Associations of toll-like receptor (TLR)-4 single nucleotide polymorphisms and rheumatoid arthritis disease progression: an observational cohort study

Targeting TLR Signaling Cascades in Systemic Lupus Erythematosus and Rheumatoid Arthritis: An Update

Evidence from animal models and human genetics implicates Toll-like Receptors (TLRs) in the pathogenesis of Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA). Endosomal TLRs sensing nucleic acids were proposed to induce lupus-promoting signaling in dendritic cells, B cells, monocytes, and macrophages. Ligation of TLR4 in synovial macrophages and fibroblast-like synoviocytes (FLSs) by endogenous ligands was suggested to induce local production of mediators that amplify RA synovitis. Inhibition of TLRs using antagonists or monoclonal antibodies (mAbs) that selectively prevent extracellular or endosomal TLR ligation has emerged as an attractive treatment strategy for SLE and RA. Despite the consistent success of selective inhibition of TLR ligation in animal models, DV-1179 (dual TLR7/9 antagonist) failed to achieve pharmacodynamic effectiveness in SLE, and NI-0101 (mAb against TLR4) failed to improve arthritis in RA. Synergistic cooperation between TLRs and functional redundancy in human diseases may require pharmacologic targeting of intracellular molecules that integrate signaling downstream of multiple TLRs. Small molecules inhibiting shared kinases involved in TLR signaling and peptidomimetics disrupting the assembly of common signalosomes ("Myddosome") are under development. Targeted degraders (proteolysis-targeting chimeras (PROTACs)) of intracellular molecules involved in TLR signaling are a new class of TLR inhibitors with promising preliminary data awaiting further clinical validation.

Aberrant B Cell Signaling in Autoimmune Diseases

Aberrant B cell signaling plays a critical in role in various systemic and organ-specific autoimmune diseases. This is supported by genetic evidence by many functional studies in B cells from patients or specific animal models and by the observed efficacy of small-molecule inhibitors. In this review, we first discuss key signal transduction pathways downstream of the B cell receptor (BCR) that ensure that autoreactive B cells are removed from the repertoire or functionally silenced. We provide an overview of aberrant BCR signaling that is associated with inappropriate B cell repertoire selection and activation or survival of peripheral B cell populations and plasma cells, finally leading to autoantibody formation. Next to BCR signaling, abnormalities in other signal transduction pathways have been implicated in autoimmune disease. These include reduced activity of several phosphates that are downstream of co-inhibitory receptors on B cells and increased levels of BAFF and APRIL, which support survival of B cells and plasma cells. Importantly, pathogenic synergy of the BCR and Toll-like receptors (TLR), which can be activated by endogenous ligands, such as self-nucleic acids, has been shown to enhance autoimmunity. Finally, we will briefly discuss therapeutic strategies for autoimmune disease based on interfering with signal transduction in B cells.

Host-pathogen protein-nucleic acid interactions: A comprehensive review

Recognition of pathogen-derived nucleic acids by host cells is an effective host strategy to detect pathogenic invasion and trigger immune responses. In the context of pathogen-specific pharmacology, there is a growing interest in mapping the interactions between pathogen-derived nucleic acids and host proteins. Insight into the principles of the structural and immunological mechanisms underlying such interactions and their roles in host defense is necessary to guide therapeutic intervention. Here, we discuss the newest advances in studies of molecular interactions involving pathogen nucleic acids and host factors, including their drug design, molecular structure and specific patterns. We observed that two groups of nucleic acid recognizing molecules, Toll-like receptors (TLRs) and the cytoplasmic retinoic acid-inducible gene (RIG)-I-like receptors (RLRs) form the backbone of host responses to pathogen nucleic acids, with additional support provided by absent in melanoma 2 (AIM2) and DNA-dependent activator of Interferons (IFNs)-regulatory factors (DAI) like cytosolic activity. We review the structural, immunological, and other biological aspects of these representative groups of molecules, especially in terms of their target specificity and affinity and challenges in leveraging host-pathogen protein-nucleic acid interactions (HP-PNI) in drug discovery.

Toll-Like Receptor Signaling and Its Role in Cell-Mediated Immunity

Innate immunity is the first defense system against invading pathogens. Toll-like receptors (TLRs) are well-defined pattern recognition receptors responsible for pathogen recognition and induction of innate immune responses. Since their discovery, TLRs have revolutionized the field of immunology by filling the gap between the initial recognition of pathogens by innate immune cells and the activation of the adaptive immune response. TLRs critically link innate immunity to adaptive immunity by regulating the activation of antigen-presenting cells and key cytokines. Furthermore, recent studies also have shown that TLR signaling can directly regulate the T cell activation, growth, differentiation, development, and function under diverse physiological conditions. This review provides an overview of TLR signaling pathways and their regulators and discusses how TLR signaling, directly and indirectly, regulates cell-mediated immunity. In addition, we also discuss how TLR signaling is critically important in the host's defense against infectious diseases, autoimmune diseases, and cancer.

Toll-Like Receptor Signaling and Its Role in Cell-Mediated Immunity

Innate immunity is the first defense system against invading pathogens. Toll-like receptors (TLRs) are well-defined pattern recognition receptors responsible for pathogen recognition and induction of innate immune responses. Since their discovery, TLRs have revolutionized the field of immunology by filling the gap between the initial recognition of pathogens by innate immune cells and the activation of the adaptive immune response. TLRs critically link innate immunity to adaptive immunity by regulating the activation of antigen-presenting cells and key cytokines. Furthermore, recent studies also have shown that TLR signaling can directly regulate the T cell activation, growth, differentiation, development, and function under diverse physiological conditions. This review provides an overview of TLR signaling pathways and their regulators and discusses how TLR signaling, directly and indirectly, regulates cell-mediated immunity. In addition, we also discuss how TLR signaling is critically important in the host's defense against infectious diseases, autoimmune diseases, and cancer.

Euphorbia Factor L2 ameliorates the Progression of K/BxN Serum-Induced Arthritis by Blocking TLR7 Mediated IRAK4/IKKβ/IRF5 and NF-kB Signaling Pathways

Toll like receptor (TLR)s have a central role in regulating innate immunity and their activation have been highlighted in the pathogenesis of rheumatoid arthritis (RA). EFL2, one of diterpenoids derived from Euphorbia seeds, is nearly unknown expect for its improving effect on acute lung injury. Our present study aimed to investigate EFL2's pharmacokinetic features, its therapeutic effect on rheumatoid arthritis, and explored the potential anti-arthritic mechanisms. K/BxN serum transfer arthritis (STA) murine model was used to assess EFL2's anti-arthritic effects. We also applied UPLC-MS method to measure the concentrations of EFL2 in plasma. The inhibitory effects of this compound on inflammatory cells infiltration and activation were determined by flow cytometry analysis and quantitative real-time polymerase chain reaction (qRT-PCR) in vivo, and immunochemistry staining and ELISA in murine macrophages and human PBMCs in vitro, respectively. The mechanism of EFL2 on TLRs mediated signaling pathway was evaluated by PCR array, Western blot, plasmid transfection and confocal observation. Intraperitoneal (i.p.) injection of EFL2, instead of oral administration, could effectively ameliorate arthritis severity of STA mice. The inflammatory cells migration and infiltration into ankles were also significantly blocked by EFL2, accompanied with dramatically reduction of chemokines mRNA expression and pro-inflammatory cytokines production. In vivo PCR microarray indicated that EFL2 exerted anti-arthritis bioactivity by suppressing TLR7 mediated signaling pathway. In vitro study confirmed the inhibitory effects of EFL2 on TLR7 or TLR3/7 synergistically induced inflammatory cytokines secretion in murine macrophages and human PBMCs. In terms of molecular mechanism, we further verified that EFL2 robustly downregulated TLR7 mediated IRAK4-IKKβ-IRF5 and NF-κB signaling pathways activation, and blocked IRF5 and p65 phosphorylation and translocation activity. Taken together, our data indicate EFL2's therapeutic potential as a candidate for rheumatoid arthritis and other TLR7-dependent diseases.

Association of TLR 9 gene polymorphisms with remission in patients with rheumatoid arthritis receiving TNF-α inhibitors and development of machine learning models

Toll-like receptor (TLR)-4 and TLR9 are known to play important roles in the immune system, and several studies have shown their association with the development of rheumatoid arthritis (RA) and regulation of tumor necrosis factor alpha (TNF-α). However, studies that investigate the association between TLR4 or TLR9 gene polymorphisms and remission of the disease in RA patients taking TNF-α inhibitors have yet to be conducted. In this context, this study was designed to investigate the effects of polymorphisms in TLR4 and TLR9 on response to TNF-α inhibitors and to train various models using machine learning approaches to predict remission. A total of six single nucleotide polymorphisms (SNPs) were investigated. Logistic regression analysis was used to investigate the association between genetic polymorphisms and response to treatment. Various machine learning methods were utilized for prediction of remission. After adjusting for covariates, the rate of remission of T-allele carriers of TLR9 rs352139 was about 5 times that of the CC-genotype carriers (95% confidence interval (CI) 1.325-19.231, p = 0.018). Among machine learning algorithms, multivariate logistic regression and elastic net showed the best prediction with the area under the receiver-operating curve (AUROC) value of 0.71 (95% CI 0.597-0.823 for both models). This study showed an association between a TLR9 polymorphism (rs352139) and treatment response in RA patients receiving TNF-α inhibitors. Moreover, this study utilized various machine learning methods for prediction, among which the elastic net provided the best model for remission prediction.

Association Between TLR4 Gene Polymorphisms and Risk of Preeclampsia: Systematic Review and Meta-Analysis

BACKGROUND Toll-like receptor 4 (TLR4) plays a pivotal role in the innate immune response and is hyperactivated in preeclampsia (PE). Several researchers have published conflicting evidence for TLR4 rs4986790 and rs4986791 single nucleotide polymorphisms (SNPs) as risk factors for PE. The present meta-analysis was conducted to obtain a more definitive conclusion about the effects of these SNPs on PE susceptibility. MATERIAL AND METHODS To determine the correlation between rs4986790 and rs4986791 polymorphisms in the TLR4 gene and susceptibility to PE, the PubMed, Web of Science, EMBASE, Chinese National Knowledge Infrastructure, and Chinese WANFANG databases were searched for eligible articles. Statistical analysis was performed with STATA software, version 12.0. Pooled odds ratios with corresponding 95% confidence intervals (CIs) were extracted for assessment of correlation strength. RESULTS We identified 5 studies including 578 cases and 631 controls for the rs4986790 SNP and 4 studies including 469 cases and 457 controls for the rs4986791 SNP, mainly from a White population. The pooled analyses showed no statistical relationship between the polymorphisms rs4986790 and rs4986791 and PE susceptibility in 5 genetic models (all P>0.05). Moreover, the allelic and dominant gene models of rs4986790 and the allelic, heterozygous, and dominant gene models of rs4986791 had high heterogeneity. The sensitivity analysis explored potential sources of heterogeneity and confirmed the findings of this meta-analysis. CONCLUSIONS TLR4 rs4986790 and rs4986791 polymorphisms may not be implicated in PE susceptibility, primarily in a White population. More high-quality studies of genetic associations with PE are warranted.

Association of Toll-like Receptor 4 Rs7873784 G/C Polymorphism with Rheumatoid Arthritis Risk in a Chinese Population

Background: The purposes of this study were to explore whether the Toll-like receptor 4 (TLR4) gene rs7873784 G/C polymorphism was related to the risk of rheumatoid arthritis (RA) and to the clinical features of the disease in Chinese subjects.Materials and Methods: We examined the TLR4 rs7873784 G/C polymorphism in 805 Chinese RA patients and 1095 healthy controls. Genotype was determined with a custom-by-design 48-Plex single nucleotide polymorphism scan™ Kit. Blood plasma levels of TLR4 in 170 RA patients and 170 matched controls were measured by ELISA.Results: The TLR4 gene rs7873784 G/C polymorphism was related to a reduced risk for RA. By stratified analysis, we found a dramatically reduced risk for RA in patients who were female, CRP-positive, RF-positive, DAS28 ≥ 3.20, or ESR ≥ 25. Compared with the controls, the average level of TLR4 protein in plasma of RA patients was increased. In addition, RA patients exhibited higher levels of TLR4 mRNA than controls (P < .05).Conclusion: These results demonstrate the TLR4 rs7873784 G/C polymorphism to relate to a decreased risk for RA in a Chinese population.

Toll-like receptor signalling in B cells during systemic lupus erythematosus

B lymphocytes have a central role in autoimmune diseases, which are often defined by specific autoantibody patterns and feature a loss of B cell tolerance. A prototypic disease associated with B cell hyperactivity is systemic lupus erythematosus (SLE). In patients with SLE, the loss of B cell tolerance to autoantigens is controlled in a cell-intrinsic manner by Toll-like receptors (TLRs), which sense nucleic acids in endosomes. TLR7 drives the extrafollicular B cell response and the germinal centre reaction that are involved in autoantibody production and disease pathogenesis. Surprisingly, TLR9 seems to protect against SLE, even though it is required for the production of autoantibodies recognizing double-stranded DNA-associated antigens, which are abundant in SLE and are a hallmark of this disease. The protective function of TLR9 is at least partly mediated by its capacity to limit the stimulatory activity of TLR7. The roles of TLR7 and TLR9 in the effector function of B cells in lupus-like disease and in patients with SLE, and the unique features of TLR signalling in B cells, suggest that targeting TLR signalling in SLE might be therapeutically beneficial.

Loss of B cell tolerance to autoantigens in systemic lupus erythematosus (SLE) is driven by TLR7, whereas TLR9 appears to protect against SLE by limiting the stimulatory activity of TLR7. The unique features of Toll-like receptor signalling in B cells implicate it as a therapeutic target in SLE.

Intrinsic TLR7 and TLR9 signalling in B cells plays an important role in the development and pathogenesis of systemic lupus erythematosus (SLE).

In patients with SLE, effector plasma cells are generated via the extrafollicular response and via the formation of spontaneous germinal centres.

TLR7 plays key roles in the extrafollicular response and the response mediated by germinal centres.

Some plasma cells produce IL-10 and can have protective roles in lupus-like disease.

Toll-like-Receptor Gene Polymorphisms in Tunisian Endemic Pemphigus Foliaceus

Pemphigus foliaceus (PF) is considered to be caused by the combined effects of susceptibility genes and environmental triggers. The polymorphisms of Toll-like receptors (TLRs) genes have been associated with the risk of various autoimmune diseases. The aim of this study was to evaluate the potential association of TLR2-3-4 and 7 gene polymorphisms with Tunisian PF. Fourteen polymorphisms were analyzed in 93 Tunisian PF patients compared to 193 matched healthy controls: rs5743703-rs5743709 and (GT)_n repeat (TLR2); rs5743305, rs3775294, and rs3775291 (TLR3), rs4986790 and rs4986791 (TLR4); and rs3853839 (TLR7). Our results showed that the genetic factors varied depending on the epidemiological feature stratification. In fact, in the whole population, no association with the susceptibility to PF was found. The TLR2 GT repeat seems to be closely associated with PF risk in patients originated from the endemic localities (group 3); the GT₁₈ allele and the heterozygous genotype GT₁₈/GT₁₉ seem to confer risk to endemic PF (P = 0.02; OR = 2.3 [1.1-4.9] and P = 0.0002, OR = 20 [2.5-171], respectively). In contrast, the GT₂₃ repeat could be considered as protector allele (P = 0.02, OR = 0.2 [0.06-0.87]). Furthermore, medium GT alleles which induce high promoter activity were also significantly more frequent in patients versus short or long GT repeats (P = 0.0018 with OR = 3.26 [1.5-7]). On the other hand, the TLR3-rs574305 AA genotype and A allele were significantly more frequent in patients whose age of the onset was above 35 years (group 2) (P = 0.038, OR = 1.78 and P = 0.009, OR = 3.92, respectively). Besides, the TLR4>rs3775294 A allele was found to be protector only in patients with sporadic features (groups 2 and 4) (P = 0.03, OR = 0.57 [0.3-0.9] and P = 0.006, OR = 0.24 [0.08-0.74], respectively). No statistically significant difference was observed in the genotypic and allelic frequencies of TLR-4 and TLR-7 gene polymorphisms. The present data suggest that TLR2and TLR3 polymorphisms are significantly associated with increased susceptibility to PF in the Tunisian population.

Toll-Like Receptors, Infections, and Rheumatoid Arthritis

Toll-like receptors (TLR) that belong to the group of protein recognition receptor (PPR) provide an innate immune response following the sensing of conserved pathogen-associated microbial patterns (PAMPs) and changes in danger-associated molecular patterns (DAMPs) that are generated as a consequence of cellular injury. Analysis of the TLR pathway has moreover offered new insights into the pathogenesis of rheumatoid arthritis (RA). Indeed, a dysfunctional TLR-mediated response characterizes RA patients and participates in establishment of a chronic inflammatory state. Such an inappropriate TLR response has been attributed (i) to the report of important alterations in the microbiota and abnormal responses to infectious agents as part of RA; (ii) to the abnormal presence of TLR-ligands in the serum and synovial fluid of RA patients; (iii) to the overexpression of TLR molecules; (iv) to the production of a large panel of pro-inflammatory cytokines downstream of the TLR pathway; and (v) to genetic variants and epigenetic factors in susceptible RA patients promoting a hyper TLR response. As a consequence, the development of promising therapeutic strategies targeting TLRs for the treatment and prevention of RA is emerging.

Innate immunity drives pathogenesis of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease affecting ∼1% of the general population. This disease is characterized by persistent articular inflammation and joint damage driven by the proliferating synovial tissue fibroblasts as well as neutrophil, monocyte and lymphocyte trafficking into the synovium. The factors leading to RA pathogenesis remain poorly elucidated although genetic and environmental factors have been proposed to be the main contributors to RA. The majority of the early studies focused on the role of lymphocytes and adaptive immune responses in RA. However, in the past two decades, emerging studies showed that the innate immune system plays a critical role in the onset and progression of RA pathogenesis. Various innate immune cells including monocytes, macrophages and dendritic cells are involved in inflammatory responses seen in RA patients as well as in driving the activation of the adaptive immune system, which plays a major role in the later stages of the disease. Here we focus the discussion on the role of different innate immune cells and components in initiation and progression of RA. New therapeutic approaches targeting different inflammatory pathways and innate immune cells will be highlighted here. Recent emergence and the significant roles of innate lymphoid cells and inflammasomes will be also discussed.

In seroconverted rheumatoid arthritis patients a multi-reactive anti-herpes IgM profile is associated with disease activity

Conflicting results have been reported regarding human herpes virus (HHV) reactivation in patients with rheumatoid arthritis (RA). To explore this link, 74 RA patients were selected and compared to 42 first degree relatives (FDR) from probands with RA and 25 healthy controls from the Tatarstan women cohort. The serological analysis was done by testing anti-HSV/CMV/EBV IgM, IgG, plus the IgG avidity index, and completed by evaluating HSV/CMV/EBV DNA by PCR. Results from these analyses reveal: (i) a long lasting infection of HHV in RA, FDR and healthy controls (IgG seroconversion >97%); (ii) an elevated IgM anti-HHV response in seroconverted RA patients which is related to HSV1/2 reactivation (HSV1/2 PCR+); and (iii) a multi-reactive IgM HHV burden profile associated with disease activity (DAS28). In conclusion, HSV1/2 reactivation in seroconverted RA patients is associated with an abnormal anti-HHV immune response, which was reflected in IgM HHV burden, and in activity disease profile.

Affinity Maturation Drives Epitope Spreading and Generation of Proinflammatory Anti-Citrullinated Protein Antibodies in Rheumatoid Arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by the presence of anti-citrullinated protein antibodies (ACPAs); nevertheless, the origin, specificity, and functional properties of ACPAs remain poorly understood. The aim of this study was to characterize the evolution of ACPAs by sequencing the plasmablast antibody repertoire at serial time points in patients with established RA.

METHODS

Blood samples were obtained at up to 4 serial time points from 8 individuals with established RA who were positive for ACPAs by the anti-cyclic citrullinated peptide test. CD19+CD3-IgD-CD14-CD20-CD27+CD38++ plasmablasts were isolated by single-cell sorting and costained with citrullinated peptide tetramers to identify ACPA-expressing plasmablasts. Cell-specific oligonucleotide barcodes were utilized, followed by large-scale sequencing and bioinformatics analysis, to obtain error-corrected, paired heavy- and light-chain antibody gene sequences for each B cell.

RESULTS

Bioinformatics analysis revealed 170 persistent plasmablast lineages in the RA blood, of which 19% included multiple isotypes. Among IgG- and IgA-expressing plasmablasts, significantly more IgA-expressing than IgG-expressing persistent lineages were observed (P < 0.01). Shared complementarity-determining region 3 sequence motifs were identified across subjects. A subset of the plasmablast lineages included members derived from later time points with divergent somatic hypermutations that encoded antibodies that bind an expanded set of citrullinated antigens. Furthermore, these recombinant, differentially mutated plasmablast antibodies formed immune complexes that stimulated higher macrophage production of tumor necrosis factor (TNF) compared to antibodies representing earlier time point-derived lineage members that were less mutated.

CONCLUSION

These findings demonstrate that established RA is characterized by a persistent IgA ACPA response that exhibits ongoing affinity maturation. This observation suggests the presence of a persistent mucosal antigen that continually promotes the production of IgA plasmablasts and their affinity maturation and epitope spreading, thus leading to the generation of ACPAs that bind additional citrullinated antigens and more potently stimulate macrophage production of TNF.

Grape seed proanthocyanidin extract ameliorates murine autoimmune arthritis through regulation of TLR4/MyD88/NF-κB signaling pathway

BACKGROUND/AIMS

Grape seed proanthocyanidin extract (GSPE) has been reported to have a beneficial effect on regulating inf lammation. However, the anti-inflammatory mechanism of GSPE remains unclear. The aim of this study was to verify the influence of GSPE on the Toll-like receptor 4 (TLR4)-mediated signaling pathway in the regulation of murine autoimmune arthritis.

METHODS

Collagen-induced arthritis (CIA) was induced in dilute brown non-agouti (DBA)/1J mice. The mice were treated with GSPE (0 or 100 mg/kg) intraperitoneally. The severity of arthritis was assessed clinically, biochemically, and histologically. Immunostaining for TLR4 was performed. The expressions of TLR4 and downstream signaling molecules were analyzed by Western blot. The effect of GSPE on lipopolysaccharide (LPS)-induced TLR4 activation was also evaluated using RAW264.7 cells and fibroblast-like synoviocytes (FLSs) from patients with rheumatoid arthritis and from those with osteoarthritis.

RESULTS

GSPE attenuated the clinical severity of arthritis and decreased histological damage. GSPE treatment reduced the number of TLR4-stained cells in the synovium of mice with CIA. GSPE also downregulated the expression of TLR4, myeloid differentiation factor 88 (MyD88) and phosphorylated IκBα synovial protein in CIA mice. Concurrently, GSPE inhibited the nuclear translocation of nuclear factor-κB (NF-κB) subunits (p65 and p50). LPS-induced TLR4 activation was suppressed by GSPE in human FLS as well as in murine macrophages in vitro.

CONCLUSIONS

Our results demonstrated that GSPE ameliorated CIA by regulating the TLR4-MyD88-NF-κB signaling pathway.

Polymorphisms within Genes Involved in Regulation of the NF-κB Pathway in Patients with Rheumatoid Arthritis

Genes involved in regulation of the nuclear factor-κB (NF-κB)-pathway are suggested to play a role in pathogenesis of rheumatoid arthritis (RA). In the present study, genetic polymorphisms of TLR2, TLR4, TLR9 and NF-κB1 genes were investigated to assess their associations with RA susceptibility, progression and response to anti-TNF-α therapy. A group of 110 RA patients and 126 healthy individuals were genotyped for TLR2 (rs111200466), TLR4 (rs4986790, rs4986791), TLR9 (rs5743836, rs187084) and NF-κB1 (rs28362491) alleles. The presence of the TLR9 -1486 T variant (p < 0.0001) and its homozygosity (p < 0.0001) were found to be associated with disease susceptibility. The TLR9 -1237 C allele was associated with predisposition to RA in females only (p = 0.005). Moreover, the TLR4 rs4986791 G (rs4986790 T) alleles were more frequently detected among patients with the stage IV disease (p = 0.045), and were associated with more effective response to anti-TNF-α therapy (p = 0.012). More efficient response to anti-TNF-α treatment was also observed in patients with del within the NF-κB1 gene (p = 0.047), while for the TLR9 -1486 T homozygotes, the treatment was ineffective (p = 0.018). TLR polymorphisms affect disease susceptibility and response to therapy with TNF-α inhibitors in RA patients of Caucasian origin.

Association of Polymorphisms in Toll-Like Receptors 4 and 9 with Autoimmune Thyroid Disease in Korean Pediatric Patients

BACKGROUND

Toll-like receptors (TLRs) have been suggested to be associated with the development of AITD.

METHODS

Fifteen single-nucleotide polymorphisms in 7 TLR genes were analyzed in 104 Korean children (girls = 86, boys = 18) with AITD (Hashimoto disease (HD) = 44, Graves' disease (GD) = 60, thyroid-associated ophthalmopathy (TAO) = 29, and non-TAO = 31) with 183 controls.

RESULTS

GD showed higher frequencies of the TLR4 rs1927911 C allele than control. TAO showed a lower frequency of the TLR4 rs1927911 CT genotype and non-TAO showed a higher frequency of the TLR4 rs1927911 CC genotype than control. The frequency of the TLR9 rs187084 CC genotype in TAO was higher than that in non-TAO. GD females showed a higher frequency of the TLR4 rs10759932 T allele, rs1927911 CC genotype, and the rs1927911 C allele than controls. GD males showed a higher frequency of the TLR4 rs10759932 CC genotype and rs1927911 TT genotype and lower frequency of the rs1927911 CT genotype than control. The frequency of the TLR4 rs10759932 CC genotype, C allele and rs1927911 TT genotype, and T allele in a GD female were lower than in a GD male.

CONCLUSIONS

Our results suggest that TLR4 and 9 polymorphisms might contribute to the pathogenesis of GD and TAO.

TLRs, future potential therapeutic targets for RA

Toll like receptors (TLR)s have a central role in regulating innate immunity and in the last decade studies have begun to reveal their significance in potentiating autoimmune diseases such as rheumatoid arthritis (RA). Earlier investigations have highlighted the importance of TLR2 and TLR4 function in RA pathogenesis. In this review, we discuss the newer data that indicate roles for TLR5 and TLR7 in RA and its preclinical models. We evaluate the pathogenicity of TLRs in RA myeloid cells, synovial tissue fibroblasts, T cells, osteoclast progenitor cells and endothelial cells. These observations establish that ligation of TLRs can transform RA myeloid cells into M1 macrophages and that the inflammatory factors secreted from M1 and RA synovial tissue fibroblasts participate in TH-17 cell development. From the investigations conducted in RA preclinical models, we conclude that TLR-mediated inflammation can result in osteoclastic bone erosion by interconnecting the myeloid and TH-17 cell response to joint vascularization. In light of emerging unique aspects of TLR function, we summarize the novel approaches that are being tested to impair TLR activation in RA patients.

MAVS is not a Likely Susceptibility Locus for Addison's Disease and Type 1 Diabetes

Mitochondrial antiviral signaling (MAVS) protein is an intracellular adaptor molecule, downstream of viral sensors, retinoid acid-inducible gene I (RIG-I)-like receptors (RLRs). Impaired antiviral cell signaling might contribute to autoimmunity. Studies have recently shown variations in genes encoding RLRs as risk factors for autoimmune diseases. We investigated whether MAVS coding polymorphisms are associated with Addison's disease (AD) and type 1 diabetes (T1D) in Polish population. We genotyped 140 AD, 532 T1D patients and 600 healthy controls for MAVS rs17857295, rs7262903, rs45437096 and rs7269320. Genotyping was performed by TaqMan assays. Distribution of the MAVS genotypes and alleles did not reveal significant differences between patients and controls (p > 0.05). This analysis did not indicate the association of the MAVS locus with susceptibility to AD and T1D.

Toll-like receptors: promising therapeutic targets for inflammatory diseases

The health of living organisms is constantly challenged by bacterial and viral threats. The recognition of pathogenic microorganisms by diverse receptors triggers a variety of host defense mechanisms, leading to their eradication. Toll-like receptors (TLRs), which are type I transmembrane proteins, recognize specific signatures of the invading microbes and activate a cascade of downstream signals inducing the secretion of inflammatory cytokines, chemokines, and type I interferons. The TLR response not only counteracts the pathogens but also initiates and shapes the adaptive immune response. Under normal conditions, inflammation is downregulated after the removal of the pathogen and cellular debris. However, a dysfunctional TLR-mediated response maintains a chronic inflammatory state and leads to local and systemic deleterious effects in host cells and tissues. Such inappropriate TLR response has been attributed to the development and progression of multiple diseases such as cancer, autoimmune, and inflammatory diseases. In this review, we discuss the emerging role of TLRs in the pathogenesis of inflammatory diseases and how targeting of TLRs offers a promising therapeutic strategy for the prevention and treatment of various inflammatory diseases. Additionally, we highlight a number of TLR-targeting agents that are in the developmental stage or in clinical trials.

Toll-like receptors and chronic inflammation in rheumatic diseases: new developments

In the past few years, new developments have been reported on the role of Toll-like receptors (TLRs) in chronic inflammation in rheumatic diseases. The inhibitory function of TLR10 has been demonstrated. Receptors that enhance the function of TLRs, and several TLR inhibitors, have been identified. In addition, the role of the microbiome and TLRs in the onset of rheumatic diseases has been reported. We review novel insights on the role of TLRs in several inflammatory joint diseases, including rheumatoid arthritis, systemic lupus erythematosus, gout and Lyme arthritis, with a focus on the signalling mechanisms mediated by the Toll-IL-1 receptor (TIR) domain, the exogenous and endogenous ligands of TLRs, and the current and future therapeutic strategies to target TLR signalling in rheumatic diseases.

The critical role of toll-like receptors--From microbial recognition to autoimmunity: A comprehensive review

Toll-like receptors (TLRs) constitute an important mechanism in the activation of innate immune cells including monocytes, macrophages and dendritic cells. Macrophage activation by TLRs is pivotal in the initiation of the rapid expression of pro-inflammatory cytokines TNF, IL-1β and IL-6 while promoting Th17 responses, all of which play critical roles in autoimmunity. Surprisingly, in inflammatory arthritis, activation of specific TLRs can not only induce but also inhibit cellular processes associated with bone destruction. The intercellular and intracellular orchestration of signals from different TLRs, their endogenous or microbial ligands and accessory molecules determine the activating or inhibitory responses. Herein, we review the TLR-mediated activation of innate immune cells in their activation and differentiation to osteoclasts and the capacity of these signals to contribute to bone destruction in arthritis. Detailed understanding of the opposing mechanisms of TLRs in the induction and suppression of cellular processes in arthritis may pave the way to develop novel therapies to treat autoimmunity.