Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by a selective loss of motor neurones accompanied by intense gliosis in lesioned areas of the brain and spinal cord. Glutamate-mediated excitotoxicity resulting from impaired astroglial uptake constitutes one of the current pathophysiological hypotheses explaining the progression of the disease. In this study, we examined the regulation of glutamate transporters by type 5 metabotropic glutamate receptor (mGluR5) in activated astrocytes derived from transgenic rats carrying an ALS-related mutated human superoxide dismutase 1 (hSOD1(G93A)) transgene. Cells from transgenic animals and wild-type littermates showed similar expression of glutamate-aspartate transporter and glutamate transporter 1 (GLT-1) after in vitro activation, whereas cells carrying the hSOD1 mutation showed a three-fold higher expression of functional mGluR5, as observed in the spinal cord of end-stage animals. In cells from wild-type animals, (S)-3,5-dihydroxyphenylglycine (DHPG) caused an immediate protein kinase C (PKC)-dependent up-regulation of aspartate uptake that reflected the activation of GLT-1. Although this effect was mimicked in both cultures by direct activation of PKC using phorbol myristate acetate, DHPG failed to up-regulate aspartate uptake in cells derived from the transgenic rats. The failure of activated mGluR5 to increase glutamate uptake in astrocytes derived from this animal model of ALS supports the theory of glutamate excitotoxicity in the pathogenesis of the disease.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Amyotrophic Lateral Sclerosis / pathology*
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Animals
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Animals, Genetically Modified
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Aspartic Acid / metabolism
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Aspartic Acid / pharmacokinetics
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Astrocytes / drug effects
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Astrocytes / metabolism*
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Blotting, Northern / methods
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Calcium / metabolism
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Carbachol / pharmacology
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Cholinergic Agonists / pharmacology
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Disease Models, Animal
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Dose-Response Relationship, Drug
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Drug Interactions
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Excitatory Amino Acid Antagonists / pharmacology
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Excitatory Amino Acid Transporter 2 / metabolism*
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Gene Expression Regulation / drug effects
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Gene Expression Regulation / physiology
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Glial Fibrillary Acidic Protein / metabolism
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Glutamic Acid / metabolism*
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Humans
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Immunohistochemistry / methods
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Male
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Methoxyhydroxyphenylglycol / analogs & derivatives
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Methoxyhydroxyphenylglycol / pharmacology
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Protein Kinase C / physiology
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Pyridines / pharmacology
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RNA, Messenger / biosynthesis
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Rats
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Receptor, Metabotropic Glutamate 5
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Receptors, Metabotropic Glutamate / metabolism*
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Reverse Transcriptase Polymerase Chain Reaction / methods
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Sodium / metabolism
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Superoxide Dismutase / genetics
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Tritium / metabolism
Substances
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Cholinergic Agonists
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Excitatory Amino Acid Antagonists
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Excitatory Amino Acid Transporter 2
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GRM5 protein, human
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Glial Fibrillary Acidic Protein
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Grm5 protein, rat
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Pyridines
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RNA, Messenger
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Receptor, Metabotropic Glutamate 5
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Receptors, Metabotropic Glutamate
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Tritium
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Aspartic Acid
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Glutamic Acid
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Methoxyhydroxyphenylglycol
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6-methyl-2-(phenylethynyl)pyridine
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Carbachol
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Sodium
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SOD1 G93A protein
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Superoxide Dismutase
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Protein Kinase C
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Calcium
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3,4-dihydroxyphenylglycol