Effects of low-dose Bisphenol A on calcium ion influx and on genes of proliferation and differentiation in immortalized human gingival cells in vitro: The role of estrogen receptor beta

Objectives. Relating to low-dose Bisphenol-A (BPA), there is still a lack of mechanistic studies in oral cells, representing the first targets of BPA by oral intake. The objective of this study was to investigate an assumed mechanistic interrelationship between both low-dose BPA-modulated Calcium ion (Ca2+) influx and cell behavior, and the estrogen receptor beta (ER(beta), in oral mucosal cells. Methods. Indirect immunofluorescence (IIF) was conducted on estrogen receptor beta (ER(beta) activity after 1, 3, and 6 days in response to 39 nM BPA, 15 mu M BPA, and 200 pM 17 beta-Estradiol (E-2). In addition to Ca2+ concentration measurement, qPCR for proliferation and differentiation biomarkers was performed, to examine cell behavior. Fulvestrant-mediated ER inhibition was employed to seek for a mechanistic role of ER beta in regulating BPA-emanating effects. Results. While both E-2 and BPA yielded ER beta activation, 39 nM BPA and 200 pM E-2 did not change MKI67 proliferation marker expression, but reduced transcription of differentiation markers. Conversely, 15 mu M BPA reduced MKI67 transcription, but significantly increased differentiation gene expression and intracellular Ca2+ levels. Fulvestrant-induced ER beta inhibition yielded complete elimination of all E-2 - and BPA-triggered modulatory effects, suggesting a mechanistic role of activated ER beta for BPA-mediated Ca2+ influx and keratinocyte differentiation. Significance. Concerning cell behavior, these findings provide significant evidence of a threshold-dependent transcription of proliferation and differentiation-related genes as well as Ca2+ influx in response to 39 nM and 15 mu M low-dose BPA, which identify a mechanistic role of activated ER beta in oral keratinocytes. (C) 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.