Ecotoxicological applications and significance of the comet assay

Abstract

Application of the single-cell gel electrophoresis or comet assay has revolutionized the field of genetic ecotoxicology or eco-genotoxicology. It is a rapid, sensitive and relatively inexpensive method providing the opportunity to study DNA damage (including oxidative damage), repair and cell death (apoptosis) in different cell types without prior knowledge of karyotype and cell turnover rate. The assay has, however, often attracted criticism for its lack of ecotoxicological relevance. In addition, in contrast to genetic toxicology where rapid technical progress has been made to improve cell- and tissue-specific adoption of the assay, only limited advancement has been made to transfer the methodologies to ecotoxicological studies. While reviewing the recent information available in the literature and underscoring the importance of induced genetic damage in natural species, the aims of this article are to (i) highlight and judiciously analyse the ecotoxicological relevance of the assay; (ii) attempt to correlate the comet response with other relevant biological responses or biomarkers; (iii) identify the technical challenges and various factors affecting its application in order to make it reliable, reproducible and robust; (iv) critically compare the technical developments in genetic toxicology and genetic ecotoxicology and (v) evaluate the future developments with respect to applications of the assay. It is suggested that while complementing other ecotoxicological parameters and further improving the methodologies, the comet assay will continue to play an important role in genetic ecotoxicology to determine induced genetic damage, which has significant consequences for short- and long-term survival of the natural or wild species. Information obtained through integrated studies using simultaneous applications of multiple biomarkers on different wild organisms could also provide an holistic dimension of toxicological impact of environmental contaminants for the protection of human health.

Evaluation of genotoxic and oxidative stress response to dimethoate in freshwater fish Channa punctatus (Bloch)

“…Some studies have previously reported on the genotoxic and mutagenic potential of organophosphate insecticide cholrprifos and monocorotofos in C.punctatus (Ali et al, 2008). It is well established that toxicants with oxidative stress have the potential to attack DNA resulting in clastogenic and molecular damages (Jha, 2008). An increase in the frequency of MN in dimethoate treated fish is an indication of chromosome damage.…”

Paternal contribution to development: Sperm genetic damage and repair in fish

“…Moreover, due to limited antioxidant protection and quite high unsaturated fatty acid content, fish sperm has been shown sensitive to oxidative stress involved in DNA damage after exposure to physical or chemical stresses (Li and Reinberg 2011;Cabrita et al 2011;Hulak et al 2013;Labbe et al 1995;. Such characteristics make spermatozoa a relevant and sensitive target to assess reproductive impairment through the loss of DNA integrity as demonstrated in several aquatic organisms exposed to environmental stressors (Galloway et al 2010;Jha AN 2008;Lacaze et al 2011;Santos et al 2013a). …”

Interaction between gene repair and mobile elements-induced activity systems after low-dose irradiation

“…The preview of the comets was processed using the program CometScore TM (version 1.5, TriTek Corp., Sumerduck, VA). The DNA DSB were assessed by the most informative and precise parameter OTM (Olive tail moment, the distance from the center of the head to the density center of the comets tail multiplied by tDNK[%]) (Olive 1999;Jha 2008). For each variant of each replicate 100 cells were counted (in total 300 cells per one variant were analyzed).…”