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Peroxynitrite triggers a phenotypic transformation in spinal cord astrocytes that induces motor neuron apoptosis

Authors

  • Patricia Cassina,

    1. Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay>
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  • Hugo Peluffo,

    1. Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay>
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  • Mariana Pehar,

    1. Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay>
    2. Departamento de Neurobiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
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  • Laura Martinez-Palma,

    1. Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay>
    2. Facultad de Veterinaria, Universidad de la República, Montevideo, Uruguay
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  • Andrés Ressia,

    1. Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay>
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  • Joseph S. Beckman,

    1. Linus Pauling Institute, Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon
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  • Alvaro G. Estévez,

    1. Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama
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  • Luis Barbeito

    Corresponding author
    1. Departamento de Neurobiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
    • Departamento de Neurobiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP 11600 Montevideo, Uruguay
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  • The first two authors contributed equally to this paper.

Abstract

Oxidative stress mediated by nitric oxide (NO) and its toxic metabolite peroxynitrite has previously been associated with motor neuron degeneration in amyotrophic lateral sclerosis (ALS). Degenerating spinal motor neurons in familial and sporadic ALS are typically surrounded by reactive astrocytes expressing the inducible form of NO synthase (iNOS), suggesting that astroglia may have a pathogenic role in ALS. We report here that a brief exposure of spinal cord astrocyte monolayers to peroxynitrite (0.25–1 mM) provoked long-lasting reactive morphological changes characterized by process-bearing cells displaying intense glial fibrillary acidic protein and iNOS immunoreactivity. Furthermore, peroxynitrite caused astrocytes to promote apoptosis of embryonic motor neurons subsequently plated on the monolayers. Neuronal death occurred within 24 hr after plating, as evidenced by the presence of degenerating motor neurons positively stained for activated caspase-3 and nitrotyrosine. Motor neuron death was largely prevented by NOS inhibitors and peroxynitrite scavengers but not by trophic factors that otherwise will support motor neuron survival in the absence of astrocytes. The bacterial lipopolysaccharide, a well-known inflammatory stimulus that induces iNOS expression in astrocytes, provoked the same effects on astrocytes as peroxynitrite. Thus, spinal cord astrocytes respond to extracellular peroxynitrite by adopting a phenotype that is cytotoxic to motor neurons through peroxynitrite-dependent mechanisms. © 2002 Wiley-Liss, Inc.

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