postconditioning (PostC) in vivo and in vitro is unknown. We tested the hypothesis that ROS are involved in PostC in the mouse heart in vivo and in the isolated adult cardiac myocyte (ACM). Mice were subjected to 30 min coronary artery occlusion followed by 2 h of reperfusion with or without ischemic or pharmacologic PostC (three cycles of 20 s reperfusion/ischemia; 1.4% isoflurane; 10 mg/kg SNC-121). Additional groups were treated with 2-mercaptopropionyl glycine (MPG), a ROS scavenger, 10 min before or after the PostC stimuli. Ischemia-, isoflurane-, and SNC-121- induced PostC reduced infarct size (24.1+/-3.2, 15.7+/-2.6, 24.9+/-2.6%, p<0.05, respectively) compared to the control group (43.4+/-3.3%). These cardiac protective effects were abolished by MPG when administered before (40.0+/-3.6, 39.3+/-3.1, 38.5+/-1.6%, respectively), but not after the PostC stimuli (26.6+/-2.3, 17.0+/-2.2, 23.9+/-1.7%, respectively). Additionally, ACM were subjected to a simulated ischemia/reperfusion protocol with isoflurane and SNC PostC. Isoflurane- and SNC-induced PostC in vitro were abolished by prior treatment with MPG. These data indicate that ROS signaling is an essential trigger of ischemic and pharmacological PostC and this is occurring at the level of the cardiac myocyte.

Post-ischemic early acidosis in cardiac postconditioning modifies the activity of antioxidant enzymes, reduces nitration, and favors protein S-nitrosylation

“…This supports the idea that the delayed recovery of intracellular pH during initial reperfusion, is mandatory to limit infarct size in PostC mainly via prevention of mPTP opening and prevention of RIRR [8,9,17,29,30,34,55]. Both in vitro and in vivo studies demonstrated that large spectrum ROSscavengers such as N-acetyl-L-cysteine (NAC) and/or N-(2-mercaptopropionyl)-glycine (MPG) given either during the PostC maneuvers [8,51,54,63] or during AB infusion [8,9,10,13] prevented their protective effects [13,51,54,63]. Moreover, addition of alkaline buffer in early reperfusion abolishes both AB-and PostC-protection [8,9,17,29,55].…”

“…Moreover, we have studied these redox effects in the isolated hearts and could not predict whether the effects can be replicated in vivo. Nevertheless, we have shown a redox signaling in PostC in isolated heart [54] and this observation has been confirmed in vivo in different laboratories [8,9,63]. Also these new results need to be confirmed in vivo.…”

“…These data indicate that specific antioxidant enzymes (SOD or CAT) can or cannot abrogate PostC-triggering. However, large spectrum antioxidants (NAC or MPG) abolish both preconditioning and PostC protection in several settings [8][9][10]13,22,38,51,54,63]. Although the infused enzymes do not easily enter into the cells, enough SOD enters, at least into endothelial cells, to perturb the redox-environment created by PostC (i.e., SOD down-regulation), thus blocking protection.…”

“…Indeed, persistence of acidosis is important for non-enzymatic NO • production [59,69]. So that ROS in concert with NO • and reactive nitrogen species (RNS) may put the heart into a protected state [26,38,46,[49][50][51][52]63].…”

“…Since ROS-scavengers (NAC or MPG) abolished AB-and PostC-induced protection [8,9,51,54,63], it is likely that the type, the concentration, and/or the compartmentalization of ROS/RNS may play a pivotal role in triggering protection at early reperfusion time. To shed some light on this scenario, we studied antioxidant-enzymes, nitration and S-nitrosylation of proteins.…”