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

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.

Increasing the Chemical Variety of Small-Molecule-Based TLR4 Modulators: An Overview

“…It is known that unsaturated fatty acids are present in TLR4 antagonists such as the LPS synthesized by Rhodobacter sphaeroides (RS-LPS) or Rhodobacter capsulatus (RC-LPS) and the synthetic Eritoran. The results reported in this paper confirm that the presence of one unsaturation in the fatty acid chains favors the switch to antagonism ( 36 ).…”

“…Two studies focused on the investigation of the structure-activity relationship (SAR) in FP monosaccharides (as depicted in Figure 5 ): one explored the effect of the length of saturated fatty on the TLR4 activity and the second investigated both the effect of unsaturated fatty chains and the suitability of succinate groups as bioisosteres of phosphate groups ( 35 , 36 ).…”

Allergic Reactions and Immunity in Response to Tick Salivary Biogenic Substances and Red Meat Consumption in the Zebrafish Model

“…The TLR4 sensors bacterial lipopolysaccharides that activate the MyD88-dependent pathway resulting in Akr2/NF-κB activation leading to the production of IFN and proinflammatory cytokines (Perrin-Cocon et al, 2017). However, pathogen-derived glycolipids and glycoproteins can antagonize TLR-mediated response to interfere with cellular immune response (Hajishengallis and Lambris, 2011;Cochet et al, 2019). Basophil levels increase and infiltrate lesions after tick infestations contributing to acquired immunity and secretion of the histamine-repellent factor in tick-resistant animals (Karasuyama et al, 2018b;Tabakawa et al, 2018).…”

TLR4 in skin cancer: From molecular mechanisms to clinical interventions

“…Remarkably, most of the pharmacologically active TLR4 agonists are derived from the lipid A moiety of LPS (including eritoran and GLA‐SE), some of which have now entered oncological clinical trials (Table ). Contemporary drug discovery is adding an additional number of MD2‐directed TLR4 agonistic small molecule candidates for future clinical use, including novel carboxylate‐based glycolipids …”

“…Contemporary drug discovery is adding an additional number of MD2-directed TLR4 agonistic small molecule candidates for future clinical use, including novel carboxylate-based glycolipids. 80 Ongoing preclinical and clinical research will define the potential of TLR4-directed approaches for skin cancer prevention and intervention and will also identify the patient population that most benefits from these specific strategies. 81 Clinically, TLR4 agonists are currently being tested for their ability to act as immune-stimulating adjuvants targeting melanoma and MCC (Table 1).…”