Endothelin-1 enhances glutamate-induced retinal cell death, possibly through ETA receptors.
OBJECTIVE
To determine the modification of the glutamate-induced death of retinal neurons by endothelin (ET)-1.


METHODS
Cultured retinal neurons from fetal rats were exposed to glutamate (1.0 mM) alone or glutamate with ET-1 (10(-10)-10(-7)M) for 10 minutes. Neuronal death was assessed by the trypan blue exclusion or TUNEL assays at 2, 6, and 24 hours after the exposure. The effects of adding BQ-123 or BQ-788, ET(A), and ET(B) receptor antagonists, respectively, in combination with ET-1 was also assessed.


RESULTS
Immunohistochemical analyses showed that the ETs as well as ET(A) and ET(B) receptors were expressed on cultured retinal neurons consisting mainly of amacrine cells. A brief exposure of the cultured retinal neurons to glutamate alone significantly increased the number of dead cells, and the addition of ET-1 with glutamate caused a further significant increase in retinal neuronal death compared with the cells exposed to glutamate alone. A significant increase in neuronal death was detected at doses of 10 nM of ET-1 and higher after a 24-hour exposure (P < 0.05, Dunnett), whereas brief exposure of neurons to up to 1 microM ET-1 alone did not cause delayed cell death of neurons. BQ-123 (10 nM) suppressed the enhancement of retinal toxicity caused by ET-1 (10 nM), whereas BQ-788 had no significant effect.


CONCLUSIONS
These results indicate that ET-1 enhances glutamate-induced retinal cell death, possibly through ET(A) receptors. ET-1 may act synergistically with glutamate to damage retinal neurons under hypoxic conditions.
Kobayashi
Takatoshi
T
Department of Ophthalmology, Osaka Medical College, Takatsuki Osaka, Japan.
Oku
Hidehiro
H
Fukuhara
Masayuki
M
Kojima
Shota
S
Komori
Asako
A
Ichikawa
Masaki
M
Katsumura
Kozo
K
Kobayashi
Masato
M
Sugiyama
Tetsuya
T
Ikeda
Tsunehiko
T
D025042:Amacrine Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D004357:Drug Synergism; D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D018698:Glutamic Acid / Q000633:toxicity*; D020287:In Situ Nick-End Labeling; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A / Q000378:metabolism*; D012160:Retina / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D014343:Trypan Blue
D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D044022:Receptor, Endothelin A; D018698:Glutamic Acid; C086539:BQ 788; D014343:Trypan Blue; C072247:cyclo(Trp-Asp-Pro-Val-Leu)