Discovery of 3-(Indol-5-yl)-indazole Derivatives as Novel Myeloid Differentiation Protein 2/Toll-like Receptor 4 Antagonists for Treatment of Acute Lung Injury.
Liu Z, Chen L, Yu P, Zhang Y, Fang B, Wu C, Luo W, Chen X, Li C, Liang G.
Acute lung injury (ALI) is often caused by systemic inflammatory responses. Targeting the myeloid differentiation protein 2/toll-like receptor 4 (MD2-TLR4) complex may be a promising way to treat Gram-negative bacterial-induced inflammatory disorders. In this study, we report the design and synthesis of a new series of 3-(indol-5-yl)-indazoles, which were evaluated for their anti-inflammatory activities in macrophages. Among the analogues generated, the promising 3-(indol-5-yl)-indazole analogue 22m inhibited lipopolysaccharide (LPS)-induced expression of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) in macrophages with IC<sub>50</sub> values of 0.89 and 0.53 μM, respectively. Compound 22m was then identified as an MD2-TLR4 antagonist in suppressing LPS-induced inflammatory responses. In vivo administration of 22m significantly inhibited macrophage infiltration and ameliorated histopathological changes in lung tissues of LPS-challenged mice. Our studies have identified a new 3-(indol-5-yl)-indazole, 22m, as a potent MD2-TLR4 inhibitor and lay the groundwork for future drug development of anti-inflammatory agents for the treatment of ALI.