Enantioselective bioaccumulation, oxidative stress, and thyroid disruption assessment of cis-metconazole enantiomers in zebrafish (Danio rerio)

Chiral triazole pesticides may cause enantioselectively adverse effects to non-target organisms. In this work, we employed zebrafish as an aquatic organism model to explore stereoselective acute toxicity, bioaccumulation, oxidative stress, and thyroid disruption of cis-metconazole enantiomers. The median lethal concentration values of (1S, 5R)-metconazole, (1R, 5S)-metconazole, and the mixture of them against zebrafish were 4.01, 2.61 and 3.17 mg???L- 1, respectively. (1R, 5S)-Metconazole was preferentially bioaccumulated in zebrafish than (1S, 5R)metconazole, and the bioconcentration factor of (1R, 5S)-metconazole was 1.28-fold larger than that of (1S, 5R)metconazole. Then, the activity order of catalase, superoxide dismutase, and glutathione-S transferase enzymes in zebrafish was expressed as (1S, 5R)-metconazole > the mixture > (1R, 5S)-metconazole, while the order of malondialdehyde content in zebrafish was (1R, 5S)-metconazole > the mixture > (1S, 5R)-metconazole. Moreover, cis-metconazole exhibited enantioselective regulation effects on the levels of triiodothyronine and thyroxine in zebrafish, and (1R, 5S)-metconazole possessed stronger thyroid disruption ability to zebrafish than the others. By virtue of molecular docking methodology, the binding affair and docking energy results supported that interactions between (1R, 5S)-metconazole and thyroid hormone receptors were much stronger than those between (1S, 5R)-metconazole and same receptors. This study of enantioselective evaluation of cis-metconazole in zebrafish can provide favorable information for risk assessments of chiral pesticides toward environment and health of aquatic organisms.

Automated summary

This study investigated the enantioselective toxicity, bioaccumulation, oxidative stress, and thyroid disruption of chiral metconazole pesticides using zebrafish as a model organism. The results showed that (1R, 5S)-metconazole exhibited stronger thyroid disruption ability and preferential bioaccumulation in zebrafish compared to (1S, 5R)-metconazole. Furthermore, molecular docking analysis supported the stronger interactions between (1R, 5S)-metconazole and thyroid hormone receptors. This study provides valuable information for the risk assessment of chiral pesticides on aquatic organisms.