Novel carboxylate-based glycolipids: TLR4 antagonism, MD-2 binding and self-assembly properties

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.TOLLerant project (H2020-MSC-ETN-642157), the Italian Ministry for Foreign Affairs and International Cooperation (MAECI) and Spanish MINECO (CTQ2014-57141-R and CTQ2017-88353-R grants) are acknowledged. Vesna Hodnik of University of Ljubljana for the help with SPR, Sandra Delgado of CIC BioGUNE for the Cryo-TEM images. RJ was partially funded by the research program P4-0176 by the Slovenian Research Agency