Phillygenin Inhibits PI3K-Akt–mTOR Signalling Pathway to Prevent bleomycin-Induced Idiopathic Pulmonary Fibrosis in Mice

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease characterised by irreversible lung structure and function. Phillygenin (PHI) is a lignan extracted from Forsythiae fructus with the activities of anti-inflammatory and antioxidant. This study aimed to explore the protective effect of PHI on IPF. The mouse model of IPF was established by bleomycin (BLM), and then treated with PHI. After 15 days of administration, the lung index was calculated. H&E staining, Masson staining and immunohistochemical methods were used to detect the effect of PHI on pulmonary fibrosis. MDA and SOD were tested to evaluate the effect of PHI on lung tissue oxidative stress. Western blot was used to detect the effect of PHI on the expressions of α-SMA, p-smad2, TGF- β1, Nrf2, HO-1 and NQO-1. Network pharmacology was used to identify the key signalling pathways for PHI to improve IPF, and Western blot was used to validate the result. The results showed that PHI prevented mice from BLM-induced IPF, manifested by reducing lung index, improving lung tissue pathological damage, inhibiting collagen deposition and expression of fibrosis markers including α-SMA, collagen1, p-smad2 and TGF-β1. PHI inhibited oxidative stress by upregulating the expressions of Nrf2, HO-1 and NQO-1. Network pharmacology revealed that PI3K-Akt–mTOR signalling pathway was the underlying target of PHI for IPF. Molecular docking indicated strong binding of PHI with PIK3CA, AKT1 and RELA. Western blot validated that PHI downregulated the PI3K-Akt–mTOR signalling pathway and stimulated autophagy. This study indicated that PHI prevented BLM-induced pulmonary fibrosis by inhibiting PI3K-Akt–mTOR signalling pathway.