Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
College of Chemistry and Chemical Engineering, Xinjiang Normal University, Urumqi, Xinjiang 830054, China.
Toxicol Sci. 2019 Apr 1;168(2):339-348. doi: 10.1093/toxsci/kfy307.
Chemical pollutants often co-occur and can interact to cause unexpected combined toxic effects. Both pentachlorophenol (PCP) and copper-1,10-phenanthroline [Cu(OP)2], used as wood preservatives, coexist in fluids and tissues of ordinary population. Our previous studies demonstrate that a combination of subtoxic PCP and Cu(OP)2 causes synergistic toxicity on Escherichia coli and hepatocarcinoma cells. However, it is not clear whether this effect also occurs in normal hepatocytes; and if so, what are the differences as compared with the hepatocarcinoma cells. We demonstrate that the combination of low-toxic PCP and Cu(OP)2 (0-1.6 µM; PCP/Cu(OP)2 molar ratio: 2:1) induces a concentration-dependent intracellular copper accumulation, apoptosis, caspase-3/9 activation, depolarization of mitochondrial membrane potential, and oxidative stress (reactive oxygen species increasing and glutathione/oxidized glutathione ratio decreasing) in both normal hepatocytes HL-7702 and hepatocarcinoma HepG2 cells. However, HepG2 cells are more susceptible to the above molecular events as compared with HL-7702 cells. Further data reveal that PCP/Cu(OP)2 markedly decreases X chromosome-linked inhibitor of apoptosis (XIAP), p-ERK-1/2, and p-JNK protein expression in HepG2, but not HL-7702. Overexpression of XIAP gene in HepG2 significantly blocks PCP/Cu(OP)2-induced cytotoxicity, caspase activity, apoptosis, ROS accumulation, and antioxidant genes expression. These results suggest that the combination of low-toxic PCP and Cu(OP)2 preferentially induce synergistic cytotoxicity in human hepatocarcinoma cells by XIAP-ROS-apoptosis pathway, compared with the normal hepatocytes. The present data not only confirm the synergistic toxicity of PCP/Cu(OP)2 combination in normal liver cells, but also suggest a possible opportunity in developing new therapeutic approaches for liver cancer by sensitizing cancer cells to chemotherapy.
化学污染物经常共同存在，并可能相互作用，导致意想不到的联合毒性效应。五氯苯酚（PCP）和铜-1,10-菲啰啉[Cu(OP)2]都被用作木材防腐剂，它们共同存在于普通人群的体液和组织中。我们之前的研究表明，亚毒性 PCP 和 Cu(OP)2 的组合对大肠杆菌和肝癌细胞具有协同毒性作用。然而，目前尚不清楚这种效应是否也发生在正常肝细胞中；如果是这样，与肝癌细胞相比有何不同。我们证明，低毒性 PCP 和 Cu(OP)2 的组合（0-1.6 μM；PCP/Cu(OP)2 摩尔比：2:1）可诱导浓度依赖性的细胞内铜积累、凋亡、半胱天冬酶-3/9 激活、线粒体膜电位去极化以及氧化应激（活性氧增加和谷胱甘肽/氧化型谷胱甘肽比例降低），这在正常肝细胞 HL-7702 和肝癌 HepG2 细胞中均有发生。然而，与 HL-7702 细胞相比，HepG2 细胞对上述分子事件更为敏感。进一步的数据显示，PCP/Cu(OP)2 显著降低了 HepG2 中 X 染色体连接的凋亡抑制剂（XIAP）、p-ERK-1/2 和 p-JNK 蛋白的表达，但对 HL-7702 细胞没有影响。在 HepG2 中转染 XIAP 基因可显著阻断 PCP/Cu(OP)2 诱导的细胞毒性、半胱天冬酶活性、凋亡、ROS 积累和抗氧化基因表达。这些结果表明，与正常肝细胞相比，低毒性 PCP 和 Cu(OP)2 的组合通过 XIAP-ROS-凋亡途径优先诱导人肝癌细胞的协同细胞毒性。这些数据不仅证实了 PCP/Cu(OP)2 组合在正常肝细胞中的协同毒性作用，而且为通过使癌细胞对化疗敏感来开发肝癌新的治疗方法提供了可能。
