Early Airway Pathological Changes in Children: New Insights into the Natural History of Wheezing

The Diverging Trend in Exposure to Environmental Tobacco Smoke Among US Children

OBJECTIVE

Environmental tobacco smoke exposure (ETSE) was race/ethnicity-specific, but how the race/ethnicity-specific ETSE has changed over time, diverging or converging, remains unclear. We examined ETSE trends by race/ethnicity in US children aged 3-11 years.

METHODS

We analyzed the data of 9678 children who participated in the biennial National Health and Nutrition Examination Surveys, 1999-2018. ETSE was defined as serum cotinine ≥ 0.05 ng/ml, with ≥ 1 ng/ml as heavy exposure. For trend description, adjusted biennial prevalence ratios (abiPR: the ratio associated with a 2-year increase in time) were estimated by race/ethnicity. The prevalence ratios between races/ethnicities were used to quantify ethnoracial differences in different survey periods. Analyses were performed in 2021.

RESULTS

The overall ETSE prevalence was cut by almost half, from 61.59% (95% confidence interval = 56.55%, 66.62%) in the 1999-2004 survey to 37.61% (33.90%, 41.31%) in 2013-2018, exceeding the national 2020 health target (47.0%). However, the decrease occurred unequally between races/ethnicities. Heavy ETSE declined significantly in white [abiPR = 0.80 (0.74, 0.86)] and Hispanic children [0.83 (0.74, 0.93)], but insignificantly in black children [0.97 (0.92, 1.03)]. Consequently, the adjusted prevalence ratio between black children and white children increased from 0.82 (0.47, 1.44) in 1999-2004 to 2.73 (1.51, 4.92) in 2013-2018 for heavy ETSE. Hispanic children remained at the lowest risk throughout the study period.

CONCLUSION

Overall ETSE prevalence was cut by half between 1999 and 2018. However, due to uneven declines, the gaps between black children and others have expanded in heavy ETSE. Special vigilance is needed in preventive medicine practice with black children.

Extracellular Vesicles (EVs) as Crucial Mediators of Cell-Cell Interaction in Asthma

Asthma is the most common chronic respiratory disorder worldwide and accounts for a huge health and economic burden. Its incidence is rapidly increasing but, in parallel, novel personalized approaches have emerged. Indeed, the improved knowledge of cells and molecules mediating asthma pathogenesis has led to the development of targeted therapies that significantly increased our ability to treat asthma patients, especially in severe stages of disease. In such complex scenarios, extracellular vesicles (EVs i.e., anucleated particles transporting nucleic acids, cytokines, and lipids) have gained the spotlight, being considered key sensors and mediators of the mechanisms controlling cell-to-cell interplay. We will herein first revise the existing evidence, mainly by mechanistic studies in vitro and in animal models, that EV content and release is strongly influenced by the specific triggers of asthma. Current studies indicate that EVs are released by potentially all cell subtypes in the asthmatic airways, particularly by bronchial epithelial cells (with different cargoes in the apical and basolateral side) and inflammatory cells. Such studies largely suggest a pro-inflammatory and pro-remodelling role of EVs, whereas a minority of reports indicate protective effects, particularly by mesenchymal cells. The co-existence of several confounding factors-including technical pitfalls and host and environmental confounders-is still a major challenge in human studies. Technical standardization in isolating EVs from different body fluids and careful selection of patients will provide the basis for obtaining reliable results and extend their application as effective biomarkers in asthma.

Chronic lung diseases: entangled in extracellular matrix

The extracellular matrix (ECM) is the scaffold that provides structure and support to all organs, including the lung; however, it is also much more than this. The ECM provides biochemical and biomechanical cues to cells that reside or transit through this micro-environment, instructing their responses. The ECM structure and composition changes in chronic lung diseases; how such changes impact disease pathogenesis is not as well understood. Cells bind to the ECM through surface receptors, of which the integrin family is one of the most widely recognised. The signals that cells receive from the ECM regulate their attachment, proliferation, differentiation, inflammatory secretory profile and survival. There is extensive evidence documenting changes in the composition and amount of ECM in diseased lung tissues. However, changes in the topographical arrangement, organisation of the structural fibres and stiffness (or viscoelasticity) of the matrix in which cells are embedded have an undervalued but strong impact on cell phenotype. The ECM in diseased lungs also changes in physical and biomechanical ways that drive cellular responses. The characteristics of these environments alter cell behaviour and potentially orchestrate perpetuation of lung diseases. Future therapies should target ECM remodelling as much as the underlying culprit cells.

"Reactance inversion" at low frequencies during lung function measurement by impulse oscillometry in children with persistent asthma. J Asthma 2021;59:1597-1603. [PMID: 34255601 DOI: 10.1080/02770903.2021.1955376]

BACKGROUND

Small airway dysfunction (SAD) in asthma can be measured by impulse oscillometry (IOS). Usually, the reactance should decrease with decreases in frequency oscillation. Sometimes an upward shift of the curve at low frequencies can be observed together with lower than expected reactance values. The actual value of the reactance at 5 Hz (X5) is calculated by the Sentry Suite application of the Jaeger Master screen iOS system™, providing the corrected X5 parameter (CX5). Our hypothesis is that correction of X5 is common in persistent asthma and it correlates better than X5 with the IOS parameters for evaluating SAD.

METHODS

In this transversal study, we evaluated 507 children (3-18 years old) using IOS-spirometry (Sentry Suite, Vyntus®). Resistance of all airways (R5), reactance area (AX), resonant frequency (Fres), X5, CX5, difference between R5 and R20 (D5-20), and spirometry parameters were analyzed. Reactance inversion and CX5 prevalence by age range was determined. The mean IOS-Spyrometry values in children with and without CX5 were compared, and correlations with each IOS-spirometry parameter in the age groups were performed.

RESULTS

CX5 was found in 83.5% of preschool children, 66.2% of schoolchildren, and 43.3% of adolescents (p < 0.001). The means of R5, AX, and D5-20 were significantly higher and FEV1 was significantly lower in children with CX5 (p < 0.05). In all ages, CX5 correlated better than X5 with IOS-spirometry parameters.

CONCLUSION

Reactance inversion and CX5 are frequent in asthmatic children, decrease with age, and correlate more closely than X5 with other IOS-spirometry parameters for evaluating SAD.

Cigarette Smoke Exposure, Pediatric Lung Disease, and COVID-19

The detrimental effects of tobacco exposure on children's health are well known. Nonetheless, the prevalence of secondhand or direct cigarette smoke exposure (CSE) in the pediatric population has not significantly decreased over time. On the contrary, the rapid incline in use of e-cigarettes among adolescents has evoked public health concerns since increasing cases of vaping-induced acute lung injury have highlighted the potential harm of these new "smoking" devices. Two pediatric populations are especially vulnerable to the detrimental effects of cigarette smoke. The first group is former premature infants whose risk is elevated both due to their prematurity as well as other risk factors such as oxygen and mechanical ventilation to which they are disproportionately exposed. The second group is children and adolescents with chronic respiratory diseases, in particular asthma and other wheezing disorders. Coronavirus disease 2019 (COVID-19) is a spectrum of diseases caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has spread worldwide over the last year. Here, respiratory symptoms ranging from mild to acute respiratory distress syndrome (ARDS) are at the forefront of COVID-19 cases among adults, and cigarette smoking is associated with worse outcomes in this population, and cigarette smoking is associated with worse outcomes in this population. Interestingly, SARS-CoV-2 infection affects children differently in regard to infection susceptibility, disease manifestations, and complications. Although children carry and transmit the virus, the likelihood of symptomatic infection is low, and the rates of hospitalization and death are even lower when compared to the adult population. However, multisystem inflammatory syndrome is recognized as a serious consequence of SARS-CoV-2 infection in the pediatric population. In addition, recent data demonstrate specific clinical patterns in children infected with SARS-CoV-2 who develop multisystem inflammatory syndrome vs. severe COVID-19. In this review, we highlight the pulmonary effects of CSE in vulnerable pediatric populations in the context of the ongoing SARS-CoV-2 pandemic.

Parental educational level and childhood wheezing and asthma: A prospective cohort study from the Japan Environment and Children's Study

BACKGROUND

The influence of mothers' and fathers' educational levels in separate evaluations of asthma has not been fully investigated. This study aims to examine the associations of the mother's and fathers' educational levels with childhood wheeze and asthma adjusting for crude and pre-and post-natal modifiable risk factors.

METHODS

We conducted a prospective cohort study using data from the Japan Environment and Children's Study, which recruited pregnant women from 2011 to 2014. The mother's and father's educational levels were surveyed by a questionnaire during the pregnancy, and childhood wheezing and doctor-diagnosed asthma were estimated using a 3-year questionnaire. Multilevel logistic regression analysis was performed to evaluate the association between the mother's and father's educational levels and childhood wheezing and asthma, adjusted for pre-and post-natal factors.

RESULTS

A total of 69,607 pairs of parents and their single infants were analyzed. We found 17.3% of children had wheezing and 7.7% had asthma. In crude analyses, lower educational level of parents was associated with an increased risk of childhood wheezing and asthma. After full adjustment, a lower educational level of mothers was associated with an increased risk of childhood asthma (junior high school (reference: high school); odds ratio (OR): 1.17, 95% CI, 1.01-1.36), and higher educational level, especially the mother's, was associated with an increased risk of childhood wheezing (technical junior college, technical/vocational college, or associate degree (ECD3); OR: 1.12, 95% CI, 1.06-1.18, bachelor's degree, or postgraduate degree; OR: 1.10, 95% CI, 1.03-1.18), and asthma (ECD3; OR: 1.13, 95% CI, 1.04-1.21).

CONCLUSIONS

Parents' lower educational level was a crude risk factor for childhood wheezing and asthma. However, an increased risk of wheezing due to mothers' higher educational level was found after adjusting for pre-and post-natal factors.

Secreted heat shock proteins control airway remodeling: Evidence from bronchial thermoplasty

BACKGROUND

Increased airway smooth muscle mass is a key pathology in asthma. Bronchial thermoplasty is a treatment for severe asthma based on selective heating of the airways that aims to reduce the mass of airway smooth muscle cells (ASMCs), and thereby bronchoconstriction. However, short heat exposure is insufficient to explain the long-lasting effect, and heat shock proteins (HSPs) have been suggested to play a role.

OBJECTIVE

We sought to determine the role of HSP70 and HSP90 in the control of airway wall remodeling by bronchial thermoplasty.

METHODS

Bronchoalveolar lavage fluid and endobronchial biopsies of 20 patients with severe asthma were obtained before and after thermoplasty. Isolated epithelial cells and ASMCs were exposed to 65^oC for 10 seconds, mimicking thermoplasty. Proteins were determined by immunohistochemistry, Western blotting, immunofluorescence, and ELISA; proliferation by cell counts and antigen Ki67 (MKI67) expression.

RESULTS

Thermoplasty significantly increased the expression of HSP70 and HSP90 in the epithelium and bronchoalveolar lavage fluid. In ASMCs, thermoplasty reduced both HSPs. These cell-type-specific effects were detectable even 1 month after thermoplasty in tissue sections. In epithelial cells, ex vivo exposure to heat (65^oC, 10 seconds) increased the expression and secretion of HSP70 and HSP90. In addition, epithelial cell proliferation was upregulated by heat or treatment with human recombinant HSP70 or HSP90. In ASMCs, heat exposure or exogenous HSPs reduced proliferation and differentiation. In both cell types, HSP70 and HSP90 activated the signaling cascade of serine/threonine-protein kinase →mammalian target of rapamycin→ribosomal protein S6 kinase 1 and CCAAT/enhancer binding protein-β→protein arginine methyltransferase 1→ mitochondria activity.

CONCLUSIONS

Epithelial cell-derived HSP70 and HSP90 improve the function of epithelial cells, but block ASMC remodeling.

Mitochondrial Function in Peripheral Blood Mononuclear Cells (PBMC) Is Enhanced, Together with Increased Reactive Oxygen Species, in Severe Asthmatic Patients in Exacerbation

Asthma is a chronic inflammatory lung syndrome with an increasing prevalence and a rare but significant risk of death. Its pathophysiology is complex, and therefore we investigated at the systemic level a potential implication of oxidative stress and of peripheral blood mononuclear cells’ (PBMC) mitochondrial function. Twenty severe asthmatic patients with severe exacerbation (GINA 4–5) and 20 healthy volunteers participated at the study. Mitochondrial respiratory chain complexes activities using different substrates and reactive oxygen species (ROS) production were determined in both groups by high-resolution respirometry and electronic paramagnetic resonance, respectively. Healthy PBMC were also incubated with a pool of plasma of severe asthmatics or healthy controls. Mitochondrial respiratory chain complexes activity (+52.45%, p = 0.015 for V_ADP) and ROS production (+34.3%, p = 0.02) were increased in asthmatic patients. Increased ROS did not originate mainly from mitochondria. Plasma of severe asthmatics significantly increased healthy PBMC mitochondrial dioxygen consumption (+56.8%, p = 0.031). In conclusion, such asthma endotype, characterized by increased PMBCs mitochondrial oxidative capacity and ROS production likely related to a plasma constituent, may reflect activation of the immune system. Further studies are needed to determine whether increased PBMC mitochondrial respiration might have protective effects, opening thus new therapeutic approaches.