Arachidonic Acid Enhances Intracellular [Ca²⁺]_i Increase and Mitochondrial Depolarization Induced by Glutamate in Cerebellar Granule Cells

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A. M. Surin^1*, A. P. Bolshakov¹, M. M. Mikhailova¹, E. G. Sorokina², Ya. E. Senilova², V. G. Pinelis², and B. I. Khodorov¹

¹Institute of General Pathology and Pathophysiology, Russian Academy of Medical Sciences, ul. Baltiiskaya 8, 125315 Moscow, Russia; fax: (495) 151-1726; E-mail: alexsurin@yahoo.com

²Scientific Center for Children's Health, Russian Academy of Medical Sciences, Lomonosovsky pr. 2/62, 119991 Moscow, Russia

^* To whom correspondence should be addressed.

Received December 1, 2005; Revision received April 13, 2006

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Maturation of primary neuronal cultures is accompanied by an increase in the proportion of cells that exhibit biphasic increase in free cytoplasmic Ca²⁺ ([Ca²⁺]_i) followed by synchronic decrease in electrical potential difference across the inner mitochondrial membrane (DeltaPsi_m) in response to stimulation of glutamate receptors. In the present study we have examined whether the appearance of the second phase of [Ca²⁺]_i change can be attributed to arachidonic acid (AA) release in response to the effect of glutamate (Glu) on neurons. Using primary culture of rat cerebellar granule cells we have investigated the effect of AA (1-20 µM) on [Ca²⁺]_i, DeltaPsi_m, and [ATP] and changes in these parameters induced by neurotoxic concentrations of Glu (100 µM, 10-40 min). At ≤10 µM, AA caused insignificant decrease in DeltaPsi_m without any influence on [Ca²⁺]_i. The mitochondrial ATPase inhibitor oligomycin enhanced AA-induced decrease in DeltaPsi_m; this suggests that AA may inhibit mitochondrial respiration. Addition of AA during the treatment with Glu resulted in more pronounced augmentation of [Ca²⁺]_i and the decrease in DeltaPsi_m than the changes in these parameters observed during independent action of AA; removal of Glu did not abolish these changes. An inhibitor of the cyclooxygenase and lipoxygenase pathways of AA metabolism, 5,8,11,14-eicosatetraynoic acid, increased the proportion of neurons characterized by Glu-induced biphasic increase in [Ca²⁺]_i and the decrease in DeltaPsi_m. Palmitic acid (30 µM) did not increase the percentage of neurons exhibiting biphasic response to Glu. Co-administration of AA and Glu caused 2-3 times more pronounced decrease in ATP concentrations than that observed during the independent effect of AA and Glu. The data suggest that AA may influence the functional state of mitochondria, and these changes may promote biphasic [Ca²⁺]_i and DeltaPsi_m responses of neurons to the neurotoxic effect of Glu.

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KEY WORDS: neurons, glutamate, calcium, mitochondrial potential, arachidonic acid

DOI: 10.1134/S0006297906080074

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