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The pesticide fipronil affects transcriptional networks related to mitochondrial dysfunction and methylation in zebrafish embryos (Danio rerio)

ABSTRACT: The phenylpyrazole fipronil is a widely used insecticide designed to inhibit γ -amino-butyric acid (GABA) receptors, the major inhibitory neurotransmitter in the central nervous system. Fipronil has been detected in some water systems in the ng/L range, and is reported to be neurotoxic. To address the risks associated with fipronil exposure, we measured morphological, physiological, and molecular responses in zebrafish (Danio rerio) embryos following a 48 hour exposure (20 ng/L – 2 mg/L). Survival was not different than controls following treatments below 200 µg fipronil/L but was ~20% higher with concentrations above 200 µg fipronil/L. Once the embryos hatched, they underwent a 7 day depuration phase. At 9 days post-fertilization (9 dpf), body length and notochord length were not different than controls for any dose. To assess sub-lethal effects, transcriptome profiling was conducted in 9 dpf larvae following 48 hour exposure + 7 dpf depuration to environmentally relevant concentrations of fipronil (200 ng fipronil/L), as well as two higher concentrations of the pesticide (200 µg fipronil/L and 2 mg fipronil/L). Transcriptome profiling revealed that all three concentrations affected pathways related to chromosome condensation and the metabolism of estrogens and androgens as well as genes related to methylation. In addition, 200 ng fipronil/L down-regulated genes related to the circadian clock, histone and DNA methylation, and histone acetylation, while the highest dose increased networks related to immune function (e.g. lectin-induced complement pathway and the alternative complement pathway). The two highest concentrations of fipronil increased the expression of transcriptional networks associated with mitochondrial respiratory chain dysfunction and mitochondrial protein transport. As such, we exposed 24 hpf embryos to fipronil for 24 hours and measured oxygen consumption rate to assess mitochondrial function. There were no differences in basal and maximal respiration in the embryos nor ATP production, and fipronil did not affect mitochondrial bioenergetics. This study suggests that fipronil at environmentally relevant concentrations does not adversely affect the survival or morphology of fish embryos, however sub-lethal endpoints should be examined to more fully characterize the long term effects of fipronil exposure in larval fish.

ORGANISM(S): Danio rerio

PROVIDER: GSE99608 | GEO | 2018/01/31

REPOSITORIES: GEO

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The pesticide fipronil affects transcriptional networks related to mitochondrial dysfunction and methylation in zebrafish embryos (Danio rerio)

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