Alterations in DNA methylation and airway hyperreactivity in response to in utero exposure to environmental tobacco smoke

Abstract

Growing evidence indicates that prenatal exposure to maternal smoking is a risk factor for the development of asthma in children. However, the effects of prenatal environmental tobacco smoke (ETS) exposure on the genome and lung immune cells are unclear. This study aims to determine whether in utero ETS exposure alters DNA methylation patterns and increases airway hyperreactivity (AHR) and inflammation. Pregnant C57BL/6 mice were exposed daily to a concentration of 1.0?mg/m³ ETS. AHR was determined in the 6-week-old offspring by measurement of airway resistance. Global and gene promoter methylation levels in lung DNA from offspring were analyzed by luminometric methylation and pyrosequencing assays, respectively. Offspring exposed to ETS showed a marked increase in the number of alveolar macrophages in the bronchoalveolar lavage fluid and level of IL-13 in the airways compared with offspring of filtered-air exposed dams (controls). ETS exposure significantly augmented AHR compared with controls. In the methylation analysis, ETS-exposed offspring had a significantly lower level of global DNA methylation than the controls. We observed a significant increase in IFN-γ, and significant decrease in IL-13 methylation levels in the ETS group compared with controls. Collectively, these data suggest that in utero ETS exposure increases the risk of pulmonary inflammation and AHR through altered DNA methylation, but additional studies are needed to fully determine the causal link between changes in methylation and cytokines levels, as well as AHR.     

Prenatal exposure to environmental tobacco smoke alters gene expression in the developing murine hippocampus

BackgroundLittle is known about the effects of passive smoke exposures on the developing brain.ObjectiveThe purpose of the current study was to identify changes in gene expression in the murine hippocampus as a consequence of in utero exposure to sidestream cigarette smoke (an experimental equivalent of environmental tobacco smoke (ETS)) at exposure levels that do not result in fetal growth inhibition.MethodsA whole body smoke inhalation exposure system was utilized to deliver ETS to pregnant C57BL/6J mice for 6 h/day from gestational days 6–17 (gd 6–17) [for microarray] or gd 6–18.5 [for fetal phenotyping].ResultsThere were no significant effects of ETS exposure on fetal phenotype. However, 61 “expressed” genes in the gd 18.5 fetal hippocampus were differentially regulated (up- or down-regulated by 1.5-fold or greater) by maternal exposure to ETS. Of these 61 genes, 25 genes were upregulated while 36 genes were down-regulated. A systems biology approach, including computational methodologies, identified cellular response pathways, and biological themes, underlying altered fetal programming of the embryonic hippocampus by in utero cigarette smoke exposure.ConclusionsResults from the present study suggest that even in the absence of effects on fetal growth, prenatal smoke exposure can alter gene expression during the “early” period of hippocampal growth and may result in abnormal hippocampal morphology, connectivity, and function.     

Perinatal exposure to environmental tobacco smoke is associated with changes in DNA methylation that precede the adult onset of lung disease in a mouse model

Prenatal and early-life environmental tobacco smoke (ETS) exposure can induce epigenetic alterations associated with inflammation and respiratory disease. The objective of this study was to address the long-term epigenetic consequences of perinatal ETS exposure on latent respiratory disease risk, which are still largely unknown. C57BL/6 mice were exposed to prenatal and early-life ETS; offspring lung pathology, global DNA, and gene-specific methylation were measured at two adult ages. Significant alterations in global DNA methylation and promoter methylation of IFN-γ and Thy-1 were found in ETS-exposed offspring at 10–12 and 20?weeks of age. These sustained epigenetic alterations preceded the onset of significant pulmonary pathologies observed at 20?weeks of age. This study suggests that perinatal ETS exposure induces persistent epigenetic alterations in global DNA, as well as IFN-γ and Thy-1 promoter methylation that precede the adult onset of fibrotic lung pathology. These epigenetic findings could represent potential biomarkers of latent respiratory disease risk.     

Effect of prenatal waterpipe tobacco smoke on airway inflammation in murine model of asthma of adult offspring mice

Objective: Worldwide popularity of waterpipe tobacco smoking has increased, including in pregnant women. This study investigates the effect of prenatal waterpipe tobacco smoke (WTS) exposure on airway inflammation in a murine model of asthma of adult offspring mice.

Materials and methods: Pregnant BALB/c mice were exposed to fresh air or WTS, using a whole-body exposure system that mimics human use during WTS. Adult male offspring mice were divided into; (1) control (prenatal fresh air, postnatal ovalbumin sensitization and saline challenge), (2) postnatal Ova S/C (prenatal fresh air, postnatal ovalbumin sensitization and challenge (Ova S/C)), (3) prenatal WTS (prenatal WTS, postnatal ovalbumin sensitization and saline challenge) and (4) prenatal WTS?+?postnatal Ova S/C. Cells from the bronchoalveolar lavage fluid, cytokines, and oxidative stress markers (superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and thiobarbituric acid reactive substances (TBARS)) from lung homogenates were evaluated.

Results: Prenatal WTS increased recruitment of cells in lungs and levels of SOD and catalase when compared to unexposed offspring’s. The levels of cytokines, GPx and TBARS were not affected by prenatal WTS. Prenatal WTS exposure and postnatal Ova S/C increased airway inflammation and activity of SOD compared to control and Ova S/C mice and reduced IL-18 levels compared to Ova S/C mice.

Discussion and conclusions: Prenatal exposure to WTS induced airway inflammation, further enhanced by a murine model of asthma in adult offspring. Prenatal exposure to WTS adversely affects the lung function of the offspring and careful strategies for increasing public awareness regarding the harmful effects of WTS during pregnancy is important.     

Maternal exposure to Δ9-tetrahydrocannabinol impairs female offspring glucose homeostasis and endocrine pancreatic development in the rat

Recent reports indicate that 7% of pregnant mothers in North America use cannabis. This is concerning given that in utero exposure to Δ9-tetrahydrocannabinol (Δ9-THC), the main psychoactive component in cannabis, causes fetal growth restriction and may alter replication and survival of pancreatic β-cells in the offspring. Accordingly, we hypothesized that maternal exposure to Δ9-THC during pregnancy would impair postnatal glucometabolic health of offspring. To test this hypothesis, pregnant Wistar rats were treated with daily intraperitoneal injections of either 3 mg/kg Δ9-THC or vehicle from gestational day 6 to birth. Offspring were subsequently challenged with glucose and insulin at 5 months of age to assess glucose tolerance and peripheral muscle insulin sensitivity. Female offspring exposed to Δ9-THC in utero were glucose intolerant, associated with blunted insulin response in muscle and increased serum insulin concentration 15 min after glucose challenge. Additionally, pancreata from male and female offspring were harvested at postnatal day 21 and 5 months of age for assessment of endocrine pancreas morphometry by immunostaining. This analysis revealed that gestational exposure to Δ9-THC reduced the density of islets in female, but not male, offspring at postnatal day 21 and 5 months, culminating in reduced β-cell mass at 5 months. These results demonstrate that fetal exposure to Δ9-THC causes female-specific impairments in glucose homeostasis, raising concern regarding the metabolic health of offspring, particularly females, exposed to cannabis in utero.     

Exposure to environmental tobacco smoke during pregnancy in rats yields less effect on indices of brain cell number and size than does postnatal exposure

While there is evidence that human perinatal exposure to environmental tobacco smoke (ETS) can result in an increased risk of respiratory disorders and sudden infant death syndrome, evidence linking ETS exposure to neurodevelopmental handicaps is suggestive but less compelling. We previously noted that postnatal ETS exposure, rather than prenatal exposure, resulted in reduced concentration of hindbrain DNA and increased protein/DNA ratio when rat brain tissue was studied at 9 weeks postnatal age. We have now evaluated the effects of ETS exposure during pregnancy on brain development by assaying brain tissue at term. ETS exposure had no detectable effects on regional brain concentrations of DNA, protein and cholesterol or on protein/DNA and cholesterol/DNA ratios. While ETS exposure during pregnancy also had no detectable effects on the weights of the individual fetuses or on the weights of various organs, certain regions of the fetal skeleton demonstrated accelerated ossification. The findings of this study are contrasted to the developmental effects of both nicotine and ETS in Rhesus macaques. Additional studies designed specifically to assess the risk of prenatal ETS exposure on brain development in non-human primates and other precocial species are warranted.     

In utero and postnatal exposure to arsenic alters pulmonary structure and function

In addition to cancer endpoints, arsenic exposures can also lead to non-cancerous chronic lung disease. Exposures during sensitive developmental time points can contribute to the adult disease. Using a mouse model, in utero and early postnatal exposures to arsenic (100 ppb or less in drinking water) were found to alter airway reactivity to methacholine challenge in 28 day old pups. Removal of mice from arsenic exposure 28 days after birth did not reverse the alterations in sensitivity to methacholine. In addition, adult mice exposed to similar levels of arsenic in drinking water did not show alterations. Therefore, alterations in airway reactivity were irreversible and specific to exposures during lung development. These functional changes correlated with protein and gene expression changes as well as morphological structural changes around the airways. Arsenic increased the whole lung levels of smooth muscle actin in a dose dependent manner. The level of smooth muscle mass around airways was increased with arsenic exposure, especially around airways smaller than 100 μm in diameter. This increase in smooth muscle was associated with alterations in extracellular matrix (collagen, elastin) expression. This model system demonstrates that in utero and postnatal exposure to environmentally relevant levels of arsenic can irreversibly alter pulmonary structure and function in the adults.     

Sex differences in effects on sexual development in rat offspring after pre- and postnatal exposure to triphenyltin chloride

Consumers are exposed to organotin compounds (OTCs) via contaminated fish and seafood due to the accumulation of these compounds in marine organisms. Certain OTCs are immunotoxic and may also have endocrine disrupting properties resulting in adverse effects on the reproductive tract in mollusks and mammals. Since effects of in utero exposure to endocrine disrupting chemicals on the reproductive system are dependent on the critical window of exposure during its development, we conducted a comprehensive study with the aim to identify the most sensitive window of exposure to TPTCl and to investigate the effects of pre- and postnatal treatment on sexual development in rats. Male and female offspring rats were exposed to 2 or 6 mg TPTCl/kg b.w. and day either in utero and during lactation (gestation day 6 until weaning on PND 21) or from gestation day 6 until termination. As previously reported, offspring in the 6 mg TPTCl dose group exhibited high perinatal mortality and therefore no further evaluation was carried out at this dose level (Grote, K., Hobler, C, Andrade, A.J.M., Wichert Grande, S., Gericke, C., Talsness, C.E., Appel, K.E., Chahoud, I., 2007. Effects of in utero and lactational exposure to triphenyltin chloride on pregnancy outcome and postnatal development in rat offspring. Toxicology 238, 177–185). In the present paper, results on postnatal development obtained from surviving offspring of dams exposed to 2 mg TPTCl/kg b.w. are reported. Male offspring were sacrificed on PND 64 or 65 and female offspring at first estrus after PND 58. A clear sex difference in response to treatment was observed. Male postnatal development was severely affected with decreases in body weight gain, reproductive organ weights and testosterone concentration as well as a significant delay in the age at preputial separation. In contrast, females exhibited a precocious completion of vaginal opening while all other endpoints were unaffected. Most of these effects were already present in animals that were only exposed until weaning indicating that these effects may be irreversible and continued treatment until termination had contributed less than expected to the severity of the observed effects. The results of the present study suggest that the sensitive window for the evaluated endpoints seems to be the period of prenatal development and that male offspring rats were more susceptible to treatment.     

The role of maternal nutrition,metabolic function and the placenta in developmental programming of renal dysfunction

The intrauterine environment is critical for the development of the foetus. Barker and colleagues were the first to identify that adverse perturbations during foetal development are associated with an increased risk of developing diseases in adulthood, including cardiorenal disease. Specifically for the kidney, perturbations in utero can lead to nephron deficits and renal dysfunction by a number of mechanisms. Altered programming of nephron number is associated with an increased risk of developing kidney disease via glomerular hypertrophy and reduced vasodilative capacity of the renal blood vessels; both of which would contribute to hypertension in adulthood, with males being more susceptible to disease outcomes. Additionally, alterations in the renin‐angiotensin system (RAS) such as an upregulation or downregulation of specific receptors, depending on the nature of the insult, have also been implicated in the development of renal dysfunction. Sex‐specific differences in the expression of the RAS during late gestation and in the early postnatal environment have also been identified. Extensive research has demonstrated that both uteroplacental insufficiency and maternal malnutrition alter renal development in utero. Equally, exposure to maternal diabetes and maternal obesity during development are also associated with an increased risk of developing renal disease, however, the mechanism behind this association is poorly understood. Therefore, identifying the link between an adverse intrauterine environment and the programmed kidney disease risk in adulthood may facilitate the development of strategies to alleviate the epidemics of cardiorenal disease worldwide, in addition to understanding why males are more susceptible to adult‐onset cardiovascular diseases.     

Youths' exposure to environmental tobacco smoke (ETS): associations with health beliefs and social pressure

Youths' exposure to environmental tobacco smoke (ETS) is a significant public health problem in the United States. This study examined the associations between health beliefs, social pressure, and exposure to ETS among high school youth. Data were collected in 65 schools in 18 California counties during the 1996-1997 school year as part of the Independent Evaluation of the California Tobacco Control, Prevention, and Education Program. The total sample (N = 6902) represents 10th grade California youth attending public schools. The multiple group analysis approach of structural equation modeling (SEM) was employed to test the associations of five constructs of the health belief model (HBM) and one construct of perceived social pressure with ETS exposure among nonsmokers and smokers. Results demonstrated that high perceived susceptibility to disease was significantly associated with lower levels of ETS exposure for both nonsmokers (beta = -0.11, P < .01) and smokers (beta = -0.20, P < .01). High social pressure to smoke was significantly associated with higher exposure to ETS for both nonsmokers (beta = 0.30, P < .01) and smokers (beta = 0.41, P < .01). Perceived barriers predicted lower exposure to ETS for nonsmokers (beta = -0.09, P < .01) but higher exposure for smokers (beta = 0.11, P < .01). Cues to action and self-efficacy were not significantly associated with ETS exposure among nonsmokers or smokers. These findings underscore the need to increase the awareness of harms associated with second hand smoke and alter social pressure, to minimize exposure to ETS.     

Fetal and offspring arrhythmia following exposure to nicotine during pregnancy

Although recent studies have demonstrated prenatal nicotine can increase cardiovascular risk in the offspring, it is unknown whether exposure to nicotine during pregnancy also may be a risk for development of arrhythmia in the offspring. In addition, in previous studies of fetal arrhythmia affected by smoking, only two patterns, bradycardia and tachycardia, were observed. The present study examined acute effects of maternal nicotine on the fetal arrhythmia in utero, and chronic influence on offspring arrhythmia at adult stage following prenatal exposure to nicotine. Nicotine was administered to pregnant ewes and rats. In the fetal sheep, intravenous nicotine not only induced changes of fetal heart rate, but also caused cardiac cycle irregularity, single and multiple dropped cardiac cycles. Although maternal nicotine had no influence on fetal blood pH, lactic acid, hemocrit, Na⁺, K⁺ levels and plasma osmolality, fetal blood PO₂ levels were significantly decreased following maternal nicotine in ewes. In offspring rats at 4–5 months after birth, prenatal exposure to nicotine significantly increased heart rate and premature ventricular contraction in restraint stress. In addition, arrhythmias induced by injection of nicotine were higher in the offspring prenatal exposure to nicotine in utero. The results provide new evidence that exposure to nicotine in pregnancy can cause fetal arrhythmia in various patterns besides tachycardia and bradycardia, the possible mechanisms for nicotine‐induced fetal arrhythmia included in utero hypoxia. Importantly, following exposure to nicotine significantly increased risk of arrhythmia in the adult offspring. The finding offers new insight for development of cardiac rhythm problems in fetal origins. Copyright © 2009 John Wiley & Sons, Ltd.     

In utero exposure to arsenite contributes to metabolic and reproductive dysfunction in male offspring of CD-1 mice

In utero exposure to arsenite (iAs) is known to increase disease risks later in life. We investigated the effect of in utero exposure to iAs in the drinking water on metabolic and reproductive parameters in male mouse offspring at postnatal and adult stages. Pregnant CD-1 mice were exposed to iAs (as sodium arsenite) in the drinking water at 0 (control), 10 ppb (EPA standard for drinking water), and 42.5 ppm (tumor-inducing dose in mice) from embryonic day (E) 10–18. At birth, pups were fostered to unexposed females. Male offspring exposed to 10 ppb in utero exhibited increase in body weight at birth when compared to controls. Male offspring exposed to 42.5 ppm in utero showed a tendency for increased body weight and a smaller anogenital distance. The body weight in iAs-exposed pups continued to increase significantly compared to control at 3 weeks and 11 weeks of age. At 5 months of age, iAs-exposed males exhibited greater body fat content and glucose intolerance. Male offspring exposed to 10 ppb in utero had higher circulating levels of leptin compared to control. In addition, males exposed to 42.5 ppm in utero exhibited decreased total number of pups born compared to controls and lower average number of litters sired over a six-month period. These results indicate that in utero exposure to iAs at either human relevant concentration or tumor-inducing concentration is a potential cause of developmental origin of metabolic and reproductive dysfunction in adult male mice.     

The relationship among IL-13, GSTP1, and CYP1A1 polymorphisms and environmental tobacco smoke in a population of children with asthma in Northern Mexico

Exposure to environmental tobacco smoke (ETS) during early childhood increases the risk of developing asthma. The intention of this study was to genotype a population of children from Coahuila state in Northern Mexico and to determine whether polymorphisms of the CYP1A1, GSTP1, and IL13 genes are associated with exposure to ETS and subsequently a higher risk for asthma. IL13 plays an important role in the development of allergic response, particularly those related with airway inflammation. CYP1A1 and GSTP1 are xenobiotic-metabolizing enzymes induced by repeated exposure to toxicants. Polymorphisms of these genes have been related with ETS exposure and increased risk for asthma. To assess the effect of IL13 (-1112 C>T and Arg110Gln), GSTP1 (Ile105Val), and CYP1A1 (Ile462Val) on asthma risk and ETS exposure, we recruited 201 unrelated children and classified them into four groups: (1) control without ETS exposure; (2) control with ETS exposure; (3) with asthma and with ETS exposure and (4) with asthma and without ETS exposure. No association among ETS exposure, asthma, and the studied polymorphisms was denoted by multivariate analysis of this population.     

Exposure of Adult Mice to Environmental Tobacco Smoke Fails to Enhance the Immune Response to Inhaled Antigen

Epidemiologic evidence supports a role for environmental tobacco smoke (ETS) in the occurrence and severity of allergies/asthma. However, neither the precise combination of ETS and allergen exposure nor the mechanism (or mechanisms) by which these factors interact and contribute to asthma induction is known. Animal model studies have failed to establish a convincing relationship between ETS exposure and asthma induction, perhaps because of methodological inadequacies. Here, we tested the hypothesis that ETS inhalation would provoke an asthmatic response by overcoming normal airway tolerance to inhaled antigens. Our protocol combined daily ETS exposure with nose-only sensitization to ovalbumin. Three strains of mice were tested, each with a different level of susceptibility to airway hypersensitivity. Immunological responses were assessed by immunoglobulin production. Airway inflammation was assessed by bronchoalveolar lavage differentials and lung histopathology. Airway hyperresponsiveness was determined by methacholine challenge. The mice produced ovalbumin-specific antibodies following ovalbumin exposure in a strain-dependent manner. Only the A/J mice produced detectable levels of ovalbumin-specific immunoglobulin (Ig) E. Both A/J and BALB/c mice produced ovalbumin-specific IgG1 antibodies. The C57Bl/6 mice did not produce detectable levels of antibodies. The A/J mice also exhibited airway inflammation following ovalbumin exposure. Neither the C57Bl/6 nor the BALB/c mice exhibited signs of airway inflammation. Exposure to ETS failed to enhance ovalbumin-specific antibody production, airway inflammation, or hyperresponsiveness. Together these results indicate that ETS exposure accompanied by nose-only allergen sensitization fails to overcome aerosol tolerance in adult mice.     

Influence of prenatal waterpipe tobacco smoke exposure on renal biomarkers in adult offspring rats

Background: Waterpipe tobacco smoke (WTS) is a popular form of tobacco consumption. Prenatal exposure to cigarette smoke altered kidney function and oxidative stress balance in offspring. However, the effect of prenatal WTS exposure on kidney function parameters, blood pressure and oxidative stress in adult offspring rats were unknown.

Methods: Pregnant Wister rats were exposed to either WTS for 2?hours per day utilizing a whole body exposure system or fresh air from day 0 of gestation to day 21. Systolic blood pressure, histological analysis of kidney, kidney function biomarkers [angiotensin converting enzyme (ACE), angiotensin I, angiotensin II, urea nitrogen, creatinine and albumin], and oxidative stress biomarkers (glutathione peroxidase (GPx), catalase and thiobarbituric acid reactive substances (TBARS)) were measured in male- and female- offspring rats on week 20.

Results: Prenatal exposure to WTS significantly decreased kidneys’ weight and glomeruli area (p?<?0.05) in offspring rats. Prenatal WTS exposure increased blood pressure in offspring rats (p?<?0.05). Further, prenatal WTS exposure increased the level of urine albumin (p?<?0.05) in offspring rats. Prenatal WTS exposure increased the level of ACE and angiotensin I (p?<?0.05) in female offspring rats. Prenatal WTS exposure increased the level of TBARS (p?<?0.05) in female offspring rats and there was a trend of decreased activity of GPx in male and female offspring rats, but was not significant (p?>?0.05).

Conclusions: Maternal WTS exposure during pregnancy resulted in detrimental effects on the renal system as indicated by altered kidney parameters and function, increased systolic blood pressure and oxidative stress in adult offspring rats.     

Differences in DNA-damage in non-smoking men and women exposed to environmental tobacco smoke (ETS)

There is much data implicating environmental tobacco smoke (ETS) in the development and progression of disease, notably cancer, yet the mechanisms for this remain unclear. As ETS is both a pro-oxidant stressor and carcinogen, we investigated the relationship of ETS exposure to intracellular and serum levels of DNA-damage, both oxidative 8-hydroxy-2-deoxyguanosine (8OHdG) and general, in non-smokers from non-smoking households, occupationally exposed to ETS. General DNA-damage consisting of single and double strand breaks, alkali-labile sites and incomplete base-excision repair, increased significantly in a dose-dependent manner with ETS exposure in men (P=0.015, n=32, Pearson) but not women (P=0.736, n=17). Intracellular 8OHdG-DNA-damage and general DNA-damage were both greater in men than women (P=0.0005 and 0.016, respectively) but 8OHdG serum levels did not differ between the genders. Neither 8OHdG-DNA-damage nor serum levels correlated with increasing ETS exposure. This is the first study to demonstrate dose-dependent increases in DNA-damage from workplace ETS exposure. Perhaps most interesting was that despite equivalent ETS exposure, significantly greater DNA-damage occurred in men than women. These data may begin to provide a mechanistic rationale for the generally higher incidence of some diseases in males due to tobacco smoke and/or other genotoxic stressors.     

Effects of maternal exposure to aflatoxin B1 during pregnancy on fertility output of dams and developmental,behavioral and reproductive consequences in female offspring using a rat model

A suboptimal in utero environment can have detrimental effects on the pregnancy and long-term adverse “programing” effects on the offspring. Aflatoxin B1 is one of the potent reproductive toxicants and currently detected in both milk and tissues. This article focuses on the effects of prenatal exposure to graded doses of aflatoxin B1 on the pregnancy outcomes of dams and postnatal developments of the female offspring, since these issues have ethological relevance in both animals and humans. Pregnant Wistar rats were injected intramuscularly with vehicle or aflatoxin B1 (10, 20, 50 or 100?μg/kg body weight/day) on days 12–19 of gestation. At parturition, newborns were observed for clinical signs of toxicity and survival. The female offspring were examined through a battery of tests in order to evaluate their developmental, behavioral and reproductive end points. All animals were born alive. The litter size of the aflatoxin B1 treated rats was comparable to the controls. However, the birth weight of the pups in the experimental group was significantly lower when compared to controls. Significant and persistent lags in cliff avoidance, negative geotaxis, surface rightening activity and ascending wire mesh, with a delay in elapsed time for vaginal opening were detected in the female progeny exposed to aflatoxin B1 during embryonic development. The locomotor activity and exploratory behavior in experimental females were significantly decreased than that of controls. Embryonic exposure to aflatoxin B1 also resulted in prolonged stress response, irregular estrus and suppressed fertility output in the progeny at their adulthood. These results indicate that in utero exposure to aflatoxin B1 severely compromised postnatal development of neonatal rats and caused irregular estrus that was accompanied by suppressed fertility output.     

Gestational atrazine exposure: effects on male reproductive development and metabolite distribution in the dam, fetus, and neonate

Few studies have investigated the long-term effects of atrazine (ATR) following in utero exposure. We evaluated the effects of gestational exposure of Sprague Dawley dams to ATR (0, 1, 5, 20, or 100 mg/kg-d) on the reproductive development of male offspring. We also quantified the distribution of ATR and its chlorinated metabolites in maternal, fetal, and neonatal fluid and tissue samples following gestational and/or lactational exposure. Dose-dependent levels of chlorotriazines, primarily diamino-s-chlorotriazine, were present in most samples analyzed, including fetal tissue. In utero exposure to 1-20 mg/kg-d ATR did not alter testosterone production, the timing of puberty, play behavior, or other androgen-dependent endpoints of male offspring. Significant maternal toxicity and postnatal mortality were observed at 100 mg/kg-d. We conclude that, although levels of chlorotriazines within the fetus were considerable, gestational exposures of 1-20 mg/kg-d do not lead to alterations in the measures of male development examined in this study.     

Environmental tobacco smoke exposure among electronic cigarette users

IntroductionExposure to environmental tobacco smoke (ETS) from combustible tobacco products causes various diseases and makes quitting smoking more difficult. However, little is known about exposure of e-cigarette users to ETS from combustible tobacco products. This study aimed to investigate e-cigarette users' exposure to ETS from tobacco smokers.MethodsThe association between ETS exposure frequency and different types of smokers including e-cigarette users was examined using ordered logistic regression analysis and nationally representative survey data on 28,765 individuals who were interviewed in the Canadian Tobacco, Alcohol and Drugs Surveys conducted during 2013 and 2015. Survey respondents were classified into one of five smoker types: smokers of tobacco only, dual users of tobacco and e-cigarettes, users of e-cigarette only, former smokers and never smokers. The analyses were conducted using the entire sample and by age group.ResultsYoung to mid-age (15–54) dual users of both regular cigarettes and e-cigarettes have higher ETS exposure than even tobacco smokers. Young to mid-age single users of e-cigarettes are less exposed to ETS than tobacco smokers, but still have higher ETS than never smokers. At older age (55+), both dual and single e-cigarette users face similar risks of ETS exposure as tobacco smokers.ConclusionsE-cigarette users are at high risk of ETS exposure. Policies that target the behaviour of e-cigarette users as well as the environments surrounding them to address their high ETS exposure risk would be beneficial.     

Effects of developmental nicotine exposure in rats on decision-making in adulthood

Exposure to tobacco smoke during pregnancy is associated with a range of adverse outcomes in offspring, including cognitive deficits and increased incidence of attention deficit-hyperactivity disorder, but there is a considerable controversy with regard to the causal role of tobacco smoke in these outcomes. To determine whether developmental exposure to the primary psychoactive ingredient in tobacco smoke, nicotine, may cause long-lasting behavioral alterations analogous to those in attention deficit-hyperactivity disorder, male Sprague-Dawley rats underwent a chronic neonatal nicotine administration regimen, which models third-trimester human exposure. Male rat pups were administered nicotine (6 mg/kg/day) by oral gastric intubation on postnatal days 1-7. In adulthood, rats were tested in two decision-making tasks (risky decision-making and delay discounting) as well as in free-operant responding for food reward and the elevated plus maze. Chronic neonatal nicotine attenuated weight gain during nicotine exposure, but there were no effects on performance in the decision-making task, and only a modest decrease in arm entries in the elevated plus maze in one subgroup of rats. These data are consistent with previous findings that developmental nicotine exposure has no effect on delay discounting, and they extend these findings to risky decision-making as well. They further suggest that at least some neurocognitive alterations associated with prenatal tobacco smoke exposure in humans may be due to genetic or other environmental factors, including non-nicotine components of tobacco smoke.