Study On The Cardiotoxic Effects And Mechanisms Of Low Arsenic Concentrations In Zebrafish Embryos

Arsenic?As?is a metal-like element that is highly toxic and is commonly distributed in nature.With the development of social economy in recent years,industrial and agricultural production and life have discharged a large amount of arsenic-containing substances into the air,soil and water bodies.These sources are collected into the water environment through various channels,making the arsenic pollution in the water body more and more serious.Aroused widespread concern.Arsenic in water mainly exists in the form of inorganic arsenic,and the valence states are mainly trivalent arsenic?AsIII?and pentavalent arsenic?AsV?.A large number of studies have reported the harm of high concentration arsenic to fish,and there are few reports about the harm of low concentration arsenic to fish,but now more and more evidence shows that low concentration arsenic has a certain potential for aquatic organisms Environmental risks.Therefore,this study takes the early development stage of zebrafish as the research object to explore the toxic effects of arsenic concentration on fish,in order to further explore and improve the toxicological effects of low-concentration inorganic arsenic on aquatic growth and development.Experimental data shows:?1?Through the acute toxicity exposure experiment,we found that:AsIII?25?g L^-1significantly inhibited the survival rate of zebrafish?p<0.05?,and the malformation rate of zebrafish embryos began to appear at?50?g L^-1 significantly increased?p<0.05?.The main morphological changes of the deformity were pericardial cysts,spine curvature,and tail curvature.In addition,by observing the fetal movement of the embryo,we found that as AsIII exposure concentration increased,the fetal movement of the exposed group decreased significantly?p<0.05?.Unlike AsIII,AsV with only 50?g L^-1 showed a significant inhibitory effect on the survival rate of zebrafish?p<0.05?,while the fetal movement was significantly reduced in the treatment group,and the toxicity of the basic indicators was relatively higher than AsIII weak.The results show that the low concentration of inorganic arsenic in the water environment has certain developmental toxicity to the zebrafish early development stage,and the valence state is different,so the toxicity will also have a certain difference.?2?Through experiments related to oxidative stress,we found that with the increase of AsIII concentration,the SOD?Superoxide dismutase?activity increased significantly?p<0.05?,and the content of lipid peroxidation product MDA?Malondialdehyde?also increased significantly?p<0.05?;In addition,25?g L^-1 AsIII induces the mRNA expression of the antioxidant system-related gene Cu/Zn-SOD,and then the expression level decreases significantly with the increase of AsIII concentration?p<0.05?,while?75?g L^-1 AsIII exposure resulted in a significant increase in HSP70 mRNA expression?p<0.05?.For the AsV exposure group,unlike the highly toxic AsIII exposure effect,the significant increase in SOD activity began to appear at?50?g L^-1,and the significant increase in MDA content showed an unstable trend,But it can still be seen that the oxidative stress caused by AsV on zebrafish embryos;in terms of the expression levels of genes related to the antioxidant system,the experimental data shows that AsV concentration of?25?g L^-1 will affect Cu/Zn-SOD and Mn-SOD has a significant induction effect,which causes the induction of HSP70 mRNA expression followed by inhibition,and the inhibition of MT-1 and MT-2 mRNA expression.The results show that low concentrations of inorganic arsenic in the water environment can induce excessive ROS production in the early development stage of zebrafish and cause oxidative damage,destroying the antioxidant system.?3?Through the detection of heart-related development indicators,it was found that the exposure of AsIII and As V can produce heart development malformation,causing the occurrence of heart rate disorder and inducing apoptosis in the heart of young zebrafish.With the increase of exposure concentration,the apoptotic cells in the two valence treatment groups gradually increased.In addition to the above indicators,the expression of cardiac development-related genes are affected by varying degrees of inhibition or activation.AsIII of?25?g L^-1 inhibited the expression level of GATA4 mRNA,on the contrary,activated the mRNA expression of GATA1,Mdm2 and MMP-2;while AsV exposed group had the expression level of GATA1 and Mdm2 mRNA at?25?g L^-1 Both had the effect of activation and then inhibition,while inhibiting the mRNA expression of GATA4 and MMP-2.It showed that exposure to inorganic arsenic in the water environment,even low concentrations of AsV,can cause abnormal development of the zebrafish embryo heart and induce cardiotoxic effects.?4?Through apoptosis-related experiments,we found that with the increase of AsIII and AsV concentrations,the activity of Caspase-3 enzymes increased significantly.In the mitochondrial-dependent apoptosis signaling pathway,the mRNA expression levels of key genes Bax,Bcl-2,Bid and Caspase-9,Caspase-3 showed different degrees of up-regulation,and the exposure of both valence inorganic arsenic destroyed Bcl-2/Bax balance;In addition,AsIII induces an increase in protein expression of Bcl-2,Bax,and Caspase-3,AsV has an inhibitory effect on the expression of Casepase-3 and Bax protein,and activates the expression of Bcl-2 protein.The results showed that the exposure of zebrafish embryos to low concentration of inorganic arsenic may be due to the exposure of low concentration of inorganic arsenic to activate the mitochondrial-dependent apoptosis initiation pathway of the heart.The study explores the toxic effects and related mechanisms of inorganic arsenic on the early development of zebrafish,especially heart development,through the use of biological experiments at different levels?including individual,cellular,and molecular levels?,to further study the environment of low concentration inorganic arsenic in the water environment Toxicology mechanism provides laboratory data support.