Particulate Matter exposure influences respiratory microbiota structure and functions

Background: human microbiota plays a highly physiological role and influences human health. Researches on microbiota structure and functions are increasing, but is still largely unknown whether the airways microbiota is influenced by airborne pollution, and if it play a role in human response to inhaled particulate matter (PM). Aim: we evaluated the effects of PM on respiratory microbiota structure and functions in healthy subjects. Methods: microbial community was examined through metabarcoding analysis of the V3-V4 16S rRNA gene regions amplified from upper-airway tracts of 40 individuals to perform α-diversity and taxonomic studies. Individual PM 10 and PM 2.5 exposure was estimated by personal sampler (worn for 24 hours before sampling) and integrated with nearest ambient monitoring station values (for mid-term exposures). Results: downstream analysis showed that microbiota composition was negatively associated with PM measured 3 days before sampling (PM-3). PM-3 decreased also the concentration of Actinobacteria (PM 10 ∆%-2,1 CI95% -3,8;-0,4 PM 2,5 ∆%-2,6 CI95% -4,7;-0,4), which is the dominant phylum in a healthy microbiota, while it sensibly increased the relative concentration of Moraxella genus (PM 10 ∆%4,9 CI95% 0,4;9,6 PM 2,5 ∆%5,8 CI95% 0,3;11,7), that includes airways-pathogen species. Discussion: this is the first study showing an effect of PM on upper-airway microbiota in healthy subjects. Further investigations are needed to explore the role of the microbiota as intermediate and possible cause of individual susceptibility to inhaled pollutants. In fact, microbiota has the potential to modulate host inflammatory response, to compete with pathogen species and finally to impact on human health.