Short-term exposure to urban PM_2.5 particles induces histopathological and inflammatory changes in the rat small intestine

Air pollution and exposure to fine airborne particles with aerodynamic diameter <2.5 μm (PM_2.5) negatively impacts human health. Airways constitute a primary route of exposure but PM_2.5-contaminated food, drinks as well as mucociliary and hepatobiliary clearance all constitute potential entry points into the intestine. This study evaluated intestinal histopathological and inflammatory changes as well as enteric neuronal numbers after short- or long-term exposure to urban PM_2.5. Using a nebulizer, male rats were exposed to a mist with a concentration of 5.3mg PM_2.5/m³ for 8 h (short term) or 1.8 mg PM_2.5/m³ for 3 h/day, 5 days/week for 8 weeks (long-term) with controls run in parallel. Samples were taken from three regions of the small intestine as well as the colon. Results showed that short-term exposure to PM_2.5 induces mucosal lesions and reduces IL1β levels in the small intestine but not colon. No significant changes were observed after long-term exposure, suggesting the presence of intestinal adaptation to environmental stressors in the PM_2.5. To our knowledge, this is the first study to systematically characterize regional effects along the intestine.