Epigenetik bei entzündlichen Systemerkrankungen

In addition to analysis of the genetic code, in recent years more and more studies have concentrated on changes in the epigenetic code. Epigenetic mechanisms determine which genes in a cell are transcribed and thus form the phenotype of a cell. The epigenetic code can be changed by environmental influences, which allows cells to adapt to longstanding changes in the environment. Therefore, it is feasible to assume that epigenetic changes are the molecular basis for long-term effects of the environment on disease development. In particular in tumors and chronic inflammatory diseases epigenetic changes were found to correlate with disease severity and progression. Knowledge about these epigenetic changes might help that epigenetic modifications can be used in the future as biomarkers, prognostic factors and therapeutic targets

Epigenetik bei entzündlichen Systemerkrankungen

Zusammenfassung: In den letzten Jahren wurden neben genetischen Studien immer mehr Analysen von Veränderungen im epigenetischen Code durchgeführt. Epigenetische Mechanismen bestimmen, welche Gene in welcher Zelle transkribiert werden. Damit formen sie den Phänotyp. Der epigenetische Code kann durch Umwelteinflüsse modifiziert werden. Dies ermöglicht den Zellen, sich an lang anhaltende Veränderungen in ihrer Umgebung anzupassen. Daher liegt der Schluss nahe, dass epigenetische Veränderungen die Grundlage für langfristige Auswirkungen von Umwelteinflüssen auf die Gesundheit sein können. Vor allem bei Tumoren und chronisch-entzündlichen Erkrankungen zeigen immer mehr Studien, dass mit dem Krankheitsverlauf epigenetische Veränderungen einhergehen. Das Wissen um epigenetische Veränderungen könnte zukünftig in der Praxis genutzt werden, sowohl als Biomarker und prognostischer Faktor wie auch als therapeutischer Ansatz

Overexpression of toll-like receptors 3 and 4 in synovial tissue from patients with early rheumatoid arthritis: Toll-like receptor expression in early and longstanding arthritis

OBJECTIVE: To analyze the expression, regulation, and biologic relevance of Toll-like receptors (TLRs) 1-10 in synovial and skin fibroblasts and to determine the expression levels of TLRs 2, 3, and 4 in synovial tissues from patients with early rheumatoid arthritis (RA), longstanding RA, and osteoarthritis (OA). METHODS: Expression of TLRs 1-10 in RA synovial fibroblasts (RASFs), OASFs, and skin fibroblasts was analyzed by real-time polymerase chain reaction (PCR). Fibroblasts were stimulated with tumor necrosis factor alpha, interleukin-1beta (IL-1beta), bacterial lipopeptide, poly(I-C), lipopolysaccharide, and flagellin. Production of IL-6 was determined by enzyme-linked immunosorbent assay and induction of TLRs 2-5, matrix metalloproteinases (MMPs) 3 and 13 messenger RNA by real-time PCR. Expression of TLRs 2-4 in synovial tissues was analyzed by immunohistochemistry. RESULTS: Synovial fibroblasts expressed TLRs 1-6, but not TLRs 7-10. Among the expressed TLRs, TLR-3 and TLR-4 were the most abundant in synovial fibroblasts, and stimulation of synovial fibroblasts with the TLR-3 ligand poly(I-C) led to the most pronounced increase in IL-6, MMP-3, and MMP-13. In contrast, skin fibroblasts did not up-regulate MMP-3 or MMP-13 after stimulation with any of the tested stimuli. In synovial tissues from patients with early RA, TLR-3 and TLR-4 were highly expressed and were comparable to the levels of patients with longstanding RA. These expression levels were elevated as compared with those in OA. CONCLUSION: Our findings of high expression of TLRs, particularly TLRs 3 and 4, at an early stage of RA and the reactivity of synovial fibroblasts in vitro to TLR ligands suggest that TLR signaling pathways resulting in persistent inflammation and joint destruction are activated early in the disease process

Abundant expression of the IL-23 subunit p19, but low levels of bioactive IL-23 in the rheumatoid synovium

OBJECTIVE: IL-23, composed of a p19 and a p40 subunit, is suggested to play key roles in rheumatoid arthritis (RA), dependent on the promotion and proliferation of IL-17-producing Th17 T-cells. However, previous studies on IL-23 expression in human tissues were based on p19 only. We aimed to study the expression and regulation of both IL-23 subunits, p19 and p40, in RA compared to osteoarthritis (OA) patients. METHODS: The expression of p19 and p40 in synovial tissues was analyzed by in-situ hybridization and immunohistochemistry. IL-23 in RA and OA synovial fluids and sera was determined by ELISA. TLR-dependent induction of p19, p40 and bioactive IL-23 was determined in RASF, monocytes and MDDC by RT-PCR, Real-time PCR, Western-blot and functional-assays. RESULTS: The p19 subunit was abundantly expressed in RA but not in OA synovial tissues. p19 was most prominently expressed by RASF in the synovial lining layer and at the site of invasion, but no heterodimeric IL-23 was detected at these sites. Correspondingly, soluble IL-23 was not detectable or found at very low levels in synovial fluids and sera of patients with RA. By in-vitro experiments, we confirmed that TLR-activated RASF expressed p19 but not p40, in contrast to monocytes, which produced IL-23 following TLR stimulation. CONCLUSION: The TLR-dependent induction of p19 but not p40 in RASF and the abundant expression of p19 along with the low or undetectable levels of IL-23 in RA patients, gives strong evidence that p19 does not necessarily indicate the presence of IL-23 as it has been proposed so far

Role of synovial fibroblast subsets across synovial pathotypes in rheumatoid arthritis: a deconvolution analysis

OBJECTIVES: To integrate published single-cell RNA sequencing (scRNA-seq) data and assess the contribution of synovial fibroblast (SF) subsets to synovial pathotypes and respective clinical characteristics in treatment-naïve early arthritis. METHODS: In this in silico study, we integrated scRNA-seq data from published studies with additional unpublished in-house data. Standard Seurat, Harmony and Liger workflow was performed for integration and differential gene expression analysis. We estimated single cell type proportions in bulk RNA-seq data (deconvolution) from synovial tissue from 87 treatment-naïve early arthritis patients in the Pathobiology of Early Arthritis Cohort using MuSiC. SF proportions across synovial pathotypes (fibroid, lymphoid and myeloid) and relationship of disease activity measurements across different synovial pathotypes were assessed. RESULTS: We identified four SF clusters with respective marker genes: PRG4(+) SF (CD55, MMP3, PRG4, THY1(neg)); CXCL12(+) SF (CXCL12, CCL2, ADAMTS1, THY1(low)); POSTN(+) SF (POSTN, collagen genes, THY1); CXCL14(+) SF (CXCL14, C3, CD34, ASPN, THY1) that correspond to lining (PRG4(+) SF) and sublining (CXCL12(+) SF, POSTN(+) + and CXCL14(+) SF) SF subsets. CXCL12(+) SF and POSTN(+) + were most prominent in the fibroid while PRG4(+) SF appeared highest in the myeloid pathotype. Corresponding, lining assessed by histology (assessed by Krenn-Score) was thicker in the myeloid, but also in the lymphoid pathotype + the fibroid pathotype. PRG4(+) SF correlated positively with disease severity parameters in the fibroid, POSTN(+) SF in the lymphoid pathotype whereas CXCL14(+) SF showed negative association with disease severity in all pathotypes. CONCLUSION: This study shows a so far unexplored association between distinct synovial pathologies and SF subtypes defined by scRNA-seq. The knowledge of the diverse interplay of SF with immune cells will advance opportunities for tailored targeted treatments

Capture Hi-C identifies a novel causal gene, IL20RA, in the pan-autoimmune genetic susceptibility region 6q23

BACKGROUND: The identification of causal genes from genome-wide association studies (GWAS) is the next important step for the translation of genetic findings into biologically meaningful mechanisms of disease and potential therapeutic targets. Using novel chromatin interaction detection techniques and allele specific assays in T and B cell lines, we provide compelling evidence that redefines causal genes at the 6q23 locus, one of the most important loci that confers autoimmunity risk. RESULTS: Although the function of disease-associated non-coding single nucleotide polymorphisms (SNPs) at 6q23 is unknown, the association is generally assigned to TNFAIP3, the closest gene. However, the DNA fragment containing the associated SNPs interacts through chromatin looping not only with TNFAIP3, but also with IL20RA, located 680 kb upstream. The risk allele of the most likely causal SNP, rs6927172, is correlated with both a higher frequency of interactions and increased expression of IL20RA, along with a stronger binding of both the NFκB transcription factor and chromatin marks characteristic of active enhancers in T-cells. CONCLUSIONS: Our results highlight the importance of gene assignment for translating GWAS findings into biologically meaningful mechanisms of disease and potential therapeutic targets; indeed, monoclonal antibody therapy targeting IL-20 is effective in the treatment of rheumatoid arthritis and psoriasis, both with strong GWAS associations to this region

CARD14 Gain-of-Function Mutation Alone Is Sufficient to Drive IL-23/IL-17-Mediated Psoriasiform Skin Inflammation In Vivo.

Rare autosomal dominant mutations in the gene encoding the keratinocyte signaling molecule CARD14, have been associated with an increased susceptibility to psoriasis, but the physiological impact of CARD14 gain-of-function mutations remains to be fully determined in vivo. Here, we report that heterozygous mice harboring a CARD14 gain-of-function mutation (Card14ΔE138) spontaneously develop a chronic psoriatic phenotype with characteristic scaling skin lesions, epidermal thickening, keratinocyte hyperproliferation, hyperkeratosis, and immune cell infiltration. Affected skin of these mice is characterized by elevated expression of anti-microbial peptides, chemokines, and cytokines (including T helper type 17 cell-signature cytokines) and an immune infiltrate rich in neutrophils, myeloid cells, and T cells, reminiscent of human psoriatic skin. Disease pathogenesis was driven by the IL-23/IL-17 axis, and neutralization of IL-23p19, the key cytokine in maintaining T helper type 17 cell polarization, significantly reduced skin lesions and the expression of antimicrobial peptides and proinflammatory cytokines. Therefore, hyperactivation of CARD14 alone is sufficient to orchestrate the complex immunopathogenesis that drives T helper type 17-mediated psoriasis skin disease in vivo

Toll-Like Receptor (TLR) and Nucleosome-binding Oligomerization Domain (NOD) gene polymorphisms and endometrial cancer risk

Background: Endometrial cancer is the most common gynaecological malignancy in women of developed countries. Many risk factors implicated in endometrial cancer trigger inflammatory events; therefore, alterations in immune response may predispose an individual to disease. Toll-like receptors (TLRs) and nucleosome-binding oligomerization domain (NOD) genes are integral to the recognition of pathogens and are highly polymorphic. For these reasons, the aim of the study was to assess the frequency of polymorphic variants in TLR and NOD genes in an Australian endometrial cancer population. Methods: Ten polymorphisms were genotyped in 191 endometrial cancer cases and 291 controls using real-time PCR: NOD1 (rs2075822, rs2907749, rs2907748), NOD2 (rs5743260, rs2066844, rs2066845), TLR2 (rs5743708), TLR4 (rs4986790) and TLR9 (rs5743836, rs187084). Results: Haplotype analysis revealed that the combination of the variant alleles of the two TLR9 polymorphisms, rs5743836 and rs187084, were protective for endometrial cancer risk: OR 0.11, 95% CI (0.03-0.44), p = 0.002. This result remained highly significant after adjustment for endometrial cancer risk factors and Bonferroni correction for multiple testing. There were no other associations observed for the other polymorphisms in TLR2, TLR4, NOD1 and NOD2. Conclusions: The variant 'C' allele of rs5743836 causes greater TLR9 transcriptional activity compared to the 'T' allele, therefore, higher TLR9 activity may be related to efficient removal of microbial pathogens within the endometrium. Clearly, the association of these TLR9 polymorphisms and endometrial cancer risk must be further examined in an independent population. The results point toward the importance of examining immune response in endometrial tumourgenesis to understand new pathways that may be implicated in disease

Endogenous Galectin-9 Suppresses Apoptosis in Human Rheumatoid Arthritis Synovial Fibroblasts

Galectin-9 (Gal9) has been postulated to have anti-infammatory properties based on the ability of exogenous Gal9 to induce apoptosis in synovial fbroblasts in animal models of rheumatoid arthritis (RA). Here we aimed to assess the potential role of endogenous Galectins, including Gal9, in the infammatory pathology of the RA synovium in humans. Firstly expression of Galectins 1–9 was determined in synovial fbroblasts (RASF) and dermal fbroblasts (DF) isolated from RA patients, the latter representing a non-infamed site. We then further challenged the cells with pro-infammatory TLR agonists and cytokines and assessed Galectin expression. Gal9 was found to be diferentially and abundantly expressed in RASF compared to DF. Agonists of TLR3 and TLR4, along with IFNgamma were also found to induce Gal9 expression in RASF. siRNA was then used to knock-down Gal9 expression in RASF and the efects of this on apoptosis and cell viability were assessed. Increased apoptosis was observed in RASF following Gal9 knock-down. We conclude that, unlike exogenous Gal9, endogenous Gal9 is protective against apoptosis and enhances synovial fbroblast viability suggesting that its role in RA is both pathogenic and pro-infammatory