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Janež Š, Guzelj S, Kocbek P, de Vlieger EA, Slütter B, Jakopin Ž. Distinctive Immune Signatures Driven by Structural Alterations in Desmuramylpeptide NOD2 Agonists. J Med Chem 2024; 67:17585-17607. [PMID: 39344184 PMCID: PMC11472310 DOI: 10.1021/acs.jmedchem.4c01577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2024] [Revised: 09/17/2024] [Accepted: 09/19/2024] [Indexed: 10/01/2024]
Abstract
Herein we report on the design, synthesis and biological evaluation of a series of nucleotide-binding oligomerization-domain-containing protein 2 (NOD2) desmuramylpeptide agonists. The structural prerequisites that shape both physicochemical and immunomodulatory profiles of desmuramylpeptide NOD2 agonists have been delineated. Within this context, we identified 3, a butyrylated desmuramylpeptide, as a potent in vitro NOD2 agonist (EC50 = 4.6 nM), exhibiting an almost 17-fold enhancement in potency compared to its unsubstituted counterpart 1 (EC50 = 77.0 nM). The novel set of desmuramylpeptides demonstrate unique in vitro immunomodulatory activities. They elicited cytokine production in peripheral blood mononuclear cells (PBMCs), both alone and in conjunction with lipopolysaccharide (LPS). The spermine-decorated 32 also stimulated the LPS-induced cytotoxic activity (2.95-fold) of PBMCs against K562 cancer cells. Notably, the cholesterol-conjugate 26 displayed anti-inflammatory actions, highlighted by its capacity to convert the inflammatory monocyte subset into an anti-inflammatory phenotype. Finally, the eicosapentaenoylated derivative 23 augmented antigen presentation by mouse bone marrow-derived dendritic cells (BMDCs), thus highlighting its potential as a vaccine adjuvant.
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Affiliation(s)
- Špela Janež
- Faculty
of Pharmacy, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - Samo Guzelj
- Faculty
of Pharmacy, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - Petra Kocbek
- Faculty
of Pharmacy, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - Eveline A. de Vlieger
- Div.
BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, 2333 CC Leiden, The Netherlands
| | - Bram Slütter
- Div.
BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, 2333 CC Leiden, The Netherlands
| | - Žiga Jakopin
- Faculty
of Pharmacy, University of Ljubljana, SI-1000 Ljubljana, Slovenia
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2
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Kamboj A, Patil MT, Petrovsky N, Salunke DB. Structure-activity relationship in NOD2 agonistic muramyl dipeptides. Eur J Med Chem 2024; 271:116439. [PMID: 38691886 PMCID: PMC11099613 DOI: 10.1016/j.ejmech.2024.116439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 01/04/2024] [Accepted: 04/18/2024] [Indexed: 05/03/2024]
Abstract
Nucleotide-binding oligomerization domain 2 (NOD2) is a receptor of the innate immune system that is capable of perceiving bacterial and viral infections. Muramyl dipeptide (MDP, N-acetyl muramyl L-alanyl-d-isoglutamine), identified as the minimal immunologically active component of bacterial cell wall peptidoglycan (PGN) is recognized by NOD2. In terms of biological activities, MDP demonstrated vaccine adjuvant activity and stimulated non-specific protection against bacterial, viral, and parasitic infections and cancer. However, MDP has certain drawbacks including pyrogenicity, rapid elimination, and lack of oral bioavailability. Several detailed structure-activity relationship (SAR) studies around MDP scaffolds are being carried out to identify better NOD2 ligands. The present review elaborates a comprehensive SAR summarizing structural aspects of MDP derivatives in relation to NOD2 agonistic activity.
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Affiliation(s)
- Aarzoo Kamboj
- Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh, 160014, India
| | - Madhuri T Patil
- Department of Chemistry, Mehr Chand Mahajan DAV College for Women, Chandigarh 160036, India
| | - Nikolai Petrovsky
- Vaxine Pty Ltd, Warradale, Australia; Australian Respiratory and Sleep Medicine Institute, Bedford Park, South Australia 5042, Australia.
| | - Deepak B Salunke
- Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh, 160014, India; National Interdisciplinary Centre of Vaccine, Immunotherapeutics and Antimicrobials, Panjab University, Chandigarh, 160014, India.
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3
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Dangerfield EM, Ishizuka S, Kodar K, Yamasaki S, Timmer MSM, Stocker BL. Chimeric NOD2 Mincle Agonists as Vaccine Adjuvants. J Med Chem 2024; 67:5373-5390. [PMID: 38507580 DOI: 10.1021/acs.jmedchem.3c01840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
There is a need for improved vaccine adjuvants to augment vaccine efficacy. One way to address this is by targeting multiple immune cell pathogen recognition receptors (PRRs) using chimeric pathogen-associated molecular patterns (PAMPs). Conjugation of the PAMPs will ensure codelivery of the immunostimulatory molecules to the same cell, enhancing adjuvant activity. The macrophage inducible C-type lectin (Mincle) is a promising PRR for adjuvant development; however, no effective chimeric Mincle adjuvants have been prepared. We addressed this by synthesizing Mincle adjuvant conjugates, MDP-C18Brar and MDP-C18Brar-dilipid, which contain PAMPs recognized by Mincle and the nucleotide-binding oligomerization domain 2 (NOD2). The two PAMPs are joined by a pH-sensitive oxyamine linker which, upon acidification at lysosomal pH, hydrolyzed to release the NOD2 ligands. The conjugates elicited the production of Th1 and Th17 promoting cytokines in vitro, and when using OVA as a model antigen, exhibited enhanced T-cell-mediated immune responses and reduced toxicity in vivo, compared to the coadministration of the adjuvants.
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Affiliation(s)
- Emma M Dangerfield
- School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
- Centre for Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Shigenari Ishizuka
- Department of Molecular Immunology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
- Laboratory of Molecular Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
| | - Kristel Kodar
- School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
- Centre for Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Sho Yamasaki
- Department of Molecular Immunology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
- Laboratory of Molecular Immunology, Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
- Division of Molecular Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Fukuoka 812-8582, Japan
- Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chiba, 260-8673, Japan
| | - Mattie S M Timmer
- School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
- Centre for Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Bridget L Stocker
- School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
- Centre for Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
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Synthesis and Immunological Evaluation of Mannosylated Desmuramyl Dipeptides Modified by Lipophilic Triazole Substituents. Int J Mol Sci 2022; 23:ijms23158628. [PMID: 35955759 PMCID: PMC9368957 DOI: 10.3390/ijms23158628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 07/30/2022] [Accepted: 08/01/2022] [Indexed: 02/05/2023] Open
Abstract
Muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine, MDP) is the smallest peptidoglycan fragment able to trigger an immune response by activating the NOD2 receptor. Structural modification of MDP can lead to analogues with improved immunostimulating properties. The aim of this work was to prepare mannosylated desmuramyl peptides (ManDMP) containing lipophilic triazole substituents to study their immunomodulating activities in vivo. The adjuvant activity of the prepared compounds was evaluated in the mouse model using ovalbumin as an antigen and compared to the MDP and referent adjuvant ManDMPTAd. The obtained results confirm that the α-position of D-isoGln is the best position for the attachment of lipophilic substituents, especially adamantylethyl triazole. Compound 6c exhibited the strongest adjuvant activity, comparable to the MDP and better than referent ManDMPTAd.
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Vacariu CM, Tanner ME. Recent Advances in the Synthesis and Biological Applications of Peptidoglycan Fragments. Chemistry 2022; 28:e202200788. [PMID: 35560956 DOI: 10.1002/chem.202200788] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Indexed: 11/09/2022]
Abstract
The biosynthesis, breakdown, and modification of peptidoglycan (PG) play vital roles in both bacterial viability and in the response of human physiology to bacterial infection. Studies on PG biochemistry are hampered by the fact that PG is an inhomogeneous insoluble macromolecule. Chemical synthesis is therefore an important means to obtain PG fragments that may serve as enzyme substrates and elicitors of the human immune response. This review outlines the recent advances in the synthesis and biochemical studies of PG fragments, PG biosynthetic intermediates (such as Park's nucleotides and PG lipids), and PG breakdown products (such as muramyl dipeptides and anhydro-muramic acid-containing fragments). A rich variety of synthetic approaches has been applied to preparing such compounds since carbohydrate, peptide, and phospholipid chemical methodologies must all be applied.
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Affiliation(s)
- Condurache M Vacariu
- Department of Chemistry, University of British Columbia, V6T 1Z1, Vancouver, British Columbia, Canada
| | - Martin E Tanner
- Department of Chemistry, University of British Columbia, V6T 1Z1, Vancouver, British Columbia, Canada
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Reddy PRS, Sambyal S, Mhamane TB, Sravanthi V, Shafi S, Khan IA, Sampath Kumar HM. Synthesis and biological evaluation of novel 2-azido muramyl dipeptide as NOD2 agonistic adjuvants. Bioorg Med Chem 2022; 66:116781. [PMID: 35569249 DOI: 10.1016/j.bmc.2022.116781] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/22/2022] [Accepted: 04/23/2022] [Indexed: 11/25/2022]
Abstract
Novel 2-Azido muramyl dipeptide was synthesized by the bio-isosteric replacement of the N-acetyl group of the muramic acid fragment with the azide functionality at the C2 position. In order to examine the effect of hydrophilic-lipophilic balance on the adjuvant activity, derivatives were synthesized by removing protecting groups sequentially to tune the polarity. Amongst five novel azido derivatives of MDP studied here, di- and mono-benzylated azido derivatives 10 and 11 exhibited good DENV specific antibody(IgG) response with Th1 polarization compared to parent compound Muramyl dipeptide (MDP) whereas all five new derivatives responded positively to NOD2 agonistic assays with compound 10 showing highest stimulation.
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Affiliation(s)
- Paturu Rama Subba Reddy
- Vaccine Immunology Laboratory, OSPC Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201 002, India
| | - Shainy Sambyal
- Vaccine Immunology Laboratory, OSPC Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201 002, India
| | - Tukaram B Mhamane
- Vaccine Immunology Laboratory, OSPC Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201 002, India
| | - Vemireddy Sravanthi
- Vaccine Immunology Laboratory, OSPC Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India
| | - Syed Shafi
- Department of Chemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, India
| | - Imran A Khan
- Department of Chemistry, School of Chemical and Life Sciences, Jamia Hamdard, New Delhi, India
| | - Halmuthur M Sampath Kumar
- Vaccine Immunology Laboratory, OSPC Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201 002, India.
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Lipid A analog CRX-527 conjugated to synthetic peptides enhances vaccination efficacy and tumor control. NPJ Vaccines 2022; 7:64. [PMID: 35739113 PMCID: PMC9226002 DOI: 10.1038/s41541-022-00484-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 05/13/2022] [Indexed: 11/09/2022] Open
Abstract
Adjuvants play a determinant role in cancer vaccination by optimally activating APCs and shaping the T cell response. Bacterial-derived lipid A is one of the most potent immune-stimulators known, and is recognized via Toll-like receptor 4 (TLR4). In this study, we explore the use of the synthetic, non-toxic, lipid A analog CRX-527 as an adjuvant for peptide cancer vaccines. This well-defined adjuvant was covalently conjugated to antigenic peptides as a strategy to improve vaccine efficacy. We show that coupling of this TLR4 agonist to peptide antigens improves vaccine uptake by dendritic cells (DCs), maturation of DCs and T cell activation in vitro, and stimulates DC migration and functional T cell priming in vivo. This translates into enhanced tumor protection upon prophylactic and therapeutic vaccination via intradermal injection against B16-OVA melanoma and HPV-related TC1 tumors. These results highlight the potential of CRX-527 as an adjuvant for molecularly defined cancer vaccines, and support the design of adjuvant-peptide conjugates as a strategy to optimize vaccine formulation.
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Built-in adjuvants for use in vaccines. Eur J Med Chem 2022; 227:113917. [PMID: 34688011 DOI: 10.1016/j.ejmech.2021.113917] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 09/30/2021] [Accepted: 10/09/2021] [Indexed: 02/08/2023]
Abstract
Vaccine refers to biological products that are produced using various pathogenic microorganisms for inoculation. The goal of vaccination is to induce a robust immune response against a specific antigen, thus preventing the organism from getting infected. In vaccines, adjuvants have been widely employed to enhance immunity against specific antigens. An ideal adjuvant should be stable, biodegradable, and low cost, not induce system rejection and promote an immune response. Various adjuvant components have been investigated across diverse applications. Typically, adjuvants are employed to meet the following objectives: (1) to improve the effectiveness of immunization with vaccines for specific populations, such as newborns and the elderly; (2) enhance the immunogenicity of highly purified or recombinant antigens; (3) allow immunization with a smaller dose of the vaccine, reducing drug dosage. In the present review, we primarily focus on chemically synthesized compounds that can be used as built-in adjuvants. We elaborate the classification of these compounds based on the induced immune activation mechanism and summarize their application in various vaccine types.
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Khan F, Khanam R, Wasim Qasim M, Wang Y, Jiang Z. Improved Synthesis of D‐Isoglutamine: Rapid Access to Desmuramyl Analogues of Muramyl Dipeptide for the Activation of Intracellular NOD2 Receptor and Vaccine Adjuvant Applications. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Farooq‐Ahmad Khan
- Third World Center (TWC) for Chemical Sciences International Center for Chemical & Biological Sciences University of Karachi-75270 Pakistan
- H.E.J. Research Institute of Chemistry International Center for Chemical & Biological Sciences University of Karachi-75270 Pakistan
| | - Rahila Khanam
- Third World Center (TWC) for Chemical Sciences International Center for Chemical & Biological Sciences University of Karachi-75270 Pakistan
- H.E.J. Research Institute of Chemistry International Center for Chemical & Biological Sciences University of Karachi-75270 Pakistan
| | - Muhammad Wasim Qasim
- Third World Center (TWC) for Chemical Sciences International Center for Chemical & Biological Sciences University of Karachi-75270 Pakistan
- H.E.J. Research Institute of Chemistry International Center for Chemical & Biological Sciences University of Karachi-75270 Pakistan
| | - Yan Wang
- H.E.J. Research Institute of Chemistry International Center for Chemical & Biological Sciences University of Karachi-75270 Pakistan
| | - Zi‐Hua Jiang
- Department of Chemistry Lakehead University 955 Oliver Rd Thunder Bay Ontario P7B 5E1 Canada
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10
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Design, Synthesis, and Biological Evaluation of Desmuramyl Dipeptides Modified by Adamantyl-1,2,3-triazole. Molecules 2021; 26:molecules26216352. [PMID: 34770761 PMCID: PMC8587862 DOI: 10.3390/molecules26216352] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/16/2021] [Accepted: 10/18/2021] [Indexed: 11/17/2022] Open
Abstract
Muramyl dipeptide (MDP) is the smallest peptidoglycan fragment able to trigger the immune response. Structural modification of MDP can lead to the preparation of analogs with improved immunostimulant properties, including desmuramyl peptides (DMPs). The aim of this work was to prepare the desmuramyl peptide (L-Ala-D-Glu)-containing adamantyl-triazole moiety and its mannosylated derivative in order to study their immunomodulatory activities in vivo. The adjuvant activity of the prepared compounds was evaluated in a murine model using ovalbumin as an antigen, and compared to the reference adjuvant ManAdDMP. The results showed that the introduction of the lipophilic adamantyl-triazole moiety at the C-terminus of L-Ala-D-Glu contributes to the immunostimulant activity of DMP, and that mannosylation of DMP modified with adamantyl-triazole causes the amplification of its immunostimulant activity.
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Fani Maleki A, Cisbani G, Laflamme N, Prefontaine P, Plante MM, Baillargeon J, Rangachari M, Gosselin J, Rivest S. Selective Immunomodulatory and Neuroprotective Effects of a NOD2 Receptor Agonist on Mouse Models of Multiple Sclerosis. Neurotherapeutics 2021; 18:889-904. [PMID: 33479802 PMCID: PMC8423880 DOI: 10.1007/s13311-020-00998-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2020] [Indexed: 12/13/2022] Open
Abstract
The significance of monocytes has been demonstrated in multiple sclerosis (MS). One of the therapeutic challenges is developing medications that induce mild immunomodulation that is solely targeting specific monocyte subsets without affecting microglia. Muramyl dipeptide (MDP) activates the NOD2 receptor, and systemic MDP administrations convert Ly6Chigh into Ly6Clow monocytes. Here, we report selective immunomodulatory and therapeutic effects of MDP on cuprizone and experimental autoimmune encephalomyelitis (EAE) mouse models of MS. MDP treatment exerted various therapeutic effects in EAE, including delaying EAE onset and reducing infiltration of leukocytes into the CNS before EAE onset. Of great interest is the robust beneficial effect of the MDP treatment in mice already developing the disease several days after EAE onset. Finally, we found that the NOD2 receptor plays a critical role in MDP-mediated EAE resistance. Our results demonstrate that MDP is beneficial in both early and progressive phases of EAE. Based on these results, and upon comprehensive basic and clinical research, we anticipate developing NOD2 agonist-based medications for MS in the future.
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MESH Headings
- Acetylmuramyl-Alanyl-Isoglutamine/pharmacology
- Acetylmuramyl-Alanyl-Isoglutamine/therapeutic use
- Adjuvants, Immunologic/pharmacology
- Adjuvants, Immunologic/therapeutic use
- Animals
- Disease Models, Animal
- Encephalomyelitis, Autoimmune, Experimental/chemically induced
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/prevention & control
- Freund's Adjuvant/toxicity
- Immunomodulating Agents/pharmacology
- Immunomodulating Agents/therapeutic use
- Male
- Mice
- Mice, Inbred C57BL
- Monocytes/drug effects
- Monocytes/immunology
- Multiple Sclerosis/chemically induced
- Multiple Sclerosis/immunology
- Multiple Sclerosis/prevention & control
- Myelin-Oligodendrocyte Glycoprotein/toxicity
- Neuroprotective Agents/pharmacology
- Neuroprotective Agents/therapeutic use
- Nod2 Signaling Adaptor Protein/agonists
- Peptide Fragments/toxicity
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Affiliation(s)
- Adham Fani Maleki
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Giulia Cisbani
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Nataly Laflamme
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Paul Prefontaine
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Marie-Michele Plante
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Joanie Baillargeon
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Manu Rangachari
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Jean Gosselin
- Laboratory of Innate Immunity, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada
| | - Serge Rivest
- Neuroscience Laboratory, CHU of Quebec Research Center and Department of Molecular Medicine, Faculty of Medicine, Laval University, 2705 Laurier Boul., Quebec City, QC, G1V 4G2, Canada.
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Li RJE, Hogervorst TP, Achilli S, Bruijns SC, Arnoldus T, Vivès C, Wong CC, Thépaut M, Meeuwenoord NJ, van den Elst H, Overkleeft HS, van der Marel GA, Filippov DV, van Vliet SJ, Fieschi F, Codée JDC, van Kooyk Y. Systematic Dual Targeting of Dendritic Cell C-Type Lectin Receptor DC-SIGN and TLR7 Using a Trifunctional Mannosylated Antigen. Front Chem 2019; 7:650. [PMID: 31637232 PMCID: PMC6787163 DOI: 10.3389/fchem.2019.00650] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 09/11/2019] [Indexed: 01/22/2023] Open
Abstract
Dendritic cells (DCs) are important initiators of adaptive immunity, and they possess a multitude of Pattern Recognition Receptors (PRR) to generate an adequate T cell mediated immunity against invading pathogens. PRR ligands are frequently conjugated to tumor-associated antigens in a vaccination strategy to enhance the immune response toward such antigens. One of these PPRs, DC-SIGN, a member of the C-type lectin receptor (CLR) family, has been extensively targeted with Lewis structures and mannose glycans, often presented in multivalent fashion. We synthesized a library of well-defined mannosides (mono-, di-, and tri-mannosides), based on known "high mannose" structures, that we presented in a systematically increasing number of copies (n = 1, 2, 3, or 6), allowing us to simultaneously study the effect of mannoside configuration and multivalency on DC-SIGN binding via Surface Plasmon Resonance (SPR) and flow cytometry. Hexavalent presentation of the clusters showed the highest binding affinity, with the hexa-α1,2-di-mannoside being the most potent ligand. The four highest binding hexavalent mannoside structures were conjugated to a model melanoma gp100-peptide antigen and further equipped with a Toll-like receptor 7 (TLR7)-agonist as adjuvant for DC maturation, creating a trifunctional vaccine conjugate. Interestingly, DC-SIGN affinity of the mannoside clusters did not directly correlate with antigen presentation enhancing properties and the α1,2-di-mannoside cluster with the highest binding affinity in our library even hampered T cell activation. Overall, this systematic study has demonstrated that multivalent glycan presentation can improve DC-SIGN binding but enhanced binding cannot be directly translated into enhanced antigen presentation and the sole assessment of binding affinity is thus insufficient to determine further functional biological activity. Furthermore, we show that well-defined antigen conjugates combining two different PRR ligands can be generated in a modular fashion to increase the effectiveness of vaccine constructs.
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Affiliation(s)
- Rui-Jun Eveline Li
- Department of Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam Infection and Immunity Institute, Amsterdam Universitair Medische Centra, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Tim P. Hogervorst
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Silvia Achilli
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, Grenoble, France
| | - Sven C. Bruijns
- Department of Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam Infection and Immunity Institute, Amsterdam Universitair Medische Centra, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Tim Arnoldus
- Department of Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam Infection and Immunity Institute, Amsterdam Universitair Medische Centra, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Corinne Vivès
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, Grenoble, France
| | - Chung C. Wong
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Michel Thépaut
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, Grenoble, France
| | - Nico J. Meeuwenoord
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Hans van den Elst
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Herman S. Overkleeft
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Gijs A. van der Marel
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Dmitri V. Filippov
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Sandra J. van Vliet
- Department of Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam Infection and Immunity Institute, Amsterdam Universitair Medische Centra, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Franck Fieschi
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, Grenoble, France
| | - Jeroen D. C. Codée
- Department of Bio-organic Synthesis, Faculty of Science, Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands
| | - Yvette van Kooyk
- Department of Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam Infection and Immunity Institute, Amsterdam Universitair Medische Centra, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
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13
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Ribić R, Stojković R, Milković L, Antica M, Cigler M, Tomić S. Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides. Beilstein J Org Chem 2019; 15:1805-1814. [PMID: 31467600 PMCID: PMC6693374 DOI: 10.3762/bjoc.15.174] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 07/11/2019] [Indexed: 12/28/2022] Open
Abstract
Muramyl dipeptide is the minimal structure of peptidoglycan with adjuvant properties. Replacement of the N-acetylmuramyl moiety and increase of lipophilicity are important approaches in the preparation of muramyl dipeptide analogues with improved pharmacological properties. Mannose receptors present on immunocompetent cells are pattern-recognition receptors and by mannose ligands binding they affect the immune system. Here we present the design, synthesis and biological evaluation of novel mannosylated desmuramyl peptide derivatives. Mannose was coupled to dipeptides containing a lipophilic adamantane on N- or C-terminus through a glycolyl or hydroxyisobutyryl linker. Adjuvant activities of synthesized compounds were investigated in the mouse model using ovalbumin as an antigen. Their activities were compared to the previously described mannosylated adamantane-containing desmuramyl peptide and peptidoglycan monomer. Tested compounds exhibited adjuvant activity and the strongest enhancement of IgG production was stimulated by compound 21 (Man-OCH2-ᴅ-(1-Ad)Gly-ʟ-Ala-ᴅ-isoGln).
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Affiliation(s)
- Rosana Ribić
- University Center Varaždin, University North, Jurja Križanića 31b, HR-42000 Varaždin, Croatia
| | - Ranko Stojković
- Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia
| | - Lidija Milković
- Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia
| | | | - Marko Cigler
- Department of Chemistry, Technical University Munich, Lichtenbergstraße 4, D-85748 Garching, Germany
| | - Srđanka Tomić
- Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10000 Zagreb, Croatia
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14
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D'Ambrosio EA, Drake WR, Mashayekh S, Ukaegbu OI, Brown AR, Grimes CL. Modulation of the NOD-like receptors NOD1 and NOD2: A chemist's perspective. Bioorg Med Chem Lett 2019; 29:1153-1161. [PMID: 30890292 PMCID: PMC7679954 DOI: 10.1016/j.bmcl.2019.03.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/05/2019] [Accepted: 03/07/2019] [Indexed: 12/13/2022]
Abstract
The innate immune system is the body's first defense against invading microorganisms, relying on the recognition of bacterial-derived small molecules by host protein receptors. This recognition event and downstream immune response rely heavily on the specific chemical features of both the innate immune receptors and their bacterial derived ligands. This review presents a chemist's perspective on some of the most crucial and complex components of two receptors (NOD1 and NOD2): starting from the structural and chemical characteristics of bacterial-derived small molecules, to the specific proposed models of molecular recognition of these molecules by immune receptors, to the subsequent post-translational modifications that ultimately dictate downstream immune signaling. Recent advances in the field are discussed, as well as the potential for the development of targeted therapeutics.
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Affiliation(s)
| | - Walter R Drake
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Siavash Mashayekh
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Ophelia I Ukaegbu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Ashley R Brown
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Catherine L Grimes
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
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15
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Zom GG, Willems MMJHP, Meeuwenoord NJ, Reintjens NRM, Tondini E, Khan S, Overkleeft HS, van der Marel GA, Codee JDC, Ossendorp F, Filippov DV. Dual Synthetic Peptide Conjugate Vaccine Simultaneously Triggers TLR2 and NOD2 and Activates Human Dendritic Cells. Bioconjug Chem 2019; 30:1150-1161. [PMID: 30865430 DOI: 10.1021/acs.bioconjchem.9b00087] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Simultaneous triggering of Toll-like receptors (TLRs) and NOD-like receptors (NLRs) has previously been shown to synergistically activate monocytes, dendritic cells, and macrophages. We applied these properties in a T-cell vaccine setting by conjugating the NOD2-ligand muramyl-dipeptide (MDP) and TLR2-ligand Pam3CSK4 to a synthetic peptide derived from a model antigen. Stimulation of human DCs with the MDP-peptide-Pam3CSK4 conjugate led to a strongly increased secretion of pro-inflammatory and Th1-type cytokines and chemokines. We further show that the conjugated ligands retain their ability to trigger their respective receptors, while even improving NOD2-triggering. Also, activation of murine DCs was enhanced by the dual triggering, ultimately leading to effective induction of vaccine-specific T cells expressing IFNγ, IL-2, and TNFα. Together, these data indicate that the dual MDP-SLP-Pam3CSK4 conjugate constitutes a chemically well-defined vaccine approach that holds promise for the use in the treatment of virus infections and cancer.
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Affiliation(s)
- Gijs G Zom
- Department of Immunohematology and Blood Transfusion , Leiden University Medical Center , P.O. Box 9600, 2300 RC Leiden , The Netherlands
| | - Marian M J H P Willems
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands
| | - Nico J Meeuwenoord
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands
| | - Niels R M Reintjens
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands
| | - Elena Tondini
- Department of Immunohematology and Blood Transfusion , Leiden University Medical Center , P.O. Box 9600, 2300 RC Leiden , The Netherlands
| | - Selina Khan
- Department of Immunohematology and Blood Transfusion , Leiden University Medical Center , P.O. Box 9600, 2300 RC Leiden , The Netherlands
| | - Herman S Overkleeft
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands
| | - Gijsbert A van der Marel
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands
| | - Jeroen D C Codee
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands
| | - Ferry Ossendorp
- Department of Immunohematology and Blood Transfusion , Leiden University Medical Center , P.O. Box 9600, 2300 RC Leiden , The Netherlands
| | - Dmitri V Filippov
- Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands
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16
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Chen XZ, Zhang RY, Wang XF, Yin XG, Wang J, Wang YC, Liu X, Du JJ, Liu Z, Guo J. Peptide-free Synthetic Nicotine Vaccine Candidates with α-Galactosylceramide as Adjuvant. Mol Pharm 2019; 16:1467-1476. [DOI: 10.1021/acs.molpharmaceut.8b01095] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Xiang-Zhao Chen
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Ru-Yan Zhang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Xi-Feng Wang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Xu-Guang Yin
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Jian Wang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Ya-Cong Wang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Xiu Liu
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Jing-Jing Du
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Zheng Liu
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
| | - Jun Guo
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, P. R. China
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17
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Gobec M, Tomašič T, Štimac A, Frkanec R, Trontelj J, Anderluh M, Mlinarič-Raščan I, Jakopin Ž. Discovery of Nanomolar Desmuramylpeptide Agonists of the Innate Immune Receptor Nucleotide-Binding Oligomerization Domain-Containing Protein 2 (NOD2) Possessing Immunostimulatory Properties. J Med Chem 2018. [PMID: 29543461 DOI: 10.1021/acs.jmedchem.7b01052] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Muramyl dipeptide (MDP), a fragment of bacterial peptidoglycan, has long been known as the smallest fragment possessing adjuvant activity, on the basis of its agonistic action on the nucleotide-binding oligomerization domain-containing protein 2 (NOD2). There is a pressing need for novel adjuvants, and NOD2 agonists provide an untapped source of potential candidates. Here, we report the design, synthesis, and characterization of a series of novel acyl tripeptides. A pivotal structural element for molecular recognition by NOD2 has been identified, culminating in the discovery of compound 9, the most potent desmuramylpeptide NOD2 agonist to date. Compound 9 augmented pro-inflammatory cytokine release from human peripheral blood mononuclear cells in synergy with lipopolysaccharide. Furthermore, it was able to induce ovalbumin-specific IgG titers in a mouse model of adjuvancy. These findings provide deeper insights into the structural requirements of desmuramylpeptides for NOD2-activation and highlight the potential use of NOD2 agonists as adjuvants for vaccines.
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Affiliation(s)
- Martina Gobec
- Faculty of Pharmacy , University of Ljubljana , Aškerčeva 7 , SI-1000 Ljubljana , Slovenia
| | - Tihomir Tomašič
- Faculty of Pharmacy , University of Ljubljana , Aškerčeva 7 , SI-1000 Ljubljana , Slovenia
| | - Adela Štimac
- Centre for Research and Knowledge Transfer in Biotechnology , University of Zagreb , Rockefellerova 10 , 10000 Zagreb , Croatia
| | - Ruža Frkanec
- Centre for Research and Knowledge Transfer in Biotechnology , University of Zagreb , Rockefellerova 10 , 10000 Zagreb , Croatia
| | - Jurij Trontelj
- Faculty of Pharmacy , University of Ljubljana , Aškerčeva 7 , SI-1000 Ljubljana , Slovenia
| | - Marko Anderluh
- Faculty of Pharmacy , University of Ljubljana , Aškerčeva 7 , SI-1000 Ljubljana , Slovenia
| | - Irena Mlinarič-Raščan
- Faculty of Pharmacy , University of Ljubljana , Aškerčeva 7 , SI-1000 Ljubljana , Slovenia
| | - Žiga Jakopin
- Faculty of Pharmacy , University of Ljubljana , Aškerčeva 7 , SI-1000 Ljubljana , Slovenia
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18
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Role of Muramyl Dipeptide in Lipopolysaccharide-Mediated Biological Activity and Osteoclast Activity. Anal Cell Pathol (Amst) 2018; 2018:8047610. [PMID: 29666781 PMCID: PMC5832107 DOI: 10.1155/2018/8047610] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 01/10/2018] [Indexed: 11/23/2022] Open
Abstract
Lipopolysaccharide (LPS) is an endotoxin and bacterial cell wall component that is capable of inducing inflammation and immunological activity. Muramyl dipeptide (MDP), the minimal essential structural unit responsible for the immunological activity of peptidoglycans, is another inflammation-inducing molecule that is ubiquitously expressed by bacteria. Several studies have shown that inflammation-related biological activities were synergistically induced by interactions between LPS and MDP. MDP synergistically enhances production of proinflammatory cytokines that are induced by LPS exposure. Injection of MDP induces lethal shock in mice challenged with LPS. LPS also induces osteoclast formation and pathological bone resorption; MDP enhances LPS induction of both processes. Furthermore, MDP enhances the LPS-induced receptor activator of NF-κB ligand (RANKL) expression and toll-like receptor 4 (TLR4) expression both in vivo and in vitro. Additionally, MDP enhances LPS-induced mitogen-activated protein kinase (MAPK) signaling in stromal cells. Taken together, these findings suggest that MDP plays an important role in LPS-induced biological activities. This review discusses the role of MDP in LPS-mediated biological activities, primarily in relation to osteoclastogenesis.
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19
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Understanding the molecular differential recognition of muramyl peptide ligands by LRR domains of human NOD receptors. Biochem J 2017; 474:2691-2711. [DOI: 10.1042/bcj20170220] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 06/27/2017] [Accepted: 07/03/2017] [Indexed: 12/28/2022]
Abstract
Human nucleotide-binding oligomerization domain proteins, hNOD1 and hNOD2, are host intracellular receptors with C-terminal leucine-rich repeat (LRR) domains, which recognize specific bacterial peptidoglycan (PG) fragments as their ligands. The specificity of this recognition is dependent on the third amino acid of the stem peptide of the PG ligand, which is usually meso-diaminopimelic acid (mesoDAP) or l-lysine (l-Lys). Since the LRR domains of hNOD receptors had been experimentally shown to confer the PG ligand-sensing specificity, we developed three-dimensional structures of hNOD1-LRR and the hNOD2-LRR to understand the mechanism of differential recognition of muramyl peptide ligands by hNOD receptors. The hNOD1-LRR and hNOD2-LRR receptor models exhibited right-handed curved solenoid shape. The hot-spot residues experimentally proved to be critical for ligand recognition were located in the concavity of the NOD-LRR and formed the recognition site. Our molecular docking analyses and molecular electrostatic potential mapping studies explain the activation of hNOD-LRRs, in response to effective molecular interactions of PG ligands at the recognition site; and conversely, the inability of certain PG ligands to activate hNOD-LRRs, by deviations from the recognition site. Based on molecular docking studies using PG ligands, we propose few residues — G825, D826 and N850 in hNOD1-LRR and L904, G905, W931, L932 and S933 in hNOD2-LRR, evolutionarily conserved across different host species, which may play a major role in ligand recognition. Thus, our integrated experimental and computational approach elucidates the molecular basis underlying the differential recognition of PG ligands by hNOD receptors.
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