The impact of tobacco chemicals and nicotine on placental development

Impact of Maternal Environment and Inflammation on Fetal Neurodevelopment

During intrauterine life, external stimuli including maternal nutrition, lifestyle, socioeconomic conditions, anxiety, stress, and air pollution can significantly impact fetal development. The human brain structures begin to form in the early weeks of gestation and continue to grow and mature throughout pregnancy. This review aims to assess, based on the latest research, the impact of environmental factors on fetal and neonatal brain development, showing that oxidative stress and inflammation are implied as a common factor for most of the stressors. Environmental insults can induce a maternal inflammatory state and modify nutrient supply to the fetus, possibly through epigenetic mechanisms, leading to significant consequences for brain morphogenesis and neurological outcomes. These risk factors are often synergic and mutually reinforcing. Fetal growth restriction and preterm birth represent paradigms of intrauterine reduced nutrient supply and inflammation, respectively. These mechanisms can lead to an increase in free radicals and, consequently, oxidative stress, with well-known adverse effects on the offspring's neurodevelopment. Therefore, a healthy intrauterine environment is a critical factor in supporting normal fetal brain development. Hence, healthcare professionals and clinicians should implement effective interventions to prevent and reduce modifiable risk factors associated with an increased inflammatory state and decreased nutrient supply during pregnancy.

Placental pathology and neonatal morbidity: exploring the impact of gestational age at birth

AIM

To evaluate placental pathology in term and post-term births, investigate differences in clinical characteristics, and assess the risk of adverse neonatal outcome.

METHODS

This prospective observational study included 315 singleton births with gestational age (GA) > 36 weeks + 6 days meeting the local criteria for referral to placental histopathologic examination. We applied the Amsterdam criteria to classify the placentas. Births were categorized according to GA; early-term (37 weeks + 0 days to 38 weeks + 6 days), term (39 weeks + 0 days to 40 weeks + 6 days), late-term (41 weeks + 0 days to 41 weeks + 6 days), and post-term births (≥ 42 weeks + 0 days). The groups were compared regarding placental pathology findings and clinical characteristics. Adverse neonatal outcomes were defined as 5-minute Apgar score < 7, umbilical cord artery pH < 7.0, admission to the neonatal intensive care unit or intrauterine death. A composite adverse outcome included one or more adverse outcomes. The associations between placental pathology, adverse neonatal outcomes, maternal and pregnancy characteristics were evaluated by logistic regression analysis.

RESULTS

Late-term and post-term births exhibited significantly higher rates of histologic chorioamnionitis (HCA), fetal inflammatory response, clinical chorioamnionitis (CCA) and transfer to neonatal intensive care unit (NICU) compared to early-term and term births. HCA and maternal smoking in pregnancy were associated with adverse outcomes in an adjusted analysis. Nulliparity, CCA, emergency section and increasing GA were all significantly associated with HCA.

CONCLUSIONS

HCA was more prevalent in late and post-term births and was the only factor, along with maternal smoking, that was associated with adverse neonatal outcomes. Since nulliparity, CCA and GA beyond term are associated with HCA, this should alert the clinician and elicit continuous intrapartum monitoring for timely intervention.

Effects of psychosocial work factors on preterm birth: systematic review and meta-analysis

OBJECTIVES

Preterm birth is one of the global public health issues that result in high rates of infant mortality and long-term health complications. We sought to explore the association between psychosocial work factors and preterm birth.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

This systematic review and meta-analysis searched relevant literature from electronic databases to explore the association between psychosocial work factors and preterm birth. The methodological quality of the included studies was evaluated through the Joanna Briggs Institute's critical appraisal method. We performed a meta-analysis using a random-effects model to combine odds ratios (ORs) from studies with similar definitions of exposure and outcome. The quality of the evidence was evaluated using the GRADE (Grade of recommendation, Assessment, development, and Evaluation) method to assess.

RESULTS

Ten studies were included, with a total of 92,815 participants. Moderate evidence indicated a positive association between high psychosocial job strain and preterm birth. The result from the meta-analysis supported the statistical significance of this relationship (OR 1.32 [95% CI (1.22-1.44)]).

CONCLUSIONS

Pregnant women who experience high levels of psychosocial job strain are more likely to give birth prematurely. In order to decrease this risk, employers should prioritise creating supportive work environments, government bodies should enact protective policies and regulations, and clinicians should give advice to pregnant working women. Pregnant women should be aware of the risk of preterm birth from psychosocial work factors.

Morphological and clinical findings in placentas and newborns with a history of tobacco, alcohol, and other substance abuse during pregnancy

BACKGROUND

Exposure to toxins during pregnancy is the main modifiable behavior that affects the placenta and, consequently, the fetus. In particular, smoking is a recognized risk factor for negative outcomes. Our study pretended to examine gross and microscopic placental features in women who reported exposure to tobacco, alcohol, or other psychoactive substances.

METHODS

In this observational case-control study, we collected 706 placentas to assess precise substance exposure histological-interaction features of in the placenta. We examined gross and microscopic placental features, and then recorded maternal and newborn clinical conditions.

RESULTS

We found that 4.8% of mothers admitted to consumption of some type of (harmful) substance. The most common pre-existing maternal condition was obesity (20.3%); predominant complications included amniotic infection (32.3%), urinary tract infection (14.5%) and hypertensive disorders of pregnancy (14.5%). In newborns, we discovered positive associations as respiratory distress syndrome. Macroscopically, exposed mothers had heavier placentas, more true knots, and single umbilical artery; microscopically, they were more likely to exhibit fetal vascular malperfusion (FVM).

CONCLUSIONS

Until our present study, no research linked umbilical cord defects to toxic substance exposure; our study results do confirm association with adverse outcomes in neonates and alterations in the neuro-cardio-placental circuit through FVM.

IMPLICATIONS

The results are confirming the importance of this modifiable risk factor and how its presence may potentially affect the course of pregnancy, as well as the health of both mother and child.

Associations between Smoking and Smoking Cessation during Pregnancy and Newborn Metabolite Concentrations: Findings from PRAMS and INSPIRE Birth Cohorts

Newborn metabolite perturbations may identify potential biomarkers or mechanisms underlying adverse, smoking-related childhood health outcomes. We assessed associations between third-trimester smoking and newborn metabolite concentrations using the Tennessee Pregnancy Risk Assessment Monitoring System (PRAMS, 2009-2019) as the discovery cohort and INSPIRE (2012-2014) as the replication cohort. Children were linked to newborn screening metabolic data (33 metabolites). Third-trimester smoking was ascertained from birth certificates (PRAMS) and questionnaires (INSPIRE). Among 8600 and 1918 mother-child dyads in PRAMS and INSPIRE cohorts, 14% and 13% of women reported third-trimester smoking, respectively. Third-trimester smoking was associated with higher median concentrations of free carnitine (C0), glycine (GLY), and leucine (LEU) at birth (PRAMS: C0: adjusted fold change 1.11 [95% confidence interval (CI) 1.08, 1.14], GLY: 1.03 [95% CI 1.01, 1.04], LEU: 1.04 [95% CI 1.03, 1.06]; INSPIRE: C0: 1.08 [95% CI 1.02, 1.14], GLY: 1.05 [95% CI 1.01, 1.09], LEU: 1.05 [95% CI 1.01, 1.09]). Smoking cessation (vs. continued smoking) during pregnancy was associated with lower median metabolite concentrations, approaching levels observed in infants of non-smoking women. Findings suggest potential pathways underlying fetal metabolic programming due to in utero smoke exposure and a potential reversible relationship of cessation.

Early-life exposure to cigarette smoke primes lung function and DNA methylation changes at Cyp1a1 upon exposure later in life

Prenatal and early-life exposure to cigarette smoke (CS) has repeatedly been shown to induce stable, long-term changes in DNA methylation (DNAm) in offspring. It has been hypothesized that these changes might be functionally related to the known outcomes of prenatal and early-life CS exposure, which include impaired lung development, altered lung function, and increased risk of asthma and wheeze. However, to date, few studies have examined DNAm changes induced by prenatal CS in tissues of the lung, and even fewer have attempted to examine the specific influences of prenatal versus early postnatal exposures. Here, we have established a mouse model of CS exposure which isolates the effects of prenatal and early postnatal CS exposures in early life. We have used this model to measure the effects of prenatal and/or postnatal CS exposures on lung function and immune cell infiltration as well as DNAm and expression of Cyp1a1, a candidate gene previously observed to demonstrate DNAm differences on CS exposure in humans. Our study revealed that exposure to CS prenatally and in the early postnatal period causes long-lasting differences in offspring lung function, gene expression, and lung Cyp1a1 DNAm, which wane over time but are reestablished on reexposure to CS in adulthood. This study creates a testable mouse model that can be used to investigate the effects of prenatal and early postnatal CS exposures and will contribute to the design of intervention strategies to mediate these detrimental effects.NEW & NOTEWORTHY Here, we isolated effects of prenatal from early postnatal cigarette smoke and showed that exposure to cigarette smoke early in life causes changes in offspring DNA methylation at Cyp1a1 that last through early adulthood but not into late adulthood. We also showed that smoking in adulthood reestablished these DNA methylation patterns at Cyp1a1, suggesting that a mechanism other than DNA methylation results in long-term memory associated with early-life cigarette smoke exposures at this gene.

The impact of smoking and nicotine exposure during pregnancy on fetal nephrogenesis: a systematic review

The effect of smoking and nicotine exposure during pregnancy on fetal nephrogenesis is a growing area of research. The objective of this systematic review is to summarise the current evidence in this research field. Our literature search identified a total of 415 articles from PubMed, Embase, Scopus, and Cochrane. After electronic sorting and manual screening, 18 eligible articles were found, 6 being human studies and 12 being animal studies. Articles that did not study nicotine or smoking, did not focus on fetal kidney development, or did not include nicotine or smoking exposure during pregnancy were excluded from the systematic review. The main outcomes of the studies were kidney weight, volume and size, kidney histopathology and morphology, and kidney function. Evidence from human studies identified a reduction in fetal kidney size, volume, and weight in offspring exposed to smoking during pregnancy; and the greatest impact was seen in offspring exposed to >5-10 cigarettes per day. Animal studies investigated kidney histopathology and highlighted kidney injury and microscopic changes in response to nicotine exposure during pregnancy. Further research is required to determine the impact on kidney function. Recreational nicotine use is evolving, and with the increasing use of urine cotinine in the evaluation of nicotine exposure, further research is needed.

Trends in smoking during pregnancy stratified by the use of opioid agonist therapy and the contribution of smoking to poor outcome in neonates prenatally exposed to opioid agonist treatment

High rates of cigarette smoking have been observed in pregnant women on opioid agonist therapy (OAT). However, it is unclear if these rates have changed overtime in line with the general population and the degree to which smoking contributes to poor outcomes in neonates born to women on OAT. Women who gave birth in Western Australia (WA) between 2003 and 2018 were identified from whole-population midwives records. Linked records were used to identify women who had been dispensed OAT during pregnancy and those who had smoking during pregnancy. Temporal changes in smoking during pregnancy were examined for women on OAT (n = 1059) and women not on OAT (n = 397,175) using Joinpoint regression. In women treated with OAT during pregnancy, neonatal outcomes were compared between smoking and non-smoking women using generalised linear models. During the study period, 76.3% of women on OAT smoked during pregnancy compared with 12.0% of the general population. There was a decrease in the prevalence of smoking during pregnancy among women not on OAT (APC: - 5.7, 95%CI: - 6.3, - 5.2), but not in women on OAT (APC: 0.8, 95%CI: - 0.4, 2.1). For women receiving OAT, smoking was associated with an increased odds of low birth weight (OR: 1.57, 95%CI: 1.06, 2.32) and neonatal abstinence syndrome (OR: 1.34, 95%CI: 1.01, 1.78) compared with non-smoking. Despite reductions in the prevalence of smoking during pregnancy in the general population, similar reductions have not occurred in pregnant women on OAT. The high prevalence of smoking in pregnant women on OAT is contributing to poor neonatal outcomes.

Preterm Birth, Developmental Smoke/Nicotine Exposure, and Life-Long Pulmonary Sequelae

This review delineates the main pulmonary issues related to preterm birth, perinatal tobacco/nicotine exposure, and its effects on offspring, focusing on respiratory health and its possible transmission to subsequent generations. We review the extent of the problem of preterm birth, prematurity-related pulmonary effects, and the associated increased risk of asthma later in life. We then review the impact of developmental tobacco/nicotine exposure on offspring asthma and the significance of transgenerational pulmonary effects following perinatal tobacco/nicotine exposure, possibly via its effects on germline epigenetics.

Use of Swedish smokeless tobacco during pregnancy: A systematic review of pregnancy and early life health risk

BACKGROUND AND AIMS

Smokeless tobacco is a heterogeneous product group with diverse composition and prevalence globally. Tobacco use during pregnancy is concerning due to the risk of adverse pregnancy outcomes and effects on child health. Nicotine may mediate several of these effects. This systematic review measured health outcomes from Swedish smokeless tobacco (snus) use during pregnancy.

METHOD

Literature search was conducted by an information specialist in May 2022. We included human studies of snus use during pregnancy compared with no tobacco use, assessed risk of bias, conducted a meta-analysis and assessed confidence in effect-estimates using Grading of Recommendations, Assessment, Development and Evaluations (GRADE).

RESULTS

We included 18 cohort studies (42 to 1 006 398 participants). Snus use during pregnancy probably (moderate confidence in risk estimates) increase the risk of neonatal apnea, adjusted odds ratio 95% confidence interval [aOR (95% CI)] 1.96 (1.30 to 2.96). Snus use during pregnancy possibly (low confidence in risk estimates) increase the risk of stillbirths aOR 1.43 (1.02 to 1.99), extremely premature births aOR 1.69 (1.17 to 2.45), moderately premature birth aOR 1.26 (1.15 to 1.38), SGA aOR 1.26 (1.09 to 1.46), reduced birth weight mean difference of 72.47 g (110.58 g to 34.35 g reduction) and oral cleft malformations aOR 1.48 (1.00 to 2.21). It is uncertain (low confidence in risk estimates, CI crossing 1) whether snus use during pregnancy affects risk of preeclampsia aOR 1.11 (0.97 to 1.28), antenatal bleeding aOR 1.15 (0.92 to 1.44) and very premature birth aOR 1.26 (0.95 to 1.66). Risk of early neonatal mortality and altered heart rate variability is uncertain, very low confidence. Snus using mothers had increased prevalence of caesarean sections, low confidence.

CONCLUSIONS

This systematic review reveals that use of smokeless tobacco (snus) during pregnancy may adversely impact the developing child.

The impact of maternal smoking during pregnancy on hemostatic profile of neonates using thromboelastometry (ROTEM). A pilot observational study

INTRODUCTION

In adults, the negative effect of smoking on hemostasis has been well established. Contrarily, data regarding the hemostatic status of neonates exposed to tobacco during pregnancy are limited. This study aimed to investigate the influence of antenatal tobacco exposure on the hemostatic profile of neonates using Thromboelastometry (ROTEM).

METHODS

This observational study included 92 healthy full-term neonates born in the maternity department of our hospital over a 5-year period. The neonates were categorized in 2 groups: neonates born to mothers who reported smoking during the entire pregnancy and neonates born to non-smoking mothers. Neonates were matched 1:1 with regards to gestational age, delivery mode, and gender. ROTEM EXTEM assay was performed on the 2nd-3rd day of life and clotting time (CT); clot formation time (CFT); clot amplitude recorded at 10 and 30 min (A10, A30); a angle (a^o); maximum clot firmness (MCF, mm); lysis index at 30 and 60 min (LI30, LI60, %); maximum clot elasticity (MCE), were measured.

RESULTS

Neonates with antenatal exposure to tobacco had shorter CT (p < 0.001) and CFT (p = 0.035), higher A10 (p = 0.043), A30 (p = 0.028) and MCE (p = 0.028) compared to those not exposed to tobacco during pregnancy. The multivariable regression analysis adjusted for gestational age, gender, birth weight and delivery mode showed that maternal tobacco use during pregnancy is associated with an accelerated activation of coagulation in neonates expressed by shorter EXTEM CT values (coefficient: -8.68, 95%,CI: -13.51--3.85, p = 0.001) while no association was found with the remaining ROTEM parameters.

DISCUSSION

Smoking during pregnancy results in a hypercoagulable profile of neonates, expressed by shorter ROTEM CT. Antenatal exposure to tobacco appears to be an aggravating factor for the hemostatic status of neonates.

Integrative exposomic, transcriptomic, epigenomic analyses of human placental samples links understudied chemicals to preeclampsia

BACKGROUND

Environmental health research has recently undergone a dramatic shift, with ongoing technological advancements allowing for broader coverage of exposure and molecular biology signatures. Approaches to integrate such measures are still needed to increase understanding between systems-level exposure and biology.

OBJECTIVES

We address this gap by evaluating placental tissues to identify novel chemical-biological interactions associated with preeclampsia. This study tests the hypothesis that understudied chemicals are present in the human placenta and associated with preeclampsia-relevant disruptions, including overall case status (preeclamptic vs. normotensive patients) and underlying transcriptomic/epigenomic signatures.

METHODS

A non-targeted analysis based on high-resolution mass spectrometry was used to analyze placental tissues from a cohort of 35 patients with preeclampsia (n = 18) and normotensive (n = 17) pregnancies. Molecular feature data were prioritized for confirmation based on association with preeclampsia case status and confidence of chemical identification. All molecular features were evaluated for relationships to mRNA, microRNA, and CpG methylation (i.e., multi-omic) signature alterations involved in preeclampsia.

RESULTS

A total of 183 molecular features were identified with significantly differentiated abundance in placental extracts of preeclamptic patients; these features clustered into distinct chemical groupings using unsupervised methods. Of these features, 53 were identified (mapping to 40 distinct chemicals) using chemical standards, fragmentation spectra, and chemical metadata. In general, human metabolites had the largest feature intensities and strongest associations with preeclampsia-relevant multi-omic changes. Exogenous drugs were second most abundant and had fewer associations with multi-omic changes. Other exogenous chemicals (non-drugs) were least abundant and had the fewest associations with multi-omic changes.

CONCLUSIONS

These global data trends suggest that human metabolites are heavily intertwined with biological processes involved in preeclampsia etiology, while exogenous chemicals may still impact select transcriptomic/epigenomic processes. This study serves as a demonstration of merging systems exposures with systems biology to better understand chemical-disease relationships.

Prenatal smoke (Nicotine) exposure and offspring's metabolic disease susceptibility in adulthood

Exposure to smoking (nicotine) during pregnancy not only directly affects fetal development, but also increases susceptibility to metabolic diseases in adulthood, but the mechanism of action remains unclear. Here, we review epidemiological and laboratory studies linking these relationships. In addition to the direct effect of nicotine on the fetus, intrauterine neuroendocrine-metabolic programming mediated by maternal glucocorticoid overexposure also plays an important role, involving glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis, hypothalamic-pituitary-adrenal (HPA) axis, renin-angiotensin system (RAS) and other endocrine systems. Epigenetics is involved in intrauterine neuroendocrine-metabolic programming, metabolic disease susceptibility and multigenerational inheritance. There are "two programming" and "two strikes" mechanisms for the occurrence of fetal-originated metabolic diseases in adulthood. These innovative research summaries and academic viewpoints provide experimental and theoretical basis for systematically elucidating the occurrence and development of fetal-originated metabolic diseases.

Understanding the Placental Biology of Tobacco Smoke, Nicotine, and Marijuana (THC) Exposures During Pregnancy

Widespread public health campaigns have reduces the prevalence of tobacco and nicotine exposures during pregnancy in the United States. However, tobacco and nicotine exposures during pregnancy persist as a common modifiable perinatal risk exposure. Furthermore, declines in tobacco use have been accompanied by parallel rises in both the prevalence and incidence of marijuana use in pregnancy. This is worrisome, as the macromolecules which comprise tobacco and marijuana smoke affect placental function. In this chapter we summarize the decades of evidence contributing to our understanding of the placental molecular pathophysiology accompanying these chemical exposures, thereby rendering risk of adverse perinatal outcomes.

Polycyclic aromatic hydrocarbons (PAHs) may explain the paradoxical effects of cigarette use on preeclampsia (PE)

Tobacco smoking and use of snus (smokeless tobacco) are associated with adverse effects on pregnancy and neonatal outcomes. Nicotine is considered a key toxicant involved in effects caused by both smoking and snus, while pyrolysis products including polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke represents the constituents most unequally divided between these two groups of tobacco products. The aim of this review was: i) to compare the impact, in terms of relative effect estimates, of cigarette smoking and use of Swedish snus on pregnancy outcomes using similar non-tobacco user controls, and ii) to examine whether exposure to PAHs from smoking could explain possible differences in impact on pregnancy outcomes. We systematically searched MEDLINE, Embase, PsycInfo, Web of Science and the Cochrane Database of Systematic Reviews up to October 2021 and identified studies reporting risks for adverse pregnancy and neonatal outcomes associated with snus use and with smoking relative to pregnant women with no use of tobacco. Both snus use and smoking were associated with increased risk of stillbirth, preterm birth, and oral cleft malformation, with comparable point estimates. These effects were likely due to comparable nicotine exposure. We also found striking differences. While both smoking and snus increased the risk of having small for gestational age (SGA) infants, risk from maternal smoking was markedly higher as was the reduction in birthweight. In contrast, the risk of preeclampsia (PE) was markedly lower in smokers than in controls, while snus use was associated with a slightly increased risk. We suggest that PAHs acting via AhR may explain the stronger effects of tobacco smoking on SGA and also to the apparent protective effect of cigarette smoking on PE. Possible mechanisms involved include: i) disrupted endocrine control of fetal development as well as placental development and function, and ii) stress adaption and immune suppression in placenta and mother.

Dose-response relationships between maternal urinary cotinine and placental weight and ratio of placental weight to birth weight: The Japan Environment and Children's Study

INTRODUCTION

Studies on the relationship between maternal self-reported smoking status and placental weight report inconsistent results. This study examined the relationships between maternal urinary cotinine concentration and placental weight and the ratio of placental weight to birth weight (PW/BW ratio). The study also examined the relationship between maternal smoking status, as determined by cotinine concentration, with placental weight and with PW/BW ratio, stratified by sex of offspring.

METHODS

Our analysis used information of 91,049 mother-child pairs enrolled in the Japan Environment and Children's Study. Maternal urinary cotinine concentration was quantified (during the second or third trimester) with high-performance liquid chromatography-tandem mass spectrometry. Using restricted cubic splines, placental weight and PW/BW ratio were plotted against natural log-transformed cotinine concentration. Taking cotinine levels of <0.17 ng/mL, 0.17 to <21.5 ng/mL (natural log-transformed values, -1.77 to 3.07), and ≥21.5 ng/mL as indicative of non-smokers, passive smokers, and active smokers, respectively, the relationships between maternal smoking status and placental weight and PW/BW ratio were examined, adjusting for confounders.

RESULTS

Placental weight and PW/BW ratio increased with increasing cotinine concentration. After cotinine reached a certain concentration, the placental weight decreased in male offspring whereas it plateaued in female offspring. Compared with not smoking, active smoking during pregnancy significantly increased placental weight and PW/BW ratio.

CONCLUSION

Placental weight responded as an inverted U-shape whereas the PW/BW ratio followed a J-shape with increasing maternal urinary cotinine concentration measured during pregnancy, suggesting exposure to tobacco smoke induces a disproportionate reduction in fetal growth. The effect of tobacco smoke on placental growth varied by sex of offspring.

Developmental Effects of Electronic Cigarette Use

Electronic cigarettes have gained widespread acceptance among adolescents and young adults. As a result of this popularity, there are concerns regarding the potential harm of primary, secondhand and thirdhand electronic cigarette exposures on fetal and postnatal development. In vitro studies have shown that constituents in electronic cigarette liquids, including nicotine, flavorings, and carrier agents can alter cellular processes and growth. Additionally, aerosolized electronic cigarette emissions have been shown to disrupt organ development and immune responses in preclinical studies. In clinical studies, an association between electronic cigarette use and frequent respiratory symptoms, greater asthma severity and impaired mucociliary clearance has been demonstrated with adolescent and young adult users of electronic cigarettes having twice the frequency of cough, mucus production, or bronchitis compared to nonusers. Along with the popularity of electronic cigarette use, secondhand electronic cigarette exposure has increased substantially; with almost one-fourth of middle and high school children reporting exposure to secondhand vapors. The health consequences of secondhand electronic cigarette exposure on children and other vulnerable populations are poorly understood but detectable levels of cotinine have been measured in nonusers. Pregnant women and their offspring are another vulnerable group at increased risk for health consequences from electronic cigarette exposure. Nicotine crosses the placenta and can disrupt brain and lung development in preclinical studies. This article will focus on the physiological and health effects associated with primary or secondhand exposure to electronic cigarettes. It is expected that with ongoing availability of electronic cigarettes as well as the accumulation of additional follow-up time for long-term outcomes, the risks associated with exposure will become better clarified. © 2022 American Physiological Society. Compr Physiol 12:3337-3346, 2022.

Pregnancy exposure to phthalates and DNA methylation in male placenta - An epigenome-wide association study

BACKGROUND

Exposure to phthalates during pregnancy may alter DNA methylation in the placenta, a crucial organ for the growth and development of the fetus.

OBJECTIVES

We studied associations between urinary concentrations of phthalate biomarkers during pregnancy and placental DNA methylation.

METHODS

We measured concentrations of 11 phthalate metabolites in maternal spot urine samples collected between 22 and 29 gestational weeks in 202 pregnant women. We analyzed DNA methylation levels in placental tissue (fetal side) collected at delivery. We first investigated changes in global DNA methylation of repetitive elements Alu and LINE-1. We then performed an adjusted epigenome-wide association study using IlluminaHM450 BeadChips and identified differentially methylated regions (DMRs) associated with phthalate exposure.

RESULTS

Monobenzyl phthalate concentration was inversely associated with placental methylation of Alu repeats. Moreover, all phthalate biomarkers except for monocarboxy-iso-octyl phthalate and mono(2-ethyl-5-hydroxyhexyl) phthalate were associated with at least one DMR. All but three DMRs showed increased DNA methylation with increased phthalate exposure. The largest identified DMR (22 CpGs) was positively associated with monocarboxy-iso-nonyl phthalate and encompassed heat shock proteins (HSPA1A, HSPA1L). The remaining DMRs encompassed transcription factors and nucleotide exchange factors, among other genes.

CONCLUSIONS

This is the first description of genome-wide modifications of placental DNA methylation in association with pregnancy exposure to phthalates. Our results suggest epigenetic mechanisms by which exposure to these compounds could affect fetal development. Of interest, four identified DMRs had been previously associated with maternal smoking, which may suggest particular sensitivity of these genomic regions to the effect of environmental contaminants.

The effect of ethanol and nicotine on ER stress in human placental villous explants

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Nicotine increased the GRP78/BiP protein in first trimester and term placental villous explants.

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Nicotine can cause endoplasmic reticulum stress in human placenta.

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Placental villous explants can be isolated from first trimester and term placenta to compare responses to toxic compounds.

Pregnant mothers continue smoking and drinking during pregnancy. To clarify the mechanisms of nicotine and ethanol toxicity during development, we have examined their effects on endoplasmic reticulum (ER) stress in human first trimester and term placental explants. First trimester and term human placental explants were treated with ethanol (2 ‰) or nicotine (15 µM), or their combination. The ER stress markers glucose regulated protein 78 (GRP78/BiP) and inositol requiring enzyme 1 α (IRE1α) were analyzed by immunoblotting. A statistically significant increase (p < 0.05) of GRP78/BiP by nicotine was noted in first trimester placental explants at 48 h, and in term placental explants at 24 h. Ethanol did not change protein expression of GRP78/BiP in either first trimester or term placental explants. IRE1α increased, although not statistically significantly, by all treatments in both first trimester and term placental explants. Thus, regardless of the known structural and functional differences in early and late placenta, both responded very similarly to the toxic compounds studied. These data support our earlier results in BeWo cells (Repo et al., 2014) implicating that nicotine induces ER stress in human placenta and may interfere with placental functions potentially disrupting fetal growth and development.

Urinary cotinine assessment of maternal smoking and environmental tobacco smoke exposure status and its associations with perinatal outcomes: a cross-sectional birth study

Tobacco consumption and environmental tobacco smoke (ETS) exposure remains an important public health concern. Pregnant women require particular attention as active and passive smoking during pregnancy are associated with multiple adverse perinatal outcomes. This study aimed to biochemically validate self-reported smoking and ETS exposure status among pregnant women, to more precisely ascertain its association with adverse perinatal outcomes. Data refers to 595 pregnant women who sought prenatal care in a public hospital in Porto, Portugal. A standard questionnaire on smoking and ETS-related variables was completed. Urinary cotinine (UC) concentrations were assessed by solid-phase competitive ELISA, in maternal urine samples collected on the day of delivery. The results showed that the optimal UC cut-off value to distinguish smokers from non-smokers and within non-smokers those who were exposed to ETS from those non-exposed in the third trimester of pregnancy was 74.1 ng/mL (sensitivity and specificity of 96.7% and 98.0%, respectively) and 1.6 ng/mL (sensitivity of 66.2% and specificity of 75.7%, respectively). The agreement between maternal self-reported and UC-based smoking status was very good (κ=0.919, p<0.001), but much lower for ETS exposure (κ=0.386, p<0.001). Maternal active smoking in the third trimester of pregnancy was associated with a significant decrease in birth weight, length and head circumference of 157.66 g (95% CI: -245.81, -69.52; p<0.001), 0.78 cm (95% CI: -1.22, -0.34; p=0.001) and 0.39 cm (95% CI: -0.70, -0.07; p=0.016), respectively. Maternal ETS exposure in the third trimester of pregnancy was associated with a non-significant increase in birth weight of 38.37 g (95% CI: -28.91, 105.64; p=0.263). Furthermore, maternal smoking cessation was associated with the increase of approximately 172 g in birth weight (95% CI: 50.00, 293.19). As such, there is an urgent need for increased public health awareness campaigns to encourage smoking cessation during pregnancy, in order to improve perinatal outcomes.

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.

Caffeine exposure during pregnancy: Is it safe?

Numerous studies have examined the association between maternal caffeine consumption and infant and childhood health outcomes and the results have been inconsistent. The study of maternal caffeine intake and infant and childhood health outcomes is prone to methodologic challenges. In this review, we examine the existing evidence juxtaposed with the epidemiologic design challenges that color the interpretation of the study results presented. In light of methodologic/interpretation challenges, it seems reasonable to infer that exposure to low levels of caffeine is probably not associated with substantial infant and childhood adversities. However, more research is needed using well designed studies that address methodologic challenges.

Association between active tobacco use during pregnancy and infant respiratory health: a systematic review and meta-analysis

OBJECTIVE

To evaluate what is known about active tobacco use during pregnancy and the association with infant respiratory health.

DESIGN

Systematic review and meta-analysis using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

DATA SOURCES

MEDLINE, EMBASE, Cochrane, CINAHL, and Maternity and Infant Care were searched thoroughly until June 2020.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

We included case-control and cohort studies estimating the association between active tobacco use during pregnancy and infant respiratory health (wheezing and apnoea) and lung function parameters in the first 12 months of life.

DATA EXTRACTION AND SYNTHESIS

Extraction and risk of bias assessment were conducted by two independent reviewers. The odds ratio, relative risk and mean differences were pooled with a 95% CI using the generic inverse variance method. Heterogeneity was assessed and expressed by percentage using I2.

RESULTS

We identified 4423 abstracts, and 21 publications met the eligibility criteria. Pooled OR showed an increase in wheezing episodes in infants born to mothers who were active tobacco users during pregnancy (OR 1.50, 95% CI 1.27 to 1.77, p<0.01). Mixed results were found on lung function parameters, and a meta-analysis including two studies with comparable methodology showed a trend towards reduced maximum flow rate at functional residual capacity of -34.59 mL/s (95% CI -72.81 to 3.63, p=0.08) in 1-month-old infants born to women who smoked during pregnancy. A higher risk of apnoea was described for infants born to mothers who used smokeless tobacco during pregnancy, while the results in infants born to women who actively smoked tobacco during pregnancy were non-conclusive.

CONCLUSION

Infants born to mothers who actively smoked during pregnancy are at higher odds of having wheeze and may have lower lung function. Smokeless tobacco use in pregnancy may increase the risk of apnoea in infancy.

PROSPERO REGISTRATION NUMBER

CRD42018083936.

Cigarette smoke induced neural tube defects by down-regulating noggin expression

BACKGROUND

Maternal smoking or passive smoking during gestation increases the risk of congenital birth defects, including neural tube defects (NTDs). Cigarette smoke is a recognized teratogen that causes NTDs, although the mechanisms are not well understood.

METHODS

An established model of passive smoking in pregnant golden hamsters was used to observe the effect of cigarette smoke on neural tube development using scanning electron microscopy. Level of noggin expression in placenta and neural tube was evaluated by immunohistochemistry.

RESULTS

Our results indicated that cigarette smoke can cause the neural tube closure of the golden hamster embryo to be delayed or not closed. In normal placental tissues noggin protein and RNA levels were highly expressed, and the expression level in the term placenta was lower than in that of the first trimester or second trimester through analyzing the Human Protein Atlas and the Gene Expression Omnibus (GEO) databases. Cigarette smoke can down-regulate noggin expression in the placenta and promote cell apoptosis. We observed that noggin expression was reduced and BMP2 expression was increased by cigarette smoke.

CONCLUSIONS

Cigarette smoke may cause cell apoptosis and accelerate placenta maturation. Meanwhile, cigarette smoke may inhibit the development of the embryo, and lead to the formation of NTDs via downregulating the expression of noggin and dis-inhibition of BMP2.