Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK S7N 5E2, Canada.
Metallomics. 2017 Jun 21;9(6):744-756. doi: 10.1039/c7mt00006e.
The present study evaluated the mechanistic underpinnings of the interactive effects of selenium (Se), both inorganic (selenite) and organic (selenomethionine (SeMet)), against arsenite (As-III) cytotoxicity using rainbow trout (Oncorhynchus mykiss) hepatocytes in primary culture. Arsenite is known to induce cytotoxic effects by disrupting cellular redox homeostasis. In contrast, Se is essential for the maintenance of cellular anti-oxidative machinery, but when present above a threshold concentration, can also induce reactive oxygen species (ROS) generation and cause oxidative damage. In this study, hepatocytes were exposed to 100 μM arsenite independently or in combination with selenite or SeMet (5-40 μM) for 24 h. Exposure to arsenite alone reduced cell viability by inducing intracellular ROS generation, which also corresponded with a concomitant decrease in cellular thiol (GSH : GSSG) ratio and the activities of enzymatic antioxidants (GPx and SOD). Both selenite and SeMet were found to ameliorate the arsenite-induced loss of cell viability and thiol balance significantly, but only at low-intermediate exposure levels (5-20 μM), with selenite being more effective than SeMet. Further analyses of cellular antioxidative pathways, using specific pharmacological treatments, revealed that selenite and SeMet mediate their protective effects against arsenite toxicity via different mechanisms. Selenite ameliorates arsenite-induced oxidative stress primarily by augmenting enzymatic antioxidants (especially SOD), whereas SeMet elicits its protective response essentially by upregulating the non-enzymatic antioxidative pathway that involves GSH. Overall, our study demonstrated that the antagonistic interactions of arsenite and Se at the cellular level are influenced by the exposure dose as well as the chemical speciation of Se.
本研究评估了硒（Se），包括无机（亚硒酸盐）和有机（硒代蛋氨酸（SeMet）），对鲤鱼（Oncorhynchus mykiss）原代培养肝细胞中砷酸盐（As-III）细胞毒性的相互作用的机制基础。砷酸盐已知通过破坏细胞内氧化还原稳态来诱导细胞毒性作用。相比之下，硒是维持细胞抗氧化机制所必需的，但当存在于阈值浓度以上时，也可以诱导活性氧（ROS）的产生并导致氧化损伤。在这项研究中，肝细胞暴露于 100 μM 砷酸盐中，单独或与亚硒酸盐或 SeMet（5-40 μM）联合暴露 24 小时。单独暴露于砷酸盐会通过诱导细胞内 ROS 生成而降低细胞活力，这也与细胞硫醇（GSH：GSSG）比率和酶抗氧化剂（GPx 和 SOD）活性的同时降低相对应。发现亚硒酸盐和 SeMet 均能显著改善砷酸盐诱导的细胞活力和硫醇平衡丧失，但仅在低-中等暴露水平（5-20 μM）下，亚硒酸盐比 SeMet 更有效。使用特定的药理学处理对细胞抗氧化途径进行进一步分析，表明亚硒酸盐和 SeMet 通过不同的机制介导其对砷酸盐毒性的保护作用。亚硒酸盐通过增强酶抗氧化剂（尤其是 SOD）来改善砷酸盐诱导的氧化应激，而 SeMet 通过上调涉及 GSH 的非酶抗氧化途径来引发其保护反应。总体而言，我们的研究表明，砷酸盐和 Se 在细胞水平上的拮抗相互作用受到暴露剂量以及 Se 的化学形态的影响。
