| With the development of industry,hazardous wastes discharged from industrial production have had an extremely serious impact on the environment.Phthalate esters(PAEs)are environmental hormone compounds and plasticizers commonly used in industry.A large amount of phthalate pollutants are discharged into the environment,during the production and use of plastic products.These PAEs can enter the organism through injection,ingestion,skin contact and inhalation,and cause harm to the organism.Blood is an important tissue in the living body,which has many important functions such as material transportation,information transmission and immunity.PAEs in the environment will enter the blood after entering the organism,and affect the cells and active substances in the blood.In this context,this study takes dimethyl phthalate(DMP),the lowest molecular weight PAEs,as the research object,and selects SD rats as the model animal.The influence of DMP on blood immune function and the mechanism of toxicity were studied from three aspects:immune cells and immune active substances,lymphocyte apoptosis and lymphocyte subsets,and apoptosis-related genes.By setting low(50 mg/Kg),medium(250 mg/Kg),high(500 mg/Kg)three DMP dose groups and the corresponding anti-oxidant experimental group,blood is taken for testing after intragastric administration to explore the toxic effects of DMP on immune cells and immune active substances in the blood of SD rats and the association between these toxic effects and oxidative stress.Compared with the control group,the superoxide dismutase activity of the high-dose DMP-exposed group decreased by 13%,the reactive oxygen content increased by 13%,and the malondialdehyde content increased by 70%in the serum of SD rats,which showed that DMP can cause oxidative stress in the body.The number of red blood cells,white blood cells and lymphocytes in the blood of SD rats in the three dose groups decreased compared with the control group.Among them,the indicators of the high-dose DMP-exposed group decreased by 17.8%,29.9%,and 29.3%respectively and all the indexes of the antioxidant group were improved compared with the non-antioxidant group at the same dose.The test results of immunologically active substances showed that the contents of immunoglobulin G,interleukin-2,interleukin-4,interleukin-6 and interferon-γin the serum of SD rats in the three dose groups decreased compared with the control group.Among them,the indicators of the high-dose DMP-exposed group decreased by 11.5%,6%,15.2%,18.6%,16.5%respectively compared with the control group,and the content of immunoglobulin G and interleukin in the antioxidant group was improved compared with the non-antioxidant group at the same dose.The above results indicate that DMP can cause a decrease in the content of immune cells and immune active substances in the blood,and this toxic effect is related to the oxidative stress response induced by DMP.Flow cytometry was used to explore the effects of DMP on blood lymphocyte apoptosis and lymphocyte subsets in SD rats.Apoptosis detection results showed that the apoptosis rate of lymphocytes in the blood of SD rats in the low,medium and high dose groups was higher than that in the control group,and showed an upward trend.The apoptosis rate in the high dose group was 18.93%.The detection of lymphocyte subsets showed that the blood CD3~+CD4~+T cell content of SD rats in the low,medium and high dose groups decreased compared with the control group,and the high dose decreased by61.8%compared with the control group.The above results prove that DMP can induce apoptosis of lymphocytes,and DMP can cause the decrease of CD3~+CD4~+T cell content,so it is speculated that DMP may significantly induce CD3~+CD4~+T cell apoptosis.SD rats were exposed to low-dose(46 mg/Kg),medium-dose(230 mg/Kg),and high-dose MMP(460 mg/Kg),and the toxic effects of DMP and its metabolite MMP on cell apoptosis were compared.The results showed that the apoptosis rate of lymphocytes in the blood of SD rats in the low,medium and high dose groups was higher than that of the control group,showing an upward trend,and the apoptosis rate of each dose group was lower than the corresponding DMP-exposed group.Therefore,DMP can induce apoptosis of lymphocytes stronger than its metabolite MMP.In order to explore the toxic effect of DMP on the immune cell apoptosis-related genes in SD rats,transcriptome analysis was performed on the blood of SD rats in the control group and the low,medium and high dose groups.The results showed that the expression of the anti-apoptotic gene Bcl-2 and the pro-apoptotic genes Bax,Bid and Bak-1 in the blood of SD rats in the three DMP dose groups were all up-regulated,which showed that DMP can induce the expression of the anti-apoptotic gene Bcl-2 and the pro-apoptotic genes Bax,Bid and Bak-1.The expression of Fas,FasL and FADD genes in the blood of rats in the three DMP dose groups were all up-regulated to varying degrees,and most of them showed a dose-dependent increase,which showed that DMP can induce the expression of Fas,FasL and FADD genes.The expression of Caspase-2,8,9,3,6,and 7genes in the blood of rats in the three DMP dose groups all increased to varying degrees,and most of them showed a dose-dependent increase,which showed that DMP can induce the expression of caspase-2,8,9,3,6,and 7 genes in the blood of SD rats.DMP can induce apoptosis of blood lymphocytes by up-regulating the expression of Bax,Bak,Bid,and Bcl-2 genes of the Bcl-2 family,Fas/FasL pathway-related genes,and Caspase-2Caspase-8、Caspase-9、Caspase-3、Caspase-6 and Caspase-7genes in the blood.This study explored the effect of DMP on the body’s blood immune function and its mechanism through in vivo experiments.It is found that DMP can induce immune cells to undergo apoptosis by causing the body to undergo oxidative stress response and induce the expression of apoptosis-related genes,which leads to a decrease in the number of immune cells,which in turn leads to a decrease in the content of immune active substances,and ultimately leads to impaired immune function of the body.The results of this study are helpful to further understand the toxic effects of DMP on the body’s blood immune function,and can provide a scientific basis for the risk assessment of PAEs in the environment and the prevention of related diseases. |
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