No abstract

New monosaccharide-based lipid A analogues were rationally designed through MD-2 docking studies. A panel of compounds with two carboxylate groups as phosphates bioisosteres, was synthesized with the same glucosamine-bis-succinyl core linked to different unsaturated and saturated fatty acid chains. The binding of the synthetic compounds to purified, functional recombinant human MD-2 was studied by four independent methods. All compounds bound to MD-2 with similar affinities and inhibited in a concentration-dependent manner the LPS-stimulated TLR4 signaling in human and murine cells, while being inactive as TLR4 agonists when provided alone. A compound of the panel was tested in vivo and was not able to inhibit the production of proinflammatory cytokines in animals. This lack of activity is probably due to strong binding to serum albumin, as suggested by cell experiments in the presence of the serum. The interesting self-assembly property in solution of this type of compounds was investigated by computational methods and microscopy, and formation of large vesicles was observed by cryo-TEM microscopy.

Despite significant advances made in the last decade in the understanding of molecular mechanisms of sepsis and in the development of clinically relevant therapies, sepsis remains the leading cause of mortality in intensive care units with increasing incidence worldwide. Toll‐like receptor 4 (TLR4)—a transmembrane pattern‐recognition receptor responsible for propagating the immediate immune response to Gram‐negative bacterial infection—plays a central role in the pathogenesis of sepsis and chronic inflammation‐related disorders. TLR4 is complexed with the lipopolysaccharide (LPS)‐sensing protein myeloid differentiation‐2 (MD‐2) which represents a preferred target for establishing new anti‐inflammatory treatment strategies. Herein we report the development, facile synthesis, and biological evaluation of novel disaccharide‐based TLR4⋅MD‐2 antagonists with potent anti‐endotoxic activity at micromolar concentrations. A series of synthetic anionic glycolipids entailing amide‐linked β‐ketoacyl lipid residues was prepared in a straightforward manner by using a single orthogonally protected nonreducing diglucosamine scaffold. Suppression of the LPS‐induced release of interleukin‐6 and tumor necrosis factor was monitored and confirmed in human immune cells (MNC and THP1) and mouse macrophages. Structure–activity relationship studies and molecular dynamics simulations revealed the structural basis for the high‐affinity interaction between anionic glycolipids and MD‐2, and highlighted two compounds as leads for the development of potential anti‐inflammatory therapeutics.