Effects of dinotefuran and its metabolites on the early life stage development of medaka (Oryzias latipes): In vivo and in silico studies

Dinotefuran (DINO), a widely used neonicotinoid insecticide, has attracted significant attention because of its environmental risks. Although DINO is metabolized in the environment, its specific toxicological risks remain unclear. In this study, we aimed to determine the effects of DINO and its metabolites, 2-nitro-1-(tetrahydro-3-furylmethyl)guanidine (FNG), 1-methyl-3-(tetrahydro-3-furylmethyl) guanidine (DN), 1-methyl-3-(tetrahydro-3-furylmethyl)-urea (UF), and N-aminodinotefuran (NAD) on the embryonic development of medaka ( Oryzias latipes ), as incorporated by a nanosecond pulsed electric field (nsPEF) technique. No acute toxicity leading to death was observed during the early developmental stages of medaka exposed to DINO and its metabolites at concentrations of 1 and 2 mM; however, some larvae malformed after hatching, indicating developmental effects caused by DINO and its metabolites. Approximately 10% of the larvae in all the treatment groups were malformed after hatching, with significant differences observed in the 2 mM NAD treatment group. Transcriptome sequencing revealed that the neuroactive ligand–receptor interaction pathway plays an important role in DINO-induced developmental toxicity. Furthermore, we constructed in silico homology model of the medaka α4β2 nicotinic acetylcholine receptor (nAChR). Molecular docking simulation revealed that DINO metabolites bind stably to nAChR. The order of the interaction potentials of DINO with medaka α4β2 nAChR was as follows: NAD > DINO > DN > FNG > UF. Overall, our findings provide fundamental data regarding the biological roles of DINO and its metabolites in the developmental toxicity responses of fish to neonicotinoids.