Distribution Characteristics Of Antimony In Zebrafish And Its Effect On Antioxidant System And Blood-Brain Barrier

As a priority control pollutant,Antimony(Sb)and its compounds are potentially toxic and carcinogenic to human health.And China,as a antimony resource powerhouse,has abundant antimony ore resources.With the rapid development of society and industry,the world’s demand for antimony is rising,and all kinds of antimony-made goods are increasing day by day,increasing the mining and utilization of antimony-containing mines.As a result,antimony pollutants such as antimony tailings,antimony-containing wastewater and antimony-containing dust are inevitably generated.These substances enter the environment and can release antimony into the environment through physical,chemical and biological pathways,seriously damaging the ecological environment and eventually affecting human health through the food chain.Based on this,in order to investigate the mechanism of antimony toxicity and toxic effects on humans,the model organism,zebrafish(Danio rerio),which has 87%genetic similarity to humans,was used as a test subject,the distribution and transformation characteristics of antimony in the liver,brain,gills and muscle of zebrafish,the detoxification mechanism of antimony stress by non-enzymatic antioxidants in zebrafish and the effect of antimony on the blood-brain barrier(BBB)of zebrafish were investigated.The following conclusions were drawn:(1)Various tissues of zebrafish were studied in four antimony concentration groups(0 mg/L(control),4.15 mg/L,8.29 mg/L,16.58 mg/L)under three antimony stress cycles(7 d,18 d,30 d)and the results showed that: Under the same stress cycle,the contents of Sb in the four tissues and organs of zebrafish showed a dose effect with the exposure concentration,and the antimony adsorption capacity in all four tissues showed that liver > gill > muscle > brain;Taking the zebrafish liver sites under the 16.58 mg/L treatment group as an example,the antimony adsorption capacity in the liver sites at 7 d,18 d and 30 d of the stress cycle was 82.09 ± 8.04 mg/g,148.68 ±1.55 mg/g and 187.26 ± 3.19 mg/g,respectively;The increase at 18 d relative to 7 d was about 81.11% and at 30 d relative to 18 d was about 25.95%.Antimony adsorption capacity in the remaining tissues was also positively correlated with time,and the increase was decreasing;A small amount(1.00% ～ 5.00%)of Sb(III)was converted to Sb(V)after entering zebrafish,and the percentage of Sb(V)in the three antimony stress concentrations gradually increased to 1.17%,1.37% and 1.75%,in order,when the stress cycle was 18 d in liver,for example.The remaining sites also showed an increase in Sb(V)conversion with increasing time of antimony stress.Sb accumulation in fish has significant tissue specificity,with the liver being the target organ for Sb accumulation and muscle and brain parts being the "inactive tissues" for Sb accumulation.(2)The results of the study of antimony stress on non-enzymatic antioxidants in the antioxidant defense system of zebrafish showed that: Total antioxidant capacity(T-AOC)in the liver,brain,gills,and muscle of zebrafish was significantly reduced after 18 d of antimony stress.Among them,at antimony concentration of 8.29 mg/L,the T-AOC levels in liver,brain and muscle were reduced by about 35.14%,50.00%and 45.45%,respectively;The cysteine(Cys)contents in the liver parts of zebrafish after treatment with four antimony concentration groups were(0.58 ± 0.01),(0.74 ±0.15),(0.87 ± 0.30),and(0.95 ± 0.08)μmol/g,showing a gradual increase in Cys content with increasing antimony stress concentration,and the Cys contents in the brain and gills also increased after antimony entered the fish The Cys content in the brain and gills also increased after the antimony entered the fish,and the most obvious was in the gills,with a relative increase of about 216.67%.However,the Cys content of muscle parts in the four treatment groups were(0.38 ± 0.02),(0.04 ± 0.01),(0.10 ± 0.00),and(0.07 ± 0.01)μmol/g tissue,respectively.Relative to the blank group,the Cys content of zebrafish muscle parts decreased after antimony stress,with the greatest decrease of 89.47% at the antimony stress concentration of 4.15 mg/L;In addition,the vitamin C(VC)contents in the liver parts of zebrafish were(1.00 ± 0.05),(0.76 ± 0.03),and(0.90 ± 0.03)μg/mgprot,respectively,after antimony stress,which decreased by about 18.03%,37.70%,and 26.23%,respectively,relative to the blank group.The vitamin E(VE)content of liver parts amounted to(22.85 ± 3.46),(26.54 ±5.10),and(28.62 ± 0.80)μg/g tissue,which were reduced by 52.85%,45.23%,and 40.94%,respectively.The remaining VC and VE contents in gill,brain and muscle parts were also reduced after antimony exposure.After antimony exposure,the zebrafish’s own endogenous VC and VE are depleted,thus slowing down the oxidative damage caused by the heavy metal antimony to the fish.(3)The changes in the blood-brain barrier of zebrafish under antimony stress were investigated by measuring the content of proteases such as apolipoprotein E4(Apo E4),matrix metalloproteinase 9(MMP-9),myelin basic protein(MBP)and5hydroxytryptamine(5-HT),combined with images of the ultrastructure of the zebrafish brain.The results of the study showed that: Apo E4 concentration in zebrafish brain in the blank group was(2.55 ± 0.22)mg/d L and MMP-9 concentration was at(15.34 ± 0.83)ng/m L;When antimony enters the fish,a small amount of antimony enters the zebrafish brain with the blood circulation,causing Apo E4 levels to increase by about 29.41%,11.76% and 26.27% to(3.30 ± 0.03),(2.85 ± 0.10)and(3.22 ± 0.28)mg/d L,respectively.It also allowed MMP-9 concentrations of(17.21 ±1.51,17.28 ± 1.91,16.87 ± 1.22)ng/m L.The antimony concentrations in this study(4.15 mg/L,8.29 mg/L,and 16.58 mg/L)all resulted in upregulation of Aop E4 and MMP-9 levels,and some of the basement membranes,tight junctions,and some nerve fibers in the zebrafish brain were dissolved after antimony stress from transmission electron microscopy(TEM)images,thus disrupting the structural integrity of the zebrafish blood-brain barrier.After the BBB was disrupted,5-HT and MBP were able to cross this barrier freely,and when the antimony concentration reached 16.58 mg/L,the antimony entering the BBB was able to react with the erythrocytes,triggering the lysis of the erythrocytes.