Preconception origins of asthma, allergies and lung function: The influence of previous generations on the respiratory health of our children

Paternal pre-conceptional smoking and semen quality in the adult son

BACKGROUND

Growing evidence suggests intergenerational effects of paternal pre-conceptional smoking through the germ line, but its specific impact on offspring semen quality remains uncertain because of challenges in isolating paternal exposure from maternal passive smoking or underreporting.

METHODS

We reran previous analyses estimating differences in semen parameters and testicular size according to paternal smoking in 867 young adult men, adding first-trimester maternal plasma cotinine to the original adjustment for maternal self-reported smoking. We also estimated differences in sperm DNA fragmentation. Paternal smoking was reported by the pregnant women around gestational week 16. Analyses were additionally adjusted for household occupational status, parental ages at birth, maternal pre-pregnancy body mass index and alcohol consumption, and abstinence time, and accounted for spillage, minutes from ejaculation to analysis, and son's own smoking.

RESULTS

We found no association between paternal preconceptional smoking and any of the semen parameters or testicular size. Adjustment for son's own smoking did not change results.

DISCUSSION

While maternal plasma cotinine offers an objective measure of tobacco exposure and allows for a more thorough adjustment of maternal smoking, the high correlation between paternal pre-conceptional smoking and maternal cotinine exposure may, have resulted in overadjustment removing some paternal effect. Inability to distinguish between paternal never smokers and former smokers, may have led to misclassification of paternal pre-conceptional smoking and underestimation of associations.

CONCLUSION

We found no support for an independent association between paternal pre-conceptional smoking and semen quality in young adult sons, but studies with more detailed paternal smoking history are needed before firm conclusions can be drawn.

[The impact of maternal smoking during pregnancy on respiratory disease in children]

Among the causes of abnormal fetal lung development, active and environmental maternal smoking represents a major potential target in preventive medicine. Prevalence of smoking among women, particularly during pregnancy, varies across the different regions of the world. We reviewed the literature on the repercussions of maternal smoking on the lungs of the fetus and the neonate. One of the main consequences is prematurity, leading to pulmonary bronchodysplasia followed by respiratory infections, which particularly affect young children. In the medium- and long-term, smoking in utero leads to asthma and allergies, and is suspected to be associated with impaired respiratory function in children and teenagers. We also report on the potential effects of e-cigarettes, which represent an emerging threat to children's respiratory health.

Maternal exposure to smoking and wheezing phenotypes in children: a cohort study of the Japan Environment and Children's Study

BACKGROUND

Previous studies have shown that prenatal maternal smoking and maternal secondhand smoke exposure during pregnancy were associated with an increased risk of wheezing and asthma development. However, few studies have examined the influence of different sources of tobacco exposure in different perinatal timeframes (preconception, prenatal, and postnatal) on wheezing phenotypes in children. Using national survey data from Japan, we investigated the effects of exposure to tobacco smoke during pregnancy on wheezing phenotypes in children before the age of 3 years.

METHODS

Pregnant women who lived in the 15 regional centers in the Japan Environment and Children's Study were recruited. We obtained information on prenatal and postnatal exposure to active and secondhand smoke (SHS) and wheeze development up to 3 years of age. Multiple logistic regression analysis was performed to determine the association between tobacco smoke exposure and wheezing phenotypes in children.

RESULTS

We analyzed 73,057 singleton births and identified four longitudinal wheezing phenotypes: never wheezing; early transient wheezing (wheezing by age 1 year but not thereafter); late-onset wheezing (wheezing by age 2-3 years but not beforehand); and persistent wheezing. Maternal smoking during pregnancy was significantly associated with early transient and persistent wheezing in children compared with no maternal smoking [early transient wheezing: 1-10 cigarettes per day, adjusted odds ratio (aOR) 1.43, 95% confidence interval (CI) 1.23-1.66; ≥ 11 cigarettes per day, aOR 1.67, 95% CI 1.27-2.20; persistent wheezing: 1-10 cigarettes per day, aOR 1.64, 95% CI 1.37-1.97; ≥ 11 cigarettes per day, aOR 2.32, 95% CI 1.70-3.19]. Smoking cessation even before pregnancy was also significantly associated with increased risk of early transient wheezing, late-onset wheezing, and persistent wheezing in children. Moreover, maternal exposure to SHS during pregnancy was significantly associated with increased risk of early transient and persistent wheezing compared with no such exposure.

CONCLUSIONS

Maternal smoking before and throughout pregnancy was associated with wheeze development in children up to 3 years of age. It appears that smoking is detrimental compared to never smoking, regardless of whether individuals quit smoking before or after becoming aware of the pregnancy.

Drosophila melanogaster as an Alternative Model to Higher Organisms for In Vivo Lung Research

COPD and asthma are lung diseases that cause considerable burden to more than 800 million people worldwide. As both lung diseases are so far incurable, it is mandatory to understand the mechanisms underlying disease development and progression for developing novel therapeutic approaches. Exposures to environmental cues such as cigarette smoke in earliest life are known to increase disease risks in the individual's own future. To explore the pathomechanisms leading to later airway disease, mammalian models are instrumental. However, such in vivo experiments are time-consuming and burdensome for the animals, which applies in particular to transgenerational studies. Along this line, the fruit fly Drosophila melanogaster comes with several advantages for research in this field. The short lifespan facilitates transgenerational studies. A high number of evolutionary conserved signaling pathways, together with a large toolbox for tissue-specific gene modification, has the potential to identify novel target genes involved in disease development. A well-defined airway microbiome could help to untangle interactions between disease development and microbiome composition. In the following article, Drosophila melanogaster is therefore presented and discussed as an alternative in vivo model to investigate airway diseases that can complement and/or replace models in higher organisms.

Causal links between immune cells and asthma: Insights from a Mendelian Randomization analysis

OBJECTIVES

Recent studies suggest immunophenotypes may play a role in asthma, but their causal relationship has not been thoroughly examined.

METHODS

We used single nucleotide polymorphism (SNP)-derived instrumental variables. Summary data from 731 immune cell profiles and asthma cases were analyzed from genome-wide association studies (GWAS) of European populations. Mendelian Randomization (MR) analyses included inverse variance weighted (IVW), weighted median, and MR-Egger methods. Pleiotropy was assessed using the MR-Egger intercept and MR pleiotropy residual sum and outlier (MR-PRESSO) tests. Reverse MR analysis explored bidirectional causation between asthma and immunophenotypes. All statistical analyses were conducted using R software.

RESULTS

MR analysis identified 108 immune signatures potentially contributing to asthma. Two immunophenotypes were significantly associated with asthma risk: CD4+ secreting Treg cells in allergic asthma (ORIVW = 1.078; 95% CI: 1.036-1.122; PIVW = 0.0002) and IgD + CD38- %lymphocyte cells in non-allergic asthma (ORIVW = 1.123; 95% CI: 1.057-1.194; PIVW = 0.0002).

CONCLUSIONS

This study highlights the causal associations between specific immunophenotypes and asthma risk, providing new insights into asthma pathogenesis.

Effect of maternal cigarette smoke exposure on COPD progression in offspring mice

OBJECTIVE

To investigate the impact of maternal smoking on chronic obstructive pulmonary disease (COPD) progression in offspring.

METHODS

Using female C57BL/6 J mice, a maternal cigarette smoke exposure (CSE) model was established. Mice were exposed to cigarette smoke for 2 hours/day, 7 days/week, with a minimum 4-hour interval between exposures. Experimental groups included control (Con), pregnancy exposure (AS), pre-pregnancy exposure (SA), and pre-pregnancy + pregnancy exposure (SS). Lung function tests (Penh, PAU, TVb, EF50, Tr) were conducted on male offspring at 7 weeks. Histopathology, electron microscopy, and protein level changes were examined.

RESULTS

Lung function tests revealed significant impairments in Penh, PAU, TVb, EF50, and Tr in offspring across all exposure scenarios. Specifically, AS experienced significant lung function impairment and mitochondrial dysfunction in offspring, with noticeable pulmonary lesions and increased apoptosis. SA showed similar or even more severe lung function impairment and cellular apoptosis. SS exhibited the most pronounced effects, with the highest levels of lung dysfunction, mitochondrial damage, and apoptosis. Histopathological analysis showed pulmonary lesions in offspring exposed to maternal CSE. Flow cytometry revealed increased apoptosis and reduced mitochondrial membrane potential in offspring lung cells. Electron microscopy confirmed mitochondrial dysfunction. Upregulation of apoptotic proteins and downregulation of anti-apoptotic protein Bcl-2 were found in offspring lung tissue exposed to maternal CSE.

CONCLUSION

Maternal smoking induces impaired lung function, pulmonary lesions, and mitochondrial dysfunction in offspring, regardless of exposure timing and duration. Additionally, it alters expression of apoptosis-related proteins in offspring lung tissue, potentially contributing to COPD susceptibility.

Advancing geospatial preconception health research in primary care through medical informatics and artificial intelligence

Established life course approaches suggest that health status in adulthood can be influenced by events that occurred during the prenatal developmental period. Yet, interventions such as diet and lifestyle changes performed during pregnancy have had a small impact on both maternal and offspring health outcomes. Currently, there is a growing body of literature that highlights the importance of maternal health before conception (months or years before pregnancy occurs) for the future health of offspring. While some studies have explored factors such as maternal body composition, nutrition, and lifestyle in this area, location-based environmental and socioeconomic exposures before conception may also contribute to future offspring health. In this line, the study of a patient's geographic history presents a promising avenue. To foster research in this direction, the integration of geospatial health, medical informatics and artificial intelligence techniques offers great potential. Importantly, novel sources of big health data sets such as electronic health records registered at the primary care level provide a unique framework due to its inherent longitudinal nature. Nonetheless, a number of privacy, ethical, and technical challenges need to be overcome for this kind of longitudinal analysis to mature and succeed. In the long-term, we support the vision of incorporating a patient's geographic history into her clinical history to equip clinicians with useful contextual information to explore.

Contribution of the seminal microbiome to paternal programming

The field of Developmental Origins of Health and Disease has primarily focused on maternal programming of offspring health. However, emerging evidence suggests that paternal factors, including the seminal microbiome, could potentially play important roles in shaping the developmental trajectory and long-term offspring health outcomes. Historically, the microbes present in the semen were regarded as inherently pathogenic agents. However, this dogma has recently been challenged by the discovery of a diverse commensal microbial community within the semen of healthy males. In addition, recent studies suggest that the transmission of semen-associated microbes into the female reproductive tract during mating has potentials to not only influence female fertility and embryo development but could also contribute to paternal programming in the offspring. In this review, we summarize the current knowledge on the seminal microbiota in both humans and animals followed by discussing their potential involvement in paternal programming of offspring health. We also propose and discuss potential mechanisms through which paternal influences are transmitted to offspring via the seminal microbiome. Overall, this review provides insights into the seminal microbiome-based paternal programing, which will expand our understanding of the potential paternal programming mechanisms which are currently focused primarily on the epigenetic modifications, oxidative stresses, and cytokines.

Use of oral moist tobacco (snus) in puberty and its association with asthma in the population-based RHINESSA study

OBJECTIVES

To investigate the association of early snus use initiation (≤15 years of age) with asthma and asthma symptoms.

DESIGN

Cross-sectional analysis of a population-based cohort.

SETTING

Study centres in Norway, Sweden, Iceland, Denmark and Estonia, from 2016 to 2019.

PARTICIPANTS

9002 male and female participants above 15 years of age of the Respiratory Health in Northern Europe, Spain and Australia study.

MAIN OUTCOME MEASURES

Current asthma and asthma symptoms.

RESULTS

The median age of study participants was 28 years (range 15-53) and 58% were women. 20% had used snus, 29% men and 14% women. Overall, 26% of males and 14% of females using snus started ≤15 years of age. Early snus use initiation was associated with having three or more asthma symptoms (OR 2.70; 95% CI 1.46 to 5.00) and a higher asthma symptom score (β-coefficient (β) 0.35; 95% CI 0.07 to 0.63) in women. These associations were weak in men (OR 1.23; 95% CI 0.78 to 1.94; β 0.16; 95% CI -0.06 to 0.38, respectively). There was evidence for an association of early snus initiation with current asthma (OR 1.72; 95% CI 0.88 to 3.37 in women; OR 1.31; 95% CI 0.84 to 2.06 in men). A sensitivity analysis among participants without smoking history showed stronger estimates for all three outcomes, in both men and women, statistically significant for three or more asthma symptoms in women (OR 3.28; 95% CI 1.18 to 9.10). Finally, no consistent associations with asthma outcomes were found for starting snus after age 15 years.

CONCLUSIONS

Snus initiation in puberty was associated with higher likelihood of asthma and asthma symptoms, with the highest estimates in females and those without smoking history. These results raise concerns about the health adversities of early snus initiation and emphasise the need for public health initiatives to protect young people from this tobacco product.

Social determinants of respiratory health from birth: still of concern in the 21st century?

Respiratory symptoms are ubiquitous in children and, even though they may be the harbinger of poor long-term outcomes, are often trivialised. Adverse exposures pre-conception, antenatally and in early childhood have lifetime impacts on respiratory health. For the most part, lung function tracks from the pre-school years at least into late middle age, and airflow obstruction is associated not merely with poor respiratory outcomes but also early all-cause morbidity and mortality. Much would be preventable if social determinants of adverse outcomes were to be addressed. This review presents the perspectives of paediatricians from many different contexts, both high and low income, including Europe, the Americas, Australasia, India, Africa and China. It should be noted that there are islands of poverty within even the highest income settings and, conversely, opulent areas in even the most deprived countries. The heaviest burden of any adverse effects falls on those of the lowest socioeconomic status. Themes include passive exposure to tobacco smoke and indoor and outdoor pollution, across the entire developmental course, and lack of access even to simple affordable medications, let alone the new biologicals. Commonly, disease outcomes are worse in resource-poor areas. Both within and between countries there are avoidable gross disparities in outcomes. Climate change is also bearing down hardest on the poorest children. This review highlights the need for vigorous advocacy for children to improve lifelong health. It also highlights that there are ongoing culturally sensitive interventions to address social determinants of disease which are already benefiting children.

Causal associations between gut microbiota, metabolites and asthma: a two-sample Mendelian randomization study

BACKGROUND

While several traditional observational studies have suggested associations between gut microbiota and asthma, these studies are limited by factors such as participant selection bias, confounders, and reverse causality. Therefore, the causal relationship between gut microbiota and asthma remains uncertain.

METHODS

We performed two-sample bi-directional Mendelian randomization (MR) analysis to investigate the potential causal relationships between gut microbiota and asthma as well as its phenotypes. We also conducted MR analysis to evaluate the causal effect of gut metabolites on asthma. Genetic variants for gut microbiota were obtained from the MiBioGen consortium, GWAS summary statistics for metabolites from the TwinsUK study and KORA study, and GWAS summary statistics for asthma from the FinnGen consortium. The causal associations between gut microbiota, gut metabolites and asthma were examined using inverse variance weighted, maximum likelihood, MR-Egger, weighted median, and weighted model and further validated by MR-Egger intercept test, Cochran's Q test, and "leave-one-out" sensitivity analysis.

RESULTS

We identified nine gut microbes whose genetically predicted relative abundance causally impacted asthma risk. After FDR correction, significant causal relationships were observed for two of these microbes, namely the class Bacilli (OR = 0.84, 95%CI = 0.76-0.94, p = 1.98 × 10-3) and the order Lactobacillales (OR = 0.83, 95%CI = 0.74-0.94, p = 1.92 × 10-3). Additionally, in a reverse MR analysis, we observed a causal effect of genetically predicted asthma risk on the abundance of nine gut microbes, but these associations were no longer significant after FDR correction. No significant causal effect of gut metabolites was found on asthma.

CONCLUSIONS

Our study provides insights into the development mechanism of microbiota-mediated asthma, as well as into the prevention and treatment of asthma through targeting specific gut microbiota.

A conversation on allergy: recognizing the past and looking to the future

Allergy is an ever-evolving group of disorders, which includes asthma, atopic dermatitis, rhinitis and food allergies and that currently affects over 1 billion people worldwide. This group of disorders has exploded in incidence since around the start of the 20th century, implying that genetics is not solely responsible for its development but that environmental factors have an important role. Here, Fabio Luciani and Jonathan Coquet, in their role as editors at Immunology & Cell Biology, asked nine prominent researchers in the field of allergy to define the term 'allergy', discuss the role of genetics and the environment, nominate the most important discoveries of the past decade and describe the best strategies to combat allergy at the population level going forward.