Flavonoids from Radix Tetrastigmae improve LPS-induced acute lung injury via the TLR4/MD-2-mediated pathway

Total flavonoids isolated from Radix Tetrastigmae (RTFs) possess immunomodulatory activity, particularly on inflammation. In mice with lipopolysaccharide (LPS)‑induced acute lung injury (ALI), treatment with RTFs at 40, 80 and 160 mg/kg significantly reduced leukocyte infiltration, improved histopathological changes in lung tissues and decreased the LPS‑induced production of several inflammatory mediators in the bronchoalveolar lavage fluid (BALF), which included the chemotatic factors, granulocyte colony‑stimulating factor, monocyte inflammatory protein‑1α and B‑lymphocyte colony inflammatory cytokines, including interleukin (IL)‑1β, IL‑6, IL‑12p40 and tumor necrosis factor‑α, in a dose‑dependent manner. In addition, the expression of the Toll‑like receptor 4 (TLR4)/myeloid differentiation factor‑2 (MD‑2) compound, the phosphorylation of p38 mitogen‑activated protein kinase (p38MAPK), c‑Jun N‑terminal kinase (JNK) and nuclear transcription factor‑κB (NF‑κB), in addition to the DNA binding activity of NF‑κB p65 in lung tissues, were all attenuated following RTF treatment. However, RTF treatment had no effect on extracellular signal‑regulated kinase (ERK). In conclusion, RTFs contributed to the regulation of LPS‑induced ALI through the TLR4/MD-2-mediated NF‑κB, JNK and p38MAPK pathways. This may be a potential therapeutic option for the treatment of inflammatory diseases.