title: Peripheral benzodiazepine receptor-induced myocardial protection is mediated by inhibition of mitochondrial membrane permeabilization.
abstract: Opening of the permeability transition pore (PTP) is a key event in ischemia-reperfusion injury and several ligands of the peripheral benzodiazepine receptor (PBR), a mitochondrial outer membrane protein possibly associated with PTP, have been demonstrated as potent cardioprotective agents. Here, we investigated the mechanisms by which the specific PBR ligand 4'-chlorodiazepam (CDZ) protected the myocardium against ischemia-reperfusion. In either global or regional models of myocardial ischemia-reperfusion in rats, CDZ reduced infarct size in a dose-dependent manner (e.g., 11 +/- 1% of the area at risk at 10 mg/kg versus 31 +/- 3% in control; p < 0.05) and to a similar extent as ischemic or diazoxide-induced preconditioning. CDZ (10 mg/kg) reduced apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labeling staining), restored mitochondrial recovery, improved oxidative phosphorylation parameters, and reduced mitochondrial membrane permeabilization with inhibition of cytochrome c and apoptosis-inducing factor releases. CDZ increased the resistance of mitochondria to Ca2+-induced PTP opening. All these cardioprotective effects of CDZ were associated with an improved stabilization of the association of Bcl-2 with the mitochondrial membrane and inhibition of the association of a cytosolic fragment of Bax, occurring during ischemia-reperfusion, with the outer mitochondrial membrane. In addition, the PTP opener atractyloside (20 microM) and the Bcl-2 inhibitor ethyl-2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate (HA14-1) (20 microM) abrogated CDZ-induced reduction of infarct size. These results demonstrate that PBR occupancy by CDZ renders the heart more resistant to ischemia-reperfusion injury by limiting mitochondrial membrane permeabilization. This is due to a reorganization of the balance between pro- and antiapoptotic proteins of the Bcl-2 family proteins at the level of mitochondrial membranes.
authors.affiliation: INSERM U841, équipe 3, Facultéde Médecine de Paris XII, 8 rue du Général Sarrail, F-94010, Créteil, France.
authors.forename: Fatou Nsoure
authors.initials: FN
authors.lastname: Obame
authors.forename: Roland
authors.initials: R
authors.lastname: Zini
authors.forename: Rachid
authors.initials: R
authors.lastname: Souktani
authors.forename: Alain
authors.initials: A
authors.lastname: Berdeaux
authors.forename: Didier
authors.initials: D
authors.lastname: Morin
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001570:Benzodiazepinones / Q000494:pharmacology / Q000627:therapeutic use; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008024:Ligands; D008929:Mitochondria, Heart / Q000378:metabolism / Q000473:pathology; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D009203:Myocardial Infarction / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D010101:Oxygen Consumption / Q000187:drug effects; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism*
chemical_list: D001570:Benzodiazepinones; D002352:Carrier Proteins; D008024:Ligands; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D011963:Receptors, GABA-A; C069997:Tspo protein, rat; C028513:4'-chlorodiazepam