Department of Biochemistry and Molecular Biology, University of Texas Medical Branch Galveston, Texas 77555-0645, USA.
Environ Health Perspect. 2013 Mar;121(3):352-8. doi: 10.1289/ehp.1205826. Epub 2013 Jan 17.
Bisphenol A (BPA) is a well-known endocrine disruptor that imperfectly mimics the effects of physiologic estrogens via membrane-bound estrogen receptors (mERα, mERβ, and GPER/GPR30), thereby initiating nongenomic signaling. Bisphenol S (BPS) is an alternative to BPA in plastic consumer products and thermal paper.
To characterize the nongenomic activities of BPS, we examined signaling pathways it evoked in GH3/B6/F10 rat pituitary cells alone and together with the physiologic estrogen estradiol (E2). Extracellular signal-regulated kinase (ERK)- and c-Jun-N-terminal kinase (JNK)-specific phosphorylations were examined for their correlation to three functional responses: proliferation, caspase activation, and prolactin (PRL) release.
We detected ERK and JNK phosphorylations by fixed-cell immunoassays, identified the predominant mER initiating the signaling with selective inhibitors, estimated cell numbers by crystal violet assays, measured caspase activity by cleavage of fluorescent caspase substrates, and measured PRL release by radioimmunoassay.
BPS phosphoactivated ERK within 2.5 min in a nonmonotonic dose-dependent manner (10-15 to 10-7 M). When combined with 10-9 M E2, the physiologic estrogen's ERK response was attenuated. BPS could not activate JNK, but it greatly enhanced E2-induced JNK activity. BPS induced cell proliferation at low concentrations (femtomolar to nanomolar), similar to E2. Combinations of both estrogens reduced cell numbers below those of the vehicle control and also activated caspases. Earlier activation of caspase 8 versus caspase 9 demonstrated that BPS initiates apoptosis via the extrinsic pathway, consistent with activation via a membrane receptor. BPS also inhibited rapid (≤ 1 min) E2-induced PRL release.
BPS, once considered a safe substitute for BPA, disrupts membrane-initiated E2-induced cell signaling, leading to altered cell proliferation, cell death, and PRL release.
双酚 A（BPA）是一种众所周知的内分泌干扰物，通过膜结合雌激素受体（mERα、mERβ 和 GPER/GPR30）模拟生理雌激素的作用，从而引发非基因组信号转导。双酚 S（BPS）是塑料消费品和热敏纸中 BPA 的替代品。
为了研究 BPS 的非基因组活性，我们单独检测了它在 GH3/B6/F10 大鼠垂体细胞中引发的信号通路，并与生理雌激素雌二醇（E2）一起检测。通过固定细胞免疫测定法检测细胞外信号调节激酶（ERK）和 c-Jun-N-末端激酶（JNK）的特异性磷酸化，以评估三种功能反应：增殖、半胱天冬酶激活和催乳素（PRL）释放的相关性。
我们通过固定细胞免疫测定法检测 ERK 和 JNK 的磷酸化，用选择性抑制剂鉴定起始信号的主要 mER，用结晶紫测定法估计细胞数量，用荧光半胱天冬酶底物的切割测量半胱天冬酶活性，用放射免疫测定法测量 PRL 释放。
BPS 以非单调剂量依赖性方式在 2.5 分钟内磷酸化激活 ERK（10-15 至 10-7 M）。当与 10-9 M E2 联合使用时，生理雌激素的 ERK 反应被减弱。BPS 不能激活 JNK，但它大大增强了 E2 诱导的 JNK 活性。BPS 在低浓度（飞摩尔至纳摩尔）下诱导细胞增殖，与 E2 相似。两种雌激素的组合使细胞数量低于载体对照，并激活半胱天冬酶。早于半胱天冬酶 8 的激活表明半胱天冬酶 9 表明 BPS 通过外源性途径引发细胞凋亡，这与通过膜受体引发的凋亡一致。BPS 还抑制了快速（≤1 分钟）E2 诱导的 PRL 释放。
BPS 曾经被认为是 BPA 的安全替代品，但它会破坏膜起始的 E2 诱导的细胞信号转导，导致细胞增殖、细胞死亡和 PRL 释放的改变。
