2,4-Dichlorophenoxyacetic Acid-induced Hematopoietic Toxicity In Zebrafish

Objective: 2,4-Dichlorophenoxyacetic acid is a synthetic auxin,widely used in the world to prevent and control agricultural weeds.The purpose of this study was to assess the effect of 2,4-dichlorophenoxyacetic acid on hematopoiesis.Methods: In this study,zebrafish embryos of 6 hour past fertilization exposed to 0,5,10,20 mg/L 2,4-Dichlorophenoxyacetic acid solution were selected to obs erve the number of embryonic death and hatching.The embryos of 24,48 and72 hour past fertilization were collected,then to observe the change in expres sion of mpx,lyz and cmyb genes.The number and distribution of neutrophils and hematopoietic progenitor cells in Tg(lyz:eGFP)and Tg(cmyb:eGFP)transg enic fish lines were recorded by fluorescence microscopy.5mM splice-blocking AhR2 morpholino was injected into the wild type zebrafish embryos at one c ell stage to knock down AhR2 and then exposed to 2,4-Dichlorophenoxyacetic acid to detect the expression of lyz.Results: Exposure to 2,4-Dichlorophenoxyacetic acid led to a decrease in prolif eration of hematopoietic progenitor cells and monocytes in zebrafish.AhR2 w as specifically enriched in hematopoietic organs of zebrafish.After AhR2 knoc kdown,embryos exposed to 2,4-Dichlorophenoxyacetic acid had less number of monocytes than the embryos directly exposed to 2,4-Dichlorophenoxyacetic aci d.Conclusion: 2,4-Dichlorophenoxyacetic acid has delayed development of hemat opoietic stem cells in both primitive and definitive hematopoiesis and has delayed development of macrophages only in the primitive hematopoiesis stage.E mbryos exposed to 2,4-Dichlorophenoxyacetic acid promotes the expression of AhR2 during primitive and definitive hematopoiesis.Embryos exposure to 2,4-Dichlorophenoxyacetic acid which are knockdown of AhR2 can reduce the tox ical effect on neutrophil development.