Regions of the mouse CD14 molecule required for toll-like receptor 2- and 4-mediated activation of NF-kappa B

NF-κB p105-mediated nuclear translocation of ERK is required for full activation of IFNγ-induced iNOS expression

Inducible nitric oxidase (iNOS) encoded by Nos2 is a representative IFNγ-inducible effector molecule that plays an important role in both innate and adaptive immunity. In the present study, we demonstrated that full-length NF-κB p105 (p105), which is a precursor of NF-κB p50 (p50), is required for full activation of IFNγ-induced iNOS expression in the RAW264.7 mouse macrophage cell line. In comparison to wild-type (WT) RAW264.7 cells, p105 KO RAW264.7 (p105 KO) cells completely lost IFNγ-induced iNOS expression. Despite the limited effect of exogenous expression of p50 in p105 KO cells on IFNγ-induced Nos2 promoter activity, p105 expression fully restored IFNγ-induced Nos2 promoter activity to a level comparable to that of WT cells, suggesting an important role for full-length p105 in IFNγ-induced iNOS expression. While the expression and phosphorylation of JAK1 and STAT1 were rather enhanced in p105 KO cells, the phosphorylation of c-Jun downstream of MAPK signaling was decreased. IFNγ-induced phosphorylation of ERK, a kinase for IFNγ-induced c-Jun phosphorylation, was not significantly reduced in p105 KO cells, although the nuclear activity of ERK was significantly decreased due to its reduced translocation to the nucleus. Expression of iNOS, nuclear translocation of ERK, and phosphorylation of c-Jun were restored by stable supplementation of p105 in p105 KO cells. These results suggest that p105 is required for the nuclear translocation of ERK and the subsequent phosphorylation of c-Jun, which are necessary for full activation of IFNγ-induced iNOS expression. Reduced nuclear translocation of ERK in p105 KO cells was also observed in the activation of ERK following serum starvation, further suggesting that the involvement of p105 in ERK nuclear translocation is not limited to IFNγ-stimulated cells but is a more general function of p105.

Exploration of gut microbiome and inflammation: A review on key signalling pathways

The gut microbiome, a crucial component of the human system, is a diverse collection of microbes that belong to the gut of human beings as well as other animals. These microbial communities continue to coexist harmoniously with their host organisms and perform various functions that affect the host's general health. Each person's gut microbiota has a unique makeup. The gut microbiota is well acknowledged to have a part in the local as well as systemic inflammation that underlies a number of inflammatory disorders (e.g., atherosclerosis, diabetes mellitus, obesity, and inflammatory bowel disease).The gut microbiota's metabolic products, such as short-chain fatty acids (butyrate, propionate, and acetate) inhibit inflammation by preventing immune system cells like macrophages and neutrophils from producing pro-inflammatory factors, which are triggered by the structural elements of bacteria (like lipopolysaccharide). The review's primary goal is to provide comprehensive and compiled data regarding the contribution of gut microbiota to inflammation and the associated signalling pathways.

Evaluation of Lipopolysaccharide and Interleukin-6 as Useful Screening Tool for Chronic Endometritis

Universal diagnostic criteria for chronic endometritis (CE) have not been established due to differences in study design among researchers and a lack of typical clinical cases. Lipopolysaccharides (LPSs) have been reported to cause inflammation in the reproductive systems of several animals. This study aimed to elucidate the influence of LPS in the pathogenesis of CE in humans. We investigated whether LPS affected cytokine production and cell proliferation in the endometrium using in vivo and in vitro experiments. LPS concentrations were analyzed between control and CE patients using endometrial tissues. LPS administration stimulated the proliferation of EM-E6/E7 cells derived from human endometrial cells. High LPS concentrations were detected in CE patients. LPS concentration was found to correlate with IL-6 gene expression in the endometrium. Inflammation signaling evoked by LPS led to the onset of CE, since LPS stimulates inflammatory responses and cell cycles in the endometrium. We identified LPS and IL-6 as suitable candidate markers for the diagnosis of CE.

Role of mucin 2 gene for growth in Anas platyrhynchos: a novel report

Introduction

The mucin gene is expressed in the mucous membrane of the inner layer of the internal organs. Intestinalmucin 2 (MUC2), amajor gel-formingmucin, represents a primary barrier component of mucus layers.

Materials and methods

This is the first report on the role of mucin genes in growth traits in animals. In this study, we randomly studied Bengal ducks (Anas platyrhynchos) reared from day old to 10 weeks of age under an organized farm and studied the growth parameters as well as body weight and average daily body weight gain.

Result and discussion

We characterized the mucin gene for Bengal ducks and observed glycosylation and EGF1 (EGF-like domain signature) as important domains for growth traits in ducks. We observed a better expression profile for the mucin gene in high-growing ducks in comparison to that of low-growing ducks with real-time PCR. Hence, the mucin gene may be employed as a marker for growth traits.

Wolbachia-induced inhibition of O'nyong nyong virus in Anopheles mosquitoes is mediated by Toll signaling and modulated by cholesterol

Enhanced host immunity and competition for metabolic resources are two main competing hypotheses for the mechanism of Wolbachia-mediated pathogen inhibition in arthropods. Using an Anopheles mosquito - somatic Wolbachia infection - O'nyong nyong virus (ONNV) model, we demonstrate that the mechanism underpinning Wolbachia-mediated virus inhibition is up-regulation of the Toll innate immune pathway. However, the viral inhibitory properties of Wolbachia were abolished by cholesterol supplementation. This result was due to Wolbachia-dependent cholesterol-mediated suppression of Toll signaling rather than competition for cholesterol between Wolbachia and virus. The inhibitory effect of cholesterol was specific to Wolbachia-infected Anopheles mosquitoes and cells. These data indicate that both Wolbachia and cholesterol influence Toll immune signaling in Anopheles mosquitoes in a complex manner and provide a functional link between the host immunity and metabolic competition hypotheses for explaining Wolbachia-mediated pathogen interference in mosquitoes. In addition, these results provide a mechanistic understanding of the mode of action of Wolbachia-induced pathogen blocking in Anophelines, which is critical to evaluate the long-term efficacy of control strategies for malaria and Anopheles-transmitted arboviruses.

Phosphatidylglycerol to Treat Chronic Skin Wounds in Diabetes

This review proposes the use of dioleoylphosphatidylglycerol (DOPG) to enhance diabetic wound healing. Initially, the characteristics of diabetic wounds are examined, focusing on the epidermis. Hyperglycemia accompanying diabetes results in enhanced inflammation and oxidative stress in part through the generation of advanced glycation end-products (AGEs), in which glucose is conjugated to macromolecules. These AGEs activate inflammatory pathways; oxidative stress results from increased reactive oxygen species generation by mitochondria rendered dysfunctional by hyperglycemia. These factors work together to reduce the ability of keratinocytes to restore epidermal integrity, contributing to chronic diabetic wounds. DOPG has a pro-proliferative action on keratinocytes (through an unclear mechanism) and exerts an anti-inflammatory effect on keratinocytes and the innate immune system by inhibiting the activation of Toll-like receptors. DOPG has also been found to enhance macrophage mitochondrial function. Since these DOPG effects would be expected to counteract the increased oxidative stress (attributable in part to mitochondrial dysfunction), decreased keratinocyte proliferation, and enhanced inflammation that characterize chronic diabetic wounds, DOPG may be useful in stimulating wound healing. To date, efficacious therapies to promote the healing of chronic diabetic wounds are largely lacking; thus, DOPG may be added to the armamentarium of drugs to enhance diabetic wound healing.

Ectopic CH60 mediates HAPLN1-induced cell survival signaling in multiple myeloma

Multiple myeloma (MM), the second most common hematological malignancy, is generally considered incurable because of the development of drug resistance. We previously reported that hyaluronan and proteoglycan link protein 1 (HAPLN1) produced by stromal cells induces activation of NF-κB, a tumor-supportive transcription factor, and promotes drug resistance in MM cells. However, the identity of the cell surface receptor that detects HAPLN1 and thereby engenders pro-tumorigenic signaling in MM cells remains unknown. Here, we performed an unbiased cell surface biotinylation assay and identified chaperonin 60 (CH60) as the direct binding partner of HAPLN1 on MM cells. Cell surface CH60 specifically interacted with TLR4 to evoke HAPLN1-induced NF-κB signaling, transcription of anti-apoptotic genes, and drug resistance in MM cells. Collectively, our findings identify a cell surface CH60-TLR4 complex as a HAPLN1 receptor and a potential molecular target to overcome drug resistance in MM cells.

RIGI, TLR7, and TLR3 Genes Were Predicted to Have Immune Response Against Avian Influenza in Indigenous Ducks

Avian influenza is a disease with every possibility to evolve as a human-to-human pandemic arising out of frequent mutations and genetic reassortment or recombination of avian influenza (AI) virus. The greatest concern is that till date, no satisfactory medicine or vaccines are available, leading to massive culling of poultry birds, causing huge economic loss and ban on export of chicken products, which emphasizes the need to develop an alternative strategy for control of AI. In the current study, we attempt to explore the molecular mechanism of innate immune potential of ducks against avian influenza. In the present study, we have characterized immune response molecules such as duck TLR3, TLR7, and RIGI that are predicted to have potent antiviral activities against the identified strain of avian influenza through in silico studies (molecular docking) followed by experimental validation with differential mRNA expression analysis. Future exploitation may include immunomodulation with the recombinant protein, and transgenic or gene-edited chicken resistant to bird flu.

Ovine CD14- an Immune Response Gene Has a Role Against Gastrointestinal Nematode Haemonchus contortus-A Novel Report

CD14 (also known as the monocyte differentiation antigen) is an important immune response gene known to be primarily responsible for innate immunity against bacterial pathogens, and as a pattern recognition receptor (PRR), binds with LPS (endotoxin), lipoproteins, and lipotechoic acid of bacteria. So far very limited work has been conducted in parasitic immunology. In the current study, we reported the role of CD14 in parasitic immunology in livestock species (sheep) for the first time. Ovine CD14 is characterized as a horse-shoe shaped bent solenoid with a hydrophobic amino-terminal pocket for CD14 along with domains. High mutation frequency was observed, out of total 41 mutations identified, 23 mutations were observed to be thermodynamically unstable and 11 mutations were deleterious in nature, causing major functional alteration of important domains of CD14, an indication of variations in individual susceptibility for sheep against Haemonchus contortus infestations. In silico studies with molecular docking reveal a role of immune response against Haemonchus contortus in sheep, which is later confirmed with experimental evidence through differential mRNA expression analysis for sheep, which revealed better expression of CD14 in Haemonchus contortus infected sheep compared to that of non-infected sheep. We confirmed the above findings with supportive evidence through haematological and biochemical analyses. Phylogenetic analysis was conducted to assess the evolutionary relationship with respect to humans and it was observed that sheep may well be used as model organisms due to better genetic closeness compared to that of mice.

Proteostasis of α-Synuclein and Its Role in the Pathogenesis of Parkinson's Disease

Aggregation of α-Synuclein, possibly caused by disturbance of proteostasis, has been identified as a common pathological feature of Parkinson’s disease (PD). However, the initiating events of aggregation have not been fully illustrated, and this knowledge may be critical to understanding the disease mechanisms of PD. Proteostasis is essential in maintaining normal cellular metabolic functions, which regulate the synthesis, folding, trafficking, and degradation of proteins. The toxicity of the aggregating proteins is dramatically influenced by its physical and physiological status. Genetic mutations may also affect the metastable phase transition of proteins. In addition, neuroinflammation, as well as lipid metabolism and its interaction with α-Synuclein, are likely to contribute to the pathogenesis of PD. In this review article, we will highlight recent progress regarding α-Synuclein proteostasis in the context of PD. We will also discuss how the phase transition status of α-Synuclein could correlate with different functional consequences in PD.

Molecular characterization of Bu-1 and TLR2 gene in Haringhata Black chicken

Haringhata Black is the only registered indigenous poultry genetic resource of West Bengal till date. Molecular characterization of HB revealed that Bu-1 to be highly glycoylated transmembrane protein unlike mammalian Bu-1, whereas TLR2 of HB chicken was observed to be rich in Leucine rich repeat. HB chicken was observed to be genetically close to chicken of Japan, while distant to chicken breed of UK and Chicago. Avian species wise evolution study indicates genetic closeness of HB chicken with turkey. Differential mRNA expression profile for the immune response genes (TLR2, TLR4 and Bu1 gene) were studied for HB chicken with respect to other chicken breed and poultry birds, which reveals that HB chicken were better in terms of B cell mediated immunity and hence better response to vaccination. Hence HB chicken is one of the best poultry genetic resources to be reared under backyard system where biosecurity measures are almost lacking.

CD14: Biology and role in the pathogenesis of disease

Human monocyte differentiation antigen CD14 is a pattern recognition receptor (PRR) that enhances innate immune responses. CD14 was first identified as a marker of monocytes to signal intracellular responses upon bacterial encounters. Given the absence of an intracellular tail, CD14 was doubted to have the signaling capacities. Later CD14 was confirmed as the TLR co-receptor for the detection of pathogen-associated molecular patterns. However, CD14 has been revealed as a multi-talented receptor. In last decade, CD14 was identified to activate NFAT to regulate the life cycle of myeloid cells in a TLR4-independent manner and to transport inflammatory lipids to induce phagocyte hyperactivation. And its influences on multiple related diseases have been further considered. In this review, we summarize advancements in the basic biology of the CD14 including its structure, binding ligands, signaling pathways, and its roles in the pathogenesis of inflammation, atherosclerosis, tumor and metabolic diseases. We also discuss the therapeutic potential of targeting the CD14 in related diseases.

Microglia Response During Parkinson's Disease: Alpha-Synuclein Intervention

The discovery of the central role played by the protein alpha-synuclein in Parkinson's disease and other Lewy body brain disorders has had a great relevance in the understanding of the degenerative process occurring in these diseases. In addition, during the last two decades, the evidence suggesting an immune response in Parkinson's disease patients have multiplied. The role of the immune system in the disease is supported by data from genetic studies and patients, as well as from laboratory animal models and cell cultures. In the immune response, the microglia, the immune cell of the brain, will have a determinant role. Interestingly, alpha-synuclein is suggested to have a central function not only in the neuronal events occurring in Parkinson's disease, but also in the immune response during the disease. Numerous studies have shown that alpha-synuclein can act directly on immune cells, such as microglia in brain, initiating a sterile response that will have consequences for the neuronal health and that could also translate in a peripheral immune response. In parallel, microglia should also act clearing alpha-synuclein thus avoiding an overabundance of the protein, which is crucial to the disease progression. Therefore, the microglia response in each moment will have significant consequences for the neuronal fate. Here we will review the literature addressing the microglia response in Parkinson's disease with an especial focus on the protein alpha-synuclein. We will also reflect upon the limitations of the studies carried so far and in the therapeutic possibilities opened based on these recent findings.

Naive CD4+ T Cells Carrying a TLR2 Agonist Overcome TGF-β-Mediated Tumor Immune Evasion

TLR agonists are effective at treating superficial cancerous lesions, but their use internally for other types of tumors remains challenging because of toxicity. In this article, we report that murine and human naive CD4⁺ T cells that sequester Pam₃Cys₄ (CD4⁺ T^Pam3) become primed for T_h1 differentiation. CD4⁺ T^Pam3 cells encoding the OVA-specific TCR OT2, when transferred into mice bearing established TGF-β-OVA-expressing thymomas, produce high amounts of IFN-γ and sensitize tumors to PD-1/programmed cell death ligand 1 blockade-induced rejection. In contrast, naive OT2 cells without Pam₃Cys₄ cargo are prone to TGF-β-dependent inducible regulatory Foxp3⁺ CD4⁺ T cell conversion and accelerate tumor growth that is largely unaffected by PD-1/programmed cell death ligand 1 blockade. Ex vivo analysis reveals that CD4⁺ T^Pam3 cells are resistant to TGF-β-mediated gene expression through Akt activation controlled by inputs from the TCR and a TLR2-MyD88-dependent PI3K signaling pathway. These data show that CD4⁺ T^Pam3 cells are capable of T_h1 differentiation in the presence of TGF-β, suggesting a novel approach to adoptive cell therapy.

NF-κB activation via MyD88-dependent Toll-like receptor signaling is inhibited by trichothecene mycotoxin deoxynivalenol

Macrophages induce the innate immunity by recognizing pathogens through Toll-like receptors (TLRs), which sense pathogen-associated molecular patterns. Myeloid differentiation factor 88 (MyD88), which is an essential adaptor molecule for most TLRs, mediates the induction of inflammatory cytokines through nuclear factor κB (NF-κB). Trichothecene mycotoxin deoxynivalenol (DON) shows immunotoxic effects by interrupting inflammatory mediators produced by activated macrophages. The present study investigates the effect of DON on NF-κB in activated macrophages through MyD88-dependent pathways. DON inhibited NF-κB-dependent reporter activity induced by MyD88-dependent TLR agonists. In addition, lipopolysaccharide-induced phosphorylation of interleukin-1 receptor-associated kinase 1 and inhibitor κBα were attenuated by DON. Furthermore, DON downregulated the expression level of MyD88. These results suggest that DON inhibits NF-κB activation in macrophages stimulated with TLR ligands via MyD88-dependent TLR signals. Therefore exposure to DON may lead to the inhibition of MyD88-dependent pathway of TLR signaling.

Liver argininosuccinate synthase binds to bacterial lipopolysaccharides and lipid A and inactivates their biological activities

The liver is known to clear and detoxify circulating lipopolysaccharide (LPS). To characterize the molecules involved in this process in the liver, we attempted to purify mouse liver protein(s) that can interact with lipid A, a biologically active portion of LPS. By partially purifying the inactivating activity against a synthetic lipid A analog, we observed the enrichment of a 45-kDa protein in the active fractions. The internal amino acid sequences of the protein were identical with those of argininosuccinate synthase (EC 6.3.4.5). To examine whether argininosuccinate synthase can interact with lipid A, we purified the enzyme from mouse liver and found the co-elevation of the specific enzyme activity and specific lipid A-inactivating activity, indicating that argininosuccinate synthase is the major lipid A-interacting protein in liver. Argininosuccinate synthase also inhibited the biological activities (macrophage activation and Limulus test) of natural lipid A and rough-type LPS but not smooth-type LPS. The enzyme activity was inhibited by lipid A and rough-type LPS and also by smooth-type LPS. Native gel electrophoresis of a mixture of argininosuccinate synthase and LPS and immunoprecipitation of a mixture of argininosuccinate synthase and [3H]-LPS with anti-argininosuccinate synthase antiserum showed that argininosuccinate synthase stably bound lipid A and LPS. These findings, together, indicate that argininosuccinate synthase can effectively bind LPS in the liver.

Elevated CD14 (Cluster of Differentiation 14) and Toll-Like Receptor (TLR) 4 Signaling Deteriorate Periapical Inflammation in TLR2 Deficient Mice

Apical periodontitis (periapical lesions) is an infection-induced chronic inflammation in the jaw, ultimately resulting in the destruction of apical periodontal tissue. Toll-like receptors (TLRs) are prominent in the initial recognition of pathogens. Our previous study showed that TLR4 signaling is proinflammatory in periapical lesions induced by a polymicrobial endodontic infection. In contrast, the functional role of TLR2 in regulation of periapical tissue destruction is still not fully understood. Using TLR2 deficient (KO), TLR2/TLR4 double deficient (dKO), and wild-type (WT) mice, we demonstrate that TLR2 KO mice are highly responsive to polymicrobial infection-induced periapical lesion caused by over activation of TLR4 signal transduction pathway that resulted in elevation of NF-kB (nuclear factor kappa B) and proinflammatory cytokine production. The altered TLR4 signaling is caused by TLR2 deficiency-dependent elevation of CD14 (cluster of differentiation 14), which is a co-receptor of TLR4. Indeed, neutralization of CD14 strikingly suppresses TLR2 deficiency-dependent inflammation and tissue destruction in vitro and in vivo. Our findings suggest that a network of TLR2, TLR4, and CD14 is a key factor in regulation of polymicrobial dentoalveolar infection and subsequent tissue destruction. Anat Rec, 299:1281-1292, 2016. © 2016 Wiley Periodicals, Inc.

Lipopolysaccharide-Induced CD300b Receptor Binding to Toll-like Receptor 4 Alters Signaling to Drive Cytokine Responses that Enhance Septic Shock

Receptor CD300b is implicated in regulating the immune response to bacterial infection by an unknown mechanism. Here, we identified CD300b as a lipopolysaccharide (LPS)-binding receptor and determined the mechanism underlying CD300b augmentation of septic shock. In vivo depletion and adoptive transfer studies identified CD300b-expressing macrophages as the key cell type augmenting sepsis. We showed that CD300b, and its adaptor DAP12, associated with Toll-like receptor 4 (TLR4) upon LPS binding, thereby enhancing TLR4-adaptor MyD88- and TRIF-dependent signaling that resulted in an elevated pro-inflammatory cytokine storm. LPS engagement of the CD300b-TLR4 complex led to the recruitment and activation of spleen tyrosine kinase (Syk) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). This resulted in an inhibition of the ERK1/2 protein kinase- and NF-κB transcription factor-mediated signaling pathways, which subsequently led to a reduced interleukin-10 (IL-10) production. Collectively, our data describe a mechanism of TLR4 signaling regulated by CD300b in myeloid cells in response to LPS.

The relation between α-synuclein and microglia in Parkinson's disease: Recent developments

Recent research suggests a complex role for microglia not only in Parkinson's disease but in other disorders involving alpha-synuclein aggregation, such as multiple system atrophy. In these neurodegenerative processes, the activation of microglia is a common pathological finding, which disturbs the homeostasis of the neuronal environment otherwise maintained, among others, by microglia. The term activation comprises any deviation from what otherwise is considered normal microglia status, including cellular abundance, morphology or protein expression. The microglial response during disease will sustain survival or otherwise promote cell degeneration. The novel concepts of alpha-synuclein being released and uptaken by neighboring cells, and their importance in disease progression, positions microglia as the main cell that can clear and handle alpha-synuclein efficiently. Microglia's behavior will therefore be a determinant on the disease's progression. For this reason we believe that the better understanding of microglia's response to alpha-synuclein pathological accumulation across brain areas and disease stages is essential to develop novel therapeutic tools for Parkinson's disease and other alpha-synucleinopathies. In this review we will revise the most recent findings and developments with regard to alpha-synuclein and microglia in Parkinson's disease.

Differential expression of Toll-like receptor 4 in healthy and diseased human gingiva

BACKGROUND AND OBJECTIVE

Lipopolysaccharide (LPS)-mediated signaling in host cells involves Toll-like receptor 4 (TLR4) accessory molecules, including LPS-binding protein (LBP), cluster of differentiation 14 (CD14) and lymphocyte antigen 96 (MD-2). However, expression of these innate defense molecules in various compartments of the human periodontium is unclear. The aim of this study was to investigate the expression profile of TLR4 in human gingiva.

MATERIAL AND METHODS

Human gingival biopsies were collected from healthy gingival or chronic periodontitis tissue. Primary gingival keratinocytes and fibroblasts were cultured. Immunohistochemical analysis for TLR4 was performed. Transcripts of TLR4, MD-2, CD14 and LBP, and their protein products, were examined using RT-PCR, immunoprecipitation and immunoblotting. The interactions between these molecules in keratinocytes and fibroblasts were investigated by co-immunoprecipitation.

RESULTS

TLR4 immunoreactivity was found in healthy gingival epithelium and periodontitis tissue, and appeared to be lower in junctional epithelium ( p ≤ 0.01). Fibroblasts and inflammatory cells stained more strongly for TLR4 in diseased periodontal tissues (p < 0.001). Three TLR4 splicing variants, two MD-2 splicing variants and one CD14 mRNA were expressed by gingival keratinocytes and fibroblasts. Expression of TLR4, CD14 and MD-2 proteins was detected in keratinocytes and fibroblasts in vitro. TLR4 protein from gingival keratinocytes and fibroblasts could be co-immunoprecipitated with CD14 or MD-2, suggesting an association between the related molecules in vivo. LBP transcript was detected in gingival biopsies, but not in primary cultures of gingival keratinocytes or fibroblasts.

CONCLUSION

TLR4, CD14 and MD-2, but not LBP, are expressed in human gingival keratinocytes and fibroblasts. The TLR4 expression level in the junctional epithelium appeared to be lowest within the periodontal epithelial barrier.

Lgr4/Gpr48 negatively regulates TLR2/4-associated pattern recognition and innate immunity by targeting CD14 expression

The recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) is pivotal in both innate and adaptive immune responses. Here we demonstrate that deletion of Lgr4/Gpr48 (G-protein-coupled receptor 48), a seven-transmembrane glycoprotein hormone receptor, potentiates TLR2/4-associated cytokine production and attenuates mouse resistance to septic shock. The expression of CD14, a co-receptor for TLR2/4-associated pathogen-associated molecular patterns, is increased significantly in Lgr4-deficient macrophages, which is consistent with the increased immune response, whereas the binding activity of cAMP-response element-binding protein is decreased significantly in Lgr4-deficient macrophages, which up-regulate the expression of CD14 at the transcriptional level. Together, our data demonstrate that Lgr4/Gpr48 plays a critical role in modulating the TLR2/4 signaling pathway and represents a useful therapeutic approach of targeting Lgr4/Gpr48 in TLR2/4-associated septic shock and autoimmune diseases.

Molecular Characterization and SNP Detection of CD14 Gene of Crossbred Cattle

CD14 is an important molecule for innate immunity that can act against a wide range of pathogens. The present paper has characterized CD14 gene of crossbred (CB) cattle (Bos indicus×Bos taurus). Cloning and sequence analysis of CD14 cDNA revealed 1119 nucleotide long open reading frame encoding 373 amino acids protein and 20 amino acids signal peptide. CB cattle CD14 gene exhibited a high percentage of nucleotide identity (59.3–98.1%) with the corresponding mammalian homologs. Cattle and buffalo appear to have diverged from a common ancestor in phylogenetic analysis. 25 SNPs with 17 amino acid changes were newly reported and the site for mutational hot-spot was detected in CB cattle CD14 gene. Non-synonymous substitutions exceeding synonymous substitutions indicate the evolution of this protein through positive selection among domestic animals. Predicted protein structures obtained from deduced amino acid sequence indicated CB cattle CD14 molecule to be a receptor with horse shoe-shaped structure. The sites for LPS binding, LPS signalling, leucine-rich repeats, putative N-linked glycosylation, O-linked glycosylation, glycosyl phosphatidyl inositol anchor, disulphide bridges, alpha helix, beta strand, leucine rich nuclear export signal, leucine zipper and domain linker were predicted. Most of leucine and cysteine residues remain conserved across the species.

IRAK-1-mediated negative regulation of Toll-like receptor signaling through proteasome-dependent downregulation of TRAF6

TRAF6 plays a crucial role in signal transduction of the Toll-like receptor (TLR). It has been reported that TRAF6 catalyzes the formation of unique Lys63-linked polyubiquitin chains, which do not lead to proteasome-mediated degradation. Here we found that stimulation of J774.1 cells with various TLR ligands led to decreases in TRAF6 protein levels that occurred at a slower rate than IκBα degradation. The decrease in TRAF6 was inhibited by proteasome inhibitors MG-132, lactacystin and N-acetyl-leucyl-leucyl-norleucinal. Among intracellular TLR signaling molecules MyD88, IRAK-4, IRAK-1, TRAF6, and IKKβ, only IRAK-1 expression downregulated TRAF6 in HEK293 cells. The amount of TRAF6 expressed either transiently or stably was also reduced by co-expression of IRAK-1 and no TRAF6 cleavage products were detected. The levels of either a TRAF6 N-terminal deletion mutant or a ubiquitin ligase-defective mutant were not affected by IRAK-1 expression. Downregulation of TRAF6 required the TRAF6-binding site (Glu544, Glu587, Glu706) of IRAK-1 but not its catalytic site (Asp340). Upon IRAK-1 transfection, no significant TRAF6 ubiquitination was detected. Instead, TRAF6-associated IRAK-1 was ubiquitinated with both Lys48- and Lys63-linked polyubiquitin chains. TRAF6 downregulation was inhibited by co-expression of the E3 ubiquitin ligase Pellino 3, whose Lys63-linked polyubiquitination on IRAK-1 is reported to compete with Lys48-linked IRAK-1 polyubiquitination. Expression of IRAK-1 inhibited IκBα phosphorylation in response to TLR2 stimulation. These results indicate that stimulation of TLRs induces proteasome-dependent downregulation of TRAF6. We conclude that TRAF6 associated with ubiquitinated IRAK-1 is degraded together by the proteasome and that IRAK-1 possesses a negative regulatory role on TLR signaling.

Toll-like receptors and their adapter molecules

Toll-like receptors (TLR) are among key receptors of the innate mammalian immune system. Receptors of this family are able to recognize specific highly conserved molecular regions (patterns) in pathogen structures, thus initiating reactions of both innate and acquired immune response finally resulting in the elimination of the pathogen. In this case every individual TLR type is able to bind a broad spectrum of molecules of microbial origin characterized by different chemical properties and structures. Recent data demonstrate the existence of a multistep mechanism of the TLR recognition of the pathogen in which, in addition to receptors proper, the involvement of different adapter molecules is necessary. However, functions of separate adapter molecules as well as the principles of formation of a multicomponent system of ligand-specific recognition are still not quite understandable. We describe all identified as well as possible (candidate) adapter TLR molecules by giving their brief characteristics, and we also propose generalized possible variants of the TLR ligand-specific recognition with involvement of adapter molecules.

Inhibitory effects of soluble MD-2 and soluble CD14 on bacterial growth

The effects of the soluble forms of the endotoxin receptor molecules sMD-2 and sCD14 on bacterial growth were studied. When Escherichia coli and Bacillus subtilis were incubated at 37 degrees C for 18 hr with either sMD-2 or sCD14, growth of these bacteria was significantly inhibited as evaluated by viable cell counts and NADPH/NADH activity. A mutant of sCD14 (sCD14d57-64) lacking a region essential for LPS binding did not inhibit the growth of E. coli, whereas this mutant did inhibit the growth of B. subtilis. Addition of excess PG to the bacterial culture reversed the inhibitory effect of sMD-2 on the growth of B. subtilis, but not on the growth of E. coli. Furthermore, when evaluated by ELISA, both sMD-2 and sCD14 bound specifically to PG. Taken together, these results indicate that sMD-2 and sCD14 inhibit the growth of both Gram-positive and Gram-negative bacteria and further suggest that binding to PG and LPS is involved in the inhibitory effect of sMD-2 on Gram-positive bacteria and of sCD14 on Gram-negative bacteria, respectively.

[Role of toll-like receptors in respiratory diseases]

There has been growing interest in the last 10 years in the study of innate immunity, in particular because of the possible role that toll-like receptors (TLR) may play in the pathogenesis of some respiratory disease such as for example, asthma, chronic obstructive pulmonary disease, and infections. TLR are a family of type 1 transmembrane proteins, responsible for recognizing molecular patterns associated with pathogens (PAMP, pathogen-associated molecular patterns), and expressed by a broad spectrum of infectious agents. This recognition leads to quick production of cytokines and chemokines which provides a long-lasting adaptive response to the pathogen. Currently, it is considered that the administration of drugs which modulate the activity of these receptors upwards or downwards may represent major therapeutic progress for handling these diseases. The aim of this review is to describe the different TLS, define their possible role in the pathogenesis of the main respiratory diseases and finally, speculate over the therapeutic possibilities which their modulation, agonist or antagonist, offers as possible therapeutic targets.

CD14 but not MD2 transmit signals from DAMP

Both pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) activate antigen-presenting cells, often through the same pattern recognition receptors (PRR), such as Toll-like receptors (TLR). The TLR4-CD14-MD2 and TLR2-CD14 complexes have been shown to play a role in the recognition of lipopolysaccharide (LPS) and peptidoglycan (PG), respectively. Since many DAMPs have also been known to activate TLR2 or TLR4 pathways, we dissected the role of each molecule in the receptor complexes (TLR2-D14-MD2) responding to DAMP (necrotic cells) or PAMP (LPS and PG). CD14 played a significant role in the activation of NF-kappaB in response to necrotic cells in the presence or absence of TLR2. However, MD2 did not play a significant role in NF-kappaB activation by necrotic cells. Intriguingly, MD2 did play a significant role in activating NF-kappaB by PG in the presence of TLR2-CD14. Compared with CD14(pos) B6 mice, CD14(neg) B6 mice showed delayed production of IL12p40 in response to necrotic cells in vivo. Microarray analysis showed that various pro-inflammatory genes of peritoneal cells were regulated in response to necrotic cells, in a CD14-dependent manner. The CD14 appears to recognize necrotic cells in addition to LPS, PG, apoptotic cells, and lipids, suggesting that CD14 might be a universal adaptor for DAMP and PAMP. On the contrary, MD2 recognizes only exogenous PAMP, when complexed with TLR2-CD14 or TLR4-CD14. Taken together, MD2 appears to discriminate between DAMP and PAMP.

[Role of toll-like receptors in respiratory diseases]

There has been growing interest in the last 10 years in the study of innate immunity, in particular because of the possible role that toll-like receptors (TLR) may play in the pathogenesis of some respiratory diseases including, asthma, chronic obstructive pulmonary disease, and infections. TLR are a family of type 1 transmembrane proteins, responsible for recognising molecular patterns associated with pathogens (PAMP, pathogen-associated molecular patterns), and expressed by a broad spectrum of infectious agents. This recognition leads to a quick production of cytokines and chemokines which provides a long-lasting adaptive response to the pathogen. At present, it is considered //It is currently considered that the administration of drugs which modulate the activity of these receptors upwards or downwards may represent major therapeutic progress for handling these diseases.

The aim of this review is to describe the different TLS, define their possible role in the pathogenesis of the main respiratory diseases and finally, speculate over the therapeutic possibilities which their modulation, agonist or antagonist, offers as possible therapeutic targets.

Structures of the toll-like receptor family and its ligand complexes

Toll-like receptors (TLRs) play central roles in the innate immune response by recognizing conserved structural patterns in diverse microbial molecules. Here, we discuss ligand binding and activation mechanisms of the TLR family. Hydrophobic ligands of TLR1, TLR2, and TLR4 interact with internal protein pockets. In contrast, dsRNA, a hydrophilic ligand, interacts with the solvent-exposed surface of TLR3. Binding of agonistic ligands, lipopeptides or dsRNA, induces dimerization of the ectodomains of the various TLRs, forming dimers that are strikingly similar in shape. In these "m"-shaped complexes, the C termini of the extracellular domains of the TLRs converge in the middle. This observation suggests the hypothesis that dimerization of the extracellular domains forces the intracellular TIR domains to dimerize, and this initiates signaling by recruiting intracellular adaptor proteins.

CD14 and TLR4 are expressed early in tammar (Macropus eugenii) neonate development

Marsupials are born in a relatively underdeveloped state and develop during a period of intensive maturation in the postnatal period. During this period, the young marsupial lacks a competent immune system, but manages to survive despite the potential of exposure to environmental pathogens. Passive immune transfer via the milk is one well-recognised strategy to compensate the neonate, but there also may be innate immune mechanisms in place. In this study, CD14 and Toll-like receptor 4 (TLR4), integral molecular components of pathogen recognition, were identified and characterised for the first time in a marsupial, the tammar wallaby (Macropus eugenii). Functional motifs of tammar CD14 and the toll/interleukin receptor (TIR) domain of TLR4 were highly conserved. The lipopolysaccharide (LPS) binding residues and the TLR4 interaction site of CD14 were conserved in all marsupials. The TIR signalling domain had 84% identity within marsupials and 77% with eutherians. Stimulation of adult tammar leukocytes resulted in the induction of a biphasic pattern of CD14 and TLR4 expression, and coincided with increased production of the pro-inflammatory cytokine TNF-alpha. Differential patterns of expression of CD14 and TLR4 were observed in tammar pouch young early in development, suggesting that early maturation of the innate immune system in these animals may have developed as an immune survival strategy to protect the marsupial neonate from exposure to microbial pathogens.

Bacterial lipopolysaccharide regulates nociceptin expression in sensory neurons

Nociceptin/orphanin FQ (N/OFQ) is an opioid-related peptide that is markedly up-regulated in sensory neurons in vivo following peripheral inflammation and plays a key role in pain physiology. To identify substances that up-regulate N/OFQ expression in sensory neurons, we carried out an in vitro screen using purified adult mouse dorsal root ganglion (DRG) neurons and identified the potent proinflammatory agent bacterial lipopolysaccharide (LPS) as a very effective inducer of N/OFQ. The robust response of these neurons to LPS enabled us to identify the components of a putative neuronal LPS receptor complex. In contrast to the immune system, where the functional LPS receptor complex is composed of CD-14 together with either MD-2 and TLR4 on myeloid cells or the homologous receptors MD-1 and RP105 on mature B cells, DRG neurons express the unusual combination of CD-14, TLR4, and MD-1. Blocking antibodies against TLR4 and MD-1 prevented induction of N/OFQ by LPS, and, in immunoprecipitation experiments, MD-1 coprecipitated with TLR4. Our findings suggest that LPS regulates N/OFN expression in sensory neurons via a novel combination of LPS receptor components and demonstrate for the first time a direct action of a key initiator of innate immune responses on neurons.

Interactions between the products of the Herpes simplex genome and Alzheimer's disease susceptibility genes: relevance to pathological-signalling cascades

The products of the Herpes simplex (HSV-1) genome interact with many Alzheimer's disease susceptibility genes or proteins. These in turn affect those of the virus. For example, HSV-1 binds to heparan sulphate proteoglycans (HSPG2), or alpha-2-macroglobulin (A2M), and enters cells via nectin receptors, which are cleaved by gamma-secretase (APH1B, PSEN1, PSEN2, PEN2, NCSTN). The virus also binds to blood-borne lipoproteins and apolipoprotein E (APOE) is able to modify its infectivity. Viral uptake is cholesterol- and lipid raft-dependent (DHCR24, HMGCR, FDPS, RAFTLIN, SREBF1). The virus is transported to the nucleus via the dynein and kinesin (KNS2) motors associated with the microtubule network (MAPT). Amyloid precursor protein (APP) plays a role in this transport. Nuclear export is mediated via disruption of the nuclear lamina and binding to LMNA. Herpes simplex activates kinases (CDC2 and casein kinase 2) whose substrates include APOE, APP, MAPT, PSEN2, and SREBF1. A viral protein is also able to delete mitochondrial DNA, a situation prevalent in Alzheimer's disease. The virus binds to the host transcription factors transcription factor CP2 (TFCP2) and POU2F1 that control many other genes associated with Alzheimer's disease. Viral latency is controlled by IL6 and IL1B and at different stages of its life cycle the virus can either promote or attenuate apoptosis via Fas and tumor necrosis factor pathways (FAS, TNF, DAPK1, PARP1). Viral evasion strategies include inhibition of the antigen processor TAP2, the production of an Fc immunoglobulin receptor mimic (FCER1G) and inhibition of the viral-activated kinase EIF2AK2. These and other host/viral interactions, targeted to certain Alzheimer's disease susceptibility genes, support the idea that some form of synergy between the pathogen and genetic factors may play a role in the pathology of late-onset Alzheimer's disease.

The Central Leucine-Rich Repeat Region of Chicken TLR16 Dictates Unique Ligand Specificity and Species-Specific Interaction with TLR2

The ligand specificity of human TLR (hTLR) 2 is determined through the formation of functional heterodimers with either hTLR1 or hTLR6. The chicken carries two TLR (chTLR) 2 isoforms, type 1 and type 2 (chTLR2t1 and chTLR2t2), and one putative TLR1/6/10 homologue (chTLR16) of unknown function. In this study, we report that transfection of HeLa cells with the various chicken receptors yields potent NF-kappaB activation for the receptor combination of chTLR2t2 and chTLR16 only. The sensitivity of this complex was strongly enhanced by human CD14. The functional chTLR16/chTLR2t2 complex responded toward both the hTLR2/6-specific diacylated peptide S-(2,3-bispalmitoyloxypropyl)-Cys-Gly-Asp-Pro-Lys-His-Pro-Lys-Ser-Phe (FSL-1) and the hTLR2/1 specific triacylated peptide tripalmitoyl-S-(bis(palmitoyloxy)propyl)-Cys-Ser-(Lys)(3)-Lys (Pam(3)CSK(4)), indicating that chTLR16 covers the functions of both mammalian TLR1 and TLR6. Dissection of the species specificity of TLR2 and its coreceptors showed functional chTLR16 complex formation with chTLR2t2 but not hTLR2. Conversely, chTLR2t2 did not function in combination with hTLR1 or hTLR6. The use of constructed chimeric receptors in which the defined domains of chTLR16 and hTLR1 or hTLR6 had been exchanged revealed that the transfer of leucine-rich repeats (LRR) 6-16 of chTLR16 into hTLR6 was sufficient to confer dual ligand specificity to the human receptor and to establish species-specific interaction with chTLR2t2. Collectively, our data indicate that diversification of the central LRR region of the TLR2 coreceptors during evolution has put constraints on both their ligand specificity and their ability to form functional complexes with TLR2.

Adjuvant TACE inhibitor treatment improves the outcome of TLR2-/- mice with experimental pneumococcal meningitis

Background

Streptococcus (S.) pneumoniae meningitis has a high lethality despite antibiotic treatment. Inflammation is a major pathogenetic factor, which is unresponsive to antibiotics. Therefore adjunctive therapies with antiinflammatory compounds have been developed. TNF484 is a TNF-alpha converting enzyme (TACE) inhibitor and has been found efficacious in experimental meningitis. Toll-like receptor 2 (TLR2) contributes to host response in pneumococcal meningitis by enhancing bacterial clearing and downmodulating inflammation. In this study, TNF484 was applied in mice, which lacked TLR2 and exhibited a strong meningeal inflammation.

Methods

10³ CFU S. pneumoniae serotype 3 was inoculated subarachnoidally into C57BL/6 wild type (wt) mice or TLR2^-/-, CD14^-/- and CD14^-/-/TLR2^-/- mice. Severity of disease and survival was followed over 9 days. Response to antibiotics (80 mg/kg ceftriaxone i.p. for 5 days) and/or TACE inhibitor treatment (1 mg/kg s.c. twice daily for 4 days) was evaluated. Animals were sacrificed after 12, 24, and 48 h for analysis of bacterial load in cerebrospinal fluid (CSF) and brain and for TNF and leukocyte measurements in CSF.

Results

TLR2^-/- mice were significantly sicker than the other mouse strains 24 h after infection. All knockout mice showed higher disease severity after 48 h and died earlier than wt mice. TNF release into CSF was significantly more elevated in TLR2^-/- than in the other strains after 24 h. Brain bacterial numbers were significantly higher in all knockout than wt mice after 24 h. Modulation of outcome by antibiotic and TACE inhibitor treatment was evaluated. With antibiotic therapy all wt, CD14^-/- and TLR2^-/-/CD14^-/- mice, but only 79% of TLR2^-/- mice, were rescued. TACE inhibitor treatment alone did not rescue, but prolonged survival in wt mice, and in TLR2^-/- and CD14^-/- mice to the values observed in untreated wt mice. By combined antibiotic and TACE inhibitor treatment 95% of TLR2^-/- mice were rescued.

Conclusion

During pneumococcal meningitis strong inflammation in TLR2-deficiency was associated with incomplete responsiveness to antibiotics and complete response to combined antibiotic and TACE inhibitor treatment. TACE inhibitor treatment offers a promising adjuvant therapeutic strategy in pneumococcal meningitis.

MyD88-dependent activation of dendritic cells and CD4(+) T lymphocytes mediates symptoms, but is not required for the immunological control of parasites during rodent malaria

We investigated the role of different TLRs and MyD88 in host resistance to infection and malaria pathogenesis. TLR2(-/-), TLR4(-/-), TLR6(-/-), TLR9(-/-) or CD14(-/-) mice showed no change in phenotypes (parasitemia, body weight and temperature) when infected with Plasmodium chabaudi chabaudi (AS). MyD88(-/-) mice displayed comparable ability to wild type animals in controlling and clearing parasitemia. Importantly, MyD88(-/-) mice exhibited impaired production of TNF-alpha and IFN-gamma as well as attenuated symptoms, as indicated by changes in body weight and temperature during parasitemia. Consistently, CD11b(+) monocytes and CD11c(+) dendritic cells from infected MyD88(-/-) mice were shown impaired for production of pro-inflammatory cytokines, and in initiating CD4(+) T cell responses. Importantly, the inhibition of T cell activation with anti-CD134L, mostly inhibited IFN-gamma, partially inhibited TNF-alpha production, and protected the animals from malaria symptoms. Our findings suggest that MyD88 and possibly its associated TLRs expressed by dendritic cells play an important role in pro-inflammatory responses, T cell activation, and pathogenesis of malaria, but are not critical for the immunological control of the erythrocytic stage of P. chabaudi.

THE IN VIVO ANTITUMORAL EFFECTS OF LIPOPOLYSACCHARIDE AGAINST GLIOBLASTOMA MULTIFORME ARE MEDIATED IN PART BY TOLL-LIKE RECEPTOR 4

OBJECTIVE

Toll-like receptor 4 (Tlr-4) mediates many biological effects of lipopolysaccharide (LPS), which has antitumoral effects on glioblastoma both in vivo and in vitro. However, the precise role of Tlr-4 in these antitumoral effects remains unknown.

METHODS

The role of Tlr-4 in the antitumoral effect of LPS on glioblastomas was assessed in wild-type BALB/c mice and in Tlr-4 knockout (KO) BALB/c mice. Mice were implanted with DBT glioblastoma cells intracranially or subcutaneously, were treated with intratumoral LPS, and were assessed by histopathological examination for degrees of tumor progression and inflammation. Flow cytometry and Western blotting with antibodies to the Tlr-4 receptor and flow cytometry to the related CD14 moiety were performed to quantitate the expression levels of these two receptors by glioblastoma cells.

RESULTS

For subcutaneous tumors, LPS caused near complete tumor elimination in wild-type mice, but only a 50% reduction in Tlr-4 KO mice. For mice implanted with intracranial glioblastomas, LPS increased survival times modestly in wild-type mice, but showed no benefit in the Tlr-4 KO mice. There were no histological differences among wild-type and Tlr-4 KO mice, except for tumor size. In both models, an early neutrophilic and later macrophage-rich inflammatory infiltrate were seen after LPS administration. Quantitative flow cytometry and Western blotting showed no Tlr-4 receptor or CD14 expression in murine and human glioblastoma cells in vitro, and Western blotting suggested that Tlr-4 effects are mediated by nontumoral elements such as microglia and inflammatory cells.

CONCLUSION

LPS-induced antitumoral effects on glioblastoma multiforme are mediated, in part, by the Tlr-4 receptor. Further understanding of this process may lead to novel treatment strategies for this uniformly fatal disease.

Cloning, characterization and mapping of porcine CD14 reveals a high conservation of mammalian CD14 structure, expression and locus organization

The cell surface protein CD14 plays a central role in innate immunity as a pattern recognition receptor. CD14 is part of a receptor complex also including toll-like receptor 4 and MD2 proteins. Binding of the ligand lipopolysaccharide to the complex on myeloid cells leads to release of pro-inflammatory cytokines and mediators from the cell. In this study, we present the cloning, characterization and tissue expression pattern of a porcine CD14 encoding cDNA, and the chromosomal localization of the porcine CD14 gene. The open reading frame is predicted to encode a protein of 373 amino acids, which shows conservation of structural as well as functional regions when compared to other mammalian species. The CD14 gene was localized to porcine chromosome 2 in a region syntenic to human chromosome 5q. Transcription analysis shows that CD14 is widely expressed in tissues examined in this study, which correlates well with expression primarily on myeloid cells.

CD14 directly binds to triacylated lipopeptides and facilitates recognition of the lipopeptides by the receptor complex of Toll-like receptors 2 and 1 without binding to the complex

It has demonstrated that the recognition of triacylated lipopeptides by Toll-like receptor (TLR) 2 requires TLR1 as a coreceptor. In the NF-kappaB reporter assay system in which human embryonic kidney 293 cells were transfected with TLR2 and TLR1 together with an NF-kappaB luciferase reporter gene, S-(2,3-bispalmitoyloxypropyl)-N-palmitoyl-Cys-Lys-Lys-Lys-Lys (Pam(3)CSK(4)) and Pam(3)CSSNA were recognized by TLR2/TLR1, but the recognition level was unexpectedly very low. However, cotransfection of CD14 drastically enhanced the recognition of triacylated lipopeptides by TLR2/TLR1. The CD14-induced enhancement did not occur without cotransfection of TLR1. Both CD14(dS39-A48), a mutant with deletion of the part of possible N-terminal ligand-binding pocket, and anti-CD14 monoclonal antibody reduced the CD14-induced enhancement. Transfection of a TIR domain-deficient mutant of TLR2 (TLR2(dE772-S784)) or TLR1 (TLR1(dQ636-K779)) completely abrogated the CD14-induced enhancement. Soluble recombinant CD14 added extracellularly enhanced the recognition of Pam(3)CSSNA by TLR2/TLR1. Immunoprecipitation analysis demonstrated that CD14 was not associated with TLR2 but that TLR1 was associated with TLR2. In addition, surface plasmon resonance-based assay demonstrated that CD14 binds to Pam(3)CSK(4) at a dissociation constant of 5.7 microM. This study suggests that CD14 directly binds to triacylated lipopeptides and facilitates recognition of the lipopeptides by the TLR2/TLR1 complex without binding to the receptor complex.

Cd14,Gbp1, andPla2g2a: three major candidate genes for experimental IBD identified by combining QTL and microarray analyses

Induction of inflammatory bowel (IBD)-like disease in mice by a targeted mutation in the Il10 gene ( Il10−/−) is inbred strain dependent. C3H/HeJBir (C3) mice are colitis susceptible, whereas C57BL/6J (B6) mice are resistant. Genetic dissection of this susceptibility revealed 10 colitogenic quantitative trait loci (QTL). The aim of this study was to identify valuable candidate genes by a combination of QTL mapping and microarray analyses. Sixteen genes were differentially expressed between B6- and C3- Il10−/−mice and were located within the QTL intervals. Three major candidate genes ( Cd14, Gbp1, Pla2g2a) showed prominent expression differences between B6- and C3- Il10−/−as well as between B6 and C3 wild-type mice, which was confirmed by semiquantitative or real-time RT-PCR. Because strain differences are known for Gbp1 and Pla2g2a, further analyses focused on Cd14. Western blot analysis revealed strain differences also on the protein level. Cd14 expression in animals with defective and intact Toll-like receptor (TLR)4 signaling (C3, C3H/HeN, B6, B6- Tlr4tm1Aki) make the TLR4 defect of C3 mice unlikely to be the reason for higher Cd14 expression. Less Cd14 expression in germ-free mice indicates a contribution of the microflora on Cd14 expression. Stimulation of naive peritoneal macrophages with bacterial antigens showed lower CD14 surface expression in B6 than in C3 mice. In conclusion, the large number of candidate genes was reduced to three major candidates that play an important role in inflammatory processes and immune response. Strain differences for them are already known or are shown in this study.

Adjuvants modulating mucosal immune responses or directing systemic responses towards the mucosa

In developing veterinary mucosal vaccines and vaccination strategies, mucosal adjuvants are one of the key players for inducing protective immune responses. Most of the mucosal adjuvants seem to exert their effect via binding to a receptor/or target cells and these properties were used to classify the mucosal adjuvants reviewed in the present paper: (1) ganglioside receptor-binding toxins (cholera toxin, LT enterotoxin, their B subunits and mutants); (2) surface immunoglobulin binding complex CTA1-DD; (3) TLR4 binding lipopolysaccharide; (4) TLR2-binding muramyl dipeptide; (5) Mannose receptor-binding mannan; (6) Dectin-1-binding ss 1,3/1,6 glucans; (7) TLR9-binding CpG-oligodeoxynucleotides; (8) Cytokines and chemokines; (9) Antigen-presenting cell targeting ISCOMATRIX and ISCOM. In addition, attention is given to two adjuvants able to prime the mucosal immune system following a systemic immunization, namely 1alpha, 25(OH)2D3 and cholera toxin.

Structural Regions of MD-2 That Determine the Agonist-Antagonist Activity of Lipid IVa

A cell surface receptor complex consisting of CD14, Toll-like receptor (TLR4), and MD-2 recognizes lipid A, the active moiety of lipopolysaccharide (LPS). Escherichia coli-type lipid A, a typical lipid A molecule, potently activates both human and mouse macrophage cells, whereas the lipid A precursor, lipid IVa, activates mouse macrophages but is inactive and acts as an LPS antagonist in human macrophages. This animal species-specific activity of lipid IVa involves the species differences in MD-2 structure. We explored the structural region of MD-2 that determines the agonistic and antagonistic activities of lipid IVa to induce nuclear factor-kappaB activation. By expressing human/mouse chimeric MD-2 together with mouse CD14 and TLR4 in human embryonic kidney 293 cells, we found that amino acid regions 57-79 and 108-135 of MD-2 determine the species-specific activity of lipid IVa. We also showed that the replacement of Thr(57), Val(61), and Glu(122) of mouse MD-2 with corresponding human MD-2 sequence or alanines impaired the agonistic activity of lipid IVa, and antagonistic activity became evident. These mutations did not affect the activation of nuclear factor-kappaB, TLR4 oligomerization, and inducible phosphorylation of IkappaBalpha in response to E. coli-type lipid A. These results indicate that amino acid residues 57, 61, and 122 of mouse MD-2 are critical to determine the agonist-antagonist activity of lipid IVa and suggest that these amino acid residues may be involved in the discrimination of lipid A structure.

Conformation-dependent swinging of the matrix loop m2 of the mitochondrial Saccharomyces cerevisiae ADP/ATP carrier

Structure-function relationships of the membrane-embedded Saccharomyces cerevisiae mitochondrial ADP/ATP carrier were investigated through two independent approaches, namely, limited proteolysis and cysteine labeling. Experiments were carried out in the presence of either carboxyatractyloside (CATR) or bongkrekic acid (BA), two specific inhibitors of the ADP/ATP transport that bind to two distinct conformers involved in the translocation process. The proteolysis approach allowed us to demonstrate (i) that N- and C-terminal extremities of ADP/ATP carrier are facing the intermembrane space and (ii) that the central region of the carrier corresponding to the matrix loop m2 is accessible to externally added trypsin in a conformation-sensitive manner, being cleaved at the Lys163-Gly164 and Lys178-Thr179 bonds in the carrier-CATR and the carrier-BA complexes, respectively. The cysteine labeling approach was carried out on the S161C mutant of the ADP/ATP carrier. This variant of the carrier is fully active, displaying nucleotide transport kinetic parameters and inhibitor binding properties similar to that of wild-type carrier. Alkylation experiments, carried out on mitochondria with the nonpermeable reagents eosin-5-maleimide and iodoacetamidyl-3,6-dioxaoctanediamine-biotin, showed that Cys 161 is accessible from the outside in the carrier-CATR complex, whereas it is masked in the carrier-BA complex. Taken together, our results indicate that the matrix loop m2 connecting the transmembrane helices H3 to H4 intrudes to some extent into the inner mitochondrial membrane. Its participation in the translocation of ADP/ATP is strongly suggested, based on the finding that its accessibility to reagents added outside mitochondria is modified according to the conformational state of the carrier.

Inflammation induces myeloid-derived suppressor cells that facilitate tumor progression

Epidemiological and experimental observations support the hypothesis that chronic inflammation contributes to cancer development and progression; however, the mechanisms underlying the relationship between inflammation and cancer are poorly understood. To study these mechanisms, we have transfected the mouse 4T1 mammary carcinoma with the proinflammatory cytokine IL-1beta to produce a chronic inflammatory microenvironment at the tumor site. Mice with 4T1/IL-1beta tumors have a decreased survival time and elevated levels of immature splenic Gr1+CD11b+ myeloid-derived cells. These myeloid suppressor cells (MSC) are present in many patients with cancer and inhibit the activation of CD4+ and CD8+ T lymphocytes. 4T1/IL-1beta-induced MSC do not express the IL-1R, suggesting that the cytokine does not directly activate MSC. Neither T or B cells nor NKT cells are involved in the IL-1beta-induced increase of MSC because RAG2-/- mice and nude mice with 4T1/IL-1beta tumors also have elevated MSC levels. MSC levels remain elevated in mice inoculated with 4T1/IL-1beta even after the primary tumor is surgically removed, indicating that the IL-1beta effect is long lived. Collectively, these findings suggest that inflammation promotes malignancy via proinflammatory cytokines, such as IL-1beta, which enhance immune suppression through the induction of MSC, thereby counteracting immune surveillance and allowing the outgrowth and proliferation of malignant cells.

Effects of Possible Endocrine Disrupting Chemicals on Bacterial Component-Induced Activation of NF-.KAPPA.B

Endocrine disrupting chemicals (EDCs) have a possibility to exacerbate infectious diseases because EDCs disturb the human immune system by interfering with endocrine balance. To assess the influence of EDCs on the innate immune function of macrophages, we investigated the effects of thirty-seven possible endocrine disruptors on lipopolysaccharide (LPS)- or bacterial lipopeptide (Pam3CSK4)-induced activation of nuclear factor kappa B (NF-kappaB). Alachlor, benomyl, bisphenol A, carbaryl, kelthane, kepone, octachlorostyrene, pentachlorophenol, nonyl phenol, p-octylphenol and ziram inhibited both LPS- and Pam3CSK4-induced activation of NF-kappaB. Simazine inhibited only LPS-induced activation. A strong inhibitory effect was observed with ziram and benomyl. On the other hand, diethylhexyl adipate and 4-nitrotoluene tended to enhance the activation induced by Pam3CSK4 and LPS, respectively. Aldicarb, amitrole, atrazine, benzophenone, butyl benzyl phthalate, 2,4-dichlorophenoxy acetic acid, dibutyl phthalate, 2,4-dichlorophenol, dicyclohexyl phthalate, diethylhexyl phthalate, diethyl phthalate, dihexyl phthalate, di-n-pentyl phthalate, dipropyl phthalate, malathion, methomyl, methoxychlor, metribuzin, nitrofen, permethrin, trifluralin, 2,4,5-trichlorophenoxyacetic acid and vinclozolin had no significant effects at 100 microM. These results indicate that some agrochemicals have the potential to inhibit macrophage function and suggest that endocrine disruptors may influence the development of bacterial infections.