What can Sjögren's syndrome-like disease in mice contribute to human Sjögren's syndrome?

A GITRL-mTORC1-GM-CSF Positive Loop Promotes Pathogenic Th17 Response in Primary Sjögren Syndrome

OBJECTIVE

Glucocorticoid-induced tumor necrosis factor receptor superfamily-related protein (GITR), with its ligand (GITRL), plays an important role in CD4+ T cell-mediated autoimmunity. This study aimed to investigate the underlying mechanisms of GITRL in primary Sjögren syndrome (pSS).

METHODS

Patients with pSS and healthy controls were recruited. Serum GITRL and Th17-related cytokines were determined. RNA sequencing was performed to decipher key signal pathways. Nonobese diabetes (NOD) mice were adopted as experimental Sjögren models and recombinant adeno-associated virus (rAAV) transduction was conducted to verify the therapeutic potentials of targeting GITRL in vivo.

RESULTS

Serum GITRL was significantly higher in patients with pSS and showed a positive correlation with leukopenia, thrombocytopenia, autoantibodies, lung involvement, and disease activity. Serum GITRL was correlated with Th17-related cytokines. GITRL promoted the expansion of Th17 and Th17.1 cells. Expansion of granulocyte-macrophage colony-stimulating factor positive (GM-CSF+) CD4+ T cells induced by GITRL could be inhibited by blockade of GITRL. Moreover, GM-CSF could stimulate GITRL expression on monocytes. RNA sequencing revealed mammalian target of rapamycin complexes 1 (mTORC1) might be the key modulator. The increased phosphorylation of S6 and STAT3 and the expansion of Th17 and Th17.1 cells induced by GITRL were effectively inhibited by rapamycin, suggesting a GITRL-mTORC1-GM-CSF positive loop in pathogenic Th17 response in pSS. Administration of an rAAV vector expressing short hairpin RNA targeting GITRL alleviated disease progression in NOD mice.

CONCLUSION

Our results identified the pathogenic role of GITRL in exacerbating disease activity and promoting pathogenic Th17 response in pSS through a GITRL-mTORC1-GM-CSF loop. These findings suggest GITRL might be a promising therapeutic target in the treatment of pSS.

CFL1 restores the migratory capacity of bone marrow mesenchymal stem cells in primary Sjögren's syndrome by regulating CCR1 expression

BACKGROUND

Primary Sjögren's syndrome (pSS) is a chronic systemic autoimmune disease. There is no relevant research on whether the migratory ability of bone marrow mesenchymal stem cells (BM-MSC) is impaired in patients with pSS (pSS-BMMSC).

METHODS

Trajectories and velocities of BM-MSC were analyzed. Transwell migration assay and wound healing assay were used to investigate the migratory capacity of BM-MSC. The proliferative capacity of BM-MSC was evaluated by EDU and CCK8 assay. RNA-seq analysis was then performed to identify the underlying mechanism of lentivirus-mediated cofilin-1 overexpression BM-MSC (BMMSCCFL1). The therapeutic efficacy of BMMSCCFL1 was evaluated in NOD mice.

RESULTS

The migratory capacity of pSS-BMMSC was significantly reduced compared to normal volunteers (HC-BMMSC). The expression of the motility-related gene CFL1 was decreased in pSS-BMMSC. Lentivirus-mediated CFL1 overexpression of pSS-BMMSC promoted the migration capacity of pSS-BMMSC. Furthermore, RNA-seq revealed that CCR1 was the downstream target gene of CFL1. To further elucidate the mechanism of CFL1 in regulating BM-MSC migration and proliferation via the CCL5/CCR1 axis, we performed a rescue experiment using BX431 (a CCR1-specific inhibitor) to inhibit CCR1. The results showed that CCR1 inhibitors suppressed the migration and proliferation capacity of MSC induced by CFL1.

CONCLUSION

The pSS-BMMSC leads to impaired migration and proliferation, and overexpression of CFL1 can rescue the functional deficiency and alleviate disease symptoms in NOD mice. Mechanically, CFL1 can regulate the expression level of the downstream CCL5/CCR1 axis to enhance the migration and proliferation of BM-MSC.

Normal and Sjogren's syndrome models of the murine lacrimal gland studied at single-cell resolution

The lacrimal gland is of central interest in ophthalmology both as the source of the aqueous component of tear fluid and as the site of autoimmune pathology in the context of Sjogren's syndrome (SjS). To provide a foundational description of mouse lacrimal gland cell types and their patterns of gene expression, we have analyzed single-cell transcriptomes from wild-type (Balb/c) mice and from two genetically based SjS models, MRL/lpr and NOD (nonobese diabetic).H2b, and defined the localization of multiple cell-type-specific protein and mRNA markers. This analysis has uncovered a previously undescribed cell type, Car6+ cells, which are located at the junction of the acini and the connecting ducts. More than a dozen secreted polypeptides that are likely to be components of tear fluid are expressed by acinar cells and show pronounced sex differences in expression. Additional examples of gene expression heterogeneity within a single cell type were identified, including a gradient of Claudin4 along the length of the ductal system and cell-to-cell heterogeneity in transcription factor expression within acinar and myoepithelial cells. The patterns of expression of channels, transporters, and pumps in acinar, Car6+, and ductal cells make strong predictions regarding the mechanisms of water and electrolyte secretion. In MRL/lpr and NOD.H2b lacrimal glands, distinctive changes in parenchymal gene expression and in immune cell subsets reveal widespread interferon responses, a T cell-dominated infiltrate in the MRL/lpr model, and a mixed B cell and T cell infiltrate in the NOD.H2b model.

Marginal Zone B (MZB) Cells: Comparison of the Initial Identification of Immune Activity Leading to Dacryoadenitis and Sialadenitis in Experimental Sjögren's Syndrome

Although multiple mouse strains have been advanced as models for Sjögren's syndrome (SS), which is a human systemic autoimmune disease characterized primarily as the loss of lacrimal and salivary gland functions, the C57BL/6.NOD-Aec1Aec2 recombinant inbred (RI) mouse derived from the NOD/ShiLtJ line is considered one of the more appropriate models exhibiting virtually all the characteristics of the human disease. This mouse model, as well as other mouse models of SS, have shown that B lymphocytes are essential for the onset and development of observed clinical manifestations. Recently, studies carried out in the C57BL/6.IL14α transgenic mouse have provided clear evidence that the marginal zone B (MZB) cell population is directly involved in the early pathological events initiating the development of the clinical SS disease, as well as late-stage lymphomagenesis resulting in B-cell lymphomas. Since MZB cells are difficult to study in vivo and in vitro, we carried out a series of ex vivo investigations that utilize temporal global RNA transcriptomic analyses to profile differentially expressed genes exhibiting temporal upregulation during the initial onset and subsequent development of pathophysiological events within the lacrimal and salivary gland tissues per se or associated with the leukocyte cell migrations into these glands. The initial transcriptomic analyses revealed that while the upregulated gene expression profiles obtained from lacrimal and salivary glands overlap, multiple genetic differences exist between the defined activated pathways. In the current study, we present a concept suggesting that the initial pathological events differ between the two glands, yet the subsequent upregulated TLR4/TLR3 signal transduction pathway that activates the type-1 interferon signature appears to be identical in the two glands and indicates an autoimmune response against dsRNA, possibly a virus. Here, we attempt to put these findings into perspective and determine how they can impact the design of future therapeutic protocols.

IFIH1 was predicted as a key biomarker in primary Sjögren's syndrome based on transcriptome analysis and experimental verification in patients and mice

OBJECTIVES

To investigate the novel key genes and biological processes that may lead to primary Sjögren' s syndrome (pSS).

METHODS

We downloaded datasets about peripheral blood samples of pSS patients and healthy controls (GSE51092, GSE84844, and GSE66795) from Gene Expression Omnibus database. The weighted co-expression network analysis and differential expression analysis first were implemented. After that, protein-protein network interaction and Support Vector Machines were applied in the meantime to take intersection for key genes. Moreover, we conducted immune cell infiltration analysis to explore the relationship between the gene expression and concentration of immune cells in peripheral blood. Lastly, the expression of key genes was verified in pSS patients and murine models by reverse-transcription polymerase chain reaction. Meanwhile, correlation analysis of gene expression and disease activity was also performed.

RESULTS

Only 1 key gene, interferon induced with helicase c domain 1 (IFIH1), was identified to be both significantly up-regulated and important for the diagnosis of pSS. The increased expression of IFIH1 in peripheral blood was confirmed in data sets, patients and non-obese diabetic (NOD) mice. Its expression was correlated with disease activity in patients as well. In addition, the IFIH1 expression was also increased in spleen and salivary glands infiltrated with lymphocytes in NOD mice. Furthermore, immune cell infiltration analysis showed that the expression of IFIH1 was positively correlated with the proportion of memory B cells and activated dendritic cells, and negatively correlated with the proportion of macrophage M0.

CONCLUSIONS

Here, bioinformatics analyses and experimental assays were performed to provide a new insight for understanding of pSS. IFIH1 may be a new diagnostic marker or therapeutic target for pSS.

A Temporal Comparative RNA Transcriptome Profile of the Annexin Gene Family in the Salivary versus Lacrimal Glands of the Sjögren's Syndrome-Susceptible C57BL/6.NOD-Aec1Aec2 Mouse

A generally accepted hypothesis for the initial activation of an immune or autoimmune response argues that alarmins are released from injured, dying and/or activated immune cells, and these products complex with receptors that activate signal transduction pathways and recruit immune cells to the site of injury where the recruited cells are stimulated to initiate immune and/or cellular repair responses. While there are multiple diverse families of alarmins such as interleukins (IL), heat-shock proteins (HSP), Toll-like receptors (TLR), plus individual molecular entities such as Galectin-3, Calreticulin, Thymosin, alpha-Defensin-1, RAGE, and Interferon-1, one phylogenetically conserved family are the Annexin proteins known to promote an extensive range of biomolecular and cellular products that can directly and indirectly regulate inflammation and immune activities. For the present report, we examined the temporal expression profiles of the 12 mammalian annexin genes (Anxa1-11 and Anxa13), applying our temporal genome-wide transcriptome analyses of ex vivo salivary and lacrimal glands from our C57BL/6.NOD-Aec1Aec2 mouse model of Sjögren's Syndrome (SS), a human autoimmune disease characterized primarily by severe dry mouth and dry eye symptoms. Results indicate that annexin genes Anax1-7 and -11 exhibited upregulated expressions and the initial timing for these upregulations occurred as early as 8 weeks of age and prior to any covert signs of a SS-like disease. While the profiles of the two glands were similar, they were not identical, suggesting the possibility that the SS-like disease may not be uniform in the two glands. Nevertheless, this early pre-clinical and concomitant upregulated expression of this specific set of alarmins within the immune-targeted organs represents a potential target for identifying the pre-clinical stage in human SS as well, a fact that would clearly impact future interventions and therapeutic strategies.

Mesenchymal stem cell transplantation alleviates Sjögren's syndrome symptoms by modulating Tim-3 expression

Mesenchymal stem cell (MSC) transplantation has been proven to be an effective treatment for Sjögren's syndrome (SS) to improve salivary gland pathology and exocrine function, but the mechanism remains unclear. A recently reported inhibitory receptor, Tim-3, also appears to be closely related to autoimmune diseases. Here, we aimed to explore the roles of Tim-3 in the pathogenesis of SS and MSC treatment. The results showed that Tim-3 was downregulated in T cells of SS patients and nonobese diabetic (NOD) mice, which is correlated with SS pathogenesis. MSC transplantation ameliorated SS-like symptoms and pathological changes in the submandibular glands with modulated Tim-3 expression, resulting in attenuation of localized inflammation, fibrosis, and epithelial-mesenchymal transition. Furthermore, Tim-3 is crucial for the inhibitory effect of MSCs on PBMC proliferation in vitro. Therefore, our work has demonstrated that MSC transplantation effectively mitigates the pathological changes of SS by regulating Tim-3 expression, which provides a novel mechanism of MSC treatment and indicates a brand-new perspective of the combination of inhibitory-receptor-targeted treatment and MSC therapy in SS.

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

Sjögren’s syndrome (SjS), characterized by keratoconjunctivitis sicca and dry mouth, is a common autoimmune disease, especially in middle-aged women. The immunopathogenesis of SjS is caused by the sequential infiltration of T and B cells into exocrine glands, including salivary and lacrimal glands. Effector cytokines produced by these immunocytes, such as interferons (IFNs), IL-17, IL-22, IL-21, IL-4, TNF-α, BAFF and APRIL, play critical roles in promoting autoimmune responses and inducing tissue damages. Epigenetic regulations, including DNA methylation, histone modification and non-coding RNAs, have recently been comprehensively studied during the activation of various immunocytes. The deficiency of key epigenetic enzymes usually leads to aberrant immune activation. Epigenetic modifications in T and B cells are usually found to be altered during the immunopathogenesis of SjS, and they are closely correlated with autoimmune responses. In particular, the important role of methylation in activating IFN pathways during SjS progression has been revealed. Thus, according to the involvement of epigenetic regulations in SjS, target therapies to reverse the altered epigenetic modifications in auto-responsive T and B cells are worthy of being considered as a potential therapeutic strategy for SjS.

Defective Efferocytosis in a Murine Model of Sjögren's Syndrome Is Mediated by Dysfunctional Mer Tyrosine Kinase Receptor

Sjögren's syndrome (SjS) is a chronic autoimmune disease primarily involving the exocrine glands in which the involvement of the innate immune system is largely uncharacterized. Mer signaling has been found to be protective in several autoimmune diseases but remains unstudied in SjS. Here, we investigated the role of Mer signaling in SjS. Mer knockout (MerKO) mice were examined for SjS disease criteria. SjS-susceptible (SjS^S) C57BL/6.NOD-Aec1Aec2 mice were assessed for defective Mer signaling outcomes, soluble Mer (sMer) levels, A disintegrin and metalloprotease 17 (ADAM17) activity, and Rac1 activation. In addition, SjS patient plasma samples were evaluated for sMer levels via ELISA, and sMer levels were correlated to disease manifestations. MerKO mice developed submandibular gland (SMG) lymphocytic infiltrates, SMG apoptotic cells, anti-nuclear autoantibodies (ANA), and reduced saliva flow. Mer signaling outcomes were observed to be diminished in SjS^S mice, as evidenced by reduced Rac1 activation in SjS^S mice macrophages in response to apoptotic cells and impaired efferocytosis. Increased sMer was also detected in SjS^S mouse sera, coinciding with higher ADAM17 activity, the enzyme responsible for cleavage and inactivation of Mer. sMer levels were elevated in patient plasma and positively correlated with focus scores, ocular staining scores, rheumatoid factors, and anti-Ro60 levels. Our data indicate that Mer plays a protective role in SjS, similar to other autoimmune diseases. Furthermore, we suggest a series of events where enhanced ADAM17 activity increases Mer inactivation and depresses Mer signaling, thus removing protection against the loss of self-tolerance and the onset of autoimmune disease in SjS^S mice.

CP-25 alleviates antigen-induced experimental Sjögren's syndrome in mice by inhibiting JAK1-STAT1/2-CXCL13 signaling and interfering with B-cell migration

The etiology of primary Sjögren's syndrome (pSS) remains unknown, and there is no complete curative drug. In this study, we treated a mouse model of the submandibular gland (SG) protein-immunized experimental Sjögren's syndrome (ESS) with paeoniflorin-6'-O-benzene sulfonate (termed CP-25) to evaluate the potential therapeutic effects of CP-25. Through in vivo experiments, we found that CP-25 increased saliva flow, alleviated the salivary gland indexes, and improved tissue integrity in the ESS model. The viability of splenocytes and B-lymphocyte migration from spleen were reduced in ESS mice. Furthermore, CP-25 decreased the expression of IgG antibodies, anti-SSA and anti-SSB antibodies and modulated the levels of cytokines in the serum of SS mice. The numbers of total B lymphocytes, plasma cells (PCs), and memory B cells diminished in the salivary gland. Increased expression of the JAK1-STAT1-CXCL13 axis and IFNα was found in human tissue isolated from pSS patients. In vitro, after stimulation with IFNα, the levels of CXCL13 mRNA and CXCL13 in human salivary gland epithelial cells (HSGEC) increased, while CP-25 counteracted the secretion of CXCL13 and downregulated the expression of CXCL13. IFN-α activated the JAK1-STAT1/2-CXCL13 signaling pathway in HSGEC, which was negatively regulated by additional CP-25. As a consequence, B-cell migration was downregulated in coculture with IFN-α-stimulated HSGEC. Taken together, this study demonstrated that the therapeutic effects of CP-25 were associated with the inhibition of the JAK1-STAT1/2-CXCL13 signaling pathway in HSGEC, which impedes the migration of B cells into the salivary gland. We identified the underlying mechanisms of the therapeutic effect of CP-25 and provided an experimental foundation for CP-25 as a potential drug in the treatment of the human autoimmune disorder pSS.

Upregulated Chemokine and Rho-GTPase Genes Define Immune Cell Emigration into Salivary Glands of Sjögren's Syndrome-Susceptible C57BL/6.NOD-Aec1Aec2 Mice

The C57BL/6.NOD-Aec1Aec2 mouse is considered a highly appropriate model of Sjögren's Syndrome (SS), a human systemic autoimmune disease characterized primarily as the loss of lacrimal and salivary gland functions. This mouse model, as well as other mouse models of SS, have shown that B lymphocytes are essential for the development and onset of observed clinical manifestations. More recently, studies carried out in the C57BL/6.IL14α transgenic mouse have indicated that the marginal zone B (MZB) cell population is responsible for development of SS disease, reflecting recent observations that MZB cells are present in the salivary glands of SS patients and most likely initiate the subsequent loss of exocrine functions. Although MZB cells are difficult to study in vivo and in vitro, we have carried out an ex vivo investigation that uses temporal global RNA transcriptomic analyses to profile differentially expressed genes known to be associated with cell migration. Results indicate a temporal upregulation of specific chemokine, chemokine receptor, and Rho-GTPase genes in the salivary glands of C57BL/6.NOD-Aec1Aec2 mice that correlate with the early appearance of periductal lymphocyte infiltrations. Using the power of transcriptomic analyses to better define the genetic profile of lymphocytic emigration into the salivary glands of SS mice, new insights into the underlying mechanisms of SS disease development and onset begin to come into focus, thereby establishing a foundation for further in-depth and novel investigations of the covert and early overt phases of SS disease at the cellular level.

Lycium barbarum Polysaccharide Ameliorates Sjögren's Syndrome in a Murine Model

SCOPE

This study aims to evaluate the therapeutic efficacy and mechanisms of Lycium barbarum polysaccharide (LBP) in primary Sjögren's syndrome (pSS).

METHODS AND RESULTS

Non-obese diabetic mice (the pSS model) are randomly divided into four groups: Low dose LBP (LBP.L, 5 mg kg-1  d-1 ), high dose LBP (10 mg kg-1  d-1 ), low dose interleukin (IL)-2 (25 000 IU/d), and control (saline water). Drugs were treated for 12 weeks. LBP.L significantly reduces the salivary gland inflammation compared with the control group (histological score p LBP.L vs Control  = 0.019; foci number: p LBP.L vs Control  = 0.038). LBP.L also remarkably reduces the effector follicular helper T (Tfh) cells and the CD4+ IL-17A+ helper T (Th17) cells in both spleen and cervical lymph node (cLN) cells. Additionally, the ratios of regulatory T cell (Treg)/Tfh cells and Treg/Th17 cells are substantially increased in mice treated with LBP.L in both spleen and cLNs. LBP also inhibits Th17 and Tfh cells and markedly increases the Treg/Tfh ratio in human peripheral blood mononuclear cells.

CONCLUSION

LBP.L inhibits the progression of pSS in mice, associated with modulation of T cell differentiation.

Characterization of Type I Interferon-Associated Chemokines and Cytokines in Lacrimal Glands of Nonobese Diabetic Mice

Type I interferons (IFNs) are required for spontaneous lacrimal gland inflammation in the nonobese diabetic (NOD) mouse model of Sjögren’s disease, but the consequences of type I IFN signaling are not well-defined. Here, we use RNA sequencing to define cytokine and chemokine genes upregulated in lacrimal glands of NOD mice in a type I IFN-dependent manner. Interleukin (IL)-21 was the highest differentially expressed cytokine gene, and Il21 knockout NOD mice were relatively protected from lacrimal gland inflammation. We defined a set of chemokines upregulated early in disease including Cxcl9 and Cxcl10, which share a receptor, CXCR3. CXCR3⁺ T cells were enriched in lacrimal glands with a dominant proportion of CXCR3⁺ regulatory T cells. Together these data define the early cytokine and chemokine signals associated with type I IFN-signaling in the development of lacrimal gland inflammation in NOD mice providing insight into the role of type I IFN in autoimmunity development.

Early Covert Appearance of Marginal Zone B Cells in Salivary Glands of Sjögren's Syndrome-Susceptible Mice: Initiators of Subsequent Overt Clinical Disease

The C57BL/6.NOD-Aec1Aec2 mouse model has been extensively studied to define the underlying cellular and molecular bioprocesses critical in the onset of primary Sjögren’s Syndrome (pSS), a human systemic autoimmune disease characterized clinically as the loss of lacrimal and salivary gland functions leading to dry eye and dry mouth pathologies. This mouse model, together with several gene knockout mouse models of SS, has indicated that B lymphocytes, especially marginal zone B (MZB) cells, are necessary for development and onset of clinical manifestations despite the fact that destruction of the lacrimal and salivary gland cells involves a classical T cell-mediated autoimmune response. Because migrations and functions of MZB cells are difficult to study in vivo, we have carried out ex vivo investigations that use temporal global RNA transcriptomic analyses to profile autoimmunity as it develops within the salivary glands of C57BL/6.NOD-Aec1Aec2 mice. Temporal profiles indicate the appearance of Notch2-positive cells within the salivary glands of these SS-susceptible mice concomitant with the early-phase appearance of lymphocytic foci (LF). Data presented here identify cellular bioprocesses occurring during early immune cell migrations into the salivary glands and suggest MZB cells are recruited to the exocrine glands by the upregulated Cxcl13 chemokine where they recognize complement (C’)-decorated antigens via their sphingosine-1-phosphate (S1P) and B cell (BC) receptors. Based on known MZB cell behavior and mobility, we propose that MZB cells activated in the salivary glands migrate to splenic follicular zones to present antigens to follicular macrophages and dendritic cells that, in turn, promote a subsequent systemic cell-mediated and autoantibody-mediated autoimmune T cell response that targets exocrine gland cells and functions. Overall, this study uses the power of transcriptomic analyses to provide greater insight into several molecular events defining cellular bioprocesses underlying SS that can be modelled and more thoroughly studied at the cellular level.

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.

Mouse Models of Sjögren's Syndrome with Ocular Surface Disease

Sjögren’s syndrome (SS) is a systemic rheumatic disease that predominantly affects salivary and lacrimal glands resulting in oral and ocular dryness, respectively, referred to as sicca symptoms. The clinical presentation of ocular dryness includes keratoconjunctivitis sicca (KCS), resulting from the inflammatory damage to the ocular surface tissues of cornea and conjunctiva. The diagnostic evaluation of KCS is a critical component of the classification criteria used by clinicians worldwide to confirm SS diagnosis. Therapeutic management of SS requires both topical and systemic treatments. Several mouse models of SS have contributed to our current understanding of immunopathologic mechanisms underlying the disease. This information also helps develop novel therapeutic interventions. Although these models address glandular aspects of SS pathology, their impact on ocular surface tissues is addressed only in a few models such as thrombospondin (TSP)-1 deficient, C57BL/6.NOD.Aec1Aec2, NOD.H2^b, NOD.Aire KO, and IL-2Rα (CD25) KO mice. While corneal and/or conjunctival damage is reported in most of these models, the characteristic SS specific autoantibodies are only reported in the TSP-1 deficient mouse model, which is also validated as a preclinical model. This review summarizes valuable insights provided by investigations on the ocular spectrum of the SS pathology in these models.

Advances in Mast Cell Activation by IL-1 and IL-33 in Sjögren's Syndrome: Promising Inhibitory Effect of IL-37

Sjögren’s syndrome (SS) is a chronic autoimmune inflammatory disease that affects primarily older women and is characterized by irreversible damage of the exocrine glands, including tear (xerophthalmia) and salivary glands (xerostomia). Secretory glands lose their functionality due to the infiltration of immune cells, which produce cytokines and cause inflammation. Primary SS is characterized by dry syndrome with or without systemic commitment in the absence of other pathologies. Secondary SS is accompanied by other autoimmune diseases with high activation of B lymphocytes and the production of autoantibodies, including the rheumatoid factor. Other cells, such as CD4⁺ T cells and mast cells (MCs), participate in SS inflammation. MCs are ubiquitous, but are primarily located close to blood vessels and nerves and can be activated early in autoimmune diseases to express a wide variety of cytokines and chemokines. In the SS acute phase, MCs react by generating chemical mediators of inflammation, tumor necrosis factor (TNF), and other pro-inflammatory cytokines such as interleukin (IL)-1 and IL-33. IL-33 is the specific ligand for ST2 capable of inducing some adaptive immunity TH2 cytokines but also has pro-inflammatory properties. IL-33 causes impressive pathological changes and inflammatory cell infiltration. IL-1 family members can have paracrine and autocrine effects by exacerbating autoimmune inflammation. IL-37 is an IL-1 family cytokine that binds IL-18Rα receptor and/or Toll-like Receptor (TLR)4, exerting an anti-inflammatory action. IL-37 is a natural inhibitor of innate and acquired immunity, and the level is abnormal in patients with autoimmune disorders. After TLR ligand activation, IL-37 mRNA is generated in the cytoplasm, with the production of pro-IL-37 and later mature IL-37 caspase-1 mediated; both precursor and mature IL-37 are biologically active. Here, we discuss, for the first time, the current knowledge of IL-37 in autoimmune disease SS and propose a new therapeutic role.

Total glucosides of paeony (TGP) alleviates Sjogren's syndrome through inhibiting inflammatory responses in mice

BACKGROUND

Sjogren's syndrome (SS) is an inflammatory autoimmune disease whose etiology is complicated. Total glucosides of paeony (TGP) has a variety of pharmacological effects.

PURPOSE

To evaluate the therapeutic effects of TGP on SS in mice and anti-inflammatory mechanism.

STUDY DESIGN

SS animal model was developed from C57BL/6J mice through immunological induction (SS mice) and NOD/ShiltJNju (NOD) mice. Inflammatory cytokines and other related indicators were measured.

METHODS

TGP (720, 360, 180 mg/kg) was intragastrically administered for 6 or 16 weeks for SS mice and NOD mice, respectively. Average food and water intake, average body weight, saliva flow, submandibular gland (SMG) and spleen index, and SMG pathology were measured. ELISA was used to evaluate serum inflammatory cytokines in SS mice and autoantigens in NOD mice. Real-time PCR, Western blot and Luminex liquid suspension chip assay were applied to analyze SMG inflammatory cytokines mRNA and protein expression of NOD mice.

RESULTS

Compared with SS mice, TGP treatment improved SMG pathological damage. TGP (720 mg/kg) treatment increased saliva flow, and reduced organ indexes and serum IL-6 and IFN-γ concentration. TGP (360 mg/kg) treatment decreased serum IFN-γ concentration. TGP (180 mg/kg) treatment for 6 weeks decreased average body weight. Compared with NOD mice, TGP treatment increased saliva flow from 9 to 15 weeks, decreased body weight, and alleviated pathological damage of SMG after 2 and 16 weeks. After 2 weeks of administration, TGP treatment inhibited serum concentration of SSB/La, SSA/Ro and α-fodrin, decreased TNF-α, IL-1β and IFN-γ in SMG, and down-regulated protein expressions of BAFF and IL-17A and mRNA expressions of BAFF, TNF-α, IL-17A, CXCL9 and CXCL13 in SMG. After 8 weeks of administration, TGP treatment decreased the concentration of α-fodrin in serum, TNF-α and IL-6 in SMG, and down-regulated mRNA expressions of IL-17A, TNF-α, CXCL9, CXCL13 and BAFF and protein expressions of IL-17A and BAFF in SMG. After 16 weeks of administration, TGP treatment reduced serum SSA/Ro, SSB/La and α-fodrin concentration, and decreased BAFF protein expression and TNF-α, CXCL9, CXCL13, IL-17A, and BAFF mRNA expressions.

CONCLUSION

TGP has a certain therapeutic effect on SS mice and NOD mice through inhibiting inflammatory responses.

Human umbilical cord mesenchymal stem cells confer potent immunosuppressive effects in Sjögren's syndrome by inducing regulatory T cells

BACKGROUND

Primary Sjögren's syndrome (SS) is a lymphoproliferative disease with a chronic autoimmune disorder characterized by mononuclear cell (MNC) infiltration of notably the lacrimal and salivary glands. As mesenchymal stem cells (MSCs) regulate series of immunological responses partially by regulating proportion of CD4⁺ T cells and inducing an immunosuppressive local milieu, umbilical cord MSCs (UC-MSCs) are being considered as a novel source for cell-based therapies against primary SS. This study aimed to investigate the feasibility of UC-MSCs in treatment of SS and to explore the possible mechanism(s) with the special emphasis on regulatory T cells (Tregs).

METHODS

Potent immunosuppressive effects of human UC-MSCs on SS were explored in vivo and in vitro. To study the effects of human UC-MSCs on the development and progression of SS, human UC-MSCs were administered before disease onset (preventive protocol) and after disease occurrence (therapeutic protocol) in non-obese diabetic (NOD) mice. In human study, the effect of human UC-MSCs on T cells from SS patients was studied.

RESULTS

In both protocols, the histopathology of submandibular and sublingual salivary glands showed decreased inflammatory infiltrates. In vitro, human UC-MSCs exhibited potent suppressive effects on responses of MNCs in NOD mice and T cells in SS patients. Such inhibitory effects were coupled with decreased production of proinflammtory cytokines interferon-γ, interleukin (IL)-6, tumor necrosis factor-α and increased production of IL-10 (n = 10, p < .01). The frequency of CD4⁺Foxp3⁺T cells in the spleen of NOD recipients was elevated (n = 6, p < .05).

CONCLUSION

Human UC-MSCs are capable of inducing CD4⁺Foxp3⁺ T cells in both NOD mice and human in vitro. Human UC-MSCs effectively interfere with the autoimmune attack in the course of SS by inducing an in vivo state of T cell unresponsiveness and the upregulation of Tregs.

Clinical significance of serum bilirubin in primary Sjögren syndrome patients

Objective

The purpose of our research was to demonstrate the clinical significance of serum bilirubin in primary Sjögren syndrome patients (pSS).

Patients and methods

A total of 116 patients with primary Sjögren syndrome and 138 matched individuals were included in our study. The laboratory parameters of patients with pSS and healthy controls were retrospectively analyzed.

Results

Serum total bilirubin, direct bilirubin, and indirect bilirubin were significantly reduced (P < .001, P = .001, P < .001) while ESR was significantly increased (P < .001) in patients with pSS when compared with healthy checkup individuals. Statistically, the AUC in patients with pSS is as follows: TBIL = 0.77, P < .001, cutoff value = 7.96; DBIL = 0.617, P = .001 cutoff value = 2.2; and IBIL = 0.786, P < .001 cutoff value = 4.5. Furthermore, our study revealed that TBIL, DBIL, and IBIL were significantly negativity related to ESR (r = −.406, P < .001; r = −.206, P = .026; r = −.429, P < .001). Interestingly, multiple linear regression analysis showed that when adjusted for sex, age, ALT, and AST, the levels of TBIL, DBIL, and IBIL in patients with pSS were independently correlated with ESR.

Conclusions

This study found that the levels of serum bilirubin were reduced and the inflammatory marker was elevated in patients with pSS. Additionally, serum bilirubin was negatively related with ESR and TBIL, DBIL, and IBIL can be used in the clinical diagnosis and follow‐up visits of the patients with pSS.

Mesenchymal stem cell transplantation alleviates experimental Sjögren's syndrome through IFN-β/IL-27 signaling axis

Rationale: Although mesenchymal stem cell (MSC) transplantation has been proved to be an effective therapeutic approach to treat experimental Sjögren's syndrome (SS), the detailed underlying mechanisms remains unknown. IL-27 has diverse influences on the regulation of T cell differentiation and was involved in SS through modulating immune response. Here we aimed to explore whether IL-27-mediated regulation of immune cells was responsible for the beneficial effects of MSC transplantation on SS.

Methods: The SS-like symptoms were evaluated in IL-27 deficient and recombinant IL-27-treated NOD mice. The MSCs were infused into NOD mice via the tail vein. The histological features of submandibular glands, saliva flow rate and serum IL-27 were examined. The effects of MSCs on the IL-27 production and Th17/Treg cell in SS patients and mice in vitro and in vivo were determined for the mechanistic study.

Results: This study showed that SS patients had decreased IL-27 level and increased ratio of Th17/Treg cells. Consistently, exacerbated SS-like symptoms were observed in IL-27 deficient NOD mice, along with increased ratio of Th17/Treg cells. Importantly, MSC transplantation alleviated SS-like symptoms by elevating the level of IL-27 to restore Th17/Treg balance in NOD mice. Mechanistically, MSC-secreted interferon-β (IFN-β) promote dendritic cells to produce IL-27.

Conclusions: Thus, we have revealed a previously unrecognized function of MSC-mediated IL-27 production by DCs in suppressing SS-like syndrome, which provided evidences for clinical application of MSC in patients with SS.

[Oral health in patients with systemic sclerosis]

The aim of this study was to conduct literature review about oral manifestations of scleroderma. Systemic sclerosis is a multisystem autoimmune disorder characterized by widespread fibrosis, vascular alterations and inflammation. Systemic sclerosis mainly affects people in age from 30 to 50 years, but the onset of disease can occur in any age. The disturbance of microcirculation with the activation and proliferation of endothelium and smooth muscle cells plays an important role in pathogenesis of sclerodrma. These changes lead to sclerosis and fibrosis of various part in human body. Orofacial manifestations of scleroderma include: reduced mouth opening, widening of periodontal ligament, teleangiectasia, bone lesions. Systemic scleroderma is often accompanied by Sjogren's syndrome. Oral manifestations of Sjogren's syndrome are recurrent parotitis, angular cheilitis, xerostomia and multiple caries. Sjogren's syndrome leads to negative impact on patients health and mental status. Orofacial manifestations of systemic sclerosis are still poorly known, that is why more researches should be made to improve dental treatment of patients with systemic sclerosis.

Ablation of the Chaperone Protein ERdj5 Results in a Sjögren's Syndrome-Like Phenotype in Mice, Consistent With an Upregulated Unfolded Protein Response in Human Patients

Objective: Sjögren's syndrome (SS) is a chronic autoimmune disorder that affects mainly the exocrine glands. Endoplasmic reticulum (ER) stress proteins have been suggested to participate in autoimmune and inflammatory responses, either acting as autoantigens, or by modulating factors of inflammation. The chaperone protein ERdj5 is an ER-resident disulfide reductase, required for the translocation of misfolded proteins during ER-associated protein degradation. In this study we investigated the role of ERdj5 in the salivary glands (SGs), in association with inflammation and autoimmunity.

Methods:In situ expression of ERdj5 and XBP1 activation were studied immunohistochemically in minor SG tissues from primary SS patients and non-SS sicca-complaining controls. We used the mouse model of ERdj5 ablation and characterized its features: Histopathological, serological (antinuclear antibodies and cytokine levels), and functional (saliva flow rate).

Results: ERdj5 was highly expressed in the minor SGs of SS patients, with stain intensity correlated to inflammatory lesion severity and anti-SSA/Ro positivity. Moreover, SS patients demonstrated higher XBP1 activation within the SGs. Remarkably, ablation of ERdj5 in mice conveyed many of the cardinal features of SS, like spontaneous inflammation in SGs with infiltrating T and B lymphocytes, distinct cytokine signature, excessive cell death, reduced saliva flow, and production of anti-SSA/Ro and anti-SSB/La autoantibodies. Notably, these features were more pronounced in female mice.

Conclusions: Our findings suggest a critical connection between the function of the ER chaperone protein ERdj5 and autoimmune inflammatory responses in the SGs and provide evidence for a new, potent animal model of SS.

Translational Preclinical Pharmacologic Disease Models for Ophthalmic Drug Development

Preclinical models of human diseases are critical to our understanding of disease etiology, pathology, and progression and enable the development of effective treatments. An ideal model of human disease should capture anatomical features and pathophysiological mechanisms, mimic the progression pattern, and should be amenable to evaluating translational endpoints and treatment approaches. Preclinical animal models have been developed for a variety of human ophthalmological diseases to mirror disease mechanisms, location of the affected region in the eye and severity. These models offer clues to aid in our fundamental understanding of disease pathogenesis and enable progression of new therapies to clinical development by providing an opportunity to gain proof of concept (POC). Here, we review preclinical animal models associated with development of new therapies for diseases of the ocular surface, glaucoma, presbyopia, and retinal diseases, including diabetic retinopathy and age-related macular degeneration (AMD). We have focused on summarizing the models critical to new drug development and described the translational features of the models that contributed to our understanding of disease pathogenesis and establishment of preclinical POC.

Interferons and Dry Eye in Sjögren's Syndrome

Various cytokines, including interferon (IFN)-γ and IL-17, are augmented, and autoreactive T cells and B cells are activated in the immune pathogenesis of Sjögren's syndrome (SS). In particular, IFNs are involved in both the early stages of innate immunity by high level of type I IFN in glandular tissue and sera and the later stages of disease progression by type I and type II IFN producing T cells and B cells through B cell activating factor in SS. Genetically modified mouse models for some of these molecules have been reported and will be discussed in this review. New findings from human SS and animal models of SS have elucidated some of the mechanisms underlying SS-related dry eye. We will discuss IFN-γ and several other molecules that represent candidate targets for treating inflammation in SS-related dry eye.

Involvement of Aquaporins in the Pathogenesis, Diagnosis and Treatment of Sjögren's Syndrome

Sjögren’s syndrome (SS) is a chronic autoimmune disease characterized by lymphocytic infiltration of salivary and lacrimal glands resulting in diminished production of saliva and tears. The pathophysiology of SS has not yet been fully deciphered. Classically it has been postulated that sicca symptoms in SS patients are a double step process whereby lymphocytic infiltration of lacrimal and salivary glands (SG) is followed by epithelial cell destruction resulting in keratoconjunctivitis sicca and xerostomia. Recent advances in the field of the pathophysiology of SS have brought in new players, such as aquaporins (AQPs) and anti AQPs autoantibodies that could explain underlying mechanistic processes and unveil new pathophysiological pathways offering a deeper understanding of the disease. In this review, we delineate the link between the AQP and SS, focusing on salivary glands, and discuss the role of AQPs in the treatment of SS-induced xerostomia.