[Saposhnikoviae Radix enhances resistance to respiratory tract infection by potentiating interferon signaling]

This study aimed to investigate the immunopharmacological mechanism of Saposhnikoviae Radix(SR) against respiratory viruses and bacteria infections based on immune signal activation. Mouse models of pneumonia induced by intranasal influenza A virus(H1N1) infection and intratracheal lipopolysaccharide(LPS) instillation were established. The effects of the water extract of SR on pulmonary CT imaging, histological damage, and inflammatory cytokine expression in lung tissues were evaluated. Using bone marrow-derived macrophages, this study analyzed the regulatory effects of the extract on macrophage proliferation and phagocytic function. RNA-seq and bioinformatics analysis, combined with molecular biology experiments, were employed to explore the regulatory role of the water extract of SR on the type Ⅰ interferon(IFN-Ⅰ) signaling pathway. The findings revealed that the water extract of SR significantly alleviated H1N1 infection-induced lung imaging and pathological damage in mice, reduced lung viral gene copies, and downregulated the expression of inflammatory cytokines such as interleukin-6(IL-6), tumor necrosis factor-α(TNF-α), and CXC motif chemokine ligand 10(CXCL10). Concurrently, drug treatment demonstrated similar lung tissue protective functions in the LPS-induced mouse pneumonia model. Cell experiments showed that the extract promoted proliferation of macrophages and enhanced their phagocytic capacity toward neutral red. Transcriptomic analysis revealed that genes upregulated by the extract of SR were significantly enriched in pathways including H1N1 infection, Toll-like receptor signaling, NOD-like receptor signaling, and IFN signaling. Finally, qRT-PCR and Western blot confirmed that the extract activated the interferon signaling pathway. In conclusion, the extract of SR activates innate immunity centered on IFN-Ⅰ signaling and enhances macrophage function, thereby improving the host's defense against viral and bacterial infections. It possesses potential preventive and therapeutic value for respiratory tract infection-associated pneumonia and lung injury.