Disruption of glial glutamate transport by reactive oxygen species produced in motor neurons.
Observations of elevated CSF glutamate in amyotrophic lateral sclerosis (ALS), together with findings that motor neurons are selectively vulnerable to glutamate receptor-mediated ("excitotoxic") injury, support an excitotoxic contribution to the motor neuron loss in the disease. However, the basis of the apparent loss of astrocytic glutamate transport capacity in affected areas of motor cortex and spinal cord, which probably underlies the extracellular glutamate elevations, is unexplained. Here, we find that glutamate induces far greater reactive oxygen species (ROS) generation in cultured motor neurons than in other spinal neurons. In addition, we found that the ROS seem to be able to leave the motor neurons and induce oxidation and disruption of glutamate uptake in neighboring astrocytes. Correspondingly, in a transgenic mouse model of ALS, protein oxidation was increased in regions immediately surrounding motor neurons. These results provide a mechanism that can account for the localized loss of glial glutamate transport seen in the disease. Furthermore, the observations lend support for a feedforward model involving reciprocal interactions between motor neurons and glia, which may prove useful in understanding ALS pathogenesis.
Rao
Shyam D
SD
Department of Anatomy and Neurobiology, University of California at Irvine, 92697-4292, USA.
Yin
Hong Z
HZ
Weiss
John H
JH
D000690:Amyotrophic Lateral Sclerosis / Q000209:etiology; D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001692:Biological Transport; D002478:Cells, Cultured; D018920:Coculture Techniques; D025461:Feedback, Physiological; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism*; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology; D013482:Superoxide Dismutase / Q000235:genetics; D000072105:Superoxide Dismutase-1
D017382:Reactive Oxygen Species; D018698:Glutamic Acid; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1