The mechanism of Shenlong Jianji treatment of idiopathic pulmonary fibrosis inhibits fibroblast-to-myofibroblast transformation via the TGF-β1/smads signaling pathway

Shenlong Jianji (SLJJ) is a Chinese herbal compound composed of traditional medicines for supplementing Qi, nourishing Yin, promoting blood circulation, and removing obstruction in channels. It is widely used to treat idiopathic pulmonary fibrosis (IPF) in China. However, the underlying mechanism of SLJJ remains unclear. To elucidate the efficacy and mechanisms of SLJJ in the treatment of IPF through in vivo and in vitro experiments. 84 Wistar rats were randomly and equally divided into 7 groups: the control group (CTRL), the sham operation group (SHAM), the model group (IPF), the low dose of SLJJ group (L-SLJJ), the middle dose of SLJJ group (M-SLJJ), the high dose of SLJJ group (H-SLJJ), and the pirfenidone group (PFD). The rats in the CTRL, SHAM, and IPF groups were given normal saline each time for 28 days; the SLJJ groups were given Shenlong Jianji (9 g kg-1·d-1, 18 g kg-1·d-1, 36 g kg-1·d-1), and pirfenidone was administered as a sequential dose. After 28 days, the general condition of the rats was evaluated, and samples were collected. The lung coefficient was measured. The pathological changes of lung in each group were observed by H&E staining and Masson staining. α-SMA, collagen 1, and E-cadherin proteins were detected by immunohistochemistry. α-SMA, collagen 1, vimentin, E-cadherin, N-cadherin, TGF-β1, smad2, and smad3 proteins were detected by WB in vivo. In vitro, A scratch test was used to assess the ratio of cell migration. α-SMA, vimentin, E-cadherin, and N-cadherin protein levels were evaluated by a cellular immunofluorescence assay. TGF-β1/smads signaling pathway was detected by WB. HPLC-Q-TOF/MS analysis was used to identify the active compounds in the SLJJ. Molecular docking determined the free binding energy of the compound with the TGF-β1 protein. SLJJ significantly improved the respiratory symptoms, heart rate, mental state, and food intake of IPF group rats and decreased the lung coefficient. In the IPF group, inflammatory cells were infiltrated, and the thickened alveoli wall and alveoli collapse were shown, while significantly alleviating pathological changes in the SLJJ and PFD groups. Masson staining showed that SLJJ and PFD decreased the collagen expression. Immunohistochemical results showed that the expressions of α-SMA, collagen 1, and N-cadherin decreased in the SLJJ and PFD groups, while E-cadherin increased significantly compared with the IPF group. SLJJ regulates TGF-β1/smads signaling pathway proteins in vivo. SLJJ decreased the ratio of migration in HFL-1 cells; SLJJ reduced the fluorescence intensity of α-SMA, vimentin, and N-cadherin and increased the fluorescence intensity of E-cadherin in primary rat lung (PRL) fibroblast cells and HFL-1 cells. WB results showed that SLJJ significantly down-regulated α-SMA, Vimentin, N-cadherin, TGF-β1, smad2, and p-smad2/3 proteins expression and up-regulated E-cadherin protein expression in vitro, whereas SRI-011381 (a TGF-β1 agonist) antagonized the effects of SLJJ. SLJJ inhibits idiopathic pulmonary fibrosis. The TGF- β1/Smads signaling pathway can be the target of SLJJ, which inhibits fibroblast-to-myofibroblast transformation and is expected to be a new drug for the treatment of IPF.