A traditional herbal formula, Deng-Shi-Qing-Mai-Tang, regulates TLR4/NF-κB signaling pathway to reduce inflammatory response in PM2.5-induced lung injury

Studies revealed that particulate matter 2.5 (PM2.5) enters the lung through the respiratory tract and can damage lung tissue resulting in lung injury primarily via imbalance between pro-inflammatory and anti-inflammatory responses. Moreover, TLR4/NF-κB signaling pathways are reported to play a role in PM2.5-induced inflammation and lung injury, which is closely related to the inflammatory responses. Therefore, the traditional herbal formula, Deng-Shi-Qing-Mai-Tang (DSQMT), has been applied to improve patients' clinical symptoms with lung injury induced by PM2.5. It can reduce inflammatory reactions in lung injury and relieve cough and phlegm. However, the underlying mechanism of DSQMT treatment is still exclusive. To clarify the preventive and therapeutic effects of DSQMT on PM2.5-induced lung injury and explore its underlying mechanism. PM2.5-induced lung injury rat model was established, and DSQMT was administered. First, PM2.5 was collected, and PM2.5 suspension was prepared. Then, a rat model with PM2.5-induced lung injury was established, and the effects of DSQMT were evaluated in vivo. Finally, the roles of DSQMT in inhibiting the TLR4/NF-κB signaling pathway were investigated in vitro using the NR8383 cell line via Western blot analysis, real-time PCR, electrophoretic mobility shift assay (EMSA), and immunofluorescence staining, respectively and analyzed. We found that DSQMT significantly attenuated pathological lung tissue damage and inflammatory responses in PM2.5-induced lung injury. We also found that after PM2.5 stimulation in vitro, DSQMT regulates the expression of TLR4, MyD88, IKK, IκB-α, NF-κB p65 in the TLR4/NF-κB signaling pathway. It also constrains activated NF-κB entry into the nucleus and further limits its binding to target DNA. In addition, we revealed that DSQMT down-regulated interleukin (IL)-1β, IL-6, IL-10, THF-α, NO, PGE2 to reduce the inflammatory response. We demonstrated that DSQMT has preventive and therapeutic effects on PM2.5-induced lung injury by down-regulation of the TLR4/NF-κB signaling pathway. Therefore, the efficacy of traditional Chinese medicine (TCM) in PM2.5 lung injury can be taken into consideration and may be improved in the future through further researches.