Department of Science, University Roma Tre, Rome, Italy.
PLoS One. 2014 Feb 20;9(2):e88961. doi: 10.1371/journal.pone.0088961. eCollection 2014.
17β-estradiol (E2)-dependent estrogen receptor (ER) α intracellular concentration is a well recognized critical step in the pleiotropic effects elicited by E2 in several target tissues. Beside E2, a class of synthetic and plant-derived chemicals collectively named endocrine disruptors (EDs) or xenoestrogens bind to and modify both nuclear and extra-nuclear ERα activities. However, at the present no information is available on the ability of EDs to hamper ERα intracellular concentration. Here, the effects of bisphenol A (BPA) and naringenin (Nar), prototypes of synthetic and plant-derived ERα ligands, have been evaluated on ERα levels in MCF-7 cells. Both EDs mimic E2 in triggering ERα Ser118 phosphorylation and gene transcription. However, only E2 or BPA induce an increase of cell proliferation; whereas 24 hrs after Nar stimulation a dose-dependent decrease in cell number is reported. E2 or BPA treatment reduces ERα protein and mRNA levels after 24 hrs. Contrarily, Nar stimulation does not alter ERα content but reduces ERα mRNA levels like other ligands. Co-stimulation experiments indicate that 48 hrs of Nar treatment prevents the E2-induced ERα degradation and hijacks the physiological ability of E2:ERα complex to regulate gene transcription. Mechanistically, Nar induces ERα protein accumulation by preventing proteasomal receptor degradation via persistent activation of p38/MAPK pathway. As a whole these data demonstrate that ERα intracellular concentration is an important target through which EDs hamper the hormonal milieu of E2 target cells driving cells to different outcomes or mimicking E2 even in the absence of the hormone.
17β-雌二醇（E2）依赖性雌激素受体（ER）α细胞内浓度是 E2 在几种靶组织中引发多效性作用的公认关键步骤。除了 E2 之外，一类合成和植物衍生的化学物质统称为内分泌干扰物（EDs）或外源性雌激素，它们可以结合并改变核内和核外 ERα 的活性。然而，目前尚无关于 EDs 干扰 ERα 细胞内浓度的能力的信息。在这里，评估了双酚 A（BPA）和柚皮素（Nar）作为合成和植物衍生 ERα 配体的原型对 MCF-7 细胞中 ERα 水平的影响。两种 EDs 均可模拟 E2 触发 ERα Ser118 磷酸化和基因转录。然而，只有 E2 或 BPA 诱导细胞增殖增加；而在 Nar 刺激 24 小时后，报告细胞数量呈剂量依赖性下降。E2 或 BPA 处理后 24 小时降低 ERα 蛋白和 mRNA 水平。相反，Nar 刺激不会改变 ERα 含量，但会像其他配体一样降低 ERα mRNA 水平。共刺激实验表明，Nar 处理 48 小时可防止 E2 诱导的 ERα 降解，并劫持 E2：ERα 复合物调节基因转录的生理能力。从机制上讲，Nar 通过持续激活 p38/MAPK 途径来阻止蛋白酶体受体降解，从而导致 ERα 蛋白积累。总的来说，这些数据表明 ERα 细胞内浓度是 EDs 干扰 E2 靶细胞激素环境的一个重要靶点，导致细胞产生不同的结果，或即使没有激素也能模拟 E2。
