Uhl Maria, Ecker Sonja, Kassie Fekadu, Lhoste Evelyne, Chakraborty Asima, Mohn Georges, Knasmüller Siegfried
Institute of Cancer Research, Borschkegasse 8A, 1090 Vienna, Austria.
Arch Toxicol. 2003 Aug;77(8):477-84. doi: 10.1007/s00204-003-0469-4. Epub 2003 Jul 11.
The aim of the present study was to investigate the antimutagenic effects of chrysin (CR), a flavonoid compound contained in many fruits, vegetables and honey. Earlier investigations with bacterial indicators showed that CR is one of the most potent antimutagens among the flavonoids. In the present study, we tested the compound in the Salmonella strains TA98 and TA100 in combination with benzo(a)pyrene (B(a)P) and 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and found pronounced protective activity over a concentration range between 10 and 100 microg/ml. The compound itself was devoid of mutagenic activity at all concentrations tested. In the micronucleus (MN) assay with human-derived HepG2 cells, a different pattern of activity was seen. CR itself caused significant induction of MN at dose levels > or =15 microg/ml; in combination experiments with B(a)P and PhIP, U-shaped dose-response curves were obtained and protection was found only in a narrow dose range (5 - 10 microg/ml). Our findings indicate that the molecular mechanisms that account for the antimutagenic effects of CR in bacterial cells are different from those responsible for the effects in HepG2 cells. Earlier reports indicate that the antimutagenic effects of CR towards B(a)P and heterocyclic amines in bacterial indicators is due to inhibition of the activity of CYP1A. In contrast to this, we found a significant induction of CYP1A1 activity in HepG2 cells by CR. It can also be excluded that induction of GST, which is involved in the detoxification of polycyclic aromatic hydrocarbons accounts for the protective effects of CR against B(a)P since this enzyme was not significantly induced in the HepG2 cells. In the case of PhIP, induction of UDGPT and/or inhibition of sulfotransferase seen in human derived HepG2 cells after exposure to CR might play a role in the antimutagenic effects. In conclusion, our findings show that data from antimutagenicity studies with bacterial indicators cannot be extrapolated to HepG2 cells, and that CR causes genotoxic effects at higher dose levels in the latter cells. The implications of these observations for human chemoprevention strategies are discussed.
本研究的目的是调查白杨素（CR）的抗诱变作用，CR是一种存在于许多水果、蔬菜和蜂蜜中的类黄酮化合物。早期使用细菌指标进行的研究表明，CR是类黄酮中最有效的抗诱变剂之一。在本研究中，我们在沙门氏菌TA98和TA100菌株中测试了该化合物与苯并(a)芘（B(a)P）和2-氨基-1-甲基-6-苯基咪唑[4,5-b]吡啶（PhIP）的组合，发现在10至100微克/毫升的浓度范围内有明显的保护活性。该化合物在所有测试浓度下均无诱变活性。在用人源HepG2细胞进行的微核（MN）试验中，观察到了不同的活性模式。CR本身在剂量水平≥15微克/毫升时会显著诱导微核；在与B(a)P和PhIP的联合实验中，获得了U形剂量反应曲线，并且仅在狭窄的剂量范围（5-10微克/毫升）内发现了保护作用。我们的研究结果表明，CR在细菌细胞中的抗诱变作用的分子机制与在HepG2细胞中的作用机制不同。早期报告表明，CR对细菌指标中B(a)P和杂环胺的抗诱变作用是由于抑制了CYP1A的活性。与此相反，我们发现CR在HepG2细胞中显著诱导了CYP1A1活性。也可以排除参与多环芳烃解毒的谷胱甘肽S-转移酶（GST）的诱导是CR对B(a)P保护作用的原因，因为该酶在HepG2细胞中未被显著诱导。就PhIP而言，在人源HepG2细胞中暴露于CR后观察到的尿嘧啶DNA糖基化酶（UDGPT）的诱导和/或磺基转移酶的抑制可能在抗诱变作用中起作用。总之，我们的研究结果表明，用细菌指标进行的抗诱变性研究的数据不能外推到HepG2细胞，并且CR在后者细胞中在较高剂量水平下会引起遗传毒性作用。讨论了这些观察结果对人类化学预防策略的影响。
