Oxidative Stress In The Liver Of Cyprinus Carpioio Under Polychlorinated Biphenyls (Aroclor 1242) Stress:Analysis Of Physiological,Biochemical And Transcriptional Levels

Polychlorinated biphenyls?PCBs?exist widely in the environment and are a kind of typical environmental persistent organic pollutants?pops?.Polychlorinated biphenyls?PCBs?have stable physical and chemical properties,and enter into the environment through various ways,which will affect the growth,development and reproduction of aquatic organisms,and can affect many kinds of organisms through the enrichment effect of food chain,and pose a threat to human health.In this experiment,the polychlorinated biphenyls?PCBs?mixture Aroclor1242 was used to study the ecotoxicological effects of Aroclor1242 on C.carpio,an important economic fish species in China.The effects of different concentrations of Aroclor1242 on antioxidant enzyme system and lipid peroxidation system in liver tissue of C.carpio were investigated.The expression of the related antioxidant genes,such as Cu/Zn-SOD,Mn-SOD,CAT,GPx1a,GPx1b,GST,heat shock protein 70?HSP70?,transcription factor?Nrf2?,aryl hydrocarbon receptor2?AhR2?,were investigated.In order to reveal its potential toxic mechanism at physiological,biochemical and transcriptional levels.The findings are as follows:1.The 96h LC₅₀0 of Aroclor1242 to C.carpio was 780?g/L,and Aroclor1242 was a highly toxic substance according to the classification standard of acute toxicity test for fish.2.Aroclor1242 exposure resulted in oxidative stress and oxidative damage in the liver of C.carpio.The results showed that Aroclor1242 could significantly change the activity of Aroclor1242 in the liver of C.carpio,and it was correlated with the concentration of Aroclor1242and the exposure time.The content of MDA increased with the increase of Aroclor1242concentration,indicating that a certain concentration of Aroclor1242 could induce lipid peroxidation and damage the membrane system.Using the above biomarkers as the basis to calculate and integrate the R_IBB value,we can more effectively evaluate the corresponding strength of these biomarkers.The results showed that the degree of damage to C.carpio tissues was different under different concentrations of Aroclor1242.The higher the concentration of Aroclor1242 at the same enrichment time,the greater the R_IBB value,that is,the greater the damage to the liver tissue of C.carpio.3.Under certain concentration of Aroclor1242,the transcription level of oxidative stress-related enzymes in the liver of C.carpio changed significantly.After exposure to moderate and high concentration of Aroclor1242 for 8 days,The expression of anti-oxidation enzyme encoding gene Cu/Zn-SOD,Mn-SOD,CAT,GPx1a,GPx1b,GST,HSP70 in C.carpio liver was significantly down-regulated in varying degrees.In addition,the expression of Nrf2,AhR2 gene in C.carpio liver was significantly down-regulated in middle and high concentration Aroclor1242 exposure group.It is suggested that Nrf2,AhR2 may be involved in the regulation of antioxidant gene expression in the liver of C.carpio exposed to Aroclor1242.