Background and Purpose Myeloid differentiation 2 (MD‐2) recognizes LPS, which is required for TLR4 activation, and represents an attractive therapeutic target for severe inflammatory disorders. We previously found that a chalcone derivative, L6H21, could inhibit LPS‐induced overexpression of TNF‐α and IL‐6 in macrophages. Here, we performed a series of biochemical experiments to investigate whether L6H21 specifically targets MD‐2 and inhibits the interaction and signalling transduction of LPS‐TLR4/MD‐2. Experimental Approach The binding affinity of L6H21 to MD‐2 protein was analysed using computer docking, surface plasmon resonance analysis, elisa, fluorescence measurements and flow cytometric analysis. The effects of L6H21 on MAPK and NF‐κB signalling were determined using EMSA, fluorescence staining, Western blotting and immunoprecipitation. The anti‐inflammatory effects of L6H21 were confirmed using elisa and RT‐qPCR in vitro. The anti‐inflammatory effects of L6H21 were also evaluated in septic C57BL/6 mice. Key Results Compound L6H21 inserted into the hydrophobic region of the MD‐2 pocket, forming hydrogen bonds with Arg90 and Tyr102 in the MD‐2 pocket. In vitro, L6H21 subsequently suppressed MAPK phosphorylation, NF‐κB activation and cytokine expression in macrophages stimulated by LPS. In vivo, L6H21 pretreatment improved survival, prevented lung injury, decreased serum and hepatic cytokine levels in mice subjected to LPS. In addition, mice with MD‐2 gene knockout were universally protected from the effects of LPS‐induced septic shock. Conclusions and Implications Overall, this work demonstrated that the new chalcone derivative, L6H21, is a potential candidate for the treatment of sepsis. More importantly, the data confirmed that MD‐2 is an important therapeutic target for inflammatory disorders.

Endotoxin-induced acute inflammatory diseases such as sepsis, mediated by excessive production of various proinflammatory cytokines, remain the leading cause of mortality in critically ill patients. Lipopolysaccharide (LPS), the characteristic endotoxin found in the outer membrane of Gram-negative bacteria, can induce the innate immunity system and through the myeloid differentiation protein 2 (MD2) and Toll-like receptor 4 (TLR4) complex, increase the production of inflammatory mediators. Our previous studies have found that a curcumin analog, L48H37 [1-ethyl-3,5-bis(3,4,5-trimethoxybenzylidene)piperidin-4-one], was able to inhibit LPS-induced inflammation, particularly tumor necrosis factor a and interleukin 6 production and gene expression in mouse macrophages. In this study, a series of biochemical experiments demonstrate L48H37 specifically targets MD2 and inhibits the interaction and signaling transduction of LPS-TLR4/ MD2. L48H37 binds to the hydrophobic region of MD2 pocket and forms hydrogen bond interactions with Arg 90 and Tyr 102. Subsequently, L48H37 was shown to suppress LPS-induced mitogenactivated protein kinase phosphorylation and nuclear factor kB activation in macrophages; it also dose dependently inhibits the cytokine expression in macrophages and human peripheral blood mononuclear cells stimulated by LPS. In LPS-induced septic mice, both pretreatment and treatment with L48H37 significantly improved survival and protected lung injury. Taken together, this work identified a new MD2 specific inhibitor, L48H37, as a potential candidate in the treatment of sepsis.

Sepsis, an acute inflammatory disease, remains the most common cause of death in intensive care units. A series of benzimidazole and imidazopyridine derivatives were synthesized and screened for anti-inflammatory activities, and the imidazopyridine series showed excellent inhibition of the expression of inflammatory cytokines in LPS-stimulated macrophages. Compounds X10, X12, X13, X14, and X15 inhibited TNF-α and IL-6 release in a dose-dependent manner, and X12 showed no cytotoxicity in hepatic cells. Furthermore, X12 exhibited a significant protection against LPS-induced septic death in mouse models. Together, these data present a series of new imidazopyridines with potential therapeutic effects in acute inflammatory diseases.

Growing evidence indicates that angiotensin II (Ang II), a potent biologically active product of RAS, is a key regulator of renal inflammation and fibrosis. In this study, we tested the hypothesis that Ang II induces renal inflammatory injury and fibrosis through interaction with myeloid differentiation protein-2 (MD2), the accessory protein of toll-like receptor 4 (TLR4) of the immune system. Results indicated that in MD2−/− mice, the Ang II-induced renal fibrosis, inflammation and kidney dysfunction were significantly reduced compared to control Ang II-infused wild-type mice. Similarly, in the presence of small molecule MD2 specific inhibitor L6H21 or siRNA-MD2, the Ang II-induced increases of pro-fibrotic and pro-inflammatory molecules were prevented in tubular NRK-52E cells. MD2 blockade also inhibited activation of NF-κB and ERK. Moreover, MD2 blockade prevented the Ang II-stimulated formation of the MD2/TLR4/MyD88 signaling complex, as well as the increased surface binding of Ang II in NRK-52E cells. In addition, Ang II directly bound recombinant MD2 protein, rather than TLR4 protein. We conclude that MD2 is a significant contributor in the Ang II-induced kidney inflammatory injury in chronic renal diseases. Furthermore, MD2 inhibition could be a new and important therapeutic strategy for preventing progression of chronic renal diseases.