title: Mechanistically distinct steps in the mitochondrial death pathway triggered by oxidative stress in cardiac myocytes.
abstract: Oxidative stress plays an important role in the pathogenesis of cardiovascular diseases. In the present study, we characterize three distinct phases of the H2O2-induced response, which leads to loss of mitochondrial membrane potential (DeltaPsi(m)) and subsequent cell death in cultured cardiac myocytes. (1) Priming: After H2O2 exposure (100 micromol/L), cells maintain a constant DeltaPsi(m) for the cell-to-cell specific latency but at the same time undergo progressive changes in inner mitochondrial membrane structure (swelling and loss of cristae by electron microscopy). An increase of matrix calcium is required, but not sufficient, for this process. (2) Depolarization: Priming is followed by sudden depolarization of DeltaPsi(m), which is mediated by mitochondrial permeability transition pore opening, as evidenced by the concomitant release of calcein from mitochondria. This process is rapid (<4 minutes), complete, and irreversible. The duration of depolarization is constant and does not depend on the length of the priming process in any given cell. (3) Fragmentation: Along with massive mitochondrial swelling and release of cytochrome c into the cytoplasm, cells undergo surface membrane alterations, such as exposure of phosphatidylserine and eventual loss of membrane integrity and cellular fragmentation. Thus, oxidant stress elicits reproducible and stereotyped responses in cardiac cells. The priming phase, during which mitochondria undergo major ultrastructural alterations but remain functional, represents a particularly attractive target for intervention in the prevention of cell death.
authors.affiliation: Institute of Molecular Cardiobiology, The Johns Hopkins University, Baltimore, Md 21205, USA.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Akao
authors.forename: Brian
authors.initials: B
authors.lastname: O'Rourke
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Teshima
authors.forename: Jegatheesan
authors.initials: J
authors.lastname: Seharaseyon
authors.forename: Eduardo
authors.initials: E
authors.lastname: Marbán
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D005456:Fluorescent Dyes; D006861:Hydrogen Peroxide / Q000494:pharmacology; D020407:Internet; D007473:Ion Channels / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D018715:Microscopy, Video; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003574:Cytochrome c Group; D005456:Fluorescent Dyes; D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D016877:Oxidants; D006861:Hydrogen Peroxide; D002118:Calcium