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.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.
Highlights
Health impacts of acute ambient particulate matter (PM) exposure, especially fine (≤2.5 μm) PM, are well-documented and include an increased risk of respiratory infections, especially in susceptible populations [1,2,3,4,5,6,7].Airway innate immune mechanisms, such as airway surface liquid (ASL) antimicrobial activity, play an important role in the development of respiratory infections, as well as the mechanism of chronic lung diseases such as cystic fibrosis [8, 9]
In order to test whether indoor air particulate matter (IAP) influences bacterial growth, we added two doses (10 and 50 μg/mL) of National Institute of Standards and Technology (NIST) IAP to S. aureus suspended in minimal media (10 mM NaPO4 buffer with 1% TSB), and assessed bacterial growth over time (RLUs at one, 2 and 3 h compared to Relative light units (RLUs) at inoculation)
Because we have demonstrated Coal Fly Ash (CFA) can inhibit ASL antimicrobial activity in human airway epithelial cells (AECs) [17], we were interested whether IAP would recapitulate this effect
Summary
Health impacts of acute ambient particulate matter (PM) exposure, especially fine (≤2.5 μm) PM, are well-documented and include an increased risk of respiratory infections, especially in susceptible populations [1,2,3,4,5,6,7].Airway innate immune mechanisms, such as airway surface liquid (ASL) antimicrobial activity, play an important role in the development of respiratory infections, as well as the mechanism of chronic lung diseases such as cystic fibrosis [8, 9]. The ASL is a thin layer of liquid coating the lungs and is responsible for immediately killing incoming pathogens It is composed of various antimicrobial peptides and proteins (AMPs), such as βdefensins, lactoferrin, lysozyme, and surfactant proteins, among others, and is instrumental in airway innate immunity [10,11,12,13]. Air contaminants, such as PM, can impair airway innate immunity and reduce immediate ASL bacterial killing [14, 15]. Particulate matter (PM) air pollution causes deleterious health effects; less is known about health effects of indoor air particulate matter (IAP)
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