Frontiers in Genetics (May 2015)
Modified comet assay to determine oxidative damage to DNA in aquatic organisms: role of confounding factors influencing the results
Abstract
In common with human health arena, oxidative damage to DNA could play an important role in the development of pathophysiological conditions and ultimately Darwinian fitness of the wild species. Despite the importance, not enough information is available in the literature pertaining to the determination of oxidative damage to DNA in wild species. Among the aquatic organisms, bivalve molluscs and fish species have been widely used for ecotoxicological studies and for the determination of DNA strand breaks using the standard comet assay. For these organisms, the widely used cell types are haemocytes for molluscs and erythrocytes for fish, although other cell types (e.g. gill cells) are also used. Whilst a large number of studies have been carried out using standard comet assay, applications of modified comet assay using bacterial enzymes to determine oxidative damage to DNA has been very limited. We have used these cell types from fish and bivalve species and have determined the oxidative damage to DNA following exposure to a range of environmental stressors (e.g. metals, nanoparticles and hypoxia). Overall these studies suggest that while in vitro optimisation studies using hydrogen peroxide provide a concentration-dependent response, the results do not always mirror the in vitro response in in vivo situations. This disparity could be attributed to different study designs, stressors used in addition to different confounding factors which influence the determination of different biological parameters. More research is therefore required to optimise the application of modified comet assay in different cell types of aquatic organisms before it is widely used for ecotoxicological studies.
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