Polysaccharide from Tetrastigma hemsleyanum Diels et Gilg attenuates Poly(I:C)-induced acute lung injury by preserving epithelial barrier integrity and modulating STING/TBK1-NF-κB and IRF1-STAT1 signaling.

ETHNOPHARMACOLOGICAL RELEVANCE: Tetrastigma hemsleyanum Diels et Gilg, traditionally used in southern China to treat fever, cough, and pneumonia, is a well-known ethnomedicinal plant. Polysaccharides extracted from its aboveground parts (leaves and canes) possess potent immunomodulatory and anti-inflammatory activities. However, the mechanisms underlying their protective effects against viral-mimic acute lung injury (ALI) remain largely unexplored.

MATERIALS AND

METHODS

Mice were pretreated with STHP-5 (1-4 mg/kg, intratracheal instillation) once daily for three days before Poly(I:C) challenge to induce ALI. Lung injury, inflammation, and barrier integrity were evaluated by histopathology (H&E), TUNEL assay, wet/dry ratio, bronchoalveolar lavage fluid (BALF) analysis, myeloperoxidase (MPO) staining, and flow cytometry of immune cells. Cytokine levels, oxidative stress, and tight-junction proteins were assessed by cytometric bead array (CBA), ROS detection, Western blotting, and quantitative real-time PCR (RT-qPCR). In vitro, bone marrow-derived macrophages (BMDMs) and BEAS-2B epithelial cells were stimulated with Poly(I:C) with or without STHP-5 pretreatment, and examined by RT-qPCR, Western blotting, immunofluorescence, and cytokine assays to evaluate the STING/TBK1/NF-κB and IRF1/STAT1 signaling axes.

RESULTS

Prophylactic administration of STHP-5 significantly alleviated pulmonary inflammation, reduced cytokine secretion, and preserved alveolar epithelial integrity in Poly(I:C)-challenged mice. Further analysis revealed that STHP-5 inhibited activation of the STING/TBK1/NF-κB and IRF1/STAT1 signaling pathways in BMDMs, thereby suppressing M1 macrophage polarization and pro-inflammatory cytokine production. Additionally, STHP-5 protected BEAS-2B cells from Poly(I:C)-induced injury by maintaining tight-junction proteins and reducing oxidative stress.

CONCLUSION

STHP-5 effectively mitigates Poly(I:C)-induced acute lung injury through coordinated suppression of innate immune hyperactivation and reinforcement of epithelial barrier defense. These findings provide new mechanistic insight into the multi-target pharmacological actions of STHP-5 and support its potential development as a safe, locally deliverable polysaccharide-based therapeutic for viral and inflammatory lung diseases.