Rapid estrogenic signaling activities of the modified (chlorinated, sulfonated, and glucuronidated) endocrine disruptor bisphenol A

Abstract

An automated in-vitro, medium-throughput screening method was designed to compare the rapid actions of 10−9M estradiol to those of modified bisphenol A (BPA) compounds: chlorinated (created due to waste water treatment) and phase II BPA metabolites. GH3/B6/F10 prolactinoma cells were treated with increasing concentrations (10−15‒10−7M) of BPA or modified BPA compounds for 5 min, and phospho-activated kinases assayed via a fixed-cell plate immunoassay. Mono- and di-chlorinated BPAs phospho-activated the extracellular signal-regulated kinase (ERK), while tri-chlorinated BPA dephosphorylated ERK to a level below vehicle-treated controls. When c-Jun-N-terminal kinase (JNK) was examined, mono-chlorinated compounds caused no responses (similar to unmodified BPA), while di- and tri-chlorinated BPAs caused extensive dephosphorylation. When deconjugation of di-sulfated and glucuronidated metabolites were inhibited, these stably conjugated compounds were unable to activate either ERK or JNK, but could inactivate them. This suggests that the modified versions of BPA (extensively chlorinated or conjugated metabolites) may alter the ability of membrane estrogen receptor-α (which mediates these rapid signaling responses) to partner with other signaling proteins. While other studies have examined the estrogenicity of modified (chlorinated and conjugated) BPA compounds in gene expression assays, this is the first to examine their actions via rapid, membrane-initiated signaling pathways.