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The energy disruptor metformin targets mitochondrial integrity via modification of calcium flux in cancer cells.

ABSTRACT: Mitochondrial integrity is critical for the regulation of cellular energy and apoptosis. Metformin is an energy disruptor targeting complex I of the respiratory chain. We demonstrate that metformin induces endoplasmic reticulum (ER) stress, calcium release from the ER and subsequent uptake of calcium into the mitochondria, thus leading to mitochondrial swelling. Metformin triggers the disorganization of the cristae and inner mitochondrial membrane in several cancer cells and tumors. Mechanistically, these alterations were found to be due to calcium entry into the mitochondria, because the swelling induced by metformin was reversed by the inhibition of mitochondrial calcium uniporter (MCU). We also demonstrated that metformin inhibits the opening of mPTP and induces mitochondrial biogenesis. Altogether, the inhibition of mPTP and the increase in mitochondrial biogenesis may account for the poor pro-apoptotic effect of metformin in cancer cells.

SUBMITTER: Loubiere C

PROVIDER: S-EPMC5506014 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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The energy disruptor metformin targets mitochondrial integrity via modification of calcium flux in cancer cells.

Loubiere Camille C Clavel Stephan S Gilleron Jerome J Harisseh Rania R Fauconnier Jeremy J Ben-Sahra Issam I Kaminski Lisa L Laurent Kathiane K Herkenne Stephanie S Lacas-Gervais Sandra S Ambrosetti Damien D Alcor Damien D Rocchi Stephane S Cormont Mireille M Michiels Jean-François JF Mari Bernard B Mazure Nathalie M NM Scorrano Luca L Lacampagne Alain A Gharib Abdallah A Tanti Jean-François JF Bost Frederic F

Scientific reports 20170711 1

Mitochondrial integrity is critical for the regulation of cellular energy and apoptosis. Metformin is an energy disruptor targeting complex I of the respiratory chain. We demonstrate that metformin induces endoplasmic reticulum (ER) stress, calcium release from the ER and subsequent uptake of calcium into the mitochondria, thus leading to mitochondrial swelling. Metformin triggers the disorganization of the cristae and inner mitochondrial membrane in several cancer cells and tumors. Mechanistica ...[more]

PMID: 28698627

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Project description:Oxidative stress is one of the main causes of osteoblast apoptosis induced by post-menopausal osteoporosis. The authors previously found that metformin can reverse the loss of bone mass in post-menopausal osteoporosis. The present study aimed to further clarify the effects and mechanisms of action of metformin in post-menopausal osteoporosis under conditions of oxidative stress. Combined with an in-depth investigation using the transcriptome database, the association between oxidative stress and mitochondrial dysfunction in post-menopausal osteoporosis was confirmed. A pre-osteoblast model of oxidative stress was constructed, and the apoptotic rate following the addition of hydrogen peroxide and metformin was detected using CCK-8 assay and Annexin V-FITC/PI staining. Mitochondrial membrane potential was detected using the JC-1 dye, the intracellular calcium concentration was detected using Fluo-4 AM, the intracellular reactive oxygen species (ROS) level was observed using DCFH-DA, and the mitochondrial superoxide level was observed using MitoSOX Red. Bay K8644 was used to increase the level of intracellular calcium. siRNA was used to interfere with the expression of glycogen synthase kinase (GSK)-3β. Western blot analysis was used to detect the expression of mitochondrial dysfunction-related proteins. The results revealed that oxidative stress decreased mitochondrial membrane potential and increased intracellular ROS, mitochondrial superoxide and cytoplasmic calcium levels in pre-osteoblasts; however, metformin improved mitochondrial dysfunction and reversed oxidative stress-induced injury. Metformin inhibited mitochondrial permeability transition pore opening, suppressed the cytoplasmic calcium influx and reversed pre-osteoblast apoptosis by promoting GSK-3β phosphorylation. Moreover, it was found that EGFR was the cell membrane receptor of metformin in pre-osteoblasts, and the EGFR/GSK-3β/calcium axis played a key role in metformin reversing the oxidative stress response of pre-osteoblasts in post-menopausal osteoporosis. On the whole, these findings provide a pharmacological basis for the use of metformin for the treatment of post-menopausal osteoporosis.

Project description:We present an integrated thermokinetic model describing control of cardiac mitochondrial bioenergetics. The model describes the tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and mitochondrial Ca(2+) handling. The kinetic component of the model includes effectors of the TCA cycle enzymes regulating production of NADH and FADH(2), which in turn are used by the electron transport chain to establish a proton motive force (Delta mu(H)), driving the F(1)F(0)-ATPase. In addition, mitochondrial matrix Ca(2+), determined by Ca(2+) uniporter and Na(+)/Ca(2+) exchanger activities, regulates activity of the TCA cycle enzymes isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase. The model is described by twelve ordinary differential equations for the time rate of change of mitochondrial membrane potential (Delta Psi(m)), and matrix concentrations of Ca(2+), NADH, ADP, and TCA cycle intermediates. The model is used to predict the response of mitochondria to changes in substrate delivery, metabolic inhibition, the rate of adenine nucleotide exchange, and Ca(2+). The model is able to reproduce, qualitatively and semiquantitatively, experimental data concerning mitochondrial bioenergetics, Ca(2+) dynamics, and respiratory control. Significant increases in oxygen consumption (V(O(2))), proton efflux, NADH, and ATP synthesis, in response to an increase in cytoplasmic Ca(2+), are obtained when the Ca(2+)-sensitive dehydrogenases are the main rate-controlling steps of respiratory flux. These responses diminished when control is shifted downstream (e.g., the respiratory chain or adenine nucleotide translocator). The time-dependent behavior of the model, under conditions simulating an increase in workload, closely reproduces experimentally observed mitochondrial NADH dynamics in heart trabeculae subjected to changes in pacing frequency. The steady-state and time-dependent behavior of the model support the hypothesis that mitochondrial matrix Ca(2+) plays an important role in matching energy supply with demand in cardiac myocytes.

Dataset Information

The energy disruptor metformin targets mitochondrial integrity via modification of calcium flux in cancer cells.

Publications

The energy disruptor metformin targets mitochondrial integrity via modification of calcium flux in cancer cells.

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