Brain-derived neurotrophic factor and the derived dodecapeptide function as Toll-like receptor 4 antagonists in acute lung injury.

The neurotrophic factor (NTF) family has recently expanded its role beyond neurological conditions, but its involvement in acute inflammatory lung diseases remains largely unclear. Using well-established acute lung injury (ALI) and sepsis models, we demonstrate that brain-derived neurotrophic factor (BDNF), a key NTF, is impaired in pulmonary epithelial cells and negatively correlates with the inflammatory response. Raising the BDNF level alleviates inflammatory lung injury, but these effects are absent in macrophage-deleted mice. Both in vivo and in vitro results show BDNF inhibits macrophage inflammation, and further proteomics analysis identifies macrophage TLR4 as a receptor that BDNF antagonizes via direct binding. The BDNF fragment (aa 104-115) is critical for BDNF-TLR4 interaction, and the corresponding synthetic BDNF-derived dodecapeptide (BDP-12) retains TLR4-antagonistic and anti-inflammatory effects both in vitro and in vivo, without pro-proliferative side effects. In conclusion, our findings reveal that epithelial-derived BDNF prevents macrophage inflammation by directly targeting TLR4 and highlights BDP-12 as a potential therapeutic agent for acute inflammatory diseases.