Myocardial Reperfusion Injury: Reactive Oxygen Species vs. NHE-1 Reactivation

Abstract

Background/Aims: Flow restoration to ischemic myocardium reduces infarct size (IS), but it also promotes reperfusion injury. A burst of reactive oxygen species (ROS) and/or NHE-1 reactivation were proposed to explain this injury. Our study was aimed to shed light on this unresolved issue. Methods: Regional infarction (40 min-ischemia/2 hs-reperfusion) was induced in isolated and perfused rat hearts. Maximal doses of N-(2-mercaptopropionyl)-glycine (MPG 2mmol/L, ROS scavenger), cariporide (10µmol/L, NHE-1 inhibitor), or sildenafil (1µmol/L, phosphodiesterase5A inhibitor) were applied at reperfusion onset. Their effects on IS, myocardial concentration of thiobarbituric acid reactive substances (TBARS), ERK1/2, p90^RSK, and NHE-1 phosphorylation were analyzed. Results: All treatments decreased IS ∼ 50% vs. control. No further protection was obtained by combining cariporide or MPG with sildenafil. Myocardial TBARS increased after infarction and were decreased by MPG or cariporide, but unaffected by sildenafil. In line with the fact that ROS induce MAPK-mediated NHE-1 activation, myocardial infarction increased ERK1/2, p90^RSK, and NHE-1 phosphorylation. MPG and cariporide cancelled these effects. Sildenafil did not reduce the phosphorylated ERK1/2-p90^RSK levels but blunted NHE-1 phosphorylation suggesting a direct dephosphorylating action. Conclusions: 1) Reperfusion injury would result from ROS-triggered MAPK-mediated NHE-1 phosphorylation (and reactivation) during reperfusion; 2) sildenafil protects the myocardium by favouring NHE-1 dephosphorylation and bypassing ROS generation.

Mitochondrial KATP channels participate in the limitation of infarct size by cariporide

“…A significant reduction in IS was obtained when 10 μM C was added to the perfusate during the first 20 min of reperfusion (Fig. 2), a result in accordance with previous reports by our and other laboratories (Fantinelli et al 2006;Garciarena et al 2011;An et al 2001;Hurtado and Pierce 2000;Xiao and Allen 2000). To determine the participation of mitoK ATP channels and PKC in the cardioprotective action of C, we next explored whether 5-HD or Chele could affect IS when co-administered with C. As shown in Fig.…”

“…However, when NHE-1 inhibition was performed during reperfusion, the results were contradictory (Gumina et al 1998;Klein et al 2000;An et al 2001;Hurtado and Pierce 2000;Xiao and Allen 2000). In previous papers, we demonstrated that administration of cariporide only at reperfusion significantly diminished IS (Fantinelli et al 2006;Garciarena et al 2011). On the other hand, many studies have shown that during reperfusion an opening of the mitochondrial permeability transition pore (mPTP) takes place (Halestrap et al 1998;Crompton 1999;Lesnefsky et al 2001;Green and Kroemer 2004).…”

“…In this regard, we recently demonstrated that C treatment applied only at reperfusion is able to diminish IS and improve postischemic cardiac recovery by decreasing ROS formation (Fantinelli et al 2006;Garciarena et al 2011), but the exact mechanism by which this compound blunted ROS formation was not described at that time. It is important to remember that the NHE-1 plays an important role in maintaining intracellular pH being at the same time one of the most important routes of Na + entry into the cell (Lazdunski et al 1985), therefore indirectly controlling cytosolic Ca 2+ homeostasis.…”

Role of licochalcone C in cardioprotection against ischemia/reperfusion injury of isolated rat heart via antioxidant, anti-inflammatory, and anti-apoptotic activities

“…During reperfusion, excessive ROS are generated by myocardial cell mitochondria and xanthine oxidase pathways, which are beyond the endogenous capability of cells [17]. The mechanism of ROS-induced myocardial injury is as follows: excessive ROS attack lipids and change the fluidity and permeability of the membrane; MDA is produced by lipid peroxidation; myocardial enzymes are released; structural proteins are attacked; and cell structures are destroyed [18]. Under normal conditions, ROS concentration can be reduced by antioxidant systems, including antioxidant enzymes such as SOD and antioxidant molecules such as GSH.…”

Cardioprotective Effects of Low-Dose Cyclosporin A Added to Histidine-Tryptophan-Ketoglutarate Cardioplegia Solution prior to Total Myocardial Ischemia: An in vitro Rabbit Heart Study

“…The sudden increase in intracellular reactive oxygen species (ROS) upon reperfusion has been linked to damaged components of the mitochondrial electron transport chain generating superoxide [25] . ROS are also potent activators of the MPTP, and opening of the MPTP can lead to further ROS production [23][24][25]33] . Our finding that CsA decreases the level of oxidative stress after reperfusion is consistent with blocking of the MPTP.…”