Glucosaminylmuramyl dipeptide-induced changes in murine macrophage metabolism

Structural basis of NLR activation and innate immune signalling in plants

Animals and plants have NLRs (nucleotide-binding leucine-rich repeat receptors) that recognize the presence of pathogens and initiate innate immune responses. In plants, there are three types of NLRs distinguished by their N-terminal domain: the CC (coiled-coil) domain NLRs, the TIR (Toll/interleukin-1 receptor) domain NLRs and the RPW8 (resistance to powdery mildew 8)-like coiled-coil domain NLRs. CC-NLRs (CNLs) and TIR-NLRs (TNLs) generally act as sensors of effectors secreted by pathogens, while RPW8-NLRs (RNLs) signal downstream of many sensor NLRs and are called helper NLRs. Recent studies have revealed three dimensional structures of a CNL (ZAR1) including its inactive, intermediate and active oligomeric state, as well as TNLs (RPP1 and ROQ1) in their active oligomeric states. Furthermore, accumulating evidence suggests that members of the family of lipase-like EDS1 (enhanced disease susceptibility 1) proteins, which are uniquely found in seed plants, play a key role in providing a link between sensor NLRs and helper NLRs during innate immune responses. Here, we summarize the implications of the plant NLR structures that provide insights into distinct mechanisms of action by the different sensor NLRs and discuss plant NLR-mediated innate immune signalling pathways involving the EDS1 family proteins and RNLs.

[Glucosaminylmuramyl dipeptide in treatment of respiratory tract diseases]

INTRODUCTION

Immunomodulators are used as part of a comprehensive therapy of respiratory tract diseases. The systematization of the accumulated data on the use of glucosaminylmuramyldipeptide (GMDP) has great scientific and practical interest.

PURPOSE

To study the data on the effectiveness and safety of GMDP in the treatment of infectious diseases of the respiratory tract.

MATERIAL AND METHODS

Literature search was carried out in Scientific Electronic Library (elibrary.ru), Google Scholar, ScienceDirect, Cochrane library, Pubmed/MEDLINE and search engines. The level of evidence reliability and methodological quality of researches were assessed.

RESULTS

17 full-text publications were selected based on the results of 13 prospective clinical trials with acceptable methodological quality (including one blind placebo-controlled trial). The effectiveness of GMDP in acute respiratory viral infections, influenza, recurrent respiratory tract infections, rhinosinusitis and chronic tonsillitis was demonstrated.

DISCUSSION

An important advantage is that a significant part of the studies was performed with the participation of the child population. Since the use of GMDP in multiple therapy significantly reduces antibiotic consumption (often unjustified). It seems reasonable to estimate the pharmacoeconomic costs of managing adult patients with respiratory tract diseases. Further research can improve understanding of the role of GMDP in the treatment of various medical conditions.

CONCLUSION

The use of GMDP in the treatment of respiratory tract diseases makes it possible to faster achieve a clinical effect, reduce the number of relapses, lengthen the relapse-free period, as well as to potentiate the effect of antibacterial therapy (if necessary), reducing the need for antibiotics.

Efficacy and safety of glucosaminylmuramyl dipeptide in treatment of human papillomavirus-associated diseases: a systematic review

Introduction. Human papillomavirus infection (HPV-infection) remains one of the most important health problems as it significantly reduces the quality of life and stigmatizes the patients. Also, the prevalence of cervical cancer – the most severe outcome of the HPV-infection is 5 % of the global burden of cancer. Although vaccination against human papillomavirus has been proved efficient, its availability in Russia continues to be limited. Therefore, it is important to review other methods of HPV-infection control. A number of studies have confirmed the efficacy of glucosaminylmuramyl dipeptide (GMDP) in the treatment of diseases associated with HPV-infection, but no systematic evaluation of these studies has been published in the available literature.

Aim: to analyze the data on the efficacy and safety of GMDP in the treatment of diseases and conditions associated with HPVinfection.

Materials and methods. We used the PRISMA approach. The search for the relevant publications was conducted in international scientific databases: the Scientific Electronic Library, the Google Scholar, the ScienceDirect, the Cochrane Community Library, the Pubmed/MEDLINE, and clinical research registries. For this systematic analysis, only full-text publications were used. We evaluated the reliability of evidence and the methodological quality of the studies.

Results. We used the following search queries: "glucosaminyl-muramyl dipeptide", "glucosamine L'muramyl dipeptide", "H-acetylglucosaminyl-H-acetylmuramyl dipeptide", "GMDP", "Licopid" (both in Russian and English transcriptions). Based on the results of the screening, 14 full-text publications were selected. At the final stage, review articles with secondary data were excluded; also excluded were original articles published in doubtful resources and those with an unclear status of peer reviewing. This systematic analysis includes 7 publications of acceptable methodological quality. Here, we summarize the consistent conclusions derived from these reports: the addition of therapy with GMDP to local (surgical) methods increases the efficacy of treatment and the duration of remission; destruction of condylomas is more effective when combined with the course of GMDP as compared to using the local destruction alone; GMDP enhances the production of cytokines that have a direct antiviral and antiproliferative effect in HPV-infection (interleukin-1, tumor necrosis factor alpha, gamma-interferon); GMDP causes normalization of cellular and humoral immunity (T-lymphocytes, T-cytotoxic lymphocytes, B-lymphocytes, CD3+, CD4+, CD8+, CD16+, and CD72+ lymphocytes, as well as the production of serum immunoglobulins IgA, IgG, and IgM). A high safety profile of GMDP is evidenced from the absence of reports on adverse events.

Discussion. The recommendation for the inclusion of GMDP into a comprehensive treatment for HPV-infection in addition to local interventions is a strong recommendation. The differences between the Russian and international approaches can be explained by the difference in the available resources and funding. We propose to test whether using GMDP for reducing the risk of recurrent HPV-infection is beneficial in terms of pharmacoeconomics. Conclusion. The high efficacy and safety of GMDP in the combined therapy of HPV-infection has been confirmed. Further carefully designed studies on GMDP are needed.

NOD1 and NOD2: Molecular targets in prevention and treatment of infectious diseases

Nucleotide-binding oligomerization domain (NOD) 1 and NOD2 are pattern-recognition receptors responsible for sensing fragments of bacterial peptidoglycan known as muropeptides. Stimulation of innate immunity by systemic or local administration of NOD1 and NOD2 agonists is an attractive means to prevent and treat infectious diseases. In this review, we discuss novel data concerning structural features of selective and non-selective (dual) NOD1 and NOD2 agonists, main signaling pathways and biological effects induced by NOD1 and NOD2 stimulation, including induction of pro-inflammatory cytokines, type I interferons and antimicrobial peptides, induction of autophagy, alterations of metabolism. We also discuss interactions between NOD1/NOD2 and Toll-like receptor agonists in terms of synergy and cross-tolerance. Finally, we review available animal data on the role of NOD1 and NOD2 in protection against infections, and discuss how these data could be applied in human infectious diseases.

Nonpyrogenic Molecular Adjuvants Based on norAbu-Muramyldipeptide and norAbu-Glucosaminyl Muramyldipeptide: Synthesis, Molecular Mechanisms of Action, and Biological Activities in Vitro and in Vivo

Fatty acyl analogues of muramyldipeptide (MDP) (abbreviated N-L18 norAbuGMDP, N-B30 norAbuGMDP, norAbuMDP-Lys(L18), norAbuMDP-Lys(B30), norAbuGMDP-Lys(L18), norAbuGMDP-Lys(B30), B30 norAbuMDP, L18 norAbuMDP) are designed and synthesized comprising the normuramyl-l-α-aminobutanoyl (norAbu) structural moiety. All new analogues show depressed pyrogenicity in both free (micellar) state and in liposomal formulations when tested in rabbits in vivo (sc and iv application). New analogues are also shown to be selective activators of NOD2 and NLRP3 (inflammasome) in vitro but not NOD1. Potencies of NOD2 and NLRP3 stimulation are found comparable with free MDP and other positive controls. Analogues are also demonstrated to be effective in stimulating cellular proliferation when the sera from mice are injected sc with individual liposome-loaded analogues, causing proliferation of bone marrow-derived GM-progenitors cells. Importantly, vaccination nanoparticles prepared from metallochelation liposomes, His-tagged antigen rOspA from Borrelia burgdorferi, and lipophilic analogue norAbuMDP-Lys(B30) as adjuvant, are shown to provoke OspA-specific antibody responses with a strong Th1-bias (dominance of IgG2a response). In contrast, the adjuvant effects of Alum or parent MDP show a strong Th2-bias (dominance of IgG1 response).

Unleashing the therapeutic potential of NOD-like receptors

Nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) are a family of intracellular sensors that have key roles in innate immunity and inflammation. Whereas some NLRs - including NOD1, NOD2, NAIP (NLR family, apoptosis inhibitory protein) and NLRC4 - detect conserved bacterial molecular signatures within the host cytosol, other members of this family sense 'danger signals', that is, xenocompounds or molecules that when recognized alert the immune system of hazardous environments, perhaps independently of a microbial trigger. In the past few years, remarkable progress has been made towards deciphering the role and the biology of NLRs, which has shown that these innate immune sensors have pivotal roles in providing immunity to infection, adjuvanticity and inflammation. Furthermore, several inflammatory disorders have been associated with mutations in human NLRgenes. Here, we discuss the effect that research on NLRs will have on vaccination, treatment of chronic inflammatory disorders and acute bacterial infections.

Muramyl peptides augment cytotoxic effect of tumor necrosis factor-alpha in combination with cytotoxic drugs on tumor cells

We have demonstrated that biologically active muramyl peptides, in particular, glucosaminylmuramyl dipeptide (GMDP), augmented in vitro cytotoxic activity of tumor necrosis factor-alpha (TNF-alpha) against murine fibrosarcoma L929 cells. The introduction of GMDP resulted in cytotoxic effect characteristic for substantially higher dose of cytokine. Even more potent was the combination of GMDP, TNF-alpha and Actinomycin D (ActD). According to clonogenic and MTT assays 100% L929 cells could be killed in culture with low doses of TNF-alpha and ActD if GMDP was present. When cisplatin was substituted for ActD similar results were obtained. GMDP also enhanced cytotoxicity of TNF-alpha and cisplatin against human breast carcinoma MCF7 and histiocytic lymphoma U937 cells. Normal cells, namely human peripheral blood leucocytes and murine peritoneal macrophages, were resistant to selected doses of TNF-alpha/cisplatin/GMDP.

Evidence of differential mycobacterial growth and modulation of mycobactericidal property by glucoaminylmuramyl dipeptide in murine macrophages

These results show that given a source of mouse tissue macrophage, there is differential mycobacterial growth with different species of mycobacteria. This suggests that each species of mycobacteria generates a differential response in a given tissue macrophage within the same host for its survival. For example, BCG-P growth becomes permissive in the presence of GMDP in splenic and peritoneal macrophages. Whereas in the same tissue M. tuberculosis growth becomes non-permissive. From Table 2 it is evident that inhibition of inflammatory responses following M. tuberculosis infection leads to reduction of viable organisms in murine macrophages.

Side-effects of peptidoglycan monomer (PGM) treatment in mice

The influence of single (4 mg/mouse) and multiple (1 mg/mouse per day for 5 consecutive days) injections of PGM on some hepatic enzymes, lipid peroxide generation in serum and liver, sialic acid concentration in serum and spleen and hepatic lysosomal membrane permeability was investigated. The studies performed showed that a single injection of PGM in vivo changed temporarily the permeability of lysosomal membranes, lipid peroxidation products and sialic acid concentration, and when administered in vitro modulated superoxide anion production and did not affect the activity of lysosomal membrane enzymes. Multiple injections of PGM did not cause significant changes in the examined parameters. Although the metabolic changes were time-limited and from the toxicological point of view, provoked transient effects, the results obtained may be of importance when using PGM in combined chemo-immunotherapy.

Apyrogenic synthetic desmuramyldipeptide, LK-409, with immunomodulatory properties

The synthesis and some immunological characteristics of a new desmuramyl dipeptide 7-oxooctanoyl-L-alanyl-D-isoglutamine (LK-409) are presented. The effects of this compound were compared with those of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP). The influence of LK-409 on the number of B and T cells in spleen and the number of peritoneal macrophages was studied; Jerne's plaque forming cells assay was performed to monitor the effect of B cell differentiation. The blast transformation of T cells stimulated with concanavalin A was used to detect the influences on T lymphocytes. The activation of macrophages was studied as well. In contrast to MDP, LK-409 was apyrogenic in the doses applied but had similar immunomodulatory properties. Tested immunological properties and the absence of pyrogenicity and low toxicity make LK-409 a candidate for an immunomodulatory drug and a model molecule suitable for studying and understanding the dual activity of the MDP and its analogues.