Comparative DNA Damage and Repair in Echinoderm Coelomocytes Exposed to Genotoxicants

The capacity to withstand and repair DNA damage differs among species and plays a role in determining an organism's resistance to genotoxicity, life history, and susceptibility to disease. Environmental stressors that affect organisms at the genetic level are of particular concern in ecotoxicology due to the potential for chronic effects and trans-generational impacts on populations. Echinoderms are valuable organisms to study the relationship between DNA repair and resistance to genotoxic stress due to their history and use as ecotoxicological models, little evidence of senescence, and few reported cases of neoplasia. Coelomocytes (immune cells) have been proposed to serve as sensitive bioindicators of environmental stress and are often used to assess genotoxicity; however, little is known about how coelomocytes from different echinoderm species respond to genotoxic stress. In this study, DNA damage was assessed (by Fast Micromethod) in coelomocytes of four echinoderm species (sea urchins Lytechinus variegatus, Echinometra lucunter lucunter, and Tripneustes ventricosus, and a sea cucumber Isostichopus badionotus) after acute exposure to H2O2 (0-100 mM) and UV-C (0-9999 J/m2), and DNA repair was analyzed over a 24-hour period of recovery. Results show that coelomocytes from all four echinoderm species have the capacity to repair both UV-C and H2O2-induced DNA damage; however, there were differences in repair capacity between species. At 24 hours following exposure to the highest concentration of H2O2 (100 mM) and highest dose of UV-C (9999 J/m2) cell viability remained high (>94.6 ± 1.2%) but DNA repair ranged from 18.2 ± 9.2% to 70.8 ± 16.0% for H2O2 and 8.4 ± 3.2% to 79.8 ± 9.0% for UV-C exposure. Species-specific differences in genotoxic susceptibility and capacity for DNA repair are important to consider when evaluating ecogenotoxicological model organisms and assessing overall impacts of genotoxicants in the environment.