Inhalational Exposure to Particulate Matter Air Pollution alters the Composition of Microbiome in Small Bowel and Colon. mouse gut metagenome

Background: Recent studies suggest an association between particulate matter (PM) air pollution and gastrointestinal (GI) disease. In addition to direct deposition, PM can be indirectly deposited in oropharynx via mucociliary clearance and upon swallowing of saliva and mucus. When in the GI tract, PM may affect the GI epithelium and alter gut microbiome.Objective: To determine the effect of PM on gut microbiome composition in a murine model of PM exposure via inhalation.Methods: C57BL/6 mice were exposed via inhalation to either concentrated ambient particles (PM2.5) (n=10) or filtered air (air) (n=10) for 8 hours per day 5 days a week for a total of 3 weeks. At the end of the exposure, the GI tract tissues (including stomach, small intestine, cecum, and colon) and feces were harvested, and gut microbiome composition was analyzed using 16S rDNA sequencing.Results: Alpha diversity was modestly altered with increases seen in primarily richness diversity indices in PM-exposed mice compared to air-exposed mice in various parts of the GI tract. Most importantly, PM-induced alterations in the composition of bacteria were very apparent in beta diversity comparisons throughout the entire GI tract and appeared to increase from the proximal to distal parts. Notable specific changes in some genera were seen and suggest that some distinct bacteria may have the capacity to bloom with PM exposure.Conclusions: Exposure to PM alters the composition of microbiome throughout the GI tract which may be a potential mechanism that explains PM induced inflammation in the GI tract.