title: Estradiol enhances the neurotoxicity of glutamate in GT1-7 cells through an estrogen receptor-dependent mechanism.
abstract: Glutamate plays an important role in neuroendocrine regulation of reproduction through acting on the N-methyl-D-asparate receptor (NMDAR) in the preoptic area (POA). However, a larger dose of glutamate is neurotoxic. Estradiol (E2) increases the responsiveness of neurons to glutamate through activation and/or expression of NMDAR. In order to investigate whether estradiol modulates the neurotoxic effect of glutamate on the neurons through estrogen receptor (ER), immortalized GT1-7 cells, which simultaneously express ER and NMDAR were used. Tamoxifen and ICI 182,780, ER antagonist, were used to investigate whether the ER is involved in the effect of estradiol on glutamate-induced neurotoxicity. MK-801, a NMDAR antagonist, was used to confirm the enhancement of NMDAR-mediated neurotoxicity by estradiol. Neurotoxicity was evaluated by cell viability and LDH efflux. Cell death was observed by flow cytometry and DNA fragmentation. The results showed that: (1) estradiol (10 nM, incubated for 3 days) significantly enhanced the glutamate-induced neuronal death; (2) the percentages of necrosis and apoptosis were elevated after glutamate treatment, and estradiol significantly enhanced the glutamate-induced cell death; (3) glutamate-induced DNA fragmentation was enhanced by E2-pretreatment; (4) the induction of cell death and increase of LDH efflux after glutamate treatment were also enhanced by E2-pretreatment; (5) both the tamoxifen and ICI 182,780 abolished the estradiol-enhanced NMDAR expression and neurotoxicity of glutamate; (6) higher dose of MK-801 (2 microM) was needed in E2-pretreated cells than in non-E2-pretreated group to block the glutamate-induced neurotoxicity. These results suggested that pretreatment of estradiol might enhance the expression of NMDAR and subsequent glutamate-induced neurotoxicity on the GT1-7 cells through an ER-dependent manner.
authors.affiliation: Department of Physiology, Kaohsiung Medical University, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan, ROC.
authors.forename: Rei-Cheng
authors.initials: RC
authors.lastname: Yang
authors.forename: Huei-Chuan
authors.initials: HC
authors.lastname: Shih
authors.forename: Hseng-Kuang
authors.initials: HK
authors.lastname: Hsu
authors.forename: Hwei-Chiu
authors.initials: HC
authors.lastname: Chang
authors.forename: Chin
authors.initials: C
authors.lastname: Hsu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004357:Drug Synergism; D004958:Estradiol / Q000633:toxicity*; D018698:Glutamic Acid / Q000633:toxicity*; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011960:Receptors, Estrogen / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism
chemical_list: D011960:Receptors, Estrogen; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D004958:Estradiol