Article

Increased NOD2-mediated recognition of N-glycolyl muramyl dipeptide

Department of Medicine, McGill University Health Centre, Montreal, Quebec H3G 1A4, Canada.
Journal of Experimental Medicine (Impact Factor: 13.91). 09/2009; 206(8):1709-16. DOI: 10.1084/jem.20081779
Source: PubMed

ABSTRACT Peptidoglycan-derived muramyl dipeptide (MDP) activates innate immunity via the host sensor NOD2. Although MDP is N-acetylated in most bacteria, mycobacteria and related Actinomycetes convert their MDP to an N-glycolylated form through the action of N-acetyl muramic acid hydroxylase (NamH). We used a combination of bacterial genetics and synthetic chemistry to investigate whether N-glycolylation of MDP alters NOD2-mediated immunity. Upon infecting macrophages with 12 bacteria, tumor necrosis factor (TNF) alpha secretion was NOD2 dependent only with mycobacteria and other Actinomycetes (Nocardia and Rhodococcus). Disruption of namH in Mycobacterium smegmatis obrogated NOD2-mediated TNF secretion, which could be restored upon gene complementation. In mouse macrophages, N-glycolyl MDP was more potent than N-acetyl MDP at activating RIP2, nuclear factor kappaB, c-Jun N-terminal kinase, and proinflammatory cytokine secretion. In mice challenged intraperitoneally with live or killed mycobacteria, NOD2-dependent immune responses depended on the presence of bacterial namH. Finally, N-glycolyl MDP was more efficacious than N-acetyl MDP at inducing ovalbumin-specific T cell immunity in a model of adjuvancy. Our findings indicate that N-glycolyl MDP has a greater NOD2-stimulating activity than N-acetyl MDP, consistent with the historical observation attributing exceptional immunogenic activity to the mycobacterial cell wall.

0 Followers
 · 
196 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Since the discovery of Toll, in the fruit fly Drosophila melanogaster, as the first described pattern recognition receptor (PRR) in 1996, many families of these receptors have been discovered and characterized. PRRs play critically important roles in pathogen recognition to initiate innate immune responses that ultimately link to the generation of adaptive immunity. Activation of PRRs leads to the induction of immune and inflammatory genes, including proinflammatory cytokines and chemokines. It is increasingly clear that many PRRs are linked to a range of inflammatory, infectious, immune, and chronic degenerative diseases. Several drugs to modulate PRR activity are already in clinical trials and many more are likely to appear in the near future. Here, we review the different families of mammalian PRRs, the ligands they recognize, the mechanisms of activation, their role in disease, and the potential of targeting these proteins to develop the anti-inflammatory therapeutics of the future. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.
    Pharmacological reviews 04/2015; 67(2):462-504. DOI:10.1124/pr.114.009928 · 18.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lactic acid bacteria (LAB) have long been used in the manufacture of yogurt and cheese. LAB inhabit the human gastrointestinal tract alongside dozens of varieties of gut bacteria, which play an essential role in modulating the innate immune response to gastrointestinal disorders. This research sought to provide a basis for the investigation of peptidoglycan (PGN) from Lactobacillus acidophilus (L. acidophilus) by macrophages phagocytosis related to the anti-inflammatory effect both in vitro and vivo. Results show that PGN, PGN hydrolysate and PGN monomer N-acetylmuramic acid (NAM) from L. acidophilus were found to have an anti-inflammatory effect on LPS-induced inflammation in RAW 264.7 cells, the profiling of iNOS mRNA levels was also inhibited in NAM-treated (100–300 µg/mL) group. The activation of the Nuclear factor κB (NF-κB) pathway is regulated by the cellular kinase p38 in mitogen-activated protein kinases (MAPK) upon NAM treatment (300 µg/mL). These findings were further supported in Escherichia coli (E. coli)-stimulated ICR mice, in which we found that oral administration of free L. acidophilus PGN and NAM from L. acidophilus exerted a potential anti-inflammatory response. NAM, as the main components of the LAB cell wall, will be a candidate for pharmaceutical application of anti-inflammatory drugs.
    Journal of Functional Foods 03/2015; 13. DOI:10.1016/j.jff.2014.12.048 · 4.48 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: M.tb, which causes TB, is a host-adapted intracellular pathogen of macrophages. Macrophage intracellular PRRs, such as NOD proteins, regulate proinflammatory cytokine production in response to various pathogenic organisms. We demonstrated previously that NOD2 plays an important role in controlling the inflammatory response and viability of M.tb and Mycobacterium bovis BCG in human macrophages. Various inflammatory mediators, such as cytokines, ROS, and RNS, such as NO, can mediate this control. iNOS (or NOS2) is a key enzyme for NO production and M.tb control during infection of mouse macrophages; however, the role of NO during infection of human macrophages remains unclear, in part, as a result of the low amounts of NO produced in these cells. Here, we tested the hypothesis that activation of NOD2 by its ligands (MDP and GMDP, the latter from M.tb) plays an important role in the expression and activity of iNOS and NO production in human macrophages. We demonstrate that M.tb or M. bovis BCG infection enhances iNOS expression in human macrophages. The M.tb-induced iNOS expression and NO production are dependent on NOD2 expression during M.tb infection. Finally, NF-κB activation is required for NOD2-dependent expression of iNOS in human macrophages. Our data provide evidence for a new molecular pathway that links activation of NOD2, an important intracellular PRR, and iNOS expression and activity during M.tb infection of human macrophages. © Society for Leukocyte Biology.
    Journal of leukocyte biology 03/2015; DOI:10.1189/jlb.3A1114-557R · 4.99 Impact Factor