Effects Of Overexpression Of Lias Gene On Fine Particulate Matter (PM_2.5) Induced Cardiotoxicity In Mice

BackgroundFine particulate matter(PM_2.5)is a risk factor for cardiovascular disease.PM_2.5 can affect the cardiovascular system directly or indirectly through oxidative stress,inflammatory reaction,myocardial ischemia and hypoxia.And it can also affect the energy metabolism of the body.In recent years,although the air pollution problem with PM_2.5 as the main pollutant has been controlled,the situation is still not optimistic.α-lipoic acid（ALA）is a strong antioxidant produced by lipoic acid synthase（Lias）in mitochondria,which can enhance the antioxidant capacity and participate in metabolism.In this study,a new antioxidant model mouse(Lias^H/H)was used to simulate the population with high antioxidant capacity.By exploring the effect and mechanism of endogenous antioxidant level on PM_2.5 induced cardiovascular system injury,we provide important experimental basis for clarifying the toxic mechanism of PM_2.5 and protecting susceptible people.Epidemiological studies and animal experiments had shown that supplementation with exogenous lipoic acid can down-mitigate the effects of PM_2.5 on lung,skeletal muscle or other tissues,while the role of endogenous antioxidant levels in PM_2.5 on the body is unclear.ObjectsIn this study,a new antioxidant model mouse(Lias^H/H)was used to simulate a population with high antioxidant capacity to investigate the effect of endogenous antioxidant levels on PM_2.5-induced damage to the cardiovascular system and its mechanism of action,thus providing an important experimental basis for elucidating the toxic mechanism of PM_2.5and protecting susceptible populations.MethodsPM_2.5 were collected for metal composition analysis from the roof of the science and technology building of Xinxiang Medical University.Forty C57BL/6J and Lias^H/H female mice were randomly divided into C57BL/6J control group,C57BL/6J+PM_2.5 exposed group,Lias^H/H control group and Lias^H/H+PM_2.5 exposed group（n=10）.The PM_2.5 exposed group were treated by intratracheal instillation of PM_2.5（b.w.）and the control group were treated by intratracheal instillation of saline for 7 days.Fasting blood glucose（FBG）,diastolic blood pressure（DBP）,systolic blood pressure（SBP）and heart rate（HR）were measured after the end of the exposure period.H＆E staining and oil red O staining were used for pathological observation.The levels of total cholesterol（TC）,triglyceride（TG）,low density lipoprotein cholesterol（LDL-C）,high density lipoprotein cholesterol（HDL-C）,total antioxidant capacity（T-AOC）,superoxide dismutase（SOD）,malondialdehyde（MDA）,reactive oxygen species（ROS）and adenosine triphosphate（ATP）were detected by biochemical kit.Interleukin-1α（IL-1α）,interleukin-6（IL-6）,monocyte chemoattractant protein-1（MCP-1）and tumor necrosis factor-α（TNF-α）in serum were detected by enzyme-linked immunosorbent assay（ELISA）.Real-time fluorescence quantitative polymerase chain reaction（q-PCR）for the detection of gene expression of cardiac Keap1,Nrf2,superoxide dismutase 2（Sod2）,uncoupling protein 2（Ucp2）,protein kinase AMP-activated catalytic subunit alpha（Prkaa）,NAD（P）H:quinone oxidoreductase（Nqo1）.Results1.PM_2.5 metal composition:The concentrations of zinc（Zn）,iron（Fe）,aluminum（Al）and lead（Pb）in PM_2.5 in Xinxiang were the highest,reaching 809.79,301.22,297.65 and234.71 ng/m~3 respectively.2.Changes of basic physical signs:Compared with C57BL/6J control group,the body weight of C57BL/6J+PM_2.5 exposed group decreased,and SBP,DBP,FBG increased（P<0.05）.Compared with Lias^H/H control group,the levels of DBP,HR and FBG in Lias^H/H+PM_2.5 exposed group decreased（P<0.05）.Compared with C57BL/6J+PM_2.5 exposed group,SBP,DBP and HR in Lias^H/H+PM_2.5 exposed group decreased（P<0.05）.3.Pathological changes:H＆E staining showed that myocardial fibers in PM_2.5 exposed group were disordered;however,compared with C57BL/6J+PM_2.5 exposed group,the degree of myocardial fiber disorder in Lias^H/H+PM_2.5 exposed group was reduced.Oil red O staining showed that there were obvious lipid plaques in the aortic sinus of PM_2.5 exposed group;compared with C57BL/6J+PM_2.5 exposed group,the area of lipid plaque in Lias^H/H+PM_2.5 exposed group was smaller.4.Biochemical index changes:Compared with C57BL/6J control group,the levels of ROS,MDA and SOD in C57BL/6J+PM_2.5 exposed group increased（P<0.01）,and the levels of T-AOC and ATP decreased（P<0.01）.Compared with Lias^H/H control group,the levels of ROS and MDA in Lias^H/H+PM_2.5 exposed group increased（P<0.01）,and the levels of T-AOC,SOD,ATP decreased（P<0.01）.Compared with C57BL/6J+PM_2.5exposed group,the levels of cardiac ROS and MDA in Lias^H/H+PM_2.5 exposed group decreased（P<0.01）,and the levels of T-AOC,ATP increased（P<0.01）.Compared with C57BL/6J control group,the levels of IL-1α,IL-6,MCP-1,TNF-α,TG,TC and LDL-C in C57BL/6J+PM_2.5 exposed group increased（P<0.01）,and the level of HDL-C decreased（P<0.01）.Compared with Lias^H/H control group,the levels of serum IL-1α,IL-6,MCP-1,TNF-α,TG,TC and LDL-C in Lias^H/H+PM_2.5 exposed group increased（P<0.05）,and the level of HDL-C decreased（P<0.05）.Compared with C57BL/6J+PM_2.5 exposed group,the levels of IL-1α,IL-6,MCP-1,TNF-α,TG,TC and LDL-C in Lias^H/H+PM_2.5 exposed group decreased（P<0.05）,and the level of HDL-C increased（P<0.05）.5.Changes of protein expression:Compared with C57BL/6J control group,the protein level of KEAP1 decreased（P<0.01）,and the protein levels of NRF2,GCLC,P-AMPK,PGC1αincreased（P<0.01）in C57BL/6J+PM_2.5 exposed group.Compared with Lias^H/Hcontrol group,the protein levels of NRF2,GCLC,P-AMPK and PGC1αdecreased in Lias^H/H+PM_2.5 exposed group（P<0.01）.Compared with C57BL/6J+PM_2.5 exposed group,the protein expression of p-AMPK and PGC1αin Lias^H/H+PM_2.5 exposed group decreased（P<0.05）.6.Changes of mRNAs expression:In mRNAs level,compared with C57BL/6J control group,the gene levels of Keap1 in C57BL/6J+PM_2.5 exposed group decreased（P<0.01）,Nrf2,Sod2,Nqo1,Prkaa and Ucp2 increased（P<0.05）.Compared with Lias^H/H control group,the gene levels of Nrf2,Sod2,Nqo1,Prkaa and Ucp2 decreased in Lias^H/H+PM_2.5exposed group（P<0.05）.And the gene levels of Nrf2 and Nqo1 in Lias^H/H+PM_2.5 exposed group were lower than those in C57BL/6J+PM_2.5 exposed group（P<0.01）.Conclusions1.Oxidative stress regulated by Lias/Nrf2 pathway is involved in PM_2.5 induced cardiotoxicity in mice.2.High antioxidant level can reduce PM_2.5 induced cardiac toxicity in mice.Its protective effect may be related to improving antioxidant capacity and inhibiting energy metabolism disorders by activating cardiac Nrf2.