Previous studies in our laboratory suggest that an acute inhibition of glycogen synthase kinase 3 (GSK3) by SB-216763 (SB21) is cardioprotective when administered just before reperfusion. However, it is unknown whether the GSK inhibitor SB21 administered 24 h before ischemia is cardioprotective and whether the mechanism involves ATP-sensitive potassium (K(ATP)) channels and the mitochondrial permeability transition pore (MPTP). Male Sprague-Dawley rats were administered the GSK inhibitor SB21 (0.6 mg/kg) or vehicle 24 h before ischemia. Subsequently, the rats were acutely anesthetized with Inactin and underwent 30 min of ischemia and 2 h of reperfusion followed by infarct size determination. Subsets of rats received either the sarcolemmal K(ATP) channel blocker HMR-1098 (6 mg/kg), the mitochondrial K(ATP) channel blocker 5-hydroxydecanoic acid (5-HD; 10 mg/kg), or the MPTP opener atractyloside (5 mg/kg) either 5 min before SB21 administration or 5 min before reperfusion 24 h later. The infarct size was reduced in SB21 compared with vehicle (44 +/- 2% vs. 61 +/- 2%, respectively; P < 0.01). 5-HD administered either before SB21 treatment or 5 min before reperfusion the following day abrogated SB21-induced protection (54 +/- 4% and 61 +/- 2%, respectively). HMR-1098 did not affect the SB21-induced infarct size reduction when administered before the SB21 treatment (43 +/- 1%); however, HMR-1098 partially abrogated the SB21-induced infarct size reduction when administered just before reperfusion 24 h later (52 +/- 1%). The MPTP opening either before SB21 administration or 5 min before reperfusion abrogated the infarct size reduction produced by SB21 (61 +/- 2% and 62 +/- 2%, respectively). Hence, GSK inhibition reduces infarct size when given 24 h before the administration via the opening K(ATP) channels and MPTP closure.
"Pre-and post-conditioning, must therefore function either by reducing calcium concentrations in the cells   , limiting over-production or accumulation of ROS or increasing the mPTP threshold  . In fact it has been shown that pharmacological opening of mPTP with atractyloside prevents preconditioning   , whilst preventing this opening with cyclosporin A (CsA) induces preconditioning in rabbit hearts . The latter prevents the binding of Cyclophilin D , whilst the former is a direct inhibitor of the adenine nucleotide transporter (ANT) . "
"In normotensive animals, except for some studies [14, 15], most of the research supports the notion that phosphorylation at Ser9/inhibition of GSK-3β is required for the cardioprotection mediated by PRE and POS [16, 17]. Protein kinases, including PI3-kinase, Akt, protein kinase A, protein kinase C, and integrin-linked kinase are implicated in Ser9 phosphorylation and inactivation of GSK-3β . "
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to examine the effects of GSK-3 β inhibitors compared with PRE and POS in spontaneously hypertensive rats (SHR). Isolated hearts were submitted to the following protocols: IC: 45 min global ischemia (GI) and 1-hour reperfusion (R); PRE: a cycle of 5 min GI and 10 minutes of R prior to 45 min GI; POS: three cycles of 30 sec GI/30 sec R at the start of R. Other hearts received lithium chloride (LiCl) or indirubin-3'-monoxime,5-iodo-(IMI) as GSK-3 β inhibitors. All interventions reduced the infarct size observed in IC group. The expressions of P-GSK-3 β and P-Akt decreased in IC and were restored after PRE, POS, and GSK-3 β inhibitors treatments. An increase of cytosolic MnSOD activity and lipid peroxidation and a decrease of GSH content observed in IC hearts were attenuated in PRE, POS, and LiCl or IMI treatments. An increase of P-GSK-3 β /VDAC physical association and a partial recovery of mitochondrial permeability were also detected after interventions. These data show that, in SHR hearts, GSK-3 β inhibitors mimic the cardioprotection afforded by PRE and POS and suggest that a decrease in mitochondrial permeability mediated by P-GSK-3 β /VDAC interaction is a crucial event.
"Several recent studies have linked the protein kinase C epsilon (PKCε), which translocation to mitochondria seems important for pre-conditioning , to mitoK ATP channel opening. Other kinases have also been involved  . "
[Show abstract][Hide abstract] ABSTRACT: Myocardial ischemia-reperfusion injury is a major cause of morbidity and mortality in developed countries. To date, the only treatment of complete ischemia is to restore blood flow; thus the search for new cardioprotective approaches is absolutely necessary to reduce the mortality associated with myocardial ischemia. Ischemia has long been considered to result in necrotic tissue damage but the reduction in oxygen supply can also lead to apoptosis. Therefore, in the last few years, mitochondria have become the subject of growing interest in myocardial ischemia-reperfusion since they are strongly involved in the regulation of the apoptotic process. Indeed, during ischemia-reperfusion, pathological signals converge in the mitochondria to induce permeabilization of the mitochondrial membrane. Two classes of mechanisms, which are not mutually exclusive, emerged to explain mitochondrial membrane permeabilization. The first occurs via a non-specific channel known as the mitochondrial permeability transition pore (mPTP) in the inner and the outer membranes causing disruption of the impermeability of the inner membrane, and ultimately complete inhibition of mitochondrial function. The second mechanism, involving only the outer membrane, induces the release of cell death effectors. Thus, drugs able to block or to limit mitochondrial membrane permeabilization may be cytoprotective during ischemia-reperfusion. The objective of this review is to examine the pharmacological strategies capable of inhibiting mitochondrial membrane permeabilization induced by myocardial ischemia-reperfusion.
Current Medicinal Chemistry 11/2009; 16(33). DOI:10.2174/092986709789712871 · 3.85 Impact Factor
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