Prenatal development is linked to bronchial reactivity: epidemiological and animal model evidence

The role of epigenetics in multi-generational transmission of asthma: An NIAID workshop report-based narrative review

There is mounting evidence that environmental exposures can result in effects on health that can be transmitted across generations, without the need for a direct exposure to the original factor, for example, the effect of grandparental smoking on grandchildren. Hence, an individual's health should be investigated with the knowledge of cross-generational influences. Epigenetic factors are molecular factors or processes that regulate genome activity and may impact cross-generational effects. Epigenetic transgenerational inheritance has been demonstrated in plants and animals, but the presence and extent of this process in humans are currently being investigated. Experimental data in animals support transmission of asthma risk across generations from a single exposure to the deleterious factor and suggest that the nature of this transmission is in part due to changes in DNA methylation, the most studied epigenetic process. The association of father's prepuberty exposure with offspring risk of asthma and lung function deficit may also be mediated by epigenetic processes. Multi-generational birth cohorts are ideal to investigate the presence and impact of transfer of disease susceptibility across generations and underlying mechanisms. However, multi-generational studies require recruitment and assessment of participants over several decades. Investigation of adult multi-generation cohorts is less resource intensive but run the risk of recall bias. Statistical analysis is challenging given varying degrees of longitudinal and hierarchical data but path analyses, structural equation modelling and multilevel modelling can be employed, and directed networks addressing longitudinal effects deserve exploration as an effort to study causal pathways.

Sex dependent effect of maternal e-nicotine on F1 Drosophila development and airways

E-cigarettes are heavily advertised as healthier alternative to common tobacco cigarettes, leading more and more women to switch from regular cigarettes to ENDS (electronic nicotine delivery system) during pregnancy. While the noxious consequences of tobacco smoking during pregnancy on the offspring health are well-described, information on the long-term consequences due to maternal use of e-cigarettes do not exist so far. Therefore, we aimed to investigate how maternal e-nicotine influences offspring development from earliest life until adulthood. To this end, virgin female Drosophila melanogaster flies were exposed to nicotine vapor (8 µg nicotine) once per hour for a total of eight times. Following the last exposure, e-nicotine or sham exposed females were mated with non-exposed males. The F1-generation was then analyzed for viability, growth and airway structure. We demonstrate that maternal exposure to e-nicotine not only leads to reduced maternal fertility, but also negatively affects size and weight, as well as tracheal development of the F1-generation, lasting from embryonic stage until adulthood. These results not only underline the need for studies investigating the effects of maternal vaping on offspring health, but also propose our established model for analyzing molecular mechanisms and signaling pathways mediating these intergenerational changes.

Early life growth and associations with lung function and bronchial hyperresponsiveness at 11-years of age

Low birthweight and being born small-for-gestational age (SGA) are linked to asthma and impaired lung function. Particularly, poor intrauterine growth followed by rapid catch-up growth during childhood may predispose for respiratory disease. Bronchial hyperresponsiveness (BHR) is an essential feature of asthma, but how foetal and early childhood growth are associated with BHR is less studied. Our hypothesis was that children born SGA or with accelerated early life growth have increased BHR and altered lung function at 11-years of age. We studied the associations between SGA and early childhood growth with lung function and BHR at 11-years of age in a subgroup of 468 children from the Norwegian Mother, Father and Child Cohort Study (MoBa), and included data from the Medical Birth Registry of Norway (MBRN). Weight at 6 months of age was positively associated with forced vital capacity (adjusted Beta: 0.121; 95% Confidence interval: 0.023, 0.219) and negatively associated with the ratio of forced expiratory flow in first second/forced vital capacity (-0.204; -0.317, -0.091) at 11-years of age. Similar patterns were found for weight at 36 months and for change in weight from birth to 6 months of age. SGA or other various variables of early childhood growth were not associated with BHR at 11-years of age. Early life growth was associated with an obstructive lung function pattern, but not with BHR in 11-year old children. Foetal growth restriction or weight gain during early childhood do not seem to be important risk factors for subsequent BHR in children.

Lung function and bronchial hyper-reactivity from 11 to 18 years in children with bronchiolitis in infancy

BACKGROUND

Various trajectories for lung function and bronchial hyper-reactivity (BHR) from early childhood to adulthood are described, including puberty as a period with excessive lung growth. Bronchiolitis in infancy may be associated with increased risk of developing chronic obstructive pulmonary disease, but the development of respiratory patterns during puberty is poorly characterized for these children. We aimed to study the development and trajectories of lung function and BHR from 11 to 18 years of age in children hospitalized for bronchiolitis in infancy.

METHODS

Infants hospitalized for bronchiolitis at the University Hospitals in Stavanger and Bergen, Norway, during 1997-1998, and an age-matched control group, were included in a longitudinal follow-up study and examined at 11 and 18 years of age with spirometry and methacholine provocation test (MPT). The MPT data were managed as dose-response slope (DRS) in the statistical analyses. Changes in lung function and DRS from 11 to 18 years of age were analyzed by generalized estimating equations, including interaction terms.

RESULTS

z-scores for forced vital capacity (FVC), forced expiratory volume in first second (FEV₁ ), FEV₁ /FVC ratio, and DRS were not different from 11 to 18 years of age in both the post-bronchiolitis and the control group. The trajectories from 11 to 18 years did not differ between the two groups. BHR at age 11 was independently associated with asthma at age 18.

CONCLUSION

Children hospitalized for bronchiolitis had stable predicted lung function and BHR from 11 to 18 years of age. The lung function trajectories were not different from controls.

Bronchial hyper-responsiveness in preterm-born subjects: A systematic review and meta-analysis

BACKGROUND

Preterm-born survivors have increased respiratory symptoms and decreased lung function, but the nature of bronchial hyper-responsiveness (BHR) is unclear. We conducted a systematic review and meta-analysis for BHR in preterm-born survivors including those with and without chronic lung disease in infancy (CLD) comparing results to term-born subjects.

METHODS

We searched eight databases up to December 2016. Included articles compared BHR in preterm-born and term-born subjects. Studies reporting BHR as decreases in forced expiratory volume in 1 second (FEV₁ ) after provocation stimuli were included. The analysis used Review Manager V5.3.

RESULTS

From 10 638 titles, 265 full articles were screened, and 28 included in a descriptive analysis. Eighteen articles were included in a meta-analysis as they reported the proportion of subjects who had BHR. Pooled odds ratio (OR) estimates (95% confidence interval) for BHR comparing the preterm and term-born groups was 1.88 (1.32, 2.66). The majority of the studies reported BHR after a methacholine challenge or an exercise test. Odds ratio was 1.89 (1.12, 3.19) after methacholine challenge and 2.59 (1.50, 4.50) after an exercise test. Nine of fifteen articles reporting BHR in CLD subjects were included in a meta-analysis. Differences for BHR including for methacholine (OR 4.35; 2.36, 8.03) and exercise (OR 5.13; 1.82, 14.47) were greater in the CLD group compared to the term group.

CONCLUSIONS

Preterm-born subjects especially those who had CLD had increased rates of BHR to direct (methacholine) and indirect (exercise) stimuli compared to term-born subjects suggesting subgroups might benefit from anti-inflammatory or bronchodilator therapies.

How best to capture the respiratory consequences of prematurity?

Chronic respiratory morbidity is a common complication of premature birth, generally defined by the presence of bronchopulmonary dysplasia, both clinically and in trials of respiratory therapies. However, recent data have highlighted that bronchopulmonary dysplasia does not correlate with chronic respiratory morbidity in older children born preterm. Longitudinally evaluating pulmonary morbidity from early life through to childhood provides a more rational method of defining the continuum of chronic respiratory morbidity of prematurity, and offers new insights into the efficacy of neonatal respiratory interventions. The changing nature of preterm lung disease suggests that a multimodal approach using dynamic lung function assessment will be needed to assess the efficacy of a neonatal respiratory therapy and predict the long-term respiratory consequences of premature birth. Our aim is to review the literature regarding the long-term respiratory outcomes of neonatal respiratory strategies, the difficulties of assessing dynamic lung function in infants, and potential new solutions.

Better measures are needed to predict chronic respiratory morbidity in survivors born prematurely http://ow.ly/1L3n30ihq9C

Bronchial hyper-responsiveness after preterm birth

Being born preterm often adversely affects later lung function. Airway obstruction and bronchial hyperresponsiveness (BHR) are common findings. Respiratory symptoms in asthma and in lung disease after preterm birth might appear similar, but clinical experience and studies indicate that symptoms secondary to preterm birth reflect a separate disease entity. BHR is a defining feature of asthma, but can also be found in other lung disorders and in subjects without respiratory symptoms. We review different methods to assess BHR, and findings reported from studies that have investigated BHR after preterm birth. The area appeared understudied with relatively few and heterogeneous articles identified, and lack of a pervasive understanding. BHR seemed related to low gestational age at delivery and a neonatal history of bronchopulmonary dysplasia. No studies reported associations between BHR after preterm birth and the markers of eosinophilic inflammatory airway responses typically found in asthma. This should be borne in mind when treating preterm born individuals with BHR and airway symptoms.

Resolvin E1, resolvin D1 and resolvin D2 inhibit constriction of rat thoracic aorta and human pulmonary artery induced by the thromboxane mimetic U46619

BACKGROUND AND PURPOSE

The ω-6 fatty acid-derived lipid mediators such as prostanoids, thromboxane and leukotrienes have well-established roles in regulating both inflammation and smooth muscle contractility. Resolvins are derived from ω-3 fatty acids and have important roles in promoting the resolution of inflammation, but their activity on smooth muscle contractility is unknown. We investigated whether resolvin E1 (RvE1), resolvin D1 (RvD1) and resolvin D2 (RvD2) can modulate contractions of isolated segments of rat thoracic aorta (RTA) or human pulmonary artery (HPA) induced by the α₁ -adrenoceptor agonist phenylephrine or the stable thromboxane A₂ mimetic U46619.

EXPERIMENTAL APPROACH

Contractile responses in RTA and HPA were measured using wire myography. Receptor expression was investigated by immunohistochemistry.

KEY RESULTS

Constriction of RTA segments by U46619, but not by phenylephrine, was significantly inhibited by pretreatment for 1 or 24 h with 10-100 nM RvE1, RvD1 or RvD2. The inhibitory effect of RvE1 was partially blocked by a chemerin receptor antagonist (CCX832). RvE1 at only 1-10 nM also significantly inhibited U46619-induced constriction of HPA segments, and the chemerin receptor, GPR32 and FPR2/ALX were identified in HPA smooth muscle.

CONCLUSION AND IMPLICATIONS

These data suggest that resolvins or their mimetics may prove useful novel therapeutics in diseases such as pulmonary arterial hypertension, which are characterized by increased thromboxane contractile activity.

Increased Bronchial Hyperresponsiveness and Higher Asymmetric Dimethylarginine Levels after Fetal Growth Restriction

Bronchial hyperresponsiveness (BHR), a feature of asthma, is observed in preterm-born children and has been linked to intrauterine growth restriction. BHR is mediated via airway smooth muscle tone and is modulated by the autonomic nervous system, nitric oxide, and airway inflammation. Interactions among these factors are insufficiently understood. Methacholine-induced BHR (Met-BHR), fractional exhaled NO, and systemic soluble markers of nitric oxide metabolism and inflammation were determined in a population-based sample of 57 eleven-year-old children born extremely preterm (gestational age [GA] < 28 wk) or with extremely low birth weight (<1,000 g), and in a matched normal-birth weight term-born control group (n = 54). Bronchopulmonary dysplasia (BPD) was defined as the need for oxygen treatment at a GA of 36 weeks. In preterm-born children, birth weight below the 10th percentile for GA was associated with increased Met-BHR and higher plasma levels of asymmetric dimethylarginine (ADMA), with an increased odds ratio for being in the upper tertile of Met-BHR (11.8; 95% confidence interval, 3.3-42.4) and of ADMA (5.2; 95% confidence interval, 1.3-20.3). Met-BHR was correlated to ADMA level (r = 0.27, P = 0.007). There were no significant differences in Met-BHR, fractional exhaled NO, or z-FEV₁ according to BPD status. No associations with systemic soluble markers of inflammation were observed for Met-BHR, birth, or BPD status. Intrauterine growth restriction in preterm-born children was associated with substantially increased Met-BHR and higher ADMA levels, suggesting altered nitric oxide regulation. These findings contribute to the understanding of the consequences from an adverse fetal environment; they should also be tested in term-born children.

Does allergy begin in utero?

It has been recognized for centuries that allergic disease runs in families, implying a role for genetic factors in determining individual susceptibility. More recently, a range of evidence shows that many of these genetic factors, together with in utero environmental exposures, lead to the development of allergic disease through altered immune and organ development. Environmental exposures during pregnancy including diet, nutrient intake and toxin exposures can alter the epigenome and interact with inherited genetic and epigenetic risk factors to directly and indirectly influence organ development and immune programming. Understanding of these factors will be essential in identifying at-risk individuals and possible development of therapeutic interventions for the primary prevention of allergic disease. In this review, we summarize the evidence that suggests allergic disease begins in utero, together with possible mechanisms for the effect of environmental exposures during pregnancy on allergic disease risk, including epigenetics.