Receptor-Mediated Monitoring of Tissue Well-Being Via Detection of Soluble Heparan Sulfate by Toll-Like Receptor 4

Johnson, Geoffrey B.; Brunn, Gregory J.; Kodaira, Yuzo; Platt, Jeffrey L.

doi:10.4049/jimmunol.168.10.5233

Cited by 591 publications

(391 citation statements)

References 68 publications

(74 reference statements)

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“…These include HMGB1 76 31, uric acid 77 , some HSPs 78 79, some defensins [G] 80 , hyaluronic acid 81 , heparan sulfate 82 , and some fragments of extracellular matrix proteins 70 . Whereas this data may well be correct, caution is warranted because TLRs can be stimulated by microbial contaminants that are easily introduced during the purification of molecules.…”

Section: Receptors For Dampsmentioning

confidence: 99%

How dying cells alert the immune system to danger

2008

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When a cell dies in vivo the event does not go unnoticed. The host has evolved mechanisms to detect the death of cells and rapidly investigate the nature of their demise. If cell death is a result of natural causes, that is, it is part of normal physiological processes, then there is little threat to the organism. In this situation, little else is done other than removing the corpse. However, if cells have died as the consequence of some violence or disease, then both defence and repair mechanisms are mobilized. The importance of this process to host defence and disease pathogenesis has only been appreciated relatively recently. This article will review our current knowledge of these processes.The immune system was recognized in ancient times and rediscovered by Jenner and Pasteur based on its ability to confer protection upon repeat exposure to a pathogen. Through subsequent studies by Von Behring and others it rapidly became apparent that the immune system had the potential to respond not only to whole microorganisms, but to virtually any molecule that was "foreign" to the host. However, whereas injection of such molecules would often provoke a robust immune response, this did not invariably occur. Immunization protocols improved in the 1920s with the discovery by Ramon and Glenny of immunostimulatory molecules (adjuvants [G]) that could boost immune responses to co-administered antigens. Adjuvants were typically of microbial origin and became widely used to promote the effectiveness of immunizations. In the 1960s, Dresser showed that a foreign protein when highly purified would only elicit an immune response if it was admixed with a microbial adjuvant 1 . Injected by itself, the antigen not only failed to elicit immunity but actually induced a state of tolerance 2 . However, the significance of these observations was not well appreciated and adjuvants remained one of those things that everyone used because they were part of standard operating procedures.In 1989 Janeway put these empirical observations into a conceptual framework 3 (Fig. 1). He proposed that the immune system did not respond to all foreign antigens but only to those that are potentially associated with infection. The underlying idea here was that the immune system evolved to protect organisms against microorganisms and this discrimination between infectious versus noninfectious antigens focused defences on real threats rather than innocuous situations.At this time, it was already recognized that in order to stimulate T cell responses, antigens had to first be acquired and presented on MHC molecules of an antigen presenting cell (APC). Moreover, it was further known that APCs also provided additional costimulatory signals necessary to activate T cells. Janeway incorporated these principles into his model (Fig. 1). He postulated that the discrimination between infectious and noninfectious non-self molecules was made by the APCs of the innate immune system through receptors that would recognize pathogen-associated molecular patterns (PAMP...

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Section: Receptors For Dampsmentioning

confidence: 99%

How dying cells alert the immune system to danger

2008

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“…Out of 13 currently known TLR members (11 in humans), TLR4 is believed to initiate inflammation and tissue injury by responding to both bacterial endotoxin (lipopolysaccharide) and multiple endogenous ligands, including hyaluronic acid, heparin sulfate, fibrinogen, beta defensin, and heat-shock proteins. 10,11 We and others have reported that TLR4 complex is involved in the initiation of IRI. [12][13][14][15][16] Indeed, we found that livers in TLR4 knockout (KO) but not TLR2 KO mice were resistant to IRI and associated intrahepatic inflammation.…”

mentioning

confidence: 97%

Absence of toll-like receptor 4 (TLR4) signaling in the donor organ reduces ischemia and reperfusion injury in a murine liver transplantation model

Shen

Zhai

et al. 2007

Liver Transpl

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This study analyzes how toll-like receptor 4 (TLR4) signaling in the donor organ affects the ischemia and reperfusion injury (IRI) sequel following liver transplantation. Isogenic orthotopic liver transplantations (OLTs) with rearterialization were performed in groups of wild-type (WT) and TLR4 knockout (KO) mice after donor liver preservation in University of Wisconsin solution at 4°C for 24 hours. Unlike WT OLTs, TLR4-deficient OLTs transplanted to either WT or TLR4 KO recipients suffered significantly less hepatocellular damage, as evidenced by serum alanine aminotransferase levels, and histological Suzuki's grading of liver IRI. Disruption of TLR4 signaling in OLTs decreased local neutrophil sequestration, CD4 ϩ T cell infiltration, interferon (IFN)-␥-inducible protein 10 (CXCL10) and an intercellular adhesion molecule (ICAM-1), as well as tumor necrosis factor (TNF)-␣, interleukin (IL)-1␤, IL-2, and IFN-␥, yet increased IL-4 and IL-10 expression. The well-functioning OLTs from TLR4 KO donors revealed attenuated activity of capase-3, and enhanced heme oygenase-1 (HO-1) expression, along with decreased levels of apoptotic endothelial cells/hepatocytes, as compared with WT OLTs with intact TLR4 signaling. Thus, the functional sentinel TLR4 complex in the donor organ plays a key role in the mechanism of hepatic IRI after OLT. Disruption of TLR4 pathway downregulated the early proinflammatory responses and ameliorated hepatic IRI. These results provide the rationale to locally modify innate TLR4 signaling in the donor organ to more efficiently control the adaptive posttransplantation IRI-dependent responses. Liver Transpl 13:1435-1443, 2007. © 2007 AASLD. Received February 7, 2007 accepted May 19, 2007.The ischemia and reperfusion injury (IRI), an antigenindependent event, is an unavoidable consequence of liver transplantation. The IRI causes up to 10% of early organ failure, and can lead to a higher incidence of both acute and chronic rejection. Indeed, IRI is more frequently observed with the use of marginal donors or following prolonged cold ischemia times. 1-3 Moreover, IRI contributes to the shortage of livers available for transplantation because of the higher susceptibility of marginal organs to the ischemic insult. Thus, minimizing the impact of IRI could significantly increase the number of patients successfully undergoing liver transplantation. The mechanisms of IRI include activation of Kupffer cells with production of reactive oxygen species, upregulation of the inducible nitric oxide synthase, release of proinflammatory cytokines, increased expres-

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“…Endogenous ligands are released upon normal cell turnover and stressful events and are likely to be abundant in the synovial compartment. The pivotal role of endogenous ligands was substantiated by the finding that such signals lead to primary immune responses under conditions of cell stress and precipitate autoimmunity in the presence of self antigens (28)(29)(30)(31). Therefore, endogenous ligands are considered to be natural initiators of autoimmunity.…”

mentioning

confidence: 99%

The expression of toll‐like receptors 3 and 7 in rheumatoid arthritis synovium is increased and costimulation of toll‐like receptors 3, 4, and 7/8 results in synergistic cytokine production by dendritic cells

Roelofs¹,

Joosten²,

Abdollahi‐Roodsaz³

et al. 2005

Arthritis & Rheumatism

294

219

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Objective. To evaluate the expression of Toll-like receptors (TLRs) 3 and 7 in synovium and to study potential differences in the maturation and cytokine production mediated by TLR-2, TLR-3, TLR-4, and TLR-7/8 by dendritic cells (DCs) from rheumatoid arthritis (RA) patients and DCs from healthy controls.Methods. Synovial expression of TLR-3 and TLR-7 in RA was studied using immunohistochemistry. Monocyte-derived DCs from RA patients and healthy controls were cultured for 6 days and subsequently stimulated for 48 hours via TLR-mediated pathways (lipoteichoic acid, Pam 3 Cys, and fibroblast-stimulating lipopeptide 1 for TLR-2, poly[I-C] for TLR-3, lipopolysaccharide and extra domain A for TLR-4, and R848 for TLR-7/8). Phenotypic DC maturation was measured using flow cytometry. The secretion of tumor necrosis factor ␣ (TNF␣), interleukin-6 (IL-6), IL-10, and IL-12 was measured using the Bio-Plex system. Cell lines expressing TLR-2 and TLR-4 were used for the detection of TLR-2 and TLR-4 ligands in serum and synovial fluid from RA patients.Results. TLR-3 and TLR-7 were highly expressed in RA synovium. All TLR ligands elicited phenotypic DC maturation equally between DCs from RA patients and those from healthy controls. TLR-2-and TLR-4-mediated stimulation of DCs from RA patients resulted in markedly higher production of inflammatory mediators (TNF␣ and IL-6) compared with DCs from healthy controls. In contrast, upon stimulation of TLR-3 and TLR-7/8, the level of cytokine production was equal between DCs from RA patients and those from healthy controls. Remarkably, both TLR-3 and TLR-7/8 stimulation resulted in a skewed balance toward IL-12. Intriguingly, the combined stimulation of TLR-4 and TLR-3-7/8 resulted in a marked synergy with respect to the production of inflammatory mediators. As a proof of concept, TLR-4 ligands were increased in the serum and synovial fluid of RA patients.Conclusion. TLRs are involved in the regulation of DC activation and cytokine production. We hypothesize that various TLR ligands in the joint trigger multiple TLRs simultaneously, favoring the breakthrough of tolerance in RA.

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Receptor-Mediated Monitoring of Tissue Well-Being Via Detection of Soluble Heparan Sulfate by Toll-Like Receptor 4

Cited by 591 publications

References 68 publications

How dying cells alert the immune system to danger

How dying cells alert the immune system to danger

Absence of toll-like receptor 4 (TLR4) signaling in the donor organ reduces ischemia and reperfusion injury in a murine liver transplantation model

The expression of toll‐like receptors 3 and 7 in rheumatoid arthritis synovium is increased and costimulation of toll‐like receptors 3, 4, and 7/8 results in synergistic cytokine production by dendritic cells

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