Influence of farming exposure on the development of asthma and asthma-like symptoms

Influence of Farm Environment on Asthma during the Life Course: A Population-Based Birth Cohort Study in Northern Finland

We investigated the influence of a farming environment on asthma at three time points from birth to 46 years using the Northern Finland Birth Cohort 1966 (n = 10,926). The prevalence of asthma was investigated by postal questionnaires at 14, 31 and 46 years of age. Exposure to a farming environment was assessed by a postal questionnaire at birth and at 31 and 46 years of age. Odds ratios (ORs) and their 95% confidence intervals (95% CIs) for the prevalence of asthma were obtained from multinomial logistic regression, stratified by sex. Being born in a farmer family was potentially causally associated with lower risk of asthma in males at 31 years of age (OR 0.56, 95% CI 0.37, 0.85) and in females at 46 years of age (OR 0.64, 95% CI 0.44, 0.95). Working as a farmer was not associated with asthma. Exposure to a farming environment in childhood may have a lifelong impact on developing asthma from birth through young adulthood and until middle age, indicating that 'immune deviation' may persist throughout life.

CC16 polymorphisms in asthma, asthma subtypes, and asthma control in adults from the Agricultural Lung Health Study

BACKGROUND

The club cell secretory protein (CC16) has anti-inflammatory and antioxidant effects and is a potential early biomarker of lung damage. The CC16 single nucleotide polymorphism (SNP) rs3741240 risk allele (A) has been inconsistently linked to asthma; other tagging SNPs in the gene have not been explored. The aim was to determine whether CC16 tagging polymorphisms are associated with adult asthma, asthma subtypes or asthma control in the Agricultural Lung Health Study (ALHS).

METHODS

The ALHS is an asthma case-control study nested in the Agricultural Health Study cohort. Asthma cases were individuals with current doctor diagnosed asthma, likely undiagnosed asthma, or asthma-COPD overlap defined by questionnaire. We also examined asthma subtypes and asthma control. Five CC16 tagging SNPs were imputed to 1000 Genomes Integrated phase 1 reference panel. Logistic regression was used to estimate associations between CC16 SNPs and asthma outcomes adjusted for covariates.

RESULTS

The sample included 1120 asthma cases and 1926 controls of European ancestry, with a mean age of 63 years. The frequency of the risk genotype (AA) for rs3741240 was 12.5% (n = 382). CC16 rs3741240 was not associated with adult asthma outcomes. A tagging SNP in the CC16 gene, rs12270961 was associated with uncontrolled asthma (n = 208, ORadj= 1.4, 95% CI 1.0, 1.9; p = 0.03).

CONCLUSION

This study, the largest study to investigate associations between CC16 tagging SNPs and asthma phenotypes in adults, did not confirm an association of rs3741240 with adult asthma. A tagging SNP in CC16 suggests a potential relationship with asthma control.

Prevalence and risk factors of asthma in dairy farmers: Ancillary analysis of AIRBAg

BACKGROUND

Prolonged occupational agricultural exposure is associated with an increase in asthma diagnosis. This study aimed to identify the prevalence and risk factors for asthma in dairy farmers.

METHODS

AIRBAg was a cross-sectional study including 1203 representative dairy farmers. They completed a self-administered questionnaire and underwent a health respiratory check-up. Referral to a pulmonologist was made for any participant with wheezing, dyspnoea, chronic bronchitis, a chronic cough or a FEV₁/FEV₆ ratio<80%. They underwent further examinations such as spirometry with a reversibility test. Controls (non-asthmatic dairy farmers and non-farm employees) were matched to each asthma case for sex and age (±5 years). The odds ratios (OR) between asthma and different risk factors were estimated using conditional multivariate logistic regression models.

RESULTS

Active asthma was diagnosed in 107 (8.9%) farmers. Compared with control dairy farmers, there was a positive association with family history of allergy (OR = 8.68; 95% CI [4.26-17.69]), personal history of eczema (OR = 3.39; 95% CI [1.61-7.13]), hay manipulation (OR = 5.36, 95% CI [1.59-18.01]), and a negative association with farm area (OR = 0.92; 95% CI [0.85-0.99]) and handling treated seeds (OR = 0.47; 95% CI [0.23-0.95]). Compared with control non-farm employees, there was a positive association between asthma and family history of allergy (OR = 95.82, 95% CI [12.55-731.47]).

CONCLUSIONS

The prevalence of active asthma in dairy farmers was somewhat higher than the rate observed in the general population but may be controlled by reducing exposure to airborne organic contaminants through occupational adaptions on farms.

Respiratory and allergic health effects in children living near agriculture: A review

BACKGROUND

Exposure to pesticides and agricultural burning are likely to co-occur in agricultural communities, but these exposures have remained distinct bodies of research. We reviewed epidemiological studies to identify the respiratory health effects of children exposed to pesticides and agricultural burning through a systematic evaluation of peer-reviewed publications of children living in industrial agricultural areas.

METHODS

Two academic search databases (PubMed and Scopus) were queried for all available studies published in English before May 31st, 2021. The initial search combining both exposure metrics (pesticides and agricultural burning) yielded zero publications and thus the queries were performed and presented separately.

RESULTS

Studies were categorized based on main exposure of interest (i.e., pesticides or agricultural burning) and by respiratory health outcome assessment (i.e., self-reported asthma, acute respiratory symptoms, and lung function measurements). In total we identified 25 studies that focused on pesticide exposures and children's respiratory health, and 12 studies that focused on exposure to agricultural burning and children's respiratory health. A majority of the pesticide studies (18/25) reported a positive association between exposure to pesticides and adverse childhood respiratory health effects. Similarly, most (11/12) of the agricultural burning studies also reported a positive association between exposure to agricultural burning and adverse respiratory health effects.

CONCLUSION

The most frequently studied health outcomes in these publications were acute respiratory symptoms (n = 11 pesticides, n = 3 agricultural burning), followed by asthma (n = 9 pesticides, n = 3 agricultural burning), and lung function measurements (n = 5 pesticides, n = 6 agricultural burning). Although health outcome assessment differed between pesticide studies and agricultural burning studies, similar adverse respiratory health effects were observed across the majority of studies.

Influence of Childhood Exposure to a Farming Environment on Age at Asthma Diagnosis in a Population-Based Study

Purpose

Asthma is a heterogeneous disease, and factors associated with different asthma phenotypes are poorly understood. Given the higher prevalence of farming exposure and late diagnosis of asthma in more rural Western Finland as compared with the capital of Helsinki, we investigated the relationship between childhood farming environment and age at asthma diagnosis.

Methods

A cross-sectional population-based study was carried out with subjects aged 20–69 years in Western Finland. The response rate was 52.5%. We included 3864 participants, 416 of whom had physician-diagnosed asthma at a known age and with data on the childhood environment. The main finding was confirmed in a similar sample from Helsinki. Participants were classified as follows with respect to asthma diagnosis: early diagnosis (0–11 years), intermediate diagnosis (12–39 years), and late diagnosis (40–69 years).

Results

The prevalence of asthma was similar both without and with childhood exposure to a farming environment (11.7% vs 11.3%). Allergic rhinitis, family history of asthma, ex-smoker, occupational exposure, and BMI ≥ 30 kg/m² were associated with a higher likelihood of asthma. Childhood exposure to a farming environment did not increase the odds of having asthma (aOR, 1.10; 95% CI, 0.87–1.40). It did increase the odds of late diagnosis (aOR, 2.30; 95% CI, 1.12–4.69), but the odds were lower for early (aOR, 0.49; 95% CI, 0.30–0.80) and intermediate diagnosis of asthma (aOR, 0.75; 95% CI, 0.47–1.18).

Conclusion

Odds were lower for early diagnosis of asthma and higher for late diagnosis of asthma in a childhood farming environment. This suggests a new hypothesis concerning the etiology of asthma when it is diagnosed late.

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The role of innate immunity in asthma development and protection: Lessons from the environment

Asthma, a complex, chronic disease characterized by airway inflammation, hyperresponsiveness and remodelling, affects over 300 million people worldwide. While the disease is typically associated with exaggerated allergen-induced type 2 immune responses, these responses are strongly influenced by environmental exposures that stimulate innate immune pathways capable of promoting or protecting from asthma. The dual role played by innate immunity in asthma pathogenesis offers multiple opportunities for both research and clinical interventions and is the subject of this review.

Nutritional Factors in Occupational Lung Disease

PURPOSE OF REVIEW

Lung diseases such as asthma and COPD are major public health issues and related to occupational exposures. While therapies to limit the development and progression of these diseases are limited, nutrition interventions could offer potential alternatives to mediate the inflammation associated with these diseases. This is a narrative review of the current state of relevant nutrients on inflammation and respiratory outcomes associated with occupational exposures.

RECENT FINDINGS

Relevant nutrients that have been investigated in recent years include omega-3 polyunsaturated fatty acids, zinc, vitamin D, dairy products, and antioxidants. These nutrients have demonstrated the potential to prevent or modify the adverse outcomes associated with occupational exposures, primarily in preclinical studies. Current therapies for respiratory consequences associated with occupational exposures are limited; therefore, addressing strategies for reducing inflammation is important in improving quality of life and limiting health care costs. More human studies are warranted to determine the effectiveness of nutrition as an intervention.

Association of Agricultural, Occupational, and Military Inhalants With Autoantibodies and Disease Features in US Veterans With Rheumatoid Arthritis

OBJECTIVE

To determine the association of inhalant exposures with rheumatoid arthritis (RA)-related autoantibodies and severity in US veterans.

METHODS

Participants in the Veterans Affairs Rheumatoid Arthritis (VARA) registry were mailed surveys assessing occupational, agricultural, and military inhalant exposures. Demographic characteristics, disease activity, functional status, and extraarticular features were obtained from the VARA registry, while HLA-DRB1 shared epitope (SE) status, anti-cyclic citrullinated peptide (anti-CCP) antibodies, and rheumatoid factor (RF) were measured using banked DNA/serum from enrollment. Associations between inhalant exposures and RA-related factors (autoantibodies, severity, and extraarticular features) were assessed using multivariable linear and logistic regression models adjusted for age, sex, race, and tobacco use and stratified by SE status. Adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

Questionnaires were returned by 797 of 1,566 participants (50.9%). Survey respondents were older, more often White or male, and less frequently smokers, and had lower disease activity compared to nonrespondents. Anti-CCP positivity was more common among veterans exposed to burn pits (OR 1.66 [95% CI 1.02, 2.69]) and military waste disposal (OR 1.74 [95% CI 1.04, 2.93]) independent of other factors. Among participants who were positive for SE alleles, burn pit exposure (OR 5.69 [95% CI 2.73, 11.87]) and military waste disposal exposure (OR 5.05 [95% CI 2.42, 10.54]) were numerically more strongly associated with anti-CCP positivity. Several inhalant exposures were associated with the presence of chronic lung disease, but not with the presence of RF or the level of disease activity.

CONCLUSION

Military burn pit exposure and military waste disposal exposure were independently associated with the presence of anti-CCP antibodies in RA patients. These findings are consistent with emerging evidence that various inhalant exposures influence autoantibody expression and RA risk.

A Review of Potential Public Health Impacts Associated With the Global Dairy Sector

Strong demand for dairy products has led to a global increase in dairy production. In many parts of the world, dairy systems are undergoing rapid intensification. While increased production may contribute to food security, higher dairy stocking rates in some regions have resulted in increased pressure on natural resources with the potential to affect public health and wellbeing. The aim of this review was to identify and describe the potential health harms and benefits associated with dairy production and consumption. Electronic databases Medline, Embase, Scopus, Web of Science, PubMed, and Google Scholar were searched for published literature that investigated human health impacts of dairy production and consumption. Occupational hazards, environmental health impacts, ecosystem health impacts, foodborne hazards, and diet-related chronic diseases were identified as potential public health hazards. Some impacts, notably climate change, extend beyond directly exposed populations. Dairy production and consumption are also associated with important health benefits through the provision of nutrients and economic opportunities. As the global dairy sector increases production, exposure to a range of hazards must be weighed with these benefits. The review of impacts presented here can provide an input into decision making about optimal levels of dairy production and consumption, local land use, and identification and management of specific hazards from this sector. Future research should consider multiple exposure routes, socioeconomic implications, and environmental factors, particularly in regions heavily dependent on dairy farming.

Amphiregulin modulates murine lung recovery and fibroblast function following exposure to agriculture organic dust

Exposure to agricultural bioaerosols can lead to chronic inflammatory lung diseases. Amphiregulin (AREG) can promote the lung repair process but can also lead to fibrotic remodeling. The objective of this study was to determine the role of AREG in altering recovery from environmental dust exposure in a murine in vivo model and in vitro using cultured human and murine lung fibroblasts. C57BL/6 mice were intranasally exposed to swine confinement facility dust extract (DE) or saline daily for 1 wk or allowed to recover for 3-7 days while being treated with an AREG-neutralizing antibody or recombinant AREG. Treatment with the anti-AREG antibody prevented resolution of DE exposure-induced airway influx of total cells, neutrophils, and macrophages and increased levels of TNF-α, IL-6, and CXCL1. Neutrophils and activated macrophages (CD11c+CD11bhi) persisted after recovery in lung tissues of anti-AREG-treated mice. In murine and human lung fibroblasts, DE induced the release of AREG and inflammatory cytokines. Fibroblast recellularization of primary human lung mesenchymal matrix scaffolds and wound closure was inhibited by DE and enhanced with recombinant AREG alone. AREG treatment rescued the DE-induced inhibitory fibroblast effects. AREG intranasal treatment for 3 days during recovery phase reduced repetitive DE-induced airway inflammatory cell influx and cytokine release. Collectively, these studies demonstrate that inhibition of AREG reduced, whereas AREG supplementation promoted, the airway inflammatory recovery response following environmental bioaerosol exposure, and AREG enhanced fibroblast function, suggesting that AREG could be targeted in agricultural workers repetitively exposed to organic dust environments to potentially prevent and/or reduce disease.

Microbial interactions in the atopic march

The human body is populated by a large number of microorganisms and exist in symbiosis with these immensely diverse communities, which are suggested to influence health and disease. The microbiota plays an essential role in the maturation and function of the immune system. The prevalence of atopic diseases has increased drastically over the past decades, and the co-occurrence of multiple allergic diseases and allergic sensitization starting in early life has gained a great deal of attention. Immune responses in different organs affected by allergic diseases (e.g. skin, intestine and lung) may be linked to microbial changes in peripheral tissues. In the current review, we provide an overview of the current understanding of microbial interactions in allergic diseases and their potential role in the atopic march.

Ovalbumin-sensitized mice have altered airway inflammation to agriculture organic dust

Agriculture exposures are associated with reducing the risk of allergy and asthma in early life; yet, repeated exposures later in life are associated with chronic bronchitis and obstructive pulmonary diseases. The objective of this study was to investigate the airway inflammatory response to organic dust extract (ODE) in mice with established ovalbumin (OVA)-induced experimental asthma. C57BL/6 mice were either OVA sensitized/aerosol-exposed or saline (Sal) sensitized/aerosol-challenged. Both groups were then subsequently challenged once with intranasal saline or swine confinement ODE to obtain 4 treatment groups of Sal-Sal, Sal-ODE, OVA-Sal, and OVA-ODE. Airway hyper-responsiveness (AHR) to methacholine, bronchiolar lavage fluid, lung tissues, and serum were collected. Intranasal inhalation of ODE in OVA-treated (asthmatic) mice (OVA-ODE) increased AHR and total cellular influx marked by elevated neutrophil and eosinophil counts. Flow cytometry analysis further demonstrated that populations of CD11chi dendritic cells (DC), CD3+ T cells, CD19+ B cells, and NKp46+ group 3 innate lymphoid cells (ILC3) were increased in lavage fluid of OVA-ODE mice as compared to ODE or OVA alone. Alveolar macrophages, DC, and T cells were significantly increased with co-exposure to OVA-ODE as compared to OVA alone. Lung ILC2 and ILC3 were only increased in OVA-Sal mice. Cytokine/chemokine levels varied with exposure to OVA-ODE reflecting an additive mixture of the pro- and allergic-inflammatory profiles. Collectively, ODE increased airway inflammatory cells and chemotactic mediator release in allergic (OVA) sensitized mice to suggest that persons with allergy/asthma be identified and warned prior to the occupational exposure of potentially worsening airway disease.

Asthma diagnosis among children along an urban-rural gradient

OBJECTIVE

Studies have reported lower asthma prevalence in rural compared to urban areas. While environmental factors have mostly been implicated for these differences, the lower asthma prevalence could also be linked to asthma under-diagnosis in rural children. We investigate if rural children experience under-diagnosis of asthma more compared to urban children.

METHODS

In 2013, we conducted a cross-sectional survey of schoolchildren across an urban-rural gradient in Saskatchewan, Canada. The participants formed sampling frame for future studies. In 2015, we approached those who gave consent in 2013 for further testing, repeated the survey, and conducted clinical testing. Based on survey responses, children were classified into "no asthma," "at-risk-for-asthma," and "diagnosed asthma." We then classified asthma status as either "no asthma" or "probable asthma" based on a validated asthma algorithm.

RESULTS

The study population of 335 schoolchildren (aged 7-17 years) comprised of 73.4% from large urban, 13.7% from small urban, and 12.8% from rural areas. Proportion with report of physician-diagnosed asthma was 28.5% (Large urban), 34.8% (Small urban), and 20.9% (Rural). Mean percent predicted FEV₁ and FEF_25%-75% were lower in rural compared to small urban and large urban children (p < 0.05). Among those not classified as with "diagnosed asthma" by the survey, the algorithm further identified presence of asthma in 5.5% large urban, 8.1% small urban, and 18.8% rural children (p = 0.03).

CONCLUSION

The study revealed evidence of asthma underdiagnosis in rural areas and further supports the use of objective measures in addition to symptoms history when investigating asthma across urban-rural gradients.

Rural Asthma: Current Understanding of Prevalence, Patterns, and Interventions for Children and Adolescents

PURPOSE OF REVIEW

Asthma is the most common chronic illness of children and adolescents in the USA. While asthma has been understood to disproportionately affect urban dwellers, recent investigations have revealed rural pediatric asthma prevalence to be very similar to urban and to be more closely correlated with socioeconomic and environmental factors than geographic location or population density.

RECENT FINDINGS

Rural children experience factors unique to location that impact asthma development and outcomes, including housing quality, cigarette smoke exposure, and small/large-scale farming. Additionally, there are challenging barriers to appropriate asthma care that frequently are more severe for those living in rural areas, including insurance status, lack of primary care providers and pulmonary specialists, knowledge deficits (both patient and provider), and a lack of culturally tailored asthma interventions. Interventions designed to address rural pediatric asthma disparities are more likely to be successful when targeted to specific challenges, such as the use of school-based services or telemedicine to mitigate asthma care access issues. Continued research on understanding the complex interaction of specific rural environmental factors with host factors can inform future interventions designed to mitigate asthma disparities.

A principal factor analysis to characterize agricultural exposures among Nebraska veterans

Agricultural workers are at an increased risk of developing chronic respiratory disorders. Accurate estimation of long-term agricultural exposures based on questionnaires has been used to improve the validity of epidemiologic investigations and subsequent evaluation of the association between agricultural exposures and chronic diseases. Our aim was to use principal factor analysis (PFA) to distill exposure data into essential variables characterizing long-term agricultural exposures. This is a cross-sectional study of veterans between the ages of 40 and 80 years and who worked on a farm for ≥2 years. Participant characteristics were: 98.1% were white males with a mean age 65±8 (SD) years and 39.8% had chronic obstructive pulmonary disease. The final model included four factors and explained 16.6% of the variance in the exposure data. Factor 1 was a heterogeneous factor; however, Factor 2 was exclusively composed of exposure to livestock such as hogs, dairy and poultry. Factor 3 included exposures from jobs on or off the farm such as wood dust, mineral dust, asbestos and spray paint. Crop exposure loaded exclusively in Factor 4 and included lifetime hours of exposure and maximum number of acres farmed in the participants' lifetime. The factors in the final model were interpretable and consistent with farming practices.

Childhood asthma, asthma severity indicators, and related conditions along an urban-rural gradient: a cross-sectional study

BACKGROUND

Asthma prevalence is generally lower in rural locations with some indication of an urban-rural gradient. However, among children with asthma, certain rural exposures thought to protect against the development of asthma could aggravate the condition. We examined childhood asthma prevalence and related conditions along an urban-rural gradient and also examined the characteristics of those with asthma along the urban-rural gradient.

METHODS

In 2013 we completed a cross-sectional survey of 3509 children aged 5-14 years living in various population densities of Saskatchewan, Canada. Location of dwelling was identified as belonging to one of the following population densities: large urban region (approximately 200,000), small urban (approximately 35,000), or rural (small town of <1,500 or farm dweller). Physician-diagnosed asthma and asthma-related symptoms were ascertained from responses in the parental-completed questionnaires.

RESULTS

Of the study population, 69% lived in a large urban region, 11% lived in a small urban centre and 20% were rural dwellers. Overall, asthma prevalence was 19.6% with differences in asthma prevalence with differences between locations (large urban = 20.7%; small urban = 21.5%; rural = 15.1%; p = 0.003). After adjustment for potential confounders, the association between location of dwelling and asthma remained significant. Despite a lower prevalence of asthma in the rural area, the prevalence and risk of ever wheeze and having more than 3 wheezing episodes in the past 12 months among those who reported asthma, was higher in rural locations after adjustment for potential confounders.

CONCLUSIONS

The results of this study support the evidence of a difference in childhood asthma prevalence between urban and rural locations and that once a child has asthma, certain rural exposures may aggravate the disease.

The Urban-Rural Gradient In Asthma: A Population-Based Study in Northern Europe

The early life environment appears to have a persistent impact on asthma risk. We hypothesize that environmental factors related to rural life mediate lower asthma prevalence in rural populations, and aimed to investigate an urban-rural gradient, assessed by place of upbringing, for asthma. The population-based Respiratory Health In Northern Europe (RHINE) study includes subjects from Denmark, Norway, Sweden, Iceland and Estonia born 1945–1973. The present analysis encompasses questionnaire data on 11,123 RHINE subjects. Six categories of place of upbringing were defined: farm with livestock, farm without livestock, village in rural area, small town, city suburb and inner city. The association of place of upbringing with asthma onset was analysed with Cox regression adjusted for relevant confounders. Subjects growing up on livestock farms had less asthma (8%) than subjects growing up in inner cities (11%) (hazard ratio 0.72 95% CI 0.57–0.91), and a significant urban-rural gradient was observed across six urbanisation levels (p = 0.02). An urban-rural gradient was only evident among women, smokers and for late-onset asthma. Analyses on wheeze and place of upbringing revealed similar results. In conclusion, this study suggests a protective effect of livestock farm upbringing on asthma development and an urban-rural gradient in a Northern European population.

Age Impacts Pulmonary Inflammation and Systemic Bone Response to Inhaled Organic Dust Exposure

Agricultural workers have high rates of airway and skeletal health disease. Studies recently demonstrated that inhaled agricultural organic dust extract (ODE)-induced airway injury is associated with bone deterioration in an animal model. However, the effect of age in governing these responses to organic dusts is unclear, but might be important in future approaches. Young (7-9 wk) and older (12-14,o) male C57BL/6 mice received intranasal (i.n.) inhalation exposure to ODE from swine confinement facilities once or daily for 3 wk. Acute ODE-induced neutrophil influx and cytokine and chemokine (tumor necrosis factor [TNF]-α, interleukin [IL]-6, keratinocyte chemoattractant [CXCL1], macrophage inflammatory protein-2 [CXCL2]) airway production were reduced in older compared to young mice. Repetitive ODE treatment, however, increased lymphocyte recruitment and alveolar compartment histopathologic inflammatory changes in older mice. Whole lung cell infiltrate analysis revealed that young, but not older, mice repetitively treated with ODE demonstrated an elevated CD4:CD8 lymphocyte response. Acute inhalant ODE exposure resulted in a 4-fold and 1.5-fold rise in blood neutrophils in young and older mice, respectively. Serum IL-6 and CXCL1 levels were elevated in young and older mice i.n. exposed once to ODE, with increased CXCL1 levels in younger compared to older mice. Although older mice displayed reduced bone measurements compared to younger mice, younger rodents demonstrated ODE-induced decrease in bone mineral density, bone volume, and bone microarchitecture quality as determined by computed tomography (CT) analysis. Collectively, age impacts the airway injury and systemic inflammatory and bone loss response to inhalant ODE, suggesting an altered and enhanced immunologic response in younger as compared to older counterparts.

MyD88 in lung resident cells governs airway inflammatory and pulmonary function responses to organic dust treatment

Inhalation of organic dusts within agriculture environments contributes to the development and/or severity of airway diseases, including asthma and chronic bronchitis. MyD88 KO (knockout) mice are nearly completely protected against the inflammatory and bronchoconstriction effects induced by acute organic dust extract (ODE) treatments. However, the contribution of MyD88 in lung epithelial cell responses remains unclear. In the present study, we first addressed whether ODE-induced changes in epithelial cell responses were MyD88-dependent by quantitating ciliary beat frequency and cell migration following wounding by electric cell-substrate impedance sensing. We demonstrate that the normative ciliary beat slowing response to ODE is delayed in MyD88 KO tracheal epithelial cells as compared to wild type (WT) control. Similarly, the normative ODE-induced slowing of cell migration in response to wound repair was aberrant in MyD88 KO cells. Next, we created MyD88 bone marrow chimera mice to investigate the relative contribution of MyD88-dependent signaling in lung resident (predominately epithelial cells) versus hematopoietic cells. Importantly, we demonstrate that ODE-induced airway hyperresponsiveness is MyD88-dependent in lung resident cells, whereas MyD88 action in hematopoietic cells is mainly responsible for ODE-induced TNF-α release. MyD88 signaling in lung resident and hematopoietic cells are necessary for ODE-induced IL-6 and neutrophil chemoattractant (CXCL1 and CXCL2) release and neutrophil influx. Collectively, these findings underscore an important role for MyD88 in lung resident cells for regulating ciliary motility, wound repair and inflammatory responses to ODE, and moreover, show that airway hyperresponsiveness appears uncoupled from airway inflammatory consequences to organic dust challenge in terms of MyD88 involvement.

A Review of the CD4+ T Cell Contribution to Lung Infection, Inflammation and Repair with a Focus on Wheeze and Asthma in the Pediatric Population

Childhood asthma and wheezing are very common, especially in those born preterm. Genetic and environmental factors are associated with developing asthma and wheezing. Respiratory syncytial virus and rhinovirus infections have been implicated in playing a causal role in the development of childhood asthma and wheezing, perhaps by altering the development of the immune system. Several subtypes of asthma and wheezing have been described which involve different mechanisms of pathophysiology. Much of the recent work in the field of asthma research has focused on describing unique aspects of these disease subtypes, which could lead to new drug targets. Alterations in CD4+ T cells have been described with alterations in the T helper 1, 2, 17 and regulatory cell balance could provide valuable targets for the development of new treatment strategies for the various subtypes of disease. This review article focuses on factors involved in childhood asthma and wheeze and potential drug targets.