Chronic Exposure to Ambient Particulate Matter Induces Gut Microbial Dysbiosis in a Rat COPD Model

Abstract

Background The role of the gut microbiota in the pathogenesis of chronic obstructive pulmonary disease following exposure to ambient particulate matter is largely unknown. We hypothesized that exposure alters gut microbial composition and metabolites and is involved in the pathogenesis of chronic obstructive pulmonary disease.Methods Fifty-four male Sprague-Dawley rats were exposed to clean air, biomass fuel, or motor vehicle exhaust for 4, 12, and 24 weeks. Lung tissue was assessed histologically and gut microbial composition was assessed by 16S rRNA pyrosequencing. Serum lipopolysaccharide levels were measured and short-chain fatty acids in colon contents were quantified.Results After a 24-week exposure to particulate matter, rats exhibited pulmonary inflammation and pathological changes characteristic of chronic obstructive pulmonary disease. The gut microbiome was characterized by decreased microbial richness and diversity, distinct overall microbial composition, lower levels of short-chain fatty acids, and higher serum lipopolysaccharide.Conclusion Chronic exposure to ambient particulate matter induces gut microbial dysbiosis and metabolite shifts in a rat model of chronic obstructive pulmonary disease. each day of exposure. DustTrak II aerosol monitors (model 8530, TSI, Shoreview, MN, USA) were used to monitored PM mass concentrations and particle size distributions. Testo 340 portable flue gas analyzers (Testo, Lenzkirch, Germany) were used to monitored gas concentrations (O 2 , carbon monoxide, nitrogen oxides, and sulfur dioxide) in the exposure rooms. The control group was exposed to clean air. xposure to BMF. We used China fir sawdust (40 g/per exposure) to produce BMF smoke, which was sent into the animal exposure room through a piston pump (5 L/min). Rats were exposed to BMF smoke for four 1-h periods, 5 days per week. The test atmosphere was measured during the first hour.Exposure to MVE. MVE was produced by a Wuyang model WY48QT-2, 1.6-Kw, 125-cm 3 , onecylinder, four-cycle, gasoline-powered motorcycle (Guangzhou, China). Premium low-sulfur gasoline (<150 ppm; Petro Inc., El Paso, TX, USA) was used to produce MVE. Prior to the exposure session, the motorcycle engine was operated in an idle state for 2 min to produce sufficient MVE. Rats were exposed for two 2-h periods, 5 days per week. The test atmosphere was measured during the first 2 h.Ambient BMF and MVE samples were collected throughout the duration of exposure, and concentrations of organic carbon, elemental carbon, polycyclic aromatic hydrocarbons, and metals were measured at the Guangzhou Institute of Chemistry, Chinese Academy of Sciences (Guangzhou, China) according to a previous method [12,13]. Sample preparationRats were sacrificed by CO 2 after 4, 12, and 24 weeks of exposure (on days 29, 85, and 169, respectively). Blood samples were collected from the heart and centrifuged at 1,700 × g for 15 min at 4°C. Serum was stored at −80°C. Colon contents were collected under sterile conditions, snap-frozen in liquid nitrogen, and stored at −...