The Associations Between Gene Methylation And Expression Of AhR,CYP1A1 And DNA Oxidative Damage In Coke-oven Plant Workers

Objective: To explore the dose response relationship of polycyclic aromatic hydrocarbons(PAHs)exposure and DNA oxidative damage in coke-oven plant workers;To investigate the association between gene methylation and expression of aryl hydrocarbon receptor(Ah R),cytochromes P4501A1(CYP1A1)in peripheral blood and DNA oxidative damage,and further to evaluate the effect of Ah R,CYP1A1 gene expression between PAHs exposure and DNA oxidative damage.Methods: We enrolled 572 participants from a coke-oven plant,of whom 428 coke oven workers,other 144 water treatment workers.An interviewer-administered questionnaire was performed by a trained interviewer.Using high performance liquid chromatography,we detected the urine biomarkers of PAHs exposure,including 2-hydroxynaphthalene(2-NAP),2-hydroxyfluorene(2-FLU),9-hydroxyphenanthrene(9-PHE)and 1-hydroxypyrene(1-OHP),and the biomarker of DNA oxidative damage [8-hydroxy deoxyguanosine,(8-OHd G)].Using pyrosequencing,we detected the methylation levels of Ah R,CYP1A1 gene promoter in peripheral blood.Using reverse transcription-real-time fluorescent quantitative polymerase chain reaction,we detected gene expression of Ah R,CYP1A1.We investigated the associations between urinary PAHs metabolites,gene methylation and expression of Ah R,CYP1A1,and DNA oxidative damage using multiple logistic regression.We quantitative evaluated the dose response relationship of urinary PAHs metabolites and DNA oxidative damage,and the interaction of personal habits and gene methylation on DNA oxidative damage using stratified analysis and multiple logistic regression.Finally,we estimated the effect of Ah R gene expression on urinary PAHs metabolites and DNA oxidative damage using mediation analysis.Results:Section 1: The median of urinary 2-NAP,2-FLU,9-PHE and 1-OHP in coke oven workers and water treatment workers were 0.73 mg/mmol creatinine(Cr)vs.0.65 mg/mmol Cr,0.30 mg/mmol Cr vs.0.20 mg/mmol Cr,0.09 mg/mmol Cr vs.0.06 mg/mmol Cr,0.06 mg/mmol Cr vs.0.04 mg/mmol Cr,respectively.The median concentrations of urinary PAHs metabolites were significantly elevated in coke oven workers(P < 0.05);Multiple logistic regression suggested increasing levels of urinary 1-OHP was positively associated with 8-OHd G.The odd ratio(OR)and 95% confidence interval(95%CI)was 2.21(1.13-4.30)for 3rd quartile,3.42(1.64-7.13)for 4th quartile,compared with 1st quartile,P trend = 0.002.Section 2: The median of gene methylation levels of Ah R,CYP1A1 in coke oven workers and water treatment workers were 0.66 vs.1.43,2.62 vs.3.49,respectively.The gene methylation levels of Ah R,CYP1A1 were significantly elevated in coke oven workers(P < 0.05);Spearman correlation analysis suggested six positions and mean value of methylation levels of Ah R gene were correlated with each other(rs = 0.43-0.90,P < 0.01).Similar results were also observed for five positions and mean values of methylation levels of CYP1A1 gene(rs = 0.25-0.79,P < 0.01).Multiple logistic regression showed smoking and Ah R gene methylation were positively associated with urinary 8-OHd G.The ORs(95% CIs)were 1.69(1.24-2.31)for smoking,and 1.70(1.12-2.58)for Ah R gene methylation.And there was an interaction between smoking and Ah R gene methylation on 8-OHd G(P interaction < 0.001).The risk of increased 8-OHd G in Ah R gene lower methylation and smoking amount > 11.25 pack years was 3.84(1.62-9.10),compared with Ah R gene higher methylation and nonsmokers.Multiple logistic regression showed smoking and CYP1A1 gene methylation were positively associated with urinary 8-OHd G.The ORs(95% CIs)were 1.46(1.11-1.92)for smoking,and 1.19(1.01-1.40)for CYP1A1 gene methylation.And there was an interaction between smoking and CYP1A1 gene methylation on 8-OHd G(P interaction = 0.002).The risk of increased 8-OHd G in CYP1A1 gene lower methylation and smoking amount > 11.25 pack years was 4.91(2.08-11.59),compared with CYP1A1 gene higher methylation and non-smokers.Section 3: Multiple logistic regression suggested increasing levels of urinary 1-OHP was positively associated with high Ah R,CYP1A1 gene expression [4th vs.1st quartile = 5.55(1.54-20.01),3.04(1.10-8.47),respectively,P trend < 0.05].A significant association between AhR gene expression and 8-OHdG was also found(4th vs.1st quartile = 3.12,95% CI: 1.37-7.06,P trend = 0.009).But we did not find the assoxiation between CYP1A1 gene expression and 8-OHd G.In addition,mediation analysis showed the effect of PAHs-related DNA oxidative damage may be mediated by Ah R expression.The Ah R expression could explain 37.1%(2.1%-94.2%)of the effect of DNA oxidative damage related to PAHs exposure.Conclusions:1.PAHs exposure was associated with DNA oxidative damage in coke-oven plant workers.And there was a dose response relationship between PAHs exposure and DNA oxidative damage.2.The hypomethylation of Ah R and CYP1A1 gene was related to DNA oxidative damage in coke-oven plant workers.And smoking and gene methylation of Ah R and CYP1A1 can interact with DNA oxidative damage in coke-oven plant workers.3.Ah R gene expression was related to DNA oxidative damage in coke-oven plant workers.And the effect of PAHs-related DNA oxidative damage may be mediated by AhR expression.