Altered in-vitro and in-vivo expression of glial glutamate transporter-1 following exposure to cerebrospinal fluid of amyotrophic lateral sclerosis patients

J Neurol Sci. 2007 Mar 15;254(1-2):9-16. doi: 10.1016/j.jns.2006.12.004. Epub 2007 Jan 24.

Abstract

Our earlier studies have shown that cerebrospinal fluid (CSF) of amyotrophic lateral sclerosis (ALS) patients causes death of motor neurons, both in in-vitro as well as in-vivo. There was an aberrant phosphorylation of neurofilaments in cultured spinal cord neurons of chick and rats following exposure to CSF of ALS patients (ALS-CSF). Other features of neurodegeneration, such as swollen neuronal soma and beading of neurites were also observed. In neonatal rat pups exposed to ALS-CSF, we observed phosphorylated neurofilaments in the soma of spinal motor neurons in addition to the increased lactate dehydrogenase activity and reactive astrogliosis. The present study examines the effect of ALS-CSF on the expression of glial glutamate transporter (GLT-1) in embryonic rat spinal cord cultures as well as in spinal astrocytes of neonatal rats. Immunostaining suggested a decrease in the expression of GLT-1 by astrocytes both in culture and in-vivo following exposure to ALS-CSF. Quantification of Western blots confirmed the decreased expression of GLT-1. Our results provide evidence that toxic factor(s) present in ALS-CSF depletes GLT-1 expression. This could lead to an increased level of glutamate in the synaptic pool causing excitotoxicity to motor neurons, possibly by triggering the 'glutamate-mediated toxicity-pathway'.

MeSH terms

  • Amyotrophic Lateral Sclerosis / cerebrospinal fluid*
  • Animals
  • Animals, Newborn
  • Astrocytes / drug effects*
  • Astrocytes / metabolism
  • Biological Factors / cerebrospinal fluid
  • Biological Factors / toxicity*
  • Cell Death / drug effects
  • Cell Death / physiology
  • Cells, Cultured
  • Cerebrospinal Fluid*
  • Enzyme Inhibitors / pharmacology
  • Excitatory Amino Acid Transporter 2 / drug effects
  • Excitatory Amino Acid Transporter 2 / metabolism*
  • Female
  • Glutamic Acid / metabolism
  • Humans
  • Immunohistochemistry
  • Injections, Spinal
  • L-Lactate Dehydrogenase / drug effects
  • L-Lactate Dehydrogenase / metabolism
  • Male
  • Middle Aged
  • NG-Nitroarginine Methyl Ester / pharmacology
  • Neurotoxins / cerebrospinal fluid
  • Presynaptic Terminals / metabolism
  • Rats
  • Spinal Cord / drug effects*
  • Spinal Cord / physiopathology
  • Up-Regulation / drug effects

Substances

  • Biological Factors
  • Enzyme Inhibitors
  • Excitatory Amino Acid Transporter 2
  • Neurotoxins
  • Glutamic Acid
  • L-Lactate Dehydrogenase
  • NG-Nitroarginine Methyl Ester