Chitinases in the salivary glands and circulation of patients with Sjögren's syndrome: macrophage harbingers of disease severity

DNA methylation profiling of labial salivary gland tissues revealed hypomethylation of B-cell-related genes in primary Sjögren's syndrome

The objective of this epigenetic study was to investigate the cellular proportions based on DNA methylation signatures and pathways of differentially methylated genes in labial salivary gland (LSG) tissues of individuals with Sjögren's syndrome (SS). Two methylation array datasets from the Gene Expression Omnibus repository (GSE166373 and GSE110007) were utilized, consisting of 159 LSG tissues from 77 SS cases and 82 non-SS controls. The raw data underwent analysis using the Chip Analysis Methylation Pipeline (ChAMP) in R statistical tool, which identified differential methylation probes and regions. The EpiDISH and minfi packages in R were employed to identify proportions of epithelial cells, fibroblasts, and immune cells, as well as immune cell subsets. The results showed that proportions of immune cells were increased, while proportions of epithelial cells and fibroblasts were significantly decreased in the LSG of individuals with SS compared to non-SS controls. Specifically, proportions of B-cells and CD8 T-cells were increased, while CD4 T-cells, Treg, monocytes, and neutrophils were decreased in the LSG of individuals with SS. Pathway analysis indicated that genes involved in immune responses to Epstein-Barr virus infection were significantly hypomethylated in SS, and gene set enrichment analysis highlighted the hypomethylation of genes involved in the somatic recombination of immune receptors in SS. Additionally, Disease Ontology analysis showed enriched pathways related to multiple myeloma, arthritis, and the human immunodeficiency virus. The study also revealed significant hypomethylation of the WAS gene on chromosome X in LSG tissues of individuals with SS. Overall, the findings suggest an increased proportion of B-cells and genes related to B-cell function, as well as hypomethylation of genes involved in immune responses and immune receptor recombination, in LSG tissues of individuals with SS compared to non-SS controls.

Mitochondrial double-stranded RNAs as a pivotal mediator in the pathogenesis of Sjӧgren's syndrome

Sjӧgren's syndrome (SS) is a systemic autoimmune disease that targets the exocrine glands, resulting in impaired saliva and tear secretion. To date, type I interferons (I-IFNs) are increasingly recognized as pivotal mediators in SS, but their endogenous drivers have not been elucidated. Here, we investigate the role of mitochondrial double-stranded RNAs (mt-dsRNAs) in regulating I-IFNs and other glandular phenotypes of SS. We find that mt-dsRNAs are elevated in the saliva and tears of SS patients (n = 73 for saliva and n = 16 for tears) and in salivary glands of non-obese diabetic mice with salivary dysfunction. Using the in-house-developed 3D culture of immortalized human salivary gland cells, we show that stimulation by exogenous dsRNAs increase mt-dsRNAs, activate the innate immune system, trigger I-IFNs, and promote glandular phenotypes. These responses are mediated via the Janus kinase 1 (JAK1)/signal transducer and activator of transcription (STAT) pathway. Indeed, a small chemical inhibitor of JAK1 attenuates mtRNA elevation and immune activation. We further show that muscarinic receptor ligand acetylcholine ameliorates autoimmune characteristics by preventing mt-dsRNA-mediated immune activation. Last, direct suppression of mt-dsRNAs reverses the glandular phenotypes of SS. Altogether, our study underscores the significance of mt-dsRNA upregulation in the pathogenesis of SS and suggests mt-dsRNAs as propagators of a pseudo-viral signal in the SS target tissue.

Dysregulated long non-coding RNA in Sjögren's disease impacts both interferon and adaptive immune responses

OBJECTIVE

Sjögren's disease (SjD) is an autoimmune disease characterised by inflammatory destruction of exocrine glands. Patients with autoantibodies to Ro/SSA (SjDRo+) exhibit more severe disease. Long non-coding RNAs (lncRNAs) are a functionally diverse class of non-protein-coding RNAs whose role in autoimmune disease pathology has not been well characterised.

METHODS

Whole blood RNA-sequencing (RNA-seq) was performed on SjD cases (n=23 Ro/SSA negative (SjDRo-); n=27 Ro/SSA positive (SjDRo+) and healthy controls (HCs; n=27). Bioinformatics and pathway analyses of differentially expressed (DE) transcripts (log2 fold change ≥2 or ≤0.5; padj<0.05) were used to predict lncRNA function. LINC01871 was characterised by RNA-seq analyses of HSB-2 cells with CRISPR-targeted LINC01871 deletion (LINC01871-/ -) and in vitro stimulation assays.

RESULTS

Whole blood RNA-seq revealed autoantibody-specific transcription profiles and disproportionate downregulation of DE transcripts in SjD cases relative to HCs. Sixteen DE lncRNAs exhibited correlated expression with the interferon (IFN)-regulated gene, RSAD2, in SjDRo+ (r≥0.65 or ≤-0.6); four antisense lncRNAs exhibited IFN-regulated expression in immune cell lines. LINC01871 was upregulated in all SjD cases. RNA-seq and pathway analyses of LINC01871-/ - cells implicated roles in cytotoxic function, differentiation and IFNγ induction. LINC01871 was induced by IFNγ in a myeloid cell line and regulated by calcineurin/NFAT pathway and T cell receptor (TCR) signalling in primary human T cells.

CONCLUSION

LINC01871 influences expression of many immune cell genes and growth factors, is IFNγ inducible, and regulated by calcineurin signalling and TCR ligand engagement. Altered LINC01871 expression may influence the dysregulated T cell inflammatory pathways implicated in SjD.

Defining the Role of Monocytes in Sjögren's Syndrome

Sjögren's syndrome is one of the most prevalent autoimmune diseases after rheumatoid arthritis, with a preference for middle age, and is characterised by exocrine glandular involvement leading to xerostomia and xerophthalmia. It can have systemic implications with vascular, neurological, renal, and pulmonary involvement, and in some cases, it may evolve to non-Hodgkin's lymphoma. For a long time, B- and T-lymphocytes have been the focus of research and have been considered key players in Sjögren's syndrome pathogenesis and evolution. With the development of new technologies, including omics, more insights have been found on the different signalling pathways that lead to inflammation and activation of the immune system. New evidence indicates that a third actor linking innate and adaptive immunity plays a leading role in the Sjögren's syndrome play: the monocyte. This review summarises the recent insights from transcriptomic, proteomic, and epigenetic studies that help us to understand more about the Sjögren's syndrome pathophysiology and redefine the involvement of monocytes in this disease.

LAMP3 inhibits autophagy and contributes to cell death by lysosomal membrane permeabilization

ABBREVIATIONS

A253-control: A253 control for LAMP3 stable overexpression; A253- LAMP3: A253 LAPM3 stable overexpression; CASP1: caspase 1; CASP3: caspase 3; CHX: cycloheximide; CTSB: cathepsin B; CTSD: cathepsin D; CQ: chloroquine; DCs: dendritic cells; ER: endoplasmic reticulum; LGALS3: galectin 3; HCV: hepatitis C virus; HSG-control: HSG control for LAMP3 stable overexpression; HSG-LAMP3: HSG LAMP3 stable overexpression; HSP: heat shock protein; HTLV-1: human T-lymphocyte leukemia virus-1; IXA: ixazomib; LAMP: lysosomal associated membrane protein; MHC: major histocompatibility complex; mAb: monoclonal antibody; OE: overexpression; pepA: pepstatin A; pAb: polyclonal antibody; pSS: primary Sjögren syndrome; qRT-PCR: quantitative real- time reverse transcriptase polymerase chain reaction; SLE: systemic lupus erythematosus; SS: Sjögren syndrome; UPR: unfolded protein response; V-ATPase: vacuolar-type proton- translocating ATPase; Y-VAD: Ac-YVAD-cmk; Z-DEVD; Z-DEVD-fmk; Z-VAD: Z-VAD- fmk.

Cellular and molecular diversity in Sjogren's syndrome salivary glands: Towards a better definition of disease subsets

Primary Sjögren's syndrome (pSS) is a highly heterogeneous disease in terms of clinical presentation ranging from a mild disease localised to the salivary and lacrimal glands, to multiorgan complications of various degrees of severity, finishing with the evolution, in around 5% of pSS patients, to B cell lymphomas most commonly arising in the inflamed salivary glands. Currently, there are poor positive or negative predictors of disease evolution able to guide patient management and treatment at early stages of the diseases. Recent understanding of the pathogenic mechanisms driving immunopathology in pSS, particularly through histological and transcriptomic analysis of minor and parotid salivary gland (SG) biopsies, has highlighted a high degree of cellular and molecular heterogeneity of the inflammatory lesions but also allowed the identification of clusters of patients with similar underlying SG immunopathology. In particular, patients presenting with high degrees of B/T cell infiltration and the formation of ectopic lymphoid structures (ELS) in the SG have been associated, albeit with conflicting results, with higher degree of disease severity and enhanced risk of lymphoma evolution, suggesting that a dysregulated adaptive immune response plays a key role in driving disease manifestations in pSS. Recent data from randomised clinical trials with novel biological therapies in pSS have also highlighted the potential role of SG immunopathology and molecular pathology in stratifying patients for trial inclusion as well as assessing proof of mechanisms in longitudinal SG biopsies before and after treatment. Although significant progress has been made in the understanding of disease pathogenesis and heterogeneity through cellular and molecular SG pathology, further work is needed to validate their clinical utility in routine clinical settings and in randomised clinical trials.

Specialized pro-resolving receptors are expressed in salivary glands with Sjögren's syndrome

Our previous studies demonstrated that resolvin D1 (RvD1) and its aspirin-trigged (AT) form AT-RvD1, are effective in decreasing inflammation while restoring saliva flow rates in a Sjögren's syndrome (SS)-like mouse model before and after disease onset. Resolvins are specialized pro-resolving mediators (SPM) that actively regulate inflammation. However, we only have extensive data within the salivary glands for RvD1 and AT-RvD1, both of which bind to the receptor ALX/FPR2. As such, the presence of other SPM receptors is unknown within salivary glands. Therefore, the goal of this study was to determine the expression of SPM receptors in non-SS and SS patients. For this purpose, six human minor salivary glands from female subjects were analyzed by H&E using the Chisholm and Mason classification to determine the degree of lymphocytic infiltration. Next, confocal immunofluorescence analysis was performed to determine the presence and distribution of different SPM receptors in mucous acini and striated ducts. We observed diffuse presence of lymphocytic infiltration and clinical data were consistent with SS diagnosis in three patients. Moreover, confocal immunofluorescence analysis indicated the presence of the receptors ALX/FPR2, BLT1 and CMKLR1 in the mucous acini and striated ducts of both non-SS and SS patients. GPR32 was absent in SS and non-SS minor salivary glands. In summary, our results showed that various SPM receptors are expressed in non-SS and SS minor salivary glands, all of which may pose as potential targets for promoting pro-epithelial and anti-inflammatory/pro-resolution signaling on SS patients.

SPM Receptor Expression and Localization in Irradiated Salivary Glands

Radiation therapy-mediated salivary gland destruction is characterized by increased inflammatory cell infiltration and fibrosis, both of which ultimately lead to salivary gland hypofunction. However, current treatments (e.g., artificial saliva and sialagogues) only promote temporary relief of symptoms. As such, developing alternative measures against radiation damage is critical for restoring salivary gland structure and function. One promising option for managing radiation therapy-mediated damage in salivary glands is by activation of specialized proresolving lipid mediator receptors due to their demonstrated role in resolution of inflammation and fibrosis in many tissues. Nonetheless, little is known about the presence and function of these receptors in healthy and/or irradiated salivary glands. Therefore, the goal of this study was to detect whether these specialized proresolving lipid mediator receptors are expressed in healthy salivary glands and, if so, if they are maintained after radiation therapy-mediated damage. Our results indicate that specialized proresolving lipid mediator receptors are heterogeneously expressed in inflammatory as well as in acinar and ductal cells within human submandibular glands and that their expression persists after radiation therapy. These findings suggest that epithelial cells as well as resident immune cells represent potential targets for modulation of resolution of inflammation and fibrosis in irradiated salivary glands.

Integrated analysis of transcriptomics to identify hub genes in primary Sjögren's syndrome

OBJECTIVE

The treatment of patients with primary Sjögren's syndrome is a clinical challenge. Gene expression profile analysis and comprehensive network methods for complex diseases can provide insight into molecular characteristics in the clinical context.

MATERIALS AND METHODS

We downloaded gene expression datasets from the Gene Expression Omnibus (GEO) database. We screened differentially expressed genes (DEG) between the pSS patients and the controls by the robust rank aggregation (RRA) method. We explored DEGs' potential function using gene function annotation and PPI network analysis.

RESULTS

GSE23117 GSE40611 GSE80805 and GSE127952were included, including 38 patients and 30 controls. The RRA integrated analysis determined 294 significant DEGs (241 upregulated and 53 downregulated), and the most significant gene aberrantly expressed in SS was CXCL9 (p = 6.39E-15), followed by CXCL13 (p = 1.53E-13). Immune response (GO:0006955; p = 4.29E-32) was the most significantly enriched biological process in GO (gene ontology) analysis. KEGG pathway enrichment analysis showed that cytokine-cytokine receptor interaction (hsa04060; p = 6.46E-10) and chemokine signaling pathway (hsa04062; p = 9.54E-09) were significantly enriched. We defined PTPRC, CD86, and LCP2 as the hub genes based on the PPI results.

CONCLUSION

Our integrated analysis identified gene signatures and helped understand molecular changes in pSS.

SELL and IFI44 as potential biomarkers of Sjögren's syndrome and their correlation with immune cell infiltration

The onset of Sjögren's syndrome (SS) is hidden, early diagnosis is difficult, and the disorder seriously endangers the physical and mental health of affected people. This study aims to identify potential biomarkers of SS and to investigate the characteristics of immune cell infiltration. We used four SS gene expression profile data series from the Gene Expression Omnibus database, and applied bioinformatics analysis and machine learning algorithms to screen two biomarkers, SELL (L-selectin) and IFI44 (interferon-induced protein 44), from 101 differentially expressed genes. The two-gene model comprising SELL and IFI44 showed good diagnostic ability for SS in the training set (AUC = 0.992) and verification set (AUC = 0.917). Analysis of infiltrating immune cells in SS identified naive B cells, resting CD4 memory T cells, activated CD4 memory T cells, gamma delta T cells, M0 macrophages, M1 macrophages, plasma cells, CD8 T cells, activated NK cells and monocytes as candidate participants in the SS process. Furthermore, SELL was associated with M2 macrophages, activated CD4 memory T cells, gamma delta T cells, resting NK cells and plasma cells, while IFI44 was associated with activated mast cells, resting NK cells, resting mast cells and CD8 T cells. This study demonstrates that SELL and IFI44 can serve as good diagnostic markers for SS and may also be new diagnostic and therapeutic targets for SS.

Predicted Disease-Specific Immune Infiltration Patterns Decode the Potential Mechanisms of Long Non-Coding RNAs in Primary Sjogren's Syndrome

Primary Sjogren’s syndrome (pSS) is a chronic progressive autoimmune disease with clinical phenotypic “Sicca symptoms”. In some cases, the diagnosis of pSS is delayed by 6–7 years due to the inefficient differential diagnosis of pSS and non-SS “Sicca”. This study aimed to investigate the difference between these two diseases, and in particular, their immunopathogenesis. Based on their gene expression profiles, we systematically defined for the first time the predicted disease-specific immune infiltration pattern of patients with pSS differentiated from normal donors and patients with non-SS “Sicca”. We found that it was characterized by the aberrant abundance and interaction of tissue-infiltrated immune cells, such as a notable shift in the subpopulation of six immune cells and the perturbed abundance of nine subpopulations, such as CD4+ memory, CD8+ T-cells and gamma delta T-cells. In addition, we identified essential genes, particularly long non-coding RNAs (lncRNAs), as the potential mechanisms linked to this predicted pattern reprogramming. Fourteen lncRNAs were identified as the potential regulators associated with the pSS-specific immune infiltration pattern in a synergistic manner, among which the CTA-250D10.23 lncRNA was highly relevant to chemokine signaling pathways. In conclusion, aberrant predicted disease-specific immune infiltration patterns and relevant genes revealed the immunopathogenesis of pSS and provided some clues for the immunotherapy by targeting specific immune cells and genes.

Deciphering potential pharmacological mechanism of Sha-Shen-Mai-Dong decoction on primary Sjogren's syndrome

Background

Sha-Shen-Mai-Dong decoction (SSMD) is a classical prescription widely used in primary Sjogren’s Syndrome (pSS) therapy. This study aims to explore the potential pharmacological mechanism of SSMD on pSS.

Methods

Active components of SSMD were obtained from Traditional Chinese Medicine Integrative Database and Traditional Chinese Medicine Systems Pharmacology databases and targets of SSMD were predicted by Pharmmapper and STITCH database. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were carried out to explore the function characteristics of SSMD. The expression matrix of microarray of pSS was obtained from Gene Expression Omnibus and we obtained 162 differentially expressed genes (DEGs). Protein-protein interaction (PPI) networks were constructed to identify the hub targets. Principal component analysis (PCA) and molecular docking were conducted to further elucidate the possibility of SSMD for pSS.

Results

SSMD contained a total of 1056 active components, corresponding to 88 targets, among which peripheral myelin protein 2(PMP2), androgen receptor (AR) and glutamic acid decarboxylase 1(GAD1) are associated with multiple active components in SSMD and may be the core targets. Moreover, these targets were closely related to tissue pathological injury in SS, such as lacrimal gland, salivary gland and nervous system injury. GO and KEGG analysis showed that 88 targets enriched in REDOX process, transcriptional regulation and negative regulation of apoptosis process. Besides, SSMD may influence the cell proliferation, gene transcription through regulating Ras and cAMP-related signaling pathways. In addition, SSMD may show effects on immune regulation, such as macrophage differentiation, Toll-like receptor 4 signaling pathway and T-helper 1 in SS. Moreover, PPI network suggested that FN1, MMP-9 may be the hub targets in SSMD. Result of PCA and molecular docking analysis further determined the feasibility of SSMD in treating pSS.

Conclusion

SSMD can regulate multiple biological processes by virtue of its multiple active components, thus showing prominent advantage in the treatment of pSS. The discovery of active ingredients and targets in SSMD provides valuable resources for drug research and development for pSS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03257-7.

New frontiers in precision medicine for Sjogren's syndrome

Introduction: Sjögren's syndrome is a unique systemic autoimmune disease, placed in the center of systemic autoimmunity and at the crossroads of autoimmunity and lymphoproliferation. The diverse clinical picture of the disease, the inefficacy of current biologic treatments, and the co-existence with lymphoma conferring to the patients' morbidity and mortality force the scientific community to review disease pathogenesis and reveal the major implicated cellular and molecular elements.Areas covered: Biomarkers for early diagnosis, prediction, stratification, monitoring, and targeted treatments can serve as a tool to interlink and switch from the clinical phenotyping of the disease into a more sophisticated classification based on the underlying critical molecular pathways and endotypes. Such a transition may define the establishment of the so-called precision medicine era in which patients' management will be based on grouping according to pathogenetically related biomarkers. In the current work, literature on Sjogren's syndrome covering several research fields including clinical, translational, and basic research has been reviewed.Expert opinion: The perspectives of clinical and translational research are anticipated to define phenotypic clustering of high-risk pSS patients and link the clinical picture of the disease with fundamental molecular mechanisms and molecules implicated in pathogenesis.

Making Sense of Intracellular Nucleic Acid Sensing in Type I Interferon Activation in Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a systemic autoimmune rheumatic disease characterized by dryness of the eyes and mucous membranes, which can be accompanied by various extraglandular autoimmune manifestations. The majority of patients exhibit persistent systemic activation of the type I interferon (IFN) system, a feature that is shared with other systemic autoimmune diseases. Type I IFNs are integral to anti-viral immunity and are produced in response to stimulation of pattern recognition receptors, among which nucleic acid (NA) receptors. Dysregulated detection of endogenous NAs has been widely implicated in the pathogenesis of systemic autoimmune diseases. Stimulation of endosomal Toll-like receptors by NA-containing immune complexes are considered to contribute to the systemic type I IFN activation. Accumulating evidence suggest additional roles for cytosolic NA-sensing pathways in the pathogenesis of systemic autoimmune rheumatic diseases. In this review, we will provide an overview of the functions and signaling of intracellular RNA- and DNA-sensing receptors and summarize the evidence for a potential role of these receptors in the pathogenesis of pSS and the sustained systemic type I IFN activation.

Circular RNA sequencing indicates circ-IQGAP2 and circ-ZC3H6 as noninvasive biomarkers of primary Sjögren's syndrome

OBJECTIVES

This study aims to characterize the expression profiles of circRNAs in primary Sjogren's Syndrome (pSS) and examine the potential of noninvasive circular RNAs (circRNAs) as biomarkers of pSS.

METHODS

We performed RNA sequencing of minor salivary gland (MSG) biopsies from four pSS and four non-pSS individuals (subjects undergoing MSG biopsies but not meeting 2012 or 2016 ACR classification criteria for SS). Differentially expressed circRNAs were identified by DESeq2, and confirmed by quantitative real-time PCR in the MSGs as well as in plasma exosomes in 37 pSS and 14 non-pSS subjects. Discriminatory capacity testing using receiver operating characteristic analysis was used to evaluate the performance of circRNAs as diagnostic biomarkers for pSS.

RESULTS

Circ-IQGAP2 and circ-ZC3H6 had significantly upregulated expression in the MSGs of pSS patients, and this elevated expression was confirmed by quantitative real-time PCR of plasma exosome RNA. The expression of these circRNAs also showed significant correlation with both clinical features, serum IgG level and MSG focus scores. Receiver operating characteristic analysis showed that the indices comprised of both the two circRNAs and clinical features were better able to distinguish pSS from non-pSS subjects with high mean areas under the curve of 0.93 in the MSGs and 0.92 in the plasma exosomes.

CONCLUSION

This study indicated the potential roles of circ-IQGAP2 and circ-ZC3H6 as noninvasive biomarkers for the diagnosis of pSS.

Transcriptomic and Network Analysis of Minor Salivary Glands of Patients With Primary Sjögren's Syndrome

Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease characterized primarily by immune-mediated destruction of exocrine tissues, such as those of the salivary and lacrimal glands, resulting in the loss of saliva and tear production, respectively. This disease predominantly affects middle-aged women, often in an insidious manner with the accumulation of subtle changes in glandular function occurring over many years. Patients commonly suffer from pSS symptoms for years before receiving a diagnosis. Currently, there is no effective cure for pSS and treatment options and targeted therapy approaches are limited due to a lack of our overall understanding of the disease etiology and its underlying pathology. To better elucidate the underlying molecular nature of this disease, we have performed RNA-sequencing to generate a comprehensive global gene expression profile of minor salivary glands from an ethnically diverse cohort of patients with pSS. Gene expression analysis has identified a number of pathways and networks that are relevant in pSS pathogenesis. Moreover, our detailed integrative analysis has revealed a primary Sjögren’s syndrome molecular signature that may represent important players acting as potential drivers of this disease. Finally, we have established that the global transcriptomic changes in pSS are likely to be attributed not only to various immune cell types within the salivary gland but also epithelial cells which are likely playing a contributing role. Overall, our comprehensive studies provide a database-enriched framework and resource for the identification and examination of key pathways, mediators, and new biomarkers important in the pathogenesis of this disease with the long-term goals of facilitating earlier diagnosis of pSS and to mitigate or abrogate the progression of this debilitating disease.

Expression of APOBEC family members as regulators of endogenous retroelements and malignant transformation in systemic autoimmunity

OBJECTIVE

To explore whether APOBEC family members are involved in the response to inappropriate expression of L1 retroelements in primary Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE), as well as in SS related lymphomagenesis.

METHODS

Minor salivary glands (MSG) and kidney biopsy (KB) specimens were obtained from 41 SS patients (10 with lymphoma) and 23 patients with SLE, respectively. PBMC and sera were also collected from 73 SLE patients. Full-length L1 transcripts, members of the APOBEC and IFN family were quantitated by real time PCR. Type I IFN activity was assessed in lupus plasma by a cell assay.

RESULTS

APOBEC3A was increased in SS MSG, SLE KB and PBMC and correlated with L1. AID and APOBEC3G were particularly overexpressed in MSG tissues derived from SS lymphoma patients.

CONCLUSION

These data reveal a previously unappreciated role of APOBEC family proteins in the pathogenesis of systemic autoimmunity and SS related lymphomagenesis.

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.

Relationships between increased circulating YKL-40, IL-6 and TNF-α levels and phenotypes and disease activity of primary Sjögren's syndrome

BACKGROUND

There is now no single score or marker useful for evaluating disease activity of primary Sjögren's syndrome (pSS). This study was designed to explore the associations of circulating YKL-40, interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) with systemic activity and phenotypes of pSS.

METHODS

This study included 58 pSS patients and 30 healthy controls (HC). The sera were measured by multiplex immunoassay for YKL-40, IL-6 and TNF-α concentrations. The disease activity of pSS patients was evaluated by European league against rheumatism (EULAR) SS disease activity index (ESSDAI). Local severity was assessed in accordance with the Tarpley score.

RESULTS

Serum YKL-40, IL-6 and TNF-α levels significantly elevated in pSS patients compared with those in HC (all P < 0.001). These cytokines correlated with ESSDAI, ESR, CRP, and IgG (all P < 0.05). Serum YKL-40 level correlated markedly with age (r = 0.405, P = 0.002), neutrophil count (r = 0.399, P = 0.002) and neutrophil-to-lymphocyte ratio (NLR) (r = 0.401, P = 0.002), while IL-6 did weakly with NLR (r = 0.296, P = 0.024) and C3 (r = 0.288, 0.036). Serum levels of all three cytokines were substantially lower in patients with eye/mouth dryness vs. those without (all P < 0.05). Additionally, patients with pulmonary, renal involvement or anemia had remarkably higher concentrations of YKL-40 (all P < 0.05), while those with leukocytopenia had lower levels (P = 0.01). Fever or anemia patients showed higher serum concentrations of IL-6 (both P < 0.05), while serum levels of TNF-α were much higher in patients with presence of ANA, anti-SSA or anti-SSB antibodies (All P < 0.05). Serum IL-6 level correlated strongly with YKL-40 (r = 0.452, P < 0.001) and TNF-α (r = 0.743, P < 0.001) in pSS patients. A significant correlation was also found between YKL-40 and TNF-α (r = 0.308, P = 0.022) .

CONCLUSION

The circulating YKL-40, IL-6 and TNF-α levels increase in pSS, and all of them are significantly correlated with indicators (ESSDAI, ESR, CRP, and IgG) for systemic inflammation of pSS. Each cytokine is separately associated with specific pSS phenotype.

Contributions of Major Cell Populations to Sjögren's Syndrome

Sjögren’s syndrome (SS) is a female dominated autoimmune disease characterized by lymphocytic infiltration into salivary and lacrimal glands and subsequent exocrine glandular dysfunction. SS also may exhibit a broad array of extraglandular manifestations including an elevated incidence of non-Hodgkin’s B cell lymphoma. The etiology of SS remains poorly understood, yet progress has been made in identifying progressive stages of disease using preclinical mouse models. The roles played by immune cell subtypes within these stages of disease are becoming increasingly well understood, though significant gaps in knowledge still remain. There is evidence for distinct involvement from both innate and adaptive immune cells, where cells of the innate immune system establish a proinflammatory environment characterized by a type I interferon (IFN) signature that facilitates propagation of the disease by further activating T and B cell subsets to generate autoantibodies and participate in glandular destruction. This review will discuss the evidence for participation in disease pathogenesis by various classes of immune cells and glandular epithelial cells based upon data from both preclinical mouse models and human patients. Further examination of the contributions of glandular and immune cell subtypes to SS will be necessary to identify additional therapeutic targets that may lead to better management of the disease.

LAMP3 induces apoptosis and autoantigen release in Sjögren's syndrome patients

Primary Sjögren's syndrome (pSS) is a complex autoimmune disease characterized by dysfunction of secretory epithelia with only palliative therapy. Patients present with a constellation of symptoms, and the diversity of symptomatic presentation has made it difficult to understand the underlying disease mechanisms. In this study, aggregation of unbiased transcriptome profiling data sets of minor salivary gland biopsies from controls and Sjögren's syndrome patients identified increased expression of lysosome-associated membrane protein 3 (LAMP3/CD208/DC-LAMP) in a subset of Sjögren's syndrome cases. Stratification of patients based on their clinical characteristics suggested an association between increased LAMP3 expression and the presence of serum autoantibodies including anti-Ro/SSA, anti-La/SSB, anti-nuclear antibodies. In vitro studies demonstrated that LAMP3 expression induces epithelial cell dysfunction leading to apoptosis. Interestingly, LAMP3 expression resulted in the accumulation and release of intracellular TRIM21 (one component of SSA), La (SSB), and α-fodrin protein, common autoantigens in Sjögren's syndrome, via extracellular vesicles in an apoptosis-independent mechanism. This study defines a clear role for LAMP3 in the initiation of apoptosis and an independent pathway for the extracellular release of known autoantigens leading to the formation of autoantibodies associated with this disease.ClinicalTrials.gov Identifier: NCT00001196, NCT00001390, NCT02327884.

Integrated systems analysis of salivary gland transcriptomics reveals key molecular networks in Sjögren's syndrome

Background

Treatment of patients with Sjögren’s syndrome (SjS) is a clinical challenge with high unmet needs. Gene expression profiling and integrative network-based approaches to complex disease can offer an insight on molecular characteristics in the context of clinical setting.

Methods

An integrated dataset was created from salivary gland samples of 30 SjS patients. Pathway-driven enrichment profiles made by gene set enrichment analysis were categorized using hierarchical clustering. Differentially expressed genes (DEGs) were subjected to functional network analysis, where the elements of the core subnetwork were used for key driver analysis.

Results

We identified 310 upregulated DEGs, including nine known genetic risk factors and two potential biomarkers. The core subnetwork was enriched with the processes associated with B cell hyperactivity. Pathway-based subgrouping revealed two clusters with distinct molecular signatures for the relevant pathways and cell subsets. Cluster 2, with low-grade inflammation, showed a better response to rituximab therapy than cluster 1, with high-grade inflammation. Fourteen key driver genes appeared to be essential signaling mediators downstream of the B cell receptor (BCR) signaling pathway and to have a positive relationship with histopathology scores.

Conclusion

Integrative network-based approaches provide deep insights into the modules and pathways causally related to SjS and allow identification of key targets for disease. Intervention adjusted to the molecular traits of the disease would allow the achievement of better outcomes, and the BCR signaling pathway and its leading players are promising therapeutic targets.

Identification of differentially expressed genes in primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a chronic systemic autoimmune disease that affects exocrine glands. To study the molecular mechanism and identify crucial genes/pathways in pSS pathogenesis, the microarray-based whole-genome gene expression profiles from salivary glands of patients with pSS and non-sicca controls were retrieved. After normalization and subsequent batch effect adjustment, significance analysis of microarrays method was applied to five available datasets, and 379 differentially expressed genes (DEGs) were identified. The 300 upregulated DEGs were enriched in Gene Ontology terms of immune and inflammatory responses, including antigen processing and presentation, interferon-mediated signaling pathway, and chemotaxis. Previously reported pSS-associated genes, including HLA-DRA, TAP2, PRDM1, and IFI16, were found to be significantly upregulated. The downregulated DEGs were enriched in pathways of salivary secretion, carbohydrate digestion and absorption, and starch and sucrose metabolism, implying dysfunction of salivary glands during pathogenesis. Next, a protein-protein interaction network was constructed, and B2M, an upregulated DEG, was shown to be a hub, suggesting its potential involvement in pSS development. In summary, we found the activation of pSS-associated genes in pathogenesis, and provide clues for salivary glands dysfunction. Experimental investigation on the identified DEGs in this study will deepen our understanding on pSS.

The Role of Monocytes and Macrophages in Autoimmune Diseases: A Comprehensive Review

Monocytes (Mo) and macrophages (Mϕ) are key components of the innate immune system and are involved in regulation of the initiation, development, and resolution of many inflammatory disorders. In addition, these cells also play important immunoregulatory and tissue-repairing roles to decrease immune reactions and promote tissue regeneration. Several lines of evidence have suggested a causal link between the presence or activation of these cells and the development of autoimmune diseases. In addition, Mo or Mϕ infiltration in diseased tissues is a hallmark of several autoimmune diseases. However, the detailed contributions of these cells, whether they actually initiate disease or perpetuate disease progression, and whether their phenotype and functional alteration are merely epiphenomena are still unclear in many autoimmune diseases. Additionally, little is known about their heterogeneous populations in different autoimmune diseases. Elucidating the relevance of Mo and Mϕ in autoimmune diseases and the associated mechanisms could lead to the identification of more effective therapeutic strategies in the future.

Elevated CCL19/CCR7 Expression During the Disease Process of Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a common chronic autoimmune disease characterized by a high prevalence of autoantibodies and lymphocyte-mediated exocrine gland damage. To enhance our understanding of the mechanisms underlying the progression of the disease and to discover potential biomarkers for the early diagnosis of pSS, we applied RNA sequencing to compare the gene expression patterns in minor salivary glands between pSS patients and non-pSS. A total of 293 differentially expressed genes (DEGs) were detected in pSS vs. non-pSS (FDR < 0.05, fold changes > 2). Of these DEGs, 285 (97.26%) were up-regulated, with most being involved in immune system activation, especially in the formation of the immunological synapse. Significantly elevated CCL19/CCR7 expression in the salivary gland was found to be related to anti-Sjögren's syndrome-related antigen A (SSA) antibody and IgG levels in pSS patients, which was further confirmed in a larger cohort. Up-regulated gene expression showed strong discriminatory accuracy in identifying pSS with area under the curve of 0.98 using receiver operating characteristic curve analysis. In conclusion, gene expression changes in pSS include strong markers of immunological activation and have good discriminatory power in identifying patients with pSS.

Significance of M2 macrophage in tubulointerstitial disease secondary to primary Sjogren's disease

Objective: M2 Macrophages could improve tubulointerstitial disease in animal models. HIF-1αpromotes macrophage polarization and is involved in tubular injury. The study aims to observe the clinicopathologic significance of M2 macrophage and HIF-1α in tubulointerstitial injury secondary to primary Sjogren's disease.

Methods: Renal tissue samples from patients with tubulointerstitial disease secondary to primary Sjogren's disease (SS, n = 10), chronic tubulointerstitial nephritis secondary to drug (CIN, n = 8) were included in this study. The expression of CD163, CD68 and HIF-1α were examined by immunohistochemistry or immunofluorescence.

Results: (1) Renal involvement was the first manifestation in seven of ten (7/10) patients with pSS, including proteinuria, renal dysfunction, renal tubular acidosis and multiple renal stone; and two patient had intractable hypokalemia. (2) There were numerous CD163- positive cells and CD68- positive cells infiltration in tubulointerstitial injury of pSS, especially in patients with hypokalemia. CD163 positive cells and HIF-1αwere mainly expressed in acute tubulointerstitial injury of pSS, which positively correlated to N-acetyl-β-D-glucosaminidase and β2-microglobulin. (3) Compared with CIN, patients with pSS had higher serum globulin level, erythrocyte sedimentation rate (ESR) and lower urinary osmotic pressure. (4) During follow-up of one year, six patients with pSS and acute tubular injury acquired improved renal function on therapy of steroid and total glucosides of peony. The remaining four patients with pSS had stable renal function.

Conclusion: M2 macrophages are involved in acute tubular injury in patients with primary Sjogren's disease. Early intervention can improve renal function of tubulointerstitial injury secondary to primary Sjogren's disease.

CCL22-Producing Resident Macrophages Enhance T Cell Response in Sjögren's Syndrome

Macrophages (MΦs) are critical regulators of immune response and serve as a link between innate and acquired immunity. The precise mechanism of involvement of tissue-resident MΦs in the pathogenesis of autoimmune diseases is not clear. Here, using a murine model for Sjögren's syndrome (SS), we investigated the role of tissue-resident MΦs in the onset and development of autoimmunity. Two unique populations of CD11b^high and CD11b^low resident MΦs were observed in the target tissue of the SS model. Comprehensive gene expression analysis of chemokines revealed effective production of CCL22 by the CD11b^high MΦs. CCL22 upregulated the migratory activity of CD4⁺ T cells by increasing CCR4, a receptor of CCL22, on T cells in the SS model. In addition, CCL22 enhanced IFN-γ production of T cells of the SS model, thereby suggesting that CCL22 may impair the local immune tolerance in the target organ of the SS model. Moreover, administration of anti-CCL22 antibody suppressed autoimmune lesions in the SS model. Finally, histopathological analysis revealed numerous CCL22-producing MΦs in the minor salivary gland tissue specimens of the SS patients. CCL22-producing tissue-resident MΦs may control autoimmune lesions by enhancing T cell response in the SS model. These results suggest that specific chemokines and their receptors may serve as novel therapeutic or diagnostic targets for SS.

Innate immunity in Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disease of exocrine tissue that primarily affects women. Although patients typically experience xerostomia and xerophthalmia, numerous systemic disease manifestations are seen. Innate immune hyperactivity is integral to many autoimmune diseases, including SS. Results from SS mouse models suggest that innate immune dysregulation drives disease and this is a seminal event in SS pathogenesis. Findings in SS patients corroborate those in mouse models, as innate immune cells and pathways are dysregulated both in exocrine tissue and in peripheral blood. We will review the role of the innate immune system in SS pathogenesis. We will discuss the etiology of SS with an emphasis on innate immune dysfunction. Moreover, we will review the innate cells that mediate inflammation in SS, the pathways implicated in disease, and the potential mechanisms governing their dysregulation. Finally, we will discuss emerging therapeutic approaches to target dysregulated innate immune signaling in SS.

Biosemantics guided gene expression profiling of Sjögren's syndrome: a comparative analysis with systemic lupus erythematosus and rheumatoid arthritis

BACKGROUND

Sjögren's syndrome (SS) shares many clinical and pathological similarities with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). These autoimmune diseases mostly affect women. In this study, concept profile analysis (CPA) and gene expression meta-analysis were used to identify genes potentially involved in SS pathogenesis.

METHODS

Human genes associated with SS, SLE, and RA were identified using the CPA tool, Anni 2.1. The differential mRNA expression of genes common to SS and SLE (SS-SLE) was determined in female peripheral blood mononuclear cells (PBMCs) using NCBI-GEO2R. Differentially expressed (DE) SS-SLE PBMC genes in common with the SS-SLE CPA-identified genes were analyzed for differential expression in salivary glands or synovial biopsies, and for genes common to SS and RA and SLE and RA, analyzing differential expression in salivary glands in SS, synovial fibroblasts in RA, and synovial fluid in SLE. Among common genes, DE genes found in salivary gland mRNA expression in patients with SS were used for gene enrichment and SS molecular network construction. Secondary analysis was performed to identify DE genes unique to the disease site tissues, by excluding PBMC and CPA common DE genes to complement the SS network.

RESULTS

We identified 22 DE genes in salivary gland datasets in SS that have not previously been clearly associated with SS pathogenesis. Among these, higher levels of checkpoint kinase 1 (CHEK1), V-Ets avian erythroblastosis virus E26 oncogene homolog 1 (ETS1), and lymphoid enhancer binding factor 1 (LEF1) were significantly correlated with higher matrix metalloproteinase 9 (MMP9) levels. Higher MMP9 levels have been implicated in degradation of salivary gland structural integrity, leading to hypo-salivation in patients with SS. Salivary gland mRNA expression of MMP9 and the expression of cytokine CXCL10 were higher in patients with SS. CXCL10 has been shown to increase MMP9 expression and therefore may also play an important role in SS pathogenesis.

CONCLUSION

Using CPA and gene expression analysis, we identified factors targeting MMP9 expression and/or function, namely CHEK1, CXCL10, ETS1, LEF1, and tissue inhibitor of metalloproteinase 1; altered mRNA expression of these could increase expression/activity of MMP9 in a concerted manner, thereby potentially impacting SS pathogenesis.

Multiomic disease signatures converge to cytotoxic CD8 T cells in primary Sjögren's syndrome

Objectives

Multiomics study was conducted to elucidate the crucial molecular mechanisms of primary Sjögren’s syndrome (SS) pathology.

Methods

We generated multiple data set from well-defined patients with SS, which includes whole-blood transcriptomes, serum proteomes and peripheral immunophenotyping. Based on our newly generated data, we performed an extensive bioinformatic investigation.

Results

Our integrative analysis identified SS gene signatures (SGS) dysregulated in widespread omics layers, including epigenomes, mRNAs and proteins. SGS predominantly involved the interferon signature and ADAMs substrates. Besides, SGS was significantly overlapped with SS-causing genes indicated by a genome-wide association study and expression trait loci analyses. Combining the molecular signatures with immunophenotypic profiles revealed that cytotoxic CD8 ­T cells­ were associated with SGS. Further, we observed the activation of SGS in cytotoxic CD8 T cells isolated from patients with SS.

Conclusions

Our multiomics investigation identified gene signatures deeply associated with SS pathology and showed the involvement of cytotoxic CD8 T cells. These integrative relations across multiple layers will facilitate our understanding of SS at the system level.

Crucial roles of macrophages in the pathogenesis of autoimmune disease

Macrophages are key players in various immune responses. In addition to functions in innate immunity such as antigen phagocytosis and cytokine production, antigen presentation by macrophage represents a link between innate and acquired immunity. During inflammatory processes, naïve monocytes differentiate into pro-inflammatory M1 and anti-inflammatory M2 macrophages. Resident monocytes/macrophages contribute to immune response that maintains tissue-specific homeostasis. In the target organs of autoimmune diseases, macrophages have dual functions in both the induction and suppression of autoimmune responses, which are mediated by production of various cytokines and chemokines, or by interaction with other immune cells. This review focuses on selected autoimmune diseases, such as systemic lupus erythematosus, multiple sclerosis, rheumatoid arthritis, and Sjögren’s syndrome, to illustrate the key roles of macrophages in the cellular or molecular pathogenesis of autoimmunity. In addition, the contribution of macrophages to each autoimmune disease is compared.

Insight into pathogenesis of Sjögren's syndrome: Dissection on autoimmune infiltrates and epithelial cells

Sjögren's syndrome (SS) is a chronic autoimmune disease with broad clinical spectrum, extending from benign exocrinopathy to severe systemic disease and lymphoma development. The glandular and extraglandular dysfunction of SS is associated with lymphocytic infiltrates that invade the epithelial structures of affected organs. The in-depth study of autoimmune lesions in the minor salivary glands (MSG), which are the major target-organ of SS responses, revealed that the lymphocytic infiltrates vary in severity and composition among SS-patients, are full-blown at diagnosis and remain unchanged thereafter. Although the pathogenetic pathways underlying SS have not yet elucidated, it is well-established that glandular epithelial cells are central regulators of local autoimmune responses. Moreover, chronic inflammation affects epithelial function and phenotype, which strengthens or weakens their immunoregulatory/secretory function, leading to deterioration of autoimmune phenomena. Herein, the current findings regarding the autoimmune lesions, the role of epithelial cells and their interaction with infiltrating lymphocytic cells are discussed.

High salivary soluble L-selectin and interleukin-7 levels in Asian Indian patients with primary Sjögren's syndrome

In present study, we aimed to study salivary soluble L-selectin (sL-selectin), interleukin-7(IjL-7), and lymphotoxin-α levels in primary Sjögren's syndrome (pSS) and their clinical as well as serological correlations. pSS patients fulfilling either the American European Consensus Group (AECG) and/or the American college of Rheumatology (ACR) criteria were recruited. Age- and sex-matched hospital staff were recruited as healthy controls. Unstimulated saliva was collected by the spitting method; sL-selectin, IL-7, and lymphotoxin-α were measured in the saliva using commercial ELISA kits. Forty-three patients with pSS and 31 healthy controls were included in the study. Increased levels of sL-selectin and IL-7 were found in the saliva of patients as compared to controls. Lymphotoxin-α was undetectable in the saliva of pSS patients and controls. Salivary sL-selectin positively correlated with rheumatoid factor (r = 0.47; p < 0.003). No other variable including ESSDAI was significantly associated with salivary sL-selectin and IL-7 levels. Indian patients with primary Sjögren's syndrome have higher salivary sL-selectin and IL-7 levels than healthy controls.

Long non-coding RNA expression profile in minor salivary gland of primary Sjögren's syndrome

BACKGROUND

To examine the roles of long noncoding RNAs (lncRNAs) in the regulation of primary Sjögren's syndrome (pSS) and reveal the expression profile of lncRNAs in labial salivary glands (LSGs) in pSS patients.

METHOD

The expression of 63,431 lncRNAs and 39,887 mRNAs were determined in the LSG of four pSS patients and four healthy controls using microarray experiments. Validation was performed in 30 pSS patients and 16 controls using real-time PCR. LncRNA-mRNA co-expression and gene-pathway networks were constructed using bioinformatics software.

RESULT

A total of 1243 lncRNAs (upregulated: 890, downregulated: 353) and 1457 mRNAs (upregulated: 1141, downregulated: 316) were differentially expressed in the LSGs of pSS patients (fold change >2, P <0.05). Eight of these lncRNAs were validated using real-time PCR. ENST00000420219.1 (3.13-fold), ENST00000455309.1 (2.51-fold), n336161 (2.45-fold), NR_002712 (2.41-fold), ENST00000546086.1 (1.94-fold), Lnc-UTS2D-1:1 (1.79-fold), n340599 (1.69-fold), and TCONS_l2_00014794 (1.28-fold) were significantly upregulated in pSS. There were strong correlations between these lncRNAs and β2 microglobulin, disease course, erythrocyte sedimentation rate (ESR), rheumatoid factor (RF), IgA, IgM, visual analogue scale (VAS) of parotid swelling and VAS of dry eyes. Computational analyses revealed that 28 of the differentially expressed (DE) mRNAs were associated with eight DE lncRNAs involved in chemokine signaling pathways, the nuclear factor-kappa B (NF-κB) signaling pathway, and tumor necrosis factor (TNF) signaling pathway.

CONCLUSIONS

Our study revealed the expression profile of lncRNAs in LSGs of pSS patients. Many novel lncRNA transcripts that play important roles in the pathogenesis of pSS were dysregulated in pSS. Therefore, this study will aid in the development of new diagnostic biomarkers and drug therapies.

Analysis of tear inflammatory mediators: A comparison between the microarray and Luminex methods

PURPOSE

Inflammatory mediators have been shown to modulate dry eye (DE) disease and may correlate with disease severity, yet the methods used and the associated findings vary significantly in the literature. The goal of this research was to compare two methods, the quantitative microarray and the magnetic bead assay, for detecting cytokine levels in extracted tear samples across three subject groups.

METHODS

Tears were collected from Schirmer strips of the right and left eyes of 20 soft contact lens wearers (CL), 20 normal non-contact lens wearers (NOR), and 20 DE subjects and stored at -80 °C. Tear proteins were eluted and precipitated using ammonium bicarbonate and acetone. The right and left eye samples were combined for each subject. Following the Bradford protein quantitation method, 10 µg of total protein was used for each of the two analyses, Quantibody® Human Inflammation Array 3 (RayBiotech) and High Sensitivity Human Cytokine Magnetic Bead Kit (Millipore). The assays were run using the GenePix® 4000B Scanner (Molecular Devices) or the Luminex MagPix® plate reader (Luminex), respectively. The data were then compared between the two instruments and the three subject groups.

RESULTS

Of the 40 proteins on the Quantibody® microarray, seven had average expression levels above the lower limit of detection: ICAM-1, MCP-1, MIG, MCSF, TIMP-1, TIMP-2, and TNF-RI. Significant differences in expression levels (p<0.05) were detected between the CL and DE groups for MCSF, TIMP-1, and TNF R1, between the NOR and DE groups for ICAM-1, and between the CL and NOR groups for ICAM-1, MCP-1, MCSF, TIMP-1, TIMP-2, and TNF-R1 when using the Student t test. Of the 13 proteins tested with Luminex, IL-1β, IL-4, IL-6, IL-7, and IL-8 had expression levels above the minimum detectable level, and these were most often detected using the Luminex assay compared to the Quantibody® microarray. Contrarily, IL-2, IL-12, IL-13, INF-g, and GM-CSF were detected more frequently using the Quantibody® microarray than the Luminex assay. Significant differences in expression levels (p<0.05) were only detected between the CL and DE groups for IL-7 and IL-8 and between the CL and NOR subjects for IL-8.

CONCLUSIONS

In addition to detecting more significant differences between the subject groups, the Quantibody® microarray detected more inflammatory cytokines in total within the range of detection than the Luminex assay. Differences were also noted in the types of cytokines each assay could detect from the limited protein samples. Both methods offer advantages and disadvantages; therefore, these factors should be considered when determining the appropriate assay for analyzing tear protein samples.

Testing differentially expressed genes in dose-response studies and with ordinal phenotypes

When testing for differentially expressed genes between more than two groups, the groups are often defined by dose levels in dose-response experiments or ordinal phenotypes, such as disease stages. We discuss the potential of a new approach that uses the levels’ ordering without making any structural assumptions, such as monotonicity, by testing for zero variance components in a mixed models framework. Since the mixed effects model approach borrows strength across doses/levels, the test proposed can also be applied when the number of dose levels/phenotypes is large and/or the number of subjects per group is small. We illustrate the new test in simulation studies and on several publicly available datasets and compare it to alternative testing procedures. All tests considered are implemented in R and are publicly available. The new approach offers a very fast and powerful way to test for differentially expressed genes between ordered groups without making restrictive assumptions with respect to the true relationship between factor levels and response.

Long noncoding RNAs could be potential key players in the pathophysiology of Sjögren's syndrome

Long noncoding RNAs (lncRNAs) are a recently discovered class of noncoding functional RNAs encoded by metazoan genomes. Recent studies suggest a larger regulatory role for lncRNAs in critical biological and disease processes. Mounting evidence on the role of lncRNAs in regulating key processes of the immune system prompted us to hypothesize the role of lncRNAs as key regulators of the pathophysiology of Sjögren's syndrome (SS). We used two similar approaches based on reanalysis of microarray expression datasets and curation of lncRNA-protein coding gene interactions from literature to derive support for our hypothesis. We also discuss potential caveats to our approach and suggest approaches to validate the hypothesis. Our analysis suggests the potential larger and hitherto unknown role of lncRNA regulatory networks in modulating the expression of key genes involved in the pathogenesis of SS and thereby modulating the pathophysiology of SS.

Macrophages: important players in primary Sjögren's syndrome?

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder characterized by immune-mediated destruction of the salivary and lacrimal glands with unknown etiology. Due to recent research utilizing human subjects as well as laboratory animal models, our understanding of the pathophysiological and immunological mechanisms of pSS has made great strides. As a consequence, targeted, immune-based therapies are gaining increased attention as the ideal way to conquer autoimmune diseases like pSS. Currently, however, there is no effective treatment to target specific immunological events or effector immune cells in the pathogenesis of pSS (discussed in other reviews of the current issue). Here, we summarize our current understanding and knowledge of the roles of monocytes/macrophages in the pathogenesis of pSS. Human studies, especially utilizing salivary gland biopsies, demonstrate the infiltration of macrophages and its correlation with disease severity. Moreover, animal model studies have shown the functional involvement of macrophages in promoting the ocular component of pSS.

Meta-analysis of differentially expressed genes in primary Sjogren's syndrome by using microarray

INTRODUCTION

The purpose of this study was to identify differentially expressed (DE) genes and biological processes associated with changes in gene expression in primary Sjogren's syndrome (pSS).

METHODS

We performed a meta-analysis using the INMEX program (integrative meta-analysis of expression data) of publicly available microarray GEO datasets of pSS. We performed Gene Ontology (GO) enrichment analyses and pathway analysis using Kyoto Encyclopedia of Genes and Genomes (KEGG).

RESULTS

Three GEO datasets including 37 cases and 33 controls were available for the meta-analysis. We identified 179 genes across the studies which were consistently DE in pSS (146 up-regulated and 33 down-regulated). The up-regulated gene with the largest effect size (ES) (ES = -2.4228) was SELL (selectin L), whose product is required for the binding and subsequent rolling of leucocytes on endothelial cells to facilitate their migration into secondary lymphoid organs and inflammation sites. The most significant enrichment was in the immune response GO category (P = 2.52 × 10(-25)). The most significant pathway in our KEGG analysis was Epstein-Barr virus infection (P = 9.91 × 10(-06)).

CONCLUSIONS

Our meta-analysis demonstrated genes that were consistently DE and biological pathways associated with gene expression changes with pSS.

IL-34 is overexpressed in the inflamed salivary glands of patients with Sjogren's syndrome and is associated with the local expansion of pro-inflammatory CD14(bright)CD16+ monocytes

OBJECTIVES

To investigate the expression of IL-34 in labial salivary glands (LSGs) of patients with primary SS (p-SS) and its role in inducing a pro-inflammatory monocyte phenotype.

METHODS

LSG biopsies were obtained from 20 patients with p-SS and 10 patients with non-Sjögren's sicca syndrome (n-SS). The expression of IL-34, IL-1β, TNF-α, IL-17 and IL-23 was assessed by real-time PCR. IL-34 expression was also investigated in LSGs by immunohistochemistry. The frequencies of subpopulations of CD14(+) monocytes were evaluated by flow cytometry among isolated mononuclear cells from peripheral blood and salivary glands from both patients and controls. The role of recombinant IL-34 on isolated peripheral blood mononuclear cells was also evaluated.

RESULTS

IL-34 m-RNA was overexpressed in the inflamed salivary glands of p-SS and associated with increased expression of TNF-α, IL-1β, IL-17 and IL-23p19. The increased expression of IL-34 was confirmed by immunohistochemistry in paraffin-embedded salivary glands from p-SS patients. IL-34 expression was accompanied by the expansion of pro-inflammatory CD14(bright)CD16(+) monocytes in the salivary glands. In vitro stimulation of peripheral blood mononuclear cells with IL-34 induced the expansion of both CD14(+)CD16(-) cells and CD14(bright)CD16(+) cells in p-SS and non-SS subjects.

CONCLUSION

IL-34 seems to be involved in the pathogenesis of salivary gland inflammation in p-SS.

Claudins and the modulation of tight junction permeability

Claudins are tight junction membrane proteins that are expressed in epithelia and endothelia and form paracellular barriers and pores that determine tight junction permeability. This review summarizes our current knowledge of this large protein family and discusses recent advances in our understanding of their structure and physiological functions.

The Listeria monocytogenes ChiA chitinase enhances virulence through suppression of host innate immunity

Environmental pathogens survive and replicate within the outside environment while maintaining the capacity to infect mammalian hosts. For some microorganisms, mammalian infection may be a relatively rare event. Understanding how environmental pathogens retain their ability to cause disease may provide insight into environmental reservoirs of disease and emerging infections. Listeria monocytogenes survives as a saprophyte in soil but is capable of causing serious invasive disease in susceptible individuals. The bacterium secretes virulence factors that promote cell invasion, bacterial replication, and cell-to-cell spread. Recently, an L. monocytogenes chitinase (ChiA) was shown to enhance bacterial infection in mice. Given that mammals do not synthesize chitin, the function of ChiA within infected animals was not clear. Here we have demonstrated that ChiA enhances L. monocytogenes survival in vivo through the suppression of host innate immunity. L. monocytogenes ΔchiA mutants were fully capable of establishing bacterial replication within target organs during the first 48 h of infection. By 72 to 96 h postinfection, however, numbers of ΔchiA bacteria diminished, indicative of an effective immune response to contain infection. The ΔchiA-associated virulence defect could be complemented in trans by wild-type L. monocytogenes, suggesting that secreted ChiA altered a target that resulted in a more permissive host environment for bacterial replication. ChiA secretion resulted in a dramatic decrease in inducible nitric oxide synthase (iNOS) expression, and ΔchiA mutant virulence was restored in NOS2^−/− mice lacking iNOS. This work is the first to demonstrate modulation of a specific host innate immune response by a bacterial chitinase.

Bacterial chitinases have traditionally been viewed as enzymes that either hydrolyze chitin as a food source or serve as a defense mechanism against organisms containing structural chitin (such as fungi). Recent evidence indicates that bacterial chitinases and chitin-binding proteins contribute to pathogenesis, primarily via bacterial adherence to chitin-like molecules present on the surface of mammalian cells. In contrast, mammalian chitinases have been linked to immunity via inflammatory immune responses that occur outside the context of infection, and since mammals do not produce chitin, the targets of these mammalian chitinases have remained elusive. This work demonstrates that a Listeria monocytogenes-secreted chitinase has distinct functional roles that include chitin hydrolysis and suppression of host innate immunity. The established link between chitinase and the inhibition of host inducible nitric oxide synthase (iNOS) expression may help clarify the thus far elusive relationship observed between mammalian chitinase enzymes and host inflammatory responses occurring in the absence of infection.

A link between interferon and augmented plasmin generation in exocrine gland damage in Sjögren's syndrome

Sjögren's syndrome is an autoimmune disease that targets exocrine glands, but often exhibits systemic manifestations. Infiltration of the salivary and lacrimal glands by lymphoid and myeloid cells orchestrates a perpetuating immune response leading to exocrine gland damage and dysfunction. Th1 and Th17 lymphocyte populations and their products recruit additional lymphocytes, including B cells, but also large numbers of macrophages, which accumulate with disease progression. In addition to cytokines, chemokines, chitinases, and lipid mediators, macrophages contribute to a proteolytic milieu, underlying tissue destruction, inappropriate repair, and compromised glandular functions. Among the proteases enhanced in this local environment are matrix metalloproteases (MMP) and plasmin, generated by plasminogen activation, dependent upon plasminogen activators, such as tissue plasminogen activator (tPA). Not previously associated with salivary gland pathology, our evidence implicates enhanced tPA in the context of inflamed salivary glands revolving around lymphocyte-mediated activation of macrophages. Tracking down the mechanism of macrophage plasmin activation, the cytokines IFNγ and to a lesser extent, IFNα, via Janus kinase (JAK) and signal transducer and activator of transcription (STAT) activation, were found to be pivotal for driving the plasmin cascade of proteolytic events culminating in perpetuation of the inflammation and tissue damage, and suggesting intervention strategies to blunt irreversible tissue destruction.

Chitinase expression in parotid glands of non-obese diabetic mice

OBJECTIVE

This investigation was a basal study that used a mouse model of xerostomia to identify protein biomarkers of xerostomia in saliva. We identified genes expressed differently in parotid glands from non-obese diabetic mice with diabetes and those from control mice; subsequently, we investigated expression of the proteins encoded by these genes in parotid glands and saliva.

MATERIALS AND METHODS

DNA microarray and real-time PCR analyses were performed to detect differences between NOD/ShiJcl and C57BL/6JJcl (control) female mice in gene expression from parotid glands or parotid acinar cells. Subsequently, protein expression was assessed using immunoblotting and immunohistochemistry. Similarly, enzyme activity in saliva was assessed using zymography.

RESULTS

Based on gene expression analyses, Chia expression was higher in diabetic mice than non-diabetic mice and control mice; similarly, expression of chitinase, the protein encoded by Chia, was higher in diabetic mice. Saliva from NOD/ShiJcl mice had more chitinase than saliva from control mice.

CONCLUSIONS

Chitinase was highly expressed in parotid acinar cells from diabetic mice compared with non-diabetic and control mice. Increased chitinase expression and enzyme activity may characterize the autoimmune diabetes in mice; however, further investigation is required to assess its use as a biomarker of xerostomia in humans.