Patlolla Anita K, Barnes Constance, Hackett Diahanna, Tchounwou Paul B
Molecular Toxicology Research Laboratory, NIH-Center for Environmental Health, CSET, Jackson State University, Jackson, MS, USA.
Int J Environ Res Public Health. 2009 Feb;6(2):643-53. doi: 10.3390/ijerph6020643. Epub 2009 Feb 12.
Chromium is a widespread industrial waste. The soluble hexavalent chromium Cr (VI) is an environmental contaminant widely recognized to act as a carcinogen, mutagen and teratogen towards humans and animals. The fate of chromium in the environment is dependent on its oxidation state. Hexavalent chromium primarily enters the cells and undergoes metabolic reduction to trivalent chromium, resulting in the formation of reactive oxygen species together with oxidative tissue damage and a cascade of cellular events. However, the results from in vitro studies are often conflicting. The aim of this study was to develop a model to establish relationships between cytotoxicity, genotoxicity and oxidative stress, in human liver carcinoma [HepG2] cells exposed to potassium dichromate. HepG2 cells were cultured following standard protocols and exposed to various concentrations [0-50 microM] of potassium dichromate [K2Cr2O7]. Following exposure to the toxic metal, the MTT assay was performed to assess the cytotoxicity, the thiobarbituric acid test to evaluate the degree of lipid peroxidation as an indicator of oxidative stress and the alkaline comet assay was used to assess DNA damage to study genotoxicity. The results of the study indicated that potassium dichromate was cytotoxic to HepG2 cells. The LD(50) values of 8.83 +/- 0.89 microg/ml, 6.76 +/- 0.99 microg/ml, respectively, for cell mortality at 24 and 48 hrs were observed, indicating a dose- and time-dependent response with regard to the cytotoxic effects of potassium dichromate. A statistically significant increase in the concentration of malondialdehyde [MDA], an indicator of lipid peroxidation, was recorded in exposed cells [15.9 - 69.9 microM] compared to control [13 microM]. Similarly, a strong dose-response relationship (p<0.05) was also obtained with respect to potassium dichromate induced DNA damage (comet assay) in HepG2 cells exposed [3.16 +/- 0.70 - 24.84 +/- 1.86 microns - mean comet tail length]; [12.4 +/- 1.45% - 76 +/- 1.49%-% tail DNA] to potassium dichromate than control [3.07 +/- 0.26 microns--mean comet tail length]; [2.69 + 0.19%-% Tail DNA], respectively. The results demonstrated that potassium dichromate was highly cytotoxic to HepG2 cells, and its cytotoxicity seems to be mediated by oxidative stress and DNA damage.
铬是一种广泛存在的工业废弃物。可溶性六价铬Cr(VI)是一种环境污染物，被广泛认为对人类和动物具有致癌、致突变和致畸作用。铬在环境中的归宿取决于其氧化态。六价铬主要进入细胞并经历代谢还原为三价铬，导致活性氧的形成以及氧化组织损伤和一系列细胞事件。然而，体外研究的结果往往相互矛盾。本研究的目的是建立一个模型，以确定在暴露于重铬酸钾的人肝癌[HepG2]细胞中细胞毒性、遗传毒性和氧化应激之间的关系。HepG2细胞按照标准方案培养，并暴露于不同浓度[0 - 50 microM]的重铬酸钾[K2Cr2O7]。暴露于有毒金属后，进行MTT试验以评估细胞毒性，硫代巴比妥酸试验以评估脂质过氧化程度作为氧化应激指标，碱性彗星试验用于评估DNA损伤以研究遗传毒性。研究结果表明，重铬酸钾对HepG2细胞具有细胞毒性。在24小时和48小时观察到细胞死亡率的半数致死剂量(LD50)值分别为8.83±0.89微克/毫升和6.76±0.99微克/毫升，表明重铬酸钾的细胞毒性作用具有剂量和时间依赖性。与对照组[13 microM]相比，暴露细胞[15.9 - 69.9 microM]中脂质过氧化指标丙二醛[MDA]浓度有统计学意义的增加。同样，在暴露于重铬酸钾的HepG2细胞[3.16±0.70 - 24.84±1.86微米 - 平均彗星尾长];[12.4±1.45% - 76±1.49% - %尾DNA]中，重铬酸钾诱导的DNA损伤(彗星试验)也获得了强剂量反应关系(p<0.05)，而对照组分别为[3.07±0.26微米 - 平均彗星尾长];[2.69 + 0.19% - %尾DNA]。结果表明，重铬酸钾对HepG2细胞具有高度细胞毒性，其细胞毒性似乎是由氧化应激和DNA损伤介导的。
