Targeting myeloid differentiation protein 2 by the new chalcone L2H21 protects LPS-induced acute lung injury

Acute inflammatory diseases are the leading causes of mortality in intensive care units. Myeloid differentiation 2 (MD-2) is required for recognizing lipopolysaccharide (LPS) by toll-like receptor 4 (TLR4), and represents an attractive therapeutic target for LPS-induced inflammatory diseases. In this study, we report a chalcone derivative, L2H21, as a new MD2 inhibitor, which could inhibit LPS-induced inflammation both in vitro and in vivo. We identify that L2H21 as a direct inhibitor of MD-2 by binding to Arg⁹⁰ and Tyr¹⁰² residues in MD-2 hydrophobic pocket using a series of biochemical experiments, including surface plasmon response, molecular docking and amino acid mutation. L2H21 dose dependently inhibited LPS-induced inflammatory cytokine expression in primary macrophages. In mice with LPS intratracheal instillation, L2H21 significantly decreased LPS-induced pulmonary oedema, pathological changes in lung tissue, protein concentration increase in bronchoalveolar lavage fluid, inflammatory cells infiltration and inflammatory gene expression, accompanied with the decrease in pulmonary TLR4/MD-2 complex. Meanwhile, administration with L2H21 protects mice from LPS-induced mortality at a degree of 100%. Taken together, this study identifies a new MD2 inhibitor L2H21 as a promising candidate for the treatment of acute lung injury (ALI) and sepsis, and validates that inhibition of MD-2 is a potential therapeutic strategy for ALI.