Impaired Tip60-mediated Foxp3 acetylation attenuates regulatory T cell development in rheumatoid arthritis

New Posttranslational Modification Lactylation Brings New Inspiration for the Treatment of Rheumatoid Arthritis

Lactic acid (LA) is an essential glycolytic metabolite and energy source in the body, which is present in high levels in the synovial fluid of patients with rheumatoid arthritis (RA) and is a reliable indicator for identifying inflammatory arthritis. LA not only acts as an inflammatory amplifier in RA, recent studies have found that novel posttranslational modification (PTM) lactylation mediated by LA may also play a key role in RA. Single-cell sequencing showed that the RA lactylation score of patients with RA was significantly increased, and core lactylation-promoting genes, including NDUFB3, NGLY1, and other genes, were found to be potential biomarkers of RA. More studies have shown that lactylation can regulate genes in various cells, such as fibroblast-like synoviocytes (FLSs) and macrophages, thus playing a special role in the development and occurrence of autoimmune diseases, neurological diseases, and cancer diseases. In this paper, we review the research on lactylation in RA-related cells and mechanisms and bring new insights into the pathogenesis, diagnosis, and treatment of RA.

Dysregulation of epigenetic modifications in inborn errors of immunity

Inborn errors of immunity (IEIs) are a group of typically monogenic disorders characterized by dysfunction in the immune system. Individuals with these disorders experience increased susceptibility to infections, autoimmunity and malignancies due to abnormal immune responses. Epigenetic modifications, including DNA methylation, histone modifications and chromatin remodeling, have been well explored in the regulation of immune cell development and effector function. Aberrant epigenetic modifications can disrupt gene expression profiles crucial for immune responses, resulting in impaired immune cell differentiation and function. Dysregulation of these processes caused by mutations in genes involving in epigenetic modifications has been associated with various IEIs. In this review article, we focus on IEIs that are caused by mutations in 13 genes involved in the regulation of DNA methylation, histone modification and chromatin remodeling.

Mendelian randomization analysis identified potential genes pleiotropically associated with gout

Background

This study aims to prioritize genes potentially involved in multifactorial or causal relationships with gout.

Methods

Using the Summary Data-based Mendelian Randomization (SMR) approach, this research analyzed expression quantitative trait loci (eQTL) data from blood and renal tissues and genome-wide association study (GWAS) data related to gout. It sought to identify genetic loci potentially involved in gout. Heterogeneity testing was conducted with the HEIDI test, and results were adjusted for the False Discovery Rate (FDR). Blood cis-eQTL data were sourced from the eQTLGen Consortium's summary-level data, and renal tissue data came from the V8 release of the GTEx eQTL summary data. Gout GWAS data was sourced from the FinnGen Documentation of the R10 release.

Result

SMR analysis identified 14 gene probes in the eQTLGen blood summary-level data significantly associated with gout. The top five ranked genes are: ENSG00000169231 (labeled THBS3, PSMR = 4.16 × 10-13), ENSG00000231064 (labeled THBS3-AS1, PSMR = 1.88 × 10-8), ENSG00000163463 (labeled KRTCAP2, PSMR = 3.88 × 10-6), ENSG00000172977 (labeled KAT5, PSMR = 1.70 × 10-5), and ENSG00000161395 (labeled PGAP3, PSMR = 3.24 × 10-5). Notably, increased expression of KRTCAP2 and PGAP3 is associated with an increased risk of gout, whereas increased expression of THBS3, THBS3-AS1, and KAT5 is associated with a reduced gout risk. No significant gene associations with gout were observed in renal tissue, likely due to the limited sample size of kidney tissue.

Conclusion

Our findings have highlighted several genes potentially involved in the pathogenesis of gout. These results offer valuable insights into the mechanisms of gout and identify potential therapeutic targets for its treatment.

Epigenetic regulation of human FOXP3+ Tregs: from homeostasis maintenance to pathogen defense

Regulatory T cells (Tregs), characterized by the expression of Forkhead Box P3 (FOXP3), constitute a distinct subset of T cells crucial for immune regulation. Tregs can exert direct and indirect control over immune homeostasis by releasing inhibitory factors or differentiating into Th-like Treg (Th-Treg), thereby actively contributing to the prevention and treatment of autoimmune diseases. The epigenetic regulation of FOXP3, encompassing DNA methylation, histone modifications, and post-translational modifications, governs the development and optimal suppressive function of Tregs. In addition, Tregs can also possess the ability to maintain homeostasis in diverse microenvironments through non-suppressive mechanisms. In this review, we primarily focus on elucidating the epigenetic regulation of Tregs as well as their multifaceted roles within diverse physiological contexts while looking forward to potential strategies involving augmentation or suppression of Tregs activity for disease management, particularly in light of the ongoing global COVID-19 pandemic.

Evaluating the Cellular Roles of the Lysine Acetyltransferase Tip60 in Cancer: A Multi-Action Molecular Target for Precision Oncology

Precision (individualized) medicine relies on the molecular profiling of tumors' dysregulated characteristics (genomic, epigenetic, transcriptomic) to identify the reliance on key pathways (including genome stability and epigenetic gene regulation) for viability or growth, and then utilises targeted therapeutics to disrupt these survival-dependent pathways. Non-mutational epigenetic changes alter cells' transcriptional profile and are a key feature found in many tumors. In contrast to genetic mutations, epigenetic changes are reversable, and restoring a normal epigenetic profile can inhibit tumor growth and progression. Lysine acetyltransferases (KATs or HATs) protect genome stability and integrity, and Tip60 is an essential acetyltransferase due to its roles as an epigenetic and transcriptional regulator, and as master regulator of the DNA double-strand break response. Tip60 is commonly downregulated and mislocalized in many cancers, and the roles that mislocalized Tip60 plays in cancer are not well understood. Here we categorize and discuss Tip60-regulated genes, evaluate Tip60-interacting proteins based on cellular localization, and explore the therapeutic potential of Tip60-targeting compounds as epigenetic inhibitors. Understanding the multiple roles Tip60 plays in tumorigenesis will improve our understanding of tumor progression and will inform therapeutic options, including informing potential combinatorial regimes with current chemotherapeutics, leading to improvements in patient outcomes.

The regulation and differentiation of regulatory T cells and their dysfunction in autoimmune diseases

The discovery of FOXP3+ regulatory T (Treg) cells as a distinct cell lineage with a central role in regulating immune responses provided a deeper understanding of self-tolerance. The transcription factor FOXP3 serves a key role in Treg cell lineage determination and maintenance, but is not sufficient to enable the full potential of Treg cell suppression, indicating that other factors orchestrate the fine-tuning of Treg cell function. Moreover, FOXP3-independent mechanisms have recently been shown to contribute to Treg cell dysfunction. FOXP3 mutations in humans cause lethal fulminant systemic autoinflammation (IPEX syndrome). However, it remains unclear to what degree Treg cell dysfunction is contributing to the pathophysiology of common autoimmune diseases. In this Review, we discuss the origins of Treg cells in the periphery and the multilayered mechanisms by which Treg cells are induced, as well as the FOXP3-dependent and FOXP3-independent cellular programmes that maintain the suppressive function of Treg cells in humans and mice. Further, we examine evidence for Treg cell dysfunction in the context of common autoimmune diseases such as multiple sclerosis, inflammatory bowel disease, systemic lupus erythematosus and rheumatoid arthritis.

Engineering Efferocytosis-Mimicking Nanovesicles to Regulate Joint Anti-Inflammation and Peripheral Immunosuppression for Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is an autoimmune disorder characterized by chronic inflammation of the synovial joints and the dysfunction of regulatory T cells (Tregs) in the peripheral blood. Therefore, an optimal treatment strategy should aim to eliminate the inflammatory response in the joints and simultaneously restore the immune tolerance of Tregs in peripheral blood. Accordingly, we developed an efferocytosis-mimicking nanovesicle that contains three functional factors for immunomodulating of efferocytosis, including "find me" and "eat me" signals for professional (macrophage) or non-professional phagocytes (T lymphocyte), and "apoptotic metabolite" for metabolite digestion. We showed that efferocytosis-mimicking nanovesicles targeted the inflamed joints and spleen of mice with collagen-induced arthritis, further recruiting and selectively binding to macrophages and T lymphocytes to induce M2 macrophage polarization and Treg differentiation and T helper cell 17 (Th17) recession. Under systemic administration, the efferocytosis-mimicking nanovesicles effectively maintained the pro-inflammatory M1/anti-inflammatory M2 macrophage balance in joints and the Treg/Th17 imbalance in peripheral blood to prevent RA progression. This study demonstrates the potential of efferocytosis-mimicking nanovesicles for RA immunotherapy.

STUB1 is acetylated by KAT5 and alleviates myocardial ischemia-reperfusion injury through LATS2-YAP-β-catenin axis

Myocardial ischemia-reperfusion injury (MIRI) is involved in the pathogenesis of multiple cardiovascular diseases. This study elucidated the biological function of lysine acetyltransferase 5 (KAT5) in cardiomyocyte pyroptosis during MIRI. Oxygen-glucose deprivation/reoxygenation and left anterior descending coronary artery ligation were used to establish MIRI models. Here we show, KAT5 and STIP1 homology and U-box-containing protein 1 (STUB1) were downregulated, while large tumor suppressor kinase 2 (LATS2) was upregulated in MIRI models. KAT5/STUB1 overexpression or LATS2 silencing repressed cardiomyocyte pyroptosis. Mechanistically, KAT5 promoted STUB1 transcription via acetylation modulation, and subsequently caused ubiquitination and degradation of LATS2, which activated YAP/β-catenin pathway. Notably, the inhibitory effect of STUB1 overexpression on cardiomyocyte pyroptosis was abolished by LATS2 overexpression or KAT5 depletion. Our findings suggest that KAT5 overexpression inhibits NLRP3-mediated cardiomyocyte pyroptosis to relieve MIRI through modulation of STUB1/LATS2/YAP/β-catenin axis, providing a potential therapeutic target for MIRI.

Heterogeneity and subtypes of CD4+ regulatory T cells: implications for tumor therapy

In the conventional view, CD4+ regulatory T cell (Treg) represents a subset of lymphocytes that involve the perception and negative regulation of the immune response. CD4+Treg plays an important role in the maintenance of immune homeostasis and immune tolerance. However, recent studies have revealed that CD4+Treg do not suppress the immune response in some diseases, but promote inflammatory injury or inhibit tissue remodeling, suggesting the functional heterogeneity of CD4+Treg. Their involvement in tumor pathogenesis is more complex than previously understood. This article reviews the relevant research on the heterogeneity of CD4+Treg, subtype classification, and their relationship with tumor therapy.

Acetylation is required for full activation of the NLRP3 inflammasome

Full activation of the NLRP3 inflammasome needs two sequential signals: a priming signal, followed by a second, assembly signal. Several studies have shown that the two signals trigger post-translational modification (PTM) of NLRP3, affecting activity of the inflammasome, however, the PTMs induced by the second signal are less well characterized. Here, we show that the assembly signal involves acetylation of NLRP3 at lysine 24, which is important for the oligomerization and the actual assembly of NLRP3 without affecting its recruitment to dispersed trans-Golgi network (dTGN). Accordingly, NLRP3 inflammasome activation is impaired in NLRP3-K24R knock-in mice. We identify KAT5 as an acetyltransferase able to acetylate NLRP3. KAT5 deficiency in myeloid cells and pharmacological inhibition of KAT5 enzymatic activity reduce activation of the NLRP3 inflammasome, both in vitro and in vivo. Thus, our study reveals a key mechanism for the oligomerization and full activation of NLRP3 and lays down the proof of principle for therapeutic targeting of the KAT5-NLRP3 axis.

ATM-AMPKα mediated LAG-3 expression suppresses T cell function in prostate cancer

Immunotherapy for prostate cancer (PCa) faces serious challenges. Therefore, the co-inhibitory receptors that regulate T cell function of PCa must be elucidated. Here we identified that the inhibitory receptor LAG3 was significantly induced in T cells from PCa patients. Gene array analysis revealed that insufficient ataxia telangiectasia mutated (ATM) gene expression in PCa T cells was responsible for the elevated LAG3 expression. Mechanistically, insufficient ATM expression impaired its ability to activate AMPKα signaling and CD4+ T cell functions, which further enhances the binding of the transcription factors XBP1 and EGR2 to LAG3 promoter. Reconstitution of ATM and inhibition of XBP1 or EGR2 in PCa T cells suppressed LAG3 expression and restored the effector function of CD4+ T cells from PCa. Our study revealed the mechanism of LAG3 upregulation in CD4+ T lymphocytes of PCa patients and may provide insights for the development of immunotherapeutic strategies for PCa treatment.

Targeting post-translational modifications of Foxp3: a new paradigm for regulatory T cell-specific therapy

A healthy immune system is pivotal for the hosts to resist external pathogens and maintain homeostasis; however, the immunosuppressive tumor microenvironment (TME) damages the anti-tumor immunity and promotes tumor progression, invasion, and metastasis. Recently, many studies have found that Foxp3+ regulatory T (Treg) cells are the major immunosuppressive cells that facilitate the formation of TME by promoting the development of various tumor-associated cells and suppressing the activity of effector immune cells. Considering the role of Tregs in tumor progression, it is pivotal to identify new therapeutic drugs to target and deplete Tregs in tumors. Although several studies have developed strategies for targeted deletion of Treg to reduce the TME and support the accumulation of effector T cells in tumors, Treg-targeted therapy systematically affects the Treg population and may lead to the progression of autoimmune diseases. It has been understood that, nevertheless, in disease conditions, Foxp3 undergoes several definite post-translational modifications (PTMs), including acetylation, glycosylation, phosphorylation, ubiquitylation, and methylation. These PTMs not only elevate or mitigate the transcriptional activity of Foxp3 but also affect the stability and immunosuppressive function of Tregs. Various studies have shown that pharmacological targeting of enzymes involved in PTMs can significantly influence the PTMs of Foxp3; thus, it may influence the progression of cancers and/or autoimmune diseases. Overall, this review will help researchers to understand the advances in the immune-suppressive mechanisms of Tregs, the post-translational regulations of Foxp3, and the potential therapeutic targets and strategies to target the Tregs in TME to improve anti-tumor immunity.

Histone and Histone Acetylation-Related Alterations of Gene Expression in Uninvolved Psoriatic Skin and Their Effects on Cell Proliferation, Differentiation, and Immune Responses

Psoriasis is a chronic immune-mediated skin disease in which the symptom-free, uninvolved skin carries alterations in gene expression, serving as a basis for lesion formation. Histones and histone acetylation-related processes are key regulators of gene expression, controlling cell proliferation and immune responses. Dysregulation of these processes is likely to play an important role in the pathogenesis of psoriasis. To gain a complete overview of these potential alterations, we performed a meta-analysis of a psoriatic uninvolved skin dataset containing differentially expressed transcripts from nearly 300 individuals and screened for histones and histone acetylation-related molecules. We identified altered expression of the replication-dependent histones HIST2H2AA3 and HIST2H4A and the replication-independent histones H2AFY, H2AFZ, and H3F3A/B. Eight histone chaperones were also identified. Among the histone acetyltransferases, ELP3 and KAT5 and members of the ATAC, NSL, and SAGA acetyltransferase complexes are affected in uninvolved skin. Histone deacetylation-related alterations were found to affect eight HDACs and members of the NCOR/SMRT, NURD, SIN3, and SHIP HDAC complexes. In this article, we discuss how histone and histone acetylation-related expression changes may affect proliferation and differentiation, as well as innate, macrophage-mediated, and T cell-mediated pro- and anti-inflammatory responses, which are known to play a central role in the development of psoriasis.

Epigenetic Regulations in Autoimmunity and Cancer: from Basic Science to Translational Medicine

Epigenetics, as a discipline that aims to explain the differential expression of phenotypes arising from the same gene sequence and the heritability of epigenetic expression, has received much attention in medicine. Epigenetic mechanisms are constantly being discovered, including DNA methylation, histone modifications, noncoding RNAs and m6A. The immune system mainly achieves an immune response through the differentiation and functional expression of immune cells, in which epigenetic modification will have an important impact. Because of immune infiltration in the tumor microenvironment, immunotherapy has become a research hotspot in tumor therapy. Epigenetics plays an important role in autoimmune diseases and cancers through immunology. An increasing number of drugs targeting epigenetic mechanisms, such as DNA methyltransferase inhibitors, histone deacetylase inhibitors, and drug combinations, are being evaluated in clinical trials for the treatment of various cancers (including leukemia and osteosarcoma) and autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis). This review summarizes the progress of epigenetic regulation for cancers and autoimmune diseases to date, shedding light on potential therapeutic strategies.

An update on epigenetic regulation in autoimmune diseases

Autoimmune diseases (AIDs) generally manifest as chronic immune disorders characterized by significant heterogeneity and complex symptoms. The discordant incidence of AIDs between monozygotic twins guided people to attach importance to environmental factors. Epigenetics is one of the major ways to be influenced, some of them can even occur years before clinical diagnosis. With the advent of high-throughput omics times, the mysterious veil of epigenetic modification in AIDs has been gradually unraveled, and some progress has been made in utilizing it as indicators of diagnosis and disease activity. For example, the hypomethylated IFI44L promoter in diagnosing systematic lupus erythematosus (SLE). More recently, newly identified noncoding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), are also believed to be involved in the etiology of AIDs while the initial factor behind those epigenetic alterations can be diverse from metabolism to microbiota. Update and comprehensive insights into epigenetics in AIDs can help us understand the pathogenesis and further orchestrate it to benefit patients in the future. Therefore, we reviewed the latest epigenetic findings in SLE, rheumatoid arthritis (RA), Type 1 diabetes (T1D), systemic sclerosis (SSc) primarily from cellular levels.

CPT1A-Mediated Fatty Acid Oxidation Promotes Precursor Osteoclast Fusion in Rheumatoid Arthritis

The overproduction of osteoclasts, leading to bone destruction in patients with rheumatoid arthritis (RA), is well established. However, little is known about the metabolic dysfunction of osteoclast precursors (OCPs) in RA. Herein, we show that increasing fatty acid oxidation (FAO) induces OCP fusion. Carnitine palmitoyltransferase IA (CPT1A), which is important for carnitine transportation and is involved in FAO in the mitochondria, is upregulated in RA patients. This metabolic change further increases the expression of clathrin heavy chain (CLTC) and clathrin light chain A (CLTA) by enhancing the binding of the transcription factor CCAAT/enhancer binding protein β (C/EBPβ) to the promoters of CLTA and CLTC. This drives clathrin-dependent endocytosis pathway, which attenuates fusion receptors in the cellular membrane and contributes to increased podosome structure formation. This study reveals a new mechanism through which FAO metabolism participates in joint destruction in RA and provides a novel therapeutic direction for the development of drugs against bone destruction in patients with RA.

The Protective Effects of KAT5 Inhibition on Ocular Inflammation by Mediating the PI3K/AKT Pathway in a Murine Model of Allergic Conjunctivitis

Purpose

We aimed to explore the effect of lysine acetyltransferase KAT5 on allergic conjunctivitis (AC).

Methods

The effect of KAT5 on inflammatory response during AC progression was analyzed in the experimental allergic conjunctivitis (EAC) mouse model.

Results

The clinical score, permeability, total IgE, ovalbumin (OVA)-specific IgE, and IgG1/IgG2a were induced in the EAC mice, in which the overexpression of KAT5 could further enhance but KAT5 inhibitor NU9056 reduce the phenotypes. The eosinophilic infiltration was induced in EAC mice, in which the overexpression of KAT5 was able to further promote but NU9056 attenuate the phenotype. The expression of Eotaxin and RANTES and the inflammatory factors were upregulated in EAC mice and KAT5 overexpression increased, but NU9056 decreased the expression in the model. Significantly, the CD11c+ dendritic cells and CD4+ T cells infiltration in the conjunctiva was enhanced in EAC mice, whereas KAT5 overexpression induced but NU9056 suppressed the effect in the model. Mechanically, the phosphorylation of PI3K and Akt and the levels of histone H3 lysine 27 acetylation (H3K27ac) were enhanced in EAC mice, whereas the overexpression of KAT5 promoted and NU9056 repressed the phenotype in the mice. The enrichment of KAT5 and H3K27ac on PI3K promoter was increased in EAC mice, and the overexpression of KAT5 further enhanced the enrichment in the mice. Significantly, we observed similar results in the KAT5 knockout mice as well. Moreover, PI3K/AKT signaling inhibitor LY294002 reversed KAT5 overexpression-mediated phenotypes and inflammatory response after induction AC in vivo.

Conclusions

Therefore we concluded that KAT5 inhibition protected against ocular inflammation by mediating the PI3K/AKT pathway in EAC mouse model.

Integrated proteome and malonylome analyses reveal the neutrophil extracellular trap formation pathway in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease of unknown etiology in which the posttranslational modifications (PTMs) of proteins play an important role. PTMs, such as those involved in the formation of neutrophil extracellular traps (NETs), have been well studied. The excessive formation and release of NETs can mediate inflammation and joint destruction in RA. It has been gradually recognized that lysine malonylation (Kmal) can regulate some biological processes in some prokaryotes and eukaryotes. However, less is known about the role of Kmal in RA. We therefore performed proteome and malonylome analyses to explore the proteomic characteristics of the peripheral blood mononuclear cells from 36 RA patients and 82 healthy subjects. In total, 938 differentially expressed proteins (DEPs) and 42 differentially malonylated proteins (DMPs) with 55 Kmal sites were detected through a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based analysis. Functional analysis showed that two DEPs with four malonylated sites and one DMP with a malonylated site were identified in the neutrophil extracellular trap formation (NETosis) pathway. Altogether, this study not only describes the characteristics of the malonylome in RA for the first time, but it also reveals that malonylation may be involved in the NETosis pathway. SIGNIFICANCE: This is the first report that reveals the proteomic features of Kmal in RA through a LC-MS/MS-based method. In this study, we found that several key DMPs were associated with the NETosis pathway, which contributes to the development of RA. The present results provide an informative dataset for the future exploration of Kmal in RA.

Regulatory T Cells in Autoimmune Vasculitis

Blood vessels are indispensable for host survival and are protected from inappropriate inflammation by immune privilege. This protection is lost in patients with autoimmune vasculitides, a heterogeneous group of diseases causing damage to arteries, arterioles, and capillaries. Vasculitis leads to vascular wall destruction and/or luminal occlusion, resulting in hemorrhage and tissue ischemia. Failure in the quantity and quality of immunosuppressive regulatory T cells (Treg) has been implicated in the breakdown of the vascular immune privilege. Emerging data suggest that Treg deficiencies are disease-specific, affecting distinct pathways in distinct vasculitides. Mechanistic studies have identified faulty CD8+ Tregs in Giant Cell Arteritis (GCA), a vasculitis of the aorta and the large aortic branch vessels. Specifically, aberrant signaling through the NOTCH4 receptor expressed on CD8+ Treg cells leads to rerouting of intracellular vesicle trafficking and failure in the release of immunosuppressive exosomes, ultimately boosting inflammatory attack to medium and large arteries. In Kawasaki’s disease, a medium vessel vasculitis targeting the coronary arteries, aberrant expression of miR-155 and dysregulated STAT5 signaling have been implicated in undermining CD4+ Treg function. Explorations of mechanisms leading to insufficient immunosuppression and uncontrolled vascular inflammation hold the promise to discover novel therapeutic interventions that could potentially restore the immune privilege of blood vessels and pave the way for urgently needed innovations in vasculitis management.

Immune, metabolism and therapeutic targets in RA (Rheumatoid Arthritis)

Rheumatoid arthritis is a classic autoimmune disease, the pathogenesis of which is closely linked to the auto-reactivity of immune cells and joint inflammation. Three cell types, namely T cells, macrophages and fibroblast-like synoviocytes (FLS), play an important role in the pathogenesis of RA. Numerous studies have pointed to a metabolic reprogramming of T cells, macrophages and FLS in the pathogenesis of RA arthritis, with alterations in different metabolic pathways of cells, mainly producing a shift from oxidative phosphorylation (OXPHOS) to glycolysis, in addition to lipid metabolism and amino acid metabolism which are also altered in the cellular activation state. Metabolic changes are regulated by metabolism-related signalling pathways, and RA is associated with two representative signalling pathways, namely the mTOR signalling pathway and the AMPK signalling pathway. In RA, both signalling pathways are activated or inhibited, and through a series of cascade reactions, different gene expressions are ultimately induced, altering intracellular metabolic pathways and promoting pro-inflammatory functions (e.g. pro-inflammatory cytokine release and FLS phenotypes), or inhibiting the expression of genes related to immune tolerance. Targeting key components of metabolic signalling pathways and key enzymes in cellular metabolic pathways in RA has emerged as a new way of finding drugs for RA, and many modulators targeting these targets have been extensively studied for their therapeutic effects in RA. In this article, we focus on cellular metabolic alterations in RA, related signalling pathways and possible drugs targeting RA metabolic pathways.

Membrane-bound IL-6R is upregulated on Th17 cells and inhibits Treg cell migration by regulating post-translational modification of VASP in autoimmune arthritis

Autoimmune arthritis is characterized by impaired regulatory T (Treg) cell migration into inflamed joint tissue and by dysregulation of the balance between Treg cells and Th17 cells. Interleukin-6 (IL-6) is known to contribute to this dysregulation, but the molecular mechanisms behind impaired Treg cell migration remain largely unknown. In this study, we assessed dynamic changes in membrane-bound IL-6 receptor (IL6R) expression levels on Th17 cells by flow cytometry during the development of collagen-induced arthritis (CIA). In a next step, bioinformatics analysis based on proteomics was performed to evaluate potential pathways affected by altered IL-6R signaling in autoimmune arthritis. Our analysis shows that membrane-bound IL-6R is upregulated on Th17 cells and is inversely correlated with IL-6 serum levels in experimental autoimmune arthritis. Moreover, IL-6R expression is significantly increased on Th17 cells from untreated patients with rheumatoid arthritis (RA). Interestingly, CD4⁺ T cells from CIA mice and RA patients show reduced phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Bioinformatics analysis based on proteomics of CD4⁺ T cells with low or high phosphorylation levels of VASP revealed that integrin signaling and related pathways are significantly enriched in cells with low phosphorylation of VASP. Specific inhibition of p-VASP reduces the migratory function of Treg cells but has no influence on effector CD4⁺ T cells. Importantly, IL-6R blockade restores the phosphorylation level of VASP, thereby improving the migratory function of Treg cells from RA patients. Thus, our results establish a link between IL6R signaling and phosphorylation of VASP, which controls Treg cell migration in autoimmune arthritis.

Analysis of Expression of Different Histone Deacetylases in Autoimmune Thyroid Disease

CONTEXT

Histone deacetylases (HDACs) and histone acetyltransferases (HAT) have an important role in the regulation of gene transcription as well as in the development and function of CD4+Foxp3+ T regulatory (Treg) cells. Our group and others have reported that patients with autoimmune thyroid disease (AITD) show abnormalities in the levels and function of different Treg cell subsets.

OBJECTIVE

We aimed to analyze the levels of expression of several HDACs and the Tip60 HAT in the thyroid gland and immune cells from patients with AITD.

METHODS

The expression of HDAC1-11 and the Tip60 HAT, at RNA and protein levels, were determined in thyroid tissue from 20 patients with AITD and 10 healthy controls and these findings were correlated with clinical data. HDAC9 and Tip60 levels were also analyzed in thyroid cell cultures, stimulated or not with proinflammatory cytokines, as well as in different cell subsets from peripheral blood mononuclear cells.

RESULTS

Altered expression of different HDACs was observed in thyroid tissue from AITD patients, including a significant increase in HDAC9, at RNA and protein levels. Likewise, HDAC9 expression was increased in peripheral blood mononuclear cells particularly in Treg cells in patients with AITD. In contrast, Tip60 expression was reduced in thyroid gland samples from patients with Hashimoto thyroiditis.

CONCLUSION

Our results indicate that HDAC expression is dysregulated in thyroid gland and immune cells from patients with AITD, suggesting involvement in the pathogenesis of this condition.

MIG/CXCL9 exacerbates the progression of metabolic-associated fatty liver disease by disrupting Treg/Th17 balance

CD4⁺CD25⁺ regulatory T (Treg) cells and Th17 cells play important roles in the progression of metabolic-associated fatty liver disease (MAFLD). However, the contribution of monokine induced by interferon-gamma (MIG)/CXCL9 to the Treg/Th17 imbalance in MAFLD is only partially understood. In the present study, we detected increased levels of MIG/CXCL9 and a Treg/Th17 imbalance in the setting of metabolic-associated steatohepatitis (MASH). Recombinant adeno-associated virus-mediated gene transfer and silencing of MIG/CXCL9 expression in mice alleviated MASH and increased the Treg/Th17 ratio. Furthermore, the percentage of Th17 cells, but not Treg cells, differentiated from splenic CD4⁺ T cells was significantly increased by administration of MIG/CXCL9. MIG/CXCL9 also promoted Th17 cell proliferation, and its effects were dose dependent. Levels of phosphorylated c-Jun N-terminal kinase (JNK) decreased dramatically when MIG/CXCL9 was inhibited in a murine MASH model. In cultured Treg cells, phosphorylated JNK levels decreased dose-dependently in response to MIG/CXCL9 inhibition, but increased in cultured Th17 cells. This effect was blocked in the presence of a JNK inhibitor. These findings underline the fundamental importance of MIG/CXCL9 in maintaining the Treg/Th17 balance in MAFLD and provide the foundations for a novel approach to preventing and treating MAFLD.

Impact of Posttranslational Modification in Pathogenesis of Rheumatoid Arthritis: Focusing on Citrullination, Carbamylation, and Acetylation

Rheumatoid arthritis (RA) is caused by prolonged periodic interactions between genetic, environmental, and immunologic factors. Posttranslational modifications (PTMs) such as citrullination, carbamylation, and acetylation are correlated with the pathogenesis of RA. PTM and cell death mechanisms such as apoptosis, autophagy, NETosis, leukotoxic hypercitrullination (LTH), and necrosis are related to each other and induce autoantigenicity. Certain microbial infections, such as those caused by Porphyromonasgingivalis, Aggregatibacter actinomycetemcomitans, and Prevotella copri, can induce autoantigens in RA. Anti-modified protein antibodies (AMPA) containing anti-citrullinated protein/peptide antibodies (ACPAs), anti-carbamylated protein (anti-CarP) antibodies, and anti-acetylated protein antibodies (AAPAs) play a role in pathogenesis as well as in prediction, diagnosis, and prognosis. Interestingly, smoking is correlated with both PTMs and AMPAs in the development of RA. However, there is lack of evidence that smoking induces the generation of AMPAs.

Dysfunctions, Molecular Mechanisms, and Therapeutic Strategies of Regulatory T Cells in Rheumatoid Arthritis

Regulatory T cells (Tregs) represent a distinct subpopulation of CD4⁺ T lymphocytes that promote immune tolerance and maintain immune system homeostasis. The dysfunction of Tregs is tightly associated with rheumatoid arthritis (RA). Although the complex pathogenic processes of RA remain unclear, studies on Tregs in RA have achieved substantial progress not only in fundamental research but also in clinical application. This review discusses the current knowledge of the characterizations, functions, and molecular mechanisms of Tregs in the pathogenesis of RA, and potential therapies for these disorders are also involved.

Single Cell RNA-Seq Analysis Identifies Differentially Expressed Genes of Treg Cell in Early Treatment-Naive Rheumatoid Arthritis By Arsenic Trioxide

Objective: Early treatment-naïve rheumatoid arthritis (RA) has defective regulatory T (Treg) cells and increased inflammation response. In this study, we aim to illustrate the regulation of Treg cells in pathogenesis of early rheumatoid arthritis by arsenic trioxide (As₂O₃).

Methods: We studied the effects of As₂O₃ on gene expression in early treatment-naïve RA Treg cells with single cell RNA-seq (scRNA-seq). Treg cells were sorted from peripheral blood mononuclear cells (PBMCs) and purified by fluorescence-activated cell sorting (FACS) and cultured with or without As₂O₃ (at 0.1 µM) for 24 h. Total RNA was isolated and sequenced, and functional analysis was performed against the Gene Ontology (GO) database. Results for selected genes were confirmed with RT-qPCR.

Results: As₂O₃ exerts no significant effect on CD4⁺ T-cell apoptosis under physical condition, and selectively modulate ^CD4+ T cells toward Treg cells not Th17 cells under special polarizing stimulators. As₂O₃ increased the expression of 200 and reduced that of 272 genes with fold change (FC) 2.0 or greater. Several genes associated with inflammation, Treg-cell activation and differentiation as well as glucose and amino acids metabolism were among the most strongly affected genes. GO function analysis identified top ten ranked significant biological process (BPs), molecular functions (MFs), and cell components (CCs) in treatment and nontreatment Treg cells. In GO analysis, genes involved in the immunoregulation, cell apoptosis and cycle, inflammation, and cellular metabolism were enriched among the significantly affected genes. The KEGG pathway enrichment analysis identified the forkhead box O (FoxO) signal pathway, apoptosis, cytokine–cytokine receptor interaction, cell cycle, nuclear factor-kappa B (NF-κB) signaling pathway, tumor necrosis factor α (TNF-α), p53 signaling pathway, and phosphatidylinositol 3′-kinase (PI3K)-Akt signaling pathway were involved in the pathogenesis of early treatment-naïve RA.

Conclusion: This is the first study investigating the genome-wide effects of As₂O₃ on the gene expression of treatment-naïve Treg cells. In addition to clear anti-inflammatory and immunoregulation effects, As₂O₃ affect amino acids and glucose metabolism in Treg cells, an observation that might be particularly important in the metabolic phenotype of treatment-naïve RA.

Association of FOXP3 and GAGE10 promoter polymorphisms and decreased FOXP3 expression in regulatory T cells with susceptibility to generalized vitiligo in Gujarat population

Alterations in regulatory T (Treg) cells have been observed in generalized vitiligo (GV) patients and decreased Forkhead Box P3 (FOXP3) has been implicated in the disease pathogenesis. The present study examined FOXP3 rs3761547(A > G), rs3761548(C > A), rs2232365(A > G) and GAGE10 rs11798415(A > T) promoter single nucleotide polymorphisms (SNPs) in 419 GV patients and 429 controls from Gujarat population using PCR-RFLP and ARMS-PCR. Real-time PCR and flow cytometry were used for assessment of FOXP3 mRNA and protein levels respectively in 96 GV patients and 90 controls. The frequency of genotypes (p < 0.001) and alleles (p = 0.012 & p = 0.040) for rs3761547(A > G) and rs11798415(A > T) SNPs significantly differed between GV patients and controls. FOXP3 mRNA and protein levels were significantly decreased (p < 0.001) in GV Tregs compared to controls. Active vitiligo (AV) Tregs showed significantly reduced FOXP3 mRNA and protein levels compared to that of stable vitiligo (SV) (p = 0.02 & p = 0.039). The correlation of genotype-phenotype of FOXP3 SNPs suggested reduced FOXP3 mRNA (p = 0.019, p < 0.001 & p < 0.001) and protein (p = 0.028, p < 0.001 & p = 0.022) levels in patients with susceptible GG, AA and GG genotypes respectively. The GAGT, GCGT & ACGT haplotypes were prevalent in GV patients (p = 0.004, p = 0.004 & p = 0.016); however, GAGT & GCGT were overrepresented in patients with AV (p = 0.044 & p = 0.024). The susceptible GAGT and GCGT haplotypes in patients exhibited reduction in FOXP3 mRNA (p = 0.014 & p = 0.019) and protein (p = 0.024 & p = 0.028). DNA-protein docking analysis revealed reduced binding for transcription factor C/EBP to the susceptible allele 'G' (rs3761547) compared to A allele. For the first time, the study suggests significant association of FOXP3 rs3761547(A > G) & GAGE10 rs11798415(A > T) SNPs with susceptibility to GV in Gujarat population. In addition, the likely role of these SNPs in altered FOXP3 expression of Tregs may possibly affect Treg suppressive function in GV.

FOXP3 and Tip60 Structural Interactions Relevant to IPEX Development Lead to Potential Therapeutics to Increase FOXP3 Dependent Suppressor T Cell Functions

Regulatory T (Treg) cells play a role in the maintenance of immune homeostasis and are critical mediators of immune tolerance. The Forkhead box P3 (FOXP3) protein acts as a regulator for Treg development and function. Mutations in the FOXP3 gene can lead to autoimmune diseases such as Immunodysregulation, polyendocrinopathy, enteropathy, and X-linked (IPEX) syndrome in humans, often resulting in death within the first 2 years of life and a scurfy like phenotype in Foxp3 mutant mice. We discuss biochemical features of the FOXP3 ensemble including its regulation at various levels (epigenetic, transcriptional, and post-translational modifications) and molecular functions. The studies also highlight the interactions of FOXP3 and Tat-interacting protein 60 (Tip60), a principal histone acetylase enzyme that acetylates FOXP3 and functions as an essential subunit of the FOXP3 repression ensemble complex. Lastly, we have emphasized the role of allosteric modifiers that help stabilize FOXP3:Tip60 interactions and discuss targeting this interaction for the therapeutic manipulation of Treg activity.

Th17/Treg-Related Transcriptional Factor Expression and Cytokine Profile in Patients With Rheumatoid Arthritis

Objectives

The aim of our study was to determine whether there is a correlation between transcription factors expression and Th17/Treg ratio, cytokine profile in the RA phenotype as well as to identify transcription factors that could be a potential biomarker for RA.

Methods

The study was conducted on 45 patients with RA, 27 patients with OA and 46 healthy controls (HCs). Th17 and Treg frequency was determined by flow cytometry (15 patients with RA/OA and 15 subjects of HC). Gene expression was estimated by qPCR, and the serum cytokine levels were determined by ELISA.

Results

The percentage of Treg (CD4+CD25highCD127-) cells in RA patients was lower than in OA patients or HCs. Proportions of Th17 (CD4+CCR6+CXCR3-) cells were higher in RA and OA in comparison to HCs. STAT5 showed a very high expression in the blood of RA patients compared to healthy subjects. The expression of STAT5 and HELIOS was not detected in Th17 cells. A positive correlation between SMAD3 and STAT3 in RA patients was observed. Negative correlations between HIF-1A and SMAD2 in RA Treg cells and DAS-28 score were observed. The range of serum of IL-17 and IL-21 were higher in RA patients than in OA patients. Concentrations of serum IL-2 and IFN-γ were higher in RA and OA patients than in healthy subjects. Based on the ROC analysis, the diagnostic potential of the combination of HIF1A, SMAD3 and STAT3, was determined at AUC 0.95 for distinguishing RA patients from HCs. For distinguishing RA patients from OA patients the diagnostic potential of the combination of SMAD2, SMAD3, SMAD4 and STAT3, was determined at AUC 0.95.

Conclusion

Based on our study, we conclude that SMAD3 and STAT3 could be potential diagnostic biomarkers for RA.

Molecular Mechanisms Controlling Foxp3 Expression in Health and Autoimmunity: From Epigenetic to Post-translational Regulation

The discovery of the transcription factor Forkhead box-p3 (Foxp3) has shed fundamental insights into the understanding of the molecular determinants leading to generation and maintenance of T regulatory (Treg) cells, a cell population with a key immunoregulatory role. Work over the past few years has shown that fine-tuned transcriptional and epigenetic events are required to ensure stable expression of Foxp3 in Treg cells. The equilibrium between phenotypic plasticity and stability of Treg cells is controlled at the molecular level by networks of transcription factors that bind regulatory sequences, such as enhancers and promoters, to regulate Foxp3 expression. Recent reports have suggested that specific modifications of DNA and histones are required for the establishment of the chromatin structure in conventional CD4⁺ T (Tconv) cells for their future differentiation into the Treg cell lineage. In this review, we discuss the molecular events that control Foxp3 gene expression and address the associated alterations observed in human diseases. Also, we explore how Foxp3 influences the gene expression programs in Treg cells and how unique properties of Treg cell subsets are defined by other transcription factors.

Tolerogenic Dendritic Cells Generated by BAFF Silencing Ameliorate Collagen-Induced Arthritis by Modulating the Th17/Regulatory T Cell Balance

Tolerogenic dendritic cells (tolDCs) have received much attention because of their capacity to restore immune homeostasis. RNA interference techniques have been used in several studies to generate tolDCs by inactivating certain molecules that regulate DC maturation and immunologic function. BAFF is a key B cell survival factor that is not only essential for B cell function but also T cell costimulation, and DCs are the major source of BAFF. In this study, we determined whether BAFF gene silencing in mature DCs could lead to a tolerogenic phenotype as well as the potential therapeutic effect of BAFF-silenced DCs on collagen-induced arthritis (CIA) in mice. Meanwhile, CRISPR/Cas9-mediated BAFF^-/- DC2.4 cells were generated to verify the role of BAFF in DC maturation and functionality. BAFF-silenced DCs and BAFF^-/- DC2.4 cells exhibited an immature phenotype and functional state. Further, the transplantation of BAFF-silenced DCs significantly alleviated CIA severity in mice, which correlated with a reduction in Th17 populations and increased regulatory T cells. In vitro, BAFF-silenced DCs promoted Foxp3 mRNA and IL-10 expression but inhibited ROR-γt mRNA and IL-17A expression in CD4⁺ T cells. Together, BAFF-silenced DCs can alleviate CIA, partly by inducing Foxp3⁺ regulatory T cells and suppressing Th17 subsets. Collectively, BAFF plays an important role in interactions between DCs and T cells, which might be a promising genetic target to generate tolDCs for autoimmune arthritis treatment.

FoxP3 in Treg cell biology: a molecular and structural perspective

Regulatory T cells (T_regs) are specialized in immune suppression and play a dominant role in peripheral immune tolerance. T_reg cell lineage development and function maintenance is determined by the forkhead box protein 3 (FoxP3) transcriptional factor, whose activity is fine‐tuned by its post‐translational modifications (PTMs) and interaction partners. In this review, we summarize current studies in the crystal structures, the PTMs and interaction partners of FoxP3 protein, and discuss how these insights may provide a roadmap for new approaches to modulate T_reg suppression, and new therapies to enhance immune tolerance in autoimmune diseases.