RelB/p50 regulates TNF production in LPS-stimulated dendritic cells and macrophages.

Dendritic cells (DCs) and macrophages are effective antigen-presenting cells, and DCs, once matured, have the ability to potently activate naïve T cells. While the canonical p65/p50 NF-κB pathway seems to have an important role during LPS-stimulation of these cells, the specific contribution of the non-canonical RelB/p50 subunits is not clear yet. We aimed to investigate the relevance of this pathway in DCs and macrophages by using replication-deficient adenoviruses overexpressing RelB and p50 subunits to test their effect on cytokine production.

Tumor necrosis factor-alpha triggers a cytokine cascade yielding postoperative cognitive decline.

Cognitive decline following surgery in older individuals is a major clinical problem of uncertain mechanism; a similar cognitive decline also follows severe infection, chemotherapy, or trauma and is currently without effective therapy. A variety of mechanisms have been proposed, and exploring the role of inflammation, we recently reported the role of IL-1β in the hippocampus after surgery in mice with postoperative cognitive dysfunction. Here, we show that TNF-α is upstream of IL-1 and provokes its production in the brain.

Nonsteroidal anti-inflammatory drugs increase TNF production in rheumatoid synovial membrane cultures and whole blood.

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase activity and hence PG production. However, the ability of NSAIDs to ameliorate pain and tenderness does not prevent disease progression in rheumatoid arthritis, a disease whose pathogenesis is linked to the presence of proinflammatory cytokines, such as TNF-alpha. To understand this observation, we have examined the effect of NSAIDs on the production of clinically validated proinflammatory cytokines.

Inhibitors of p38 suppress cytokine production in rheumatoid arthritis synovial membranes: does variable inhibition of interleukin-6 production limit effectiveness in vivo?

Objective: The activity of p38 MAPK regulates lipopolysaccharide (LPS)-stimulated production of key proinflammatory cytokines such as tumor necrosis factor α (TNFα). Consequently, p38 MAPK inhibitors have attracted considerable interest as potential treatments of rheumatoid arthritis (RA), and studies in murine models of arthritis have yielded promising results. However, the performance of several compounds in human clinical trials has been disappointing.

SIGIRR/TIR-8 is an inhibitor of Toll-like receptor signaling in primary human cells and regulates inflammation in models of rheumatoid arthritis.

Objective: Single-immunoglobulin interleukin-1 receptor-related (SIGIRR), which is also known as Toll/interleukin-1 receptor 8 (TIR-8), is a member of the TIR domain-containing family of receptors and was first characterized as an inhibitor of interleukin-1 receptor (IL-1R) and Toll-like receptor (TLR) signaling. In the Dextran sulfate sodium-induced colitis model, SIGIRR(-/-) mice were shown to have increased inflammation and to be more susceptible to endotoxin challenge. Increasing evidence implicates TLR and IL-1R signaling in the pathology of rheumatoid arthritis (RA).

Oral activated charcoal prevents experimental cerebral malaria in mice and in a randomized controlled clinical trial in man did not interfere with the pharmacokinetics of parenteral artesunate.

Background: Safe, cheap and effective adjunct therapies preventing the development of, or reducing the mortality from, severe malaria could have considerable and rapid public health impact. Oral activated charcoal (oAC) is a safe and well tolerated treatment for acute poisoning, more recently shown to have significant immunomodulatory effects in man. In preparation for possible efficacy trials in human malaria, we sought to determine whether oAC would i) reduce mortality due to experimental cerebral malaria (ECM) in mice, ii) modulate immune and inflammatory responses associated with ECM, and iii) affect the pharmacokinetics of parenteral artesunate in human volunteers.

Toll-like receptor-2 mediates inflammation and matrix degradation in human atherosclerosis.

Background: Inflammation and matrix degradation are the hallmarks of high-risk atherosclerosis that leads to myocardial infarction and stroke. Toll-like receptors (TLRs), key players in innate immunity, are upregulated in atherosclerotic lesions, but their functional role in human atherosclerosis is unknown. We explored the effects of blocking TLR-2, TLR-4, and myeloid differentiation primary response gene 88 (MyD88), a signaling adaptor shared by most TLRs and interleukin-1 receptor (IL-1R), in an in vitro model of human atherosclerosis.

The role of toll-like receptors in chronic inflammation.

The role of Toll-like receptors (TLRs) in innate immunity and their ability to recognise microbial products has been well characterised. TLRs are also able to recognise endogenous molecules which are released upon cell damage and necrosis and have been shown to be present in numerous autoimmune diseases. Therefore, the release of endogenous TLR ligands during inflammation and consequently the activation of TLR signalling pathways may be one mechanism initiating and driving autoimmune diseases.

TREM-1 expression is increased in the synovium of rheumatoid arthritis patients and induces the expression of pro-inflammatory cytokines.

Objectives: To investigate the expression and function of triggering receptor expressed on myeloid cells-1 (TREM-1) in the synovium of human RA patients as well as the level of soluble TREM-1 in the plasma of RA patients.

Methods: Twenty-four RA synovial samples were analysed by gene expression oligonucleotide microarrays. Expression levels of TREM-1 mRNA in murine CIA paws were determined by quantitative PCR (qPCR).

RelB/p50 regulates CCL19 production, but fails to promote human DC maturation.

DC, when fully matured are the APC best able to activate naïve T cells. Recently, we demonstrated using adenoviruses overexpressing IkappaBalpha and proteosome inhibitors that NF-kappaB is involved in DC activation, but the role of the individual subunits is still not clear. We investigated the role of the NF-kappaB subunits RelB and p50 in human DC activation using adenoviral vectors expressing RelB or p50.

Disordered macrophage cytokine secretion underlies impaired acute inflammation and bacterial clearance in Crohn's disease.

The cause of Crohn's disease (CD) remains poorly understood. Counterintuitively, these patients possess an impaired acute inflammatory response, which could result in delayed clearance of bacteria penetrating the lining of the bowel and predispose to granuloma formation and chronicity. We tested this hypothesis in human subjects by monitoring responses to killed Escherichia coli injected subcutaneously into the forearm.

The role of transposable elements in the regulation of IFN-lambda1 gene expression.

IFNs lambda1, lambda2, and lambda3, or type III IFNs, are recently identified cytokines distantly related to type I IFNs. Despite an early evolutionary divergence, the 2 types of IFNs display similar antiviral activities, and both are produced primarily in dendritic cells. Although virus induction of the type I IFN-beta gene had served as a paradigm of gene regulation, relatively little is known about the regulation of IFN-lambda gene expression.

Tenascin-C is an endogenous activator of Toll-like receptor 4 that is essential for maintaining inflammation in arthritic joint disease.

Although there have been major advances in the treatment of rheumatoid arthritis with the advent of biological agents, the mechanisms that drive cytokine production and sustain disease chronicity remain unknown. Tenascin-C (encoded by Tnc) is an extracellular matrix glycoprotein specifically expressed at areas of inflammation and tissue damage in inflamed rheumatoid joints. Here we show that mice that do not express tenascin-C show rapid resolution of acute joint inflammation and are protected from erosive arthritis.

Mycolactone inhibits monocyte cytokine production by a posttranscriptional mechanism.

The virulence and immunosuppressive activity of Mycobacterium ulcerans is attributed to mycolactone, a macrolide toxin synthesized by the bacteria. We have explored the consequence and mechanism of mycolactone pretreatment of primary human monocytes activated by a wide range of TLR ligands. The production of cytokines (TNF, IL-1beta, IL-6, IL-10, and IFN-gamma-inducible protein-10), chemokines (IL-8), and intracellular effector molecules (exemplified by cyclooxygenase-2) was found to be powerfully and dose dependently inhibited by mycolactone, irrespective of the stimulating ligand.

Tyrosine kinases and inflammatory signalling.

The activity of tyrosine kinases is central to many cellular processes, and accumulating evidence suggests that their role in inflammation is no less profound. Three main tyrosine kinase families, the Src, Tec and Syk kinase families are intimately involved in TLR signalling, the critical first step in cellular recognition of invading pathogens and tissue damage. Their activity results in changes in gene expression in affected cells.

Tolerance induced via TLR2 and TLR4 in human dendritic cells: role of IRAK-1.

Background: While dendritic cells (DCs) can induce tolerance in T cells, little is known about tolerance induction in DCs themselves. We have analysed tolerance induced in human in-vitro generated DCs by repeated stimulation with ligands for TLR4 and TLR2.

Results: DCs stimulated with the TLR4 ligand LPS did show a rapid and pronounced expression of TNF mRNA and protein.

Inhibitors of TLR8 reduce TNF production from human rheumatoid synovial membrane cultures.

The advent of anti-TNF biologicals has been a seminal advance in the treatment of rheumatoid arthritis (RA) and has confirmed the important role of TNF in disease pathogenesis. However, it is unknown what sustains the chronic production of TNF. In this study, we have investigated the anti-inflammatory properties of mianserin, a serotonin receptor antagonist.

Cell signalling in macrophages, the principal innate immune effector cells of rheumatoid arthritis.

Rheumatoid arthritis is a multisystemic auto-inflammatory disease affecting up to 1% of the population and leading to the destruction of the joints. Evidence exists for the involvement of the innate as well as the adaptive immune systems in the pathology of the disease. The success of anti-tumour necrosis factor-alpha indicates the importance of pro-inflammatory mediators produced by innate immune cells in rheumatoid arthritis progression.

The scaffold MyD88 acts to couple protein kinase Cepsilon to Toll-like receptors.

Mice lacking protein kinase Cepsilon (PKCepsilon) are hypersensitive to both Gram-positive and Gram-negative bacterial infections; however, the mechanism of PKCepsilon coupling to the Toll-like receptors (TLRs), responsible for pathogen detection, is poorly understood. Here we sought to investigate the mechanism of PKCepsilon involvement in TLR signaling and found that PKCepsilon is recruited to TLR4 and phosphorylated on two recently identified sites in response to lipopolysaccharide (LPS) stimulation. Phosphorylation at both of these sites (Ser-346 and Ser-368) resulted in PKCepsilon binding to 14-3-3beta.

Jund is a determinant of macrophage activation and is associated with glomerulonephritis susceptibility.

Crescentic glomerulonephritis is an important cause of human kidney failure for which the underlying molecular basis is largely unknown. In previous studies, we mapped several susceptibility loci, Crgn1-Crgn7, for crescentic glomerulonephritis in the Wistar Kyoto (WKY) rat. Here we show by combined congenic, linkage and microarray studies that the activator protein-1 (AP-1) transcription factor JunD is a major determinant of macrophage activity and is associated with glomerulonephritis susceptibility.

Role of STAT3 in glucocorticoid-induced expression of the human IL-10 gene.

In the present report we have determined the molecular mechanisms, which govern the expression of the human IL-10 gene when induced by the glucocorticoid Methyl-Prednisolone (MP). Treatment of cells with MP at 10(-6) M will readily induce IL-10 in CD19+ primary B cells and in a human B cell line. Analysis of the IL-10 promoter showed a robust 18-fold induction and demonstrated that a potential GRE motif was not required, while mutation of the -120 STAT-motif strongly reduced MP-induced trans-activation.

Bmx regulates LPS-induced IL-6 and VEGF production via mRNA stability in rheumatoid synovial fibroblasts.

Discordant cytokine production is characteristic of chronic inflammatory conditions like rheumatoid arthritis (RA), and anti-cytokine therapeutics are becoming routinely used to treat RA in the clinic. Fibroblasts from rheumatoid synovium have been shown to contribute to cytokine production in inflamed joints; likewise these cells also produce cytokines in response to inflammatory mediators signalling through Toll like receptors (TLRs). Tyrosine kinase activity is essential to LPS-induced cytokine production, and we have previously implicated a role for the Tec kinase, Bmx, in inflammatory cytokine production.

Targeting intracellular signaling: a novel approach to vaccination.

Vaccination is well known to control many current infectious diseases. However, the development of cellular (Th1) immunity to control viral pathogens, among others, requires the development of new vaccine adjuvants. The use of Toll-like receptor ligands or cytokines has shown much promise, although specificity and toxicity are issues with these strategies.

Rac mediates TNF-induced cytokine production via modulation of NF-kappaB.

TNF is a key factor in a variety of inflammatory diseases. Here we report that TNF induced pro-inflammatory cytokine synthesis of IL-6 and IL-8 is mediated by the Rho GTPase Rac. TNF induces p42/p44, p54 and p38 MAPK kinase; these kinases have been implicated in control of cytokine synthesis.

Cutting edge: A transcriptional repressor and corepressor induced by the STAT3-regulated anti-inflammatory signaling pathway.

IL-10 regulates anti-inflammatory signaling via the activation of STAT3, which in turn controls the induction of a gene expression program whose products execute inhibitory effects on proinflammatory mediator production. In this study we show that IL-10 induces the expression of an ETS family transcriptional repressor, ETV3, and a helicase family corepressor, Strawberry notch homologue 2 (SBNO2), in mouse and human macrophages. IL-10-mediated induction of ETV3 and SBNO2 expression was dependent upon both STAT3 and a stimulus through the TLR pathway.