Opening of mitochondrial permeability transition pore in cardiomyocytes: Is ferutinin a suitable tool for its assessment? Juliette Bréhat, Mathieu Panel, Bijan Ghaleh, Didier Morin Fundamental and Clinical Pharmacology, 2023 Mitochondrial permeability transition pore (mPTP) opening is a critical event leading to cell injury during myocardial ischemia–reperfusion but having a reliable cellular model to study the effect of drugs targeting mPTP is an unmet need. This study evaluated whether the Ca2+ electrogenic ionophore ferutinin is a relevant tool to induce mPTP in cardiomyocytes. mPTP opening was monitored using the calcein/cobalt fluorescence technique in adult cardiomyocytes isolated from wild‐type and cyclophylin D (CypD) knock‐out mice. Concomitantly, the effect of ferutinin was assessed in isolated myocardial mitochondria. Our results confirmed the Ca2+ ionophoric effect of ferutinin in isolated mitochondria and cardiomyocytes. Ferutinin induced all the hallmarks of mPTP opening in cells (loss of calcein, of mitochondrial potential and cell death), but none of them could be inhibited by CypD deletion or cyclosporine A, indicating that mPTP opening was not the major contributor to the effect of ferutinin. This was confirmed in isolated mitochondria where ferutinin acts by different mechanisms dependent and independent of the mitochondrial membrane potential. At low ferutinin/mitochondria concentration ratio, ferutinin displays protonophoric‐like properties, lowering the mitochondrial membrane potential and limiting oxidative phosphorylation without mitochondrial swelling. At high ferutinin/mitochondria ratio, ferutinin induced a sudden Ca2+ independent mitochondrial swelling, which is only partially inhibited by cyclosporine A. Together, these result show that ferutinin is not a suitable tool to investigate CypD‐dependent mPTP opening in isolated cardiomyocytes because it possesses other mitochondrial properties such as swelling induction and mitochondrial uncoupling properties which impede its utilization.
Brain and Myocardial Mitochondria Follow Different Patterns of Dysfunction After Cardiac Arrest Matthias Kohlhauer, Mathieu Panel, Marine Vermot des Roches, Estelle Faucher, Yara Abi Zeid Daou, Emilie Boissady, Fanny Lidouren, Bijan Ghaleh, Didier Morin, Renaud Tissier Shock, 2021 Mitochondria is often considered as the common nexus of cardiac and cerebral dysfunction after cardiac arrest. Here, our goal was to determine whether the time course of cardiac and cerebral mitochondrial dysfunction is similar after shockable versus non-shockable cardiac arrest in rabbits. Anesthetized rabbits were submitted to 10 min of no-flow by ventricular fibrillation (VF group) or asphyxia (non-shockable group). They were euthanized at the end of the no-flow period or 30 min, 120 min, or 24 h after resuscitation for in vitro evaluation of oxygen consumption and calcium retention capacity. In the brain (cortex and hippocampus), moderate mitochondrial dysfunction was evidenced at the end of the no-flow period after both causes of cardiac arrest versus baseline. It partly recovered at 30 and 120 min after cardiac arrest, with lower calcium retention capacity and higher substrate-dependant oxygen consumption after VF versus non-shockable cardiac arrest. However, after 24 h of follow-up, mitochondrial dysfunction dramatically increased after both VF and non-shockable cardiac arrest, despite greater neurological dysfunction after the latter one. In the heart, mitochondrial dysfunction was also maximal after 24 h following resuscitation, with no significant difference among the causes of the cardiac arrest. During the earlier timing of evaluation, calcium retention capacity and ADP-dependant oxygen consumption were lower and higher, respectively, after non-shockable cardiac arrest versus VF. In conclusion, the kinetics of cardiac and cerebral mitochondrial dysfunction suggests that mitochondrial function does not play a major role in the early phase of the post-resuscitation process but is only involved in the longer pathophysiological events.
A phenyl-pyrrolidine derivative reveals a dual inhibition mechanism of myocardial mitochondrial permeability transition pore, which is limited by its myocardial distribution Mathieu Panel, Abdelhakim Ahmed-Belkacem, Isaac Ruiz, Jean-François Guichou, Jean-Michel Pawlotsky, Bijan Ghaleh, Didier Morin Journal of Pharmacology and Experimental Therapeutics, 2021 Mitochondrial permeability transition pore (mPTP) opening is a key event in cell death during myocardial ischemia reperfusion. Inhibition of its modulator cyclophilin D (CypD) by cyclosporine A (CsA) reduces ischemia-reperfusion injury. The use of cyclosporine A in this indication is debated; however, targeting mPTP remains a major goal to achieve. We investigated the protective effects of a new original small-molecule cyclophilin inhibitor C31, which was specifically designed to target CypD. CypD peptidylprolyl cis-trans isomerase (PPIase) activity was assessed by the standard chemotrypsin-coupled assay. The effects of C31 on mPTP opening were investigated in isolated mouse cardiac mitochondria by measuring mitochondrial swelling and calcium retention capacity (CRC) in rat H9C2 cardiomyoblasts and in adult mouse cardiomyocytes by fluorescence microscopy in isolated perfused mouse hearts and ex vivo after drug infusion in mice. C31 potently inhibited CypD PPIase activity and mitochondrial swelling. C31 was more effective at increasing mitochondrial CRC than CsA and was still able to increase CRC in Ppif−/− (CypD-inactivated) cardiac mitochondria. C31 delayed both mPTP opening and cell death in cardiomyocytes subjected to hypoxia reoxygenation. However, high concentrations of both drugs were necessary to reduce mPTP opening in isolated perfused hearts, and neither CsA nor C31 inhibited mPTP opening in heart after in vivo infusion, underlying the importance of myocardial drug distribution for cardioprotection. C31 is an original inhibitor of mPTP opening involving both CypD-dependent and -independent mechanisms. It constitutes a promising new cytoprotective agent. Optimization of its pharmacokinetic properties is now required prior to its use against cardiac ischemia-reperfusion injury. SIGNIFICANCE STATEMENT This study demonstrates that the new cyclophilin inhibitor C31 potently inhibits cardiac mitochondrial permeability transition pore (mPTP) opening in vitro and ex vivo. The dual mechanism of action of C31 allows the prevention of mPTP opening beyond cyclophilin D inhibition. Further development of the compound might bring promising drug candidates for cardioprotection. However, the lack of effect of both C31 and cyclosporine A after systemic administration demonstrates the difficulties of targeting myocardial mitochondria in vivo and should be taken into account in cardioprotective strategies.
Metformin Reverses the Enhanced Myocardial SR/ER–Mitochondria Interaction and Impaired Complex I-Driven Respiration in Dystrophin-Deficient Mice Claire Angebault, Mathieu Panel, Mathilde Lacôte, Jennifer Rieusset, Alain Lacampagne, Jérémy Fauconnier Frontiers in Cell and Developmental Biology, 2021 Besides skeletal muscle dysfunction, Duchenne muscular dystrophy (DMD) exhibits a progressive cardiomyopathy characterized by an impaired calcium (Ca2+) homeostasis and a mitochondrial dysfunction. Here we aimed to determine whether sarco-endoplasmic reticulum (SR/ER)–mitochondria interactions and mitochondrial function were impaired in dystrophic heart at the early stage of the pathology. For this purpose, ventricular cardiomyocytes and mitochondria were isolated from 3-month-old dystrophin-deficient mice (mdx mice). The number of contacts points between the SR/ER Ca2+ release channels (IP3R1) and the porine of the outer membrane of the mitochondria, VDAC1, measured using in situ proximity ligation assay, was greater in mdx cardiomyocytes. Expression levels of IP3R1 as well as the mitochondrial Ca2+ uniporter (MCU) and its regulated subunit, MICU1, were also increased in mdx heart. MICU2 expression was however unchanged. Furthermore, the mitochondrial Ca2+ uptake kinetics and the mitochondrial Ca2+ content were significantly increased. Meanwhile, the Ca2+-dependent pyruvate dehydrogenase phosphorylation was reduced, and its activity significantly increased. In Ca2+-free conditions, pyruvate-driven complex I respiration was decreased whereas in the presence of Ca2+, complex I-mediated respiration was boosted. Further, impaired complex I-mediated respiration was independent of its intrinsic activity or expression, which remains unchanged but is accompanied by an increase in mitochondrial reactive oxygen species production. Finally, mdx mice were treated with the complex I modulator metformin for 1 month. Metformin normalized the SR/ER-mitochondria interaction, decreased MICU1 expression and mitochondrial Ca2+ content, and enhanced complex I-driven respiration. In summary, before any sign of dilated cardiomyopathy, the DMD heart displays an aberrant SR/ER-mitochondria coupling with an increase mitochondrial Ca2+ homeostasis and a complex I dysfunction. Such remodeling could be reversed by metformin providing a novel therapeutic perspective in DMD.
Small-Molecule Inhibitors of Cyclophilins Block Opening of the Mitochondrial Permeability Transition Pore and Protect Mice From Hepatic Ischemia/Reperfusion Injury Mathieu Panel, Isaac Ruiz, Rozenn Brillet, Fouad Lafdil, Fatima Teixeira-Clerc, Cong Trung Nguyen, Julien Calderaro, Muriel Gelin, Fred Allemand, Jean-François Guichou, Bijan Ghaleh, Abdelhakim Ahmed-Belkacem, Didier Morin, Jean-Michel Pawlotsky Gastroenterology, 2019 BACKGROUND & AIMS Hepatic ischemia-reperfusion injury is a complication of liver surgery that involves mitochondrial dysfunction resulting from mitochondrial permeability transition pore (mPTP) opening. Cyclophilin D (PPIF or CypD) is a peptidyl-prolyl cis-trans isomerase that regulates mPTP opening in the inner mitochondrial membrane. We investigated whether and how recently created small-molecule inhibitors of CypD prevent opening of the mPTP in hepatocytes and the resulting effects in cell models and livers of mice undergoing ischemia-reperfusion injury. METHODS We measured the activity of 9 small-molecule inhibitors of Cyps in an assay of CypD activity. The effects of the small-molecule CypD inhibitors or vehicle on mPTP opening were assessed by measuring mitochondrial swelling and calcium retention in isolated liver mitochondria from C57BL/6J (wild-type) and Ppif-/- (CypD knock-out) mice, and in primary mouse and human hepatocytes by fluorescence microscopy. We induced ischemia-reperfusion injury in livers of mice given a small-molecule CypD inhibitor or vehicle before and during reperfusion, and collected samples of blood and liver for histologic analysis. RESULTS The compounds inhibited peptidyl-prolyl isomerase activity (IC50 values, 0.2 to 16.2 μM) and, as a result, calcium-induced mitochondrial swelling, by preventing mPTP opening (IC50 values, 1.4 to 132 μM) in a concentration-dependent manner. The most potent inhibitor (C31) bound CypD with high affinity and inhibited swelling in mitochondria from livers of wild-type and Ppif-/- mice (indicating an additional, CypD-independent effect on mPTP opening) and in primary human and mouse hepatocytes. Administration of C31 in mice with ischemia-reperfusion injury before and during reperfusion restored hepatic calcium retention capacity and oxidative phosphorylation parameters and reduced liver damage compared with vehicle. CONCLUSIONS Recently created small-molecule inhibitors of CypD reduced calcium-induced swelling in mitochondria from mouse and human liver tissues. Administration of these compounds to mice during ischemia-reperfusion restored hepatic calcium retention capacity and oxidative phosphorylation parameters and reduced liver damage. These compounds might be developed to protect patients from ischemia-reperfusion injury after liver surgery or for other hepatic or non-hepatic disorders related to abnormal mPTP opening.
