Environmental factors and developmental outcomes in the lung

Ozone as u-shaped dose responses molecules (hormetins)

Redox environment involves a broad network of pro-oxidant and antioxidant components. Health benefit or damage can be induced as a consequence of an adaptive cellular stress response. A consequence of hormetic amplification is an increase in the homeodynamic space of a living system in terms of an increased defense capacity and a reduced load of damaged macromolecules. Ozone, when used at appropriate doses, promotes the formation of reactive oxygen species and lipid peroxides allows them to become late and long-lasting messengers. Healthy aging may be achieved by hormesis through mild and periodic, but not severe or chronic, physical and mental challenges, and by the use of nutritional hormesis incorporating mild stress-inducing molecules called hormetins. The paradoxical concept that ozone eventually induces an antioxidant response capable of reversing a chronic oxidative stress is common in the animal and vegetal kingdom; it is already supported by findings of an increased level of antioxidant enzymes during ozone therapy. Those facts can include ozone as a hormetin. The established scientific foundations of hormesis are ready to pave the way for new and effective approaches in redox-related disease research and intervention; ozone therapy can be a good candidate.

Early alterations in cytokine expression in adult compared to developing lung in mice after radiation exposure

To assess early changes in the lung after low-dose radiation exposure that may serve as targets for mitigation of lung injury in the aftermath of a terrorist event, we analyzed cytokine expression after irradiation. Adult mice were studied after whole-lung or total-body irradiation. Mouse pups of different ages were also investigated after total-body irradiation. mRNA abundance was analyzed in tissue and plasma, and pathological changes were assessed. In lung tissue, dose-related changes were seen in IL1B, IL1R2 and CXCR2 mRNA expression at 1 and 6 h after irradiation, concurrent with increases in plasma protein levels of KC/CXCL1 and IL6. However, in the pups, changes in IL1 abundance were not detected until 28 days of age, coincident with the end of postnatal lung growth, although apoptosis was detected at all ages. In conclusion, although cytokines were expressed after low doses of radiation, their role in the progression of tissue response is yet to be determined. They may be candidates for use in marker-based biodosimetry. However, the lack of cytokine induction in early life suggests that different end points (and mitigating treatments) may be required for children.

Perinatal stress and early life programming of lung structure and function

Exposure to environmental toxins during critical periods of prenatal and/or postnatal development may alter the normal course of lung morphogenesis and maturation, potentially resulting in changes that affect both structure and function of the respiratory system. Moreover, these early effects may persist into adult life magnifying the potential public health impact. Aberrant or excessive pro-inflammatory immune responses, occurring both locally and systemically, that result in inflammatory damage to the airway are a central determinant of lung structure-function changes throughout life. Disruption of neuroendocrine function in early development, specifically the hypothalamic-pituitary-adrenal (HPA) axis, may alter functional status of the immune system. Autonomic nervous system (ANS) function (sympathovagal imbalance) is another integral component of airway function and immunity in childhood. This overview discusses the evidence linking psychological factors to alterations in these interrelated physiological processes that may, in turn, influence childhood lung function and identifies gaps in our understanding.

Who is affected more by air pollution-sick or healthy? Some evidence from a health survey of schoolchildren living in the vicinity of a coal-fired power plant in Northern Israel

OBJECTIVE

To evaluate the effects of exposure to air pollution by NO(x) and SO(2) on the development of pulmonary function of children, characterized by different health status.

METHODS

A cohort of 1181 schoolchildren from the 2nd to 5th grades, residing near a major coal-fired power plant in the Hadera district of Israel, were subdivided into three health status groups, according to the diagnosis given by a physician at the beginning of the study period in 1996: (a) healthy children; (b) children experiencing chest symptoms, and (c) children with asthma or spastic bronchitis. Pulmonary Function Tests (PFTs) were performed twice (in 1996 and 1999) and analyzed in conjunction with air pollution estimates at the children's places of residence and several potential confounders-height, age, gender, parental education, passive smoking, housing density, length of residence in the study area and proximity to the main road.

RESULTS

A significant negative association was found between changes in PFT results and individual exposure estimates to air pollution, controlled for socio-demographic characteristics of children and their living conditions. A sensitivity analysis revealed a decrease in the Forced Expiratory Volume during the First Second (FEV(1)) of about 19.6% for children with chest symptoms, 11.8% for healthy children, and approximately 7.9% for children diagnosed with asthma. Results of a sensitivity test for the Forced Vital Capacity (FVC) were found to be similar.

CONCLUSION

Exposure to air pollution appeared to have had the greatest effect on children with chest symptoms. This phenomenon may be explained by the fact that this untreated symptomatic group might experience the most severe insult on their respiratory system as a result of exposure to ambient air pollution, which is reflected by a considerable reduction in their FEV(1) and FVC. Since asthmatic children have lower baseline and slower growth rates, their PFT change may be affected less by exposure to air pollution, reflecting a well known relationship between pulmonary function change and height growth, according to which age-specific height is very similar for preadolescent children, but shifts upward with age during the growth spurt.

Review Series: What goes around, comes around: childhood influences on later lung health?: Relationship between environmental exposures in children and adult lung disease: The case for outdoor exposures

There is a growing understanding that chronic respiratory diseases in adults have their origins in early life. Adverse environmental exposures occurring in vulnerable periods during lung growth and development in the fetal period and in early childhood that alter lung structure and limit the growth in lung function may have lifelong consequences. Evidence is increasing that exposure to the ambient environment, including air pollutants, persistent toxic substances, water pollutants and respiratory viral infections, can inhibit lung function growth and predispose to chronic non-malignant lung diseases. These exposures generally interact with a genetic predisposition, and gene—environment interactions and epigenetic phenomena are attracting considerable study. An understanding of how ambient exposures impact on normal lung growth and development will aid in understanding of how chronic respiratory diseases of adults develop and may lead to new preventative strategies.

Neonatal oxygen adversely affects lung function in adult mice without altering surfactant composition or activity

Despite its potentially adverse effects on lung development and function, supplemental oxygen is often used to treat premature infants in respiratory distress. To understand how neonatal hyperoxia can permanently disrupt lung development, we previously reported increased lung compliance, greater alveolar simplification, and disrupted epithelial development in adult mice exposed to 100% inspired oxygen fraction between postnatal days 1 and 4. Here, we investigate whether oxygen-induced changes in lung function are attributable to defects in surfactant composition and activity, structural changes in alveolar development, or both. Newborn mice were exposed to room air or 40%, 60%, 80%, or 100% oxygen between postnatal days 1 and 4 and allowed to recover in room air until 8 wk of age. Lung compliance and alveolar size increased, and airway resistance, airway elastance, tissue elastance, and tissue damping decreased, in mice exposed to 60-80% oxygen; changes were even greater in mice exposed to 100% oxygen. These alterations in lung function were not associated with changes in total protein content or surfactant phospholipid composition in bronchoalveolar lavage. Moreover, surface activity and total and hydrophobic protein content were unchanged in large surfactant aggregates centrifuged from bronchoalveolar lavage compared with control. Instead, the number of type II cells progressively declined in 60-100% oxygen, whereas levels of T1alpha, a protein expressed by type I cells, were comparably increased in mice exposed to 40-100% oxygen. Thickened bundles of elastin fibers were also detected in alveolar walls of mice exposed to > or = 60% oxygen. These findings support the hypothesis that changes in lung development, rather than surfactant activity, are the primary causes of oxygen-altered lung function in children who were exposed to oxygen as neonates. Furthermore, the disruptive effects of oxygen on epithelial development and lung mechanics are not equivalently dose dependent.

Choice of environmental components for a longitudinal birth cohort study

Various aspects of the environment of the mother and child may have major influences on the health and development of the child. Long-term influences can even affect chronic diseases of adulthood. Here we describe the major psychosocial and physical environmental factors that should be measured in longitudinal birth cohort studies.

Early-life environment, developmental immunotoxicology, and the risk of pediatric allergic disease including asthma

Incidence of childhood allergic disease including asthma (AD-A) has risen since the mid-20th century with much of the increase linked to changes in environment affecting the immune system. Childhood allergy is an early life disease where predisposing environmental exposures, sensitization, and onset of symptoms all occur before adulthood. Predisposition toward allergic disease (AD) is among the constellation of adverse outcomes following developmental immunotoxicity (DIT; problematic exposure of the developing immune system to xenobiotics and physical environmental factors). Because novel immune maturation events occur in early life, and the pregnancy state itself imposes certain restrictions on immune functional development, the period from mid-gestation until 2 years after birth is one of particular concern relative to DIT and AD-A. Several prenatal-perinatal risk factors have been identified as contributing to a DIT-mediated immune dysfunction and increased risk of AD. These include maternal smoking, environmental tobacco smoke, diesel exhaust and traffic-related particles, heavy metals, antibiotics, environmental estrogens and other endocrine disruptors, and alcohol. Diet and microbial exposure also significantly influence immune maturation and risk of allergy. This review considers (1) the critical developmental windows of vulnerability for the immune system that appear to be targets for risk of AD, (2) a model in which the immune system of the DIT-affected infant exhibits immune dysfunction skewed toward AD, and (3) the lack of allergy-relevant safety testing of drugs and chemicals that could identify DIT hazards and minimize problematic exposure of pregnant women and children.

Variation in the GST mu locus and tobacco smoke exposure as determinants of childhood lung function

RATIONALE

The glutathione S-transferases (GSTs) are important detoxification enzymes.

OBJECTIVES

To investigate effects of variants in GST mu genes on lung function and assess their interactions with tobacco smoke exposure.

METHODS

In this prospective study, 14,836 lung function measurements were collected from 2,108 children who participated in two Southern California cohorts. For each child, tagging single nucleotide polymorphisms in GSTM2, GSTM3, GSTM4, and GSTM5 loci were genotyped. Using principal components and haplotype analyses, the significance of each locus in relation to level and growth of FEV1, maximum midexpiratory flow rate (MMEF), and FVC was evaluated. Interactions between loci and tobacco smoke on lung function were also investigated.

MEASUREMENTS AND MAIN RESULTS

Variation in the GST mu family locus was associated with lower FEV1 (P = 0.01) and MMEF (0.04). Two haplotypes of GSTM2 were associated with FEV1 and MMEF, with effect estimates in opposite directions. One haplotype in GSTM3 showed a decrease in growth for MMEF (-164.9 ml/s) compared with individuals with other haplotypes. One haplotype in GSTM4 showed significantly decreased growth in FEV1 (-51.3 ml), MMEF (-69.1 ml/s), and FVC (-44.4 ml), compared with all other haplotypes. These results were consistent across two independent cohorts. Variation in GSTM2 was particularly important for FVC and FEV(1) among children whose mothers smoked during pregnancy.

CONCLUSIONS

Genetic variation across the GST mu locus is associated with 8-year lung function growth. Children of mothers who smoked during pregnancy and had variation in GSTM2 had lower lung function growth.

Chronic exposure to ambient levels of urban particles affects mouse lung development

RATIONALE

Chronic exposure to air pollution has been associated with adverse effects on children's lung growth.

OBJECTIVES

We analyzed the effects of chronic exposure to urban levels of particulate matter (PM) on selected phases of mouse lung development.

METHODS

The exposure occurred in two open-top chambers (filtered and nonfiltered) placed 20 m from a street with heavy traffic in São Paulo, 24 hours/day for 8 months. There was a significant reduction of the levels of PM(2.5) inside the filtered chamber (filtered = 2.9 +/- 3.0 microg/m(3), nonfiltered = 16.8 +/- 8.3 microg/m(3); P = 0.001). At this exposure site, vehicular sources are the major components of PM(2.5) (PM <or= 2.5 microm). Exposure of the parental generation in the two chambers occurred from the 10th to the 120th days of life. After mating and birth of offspring, a crossover of mothers and pups occurred within the chambers, resulting in four groups of pups: nonexposed, prenatal, postnatal, and pre+postnatal. Offspring were killed at the age of 15 (n = 42) and 90 (n = 35) days; lungs were analyzed by morphometry for surface to volume ratio (as an estimator of alveolization). Pressure-volume curves were performed in the older groups, using a 20-ml plethysmograph.

MEASUREMENTS AND MAIN RESULTS

Mice exposed to PM(2.5) pre+postnatally presented a smaller surface to volume ratio when compared with nonexposed animals (P = 0.036). The pre+postnatal group presented reduced inspiratory and expiratory volumes at higher levels of transpulmonary pressure (P = 0.001). There were no differences among prenatal and postnatal exposure and nonexposed animals.

CONCLUSIONS

Our data provide anatomical and functional support to the concept that chronic exposure to urban PM affects lung growth.

Detrimental effects of tobacco smoke exposure during development on postnatal lung function and asthma

Exposure to environmental tobacco smoke (ETS) during fetal development and early postnatal life is perhaps the most ubiquitous and hazardous of children's environmental exposures. The developing lung is highly susceptible to ETS. A large body of literature links both prenatal maternal smoking and children's ETS exposure to decreased lung growth. This review summarizes the state of the knowledge, including both human epidemiology and laboratory animal experiments, linking ETS, lung development, and respiratory outcomes. Important issues discussed include lung development and lung function and asthma in relation to ETS exposure during critical windows of growth. Prenatal exposure to ETS is associated with impaired lung function and increased risk of developing asthma, whereas postnatal exposure mainly acts to trigger respiratory symptoms and asthma attacks, but it also plays an important role in the occurrence of asthma in children. This review provides evidence that avoidance of ETS exposure both before and after birth is beneficial to long-term respiratory health, because airway function in later life is believed to be largely determined by lung development occurring in utero and in early infancy.

Lung growth and development

Human lung growth starts as a primitive lung bud in early embryonic life and undergoes several morphological stages which continue into postnatal life. Each stage of lung growth is a result of complex and tightly regulated events governed by physical, environmental, hormonal and genetic factors. Fetal lung liquid and fetal breathing movements are by far the most important determinants of lung growth. Although timing of the stages of lung growth in animals do not mimic that of human, numerous animal studies, mainly on sheep and rat, have given us a better understanding of the regulators of lung growth. Insight into the genetic basis of lung growth has helped us understand and improve management of complex life threatening congenital abnormalities such as congenital diaphragmatic hernia and pulmonary hypoplasia. Although advances in perinatal medicine have improved survival of preterm infants, premature birth is perhaps still the most important factor for adverse lung growth.

Arterial stiffness is independently associated with emphysema severity in patients with chronic obstructive pulmonary disease

RATIONALE

More patients with chronic obstructive pulmonary disease (COPD) die of cardiovascular causes than of respiratory causes, and patients with COPD have increased morbidity and mortality from stroke and coronary heart disease. Arterial stiffness independently predicts cardiovascular risk, is associated with atheromatous plaque burden, and is increased in patients with COPD compared with control subjects matched for cardiovascular risk factors. Elastin fragmentation and changes in collagen are found in the connective tissue of both emphysematous lungs and stiff arteries, but it is not known whether the severity of arterial stiffness in patients with COPD is associated with the severity of emphysema.

OBJECTIVES

To identify whether the extent of arterial stiffness is associated with emphysema severity.

METHODS

We performed a cross-sectional study in 157 patients with COPD.

MEASUREMENTS AND MAIN RESULTS

We measured pulse wave velocity (a validated measure of arterial stiffness), blood pressure, smoking pack-years, glucose, cholesterol, and C-reactive protein in 157 patients with COPD. We assessed emphysema using quantitative computed tomography scanning in a subgroup of 73 patients. We found that emphysema severity was associated with arterial stiffness (r = 0.471, P < 0.001). The association was independent of smoking, age, sex, FEV(1)% predicted, highly sensitive C-reactive protein and glucose concentrations, cholesterol-high-density lipoprotein ratio, and pulse oximetry oxygen saturations.

CONCLUSIONS

Emphysema severity is associated with arterial stiffness in patients with COPD. Similar pathophysiological processes may be involved in both lung and arterial tissue and further studies are now required to identify the mechanism underlying this newly described association.

Poor airway function in early infancy and lung function by age 22 years: a non-selective longitudinal cohort study

BACKGROUND

Together with smoking, the lung function attained in early adulthood is one of the strongest predictors of chronic obstructive pulmonary disease. We aimed to investigate whether lung function in early adulthood is, in turn, affected by airway function measured shortly after birth.

METHODS

Non-selected infants were enrolled at birth in the Tucson Children's Respiratory Study between 1980 and 1984. We measured maximal expiratory flows at functional residual capacity (Vmax(FRC)) in 169 of these infants by the chest compression technique at a mean of 2.3 months (SD 1.9). We also obtained measurements of lung function for 123 of these participants at least once at ages 11, 16, and 22 years. Indices were forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and forced expiratory flow between 25% and 75% of FVC (FEF25-75), both before and after treatment with a bronchodilator (180 microg of albuterol).

FINDINGS

Participants who had infant Vmax(FRC) in the lowest quartile also had lower values for the FEV1/FVC ratio (-5.2%, p<0.0001), FEF25-75 (-663 mL/s, p<0.0001), and FEV1 (-233 mL, p=0.001) up to age 22, after adjustment for height, weight, age, and sex, than those in the upper three quartiles combined. The magnitude and significance of this effect did not change after additional adjustment for wheeze, smoking, atopy, or parental asthma.

INTERPRETATION

Poor airway function shortly after birth should be recognised as a risk factor for airflow obstruction in young adults. Prevention of chronic obstructive pulmonary disease might need to start in fetal life.