Opening of the mitochondrial permeability transition pore causes matrix expansion and outer membrane rupture in fas-mediated hepatic apoptosis in mice

Authors

  • Gérard Feldmann M.D.,

    Corresponding author
    1. Laboratoire de Biologie Cellulaire, INSERM U327, Faculté de Médecine Xavier Bichat, Paris, France
    • INSERM U327, Faculté de Médecine Xavier Bichat, BP 416 - 75870 Paris Cedex 18, France. fax: (33) 1 44 85 92 79
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    • G.F. and D.H. contributed equally to this work.

  • Delphine Haouzi,

    1. Laboratoire de Biologie Cellulaire, INSERM U327, Faculté de Médecine Xavier Bichat, Paris, France
    2. INSERM U481 and Centre Claude Bernard sur Les Hépatites Virales, Hôpital Beaujon, Clichy, France; and Université Paris 7, Denis-Diderot, Paris, France
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    • G.F. and D.H. contributed equally to this work.

  • Alain Moreau,

    1. Laboratoire de Biologie Cellulaire, INSERM U327, Faculté de Médecine Xavier Bichat, Paris, France
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  • Anne-Marie Durand-Schneider,

    1. Laboratoire de Biologie Cellulaire, INSERM U327, Faculté de Médecine Xavier Bichat, Paris, France
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  • Annie Bringuier,

    1. Laboratoire de Biologie Cellulaire, INSERM U327, Faculté de Médecine Xavier Bichat, Paris, France
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  • Alain Berson,

    1. INSERM U481 and Centre Claude Bernard sur Les Hépatites Virales, Hôpital Beaujon, Clichy, France; and Université Paris 7, Denis-Diderot, Paris, France
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  • Abdellah Mansouri,

    1. INSERM U481 and Centre Claude Bernard sur Les Hépatites Virales, Hôpital Beaujon, Clichy, France; and Université Paris 7, Denis-Diderot, Paris, France
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  • Daniel Fau,

    1. INSERM U481 and Centre Claude Bernard sur Les Hépatites Virales, Hôpital Beaujon, Clichy, France; and Université Paris 7, Denis-Diderot, Paris, France
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  • Dominique Pessayre

    1. INSERM U481 and Centre Claude Bernard sur Les Hépatites Virales, Hôpital Beaujon, Clichy, France; and Université Paris 7, Denis-Diderot, Paris, France
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Abstract

Although Fas stimulation has been reported to cause outer mitochondrial membrane rupture in Jurkat cells, the mechanism of this effect is debated, and it is not known if outer membrane rupture also occurs in hepatocyte mitochondria. We studied the in vivo effects of Fas stimulation on ultrastructural lesions and mitochondrial function in mice. Four hours after administration of an agonistic anti-Fas antibody (8 μg/animal), caspase activity increased 5.4-fold. Nuclear DNA showed internucleosomal fragmentation, whereas supercoiled mitochondrial DNA was replaced by circular and linear forms. Mitochondrial cytochrome c was partly released into the cytosol. Ultrastructurally, mitochondrial lesions were observed in both apoptotic hepatocytes (with nuclear chromatin condensation/fragmentation) and nonapoptotic hepatocytes (without nuclear changes). In nonapoptotic cells, outer mitochondrial membrane rupture allowed herniation of the inner membrane and matrix through the outer membrane gap. In apoptotic hepatocytes, the matrix became electron-lucent and no longer protruded through the outer membrane gap. Mitochondria clustered around the nucleus, whereas rough endoplasmic reticulum cisternae became peripheral. In liver mitochondria isolated after Fas stimulation, the membrane potential decreased, whereas basal respiration increased. Pretreatment with either z-VAD-fmk (an inhibitor of caspases) or cyclosporin A (a permeability transition inhibitor) totally or mostly prevented mitochondrial outer membrane rupture, membrane potential decrease, cytochrome c release, and apoptosis. In conclusion, in vivo Fas stimulation causes caspase activation, mitochondrial permeability transition (decreasing the membrane potential and increasing basal respiration), mitochondrial matrix expansion (as shown by matrix herniation), outer mitochondrial membrane rupture, and cytochrome c release.

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