Role Of TLRs Research Articles

Toll-like Receptors: Key Players in Squamous Cell Carcinoma Progression.

Background/Objectives Lung squamous cell carcinoma (SCC) is one of the major subtypes of lung cancer, characterized by diverse molecular pathways and variable clinical outcomes. This study focused on assessing the levels of TLR-2, TLR-3, TLR-4, TLR-7, TLR-8, and TLR-9 on peripheral blood lymphocytes in patients with newly diagnosed SCC compared to a group of healthy controls, in the context of disease development and patient survival, conducted over three years. The study aimed to investigate the differences in TLR expression between SCC patients and healthy people and to understand their role in the development of the disease and patient survival over three years. Methods: The study included the assessment of TLR-2, TLR-3, TLR-4, TLR-7, TLR-8, and TLR-9 levels on peripheral blood lymphocytes in patients with newly diagnosed SCC and in the control group. The expression of TLRs was measured using flow cytometry, and the soluble forms of the tested TLRs were measured using enzyme-linked immunosorbent assays. All the analyses were conducted over a three-year period from the time patients were recruited to the study. The obtained test results were statistically analyzed. Results: Results showed statistically significant differences in TLR expression between the groups, with higher TLR levels correlating with an advanced stage of disease and poorer survival rates. This suggests that the deregulation of TLR levels may be involved in promoting tumor development and influencing its microenvironment. Conclusions: The research, conducted over three years, indicates the need for further research on the role of TLRs in SCC, including their potential use as therapeutic targets and biomarkers. This may help to increase the effectiveness of standard treatments and improve clinical outcomes in patients with SCC.

Mechanisms of TRAF3 regulation of TLR signaling in B lymphocytes

Abstract Toll-like receptors (TLRs) are pattern recognition receptors that bridge the innate and adaptive immune system and are critical for host defense. TLR signaling to B cells is important in normal immunity, but also implicated in autoimmune disease and B cell lymphomas (BCL). Most studies focus on the role of TLRs in myeloid cell populations. However, B cells express most TLRs and are highly responsive to TLR ligands, yet TLR-mediated B cell pathways are understudied. Previous studies from our lab show that TRAF3 inhibits B cell TLR functions, including cytokine production, Ig isotype switching, and antibody production in response to ligands for TLRs 3, 4, 7/8 and 9. A key knowledge gapis identifying the molecular mechanisms by which TRAF3 mediates this regulation. Our working hypothesisis that B cell-TRAF3 regulates the recruitment and/or post-translational modification of specific TLR complex signaling proteins. Our recent data show that B cell-TRAF3 forms a heterocomplex with TRAF6, associating with the tyrosine kinase Syk. In the absence of TRAF3, TRAF6 shows a greater association with several TLR signaling proteins, including MyD88, IRAK1 and Syk. This suggests that TRAF3 may inhibit TRAF6 access to the TLR signaling complex, and thus early TLR signaling. In addition, our work introduces a role for Syk in TLR signaling in B cells. In the absence of TRAF3, activation of Syk is enhanced in response to ligands for TLRs 4 and 7. Inhibition of Syk activation also revealed downstream effects on TLR-mediated NFκB activation. Further studies aim at providing new insights into molecular mechanisms contributing to the regulation of B cell-TRAF3 in TLR signaling. VA Merit Review I01 BX001702 NIH P50 CA97274 RO1 AI5107312000000113259002001 NIH T32 Training Grant AI07485 RO1 AI1762656

The role of TLR-2 and TLR-4 gene polymorphisms in the development of sepsis in children with severe burns

Recently, many studies are based on the study of innate immunity genes, namely the role of TLRs in the development of various diseases. Severe burn injury is characterized by the development of hyperimmune reactions, which further leads to the development of multiple organ complications and sepsis. The aim of our study was to identify the frequency and prognostic value of polymorphism of TLR-2 Arg753Gln and TLR-4 Thr399 Ile genes and their role in the development of sepsis and MOD in children with severe burns. Materials and methods: genetic analysis of TLR-2 Arg 753 Gln and TLR-4 Thr399 Ile gene polymorphisms was performed in children with severe and extremely severe burns (n ​​= 22) who were treated in the anesthesiology department with intensive care beds. Results: as a result of the obtained data, the heterozygous genotype TLR-2 Arg 753 Gln was detected in 69.5% (n = 16), in 31.8% (n = 7) patients with burn injury polymorphism was not detected. In 13.6% (n = 3) cases, polymorphism was associated with sepsis and MOD. Sepsis and normal homozygous genotype were diagnosed in 4.5% (n = 1). Heterozygous genotype TLR-4 Thr399 Ile was observed in 18.2% (n = 4) patients, of which only 4.5% (n = 1) patients had polymorphism associated with sepsis and MOD. Analysis of the association of TLR 2 genotypes and markers of acute inflammation revealed statistically significant differences between the heterozygous TLR 2 Arg 753 Gln genotype and C-reactive protein (CRP) levels in the blood of patients on day 3 of burn disease. Conclusions: The study of the role of innate immune system genes is promising in predicting the development of sepsis and complications in severe burns and requires further careful study.

Toll-like receptor 3 is a potential prognosis marker and associated with immune infiltration in stomach adenocarcinoma.

Toll-like receptors participate in various biological mechanisms, mainly including the immune response and inflammatory response. Nevertheless, the role of TLRs in STAD remains unclear. We aimed to explore the expression, prognosis performance of TLRs in STAD and their relationship with immune infiltration. Student's t-test was used to evaluate the expression of TLRs between STAD tissues and normal tissues. Kaplan-Meier method was applied to explored the prognosis value of TLRs in STAD. And qRT-PCR validated their expression and prognosis value. Spearman's correlation analysis and Wilcoxon rank-sum test were used to assess the association between TLRs and immune infiltration in STAD. The mRNA level of TLR3 was downregulated in STAD. We summarized genetic mutations and CNV alteration of TLRs in STAD cohort. Prognosis analysis revealed that STAD patients with high TLR3 expression showed better prognosis in OS, FP and PPS. The result of qRT-PCR suggested that TLR3 expression was decreased in STAD tissues and STAD patients with high TLR3 mRNA level had a better OS. Univariate and multivariate cox regression analysis suggested TLR3 expression and clinical stage as independent factors affecting STAD patients' prognosis. A positive association existed between TLR3 expression and the abundance of immune cells and the expression of various immune biomarkers. Furthermore, key targets related to TLR3 were identified in STAD, mainly including MIR-129 (GCAAAAA), PLK1, and V$IRF1_01. Our result demonstrated TLR3 as a prognosis marker and associated with immune infiltration in STAD.

The Role of TLRs in the Immunomodulation of Tumor Microenvironment

The review focuses on the modulation of the Tumor Microenvironment through toll-like receptors expressed on the tumor cells and the immune cells found in the vicinity of the tumor mass. The expression of these TLRs is effectively up-regulated and downregulated to abrogate the tumor growth. The function of immune cells like Treg cells, CAFs etc. is also altered in the tumor microenvironment leading to either promotion or regression of the tumor mass. Various molecules including some plant-derived polysaccharides have recently come up as potential therapeutic molecules that enhance the TLR tumorkilling activity. A few TLR agonists are known to increase the chemotherapeutic drug’s efficacy, for instance, co-administration of Resiquimod with Oxaliplatin. Even after the continuous advancements in the knowledge of tumor microenvironment and its regulation, this sphere holds immense potential for further research. According to the studies, the prospect of immunomodulation of tumor microenvironment using TLR regulation lies in finding more plant-based agonists for various TLR molecules.

Trauma-induced lung injury is associated with infiltration of activated TLR expressing myeloid cells

IntroductionTraumatic injury with hemorrhage (TH) induces an inflammatory response in the lung resulting in lung injury involving activation of immune cells including myeloid cells (i.e., monocytes, granulocytes and macrophages), in part through TLRs. TLRs, via the recognition of damage associated molecular patterns (DAMPs), are a key link between tissue injury and inflammation. Nonetheless, the role of TLRs in myeloid cell activation and TH-induced lung injury remains ill defined. MethodsC57BL/6 male mice were subjected to TH or sham treatment (n = 4–6 /group). Lung tissues were collected two hrs. after injury. Single cells were isolated from the lungs by enzymatic digestion and myeloid cell TLR expression and activation (i.e., cytokine production) were assessed using flow cytometry techniques. ResultsThe injury was associated with a profound change in the lung myeloid cell population. TH markedly increased lung CD11b+ monocyte numbers and Gr1+ granulocyte numbers as compared to sham mice. The number of cells expressing TLR2, TLR4, and TLR9 were increased 4–7 fold in the TH mice. Activation for elevated cytokine (TNFα, IL-10) production was observed in the lung monocyte population of the TH mice. ConclusionsTrauma-induced lung injury is associated with infiltration of the lungs with TLR expressing myeloid cells that are activated for elevated cytokine responses. This elevation in TLR expression may contribute to DAMP-mediated pulmonary complications of an inflammatory nature and warrants further investigation.

Role of sToll-like receptors 2 and 4 in stage 2 periodontitis patients with and without type 2 diabetes: A randomized clinical control trial

Objective: The role of TLRs as principal signaling receptors in recognizing endotoxins on gram positive and negative bacteria is facilitated by TLRs and further enhances its role as a potential biomarker in assessing periodontal disease. The study aimed at evaluating the expression of sTLR2 and sTLR4 among healthy, periodontal and diabetic patients and further if there a comparable expression among the TLRs among genders. Material and Methods: Patients were selected according to pocket depth, Clinical attachment loss and radiographic bone loss. Unstimulated whole saliva was collected. sTLR2 and sTLR4 quantification was estimated by ELISA. Comparison of sTLRs between the study groups were performed using ANOVA followed by Tukey post Hoc test. Independent sample t test was used to compare between the genders. (p≤0.05) Result: Expression of sTLR2 was higher among periodontitis patients compared to diabetic patients, this was also evident with relation to genders. sTLR4 showed significant expression among the three groups and also among the genders. Conclusion: The expression of sTLR2 was higher among periodontitis patients compared to diabetic patients. More studies need to be carried out to evaluate TLRs values among genders.

Histone H4 aggravates inflammatory injury through TLR4 in chlorine gas-induced acute respiratory distress syndrome

BackgroundChlorine gas (Cl2) exposure remains a public health concern in household, occupational, and transportation accidents around the world. The death rate associated with acute respiratory distress syndrome (ARDS) caused by high concentrations of Cl2 is very high, mainly because the pathogenesis of ARDS remains unclear. Histone H4 has been identified as an important endogenous pro-inflammatory molecule. The present study aimed to examine the pathogenic role of histone H4 in Cl2-induced ARDS.MethodsARDS was induced by Cl2 exposure in male C57BL/6 mice. Circulating histone H4, blood gas, pulmonary edema, endothelial activation, and neutrophil infiltration were measured during acute lung injury (ALI). Histone H4 or anti-H4 antibody was administered through the tail vein 1 h prior to Cl2 exposure to study the pathogenic role of histone H4. Toll-like receptor 2 knock-out (Tlr2-KO) and Tlr4-KO mice were used in conjunction with blocking antibody against TLR1, TLR2, TLR4, or TLR6 to explore the mechanism involved in histone H4-mediated injury.ResultsCl2 exposure induced a concentration-dependent ALI. The levels of circulating histone H4 were positively correlated with Cl2 concentrations. Pretreatment with intravenous histone H4 further aggravated lethality rate, blood gas, endothelial activation, and neutrophil infiltration, while anti-H4 antibody showed protective effects. Tlr4 deficiency improved lethality rate, blood gas, and pulmonary edema, and prevented endothelial and neutrophil activation caused by Cl2 exposure. More importantly, Tlr4 gene deletion greatly diminished the effect of histone H4 or anti-H4 antibody observed in wild-type (WT) mice. The impact of Tlr2 on inflammatory injury was not significant. The role of TLRs was also validated by endothelial activation mediated by histone H4 in vitro.ConclusionsCirculating histone H4 played a pro-inflammatory role in ARDS caused by Cl2. TLR4 was closely involved in histone H4-mediated inflammatory injury. Therefore, intervention targeting histone H4 is potentially protective.

Phagocyte Escape of Leptospira: The Role of TLRs and NLRs.

The spirochetal bacteria Leptospira spp. are causative agents of leptospirosis, a globally neglected and reemerging zoonotic disease. Infection with these pathogens may lead to an acute and potentially fatal disease but also to chronic asymptomatic renal colonization. Both forms of disease demonstrate the ability of leptospires to evade the immune response of their hosts. In this review, we aim first to recapitulate the knowledge and explore the controversial data about the opsonization, recognition, intracellular survival, and killing of leptospires by scavenger cells, including platelets, neutrophils, macrophages, and dendritic cells. Second, we will summarize the known specificities of the recognition or escape of leptospire components (the so-called microbial-associated molecular patterns; MAMPs) by the pattern recognition receptors (PRRs) of the Toll-like and NOD-like families. These PRRs are expressed by phagocytes, and their stimulation by MAMPs triggers pro-inflammatory cytokine and chemokine production and bactericidal responses, such as antimicrobial peptide secretion and reactive oxygen species production. Finally, we will highlight recent studies suggesting that boosting or restoring phagocytic functions by treatments using agonists of the Toll-like or NOD receptors represents a novel prophylactic strategy and describe other potential therapeutic or vaccine strategies to combat leptospirosis.

Free light chains injure proximal tubule cells through the STAT1/HMGB1/TLR axis.

Free light chains (FLCs) induce inflammatory pathways in proximal tubule cells (PTCs). The role of TLRs in these responses is unknown. Here we present findings on the role of TLRs in FLC-induced PTC injury. We exposed human kidney PTC cultures to κ and λ FLCs and used cell supernatants and pellets for ELISA and gene expression studies. We also analyzed tissues from Stat1-/- and littermate control mice treated with daily i.p. injections of a κ FLC for 10 days. FLCs increased the expression of TLR2, TLR4, and TLR6 via HMGB1, a damage-associated molecular pattern. Countering TLR2, TLR4, and TLR6 through GIT-27 or specific TLR siRNAs reduced downstream cytokine responses. Blocking HMGB1 through siRNA or pharmacologic inhibition, or via STAT1 inhibition, reduced FLC-induced TLR2, TLR4, and TLR6 expression. Blocking endocytosis of FLCs through silencing of megalin/cubilin, with bafilomycin A1 or hypertonic sucrose, attenuated FLC-induced cytokine responses in PTCs. IHC showed decreased TLR4 and TLR6 expression in kidney sections from Stat1-/- mice compared with their littermate controls. PTCs exposed to FLCs released HMGB1, which induced expression of TLR2, TLR4, and TLR6 and downstream inflammation. Blocking FLCs' endocytosis, Stat1 knockdown, HMGB1 inhibition, and TLR knockdown each rescued PTCs from FLC-induced injury.

Mechanisms of innate immunity in pathogenesis of psoriasis: approaches to targeted therapy

Psoriasis is a chronic auto-inflammatory, genetically determined dermatosis, being multifactorial by origin, characterized by hyperproliferation of epidermis, affected keratinocyte differentiation and inflammatory reaction in dermis. The disease is characterized by a tendency to spread over the area of lesion, and involvement of articular tissue in the pathological process, which significantly affects the living standards of patients and causes their disability. There are many provoking factors that contribute to occurrence of psoriasis, or progression of existing psoriatic process in individuals with a genetic predisposition. These factors include adverse climatic conditions, skin trauma, exposure to ultraviolet light, burns, infections, etc.This review describes the role of innate immunity in pathogenesis of psoriasis, and describes in detail the mechanisms involved into induction of inflammation of PAMPs and DAMPs. In psoriasis, positively charged catelicidin is considered one of the most important DAMPs, which can form a complex with negatively charged cell polyanions-LL-37/auto-RNA and LL-37/auto-DNA. The interaction of PAMP/DAMP ligands with specific PRR receptors leads to signal activation of effector components of immune system, i.e., assembly of inflammasome complex, caspase activation, synthesis of inflammatory cytokines and processing of their immature forms. The review focuses on the role of TLRs under the conditions of physiological norm, which recognize danger signals and provide protection from pathogens and their timely elimination, and in development of pathological process. Activation of TLRs induces the production of pro-inflammatory cytokines, interferons and antimicrobial peptides, chemokines that support the development of psoriatic inflammation.In addition to TLRs, the mechanisms of involvement of inflammasomes in the development of psoriasis, which provides processing of mature forms of IL-1β and IL-18, are described in detail. Mature forms of these cytokines mediate the development of inflammation in psoriatic focus. In addition, processing of these cytokines by caspases using the positive feedback mechanism provides an additional signal to activate transcriptional activity of their genes and contributes to perpetuated inflammation.The review presents data confirming participation of inflammasomes in the pathogenesis of psoriasis. Much attention is paid to description of pharmacological inhibitors of inflammasomes, which in the future may be the drugs of choice for treatment of inflammatory diseases. The study of molecular mechanisms of the innate immune system will reveal new approaches to prognosis and development of targeted therapy for psoriasis.

Toll-like receptor 3 controls QT interval on the electrocardiogram by targeting the degradation of Kv4.2/4.3 channels in the endoplasmic reticulum.

TLRs have been proven to be essential mediators for the early innate immune response. Overactivation of TLR-mediated immune signaling promotes deterioration of cardiovascular diseases; however, the role of TLRs in the heart under physiologic conditions remains neglected. Here, we show that Tlr3 deficiency induced the endoplasmic reticulum (ER) retention of Kv4.2/4.3 proteins and consequent degradation via the ubiquitin-proteasome pathway. Knockout of Tlr3 resulted in a prolonged QT interval (the space between the start of the Q wave and the end of the T wave) in mice with no significant signs of inflammation and tissue abnormality in cardiac muscles. Prolongation of action potential duration resulted from the depression of transient outward potassium channel (Ito) currents in Tlr3-deficient ventricular myocytes mirrored the change in QT interval. Mechanistically, we found that Tlr3 was exclusively localized in the ER of cardiomyocytes where it interacted with Kv4.2/4.3 subunits of Ito channel. Thus, our data indicated that TLR3 directly regulates Ito channel protein dynamics to maintain cardiac repolarization, which may implicate a new molecular surveillance system for cardiac electrophysiological homeostasis.-Gao, X., Gao, S., Guan, Y., Huang, L., Huang, J., Lin, L., Liu, Y., Zhao, H., Huang, B., Yuan, T., Liu, Y., Liang, D., Zhang, Y., Ma, X., Li, L., Li, J., Zhou, D., Shi, D., Xu, L., Chen, Y.-H. Toll-like receptor 3 controls QT interval on the electrocardiogram by targeting the degradation of Kv4.2/4.3 channels in the endoplasmic reticulum.

THE ROLE OF INNATE IMMUNITY RECEPTORS (TLRs) IN MAINTAINING THE HOMEOSTASIS OF THE FEMALE GENITAL TRACT IN DEVELOPING PREGNANCY AND INTRAUTERINE INFECTION

The aim of the present systematic literature review is to summarize data on the role of TLRs in maintaining homeostasis of the female genitals, in maintaining the physiological development of pregnancy, provision of anti-infective resistance in pregnant women with intrauterine infection. The review substantiates the importance of TLRs of female genitals as a necessary and determining factor in the reaction to various changes in the environment, and also responsible for changes in metabolic, structural, or energy, in the maintenance of anti-infective resistance and homeostasis. As universal regulators of vital activity of organism TLRs in conjunction with other receptors of innate immunity provide maintaining the general reactivity and anti-infective resistance at the physiological level. In physiologically developing pregnancy in a background of immunosuppression in response to pregnancy TLRs during contact with infectious and non-infectious pathogens stimulate the production of nonspecific adaptive immunity factors (defensins, cathelicidins, histatines, etc.), which together with the non-specific innate factors lysozyme, complement, properdin, etc. support antiinfective resistance of the female genitals at a high level at the beginning of the infectious process. Possible violations of the development of pregnancy may be accompanied by changes in the response of TLRs to infectious and non-infectious factors until hyper-reaction, excessive inflammation or apoptosis, which requires adequate management of pregnancy. Was established the significance of the influence of pathogens of infectious and noninfectious origin in intrauterine infection indirectly through TLRs in the homeostasis of the organism, on the formation of breaches in anti-infective resistance at the organism and community level the identification of new pathophysiological and immunological pathogenetic mechanisms of development of pathological processes. IUI is a penetration of microorganisms into the tissues of fetus and it’s infection. The inhibition of the functional activity of TLRs is accompanied by the direct effect of the pathogen on the tissues, and during hyper-reaction of TLRs to pathogens revealed a pronounced inflammatory response in the fetus. The level of expression of TLRs correlates directly with the severity of the process that can be considered as early markers of infection. Depending on the nature of the pathogen an increased expression of one or the other TLRs is observed. Explained the lack of symptoms, the possibility of atypical manifestations, the asymptomatic course of infection.

TLR3 Modulates the Response of NK Cells against Schistosoma japonicum.

Natural killer (NK) cells are classic innate immune cells that play roles in many types of infectious diseases. NK cells possess many kinds of TLRs that allow them to sense and respond to invading pathogens. Our previous study found that NK cells could modulate the immune response induced by Schistosoma japonicum (S. japonicum) in C57BL/6 mice. In the present study, the role of TLRs in the progress of S. japonicum infection was investigated. Results showed that the expression of TLR3 on NK cells increased significantly after S. japonicum infection by using RT-PCR and FACS (P < 0.05). TLR3 agonist (Poly I:C) increased IFN-γ and IL-4 levels in the supernatant of cultured splenocytes and induced a higher percentage of IFN-γ- and IL-4-secreting NK cells from infected mouse splenocytes (P < 0.05). Not only the percentages of MHC II-, CD69-, and NKG2A/C/E-expressing cells but also the percentages of IL-4-, IL-5-, and IL-17-producing cells in TLR3+ NK cells increased significantly after infection (P < 0.05). Moreover, the expression of NKG2A/C/E, NKG2D, MHC II, and CD69 on the surface of splenic NK cells was changed in S. japonicum-infected TLR3−/− (TLR3 KO mice, P < 0.05); the abilities of NK cells in IL-4, IL-5, and IL-17 secretion were decreased too (P < 0.05). These results indicate that TLR3 is the primary molecule which modulates the activation and function of NK cells during the course of S. japonicum infection in C57BL/6 mice.

Epigenetic regulation of Toll-like receptors and its roles in type 1 diabetes.

The immune system can be divided into adaptive immunity and innate immunity. Adaptive immunity has been confirmed to be involved in the pathogenesis of autoimmune diseases, including type 1 diabetes (T1D). However, the role of innate immunity in T1D has only been studied recently. T1D is caused by selective autoimmune destruction of pancreatic islet β cells. A series of studies have suggested that TLRs play a critical role in the pathogenesis of T1D. Aberrant TLR signaling will change immune homeostasis and result in immunopathological conditions such as endotoxin shock and autoimmune responses. Thus, TLR signaling pathways are supposed to be strictly and finely regulated. Epigenetics has recently been proven to be a new regulator of TLR expression. DNA methylation, histone modification, and microRNAs are the three main epigenetic modifications. This review will mainly focus on these epigenetic mechanisms of regulation of TLRs and the role of TLRs in the pathogenesis of T1D.

Inflammation-dependent cerebrospinal fluid hypersecretion by the choroid plexus epithelium in posthemorrhagic hydrocephalus.

The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type stress kinase SPAK, which binds, phosphorylates, and stimulates the NKCC1 co-transporter at the CPE apical membrane. Genetic depletion of TLR4 or SPAK normalizes hyperactive CSF secretion rates and reduces PHH symptoms, as does treatment with drugs that antagonize TLR4-NF-κB signaling or the SPAK-NKCC1 co-transporter complex. These data uncover a previously unrecognized contribution of CSF hypersecretion to the pathogenesis of PHH, demonstrate a new role for TLRs in regulation of the internal brain milieu, and identify a kinase-regulated mechanism of CSF secretion that could be targeted by repurposed US Food and Drug Administration (FDA)-approved drugs to treat hydrocephalus.

Frontline Science: Human bone cells as a source of IL-27 under inflammatory conditions: role of TLRs and cytokines.

IL-27 regulates immune responses as well as hematopoiesis and bone remodeling, but its cellular sources in the bone remain unknown. In this study, we investigated whether osteoclasts and osteoblasts-the 2 cell types orchestrating bone homeostasis-could be a source of IL-27 and identified stimuli that induce its expression in vitro. We observed that human monocyte-derived osteoclasts expressed a broader range of TLRs than did human primary osteoblasts and that both cell types exhibited a differential induction of IL-27 expression in response to TLR or cytokine stimulation. Whereas several TLR agonists, notably TLR4 and TLR7/8 agonists, induced substantial expression of IL-27 by osteoclasts, stimulation of osteoblasts with agonists of TLR3 and/or TLR4-the 2 TLRs selectively expressed by these cells-resulted in no or low IL-27 expression. In addition, IL-27 increased TLR3 expression in osteoclasts and enhanced poly(I:C)-mediated induction of IL-27 in these cells. IFN-γ, when combined with either IL-1β plus TNF-α, IL-11, or CNTF, induced significant levels of IL-27 in osteoclasts but not in osteoblasts. In the latter cells, the addition of type I IFN, together with proinflammatory cytokines, was necessary to induce substantial levels of IL-27. Immunohistochemical studies of inflamed and remodeling bone tissue, including cases of infectious osteomyelitis and bone metastases, provided evidence that osteoclasts, osteoblasts, and occasionally osteocytes or chondrocytes, could express IL-27 in situ. This autocrine production of IL-27 by TLR- or cytokine-activated bone cells might constitute a negative-feedback mechanism to limit bone erosion and to dampen T cell-mediated immune pathology during bone inflammation.

Hybrid Cells Derived from Human Breast Cancer Cells and Human Breast Epithelial Cells Exhibit Differential TLR4 and TLR9 Signaling.

TLRs are important receptors of cells of the innate immune system since they recognize various structurally conserved molecular patterns of different pathogens as well as endogenous ligands. In cancer, the role of TLRs is still controversial due to findings that both regression and progression of tumors could depend on TLR signaling. In the present study, M13SV1-EGFP-Neo human breast epithelial cells, MDA-MB-435-Hyg human breast cancer cells and two hybrids M13MDA435-1 and -3 were investigated for TLR4 and TLR9 expression and signaling. RT-PCR data revealed that LPS and CpG-ODN induced the expression of pro-inflammatory cytokines, like IFN-β, TNF-α, IL-1β and IL-6 in hybrid cells, but not parental cells. Interestingly, validation of RT-PCR data by Western blot showed detectable protein levels solely after LPS stimulation, suggesting that regulatory mechanisms are also controlled by TLR signaling. Analysis of pAKT and pERK1/2 levels upon LPS and CpG-ODN stimulation revealed a differential phosphorylation pattern in all cells. Finally, the migratory behavior of the cells was investigated showing that both LPS and CpG-ODN potently blocked the locomotory activity of the hybrid cells in a dose-dependent manner. In summary, hybrid cells exhibit differential TLR4 and TLR9 signaling.

The Role of TLRs in the Pathogenesis of Periodontal Diseases

The Role of TLRs in the Pathogenesis of Periodontal Diseases

The TLR2 is activated by sporozoites and suppresses intrahepatic rodent malaria parasite development.

TLRs (Toll-like receptors) play an important role in the initiation of innate immune responses against invading microorganisms. Although several TLRs have been reported to be involved in the innate immune response against the blood-stage of malaria parasites, the role of TLRs in the development of the pre-erythrocytic stage is still largely unknown. Here, we found that sporozoite and its lysate could significantly activate the TLR2, and induce macrophages to release proinflammatory cytokines, including IL-6, MCP-1 and TNF-α, in a TLR2-dependent manner. Further studies showed that sporozoite and its lysate could be recognized by either TLR2 homodimers or TLR2/1 and TLR2/6 heterodimers, implicating the complexity of TLR2 agonist in sporozoite. Interestingly, the TLR2 signaling can significantly suppress the development of the pre-erythrocytic stage of Plasmodium yoelii, as both liver parasite load and subsequent parasitemia were significantly elevated in both TLR2- and MyD88-deficient mice. Additionally, the observed higher level of parasite burden in TLR2−/− mice was found to be closely associated with a reduction in proinflammatory cytokines in the liver. Therefore, we provide the first evidence that sporozoites can activate the TLR2 signaling, which in turn significantly inhibits the intrahepatic parasites. This may provide us with novel clues to design preventive anti-malaria therapies.