Protective effect of the mixture of Lactiplantibacillus plantarum KC3 and Leonurus Japonicas Houtt extract on respiratory disorders.

Air pollutants, such as particulate matter (PM) and diesel exhaust particles (DEP), are associated with respiratory diseases. Therefore, preventive and therapeutic strategies against PM-and DEP (PMD)-induced respiratory diseases are needed. Herein, we evaluate the protective effects of a mixture of Lactiplantibacillus plantarum KC3 and Leonurus Japonicas Houtt (LJH) extract against airway inflammation associated with exposure to PMD. To determine the anti-inflammatory effects of the LJH extract, reactive oxygen species (ROS) production and the expression of inflammatory pathways were determined in PM-induced MH-S cells. For the respiratory protective effects, BALB/c mice were exposed to PMD via intranasal injection, and a mixture of L. plantarum KC3 and LJH extract was administered orally for 12 days. LJH extract inhibited ROS production and the phosphorylation of downstream factors of NF-κB in PM-stimulated MH-S cells. The mixture of L. plantarum KC3 and LJH repressed the infiltration of neutrophils, reduced the immune cells number, and suppressed the proinflammatory mediators and cyclooxygenase (COX)-2 expressions in PMD-induced airway inflammation with reduced phosphorylation of downstream factors of NF-κB. In addition, these effects were not observed in an alveolar macrophage depleted PMD-induced mouse model using clodronate liposomes. The extract mixture also regulated gut microbiota in feces and upregulated the mRNA expression of Foxp3, transforming growth factor (TGF)-β1, and interleukin (IL)-10 in the colon. The L. plantarum KC3 and LJH extract mixture may inhibit alveolar macrophage- and neutrophil-mediated inflammatory responses and regulate gut microbiota and immune response in PMD-induced airway inflammation, suggesting it is a potential remedy to prevent and cure airway inflammation and respiratory disorders.