The expressions of Toll-like receptor 9 and T-bet in circulating B and T cells in newly diagnosed, untreated systemic lupus erythematosus and correlations with disease activity and laboratory data in a Chinese population

Elevated toll-like receptor 9 is associated with disease severity and kidney involvement in systemic lupus erythematosus

OBJECTIVES

Systemic lupus erythematosus (SLE) is associated with the activation of both innate and adaptive immune system. Infection is a significant environmental factor that is responsible for the development of SLE. Toll-like receptors (TLRs) are responsible for recognizing pathogens, and the expression of TLRs has been found to differ in SLE patients. Additionally, various infections have been reported to influence TLR expression. This study aimed to explore the relationship between TLRs and the onset, severity, and symptoms of SLE in the eastern Indian population.

METHODS

The study included 70 SLE patients and a control group matched for age and sex. RT-PCR was used to evaluate mRNA expression of TLRs 2, 4, 7, and 9. Statistical analyses were performed using GraphPad Prism software v.10.2.3.

RESULTS

Patients with SLE expressed significantly higher levels of TLR2 (p < 0.0001) and TLR9 (p = 0.012) than healthy controls. In lupus nephritis, TLR9 expression was higher than in SLE patients without kidney involvement (p = 0.037). Furthermore, a significant relationship was found between TLR9 expression and systemic lupus erythematosus disease activity index (SLEDAI) scores (p < 0.0001, Spearman's r = 0.47), implying the potential role of TLRs in SLE development. However, mRNA expression of TLR4 and TLR7 was not associated with SLE, clinical indices, or disease severity.

CONCLUSIONS

TLR9 is associated with SLE pathogenesis and clinical severity, making it a promising molecule for targeted therapy in SLE management.

Th1-related transcription factors and cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an inflammatory disorder related to immunity dysfunction. The Th1 cell family including Th1 cells, transcription factor T-bet, and related cytokines IFNγ, TNFα, IL-2, IL-18, TGF-β, and IL-12 have been widely discussed in autoimmunity, such as SLE. In this review, we will comprehensively discuss the expression profile of the Th1 cell family in both SLE patients and animal models and clarify how the family members are involved in lupus development. Interestingly, T-bet-related age-associated B cells (ABCs) and low-dose IL-2 treatment in lupus were emergently discussed as well. Collection of the evidence will better understand the roles of the Th1 cell family in lupus pathogenesis, especially targeting IL-2 in lupus.

Association analysis between the TLR9 gene polymorphism rs352140 and type 1 diabetes

Background

To a great extent, genetic factors contribute to the susceptibility to type 1 diabetes (T1D) development, and by triggering immune imbalance, Toll-like receptor (TLR) 9 is involved in the development of T1D. However, there is a lack of evidence supporting a genetic association between polymorphisms in the TLR9 gene and T1D.

Methods

In total, 1513 individuals, including T1D patients (n=738) and healthy control individuals (n=775), from the Han Chinese population were recruited for an association analysis of the rs352140 polymorphism of the TLR9 gene and T1D. rs352140 was genotyped by MassARRAY. The allele and genotype distributions of rs352140 in the T1D and healthy groups and those in different T1D subgroups were analyzed by the chi-squared test and binary logistic regression model. The chi-square test and Kruskal-Wallis H test were performed to explore the association between genotype and phenotype in T1D patients.

Results

The allele and genotype distributions of rs352140 were significantly different in T1D patients and healthy control individuals (p=0.019, p=0.035). Specifically, the T allele and TT genotype of rs352140 conferred a higher risk of T1D (OR=1.194, 95% CI=1.029-1.385, p=0.019, OR=1.535, 95% CI=1.108-2.126, p=0.010). The allele and genotype distributions of rs352140 were not significantly different between childhood-onset and adult-onset T1D and between T1D with a single islet autoantibody and T1D with multiple islet autoantibodies (p=0.603, p=0.743). rs352140 was associated with T1D susceptibility according to the recessive and additive models (p=0.015, p=0.019) but was not associated with T1D susceptibility in the dominant and overdominant models (p=0.117, p=0.928). Moreover, genotype-phenotype association analysis showed that the TT genotype of rs352140 was associated with higher fasting C-peptide levels (p=0.017).

Conclusion

In the Han Chinese population, the TLR9 polymorphism rs352140 is associated with T1D and is a risk factor for susceptibility to T1D.

TLR9 signalling activation via direct ligation and its functional consequences in CD4 + T cells

CpG Oligodeoxynucleotides (ODNs) are established TLR9 ligands; however, their functional responses in CD4+ T cells are believed to be independent of TLR9 and MyD88. We studied ligand-receptor interactions of ODN 2216 and TLR9 in human CD4+ T cells and assessed their consequences in terms of TLR9 signalling and cell phenotype. We demonstrated that the uptake of ODN 2216, a synthetic TLR9 agonist, is controlled by TLR9 signalling molecules and results in an increase in the expression of TLR9 signalling molecules, regulated via a feedback mechanism. Next, the uptake of ODN 2216 resulted in TLR9 signalling dependent but MyD88 independent increase in expression of TGF-β. Finally, ODN 2216 treated CD4+ T cells showed an anti-inflammatory phenotype that was similar to Th3 type of regulatory T cells. These Th3-like cells were able to suppress the proliferation of untreated CD4+ T cells. Collectively, our results demonstrate a direct and interdependent relationship between ODN 2216 uptake and TLR9 signalling in CD4+ T cells. Our findings thus pave the way for future research to explore direct modulation of adaptive immune cells, using innate immune ligands, to subvert exaggerated inflammatory responses.

Adenosine receptor 2a agonists target mouse CD11c+T-bet+ B cells in infection and autoimmunity

CD11c+T-bet+ B cells are recognized as an important component of humoral immunity and autoimmunity. These cells can be distinguished from other B cells by their higher expression of the adenosine receptor 2a. Here we address whether A2A receptor activation can affect CD11c+T-bet+ B cells. We show that administration of the A2A receptor agonist CGS-21680 depletes established CD11c+T-bet+ B cells in ehrlichial-infected mice, in a B cell-intrinsic manner. Agonist treatment similarly depletes CD11c+T-bet+ B cells and CD138+ B cells and reduces anti-nuclear antibodies in lupus-prone mice. Agonist treatment is also associated with reduced kidney pathology and lymphadenopathy. Moreover, A2A receptor stimulation depletes pathogenic lymphocytes and ameliorates disease even after disease onset, highlighting the therapeutic potential of this treatment. This study suggests that targeting the adenosine signaling pathway may provide a method for the treatment of lupus and other autoimmune diseases mediated by T-bet+ B cells.

Association of toll-like receptor 9 expression with prognosis of systemic lupus erythematosus

The current study assessed the association between toll-like receptor 9 (TLR9) and systemic lupus erythematosus (SLE) and subsequently determined the predictive value of TLR9 in assessing the prognosis of SLE. A total of 90 newly diagnosed patients with SLE and 49 healthy control subjects were enrolled in the current study. The expression of TLR9 mRNA was measured in whole blood samples from patients and controls. All patients were followed up for ≥2 years and their clinical parameters were recorded. After 2 years, 30 patients were randomly chosen from patient subgroups with high (n=20) or low (n=10) TLR9 levels and the expression of TLR9 mRNA were measured again. Cox proportional hazards regression was used to identify the risk factors of SLE prognosis. Patients with SLE and high SLE disease activity exhibited significantly increased TLR9 expression (P<0.05). Persistent proteinuria of >0.5 g/day [hazard ratio (HR), 6.314; 95% confidence interval (CI), 2.858-13.947], C-reactive protein levels (HR, 1.013; 95% CI, 1.007-1.019) and high-TLR9 mRNA expression (HR, 3.852; 95% CI, 1.931-7.684) were independent risk factors of poor prognosis during a 2-year follow-up period, whereas patient treatment with >1 immunosuppressant (HR, 0.374; 95% CI, 0.173-0.808) was a factor indicating favorable prognosis. Furthermore, the expression of TLR9 mRNA remained high in patients with poor prognosis at the end of a 2-year follow-up period but in patients with a favorable prognosis, TLR9 mRNA expression was significantly reduced compared with the levels measured at SLE onset (P<0.0001). Therefore, the expression of TLR9 mRNA in whole blood samples at SLE onset is associated with SLE disease activity and its expression may be used as an indicator of poor prognosis in patients with SLE.

Type I and II interferons commit to abnormal expression of chemokine receptor on B cells in patients with systemic lupus erythematosus

Memory B cells are increased in systemic lupus erythematosus (SLE) cases, but the qualitative abnormalities and induction mechanism of these cells are unclear. Here, we subclassified B cells by their chemokine receptor expression and investigated their induction mechanism. The peripheral blood of patients with SLE showed higher levels of CXCR5^- and CXCR3⁺ B cells. CXCR5^-CXCR3⁺ B cell levels were elevated in patients with active SLE, which decreased with improving disease conditions. Interferon (IFN)-γ stimulation increased CXCR3 expression, whereas IFN-β stimulation reduced CXCR5 expression in B cells. Furthermore, CXCR5^-CXCR3⁺ B cells were induced by a combination of IFN-β and IFN-γ stimulation. Renal tissue examination of patients with active lupus nephritis confirmed the presence of CD19⁺CXCR3⁺ B cells. Collectively, the results revealed qualitative abnormalities accompanying reduced CXCR5 expression via type I IFN and enhanced CXCR3 expression via type II IFN in SLE, suggesting their involvement in B cell infiltration into tissues and inflammatory pathogenesis.

The Role of Nucleic Acid Sensing in Controlling Microbial and Autoimmune Disorders

Innate immunity, the first line of defense against invading pathogens, is an ancient form of host defense found in all animals, from sponges to humans. During infection, innate immune receptors recognize conserved molecular patterns, such as microbial surface molecules, metabolites produces during infection, or nucleic acids of the microbe's genome. When initiated, the innate immune response activates a host defense program that leads to the synthesis proteins capable of pathogen killing. In mammals, the induction of cytokines during the innate immune response leads to the recruitment of professional immune cells to the site of infection, leading to an adaptive immune response. While a fully functional innate immune response is crucial for a proper host response and curbing microbial infection, if the innate immune response is dysfunctional and is activated in the absence of infection, autoinflammation and autoimmune disorders can develop. Therefore, it follows that the innate immune response must be tightly controlled to avoid an autoimmune response from host-derived molecules, yet still unencumbered to respond to infection. In this review, we will focus on the innate immune response activated from cytosolic nucleic acids, derived from the microbe or host itself. We will depict how viruses and bacteria activate these nucleic acid sensing pathways and their mechanisms to inhibit the pathways. We will also describe the autoinflammatory and autoimmune disorders that develop when these pathways are hyperactive. Finally, we will discuss gaps in knowledge with regard to innate immune response failure and identify where further research is needed.

Suppression of Th1 and Th17 Responses and Induction of Treg Responses by IL-18-Expressing Plasmid Gene Combined with IL-4 on Collagen-Induced Arthritis

OBJECTIVES

IL-18 is a proinflammatory cytokine with multiple immunoregulatory properties. We studied the effect of IL-18 gene therapy on the development of murine collagen-induced arthritis (CIA).

METHODS

Plasmid pCAGGS-IL-18 along or in combination with IL-10 or IL-4 was administered to CIA mice. The incidence and severity of arthritis of the paws were determined by a visual scale. Joint destruction was determined by histology. The levels of a panel of cytokines and transcription factors in the synovium were determined by reverse transcription polymerase chain reaction and quantitative RT-PCR. Quantitative RT-PCR was employed to detect the mRNA expression of TLRs and their pathway on the surface of DCs.

RESULTS

IL-18 gene therapy had no therapeutic effect on CIA mice. Additional coadministration with low dosage of recombinant IL-4 ameliorated the disease progression. Histopathological examination of the joints showed intact cartilage surface in IL-18 gene combined with IL-4-treated mice. The synovium of IL-18 gene combined with rIL4-treated mice had lower expression of TNF-α, IFN-γ, and IL-17 and higher expression of IL-10. The mechanism of this response appeared to involve modulation of transcription factors FoxP3 and GATA-3. The DCs in the spleen and lymph nodes of IL-18 gene combined with rIL4-treated mice had lower expression of TLR2, MyD88, and NF-kB.

CONCLUSIONS

Our findings indicate that pIL-18 gene combined with IL-4 ameliorates arthritis in the CIA mouse by suppression of Th1 and Th17 cytokines and increasing expression of FoxP3 and GATA-3. The plasmid backbone and multiple immunoregulatory properties of IL-18 appear to play a major role in the pIL-18 coadministration with rIL-4-mediated immunomodulation of arthritis through blocking the TLR2/MyD88/NF-kappa B signaling pathway.

The role of the innate immune system in destruction of pancreatic beta cells in NOD mice and humans with type I diabetes

Type 1 diabetes (T1D) is an organ-specific autoimmune disease characterized by T cell-mediated destruction of the insulin-producing pancreatic β cells. A combination of genetic and environmental factors eventually leads to the loss of functional β cell mass and hyperglycemia. Both innate and adaptive immunity are involved in the development of T1D. In this review, we have highlighted the most recent findings on the role of innate immunity, especially the pattern recognition receptors (PRRs), in disease development. In murine models and human studies, different PRRs, such as toll-like receptors (TLRs) and nucleotide-binding domain, leucine-rich repeat-containing (or Nod-like) receptors (NLRs), have different roles in the pathogenesis of T1D. These PRRs play a critical role in defending against infection by sensing specific ligands derived from exogenous microorganisms to induce innate immune responses and shape adaptive immunity. Animal studies have shown that TLR7, TLR9, MyD88 and NLPR3 play a disease-predisposing role in T1D, while controversial results have been found with other PRRs, such as TLR2, TLR3, TLR4, TLR5 and others. Human studies also shown that TLR2, TLR3 and TLR4 are expressed in either islet β cells or infiltrated immune cells, indicating the innate immunity plays a role in β cell autoimmunity. Furthermore, some human genetic studies showed a possible association of TLR3, TLR7, TLR8 or NLRP3 genes, at single nucleotide polymorphism (SNP) level, with human T1D. Increasing evidence suggest that the innate immunity modulates β cell autoimmunity. Thus, targeting pathways of innate immunity may provide novel therapeutic strategies to fight this disease.

Toll-like receptors and B cells: functions and mechanisms

Numerous reports have described Toll-like receptor (TLR) functions in myeloid cells such as dendritic cells (DCs) and macrophages, but relatively fewer studies have examined TLR responses in B lymphocytes. B cells express a wide variety of TLRs and are highly activated after TLR ligation, leading to enhancements in B cell survival, surface molecule expression, cytokine and antibody production, and antigen presentation. During an immune response, B cells can receive signals through TLRs as well as the B cell antigen receptor (BCR) and/or CD40. TLR ligation synergizes with signals through these receptors and augments both innate and adaptive immune functions of B lymphocytes. Additionally, targeting B cell TLRs may provide new therapies against certain types of cancer as well as autoimmune diseases. Here, we summarize TLR expression and contributions to both normal and pathogenic functions in mouse and human B cells.

Genetic polymorphisms of dsRNA ligating pattern recognition receptors TLR3, MDA5, and RIG-I. Association with systemic lupus erythematosus and clinical phenotypes

This study aimed to demonstrate possible associations between genetic polymorphisms in Toll-like receptor 3, interferon induced with helicase C domain 1 (IFIH1) and DEAD (Asp-Glu-Ala-Asp) box polypeptide 58 and systemic lupus erythematosus (SLE), including the phenotypes lupus nephritis and malar rash, as well as the presence of autoantibodies against nucleic acid-containing complexes. Genotyping was carried out in two Danish cohorts [Copenhagen (CPH) and Odense (ODE)] totaling 344 patients and was compared with 641 previously genotyped healthy controls. In the ODE cohort, the patients were only genotyped for the rs1990760 polymorphism of IFIH1. Single nucleotide polymorphisms (SNPs) were determined by a multiplex bead-based assay (CPH cohort) or real-time PCR (ODE cohort). Associations were investigated using the Cochran-Armitage trend test. The odds ratio (OR) for minor allele homozygotes versus major allele homozygotes suggested a protective effect of the IFIH1 rs1990760 SNP for SLE in the ODE cohort [OR 0.52, 95 % confidence intervals (95 % CI) 0.31-0.88, Pcorr. = 0.05] but not in the CPH cohort, although the OR suggested a trend in the same direction, and when combining the two patient cohorts, ORs were 0.57, 95 % CI 0.37-0.88. None of the other investigated polymorphisms showed any association with SLE. Regarding phenotypes, we found a statistically significant association between rs1990760 and malar rash in the CPH cohort, with ORs suggesting a protective effect (OR 0.28, 95 % CI 0.13-0.62 for heterozygotes and OR 0.11, 95 % CI 0.03-0.41 for homozygotes, Pcorr. = 0.0001). There were no significant associations between rs1990760 and presence of anti-dsDNA, anti-U1RNP, or anti-Smith antibodies. Our study supports previous findings of an association between the rs1990760 polymorphism of IFIH1 and SLE and indicates that this SNP may also be associated with malar rash in SLE patients although this finding needs confirmation.

Expression of toll-like receptors 3, 7, and 9 in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown aetiology. The results of experimental studies point to the involvement of innate immunity receptors-toll-like receptors (TLR)-in the pathogenesis of the disease. The aim of the study was to assess the expression of TLR3, 7, and 9 in the population of peripheral blood mononuclear cells (PBMC) and in B lymphocytes (CD19(+)), T lymphocytes (CD4(+) and CD8(+)) using flow cytometry. The study group included 35 patients with SLE and 15 healthy controls. The patient group presented a significantly higher percentage of TLR3- and TLR9-positive cells among all PBMCs and their subpopulations (CD3(+), CD4(+), CD8(+), and CD19(+) lymphocytes) as well as TLR7 in CD19(+) B-lymphocytes, compared to the control group. There was no correlation between the expression of all studied TLRs and the disease activity according to the SLAM scale, and the degree of organ damage according to the SLICC/ACR Damage Index. However, a correlation was observed between the percentage of various TLR-positive cells and some clinical (joint lesions) and laboratory (lymphopenia, hypogammaglobulinemia, anaemia, and higher ESR) features and menopause in women. The results of the study suggest that TLR3, 7, and 9 play a role in the pathogenesis of SLE and have an impact on organ involvement in SLE.

TLR7 and TLR9 in SLE: when sensing self goes wrong

Autoreactive B and T cells are present in healthy, autoimmunity-free individuals, but they are kept in check by various regulatory mechanisms. In systemic lupus erythematosus (SLE) patients, however, autoreactive cells are expanded, activated, and produce large quantities of autoantibodies, directed especially against nuclear antigens. These antibodies form immune complexes with self-nucleic acids present in SLE serum. Since self-DNA and self-RNA in the form of protein complexes can act as TLR9 and TLR7 ligands, respectively, TLR stimulation is suggested as an additional signal contributing to activation and/or modulation of the aberrant adaptive immune response. Data from mouse models suggest a pathogenic role for TLR7 and a protective role for TLR9 in the pathogenesis of SLE. Future investigations are needed to elucidate the underlying modulatory mechanisms and the role of TLR7 and TLR9 in the complex pathogenesis of human SLE.

The largely normal response to Toll-like receptor 7 and 9 stimulation and the enhanced expression of SIGIRR by B cells in systemic lupus erythematosus

Background

Altered Toll-like receptor (TLR) signaling has been implicated in the pathogenesis of systemic lupus erythematosus (SLE). The present study was undertaken to characterize responses of B cells from SLE patients to TLR7 and TLR9 stimulation and to explore the potential role of single immunoglobulin interleukin-1 receptor related molecule (SIGIRR) in the regulation of TLR-mediated responses of SLE B cells.

Methodology/Principal Findings

Peripheral blood mononuclear cells (PBMC) were isolated from 64 patients with SLE and 37 healthy donors. CD19+ B cells purified using microbeads were cultured with TLR7 or TLR9 agonists. Cell proliferation was measured by thymine incorporation and the frequency of antibody-secreting cells was determined by ELISPOT assay. SIGIRR expression in PBMCs and B cells was analyzed using flow cytometry analysis. In contrast to the enhanced proliferation following B cell receptor (BCR) engagement, B cells from SLE patients exhibited a virtually normal proliferative response to TLR7 or TLR9 stimulation. Moreover, B cells from SLE patients and healthy donors were almost equally competent to differentiate into antibody-secreting cells upon TLR engagement except for a reduction in the generation of IgG-secreting cells by TLR9-stimulated lupus B cells. In line with these somehow unexpected observations, SLE B cells were found to express a significantly higher level of SIGIRR than normal B cells.

Conclusions/Significance

Despite the reported upregulation of TLR7 and TLR9 expression in B cell from SLE patients, their responses to TLR stimulation were largely normal. The increased expression of the negative regulator SIGIRR may be partly responsible for the “balance of terror”.

Differentiation and transplantation of functional pancreatic beta cells generated from induced pluripotent stem cells derived from a type 1 diabetes mouse model

The nonobese diabetic (NOD) mouse is a classical animal model for autoimmune type 1 diabetes (T1D), closely mimicking features of human T1D. Thus, the NOD mouse presents an opportunity to test the effectiveness of induced pluripotent stem cells (iPSCs) as a therapeutic modality for T1D. Here, we demonstrate a proof of concept for cellular therapy using NOD mouse-derived iPSCs (NOD-iPSCs). We generated iPSCs from NOD mouse embryonic fibroblasts or NOD mouse pancreas-derived epithelial cells (NPEs), and applied directed differentiation protocols to differentiate the NOD-iPSCs toward functional pancreatic beta cells. Finally, we investigated whether the NPE-iPSC-derived insulin-producing cells could normalize hyperglycemia in transplanted diabetic mice. The NOD-iPSCs showed typical embryonic stem cell-like characteristics such as expression of markers for pluripotency, in vitro differentiation, teratoma formation, and generation of chimeric mice. We developed a method for stepwise differentiation of NOD-iPSCs into insulin-producing cells, and found that NPE-iPSCs differentiate more readily into insulin-producing cells. The differentiated NPE-iPSCs expressed diverse pancreatic beta cell markers and released insulin in response to glucose and KCl stimulation. Transplantation of the differentiated NPE-iPSCs into diabetic mice resulted in kidney engraftment. The engrafted cells responded to glucose by secreting insulin, thereby normalizing blood glucose levels. We propose that NOD-iPSCs will provide a useful tool for investigating genetic susceptibility to autoimmune diseases and generating a cellular interaction model of T1D, paving the way for the potential application of patient-derived iPSCs in autologous beta cell transplantation for treating diabetes.

Chaetoglobosin F, a small molecule compound, possesses immunomodulatory properties on bone marrow-derived dendritic cells via TLR9 signaling pathway

Chaetoglobosin F (Cha F), a cytochalasan-based alkaloid, was obtained from the EtOAc extract of a solid culture of Chaetomium globosum IFB-E019. Dendritic cells (DCs), the most potent antigen presenting cells, are considered as the major target in the modulation of excessive immune responses. Recognition of CpG-DNA by Toll-like receptor 9 (TLR9) on DCs is an important step in the pathogenesis of autoimmune diseases. However, the effect of Cha F on the maturation and immunostimulatory function of CpG-stimulated DCs remains unclear. This study investigated the effects of Cha F on bone marrow (BM)-derived DCs. We found that Cha F inhibits the CpG-induced DCs maturation and function by suppressing the expression of surface molecules (CD40, CD80, CD86 and MHC-II), reducing the production of cytokines and chemokines (IL-12 and CXCL-10), inhibiting the CpG-induced DCs-elicited allogeneic T-cell proliferation, and impairing the migration ability to chemokines. The Cha F-treated DCs were highly efficient at Ag capture, via mannose receptor-mediated endocytosis. Additionally, Cha F was also demonstrated to inhibit CpG-induced activation of MAPKs (p38 and JNK, but not ERK) and the nuclear translocation of NF-κB and STAT1. Furthermore, we confirmed that Cha F was able to suppress TLR9 expression of CpG-induced DCs. Collectively, these findings provide novel insight into the immunopharmacological functions of Cha F, especially with regard to their impact on CpG-induced DCs. These immunosuppressive properties of Cha F may prove useful in controlling DCs-associated autoimmune and/or inflammatory diseases.

Expression of Toll-like receptors and their detection of nuclear self-antigen leading to immune activation in JSLE

OBJECTIVES

Toll-like receptors (TLRs) essential in the functioning of the immune system have been implicated in the development of autoimmunity. TLR3, 7, 8 and 9 are capable of recognizing nucleic autoantigens typical of SLE. Their expression correlates positively with disease activity in adult-onset SLE. This study aimed to determine the role of TLRs in JSLE and whether apoptotic neutrophils are a source of nuclear autoantigen being detected through TLR3, 7, 8 and 9, leading to an inflammatory response.

METHODS

TLR3, 7, 8 and 9 mRNA and protein expression were measured in peripheral blood mononuclear cells (PBMCs) in JSLE patients compared with JIA and non-inflammatory controls. Activation of the TLRs by JSLE serum-induced apoptotic neutrophils was detected by measuring IFN-α mRNA and protein expression, and confirmed using myeloid differentiation factor 88 (MyD88) and TIR domain-containing adapter-inducing IFN-β (TRIF) inhibitors.

RESULTS

JSLE patients have increased TLR3, 8 and 9 mRNA and protein expression compared with controls (P < 0.05). Incubation of PBMCs with apoptotic neutrophils demonstrated a dose-response relationship for IFN-α mRNA expression. Inhibition of TLR signalling by blocking MyD88 and TRIF signalling decreased IFN-α mRNA expression in PBMCs incubated with apoptotic neutrophils (P < 0.05).

CONCLUSIONS

This study demonstrated significantly increased TLR expression in JSLE compared with controls. Our data indicate that apoptotic neutrophils trigger TLR activation through their presentation of autoantigens. The role of TLRs in this inflammatory response was demonstrated by a dose-response relationship to apoptotic neutrophil concentration and confirmed by a decrease in IFN-α production after inhibition of TLR signalling.

DNA from Porphyromonas gingivalis and Tannerella forsythia induce cytokine production in human monocytic cell lines

Toll-like receptor 9 (TLR9) expression is increased in periodontally diseased tissues compared with healthy sites indicating a possible role of TLR9 and its ligand, bacterial DNA (bDNA), in periodontal disease pathology. Here, we determine the immunostimulatory effects of periodontal bDNA in human monocytic cells (THP-1). THP-1 cells were stimulated with DNA of two putative periodontal pathogens: Porphyromonas gingivalis and Tannerella forsythia. The role of TLR9 in periodontal bDNA-initiated cytokine production was determined either by blocking TLR9 signaling in THP-1 cells with chloroquine or by measuring IL-8 production and nuclear factor-kappaB (NF-kappaB) activation in HEK293 cells stably transfected with human TLR9. Cytokine production (IL-1beta, IL-6, and TNF-alpha) was increased significantly in bDNA-stimulated cells compared with controls. Chloroquine treatment of THP-1 cells decreased cytokine production, suggesting that TLR9-mediated signaling pathways are operant in the recognition of DNA from periodontal pathogens. Compared with native HEK293 cells, TLR9-transfected cells demonstrated significantly increased IL-8 production (P < 0.001) and NF-kappaB activation in response to bDNA, further confirming the role of TLR9 in periodontal bDNA recognition. The results of PCR arrays demonstrated upregulation of proinflammatory cytokine and NF-kappaB genes in response to periodontal bDNA in THP-1 cells, suggesting that cytokine induction is through NF-kappaB activation. Hence, immune responses triggered by periodontal bacterial nucleic acids may contribute to periodontal disease pathology by inducing proinflammatory cytokine production through the TLR9 signaling pathway.

Nucleic acid sensing receptors in systemic lupus erythematosus: development of novel DNA- and/or RNA-like analogues for treating lupus

Double-stranded (ds) DNA, DNA- or RNA-associated nucleoproteins are the primary autoimmune targets in SLE, yet their relative inability to trigger similar autoimmune responses in experimental animals has fascinated scientists for decades. While many cellular proteins bind non-specifically negatively charged nucleic acids, it was discovered only recently that several intracellular proteins are involved directly in innate recognition of exogenous DNA or RNA, or cytosol-residing DNA or RNA viruses. Thus, endosomal Toll-like receptors (TLR) mediate responses to double-stranded RNA (TLR-3), single-stranded RNA (TLR-7/8) or unmethylated bacterial cytosine (phosphodiester) guanine (CpG)-DNA (TLR-9), while DNA-dependent activator of IRFs/Z-DNA binding protein 1 (DAI/ZBP1), haematopoietic IFN-inducible nuclear protein-200 (p202), absent in melanoma 2 (AIM2), RNA polymerase III, retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) mediate responses to cytosolic dsDNA or dsRNA, respectively. TLR-induced responses are more robust than those induced by cytosolic DNA- or RNA- sensors, the later usually being limited to interferon regulatory factor 3 (IRF3)-dependent type I interferon (IFN) induction and nuclear factor (NF)-kappaB activation. Interestingly, AIM2 is not capable of inducing type I IFN, but rather plays a role in caspase I activation. DNA- or RNA-like synthetic inhibitory oligonucleotides (INH-ODN) have been developed that antagonize TLR-7- and/or TLR-9-induced activation in autoimmune B cells and in type I IFN-producing dendritic cells at low nanomolar concentrations. It is not known whether these INH-ODNs have any agonistic or antagonistic effects on cytosolic DNA or RNA sensors. While this remains to be determined in the future, in vivo studies have already shown their potential for preventing spontaneous lupus in various animal models of lupus. Several groups are exploring the possibility of translating these INH-ODNs into human therapeutics for treating SLE and bacterial DNA-induced sepsis.