Abstract:This study examines the effect of co‐administration of antimicrobial peptides and the synthetic glycolipid FP7, which is active in inhibiting inflammatory cytokine production caused by TLR4 activation and signaling. The co‐administration of two lipopolysaccharide (LPS)‐neutralizing peptides (a cecropin A–melittin hybrid peptide and a human cathelicidin) enhances by an order of magnitude the potency of FP7 in blocking the TLR4 signal. Interestingly, this is not an additional effect of LPS neutralization by pept… Show more
“…We have recently described the aggregation behavior of FP7 glycolipid, a related molecule to those described herein 51 . In particular, the analysis of the obtained NMR and TEM data (cryogenic and negative staining) permitted to show that FP7 forms micelle structures 36 . Indeed, previous investigations had demonstrated that FP7 has a CMC of about 9 µM 56 .…”
Section: Resultsmentioning
confidence: 99%
“…1) 25,33 or have a chemical structure unrelated to lipid A 34 . Eritoran and FP7 are the only lipid A mimetics whose direct binding to MD-2 and the competition with natural MD-2 ligands LPS and LOS have been reported 20,26,35,36 .Figure 1Chemical structures. Natural E .…”
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.
“…We have recently described the aggregation behavior of FP7 glycolipid, a related molecule to those described herein 51 . In particular, the analysis of the obtained NMR and TEM data (cryogenic and negative staining) permitted to show that FP7 forms micelle structures 36 . Indeed, previous investigations had demonstrated that FP7 has a CMC of about 9 µM 56 .…”
Section: Resultsmentioning
confidence: 99%
“…1) 25,33 or have a chemical structure unrelated to lipid A 34 . Eritoran and FP7 are the only lipid A mimetics whose direct binding to MD-2 and the competition with natural MD-2 ligands LPS and LOS have been reported 20,26,35,36 .Figure 1Chemical structures. Natural E .…”
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.
“…Interestingly, the synergy was observed also in a case where TLR4 was activated with lectins. DOSY NMR experiments and TEM microscopy images suggest a change in the supramolecular aggregation state of peptides caused by the interaction with FP7 ( 78 ).…”
“…The synergistic action of FP monosaccharides with antibacterial peptides neutralizing LPS was recently investigated ( 78 ). After LPS stimulation, FP7 was co-administrated to cells together with two anti-microbial peptides: cecropin A–melittin (CA–M) or LL-37, a human cathelicidin that binds to and neutralize LPS ( 79 , 80 ).…”
Toll-Like Receptor 4 (TLR4) is one of the receptors of innate immunity. It is activated by Pathogen- and Damage-Associated Molecular Patterns (PAMPs and DAMPs) and triggers pro-inflammatory responses that belong to the repertoire of innate immune responses, consequently protecting against infectious challenges and boosting adaptive immunity. Mild TLR4 stimulation by non-toxic molecules resembling its natural agonist (lipid A) provided efficient vaccine adjuvants. The non-toxic TLR4 agonist monophosphoryl lipid A (MPLA) has been approved for clinical use. This suggests the development of other TLR4 agonists as adjuvants or drugs for cancer immunotherapy. TLR4 excessive activation by a Gram-negative bacteria lipopolysaccharide (LPS) leads to sepsis, while TLR4 stimulation by DAMPs is a common mechanism in several inflammatory and autoimmune diseases. TLR4 inhibition by small molecules and antibodies could therefore provide access to innovative therapeutics targeting sepsis as well as acute and chronic inflammations. The potential use of TLR4 antagonists as anti-inflammatory drugs with unique selectivity and a new mechanism of action compared to corticosteroids or other non-steroid anti-inflammatory drugs fueled the search for compounds of natural or synthetic origin able to block or inhibit TLR4 activation and signaling. The wide spectrum of clinical settings to which TLR4 inhibitors can be applied include autoimmune diseases (rheumatoid arthritis, inflammatory bowel diseases), vascular inflammation, neuroinflammations, and neurodegenerative diseases. The last advances (from 2017) in TLR4 activation or inhibition by small molecules (molecular weight <2 kDa) are reviewed here. Studies on pre-clinical validation of new chemical entities (drug hits) on cellular or animal models as well as new clinical studies on previously developed TLR4 modulators are reported. Innovative TLR4 modulators discovered by computer-assisted drug design and an artificial intelligence approach are described. Some “old” TLR4 agonists or antagonists such as MPLA or Eritoran are under study for repositioning in different pharmacological contexts. The mechanism of action of the molecules and the level of TLR4 involvement in their biological activity are critically discussed.
“…The combination of peptides with other classes of molecules is also of pharmacological interest, since synergism between two compounds can result in inactivation of the TLR4 receptor. These results were clarified by researchers that surveyed the combined action between the anionic glycolipid FP7 (diphosphorylated glucosamine monosaccharide) and cationic peptides, reporting that it can boost the activity of AMPs of the cecropin class ( Facchini et al, 2018 ). The results showed that cationic peptides can increase the activity of cecropin AMPs (cecropin A melittin).…”
Section: Antimicrobial Peptides Activity On Toll-like Receptormentioning
Antimicrobial peptides are part of the organism’s defense system. They are multifunctional molecules capable of modulating the host’s immune system and recognizing molecules present in pathogens such as lipopolysaccharides (LPSs). LPSs are recognized by molecular patterns associated with pathogens known as Toll-like receptors (TLRs) that protect the organism from pathological microorganisms. TLR4 is responsible for LPS recognition, thus inducing an innate immune response. TLR4 hyperstimulation induces the uncontrolled inflammatory process that is observed in many illnesses, including neurodegenerative, autoimmune and psoriasis). Molecules that act on TLR4 can antagonize the exacerbated inflammatory process. In this context, antimicrobial peptides (AMPs) are promising molecules capable of mediating toll-like receptor signaling. Therefore, here we address the AMPs studied so far with the aim of inhibiting the intense inflammatory process. In addition, we aim to explore some of the interactions between exogenous AMPs and TLR4.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
