Peroxynitrite triggers a phenotypic transformation in spinal cord astrocytes that induces motor neuron apoptosis.
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.
Cassina
Patricia
P
Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
Peluffo
Hugo
H
Pehar
Mariana
M
Martinez-Palma
Laura
L
Ressia
Andrés
A
Beckman
Joseph S
JS
Estévez
Alvaro G
AG
Barbeito
Luis
L
D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D016166:Free Radical Scavengers / Q000494:pharmacology; D005911:Gliosis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000378:metabolism* / Q000633:toxicity; D010641:Phenotype; D051381:Rats; D020800:Receptor, Nerve Growth Factor / Q000187:drug effects / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology
D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D008070:Lipopolysaccharides; D020800:Receptor, Nerve Growth Factor; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase