Permeabilité membranaire mitochondriale et protection du myocarde lors de l'ischemie-reperfusion experimentale

• Auteur / Autrice : Fatou Nsoure Obame
• Direction : Alain Berdeaux
• Type : Thèse de doctorat
• Discipline(s) : Pharmacologie
• Date : Soutenance en 2009
• Etablissement(s) : Paris 11

Mots clés

Mots clés contrôlés

Cytochrome c

Apoptose

Mots clés libres

Ischémie-reperfusion

Permeabilite membranaire mitochondriale

Résumé

Dans ce travail, nous avons montré qu'un effet cardioprotecteur peut être obtenu en inhibant l'ouverture du pore de transition de permeabilité mitochondrial au cours de l'ischémie-reperfusion myocardique, soit directement en agissant sur le recepteur périphérique aux benzodiazépines, soit indirectement en inactivant la GSK-3beta, ces deux stratégies ayant potentiellement en commun un effet antioxydant indispensable à la protection du cardiomyocyte.

Myocradial ischemia-reperfusion injuries require cardiprotective approaches to improve the repermeabilization of coronaries arteries. So in this work we looked at the mitochondrial permeability transition pore (mPTP) inhibition as this pore is implicated in ischemia-reperfusion injury. We used two pharmalogical strategies to inhibit it. (i) the first one targeted a mitonchondrial outer membrane receptor, the peripheral benzodiazepine (PBR), which is a putative component of mPTP. The cardioprotectio, mediated by PBR was evaluated by 4'-chlorodiazépam (CDZ) a specific PBR ligand. We used a model of global ischemia-reperfusion in isolated rat hearts and a model of regional myocardial ischemia-reperfusion in anaestheized rat. We showed that CDZ reduced infarct size afetr ischemia-reperfusion, improved mitochondrial funcions and decreased apotosis. We observed a reduction of cytochrome C and apoptosis inducing factors (AIF) release with a limitation of membrane permeability and with mPTP inhibition. We also demonstrated that this effect was related to a modification of the balance of the Bel-2 family proteins at the level of the mitochondrial outer member. Indeed, DCZ stabilized the association of bel-2 with the mitochondrial membrane and reduced the interaction of Bax. (ii) The second strategy aimed at stimulation the reperfusion injury salavage kinase (RISK), an endogenous protection cascade implied in pre and postconditioning, asthe cardioprotective effect mediated by RISK was suggested to be linked to mPTP inhibition. We used morphine a well-known cardioprotective opioid ligand which was shown to activated the RISK pathway and to inihibit glycogen synthase kinase -3beta (GSK-3beta). We showed that morphine reduced infarct size in a model of regional myocardial ischemia-reperfusion in rats improved mitochondrials functions. This cardioprotective effect was confirmed in isolated adult rat cardiomyocytes subjected to anoxia-reoxygenation as morphine delayed mPTP opening and increased cell survival. The protection afforded by morphine in vitro and in vivo was mimicked by the GSK-3Beta inhibitor SB16763, and was abolished by mortmannine a PI3K inhibitor. These results confirmed the involvement of the RISK pathway in the cardioprotective effect of both morphine and SB216763 and demonstrated a link between this pathway and mPTP inhibition. In a last part we showed that these two strategies had in common an antioxydant effect which appears necessary ti inhibit mPTP and to protect cardiomyocytes. Taken together these results demonstrate and pharmacological strategy limiting the mitochondrial permeability acting on mPTP is essential to protect the myocardium.