title: Long-term ovariectomy increases BDNF gene methylation status in mouse hippocampus.
abstract: Estradiol (E) has been suggested to have a neuroprotective effect in young animals but has neutral or harmful effects when it is administered to aged animals. In the present study, we determined whether the post-ovariectomy (post-OVX) timeframe elapsed before the initiation of chronic E treatment is critical for the estrogenic induction of neurotrophins (brain-derived neurotrophic factor, BDNF, and synaptophysin, SYN) in the rodent hippocampus. Adult mice were OVX and, a short period (short-term E (STE) animals) or a long period (long-term E (LTE) animals) after the OVX, were daily treated with E. Control animals were treated with sesame oil (short-term control (STC) and long-term control (LTC) animals). Protein expression was determined using an immunohistochemical approach. Transcriptional activity in the hippocampus of individual BDNF promoters was assessed by real-time quantitative RT-PCR, and the methylation levels of regulatory regions were analyzed by methylation-specific PCR and combined bisulfite restriction analysis. STE animals showed increased BDNF and SYN protein expression and a higher activity of BDNF II, IV, and V promoters. In contrast, LTE animals did not show E induction of neurotrophins. In these animals, the methylation levels of regulatory sequences of the BDNF were higher than in the STE animals in a CpG island of promoter V and in the CRE regulatory site located in promoter IV. With this experiment, we determined that a prolonged period of hypoestrogenicity disrupts the E-induction of neurotrophins, and we postulated that DNA methylation is one of the epigenetic mechanisms that could explain the E-insensitivity of the BDNF after a long period post-OVX.
authors.affiliation: Laboratorio de Endocrinología y Tumores Hormonodependientes, Facultad de Bioquímica y Cs. Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, 3000 Santa Fe, Argentina. Electronic address: gmoreno@fbcb.unl.edu.ar.
authors.forename: Guillermo S
authors.initials: GS
authors.lastname: Moreno-Piovano
authors.affiliation: Laboratorio de Endocrinología y Tumores Hormonodependientes, Facultad de Bioquímica y Cs. Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, 3000 Santa Fe, Argentina. Electronic address: varayoud@fbcb.unl.edu.ar.
authors.forename: Jorgelina
authors.initials: J
authors.lastname: Varayoud
authors.affiliation: Laboratorio de Endocrinología y Tumores Hormonodependientes, Facultad de Bioquímica y Cs. Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, 3000 Santa Fe, Argentina. Electronic address: eluque@fbcb.unl.edu.ar.
authors.forename: Enrique H
authors.initials: EH
authors.lastname: Luque
authors.affiliation: Laboratorio de Endocrinología y Tumores Hormonodependientes, Facultad de Bioquímica y Cs. Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, 3000 Santa Fe, Argentina; Departamento de Bioquímica Clínica, Facultad de Bioquímica y Cs. Biológicas, Universidad Nacional del Litoral, Casilla de Correo 242, 3000 Santa Fe, Argentina. Electronic address: gramos@fbcb.unl.edu.ar.
authors.forename: Jorge G
authors.initials: JG
authors.lastname: Ramos
mesh_terms: D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D004334:Drug Administration Schedule; D044127:Epigenesis, Genetic; D004958:Estradiol / Q000008:administration & dosage* / Q000097:blood; D047628:Estrogen Receptor alpha / Q000378:metabolism; D004967:Estrogens / Q000008:administration & dosage* / Q000097:blood; D005260:Female; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D008807:Mice, Inbred BALB C; D010052:Ovariectomy; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D016708:Synaptophysin / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D047628:Estrogen Receptor alpha; D004967:Estrogens; D012333:RNA, Messenger; D016708:Synaptophysin; C569015:Syp protein, mouse; D004958:Estradiol
keywords: Brain-derived neurotrophic factor; DNA methylation; Estrogen; Hippocampus