The Mediating Role Of Placental Inflammation In The Effect Of Opes And Paes Exposure During Pregnancy On Cognitive Development Among Preschool Children:A Birth Cohort Study

BackgroundOPEs have been widely used as alternative flame retardants(FRs)and plasticizers in various industrial products and daily consumers in recent decades.Animal studies have provided evidence that OPEs exposure can significantly affect the neurodevelopment.However,studies on the effects of OPEs on childhood neurodevelopment is still limited and controversial,additional cohort studies with a larger sample size would be necessary to continue exploring potential associations more fully.PAEs are widely utilized in industrial products and daily consumers as plasticizers,numerous studies have reported the effects of prenatal PAEs on children neurodevelopment.Notably,OPEs and PAEs are applied as additives rather than chemically bound to a wide variety of industrial and consumer products,thus they will easily discharge into surrounding environments and media during their production and use.Humans were co-exposed to PAEs and OPEs through multiple routes,including dermal contact,dust ingestion,inhalation and dietary intake.Considering the additive effect of mixed exposure,lower doses cumulative exposure to multiple compounds may affect human health even if the exposure to individual chemicals is below the regulated dose.Accessible epidemiological studies of coexposure of PAEs and OPEs on neurodevelopment are limited,and the underlying mechanism were poorly defined.In addition,exposure to environmental chemicals was an important factor affecting health,and vitamin D level during pregnancy may ameliorate the adverse health effects of environmental exposure.Exploring its role in modifying the effects of environmental exposure on offspring neurodevelopment was not only of research significance,but also of certain public health value.ObjectivesTo reveal the linear and nonlinear associations between prenatal OPEs exposure and preschooler cognitive developmen.To determine the joint effect of prenatal PAEs and OPEs exposure on preschooler cognitive development.To further elucidate the mediating role of placental inflammation in the association between PAEs and OPEs exposure during pregnancy and cognitive development among preschool children.MethodsBased on the Ma’anshan Birth Cohort,a total of 3 474 pregnant women were recruited between May 2013 and September 2014 in the Maternal and Child Health(MCH)Care Center of Ma’anshan city.We excluded spontaneous abortion(120 cases),induced labor(30 cases),stillbirth(10 cases),ectopic pregnancies(2 cases)and twins pregnancies(39 cases)and 3 273 single live births were confirmed by April 2015.In research 1,we further excluded participants lack of urine samples in any period(n =46)and 1 106 children refused the assessment of cognitive development aged 3.0–6.0years,finally,2120 mother-child pairs were included in this study.In research 2,participants with no placental samples(n = 478)were excluded,and the remaining1642 mother-child pairs were included.The one OPE [tris(2-chloroethyl)phosphate(TCEP)],six OPE metabolites and seven PAEs metabolites were quantified with an isotope internal standard method by solid-phase extraction-high-performanceliquid chromatographytandem mass spectrometry(due to low detection rates,MBz P and DBz P were not included in this study).Preschooler cognitive development was assessed at 3.0–6.0 years of age by the Chinese version of the Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition(WPPSI-IV).Generalized linear regression models(GLMs)were used to estimate the relationships of single OPEs with neurodevelopment.The restricted cubic spline(RCS)was employed to explore the non-linear associations between individual OPEs exposure and cognitive development.To determine the joint associations of coexposure of PAEs and OPEs with cognitive development,we conducted the quantilebased g-computation(QGC)and Bayesian kernel machine regression(BKMR)models simultaneously.In addition,stratified analyses were conducted in the QGC method by gestational vitamin D levels.To determine the moderating effect of prenatal vitamin D levels in the mixture exposure–neurodevelopment association.In order to explore the possible mechanisms of the effects of OPEs and PAEs exposure on neurodevelopment based on observational studies,counterfactual causal mediation analysis(CMA)was fit to explore the mediating role of placental cytokines in the association of the individual OPEs and PAEs exposure with preschoolers’ cognitive development.To further determine the possible mechanism of the effects of co-exposure to OPEs and PAEs on neurodevelopment,Bayesian kernel machine regression-causal mediation analysis(BKMR-CMA)model was used to explore the mediating role of placental inflammatory cytokines in the association between exposure mixture exposure levels of OPEs and PAEs in the first trimester and cognitive development of preschool children.ResultsMMP,MBP,MEP,MEHP,MEOHP,MEHHP,DBP,DPHP,and BCIPP were detected in most urine samples(detection rate>90%).PAEs and OPEs concentrations in different periods had significant differences,Most PAEs and OPEs concentrations were significantly correlated with each other.In the individual OPEs exposure model,GLMs shows that each ln-transformed concentration increase in BBOEP and BCIPP was associated with decrease of 0.450scores(95% CI:-0.866,-0.034)and 0.782 scores(95%CI:-1.405,-0.159)in FSIQ in the first trimester;In the second trimester,each ln-transformed concentration increase in TCEP was associated with 0.439 scores(95%CI:-0.851,-0.026)decreased in FSIQ,additionally,each ln-transformed concentration increase in BEHP was associated with0.464 scores(95%CI:-0.829,-0.098)and 0.444 scores(95%CI:-0.838,-0.050)decreased in FSIQ and WMI respectively.In the third trimester,each ln-transformed DPHP increase was associated with decrease of 0.611(95%CI:-1.159,-0.062)and0.690(95%CI:-1.279,-0.102)in FSIQ and WMI respectively.Through the RCS analysis,in the first trimester,we have observed a significant nonlinear association between ln(DBP)and FSIQ scores.Besides,a significant nonlinear relationship was observed in ln(BBOEP)and ln(DBP)with WMI.In the second trimester,ln(BEHP)was nonlinearly correlated with FSIQ,VCI,and VSI.In the third trimester,we found nonlinear association between ln(BCIPP)and PSI.In the model PAEs and OPEs mixture exposure,through the QGC analyses,during the first trimester,every quantile increase in mixture concentrations was significantly associated with decrease of 1.392 scores(95% CI:-2.738,-0.047)for FSIQ,and exposure to MBP(weight: 24%),BCIPP(weight: 21%),DPHP(weight:20%)may be the dominant contributors to FSIQ scores decrease.A similar result was observed in BKMR model,The FSIQ and FRI scores decreased significantly with14increasing total OPEs and PAEs mixture levels in the first trimester.There were no statistically significant associations between prenatal OPEs and PAEs mixture exposure and preschooler cognitive development during the second and third trimesters in both two mixture model.When we further stratified the comparisons by blood vitamin D levels,we observed that the joint effects of OPEs and PAEs on cognitive development were more pronounced in women with vitamin D deficiency.Sensitivity analysis results were essentially robust.Placental HIF-1α,TNF-α,IL-6,IL-8,CD68,and IFN-γ m RNA expression levels were negatively correlated with FSIQ scores in preschoolers.TCEP,BCIPP,MBP,and MEHHP exposure during the first trimester were positively correlated with multiple placental cytokines expression levels,BEHP was negatively correlated with the expression levels of several placental cytokines(MCP-1,CRP,HIF-1α,GRP78,TNF-α,IL-6,and CD68).During the second trimester,DBP exposure was positively correlated with IL-1β,HO-1,and CRP78 m RNA expression levels,MEP exposure was positively correlated with IL-1β m RNA expression levels,while most OPEs and PAEs exposure(BBOEP,BCIPP,TCEP,DPHP,MMP,MEP,MBP,MEHP,MEOHP,and MEHHP)were negatively correlated with placental inflammatory cytokine m RNA expression.During the third trimester,DBP exposure was positively correlated with the expression level of IL-4,while other OPEs and PAEs(BEHP,MMP,MEP,MBP,MEHP and MEHHP)were negatively correlated with the expression level of placental cytokines.Causal mediation analysis showed that IL-6,and CD68 m RNA expression levels in placenta play a mediating role in the association between BCIPP exposure in the first trimester and the FSIQ scores in preschoolers,with the mediating effect of7.226% and 5.982%,respectively.In addition,The m RNA expression levels of IL-6,HIF-1α and CD68 in placenta also played a mediating role in the association between MBP exposure in the first trimester and the FSIQ scores in preschoolers,with the mediating effect accounting for 8.510%,6.458% and 7.910%,respectively.The mixture exposure of OPEs and PAEs in the first trimester were positively correlated with the m RNA expression levels of IL-6,IL-1β,CRP and MCP-1 in the placenta.The BKMR-CMA model did not find statistical significance in the mediating effect of placental cytokine expression levels in the association between the mixture exposure of OPEs and PAEs in the first trimester and the FSIQ scores in preschoolers.Conclusions(1)Our study indicates that prenatal individual OPEs exposure impairs the preschooler cognitive development,meanwhile co-exposure to OPEs and PAEs during pregnancy was associated with preschooler cognitive development,and the first trimester might be the critical period to mixture exposure with regards to neurotoxicity.Notably,the effect of OPEs and PAEs mixture on cognitive development in pregnancy is more pronounced in women with vitamin D deficiency.(2)BCIPP and MBP exposure in the first trimester can adversely affect cognitive development among preschool-aged children by increasing placental cytokines levels and inducing placental inflammation.No evidence was found that the mixture of OPEs and PAEs affected the cognitive development of preschool children by interfering with the expression of placental inflammatory cytokines,which may suggest the complexity in the interference mechanism of the mixture exposure.