Liao Yi-Chun, Chen Yi-Fan, Lee Te-Chang
Institute of Pharmacology, National Yang-Ming University, Taipei, 112, Taiwan.
Institute of Biomedical Sciences, Academia Sinica, 128, Sec. 2, Academia Road, Taipei, 11529, Taiwan.
Arch Toxicol. 2015 Nov;89(11):1971-9. doi: 10.1007/s00204-014-1344-1. Epub 2014 Sep 9.
Inorganic arsenite (iAs) is a human carcinogen. Numerous studies have shown that mutation-activated H-Ras is frequently observed in human urothelial carcinomas. The interaction between iAs, an environmental factor, and H-Ras, an oncogene, is not clear. In this study, we explored the genotoxic effects of iAs in human urothelial cells ectopically expressing H-Ras (G12V) an activated H-Ras oncogene. Our results showed that H-Ras(G12V)-transformed human urothelial cells (HUC-RAS) were more susceptible to arsenite-induced cell death, DNA damage, micronuclei formation and anchorage-independent growth than control cells (HUC-neo). Furthermore, iAs treatment induced higher intracellular levels of reactive oxygen species (ROS) in the HUC-RAS cells than in the HUC-neo cells. N-acetyl-L-cysteine could suppress the iAs-induced increases in ROS and genetic damage. We further demonstrated that the intracellular glutathione levels were significantly elevated by the iAs treatment of the HUC-neo cells, but that this effect was not observed in the HUC-RAS cells. The iAs treatment induced higher superoxide dismutase activity in the HUC-neo cells than in the HUC-RAS cells. Alternatively, catalase activity was higher in the HUC-RAS cells than in the HUC-neo cells, but this enzyme was significantly suppressed by iAs. Moreover, iAs activated the ERK and JNK signaling pathways, which are involved in iAs-induced ROS production and genetic damage. Taken together, our present results suggest that elevated catalase activity in H-Ras(G12V)-transformed cells is significantly suppressed by iAs via activation of ERK and JNK signaling pathways and hence attenuate the defense of the neoplastic transformed cells against iAs-induced oxidative injuries.
无机亚砷酸盐（iAs）是一种人类致癌物。大量研究表明，在人类尿路上皮癌中经常观察到突变激活的H-Ras。作为环境因素的iAs与作为癌基因的H-Ras之间的相互作用尚不清楚。在本研究中，我们探讨了iAs对异位表达激活的H-Ras癌基因（G12V）的人类尿路上皮细胞的遗传毒性作用。我们的结果表明，与对照细胞（HUC-neo）相比，H-Ras（G12V）转化的人类尿路上皮细胞（HUC-RAS）对亚砷酸盐诱导的细胞死亡、DNA损伤、微核形成和锚定非依赖性生长更敏感。此外，iAs处理在HUC-RAS细胞中诱导的细胞内活性氧（ROS）水平高于HUC-neo细胞。N-乙酰-L-半胱氨酸可以抑制iAs诱导的ROS增加和遗传损伤。我们进一步证明，iAs处理HUC-neo细胞可使细胞内谷胱甘肽水平显著升高，但在HUC-RAS细胞中未观察到这种效应。iAs处理在HUC-neo细胞中诱导的超氧化物歧化酶活性高于HUC-RAS细胞。另外，过氧化氢酶活性在HUC-RAS细胞中高于HUC-neo细胞，但该酶被iAs显著抑制。此外，iAs激活了ERK和JNK信号通路，这些通路参与了iAs诱导的ROS产生和遗传损伤。综上所述，我们目前的结果表明，iAs通过激活ERK和JNK信号通路显著抑制了H-Ras（G12V）转化细胞中升高的过氧化氢酶活性，从而削弱了肿瘤转化细胞对iAs诱导的氧化损伤的防御能力。
