A product of incomplete combustion of diesel fuel, 3-nitrobenzanthrone (3-NBA), has been classified as a cancer-causing substance. It first gained attention as a potential urinary bladder carcinogen due to the presence of its metabolite in urine and formation of DNA adducts. The aim of the present study was to characterize the dose–response relationship of 3-NBA in human urothelial cancer cell line (RT4) exposed to concentrations ranging from 0.0003 μM (environmentally relevant) to 80 μM by utilizing toxicological and metabolomic approaches. We observed that the RT4 cells were capable of bioactivation of 3-NBA within 30 min of exposure. Activity measurements of various enzymes involved in the conversion of 3-NBA in RT4 cells demonstrated NAD(P)H:quinone oxidoreductase (NQO1) as the main contributor for its bioactivation. Moreover, cytotoxicity assessment exhibited an initiation of adaptive mechanisms at low dosages, which diminished at higher doses, indicating that the capacity of these mechanisms no longer suffices, resulting in increased levels of intracellular reactive oxygen species, reduced proliferation, and hyperpolarisation of the mitochondrial membrane. To characterize the underlying mechanisms of this cellular response, the metabolism of 3-NBA and metabolomic changes in the cells were analyzed. The metabolomic analysis of the cells (0.0003, 0.01, 0.08, 10, and 80 μM 3-NBA) showed elevated levels of various antioxidants at low concentrations of 3-NBA. However, at higher exposure concentrations, it appeared that the cells reprogrammed their metabolism to maintain the cell homeostasis via activation of pentose phosphate pathway (PPP).
柴油不完全燃烧的产物
3-硝基苯并蒽酮(3-NBA)已被列为致癌物质。由于其在尿液中的代谢产物和DNA加合物,它首次引起了人们对潜在膀胱癌的关注。本研究的目的是利用毒理学和代谢组学方法,研究3-NBA在暴露于浓度为0.0003 μM(环境相关浓度)至80 μM的人类尿路上皮癌
细胞系(RT4)中的剂量反应关系。我们观察到,RT4细胞能够在暴露30分钟内对3-NBA进行
生物活化。对RT4细胞中参与3-NBA转化过程的各种酶的活性测量表明,
NAD(P)H:醌氧化还原酶(NQO1)是其
生物活化的主要贡献者。此外,细胞毒性评估显示,在低剂量下,适应性机制开始启动,而在高剂量下,适应性机制减弱,表明这些机制的能力不再足够,导致细胞内活性氧
水平增加,增殖减少,线粒体膜超极化。为了描述这种细胞反应的潜在机制,我们分析了3-NBA的代谢和细胞中的代谢组学变化。对细胞(0.0003、0.01、0.08、10和80 μM 3-NBA)的代谢组学分析表明,在低浓度的3-NBA中,各种
抗氧化剂的
水平升高。然而,在更高的