Maternal smoking and the retinoid pathway in the developing lung

β-escin activates ALDH and prevents cigarette smoke-induced cell death

BACKGROUND

The tobacco use is one of the biggest public health threats worldwide. Cigarette smoke contains over 7000 chemicals among other aldehydes, regarded as priority toxicants. β-escin (a mixture of triterpenoid saponins extracted from the Aesculus hippocastanum. L) is a potent activator of aldehyde dehydrogenase (ALDH) - an enzyme catalyzing oxidation of aldehydes to non-toxic carboxylic acids.

PURPOSE

The aim of this study was to evaluate the effect of β-escin on ALDH activity, ALDH isoforms mRNA expression and cytotoxicity in nasal epithelial cells exposed to cigarette smoke extract (CSE).

METHODS

Nasal epithelial cells from healthy non-smokers were treated with β-escin (1 µM) and exposed to 5% CSE. After 6- or 24-hours of stimulation cell viability, DNA damage, ALDH activity and mRNA expression of ALDH isoforms were examined.

RESULTS

24 h β-escin stimulation revised CSE induced cytotoxicity and DNA damage. Cells cultured with β-escin or exposed to CSE responded with strong increase in ALDH activity. This effect was more pronounced in cultures treated with combination of β-escin and CSE. The strongest stimulatory effect on ALDH isoform mRNA expression was observed in cells cultured simultaneously with β-escin and CSE: at 6 h for ALDH1A1 and ALDH3A1, and at 24 h for ALDH1A3, ALDH3A2, ALDH3B1, and ALDH18A1. Combined β-escin and CSE treatment prevented the CSE-induced inhibition of ALDH2 expression at 24 h.

CONCLUSIONS

β-escin is an effective ALDH stimulatory and cytoprotective agent and might be useful in the prevention or supportive treatment of tobacco smoke-related diseases.

Air pollution as an early determinant of COPD

COPD is a progressive and debilitating disease often diagnosed after 50 years of age, but more recent evidence suggests that its onset could originate very early on in life. In this context, exposure to air pollution appears to be a potential contributor. Although the potential role of air pollution as an early determinant of COPD is emerging, knowledge gaps still remain, including an accurate qualification of air pollutants (number of pollutants quantified and exact composition) or the "one exposure-one disease" concept, which might limit the current understanding. To fill these gaps, improvements in the field are needed, such as the use of atmosphere simulation chambers able to realistically reproduce the complexity of air pollution, consideration of the exposome, as well as improving exchanges between paediatricians and adult lung specialists to take advantage of reciprocal expertise. This review should lead to a better understanding of the current knowledge on air pollution as an early determinant of COPD, as well as identify the existing knowledge gaps and opportunities to fill them. Hopefully, this will lead to better prevention strategies to scale down the development of COPD in future generations.

Maternal cigarette smoking and alcohol consumption and congenital diaphragmatic hernia

Background

Congenital diaphragmatic hernia (CDH) occurs when abnormal diaphragm development allows herniation of abdominal organs into the thoracic cavity. Its etiopathogenesis is not well understood, but cigarette smoking and alcohol exposure may impact diaphragm development. Using data from a large, population‐based case–control study, we examined associations between maternal cigarette smoking and alcohol consumption and CDH in offspring.

Methods

We analyzed maternal interview reports of cigarette smoking and alcohol consumption during early pregnancy for 831 children with CDH and 11,416 children without birth defects with estimated dates of delivery during 1997–2011. Generalized linear mixed effects models with a random intercept for study site were used to estimate associations between measures of exposure to smoking (any, type, frequency, duration) and alcohol (any, quantity, frequency, variability, type) for all CDH combined and selected subtypes (Bochdalek and Morgagni).

Results

Mothers of 280 (34.0%) case and 3,451 (30.3%) control children reported early pregnancy exposure to cigarette smoking. Adjusted odds ratios for all CDH were increased for any (1.3; 95% confidence interval 1.1–1.5), active (1.3, 1.0–1.7), and passive (1.4, 1.1–1.7) smoking. Early pregnancy alcohol consumption was reported by mothers of 286 (34.9%) case and 4,200 (37.0%) control children; odds were near the null for any consumption (0.9, 0.8–1.1) and consumption with (0.9, 0.7, 1.1) or without (0.9, 0.8, 1.1) binging. Estimates for smoking and alcohol tended to be higher for Bochdalek CDH and Morgagni CDH than those for all CDH.

Conclusions

Findings suggest that maternal early pregnancy exposure to cigarette smoking, but less so to alcohol consumption, contributes to CDH. These findings need to be replicated in additional large studies that use systematic case ascertainment and classification, detailed exposure assessment, and examine subtype‐specific associations.

Prenatal smoke exposure dysregulates lung epithelial cell differentiation in mouse offspring: role for AREG-induced EGFR signaling

Prenatal smoke exposure is a risk factor for impaired lung development in children. Recent studies have indicated that amphiregulin (AREG), which is a ligand of the epidermal growth factor receptor (EGFR), has a regulatory role in airway epithelial cell differentiation. In this study, we investigated the effect of prenatal smoke exposure on lung epithelial cell differentiation and linked this with AREG-EGFR signaling in 1-day-old mouse offspring. Bronchial and alveolar epithelial cell differentiations were assessed by immunohistochemistry. Areg, epidermal growth factor (Egf), and mRNA expressions of specific markers for bronchial and alveolar epithelial cells were assessed by RT-qPCR. The results in neonatal lungs were validated in an AREG-treated three-dimensional mouse lung organoid model. We found that prenatal smoke exposure reduced the number of ciliated cells and the expression of the cilia-related transcription factor Foxj1, whereas it resulted in higher expression of mucus-related transcription factors Spdef and Foxm1 in the lung. Moreover, prenatally smoke-exposed offspring had higher numbers of alveolar epithelial type II cells (AECII) and lower expression of the AECI-related Pdpn and Gramd2 markers. This was accompanied by higher expression of Areg and lower expression of Egf in prenatally smoke-exposed offspring. In bronchial organoids, AREG treatment resulted in fewer ciliated cells and more basal cells when compared with non-treated bronchiolar organoids. In alveolar organoids, AREG treatment led to more AECII cells than non-treated AECII cells. Taken together, the observed impaired bronchial and alveolar cell development in prenatally smoke-exposed neonatal offspring may be induced by increased AREG-EGFR signaling.

Changes of DNA methylation are associated with changes in lung function during adolescence

BACKGROUND

Adolescence is a significant period for the gender-dependent development of lung function. Prior studies have shown that DNA methylation (DNA-M) is associated with lung function and DNA-M at some cytosine-phosphate-guanine dinucleotide sites (CpGs) changes over time. This study examined whether changes of DNA-M at lung-function-related CpGs are associated with changes in lung function during adolescence for each gender, and if so, the biological significance of the detected CpGs.

METHODS

Genome-scale DNA-M was measured in peripheral blood samples at ages 10 (n = 330) and 18 years (n = 476) from the Isle of Wight (IOW) birth cohort in United Kingdom, using Illumina Infinium arrays (450 K and EPIC). Spirometry was conducted at both ages. A training and testing method was used to screen 402,714 CpGs for their potential associations with lung function. Linear regressions were applied to assess the association of changes in lung function with changes of DNA-M at those CpGs potentially related to lung function. Adolescence-related and personal and family-related confounders were included in the model. The analyses were stratified by gender. Multiple testing was adjusted by controlling false discovery rate of 0.05. Findings were further examined in two independent birth cohorts, the Avon Longitudinal Study of Children and Parents (ALSPAC) and the Children, Allergy, Milieu, Stockholm, Epidemiology (BAMSE) cohort. Pathway analyses were performed on genes to which the identified CpGs were mapped.

RESULTS

For females, 42 CpGs showed statistically significant associations with change in FEV1/FVC, but none for change in FEV1 or FVC. No CpGs were identified for males. In replication analyses, 16 and 21 of the 42 CpGs showed the same direction of associations among the females in the ALSPAC and BAMSE cohorts, respectively, with 11 CpGs overlapping across all the three cohorts. Through pathway analyses, significant biological processes were identified that have previously been related to lung function development.

CONCLUSIONS

The detected 11 CpGs in all three cohorts have the potential to serve as the candidate epigenetic markers for changes in lung function during adolescence in females.

In utero exposure to cigarette smoke and effects across generations: A conference of animals on asthma

BACKGROUND

The prevalence of asthma and chronic obstructive pulmonary disease (COPD) has risen markedly over the last decades and is reaching epidemic proportions. However, underlying molecular mechanisms are not fully understood, hampering the urgently needed development of approaches to prevent these diseases. It is well established from epidemiological studies that prenatal exposure to cigarette smoke is one of the main risk factors for aberrant lung function development or reduced fetal growth, but also for the development of asthma and possibly COPD later in life. Of note, recent evidence suggests that the disease risk can be transferred across generations, that is, from grandparents to their grandchildren. While initial studies in mouse models on in utero smoke exposure have provided important mechanistic insights, there are still knowledge gaps that need to be filled.

OBJECTIVE

Thus, in this review, we summarize current knowledge on this topic derived from mouse models, while also introducing two other relevant animal models: the fruit fly Drosophila melanogaster and the zebrafish Danio rerio.

METHODS

This review is based on an intensive review of PubMed-listed transgenerational animal studies from 1902 to 2018 and focuses in detail on selected literature due to space limitations.

RESULTS

This review gives a comprehensive overview of mechanistic insights obtained in studies with the three species, while highlighting the remaining knowledge gaps. We will further discuss potential (dis)advantages of all three animal models.

CONCLUSION/CLINICAL RELEVANCE

Many studies have already addressed transgenerational inheritance of disease risk in mouse, zebrafish or fly models. We here propose a novel strategy for how these three model organisms can be synergistically combined to achieve a more detailed understanding of in utero cigarette smoke-induced transgenerational inheritance of disease risk.

Transgenerational and intergenerational epigenetic inheritance in allergic diseases

It has become clear that early life (including in utero exposures) is a key window of vulnerability during which environmental exposures can alter developmental trajectories and initiate allergic disease development. However, recent evidence suggests that there might be additional windows of vulnerability to environmental exposures in the parental generation before conception or even in previous generations. There is evidence suggesting that information of prior exposures can be transferred across generations, and experimental animal models suggest that such transmission can be conveyed through epigenetic mechanisms. Although the molecular mechanisms of intergenerational and transgenerationational epigenetic transmission have yet to be determined, the realization that environment before conception can alter the risks of allergic diseases has profound implications for the development of public health interventions to prevent disease. Future research in both experimental models and in multigenerational human cohorts is needed to better understand the role of intergenerational and transgenerational effects in patients with asthma and allergic disease. This will provide the knowledge basis for a new approach to efficient intervention strategies aimed at reducing the major public health challenge of these conditions.

Air pollutants and early origins of respiratory diseases

Air pollution is a global health threat and causes millions of human deaths annually. The late onset of respiratory diseases in children and adults due to prenatal or perinatal exposure to air pollutants is emerging as a critical concern in human health. Pregnancy and fetal development stages are highly susceptible to environmental exposure and tend to develop a long-term impact in later life. In this review, we briefly glance at the direct impact of outdoor and indoor air pollutants on lung diseases and pregnancy disorders. We further focus on lung complications in later life with early exposure to air pollutants. Epidemiological evidence is provided to show the association of prenatal or perinatal exposure to air pollutants with various adverse birth outcomes, such as preterm birth, lower birth weight, and lung developmental defects, which further associate with respiratory diseases and reduced lung function in children and adults. Mechanistic evidence is also discussed to support that air pollutants impact various cellular and molecular targets at early life, which link to the pathogenesis and altered immune responses related to abnormal respiratory functions and lung diseases in later life.

Multigenerational effects of maternal cigarette smoke exposure during pregnancy on sperm counts of F1 and F2 male offspring

Animal models and human studies showed that in utero cigarette smoke exposure decreases sperm counts of offspring. This study used a mouse model to investigate the effects of maternal exposure to cigarette smoke on reproductive systems in F1 and F2 male offspring. Female ICR mice were exposed either to clean air or to cigarette smoke during pregnancy at the post-implantation stage. Epididymal sperm counts were decreased in a cigarette smoke dose-dependent manner in F1 (by 40-60%) and F2 males (by 23-40%) at postnatal day 56. In F1, the seminiferous epithelium heights were lower in the cigarette smoke-exposed groups than in the control group, and these effects were sustained in F2 males. Results suggest that maternal cigarette smoke exposure during pregnancy can have a multigenerational adverse effect on sperm counts in male offspring, which is mediated through in utero exposure of fetal germ cells to cigarette smoke.

Cigarette smoke condensate affects the retinoid pathway in human amnion

INTRODUCTION

The preterm premature rupture of membranes (PPROM) is a frequent pathology responsible of more than 30% of preterm births. Tobacco smoking is one of the most frequently described risk factors identified and contributes to the pre term weakening of fetal membranes. As previously demonstrated, all-trans retinoic acid (atRA) regulates several genes involved in the extracellular matrix dynamics, an essential actor in fetal membrane ruptures. We hypothesized that cigarette smoke may affect this pathway in human amnion.

METHODS

Amnion was obtained from full-term fetal membranes collected from non-smoking women after cesarean births and used either as explants or for the isolation of derived epithelial cells. The pro-healing and transcriptomic effects of atRA were studied by a scratch assay experiment and quantitative RT-PCR, respectively, after treatment with dimethyl sulfoxyde (DMSO), atRA, DMSO + cigarette smoke condensate (CSC), or atRA + CSC.

RESULTS

Our results show a strong alteration of the retinoid pathway after CSC treatment on amnion-derived epithelial cells and explants. We first demonstrated that CSC inhibits the activity of the RARE reporter gene in amnion-derived epithelial cells. Then, atRA's effects on both the transcription of its target genes and wound healing were demonstrated to be inhibited or at least decreased by the CSC in human amnion epithelial cells.

DISCUSSION

Here, we demonstrated that CSC altered the retinoid signal, already known to have roles in fetal membrane physiopathology. These results highlight a potential negative action of maternal smoking on the retinoid pathway in human amnion and more generally on pregnancy.

Maternal smoke exposure decreases mesenchymal proliferation and modulates Rho-GTPase-dependent actin cytoskeletal signaling in fetal lungs

The present study tested the hypothesis that maternal smoke exposure results in fetal lung growth retardation due to dysregulation in various signaling pathways, including the Wnt (wingless-related integration site)/β-catenin pathway. Pregnant female C57BL/6J mice were exposed to cigarette smoke (100-150 mg/m³) or room air, and offspring were humanely killed on 12.5, 14.5, 16.5, and 18.5 d post coitum (dpc). We assessed lung stereology with Cavalieri estimation; apoptosis with proliferating cell nuclear antigen, TUNEL, and caspase assays; and gene expression with quantitative PCR (qPCR) and RNA sequencing on lung epithelium and mesenchyme retrieved by laser capture microdissection. Results demonstrated a significant decrease in body weight and lung volume of smoke-exposed embryos. At 16.5 dpc, the reduction in lung volume was due to loss of lung mesenchymal tissue correlating with a decrease in cell proliferation (n = 10; air: 61.65% vs. smoke: 44.21%, P < 0.05). RNA sequence analysis demonstrated an alteration in the Wnt pathway, and qPCR confirmed an increased expression of secreted frizzled-related protein 1 (sFRP-1) [n = 12; relative quantification (RQ) 1 vs. 2.33, P < 0.05] and down-regulation of Cyclin D1 (n = 7; RQ 1 vs. 0.61, P < 0.05) in mesenchymal tissue. Furthermore, genome expression studies revealed a smoke-induced up-regulation of Rho-GTPase-dependent actin cytoskeletal signaling that can lead to loss of tissue integrity.-Unachukwu, U., Trischler, J., Goldklang, M., Xiao, R., D'Armiento, J. Maternal smoke exposure decreases mesenchymal proliferation and modulates Rho-GTPase-dependent actin cytoskeletal signaling in fetal lungs.

Linking bronchopulmonary dysplasia to adult chronic lung diseases: role of WNT signaling

Bronchopulmonary dysplasia (BPD) is one of the most common chronic lung diseases in infants caused by pre- and/or postnatal lung injury. BPD is characterized by arrested alveolarization and vascularization due to extracellular matrix remodeling, inflammation, and impaired growth factor signaling. WNT signaling is a critical pathway for normal lung development, and its altered signaling has been shown to be involved in the onset and progression of incurable chronic lung diseases in adulthood, such as chronic obstructive pulmonary disease (COPD) or idiopathic pulmonary fibrosis (IPF). In this review, we summarize the impact of WNT signaling on different stages of lung development and its potential contribution to developmental lung diseases, especially BPD, and chronic lung diseases in adulthood.

Nasoethmoidal meningocele in a child presenting bilateral congenital cystic adenomatoid malformation: Evidence for a new entity or consequence of gestational exposures?

BACKGROUND

Nasoethmoidal meningocele is considered an uncommon type of cephalocele, and congenital cystic adenomatoid malformation (CCAM) is a rare lung disorder characterized by overgrowth of the terminal bronchioles.

CASE

We report the unusual association between a nasoethmoidal meningocele and CCAM type II in a fetus exposed to valproic acid and misoprostol. The mother was an 18-year-old woman on her first pregnancy. She had a history of absence seizures since she was 5 years old. She took valproic acid from the beginning of the gestation until the end of the third month. At the end of the third month, she attempted interruption of her pregnancy using misoprostol. The fetal nasoethmoidal meningocele and CCAM type II were identified through morphological ultrasound examination and magnetic resonance imaging. A genome-wide study detected one copy number variation classified as rare, entirely contained into the SPATA5 gene. However, it does not seem to be associated to the clinical findings of the patient.

CONCLUSION

To our knowledge, there is only one case reported in the literature showing the same association between a nasoethmoidal meningocele and CCAM. Thus, the malformations observed in our patient may be related to the gestational exposures. Also, we cannot rule out that the patient may present the same condition characterized by a cephalocele and CCAM described by some authors, or even an undescribed entity, because some hallmark features, such as laryngeal atresia and limb defects, were not observed in our case. Further reports will be very important to better understand the associations described in our study.

N-Acetyltransferase 2 Genotypes Are Associated With Diisocyanate-Induced Asthma

OBJECTIVE

To investigate whether genetic variants of N-acetyltransferase (NAT) genes are associated with diisocyanate asthma (DA).

METHODS

The study population consisted of 354 diisocyanate-exposed workers. Genotyping was performed using a 5'-nuclease polymerase chain reaction assay.

RESULTS

The NAT2 rs2410556 and NAT2 rs4271002 variants were significantly associated with DA in the univariate analysis. In the first logistic regression model comparing DA+ and asymptomatic worker groups, the rs2410556 (P = 0.004) and rs4271002 (P < 0.001) single nucleotide polymorphisms and the genotype combination, NAT2 rs4271002*NAT1 rs11777998, showed associations with DA risk (P = 0.014). In the second model comparing DA+ and DA- groups, NAT2 rs4271002 variant and the combined genotype, NAT1 rs8190845*NAT2 rs13277605, were significantly associated with DA risk (P = 0.022, P = 0.036, respectively).

CONCLUSIONS

These findings suggest that variations in the NAT2 gene and their interactions contribute to DA susceptibility.

Inter- and transgenerational epigenetic inheritance: evidence in asthma and COPD?

Evidence is now emerging that early life environment can have lifelong effects on metabolic, cardiovascular, and pulmonary function in offspring, a concept also known as fetal or developmental programming. In mammals, developmental programming is thought to occur mainly via epigenetic mechanisms, which include DNA methylation, histone modifications, and expression of non-coding RNAs. The effects of developmental programming can be induced by the intrauterine environment, leading to intergenerational epigenetic effects from one generation to the next. Transgenerational epigenetic inheritance may be considered when developmental programming is transmitted across generations that were not exposed to the initial environment which triggered the change. So far, inter- and transgenerational programming has been mainly described for cardiovascular and metabolic disease risk. In this review, we discuss available evidence that epigenetic inheritance also occurs in respiratory diseases, using asthma and chronic obstructive pulmonary disease (COPD) as examples. While multiple epidemiological as well as animal studies demonstrate effects of 'toxic' intrauterine exposure on various asthma-related phenotypes in the offspring, only few studies link epigenetic marks to the observed phenotypes. As epigenetic marks may distinguish individuals most at risk of later disease at early age, it will enable early intervention strategies to reduce such risks. To achieve this goal further, well designed experimental and human studies are needed.

Proteomic differences with and without ozone-exposure in a smoking-induced emphysema lung model

BACKGROUND/AIMS

Acute exacerbations in chronic obstructive pulmonary disease may be related to air pollution, of which ozone is an important constituent. In this study, we investigated the protein profiles associated with ozone-induced exacerbations in a smoking-induced emphysema model.

METHODS

Mice were divided into the following groups: group I, no smoking and no ozone (NS + NO); group II, no smoking and ozone (NS + O); group III, smoking and no ozone (S + NO); and group IV, smoking and ozone (S + O). Bronchoalveolar lavage, the mean linear intercept (MLI) on hematoxylin and eosin staining, nano-liquid chromatography-tandem mass spectrometry (LC-MS/MS), and Western blotting analyses were performed.

RESULTS

The MLIs of groups III (S + NO) and IV (S + O) (45 ± 2 and 44 ± 3 µm, respectively) were significantly higher than those of groups I (NS + NO) and II (NS + O) (26 ± 2 and 23 ± 2 µm, respectively; p < 0.05). Fourteen spots that showed significantly different intensities on image analyses of two-dimensional (2D) protein electrophoresis in group I (NS + NO) were identified by LC-MS/MS. The levels of six proteins were higher in group IV (S + O). The levels of vimentin, lactate dehydrogenase A, and triose phosphate isomerase were decreased by both smoking and ozone treatment in Western blotting and proteomic analyses. In contrast, TBC1 domain family 5 (TBC1D5) and lamin A were increased by both smoking and ozone treatment.

CONCLUSIONS

TBC1D5 could be a biomarker of ozone-induced lung injury in emphysema.

Damaging legacy: maternal cigarette smoking has long-term consequences for male offspring fertility

STUDY QUESTION

What are the effects on fertility of cigarette smoke-induced toxicity on male offspring exposed during the gestational/weaning period?

SUMMARY ANSWER

Maternal cigarette smoke exposure during the gestational/weaning period causes long-term defects in male offspring fertility.

WHAT IS KNOWN ALREADY

Cigarette smoke is a well-known reproductive toxicant which is particularly harmful to both fetal and neonatal germ cells. However, recent studies suggest a significant portion of young mothers in the developed world still smoke during pregnancy. In the context of male reproductive health, our understanding of the effects of in utero exposure on offspring fertility is limited.

STUDY DESIGN, SIZE, DURATION

In this study, 27 C57BL/6 5-week-old female mice were exposed via the nose-only to cigarette smoke (treatment) or 27 were exposed to room air (control) for 6 weeks before being housed with stud males to produce litters. In the treatment group, smoke exposure continued throughout mating, pregnancy and lactation until weaning of pups at 21 days post birth. Male offspring were examined at post-natal days 3, 6, 12, 21 and 98 (adult).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Approximately 108 maternal smoke-exposed C57BL/6 offspring and controls were examined. Spermatogenesis was examined using testicular histology and apoptosis/DNA damage was assessed using caspase immunohistochemistry and TUNEL. Sertoli cell morphology and fluctuations in the spermatogonial stem cell population were also examined using immunohistochemistry. Microarray and QPCR analysis were performed on adult testes to examine specific long-term transcriptomic alteration as a consequence of maternal smoke exposure. Sperm counts and motility, zona/oolemma binding assays, COMET analysis and mitochondrial genomic sequencing were also performed on spermatozoa obtained from adult treated and control mice. Fertility trials using exposed adult male offspring were also performed.

MAIN RESULTS AND THE ROLE OF CHANCE

Maternal cigarette smoke exposure caused increased gonocyte and meiotic spermatocyte apoptosis (P < 0.01) as well as germ cell depletion in the seminiferous tubules of neonatal and juvenile offspring. Aberrant testicular development characterized by abnormal Sertoli and germ cell organization, a depleted spermatogonial stem cell population (P < 0.01), atrophic seminiferous tubules and increased germ cell DNA damage (P < 0.01) persisted in adult offspring 11 weeks after exposure. Microarray analysis of adult offspring testes associated these defects with meiotic germ cell development, sex hormone metabolism, oxidative stress and Sertoli cell signalling. Next generation sequencing also revealed a high mitochondrial DNA mutational load in the testes of adult offspring (P < 0.01). Adult maternal smoke-exposed offspring also had reduced sperm counts with spermatozoa exhibiting morphological abnormalities (P < 0.01), affecting motility and fertilization potential. Odf2, a spermatozoa flagellum component required for coordinated ciliary beating, was also significantly down-regulated (P < 0.01) in maternal smoke-exposed adult offspring, with aberrant localization along the spermatozoa flagellum. Adult maternal smoke-exposed offspring took significantly longer to impregnate control females and had a slight but significant (P < 0.01) reduction in litter size.

LIMITATIONS, REASONS FOR CAUTION

This study examined only one species (mouse) using a smoking model which only simulates human cigarette smoke exposure.

WIDER IMPLICATIONS OF THE FINDINGS

This study represents the first comprehensive animal model of maternal smoking on male offspring reproductive function, suggesting that exposure during the gestational/weaning period causes long-term defects in male offspring fertility. This is due to a compromised spermatogonial stem cell population resulting from gonocyte apoptosis and impaired spermatogenic development. This results in significant germ cell damage and Sertoli cell dysfunction, impacting germ cell number, tubule organization, DNA damage and spermatozoa in adult offspring. This study strengthens the current literature suggesting that maternal exposure impairs male offspring fertility, which is currently debated due to conflicting studies.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by the Australian Research Council, Hunter Medical Research Institute, National Health and Medical Research Council of Australia and the Newcastle Permanent Building Society Charitable Trust. The authors declare no conflict of interest.

Potential risk of asthma associated with in utero exposure to xenobiotics

The incidence of asthma, a complex disease and significant public health problem, has been increasing over the last 30 years for unknown reasons. Changes in environmental exposures or lifestyle may be involved. In some cases asthma may originate in utero or in early life. Associations have been found between in utero exposures to several xenobiotics and increased risk of asthma. There is convincing evidence that maternal smoking and/or in utero and perinatal exposure to environmental tobacco smoke are associated with increased risk of asthma. Similar effects have been demonstrated in animal models of allergic asthma. Evidence also suggests that in utero and/or early-life exposures to various ambient air pollutants may increase the risk of asthma although supporting animal data are very limited. A few studies have suggested that in utero exposure to acetaminophen is associated with increased risk of asthma; however, animal data are lacking. Various vitamin deficiencies and supplements during pregnancy have been studied. In general, it appears that vitamins A, C, and E have protective effects and vitamins D and B may, in some instances, increase the risk, but the data are not conclusive. Some studies related to in utero exposures to polychlorinated biphenyls and bisphenol A and asthma risk are also reported. The underlying mechanisms for an association between xenobiotic exposures and asthma remain a matter of speculation. Genetic predisposition and epigenetic changes have been explored. The developing immune, respiratory, and nervous systems are potential targets. Oxidative stress and modulation of inflammation are thought to be involved.

Oxygen, gastrin-releasing Peptide, and pediatric lung disease: life in the balance

Excessive oxygen (O2) can cause tissue injury, scarring, aging, and even death. Our laboratory is studying O2-sensing pulmonary neuroendocrine cells (PNECs) and the PNEC-derived product gastrin-releasing peptide (GRP). Reactive oxygen species (ROS) generated from exposure to hyperoxia, ozone, or ionizing radiation (RT) can induce PNEC degranulation and GRP secretion. PNEC degranulation is also induced by hypoxia, and effects of hypoxia are mediated by free radicals. We have determined that excessive GRP leads to lung injury with acute and chronic inflammation, leading to pulmonary fibrosis (PF), triggered via ROS exposure or by directly treating mice with exogenous GRP. In animal models, GRP-blockade abrogates lung injury, inflammation, and fibrosis. The optimal time frame for GRP-blockade and the key target cell types remain to be determined. The concept of GRP as a mediator of ROS-induced tissue damage represents a paradigm shift about how O2 can cause injury, inflammation, and fibrosis. The host PNEC response in vivo may depend on individual ROS sensing mechanisms and subsequent GRP secretion. Ongoing scientific and clinical investigations promise to further clarify the molecular pathways and clinical relevance of GRP in the pathogenesis of diverse pediatric lung diseases.

Cotinine in human placenta predicts induction of gene expression in fetal tissues

Maternal cigarette smoking during pregnancy is associated with increased risk of perinatal morbidity and mortality. However, the mechanisms underlying adverse birth outcomes following prenatal exposure to cigarette smoke remain unknown due, in part, to the absence or unreliability of information regarding maternal cigarette smoke exposure during pregnancy. Our goal was to determine if placental cotinine could be a reliable biomarker of fetal cigarette smoke exposure during pregnancy. Cotinine levels were determined in placentas from 47 women who reported smoking during pregnancy and from 10 women who denied cigarette smoke exposure. Cotinine levels were significantly higher in placentas from women reporting cigarette smoking (median = 27.2 ng/g) versus women who reported no smoke exposure (2.3 ng/g, P < 0.001). Receiver operating characteristic curve analysis identified an optimal cut point of 7.5 ng/g (sensitivity = 78.7%, specificity = 100%) to classify placenta samples from mothers who smoked versus those from mothers who did not. Among 415 placentas for which maternal cigarette smoking status was unavailable, 167 had cotinine levels > 7.5 ng/g and would be considered positive for cigarette smoke exposure. Data from quantitative reverse-transcription polymerase chain reaction analyses demonstrated that in utero cigarette smoke exposure predicted by cotinine in placenta is associated with changes in the expression of xenobiotic-metabolizing enzymes in fetal tissues. CYP1A1 mRNA in fetal lung and liver tissue and CYP1B1 mRNA in fetal lung tissue were significantly induced when cotinine was detected in placenta. These findings indicate that cotinine in placenta is a reliable biomarker for fetal exposure and response to maternal cigarette smoking during pregnancy.