Aerosol inhalation of total ginsenosides repairs acute lung injury and inhibits pulmonary fibrosis through SMAD2 signaling-mediated mechanism.

BACKGROUND

Pulmonary fibrosis (PF) is a progressive lung disease caused by previous acute lung injury (ALI), but there is currently no satisfactory therapy available. Aerosol inhalation of medicine is an effective way for treating PF. Total ginsenosides (TG) shows potential for the treatment of ALI and PF, but the effects of inhaled TG remain unclear.

PURPOSE

To determine the therapeutic effects of TG in ALI and PF, to assess the superiority of the inhaled form of TG over the routine form, and to clarify the mechanism of action of inhaled TG.

METHODS

Ultrahigh-performance liquid chromatography coupled with Q-Exactive Orbitrap mass spectrometry (UPLC-QE-MS) was applied to determine the chemoprofile of TG. A mouse model of ALI and PF was established to evaluate the effects of inhaled TG by using bronchoalveolar lavage fluid (BALF) analysis, histopathological observation, hydroxyproline assay, and immunohistochemical analysis. Primary mouse lung fibroblasts (MLF) and human lung fibroblast cell line (HFL1) were applied to determine the in vitro effects and mechanism of TG by using cell viability assay, quantitative real time PCR (qPCR) assay, and western blot (WB) analysis.

RESULTS

The UPLC-QE-MS results revealed the main types of ginsenosides in TG, including Re (14.15 ± 0.42%), Rd (8.42 ± 0.49%), Rg1 (6.22 ± 0.42%), Rb3 (3.28 ± 0.01%), Rb2 (3.09 ± 0.00%), Rc (2.33 ± 0.01%), Rg2 (2.09 ± 0.04%), Rb1 (1.43 ± 0.24%), and Rf (0.13 ± 0.06%). Inhaled TG, at dosages of 10, 20, and 30 mg/kg significantly alleviated both ALI and PF in mice. Analyses of BALF and HE staining revealed that TG modulated the levels of IFN-γ, IL-1β, and TGF-β1, reduced inflammatory cell infiltration, and restored the alveolar architecture of the lung tissues. Furthermore, HE and Masson's trichrome staining demonstrated that TG markedly decreased fibroblastic foci and collagen fiber deposition, evidenced by the reduction of blue-stained collagen fibers. Hydroxyproline assay and immunohistochemical analyses indicated that TG significantly decreased hydroxyproline level and down-regulated the expression of Col1a1, Col3a1, and α-sma. The inhaled administration of TG demonstrated enhanced efficacy over the oral route when comparable doses were used. Additionally, inhaled TG showed superior safety and therapeutic profiles compared to pirfenidone, as evidenced by a CCK8 assay, which confirmed that TG concentrations ranging from 20 to 120 μg/ml were non-cytotoxic. qPCR and WB analyses revealed that TG, at concentrations of 25, 50, and 100 μg/ml, significantly suppressed the phosphorylation of smad2 induced by TGF-β1 and down-regulated the expression of fibrotic genes and proteins, including α-sma, Col1a1, Col3a1, and FN1, suggesting an anti-fibrotic mechanism mediated by the smad2 signaling pathway. In vitro, TG's safety and efficacy were also found to be superior to those of pirfenidone.

CONCLUSIONS

This study demonstrates, for the first time, the therapeutic efficacy of inhaled TG in treating ALI and PF. Inhaled TG effectively inhibits inflammation and reduces collagen deposition, with a particular emphasis on its role in modulating the Smad2 signaling pathway, which is implicated in the anti-fibrotic mechanism of TG. The study also highlights the superiority of inhaled TG over the oral route and its favorable safety profile in comparison to pirfenidone, positioning it as an ideal alternative for ALI and PF therapy.