Kellert Marco, Brink Andreas, Richter Ingrid, Schlatter Josef, Lutz Werner K
Department of Toxicology, University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany.
Mutat Res. 2008 Dec 8;657(2):127-32. doi: 10.1016/j.mrgentox.2008.08.014. Epub 2008 Aug 28.
Furan is found in various food items and is cytotoxic and carcinogenic in the liver of rats and mice. Metabolism of furan includes the formation of an unsaturated dialdehyde, cis-2-butene-1,4-dial (BDA). In view of the multifunctional electrophilic reactivity of BDA, adduct formation with protein and DNA may explain some of the toxic effects. Short-term tests for genotoxicity of furan in mammalian cells are inconclusive, little is known for BDA. We investigated BDA generated by hydrolysis of 2,5-diacetoxy-2,5-dihydrofuran for genotoxicity in L5178Y tk+/- mouse lymphoma cells using standard procedures for the comet assay, the micronucleus test, and the mouse lymphoma thymidine kinase gene mutation assay, using 4-h incubation periods. Cytotoxicity was remarkable: cell viability at concentrations>or=50 microM was reduced to <50%. In the dose range up to 25 microM, viability was >90%. Measures of comet-tail length and thymidine-kinase mutant frequency were increased 1.6- and 2.4-fold above control, respectively. Analysis of three fully independent replicates with a linear mixed-effects model showed a highly significant increase with concentration for both endpoints. Compared to methyl methanesulfonate used as a positive control, BDA was of similar potency with respect to genotoxicity, but it was much more cytotoxic. Furan added to cell cultures at doses that resulted in time-averaged effective concentrations of up to 3100 microM was neither cytotoxic nor genotoxic. A potential cross-linking activity of BDA was investigated by checking whether gamma radiation-induced DNA migration in the comet assay could be reduced by pre-treatment with BDA. In contrast to the effect of the positive control glutaraldehyde, BDA treatment did not reduce the comet tail length. On the contrary, an increase was observed at >or=100 microM BDA, which was attributable to early apoptotic cells. Although BDA was found to be a relatively potent genotoxic agent in terms of the concentration necessary to double the background measures, cytotoxicity strongly limited the concentration range that produced interpretable results. This may explain some of the inconclusive results and indicates that non-genotoxic effects must be taken into account in the discussion of the modes of toxic and carcinogenic action of furan.
呋喃存在于多种食品中，对大鼠和小鼠的肝脏具有细胞毒性和致癌性。呋喃的代谢包括形成一种不饱和二醛，即顺式-2-丁烯-1,4-二醛（BDA）。鉴于BDA具有多官能亲电反应性，其与蛋白质和DNA形成加合物可能解释了部分毒性作用。呋喃在哺乳动物细胞中的遗传毒性短期试验结果尚无定论，而关于BDA的情况则知之甚少。我们使用彗星试验、微核试验和小鼠淋巴瘤胸苷激酶基因突变试验的标准程序，对由2,5-二乙酰氧基-2,5-二氢呋喃水解产生的BDA在L5178Y tk+/-小鼠淋巴瘤细胞中的遗传毒性进行了研究，孵育时间为4小时。细胞毒性显著：浓度≥50微摩尔时细胞活力降至50%以下。在高达25微摩尔的剂量范围内，活力>90%。彗星尾长和胸苷激酶突变频率的测量值分别比对照增加了1.6倍和2.4倍。用线性混合效应模型对三个完全独立的重复实验进行分析表明，两个终点指标均随浓度显著增加。与用作阳性对照的甲基磺酸甲酯相比，BDA在遗传毒性方面效力相似，但细胞毒性更强。以导致时间平均有效浓度高达3100微摩尔的剂量添加到细胞培养物中的呋喃既无细胞毒性也无遗传毒性。通过检查在彗星试验中γ辐射诱导的DNA迁移是否能通过BDA预处理而减少，研究了BDA潜在的交联活性。与阳性对照戊二醛的作用相反，BDA处理并未缩短彗星尾长。相反，在BDA浓度≥100微摩尔时观察到增加，这归因于早期凋亡细胞。尽管就使背景测量值加倍所需的浓度而言，BDA被发现是一种相对有效的遗传毒性剂，但细胞毒性强烈限制了产生可解释结果的浓度范围。这可能解释了一些不确定的结果，并表明在讨论呋喃的毒性和致癌作用模式时必须考虑非遗传毒性效应。
