Biomarkers Of Prenatal Exposure To PAHs And The Interactive Effects On Fetal Growth Between PAHs Exposure And Genetic Polymorphisms

BackgroundEvidence has shown that fetuses and infants are more vulnerable than adults to a variety of environmental toxicants because of their differential exposure patterns, physical immaturity and a longer lifetime over which disease initiated in early life can develop.Polycyclic aromatic hydrocarbons(PAHs) are among the best-characterized environmental toxicants.A number of PAHs are reproductive and developmental toxicants,as well as mutagens and carcinogens.In addition to their ability to bind to and damage DNA,PAHs such as benzo[a]pyrene are capable of disrupting the endocrine system by altering metabolic pathways of natural hormones or interfering with their activity.Laboratory studies have found an association between transplacental exposure to certain PAHs and adverse reproductive outcomes.And more and more evidences have appeared to indicate that there is an association between air pollution and adverse birth outcomes in human.Furthermore,PAHs may be the most prominent agents in polluted urban air.Birth outcomes are important because they are indicators of the health of the newborns and infants.In addition,low birth weight and impaired growth in the first year of life are known to influence the subsequent health status of individuals,including increased mortality and morbidity in childhood and an elevated risk of hypertension,coronary heart disease,and non-insulin-dependent diabetes in adulthood.Most of the research to date has lacked adequate exposure and dosimeter data to forge causal links between common environmental factors and health effects in the young.In this regard,molecular epidemiology using biomarkers can be a valuable tool in defining environment-susceptibility relationships when used in conjunction with sound monitoring and epidemiologic methodologies.Meanwhile,health and disease are influenced by genetic and environmental factors simultaneously,and human's response to the environmental toxicants or other deleterious factors is strongly linked to not only the dosage or degree of the environmental factors but also the genetic susceptibility.To explore the interactions between exposure and genetic polymorphisms has been the focus in environmental health fields.Fetus exposed to PAHs through the placenta and exposure evaluation is very complicated due to the highly selectivity,enzyme activity in placenta and the genetic polymorphisms both of maternal and newborns.To date,few studies have focused the effective biomarkers to evaluate the extent and impacts of prenatal exposure to PAHs. Though several studies have explored the modification of the genetic polymorphisms to the metabolism of PAHs and the interactions on fetal growth and development,the results are inconsistent.So it is urgent to explore the association.Environmental surveillance data shows that air in Taiyuan City is always heavily polluted and especially by the particulate matter(PM) and PAHs.Further,Birth defects incidence is high and used to be called the "Everest".Beside,adverse birth outcomes are also high.Therefore it is very important to discuss the prenatal exposure to PAHs for the specific biomarkers and the health impacts,further to help to identify high-risk population and improve the health risk evaluation.ObjectivesTo study the present PAHs exposure levels of pregnant and fetus in Taiyuan city by epidemiology investigation and biological surveillance;To explore the relationship between maternal and infant exposure and the related factors;To facilitate more effective discussions on the specific biomarkers which can be used to indicate the prenatal exposure;To estimate the modification role of metabolic genetic polymorphisms on the PAHs metabolism;To investigate the interactions of prenatal exposure to PAHs and the metabolic genetic polymorphisms;In sum,to provide scientific data for more effectively identification of high risk population,for more effective prevention and protection and for more pr(?)cised risk evaluation.Methods1 Air monitoringHigh-performance liquid chromatography(HPLC) with subsequent fluorescence detection was used to determine the PAHs(nine kinds) levels adhered to PM2.5.2 Epidemiology investigationsField study was conducted in Taiyuan city.A detailed,validated questionnaire administered to the mother within 2 days postpartum included information on the demography,smoking and drinking,residential and environmental exposures,disease and pregnant history,newborn development indexes.3 Sampling and measuringMaternal blood(10ml) was collected within 1 day postpartum,and umbilical cord blood(20ml) was collected at delivery.Samples were transported to the laboratory immediately after collection.About 0.5ml whole blood(both maternal and newborn) were cultured in culture medium to analyze the micronuclei frequency;the other blood were centrifuged to gain the serum for the PAHs measuring;and genomic DNA was extracted from lymphocytes by standard techniques.The genotyping of CYP1A1 MspI,GSTM1,GSTT1 and GSTP1 was performed in duplicate,using techniques based on PCR or PCR-RFLP.Each participant was asked to provide a 50 ml urine sample.Urine 1-OHPy concentration was measured using a modification of the HPLC method incubated for 4h in 37℃withβ- glucuronidase.ResultsPartⅠAir monitoringNine kinds of carcinogenic PAHs were detected in Taiyuan.B(a)P concentration is 0.0303μg/m~3,which is two times higher than the air standard(0.01μg/m~3).It shows that PAHs pollution is heavy in the study field.PartⅡPAHs exposure and the related factors1 In our study,the percentage of detectable samples in urine was 93.8%.1-OHPy concentration(μmol/mol Cr) was 0.794(median) and IQR was 0.519～1.369 (μmol/mol Cr).92.5%of the maternal urine 1-OHPy level were higher than that in the common residents(0.11μmol/mol Cr) and 13.3%of the maternal urine 1-OHPy level were higher than the exposure limit of Coke-oven workers (1.90μmol/mol Cr).2 There were several factors related to the 1-OHPy concentration,such as education, usage of cooking fume extractor and the kitchen separated from the sitting room or living room.Cooking frequencies,passive smoking and residential heating are the independent factors to the 1-OHPy level after controlling the other confounders in multiple linear regression models.3 Several kinds of carcinogenic PAHs were detected in nearly all the serum of both the mothers and newborns.The serum concentration of B(k)F,B(a)P,DB(a,h)A and T value in fetal were significantly higher than paired mother tissues.4 Every PAHs in serum was positively related to the other PAHs both in mother and newborn.And the PAHs in umbilical cord blood were also related to the same PAHs in paired mother tissues.5 1-OHPy concentration was positively correlated to the total PAHs,but no relationship were observed between the 1-OHPy and the PAHs level in umbilical cord blood.PartⅢMetabolic genetic polymorphisms and PAHs exposure1 The PAHs levels in serum both of mothers and newborns were higher in mothers with genotype TC/CC at CYP1A1 MspI,AG/GG at GSTP1,GSTM1 null or GSTT1 null genotype than that with the wild genotype or non-null genotype.But no significant difference was observed by Mann-Whitney Test.2 All the seven kinds of PAHs,the total PAHs and the T value in umbilical cord blood were higher in newborn with GSTM1 null genotype than that with GSTM1 non-null genotype.And significant difference were found only for the B(b)F,B(a)P,B(ghi)P and TPAHs level between the GST null and non-null genotypes.3 The same results were evident in newborns with the GSTM1 null and GSTT1 null combination than that with present genotype.4 1-OHPy level is significantly higher in urine of mothers with CYP1A1 homozygous at CC than that in wild genotype(1.6530 vs 1.1624μmol/molCr, P=0.047).And the mothers with homozygous GG at GSTP1 had a significantly higher level of 1-OHPy than the wild genotype group(1.0076 vs 0.9622μmol/molCr,P=0.009.)5 CYP1A1 and GSTP1 could modify the 1-OHPy concentration in the multi-gene model.R~2=0.262.6 Urinary 1-OHPy concentration could be influenced by CYP1A1 and GSTM1 polymorphisms when taking account into the some two way gene-gene interaction.PartⅣGenetic damage and the gene-exposure interaction to the fetal development1 MN frequency in blood was correlated between the paired mothers and newborns (R=0.212,P=0.037 )and MN frequency was higher in maternal blood than that in umbilical cord blood(Wilconxon signed ranks test,Z=-3.325,P＜0.05 ).2 A significant(P=0.038) higher MN frequency was found in lymphocytes of mothers with no usage of cooking fume extractor when cooking.MN frequency increased with age(P=0.024) in this adult population aged 18-42 years.3 MN frequency was higher in umbilical cord blood when the paired mother used to eat more fried or fumed food during pregnancy(P＜0.05 ).4 Newborns showed the same MN frequency regardless of sex(P＞0.05).5 MN frequency showed no significant difference among the different PAHs exposure levels(P＞0.05).6 There was no significant correlation between the four metabolic genetic polymorphisms and the MN frequency in the blood both of mother and newborn (P＞0.05).7 No interactive effect of exposure to PAHs and metabolic genetic polymorphisms was found on MN frequency in umbilical cord blood.8 Birth weight were lower in newborns with genotype AG/GG at GSTP1 within the high PAHs exposure group but were higher within the low PAHs group,whereas the interactive effect was not statistically significant(F=3.383,P=0.086)9 The birth head circumference reduced in the newborns with AG/GG genotype at GSTP1 after adjusting for age,education,passive smoking,history of pregnancy, residential heating,cooking frequency,pre-pregnancy height and weight,infant sex and gestational age(P=0.095). 10 An interactive effects were found between GSTP1 gene polymorphism and prenatal exposure to PAHs(F=3.397,P=0.069)11 There were interactive effects between PAHs exposure and CYP1A1 or GSTM1 gene polymorphism after adjusting the other confounders such as mother age, education,passive smoking,history of pregnancy,residential heating,air ventilating,cooking frequency,pre-pregnancy height and weight,infant sex and gestational age(P=0.034 and P=0.062,respectively).Conclusions1 Taiyuan is heavily polluted by PAHs.2 Several carcinogenic PAHs were detected in almost all the paired mother and newborns.The levels in umbilical cord blood were similar or higher compared to the paired mothers and a correlation could be found between the mothers and newborns.So we suggested that the PAHs levels(especially Pyr) in materal serum may be used to as biomarkers of the level of fetus in utero.3 Residential heating style,cooking frequency and passive smoking were the important factors associated to the PAHs exposure during the pregnancy period. Not only passive smoking and cooking frequency,but also residential heating style and cooking frequency have a joint effect on the 1-OHPy levels.The highest 1-OHPy level exists in the subjects with passive smoking and more cooking frequency or the subjects with coal-stove heating and more cooking frequency.4 Genetic polymorphisms play an important role in modulating the PAHs -metabolizing.5 It demonstrated that there are interactive effects on the fetus growth and development between the prenatal PAHs exposure and metabolic genetic polymorphisms.In summary,the study subjects showed higher exposure levels to PAHs and the fetus may be damaged through the placenta.Metabolic genetic polymorphisms may play a modulating role in the exposure and effective evaluation.Due to the limitation of the cross-section study,we suggest that additional cohort studies with larger samples and more metabolic genetic polymorphisms will be needed to confirm the findings and to explore the mechanism or the relationship.