A neutral polysaccharide from platycodonis radix ameliorated PM2.5-induced lung injury by inhibiting the TLR4/NF-kappaB p65 pathway and regulating lung and gut microbiome.

Platycodonis radix (PR) is a common vegetable that has the effect of relieving cough and resolving phlegm. However, the reparative effect and mechanism of PR polysaccharides (PRP) on fine particulate matter (PM2.5)-induced lung injury are still unclear. Here, a neutral polysaccharide (MW: 244.56 kDa) was isolated from PR, mainly composed of Rha, Ara, Gal, Glc, Xyl, and Man with a molar ratio of 14.2:30.7:22.4:13.5:9.4:9.7. PRP significantly improved PM2.5-induced pulmonary edema, oxidative damage, and cell apoptosis, and downregulated inflammatory factor levels in bronchoalveolar lavage fluid. Mechanismly, PRP reduced intestinal mucosal barrier damage, thereby lowering serum lipopolysaccharide levels and inhibiting TLR4/NF-kappaB signaling pathway. Notably, we analyzed for the first time the effects of PRP on the lung microbiota. PRP optimized the composition of pulmonary and intestinal microbiota, and increased the levels of acetate, butyrate and isovalerate.Therefore, PRP might have potential applications in preventing or repairing lung injury caused by PM2.5.