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|Title:||POST TREATMENT WITH CONJUGATED LINOLEIC ACID PROTECTS CULTURED CORTICAL NEURONS FROM GLUTAMATE EXCITOTOXICITY|
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|Authors/Affiliations:||1 Waylon Hunt*; 1 Christopher Anderson; |
1 University of Manitoba, Winnipeg, MB, Canada
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|Content:||Intoduction: Linoleic acid is an 18-carbon polyunsaturated fatty acid with cis double bonds at carbons 9 & 12. In contrast, conjugated linoleic acid (CLA) refers to an isomeric mixture of linoleic acid with conjugated double bonds in cis or trans configurations. Humans acquire CLA through dietary sources (mostly dairy and meat products from ruminant animals). Significant interest in CLA as a food constituent and nutraceutical arises from its reported benefits in cancer, diabetes, atherosclerosis, and weight-partitioning; however, it has also been reported to play a role in immunomodulation and inflammation. The potential therapeutic benefits of CLA in CNS injury and neurodegeneration are poorly understood. Glutamate is a vital neurotransmitter in the CNS that is released in toxic excess in cerebral ischemia and brain injury. Objective: To determine whether CLA is able to protect neurons from glutamate excitotoxicity in an in vitro tissue culture model. |
Materials and Methods: Cortical neurons cultured from day-16 mouse embryos were exposed to glutamate for 1 hour. A commercial CLA mixture containing 50% cis 9-trans 11 isomer and 50% trans 10-cis 12 isomer was added during or after glutamate exposure to test for neuroprotective effects. Cell survival was identified 18-24 hours later as the proportion of cells able to take up and convert calcein acetoxymethyl ester to fluorescent calcein. Intracellular calcein fluorescence was assessed quantitatively by a high-throughput fluorimeter.
Results: Glutamate dose-dependently reduced neuronal survival, having little effect at 0.3 μM and producing maximal cell death at 100 μM. CLA significantly attenuated glutamate toxicity of neurons in a concentration-dependent fashion, reducing neuron death from (73.6 ▒ 6.5%) for neurons treated with 3 ÁM glutamate alone to (32.1 ▒ 5.6%) for neurons co-treated with 10 ÁM CLA (p<0.01). The level of glutamate-induced neuron death observed with 10 ÁM CLA is not significantly different (p>0.05) from that observed in controls receiving no glutamate, suggesting virtually complete protection at this level. CLA significantly protected against 3 ÁM glutamate-induced neuron death even when administered 3 hours after glutamate exposure (p<0.01). Linoleic acid had no effect on glutamate-induced neuron death, indicating that neuroprotection requires the conjugated form of linoleic acid. Neither of the component positional isomers of CLA (cis 9-trans 11 nor trans 10-cis 12) protected neurons against glutamate toxicity individually, suggesting that both isomers of CLA are required for protection against glutamate excitotoxicity. Conclusion: These studies show that CLA can protect neurons in vitro from glutamate toxicity. Since glutamate toxicity is a precursor for neuron death common to both acute neuronal injury and long-term degeneration of neurons, CLA is a potential target of therapeutic investigation as a nutraceutical in a wide range of neurological disorders, including stroke, Alzheimer's Disease and Amyotrophic Lateral Sclerosis (ALS).
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