The protective effects of Mai-Luo-Ning injection against LPS-induced acute lung injury via the TLR4/NF-κB signalling pathway

Acute lung injury (ALI) is a severe inflammatory disorder associated with high morbidity and mortality rates. Various therapeutic strategies for ALI have been proposed over the last few decades; however, the treatment options remain limited. Mai-Luo-Ning injection (MLN), a traditional Chinese medical formulation, has been extensively used for the treatment of respiratory diseases. Nevertheless, the effects of MLN on ALI remain unclear. This study aimed to investigate the protective and therapeutic effects of MLN on lipopolysaccharide-induced ALI mouse models and RAW 264.7 cells, and further explore the underlying mechanism of these effects. The therapeutic activity of MLN was evaluated using an in vivo ALI model and an in vitro model of RAW 264.7 macrophages. UHPLC-ESI-Q-TOF-MS/MS was used to investigate the chemical constituents of the MLN. The material basis and potential protective mechanism of MLN were analyzed using network pharmacology. The roles of MLN in inhibiting the Toll-like receptor 4 (TLR4)/ nuclear factor kappa B (NF-κB) signalling pathway were investigated via western blotting, real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and immunofluorescence staining. In vivo experiments demonstrated that MLN ameliorated LPS-induced histological changes in lung tissues and reduced lung wet/dry weight ratio, total protein concentration in the bronchoalveolar lavage fluid and myeloperoxidase activity. Furthermore, MLN downregulated the in vivo and in vitro expression of pro-inflammatory cytokines such as tumour necrosis factor-alpha, interleukin-6, and interleukin-1β. Network pharmacology analysis revealed that MLN could act synergistically through multiple targets and pathways and exert a protective effect, possibly through inhibiting TLR4/ NF-κB signalling pathways. Western blotting and immunofluorescence experiments further confirmed that MLN could regulate the expression of TLR4, MyD88, phospho-IκB-α, and phospho-NF‐κB p65 in the TLR4/NF-κB signalling pathway and decrease the translocation of phospho-NF‐κB p65 into the nucleus. This study suggests that MLN has a potential protective effect against LPS-induced ALI, which might be associated with the inhibition of the TLR4/NF-κB signalling pathway. Therefore, MLN is worthy of further investigation as a potential candidate for the treatment of ALI in the future.