Developmental Toxicity by the E,E-Trifloxystrobin Enantiomer in Early-Stage Zebrafish (Danio Rerio) Embryos: Treatment with E,E-Trifloxystrobin Induces Cardiac Abnormalities and Vasotoxic Effects in Vessel Development

Abstract

Pesticides to eradicate pests may be composed of isomers, and in the strobilurin fungicides, trifloxystrobin (TFS) is an enantioselective fungicide with the active form of E,E-TFS. This study aimed to assess the acute toxicity of four enantiomers, E,E-, E,Z-, Z,E-, and Z,Z-TFS in zebrafish (Danio rerio) embryos. Only E,E-TFS was acutely toxic under experimental conditions, and the LC50 value ​​of E,E-TFS were estimated as 0.68 mg/L. After treatment with E,E-TFS, phenotypic changes were observed in the treated embryos, including pericardial and yolk-sac edema, spine curvature, and blood pooling. E,E-TFS shortened whole body length in the treated embryos by increasing the total intersegmental vessel numbers using a Tg(Fli1:EGFP) zebrafish line. Moreover, E,E-TFS treatment on a Tg(cmlc2;EGFP) zebrafish line was related to cardiac malformation at the treated concentration of 0.25 mg/L with a failure of heart function, lowering heartbeat rate. With the differential gene expression related to heart development, vmhc and cacna1c genes were significantly down-regulated, encoding ventricular myosin heavy chain and calcium voltage-gated channel subunit alpha 1C. Taken together, it is necessary to monitor E,E-TFS enantiomers regularly with high caution after field application, and further studies should be conducted on the chronic exposure of environmental organisms to these isomers.

Keywords: E, E-trifloxystrobin, enantioselective toxicity, abnormal development, cardiac function failure, calcium voltage-gated channel