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

Abstract

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. Stapleton et al. Indoor PM Affects Respiratory Health 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.

Urban Particulate Matter Impairment of Airway Surface Liquid–Mediated Coronavirus Inactivation

“…It is established that ASL can be antimicrobial, and this is often mediated by AMPs [ 1 , 2 , 4 ]. Our findings are the first to demonstrate that primary human airway ASL significantly inactivates CoV-229E and SARS-CoV-2 in vitro ( Figure 1A ).…”

“…After informed written consent was obtained, human donor lungs, confirmed with polymerase chain reaction to be negative for SARS-CoV-2 infection at the time of tissue retrieval, were dissected to obtain bronchial and tracheal cells. Cells were seeded onto collagen-coated filters at the air-liquid interface by the University of Iowa (UI) Cell Culture Core Repository and then washed to obtain endogenous ASL (n>4 donors/experiment), as described elsewhere [ 4 ]. For donor demographics see Supplementary Table 1 .…”

“…Airway innate immunity is disrupted by air pollution. Stapleton et al [ 4 ] have previously demonstrated that indoor and ambient air pollution particulate matter (PM) inhibits ASL-mediated bacterial killing, in part owing to competition between cationic AMPs and negatively charged PM and bacteria. Ambient PM is also associated with increased coronavirus infection incidence and mortality rates in epidemiological studies [ 5 ].…”

Vitamin D-mediated effects on airway innate immunity in vitro

“…Bioluminescent S . aureus (Xen29, Caliper Lifesciences Bioware®) sub-cultured to log-phase growth was suspended in minimal media (5% TSB) and challenged (1:1) by ASL from calcitriol supplemented hAECs and by un-supplemented hAEC ASL [ 25 ]. Briefly, ASL was collected by serially washing (20 μl/well DI H 2 0) hAEC apical surfaces from paired donor cells (n = 4 per experiment), after which media was changed back to baseline media for a >72h washout period.…”

Editorial: Environment and Health

“…The preliminary results suggest higher adverse effects of outdoor air pollution on cognitive function in women, indicating specific actions for prevention and intervention. Stapleton et al (2020) reported on a pilot study in 21 homes selected from the NIH funded cohort residing in Iowa of current and former smokers, with and without a history of respiratory exacerbations. The aim of the research was at assessing whether indoor air particulate collected from their homes would affect in vitro bacterial growth, biofilm formation, and primary human airway surface liquid antimicrobial activity, identifying mechanisms in the development of respiratory tract infections, including bacterial growth, biofilm formation, and innate immunity.…”