Ginsenoside Rh2 ameliorates pulmonary fibrosis via HSP70-dependent autophagic flux regulation and senescence arrest

ETHNOPHARMACOLOGICAL RELEVANCE: Panax ginseng C.A. Meyer, a prominent Qi-tonifying herb in Traditional Chinese Medicine (TCM), has been traditionally used to enhance spleen and pulmonary functions through Qi regulation, consistent with the TCM doctrine of "fortifying vital qi while dispelling pathogens". Ginsenoside Rh2 (G-Rh2), a primary bioactive constituent of P. ginseng, exhibits diverse pharmacological activities. However, its molecular targets and anti-fibrotic mechanisms in pulmonary fibrosis (PF) have not been fully elucidated. AIM OF THE STUDY: This study aimed to evaluate the therapeutic potential of G-Rh2 against PF and delineate its molecular mechanisms. METHODS: Male C57BL/6 mice received a single intratracheal dose of bleomycin (5 mg/kg) to induce PF. From day 4 post-induction, G-Rh2 (2.5 or 5 mg/kg/day) or pirfenidone (100 mg/kg/day) was administered orally for 24 days. Concurrently, bleomycin-treated type II alveolar epithelial cells and HSP70-knockdown models were established. Multimodal analyses included western blotting, immunofluorescence, histopathology, and transmission electron microscopy. RESULTS: G-Rh2 ameliorated pulmonary dysfunction and attenuated PF progression by inhibiting p53/p21-dependent senescence and restoring PINK1/Parkin-mediated mitophagy. In vitro, G-Rh2 significantly reduced bleomycin-induced extracellular matrix deposition and senescence-associated changes. Mechanistically, G-Rh2 bound directly to HSP70, reversing its suppression. Notably, knockdown of HSP70 abrogated G-Rh2 effects on autophagy and senescence. CONCLUSIONS: Our findings demonstrate that G-Rh2 ameliorated PF through HSP70-dependent modulation of autophagic flux and senescence inhibition, highlighting its potential as a novel therapeutic candidate for fibrotic lung diseases.