In utero exposure to maternal smoking is associated with DNA methylation alterations and reduced neuronal content in the developing fetal brain

Transgenerational Epigenetic Inheritance of Cardiovascular Diseases: A Network Medicine Perspective

INTRODUCTION

The ability to identify early epigenetic signatures underlying the inheritance of cardiovascular risk, including trans- and intergenerational effects, may help to stratify people before cardiac symptoms occur.

METHODS

Prospective and retrospective cohorts and case-control studies focusing on DNA methylation and maternal/paternal effects were searched in Pubmed from 1997 to 2023 by using the following keywords: DNA methylation, genomic imprinting, and network analysis in combination with transgenerational/intergenerational effects.

RESULTS

Maternal and paternal exposures to traditional cardiovascular risk factors during critical temporal windows, including the preconceptional period or early pregnancy, may perturb the plasticity of the epigenome (mainly DNA methylation) of the developing fetus especially at imprinted loci, such as the insulin-like growth factor type 2 (IGF2) gene. Thus, the epigenome is akin to a "molecular archive" able to memorize parental environmental insults and predispose an individual to cardiovascular diseases onset in later life. Direct evidence for human transgenerational epigenetic inheritance (at least three generations) of cardiovascular risk is lacking but it is supported by epidemiological studies. Several blood-based association studies showed potential intergenerational epigenetic effects (single-generation studies) which may mediate the transmittance of cardiovascular risk from parents to offspring.

DISCUSSION

In this narrative review, we discuss some relevant examples of trans- and intergenerational epigenetic associations with cardiovascular risk. In our perspective, we propose three network-oriented approaches which may help to clarify the unsolved issues regarding transgenerational epigenetic inheritance of cardiovascular risk and provide potential early biomarkers for primary prevention.

Exposures during pregnancy and at birth are associated with the risk of offspring eating disorders

BACKGROUND

Eating disorders (ED) are severe psychiatric disorders, commonly debuting early. Aberrances in the intrauterine environment and at birth have been associated with risk of ED. Here, we explore if, and at what effect size, a variety of such exposures associate with offspring ED, that is, anorexia nervosa (AN), bulimia nervosa (BN), and eating disorder not otherwise specified (EDNOS).

METHODS

This population-based cohort study, conducted from September 2021 to August 2023, used Finnish national registries of all live births in 1996-2014 (N = 1,097,753). Cox proportional hazards modeling was used to compare ED risk in exposed versus unexposed offspring, adjusting for potential confounders and performing sex-stratified analyses.

RESULTS

A total of 6614 offspring were diagnosed with an ED; 3668 AN, 666 BN, and 4248 EDNOS. Lower risk of offspring AN was seen with young mothers, continued smoking, and instrumental delivery, while higher risk was seen with older mothers, inflammatory disorders, prematurity, small for gestational age, and low Apgar. Offspring risk of BN was higher with continued smoking and prematurity, while lower with postmature birth. Offspring risk of EDNOS was lower with instrumental delivery, higher for older mothers, polycystic ovary syndrome, insulin-treated pregestational diabetes, antibacterial treatment, prematurity, and small for gestational age. Sex-specific associations were found.

CONCLUSIONS

Several prenatal and at birth exposures are associated with offspring ED; however, we cannot exclude confounding by maternal BMI. Nevertheless, several exposures selectively associate with risk of either AN, BN, or EDNOS, and some are sex-specific, emphasizing the importance of subtype- and sex-stratified analyses of ED.

PUBLIC SIGNIFICANCE

We define environmental factors involved in the development of different ED, of importance as preventive measure, but also in order to aid in defining the molecular pathways involved and thus in the longer perspective contribute to the development of pharmacological treatment of ED.

Neuroepigenetics of ageing and neurodegeneration-associated dementia: An updated review

Gene expression is tremendously altered in the brain during memory acquisition, recall, and forgetfulness. However, non-genetic factors, including environmental elements, epigenetic changes, and lifestyle, have grabbed significant attention in recent years regarding the etiology of neurodegenerative diseases (NDD) and age-associated dementia. Epigenetic modifications are essential in regulating gene expression in all living organisms in a DNA sequence-independent manner. The genes implicated in ageing and NDD-related memory disorders are epigenetically regulated by processes such as DNA methylation, histone acetylation as well as messenger RNA editing machinery. The physiological and optimal state of the epigenome, especially within the CNS of humans, plays an intricate role in helping us adjust to the changing environment, and alterations in it cause many brain disorders, but the mechanisms behind it still need to be well understood. When fully understood, these epigenetic landscapes could act as vital targets for pharmacogenetic rescue strategies for treating several diseases, including neurodegeneration- and age-induced dementia. Keeping this objective in mind, this updated review summarises the epigenetic changes associated with age and neurodegeneration-associated dementia.

Maternal adherence to healthy lifestyle and risk of depressive symptoms in the offspring: mediation by offspring lifestyle

BACKGROUND

Adherence to healthy lifestyles can be beneficial for depression among adults, but the intergenerational impact of maternal healthy lifestyles on offspring depressive symptoms is unknown.

METHODS

In total, 10 368 mothers in Nurses' Health Study II and 13 478 offspring in the Growing Up Today Study were paired. Maternal and offspring healthy lifestyles were defined as a composite score including a healthy diet, normal body mass index (BMI), never-smoking, light-to-moderate consumption of alcohol, and regular moderate-to-vigorous physical activity. Maternal lifestyles were assessed during their offspring's childhood. Offspring depressive symptoms were repeatedly assessed five times using the Center for Epidemiological Studies Depression Scale-10 (CESD-10); the offspring were between the ages of 14 and 30 when the first CESD-10 was assessed. Covariates included maternal variables (age at baseline, race/ethnicity, antidepressant use, pregnancy complications, etc.) and offspring age and sex.

RESULTS

Children of mothers with the healthiest lifestyle had significantly fewer depressive symptoms (a 0.30 lower CESD-10 score, 95% confidence interval (CI) 0.09-0.50) in comparison with children of mothers with the least healthy lifestyle. The association was only found significant in female offspring but not in males. For individual maternal lifestyle factors, a normal BMI, never-smoking, and adherence to regular physical activity were independently associated with fewer depressive symptoms among the offspring. The association between maternal healthy lifestyles and offspring depressive symptoms was mediated by offspring's healthy lifestyles (mediation effect: 53.2%, 95% CI 15.8-87.3).

CONCLUSIONS

Our finding indicates the potential mechanism of intergenerational transmission of healthy lifestyles to reduce the risk of depressive symptoms in offspring.

The impact of exposure to tobacco smoking and maternal trauma in fetal life on risk of migraine

Introduction

Prenatal period is the key time in human development. Many prenatal factors are well-known and increase the risk of developing diseases' after birth. Few studies indicated the link between the prenatal period and the prevalence of migraine in childhood and adolescence so far. We decided to broaden current knowledge and investigate whether the prenatal factors influence the prevalence of migraine in adulthood. The objective of this study is to provide evidence of relationship between in utero environment and risk of migraine.

Methods

In total 266 females (136 in the migraine group, 130 in the control group) and 80 males (35 in the migraine group, 45 in the control group), aged 18-65 participated in the study. The quality of prenatal environment was characterized on the basis of mother's and father's education, tobacco smoke exposure, alcohol consumption, and traumatic event during pregnancy, which are considered as prenatal factors and affect on fetal development.

Results

Migraine occurrence in adulthood was significantly associated with maternal tobacco smoking during pregnancy (OR 3.42, 95% CI 1.54-7.61, p = 0.036) and traumatic event during pregnancy (OR 2.27, 95% CI 1.24-4.13, p = 0.020).

Discussion

Our study suggests that the fetal programming effect of tobacco smoking exposure and maternal trauma is not limited to prenatal life and is suggested as having a role in adulthood. Our findings support evidence that migraine adulthood can be partly influenced by early life conditions.

Prenatal Exposure to Tobacco and Childhood Cognition and Behavior: Effect Modification by Maternal Folate Intake and Breastfeeding Duration

In this exploratory analysis, we assessed whether nutrition modified the association between prenatal exposure to tobacco and childhood cognition/behavior among 366 Colorado-based mothers and their offspring (born ≥ 37 weeks with birthweights ≥ 2500 g). Interaction by folate ( 5 months, but not for shorter durations. Our findings support the need for smoking cessation campaigns throughout pregnancy and throughout the postpartum period breastfeeding to reduce neurobehavioral risks in the offspring.

Nicotine on the developing brain

Developmental periods such as gestation and adolescence have enhanced plasticity leaving the brain vulnerable to harmful effects from nicotine use. Proper brain maturation and circuit organization is critical for normal physiological and behavioral outcomes. Although cigarette smoking has declined in popularity, noncombustible nicotine products are readily used. The misperceived safety of these alternatives lead to widespread use among vulnerable populations such as pregnant women and adolescents. Nicotine exposure during these sensitive developmental windows is detrimental to cardiorespiratory function, learning and memory, executive function, and reward related circuitry. In this review, we will discuss clinical and preclinical evidence of the adverse alterations in the brain and behavior following nicotine exposure. Time-dependent nicotine-induced changes in reward related brain regions and drug reward behaviors will be discussed and highlight unique sensitivities within a developmental period. We will also review long lasting effects of developmental exposure persisting into adulthood, along with permanent epigenetic changes in the genome which can be passed to future generations. Taken together, it is critical to evaluate the consequences of nicotine exposure during these vulnerable developmental windows due to its direct impact on cognition, potential trajectories for other substance use, and implicated mechanisms for the neurobiology of substance use disorders.

Maternal smoking during pregnancy negatively affects brain volumes proportional to intracranial volume in adolescents born very preterm

Background

Maternal smoking during pregnancy has been shown to associate with smaller frontal lobe and cerebellar volumes in brain magnetic resonance imaging (MRI) at term age in very preterm infants. The aim of this study was to examine the effect of maternal smoking during pregnancy on volumetric brain MRI findings at 13 years. We hypothesized that adverse effects of smoking during pregnancy on brain volumes are still seen during adolescence.

Methods

Included adolescents were born very preterm (gestational age < 32 weeks and/or birth weight ≤ 1,500 g) between April 2004 and December 2006 at the Turku University Hospital, Finland. Information on maternal smoking status (yes or no) during pregnancy was collected from medical records and maternal questionnaires before discharge. Adolescents underwent volumetric brain MRI at 13 years of age. Image post-processing was performed with FreeSurfer. Regional volumes, cortical thickness, surface area, and curvature were computed from 33 cortical regions of interest (ROIs). Additionally, volumes were calculated for 18 subcortical regions, as well as for white matter, gray matter, and intracranial volume. We normalized quantified absolute volumes for head size by dividing volumes with corresponding intracranial volumes. false discovery rate (FDR) correction for multiple comparisons across regions was used.

Results

A total of 9/44 (21%) adolescents had been exposed to maternal smoking during pregnancy. No statistically significant differences in absolute volumes were observed between the groups (p > 0.05). Regarding volumes proportional to intracranial volume, the adolescents in the exposed group exhibited smaller gray matter volumes in the inferotemporal (FDR corrected p = 0.022) and parahippocampal (p = 0.018) regions compared to the unexposed group. The surface area in the exposed group was also smaller in the parahippocampal (p = 0.046) and postcentral (p = 0.046) regions compared to the unexposed group. No statistically significant differences after correction for multiple comparisons were found for either curvature or cortical thickness between the groups.

Conclusion

Maternal smoking exposure during pregnancy may have long-term effects on brain volumes up to 13 years in adolescents born very preterm. Our findings emphasize the importance of smoking-free pregnancy.

A prospective birth cohort study of maternal prenatal cigarette smoking assessed by self-report and biomarkers on childhood risk of overweight or obesity

Background

Most studies on the association of in utero exposure to cigarette smoking and childhood overweight or obesity (OWO) were based on maternal self-reported smoking status, and few were based on objective biomarkers. The concordance of self-report smoking, and maternal and cord blood biomarkers of cigarette smoking as well as their effects on children's long-term risk of overweight and obesity are unclear.

Methods

In this study, we analyzed data from 2351 mother-child pairs in the Boston Birth Cohort, a sample of US predominantly Black, indigenous, and people of color (BIPOC) that enrolled children at birth and followed prospectively up to age 18 years. In utero smoking exposure was measured by maternal self-report and by maternal and cord plasma biomarkers of smoking: cotinine and hydroxycotinine. We assessed the individual and joint associations of each smoking exposure measure and maternal OWO with childhood OWO using multinomial logistic regressions. We used nested logistic regressions to investigate the childhood OWO prediction performance when adding maternal and cord plasma biomarkers as input covariates on top of self-reported data.

Results

Our results demonstrated that in utero cigarette smoking exposure defined by self-report and by maternal or cord metabolites was consistently associated with increased risk of long-term child OWO. Children with cord hydroxycotinine in the fourth quartile (vs. first quartile) had 1.66 (95% confidence interval [CI] 1.03-2.66) times the odds for overweight and 1.57 (95% CI 1.05-2.36) times the odds for obesity. The combined effect of maternal OWO and smoking on offspring risk of obesity is 3.66 (95% CI 2.37-5.67) if using self-reported smoking. Adding maternal and cord plasma biomarker information to self-reported data improved the prediction accuracy of long-term child OWO risk.

Conclusions

This longitudinal birth cohort study of US BIPOC underscored the role of maternal smoking as an obesogen for offspring OWO risk. Our findings call for public health intervention strategies to focus on maternal smoking - as a highly modifiable target, including smoking cessation and countermeasures (such as optimal nutrition) that may alleviate the increasing obesity burden in the United States and globally.

Sex-specific DNA methylation and associations with in utero tobacco smoke exposure at nuclear-encoded mitochondrial genes

Sex-linked differences in mitochondrial ATP production, enzyme activities, and reactive oxygen species generation have been reported in multiple tissue and cell types. While the effects of reproductive hormones underlie many of these differences, regulation of sexually dimorphic mitochondrial function has not been fully characterized. We hypothesized that sex-specific DNA methylation contributes to sex-specific expression of nuclear genes that influence mitochondrial function. Herein, we analysed DNA methylation data specifically focused on nuclear-encoded mitochondrial genes in 191 males and 190 females. We found 596 differentially methylated sites (DMSs) (FDR p < 0.05), corresponding to 324 genes, with at least a 1% difference in methylation between sexes. To investigate the potential functional significance, we utilized gene expression microarray data. Of the 324 genes containing DMSs, 17 showed differences in gene expression by sex. Particularly striking was that ATP5G2, encoding subunit C of ATP synthase, contains seven DMSs and exhibits a sex difference in expression (p = 0.04). Finally, we also found that alterations in DNA methylation associated with in utero tobacco smoke exposure were sex-specific in these nuclear-encoded mitochondrial genes. Interestingly, the level of sex differences in DNA methylation at nuclear-encoded mitochondrial genes and the level of methylation changes associated with smoke exposure were less prominent than that of other genes. This suggests more conservative regulation of DNA methylation at these nuclear-encoded mitochondrial genes as compared to others. Overall, our findings suggest that sex-specific DNA methylation may help establish sex differences in expression and function and that sex-specific alterations in DNA methylation in response to exposures could contribute to sex-variable toxicological responses.

A prospective birth cohort study of maternal prenatal cigarette smoking assessed by self-report and biomarkers on childhood risk of overweight or obesity

Background

Most studies on the association of in utero exposure to cigarette smoking and childhood overweight or obesity (OWO) were based on maternal self-reported smoking status, and few were based on objective biomarkers.

Objective

We aim to assess the concordance of self-report smoking, and maternal and cord blood biomarkers of cigarette smoking as well as to quantify the in utero cigarette smoking on child long-term risk of overweight and obesity.

Methods

In this study, we analyzed data from 2351 mother-child pairs in the Boston Birth Cohort, a sample of US predominantly Black, indigenous, and people of color (BIPOC) that enrolled children at birth and followed prospectively up to age 18 years. In utero smoking exposure was measured by maternal self-report and by maternal and cord plasma biomarkers of smoking: cotinine and hydroxycotinine. We assessed the individual and joint associations of each smoking exposure measure and maternal OWO with childhood OWO using multinomial logistic regressions. We used nested logistic regressions to investigate the childhood OWO prediction performance when adding maternal and cord plasma biomarkers as input covariates on top of self-reported data.

Results

Our results demonstrated that in utero cigarette smoking exposure defined by self-report and by maternal or cord metabolites was consistently associated with increased risk of long-term child OWO. Children with cord hydroxycotinine in the 4th quartile (vs. 1st quartile) had 1.66 (95% CI 1.03-2.66) times the odds for overweight and 1.57 (95% CI 1.05-2.36) times the odds for obesity. The combined effect of maternal overweight or obesity and smoking on offspring risk of obesity is 3.66 (95% CI 2.37-5.67) if using self-reported smoking. Adding maternal and cord plasma biomarker information to self-reported data improved the prediction accuracy of long-term child OWO risk.

Conclusions

This longitudinal birth cohort study of US BIPOC underscored the role of maternal smoking as an obesogen for offspring OWO risk. Our findings call for public health intervention strategies to focus on maternal smoking - as a highly modifiable target, including smoking cessation and countermeasures (such as optimal nutrition) that may alleviate the increasing obesity burden in the U.S. and globally.

The prevalence of and potential risk factors for Developmental Language Disorder at 10 years in the Raine Study

AIM

This study sought to determine the prevalence of Developmental Language Disorder (DLD) in Australian school-aged children and associated potential risk factors for DLD at 10 years.

METHODS

This study used a cross-sectional design to estimate the prevalence of DLD in Generation 2 of the prospective Raine Study. Participants included 1626 children aged 10 years with available language data. Primary outcomes included variables matching diagnostic criteria for DLD. Associations of other potential prenatal and environmental variables were analysed as secondary outcomes.

RESULTS

The prevalence of DLD in this sample was 6.4% (n = 104) at 10 years. This sub-cohort comprised 33.7% (n = 35) with expressive language deficits, 20.2% (n = 21) with receptive language deficits, and 46.2% (n = 48) with receptive-expressive deficits. No significant difference in sex distribution was observed (52.9% male, p = 0.799). Children who were exposed to smoke in utero at 18 weeks gestation were at increased risk of DLD at 10 years (OR = 2.56, CI = 1.23-5.35, p = 0.012).

CONCLUSIONS

DLD is a relatively prevalent condition in Australian children, even when assessed in middle childhood years. These findings can inform future research priorities, and public health and educational policy which account for the associations with potential risk factors.

Maternal smoking around birth may lower the protective effects of breastfeeding on anxiety, depression and neuroticism in adult offspring: a UK biobank study

We aim to explore the combined effects of the smoking and breastfeeding on offspring mental health outcomes. We used data from UK biobank (N = 342,846) to evaluate joint effect of breastfeeding and maternal smoke during pregnancy (MSDP) on seven adult offspring mental health outcomes (self-reported depression, depression score, self-reported anxiety, anxiety score, neuroticism score, self-harm, suicide). We stratified individuals to MSDP group and non-MSDP group as well as breastfeeding group and non-breastfeeding group. Multiple linear regression and logistic regressions analysis were performed between independent variables (MSDP or breastfeeding) and dependent variables separately (seven mental health outcomes) in each stratum. Effect estimates were expressed as β values and OR values. Sex, age, 10 principle components of population structure, smoking, alcohol use, and Townsend deprivation index were examined as covariates. At MSDP grouping level, coefficients (odds ratio [OR]) for association of breastfed as a baby with self-reported anxiety (category variable) were 0.87 (95%CI, (0.82-0.93), P = 1.74 × 10^-5) in the MSDP group and 0.83 (95%CI, (0.79-0.87), P = 2.76 × 10^-17) in the non-MSDP group. At breastfeeding grouping level, OR for association of MSDP and self-reported anxiety were 1.15 (95%CI, (1.10-1.20), P = 5.36 × 10^-11) in breastfeeding group and 1.12(95%CI, (1.06-1.20), P = 2.02 × 10^-4) in non-breastfeeding group. At MSDP grouping level, negatively associations were found for breastfeeding and anxiety score (continuable variable) in MSDP group (-0.04 SD change per SD change in MSDP, 95% CI, (- 0.06, - 0.02), P = 2.42 × 10^-3) and non-MSDP group (-0.06 SD change per SD change in MSDP, 95%CI, (- 0.07, - 0.04), P = 1.70 × 10^-11). At breastfeeding grouping level, positive association was found for MSDP and anxiety score in the breastfeeding group (0.07 SD change per SD change in MSDP, 95%CI, (0.06-0.09), P = 1.49 × 10^-20) and non-breastfeeding group (0.07 SD change per SD change in MSDP, 95%CI, (0.05-0.09), P = 7.19 × 10^-8). Compared with non-MSDP group, the protective effect (reflected by coefficients) of breastfeeding on anxiety in the MSDP decreased. Our preliminary study found MSDP may lower the protective effect of breastfeeding on the adult offspring anxiety, depression and neuroticism, providing useful recommendations for health care service via quitting smoking during pregnancy and encouraging prolonged breastfeeding.

Prenatal Maternal Smoke, DNA Methylation, and Multi-omics of Tissues and Child Health

PURPOSE OF REVIEW

Maternal tobacco smoking during pregnancy is of public health concern, and understanding the biological mechanisms can help to promote smoking cessation campaigns. This non-systematic review focuses on the effects of maternal smoking during pregnancy on offspring's epigenome, consistent in chemical modifications of the genome that regulate gene expression.

RECENT FINDINGS

Recent meta-analyses of epigenome-wide association studies have shown that maternal smoking during pregnancy is consistently associated with offspring's DNA methylation changes, both in the placenta and blood. These studies indicate that effects on blood DNA methylation can persist for years, and that the longer the duration of the exposure and the higher the dose, the larger the effects. Hence, DNA methylation scores have been developed to estimate past exposure to maternal smoking during pregnancy as biomarkers. There is robust evidence for DNA methylation alterations associated with maternal smoking during pregnancy; however, the role of sex, ethnicity, and genetic background needs further exploration. Moreover, there are no conclusive studies about exposure to low doses or during the preconception period. Similarly, studies on tissues other than the placenta and blood are scarce, and cell-type specificity within tissues needs further investigation. In addition, biological interpretation of DNA methylation findings requires multi-omics data, poorly available in epidemiological settings. Finally, although several mediation analyses link DNA methylation changes with health outcomes, they do not allow causal inference. For this, a combination of data from multiple study designs will be essential in the future to better address this topic.

Tobacco use during pregnancy

The use of tobacco during pregnancy is the leading preventable cause of pregnancy complications and adverse birth outcomes. In high-income countries, around one in 10 pregnant women smokes tobacco, while smokeless tobacco is the primary form of tobacco used in many low- and middle-income countries. Although the risk of tobacco-related harms can be reduced substantially if mothers cease smoking in the first trimester of pregnancy, the proportion of women who successfully quit smoking during pregnancy remains modest. Psychosocial interventions are first-line treatment, with some high-quality evidence showing that counselling is effective in promoting smoking cessation among pregnant women. There is insufficient evidence regarding the efficacy and safety of smoking cessation pharmacotherapies when used during pregnancy, although in some countries nicotine replacement therapy is recommended for pregnant women who have been unable to quit without pharmacological assistance. E-cigarettes are increasingly being used as a smoking cessation aid in the general population of smokers, but more research is needed to determine if e-cigarettes are a safe and effective treatment option for pregnant women.

Prenatal earthquake stress exposure in different gestational trimesters is associated with methylation changes in the glucocorticoid receptor gene (NR3C1) and long-term working memory in adulthood

Prenatal stress exposure is thought to affect the long-term development of the foetal brain via the HPA axis and to change health outcomes in adulthood, including working memory (WM). The potential mechanism is that there is a critical period of brain development of the foetus, which is a result of selective adaptation to the external environment. The human glucocorticoid gene (NR3C1) is associated with memory and cognition. This study investigates the association between earthquake stress during pregnancy and CpG methylation of the NR3C1 exon 1_F promoter and its influence on working memory in adulthood. DNA methylation analysis using bisulfite sequencing PCR was quantified in 176 subjects who were exposed or not exposed to intrauterine earthquake and were divided into three groups based on the pregnancy trimester. The Hopkins Verbal Learning Test-Revised (HVLT-R) and Brief Visuospatial Memory Test-Revised (BVMT-R) were used to assess working memory performance. The methylated NR3C1 exon 1_F promoter of the prenatal earthquake exposure (PEE) group was significantly higher than that of the control group (CN). Analysis of subgroups indicated that the subjects in the second trimester of PEE group showed significantly higher methylation than those in the third trimester. Significantly low BVMT-R scores were detected in those who experienced prenatal earthquake in the second trimester of PEE group. Methylated CpG site 1 may play a critical role in contributing to lower BVMT-R scores in the second trimester in the PEE group, and may offer a potential epigenetic mechanism that links prenatal stress and long-term effects on working memory.

Maternal tobacco smoking and offspring autism spectrum disorder or traits in ECHO cohorts

Given inconsistent evidence on preconception or prenatal tobacco use and offspring autism spectrum disorder (ASD), this study assessed associations of maternal smoking with ASD and ASD-related traits. Among 72 cohorts in the Environmental Influences on Child Health Outcomes consortium, 11 had ASD diagnosis and prenatal tobaccosmoking (n = 8648). and 7 had Social Responsiveness Scale (SRS) scores of ASD traits (n = 2399). Cohorts had diagnoses alone (6), traits alone (2), or both (5). Diagnoses drew from parent/caregiver report, review of records, or standardized instruments. Regression models estimated smoking-related odds ratios (ORs) for diagnoses and standardized mean differences for SRS scores. Cohort-specific ORs were meta-analyzed. Overall, maternal smoking was unassociated with child ASD (adjusted OR, 1.08; 95% confidence interval [CI], 0.72-1.61). However, heterogeneity across studies was strong: preterm cohorts showed reduced ASD risk for exposed children. After excluding preterm cohorts (biased by restrictions on causal intermediate and exposure opportunity) and small cohorts (very few ASD cases in either smoking category), the adjusted OR for ASD from maternal smoking was 1.44 (95% CI, 1.02-2.03). Children of smoking (versus non-smoking) mothers had more ASD traits (SRS T-score + 2.37 points, 95% CI, 0.73-4.01 points), with results homogeneous across cohorts. Maternal preconception/prenatal smoking was consistently associated with quantitative ASD traits and modestly associated with ASD diagnosis among sufficiently powered United States cohorts of non-preterm children. Limitations resulting from self-reported smoking and unmeasured confounders preclude definitive conclusions. Nevertheless, counseling on potential and known risks to the child from maternal smoking is warranted for pregnant women and pregnancy planners. LAY SUMMARY: Evidence on the association between maternal prenatal smoking and the child's risk for autism spectrum disorder has been conflicting, with some studies reporting harmful effects, and others finding reduced risks. Our analysis of children in the ECHO consortium found that maternal prenatal tobacco smoking is consistently associated with an increase in autism-related symptoms in the general population and modestly associated with elevated risk for a diagnosis of autism spectrum disorder when looking at a combined analysis from multiple studies that each included both pre- and full-term births. However, this study is not proof of a causal connection. Future studies to clarify the role of smoking in autism-like behaviors or autism diagnoses should collect more reliable data on smoking and measure other exposures or lifestyle factors that might have confounded our results.

The methylome in females with adolescent Conduct Disorder: Neural pathomechanisms and environmental risk factors

Conduct Disorder (CD) is an impairing psychiatric disorder of childhood and adolescence characterized by aggressive and dissocial behavior. Environmental factors such as maternal smoking during pregnancy, socio-economic status, trauma, or early life stress are associated with CD. Although the number of females with CD is rising in Western societies, CD is under-researched in female cohorts. We aimed at exploring the epigenetic signature of females with CD and its relation to psychosocial and environmental risk factors. We performed HpaII sensitive genome-wide methylation sequencing of 49 CD girls and 50 matched typically developing controls and linear regression models to identify differentially methylated CpG loci (tags) and regions. Significant tags and regions were mapped to the respective genes and tested for enrichment in pathways and brain developmental processes. Finally, epigenetic signatures were tested as mediators for CD-associated risk factors. We identified a 12% increased methylation 5’ of the neurite modulator SLITRK5 (FDR = 0.0046) in cases within a glucocorticoid receptor binding site. Functionally, methylation positively correlated with gene expression in lymphoblastoid cell lines. At systems-level, genes (uncorr. P < 0.01) were associated with development of neurons, neurite outgrowth or neuronal developmental processes. At gene expression level, the associated gene-networks are activated perinatally and during early childhood in neocortical regions, thalamus and striatum, and expressed in amygdala and hippocampus. Specifically, the epigenetic signatures of the gene network activated in the thalamus during early childhood correlated with the effect of parental education on CD status possibly mediating its protective effect. The differential methylation patterns identified in females with CD are likely to affect genes that are expressed in brain regions previously indicated in CD. We provide suggestive evidence that protective effects are likely mediated by epigenetic mechanisms impairing specific brain developmental networks and therefore exerting a long-term effect on neural functions in CD. Our results are exploratory and thus, further replication is needed.

DNA methylome perturbations: an epigenetic basis for the emergingly heritable neurodevelopmental abnormalities associated with maternal smoking and maternal nicotine exposure†

Maternal smoking during pregnancy is associated with an ensemble of neurodevelopmental consequences in children and therefore constitutes a pressing public health concern. Adding to this burden, contemporary epidemiological and especially animal model research suggests that grandmaternal smoking is similarly associated with neurodevelopmental abnormalities in grandchildren, indicative of intergenerational transmission of the neurodevelopmental impacts of maternal smoking. Probing the mechanistic bases of neurodevelopmental anomalies in the children of maternal smokers and the intergenerational transmission thereof, emerging research intimates that epigenetic changes, namely DNA methylome perturbations, are key factors. Altogether, these findings warrant future research to fully elucidate the etiology of neurodevelopmental impairments in the children and grandchildren of maternal smokers and underscore the clear potential thereof to benefit public health by informing the development and implementation of preventative measures, prophylactics, and treatments. To this end, the present review aims to encapsulate the burgeoning evidence linking maternal smoking to intergenerational epigenetic inheritance of neurodevelopmental abnormalities, to identify the strengths and weaknesses thereof, and to highlight areas of emphasis for future human and animal model research therein.

Novel epigenetic clock for fetal brain development predicts prenatal age for cellular stem cell models and derived neurons

Induced pluripotent stem cells (iPSCs) and their differentiated neurons (iPSC-neurons) are a widely used cellular model in the research of the central nervous system. However, it is unknown how well they capture age-associated processes, particularly given that pluripotent cells are only present during the earliest stages of mammalian development. Epigenetic clocks utilize coordinated age-associated changes in DNA methylation to make predictions that correlate strongly with chronological age. It has been shown that the induction of pluripotency rejuvenates predicted epigenetic age. As existing clocks are not optimized for the study of brain development, we developed the fetal brain clock (FBC), a bespoke epigenetic clock trained in human prenatal brain samples in order to investigate more precisely the epigenetic age of iPSCs and iPSC-neurons. The FBC was tested in two independent validation cohorts across a total of 194 samples, confirming that the FBC outperforms other established epigenetic clocks in fetal brain cohorts. We applied the FBC to DNA methylation data from iPSCs and embryonic stem cells and their derived neuronal precursor cells and neurons, finding that these cell types are epigenetically characterized as having an early fetal age. Furthermore, while differentiation from iPSCs to neurons significantly increases epigenetic age, iPSC-neurons are still predicted as being fetal. Together our findings reiterate the need to better understand the limitations of existing epigenetic clocks for answering biological research questions and highlight a limitation of iPSC-neurons as a cellular model of age-related diseases.

Genetic and epigenetic modifications of F1 offspring's sperm cells following in utero and lactational combined exposure to nicotine and ethanol

It is well established that maternal lifestyle during pregnancy and lactation affects the intrauterine programming of F1 offspring. However, despite the co-use of alcohol and nicotine is a common habit, the effects of exposure to both substances on the reproductive system of F1 male offspring and the underlying mechanisms of developmental programming have not been investigated. The present study aimed to examine pre- and postnatal concurrent exposure to these substances on genetic and epigenetic alterations of sperm cells as well as testis properties of F1 offspring compared with exposure to each substance alone. Pregnant dams in the F0 generation randomly received normal saline, nicotine, ethanol, and combinations throughout full gestation and lactation periods. Sperm cells and testes of F1 male offspring were collected at postnatal day 90 for further experiments. High levels of sperm DNA fragmentation were observed in all exposed offspring. Regarding epigenetic alterations, there was a significant increase in the relative transcript abundance of histone deacetylase 1 and 2 in all exposed sperm cells. Moreover, despite a decrease in the expression level of DNA methyltransferase (DNMT) 3A, no marked differences were found in the expression levels of DNMT1 and 3B in any of the exposed sperm cells compared to non-exposed ones. Interestingly, combined exposure had less prominent effects relative to exposure to each substance alone. The changes in the testicular and sperm parameters were compatible with genetic and epigenetic alterations. However, MDA level as an oxidative stress indicator increased in all exposed pups, which may be responsible for such outputs. In conclusion, maternal co-exposure to these substances exhibited epigenotoxicity effects on germline cells of F1 male offspring, although these effects were less marked relative to exposure to each substance alone. These counteracting effects may be explained by cross-tolerance and probably less impairment of the antioxidant defense system.

Epigenetic Alterations of Maternal Tobacco Smoking during Pregnancy: A Narrative Review

In utero exposure to maternal tobacco smoking is the leading cause of birth complications in addition to being associated with later impairment in child’s development. Epigenetic alterations, such as DNA methylation (DNAm), miRNAs expression, and histone modifications, belong to possible underlying mechanisms linking maternal tobacco smoking during pregnancy and adverse birth outcomes and later child’s development. The aims of this review were to provide an update on (1) the main results of epidemiological studies on the impact of in utero exposure to maternal tobacco smoking on epigenetic mechanisms, and (2) the technical issues and methods used in such studies. In contrast with miRNA and histone modifications, DNAm has been the most extensively studied epigenetic mechanism with regard to in utero exposure to maternal tobacco smoking. Most studies relied on cord blood and children’s blood, but placenta is increasingly recognized as a powerful tool, especially for markers of pregnancy exposures. Some recent studies suggest reversibility in DNAm in certain genomic regions as well as memory of smoking exposure in DNAm in other regions, upon smoking cessation before or during pregnancy. Furthermore, reversibility could be more pronounced in miRNA expression compared to DNAm. Increasing evidence based on longitudinal data shows that maternal smoking-associated DNAm changes persist during childhood. In this review, we also discuss some issues related to cell heterogeneity as well as downstream statistical analyses used to relate maternal tobacco smoking during pregnancy and epigenetics. The epigenetic effects of maternal smoking during pregnancy have been among the most widely investigated in the epigenetic epidemiology field. However, there are still huge gaps to fill in, including on the impact on miRNA expression and histone modifications to get a better view of the whole epigenetic machinery. The consistency of maternal tobacco smoking effects across epigenetic marks and across tissues will also provide crucial information for future studies. Advancement in bioinformatic and biostatistics approaches is key to develop a comprehensive analysis of these biological systems.

Epigenetic predictors of lifestyle traits applied to the blood and brain

Modifiable lifestyle factors influence the risk of developing many neurological diseases. These factors have been extensively linked with blood-based genome-wide DNA methylation, but it is unclear if the signatures from blood translate to the target tissue of interest-the brain. To investigate this, we apply blood-derived epigenetic predictors of four lifestyle traits to genome-wide DNA methylation from five post-mortem brain regions and the last blood sample prior to death in 14 individuals in the Lothian Birth Cohort 1936. Using these matched samples, we found that correlations between blood and brain DNA methylation scores for smoking, high-density lipoprotein cholesterol, alcohol and body mass index were highly variable across brain regions. Smoking scores in the dorsolateral prefrontal cortex had the strongest correlations with smoking scores in blood (r = 0.5, n = 14, P = 0.07) and smoking behaviour (r = 0.56, n = 9, P = 0.12). This was also the brain region which exhibited the largest correlations for DNA methylation at site cg05575921 - the single strongest correlate of smoking in blood-in relation to blood (r = 0.61, n = 14, P = 0.02) and smoking behaviour (r = -0.65, n = 9, P = 0.06). This suggested a particular vulnerability to smoking-related differential methylation in this region. Our work contributes to understanding how lifestyle factors affect the brain and suggest that lifestyle-related DNA methylation is likely to be both brain region dependent and in many cases poorly proxied for by blood. Though these pilot data provide a rarely-available opportunity for the comparison of methylation patterns across multiple brain regions and the blood, due to the limited sample size available our results must be considered as preliminary and should therefore be used as a basis for further investigation.

DNA Methylation of Fluoxetine Response in Child and Adolescence: Preliminary Results

Purpose

The search for predictors of antidepressant response is gaining increasing attention, with epigenetic markers attracting a great deal of interest. We performed a genome-wide study assessing baseline differences in DNA methylation between Responders and Non-Responders.

Patients and Methods

Twenty-two children and adolescents, receiving fluoxetine treatment for the first time, were classified as Responders or Non-Responders according to CGI-I score after 8 weeks of fluoxetine treatment. Genome-wide DNA methylation was profiled using the Illumina Infinium MethylationEPIC BeadChip Kit and analyzed using the Chip Analysis Methylation Pipeline (ChAMP).

Results

We identified 21 CpG sites significantly (FDR<0.05) associated with fluoxetine response that showed meaningful differences (Δβ> ±0.2) in methylation level between Responders and Non-Responders. Two genes, RHOJ (Ras Homolog Family Member J) and OR2L13 (Olfactory Receptor family 2 subfamily L member 13), presented more than one significant CpG sites.

Conclusion

Our findings provide new insights into the molecular mechanisms underlying the complex phenotype of antidepressant response, indicating that methylation at specific genes could be a promising biomarker that needs further replication in large cohorts.

Prenatal tobacco smoke exposure and neurological impairment at 10 years of age among children born extremely preterm: a prospective cohort

OBJECTIVE

To determine the association between prenatal tobacco smoke exposure and neurological impairment at 10 years of age among children born extremely preterm (<28 weeks of gestation).

DESIGN

The Extremely Low Gestational Age Newborn (ELGAN) Study, a prospective cohort.

SETTING

Ten-year follow-up of extremely preterm infants born at 14 US hospitals between 2002 and 2004.

METHODS

Prenatal tobacco smoke exposure was defined as a mother's report at enrolment of active (i.e. maternal) and passive smoking during pregnancy. Poisson regression with generalized estimating equations was used. Models adjusted for mother's age, race/ethnicity, education, insurance, pre-pregnancy body mass index, US region, multiple gestation and infant's sex; and in sensitivity analysis, gestational age at delivery and clinical subtype of preterm birth, given their classification as intermediate and non-confounding variables.

MAIN OUTCOMES

Neurological impairment at 10 years, epilepsy, cerebral palsy and cognitive impairment.

RESULTS

Of 1200 ELGAN study survivors, 856 were assessed at 10 years of age with neurological outcomes, of whom 14% (118/856) had active tobacco exposure during pregnancy and 24% (207/852) had passive tobacco exposure. Compared with children who were not exposed prenatally to tobacco, children exposed to active tobacco use during pregnancy had a higher risk of epilepsy (14% versus 5%; adjusted relative risk: 1.68, 95% CI 1.45-1.92). This risk remained after adjustment for gestational age at delivery and clinical subtype of preterm birth. Prenatal tobacco smoke exposure was not associated with other assessed neurological outcomes, including cerebral palsy and multiple measures of cognitive impairment.

CONCLUSIONS

Among children born extremely preterm, prenatal active tobacco smoke exposure was associated with an increased risk of epilepsy at 10 years of life.

TWEETABLE ABSTRACT

Among infants born before 28 weeks of gestation, prenatal active tobacco smoke exposure was associated with an increased risk of epilepsy at 10 years of life.

Epimutational effects of electronic cigarettes

Electronic cigarettes (e-cigarettes), since they do not require tobacco combustion, have traditionally been considered less harmful than conventional cigarettes (c-cigarettes). In recent years, however, researchers have found many toxic compounds in the aerosols of e-cigarettes, and numerous studies have shown that e-cigarettes can adversely affect the human epigenome. In this review, we provide an update on recent findings regarding epigenetic outcomes of e-cigarette aerosols. Moreover, we discussed the effects of several typical e-cigarette ingredients (nicotine, tobacco-specific nitrosamines, volatile organic compounds, carbonyl compounds, and toxic metals) on DNA methylation, histone modifications, and noncoding RNA expression. These epigenetic effects could explain some of the diseases caused by e-cigarettes. It also reminds the public that like c-cigarettes, inhaling e-cigarette aerosols could also be accompanied with potential epigenotoxicity on the human body.

Multidimensional Intersection of Nicotine, Gene Expression, and Behavior

The cholinergic system plays a crucial role in nervous system function with important effects on developmental processes, cognition, attention, motivation, reward, learning, and memory. Nicotine, the reinforcing component of tobacco and e-cigarettes, directly acts on the cholinergic system by targeting nicotinic acetylcholine receptors (nAChRs) in the brain. Activation of nAChRs leads to a multitude of immediate and long-lasting effects in specific cellular populations, thereby affecting the addictive properties of the drug. In addition to the direct actions of nicotine in binding to and opening nAChRs, the subsequent activation of circuits and downstream signaling cascades leads to a wide range of changes in gene expression, which can subsequently alter further behavioral expression. In this review, we provide an overview of the actions of nicotine that lead to changes in gene expression and further highlight evidence supporting how these changes can often be bidirectional, thereby inducing subsequent changes in behaviors associated with further drug intake.

Prenatal Tobacco Exposure and Childhood Neurodevelopment among Infants Born Prematurely

OBJECTIVE

Nicotine is an established neuroteratogen, and prenatal tobacco exposure alters the structure of the developing nervous system. An association between prenatal tobacco exposure and impaired neurologic function is less well established. We examine the association between prenatal tobacco exposure and childhood neurodevelopment among infants born preterm.

STUDY DESIGN

Secondary analysis of a multicenter randomized controlled trial assessing the benefits of magnesium sulfate for the prevention of cerebral palsy in preterm infants. Women were included if they delivered a singleton and nonanomalous infant before 37 weeks. Exposure was any self-reported prenatal tobacco use. Primary outcome was the original trial composite outcome of moderate or severe cerebral palsy at 2 years of age, or stillbirth, or infant death by 1 year of age. Secondary outcomes included components of the composite and mild cerebral palsy at 2 years, Bayley Scales of Infant Development II motor and mental scores, death before two years, and use of auditory aids or corrective lenses. Multivariable logistic regression models were performed to estimate adjusted odds ratios (aOR) with 95% confidence intervals.

RESULTS

Of 1,826 women included, 503 (27.5%) used tobacco. Tobacco users were more likely to be older, unmarried, and white; have a prior preterm birth; have received no prenatal care; and to use illicit drugs or alcohol. Gestational age at delivery, betamethasone exposure, and magnesium exposure were not different between groups. There were no differences in the composite primary outcome or in rates of cerebral palsy by tobacco use. Moderate developmental delay was more common among tobacco exposed in bivariate but not adjusted analysis (20.5 vs. 15.9%, p = 0.035). In adjusted analysis, tobacco exposure was associated with increased use of corrective lenses (5.0 vs. 2.9%, aOR: 2.28, 95% confidence interval: 1.28-4.07).

CONCLUSION

Prenatal tobacco exposure is not associated with neurodevelopmental impairment in infants born preterm. However, tobacco exposure may be associated with impaired vision.

KEY POINTS

· Tobacco exposure is not associated with impaired neurodevelopment in this preterm population.. · Prenatal tobacco exposure is associated with increased need for corrective lenses.. · Tobacco use in pregnancy may be a risk factor for poorer visual acuity in children..

Adolescent Substance Abuse, Transgenerational Consequences and Epigenetics

Adolescence is the transitional period between childhood and adulthood and a critical period in brain development. Adolescence in humans is also associated with increased expression of risk-taking behaviors. Epidemiological and clinical studies, for example, show a surge of drug abuse and raise the hypothesis that the adolescent brain undergoes critical changes resulting in diminished control. Determining how substance abuse during this critical period might cause longterm neurobiological changes in cognition and behavior is therefore critically important. The present work aims to provide an evaluation of the transgenerational and multi-generational phenotypes derived from parent animals exposed to drugs of abuse only during their adolescence. Specifically, we will consider changes found following the administration of cannabinoids, nicotine, alcohol and opiates. In addition, epigenetic modifications of the genome following drug exposure will be discussed as emerging evidence of the underlying adverse transgenerational effects. Notwithstanding, much of the new data discussed here is from animal models, indicating that future clinical studies are much needed to better understand the neurobiological consequences and mechanisms of drug actions on the human brains' development and maturation.

Disruptive Behavior in Siblings Discordant for Exposure to Maternal Smoking During Pregnancy: A Multi-rater Approach

INTRODUCTION

Maternal smoking during pregnancy (SDP) is associated with disruptive behavior. However, there is debate whether the SDP-disruptive behavior association is a potentially causal pathway or rather a spurious effect confounded by shared genetic and environmental factors.

AIMS AND METHODS

The Missouri Mothers and Their Children Study is a sibling comparison study that includes families (n = 173) selected for sibling pairs (aged 7-16 years) discordant for SDP. Critically, the sibling comparison design is used to disentangle the effects of SDP from familial confounds on disruptive behavior. An SDP severity score was created for each child using a combination of SDP indicators (timing, duration, and amount of SDP). Multiple informants (parents and teachers) reported on disruptive behavior (i.e., DSM-IV semi-structured interview, the Child Behavior Checklist, and Teacher Report Form).

RESULTS

The variability in disruptive behavior was primarily a function of within-family differences (66%-100%). Consistent with prior genetically informed approaches, the SDP-disruptive behavior association was primarily explained by familial confounds (genetic and environmental). However, when using a multi-rater approach (parents and teachers), results suggest a potentially causal effect of SDP on disruptive behavior (b = 0.09, SE = 0.04, p = 0.03). The potentially causal effect of SDP remained significant in sensitivity analyses.

DISCUSSION

These findings suggest that familial confounding likely plays a complex role in the SDP-disruptive behavior association when examining both parent and teacher reports of behavior. Importantly, the current study highlights the importance of multiple raters, reflecting a more comprehensive measure of complex behaviors (e.g., disruptive behavior) to examine the teratogenic effects of SDP.

IMPLICATIONS

Our study provides additional evidence that controlling for genetic and family factors is essential when examining the effect of SDP on later behavioral problems, as it explains a portion of the association between SDP and later behavioral problems. However, we found a significant association between SDP and disruptive behavior when using a multi-rater approach that capitalizes on both parent and teacher report, suggesting that parent and teacher ratings capture a unique perspective that is important to consider when examining SDP-behavior associations.

Developmental effects of maternal smoking during pregnancy on the human frontal cortex transcriptome

Cigarette smoking during pregnancy is a major public health concern. While there are well-described consequences in early child development, there is very little known about the effects of maternal smoking on human cortical biology during prenatal life. We therefore performed a genome-wide differential gene expression analysis using RNA sequencing (RNA-seq) on prenatal (N = 33; 16 smoking-exposed) as well as adult (N = 207; 57 active smokers) human postmortem prefrontal cortices. Smoking exposure during the prenatal period was directly associated with differential expression of 14 genes; in contrast, during adulthood, despite a much larger sample size, only two genes showed significant differential expression (FDR < 10%). Moreover, 1,315 genes showed significantly different exposure effects between maternal smoking during pregnancy and direct exposure in adulthood (FDR < 10%)-these differences were largely driven by prenatal differences that were enriched for pathways previously implicated in addiction and synaptic function. Furthermore, prenatal and age-dependent differentially expressed genes were enriched for genes implicated in non-syndromic autism spectrum disorder (ASD) and were differentially expressed as a set between patients with ASD and controls in postmortem cortical regions. These results underscore the enhanced sensitivity to the biological effect of smoking exposure in the developing brain and offer insight into how maternal smoking during pregnancy affects gene expression in the prenatal human cortex. They also begin to address the relationship between in utero exposure to smoking and the heightened risks for the subsequent development of neuropsychiatric disorders.

Systematic review showed that low and moderate prenatal alcohol and nicotine exposure affected early child development

AIM

We systematically reviewed the literature on the influence of low and moderate amounts of prenatal alcohol and nicotine exposure on early child development. This paper also suggests possible directions for future research in order to tackle the controversial findings identified.

METHODS

The PubMed and Web of Science electronic databases were searched together with the reference lists of the selected papers. Empirical studies were included if they focused on the effects of low or moderate exposure, reported outcomes on child development within the first 2 years of life and were published in English between January 2009 and December 2019. The eligibility of the included studies was based on three authors reading the full text.

RESULTS

The final sample comprised 17 papers. Of these, 13 focused on the effects of prenatal alcohol exposure and they reported decreased sensory sensibility, smaller body sizes and increased cognitive capacities. The other four looked at prenatal nicotine exposure, and they primarily found impairments in children's orienting, communication and motor skills.

CONCLUSION

Any amount of prenatal alcohol and nicotine exposure appeared to risk healthy child development. There were many reasons for consumption and numerous effects on the child, but representative data from interdisciplinary research were missing.

Differential gene expression and limited epigenetic dysregulation at the materno-fetal interface in preeclampsia

Despite the many advances made in the diagnosis and management of preeclampsia, this syndrome remains a leading cause of maternal mortality and life-long morbidity, as well as adverse fetal outcomes. Successful prediction and therapeutic intervention require an improved understanding of the molecular mechanisms, which underlie preeclampsia pathophysiology. We have used an integrated approach to discover placental genetic and epigenetic markers of preeclampsia and validated our findings in an independent cohort of women. We observed the microRNA, MIR138, to be upregulated in singleton preeclamptic placentas; however, this appears to be a female infant sex-specific effect. We did not identify any significant differentially methylated positions (DMPs) in singleton pregnancies, indicating that DNA methylation changes in mild forms of the disease are likely limited. However, we identified infant sex-specific preeclampsia-associated differentially methylated regions among singletons. Disease-associated DMPs were more obvious in a limited sampling of twin pregnancies. Interestingly, 2 out of the 10 most significant changes in methylation over larger regions overlap between singletons and twins and correspond to NAPRT1 and ZNF417.

Substantia Nigra Abnormalities Provide New Insight on the Neural Mechanisms Underlying the Sleep-Arousal Phase Dysfunctions in Sudden Infant Death Syndrome

The purpose of this study was to research possible developmental alterations of the substantia nigra (SN) in sudden infant death syndrome (SIDS), a syndrome frequently attributed to arousal failure from sleep. Brain stems of 46 victims of sudden infant death, aged from 1 to about 7 months (4 to 30 postnatal weeks), were investigated. Twenty-six of these cases were diagnosed as SIDS, due to the lack of any pathological finding, while the remaining 20 cases in which the cause of death was determined at autopsy served as controls. Maternal smoking was reported in 77% of SIDS and 10% of controls. Histopathological examination of the SN was done on 5-µm-thick sections of caudal midbrain stained with both hematoxylin-eosin and Klüver-Barrera. Densitometry, immunohistochemistry and histochemistry were applied to highlight the neuronal concentration, the tyrosine hydroxylase (TH) expression, and the presence of neuromelanin (NM) in this structure. Hypoplasia of the pars compacta portion of the SN was observed in 69% of SIDS but never in controls; TH expression was significantly higher in controls than in SIDS; and NM was observed only in 4 infants of the control group but not in SIDS. A significant correlation was found between SIDS, hypoplasia/low neuronal density, low TH expression in the pars compacta, and maternal smoking. Because the SN pars compacta, being the major dopamine brain center, controls many functions, including the sleep-arousal phase, its alterations, especially concurrently with smoking exposure, may contribute to explain the pathogenesis of SIDS that occur in the great part of cases at awakening from sleep.

Sperm DNA methylation altered by THC and nicotine: Vulnerability of neurodevelopmental genes with bivalent chromatin

Men consume the most nicotine and cannabis products but impacts on sperm epigenetics are poorly characterized. Evidence suggests that preconception exposure to these drugs alters offspring neurodevelopment. Epigenetics may in part facilitate heritability. We therefore compared effects of exposure to tetrahydrocannabinol (THC) and nicotine on DNA methylation in rat sperm at genes involved in neurodevelopment. Reduced representation bisulfite sequencing data from sperm of rats exposed to THC via oral gavage showed that seven neurodevelopmentally active genes were significantly differentially methylated versus controls. Pyrosequencing data revealed majority overlap in differential methylation in sperm from rats exposed to THC via injection as well as those exposed to nicotine. Neurodevelopmental genes including autism candidates are vulnerable to environmental exposures and common features may mediate this vulnerability. We discovered that autism candidate genes are significantly enriched for bivalent chromatin structure, suggesting this configuration may increase vulnerability of genes in sperm to disrupted methylation.

Transgenerational transmission of neurodevelopmental disorders induced by maternal exposure to PM2.5

The pathological traits or diseases susceptibility caused by maternal exposure to environmental adverse insults (infection, malnutrition, environmental toxicants) could be transmitted across generations. It remains uncertain, however, whether the neurodevelopmental disturbances of offspring induced by maternal exposure to PM2.5 during early life can be inherited by subsequent generations without further exposure. In the current study, using transgenerational animal models, we found that F1 female showed poorer performance in Morris Water Maze (MWM), and the deficits in spatial learning and memory similarly presented in F2-F3 female. The transgenerationally-transmitted neurobehavioral disorders were mediated both via maternal and paternal lineage. Since the epigenetic modifications have been reported to be involved in the disturbed neurodevelopment induced by maternal exposure to detrimental environmental factors during early life, we further explored the possible epigenetic mechanism of the transgenerational effects. Intriguingly, the results displayed the significant increase in expression of Dnmt3a in F1 female offspring. And the hypermethylation of Bdnf promoter Ⅳ and downregulated expression of Bdnf in hippocampus were stably transmitted across the generations until the third generation. There was another interesting finding that the transgenerational effects were sex-specific and only emerged in female offspring. Together, our study indicated for the first time that maternal exposure to PM2.5 during early life could detrimentally affect neurobehaviors in multiple generations, and the declined expression of Bdnf induced by hypermethylation of Bdnf promoter Ⅳ mediated by Dnmts might be the potential molecular mechanism.

Investigation of Schizophrenia with Human Induced Pluripotent Stem Cells

Schizophrenia is a chronic and severe neuropsychiatric condition manifested by cognitive, emotional, affective, perceptual, and behavioral abnormalities. Despite decades of research, the biological substrates driving the signs and symptoms of the disorder remain elusive, thus hampering progress in the development of treatments aimed at disease etiologies. The recent emergence of human induced pluripotent stem cell (hiPSC)-based models has provided the field with a highly innovative approach to generate, study, and manipulate living neural tissue derived from patients, making possible the exploration of fundamental roles of genes and early-life stressors in disease-relevant cell types. Here, we begin with a brief overview of the clinical, epidemiological, and genetic aspects of the condition, with a focus on schizophrenia as a neurodevelopmental disorder. We then highlight relevant technical advancements in hiPSC models and assess novel findings attained using hiPSC-based approaches and their implications for disease biology and treatment innovation. We close with a critical appraisal of the developments necessary for both further expanding knowledge of schizophrenia and the translation of new insights into therapeutic innovations.

DDT exposure during pregnancy and DNA methylation alterations in female offspring in the Child Health and Development Study

Studies measuring dichlorodiphenyltrichloroethane (DDT) exposure during key windows of susceptibility including the intrauterine period suggest that DDT exposure is associated with breast cancer risk. We hypothesized that prenatal DDT exposure is associated with DNA methylation. Using prospective data from 316 daughters in the Child Health and Development Study, we examined the association between prenatal exposure to DDTs and DNA methylation in blood collected in midlife (mean age: 49 years). To identify differentially methylated regions (DMRs) associated with markers of DDTs (p,p'-DDT and the primary metabolite of p,p'-DDT, p,p'-DDE, and o,p'-DDT, the primary constituents of technical DDT), we measured methylation in 30 genes important to breast cancer. We observed DDT DMRs in three genes, CCDC85A, CYP1A1 and ZFPM2, each of which has been previously implicated in pubertal development and breast cancer susceptibility. These findings suggest prenatal DDT exposure may have life-long consequence through alteration in genes relevant to breast cancer.

Effects of maternal smoking on body size and proportions at birth: a register-based cohort study of 1.4 million births

OBJECTIVES

The aim of our work was to analyse the effect of maternal smoking on body size and body proportions of newborns when the mother had smoked only during the first trimester, in comparison with continued smoking after the first trimester. Furthermore, we have evaluated how growth restriction associated with maternal smoking contributes to changes in body proportions.

DESIGN

Register-based cohort study SETTING: Maternal Exposure (MATEX) cohort identified from the Finnish Medical Birth Register.

PARTICIPANTS

Singleton births without congenital anomalies and missing data (1.38 million) from 1 January 1991 to 31 December 2016.

METHODS

Logistic regression was used to quantify the effect of maternal smoking, stratified by the maternal smoking status.

OUTCOME MEASURES

Body proportions indicated by low brain-to-body ratio (defined as <10th percentile); high ponderal index and high head-to-length ratio (defined as >90th percentile); small body size for gestational age at birth (defined as weight, length or head circumference <10th percentile) and preterm birth (<37 weeks) and low birth weight (2500 g).

RESULTS

Continued smoking after the first trimester was associated with high ponderal index (OR 1.26, 95% CI 1.23 to 1.28), low brain-to-body ratio (1.11, 1.07-1.15) and high head-to-length ratio (1.22, 1.19-1.26), corresponding with absolute risks of 22%, 10% and 19%, respectively). The effects were slightly lower when smoking had been quit during the first trimester. Similar effects were seen for the body size variables and low birth weight. Preterm birth was not associated with smoking only during first trimester.

CONCLUSIONS

Maternal smoking, independent of smoking duration during pregnancy, was associated with abnormal body proportions resulting from larger reduction of length and head circumference in comparison to weight. The effects of having quit smoking during the first trimester and having continued smoking after the first trimester were similar, suggesting the importance of early pregnancy as a sensitive exposure window.

Nicotine Suppresses the Invasiveness of Human Trophoblasts by Downregulation of CXCL12 Expression through the Alpha-7 Subunit of the Nicotinic Acetylcholine Receptor

Smoke exposure during pregnancy has detrimental effects upon numerous fetal and neonatal outcomes. Nicotine (the main component of tobacco) has been suggested to affect placental development. During placental development, efficient invasion by trophoblasts is required for establishment of the fetus–maternal circulation. In this study we explored the regulation of trophoblast invasion by nicotine. An immortalized first trimester extravillous trophoblast cell line (HTR-8/SVneo cells) was used for all the experiments, which were treated by nicotine, methyllycaconitine, and C-X-C motif chemokine ligand 12 (CXCL12). Total RNA and protein were used to study the expressions of nicotinic acetylcholine receptors (nAChRs), and transwell assay was used to study invasiveness. Changes of RNA expression due to nicotine treatment were detected by RNA sequence. Level of CXCL12 mRNA was verified by quantitative PCR. We showed that HTR-8/SVneo expressed subunits α2–4, α7, α9, β1, and β2 of nAChRs. Nicotine downregulated CXCL12 expression and inhibited trophoblast invasion. Methyllycaconitine, as an antagonist of the α7 homopolymer, blocked the inhibitory effect of nicotine. CXCL12 could rescue the nicotine-induced inhibitory effect on invasion of HTR-8/SVneo cells. These results suggest that the α7 subunit of the nAChR has important roles in modulating trophoblast invasion through CXCL12.

Sudden intrauterine unexplained death: time to adopt uniform postmortem investigative guidelines?

Background

Worldwide approximately 2.6 million are stillborn, mostly occurring in developing countries. In the great part these deaths are inexplicable. The evenness and standardisation of the diagnostic criteria are prerequisites to understand their pathogenesis. The core goal of this article is to propose new evidence based investigative post-mortem guidelines that should be adopted in all the Institutions especially when a fetal death, after a routine autopsy procedure, is diagnosed as “unexplained”. The proposed protocol is mainly focused on the anatomopathological examination of the autonomic nervous system and in particular of the brainstem where the main centers that control vital functions are located.

Methods

Updated investigative guidelines for the examination of unexplained stillbirths, prevalently focused on the histological examination of the brainstem, where the main centers that are involved in monitoring the vital functions are located, are here presented. A section of this protocol concerns the Immunohistochemical evaluation of specific functional markers such as the neuronal nuclear antigen, nicotinic acetylcholine receptors, serotonin, orexin, apoptosis and gliosis. The important role of risk factors, having regard in particular to maternal smoking and air pollution is also contemplated in these guidelines.

Results

Specific morphological and/or functional alterations of vital brainstem structures have been found with high incidence in over 100 cases of unexplained fetal death sent to the “Lino Rossi Research Center” of the Milan University according to the Italian law. These alterations were rarely detected in a group of control cases.

Conclusions

We hope this protocol can be adopted in all the Institutions notably for the examination of unexplained fetal deaths, in order to make uniform investigations. This will lead to identify a plausible explanation of the pathogenetic mechanism behind the unexplained fetal deaths and to design preventive strategies to decrease the incidence of these very distressing events for both parents and clinicians.

Trial registration

not applicable for this study.

Altered Cortical Brain Structure and Increased Risk for Disease Seen Decades After Perinatal Exposure to Maternal Smoking: A Study of 9000 Adults in the UK Biobank

Secondhand smoke exposure is a major public health risk that is especially harmful to the developing brain, but it is unclear if early exposure affects brain structure during middle age and older adulthood. Here we analyzed brain MRI data from the UK Biobank in a population-based sample of individuals (ages 44-80) who were exposed (n = 2510) or unexposed (n = 6079) to smoking around birth. We used robust statistical models, including quantile regressions, to test the effect of perinatal smoke exposure (PSE) on cortical surface area (SA), thickness, and subcortical volumes. We hypothesized that PSE would be associated with cortical disruption in primary sensory areas compared to unexposed (PSE-) adults. After adjusting for multiple comparisons, SA was significantly lower in the pericalcarine (PCAL), inferior parietal (IPL), and regions of the temporal and frontal cortex of PSE+ adults; these abnormalities were associated with increased risk for several diseases, including circulatory and endocrine conditions. Sensitivity analyses conducted in a hold-out group of healthy participants (exposed, n = 109, unexposed, n = 315) replicated the effect of PSE on SA in the PCAL and IPL. Collectively our results show a negative, long term effect of PSE on sensory cortices that may increase risk for disease later in life.

What lessons have we learnt about the impact of maternal cigarette smoking from animal models?

Maternal first- or second-hand tobacco smoking during pregnancy is still common albeit that the detrimental effects to the unborn child are well known. Maternal tobacco cigarette smoking can affect multiple organ systems in the offspring, rendering them at increased risk of various conditions throughout life (eg. intrauterine underdevelopment, asthma, substance abuse, diabetes). However, this review will only focus on its impact on the brain and the related molecular changes in the offspring based on evidence from animal studies. Although epidemiological studies have identified the associations between maternal cigarette smoke exposure (SE) and brain disorders, animal models can help identify the underlying mechanisms and test interventions. Human studies have found that maternal SE is closely linked to small brain size and changes in brain structure and associated with a high risk of cognitive defects. Animal models suggest that this may be due to increased brain oxidative stress and inflammation during the neonatal period, leading to increased brain cell apoptosis in adulthood. There is a distinct gender bias of such impacts, where male offspring are more affected than females. Female offspring seem to have developed the adaptation by increasing endogenous antioxidant levels. Indeed, animal studies have shown that using antioxidant supplementation during pregnancy can improve neurological outcomes in male offspring, however, the efficacy in humans is yet to be confirmed. Furthermore, some animal studies suggested nicotine as the key player in intrauterine underdevelopment due to maternal SE, while human clinical trials using nicotine replacement therapy do not support this mechanism. This review will discuss the possible reasons.

Prenatal Nicotine Exposure in Rodents: Why Are There So Many Variations in Behavioral Outcomes?

Introduction

The World Health Organization (WHO) reported that smoking cessation rates among women have stagnated in the past decade and estimates that hundreds of millions of women will be smokers in the next decade. Social, environmental, and biological conditions render women more susceptible to nicotine addiction, imposing additional challenges to quit smoking during gestation, which is likely why more than 8% of pregnancies in Europe are associated with smoking. In epidemiological investigations, individuals born from gestational exposure to smoking exhibit a higher risk of development of attention-deficit/hyperactive disorder (ADHD) and liability to drug dependence. Among other teratogenic compounds present in tobacco smoke, nicotine actions during neuronal development could contribute to the observed outcomes as nicotine misleads signaling among progenitor cells during brain development. Several experimental approaches have been developed to address the consequences of prenatal nicotine exposure (PNE) to the brain and behavior but, after four decades of studies, inconsistent data have been reported and the lack of consensus in the field has compromised the hypothesis that gestational nicotine exposure participates in cognitive and emotional behavioral deficits.

Aims

In this review, we discuss the most commonly used PNE models with focus on their advantages and disadvantages, their relative validity, and how the different technical approaches could play a role in the disparate outcomes.

Results

We propose methodological considerations, which could improve the translational significance of the PNE models.

Conclusions

Such alterations might be helpful in reconciling experimental findings, as well as leading to development of treatment targets for maladaptive behaviors in those prenatally exposed.

Implications

In this article, we have reviewed the advantages and disadvantages of different variables of the commonly used experimental models of PNE. We discuss how variations in the nicotine administration methods, the timing of nicotine exposure, nicotine doses, and species employed could contribute to the disparate findings in outcomes for PNE offspring, both in behavior and neuronal changes. In addition, recent findings suggest consideration of epigenetic effects extending across generations. Finally, we have suggested improvements in the available PNE models that could contribute to the enhancement of their validity, which could assist in the reconciliation of experimental findings.

Does early maternal responsiveness buffer prenatal tobacco exposure effects on young children's behavioral disinhibition?

Children with prenatal tobacco exposure (PTE) exhibit early self-regulatory impairments, reflecting a life-course persistent propensity toward behavioral disinhibition. Previously, we demonstrated the protective role of parental responsiveness for reducing the risk of exposure-related disruptive behavior in adolescence. Here, we expanded this line of inquiry, examining whether responsiveness moderates the relation of PTE to a broader set of behavioral disinhibition features in early childhood and testing alternative diathesis-stress versus differential susceptibility explanatory models. PTE was assessed prospectively using interviews and bioassays in the Midwestern Infant Development Study (MIDS). Mother-child dyads (N = 276) were re-assessed at approximately 5 years of age in a preschool follow-up. We quantified maternal responsiveness and child behavioral disinhibition using a combination of directly observed activities in the lab and developmentally sensitive questionnaires. Results supported a diathesis-stress pattern. Children with PTE and less responsive mothers showed increased disruptive behavior and lower effortful control compared with children without PTE. In contrast, exposed children with more responsive mothers had self-regulatory profiles similar to their non-exposed peers. We did not observe sex differences. Findings provide greater specification of the protective role of maternal responsiveness for self-regulation in children with PTE and help clarify mechanisms that may underscore trajectories of exposure-related behavioral disinhibition.

Generation of a Triple-Transgenic Zebrafish Line for Assessment of Developmental Neurotoxicity during Neuronal Differentiation

: The developing brain is extremely sensitive to many chemicals. Exposure to neurotoxicants during development has been implicated in various neuropsychiatric and neurological disorders, including autism spectrum disorders and schizophrenia. Various screening methods have been used to assess the developmental neurotoxicity (DNT) of chemicals, with most assays focusing on cell viability, apoptosis, proliferation, migration, neuronal differentiation, and neuronal network formation. However, assessment of toxicity during progenitor cell differentiation into neurons, astrocytes, and oligodendrocytes often requires immunohistochemistry, which is a reliable but labor-intensive and time-consuming assay. Here, we report the development of a triple-transgenic zebrafish line that expresses distinct fluorescent proteins in neurons (Cerulean), astrocytes (mCherry), and oligodendrocytes (mCitrine), which can be used to detect DNT during neuronal differentiation. Using in vivo fluorescence microscopy, we could detect DNT by 6 of the 10 neurotoxicants tested after exposure to zebrafish from 12 h to 5 days' post-fertilization. Moreover, the chemicals could be clustered into three main DNT groups based on the fluorescence pattern: (i) inhibition of neuron and oligodendrocyte differentiation and stimulation of astrocyte differentiation; (ii) inhibition of neuron and oligodendrocyte differentiation; and (iii) inhibition of neuron and astrocyte differentiation, which suggests that reporter expression reflects the toxicodynamics of the chemicals. Thus, the triple-transgenic zebrafish line developed here may be a useful tool to assess DNT during neuronal differentiation.

Integrating -Omics Approaches into Human Population-Based Studies of Prenatal and Early-Life Exposures

PURPOSE OF REVIEW

We present the study design and methodological suggestions for population-based studies that integrate molecular -omics data and highlight recent studies that have used such data to examine the potential impacts of prenatal environmental exposures on fetal health.

RECENT FINDINGS

Epidemiologic studies have observed numerous relationships between prenatal exposures (smoking, toxic metals, endocrine disruptors) and fetal and early-life molecular profiles, though such investigations have so far been dominated by epigenomic association studies. However, recent transcriptomic, proteomic, and metabolomic studies have demonstrated their promise for the identification of exposure and response biomarkers. Molecular -omics have opened new avenues of research in environmental health that can improve our understanding of disease etiology and contribute to the development of exposure and response biomarkers. Studies that incorporate multiple -omics data from different molecular domains in longitudinally collected samples hold particular promise.