Hepatotoxic Effects Of Combined Exposure To Benzo[a] Pyrene And Chronic Stress Based On Metabolomics Approaches

Environmental pollutants and chronic stress are two common risk factors that have great impact on human health.Environmental pollution is a widespread problem,which has seriously threatened human health and led to an increase in human diseases,significantly reduced physiological functions and immunity under chronic stress,and may have more complex effects on the response to environmental exposure,but there have been no clear studies on the response and interaction of the combined exposure.In this study,potential interactions between these two factors were explored by characterizing the effects of benzo[a]pyrene（B[a]P）,or chronic stress,or their combination,on liver metabolism of C57BL/6J mice using untargeted metabolomics and targeted metabolomics followed by multivariate statistical analysis.The results showed that that exposure to B[a]P alone primarily affected liver glycerolipid metabolism in mice.2.0 mg·kg^-1bw B[a]P mainly affected ceramides,lysophosphatidylcholine and lysophosphoglycerol,and the content was significantly down-regulated,the content of phosphatidylethanol and sphingomyelins was significantly regulated,and phosphatidylcholine and phosphatidylethanolamine were disordered.20.0 mg·kg^-1bw B[a]P led to a significant increase in the content of PC（21:2/21:2）and a significant decrease in the level of PE（19:0/20:4）in the liver of mice.CUMS mainly significantly down-regulated triglycerides（TGs）in mice.The combined exposure of 2.0 mg·kg^-1bw B[a]P and CUMS resulted in significant changes in 70 lipid metabolites in the liver of mice,and the combined exposure of 20.0 mg·kg^-1bw B[a]P and CUMS caused significant changes in 22 lipid metabolites in mice,mainly in glycerophospholipid metabolism and glyceride metabolism.It was found that the hepatic levels of alanine and glutamine were significantly up-and down-regulated respectively after 21 days of exposure to 2.0 or 20.0 mg·kg^-1bw B[a]P.But only in the 2.0 mg·kg^-1case did we observe the up-regulation of argininosuccinic acid and arginine,suggesting that the B[a]P-induced alterations in amino acid metabolism were dose dependent.Moreover,chronic stress stimulus was found associated with an significant decrease in the hepatic level of homocysteine.Also,we evaluated the effects of combined exposure on the hepatic metabolism based on the metabolic effect level index（MELI）.Specifically,the combined exposure to 2.0 mg·kg^-1bw B[a]P and chronic stress exhibited antagonistic effects on amino acid metabolism and glycerol phospholipid metabolism,and additive effects on fatty acid metabolism and bile acid metabolism,respectively.the combined exposure to 2.0 or20.0 mg·kg^-1bw B[a]P and chronic stress showed synergistic and antagonistic effects on both TCA cycle and sterol lipid metabolism,respectively.In contrast,the combined exposure to 20.0 mg·kg^-1bw B[a]P and chronic stress showed additive effects on amino acid metabolism,bile acid metabolism and glycerol phospholipid metabolism.The combined exposure to 20.0 mg·kg^-1bw B[a]P and chronic stress showed antagonistic effects on both fatty acid metabolism and sterol lipid metabolism.The combined exposure to 2.0 or 20.0 mg·kg^-1bw B[a]P and chronic stress showed antagonistic effects on both glyceryl metabolism and saccharolipids metabolism,and synergistic effects on sphingolipid metabolism,respectively.We conclude that the exposure to both B[a]P and chronic stress can trigger significant disorders in lipid metabolism,amino acid and bile acid metabolism,which,notably,differ from those caused by exposure to either alone and were closely related to the exposure dose of B[a]P.