Study On Toxic Mechanism Of Atmospheric Submicron Particles Based On Metabolomics

Atmospheric particulate matter is the primary pollutant of air pollution in cities across the country,and its relationship with human health effects has attracted the attention of many experts and scholars.At present,the research about the health effects of atmospheric particulate matter is mainly around PM₁₀and PM_2.5,and relatively few studies have been implemented on atmospheric submicron particulate matter PM₁（aerodynamic diameter≤1μm）.Due to the ultra-fine particle size,PM₁can penetrate the alveolar cells after entering the human body,and even enter the blood circulation system through the vascular barrier.Compared to PM₁₀and PM_2.5,PM₁possesses the higher exposure risk for human health.Therefore,in this study,ICR mice were used as the model organisms to study the toxic mechanism of PM₁based on metabolomics and lipidomics methods.The control group（0μg/m³）,low-dose group（15μg/m³）,medium-dose group（75μg/m³）and high-dose group（250μg/m³）were set.The ELISA kits were used to detect the ratio of GSH/GSSG and the expression levels of inflammatory factors（TNF-α,IL-6 and IL-17）and anti-inflammatory factor IL-10 in the serum of mice.The results showed that the ratio of GSH/GSSG in the serum of exposed mice was significantly lower than that in the control group（P<0.05）.As the dose of PM₁was increased,the ratio of GSH/GSSG in the serum of exposed mice was significantly decreased（P<0.05）,exhibiting an obvious dose-response relationship.Furthermore,with the increase of PM₁exposure,the levels of inflammatory factors including IL-6,IL-17 and TNF-αin the serum of exposed mice were significantly increased（P<0.05）,while that of anti-inflammatory factor IL-10was significantly decreased（P<0.05）,all exhibiting an obvious dose-response relationship.The results of LC-MS-based metabolomics showed that 125 metabolites were identified in the serum of mice in positive ion mode and 71 metabolites were identified in negative ion mode.Using the methods of multivariate statistical analysis such as PCA,PLS-DA and one-way analysis of variance,14,16 and 37 differential metabolites were screened from the serum of mice in the low,medium and high dose groups,respectively.The analysis of metabolic pathways was carried out by Metabo Analyst and KEGG database,revealing that four metabolic pathways,including glutamine and glutamate metabolism,phenylalanine,tyrosine and tryptoph-an biosynthesis,alanine,aspartate and glutamate metabolism,tyrosine metabolism,were disturbed in all exposed groups.Compared with the low-dose group,the abnormal metabolic pathways of mice in the medium-dose group are also manifested in arginine and proline metabolism.Compared with the medium-dose groups,the abnormal metabolic pathways of mice in the high-dose group were also manifested in valine,leucine and isoleucine biosynthesis,tryptophan metabolism.The results of LC-MS-based lipidomics showed that 250 lipid compounds were identified in the serum of mice,covering 8 kinds of lipid metabolites including phosphatidylcholine（PC）,phosphatidylethanolamine（PE）,lysophosphatidylcholine（LPC）,lysophosphatidylethanolamine（LPE）,sphingomyelin（SM）,ceramide（Cer）,cholesterol ester（CE）and glyceride（AG）.Using the methods of multivariate statistical analysis such as PCA,PLS-DA and one-way analysis of variance,54,58and 83 lipid differential lipid compounds were screened for the low,medium and high dose groups,respectively.The analysis of lipid metabolism pathways was carried out by the lipid database,revealing that the glycerophospholipid metabolism and sphingolipid metabolism were disturbed in all exposed groups.