The Microbiome and EpidemiologyThe respiratory microbiome: an underappreciated player in the human response to inhaled pollutants?
Section snippets
What do we know about the respiratory microbiome?
For over 100 years, traditional wisdom was that in those without lung diseases, microbial communities resided only in the upper (i.e., mouth and nose) but not the lower (i.e., lungs) airways. More recently, however, the use of culture-independent, sequence-based techniques has clearly shown that the lungs are not sterile [13], [14]. A summary of the current state of the science can be found in several excellent review articles [15], [16], [17], [18] with brief highlights in the following
How might the respiratory microbiome influence the human response to inhaled irritants/toxicants?
There is a growing understanding that our microbiota plays a critical role in the development and mediation of many human processes. As some of the first cells in the body encountering inhaled environmental toxicants, it is likely that the respiratory microbiome is both affected by these exposures and affects these exposures (Fig. 1). In the ideal world, the microbiome would serve as a protective shield for human host. However, it is also likely that the human host gets caught in the
What evidence is there of a respiratory microbiome response to environmental pollutants?
An extremely small literature on smoking supports the hypothesis that inhaled air irritants/toxicants may impact the respiratory microbiome. Most such research, however, is short term and from the subgingival environment. In this environment, lower abundances of health-promoting microbes and higher abundances of pathogens have been reported with smoking exposures [52]. Interestingly, smoking appears to have a rapid impact on the oral microbiome with changes in bacterial colonization reported
What challenges do we face in studying the role of the respiratory microbiome?
One of the key challenges to clinical and epidemiologic research on environmental exposures and the respiratory microbiome relates to existing measurement techniques. Approaches to study microbial communities of the lungs have traditionally included bronchoalveolar lavage and induced sputum [17]. Although previous concerns about the potential for contamination during the bronchoscopic process have been allayed based on results of protected specimen brushing [20], [23], both bronchoalveolar
Summary and implications
There is a growing understanding that the human responsiveness to external assaults can be shaped by our microbiome. In this article, we presented evidence that the respiratory microbiome is an active player in human health and proposed mechanisms by which the microbiome might plausibly mediate or modify the human health response to inhaled irritants/toxicants. Such a role would have several important implications for our understanding of how inhaled irritants/toxicants impact health and who is
References (78)
- et al.
Air pollution and health
Lancet
(2002) - et al.
A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010
Lancet
(2013) - et al.
The microbiome of the lung
Transl Res
(2012) - et al.
The role of the microbiome in exacerbations of chronic lung diseases
Lancet
(2014) - et al.
Active and passive smoking and risk of colds in women
Ann Epidemiol
(2001) - et al.
Cigarette smoking and respiratory tract infection
Clin Chest Med
(1987) - et al.
The microbiome in asthma
J Allergy Clin Immunol
(2015) - et al.
Assessment of indirect human exposure to environmental sources of nickel: oral exposure and risk characterization for systemic effects
Sci Total Environ
(2012) - et al.
Reduction in fine particulate air pollution and mortality—extended follow-up of the Harvard six cities study
Am J Respir Crit Care Med
(2006) - et al.
Cardiovascular events following smoke-free legislations: an updated systematic review and meta-analysis
Curr Environ Health Rep
(2014)
Fine particulate air pollution and life expectancy in the United States
N Engl J Med
Effect of air pollution control on life expectancy in the United States: an analysis of 545 U.S. Counties for the period from 2000 to 2007
Epidemiology
Evidence on vulnerability and susceptibility to health risks associated with short-term exposure to particulate matter: a systematic review and meta-analysis
Am J Epidemiol
Particulate matter-induced health effects: who is susceptible?
Environ Health Perspect
The Human Microbiome: At the interface of health and disease
Nat Rev Genet
Human colon microbiota transform polycyclic aromatic hydrocarbons to estrogenic metabolites
Environ Health Perspect
Metabolism of the food-associated carcinogen 2-amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine by human intestinal microbiota
J Agric Food Chem
Metabolism of Maillard reaction products by the human gut microbiota–implications for health
Mol Nutr Food Res
Disordered microbial communities in asthmatic airways
PLoS One
Analysis of the lung microbiome in the “healthy” smoker and in COPD
PLoS One
The role of the lung microbiome in health and disease. A National Heart, Lung, and Blood Institute workshop report
Am J Respir Crit Care Med
The lung microbiome: new principles for respiratory bacteriology in health and disease
PLoS Pathog
Mini-review of the concentration variations found in the alfresco atmospheric bacterial populations
Aerobiologia
Spatial variation in the healthy human lung microbiome and the adapted island model of lung biogeography
Ann Am Thorac Soc
Changes in the lung microbiome following lung transplantation include the emergence of two distinct Pseudomonas species with distinct clinical associations
PLoS One
Topographical continuity of bacterial populations in the healthy human respiratory tract
Am J Respir Crit Care Med
Analysis of the upper respiratory tract microbiotas as the source of the lung and gastric microbiotas in healthy individuals
MBio
Phylogenetic analysis of the human gut microbiota using 16S rDNA clone libraries and strictly anaerobic culture-based methods
Microbiol Immunol
Airway microbiota and bronchial hyperresponsiveness in patients with suboptimally controlled asthma
J Allergy Clin Immunol
Asthma-associated differences in microbial composition of induced sputum
J Allergy Clin Immunol
The effects of airway microbiome on corticosteroid responsiveness in asthma
Am J Respir Crit Care Med
A persistent and diverse airway microbiota present during chronic obstructive pulmonary disease exacerbations
OMICS
Enrichment of lung microbiome with supraglottic taxa is associated with increased pulmonary inflammation
Microbiome
Potentially pathogenic airway bacteria and neutrophilic inflammation in treatment resistant severe asthma
PLoS One
A novel microbiota stratification system predicts future exacerbations in bronchiectasis
Ann Am Thorac Soc
Probiotic supplementation affects pulmonary exacerbations in patients with cystic fibrosis: a pilot study
Pediatr Pulmonol
Early life antibiotic-driven changes in microbiota enhance susceptibility to allergic asthma
EMBO Rep
Integrated Science Assessment for Particulate Matter
Particulate matter air pollution and cardiovascular disease: an update to the scientific statement from the American Heart Association
Circulation
Cited by (59)
High temperature exacerbates ozone-induced airway inflammation: Implication of airway microbiota and metabolites
2023, Science of the Total EnvironmentAssociation between short-term exposure to PM<inf>2.5</inf> and nasal microbiota dysbiosis, inflammation and oxidative stress: A panel study of healthy young adults
2023, Ecotoxicology and Environmental SafetyExposure to diesel exhaust alters the functional metagenomic composition of the airway microbiome in former smokers
2023, Environmental ResearchCitation Excerpt :While the role of a healthy respiratory microbiome in providing resistance against respiratory pathogens is established, whether or not the airway microbiome modifies the host's response to pollutants or vice versa, is unknown (Adar et al., 2016). It has been hypothesized that inhaled pollutants and the airway microbiota interact and that the respiratory tract microbiota can even metabolize noxious components present in polluted air (Adar et al., 2016). Even though the later assertion seems to put the microbiota at the frontline of the host response to air pollutants, tangible data from human studies to support this assertion is missing.
Air pollution and endocrine disruptors induce human microbiome imbalances: A systematic review of recent evidence and possible biological mechanisms
2022, Science of the Total EnvironmentAir pollution and the respiratory microbiome
2021, Journal of Allergy and Clinical ImmunologyParticulate matter and airborne endotoxin concentration in calf barns and their association with lung consolidation, inflammation, and infection
2021, Journal of Dairy ScienceCitation Excerpt :Small particulates can penetrate deep into the respiratory tract, causing oxidative stress, as well as damage the respiratory tract and induce airway inflammation. This could favor bacterial growth and increases susceptibility to respiratory tract infection and subsequent pneumonia (Ghio, 2014; Zhao et al., 2014; Adar et al., 2016). After inhalation, particles are normally removed by the mucociliary clearance system.
The authors have no conflicts of interest to disclose.