Institute of Environmental Pollution and Health, School of Environmental and Chemical Engineering, Shanghai University , Shanghai 200444, P. R. China.
Environ Sci Technol. 2013;47(21):12434-40. doi: 10.1021/es401791s. Epub 2013 Oct 22.
We investigated the effects of hexabromocyclododecanes (HBCDs) at environmentally relevant concentrations on human L02 hepatocytes and explored possible underlying molecular mechanism(s), focusing on functional interactions between the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) and nuclear factor-erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) pathways. The results showed that low concentrations of HBCDs could stimulate cell proliferation in a "DNA-dependent protein kinase catalytic subunit" (DNA-PKcs)-dependent manner, increase protein levels and nuclear translocation of transcription factor Nrf2, and upregulate expression of its target gene heme oxygenase-1 (HO-1). Electrophoretic mobility-shift assays (EMSAs) showed that ARE was a prominent element for HO-1 induction after low-concentration HBCDs exposure. The relationship between PI3K/Akt pathway and Nrf2/HO-1 axis was demonstrated by the finding that pretreatment with PI3K inhibitors (wortmannin, LY294002) attenuated the upregulation of Nrf2 expression induced by HBCDs exposure. Furthermore, knock-down of DNA-PKcs through small interfering RNA blocked Nrf2/HO-1 axis activation in L02 cells exposed to low-concentration HBCDs. Moreover, DNA-PKcs and phosphorylated Akt at Ser(473) proved to be crucial in regulating the Nrf2-ARE pathway. Thus, the PI3K/Akt pathway is essential in regulating Nrf2-ARE pathway activation in L02 cells induced by low-concentration HBCDs.
我们研究了环境相关浓度的六溴环十二烷 (HBCDs) 对人 L02 肝细胞的影响，并探索了可能的潜在分子机制，重点关注磷酸肌醇 3-激酶/蛋白激酶 B (PI3K/Akt) 和核因子-红细胞 2 相关因子 2/抗氧化反应元件 (Nrf2/ARE) 途径之间的功能相互作用。结果表明，低浓度的 HBCDs 可以以“DNA 依赖性蛋白激酶催化亚基”(DNA-PKcs) 依赖性方式刺激细胞增殖，增加转录因子 Nrf2 的蛋白水平和核转位，并上调其靶基因血红素加氧酶-1 (HO-1) 的表达。电泳迁移率变动分析 (EMSA) 表明，ARE 是低浓度 HBCDs 暴露后诱导 HO-1 的主要元件。PI3K/Akt 途径与 Nrf2/HO-1 轴之间的关系通过以下发现得到证明：用 PI3K 抑制剂 (wortmannin、LY294002) 预处理可减弱 HBCDs 暴露诱导的 Nrf2 表达上调。此外，通过小干扰 RNA 敲低 DNA-PKcs 可阻止低浓度 HBCDs 暴露的 L02 细胞中 Nrf2/HO-1 轴的激活。此外，DNA-PKcs 和磷酸化 Akt 在 Ser(473) 被证明是调节 Nrf2-ARE 途径的关键。因此，PI3K/Akt 途径对于调节低浓度 HBCDs 诱导的 L02 细胞中 Nrf2-ARE 途径的激活是必不可少的。
