Increased ENaC-mediated liquid absorption across vitamin-D deficient human airway epithelia

Vitamin D deficiency is a risk factor for exacerbation of obstructive airway disease, a hallmark of which is mucus dehydration and plugging. Calcitriol (the active form of vitamin D) deficiency in cultured human airway epithelia resulted in increased SCNN1G and ATP1B1 mRNAs encoding subunits of ENaC and the Na-K pump compared with supplemented epithelia. These drive the absorption of airway surface liquid. Consistently, calcitriol-deficient epithelia absorbed liquid faster than supplemented epithelia. Calcitriol deficiency also increased amiloride-sensitive Isc and Gt without altering Na-K pump activity, indicating the changes in amiloride-sensitivity arose from ENaC. ENaC activity can be regulated by trafficking, proteases, and channel abundance. We found the effect was likely not induced by changes to endocytosis of ENaC given that calcitriol did not affect the half-lives of amiloride-sensitive Isc and Gt. Furthermore, trypsin nominally increased Isc produced by epithelia ± calcitriol, suggesting calcitriol did not affect proteolytic activation of ENaC. Consistent with mRNA and functional data, calcitriol deficiency resulted in increased γENaC protein. These data indicate that the vitamin D receptor response controls ENaC function and subsequent liquid absorption, providing insight into the relationship between vitamin D deficiency and respiratory disease.NEW & NOTEWORTHY It is unknown why calcitriol (active vitamin D) deficiency worsens pulmonary disease outcomes. Results from mRNA, immunoblot, Ussing chamber, and absorption experiments indicate that calcitriol deficiency increases ENaC activity in human airway epithelia, decreasing apical hydration. Given that epithelial hydration is required for mucociliary transport and airway innate immune function, the increased ENaC activity observed in calcitriol-deficient epithelia may contribute to respiratory pathology observed in vitamin D deficiency.

Imaging-based assessment of lung function in a population cooking indoors with biomass fuel: a pilot study

Biomass fuels (wood) are commonly used indoors in underventilated environments for cooking in the developing world, but the impact on lung physiology is poorly understood. Quantitative computed tomography (qCT) can provide sensitive metrics to compare the lungs of women cooking with wood vs. liquified petroleum gas (LPG). We prospectively assessed (qCT and spirometry) 23 primary female cooks (18 biomass, 5 LPG) with no history of cardiopulmonary disease in Thanjavur, India. CT was obtained at coached total lung capacity (TLC) and residual volume (RV). qCT assessment included texture-derived ground glass opacity [GGO: Adaptive Multiple Feature Method (AMFM)], air-trapping (expiratory voxels ≤ -856HU) and image registration-based assessment [Disease Probability Measure (DPM)] of emphysema, functional small airways disease (%AirTrapDPM), and regional lung mechanics. In addition, within-kitchen exposure assessments included particulate matter <2.5 μm(PM2.5), black carbon, β-(1, 3)-d-glucan (surrogate for fungi), and endotoxin. Air-trapping went undetected at RV via the threshold-based measure (voxels ≤ -856HU), possibly due to density shifts in the presence of inflammation. However, DPM, utilizing image-matching, demonstrated significant air-trapping in biomass vs. LPG cooks (P = 0.049). A subset of biomass cooks (6/18), identified using k-means clustering, had markedly altered DPM-metrics: greater air-trapping (P < 0.001), lower TLC-RV volume change (P < 0.001), a lower mean anisotropic deformation index (ADI; P < 0.001), and elevated % GGO (P < 0.02). Across all subjects, a texture measure of bronchovascular bundles was correlated to the log-transformed β-(1, 3)-d-glucan concentration (P = 0.026, R = 0.46), and black carbon (P = 0.04, R = 0.44). This pilot study identified environmental links with qCT-based lung pathologies and a cluster of biomass cooks (33%) with significant small airways disease.NEW & NOTEWORTHY Quantitative computed tomography has identified a cluster of women (33%) cooking with biomass fuels (wood) with image-based markers of functional small airways disease and associated alterations in regional lung mechanics. Texture and image registration-based metrics of lung function may allow for early detection of potential inflammatory processes that may arise in response to inhaled biomass smoke, and help identify phenotypes of chronic lung disease prevalent in nonsmoking women in the developing world.

Vitamin D-mediated effects on airway innate immunity in vitro

INTRODUCTION

Vitamin D supplementation has been suggested to enhance immunity during respiratory infection season. We tested the effect of active vitamin D (calcitriol) supplementation on key airway innate immune mechanisms in vitro.

METHODS

Primary human airway epithelial cells (hAECs) grown at the air liquid interface were supplemented with 10-7 M calcitriol for 24 hours (or a time course) and their antimicrobial airway surface liquid (ASL) was tested for pH, viscoscity, and antibacterial and antiviral properties. We also tested hAEC ciliary beat frequency (CBF). Next, we assessed alterations to hAEC gene expression using RNA sequencing, and based on results, we measured neutrophil migration across hAECs.

RESULTS

Calcitriol supplementation enhanced ASL bacterial killing of Staphylococcus aureus (p = 0.02) but did not enhance its antiviral activity against 229E-CoV. It had no effect on ASL pH or viscosity at three timepoints. Lastly, it did not affect hAEC CBF or neutrophil migration, although there was a trend of enhanced migration in the presence of a neutrophil chemokine (p = 0.09). Supplementation significantly altered hAEC gene expression, primarily of AMP-related genes including CAMP and TREM1.

CONCLUSION

While vitamin D supplementation did not have effects on many airway innate immune mechanisms, it may provide a useful tool to resolve respiratory bacterial infections.

Observed vs. self-reported agricultural activities: Evaluating 24-hr recall in a pilot study

Few studies have evaluated the validity of self-report of work activities because of challenges in obtaining objective measures. In this study, farmers' recall of the previous day's agricultural activities was compared to activities observed by field staff during air monitoring. Recall was assessed in 32 farmers from the Biomarkers of Exposure and Effect in Agriculture Study, a subset of a prospective cohort study. The farmers participated in 56 visits that comprised air monitoring the day before an interview. The answers for 14 agricultural activities were compared to activities observed by field staff during air monitoring (median duration 380 min, range 129-486). For each task, evaluated as yes/no, overall agreement, sensitivity, specificity, and kappa were calculated. Median prevalence of the 14 activities was 8% from observation and 13% from participants (range: 2-54%). Agreement was generally good to perfect, with a median overall agreement of 95% (range: 89-100%), median sensitivity of 84% (50-100%), median specificity of 95% (88-100%), and median kappa of 0.65 (0.31-1.0). Reasons for disagreement included activities occurring when the field staff was not present (i.e., milking cows), unclear timing notes that made it difficult to determine whether the activity occurred the day of and/or day before the interview, definition issues (i.e., participant included hauling in the definition of harvesting), and difficulty in observing details of an activity (i.e., whether hay was moldy). This study provides support for accurate participant recall the day after activities.

Urban particulate matter impairs airway-surface-liquid-mediated coronavirus inactivation

Air pollution particulate matter (PM) is associated with SARS-CoV-2 infection and severity, although mechanistic studies are lacking. We tested whether airway surface liquid (ASL) from primary human airway epithelial cells is antiviral against SARS-CoV-2 and human alphacoronavirus 229E (CoV-229E) (responsible for common colds), and whether PM (urban, indoor air pollution [IAP], volcanic ash) affected ASL antiviral activity. ASL inactivated SARS-CoV-2 and CoV-229E. Independently, urban PM also decreased SARS-CoV-2 and CoV-229E infection, and IAP PM decreased CoV-229E infection. However, in combination, urban PM impaired ASL’s antiviral activity against both viruses, and the same effect occurred for IAP PM and ash against SARS-CoV-2, suggesting that PM may enhance SARS-CoV-2 infection.

Patterns of medication use and imaging following initial diagnosis of sarcoidosis

INTRODUCTION

Sarcoidosis is a rare inflammatory disease with unclear natural history. Using a large, retrospective, longitudinal, population-based cohort, we sought to define its natural history in order to guide future clinical studies.

METHODS

We identified 722 newly diagnosed cases of sarcoidosis within Kaiser Permanente Northwest health care records between 1995 and 2015. We investigated immunosuppressive medication use in the two years following diagnosis, analyzed demographic and clinical characteristics, and quantified chest imaging and pulmonary function testing (PFTs) across the clinical course.

RESULTS

Over two years of follow-up, 41% of patients were treated with prednisone. Of those, 75% tapered off their first course within 100 days, although half of those patients required recurrent therapy. Five percent of the entire cohort remained on prednisone for longer than one year, with an average daily dose of 10-20 mg. Chest imaging was associated with early prednisone use, and chest CT was associated with changes in prednisone dose. PFTs or demographics were not associated with prednisone use. Cumulative prednisone doses were significantly higher in African Americans (1,845 mg additional) and those who had a chest CT (2,015 mg additional). Overall, PFTs were less frequently obtained than chest imaging and had no significant change over disease course.

DISCUSSION

The natural history of sarcoidosis varies greatly. For those requiring therapy, corticosteroid burden is high. Chest imaging drives medication dose changes as compared to PFTs, but neither outcome fully captures the entire history of disease. Prospective cohorts are needed with purposefully collected, repeated measures that include objective clinical assessments and symptoms.

Indoor Air Pollution and Susceptibility to Tuberculosis Infection in Urban Vietnamese Children

RATIONALE

The Southeast Asian tuberculosis burden is high, and it remains unclear if urban indoor air pollution in this setting is exacerbating the epidemic.

OBJECTIVES

To determine the associations of latent tuberculosis with common urban indoor air pollution sources (secondhand smoke, indoor motorcycle emissions, and cooking) in Southeast Asia.

METHODS

We enrolled child household contacts of patients with microbiologically confirmed active tuberculosis in Vietnam, July 2017-December 2019. We tested children for latent tuberculosis and evaluated air pollution exposures with questionnaires and personal aerosol sampling. We tested hypotheses using generalized estimating equations.

MEASUREMENTS AND MAIN RESULTS

We enrolled 72 tuberculosis patients (27% with cavitary disease) and 109 of their child household contacts. Of household contacts, 58 (53%) were diagnosed with latent tuberculosis at baseline visit. Children experienced a 2.56-fold increased odds of latent tuberculosis for each additional household member who smoked (95%CI 1.27-5.16). Odds were highest among children exposed to indoor smokers and children under five years old exposed to household smokers. Each residential floor above street-level pollution decreased the odds of latent tuberculosis by 36% (aOR 0.64, 95%CI 0.42-0.96). Motorcycles parked inside children's homes and cooking with liquid petroleum gas compared to electricity increased the odds of latent tuberculosis while kitchen ventilation decreased the effect, but these findings were not statistically significant.

CONCLUSION

Common urban indoor air pollution sources were associated with increased odds of latent tuberculosis infection in child household contacts of active tuberculosis patients.

Lung function of primary cooks using LPG or biomass and the effect of particulate matter on airway epithelial barrier integrity

BACKGROUND

Cooks exposed to biomass fuel experience increased risk of respiratory disease and mortality. We sought to characterize lung function and environmental exposures of primary cooking women using two fuel-types in southeastern India, as well as to investigate the effect of particulate matter (PM) from kitchens on human airway epithelial (HAE) cells in vitro.

METHODS

We assessed pre- and post-bronchodilator lung function on 25 primary female cooks using wood biomass or liquified petroleum gas (LPG), and quantified exposures from 34 kitchens (PM_2.5, PM < 40 μm, black carbon, endotoxin, and PM metal and bacterial content). We then challenged HAE cells with PM, assessing its cytotoxicity to small-airway cells (A549) and its effect on: transepithelial conductance and macromolecule permeability (NuLi cells), and antimicrobial activity (using airway surface liquid, ASL, from primary HAE cells).

RESULTS

Lung function was impaired in cooks using both fuel-types. 60% of participants in both fuel-types had respiratory restriction (post bronchodilator FEV₁/FVC>90). The remaining 40% in the LPG group had normal spirometry (post FEV₁/FVC = 80-90), while only 10% of participants in the biomass group had normal spirometry, and the remaining biomass cooks (30%) had respiratory obstruction (post FEV₁/FVC<80). Significant differences were found in environmental parameters, with biomass kitchens containing greater PM_2.5, black carbon, zirconium, arsenic, iron, vanadium, and endotoxin concentrations. LPG kitchens tended to have more bacteria (p = 0.14), and LPG kitchen PM had greater sulphur concentrations (p = 0.02). In vitro, PM induced cytotoxicity in HAE A549 cells in a dose-dependent manner, however the effect was minimal and there were no differences between fuel-types. PM from homes of participants with a restrictive physiology increased electrical conductance of NuLi HAE cells (p = 0.06) and decreased macromolar permeability (p ≤ 0.05), while PM from homes of those with respiratory obstruction tended to increase electrical conductance (p = 0.20) and permeability (p = 0.07). PM from homes of participants with normal spirometry did not affect conductance or permeability. PM from all homes tended to inhibit antimicrobial activity of primary HAE cell airway surface liquid (p = 0.06).

CONCLUSIONS

Biomass cooks had airway obstruction, and significantly greater concentrations of kitchen environmental contaminants than LPG kitchens. PM from homes of participants with respiratory restriction and obstruction altered airway cell barrier function, elucidating mechanisms potentially responsible for respiratory phenotypes observed in biomass cooks.

Continuous in-home PM2.5 concentrations of smokers with and without a history of respiratory exacerbations in Iowa, during and after an air purifier intervention

BACKGROUND

Americans spend most of their time indoors. Indoor particulate matter (PM) 2.5 µm and smaller (PM_2.5) concentrations often exceed ambient concentrations. Therefore, we tested whether the use of an air purifying device (electrostatic precipitator, ESP) could reduce PM_2.5 in homes of smokers with and without respiratory exacerbations, compared with baseline.

METHODS

We assessed PM_2.5 concentrations in homes of subjects with and without a recent (≤3 years) history of respiratory exacerbation. We compared PM_2.5 concentrations during 1 month of ESP use with those during 1 month without ESP use.

RESULTS

Our study included 19 subjects (53-80 years old), nine with a history of respiratory exacerbation. Geometric mean (GM) PM_2.5 and median GM daily peak PM_2.5 were significantly lower during ESP deployment compared with the equivalent time-period without the ESP (GSD = 0.50 and 0.37 µg/m³, respectively, p < 0.001). PM_2.5 in homes of respiratory exacerbators tended (p < 0.14) to be higher than PM_2.5 in homes of those without a history of respiratory exacerbation.

CONCLUSIONS

Subjects with a history of respiratory exacerbation tended to have higher mean, median, and mean peak PM_2.5 concentrations compared with homes of subjects without a history of exacerbations. The ESP intervention reduced in-home PM_2.5 concentrations, demonstrating its utility in reducing indoor exposures.

NOVELTY OF STUDY

Our work characterizes PM air pollution concentrations in homes of study subjects with and without respiratory exacerbations. We demonstrate that PM concentrations tend to be higher in homes of participants with respiratory exacerbations, and that the use of an inexpensive air purifier resulted in significantly lower daily average PM concentrations than when the purifier was not present. Our results provide a helpful intervention strategy for purifying indoor air and may be useful for susceptible populations.

Characterization of inhalable endotoxin, glucan, and dust exposures in Iowa farmers

BACKGROUND

The observed deficit of lung cancer in farmers has been partly attributed to exposure to organic dusts and endotoxins based largely on surrogate metrics. To move beyond these surrogates for etiological studies, we characterized task-based and time-weighted average (TWA) exposure to inhalable endotoxin, (1 → 3)-β-D-glucan, and dust in Iowa farmers.

METHODS

We collected 320 personal inhalable dust samples from 32 farmers during 69 sample days in 2015 and 2016. Samples were collected using Button aerosol samplers and analyzed for endotoxin using a kinetic chromogenic amebocyte lysate assay, and for (1 → 3)-β-D-glucan using a Limulus endpoint assay. We assessed relationships between bioaerosol concentrations and selected tasks and farm characteristics using linear mixed-effects models.

RESULTS

Bedding work, hog handling, and working in barn/confinement buildings, grain bins, and grain elevators were associated with higher endotoxin exposure. We found a monotonic trend between higher endotoxin concentrations and increasing number of animals. Bedding work, cleaning, and feed/grain storage work were associated with higher (1 → 3)-β-D-glucan concentrations. The median concentrations by task spanned one order of magnitude for inhalable dust and two orders of magnitude for endotoxin and (1 → 3)-β-D-glucan. Pearson correlations between endotoxin and glucan concentrations were 0.22 for TWA exposure and 0.56 for task samples.

CONCLUSIONS

This characterization of exposure factors that influence bioaerosol concentrations can support the development of refined bioaerosol exposure metrics for future etiologic analyses of cancer and other health outcomes in farmers.

Diesel Exhaust Exposure during Farming Activities: Statistical Modeling of Continuous Black Carbon Concentrations

OBJECTIVES

Daily driving of diesel-powered tractors has been linked to increased lung cancer risk in farmers, yet few studies have quantified exposure levels to diesel exhaust during tractor driving or during other farm activities. We expanded an earlier task-based descriptive investigation of factors associated with real-time exposure levels to black carbon (BC, a surrogate of diesel exhaust) in Iowa farmers by increasing the sample size, collecting repeated measurements, and applying statistical models adapted to continuous measurements.

METHODS

The expanded study added 43 days of sampling, for a total of 63 sample days conducted in 2015 and 2016 on 31 Iowa farmers. Real-time, continuous monitoring (30-s intervals) of personal BC concentrations was performed using a MicroAeth AE51 microaethelometer affixed with a micro-cyclone. A field researcher recorded information on tasks, fuel type, farmer location, and proximity to burning biomass. We evaluated the influence of these variables on log-transformed BC concentrations using a linear mixed-effect model with random effects for farmer and day and a first-order autoregressive structure for within-day correlation.

RESULTS

Proximity to diesel-powered equipment was observed for 42.5% of the overall sampling time and on 61 of the 63 sample days. Predicted geometric mean BC concentrations were highest during grain bin work, loading, and harvesting, and lower for soil preparation and planting. A 68% increase in BC concentrations was predicted for close proximity to a diesel-powered vehicle, relative to far proximity, while BC concentrations were 44% higher in diesel vehicles with open cabins compared with closed cabins. Task, farmer location, fuel type, and proximity to burning biomass explained 8% of within-day variance in BC concentrations, 2% of between-day variance, and no between-farmer variance.

CONCLUSION

Our findings showed that farmers worked frequently near diesel equipment and that BC concentrations varied between tasks and by fuel type, farmer location, and proximity to burning biomass. These results could support the development of exposure models applicable to investigations of health effects in farmers associated with exposure to diesel engine exhaust.

Residential urban tree canopy is associated with decreased mortality during tuberculosis treatment in California

Trees can sequester air pollutants, and air pollution is associated with poor tuberculosis outcomes. However, the health impacts of urban trees on tuberculosis patients are unknown. To elucidate the effects of urban tree canopy on mortality during tuberculosis treatment, we evaluated patients diagnosed with active tuberculosis in California from 2000 through 2012, obtaining patient data from the California tuberculosis registry. Our primary outcome was all-cause mortality during tuberculosis treatment. We determined percent tree cover using 1 mresolution color infrared orthoimagery categorized into land cover classes, then linked tree cover to four circular buffer zones of 50-300 m radii around patient residential addresses. We used the Kaplan-Meier method to estimate survival probabilities and Cox regression models to determine mortality hazard ratios, adjusting for demographic, socioeconomic, and clinical covariates. Our cohort included 33,962 tuberculosis patients of median age 47, 59% male, 51% unemployed, and 4.9% HIV positive. Tuberculosis was microbiologically confirmed in 79%, and 1.17% were multi-drug resistant (MDR). Median tree cover was 7.9% (50 m buffer). Patients were followed for 23,280 person-years with 2370 deaths during tuberculosis treatment resulting in a crude mortality rate of 1018 deaths per 10,000 person-years. Increasing tree cover quintiles were associated with decreasing mortality risk during tuberculosis treatment in all buffers, and the magnitude of association decreased incrementally with increasing buffer radius: In the 50 m buffer, patients living in neighborhoods with the highest quintile tree cover experienced a 22% reduction in mortality (HR 0.78, 95%CI 0.68-0.90) compared to those living in lowest quintile tree cover; whereas for 100, 200, and 300 m buffers, a 21%, 13%, and 11% mortality risk reduction was evident. In conclusion, urban tree canopy was associated with decreased mortality during tuberculosis treatment even after adjusting for multiple demographic, socioeconomic, and clinical factors, suggesting that trees might play a role in improving tuberculosis outcomes.

Indoor Particulate Matter From Smoker Homes Induces Bacterial Growth, Biofilm Formation, and Impairs Airway Antimicrobial Activity. A Pilot Study

Background: Particulate matter (PM) air pollution causes deleterious health effects; however, less is known about health effects of indoor air particulate matter (IAP). Objective: To understand whether IAP influences distinct mechanisms in the development of respiratory tract infections, including bacterial growth, biofilm formation, and innate immunity. Additionally, we tested whether IAP from Iowa houses of subjects with and without recent respiratory exacerbations recapitulated the National Institute of Standards and Technology (NIST) IAP findings. Methods: To test the effect of NIST and Iowa IAP on bacterial growth and biofilm formation, we assessed Staphylococcus aureus growth and Pseudomonas aeruginosa biofilm formation with and without the presence of IAP. To assess the effect of IAP on innate immunity, we exposed primary human airway surface liquid (ASL) to NIST, and Iowa IAP. Lastly, we tested whether specific metals may be responsible for effects on airway innate immunity. Results: NIST and Iowa IAP significantly enhanced bacterial growth and biofilm formation. NIST IAP (whole particle and the soluble portion) impaired ASL antimicrobial activity. IAP from one Iowa home significantly impaired ASL antimicrobial activity (p < 0.05), and five other homes demonstrated a trend (p ≤ 0.18) of impaired ASL antimicrobial activity. IAP from homes of subjects with a recent history of respiratory exacerbation tended (p = 0.09) to impair ASL antimicrobial activity more than IAP from homes of those without a history respiratory exacerbation. Aluminum and Magnesium impaired ASL antimicrobial activity, while copper was bactericidal. Combining metals varied their effect on ASL antimicrobial activity. Conclusions: NIST IAP and Iowa IAP enhanced bacterial growth and biofilm formation. ASL antimicrobial activity was impaired by NIST IAP, and Iowa house IAP from subjects with recent respiratory exacerbation tended to impair ASL antimicrobial activity. Individual metals may explain impaired ASL antimicrobial activity; however, antimicrobial activity in the presence of multiple metals warrants further study.

A task-based analysis of black carbon exposure in Iowa farmers during harvest

Diesel exhaust has been associated with adverse human health effects. Farmers are often exposed to diesel exhaust; however, their diesel exposure has not been well characterized. In this descriptive study, we measured black carbon concentrations as a proxy for diesel exhaust exposure in 16 farmers over 20 sampling days during harvest in southeast Iowa. Farmers wore a personal aethalometer which measured real-time black carbon levels throughout the working day, and their activities were recorded by a field researcher. Black carbon concentrations were characterized for each farmer, and by activity, vehicle fuel type, and microenvironment. Overall, 574 discrete tasks were monitored with a median task duration of 5.5 min. Of these tasks, 39% involved the presence of a diesel vehicle. Farmers' daily black carbon geometric mean exposures ranged from 0.1-2.3 µg/m³, with a median daily geometric mean of 0.3 µg/m³. The highest black carbon concentrations were measured on farmers who used or worked near diesel vehicles (geometric mean ranged from 0.5 µg/m³ while harvesting to 4.9 µg/m³ during animal work). Higher geometric means were found for near vs. far proximity to diesel-fueled vehicles and equipment (2.9 vs. 0.3 µg/m³). Indoor, bystander proximity to diesel-operated vehicles resulted in the highest geometric mean black carbon concentrations (18 µg/m³). Use of vehicles with open cabs had higher mean black carbon concentrations than closed cabs (2.1-3.2 vs. 0.4-0.9 µg/m³). In summary, our study provided evidence that farmers were frequently exposed to black carbon associated with diesel-related activities at levels above urban ambient concentrations in their daily work during harvest.