title: Ontogeny of rapid estrogen-mediated extracellular signal-regulated kinase signaling in the rat cerebellar cortex: potent nongenomic agonist and endocrine disrupting activity of the xenoestrogen bisphenol A.
abstract: In addition to regulating estrogen receptor-dependent gene expression, 17beta-estradiol (E(2)) can directly influence intracellular signaling. In primary cultured cerebellar neurons, E(2) was previously shown to regulate growth and oncotic cell death via rapid stimulation of ERK1/2 signaling. Here we show that ERK1/2 signaling in the cerebellum of neonatal and mature rats was rapidly responsive to E(2) and during development to the environmental estrogen bisphenol A (BPA). In vivo dose-response analysis for each estrogenic compound was performed by brief (6-min) intracerebellar injection, followed by rapid fixation and phosphorylation-state-specific immunohistochemistry to quantitatively characterize changes in activated ERK1/2 (pERK) immunopositive cell numbers. Beginning on postnatal d 8, E(2) significantly influenced the number of pERK-positive cells in a cell-specific manner that was dependent on concentration and age but not sex. In cerebellar granule cells on postnatal d 10, E(2) or BPA increased pERK-positive cell numbers at low doses (10(-12) to 10(-10) M) and at higher (10(-7) to 10(-6) M) concentrations. Intermediate concentrations of either estrogenic compound did not modify basal ERK signaling. Rapid E(2)-induced increases in pERK immunoreactivity were specific to the ERK1/2 pathway as demonstrated by coinjection of the mitogen-activated, ERK-activating kinase (MEK)1/2 inhibitor U0126. Coadministration of BPA (10(-12) to 10(-10) M) with 10(-10) M E(2) dose-dependently inhibited rapid E(2)-induced ERK1/2 activation in developing cerebellar neurons. The ability of BPA to act as a highly potent E(2) mimetic and to also disrupt the rapid actions of E(2) at very low concentrations during cerebellar development highlights the potential low-dose impact of xenoestrogens on the developing brain.
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575, USA.
authors.forename: Attila
authors.initials: A
authors.lastname: Zsarnovszky
authors.forename: Hoa H
authors.initials: HH
authors.lastname: Le
authors.forename: Hong-Sheng
authors.initials: HS
authors.lastname: Wang
authors.forename: Scott M
authors.initials: SM
authors.lastname: Belcher
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001559:Benzhydryl Compounds; D002525:Cerebellar Cortex / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004703:Endocrine System / Q000187:drug effects*; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D004968:Estrogens, Non-Steroidal / Q000008:administration & dosage / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D010636:Phenols / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D004338:Drug Combinations; D004958:Estradiol; D004968:Estrogens, Non-Steroidal; D048049:Extracellular Signal-Regulated MAP Kinases; D010636:Phenols; C006780:bisphenol A; D000098826:Bisphenol A Compounds