%0 Journal Article
%T Heavy Metal-Induced Oxidative DNA Damage in Earthworms: A Review
%A Takeshi Hirano
%A Kazuyoshi Tamae
%J Applied and Environmental Soil Science
%D 2010
%I Hindawi Publishing Corporation
%R 10.1155/2010/726946
%X Earthworms can be used as a bio-indicator of metal contamination in soil, Earlier reports claimed the bioaccumulation of heavy metals in earthworm tissues, while the metal-induced mutagenicity reared in contaminated soils for long duration. But we examined the metal-induced mutagenicity in earthworms reared in metal containing culture beddings. In this experiment we observed the generation of 8-oxoguanine (8-oxo-Gua) in earthworms exposed to cadmium and nickel in soil. 8-oxo-Gua is a major premutagenic form of oxidative DNA damage that induces GC-to-TA point mutations, leading to carcinogenesis. 1. Introduction Molecular oxygen is essential for the survival of all aerobic organisms, and reactive oxygen species (ROS), which are byproducts of oxygen metabolism, are harmful for living organisms. Thus, oxygen is a double-edged sword. In fact, ROS are known to directly attack vital cellular components, including proteins, lipids, and nucleic acids. The oxidation of these molecules is associated with cellular dysfunction, leading to various biological responses, such as inflammation and apoptosis. Since ROS, such as superoxide radical , H2O2, and hydroxyl radical , are constantly generated in vivo as byproducts of respiration, agent metabolism, or pathophysiological conditions [1¨C3], it is difficult to completely prevent their harmful effects on cellular components. When ROS attack DNA, oxidized bases are frequently generated [4]. Among the various forms of oxidative DNA damage, 8-oxoguanine (7, 8-dihydro-8-oxoguanine, abbreviated as 8-oxo-Gua or 8-OH-Gua) has been most extensively investigated [5]. Since 8-oxo-Gua is premutagenic, it has been suggested to contribute to human diseases [6, 7]. On the other hand, living organisms have repair systems for oxidative DNA damage, to preserve genetic stability. Recent studies have revealed the complicated network of 8-oxo-Gua repair systems (termed as the ˇ°GO systemˇ±) [8]. However, if unrepaired oxidative DNA damage remains in DNA, then it can induce point mutations. Therefore, the ability to repair the damage is critical in terms of genetic stability. Such measurements of 8-oxo-Gua and its repair ability may open new fields in the studies of risk assessment, molecular epidemiology, and health promotion. Among the many kinds of organisms living in soil, the earthworm is a quite useful organism for the evaluation of metal contamination in soil, because significant positive correlations have been found between the metal concentrations in the earthworm and the cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn)
%U http://www.hindawi.com/journals/aess/2010/726946/