MD-2 as the Target of Nonlipid Chalcone in the Inhibition of Endotoxin LPS-Induced TLR4 Activity

Myeloid differentiation 2 (MD-2) recognizes endotoxin lipopolysaccharide (LPS), which is required for Toll-like receptor 4 (TLR4) activity. MD-2 represents a more attractive therapeutic target than TLR4 for intervention in severe inflammatory disorders due to microbial infection. Here, we suggest MD-2 as a molecular target of nonlipid chalcone in the inhibition of LPS-induced cellular inflammation. A chalcone derivative, 2',4-dihydroxy-6'-isopentyloxychalcone (JSH) competitively displaced LPS from MD-2, and was fitted into the ligand-binding site on the crystal structure of MD-2 under the most energetically favorable simulation. JSH nullified TLR4 activation mechanism and sequentially inhibited nuclear factor-kappa B (NF-kappa B) activation that involves the phosphorylation and degradation of inhibitory kappa Bs and the nuclear import and transcriptional activity of NF-kappa B in LPS-activated macrophages. Moreover, JSH suppressed NF-kappa B-target inflammatory genes such as inducible nitric oxide synthase, cyclooxygenase-2, interleukin-1 beta (IL-1 beta) and IL-6. Taken together, this study assigns the chalcone structure as an LPS antagonist binding to MD-2 with therapeutic potential against inflammatory conditions.