Airborne Magnetite Nanoparticles Incurred Early Pathological Characteristics Of Atherosclerosis Involved Disorder Of Lipid Metabolism Dynamics

Objective:Cardiovascular disease(CVD)is a significant health issue in China,and air pollution has been identified as the fourth most important risk factor for this disease.In recent years,airborne magnetite nanoparticles(MNPs)have been detected in human blood samples,and their potential impact on cardiovascular health cannot be ignored.Atherosclerosis is a chronic inflammatory disease of blood vessels related to lipid metabolism disorder and is the underlying cause of many cardiovascular diseases.When airborne MNPs enter the circulatory system,they come into direct contact with blood vessels,potentially increasing the risk of atherosclerosis development.However,little is known about the specific pathological characteristics of atherosclerosis caused by MNPs.This study aims to clarify the early pathological characteristics of atherosclerosis induced by airborne MNPs,and focus on the dynamic process of "hepatic lipid synthesis-lipid transport-arterial lipid deposition" to reveal the key regulatory mechanisms of atherosclerosis induced by MNPs.The findings of this study will provide important scientific data for understanding the molecular mechanisms of cardiovascular diseases induced by exposure to air pollutants.Methods:The study extensively utilized the nonsurgical intratracheal instillation experiment model and the whole-body ambient inhalational particulate matter exposure model,which were previously established by the team.At the conclusion of the exposure,the mice in each group were carefully dissected to isolate the aorta,serum,and liver.The aorta underwent a thorough pathological evaluation through H&E staining,while the infiltration of macrophages on the aorta and the expression of inflammatory factors were assessed through immunohistochemical staining and q PCR,respectively.These tests aimed to evaluate the impact of MNPs and PM exposure on atherosclerosis.Using the three analysis methods of principal component analysis(PCA),heatmaphierarchical cluster analysis(HM-HCA)and generalized linear mixed models(GLMM),the quantitative indicators of atherosclerotic effect were included to comprehensively compare the similarities and differences of the effects on atherosclerosis between the MNPs exposure group and the PM exposure group,so as to determine whether MNPs is the key toxic component of PM induced atherosclerosis.In terms of the study on the dynamic process of lipid metabolism,the influence of MNPs on lipid deposition level in aorta was evaluated by oil red O staining.Then the changes of blood lipid composition and content were determined by blood biochemical analysis.Oil red O staining and biochemical methods were used to evaluate the overall lipid deposition level in the liver.Finally,the changes of all lipids in the liver were analyzed by liver lipomics system and the expression levels of major lipid metabolizing enzymes in the liver were detected by q PCR to comprehensively elucidate the effects of MNPs on lipid anabolism in the liver.To identify the key regulatory pathways affected by MNPs exposure,we analyzed the transcriptional changes of key response pathways in the liver using a transcriptomics database after exposure to defocused particulate matter.We then verified the changes in these pathways under MNPs exposure using q PCR and immunohistochemical methods.Results:The results of aortic H&E staining revealed that the aorta of mice exposed to MNPs was abnormally thickened compared to the control group.Additionally,elastic fibers were disordered and locally broken.The q PCR results showed upregulation of inflammatory factors,including IL-18,ICAM-1,and VCAM-1 genes,in the aorta.Furthermore,the immunohistochemical results demonstrated an increase in the content of aortic macrophages.These findings strongly suggest that MNPs exposure leads to early atherosclerosis.Based on the results of PCA and HM-HCA analysis,the pro-atherosclerotic effects of MNPs exposure group and PM exposure group,with the same actual content of MNPs,were found to be similar and could be clustered into one group.However,the results of GLMM analysis revealed significant differences in the pro-atherosclerotic effect between the MNPs exposure group and the PM exposure group with different actual MNPs content.These findings indicate that MNPs is a crucial toxic component that may promote the occurrence and development of atherosclerosis due to PM exposure.The results of aortic oil red O staining and blood biochemical tests revealed that MNPs exposure caused aortic lipid deposition and abnormal blood lipids,with elevated serum TC and LDL-C levels of 0.77 and 0.16 mmol/L and decreased serum HDL-C levels of 0.14mmol/L.Similarly,the results of liver oil red O and biochemical tests demonstrated that MNPs exposure led to lipid deposition in the liver,with increased levels of TC and TG.Further analysis using liver lipomics and q PCR indicated that MNPs exposure promoted the expression of liver lipid synthase gene and inhibited the expression of triglyceride decomposing enzyme gene,resulting in an increase in liver triglyceride level and lipid deposition.These findings suggest that MNPs exposure disrupts hepatic lipid metabolism and leads to abnormal dynamic processes of lipid metabolism.Two of transcriptome expression data sets of the liver exposed to particulate matter were obtained through screening in the database.Through differential gene analysis,enrichment analysis showed that JAK-STAT pathway was one of the key functional pathways for particulate matter exposure to regulate lipid metabolism;Further q PCR and immunohistochemistry results showed that MNPs inhibited the expression of STAT3 gene by up-regulating the expression of cell signal transduction inhibitor SOCS3 in the liver,thus inhibiting the JAK-STAT pathway.Conclusions:This study,for the first time,clarified the early pathological characteristics of atherosclerosis caused by atmospheric MNPs exposure,and provided scientific evidence that airborne MNPs is the key toxic component of atmospheric fine particulate matter causing atherosclerosis.We also elucidated for the first time the toxic mechanism of airborne MNPs causing atherosclerosis by focusing on the whole-chain process of lipid metabolism including " liver lipid synthesis – lipid transport – lipid deposition in arteries" and the key pathways regulating lipid metabolism,and provided a comprehensive perspective and thought for the study of toxicological mechanisms related to cardiovascular diseases caused by exposure to pollutants.