Pathogenetic mechanisms in the initiation and perpetuation of Sjögren's syndrome

Immunometabolic alteration of CD4+ T cells in the pathogenesis of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a prevalent autoimmune disorder wherein CD4+ T cells play a pivotal role in its pathogenesis. However, the underlying mechanisms driving the hyperactivity of CD4+ T cells in pSS remain poorly understood. This study aimed to investigate the potential role of immunometabolic alterations in driving the hyperactivity of CD4+ T cells in pSS. We employed Seahorse XF assay to evaluate the metabolic phenotype of CD4+ T cells, conducted flow cytometry to assess the effector function and differentiation of CD4+ T cells and measured the level of intracellular reactive oxygen species (ROS). Additionally, transcriptome sequencing, PCR, and Western blotting were utilized to examine the expression of glycolytic genes. Our investigation revealed that activated CD4+ T cells from pSS patients exhibited elevated aerobic glycolysis, rather than oxidative phosphorylation, resulting in excessive production of IFN-γ and IL-17A. Inhibition of glycolysis by 2-Deoxy-D-glucose reduced the expression of IFN-γ and IL-17A in activated CD4+ T cells and mitigated the differentiation of Th1 and Th17 cells. Furthermore, the expression of glycolytic genes, including CD3E, CD28, PIK3CA, AKT1, mTOR, MYC, LDHA, PFKL, PFKFB3, and PFKFB4, was upregulated in activated CD4+ T cells from pSS patients. Specifically, the expression and activity of LDHA were enhanced, contributing to an increased level of intracellular ROS. Targeting LDHA with FX-11 or inhibiting ROS with N-acetyl-cysteine had a similar effect on reversing the dysfunction of activated CD4+ T cells from pSS patients. Our study unveils heightened aerobic glycolysis in activated CD4+ T cells from pSS patients, and inhibition of glycolysis or its metabolite normalizes the dysfunction of activated CD4+ T cells. These findings suggest that aerobic glycolysis may be a promising therapeutic target for the treatment of pSS.

Endogenous IL-22 contributes to the pathogenesis of salivary gland dysfunction in the non-obese diabetic model of Sjögren's syndrome

Sjӧgren's syndrome is a systemic autoimmune disease primarily targeting the salivary and lacrimal glands. Our previous investigations have shown that administration of interleukin-22 (IL-22), an IL-10 family cytokine known for its complex and context-dependent effects on tissues, either protective- or detrimental, to salivary glands leads to hypofunction and pathological changes of salivary glands in C57BL/6 mice and in non-obese diabetic (NOD) mice, the latter being a commonly used model of Sjӧgren's syndrome. This study aims to delineate the pathophysiological roles of endogenously produced IL-22 in the development of salivary gland pathologies and dysfunction associated with Sjӧgren's disease in the NOD mouse model. Our results reveal that neutralizing IL-22 offered a protective effect on salivary gland function without significantly affecting the immune cell infiltration of salivary glands or the autoantibody production. Blockade of IL-22 reduced the levels of phosphorylated STAT3 in salivary gland tissues of NOD mice, while its administration to salivary glands had the opposite effect. Correspondingly, the detrimental impact of exogenously applied IL-22 on salivary glands was almost completely abrogated by a specific STAT3 inhibitor. Moreover, IL-22 blockade led to a downregulation of protein amounts of Ten-Eleven-Translocation 2, a methylcytosine dioxygenase critical for mediating interferon-induced responses, in salivary gland epithelial cells. IL-22 neutralization also exerted a protective effect on the salivary gland epithelial cells that express high levels of surface EpCAM and bear the stem cell potential, and IL-22 treatment in vitro hampered the survival/expansion of these salivary gland stem cells, indicating a direct negative impact of IL-22 on these cells. In summary, this study has uncovered a critical pathogenic role of the endogenous IL-22 in the pathogenesis of Sjögren's disease-characteristic salivary gland dysfunction and provided initial evidence that this effect is dependent on STAT3 activation and potentially achieved through fostering Tet2-mediated interferon responses in salivary gland epithelial cells and negatively affecting the EpCAMhigh salivary gland stem cells.

Emerging biologic frontiers for Sjogren's syndrome: Unveiling novel approaches with emphasis on extra glandular pathology

Primary Sjögren's Syndrome (pSS) is a complex autoimmune disorder characterized by exocrine gland dysfunction, leading to dry eyes and mouth. Despite growing interest in biologic therapies for pSS, FDA approval has proven challenging due to trial complications. This review addresses the absence of a molecular-target-based approach to biologic therapy development and highlights novel research on drug targets and clinical trials. A literature search identified potential pSS treatment targets and recent advances in molecular understanding. Overlooking extraglandular symptoms like fatigue and depression is a notable gap in trials. Emerging biologic agents targeting cytokines, signal pathways, and immune responses have proven efficacy. These novel therapies could complement existing methods for symptom alleviation. Improved grading systems accounting for extraglandular symptoms are needed. The future of pSS treatment may involve gene, stem-cell, and tissue-engineering therapies. This narrative review offers insights into advancing pSS management through innovative biologic interventions.

Melatonin improves salivary gland damage and hypofunction in pSS by inhibiting IL-6/STAT3 signaling through its receptor-dependent manner

OBJECTIVE

Primary Sjogren's syndrome (pSS) is an autoimmune disease of the exocrine glands with no specific or efficient treatments. Melatonin, a natural hormone, is revealed to show multiple biological functions, both receptor-dependent and independent effects, including anti-apoptotic, antioxidant, and anti-inflammatory activities. However, the potential mechanism by which melatonin protects salivary glands (SGs) of pSS from damage needs to be clarified. The purpose of current study was to explore the role and receptor-related mechanisms of melatonin in pSS-induced glandular damage.

METHODS AND RESULTS

NOD/Ltj mice were used to spontaneously mimic pSS-induced glandular hypofunction in vivo and primary human salivary gland epithelial (HSGE) cells were stimulated by interferon-γ (IFN-γ) to mimic pSS-induced inflammation in SGs cells in vitro. Melatonin-treated mice exhibited a significant reduction in SG injury of NOD/Ltj mice, which was accompanied by an increase in salivary flow rate, a decrease in inflammatory infiltration within the gland, and a suppression of oxidative stress indicators as well as cell apoptosis. Notably, both melatonin membrane receptors and nuclear receptors played an important role in the anti-apoptotic effects of melatonin on the SGs of NOD/Ltj mice. Furthermore, melatonin blocked the IL-6/STAT3 pathway through receptor-dependent manners in IFN-γ-stimulated HSGE cells. However, it was evident that the anti-oxidative and anti-apoptotic properties of melatonin on IFN-γ-stimulated HSGE cells were diminished by IL-6 treatment.

CONCLUSION

Melatonin had the potential to mitigate inflammation, oxidative stress, and apoptosis in SGs of pSS by inhibiting the IL-6/STAT3 pathway through receptor-dependent mechanisms. This intervention effectively prevented glandular damage and preserved functional integrity.

Identification and verification of inflammatory biomarkers for primary Sjögren's syndrome

INTRODUCTION

Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by inflammatory infiltration, and dysfunction of the salivary and lacrimal glands. This research aimed to explore the disease pathogenesis and improve the diagnosis and treatment of pSS by mining inflammation-associated biomarkers.

METHODS

Five pSS-related datasets were retrieved from the Gene Expression Omnibus (GEO) database. Inflammation-associated biomarkers were determined by the least absolute shrinkage and selection operator (LASSO) and support vector machines recursive feature elimination (SVM-RFE). Single sample gene set enrichment analysis (ssGSEA) was implemented to profile the infiltration levels of immune cells. Real-time quantitative PCR (RT-qPCR) verified the expression of biomarkers in clinical samples.

RESULTS

Four genes (LY6E, EIF2AK2, IL15, and CXCL10) were screened as inflammation-associated biomarkers in pSS, the predictive performance of which were determined among three pSS-related datasets (AUC > 0.7). Functional enrichment results suggested that the biomarkers were involved in immune and inflammation-related pathways. Immune infiltration analysis revealed that biomarkers were notably connected with type 2 T helper cells, regulatory T cells which were significantly expressed between pSS and control. TESTOSTERONE and CYCLOSPORINE were predicted to take effect by targeting CXCL10 and IL15 in pSS, respectively.

CONCLUSION

Four inflammation-associated biomarkers (LY6E, EIF2AK2, IL15, and CXCL10) were explored, and the underlying regulatory mechanisms and targeted drugs associated with these biomarkers were preliminarily investigated according to a series of bioinformatics methods based on the online datasets of pSS, which provided a reference for understanding the pathogenesis of pSS. Key Points • Inflammation-associated biomarkers (LY6E, EIF2AK2, IL15, and CXCL10) were firstly identified in Sjögren's syndrome based on LASSO and SVM-RFE analyses. • CXCL10, EIF2AK2 and LY6E were prominently positively correlated with immature B cells, while IL15 were significantly negatively correlated with memory B cells in Sjögren's syndrome. • LY6E, EIF2AK2, IL15, and CXCL10 were significantly more highly expressed in clinical Sjögren's syndrome samples compared to healthy control samples, which was consistent with the analysis results of the GEO database. •LY6E, EIF2AK2, IL15, and CXCL10 might be used as the biomarkers for the treatment and diagnosis of Sjögren's syndrome.

Skin neuropathy and immunomodulation in diseases

Skin is a vital barrier tissue of the body. Immune responses in the skin must be precisely controlled, which would otherwise cause severe disease conditions such as psoriasis, atopic dermatitis, or pathogenic infection. Research evidence has increasingly demonstrated the essential roles of neural innervations, i.e., sensory and sympathetic signals, in modulating skin immunity. Notably, neuropathic changes of such neural structures have been observed in skin disease conditions, implicating their direct involvement in various pathological processes. An in-depth understanding of the mechanism underlying skin neuropathy and its immunomodulatory effects could help reveal novel entry points for therapeutic interventions. Here, we summarize the neuroimmune interactions between neuropathic events and skin immunity, highlighting the current knowledge and future perspectives of this emerging research frontier.

B Cells Dynamic in Aging and the Implications of Nutritional Regulation

Aging negatively affects B cell production, resulting in a decrease in B-1 and B-2 cells and impaired antibody responses. Age-related B cell subsets contribute to inflammation. Investigating age-related alterations in the B-cell pool and developing targeted therapies are crucial for combating autoimmune diseases in the elderly. Additionally, optimal nutrition, including carbohydrates, amino acids, vitamins, and especially lipids, play a vital role in supporting immune function and mitigating the age-related decline in B cell activity. Research on the influence of lipids on B cells shows promise for improving autoimmune diseases. Understanding the aging B-cell pool and considering nutritional interventions can inform strategies for promoting healthy aging and reducing the age-related disease burden.

Association of endometriosis with Sjögren's syndrome: Genetic insights (Review)

Patients with a history of endometriosis have an increased risk of developing various autoimmune diseases such as rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, multiple sclerosis and celiac disease. There is a potential association between endometriosis and an increased susceptibility for Sjögren's syndrome (SS). SS is a common chronic, inflammatory, systemic, autoimmune, multifactorial disease of complex pathology, with genetic, epigenetic and environmental factors contributing to the development of this condition. It occurs in 0.5‑1% of the population, is characterized by the presence of ocular dryness, lymphocytic infiltrations and contributes to neurological, gastrointestinal, vascular and dermatological manifestations. Endometriosis is an inflammatory, estrogen‑dependent, multifactorial, heterogeneous gynecological disease, affecting ≤10% of reproductive‑age women. It is characterized by the occurrence of endometrial tissue outside the uterine cavity, mainly in the pelvic cavity, and is associated with pelvic pain, dysmenorrhea, deep dyspareunia and either subfertility or infertility. It is still unclear whether SS appears as a secondary response to endometriosis, or it is developed due to any potential shared mechanisms of these conditions. The aim of the present review was to explore further the biological basis only of the co‑occurrence of these disorders but not their association at clinical basis, focusing on the analysis of the partially shared genetic background between endometriosis and SS, and the clarification of the possible similarities in the underlying pathogenetic mechanisms and the relevant molecular pathways.

Immunotherapeutic approaches for systemic lupus erythematosus: early overview and future potential

Systemic lupus erythematosus (SLE) is a complex autoimmune disease. Current SLE therapies include immunosuppressants, antimalarial drugs, non-steroidal anti-inflammatory drugs (NSAIDs), and corticosteroids, but these treatments can cause substantial toxicities to organs and may not be effective for all patients. In recent years, significant progress has been made in the treatment of SLE using immunotherapy, including Benlysta and Saphnelo. These advances in immunotherapy hold promise for SLE patients, providing new therapeutic options that may offer better clinical benefit and effectiveness. Simultaneously, several new biological therapies focusing on cytokines, peptides, targeted antibodies, and cell-based approaches are under clinical evaluation and have shown immense potential for the treatment of SLE. However, the complexity of SLE immunopathogenesis and disease heterogeneity present significant challenges in the development of effective immunological therapies. This review aims to discuss past experiences and understanding of diverse immunological targeting therapies for SLE and highlight future perspectives for the development of novel immunological therapies.

Extracellular vesicle-encapsulated miR-10a-5p derived from MDSCs restrains germinal center B cells in experimental Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a progressive systemic autoimmune disease characterized by chronic inflammation of the exocrine glands, resulting in damage to the salivary and lacrimal glands. Our group and other researchers have reported that myeloid-derived suppressor cell-derived extracellular vesicles (MDSC-EVs) could attenuate the progression of autoimmune disease by impairing T-cell function. However, the effect of MDSC-EVs on B-cell function and the underlying mechanism remains largely unknown. In this study, we found that MDSC-EVs significantly attenuated the progression of experimental Sjögren's syndrome (ESS). Moreover, treatment with MDSC-EVs via intravenous injection markedly reduced the percentage of germinal center (GC) B cells in ESS mice. In vitro, MDSC-EVs could directly suppress the generation of GC B cells and the expression of B cell lymphoma 6 (Bcl-6) in B cells under GC B-cell-polarizing conditions. Mechanistically, miR-10a-5p carried by MDSC-EVs regulated the differentiation of GC B cells by targeting Bcl-6, and inhibition of miR-10a-5p in MDSC-EVs significantly reversed the effect of MDSC-EVs involved in alleviating the development of ESS. Taken together, our findings demonstrated that miR-10a-5p carried by MDSC-EVs inhibited the generation of B cells by targeting Bcl-6 and eventually alleviated the progression of ESS, which may provide novel therapeutic targets for the treatment of pSS.

Butyrophilin 2a2 (Btn2a2) expression on thymic epithelial cells promotes central T cell tolerance and prevents autoimmune disease

Butyrophilins are surface receptors belonging to the immunoglobulin superfamily. While several members of the butyrophilin family have been implicated in the development of unconventional T cells, butyrophilin 2a2 (Btn2a2) has been shown to inhibit conventional T cell activation. Here, we demonstrate that in steady state, the primary source of Btn2a2 are thymic epithelial cells (TEC). Absence of Btn2a2 alters thymic T cell maturation and bypasses central tolerance mechanisms. Furthermore, Btn2a2-/- mice develop spontaneous autoimmunity resembling human primary Sjögren's Syndrome (pSS), including formation of tertiary lymphoid structures (TLS) in target organs. Ligation of Btn2a2 on developing thymocytes is associated with reduced TCR signaling and CD5 levels, while absence of Btn2a2 results in increased TCR signaling and CD5 levels. These results define a novel role for Btn2a2 in promoting central tolerance by modulating TCR signaling strength and indicate a potential mechanism of pSS development.

B-Cell Receptor Signaling Is Thought to Be a Bridge between Primary Sjogren Syndrome and Diffuse Large B-Cell Lymphoma

Primary Sjogren syndrome (pSS) is the second most common autoimmune disorder worldwide, which, in the worst scenario, progresses to Non-Hodgkin Lymphoma (NHL). Despite extensive studies, there is still a lack of knowledge about developing pSS for NHL. This study focused on cells' signaling in pSS progression to the NHL type of diffuse large B-cell lymphoma (DLBCL). Using bulk RNA and single cell analysis, we found five novel pathologic-independent clusters in DLBCL based on cells' signaling. B-cell receptor (BCR) signaling was identified as the only enriched signal in DLBCL and pSS peripheral naive B-cells or salivary gland-infiltrated cells. The evaluation of the genes in association with BCR has revealed that targeting CD79A, CD79B, and LAMTOR4 as the shared genes can provide novel biomarkers for pSS progression into lymphoma.

Inhibition of NLRP3 inflammasome activity by MCC950 leads to exacerbation of Sjӧgren's syndrome pathologies in non-obese diabetic mice

Sjӧgren's syndrome (SS) is an autoimmune inflammatory disease characterized by chronic inflammation and dysfunction of exocrine glands and causes dry mouth, dry eyes and various systemic health problems. The objective of this study is to define the in vivo actions of the endogenous NLRP3 inflammasome, a key initiator and mediator of various immune and inflammatory conditions, in newly established SS disease. MCC950, a highly specific small-molecule inhibitor of NLRP3 inflammasome formation and activation, was intraperitoneally administered to the female non-obese diabetic (NOD) mice aged 11 weeks, which have newly established SS-like hyposalivation and pathologies. The injection was conducted three times weekly for three consecutive weeks and mice were analysed for characteristic SS pathologies at the end of the treatments. MCC950 treatment resulted in a marked reduction in salivary secretion and an exacerbation of leukocyte infiltration of submandibular glands. The disease-worsening effect of MCC950 treatment was accompanied by increased T and B cell numbers, enhanced T helper 1 response and reduced aquaporin 5 expression in submandibular glands. Hence, ablation of endogenous NLRP3 inflammasome activity by MCC950 with established autoimmune exocrinopathy exacerbates salivary gland dysfunction and inflammation, indicating a disease-alleviating and inflammation-dampening action of the endogenous NLRP3 inflammasome activity during established SS disease in the non-obese diabetic mouse model.

Melatonin: a potential therapeutic approach for the management of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease that primarily affects the exocrine glands and is mainly characterized by sicca symptoms of the eyes and mouth. Approximately 30-50% of pSS patients develop systemic multi-organ disorders including malignant lymphoma. The etiology of pSS is not well understood; growing evidence suggests that uncontrolled immune/inflammatory responses, excessive oxidative stress, defected apoptosis, dysregulated autophagy, exosomes, and exogenous virus infections may participate in the pathogenesis of pSS. There is no ideal therapeutic method for pSS; the management of pSS is mainly palliative, which aims to alleviate sicca symptoms. Melatonin, as the main secretory product of the pineal gland, has been evidenced to show various physiological functions, including effects of immunoregulation, capability of antioxidation, moderation of autophagy, suppressive activities of apoptosis, regulative capacity of exosomes, properties of anti-infection, and improvement of sleep. The beneficial effects of melatonin have been already validated in some autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes mellitus (T1DM), systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD). However, our previous research firstly revealed that melatonin might inhibit pathogenic responses of peripheral Th17 and double-negative (DN) T cells in pSS. More importantly, melatonin administration alleviated the development of pSS in animal models with reduced infiltrating lymphocytes, improved functional activity of salivary gland, and decreased production of inflammatory factors as well as autoantibodies. Owing to the important biological properties reported in melatonin are characteristics closely related to the treatment of pSS; the potential role and underlying mechanisms of melatonin in the administration of pSS are certainly worth further investigations. Consequently, the aim of this review is to give a deep insight to the therapeutic potency of melatonin for pSS.

Interleukin-22 Exerts Detrimental Effects on Salivary Gland Integrity and Function

Interleukin-22 (IL-22) affects epithelial tissue function and integrity in a context-dependent manner. IL-22 levels are elevated in salivary glands of Sjögren’s syndrome (SS) patients, but its role in the pathogenesis of this disease remains unclear. The objective of this study is to elucidate the impact of IL-22 on salivary gland tissue integrity and function in murine models. We showed that IL-22 levels in sera and salivary glands increased progressively in female non-obese diabetic (NOD) mice, accompanying the development of SS. Administration of IL-22 to the submandibular glands of NOD mice prior to the disease onset reduced salivary secretion and induced caspase-3 activation in salivary gland tissues, which were accompanied by alterations in multiple genes controlling tissue integrity and inflammation. Similarly, IL-22 administration to submandibular glands of C57BL/6 mice also induced hyposalivation and caspase-3 activation, whereas blockade of endogenous IL-22 in C57BL/6 mice treated with anti-CD3 antibody mitigated hyposalivation and caspase-3 activation. Finally, IL-22 treatment reduced the number of viable C57BL/6 mouse submandibular gland epithelial cells cultured in vitro, indicating a direct impact of this cytokine on these cells. We conclude that IL-22 exerts a detrimental impact on salivary gland tissues.

Machine learning based on metabolomics reveals potential targets and biomarkers for primary Sjogren’s syndrome

Background: Using machine learning based on metabolomics, this study aimed to construct an effective primary Sjogren’s syndrome (pSS) diagnostics model and reveal the potential targets and biomarkers of pSS.

Methods: From a total of 39 patients with pSS and 38 healthy controls (HCs), serum specimens were collected. The samples were analyzed by ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry. Three machine learning algorithms, including the least absolute shrinkage and selection operator (LASSO), random forest (RF), and extreme gradient boosting (XGBoost), were used to build the pSS diagnosis models. Afterward, four machine learning methods were used to reduce the dimensionality of the metabolomics data. Finally, metabolites with significant differences were screened and pathway analysis was conducted.

Results: The area under the curve (AUC), sensitivity, and specificity of LASSO, RF and XGBoost test set all reached 1.00. Orthogonal partial least squares discriminant analysis was used to classify the metabolomics data. By combining the results of the univariate false discovery rate and the importance of the variable in projection, we identified 21 significantly different metabolites. Using these 21 metabolites for diagnostic modeling, the AUC, sensitivity, and specificity of LASSO, RF, and XGBoost all reached 1.00. Metabolic pathway analysis revealed that these 21 metabolites are highly correlated with amino acid and lipid metabolisms. On the basis of 21 metabolites, we screened the important variables in the models. Further, five common variables were obtained by intersecting the important variables of three models. Based on these five common variables, the AUC, sensitivity, and specificity of LASSO, RF, and XGBoost all reached 1.00.2-Hydroxypalmitic acid, L-carnitine and cyclic AMP were found to be potential targets and specific biomarkers for pSS.

Conclusion: The combination of machine learning and metabolomics can accurately distinguish between patients with pSS and HCs. 2-Hydroxypalmitic acid, L-carnitine and cyclic AMP were potential targets and biomarkers for pSS.

The role of PET/CT in connective tissue disorders: systemic sclerosis, Sjögren's syndrome and systemic lupus erythematosus

Advanced imaging techniques are needed to help clinicians in the diagnosis, in the choice of the right time for therapeutic interventions or for modifications and monitoring of treatment response in patients with autoimmune connective tissue diseases. Nuclear medicine imaging, especially PET/CT and PET/MRI, may play an important role in detecting disease activity, assessing early treatment response as well as in clarifying the complex mechanisms underlying systemic sclerosis, Sjögren's syndrome or systemic lupus erythematosus. In addition, [¹⁸F]FDG PET/CT may help in excluding or detecting coexisting malignancies. Other more specific radiopharmaceuticals are being developed and investigated, targeting specific cells and molecules involved in connective tissue diseases. Further larger studies with standardized imaging protocol and image interpretation are strongly required before including PET/CT in the diagnostic work-up of subsets of patients with autoimmune connective tissue diseases.

TAFRO syndrome: A severe manifestation of Sjogren's syndrome? A systematic review

BACKGROUND

Sjögren's syndrome (SjS) is a systemic autoimmune disease characterized by lymphocytic infiltration of the salivary and lacrimal glands associated with sicca syndrome. TAFRO syndrome is a systemic inflammatory disease of unknown cause, characterized by Thrombocytopenia, Anasarca, Fever, Reticulin fibrosis, Renal dysfunction and Organomegaly, first reported in 2010 in Japanese patients. Despite their rarity, both conditions have been concurrently reported in several patients during the recent years, hence questioning the existence of shared or related features.

METHODS

A systematic review of the literature regarding SjS associated with TAFRO syndrome (SjS-TAFRO) was performed. The 2019 updated Masaki diagnostic criteria were used for TAFRO syndrome and SjS was considered when the diagnosis was mentioned by the authors, necessarily with either anti-Sjogren's Syndrome A (SSA) ± anti-Sjogren's Syndrome B (SSB) antibodies and/or histological evidence of focal lymphocytic sialadenitis.

RESULTS

Ten cases of SjS-TAFRO have been reported in the literature to date. Compared to SjS patients without TAFRO syndrome, these 10 SjS-TAFRO had a lower female predominance (2.3:1 vs 9:1 women to man ratio) and a higher frequency of anti-SSA antibodies (90% vs 70%). All fulfilled the three major Masaki criteria i.e., anasarca, thrombocytopenia, and systemic inflammation. Seven of them (70%) had megakaryocyte hyperplasia or reticulin fibrosis in the bone marrow. Lymph node biopsy was performed in 8 out of 10 cases (80%) and results were consistent with Castleman disease in 6 (75%). Eight of them had developed renal failure (80%) within six months. Nine of them (90%) had organomegaly, with hepatosplenomegaly in 8 cases and splenomegaly alone in 1.

CONCLUSION

This review brings new insights regarding TAFRO syndrome and suggests it could be a severe manifestation of SjS. The identification of shared abnormal signaling pathways could help in the therapeutic management of both diseases, which face an unmet therapeutic need.

Sjögren's Syndrome-Related Organs Fibrosis: Hypotheses and Realities

Sjögren's syndrome (SS) is a systemic chronic autoimmune disorder characterized by lymphoplasmacytic infiltration of salivary glands (SGs) and lacrimal glands, causing glandular damage. The disease shows a combination of dryness symptoms found in the oral cavity, pharynx, larynx, and vagina, representing a systemic disease. Recent advances link chronic inflammation with SG fibrosis, based on a molecular mechanism pointing to the epithelial to mesenchymal transition (EMT). The continued activation of inflammatory-dependent fibrosis is highly detrimental and a common final pathway of numerous disease states. The important question of whether and how fibrosis contributes to SS pathogenesis is currently intensely debated. Here, we collect the recent findings on EMT-dependent fibrosis in SS SGs and explore clinical evidence of multi-organ fibrosis in SS to highlight potential avenues for therapeutic investigation.

Digital image analysis of intraepithelial B-lymphocytes to assess lymphoepithelial lesions in salivary glands of Sjögren's syndrome patients

OBJECTIVE

Salivary glands of primary SS (pSS) patients characteristically harbour periductal infiltrates, in which lymphoepithelial lesions (LELs) can develop. LELs are composed of hyperplastic ductal epithelium with infiltrating lymphocytes and may assist in the challenging diagnostic process of pSS. As manual identification of LELs remains difficult, we aimed to identify LELs by using an objective digital image analysis (DIA) algorithm that detects intraepithelial lymphocytes.

METHODS

A virtual triple-staining technique developed for this study was used to count intraepithelial lymphocytes in consecutive slides stained for CD3 (T-lymphocytes), high-molecular-weight cytokeratin (hmwCK) (striated ducts) and CD20 (B-lymphocytes) in labial and parotid gland biopsies in a diagnostic cohort of 109 sicca patients. Patients were classified as having pSS or non-SS according to the ACR-EULAR classification criteria.

RESULTS

T-lymphocytes were detected in almost all analysed ducts of pSS and non-SS sicca patients, whereas intraepithelial B-lymphocytes were present in 59-68% of labial and parotid gland biopsies of pSS patients, against only 2-3% of patients classified as non-SS. Intraepithelial B-lymphocytes were found in almost all striated ducts with hyperplasia (LELs). Remarkably, ∼25% of analysed striated ducts without hyperplasia of pSS patients also contained B-lymphocytes (precursor-LELs). Furthermore, presence of intraepithelial B-lymphocytes was associated with clinical parameters of pSS (i.e. serology).

CONCLUSION

The presence of intraepithelial B-lymphocytes in salivary gland biopsies of sicca patients is a clear indicator of pSS and can be used as an objective alternative to LEL scoring. Therefore, identification of B-lymphocyte-containing ducts should be added to the diagnostic histopathological work-up of patients suspected of pSS.

Double-negative T cells: Setting the stage for disease control or progression

Double-negative (DN) T cells are present at relatively low frequencies in human peripheral blood, and are characterized as expressing the alpha-beta or gamma-delta T-cell receptor (TCR), but not the CD4 nor the CD8 co-receptors. Despite their low frequencies, these cells are potent producers of cytokines and, thus, are key orchestrators of immune responses. DN T cells were initially associated with induction of peripheral immunological tolerance and immunomodulatory activities related to disease prevention. However, other studies demonstrated that these cells can also display effector functions associated with pathology development. This apparent contradiction highlighted the heterogeneity of the DN T-cell population. Here, we review phenotypic and functional characteristics of DN T cells, emphasizing their role in human diseases. The need for developing biomarkers to facilitate the translation of studies from animal models to humans will also be discussed. Finally, we will examine DN T cells as promising therapeutic targets to prevent or inhibit human disease development.

Gene Variation at Immunomodulatory and Cell Adhesion Molecules Loci Impacts Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease triggered by a combination of environmental and host genetic factors, which results in the focal lymphocytic infiltration of exocrine glands causing eye and mouth dryness. Glandular infiltrates include T and B cell subsets positive for CD5 and/or CD6, two surface scavenger receptors involved in the fine-tuning of intracellular signals mediated by the antigen-specific receptor complex of T (TCR) and B (BCR) cells. Moreover, the epithelial cells of inflamed glands overexpress CD166/ALCAM, a CD6 ligand involved in homo and heterotypic cell adhesion interactions. All this, together with the reported association of functionally relevant single nucleotide polymorphisms (SNPs) of CD5, CD6, and CD166/ALCAM with the risk or prognosis of some immune-mediated inflammatory disorders, led us to investigate similar associations in a local cohort of patients with pSS. The logistic regression analyses of individual SNPs showed the association of CD5 rs2241002^T with anti-Ro/La positivity, CD6 rs17824933^C with neutropenia, and CD6 rs11230563^T with increased leukopenia and neutropenia but decreased peripheral nervous system EULAR Sjögren's syndrome disease activity index (ESSDAI). Further analyses showed the association of haplotypes from CD5 (rs2241002^T-rs2229177^C) with anemia and thrombocytopenia, CD6 (rs17824933^G-rs11230563^C-rs12360861^G) with cutaneous ESSDAI, and CD166/ALCAM (rs6437585^C-rs579565^A-rs1044243^C and rs6437585^C-rs579565^G-rs1044243^T) with disease susceptibility and several analytical parameters (anti-nuclear antibodies, neurological ESSDAI, and hematologic cytopenias). These results support the relevance of gene variation at loci coding for cell surface receptors involved in the modulation of T and B lymphocyte activation (CD5, CD6) and epithelial-immune cell adhesion (CD166/ALCAM) in modulating the clinical and analytical outcomes in patients with pSS.

ICOS Gene Polymorphisms (IVS1 + 173 T/C and c. 1624 C/T) in Primary Sjögren's Syndrome Patients: Analysis of ICOS Expression

Background: Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease, which affects exocrine glands. T cell activation is a trigger mechanism in the immune response. Hyperreactivity of T cells and antibody production are features in pSS. ICOS can be critical in the pathogenesis of pSS. Methods: A total of 134 pSS patients and 134 control subjects (CS) were included. Genotyping was performed by PCR-RFLP. ICOS mRNA expression was quantified by real-time PCR, and CD4+ ICOS+ T cells were determined by flow cytometry. Results: The ICOS IVS1 + 173 T>C polymorphisms were not associated with susceptibility to pSS (p = 0.393, CI = 0.503−1.311). However, the c.1624 C>T polymorphism was associated with a reduction in the risk of development of pSS (p = 0.015, CI = 0.294−0.884). An increase in ICOS mRNA expression in patients was observed (3.7-fold). Furthermore, pSS patients showed an increase in membranal-ICOS expression (mICOS). High expression of mICOS (MFI) was associated with lymphocytic infiltration. Conclusions: The IVS1 + 173 polymorphism is not a genetic marker for the development of pSS, while c.1624 T allele was associated with a low risk. However, elevated mICOS expression in pSS patients with high lymphocytic infiltration was found. ICOS may have an important role in the immunopathogenesis of pSS and should be analyzed in T cell subsets in pSS patients as a possible disease marker.

Plasmacytoid dendritic cells promote the pathogenesis of Sjögren's syndrome

Plasmacytoid dendritic cells (pDCs) produce type I interferons (IFNs) and promote pathogenesis of multiple autoimmune diseases. Autoimmune Sjögren's syndrome (SS) primarily affects salivary and lacrimal glands, causing their inflammation, destruction and dysfunction. pDCs and type I IFN activity are elevated in salivary glands of SS patients, and this study seeks to elucidate the in vivo actions of pDCs in SS pathogenesis using the non-obese diabetic (NOD) mouse model. We confirmed the type I IFN-dependency of SS development in female NOD mice and elevation of pDC-type I IFN in their submandibular glands (SMGs). We administered a pDC-depleting anti-BST2/CD317 antibody to female NOD mice from 4 to 7 weeks of age at the early stage of SS, and assessed SS pathologies at age 10 weeks, the time of disease onset. Depletion of pDCs impeded the development of SMG inflammation and secretory dysfunction. It drastically reduced the amount of type I IFN mRNA and the number of total leukocytes, and T- and B lymphocytes in SMGs. Gene expression analyses showed that pDC depletion markedly diminished SMG expression of IL-7, BAFF, TNF-α, IFN-γ, CXCL9, CXCL11, CD40, CD40L, Lt-α, Lt-β and NOS2. Hence, pDCs critically contribute to the development and onset of SS-like salivary gland exocrinopathy.

GABA Administration Ameliorates Sjogren’s Syndrome in Two Different Mouse Models

Sjögren’s syndrome (SS) is a chronic autoimmune disease characterized by lymphocytic infiltrates in the salivary and lachrymal glands resulting in oral and ocular dryness. There are no clinically approved therapies to slow the progression of SS. Immune cells possess receptors for the neurotransmitter GABA (GABA-Rs) and their activation has immunoregulatory actions. We tested whether GABA administration has potential for amelioration of SS in NOD.B10-H2^b and C57BL/6.NOD-Aec1Aec2 mice, two spontaneous SS models. Oral GABA treatment was initiated (1) after the development of sialadenitis but before the onset of overt symptoms, or (2) after the appearance of overt symptoms. When assessed weeks later, GABA-treated mice had greater saliva and tear production, as well as quicker times to salvia flow, in both SS mouse models. This was especially evident when GABA treatment was initiated after the onset of overt disease. This preservation of exocrine function was not accompanied by significant changes in the number or area of lymphocytic foci in the salivary or lachrymal glands of GABA-treated mice and we discuss the possible reasons for these observations. Given that GABA-treatment preserved saliva and tear production which are the most salient symptoms of SS and is safe for consumption, it may provide a new approach to help ameliorate SS.

Why Should We Consider Potential Roles of Oral Bacteria in the Pathogenesis of Sjögren Syndrome?

Sjögren syndrome (SS) is a chronic autoimmune disorder that primarily targets the salivary and lacrimal glands. The pathology of these exocrine glands is characterized by periductal focal lymphocytic infiltrates, and both T cell-mediated tissue injury and autoantibodies that interfere with the secretion process underlie glandular hypofunction. In addition to these adaptive mechanisms, multiple innate immune pathways are dysregulated, particularly in the salivary gland epithelium. Our understanding of the pathogenetic mechanisms of SS has substantially improved during the past decade. In contrast to viral infection, bacterial infection has never been considered in the pathogenesis of SS. In this review, oral dysbiosis associated with SS and evidence for bacterial infection of the salivary glands in SS were reviewed. In addition, the potential contributions of bacterial infection to innate activation of ductal epithelial cells, plasmacytoid dendritic cells, and B cells and to the breach of tolerance via bystander activation of autoreactive T cells and molecular mimicry were discussed. The added roles of bacteria may extend our understanding of the pathogenetic mechanisms and therapeutic approaches for this autoimmune exocrinopathy.

Asymptomatic myocardial dysfunction was revealed by feature tracking cardiac magnetic resonance imaging in patients with primary Sjögren's syndrome

AIM

To evaluate subclinical left ventricular (LV) regional dysfunction in patients with primary Sjögren's syndrome (pSS) using feature tracking cardiac magnetic resonance (FT-CMR) imaging and to identify pSS characteristics independently associated with LV regional dysfunction.

METHOD

Fifty patients with pSS and 20 controls without cardiovascular disease underwent non-contrast CMR imaging. Labial gland biopsy was performed in 42 patients (84%). Disease activity was assessed using the European League Against Rheumatism Sjögren's syndrome disease activity index (ESSDAI). LV global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS) were measured using FT-CMR.

RESULTS

No significant differences in cardiovascular risk factors were found between the pSS group and controls. The pSS group had significantly lower GLS (P = .015) and GCS (P = .008) than the control group. Multiple linear regression analysis indicated that GCS was significantly associated with Raynaud's phenomenon (P = .015), focus score ≥2 (P = .032), and total ESSDAI score ≥8 (P = .029).

CONCLUSION

FT-CMR can reveal subclinical LV regional dysfunction in patients with pSS without cardiovascular disease. Furthermore, patients with pSS and Raynaud's phenomenon, a focus score ≥2, or an ESSDAI score ≥8 were considered to be at high risk for myocardial dysfunction.

A comprehensive review of the influence of Epigallocatechin gallate on Sjögren's syndrome associated molecular regulators of exocytosis (Review)

Sjögren's syndrome (SS) is an autoimmune disorder that affects the salivary glands, leading to reduced secretory functions and oral and ocular dryness. The salivary glands are composed of acinar cells that are responsible for the secretion and production of secretory granules, which contain salivary components, such as amylase, mucins and immunoglobulins. This secretion process involves secretory vesicle trafficking, docking, priming and membrane fusion. A failure during any of the steps in exocytosis in the salivary glands results in the altered secretion of saliva. Soluble N-ethylmaleimide-sensitive-factor attachment protein receptors, actin, tight junctions and aquaporin 5 all serve an important role in the trafficking regulation of secretory vesicles in the secretion of saliva via exocytosis. Alterations in the expression and distribution of these selected proteins leads to salivary gland dysfunction, including SS. Several studies have demonstrated that green tea polyphenols, most notably Epigallocatechin gallate (EGCG), possess both anti-inflammatory and anti-apoptotic properties in normal human cells. Molecular, cellular and animal studies have indicated that EGCG can provide protective effects against autoimmune and inflammatory reactions in salivary glands in diseases such as SS. The aim of the present article is to provide a comprehensive and up-to-date review on the possible therapeutic interactions between EGCG and the selected molecular mechanisms associated with SS.

Autoimmunity in dry eye disease - An updated review of evidence on effector and memory Th17 cells in disease pathogenicity

The classic Th1/Th2 dogma has been significantly reshaped since the subsequent introduction of several new T helper cell subsets, among which the most intensively investigated during the last decade is the Th17 lineage that demonstrates critical pathogenic roles in autoimmunity and chronic inflammation - including the highly prevalent dry eye disease. In this review, we summarize current concepts of Th17-mediated disruption of ocular surface immune homeostasis that leads to autoimmune inflammatory dry eye disease, by discussing the induction, activation, differentiation, migration, and function of effector Th17 cells in disease development, highlighting the phenotypic and functional plasticity of Th17 lineage throughout the disease initiation, perpetuation and sustention. Furthermore, we emphasize the most recent advance in Th17 memory formation and function in the chronic course of dry eye disease, a major area to be better understood for facilitating the development of effective treatments in a broader field of autoimmune diseases that usually present a chronic course with recurrent episodes of flare in the target tissues or organs.

Sclerosing Sialadenitis Is Associated With Salivary Gland Hypofunction and a Unique Gene Expression Profile in Sjögren's Syndrome

Purpose

To develop a novel method to quantify the amount of fibrosis in the salivary gland and to investigate the relationship between fibrosis and specific symptoms associated with Sjögren’s syndrome (SS) using this method.

Materials and Methods

Paraffin-embedded labial salivary gland (LSG) slides from 20 female SS patients and their clinical and LSG pathology data were obtained from the Sjögren’s International Collaborative Clinical Alliance. Relative interstitial fibrosis area (RIFA) in Masson’s trichrome-stained LSG sections was quantified from digitally scanned slides and used for correlation analysis. Gene expression levels were assessed by microarray analysis. Core promoter accessibility for RIFA-correlated genes was determined using DNase I hypersensitive sites sequencing analysis.

Results

RIFA was significantly correlated with unstimulated whole saliva flow rate in SS patients. Sixteen genes were significantly and positively correlated with RIFA. In a separate analysis, a group of differentially expressed genes was identified by comparing severe and moderate fibrosis groups. This combined set of genes was distinct from differentially expressed genes identified in lung epithelium from idiopathic pulmonary fibrosis patients compared with controls. Single-cell RNA sequencing analysis of salivary glands suggested most of the RIFA-correlated genes are expressed by fibroblasts in the gland and are in a permissive chromatin state.

Conclusion

RIFA quantification is a novel method for assessing interstitial fibrosis and the impact of fibrosis on SS symptoms. Loss of gland function may be associated with salivary gland fibrosis, which is likely to be driven by a unique set of genes that are mainly expressed by fibroblasts.

Sex Differences in Otolaryngology: Focus on the Emerging Role of Estrogens in Inflammatory and Pro-Resolving Responses

Otolaryngology (also known as ear, nose, and throat (ENT)) diseases can be significantly affected by the level of sex hormones, which indicates that sex differences affect the manifestation, pathophysiology, and outcomes of these diseases. Recently, increasing evidence has suggested that proinflammatory responses in ENT diseases are linked to the level of sex hormones. The sex hormone receptors are present on a wide variety of immune cells; therefore, it is evident that they play crucial roles in regulating the immune system and hence affect the disease progression of ENT diseases. In this review, we focus on how sex hormones, particularly estrogens, regulate ENT diseases, such as chronic rhinosinusitis, vocal fold polyps, thyroid cancer, Sjögren’s syndrome, and head and neck cancers, from the perspectives of inflammatory responses and specialized proresolving mediator-driven resolution. This paper aims to clarify why considering sex differences in the field of basic and medical research on otolaryngology is a key component to successful therapy for both males and females in the future.

Inflammatory Stratification in Primary Sjögren's Syndrome Reveals Novel Immune Cell Alterations in Patients' Minor Salivary Glands

There is a critical need to deconvolute the heterogeneity displayed by the minor salivary glands of primary Sjögren’s syndrome (pSS) patients. This is challenging primarily because the disease etiology remains unknown. The hypothesis includes that initial events in the disease pathogenesis target the salivary glands, thereby triggering the development of focal infiltrates (≥50 mononuclear cells) and finally germinal center-like structures. However, the proportion of key mononuclear immune cells residing at these sites, in combination with the overall ratio of morphometric tissue atrophy and adipose infiltration within the minor salivary glands (MSG) parenchyma at distinct phases of inflammatory disease establishment and progression have not been quantified in detail. In this cross-sectional study, we intended to address this problem by stratifying 85 patients into mild (S1), moderate (S2), and severe (S3) stages using the Inflammatory severity index. We found that mild (<3%) and marked (≥3%) levels of atrophy were accompanied by the respective levels of adipose infiltration in the non-SS sicca controls (p <0.01), but not in pSS patients. The percentage of adipose infiltration significantly correlated with the age of patients (r = 0.458, p <0.0001) and controls (r = 0.515, p <0.0001). The CD4⁺ T helper cell incidence was reduced in the focal infiltrates of the MSG of S2 patients compared to S1 (p <0.01), and in S2 compared to S1 and S3 combined (p <0.05). CD20⁺ B cells increased from S1 to S3 (p <0.01) and S2 to S3 (p <0.01), meanwhile CD138⁺ plasma cells diminished in S3 patients compared to both S1 and S2 groups combined (p <0.01). The proportion of patients with anti-Ro/SSA⁺, anti-La/SSB⁺, and RF⁺ increased over the course of inflammatory disease progression and they were significantly more common in the S3 group relative to S1 (p <0.05). On the other hand, S2 patients measured a higher mean salivary flow relative to S1 and S3 patients combined (p <0.05). Our results demonstrate how the proposed Inflammatory severity index stratification revealed pathological cell and tissue-associated aberrations in the salivary component over the course of inflammatory progression, and their correlations to clinical outcomes. This could be directly transferred to the optimization of available diagnostic strategies applied for pSS patients.

The Multiple Roles of B Cells in the Pathogenesis of Sjögren's Syndrome

Primary Sjögren’s syndrome (pSS) is a chronic autoimmune disease characterized by lymphocytic infiltration and tissue destruction of exocrine glands such as salivary glands. Although the formation of ectopic lymphoid tissue in exocrine glands and overproduction of autoantibodies by autoreactive B cells highlight the critical involvement of B cells in disease development, the precise roles of various B cell subsets in pSS pathogenesis remain partially understood. Current studies have identified several novel B cell subsets with multiple functions in pSS, among which autoreactive age-associated B cells, and plasma cells with augmented autoantibody production contribute to the disease progression. In addition, tissue-resident Fc Receptor-Like 4 (FcRL4)⁺ B cell subset with enhanced pro-inflammatory cytokine production serves as a key driver in pSS patients with mucosa-associated lymphoid tissue (MALT)-lymphomas. Recently, regulatory B (Breg) cells with impaired immunosuppressive functions are found negatively correlated with T follicular helper (Tfh) cells in pSS patients. Further studies have revealed a pivotal role of Breg cells in constraining Tfh response in autoimmune pathogenesis. This review provides an overview of recent advances in the identification of pathogenic B cell subsets and Breg cells, as well as new development of B-cell targeted therapies in pSS patients.

Sjögren's syndrome with adult-onset Still's disease: an overlap syndrome?

Adult-onset Still's disease (AOSD) is a rare systemic auto-inflammatory disease that is an exclusive diagnosis that needs to previously exclude infections, tumors, and rheumatic diseases. There are few reports on AOSD overlapping with other rheumatic diseases. We reported a 55-year-old male who presented with a high, daily spiking fever associated with an evanescent salmon-pink rash, arthralgia, and sore throat. He had a history of dryness of the mouth and eyes for decades with no medical treatment. On admission, tests for antinuclear antibody (ANA) and anti-SSA/Ro-52 antibody were positive, and salivary gland biopsy showed focal lymphocytic sialadenitis with a focus score of ≥ 1 foci/4 mm², which was consistent with a diagnosis of primary Sjögren's syndrome (SS). However, the disease activity of SS was low at the time of the report. Combined with significantly elevated acute phase reactants, the patient also met the classification criteria of both Yamakuchi and Futel for AOSD. His clinical symptoms were relieved quickly with glucocorticoid therapy. We also reviewed the literature on SS with AOSD and AOSD with other rheumatic diseases, and scattered case reports were retrieved. So we think that AOSD is not an absolutely exclusive diagnosis and can occur in patients with other rheumatic diseases. To our knowledge, this is the only literature review of a reported AOSD case in a SS patient.

Intratracheal Poly(I:C) Exposure Accelerates the Immunological Disorder of Salivary Glands in Sjogren's-Like NOD/ShiLtJ Mice

Evidences have suggested that Sjogren's syndrome (SS) is associated with viral infection. The aim of this study was to investigate the involvement of respiratory viral poly(I:C) in the pathogenesis of SS and potential mechanisms using a SS-like NOD/ShiLtJ (NOD) mouse model. 5-week female NOD mice were intratracheally administered poly(I:C) every other day for 5 times to mimic viral infection. Pilocarpine induced saliva secretion was determined every 8 days. Submandibular glands (SMG) and lungs were harvested for the detection of pathological changes. We found that intratracheal administration of poly(I:C) significantly advanced and enhanced the reduction of saliva flow rate in NOD mice. Furthermore, poly(I:C) treatment aggravated the histopathological lesions and inflammatory cells infiltration in SMG. Accompanied by elevated expression of IFN cytokines and IL-33, Th1 activation was enhanced in SMG of poly(I:C)-treated NOD mice, but Th17 cells activation was unchanged among the groups. In addition, intratracheal poly(I:C) exposure promoted the expression of IL-33 and increased T cells proportion in the lung, which were consistent with the change in SMG. Therefore, intratracheal poly(I:C) exposure aggravated the immunological and function disorder of SMG in NOD mice.

NK Cells in Autoimmune Diseases: Protective or Pathogenic?

Autoimmune diseases generally result from the loss of self-tolerance (i.e., failure of the immune system to distinguish self from non-self), and are characterized by autoantibody production and hyperactivation of T cells, which leads to damage of specific or multiple organs. Thus, autoimmune diseases can be classified as organ-specific or systemic. Genetic and environmental factors contribute to the development of autoimmunity. Recent studies have demonstrated the contribution of innate immunity to the onset of autoimmune diseases. Natural killer (NK) cells, which are key components of the innate immune system, have been implicated in the development of multiple autoimmune diseases such as systemic lupus erythematosus, type I diabetes mellitus, and autoimmune liver disease. However, NK cells have both protective and pathogenic roles in autoimmunity depending on the NK cell subset, microenvironment, and disease type or stage. In this work, we review the current knowledge of the varied roles of NK cell subsets in systemic and organic-specific autoimmune diseases and their clinical potential as therapeutic targets.

Double-negative T cells in autoimmune diseases

PURPOSE OF REVIEW

TCRαβ+CD4-CD8- double-negative T (DNT) cells, a principal subset of mature T lymphocytes, have been closely linked with autoimmune/inflammatory conditions. However, controversy persists regarding their ontogeny and function. Here, we present an overview on DNT cells in different autoimmune diseases to advance a deeper understanding of the contribution of this population to disease pathogenesis.

RECENT FINDINGS

DNT cells have been characterized in various chronic inflammatory diseases and they have been proposed to display pathogenic or regulatory function. The tissue location of DNT cells and the effector cytokines they produce bespeak to their active involvement in chronic inflammatory diseases.

SUMMARY

By producing various cytokines, expanded DNT cells in inflamed tissues contribute to the pathogenesis of a variety of autoimmune inflammatory diseases. However, it is unclear whether this population represents a stable lineage consisting of different subsets similar to CD4+ T helper cell subset. Better understanding of the possible heterogeneity and plasticity of DNT cells is needed to reveal interventional therapeutic opportunities.

Short-chain fatty acid butyrate induces IL-10-producing B cells by regulating circadian-clock-related genes to ameliorate Sjögren's syndrome

OBJECTIVES

Sjögren's syndrome (SS) is an autoimmune disease caused by inflammation of the exocrine gland. The pathological hallmark of SS is the infiltration of lymphocytes into the salivary glands. Increased infiltration of T and B cells into salivary glands exacerbates symptoms of SS. Several recent studies have identified the role of gut microbiota in SS. Butyrate, one of the metabolites of the gut microbiota, regulates T cells; however, its effects on B cells and SS remain unknown. This study determined the therapeutic effect of butyrate on regulating B cells in SS.

METHODS

Various concentrations of butyrate were intraperitoneally injected three times per week in NOD/ShiLtJ (NOD) mice, the prototype animal model for SS, and observed for more than 10 weeks. Whole salivary flow rate and the histopathology of salivary glands were investigated. Human submandibular gland (HSG) cells and B cells in mouse spleen were used to confirm the anti-inflammatory and immunomodulatory effects of butyrate.

RESULTS

Butyrate increased salivary flow rate in NOD mice and reduced inflammation of salivary gland tissues. It also regulated cell death and the expression of circadian-clock-related genes in HSG cells. Butyrate induced B cell regulation by increasing IL-10-producing B (B10) cells and decreasing IL-17-producing B cells, through the circadian clock genes RAR-related orphan receptor alpha and nuclear receptor subfamily 1 group D member 1.

CONCLUSION

The findings of this study imply that butyrate may ameliorate SS via reciprocal regulation of IL-10- and IL-17-producing B cells.

Role of the IL-23/IL-17 Pathway in Rheumatic Diseases: An Overview

Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, IL-23A (p19) and IL-12/23B (p40), the latter shared with Interleukin-12 (IL-12). IL-23 is mainly produced by macrophages and dendritic cells, in response to exogenous or endogenous signals, and drives the differentiation and activation of T helper 17 (Th17) cells with subsequent production of IL-17A, IL-17F, IL-6, IL-22, and tumor necrosis factor α (TNF-α). Although IL-23 plays a pivotal role in the protective immune response to bacterial and fungal infections, its dysregulation has been shown to exacerbate chronic immune-mediated inflammation. Well-established experimental data support the concept that IL-23/IL-17 axis activation contributes to the development of several inflammatory diseases, such as PsA, Psoriasis, Psoriatic Arthritis; AS, Ankylosing Spondylitis; IBD, Inflammatory Bowel Disease; RA, Rheumatoid Arthritis; SS, Sjogren Syndrome; MS, Multiple Sclerosis. As a result, emerging clinical studies have focused on the blockade of this pathogenic axis as a promising therapeutic target in several autoimmune disorders; nevertheless, a greater understanding of its contribution still requires further investigation. This review aims to elucidate the most recent studies and literature data on the pathogenetic role of IL-23 and Th17 cells in inflammatory rheumatic diseases.

Pathophysiologic role of Interleukin-33/ST2 in Sjögren's syndrome

Interleukin-33 (IL-33) is a member of the IL-1 family and has dual functions as a nuclear factor as well as a cytokine. The pivotal role of IL-33 as an active player contributing to aberrant local and systemic damage has been highlighted in several inflammatory and autoimmune diseases. Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by dry eyes and mouth syndrome due to local dysfunctions of exocrine glands, but also accompanied with systemic manifestations. The pathophysiology of pSS has been advocated as a conjecture of activated B and T cells as well as the production of inflammatory cytokines and autoantibodies, driving epithelial tissue damage and disease progression. In pSS, IL-33 is released in the extracellular space from damaged salivary cells upon pro-inflammatory stimuli and/or dysfunction of epithelial barrier. Counter-regulatory mechanisms are initiated to limit the pro-inflammatory actions of IL-33 as portrayed by an increase in the decoy receptor for IL-33, the soluble form of ST2 (sST2). In pSS and associated diseases, the levels of IL-33 are significantly elevated in the serum or tears of patients. Mechanistically, IL-33 acts in synergy with IL-12 and IL-23 on NK and NKT cells to boost the production of IFN-γ contributing to inflammation. TNF-α, IL-1β and IFN-γ in turn further increase the activation of IL-33/ST2 pathway, thereby constituting a vicious inflammatory loop leading to disease exacerbation. IL-33/ST2 axis is involved in Sjögren's syndrome and opens new perspectives as therapeutic target of one of the culprits in the inflammatory perpetuation.

MicroRNA-146a-5p enhances T helper 17 cell differentiation via decreasing a disintegrin and metalloprotease 17 level in primary sjögren's syndrome

In clinical practice, we found that microRNA (miR)-146a-5p is significantly up-regulated in peripheral blood mononuclear cells (PBMCs) of primary sjögren’s syndrome (pSS) patients. In vitro experiments confirmed that miR-146a-5p promotes T helper 17 (Th17) cell differentiation, but the specific mechanism is still unknown. To solve this problem, 20 pSS patients and 20 healthy subjects were enrolled in this study and PBMCs were isolated from their blood. The expression of the membrane IL-23 R (mIL-23 R) in PBMCs was determined. CD3⁺ T cells were also isolated and used to further analyze the relationship between the ectodomain shedding of mIL-23 R and a disintegrin and metalloprotease 17 (ADAM17). Finally, miR-146a-5p inhibitor and mimics were transfected into PBMCs to evaluate the relationship between ADAM17 and mIL-23 R, and explore the role of mIL-23 R and ADAM17 in Th17 cell differentiation. Our results revealed a significantly increased expression of miR-146a-5p in PBMCs from pSS patients and significantly increased percentage of Th17 cells compared to PBMCs from healthy controls. Under polarization culture conditions, pSS patient-derived PBMCs can more easily differentiate into Th17 cells, which was, to a great extent, attributable to the increased expression of mIL-23 R. Moreover, ADAM17, an ectodomain sheddase of mIL-23 R, was targeted and negatively regulated by miR-146a-5p, which reduced the ectodomain shedding of mIL-23 R. Overall, our results suggested that miR-146a-5p could promote Th17 cell differentiation through targeting and negatively regulating ADAM17. Thus, these results might offer a new approach in the treatment of pSS.

Olfactory ecto-mesenchymal stem cell-derived exosomes ameliorate murine Sjögren's syndrome by modulating the function of myeloid-derived suppressor cells

Sjögren’s syndrome (SS) is a systemic autoimmune disease characterized by progressive inflammation and tissue damage in salivary glands and lacrimal glands. Our previous studies showed that myeloid-derived suppressor cells (MDSCs) exhibited impaired immunosuppressive function during disease progression in patients with SS and mice with experimental Sjögren’s syndrome (ESS), but it remains unclear whether restoring the function of MDSCs can effectively ameliorate the development of ESS. In this study, we found that murine olfactory ecto-mesenchymal stem cell-derived exosomes (OE-MSC-Exos) significantly enhanced the suppressive function of MDSCs by upregulating arginase expression and increasing ROS and NO levels. Moreover, treatment with OE-MSC-Exos via intravenous injection markedly attenuated disease progression and restored MDSC function in ESS mice. Mechanistically, OE-MSC-Exo-secreted IL-6 activated the Jak2/Stat3 pathway in MDSCs. In addition, the abundant S100A4 in OE-MSC-Exos acted as a key factor in mediating the endogenous production of IL-6 by MDSCs via TLR4 signaling, indicating an autocrine pathway of MDSC functional modulation by IL-6. Taken together, our results demonstrated that OE-MSC-Exos possess therapeutic potential to attenuate ESS progression by enhancing the immunosuppressive function of MDSCs, possibly constituting a new strategy for the treatment of Sjögren’s syndrome and other autoimmune diseases.

The complement system in primary Sjögren's syndrome: the expression of certain cascade and regulatory proteins in labial salivary glands - observational study

Introduction

The complement cascade and regulatory proteins are involved in the pathogenesis of the Sjögren's syndrome and other autoimmune diseases. The complement activation via the alternative pathway was recognized as a major pathogenic mechanism in autoimmune conditions. The aim of this study was to assess expression of complement cascade components and regulatory proteins in minor salivary glands in patients with primary Sjögren's syndrome (pSS).

Materials and methods

The expression of C1q and C5b-9 - membrane attack complex and regulatory proteins such as: membrane cofactor protein (MCP), decay-accelerating factor (DAF) and protectin were examined using immunochemistry method in specimens from biopsy of minor salivary glands in pSS patients. The biopsy material was obtained from 20 pSS patients, 5 patients with non-specific sialadenitis and from 5 patients with suspicion of dryness syndrome without sialadenitis confirmation.

Results

None of the examined samples showed the expression of C1q or the effector C5b-9. Membrane cofactor protein expression was lower in pSS group than in both non-specific sialadenitis and noninflamed salivary glands. The inflammatory cells in pSS samples partially expressed MCP. There were differences in the sites and intensity of membrane protectin expression exclusively on the luminal surfaces in pSS; on the luminal and, partially, antiluminal surface in non-specific inflammation, and on the entire cell surface in unaffected salivary glands. There were no DAF expression in salivary gland tissue in biopsy specimens in all studied subjects.

Conclusions

The study demonstrated the absence of complement-cascade proteins (C1q, MAC) in the salivary glands of pSS patients, which may indicated a lack of local complement activation via the classical pathway and the observed gland tissue damage being due to a mechanism other than MAC-induced cytolysis. The differences in the expression of complement regulatory proteins between pSS, non-specific sialadenitis, and normal salivary glands may indicate that alternative functions of these regulatory proteins may be of greater significance in pSS. Low MCP expression in pSS in comparison with non-specific sialadenitis and normal salivary glands, may suggest altered modulation of cell-mediated immunity in pSS. The differences in the location and intensity of protectin (CD59) expression indicates a possibility of reducing the proinflammatory effect of protectin in pSS.

Innate Immunity and Biological Therapies for the Treatment of Sjögren's Syndrome

Sjögren's syndrome (SS) is a systemic autoimmune disorder affecting approximately 3% of the population in the United States. This disease has a female predilection and affects exocrine glands, including lacrimal and salivary glands. Dry eyes and dry mouths are the most common symptoms due to the loss of salivary and lacrimal gland function. Symptoms become more severe in secondary SS, where SS is present along with other autoimmune diseases like systemic lupus erythematosus, systemic sclerosis, or rheumatoid arthritis. It is known that aberrant activation of immune cells plays an important role in disease progression, however, the mechanism for these pathological changes in the immune system remains largely unknown. This review highlights the role of different immune cells in disease development, therapeutic treatments, and future strategies that are available to target various immune cells to cure the disease.

Pathogenetic Mechanisms Implicated in Sjögren's Syndrome Lymphomagenesis: A Review of the Literature

Sjögren's Syndrome (SS) is a chronic autoimmune disorder characterized by focal mononuclear cell infiltrates that surround the ducts of the exocrine glands, impairing the function of their secretory units. Compared to other autoimmune disorders, SS is associated with a notably high incidence of non-Hodgkin lymphoma (NHL) and more frequently mucosa associated lymphoid tissue (MALT) lymphoma, leading to increased morbidity and mortality rates. High risk features of lymphoma development include systemic extraepithelial manifestations, low serum levels of complement component C4 and mixed type II cryoglobulinemia. The discrimination between reactive and neoplastic lymphoepithelial lesion (LEL) is challenging, probably reflecting a continuum in the evolution from purely inflammatory lymphoid infiltration to the clonal neoplastic evolution. Early lesions display a predominance of activated T cells, while B cells prevail in severe histologic lesions. This strong B cell infiltration is not only a morphologic phenomenon, but it is also progressively associated with the presence of ectopic germinal centers (GCs). Ectopic formation of GCs in SS represents a complex process regulated by an array of cytokines, adhesion molecules and chemokines. Chronic antigenic stimulation is the major driver of specific B cell proliferation and increases the frequency of their transformation in the ectopic GCs and marginal zone (MZ) equivalents. B cells expressing cell surface rheumatoid factor (RF) are frequently detected in the salivary glands, suggesting that clonal expansion might arise from antigen selection of RF-expressing B cells. Abnormal stimulation and incomplete control mechanisms within ectopic lymphoid structures predispose RF MZ like cells to lymphoma development. Immunoglobulin recombination, somatic mutation and isotype switching during B cell development are events that may increase the translocation of oncogenes to immunoglobulin loci or tumor suppressor gene inactivation, leading to monoclonal B cell proliferation and lymphoma development. Concerning chronic antigenic stimulation, conclusive data is so far lacking. However immune complexes containing DNA or RNA are the most likely candidates. Whether additional molecular oncogenic events contribute to the malignant overgrowth remains to be proved.

Natural Killer Cell Transcript 4 promotes the development of Sjӧgren's syndrome via activation of Rap1 on B cells

Autoimmune disorders are the third most common diseases in the United States, and affect the daily lives of millions of people. In this study, we analyzed patient samples, utilized a transgenic mouse model and human B cells to reveal Natural Killer Cell Transcript 4 (NK4) as a novel regulator that promotes the development of autoimmune disorders. NK4 was significantly elevated in samples from patients with Sjӧgren's Syndrome (SS). SS patients show elevated NK4 levels. There is a strong and positive correlation between the increased levels of NK4 and the duration of SS. Interestingly, transgenic expression of NK4 in a mouse model led to the development of autoantibodies and lymphocytic infiltration in salivary glands similar to those in SS patients. Those phenotypes were associated with increased B1a cells in the peritoneum, plasma cells in the spleen, and increased IgM, IgA, and IgG2a in serum of the NK4 transgenic mice. The autoimmune phenotypes became more severe in older mice. Moreover, after NK4 transfection, human naïve B cells were activated and memory B cells differentiation into IgG and IgA-plasmablasts, resulting in an increased production of autoantibodies.NK4 regulated the differentiation and activation of B cells through activating Rap1 activity. NK4 also promoted B cell migration in a paracrine fashion through an induction of CXCL13 in endothelial cells. Collectively, these findings identify NK4 as a promoter of the development of autoimmune disorders through its roles on B cells. Therefore, NK4 may be a novel therapeutic target for the treatment of autoimmune diseases.

LncRNA Neat1 positively regulates MAPK signaling and is involved in the pathogenesis of Sjögren's syndrome

OBJECTIVE

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease characterized by lymphocytic infiltration of the exocrine glands. Recent, studies have shown that the long noncoding RNA (lncRNA) NEAT1 plays a crucial role in regulating the immune response. However, studies on the lncRNA NEAT1 in pSS are limited. Exploring the role of the lncRNA NEAT1 in the pathogenesis of pSS was the purpose of this study.

METHODS

The expression of NEAT1 in peripheral blood mononuclear cells (PBMCs) of patients with pSS and healthy controls (HCs) was analyzed by real-time polymerase chain reaction (RT-PCR). Antisense oligonucleotides (ASOs) and siRNA or immune stimulation with PMA/ionomycin were used to perform loss-and-gain-of-function experiments. RT-PCR, enzyme-linked immunosorbent assay (ELISA), and Western blot were performed to detect the RNA and protein levels of specific genes induced by PMA/ionomycin stimulation. Microarray analysis was used to generate an overview of the genes that might be regulated by NEAT1.

RESULTS

Compared with that in HC patient cells, the expression of NEAT1 in pSS patients was mainly increased in peripheral T cells, including CD4⁺ and CD8⁺ T cells. Additionally, the expression of NEAT1 in CD4⁺ T cells of patients with pSS was positively correlated with the course of disease. NEAT1 expression in Jurkat cells was induced by PMA/ionomycin stimulation upon activation of the TCR-p38 pathway. Upregulation of NEAT1 expression also increased the expression of CXCL8 and TNF-α. Knocking down NEAT1 expression with an ASO suppressed the expression of CXCL8 and TNF-α in PMA/ionomycin-stimulated Jurkat cells. Then, we found that NEAT1 regulated the activation of MAPK pathway to regulate NEAT1-induced factors, selectively activating the expression of p-p38 and p-ERK1/2. Furthermore, we also detected the expression profile of Jurkat cells stimulated by PMA/ionomycin when NEAT1 was silenced or not, in order to produce an overview of NEAT1-regulated genes.

CONCLUSION

These results provide a new understanding of the mechanisms of pSS and reveal that NEAT1 is a positive regulator of pSS, which is of substantial significance to its pathogenesis. Thus, NEAT1 provides a potential therapeutic target for pSS.