Protective effect of arachidonic acid on glutamate neurotoxicity in rat retinal ganglion cells.
OBJECTIVE
Low concentrations of excitotoxic agents such as glutamate decrease survival of retinal ganglion cells (RGCs) and may be an important cause of RGC death in a variety of retinal diseases. Arachidonic acid (AA), an intercellular messenger in the central nervous system, has been reported to have multiple effects on glutamate receptors, including an inhibitory effect on non-N-methyl-D-aspartate (NMDA) receptors. The purpose of this study was to test the hypothesis that AA could protect RGCs from glutamate neurotoxicity.


METHODS
RGCs were purified from the rat retina on postnatal days 7 and 8 by a modified two-step panning method. Survival of RGCs after exposure to glutamate, with or without AA treatment, was measured after 3 days in culture. To visualize calcium signals, RGCs were loaded with a calcium indicator dye, fluo-3 acetoxymethyl ester, and the fluorescence was measured by laser scanning confocal microscopy. Electrophysiological effects of AA on non-NMDA ionotropic receptors were examined by using whole-cell patch clamp configurations.


RESULTS
Incubation of RGCs with 25 microM glutamate caused 60% loss of RGCs. This glutamate neurotoxicity was significantly ameliorated by low concentrations of AA. Concentrations of AA above 10 microM were toxic to RGCs. Calcium imaging showed that glutamate-, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid- (AMPA) and kainate-induced intracellular calcium accumulation in these cells was reduced by AA. Electrophysiological recordings revealed that currents mediated by non-NMDA ionotropic receptors were inhibited by AA in a dose-dependent manner.


CONCLUSIONS
Low concentrations of AA can reduce glutamate neurotoxicity to RGCs by the inhibition of non-NMDA ionotropic receptors. These results suggest that endogenous or exogenous AA may be used to protect RGCs from glutamate neurotoxicity and that AA may be one potential treatment for RGC loss in a variety of eye diseases, including glaucoma.
Kawasaki
Atsushi
A
Departments of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut 06520-8061, USA.
Han
Ming-Hu
MH
Wei
Ji-Ye
JY
Hirata
Keiji
K
Otori
Yasumasa
Y
Barnstable
Colin J
CJ
D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D016718:Arachidonic Acid / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005456:Fluorescent Dyes / Q000378:metabolism; D018698:Glutamic Acid / Q000633:toxicity*; D018613:Microscopy, Confocal; D018696:Neuroprotective Agents / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D051381:Rats; D020318:Rats, Long-Evans; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000378:metabolism; D014966:Xanthenes / Q000378:metabolism
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D018696:Neuroprotective Agents; D016194:Receptors, N-Methyl-D-Aspartate; D014966:Xanthenes; C059715:Fluo-3; D016718:Arachidonic Acid; D018698:Glutamic Acid; D002118:Calcium