Epigenetic contributions in the development of rheumatoid arthritis

Regulation of cytokine and chemokine expression by histone lysine methyltransferase MLL1 in rheumatoid arthritis synovial fibroblasts

Histone lysine methylation is thought to play a role in the pathogenesis of rheumatoid arthritis (RA). We previously reported aberrant expression of the gene encoding mixed-lineage leukemia 1 (MLL1), which catalyzes methylation of histone H3 lysine 4 (H3K4), in RA synovial fibroblasts (SFs). The aim of this study was to elucidate the involvement of MLL1 in the activated phenotype of RASFs. SFs were isolated from synovial tissues obtained from patients with RA or osteoarthritis (OA) during total knee joint replacement. MLL1 mRNA and protein levels were determined after stimulation with tumor necrosis factor α (TNFα). We also examined changes in trimethylation of H3K4 (H3K4me3) levels in the promoters of RA-associated genes (matrix-degrading enzymes, cytokines, and chemokines) and the mRNA levels upon small interfering RNA-mediated depletion of MLL1 in RASFs. We then determined the levels of H3K4me3 and mRNAs following treatment with the WD repeat domain 5 (WDR5)/MLL1 inhibitor MM-102. H3K4me3 levels in the gene promoters were also compared between RASFs and OASFs. After TNFα stimulation, MLL1 mRNA and protein levels were higher in RASFs than OASFs. Silencing of MLL1 significantly reduced H3K4me3 levels in the promoters of several cytokine (interleukin-6 [IL-6], IL-15) and chemokine (C-C motif chemokine ligand 2 [CCL2], CCL5, C-X-C motif chemokine ligand 9 [CXCL9], CXCL10, CXCL11, and C-X3-C motif chemokine ligand 1 [CX3CL1]) genes in RASFs. Correspondingly, the mRNA levels of these genes were significantly decreased. MM-102 significantly reduced the promoter H3K4me3 and mRNA levels of the CCL5, CXCL9, CXCL10, and CXCL11 genes in RASFs. In addition, H3K4me3 levels in the promoters of the IL-6, IL-15, CCL2, CCL5, CXCL9, CXCL10, CXCL11, and CX3CL1 genes were significantly higher in RASFs than OASFs. Our findings suggest that MLL1 regulates the expression of particular cytokines and chemokines in RASFs and is associated with the pathogenesis of RA. These results could lead to new therapies for RA.

DNA hypomethylation ameliorates erosive inflammatory arthritis by modulating interferon regulatory factor-8

Epigenetic regulation plays a crucial role in the pathogenesis of autoimmune diseases such as inflammatory arthritis. DNA hypomethylating agents, such as decitabine (DAC), have been shown to dampen inflammation and restore immune homeostasis. In the present study, we demonstrate that DAC elicits potent anti-inflammatory effects and attenuates disease symptoms in several animal models of arthritis. Transcriptomic and epigenomic profiling show that DAC-mediated hypomethylation regulates a wide range of cell types in arthritis, altering the differentiation trajectories of anti-inflammatory macrophage populations, regulatory T cells, and tissue-protective synovial fibroblasts (SFs). Mechanistically, DAC-mediated demethylation of intragenic 5'-Cytosine phosphate Guanine-3' (CpG) islands of the transcription factor Irf8 (interferon regulatory factor 8) induced its re-expression and promoted its repressor activity. As a result, DAC restored joint homeostasis by resetting the transcriptomic signature of negative regulators of inflammation in synovial macrophages (MerTK, Trem2, and Cx3cr1), TREGs (Foxp3), and SFs (Pdpn and Fapα). In conclusion, we found that Irf8 is necessary for the inhibitory effect of DAC in murine arthritis and that direct expression of Irf8 is sufficient to significantly mitigate arthritis.

Upregulation of KAT2B and ESCO2 gene expression level in patients with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune condition that causes progressive inflammation. It seems that alternations in epigenetic modifications contribute to RA development. The present study aimed to assess the expression pattern of K (lysine) acetyltransferase 1 (KAT1; HAT1) and lysine acetyltransferase 2B (KAT2B; PCAF), and the establishment of sister chromatid cohesion N-acetyltransferase 2 (ESCO2) in peripheral blood mononuclear cells (PBMCs) from RA patients.

METHOD AND MATERIAL

In this case-control study, we studied 50 cases with RA in comparison to 50 age- and gender-matched healthy subjects. Separation of PBMCs samples from whole blood, extraction of RNA, and reverse transcription were performed. Gene transcript levels of KAT1, KAT2B, and ESCO2 were determined using SYBR green real-time quantitative PCR.

RESULTS

Our results exhibited a significant upregulation in the expression levels of ESCO2 and KAT2B genes in patients with RA compared to normal individuals (P-value < 0.0001). Similarly, we observed higher expression of KAT1 in the patients' group when compared to the healthy controls, although the difference in expression level failed to show any significant changes (P-value = 0.485). Also, we found a positive correlation between ESCO2 and the level of erythrocyte sedimentation rate (ESR) in patients.

CONCLUSION

Collectively, our results suggest that upregulated expression of KAT2B and ESCO2 genes may be correlated to RA development. Further studies with larger sample sizes are required for understanding the potential contribution of these enzymes in the pathology of RA. Key Points • Dysregulated expression level of epigenetics enzymes was observed in PBMCs from RA patients. • The expression of KAT2B was 2.44 times higher in the PBMCs of RA patients than in the healthy subjects. • The expression of ESCO2 was upregulated (2.75 times) in the PBMCs of RA patients compared to the control group. • There was a positive correlation between ESCO2 expression and the ESR level in patients.

Identification of a Novel Serological Marker in Seronegative Rheumatoid Arthritis Using the Peptide Library Approach

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation mainly affecting the joints leading to cartilage and bone destruction. The definition of seropositive or seronegative RA is based on the presence or absence of rheumatoid factor (RF) and anti-citrullinated peptide antibodies (ACPAs). Other autoantibodies have been identified in the last decade such as antibodies directed against carbamylated antigens, peptidyl-arginine deiminase type 4 and v-Raf murine sarcoma viral oncogene homologue B. In order to identify relevant autoantigens, we screened a random peptide library (RPL) with pooled IgGs obtained from 50 patients with seronegative RA. Patients’ sera were then used in an ELISA test to identify the most frequently recognized peptide among those obtained by screening the RPL. Sera from age- and sex-matched healthy subjects were used as controls. We identified a specific peptide (RA-peptide) recognized by RA patients’ sera, but not by healthy subjects or by patients with other immune-mediated diseases. The majority of sera from seronegative and seropositive RA patients (73.8% and 63.6% respectively) contained IgG antibodies directed against the RA-peptide. Interestingly, this peptide shares homology with some self-antigens, such as Protein-tyrosine kinase 2 beta, B cell scaffold protein, Liprin-alfa1 and Cytotoxic T lymphocyte protein 4. Affinity purified anti-RA-peptide antibodies were able to cross react with these autoantigens. In conclusion, we identified a peptide that is recognized by seropositive and, most importantly, by seronegative RA patients’ sera, but not by healthy subjects, conferring to this epitope a high degree of specificity. This peptide shares also homology with other autoantigens which can be recognized by autoantibodies present in seronegative RA sera. These newly identified autoantibodies, although present also in a percentage of seropositive RA patients, may be considered as novel serum biomarkers for seronegative RA, which lacks the presence of RF and/or ACPAs.

Cell-specific epigenetic drivers of pathogenesis in rheumatoid arthritis

Rheumatoid arthritis is a complex, inflammatory autoimmune disease, which is characterized by pain, swelling and joint damage driven by the altered behavior of a number of different cell types such as synovial fibroblasts macrophages and lymphocytes. The mechanism underlying pathogenesis is unclear but increasing evidence points to altered epigenetic regulation within these cell types which promotes the activated destructive behavior that underlies disease pathogenesis. This review summarizes the key epigenetic modifications in the most important cells types in rheumatoid arthritis, which are associated with disease activity. We also discuss emerging avenues of research focusing on readers of epigenetic markers which may serve to be potential therapeutic targets.

Electrospun Scaffold Micro-Architecture Induces an Activated Transcriptional Phenotype within Tendon Fibroblasts

Biomaterial augmentation of surgically repaired rotator cuff tendon tears aims to improve the high failure rates (∼40%) of traditional repairs. Biomaterials that can alter cellular phenotypes through the provision of microscale topographical cues are now under development. We aimed to systematically evaluate the effect of topographic architecture on the cellular phenotype of fibroblasts from healthy and diseased tendons. Electrospun polydioxanone scaffolds with fiber diameters ranging from 300 to 4000 nm, in either a highly aligned or random configuration, were produced. Healthy tendon fibroblasts cultured for 7 days on scaffolds with highly aligned fibers demonstrated a distinctive elongated morphology, whilst those cultured on randomly configured fibers demonstrated a flattened and spread morphology. The effect of scaffold micro-architecture on the transcriptome of both healthy and diseased tendon fibroblasts was assessed with bulk RNA-seq. Both healthy (n = 3) and diseased tendon cells (n = 3) demonstrated a similar transcriptional response to architectural variants. Gene set enrichment analysis revealed that large diameter (≥2000 nm) aligned scaffolds induced an upregulation of genes involved in cellular replication and a downregulation of genes defining inflammatory responses and cell adhesion. Similarly, PDPN and CD248, markers of inflammatory or "activated" fibroblasts, were downregulated during culture of both healthy and diseased fibroblasts on aligned scaffolds with large (≥2000 nm) fiber diameters. In conclusion scaffold architectures resembling that of disordered type III collagen, typically present during the earlier phases of wound healing, resulted in tendon fibroblast activation. Conversely, scaffolds mimicking aligned diameter collagen I fibrils, present during tissue remodelling, did not activate tendon derived fibroblasts. This has implications for the design of scaffolds used during rotator cuff repair augmentation.

Hypermethylation of the miR-155 gene in the whole blood and decreased plasma level of miR-155 in rheumatoid arthritis

Objectives

miR-155 plays a critical role in the inflammatory process and in diseases such as rheumatoid arthritis (RA). miR155 gene expression is regulated by its gene promoter region CpG island methylation. Previous studies have shown inconsistent changes in circulating levels of mir-155 in RA patients. The aims of our study were to evaluate miR-155 levels in plasma, to investigate its gene methylation level, and to correlate these levels with RA disease activity.

Methods

One hundred and twenty-five patients with RA, and 30 age and sex-matched healthy controls (HC) were enrolled. Whole blood and plasma samples were collected and stored at -80°C until analysis. DAS28 score at the time of the blood draw was used to assess RA disease activity. The methylation status of miR-155 host gene was determined in whole blood by quantitative real-time methylation-specific PCR (qPCR). miR-155 expression levels were evaluated by quantitative reverse transcription PCR.

Results

We found significantly lower circulating miR155 levels in RA patients compared to HC. Interestingly, the miR-155 gene methylation level was significantly higher in RA patients than in HC. miR-155 levels did not correlate with ACPA or RF positivity or disease activity.

Conclusions

We show here higher miR-155 methylation in whole blood and lower plasma miR155 expression in RA patients in comparison to HC. The evaluation of miR-155 host gene methylation status or miR155 plasma level might be a potentially useful marker in RA determination.

Epigenetics in rheumatoid arthritis; fibroblast-like synoviocytes as an emerging paradigm in the pathogenesis of the disease

Rheumatoid arthritis (RA) is characterized by immune dysfunctions and chronic inflammation that mainly affects diarthrodial joints. Genetics has long been surveyed in searching for the etiopathogenesis of the disease and partially clarified the conundrums within this context. Epigenetic alterations, such as DNA methylation, histone modifications, and noncoding RNAs, which have been considered to be involved in RA pathogenesis, likely explain the nongenetic risk factors. Epigenetic modifications may influence RA through fibroblast-like synoviocytes (FLSs). It has been shown that FLSs play an essential role in the onset and exacerbation of RA, and therefore, they may illustrate some aspects of RA pathogenesis. These cells exhibit a unique DNA methylation profile in the early stage of the disease that changes with disease progression. Histone acetylation profile in RA FLSs is disrupted through the imbalance of histone acetyltransferases and histone deacetylase activity. Furthermore, dysregulation of microRNAs (miRNAs) is immense. Most of these miRNAs have shown an aberrant expression in FLSs that are involved in proliferation and cytokine production. Besides, dysregulation of long noncoding RNAs in FLSs has been revealed and attributed to RA pathogenesis. Further investigations are needed to get a better view of epigenetic alterations and their interactions. We also discuss the role of these epigenetic alterations in RA pathogenesis and their therapeutic potential.

Suberoylanilide Hydroxamic Acid Attenuates Autoimmune Arthritis by Suppressing Th17 Cells through NR1D1 Inhibition

Rheumatoid arthritis (RA) is a type of systemic autoimmune arthritis that causes joint inflammation and destruction. One of the pathological mechanisms of RA is known to involve histone acetylation. Although the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) can attenuate arthritis in animal models of RA, the mechanism underlying this effect is poorly understood. This study was performed to examine whether SAHA has therapeutic potential in an animal model of RA and to investigate its mechanism of action. Collagen-induced arthritis (CIA) mice were orally administered SAHA daily for 8 weeks and examined for their arthritis score and incidence of arthritis. CD4⁺ T cell regulation following SAHA treatment was confirmed in splenocytes cultured under type 17 helper T (Th17) cell differentiation conditions. Clinical scores and the incidence of CIA were lower in mice in the SAHA treatment group compared to the controls. In addition, SAHA inhibited Th17 cell differentiation, as well as decreased expression of the Th17 cell-related transcription factors pSTAT3 Y705 and pSTAT3 S727. In vitro experiments showed that SAHA maintained regulatory T (Treg) cells but specifically reduced Th17 cells. The same results were obtained when mouse splenocytes were cultured under Treg cell differentiation conditions and then converted to Th17 cell differentiation conditions. In conclusion, SAHA was confirmed to specifically inhibit Th17 cell differentiation through nuclear receptor subfamily 1 group D member 1 (NR1D1), a factor associated with Th17 differentiation. The results of the present study suggested that SAHA can attenuate CIA development by inhibition of the Th17 population and maintenance of the Treg population through NR1D1 inhibition. Therefore, SAHA is a potential therapeutic candidate for RA.

Proliferation of rheumatoid arthritis fibroblast-like synoviocytes is enhanced by IL-17-mediated autophagy through STAT3 activation

Fibroblast-like synoviocytes (FLSs), with their tumor-like proliferation, play an important role in rheumatoid arthritis (RA), and interleukin-17 (IL-17) participates in RA pathology by affecting FLSs. The aims of this study were to investigate the effects of IL-17 on the proliferation and autophagy of FLSs and the role of signal transducer and activator of transcription-3 (STAT3) in RA. FLSs were treated with IL-17 at different concentrations (0, 1, 10, and 20 ng/mL); then, autophagy was assayed with western blotting, immunofluorescence, and transmission electron microscopy. The effects of IL-17 on FLSs proliferation were measured with the Cell Counting Kit-8 assay and flow cytometry to analyze cell cycle distribution, and proliferating cell nuclear antigen (PCNA) was detected by western blotting. The autophagy inhibitors, 3-methyladenine (3-MA) and chloroquine (CQ), were used to determine the effect of autophagy on proliferation in IL-17-treated FLSs. Finally, the STAT3 inhibitor STA21 was used to examine the relationship between STAT3 and autophagy in IL-17-treated FLSs. Our results showed that IL-17 positively affected autophagy and proliferation in FLSs. Inhibition of autophagy suppressed the IL-17-mediated proliferation of FLSs. Additionally, suppression of STAT3 activation decreased autophagy in IL-17-treated FLSs. Our findings showed that IL-17 promoted the tumor-like proliferation of FLSs by upregulating autophagy via STAT3 activation.

Trained Innate Immunity Not Always Amicable

The concept of &bdquo;trained innate immunity" is understood as the ability of innate immune cells to remember invading agents and to respond nonspecifically to reinfection with increased strength. Trained immunity is orchestrated by epigenetic modifications leading to changes in gene expression and cell physiology. Although this phenomenon was originally seen mainly as a beneficial effect, since it confers broad immunological protection, enhanced immune response of reprogrammed innate immune cells might result in the development or persistence of chronic metabolic, autoimmune or neuroinfalmmatory disorders. This paper overviews several examples where the induction of trained immunity may be essential in the development of diseases characterized by flawed innate immune response.

The role of protein SUMOylation in rheumatoid arthritis

Small ubiquitin-like modifier (SUMO) proteins, as a subgroup of post-translational modifiers, act to change the function of proteins. Through their interactions with different targets, immune pathways, and the responses they elicit, can be affected by these SUMO conjugations. Thus, both a change to protein function and involvement in immune pathways has the potential to promote an efficient immune response to either a pathogenic challenge, or the development of an imbalance that could lead to an autoimmune-based disease. Also, a variety of changes such as mutations and polymorphisms can interfere with common functions of these modifications and move an effective immune response in the direction of an autoimmune disease. The present review discusses the general characteristics of SUMO proteins and focuses on their involvement in rheumatoid arthritis as an autoimmune disease.

Cimifugin Inhibits Inflammatory Responses of RAW264.7 Cells Induced by Lipopolysaccharide

BACKGROUND RAW264.7 cells are induced by lipopolysaccharide (LPS) as a rheumatoid arthritis (RA) model. The present study investigated the effect of cimifugin on the proliferation, migration, chemotaxis, and release of inflammation-related factors and inflammation-related signaling pathways of LPS-induced RAW264.7 cells. MATERIAL AND METHODS MTS assay was used to determine the proliferation of RAW264.7 cells. Transwell assay was employed to examine the migration and chemotaxis of the cells. ELISA was performed to measure the contents of chemotactic factors and inflammatory factors in cell culture supernatants. Western blotting was carried out to detect the expression of factors related with MAPKs and NF-κB signaling pathways. RESULTS Cimifugin (0-100 mg/L) had no cytotoxicity for RAW264.7 cells. LPS stimulation induced morphological differentiation of RAW264.7 cells, but intervention by cimifugin inhibited the activation effect by LPS by about 50%. Cimifugin (100 mg/L) decreased the migration and chemotaxis of RAW264.7 cells to 1/3 of that in control cells by decreasing the release of migration- and chemotaxis-associated factors by at least 30%. Cimifugin (100 mg/L) suppressed the release of inflammatory factors from RAW264.7 cells to less than 60% of that in the LPS group. In addition, cimifugin (100 mg/L) inhibited the activities of MAPKs and NF-κB signaling pathways. CONCLUSIONS The present study demonstrates that cimifugin reduces the migration and chemotaxis of RAW264.7 cells and inhibits the release of inflammatory factors and activation of related signaling pathways induced by LPS. Cimifugin may have potential pharmacological effects against RA.

Pathologic Fibroblasts in Idiopathic Subglottic Stenosis Amplify Local Inflammatory Signals

OBJECTIVE

To characterize the phenotype and function of fibroblasts derived from airway scar in idiopathic subglottic stenosis (iSGS) and to explore scar fibroblast response to interleukin 17A (IL-17A).

STUDY DESIGN

Basic science.

SETTING

Laboratory.

SUBJECTS AND METHODS

Primary fibroblast cell lines from iSGS subjects, idiopathic pulmonary fibrosis subjects, and normal control airways were utilized for analysis. Protein, molecular, and flow cytometric techniques were applied in vitro to assess the phenotype and functional response of disease fibroblasts to IL-17A.

RESULTS

Mechanistically, IL-17A drives iSGS scar fibroblast proliferation ( P < .01), synergizes with transforming growth factor ß1 to promote extracellular matrix production (collagen and fibronectin; P = .04), and directly stimulates scar fibroblasts to produce chemokines (chemokine ligand 2) and cytokines (IL-6 and granulocyte-macrophage colony-stimulating factor) critical to the recruitment and differentiation of myeloid cells ( P < .01). Glucocorticoids abrogated IL-17A-dependent iSGS scar fibroblast production of granulocyte-macrophage colony-stimulating factor ( P = .02).

CONCLUSION

IL-17A directly drives iSGS scar fibroblast proliferation, synergizes with transforming growth factor ß1 to promote extracellular matrix production, and amplifies local inflammatory signaling. Glucocorticoids appear to partially abrogate fibroblast-dependent inflammatory signaling. These results offer mechanistic support for future translational study of clinical reagents for manipulation of the IL-17A pathway in iSGS patients.

Characterization of a Synovial B Cell-Derived Recombinant Monoclonal Antibody Targeting Stromal Calreticulin in the Rheumatoid Joints

Rheumatoid arthritis (RA) is characterized by formation of synovial ectopic lymphoid structures (ELS) supporting B cell autoreactivity toward locally generated citrullinated (cit) antigens, including those contained in neutrophil extracellular traps (NETs). However, only a minority of RA-rmAbs from B cells isolated from ELS⁺ RA tissues react against NETs. Thus, alternative cellular sources of other potential autoantigens targeted by locally differentiated B cells remain undefined. RA fibroblast-like synoviocytes (FLS) have been implicated in the release of RA-associated autoantigens. In this study, we aimed to define stromal-derived autoantigens from RA-FLS targeted by RA-rmAbs. Seventy-one RA-rmAbs were screened toward RA-FLS by living-cell immunofluorescence (IF). Western blotting was used to identify potential autoantigens from RA-FLS protein extracts. Putative candidates were validated using colocalization immunofluorescence confocal microscopy, ELISA, immunoprecipitation assay, and surface plasmon resonance on unmodified/cit proteins. Serum immunoreactivity was tested in anti-citrullinated peptide/protein Abs (ACPA)⁺ versus ACPA^- RA patients. Ten out of 71 RA-rmAbs showed clear reactivity toward RA-FLS in immunofluorescence with no binding to NETs. One stromal-reactive RA-rmAb (RA057/11.89.1) decorated a ∼58-kDa band that mass spectrometry and Western blotting with a commercial Ab identified as calreticulin (CRT). Confocal microscopy demonstrated significant cellular colocalization between anti-CRT RA057/11.89.1 in RA-FLS. RA057/11.89.1 was able to immunoprecipitate rCRT. Deimination of CRT to cit-CRT moderately increased RA057/11.89.1 immunoreactivity. cit-CRT displayed increased blocking capacity compared with unmodified CRT in competitive binding assays. Finally, anti-cit-CRT Abs were preferentially detected in ACPA⁺ versus ACPA^- RA sera. We identified a synovial B cell-derived RA-rmAb locally differentiated within the ELS⁺ RA synovium reacting toward CRT, a putative novel autoantigen recently described in RA patients, suggesting that FLS-derived CRT may contribute to fuel the local autoimmune response.

Evaluating the bromodomain protein BRD1 as a therapeutic target in rheumatoid arthritis

Targeting epigenetic reader proteins by small molecule inhibitors represents a new therapeutic concept in autoimmune diseases such as rheumatoid arthritis (RA). Although inhibitors targeting bromodomain protein 1 (BRD1) are in development, the function of BRD1 has hardly been studied. We investigated the therapeutic potential of BRD1 inhibition in joint-resident cells in RA, synovial fibroblasts (SF) and macrophages. The proliferation of SF was decreased upon BRD1 silencing, accompanied by the downregulation of genes involved in cell cycle regulation. Silencing of BRD1 in SF decreased the basal expression of MMP1 but increased TNF-α- and LPS-induced levels of MMP3, IL6 and IL8. In monocyte-derived macrophages (MDM), silencing of BRD1 decreased the LPS-induced expression of TNF-α, but did not significantly affect basal and the TNF-α- and LPS-induced expression of IL6 and IL8. Our data point to a cell type- and a stimulus-specific function of BRD1. Inhibiting BRD1 could have potential beneficial effects in RA via decreasing the proliferation of SF. Anti-inflammatory effects were limited and only observed in MDM.

TNF inhibits catecholamine production from induced sympathetic neuron-like cells in rheumatoid arthritis and osteoarthritis in vitro

Synovial adipose stem cells (sASC) can be differentiated into catecholamine-expressing sympathetic neuron-like cells to treat experimental arthritis. However, the pro-inflammatory tumor necrosis factor (TNF) is known to be toxic to catecholaminergic cells (see Parkinson disease), and this may prevent anti-inflammatory effects in inflamed tissue. We hypothesized that TNF exhibits inhibitory effects on human differentiated sympathetic tyrosine hydroxylase-positive (TH+) neuron-like cells. For the first time, iTH+ neuron-like sympathetic cells were generated from sACSs of rheumatoid arthritis (RA) and osteoarthritis (OA) synovial tissue. Compared to untreated controls in both OA and RA, TNF-treated iTH+ cells demonstrated a weaker staining of catecholaminergic markers in cell cultures of RA/OA patients, and the amount of produced noradrenaline was markedly lower. These effects were reversed by etanercept. Exposure of iTH+ cells to synovial fluid of RA patients showed similar inhibitory effects. In mixed synovial cells, significant effects of TNF on catecholamine release were observed only in OA. This study shows that TNF inhibits iTH+ synovial cells leading to the decrease of secreted noradrenaline. This might be a reason why discovered newly appearing TH+ cells in the synovium are not able to develop their possible full anti-inflammatory role in arthritis.

Right drug, right patient, right time: aspiration or future promise for biologics in rheumatoid arthritis?

Individualising biologic disease-modifying anti-rheumatic drugs (bDMARDs) to maximise outcomes and deliver safe and cost-effective care is a key goal in the management of rheumatoid arthritis (RA). Investigation to identify predictive tools of bDMARD response is a highly active and prolific area of research. In addition to clinical phenotyping, cellular and molecular characterisation of synovial tissue and blood in patients with RA, using different technologies, can facilitate predictive testing. This narrative review will summarise the literature for the available bDMARD classes and focus on where progress has been made. We will also look ahead and consider the increasing use of 'omics' technologies, the potential they hold as well as the challenges, and what is needed in the future to fully realise our ambition of personalised bDMARD treatment.

High-Throughput Study of the Effects of Celastrol on Activated Fibroblast-Like Synoviocytes from Patients with Rheumatoid Arthritis

Celastrol, a natural triterpene, exhibits potential anti-inflammatory activity in a variety of inflammatory diseases. The present study aimed to investigate its biological effect on activated fibroblast-like synoviocytes (FLSs) from patients with rheumatoid arthritis (RA). The primary FLSs of the synovial tissues were obtained from synovial biopsies of patients with RA. The normal human FLS line (HFLS) was used as a control. After the RA–FLSs and HFLSs were treated with or without celastrol, various approaches, including the WST-1 assay, transwell assay, real-time PCR and ELISA analysis, were performed to estimate proliferation, invasion and expression of pro-inflammatory cytokines of the RA–FLSs. Microarray analysis was performed to screen for differentially expressed genes in RA–FLSs before and after celastrol treatment. The results showed that treatment of celastrol attenuated both the proliferation and invasion of the RA–FLSs. The expression of several chemokine genes, including CCL2, CXCL10, CXCL12, CCR2 and CXCR4, was significantly changed after celastrol treatment. The genes involved in the NF-κB signaling pathway appeared to be regulated by celastrol.

Mithramycin has inhibitory effects on gliostatin and matrix metalloproteinase expression induced by gliostatin in rheumatoid fibroblast-like synoviocytes

OBJECTIVES

Gliostatin (GLS) has angiogenic and arthritogenic activities and enzymatic activity as thymidine phosphorylase. Aberrant GLS production has been observed in the synovial membranes of patients with rheumatoid arthritis (RA). Matrix metalloproteinases (MMPs) are involved in joint destruction. Promoters of GLS and some MMP genes contain Sp1 binding sites. We examined the inhibitory effect of the Sp1 inhibitor mithramycin on GLS-induced GLS and MMP expression in cultured fibroblast-like synoviocytes (FLSs).

METHODS

Synovial tissue samples were obtained from patients with RA. FLSs pretreated with mithramycin were cultured with GLS. The mRNA expression levels of GLS and MMP-1, MMP-2, MMP-3, MMP-9, and MMP-13 were determined using reverse transcription polymerase chain reactions. Protein levels were measured using enzyme immunoassay and gelatin zymography.

RESULTS

GLS upregulated the expression of GLS itself and of MMP-1, MMP-3, MMP-9, and MMP-13, an effect significantly reduced by treatment with mithramycin. GLS and mithramycin had no effect on MMP-2 expression.

CONCLUSIONS

Mithramycin downregulated the increased expression of GLS and MMP-1, MMP-3, MMP-9, and MMP-13 in FLSs treated with GLS. Because GLS plays a pathological role in RA, blocking GLS stimulation using an agent such as mithramycin may be a novel approach to antirheumatic therapy.

Altered Expression of MicroRNAs in Rheumatoid Arthritis

Rheumatoid arthritis is one of the most common types of inflammatory joint diseases. Women, smokers, and people with positive family history are more susceptible to this disease. Diagnostic criteria include at least one swollen joint that has not been caused by other diseases. MicroRNAs are non-coding RNAs that are evolutionarily conserved and have a length of 18-25 nucleotides. MicroRNAs control gene expression at the post-transcriptional level via promoting mRNA degradation or translational repression. Recognition of alterations in microRNA status and their respective targets, may offer an opportunity to better identify the pathways that are involved in the etiopathogenesis of autoimmune diseases. It has been suggested that microRNAs may serve as potential biomarkers for both diagnosis and prognosis of autoimmune diseases. Here, we review the available evidence on the deregulations of microRNA expression in rheumatoid arthritis. More precisely, this review focuses on the microRNA involved in T cell regulation and gives perspectives on the use of this microRNA as biomarkers of diagnosis, prognosis, or intervention efficacy. J. Cell. Biochem. 119: 478-487, 2018. © 2017 Wiley Periodicals, Inc.

Pathogenetic insights from the treatment of rheumatoid arthritis

Rheumatoid arthritis is a chronic autoimmune disease that causes progressive articular damage, functional loss, and comorbidity. The development of effective biologics and small-molecule kinase inhibitors in the past two decades has substantially improved clinical outcomes. Just as understanding of pathogenesis has led in large part to the development of drugs, so have mode-of-action studies of these specific immune-targeted agents revealed which immune pathways drive articular inflammation and related comorbidities. Cytokine inhibitors have definitively proven a critical role for tumour necrosis factor α and interleukin 6 in disease pathogenesis and possibly also for granulocyte-macrophage colony-stimulating factor. More recently, clinical trials with Janus kinase (JAK) inhibitors have shown that cytokine receptors that signal through the JAK/STAT signalling pathway are important for disease, informing the pathogenetic function of additional cytokines (such as the interferons). Finally, successful use of costimulatory blockade and B-cell depletion in the clinic has revealed that the adaptive immune response and the downstream events initiated by these cells participate directly in synovial inflammation. Taken together, it becomes apparent that understanding the effects of specific immune interventions can elucidate definitive molecular or cellular nodes that are essential to maintain complex inflammatory networks that subserve diseases like rheumatoid arthritis.

Cellular and molecular pathways of structural damage in rheumatoid arthritis

Structural damage of cartilage and bone tissue is a hallmark of rheumatoid arthritis (RA). The resulting joint destruction constitutes one of the major disease consequences for patients and creates a significant burden for the society. The main cells executing bone and cartilage degradation are osteoclasts and fibroblast-like synoviocytes, respectively. The function of both cell types is heavily influenced by the immune system. In the last decades, research has identified several mediators of structural damage, ranging from infiltrating immune cells and inflammatory cytokines to autoantibodies. These factors result in an inflammatory milieu in the affected joints which leads to an increased development and function of osteoclasts and the transformation of fibroblast-like synoviocytes towards a highly migratory and destructive phenotype. In addition, repair mechanisms mediated by osteoblasts and chondrocytes are strongly impaired by the presence of pro-inflammatory cytokines. This article will review the current knowledge on the mechanisms of joint inflammation and the destruction of bone and cartilage.

Fibroblast-like synoviocyte metabolism in the pathogenesis of rheumatoid arthritis

An increasing number of studies show how changes in intracellular metabolic pathways alter tumor and immune cell function. However, little information about metabolic changes in other cell types, including synovial fibroblasts, is available. In rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) are the most common cell type at the pannus–cartilage junction and contribute to joint destruction through their production of cytokines, chemokines, and matrix-degrading molecules and by migrating and invading joint cartilage. In this review, we show that these cells differ from healthy synovial fibroblasts, not only in their marker expression, proto-oncogene expression, or their epigenetic changes, but also in their intracellular metabolism. These metabolic changes must occur due to the stressful microenvironment of inflamed tissues, where concentrations of crucial nutrients such as glucose, glutamine, and oxygen are spatially and temporally heterogeneous. In addition, these metabolic changes will increase metabolite exchange between fibroblast and other synovial cells, which can potentially be activated. Glucose and phospholipid metabolism as well as bioactive lipids, including sphingosine-1-phosphate and lysophosphatidic acid, among others, are involved in FLS activation. These metabolic changes likely contribute to FLS involvement in aspects of immune response initiation or abnormal immune responses and strongly contribute to joint destruction.

Upregulated KAT7 in synovial fibroblasts promotes Th17 cell differentiation and infiltration in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease involving multiple cellular participants, of which synovial fibroblasts (SFs) are tightly connected with the development and progression of RA. Here, we provide evidence confirming that KAT7, an H4-specific histone acetylase, is upregulated in SFs of RA patients, which is at least attributed to the stimulation by RA-associated proinflammatory cytokines, such as TNF-α, IL-1β or IFN-γ. In addition, KAT7 overexpression in cultured human fibroblast-like synoviocytes (HFLSs) induces IL-6 and TGF-β expression through an epigenetic mechanism, and in vitro T helper 17 (Th17) cell polarization cultured in these supernatants shows promoted cell differentiation. Moreover, KAT7 overexpression in HFLSs induces CCL20 expression via p44/42 MAPK pathway, whereby promoting Th17 cell migration. These two activities of KAT7 in RA SFs indicate its potential roles in accelerating RA pathology. Overall, these results demonstrate some connections between KAT7 upregulated in RA SFs and RA progression and present the inhibition of KAT7 activity as a novel therapeutic target for interfering RA disease.

The Mechanisms Underlying Chronic Inflammation in Rheumatoid Arthritis from the Perspective of the Epigenetic Landscape

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that is characterized by synovial hyperplasia and progressive joint destruction. The activation of RA synovial fibroblasts (SFs), also called fibroblast-like synoviocytes (FLS), contributes significantly to perpetuation of the disease. Genetic and environmental factors have been reported to be involved in the etiology of RA but are insufficient to explain it. In recent years, accumulating results have shown the potential role of epigenetic mechanisms, including histone modifications, DNA methylation, and microRNAs, in the development of RA. Epigenetic mechanisms regulate chromatin state and gene transcription without any change in DNA sequence, resulting in the alteration of phenotypes in several cell types, especially RASFs. Epigenetic changes possibly provide RASFs with an activated phenotype. In this paper, we review the roles of epigenetic mechanisms relevant for the progression of RA.

One-carbon metabolism and epigenetics

The function of one-carbon metabolism is that of regulating the provision of methyl groups for biological methylation reactions including that of DNA and histone proteins. Methylation at specific sites into the DNA sequence and at histone tails are among the major epigenetic feature of mammalian genome for the regulation of gene expression. The enzymes within one-carbon metabolism are dependent from a number of vitamins or nutrients that serve either as co-factors or methyl acceptors or donors among which folate, vitamin B12, vitamin B6, betaine, choline and methionine have a major role. Several evidences show that there is a strict inter-relationship between one-carbon metabolism nutrients and epigenetic phenomena. Epigenetics is closely involved in gene transcriptional regulation through modifications super-imposed to the nucleotide sequence of DNA, such as DNA methylation, through chromatin remodeling systems that involves post-translational modifications of histones or through non-coding RNAs-based mechanisms. The epigenetic features of the genome are potentially modifiable by the action of several environmental factors among which nutrients cover a special place and interest considering their potential of influencing regulatory pathways at a molecular level by specific nutritional intervention and eventually influence disease prevention and outcomes. The present review will focus on the link between one-carbon nutrients and epigenetic phenomena based on the current knowledge from findings in cell culture, animal models and human studies.

Different Patterns of Acetylation and Dimethylation of Histone H3 between Young and Aged Cases with Chronic Tonsillitis: Influences of Inflammation and Aging

INTRODUCTION

Epigenetics is now considered to be crucially involved in normal genetics and differentiation and in pathological conditions, such as cancer, aging, and inflammation. Epigenetic mechanisms involve DNA methylation and histone modifications. The purpose of this study was to investigate the effects of inflammation on epigenetics in young subjects and the effect of aging.

MATERIALS AND METHODS

The palatine tonsils were extracted from child and adult patients with chronic tonsillitis. Hematoxylin-eosin staining was performed to examine the morphology of the palatine tonsils. A fluorescence immunological examination was also performed to detect acetyl-histone H3 or dimethyl-histone H3. Confocal scanning microscopy was used for observations.

RESULTS

Acetylated histone H3 was detected in tonsils from child patients but not from adult patients. Dimethylated histone H3 was not detected in tonsils from either group of patients. Degeneration of the tonsillar structures was apparent in tonsils from adult patients.

DISCUSSION

The differential expression of acetylated histone H3 Lys9 may reflect immunological differences between young and aged tonsils. The decrease observed in the activity of histone methyltransferase induced the down-regulated expression of methylated histone H3.

CONCLUSION

Our results suggest that epigenetic changes participate in chronic inflammation and aging in the palatine tonsils. Although the results do not lead to a direct treatment, the epigenetic pathogenesis of chronic inflammation, such as immunoglobulin A nephropathy, by focal infections will be described in greater detail in future studies, which will lead to new treatments being developed.

DNA methylation and hypertension: emerging evidence and challenges

Hypertension is a multifactorial disease influenced by an interaction of environmental and genetic factors. The exact molecular mechanism of hypertension remains unknown. Aberrant DNA methylation is the most well-defined epigenetic modification that regulates gene transcription. However, studies on the association between DNA methylation and hypertension are still in their infancy. This review summarizes the latest evidence and challenges regarding the role of DNA methylation on hypertension.

Effects of Wutou Decoction on DNA Methylation and Histone Modifications in Rats with Collagen-Induced Arthritis

Background. Wutou decoction (WTD) has been wildly applied in the treatment of rheumatoid arthritis and experimental arthritis in rats for many years. Epigenetic deregulation is associated with the aetiology of rheumatoid arthritis; however, the effects of WTD on epigenetic changes are unclear. This study is set to explore the effects of WTD on DNA methylation and histone modifications in rats with collagen-induced arthritis (CIA). Methods. The CIA model was established by the stimulation of collagen and adjuvant. The knee synovium was stained with hematoxylin and eosin. The DNA methyltransferase 1 (DNMT1) and methylated CpG binding domain 2 (MBD2) expression of peripheral blood mononuclear cells (PBMCs) were determined by Real-Time PCR. The global DNA histone H3-K4/H3-K27 methylation and total histones H3 and H4 acetylation of PBMCs were detected. Results. Our data demonstrated that the DNMT1 mRNA expression was significantly lowered in group WTD compared to that in group CIA (P < 0.05). The DNA methylation level was significantly reduced in group WTD compared to that in group CIA (P < 0.05). Moreover, H3 acetylation of PBMCs was overexpressed in WTD compared with CIA (P < 0.05). Conclusions. WTD may modulate DNA methylation and histone modifications, functioning as anti-inflammatory potential.

Deregulation and therapeutic potential of microRNAs in arthritic diseases

Epigenetic abnormalities are part of the pathogenetic alterations involved in the development of rheumatic disorders. In this context, the main musculoskeletal cell lineages, which are generated from the pool of mesenchymal stromal cells (MSCs), and the immune cells that participate in rheumatic diseases are deregulated. In this Review, we focus on microRNA (miRNA)-mediated regulatory pathways that control cell proliferation, drive the production of proinflammatory mediators and modulate bone remodelling. The main studies that identify miRNAs as regulators of immune cell fate, MSC differentiation and immunomodulatory properties - parameters that are altered in rheumatoid arthritis (RA) and osteoarthritis (OA) - are also discussed, with emphasis on the importance of miRNAs in the regulation of cellular machinery, extracellular matrix remodelling and cytokine release. A deeper understanding of the involvement of miRNAs in rheumatic diseases is needed before these regulatory pathways can be explored as therapeutic approaches for patients with RA or OA.

Genome-wide profiling in treatment-naive early rheumatoid arthritis reveals DNA methylome changes in T and B lymphocytes

AIM

Although aberrant DNA methylation has been described in rheumatoid arthritis (RA), no studies have interrogated this epigenetic modification in early disease. Following recent investigations of T and B lymphocytes in established disease, we now characterize in these cell populations genome-wide DNA methylation in treatment-naive patients with early RA.

PATIENTS & METHODS

HumanMethylation450 BeadChips were used to examine genome-wide DNA methylation in lymphocyte populations from 23 early RA patients and 11 healthy individuals.

RESULTS

Approximately 2000 CpGs in each cell type were differentially methylated in early RA. Clustering analysis identified a novel methylation signature in each cell type (150 sites in T lymphocytes, 113 sites in B lymphocytes) that clustered all patients separately from controls. A subset of sites differentially methylated in early RA displayed similar changes in established disease.

CONCLUSION

Treatment-naive early RA patients display novel disease-specific DNA methylation aberrations, supporting a potential role for these changes in the development of RA.

Epigenetic regulation of chronic pain

Chronic pain arising from peripheral inflammation and tissue or nerve injury is a common clinical symptom. Although intensive research on the neurobiological mechanisms of chronic pain has been carried out during previous decades, this disorder is still poorly managed by current drugs such as opioids and nonsteroidal anti-inflammatory drugs. Inflammation, tissue injury and/or nerve injury-induced changes in gene expression in sensory neurons of the dorsal root ganglion, spinal cord dorsal horn and pain-associated brain regions are thought to participate in chronic pain genesis; however, how these changes occur is still elusive. Epigenetic modifications including DNA methylation and covalent histone modifications control gene expression. Recent studies have shown that peripheral noxious stimulation changes DNA methylation and histone modifications and that these changes may be related to the induction of pain hypersensitivity under chronic pain conditions. This review summarizes the current knowledge and progress in epigenetic research in chronic pain and discusses the potential role of epigenetic modifications as therapeutic antinociceptive targets in this disorder.

DNA methylation: roles in rheumatoid arthritis

Rheumatoid arthritis (RA) is an immune-mediated disease of unknown cause that primarily affects the joints and ultimately leads to joint destruction. In recent years, the potential role of DNA methylation in the development of RA is raising great expectations among clinicians and researchers. DNA methylation influences diverse aspects of the disease and regulates epigenetic silencing of genes and behavior of several cell types, especially fibroblast-like synoviocytes (FLS), the most resident cells in joints. The activation of FLS is generally regarded as a key process in the development of RA that actively results in the promotion of ongoing inflammation and joint damage. It has also been shown that aberrant DNA methylation occurs in the pathogenesis of RA and contributes to the development of the disease. Recently, there has been an impressive increase in studies involving DNA methylation in RA. In this paper, we consider the role of DNA methylation in the development of RA.

The epigenome of synovial fibroblasts: an underestimated therapeutic target in rheumatoid arthritis

Perturbed epigenetic landscape and deregulated microRNA networks are central to the permanent activation and aggressiveness of synovial fibroblasts in rheumatoid arthritis. Current anti-cytokine therapies, although effectively halting synovitis, cannot reverse the stably activated destructive phenotype of rheumatoid arthritis synovial fibroblasts,offering rather limited protection against ongoing joint destruction in rheumatoid arthritis. Targeting the deregulated epigenome of rheumatoid arthritis synovial fibroblasts is key to developing joint-protective strategies in rheumatoid arthritis. To date, different pathogenic mechanisms have been identified that can profoundly impact the epigenetic derangements in rheumatoid arthritis synovial fibroblasts, including increased consumption of S-adenosylmethionine,a principal methyl donor in DNA methylation reactions, together with deregulation of crucial DNA- and histonemodifying enzymes. Re-establishing globally disturbed DNA methylation patterns in rheumatoid arthritis synovial fibroblasts by supplementing S-adenosylmethionine while preventing its leakage into polyamine cycles may bea promising therapeutic strategy in rheumatoid arthritis and the first epigenetic treatment to target rheumatoid arthritis synovial fibroblasts at the scene of the crime. Given the dynamic nature and reversibility of epigenetic modifications, their involvement in human diseases and recent perspectives on epigenetic therapies in cancer, epigenetic targeting of rheumatoid arthritis synovial fibroblasts should be within future reach.

SIRT6 regulates the cigarette smoke-induced signalling in rheumatoid arthritis synovial fibroblasts

Cigarette smoking is a recognized environmental risk factor for the development and progression of rheumatoid arthritis (RA). RA synovial fibroblasts (RASF) actively contribute to inflammation and joint destruction in this chronic inflammatory autoimmune disease. In the current study, we investigated the influence of cigarette smoke on the inflammatory and matrix-destructive properties of RASF. Furthermore, the functional role of Sirtuin 6 (SIRT6) in the regulation of the signalling induced by cigarette smoke or by tumor necrosis factor alpha (TNFα) was elucidated. We demonstrated that stimulation with cigarette smoke extract (CSE) enhances the pro-inflammatory and matrix-destructive potential of RASF by inducing the production of pro-inflammatory cytokine interleukin 8 (IL8) and the matrix-destructive enzyme matrix metalloproteinase 1 (MMP1), but not of IL6 and MMP3. Moreover, we could show that the expression of MMP1 is specifically regulated by SIRT6. Treatment of RASF with CSE or TNFα increased the levels of SIRT6. The expression of SIRT6 was also enhanced in vivo in synovial tissues of RA smokers and in joints of mice exposed to cigarette smoke. Silencing of SIRT6 specifically increased basal as well as CSE- and TNFα-induced production of MMP1, demonstrating that SIRT6 plays an important role in restricting MMP1 expression. In conclusion, the upregulation of SIRT6 in RASF under CSE or TNFα stimulation functions as a counterregulatory mechanism attenuating the production of the matrix-destructive enzyme MMP1. This is the first study revealing the protective function of SIRT6 in the cigarette smoke-induced signalling.

KEY MESSAGES

Cigarette smoke induces pro-inflammatory and matrix-destructive responses in RASF. Cigarette smoke enhances the expression of SIRT6 in vitro and in vivo. TNFα increases the levels of SIRT6. SIRT6 diminishes MMP1 production under cigarette smoke extract and TNFα stimulation.

ADAMTS-12: a multifaced metalloproteinase in arthritis and inflammation

ADAMTS-12 is a member of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family of proteases, which were known to play important roles in various biological and pathological processes, such as development, angiogenesis, inflammation, cancer, arthritis, and atherosclerosis. In this review, we briefly summarize the structural organization of ADAMTS-12; concentrate on the emerging role of ADAMTS-12 in several pathophysiological conditions, including intervertebral disc degeneration, tumorigenesis and angioinhibitory effects, pediatric stroke, gonad differentiation, trophoblast invasion, and genetic linkage to schizophrenia and asthma, with special focus on its role in arthritis and inflammation; and end with the perspective research of ADAMTS-12 and its potential as a promising diagnostic and therapeutic target in various kinds of diseases and conditions.

Significance of epigenetic landscape in cartilage regeneration from the cartilage development and pathology perspective

Regenerative therapies for cartilage defects have been greatly advanced by progress in both the stem cell biology and tissue engineering fields. Despite notable successes, significant barriers remain including shortage of autologous cell sources and generation of a stable chondrocyte phenotype using progenitor cells. Increasing demands for the treatment of degenerative diseases, such as osteoarthritis and rheumatoid arthritis, highlight the importance of epigenetic remodeling in cartilage regeneration. Epigenetic regulatory mechanisms, such as microRNAs, DNA methylation, and histone modifications, have been intensively studied due to their direct regulatory role on gene expression. However, a thorough understanding of the environmental factors that initiate these epigenetic events may provide greater insight into the prevention of degenerative diseases and improve the efficacy of treatments. In other words, if we could identify a specific factor from the environment and its downstream signaling events, then we could stop or retard degradation and enhance cartilage regeneration. A more operational definition of epigenetic remodeling has recently been proposed by categorizing the signals during the epigenetic process into epigenators, initiators, and maintainers. This review seeks to compile and reorganize the existing literature pertaining to epigenetic remodeling events placing emphasis on perceiving the landscape of epigenetic mechanisms during cartilage regeneration with the new operational definition, especially from the environmental factors' point of view. Progress in understanding epigenetic regulatory mechanisms could benefit cartilage regeneration and engineering on a larger scale and provide more promising therapeutic applications.

Genomics of lymphoid malignancies reveal major activation pathways in lymphocytes

Breakdown of tolerance leads to autoimmunity due to emergence of autoreactive T or B cell clones. Autoimmune diseases predispose to lymphoid malignancies and lymphoid malignancies, conversely, can manifest as autoimmune diseases. While it has been clear for a long time that a competitive advantage and uncontrolled growth of lymphocytes contribute to the pathogenesis of both lymphoid malignancies as well as autoimmune diseases, the overlap of the underlying mechanisms has been less well described. Next generation sequencing has led to massive expansion of the available genomic data in many diseases over the last five years. These data allow for comparison of the molecular pathogenesis between autoimmune diseases and lymphoid malignancies. Here, we review the similarities between autoimmune diseases and lymphoid malignancies: 1) Both, autoimmune diseases and lymphoid malignancies are characterized by activation of the same T and B cell signaling pathways, and dysregulation of these pathways can occur through genetic or epigenetic events. 2) In both scenarios, clonal and subclonal evolution of lymphocytes contribute to disease. 3) Development of both diseases not only depends on T or B cell intrinsic factors, such as germline or somatic mutations, but also on environmental factors. These include infections, the presence of other immune cells in the microenvironment, and the cytokine milieu. A better mechanistic understanding of the parallels between lymphomagenesis and autoimmunity may help the development of precision treatment strategies with rationally designed therapeutic agents.