The hormone estradiol affects the auditory system both by itself and by its interaction with neuroprotective factors. In this study, we examined the role of estrogen receptors (ERs) in response to auditory trauma. We found a ligand-dependent protective role for ERβ in the auditory system by investigating mice deficient in ERα (ERKO mice), ERβ (BERKO mice), and aromatase (ARKO mice). Basal auditory brainstem response (ABR) thresholds were similar in all animals. An acoustic trauma causing a temporary hearing loss raised ABR thresholds in male and female BERKO and ARKO mice compared with WT and ERKO mice. The ERα-selective agonist, propyl(1H) pyrazole-1,3,5-triyl-trisphenol (PPT), partially protected ARKO mice from trauma, while the ERβ-selective agonist, 2,3-bis (4-hydroxyphenyl)-propionitrile (DPN), protected WT and ARKO mice. Immunohistochemistry and western blotting confirmed the expression of ERβ in cochlea of WT males and females. Levels of brain-derived neurotrophic factor (BDNF), a neuroprotective peptide that can be induced by estrogen, was lower in BERKO and ARKO mice compared with WT. DPN treatment increased BDNF expression in ARKO mice. These data indicate ERβ-mediated neuroprotection involving BDNF in the auditory system of males and females.
Inna Meltser, Yeasmin Tahera, Evan Simpson, Malou Hultcrantz, Konstantina Charitidi, Jan-Åke Gustafsson, Barbara Canlon
ABR threshold shifts 24 h after acoustic trauma.