Blocking IAg7 class II major histocompatibility complex by drug-like small molecules alleviated Sjögren's syndrome in NOD mice

Human umbilical cord mesenchymal stem cells improve disease characterization of Sjogren's syndrome in NOD mice through regulation of gut microbiota and Treg/Th17 cellular immunity

BACKGROUND

For the unclear pathogenesis of Sjogren's syndrome (SS), further exploration is necessary. Mesenchymal stem cells (MSCs) and derived exosomes (MSCs-exo) have exhibited promising results in treating SS.

OBJECT

This study aimed to investigate the effect and mechanism of human umbilical cord MSCs (UC-MSCs) on SS.

METHODS

Nonobese Diabetic (NOD) mouse splenic T cells were co-cultured with UC-MSCs and UC-MSCs-exo, and interferon-gamma (IFN-γ), interleukin (IL)-6, IL-10, prostaglandin E2 (PGE2), and transforming growth factor-β1 (TGF-β1) levels in the supernatant were assessed by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Co-cultured T cells were injected into NOD mice via the tail vein. The inflammatory cell infiltration in the intestine and the submandibular gland was characterized by hematoxylin-eosin staining. Treg/Th17 homeostasis within the spleen was determined by flow cytometry. Gut microbiota was detected by 16S rRNA sequencing, and the relationship between differential microbiota and Treg/Th17 cytokines was analyzed by the Pearson correlation coefficient.

RESULTS

UC-MSCs, UC-MSCs-exo, and NOD mouse splenic T cells were successfully cultured and identified. After T cells were co-cultured with UC-MSCs and UC-MSCs-exo, both IFN-γ and IL-6 were decreased while IL-10, PGE2, and TGF-β1 were increased in transcriptional and translational levels. UC-MSCs and UC-MSCs-exo partially restored salivary secretion function, reduced Ro/SSA antibody and α-Fodrin immunoglobulin A levels, reduced inflammatory cell infiltration in the intestine and submandibular gland, raised proportion of Treg cells, decreased IFN-γ, IL-6, IL-2, IL-17, lipopolysaccharide, and tumor necrosis factor-alpha levels, and raised IL-10, Foxp3, and TGF-β1 levels by affecting co-cultured T cells. The intervention of UC-MSCs and UC-MSCs-exo improved intestinal homeostasis in NOD mice by increasing microbiota diversity and richness. Additionally, differential microbiota was significantly associated with Treg/Th17 cytokine levels.

CONCLUSION

Human UC-MSCs and UC-MSCs-exo improved disease characterization of SS in NOD mice through regulation of gut microbiota and Treg/Th17 cellular immunity.

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.

MHC Class II Presentation in Autoimmunity

Antigen presentation by major histocompatibility complex class II (MHC-II) molecules is crucial for eliciting an efficient immune response by CD4+ T cells and maintaining self-antigen tolerance. Some MHC-II alleles are known to be positively or negatively associated with the risk of the development of different autoimmune diseases (ADs), including those characterized by the emergence of autoreactive T cells. Apparently, the MHC-II presentation of self-antigens contributes to the autoimmune T cell response, initiated through a breakdown of central tolerance to self-antigens in the thymus. The appearance of autoreactive T cell might be the result of (i) the unusual interaction between T cell receptors (TCRs) and self-antigens presented on MHC-II; (ii) the posttranslational modifications (PTMs) of self-antigens; (iii) direct loading of the self-antigen to classical MHC-II without additional nonclassical MHC assistance; (iv) the proinflammatory environment effect on MHC-II expression and antigen presentation; and (v) molecular mimicry between foreign and self-antigens. The peculiarities of the processes involved in the MHC-II-mediated presentation may have crucial importance in the elucidation of the mechanisms of triggering and developing ADs as well as for clarification on the protective effect of MHC-II alleles that are negatively associated with ADs.

Evidence of a Sjögren's disease-like phenotype following COVID-19

Objectives

Sjögren's Disease (SjD) is a chronic and systemic autoimmune disease characterized by lymphocytic infiltration and the development of dry eyes and dry mouth resulting from the secretory dysfunction of the exocrine glands. SARS-CoV-2 may trigger the development or progression of autoimmune diseases, as evidenced by increased autoantibodies in patients and the presentation of cardinal symptoms of SjD. The objective of the study was to determine whether SARS-CoV-2 induces the signature clinical symptoms of SjD.

Methods

The ACE2-transgenic mice were infected with SARS-CoV-2. SJD profiling was conducted. COVID-19 patients' sera were examined for autoantibodies. Clinical evaluations of convalescent COVID-19 subjects, including minor salivary gland (MSG) biopsies, were collected. Lastly, monoclonal antibodies generated from single B cells of patients were interrogated for ACE2/spike inhibition and nuclear antigens.

Results

Mice infected with the virus showed a decreased saliva flow rate, elevated antinuclear antibodies (ANAs) with anti-SSB/La, and lymphocyte infiltration in the lacrimal and salivary glands. Sera of COVID-19 patients showed an increase in ANA, anti-SSA/Ro52, and anti-SSB/La. The male patients showed elevated levels of anti-SSA/Ro52 compared to female patients, and female patients had more diverse ANA patterns. Minor salivary gland biopsies of convalescent COVID-19 subjects showed focal lymphocytic infiltrates in four of six subjects, and 2 of 6 subjects had focus scores >2. Lastly, we found monoclonal antibodies produced in recovered patients can both block ACE2/spike interaction and recognize nuclear antigens.

Conclusion

Overall, our study shows a direct association between SARS-CoV-2 and SjD. Hallmark features of SjD salivary glands were histologically indistinguishable from convalescent COVID-19 subjects. The results potentially implicate that SARS-CoV-2 could be an environmental trigger for SjD.

Key Messages

What is already known about this subject?SAR-CoV-2 has a tropism for the salivary glands. However, whether the virus can induce clinical phenotypes of Sjögren's disease is unknown.What does this study add?Mice infected with SAR-CoV-2 showed loss of secretory function, elevated autoantibodies, and lymphocyte infiltration in glands.COVID-19 patients showed an increase in autoantibodies. Monoclonal antibodies produced in recovered patients can block ACE2/spike interaction and recognize nuclear antigens.Minor salivary gland biopsies of some convalescent subjects showed focal lymphocytic infiltrates with focus scores.How might this impact on clinical practice or future developments?Our data provide strong evidence for the role of SARS-CoV-2 in inducing Sjögren's disease-like phenotypes.Our work has implications for how patients will be diagnosed and treated effectively.

Composition and regulation of the immune microenvironment of salivary gland in Sjögren’s syndrome

Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease characterized by exocrine gland dysfunction and inflammation. Patients often have dry mouth and dry eye symptoms, which seriously affect their lives. Improving dry mouth and eye symptoms has become a common demand from patients. For this reason, researchers have conducted many studies on external secretory glands. In this paper, we summarize recent studies on the salivary glands of pSS patients from the perspective of the immune microenvironment. These studies showed that hypoxia, senescence, and chronic inflammation are the essential characteristics of the salivary gland immune microenvironment. In the SG of pSS, genes related to lymphocyte chemotaxis, antigen presentation, and lymphocyte activation are upregulated. Interferon (IFN)-related genes, DNA methylation, sRNA downregulation, and mitochondrial-related differentially expressed genes are also involved in forming the immune microenvironment of pSS, while multiple signaling pathways are involved in regulation. We further elucidated the regulation of the salivary gland immune microenvironment in pSS and relevant, targeted treatments.

Exploration of the pathogenesis of Sjögren's syndrome via DNA methylation and transcriptome analyses

OBJECTIVES

Sjögren's syndrome (SS), a systemic autoimmune disorder, is characterized by dry mouth and eyes. However, SS pathogenesis is poorly understood. We performed bioinformatics analysis to investigate the potential targets and molecular pathogenesis of SS.

METHODS

Gene expression profiles (GSE157159) and methylation data (GSE110007) associated with SS patients were obtained from the Gene Expression Omnibus (GEO) database. Differentially methylated positions (DMPs) and differentially expressed genes (DEGs) were identified by the R package limma. The potential biological functions of DEGs were determined using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Key DMPs were selected by overlap and the shrunken centroid algorithm, and corresponding genes were identified as hub genes, with their diagnostic value assessed by receiver operating characteristic (ROC) curves. The potential molecular mechanisms of hub genes were analyzed by protein-protein interaction (PPI) networks and single-gene gene set enrichment analysis (GSEA). Peripheral blood mononuclear cells (PBMCs) were collected from control and SS patients at The Affiliated Hospital of Southwest Medical University and Dazhou Central Hospital. The mRNA levels of hub genes were verified by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

We identified 788 DMPs and 2457 DEGs between the two groups. Functional enrichment analysis suggested that the DEGs were significantly enriched in T cell activation, leukocyte cell-cell adhesion, and cytokine-cytokine receptor interaction. TSS200, TSS1500, and 1stExon were identified as highly enriched areas of differentially methylated promoter CpG islands (DMCIs). In total, 61 differentially methylated genes (DMGs) were identified by the overlap of 2457 DEGs and 507 genes related to DMPs (DMPGs), of which 21 genes located near TSS200, TSS1500, and 1stExon were selected. Then, three key DMPs and the corresponding hub genes (RUNX3, HLA-DPA1, and CD6) were screened by the shrunken centroid algorithm and calculated to have areas under the ROC curve of 1.000, 0.931, and 0.986, respectively, indicating good diagnostic value. The GSEA results suggested that all three hub genes were highly associated with the immune response. Finally, positive mRNA expression of the three hub genes in clinical SS samples was verified by qRT-PCR, consistent with the GSE157159 data.

CONCLUSIONS

The identification of three hub genes provides novel insight into molecular mechanisms and therapeutic targets for SS. Key Points • Hub genes were screened by DNA methylation and transcriptome analyses. • The relative expression of hub genes in peripheral blood samples was verified by qRT-PCR. • HLA-DPA1 was correlated with the pathogenic mechanism of SS.