Insects experience a diversity of subtoxic and/or toxic xenobiotics through exposure to pesticides and, in the case of herbivorous insects, through plant defensive compounds in their diets. Many insects are also concurrently exposed to antioxidants in their diets. The impact of dietary antioxidants on the toxicity of xenobiotics in insects is not well understood, in part due to the challenge of developing appropriate systems in which doses and exposure times (of both the antioxidants and the xenobiotics) can be controlled and outcomes can be easily measured. However, in Drosophila melanogaster, a well-established insect model system, both dietary factors and pesticide exposure can be easily controlled. Additionally, the mode of action and xenobiotic metabolism of dichlorodiphenyltrichloroethane (DDT), a highly persistent neurotoxic organochlorine insecticide that is detected widely in the environment, have been well studied in DDT-susceptible and -resistant strains. Using a glass-vial bioassay system with blue diet as the food source, seven compounds with known antioxidant effects (ascorbic acid, β-carotene, glutathione, α-lipoic acid, melatonin, minocycline, and serotonin) were orally tested for their impact on DDT toxicity across three strains of D. melanogaster: one highly susceptible to DDT (Canton-S), one mildly susceptible (91-C), and one highly resistant (91-R). Three of the antioxidants (serotonin, ascorbic acid, and β-carotene) significantly impacted the toxicity of DDT in one or more strains. Fly strain and gender, antioxidant type, and antioxidant dose all affected the relative toxicity of DDT. Our work demonstrates that dietary antioxidants can potentially alter the toxicity of a xenobiotic in an insect population.

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Published in PLOS ONE, v. 15, issue 8, e0237986.

© 2020 Abdu-Allah et al.

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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This work was primarily supported by MSU Foundation Professor and AgBioResearch funds provided to BRP and partially funded by an Egyptian government grant (No: SAB-2154).

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All relevant data are within the manuscript and its Supporting Information files.

The Supplementary Information files are available for download as the additional files listed at the end of this record.

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S1 Fig. LC50 (μg/vial DDT) values with 95% confidence limits for adult females and males of D. melanogaster strains Canton-S, 91-C, and 91-R without antioxidant treatment. https://doi.org/10.1371/journal.pone.0237986.s001

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S2 Fig. https://doi.org/10.1371/journal.pone.0237986.s002

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S3 Fig. https://doi.org/10.1371/journal.pone.0237986.s003

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S4 Fig. https://doi.org/10.1371/journal.pone.0237986.s004

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S5 Fig. https://doi.org/10.1371/journal.pone.0237986.s005

pone.0237986.s006.docx (19 kB)
S1 Table. LC50 (μg/vial DDT) values with 95% confidence limits (CL), slope, χ2, and resistance ratio (RR) for D. melanogaster Canton-S adult females and males fed on the indicated serotonin doses. https://doi.org/10.1371/journal.pone.0237986.s006

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