Effects And Mechanisms Of Microcystin-LR On Kidney And Hatchability Of Offspring In Zebrafish

In recent years,cyanobacterial blooms and the produced cyanotoxins pose a serious threat to environment and human health.Microcystins(MCs)are the most widely distributed and most poisonous cyanotoxins,among which microcystin-LR(MCLR)is the most toxic.Considering the potential harms caused by MCLR to ecological environment and human beings,zebrafish were selected as a model to investigate the toxicological effects on renal and hatchability.The main results are as below:1.In a renal toxic experiment,adult female zebrafish were exposed to MCLR(0,1,5 and 25 ?g/L)for 60 days.We found that exposure to MCLR caused histopathological lesions,which were characterized by cytoplasm disappearance,the volume of nucleus increaser,epithelia cells irregular shapes,deeper epithelial cells stain,necrosis,and reduced renal space.RNA-Seq analysis indicated that exposure to MCLR significantly interfered with renal gene expressions,and a total of 514 up-regulated and 9937 down-regulated genes were got from RNA-Seq.Through GO analysis,it was found that organelle membrane,the transport and synthesis of DNA and protein were dysfunction.KEGG pathway enrichment analysis showed that oxidative phosphorylation,cell cycle,and protein processing in endoplasmic reticulum,which were related to oxidative stress and apoptosis,were influenced.We speculated that oxidative stress and apoptosis were the main primary cases of MCLR-induced nephrotoxicity.Furthermore,terminal deoxynucleotide transferase-mediated deoxyUTP nick end labelling(TUNEL)assay,negative changes of the reactive oxygen species(ROS)level as well as apoptotic-related gene,protein expressions and enzyme activities showed that MCLR exposure induced renal cell apoptosis.The results suggested that apoptosis is a primary case of MCLR-induced nephrotoxicity.2.In a hatchability experiment,adult zebrafish were exposed to MCLR(0,0.9,4.5 and 22.5 ?g/L)for 45 days.The results showed that MCLR could potentially be transferred from parents to offspring,and reducing hatchability of zebrafish.The possible mechanisms may be that(1)The hatch enzyme activity and secretion is inhibited,which resulted in breaking chorion harder;(2)MCLR inhibits the genes expressions,which relate to development of hatching gland,and that may reduce hatch ability of zebrafish.Furthermore,the hatchability effects of MCLR in the presence of nano-polystyrene(NPS)were also detected in this study.The results showed that the hatching rate was further reduced and the contents of MCLR in embryo were increased in comparison with MCLR exposure alone.We speculated that NPS could adsorb MCLR,following by enhancing the toxicity of MCLR.