title: Neuroprotective effect of 17beta-estradiol against N-methyl-D-aspartate-induced retinal neurotoxicity via p-ERK induction.
abstract: We investigated whether the neuroprotective effect of estrogen is mediated by the estrogen receptor (ER) and whether extracellular signal-regulated kinase (ERK) is involved in the protective effect of estrogen against N-methyl-D-aspartate (NMDA)-induced retinal neurotoxicity. Retrograde labeling of retinal ganglion cells (RGCs) showed that pretreatment with 17beta-estradiol (E2) using a silastic implant significantly attenuated the loss of RGCs induced by intravitreal injection of NMDA. Simultaneous administration of U0126, an ERK inhibitor, with NMDA completely abolished the protective effect of E2. Moreover, ICI182,780, an ER antagonist, also significantly diminished the protective effect of E2. Pretreatment with E2 significantly reduced the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells in the retinal ganglion cell layer (RGCL) and the inner nuclear layer (INL) 12 hr after NMDA injection. Moreover, ICI182,780 inhibited the ameliorative effect of E2 on TUNEL-positive cells in a dose-dependent manner. Immunostaining of anti-ERalpha monoclonal antibody was observed mainly in the RGCL and the INL. Western blot analysis showed a significant increase in the level of phosphorylated ERK (p-ERK) 6 hr after NMDA injection. However, NMDA did not increase the level of p-ERK protein 7 days after injection. Pretreatment of E2 induced further increases of p-ERK expression 6 hr and 7 days after NMDA injection, and U0126 and ICI182,780 significantly inhibited E2-induced p-ERK expression after 6 hr. These results suggest that E2 has an ER-mediated neuroprotective effect against NMDA-induced retinal neurotoxicity and that this effect may be associated with induction of p-ERK in the retina.
authors.affiliation: Department of Ophthalmology, St. Marianna University School of Medicine, Miyamae-ku, Kawasaki-shi, Kanagawa, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kitaoka
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Munemasa
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Ohtani-Kaneko
authors.forename: Takefumi
authors.initials: T
authors.lastname: Kikusui
authors.forename: Akira
authors.initials: A
authors.lastname: Uematsu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takeda
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Hirata
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mori
authors.forename: Satoki
authors.initials: S
authors.lastname: Ueno
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D000077267:Fulvestrant; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008297:Male; D016202:N-Methylaspartate / Q000633:toxicity*; D018696:Neuroprotective Agents / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology
chemical_list: D002070:Butadienes; D004791:Enzyme Inhibitors; D004965:Estrogen Antagonists; D018696:Neuroprotective Agents; D009570:Nitriles; C113580:U 0126; D000077267:Fulvestrant; D004958:Estradiol; D016202:N-Methylaspartate; D048049:Extracellular Signal-Regulated MAP Kinases