Nakashima Tamiji, Okada Toshihiro, Asahi Junpei, Yamashita Akihisa, Kawai Kazuaki, Kasai Hiroshi, Matsuno Koji, Gamou Shinobu, Hirano Takeshi
Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, Japan, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, Fukuoka 807-8555, Japan.
Mutat Res. 2008 Jul 31;654(2):138-44. doi: 10.1016/j.mrgentox.2008.05.011. Epub 2008 Jun 7.
Heavy metal pollution of soil causes biological problems, such as mutagenicity to living organisms, including human beings. However, few methods have been developed to assess metal mutagenicity in soil. To avoid metal mutagenicity, an adequate bio-monitoring method is required. In the present study, to determine if the analysis of oxidative DNA damage generated in the earthworm is a useful bio-monitoring method for soil mutagenicity, the accumulation of 8-hydroxydeoxyguanosine (8-OH-dG), a major form of oxidative DNA damage, in Eisenia fetida (Savigny, 1826) treated with cadmium chloride (CdCl2) or nickel chloride (NiCl2) was analyzed. E. fetida was treated with Cd (10 or 200 microg/g soil) or Ni (10 or 200 microg/g soil) for 1, 2, and 3 weeks or 3 months. After metal exposure, the metal concentration in E. fetida was analyzed by atomic absorption spectrometry and the 8-OH-dG accumulated in E. fetida was analyzed by HPLC analyses and immunohistochemistry. Atomic absorption spectrometry revealed that Cd, but not Ni, accumulated within E. fetida. The 8-OH-dG levels in the DNA of E. fetida treated with Cd for 3 months were significantly higher than those in control E. fetida. Moreover, immunohistochemical analyses revealed that positive signals for 8-OH-dG accumulation in seminal vesicles were detected only in E. fetida treated with 10 microg of Cd for 3 months. Although some points remain unresolved, a bio-monitoring system analyzing the DNA damage generated in the earthworm might be useful for the assessment of the mutagenicity of soil contaminated with various heavy metals, such as Cd.
土壤中的重金属污染会引发生物学问题，比如对包括人类在内的生物产生致突变性。然而，目前用于评估土壤中金属致突变性的方法却很少。为避免金属致突变性，需要一种合适的生物监测方法。在本研究中，为确定对蚯蚓体内产生的氧化性DNA损伤进行分析是否是一种用于监测土壤致突变性的有效生物监测方法，我们分析了用氯化镉（CdCl2）或氯化镍（NiCl2）处理后的赤子爱胜蚓（Eisenia fetida，Savigny，1826）体内8-羟基脱氧鸟苷（8-OH-dG，氧化性DNA损伤的主要形式）的积累情况。将赤子爱胜蚓分别用镉（10或200微克/克土壤）或镍（10或200微克/克土壤）处理1、2、3周或3个月。金属暴露后，通过原子吸收光谱法分析赤子爱胜蚓体内的金属浓度，通过高效液相色谱分析和免疫组织化学分析赤子爱胜蚓体内积累的8-OH-dG。原子吸收光谱法显示，镉而非镍在赤子爱胜蚓体内积累。用镉处理3个月的赤子爱胜蚓DNA中的8-OH-dG水平显著高于对照赤子爱胜蚓。此外，免疫组织化学分析显示，仅在经10微克镉处理3个月的赤子爱胜蚓精囊中检测到8-OH-dG积累的阳性信号。尽管一些问题仍未解决，但分析蚯蚓体内产生的DNA损伤的生物监测系统可能有助于评估受镉等各种重金属污染的土壤的致突变性。
