The Role Of BACE1-AS In Aluminum-induced Cognitive Function Decline And Aβ1-42 Increase

Objective:To evaluate the impact of occupational aluminum exposure on the expression of BACE1-AS,non-coding antisense transcripts ofβ-site amyloid precursor protein cleaving enzyme 1（BACE1）,and cognitive function of workers.To explore the role of BACE1-AS in the mechanism of increased BACE1 andβ-amyloid 1-42（Aβ1-42）induced by aluminum through cell transfection experiments.Methods:The cross-sectional survey was conducted among 440 male workers selected randomly from an aluminum factory.Demographics and general information of the workers were collected with a self-designed questionnaire.Mini-mental state exami-nation（MMSE）,the clock drawing test（CDT）,fuld object memory evaluation（FOM）,Verbal fluency tests（VFT）,Digit Span（DS）were adopted in evaluateons on the workers cognitive function.Plasma Al concentration was measured with inductively coupled plasma-mass spectrometry（ICP-MS）to assess the workers’internal exposure and the expression level of BACE1-AS in peripheral blood is detected by Real Time-quantitative Polymerase Chain Reaction（RT-q PCR）.The cell model silented BACE1-AS gene was established by transfecting human embryonic kidney 293 cells（HEK-293 cells）with small interfering RNA（si RNA）.Seting up 9 groups according to different operations:control,10μmol/L aluminum maltol（Al（mal）₃）,20μmol/L Al（mal）₃,40μmol/L Al（mal）₃,negative transfection,si RNA transfection,si RNA+10μmol/L Al（mal）₃,si RNA+20μmol/L Al（mal）₃ and si RNA+40μmol/L Al（mal）₃.RT-q PCR was used for showing the levels of BACE1-AS and BACE1m RNA,and ELISA for the expression of BACE1 in cells and Aβ1-42 in supernatant.Results:The study subjects were divided into four groups according their quartile values of plasma Al（namely Q1,Q2,Q3,and Q4 for the lowest,the second,the third,and the highest quartile）.In analysis of variance（ANOVA）,significant differences were detected in MMSE（total score,attention and calculation,memory,language and visual spatial structure）,CDT,FOM,VFT and reverse DS among the workers of the four groups after adjusting for age,years of education,and working years（P<0.05）.And there were no significant differences in orientation,FOM time,DS and sequential DS（P>0.05）.The levels of BACE1-AS extracted from peripheral blood increased significantly in the groups of the works with the plasma Al of Q3 and Q4 after adjusting the covariates（F=18.832,P<0.001）.Correlation analysis shows that plasma aluminum content is negatively correlated with each test,and positively correlated with BACE1-AS expression（r=0.424,P<0.01）.BACE1-AS expression is negatively correlated with MMSE,FOM,VFT,and DS.However it has no obvious correlation with CDT.BACE1-AS plays a mediating effect in the prediction of MMSE score by plasma Al concentration（effects accounted for 25.25%）.Working years and age played a regulatory role in the direct prediction of MMSE scores by blood aluminum concentration respectively.The mediation model test with adjustment shows that the product of plasma Al concentration and working years had a significant predictive effect on the MMSE score（B=-0.0009,t=-2.42,P=0.02）,but had no significant predictive effect on the expression of BACE1-AS（P=0.13）.Compared with the control group,the expression of BACE1-AS in HEK293 cells was increased in Al（mal）₃ groups（P<0.05）.And there were lower BACE1-AS expression in si RNA transfection group,si RNA transfection+Al（mal）₃ groups than it in control group（P<0.05）.The expression of BACE1-AS was increased in the si RNA+40μmol/L Al（mal）₃group compared with it in si RNA transfection group（P<0.05）.And no significant difference of BACE1-AS expression among the groups of si RNA+10μmol/L Al（mal）₃,si RNA+20μmol/L and si RNA transfection（P>0.05）.There were higher expression of BACE1m RNA,BACE1 and Aβ1-42 in the Al（mal）₃ groups of 20μmol/L and 40μmol/L compared with it in control group（P<0.05）.The levels of BACE1m RNA was lower in the groups of si RNA transfection,si RNA+10μmol/L Al（mal）₃ and si RNA+20μmol/LAl（mal）₃than it in control group（P<0.05）and it was higher in si RNA+40μmol/L Al（mal）₃group than it in si RNA transfection group.The expression levels of BACE1 and Aβ1-42 in the groups of si RNA transfection,and si RNA+Al（mal）₃were lower than that in the control group,respectively（P<0.05）.And there were no different of the levels of BACE1 and Aβ1-42 in si RNA+Al（mal）₃groups compared with it in si RNA transfection group.The expression of BACE1-AS,BACE1m RNA,BACE1 and Aβ1-42 in HEK293 cells in si RNA+Al（mal）₃groups were lower than that of the Al（mal）₃groups which was same dose（P<0.05）.Conclusion:The plasma Al concentration is an important factor affecting cognitive function.BACE1-AS gene expression may plays a part of the mediating effect and participates in the damage of aluminum to cognitive function.Working years played a regulatory role in the prediction of MMSE scores by plasma Al concentration,but had no regulatory role in the BACE1-AS expression predicted by plasma Al concentration and MMSE scores predicted by BACE1-AS expression.Aluminum exposure may increase the expression of BACE1-AS in cells,thereby affecting the regulation of BACE1m RNA and leading to increased expression of BACE1 and Aβ1-42.