RNA-seq analysis and in vivo experiments identified the protective effect of kaempferol on idiopathic pulmonary fibrosis by regulating the PPARG/TNC signaling pathway to reduce ECM deposition†

Idiopathic pulmonary fibrosis (IPF) is a chronic age-related lung disease with a high mortality rate. Kaempferol (KMP), an active ingredient in common plants and foods with anti-inflammatory, antioxidant and immunomodulatory properties, has been shown to be effective against fibrotic diseases. However, the molecular mechanisms underlying the treatment of IPF with KMP remain unclear. Therefore, IPF mice were established by intratracheal instillation of bleomycin (BLM) to explore the efficacy and underlying mechanism of KMP in the treatment of IPF. We found that KMP improved the body weight changes of BLM-induced IPF mice, alleviated inflammatory infiltration and collagen deposition, and decreased the expression levels of hydroxyproline, α-SMA, Col3a1, Mmp2, Timp1, Vim, Fn, TNF-α, TGF-β₁, IL-6 and IL-8, while up-regulating the expression E-cadherin in lung tissues. The transcriptomic results showed that KMP may exert therapeutic effects against IPF by regulating the PPARG/TNC signaling pathway to reduce extracellular matrix (ECM) deposition. Interestingly, ROC curve analysis suggested that TNC and PPARG had good diagnostic performance for IPF, and TF prediction revealed that PPARG is an important upstream gene regulating TNC, and the IF experiment confirmed the co-localization of TNC and PPARG. Molecular docking showed that KMP bound well to PPARG and TNC, and IF results revealed that KMP significantly reduced the interaction between PPARG and TNC. Furthermore, RT-PCR, WB, IHC and IF experiments confirmed that KMP elevated the expression of PPARG and inhibited the expression of TNC, thus inhibiting the ECM–receptor interaction pathway and ultimately serving as a therapeutic treatment for IPF mice. These findings revealed that KMP reduced inflammatory infiltration and collagen deposition in the lungs of IPF mice and that the PPARG/TNC signaling pathway may be an important mechanism for the treatment of IPF with KMP, which provides a new perspective for the development of therapeutic approaches for IPF.