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At least 595 records · Page 33Linked to original sources
PubMed2003

Haplotype variation in bovine Toll-like receptor 4 and computational prediction of a positively selected ligand-binding domain.

Toll-like receptor 4 (TLR4) is a cell-surface receptor that activates innate and adaptive immune responses. Because it recognizes a broad class of pathogen-associated molecular patterns presented by lipopolysaccharides and lipoteichoic acid, TLR4 is a candidate gene for resistance to a large number of diseases. In particular, mouse models suggest TLR4 as a candidate gene for resistance to major agents in bovine respiratory disease and Johne's disease. The coding sequence of bovine TLR4 is divided into three exons, with intron/exon boundaries and intron sizes similar to those of human TLR4 transcript variant 1. We amplified each exon in 40 individuals from 11 breeds and screened the sequence for single-nucleotide polymorphisms (SNPs). We identified 32 SNPs, 28 of which are in the coding sequence, for an average of one SNP per 90 bp of coding sequence. Eight SNPs were nonsynonymous and potentially alter specificity of pathogen recognition or efficiency of signaling. To evaluate the functional importance of these SNPs, we used codon-substitution models to detect diversifying selection in an extracellular region that may physically interact with ligands. One nonsynonymous SNP is located within this region, and other substitutions are in adjacent regions that may interact with coreceptor molecules. The 32 SNPs were found in 20 haplotypes that can be assigned to geographic ranges of origin. Haplotype-tagging SNP analysis indicated that 12 SNPs need to be genotyped to distinguish these 20 haplotypes. These data provide a basic understanding of bovine TLR4 sequence variation and supply haplotype markers for disease association studies.

Animals↗
PubMed1999

Toll-like receptor-4 mediates lipopolysaccharide-induced signal transduction.

TLR4 is a member of the recently identified Toll-like receptor family of proteins and has been putatively identified as Lps, the gene necessary for potent responses to lipopolysaccharide in mammals. In order to determine whether TLR4 is involved in lipopolysaccharide-induced activation of the nuclear factor-kappaB (NF-kappaB) pathway, HEK 293 cells were transiently transfected with human TLR4 cDNA and an NF-kappaB-dependent luciferase reporter plasmid followed by stimulation with lipopolysaccharide/CD14 complexes. The results demonstrate that lipopolysaccharide stimulates NF-kappaB-mediated gene expression in cells transfected with the TLR4 gene in a dose- and time-dependent fashion. Furthermore, E5531, a lipopolysaccharide antagonist, blocked TLR4-mediated transgene activation in a dose-dependent manner (IC50 approximately 30 nM). These data demonstrate that TLR4 is involved in lipopolysaccharide signaling and serves as a cell-surface co-receptor for CD14, leading to lipopolysaccharide-mediated NF-kappaB activation and subsequent cellular events.

Animals↗
PubMed2001

Saturated fatty acids, but not unsaturated fatty acids, induce the expression of cyclooxygenase-2 mediated through Toll-like receptor 4.

Results from our previous studies demonstrated that activation of Toll-like receptor 4 (Tlr4), the lipopolysaccharide (LPS) receptor, is sufficient to induce nuclear factor kappaB activation and expression of inducible cyclooxygenase (COX-2) in macrophages. Saturated fatty acids (SFAs) acylated in lipid A moiety of LPS are essential for biological activities of LPS. Thus, we determined whether these fatty acids modulate LPS-induced signaling pathways and COX-2 expression in monocyte/macrophage cells (RAW 264.7). Results show that SFAs, but not unsaturated fatty acids (UFAs), induce nuclear factor kappaB activation and expression of COX-2 and other inflammatory markers. This induction is inhibited by a dominant-negative Tlr4. UFAs inhibit COX-2 expression induced by SFAs, constitutively active Tlr4, or LPS. However, UFAs fail to inhibit COX-2 expression induced by activation of signaling components downstream of Tlr4. Together, these results suggest that both SFA-induced COX-2 expression and its inhibition by UFAs are mediated through a common signaling pathway derived from Tlr4. These results represent a novel mechanism by which fatty acids modulate signaling pathways and target gene expression. Furthermore, these results suggest a possibility that propensity of monocyte/macrophage activation is modulated through Tlr4 by different types of free fatty acids, which in turn can be altered by kinds of dietary fat consumed.

Adenocarcinoma↗
PubMed2002

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

Regions of mouse CD14 required for Toll-like receptor 2 (TLR2)- and TLR4-mediated activation of NF-kappaB were studied in transiently transfected 293 cells. Wild-type CD14 enhanced lipopolysaccharide (LPS)-induced NF-kappaB-dependent reporter activity in cells expressing TLR4/MD-2, and deletion of amino acid regions 35-44, 144-153, 235-243, and 270-275 impaired the TLR4-mediated activation. Unlike human CD14, mouse CD14 truncated at amino acid 151 lost the activity. Deletion of amino acids 35-44 or 235-243 also abrogated TLR2-mediated activation of NF-kappaB, whereas mutants lacking 144-153 and 270-275 retained the activity. Deletion and alanine substitution experiments revealed that amino acids 151-153 and 273-275 were required for the TLR4-mediated activation. Both deletion mutants lacking amino acids 35-44 and 235-243 and alanine substitution mutants in regions 151-153 and 273-275 were expressed on the cell surface and retained the ability to associate with TLR4. A cross-linking study with photoreactive LPS showed that the labeling intensities to CD14 mutants/TLR4/MD-2 were paralleled by the ability of CD14 mutants to increase TLR4-mediated activation. These results indicate that different regions of mouse CD14 are required for TLR4- and TLR2-mediated activation of NF-kappaB and suggest that amino acids 35-44, 151-153, 235-243, and 273-275 of mouse CD14 play an important role in LPS binding and its transfer to TLR4/MD-2.

Animals↗
PubMed2003

TIR-containing adapter molecule (TICAM)-2, a bridging adapter recruiting to toll-like receptor 4 TICAM-1 that induces interferon-beta.

Lipopolysaccharide (LPS) is an agonist for Toll-like receptor (TLR) 4 and expresses many genes including NF-kappaB- and interferon regulatory factor (IRF)-3/IFN-inducible genes in macrophages and dendritic cells (DCs). TICAM-1/TRIF was identified as an adapter that facilitates activation of IRF-3 followed by expression of interferon (IFN)-beta genes in TLR3 signaling, but TICAM-1 does not directly bind TLR4. Although MyD88 and Mal/TIRAP adapters functions downstream of TLR4, DC maturation and IFN-beta induction are independent of MyD88 and Mal/TIRAP. In this investigation, we report the identification of a novel adapter, TICAM-2, that physically bridges TLR4 and TICAM-1 and functionally transmits LPS-TLR4 signaling to TICAM-1, which in turn activates IRF-3. In its structural features, TICAM-2 resembled Mal/TIRAP, an adapter that links TLR2/4 and MyD88. However, TICAM-2 per se exhibited minimal ability to activate NF-kappaB and the IFN-beta promoter. Hence, in LPS signaling TLR4 recruits two types of adapters, TIRAP and TICAM-2, to its cytoplasmic domain that are indirectly connected to two effective adapters, MyD88 and TICAM-1, respectively. We conclude that for LPS-TLR4-mediated activation of IFN-beta, the adapter complex of TICAM-2 and TICAM-1 plays a crucial role. This results in the construction of MyD88-dependent and -independent pathways separately downstream of the two distinct adapters.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Saturated fatty acid activates but polyunsaturated fatty acid inhibits Toll-like receptor 2 dimerized with Toll-like receptor 6 or 1.

Toll-like receptor 4 (TLR4) and TLR2 agonists from bacterial origin require acylated saturated fatty acids in their molecules. Previously, we reported that TLR4 activation is reciprocally modulated by saturated and polyunsaturated fatty acids in macrophages. However, it is not known whether fatty acids can modulate the activation of TLR2 or other TLRs for which respective ligands do not require acylated fatty acids. A saturated fatty acid, lauric acid, induced NFkappaB activation when TLR2 was co-transfected with TLR1 or TLR6 in 293T cells, but not when TLR1, 2, 3, 5, 6, or 9 was transfected individually. An n-3 polyunsaturated fatty acid (docosahexaenoic acid (DHA)) suppressed NFkappaB activation and cyclooxygenase-2 expression induced by the agonist for TLR2, 3, 4, 5, or 9 in a macrophage cell line (RAW264.7). Because dimerization is considered one of the potential mechanisms for the activation of TLR2 and TLR4, we determined whether the fatty acids modulate the dimerization. However, neither lauric acid nor DHA affected the heterodimerization of TLR2 with TLR6 as well as the homodimerization of TLR4 as determined by co-immunoprecipitation assays in 293T cells in which these TLRs were transiently overexpressed. Together, these results demonstrate that lauric acid activates TLR2 dimers as well as TLR4 for which respective bacterial agonists require acylated fatty acids, whereas DHA inhibits the activation of all TLRs tested. Thus, responsiveness of different cell types and tissues to saturated fatty acids would depend on the expression of TLR4 or TLR2 with either TLR1 or TLR6. These results also suggest that inflammatory responses induced by the activation of TLRs can be differentially modulated by types of dietary fatty acids.

Animals↗
PubMed2004

A complex of soluble MD-2 and lipopolysaccharide serves as an activating ligand for Toll-like receptor 4.

MD-2, a glycoprotein that is essential for the innate response to lipopolysaccharide (LPS), binds to both LPS and the extracellular domain of Toll-like receptor 4 (TLR4). Following synthesis, MD-2 is either secreted directly into the medium as a soluble, active protein, or binds directly to TLR4 in the endoplasmic reticulum before migrating to the cell surface. Here we investigate the function of the secreted form of MD-2. We show that secreted MD-2 irreversibly loses activity over a 24-h period at physiological temperature. LPS, but not lipid A, prevents this loss in activity by forming a stable complex with MD-2, in a CD14-dependent process. Once formed, the stable MD-2.LPS complex activates TLR4 in the absence of CD14 or free LPS indicating that the activating ligand of TLR4 is the MD-2.LPS complex. Finally we show that the MD-2.LPS complex, but not LPS alone, induces epithelial cells, which express TLR4 but not MD-2, to secrete interleukin-6 and interleukin-8. We propose that the soluble MD-2.LPS complex plays a crucial role in the LPS response by activating epithelial and other TLR4(+)/MD-2(-) cells in the inflammatory microenvironment.

Antigens, Surface↗
PubMed2004

Stimulation of toll-like receptor 2 by Coxiella burnetii is required for macrophage production of pro-inflammatory cytokines and resistance to infection.

Innate and adaptive immune responses are initiated upon recognition of microbial molecules by Toll-like receptors (TLRs). We have investigated the importance of these receptors in the induction of pro-inflammatory cytokines and macrophage resistance to infection with Coxiella burnetii, an obligate intracellular bacterium and the etiological agent of Q fever. By using a Chinese hamster ovary/CD14 cell line expressing either functional TLR2 or TLR4, we determined that C. burnetii phase II activates TLR2 but not TLR4. Macrophages deficient for TLR2, but not TLR4, produced less tumor necrosis factor-alpha and interleukin-12 upon C. burnetii infection. Furthermore, it was found that TLR2 activation interfered with C. burnetii intracellular replication, as macrophages from TLR2-deficient mice were highly permissive for C. burnetii growth compared with macrophages from wild type mice or TLR4-deficient mice. Although LPS modifications distinguish virulent C. burnetii phase I bacteria from avirulent phase II organisms, electrospray ionization-mass spectrometry analysis showed that the lipid A moieties isolated from these two phase variants are identical. Purified lipid A derived from either phase I or phase II LPS failed to activate TLR2 and TLR4. Indeed, the lipid A molecules were able to interfere with TLR4 signaling in response to purified Escherichia coli LPS. These studies indicate that TLR2 is an important host determinant that mediates recognition of C. burnetii and a response that limits growth of this intracellular pathogen.

Animals↗
PubMed2006

Specific high affinity interactions of monomeric endotoxin.protein complexes with Toll-like receptor 4 ectodomain.

Potent Toll-like receptor 4 (TLR4) activation by endotoxin has been intensely studied, but the molecular requirements for endotoxin interaction with TLR4 are still incompletely defined. Ligand-receptor interactions involving endotoxin and TLR4 were characterized using monomeric endotoxin.protein complexes of high specific radioactivity. The binding of endotoxin.MD-2 to the TLR4 ectodomain (TLR4ECD) and transfer of endotoxin from CD14 to MD-2/TLR4ECD were demonstrated using HEK293T-conditioned medium containing TLR4ECD+/-MD-2. These interactions are specific, of high affinity (KD<300 pm), and consistent with the molecular requirements for potent cell activation by endotoxin. Both reactions result in the formation of a Mr approximately 190,000 complex composed of endotoxin, MD-2, and TLR4ECD. CD14 facilitates transfer of endotoxin to MD-2 (TLR4) but is not a stable component of the endotoxin.MD-2/TLR4 complex. The ability to assay specific high affinity interactions of monomeric endotoxin.protein complexes with TLR4ECD should allow better definition of the structural requirements for endotoxin-induced TLR4 activation.

Acylation↗
PubMed2002

Toll-like receptor 4 resides in the Golgi apparatus and colocalizes with internalized lipopolysaccharide in intestinal epithelial cells.

Toll-like receptor (TLR) 4 is mainly found on cells of the myelopoietic lineage. It recognizes lipopolysaccharide (LPS) and mediates cellular activation and production of proinflammatory cytokines. Less is known about the distribution and role of TLR4 in epithelial cells that are continuously exposed to microbes and microbial products. Here we show that the murine small intestinal epithelial cell line m-IC(cl2) is highly responsive to LPS and expresses both CD14 and TLR4. Transcription and surface membrane staining for CD14 were up-regulated upon LPS exposure. Surprisingly, TLR4 immunostaining revealed a strictly cytoplasmic paranuclear distribution. This paranuclear compartment could be identified as the Golgi apparatus. LPS added to the supernatant was internalized by m-IC(cl2) cells and colocalized with TLR4. Continuous exposure to LPS led to a tolerant phenotype but did not alter TLR4 expression nor cellular distribution. Thus, intestinal epithelial cells might be able to provide the initial proinflammatory signal to attract professional immune cells to the side of infection. The cytoplasmic location of TLR4, which is identical to the final location of internalized LPS, further indicates an important role of cellular internalization and cytoplasmic traffic in the process of innate immune recognition.

Amino Acid Sequence↗
PubMed2004

Anthrolysin O and other gram-positive cytolysins are toll-like receptor 4 agonists.

Exposure of bone marrow-derived macrophages (BMDMs) to low concentrations of Bacillus anthracis lethal toxin (LT), whose catalytic subunit is lethal factor (LF), results in induction of a robust apoptotic response dependent on activation of Toll-like receptor (TLR)4. A similar TLR4-dependent apoptotic response is observed when BMDMs are infected with live B. anthracis (Sterne strain). However, TLR4 is considered to be a specific signaling receptor for lipopolysaccharide (LPS), a typical product of gram-negative bacteria, whereas B. anthracis is gram-positive. To understand how B. anthracis can activate TLR4, we analyzed its culture supernatants and found them to contain a potent TLR4-stimulating activity that can also induce apoptosis in macrophages in which the antiapoptotic p38 MAP kinase (whose activation is prevented by LF) was inhibited. Purification of this activity suggested it consists of anthrolysin O (ALO), a member of the cholesterol-dependent cytolysin (CDC) family. We show that recombinant ALO can activate TLR4 in a manner independent of LPS contamination and, together with LT, can induce macrophage apoptosis. We also provide genetic evidence that ALO is required for induction of macrophage apoptosis in response to infection with live B. anthracis and that other CDC family members share the ability to activate TLR4.

Animals↗
PubMed2006

Oxidative stress generated by hemorrhagic shock recruits Toll-like receptor 4 to the plasma membrane in macrophages.

Oxidative stress generated by ischemia/reperfusion is known to prime inflammatory cells for increased responsiveness to subsequent stimuli, such as lipopolysaccharide (LPS). The mechanism(s) underlying this effect remains poorly elucidated. These studies show that alveolar macrophages recovered from rodents subjected to hemorrhagic shock/resuscitation expressed increased surface levels of Toll-like receptor 4 (TLR4), an effect inhibited by adding the antioxidant N-acetylcysteine to the resuscitation fluid. Consistent with a role for oxidative stress in this effect, in vitro H2O2 treatment of RAW 264.7 macrophages similarly caused an increase in surface TLR4. The H2O2-induced increase in surface TLR4 was prevented by depleting intracellular calcium or disrupting the cytoskeleton, suggesting the involvement of receptor exocytosis. Further, fluorescent resonance energy transfer between TLR4 and the raft marker GM1 as well as biochemical analysis of the raft components demonstrated that oxidative stress redistributes TLR4 to lipid rafts in the plasma membrane. Preventing the oxidant-induced movement of TLR4 to lipid rafts using methyl-beta-cyclodextrin precluded the increased responsiveness of cells to LPS after H2O2 treatment. Collectively, these studies suggest a novel mechanism whereby oxidative stress might prime the responsiveness of cells of the innate immune system.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Induction of tumor necrosis factor- alpha secretion and toll-like receptor 2 and 4 mRNA expression by genital mucosal fluids from women with bacterial vaginosis.

BACKGROUND: Bacterial vaginosis (BV) is associated with complications of pregnancy and increased susceptibility to human immunodeficiency virus (HIV) sexual transmission. METHODS: The ability of genital mucosal fluids from women with BV and of microbial flora associated with BV to induce tumor necrosis factor (TNF)- alpha secretion and Toll-like receptor (TLR) 2 and TLR4 mRNA expression was assessed. RESULTS: Primary peripheral-blood mononuclear cells and THP-1 monocytic cells secreted TNF- alpha in response to cervicovaginal lavage (CVL) samples from women with BV. Mycoplasma hominis and Gardnerella vaginalis also stimulated TNF- alpha secretion. Strikingly, CVL samples from women with BV induced up to 60-fold increases in TLR4 mRNA expression, compared with CVL samples from women without BV and with bacteria not associated with BV. Anti-TNF- alpha antibody blocked increases in TLR4 mRNA expression induced by CVL samples from women with BV, indicating that TNF- alpha plays a critical role in induction of TLR4. Both TLR2 and TLR4 mRNA expression were approximately 60-fold higher in cells isolated from the lumen of the genital tract than in cervical mucosal tissue, but lumen TLR mRNA levels did not change significantly after BV treatment. CONCLUSIONS: These experiments show that genital mucosal fluids and certain bacteria from women with BV stimulate TNF- alpha secretion and TLR4 mRNA expression, suggesting mechanisms whereby BV affects pregnancy and HIV transmission.

Cell Line, Tumor↗
PubMed2006

Role of toll-like receptor signalling in Abeta uptake and clearance.

Deposits of amyloid beta-protein (Abeta) in neuritic plaques and cerebral vessels are a pathological hallmark of Alzheimer's disease. Fibrillar Abeta deposits are closely associated with inflammatory responses such as activated microglia in brain with this disease. Increasing lines of evidence support the hypothesis that activated microglia, innate immune cells in the CNS, play a pivotal role in the progression of the disease: either clearing Abeta deposits by phagocytic activity or releasing cytotoxic substances and pro-inflammatory cytokines. Toll-like receptors (TLRs) are a family of pattern-recognition receptors in the innate immune system. Exogenous and endogenous TLR ligands activate microglia. To investigate the role of TLR4 in the amyloidogenesis in vivo, we determined the amounts of cerebral Abeta in Alzheimer's disease mouse models with different genotypes of TLR4 using three distinct methods. We show that mouse models (Mo/Hu APPswe PS1dE9 mice) homozygous for a destructive mutation of TLR4 (Tlr(Lps-d)/Tlr(Lps-d)) had increases in diffuse and fibrillar Abeta deposits by immunocytochemistry, fibrillar Abeta deposits by thioflavine-S staining and buffer-soluble and insoluble Abeta by ELISA in the cerebrum, as compared with TLR4 wild-type mouse models. Although the differences in these parameters were less significant, mouse models heterozygous for the mutation (Tlr(Lps-d)/) showed co-dominant phenotypes. Consistent with these observations in vivo, cultured microglia derived from Tlr(Lps-d)/Tlr(Lps-d) mice failed to show an increase in Abeta uptake after stimulation with a TLR4 ligand but not with a TLR9 ligand in vitro. Furthermore, activation of microglia (BV-2 cell) with a TLR2, TLR4 or TLR9 ligand, markedly boosted ingestion of Abeta in vitro. These results suggest that TLR signalling pathway(s) may be involved in clearance of Abeta-deposits in the brain and that TLRs can be a therapeutic target for Alzheimer's disease.

Alzheimer Disease↗
PubMed2003

JNK-interacting protein 3 associates with Toll-like receptor 4 and is involved in LPS-mediated JNK activation.

Lipopolysaccharide (LPS) is recognized by Toll-like receptor (TLR) 4 and activates NF-kappaB and a set of MAP kinases. Here we have investigated proteins associated with the cytoplasmic domain of mouse TLR4 by yeast two-hybrid screening and identified JNK-interacting protein 3 (JIP3), a scaffold protein for JNK, as a TLR4-associated protein. In mammalian cells, JIP3, through its N-terminal region, constitutively associates with TLR4. The association is specific to JIP3, as the two other JIPs, JIP1 and JIP2, failed to bind TLR4. In HEK 293 cells exogenously expressing TLR4, MD2 and CD14, co-expression of JIP3 significantly increased the complex formation of TLR4-JNK and LPS-mediated JNK activation. In contrast, expression of C-terminally truncated forms of JIP3 impaired LPS-induced JNK activation in a mouse macrophage cell line, RAW264.7. Moreover, RNA interference of JIP3 inhibited LPS-mediated JNK activation. In RAW264.7 cells, JIP3 associates MEKK-1, but not with TAK-1. Finally, JIP3 also associates with TLR2 and TLR9, but not with TLR1 or TLR6. Altogether, our data indicate the involvement of JIP3 in JNK activation in downstream signals of some TLRs.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Differential involvement of IFN-beta in Toll-like receptor-stimulated dendritic cell activation.

Toll-like receptor (TLR) can activate dendritic cells (DC) through common signaling pathways requiring a cytoplasmic adapter, MyD88. However, the signaling is differentially regulated among TLR family members. TLR4 can activate MyD88-deficient bone marrow-derived DC (BMDC), and lead to induction of IFN-inducible genes and up-regulation of co-stimulatory molecules such as CD40, implying that the MyD88-independent signaling pathway functions downstream of TLR4. Because these effects can also be induced by type I IFN, we have analyzed whether type I IFN is involved in TLR4-induced responses. In response to lipopolysaccharide (LPS), IFN-beta gene expression was augmented in both wild-type and MyD88-deficient BMDC. Expression of all IFN-inducible genes except immune-responsive gene 1 (IRG1) was abolished and CD40 up-regulation was decreased in LPS-stimulated BMDC lacking either IFN-alpha/beta receptor (IFN-alpha/betaR) or signal transducer and activator of transcription 1 (STAT-1). Similar to the LPS response, TLR9 signaling can also induce expression of IFN-beta and IFN-inducible genes, and up-regulation of CD40. However, all these effects were MyD88 dependent. Thus, in TLR4 signaling, IFN-beta expression can be induced either by the MyD88-dependent or -independent pathway, whereas, in TLR9 signaling, it is dependent on MyD88. In CpG DNA-stimulated DC, expression of IFN-inducible genes except IRG1 was dependent on type I IFN signaling as in LPS-stimulated DC. However, in contrast to TLR4 signaling, TLR9 signaling requires type I IFN signaling for CD40 up-regulation. Taken together, this study demonstrates differential involvement of type I IFN in TLR4- and TLR9-induced effects on DC.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Toll-like receptor 4 in butylated hydroxytoluene-induced mouse pulmonary inflammation and tumorigenesis.

Because chronic pulmonary diseases predispose to lung neoplasia, the identification of the molecular mechanisms involved could provide novel preventive, diagnostic, and therapeutic strategies. Toll-like receptors (TLRs) transduce exogenous and endogenous signals into the production of inflammatory cytokines to coordinate adaptive immune responses. To determine the role of Tlr4 in chronic lung inflammation, we compared lung permeability, leukocyte infiltration, and nuclear factor kappa B (NFkappaB) and activator protein 1 (AP-1) DNA binding in butylated hydroxytoluene (BHT)-treated (four weekly injections of 125-200 mg/kg each) inbred mouse strains with functional Tlr4 (OuJ and BALB) and mutated Tlr4 (HeJ and BALB(Lps-d)). We also measured primary tumor formation in these mice after single-carcinogen injection (3-methylcholanthrene; 10 microg/kg), followed by BHT treatment (six weekly injections of 125-200 mg/kg each). Mice with functional Tlr4 had reduced lung permeability, leukocyte inflammation, and primary tumor formation (BALB(Lps-d), mean = 22.3 tumors/mouse, versus BALB, mean = 13.9 tumors/mouse, difference = 8.4 tumors/mouse, 95% confidence interval = 4.6 to 12.1 tumors/mouse; P = .025) compared with mice with mutated Tlr4. NFkappaB DNA binding activity was higher in OuJ than in HeJ mice; however, AP-1 activity was elevated in HeJ mice. To our knowledge, this is the first model to demonstrate a modulatory role for Tlr4 in chronic lung inflammation and tumorigenesis.

Animals↗
PubMed2006

Toll-like receptor 4 in rat prostate: modulation by testosterone and acute bacterial infection in epithelial and stromal cells.

The prostate gland is the most inflammation-prone organ in the male reproductive tract. However, little information is available regarding the immunobiology of this gland. Toll-like receptor 4 (TLR4) is considered to be a major sensor of danger signals and a key trigger of the innate immune responses. TLRs have also been implicated in the development of different inflammatory diseases in organs in which epithelial-stromal interactions are critical for homeostasis. The purpose of this work was to evaluate the presence and regulation of TLR4 in the rat prostate. Western blot and immunocytochemical studies revealed that constitutive expression of TLR4 in the rat ventral prostate was localized in the epithelial cells, mainly associated with the rough endoplasmic reticulum, as well as in smooth muscle cells in the stroma. In addition, increased concentrations of TLR4 were found in castrated rats, predominantly in hypertrophied smooth muscle cells. On the other hand, using a bacterial prostatitis model, we observed an increment in the TLR4 cytoplasmic content and migration of this receptor to the apical plasmatic membranes of epithelial cells at 24 h and 48 h post-infection. These findings suggest that the prostate gland is able to recognize pathogens and to initiate immune responses. In addition, TLR4 appears to be implicated in the vital stromal-epithelial interactions that maintain prostate homeostasis during prostatitis, as well as following androgen deprivation.

Actins↗