Genetic basis of Sjögren's syndrome. How strong is the evidence?

Association of Inflammatory Cytokine Levels with Extra Glandular Manifestations, Fatigue, and Disease Activity in Primary Sjögren's Syndrome in Saudi Patients: A Cross-Sectional Study

BACKGROUND

Primary Sjögren's syndrome (pSS) is an autoimmune disease that can cause fatigue and extraglandular manifestations (EGMs). pSS is associated with cytokine network dysregulation, which may be related to the immune-mediated destruction of exocrine glands.

OBJECTIVE

We determined cytokine levels and their relationship to EGMs, the European League Against Rheumatism (EULAR) Sjögren's syndrome disease activity index (ESSDAI), and fatigue in Saudi patients with pSS.

METHODS

This study was a cross-sectional, single-center study. We included forty-one patients and 71 controls. Serum samples were collected from random healthy people and pSS patients who were followed in the rheumatology and pulmonary clinics of King Saud University Medical City in Riyadh, Saudi Arabia. Levels of the frequently studied cytokines were measured using Luminex xMAP technology. Each ESSDAI score and EGM were recorded, and the Arabic version of the fatigue severity scale (FSS) was applied to assess fatigue. The main outcome measures were cytokine levels in pSS Saudi patients using/not using immune-suppressive medications (ISMs).

RESULTS

Thirty-six (87.8%) patients had one or more EGMs, and the mean ESSDAI score was 9.95 ± 7.73. There was a significant decrease in TNFα and IL-21 levels in the pSS group compared to those in the control group (p = 0.034 and p < 0.001, respectively), whereas IL-12 levels were significantly elevated in the pSS group (p = 0.002). Cytokine levels in patients who used ISMs were the same as those in patients who did not use medications. Decreased IL-1β (p = 0.014), IL-2 (p = 0.035), IL-6 (p = 0.014), and IL-35 (p = 0.010) levels were observed in patients who had EGMs. Patients who had low disease activity exhibited low IL-10 (p = 0.018) and high IFN-α (p = 0.049), IFN-β (p = 0.049), IL-1β (p = 0.006), and IL-35 (p = 0.032) levels compared to patients with high disease activity. A negative association between a positive fatigue score and IL-1β (p = 0.010), IL-2 (p = 0.037), IFN-α (p = 0.025), TNFα (p = 0.030), IL-17 (p = 0.029), IL-12 (p = 0.046), and IL-21 (p = 0.005) levels was found.

CONCLUSIONS

Cytokine profiles correlate with EGMs, ESSDAI, and fatigue. Patients with controlled disease activity have a normal cytokine profile that is similar to that of controls.

Studying Sjögren's syndrome in mice: What is the best available model?

Sjögren's syndrome (SS) is a common autoimmune disease characterized by lymphocytic infiltration and destruction of exocrine glands. The disease manifests primarily in the salivary and lacrimal glands, but other organs are also involved, leading to dry mouth, dry eyes, and other extra-glandular manifestations. Studying the disease in humans is entailed with many limitations and restrictions; therefore, the need for a proper mouse model is mandatory. SS mouse models are categorized, depending on the disease emergence into spontaneous or experimentally manipulated models. The usefulness of each mouse model varies depending on the SS features exhibited by that model; each SS model has advanced our understanding of the disease pathogenesis. In this review article, we list all the available murine models which have been used to study SS and we comment on the characteristics exhibited by each mouse model to assist scientists to select the appropriate model for their specific studies. We also recommend a murine strain that is the most relevant to the ideal SS model, based on our experience acquired during previous and current investigations.

Collagenous Colitis Is Associated With HLA Signature and Shares Genetic Risks With Other Immune-Mediated Diseases

BACKGROUND & AIMS

Collagenous colitis (CC) is an inflammatory bowel disorder with unknown etiopathogenesis involving HLA-related immune-mediated responses and environmental and genetic risk factors. We carried out an array-based genetic association study in a cohort of patients with CC and investigated the common genetic basis between CC and Crohn's disease (CD), ulcerative colitis (UC), and celiac disease.

METHODS

DNA from 804 CC formalin-fixed, paraffin-embedded tissue samples was genotyped with Illumina Immunochip. Matching genotype data on control samples and CD, UC, and celiac disease cases were provided by the respective consortia. A discovery association study followed by meta-analysis with an independent cohort, polygenic risk score calculation, and cross-phenotype analyses were performed. Enrichment of regulatory expression quantitative trait loci among the CC variants was assessed in hemopoietic and intestinal cells.

RESULTS

Three HLA alleles (HLA-B∗08:01, HLA-DRB1∗03:01, and HLA-DQB1∗02:01), related to the ancestral haplotype 8.1, were significantly associated with increased CC risk. We also identified an independent protective effect of HLA-DRB1∗04:01 on CC risk. Polygenic risk score quantifying the risk across multiple susceptibility loci was strongly associated with CC risk. An enrichment of expression quantitative trait loci was detected among the CC-susceptibility variants in various cell types. The cross-phenotype analysis identified a complex pattern of polygenic pleiotropy between CC and other immune-mediated diseases.

CONCLUSIONS

In this largest genetic study of CC to date with histologically confirmed diagnosis, we strongly implicated the HLA locus and proposed potential non-HLA mechanisms in disease pathogenesis. We also detected a shared genetic risk between CC, celiac disease, CD, and UC, which supports clinical observations of comorbidity.

Mechanisms of Disease in Sjögren Syndrome-New Developments and Directions

Sjögren Syndrome (SS) is an autoimmune disease that affects the exocrine glands, mainly salivary and lacrimal glands [...].

Molecular Evidence for Precursors of Sjögren's Foci in Histologically Normal Lacrimal Glands

Understanding the formation of Sjogren’s lymphocytic infiltrates could permit earlier diagnosis and better outcomes. We submitted gene transcript abundances in histologically normal rabbit lacrimal glands to principal component analysis. The analysis identified a cluster of transcripts associated with Sjögren’s foci, including messenger RNAs (mRNAs) for C–X–C motif chemokine ligand 13 (CXCL13) and B-cell activating factor (BAFF), which dominated the major principal component. We interpreted the transcript cluster as the signature of a cluster of integrally functioning cells. Pregnancy and dryness increased the likelihood that the cluster would develop to high levels, but responses were subject to high levels of stochasticity. Analyzing microdissected samples from high- and low-cluster-level glands, we found that certain transcripts, including mRNAs for C–C motif chemokine ligand 21 (CCL21), CXCL13, cluster of differentiation 4 (CD4), CD28, CD25, BAFF, and interleukin 18 (IL-18) were significantly more abundant in immune cell clusters (ICs) from the high-cluster-level gland; mRNAs for CCL2, CD25, and IL-1RA were significantly more abundant in acinus-duct axis samples; mRNAs for CCL4, BAFF, IL-6, and IL-10 were more abundant in some acinus-duct samples; cells with high prolactin immunoreactivity were more frequent in interacinar spaces. In conclusion, integrated functional networks comprising Sjögren’s infiltrates, such as ICs, acinar cells, ductal cells, and interacinar cells, can form in histologically normal glands, and it is feasible to detect their molecular signatures.

Autoimmune diseases and 8.1 ancestral haplotype: An update

The aim of the present review is to provide an update of the current research into the pathogenesis of autoimmune diseases associated with 8.1 ancestral haplotype. This is a common Caucasoid haplotype carried by most people who type for HLA-B8, DR3. Numerous genetic studies reported that individuals with certain HLA alleles have a higher risk of specific autoimmune disorders than those without these alleles. However, much remains to be learned about the heritability of autoimmune conditions. Recently, progress and advances in the field of genome-wide-association studies have revolutionized the capacity to perform large, economically feasible, and statistically robust analyses of HLA within 8.1 ancestral haplotype, and understand its contribute to autoimmune events. In this paper, the characteristic features of this haplotype that might give rise to diverse autoimmune phenotypes are reviewed, focusing on the contribution of the HLA-DRB1 gene, the most polymorphic sequence within the HLA II region.

The potential relationship between Flammer and Sjögren syndromes: the chime of dysfunction

Flammer syndrome (FS) is a term to blanket a cluster of vascular and nonvascular signs and symptoms linked to primary vascular dysregulation (PVD), increased sensitivity to various stimuli (stress, drugs, etc.) and altered sense regulation such as pain, smell and thirst perception. On one hand, disruption of blood barrier and homeostasis of the body are the main targets of vascular irregularity. Inflammation and immune disorders including autoimmunity are considered as a consequence of the abnormal vascular regulation processes. On the other hand, decreased thirst feeling typical for FS-affected individuals may lead to extensive body dehydration resulting in dry eye appearance and breast cancer (BC) risk, amongst others. To this end, recent research demonstrated FS as linked to BC development and progression into the metastatic disease. On the other side, Sjögren syndrome (SS) is an autoimmune disease characterised by a progressive sicca syndrome associated with the dry eye symptoms, specific immunologic complex and/or significant infiltrate at minor salivary gland biopsy. SS is relatively frequent, with a clinical diagnosis predominantly amongst women. Its physiopathology is a complex battery of both environmental and genetic factors. If left untreated, SS may be associated with and/or resulted in severe arthritis and the development of B cell lymphoma. In this mini-review, we summarise the facts and hypotheses connecting FS and SS symptoms together and mechanisms potentially overlapping in both syndromes. Unraveling the common denominators between these two syndromes not only providing more evidence for interaction between altered sense regulation, vascular dysregulation, immune system dysfunction but also focusing on the individual outcomes in terms of severity grade and potential complications exploring novel diagnostic, prognostic and treatment modalities. Multi-professional considerations presented here are an example how to effectively enter the new era of preventive, predictive and personalised medicine benefiting the patients and healthcare system as the whole.

Genetics of systemic lupus erythematosus and Sjögren's syndrome: an update

PURPOSE OF REVIEW

To describe the recent studies on the genetics of systemic lupus erythematosus (SLE) and Sjögren's syndrome.

RECENT FINDINGS

We overview the most recent findings on the genetic susceptibility of the diseases and provide information on their genetic similarities and differences.

SUMMARY

SLE and Sjögren's syndrome are two closely related systemic autoimmune diseases that share multiple clinical and molecular aspects, including a significant number of susceptibility genes. Several genome-wide association studies were recently published in different populations that provide a better picture of their molecular mechanisms. It is becoming clear that their genetic architecture is quite well established, but more information is required on expression quantitative trait loci, epigenetic genome-wide analyses, gene × gene interactions and the role of rare variants.

Altered Mucosal Microbiome Diversity and Disease Severity in Sjögren Syndrome

There is mounting evidence that the microbiome has potent immunoregulatory functions. We assessed the effects of intestinal dysbiosis in a model of Sjögren syndrome (SS) by subjecting mice to desiccating stress (DS) and antibiotics (ABX). We characterized the conjunctival, tongue and fecal microbiome profiles of patients with SS. Severity of ocular surface and systemic disease was graded. 16S ribosomal RNA gene sequencing characterized the microbiota. ABX + DS mice had a significantly worse dry eye phenotype compared to controls, a decrease in Clostridium and an increase in Enterobacter, Escherichia/Shigella, and Pseudomonas in stool after ABX + DS for 10 days. Goblet cell density was significantly lower in ABX treated groups compared to controls. Stool from SS subjects had greater relative abundances of Pseudobutyrivibrio, Escherichia/Shigella, Blautia, and Streptococcus, while relative abundance of Bacteroides, Parabacteroides, Faecalibacterium, and Prevotella was reduced compared to controls. The severity of SS ocular and systemic disease was inversely correlated with microbial diversity. These findings suggest that SS is marked by a dysbiotic intestinal microbiome driven by low relative abundance of commensal bacteria and high relative abundance of potentially pathogenic genera that is associated with worse ocular mucosal disease in a mouse model of SS and in SS patients.

Genetic, genomic and epigenetic studies as tools for elucidating disease pathogenesis in primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is characterized by lymphoid infiltration of lacrimal and salivary glands leading to xerophthalmia and xerostomia. pSS is a complex disease involving both genetic and environmental risk factors. Technological advances over the past 10 years have revolutionized genetics and genomics research enabling high-throughput characterization and analysis of DNA and RNA in patient samples on a genome-wide scale. Further, application of high-throughput methods for characterization of epigenetic variation, such as DNA methylation status, is increasingly being applied to AID populations and will likely further define additional risk factors for disease risk and outcome. Main results obtain in pSS through these various approaches are reviewed here.

Comparison of the American-European Consensus Group Sjogren's syndrome classification criteria to newly proposed American College of Rheumatology criteria in a large, carefully characterised sicca cohort

OBJECTIVE

To compare the performance of the American-European Consensus Group (AECG) and the newly proposed American College of Rheumatology (ACR) classification criteria for Sjögren's Syndrome (SS) in a well-characterised sicca cohort, given ongoing efforts to resolve discrepancies and weaknesses in the systems.

METHODS

In a multidisciplinary clinic for the evaluation of sicca, we assessed features of salivary and lacrimal gland dysfunction and autoimmunity as defined by tests of both AECG and ACR criteria in 646 participants. Global gene expression profiles were compared in a subset of 180 participants.

RESULTS

Application of the AECG and ACR criteria resulted in classification of 279 and 268 participants with SS, respectively. Both criteria were met by 244 participants (81%). In 26 of the 35 AECG+/ACR participants, the minor salivary gland biopsy focal score was ≥1 (74%), while nine had positive anti-Ro/La (26%). There were 24 AECG-/ACR+ who met ACR criteria mainly due to differences in the scoring of corneal staining. All patients with SS, regardless of classification, had similar gene expression profiles, which were distinct from the healthy controls.

CONCLUSIONS

The two sets of classification criteria yield concordant results in the majority of cases and gene expression profiling suggests that patients meeting either set of criteria are more similar to other SS participants than to healthy controls. Thus, there is no clear evidence for increased value of the new ACR criteria over the old AECG criteria from the clinical or biological perspective. It is our contention, supported by this report, that improvements in diagnostic acumen will require a more fundamental understanding of the pathogenic mechanisms than is at present available.

Sjögren's syndrome in older patients: aetiology, diagnosis and management

Sjögren's syndrome (SS) is a systemic autoimmune disease, characterized by chronic inflammation of exocrine glands that results in development of xerostomia and keratoconjunctivitis sicca. The disease activity of SS is not restricted to exocrine glands, and many other organs and organ systems can be involved. Diagnosis of SS in the elderly population can be challenging because xerostomia, dry eyes, symptoms of fatigue, weight loss and muscle pain are also common features of old age. Delay between clinical onset and diagnosis of SS in the elderly may be due to the shared features of SS and old age. The 2002 revised American-European Consensus Group (AECG) classification criteria for SS are the preferred tool used to confirm diagnosis of SS, but recently alternative criteria have been put forward by the American College of Rheumatology (ACR). The AECG criteria set combines subjective symptoms of dry eyes and dry mouth with objective signs of keratoconjunctivitis sicca, salivary gland dysfunction and histopathological (salivary gland biopsy) and serological (autoantibodies against SSA/Ro and SSB/La antigens) features. Treatment of SS in the elderly does not differ from that in younger patients. The aims of the treatment of SS are to control glandular and extraglandular manifestations, to prevent damage to organ systems and loss of function, and to decrease morbidity and mortality. Treatment of the elderly can be complicated by co-morbidities, an increased rate of adverse events related to therapeutic agents, and polypharmacy. Therefore, careful follow-up of the treatment is required.

Synchronous Onset of Secondary Raynaud's Phenomenon in Monozygotic Twins

The heritability of primary Raynaud's phenomenon has been reported in previous works. In this paper we describe the simultaneous onset of Raynaud's phenomenon, rapidly evolved in acrocyanosis and diagnosed as secondary Raynaud's phenomenon, observed in monozygotic twins. This case supports the role of genetic factors in the pathogenesis of such disorder. Moreover, the singular synchronism of its appearance is discussed.

HLA and Sjögren's syndrome susceptibility. A meta-analysis of worldwide studies

The aim of this work was to identify common HLA Class II alleles contributing to primary Sjögren's syndrome (pSS) susceptibility worldwide and to analyze their biological implications through a binding prediction approach of peptides from major pSS auto-antigens. Case-control studies on HLA-DQ and HLA-DR in pSS were searched in various literature databases through April 2011 by a systematic review. The effect summary odds ratios and 95% confidence intervals were obtained by means of the random effect model. A total of 1166 cases and 6470 controls from 23 studies were analyzed. At the allelic level, DQA1*05:01, DQB1*02:01, and DRB1*03:01 alleles were found to be risk factors for disease. Conversely, the DQA1*02:01, DQA1*03:01 and DQB1*05:01 alleles were protective factors. The current study stresses the significant size effect HLA exhibits in the development of pSS. Analysis of susceptibility and protective alleles revealed physicochemical differences in critical amino acids located within the antigen-binding groove of DRβ, DQα and DQβ chains, allowing us to infer a mechanistic approach to understand the role of HLA in pSS and other autoimmune diseases.

Evaluation of genetic association between an ITGAM non-synonymous SNP (rs1143679) and multiple autoimmune diseases

Many autoimmune diseases (ADs) share similar underlying pathology and have a tendency to cluster within families, supporting the involvement of shared susceptibility genes. To date, most of the genetic variants associated with systemic lupus erythematosus (SLE) susceptibility also show association with others ADs. ITGAM and its associated 'predisposing' variant (rs1143679, Arg77His), predicted to alter the tertiary structures of the ligand-binding domain of ITGAM, may play a key role for SLE pathogenesis. The aim of this study is to examine whether the ITGAM variant is also associated with other ADs. We evaluated case-control association between rs1143679 and ADs (N=18,457) including primary Sjögren's syndrome, systemic sclerosis, multiple sclerosis, rheumatoid arthritis, juvenile idiopathic arthritis, celiac disease, and type-1 diabetes. We also performed meta-analyses using our data in addition to available published data. Although the risk allele 'A' is relatively more frequent among cases for each disease, it was not significantly associated with any other ADs tested in this study. However, the meta-analysis for systemic sclerosis was associated with rs1143679 (p(meta)=0.008). In summary, this study explored the role of ITGAM in general autoimmunity in seven non-lupus ADs, and only found association for systemic sclerosis when our results were combined with published results. Thus ITGAM may not be a general autoimmunity gene but this variant may be specifically associated with SLE and systemic sclerosis.

Activation of the interferon pathway in peripheral blood of patients with Sjogren's syndrome

OBJECTIVE

DNA microarray analysis and quantitative real-time polymerase chain reaction (PCR) were performed to identify key target genes in peripheral blood from patients with Sjögren's syndrome (SS).

METHODS

DNA microarray analysis was performed in 19 patients with SS (all women) and 10 healthy controls (5 men and 5 women) using a low-density DNA microarray system with 778 genes. For confirmation, the expression of upregulated genes was analyzed by quantitative real-time PCR in another 37 SS patients (35 women and 2 men) and 9 healthy controls (8 women and 1 man). Relationships between gene signatures and various clinical measures, such as disease duration, symptoms and signs, complications, immunological findings, and salivary and lacrimal functions, were analyzed.

RESULTS

Interferon-α (IFN-α)-inducible protein 27 (IFI27) showed the most significant difference between SS patients and controls in the microarray screening. We performed quantitative RT-PCR for IFI27. IFI27 gene expression level was increased in patients with SS compared with controls (p < 0.01) by real-time PCR, supporting our observations from the microarray data. The level of IFI27 was significantly correlated with serum IgG levels (r = 0.462, p < 0.01) and ß(2)-microglobulin (r = 0.385, p < 0.05), soluble interleukin 2 receptor (r = 0.473, p < 0.01), erythrocyte sedimentation rate (r = 0.333, p < 0.05), and antinuclear antibody titer (speckled pattern; r = 0.445, p < 0.01).

CONCLUSION

Our results suggest that upregulation of IFN-inducible genes in SS patients is a systemic phenomenon, and IFN may play an important role in the pathogenesis of SS. The expression level of IFI27 could be an effective and specific biomarker associated with SS.

Genetics of systemic lupus erythematosus and Sjögren's syndrome

PURPOSE OF REVIEW

To determine the advances made in the genetics of systemic lupus erythematosus (SLE) or Sjögren's syndrome as the era of genome-wide association and high-throughput single nucleotide typing begins.

RECENT FINDINGS

Several genome-wide association studies have been performed in SLE but there are no such studies published or in progress for Sjögren's syndrome. Genetics and the functional significance of risk alleles in the interferon pathway are being worked out in detail. This is especially true for STAT4 and IRF5. Gene copy number variation, a major source of genetic variability, is important for several genes that impart risk for SLE. An X chromosome copy number dose effect has recently been identified. Genetic evaluation of Sjögren's syndrome is limited to small studies that have concentrated on genes already shown to be risk factors in SLE.

SUMMARY

Knowledge of the genetics of SLE is advancing rapidly, whereas that of Sjögren's syndrome lags behind considerably.

Autoimmunity and lymphomagenesis

For more than 50 years, links between autoimmunity and lymphomas have been described based on human and animal studies. Over the last 3 decades, many studies have addressed specific hypotheses about these associations using population level data. This has been accomplished by assessing previous autoimmune history in case-control studies of patients with lymphoma (mainly non-Hodgkin lymphoma) and myeloma, and by following cohorts of patients with various autoimmune diseases for subsequent development of lymphoma and multiple myeloma. In this article, we review our recently published series of association studies based on data from Scandinavia and from US Veterans and other relevant findings. We also discuss what these associations have revealed about the mechanisms and pathways underlying both autoimmunity and lymphoma. Finally, we discuss the future directions involving a combination of population and molecular studies that are needed to better define underlying biological mechanisms.

The influence of the NOD Nss1/Idd5 loci on sialadenitis and gene expression in salivary glands of congenic mice

The nonobese diabetic (NOD) Nss1 and Idd5 loci have been associated with sialadenitis development in mice. In this study the NOD Nss1 and Idd5 loci were backcrossed onto the healthy control strain B10.Q by using the speed congenic breeding strategy, resulting in three congenic strains: B10.Q.Nss1, B10.Q.Nss1/Idd5 heterozygous and B10.Q.Nss1/Idd5 homozygous. We investigated the effects of the Nss1 and Idd5 loci on sialadenitis and gene expression in NOD congenic mice. One submandibular salivary gland from each mouse was used for histological analysis of sialadenitis, whereas the contralateral salivary gland was used for gene expression profiling with the Applied Biosystems Mouse Genome Survey chip v.1.0. The results were validated using quantitative reverse transcriptase PCR. The NOD Nss1 and Idd5 loci had clear influence on the onset and progression of sialadenitis in congenic mice. Double congenic mice exhibited the most severe phenotype. We successfully identified several genes that are located in the NOD congenic regions to be differentially expressed between the congenic strains and the control strain. Several of these were found to be co-regulated, such as Stat1, complement component C1q genes and Tlr12. Also, a vast contingency of interferon-regulated genes (such as Ltb, Irf7 and Irf8) and cytokine and chemokine genes (such as Ccr7 and Ccl19) were differentially expressed between the congenic strains and the control strain. Over-representation of inflammatory signalling pathways was observed among the differentially expressed genes. We have found that the introgression of the NOD loci Nss1 and Idd5 on a healthy background caused sialadenitis in NOD congenic mouse strains, and we propose that genes within these loci are important factors in the pathogenesis. Furthermore, gene expression profiling has revealed several differentially expressed genes within and outside the NOD loci that are similar to genes found to be differentially expressed in patients with Sjögren's syndrome, and as such are interesting candidates for investigation to enhance our understanding of disease mechanisms and to develop future therapies.

Biomarkers for type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disorder characterized by the immune destruction of the insulin producing beta cells of the pancreatic islets. Autoimmunity towards pancreatic antigens results from complex interactions between multiple genes, environmental factors and the immune system. The autoimmune process may occur many years before the onset of clinical diabetes and this long asymptomatic period provides excellent opportunities for the prediction and prevention of the disease. Research in past four decades has identified a number of risk factors including susceptibility genes, gene and protein expression changes, cellular changes as well as environmental triggers, which may serve as excellent biomarkers for risk assessment. Furthermore, demographic and clinical parameters such as age and family history of diabetes and other autoimmune diseases are also important for risk assessment. Despite the identification of multiple useful biomarkers, the existing tests for T1D prediction are still imperfect and earlier biomarkers are also urgently needed. Because of the insufficient predictive power of individual risk factors, future biomarkers with better predictive power will most likely take advantage of the combinatorial power of multiple biomarkers of different nature and the integration of various biomarkers and demographic/clinical information will be the key to success.