| Objective:The chicken embryo exposure model was used to investigate the toxic effects of exposure to different doses of PM2.5 on the developing chicken embryos’ heart and liver and the potential mechanisms.The purpose of this study is to provide a theoretical basis for the toxic mechanism of PM2.5 exposure to the development of heart and liver in offspring.Methods:210 fertilized eggs were purchased,and 120 eggs of them were divided into six PM2.5dose groups(0,0.05,0.2,0.5,2,and 5mg/kg)randomly according to the weight of the eggs.According to the experimental results of the first batch of chicken embryos,we excluded the 0.05 mg/kg and 5 mg/kg PM2.5 dose groups in the second batch of 90 eggs.They were divided into four groups.The doses of PM2.5 were 0,0.2,0.5 and 2mg/kg,respectively.The egg surface was sterilized and we injected different doses of PM2.5 into the air chamber,and then put them into the incubator for hatching.And the hatching conditions of the two batches of eggs were the same.When the chicken embryos were incubated for 4and 15 days,the chicken embryos of each group were sampled,the development of chicken embryo heart was observed and the 4-day chicken embryo heart area and the 15-day chicken embryo heart cross-sectional area were measured.After hatching,the heart rate of hatched chickens was measured,and the biochemical indicators which reflect liver function of hatched chickens were measured.HE staining was used to observe the pathology of heart and liver of hatched chickens,and the thickness of right heart wall was measured.The expression of NF-k B p65 protein in heart and liver of hatched chickens was detected by immunohistochemistry.The expression of i NOS and MMP9 protein in heart and liver of hatched chickens was detected by Western blot.Results:(1)After hatched chicken embryos were exposed to PM2.5,the heart area of chicken embryos incubated for 4 and 15 days increased significantly,which was significantly different from that of the control group(P<0.05).(2)Compared with the control group,the survival rate of chicken embryos in 5 mg/kg PM2.5 exposure group decreased significantly(P<0 05).(3)The results of heart rate measurement of hatched chicks showed that,compared with the control group,PM2.5 exposure significantly increased the heart rate of hatched chicks(P<0 05).(4)The results of HE staining of hatched chicks showed that,compared with the control group,PM2.5 exposure could significantly increase the thickness of the right cardiac wall of hatched chicks(P<0 05).HE staining results showed that PM2.5 exposure could lead to hepatic steatosis and increased hepatic inflammatory cell infiltration in hatched chickens.(5)The results of liver function test showed that,compared with the control group,the levels of ALT and AST in serum of hatched chickens in 0.5mg/kg and 2mg/kg PM2.5groups were significantly higher(P<0.05).(6)The immunohistochemical results of heart and liver of hatched chickens in each PM2.5 dose group showed that,compared with the control group,the expression levels of NF-Kb p65 protein in heart and liver of hatched chickens in 0.5mg/kg and 2mg/kg PM2.5groups were significantly up-regulated(P<0.05).(7)The results of Western blot analysis showed that,compared with the control group,the protein expression levels of i NOS and MMP9 in the hatching chicks of the 0.2mg/kg and 0.5mg/kg PM2.5 groups were significantly up-regulated(P<0.05).However,under the dose of 2mg/kg,the protein expression levels of i NOS and MMP9 in heart tissue did not increase,showing an inverted U-shaped dose-response curve.In liver tissue,compared with the control group,the expression of i NOS and MMP9 was significantly increased(P<0.05).Conclusion:PM2.5 exposure can damage the heart of developing chicken embryo,leading to an increased cross-sectional area,the thickening of right venticular wall and the heart rate of developing chicken embryo.And it can induce liver steatosis and inflammatory injury,suggesting that exposure to PM2.5 has potential risks to the development of heart and liver in young chickens.In addition,PM2.5 exposure significantly increased the expression of NF-k B p65,i NOS and MMP9 in the heart and liver of hatched chickens,suggesting that inflammatory response may be one of the mechanisms of heart and liver injury induced by PM2.5exposure in developing chicken embryos. |
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