Polyphyllin <scp>VI</scp> Ameliorates Pulmonary Fibrosis by Suppressing the <scp>MAPK</scp>/<scp>ERK</scp> and <scp>PI3K</scp>/<scp>AKT</scp> Signaling Pathways via Upregulating <scp>DUSP6</scp>

Pulmonary fibrosis (PF) is a lethal disease caused by inordinate repair of damaged lungs, for which limited strategies are available. Polyphyllin VI (PPVI), extracted and isolated from Paris polyphylla Smith var. chinensis (Franch.) Hara, has been regarded as an important traditional Chinese herbal medicine for the treatment of respiratory system diseases. This study evaluated effects of PPVI on PF and its underlying mechanism. Experimental procedure For evaluating the anti-PF effect of PPVI, we established an in vivo PF mouse model via intratracheal infusion of bleomycin (BLM) in mice and an in vitro PF model induced by TGF-β1 in NIH/3T3, HPF and A549, respectively. Subsequently, the mechanism of PPVI effects was further explored using RNA sequencing (RNA-Seq). The in vivo and in vitro results demonstrated that PPVI significantly inhibited inflammation, oxidative damage, and epithelial-mesenchymal transition. Furthermore, RNA sequencing indicated that PPVI ameliorated PF by modulating inflammation and oxidative stress responses. Furthermore, dual specificity phosphatase 6 (DUSP6), was the shared and most significant differentially expressed gene associated with inflammation and oxidative stress response after PPVI treatment. Mechanistically, silencing DUSP6 can eliminate the suppressive impact on PPVI for the activation of fibroblast and the phosphorylation of ERK and AKT. Summarily, our findings revealed the potential of PPVI in mitigating PF via upregulating DUSP6 and highlighted the regulatory function of DUSP6 in the pathogenesis of PF.