Abnormal Epigenetic Regulations in the Immunocytes of Sjögren's Syndrome Patients and Therapeutic Potentials

Sjogren's syndrome: Everything you always wanted to know about genetic and epigenetic factors

Primary Sjögren's syndrome (pSS) is a chronic, systemic autoimmune disease characterized by a wide spectrum of glandular and extra-glandular features. Genetic and epigenetic factors play an important role in the disease susceptibility and phenotype. There are a multitude of genes that have been identified as implicated in the pathogenesis of pSS, both in HLA and extra-HLA regions with a strong contribution given by genes in interferon signalling pathways. Among the HLA alleles, the most consistent associations have been found with DR2 and DR3 alleles at the DRB1 locus. Moreover, several gene variants outside the MHC locus are in genes involved in NF-κB signalling, B- and T-cell function and methylation processes possibly responsible for lymphomagenesis. There is still a lack of knowledge on precise genetic patterns and prediction models of diseases, and data on pharmacogenetics is scarce. A comprehensive summary of the common genetic factors and an extensive analysis of novel epigenetic aspects is provided, together with a view on the relationships between novel therapeutic agents for pSS and genetic targets in signalling pathways, aiming at improving tailored treatment strategies in the view of a more personalized medicine.

Functional significance of DNA methylation: epigenetic insights into Sjögren's syndrome

Sjögren's syndrome (SjS) is a systemic, highly diverse, and chronic autoimmune disease with a significant global prevalence. It is a complex condition that requires careful management and monitoring. Recent research indicates that epigenetic mechanisms contribute to the pathophysiology of SjS by modulating gene expression and genome stability. DNA methylation, a form of epigenetic modification, is the fundamental mechanism that modifies the expression of various genes by modifying the transcriptional availability of regulatory regions within the genome. In general, adding a methyl group to DNA is linked with the inhibition of genes because it changes the chromatin structure. DNA methylation changes the fate of multiple immune cells, such as it leads to the transition of naïve lymphocytes to effector lymphocytes. A lack of central epigenetic enzymes frequently results in abnormal immune activation. Alterations in epigenetic modifications within immune cells or salivary gland epithelial cells are frequently detected during the pathogenesis of SjS, representing a robust association with autoimmune responses. The analysis of genome methylation is a beneficial tool for establishing connections between epigenetic changes within different cell types and their association with SjS. In various studies related to SjS, most differentially methylated regions are in the human leukocyte antigen (HLA) locus. Notably, the demethylation of various sites in the genome is often observed in SjS patients. The most strongly linked differentially methylated regions in SjS patients are found within genes regulated by type I interferon. This demethylation process is partly related to B-cell infiltration and disease progression. In addition, DNA demethylation of the runt-related transcription factor (RUNX1) gene, lymphotoxin-α (LTA), and myxovirus resistance protein A (MxA) is associated with SjS. It may assist the early diagnosis of SjS by serving as a potential biomarker. Therefore, this review offers a detailed insight into the function of DNA methylation in SjS and helps researchers to identify potential biomarkers in diagnosis, prognosis, and therapeutic targets.

Integrated DNA Methylation and Transcriptomics Analyses of Lacrimal Glands Identify the Potential Genes Implicated in the Development of Sjögren's Syndrome-Related Dry Eye

Purpose

Sjögren's syndrome-related dry eye (SS-related dry eye) is an intractable autoimmune disease characterized by chronic inflammation of lacrimal glands (LGs), where epigenetic factors are proven to play a crucial role in the pathogenesis of this disease. However, the alteration of DNA methylation in LGs and its role in the pathogenesis of SS-related dry eye is still unknown. Here, we performed an integrated analysis of DNA methylation and RNA-Seq data in LGs to identify novel DNA methylation-regulated differentially expressed genes (MeDEGs) in the pathogenesis of SS-related dry eye.

Methods

The DNA methylation and transcription profiles of LGs in NOD mice at different stages of SS-related dry eye (4-, 8-, 12- and 16 weeks old) were generated by reduced representation bisulfite sequencing (RRBS) and RNA-Seq. The differentially methylated genes (DMGs) and differentially expressed genes (DEGs) were analyzed by MethylKit R package and edgeR. Correlation analysis between methylation level and mRNA expression was conducted with R software. The functional correlation of DMGs and DEGs was analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Finally, LG tissues from another litter of NOD mice were collected for methylation-specific polymerase chain reaction (MSP) and quantitative real-time PCR (qRT-PCR) to validate the methylation and expression levels of key genes. CD4+ cell infiltration of LGs was detected by immunofluorescence staining.

Results

Hypermethylation of LGs was identified in NOD mice with the progression of SS-related dry eye and the DMGs were mainly enriched in the GTPases activation and Ras signaling pathway. RNA-seq analysis revealed 1321, 2549, and 3712 DEGs in the 8-, 12- and 16-week-old NOD mice compared with 4-week-old normal control mice. For GO analysis, the DEGs were mainly enriched in T cell immune responses. Further, a total of 140 MeDEGs were obtained by integrated analysis of methylome and transcriptome, which were primarily enriched in T cell activation, proliferation and differentiation. Based on the main GO terms and KEGG pathways of MeDEGs, 8 genes were screened out. The expression levels of these key genes, especially Itgal, Vav1, Irf4 and Icosl, were verified to elevate after the onset of SS-related dry eye in NOD mice and positively correlated with the extent of inflammatory cell infiltration in LGs. Immunofluorescence assay revealed that CD4+ cell infiltration dramatically increased in LGs of SS-related dry eye mice compared with the control mice. And the expression levels of four genes showed significantly positive correlation with the extent of CD4+ cell infiltration in LGs. MSP showed the hypomethylation of the Irf4 and Itgal promoters in NOD mice with SS-related dry eye compared to control group.

Conclusion

Our study revealed the critical role of epigenetic regulation of T cell immunity-related genes in the progression of SS-related dry eye and reminded us that DNA methylation-regulated genes such as Itgal, Vav1, Irf4 and Icosl may be used as new targets for SS-related dry eye therapy.

What exactly is the relationship between plasma cytokines and the clinical phenotype of primary sjögren's syndrome? a single-centre retrospective study

BACKGROUND

The pathogenesis of primary Sjögren's syndrome (pSS) remains unclear. Accumulating evidence suggests that an imbalance of multiple cytokines contributes to the occurrence and development of pSS. To our knowledge, there are few studies on the relationship between plasma cytokines and pSS clinical phenotype (including disease activity), and the available results are controversial. Cytokine-targeted therapy failed to achieve satisfactory effects.

METHODS

We collected the demographic and clinical characteristics (laboratory indicators and clinical presentation) of pSS patients and calculated the European League Against Rheumatism SS disease activity index (ESSDAI) scores and ClinESSDAI. Associations between plasma cytokines and pSS continuous and categorical variables, and between various cytokines were analysed separately.

RESULTS

348 patients were finally included in the analysis, with a female to male ratio of 13.5:1. The disease activity was mild to moderate in 86.78% of patients, with the most and least involved organs being the exocrine glands and neurological system respectively. Among the various cytokines analysed, plasma interleukin(IL)-6 levels were elevated and correlated with a variety of inflammatory indicators and clinical manifestations. A weak positive correlation was found between IL - 10 and ESSDAI. Various degrees of correlation were observed between cytokines and clinical manifestations of pSS and between multiple cytokines.

CONCLUSION

Our study shows that different cytokines are closely associated with the clinical phenotype of pSS. Plasma IL-10 can be used to monitor pSS disease activity. Multiple cytokines form a systemic network and participate in the pathological process of pSS. This study provides a solid foundation for further exploring the pathogenesis of pSS and establishing more effective cytokine-targeted therapeutic regimens.

Role of microbiota short-chain fatty acid chains in the pathogenesis of autoimmune diseases

There is emerging evidence that microbiota and its metabolites play an important role in helath and diseases. In this regard, gut microbiota has been found as a crucial component that influences immune responses as well as immune-related disorders such as autoimmune diseases. Gut bacterial dysbiosis has been shown to cause disease and altered microbiota metabolite synthesis, leading to immunological and metabolic dysregulation. Of note, microbiota in the gut produce short-chain fatty acids (SCFAs) such as acetate, butyrate, and propionate, and remodeling in these microbiota metabolites has been linked to the pathophysiology of a number of autoimmune disorders such as type 1 diabetes, multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, celiac disease, and systemic lupus erythematosus. In this review, we will address the most recent findings from the most noteworthy studies investigating the impact of microbiota SCFAs on various autoimmune diseases.

Abnormal expression of CXCL13, MIF and IL-35 in patients with primary Sjögren's syndrome and its relationship with disease severity

Introduction

The aim of the study was to detect the saliva chemokine (C-X-C motif) ligand 13 (CXCL13), macrophage migration inhibitory factor (MIF), and interleukin 35 (IL-35) levels in patients with primary Sjögren's syndrome (pSS) and pSS-associated interstitial lung disease (pSS-ILD), and to explore the relationship between CXCL13, MIF, IL-35 levels, and disease severity.

Material and methods

ESSDAI score was used to evaluate the disease activity of pSS patients, and the levels of CXCL13, MIF and IL-35 in saliva of subjects were detected and analyzed, and the relationship between CXCL13, MIF, IL-35 and the occurrence of pSS was evaluated. Pearson's correlation coefficient was used to analyze the correlation between CXCL13, MIF, IL-35 and ESSDAI score. ROC curve analysis was conducted to assess the diagnostic value of CXCL13, MIF, IL-35 and their combined application in pSS.

Results

The levels of CXCL13, MIF, and IL-35 in saliva were positively correlated with ESSDAI score. Saliva CXCL13 and IL-35 are risk factors for the development of pSS into pSS-ILD. The ROC curve shows that the combination of saliva CXCL13, MIF and IL-35 has the highest diagnostic efficiency for pSS-ILD.

Conclusions

CXCL13, MIF and IL-35 are related to the activity of pSS, and the combined diagnosis of these three indexes is expected to be an important method to predict the occurrence and development of pSS.

Trained immunity as a possible newcomer in autoinflammatory and autoimmune diseases pathophysiology

Autoimmune disorders have been well characterized over the years and many pathways-but not all of them-have been found to explain their pathophysiology. Autoinflammatory disorders, on the other hand, are still hiding most of their molecular and cellular mechanisms. During the past few years, a newcomer has challenged the idea that only adaptive immunity could display memory response. Trained immunity is defined by innate immune responses that are faster and stronger to a second stimulus than to the first one, being the same or not. In response to the trained immunity inducer, and through metabolic and epigenetic changes of hematopoietic stem and progenitor cells in the bone marrow that are transmitted to their cellular progeny (peripheral trained immunity), or directly of tissue-resident cells (local innate immunity), innate cells responsiveness and functions upon stimulation are improved in the long-term. Innate immunity can be beneficial, but it could also be detrimental when maladaptive. Here, we discuss how trained immunity could contribute to the physiopathology of autoimmune and autoinflammatory diseases.