Magnesium sulfate protects against the bioenergetic consequences of chronic glutamate receptor stimulation.
Extracellular glutamate is elevated following brain ischemia or trauma and contributes to neuronal injury. We tested the hypothesis that magnesium sulfate (MgSO4, 3 mM) protects against metabolic failure caused by excitotoxic glutamate exposure. Rat cortical neuron preparations treated in medium already containing a physiological concentration of Mg(2+) (1 mM) could be segregated based on their response to glutamate (100 µM). Type I preparations responded with a decrease or small transient increase in oxygen consumption rate (OCR). Type II neurons responded with >50% stimulation in OCR, indicating a robust response to increased energy demand without immediate toxicity. Pre-treatment with MgSO4 improved the initial bioenergetic response to glutamate and ameliorated subsequent loss of spare respiratory capacity, measured following addition of the uncoupler FCCP, in Type I but not Type II neurons. Spare respiratory capacity in Type I neurons was also improved by incubation with MgSO4 or NMDA receptor antagonist MK801 in the absence of glutamate treatment. This finding indicates that the major difference between Type I and Type II preparations is the amount of endogenous glutamate receptor activity. Incubation of Type II neurons with 5 µM glutamate prior to excitotoxic (100 µM) glutamate exposure recapitulated a Type I phenotype. MgSO4 protected against an excitotoxic glutamate-induced drop in neuronal ATP both with and without prior 5 µM glutamate exposure. Results indicate that MgSO4 protects against chronic moderate glutamate receptor stimulation and preserves cellular ATP following treatment with excitotoxic glutamate.
Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
Pascaline
P
Clerc
Christina A
CA
Young
Evan A
EA
Bordt
Alina M
AM
Grigore
Gary
G
Fiskum
Brian M
BM
Polster
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019069:Cell Respiration / Q000187:drug effects; D002478:Cells, Cultured; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D006019:Glycolysis / Q000187:drug effects; D008278:Magnesium Sulfate / Q000494:pharmacology*; D008928:Mitochondria / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010101:Oxygen Consumption; D010641:Phenotype; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D017470:Receptors, Glutamate / Q000378:metabolism*
D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D008278:Magnesium Sulfate; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate