Effects And Mechanisms Of Water Pollutant Tris(1,3-dichloro-2-propyl)phosphate On Growth And Development In Fish

As one of the main substitutes for brominated flame retardants,tris(1,3-dichloro-2-propyl)phosphate(TDCIPP)has been commonly added in a variety of products.As an additive flame retardant(FR),TDCIPP is easily released into the surrounding environment during its manufacturing,using,disposal and recycling process and runoff into aquatic environment finally.TDCIPP has been frequently detected in a variety of aquatic media around the world.Therefore,the potential risks of TDCIPP to aquatic organisms(such as fish)are of particular concern.Therefore,based on the previous research in our laboratory,this study first use zebrafish as the experimental model and performed the second-generation exposure,the effects of TDCIPP on the growth,gonadal development,gametes damage and offspring development of F1 generation zebrafish and the possible mechanism were explored.In addition,crucian carp(Carassius auratus)which widely distributed in natural waters was used to evaluated the growth effect of TDCIPP on fish and illustrated the potential molecular mechanism of TDCIPP inhibiting fish growth.(1)We investigated developmental toxicity of environmentally relevant concentrations of(0,50,500 or 5000 ng/L)TDCIPP in F1 generation zebrafish larvae.After exposure,TDCIPP caused stronger growth inhibition in F1 generation zebrafish larvae compared with F0,and down regulated the expression of genes(gh,igf1,igf2b)involved in GH/IGF axis.Besides,we found that after exposure,the concentration of TDCIPP in F1 generation zebrafish were significantly higher than that in F0 generation.These results indicated that with the increase exposure of time and generations,the increased accumulation of TDCIPP resulting in a stronger growth-inhibiting effect.(2)The effects of TDCIPP on gonadal development and offspring growth of F1 generation zebrafish were conducted.The results showed that after exposure to 150 dpf,TDCIPP decreased cumulative production and GSI in F1 generation females,and down regulated the expression of gene associated with gonadal development(igf3),but had no effect on males.Although a few genes expression were changed in the HPG axis,but no significant changes were observed in the ovarian tissue sections and sex hormone levels in plasma.These results suggested that TDCIPP may inhibit the gonad development of females through down regulated the expression of igf3.Furthermore,TDCIPP decreased sperm motility of males and caused abnormal micropyle on eggs,which decreased the fertilization rate of offspring.Besides,this research found that maternal(F1 generation)exposure to TDCIPP resulted in growth inhibition of offspring(F2 generation).(3)The effect and mechanisms of maternal transfer of TDCIPP on offspring survival and growth was investigated.The results showed that maternal exposure of TDCIPP inhibited the growth of offspring zebrafish larvae.Although TDCIPP was detected in the eggs of offspring(about 1 ng/embryo),but after injected the same concentrations of TDCIPP in normal embryos,no significant effect on the survival rate and growth of zebrafish were observed.However,concentrations of some m RNA and proteins in offspring eggs were significant changed after maternal exposure to TDCIPP and these changes were related to the early embryonic development of zebrafish.This suggested that changes of biological substances in eggs play an important role in maternal transfer toxicity of TDCIPP.(4)The effect on TDCIPP on crucian carp(Carassius auratus)growth was evaluated and related molecular mechanisms were explored.Results demonstrated that TDCIPP treatment significantly inhibited growth of crucian carp,down-regulated the expression of ghs,and decreased the secretion of growth hormones.Vitro exposure,molecular docking and luciferase experiments demonstrated that TDCIPP could bind to growth hormone releasing hormone receptor(Ghrhr)protein of crucian carp,and activate c AMP signaling pathway to promote the expression of ghs.But in normal physiological conditions(normal levels of endogenous hormones),TDCIPP disturbed the stimulation of growth hormone releasing hormone to the expression of ghs and secretion of growth hormones,resulting in the growth inhibition of crucian carp.