SMAD2 and pulmonary fibrosis: Unlike Lactobacillus rhamnosus GG, which was shown to attenuate radiation-induced pulmonary fibrosis through direct regulation of the lncRNA SNHG17/PTBP1/NICD axis, LP03 exerts its antifibrotic effects by partially restoring the disrupted gut microbiota composition in the pulmonary fibrosis model—enriching beneficial genera (e.g., Ligilactobacillus, Akkermansia) while reducing pathogenic genera (e.g., Listeria, Acinetobacter)—and by modulating host lipid metabolism, particularly through elevating endogenous PEA levels and suppressing TGF-β1/Smad2/3 signaling.