Flowchart: Preparation: TLR



Text Box: ARPE-1                                                    



Text Box: TLR




Text Box: NF-kappaB                                                           

Text Box: AGEs                                                  






Int Immunopharmacol. 2008 Mar;8(3):495-501. Epub 2008 Jan 14.Click here to read Links

Selenium suppresses the activation of transcription factor NF-kappaB and IRF3 induced by TLR3 or TLR4 agonists.

Youn HS, Lim HJ, Choi YJ, Lee JY, Lee MY, Ryu JH.

Department of Biomedical Laboratory Science, College of Medical Sciences, Soonchunhyang University, Asan-Si, Chungnam 336-745, South Korea.

Toll-like receptors (TLRs) play an important role in recognition of microbial components and induce innate immune responses by recognizing invading microbial pathogens leading to the activation of the adaptive immune responses. The microbial components trigger the activation of two downstream signaling pathways of TLRs; MyD88- and TRIF-dependent pathways leading to the expression of pro-inflammatory cytokines and type I interferons (IFNs). The MyD88- and TRIF-dependent pathways lead to the activation of NF-kappaB and IRF3 through the activation of IKK-beta and TBK1, respectively. Selenium is an essential trace element nutrient possessing anticarcinogenic properties. Here, we attempted to identify the molecular targets of selenium in TLR signaling pathways. Selenium inhibited NF-kappaB activation induced by poly[I:C] (TLR3 agonist), LPS (TLR4 agonist) or overexpression of MyD88 or IKK-beta which is the key kinase of MyD88-dependent signaling pathway. Selenium inhibited IRF3 activation induced by poly[I:C], LPS or the overexpression of TRIF or TBK1. Selenium also suppressed the expression of COX-2 and iNOS and the endogenous IFNbeta mRNA induced by poly[I:C] or LPS. Therefore, our results suggest that selenium can modulate both MyD88- and TRIF-dependent signaling pathways of TLRs leading to decreased inflammatory gene expression.

PMID: 18279804 [PubMed - in process]

Curr Drug Targets. 2007 Dec;8(12):1230-8.Click here to read Links

The toll of Toll-like receptors, especially toll-like receptor 2, on murine atherosclerosis.

Curtiss LK, Tobias PS.

The Scripps Research Institute, Department of Immunology, IMM-17, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA. lcurtiss@scripps.edu

At one time, atherosclerosis was thought to be a simple lipid storage disease. However, it is now recognized as a chronic and progressive inflammation of the arterial wall. Gene deletion experiments in murine models of atherosclerosis that reduce the inflammatory process also reduce disease severity. Identifying the initiators and mediators of that inflammation can provide promising avenues for prevention or therapy. Two prominent risk factors, hyperlipidemia and infectious disease, point to innate immune mechanisms as potential contributors to proatherogenic inflammation. The Toll-like receptors (TLR), proinflammatory sensors of pathogens, are potential links between inflammation, infectious disease and atherosclerosis. There is increasing evidence that TLRs also recognize host-derived ligands and this also connects TLRs to diseases that may not have an etiology that is associated directly with infection. A mechanism for hyperlipidemic initiation of sterile inflammation can be postulated because oxidized lipoproteins or their component oxidized lipids have been identified as TLR ligands. Moreover, infectious agents are correlated with atherosclerosis risk. There are multiple published reports that TLR4 activation is relevant to the inflammation of atherosclerosis in mice and humans. In addition, we have identified a role for TLR2 in atherosclerosis in low density lipoprotein receptor-deficient (LDLr-/-) mice. Proatherogenic TLR2 responses to unknown endogenous or unknown endemic exogenous agonists are mediated by non-bone marrow-derived cells, which can include endothelial cells, adventitial fibroblasts and vascular smooth muscle cells. This is in contrast to the proatherogenic TLR2 response to defined synthetic exogenous agonists, which is mediated at least in part by bone marrow-derived cells, which can include lymphocytes, monocytes/macrophages, NK cells and dendritic cells. Thus, TLR2-mediated cell activation in response to endogenous and exogenous agents is proatherogenic in hyperlipidemic mice.

PMID: 18220700 [PubMed - in process]



























Lin L.

Laboratory of Cardiovascular Sciences, National Institute on Aging, 5600 Nathan Shock Drive, Baltimore, Maryland 21224, USA. linli@mail.nih.gov

Mammalian Toll-like receptors (TLRs) are cellular pattern-recognizing receptors (PRRs) that recognize the molecular patterns of pathogens. After engaging the pathogenic patterned ligands, the cytosolic portion of the TLRs in monocytes and macrophages, recruits adaptor proteins, via a receptor-driven signaling cascade, activates the transcription factor NF-kappaB, leading to the expression of proinflammatory cytokines, which trigger inflammation. Such rapid, innate cellular responses serve as the first line of host defense against infection by pathogens, and also stimulate the adaptive immune system to clear the invading microbes. Increasing evidence suggests that TLRs also recognize host-derived ligands, linking this group of PRRs to diseases that may not have an etiology that is associated directly with infections. Advanced glycation end products (AGEs) are nonenzymatically glycated or oxidated proteins, lipids and nucleic acids that are formed in the environment of oxidant stress and hyperglycemia. Binding of AGEs to their receptor RAGE initiates cellular signals that activate NF-kappaB, which results in transcription of proinflammatory factors. RAGE can also interact with other endogenous ligands generated by cell death and tissue injuries. RAGE has been implicated in chronic diseases such as diabetes, atherosclerosis, neurodisorders, cancers, as well as aging. This review discusses the possible role of RAGE as a PRR that may use signaling mechanisms parallel to TLRs', to solicit inflammatory reactions. Thus, in this scenario, RAGE may play a prominent role in the regulation of cellular homeostasis in the context of complex disease progression.

PMID: 17092432 [PubMed - indexed for MEDLINE]














































Chronic Immune Therapy Induces a Progressive Increase in Intratumoral T Suppressor Activity and a Concurrent Loss of Tumor-Specific CD8+ T Effectors in her-2/neu Transgenic Mice Bearing Advanced Spontaneous Tumors.

Nair RE, Kilinc MO, Jones SA, Egilmez NK.

James Graham Brown Cancer Center and Department of Microbiology and Immunology, School of Medicine, University of Louisville, Louisville, KY 40202.

A single intratumoral injection of IL-12 and GM-CSF-encapsulated microspheres induces the complete regression of advanced spontaneous tumors in her-2/neu transgenic mice. However, tumor regression in this model is transient and long-term cure is not achieved due to recurrence. Posttherapy molecular analysis of immune activation/suppression markers within the tumor microenvironment demonstrated a dramatic up-regulation of IFN-gamma and a concomitant down-regulation of Forkhead/winged-helix protein 3 (Foxp3), TGFbeta, and IL-10 expression. Therapy-induced reversion of immune suppression was transient since all three markers of suppression recovered rapidly and surpassed pretherapy levels by day 7 after treatment, resulting in tumor resurgence. Repeated treatment enhanced short-term tumor regression, but did not augment long-term survival. Serial long-term analysis demonstrated that although chronic stimulation enhanced the IFN-gamma response, this was countered by a parallel increase in Foxp3, TGFbeta, and IL-10 expression. Analysis of tumor-infiltrating T lymphocyte populations showed that the expression of Foxp3 and IL-10 was associated with CD4(+)CD25(+) T cells. Repeated treatment resulted in a progressive increase in tumor-infiltrating CD4(+)CD25(+)Foxp3(+) T suppressor cells establishing their role in long-term neutralization of antitumor activity. Analysis of tumor-infiltrating CD8(+) T cells demonstrated that although treatment enhanced IFN-gamma production, antitumor cytotoxicity was diminished. Monitoring of CD8(+) T cells that specifically recognized a dominant MHC class I her-2/neu peptide showed a dramatic increase in tetramer-specific CD8(+) T cells after the first treatment; however, continuous therapy resulted in the loss of this population. These results demonstrate that both enhanced suppressor activity and deletion of tumor-specific T cells are responsible for the progressive loss of efficacy that is associated with chronic immune therapy.

PMID: 16751376 [PubMed - in process]


Lab Invest. 2006 May 15; [Epub ahead of print]

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UBD, a downstream element of FOXP3, allows the identification of LGALS3, a new marker of human regulatory T cells.

Ocklenburg F, Moharregh-Khiabani D, Geffers R, Janke V, Pfoertner S, Garritsen H, Groebe L, Klempnauer J, Dittmar KE, Weiss S, Buer J, Probst-Kepper M.

1Junior Research Group for Xenotransplantation, Department of Visceral and Transplant Surgery,
Hannover Medical School, Hannover, Germany.

Here, we report the identification of the ubiquitin-like gene UBD as a downstream element of FOXP3 in human activated regulatory CD4(+)CD25(hi) T cells (T(reg)). Retroviral transduction of UBD in human allo-reactive effector CD4(+) T helper (T(h)) cells upregulates CD25 and mediates downregulation of IL4 and IL5 expression similar to overexpression of FOXP3. Moreover, UBD impairs T(h) cell proliferation without upregulation of FOXP3 and impairs calcium mobilization. In the presence of ionomycin, overexpression of UBD in T(h) cells leads to the induction of IL1R2 that resemble FOXP3-transduced T(h) cells and naturally derived T(reg) cells. A comparison of the transcriptome of FOXP3- and UBD-transduced T(h) cells with T(reg) cells allowed the identification of the gene LGALS3. However, high levels of LGALS3 protein expression were observed only in human CD4(+)CD25(hi) derived T(reg) cells and FOXP3-transduced T(h) cells, whereas little was induced in UBD-transduced T(h) cells. Thus, UBD contributes to the anergic phenotype of human regulatory T cells and acts downstream in FOXP3 induced regulatory signaling pathways, including regulation of LGALS3 expression. High levels of LGALS3 expression represent a FOXP3-signature of human antigen-stimulated CD4(+)CD25(hi) derived regulatory T cells.Laboratory Investigation advance online publication, 15 May 2006; doi:10.1038/labinvest.3700432.

PMID: 16702978 [PubMed - as supplied by publisher]































J Bone Miner Res. 2006 Jun;21(6):946-55.

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Fibroblast growth factor-2 is an immediate-early gene induced by mechanical stress in osteogenic cells.

Li CF, Hughes-Fulford M.

Laboratory of Cell Growth, Northern California Institute for Research and Education, San Francisco, California, USA.

Fifteen minutes of physiological MS induces FGF-2 in osteogenic cells. Here, we show that MS induced proliferation in both MC3T3-E1 and BMOp cells isolated from Fgf2(+/+) mice; Fgf2(-/-) BMOp cells required exogenous FGF-2 for a normal proliferation response. The induction of fgf-2 is mediated by PKA and ERK pathways. INTRODUCTION: Mechanical stress (MS) induces gene expression and proliferation of osteogenic MC3T3-E1 cells. We have previously shown that physiological levels of MS in MC3T3-E1 cells causes extracellular signal-regulated kinase (ERK)1/2 phosphorylation. Here we evaluate the induction and importance of fibroblast growth factor-2 (FGF-2) for MS-induced proliferation. MATERIALS AND METHODS: We characterized the MS induction of fgf-2 using a 15-minute pulse of 120 mustrain and studied the stability of fgf-2 message using actinomycin D. Bone marrow stromal cells (BMOp) isolated from Fgf2(-/-) and Fgf2(+/+) mice were used to study the importance of FGF-2 in MS-induced proliferation. RESULTS: We found that the induction of fgf-2 by MS is dependent on both protein kinase A (PKA) and ERK pathways. MS transiently induces fgf-2 within 30 minutes. FGF-2 receptor (FGFR2) was also significantly increased within 1 h. All three isoforms of FGF-2 (24, 22, and 18 kDa) were significantly increased by MS. The MS-mediated increase of fgf-2 mRNA was caused by new synthesis and not stabilization. Pretreatment of MC3T3-E1 cells with cycloheximide showed that the induction of fgf-2 did not require new protein synthesis. Pretreating MC3T3-E1 cells with the mitogen-activated protein kinase (MAPK)/ERK kinase 1/2 (MEK1/2) inhibitor, U0126, or H-89, a PKA inhibitor, significantly inhibited the induction of fgf-2, showing that mechanical induction of fgf-2 is dependent on ERK and PKA signaling pathways. The downstream consequence of a single 15-minute stress pulse was a 3.5-fold increase in cell number in MC3T3-E1 compared with growth in nonstressed control cells. In studies using bone marrow osteoprogenitor cells (BMOp) isolated from Fgf2(+/+)and Fgf2(-/-) mice, we found that FGF-2 was necessary for a full proliferative response to MS. CONCLUSIONS: These studies show that FGF-2 is an immediate-early gene induced by MS, and its expression is mediated by both the PKA and MAPK signal transduction pathways. FGF-2 was required for a full proliferative response.

PMID: 16753025 [PubMed - in process]