Progress in understanding autoimmune exocrinopathy using the non-obese diabetic mouse: an update

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.

Gene expression profiling of early-phase Sjögren's syndrome in C57BL/6.NOD-Aec1Aec2 mice identifies focal adhesion maturation associated with infiltrating leukocytes

PURPOSE

Despite considerable efforts, the molecular and cellular events in lacrimal gland tissues initiating inflammatory responses leading to keratoconjunctivitis sicca (KCS), autoimmunity, and Sjögren's syndrome (SjS) have yet to be defined. To determine whether altered glandular homeostasis occurs before the onset of autoimmunity, a temporal transcriptome study was carried out in an animal model of primary SjS.

METHODS

Using oligonucleotide microarrays, gene expression profiles were generated for lacrimal glands of C57BL/6.NOD-Aec1Aec2 mice 4 to 20 weeks of age. Pairwise analyses identified genes differentially expressed, relative to their 4-week expression, during the development of SjS-like disease. Statistical analyses defined differentially and coordinately expressed gene sets. The PANTHER (Protein ANalysis THrough Evolutionary Relationships) classification system was used to define annotated biological processes or functions.

RESULTS

Temporal transcript expression profiles of C57BL/6.NOD-Aec1Aec2 lacrimal glands before, or concomitant with, the first appearance of inflammatory cells revealed a highly restricted subset of differentially expressed genes encoding interactive extracellular matrix proteins, fibronectin, integrins, and syndecans. In contrast, genes encoding interepithelial junctional complex proteins defined alterations in tight junctions (TJ), adherens, desmosomes, and gap junctions, suggesting perturbations in the permeability of the paracellular spaces between epithelial barriers. Correlating with this were gene sets defining focal adhesion (FA) maturation and Ras/Raf-Mek/Erk signal transduction. Immunohistochemically, FAs were associated with infiltrating leukocytes and not with lacrimal epithelial cells.

CONCLUSIONS

For the first time, FA maturations are implicated as initial biomarkers of impending autoimmunity in lacrimal glands of SjS-prone mice. Changes in TJ complex genes support an increased movement of cells through paracellular spaces.

Sjögren's syndrome: studying the disease in mice

Sjögren's syndrome (SS), a systemic autoimmune disease, is characterized by inflammation of exocrine tissues accompanied by a significant loss of their secretory function. Clinical symptoms develop late and there are no diagnostic tests enabling early diagnosis of SS. Thus, particularly to study these covert stages, researchers turn to studying animal models where mice provide great freedom for genetic manipulation and testing the effect of experimental intervention. The present review summarizes current literature pertaining to both spontaneous and extrinsic-factor induced SS-like diseases in mouse models, discussing advantages and disadvantages related to the use of murine models in SS research.

Dysfunction of lacrimal and salivary glands in Sjögren's syndrome: nonimmunologic injury in preinflammatory phase and mouse model

Sjögren's syndrome (SjS) is a chronic autoimmune disorder characterized by dry eyes and dry mouth due to dacryoadenitis and sialoadenitis with SS-A/Ro and/or SS-B/La autoantibodies in genetically predisposed individuals. Destruction of lacrimal and salivary glands by autoimmune reactions may lead to clinical manifestation. However, the mechanisms behind the decreased volume of secretions in tears and saliva are complex and are not fully understood. Exocrine gland dysfunction may precede autoimmunity (acquired immunity) or represent a process independent from inflammation in the pathogenesis of SjS. The preceded functional and morphologic changes of those tissues by nonimmunologic injury before the development of inflammation at the sites of target organs have been implicated. This paper focuses on the several factors and components relating to glandular dysfunction and morphologic changes by nonimmunologic injury during the preinflammatory phase in mouse model, including the factors which link between innate immunity and adaptive immunity.

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

Sjögren's syndrome (SS), a chronic autoimmune disorder, particularly compromises the function of exocrine glands. The involvement of these glands is characterized by focal, mononuclear cell infiltrates that surround the ducts and replace the secretory units. The pathogenetic mechanisms of this autoimmune exocrinopathy have not been fully elucidated. Immunologically-activated or apoptotic glandular epithelial cells that expose autoantigens in genetically predisposed individuals might drive autoimmune-mediated tissue injury. Alterations in several immune mediators, such as upregulation of type I interferon-regulated genes, abnormal expression of B-cell-activating factor and activation of the interleukin-23-type 17 T-helper cell pathway, have been reported. Extension of the pathological process that affects the exocrine glands into periepithelial and extraepithelial tissue can cause a considerable percentage of patients to exhibit systemic findings that involve the lungs, liver or kidneys. These manifestations develop as a result of lymphocytic invasion or an immune-complex-mediated process, or both, and present as skin vasculitis coupled with peripheral neuropathy or glomerulonephritis (or both). Patients with systemic extraepithelial manifestations display low serum levels of the complement component C4 and mixed type II cryoglobulins, and show an increased risk of developing non-Hodgkin lymphoma, thereby reflecting an overall worse prognosis with higher mortality rates than those without extraepithelial manifestations.

An autoimmune response to odorant binding protein 1a is associated with dry eye in the Aire-deficient mouse

Sjögren's Syndrome (SS) is a human autoimmune disease characterized by immune-mediated destruction of the lacrimal and salivary glands. In this study, we show that the Aire-deficient mouse represents a new tool to investigate autoimmune dacryoadenitis and keratoconjunctivitis sicca, features of SS. Previous work in the Aire-deficient mouse suggested a role for alpha-fodrin, a ubiquitous Ag, in the disease process. Using an unbiased biochemical approach, however, we have identified a novel lacrimal gland autoantigen, odorant binding protein 1a, targeted by the autoimmune response. This novel autoantigen is expressed in the thymus in an Aire-dependent manner. The results from our study suggest that defects in central tolerance may contribute to SS and provide a new and clinically relevant model to investigate the pathogenic mechanisms in lacrimal gland autoimmunity and associated ocular surface sequelae.

Differential gene expression in the salivary gland during development and onset of xerostomia in Sjögren's syndrome-like disease of the C57BL/6.NOD-Aec1Aec2 mouse

INTRODUCTION

Recently, we reported the development of the C57BL/6.NOD-Aec1Aec2 mouse that carries two genetic intervals derived from the non-obese diabetic (NOD) mouse capable of conferring Sjögren's syndrome (SjS)-like disease in SjS-non-susceptible C57BL/6 mice. In an attempt to define the molecular bases underlying the onset of stomatitis sicca (xerostomia) in this C57BL/6.NOD-Aec1Aec2 mouse model, we have carried out a study using genomic microarray technology.

METHODS

By means of oligonucleotide microarrays, gene expression profiles of salivary glands at 4, 8, 12, 16, and 20 weeks of age were generated for C57BL/6.NOD-Aec1Aec2 male mice. Using Linear Models for Microarray Analysis and B-statistics software, 480 genes were identified as being differentially expressed (P < 0.01 and Q < 0.0001) during the development of SjS-like disease in the salivary glands.

RESULTS

The 480 genes could be arranged into four clusters, with each cluster defining a unique pattern of temporal expression, while the individual genes within each cluster could be grouped according to related biological functions. By means of pair-wise analysis, temporal changes in transcript expressions provided profiles indicating that many additional genes are differentially expressed at specific time points during the development of disease. Multiple genes reportedly showing an association with autoimmunity and/or SjS, in either humans or mouse models, were found to exhibit differential expressions, both quantitatively and temporally. Selecting various families of genes associated with specific functions (for example, antibody production, complement, and chemokines), we noted that only a limited number of family members showed differential expressions and these correlated with specific phases of disease.

CONCLUSIONS

Taking advantage of known functions of these genes, investigators can construct interactive gene pathways, leading to modeling of possible underlying events inducing salivary gland dysfunction. Thus, these different approaches to analyzing microarray data permit the identification of multiple sets of genes of interest whose expressions and expression profiles may correlate with molecular mechanisms, signaling pathways, and/or immunological processes involved in the development and onset of SjS.

Genes and Sjögren's syndrome

The evidence for a strong genetic component conferring susceptibility to primary Sjögren's syndrome (SS) is mounting. Several associations with SS have been reported and provide evidence that the HLA region harbors important susceptibility loci and that multiple genes outside the HLA region play a role. Genetic discovery lags behind success observed in related autoimmune diseases. Identifying genetic factors that cause SS will allow more precise definition of pathogenic mechanisms leading to the overall SS phenotype and clinically heterogeneous subsets of patients. Critical opportunities are certain to follow for translation into improved diagnosis and therapies for SS and its spectrum diseases.

Aquaporins in secretory glands and their role in Sjögren's syndrome

Salivary, lacrimal and pancreatic secretions are known to account for multiple physiological functions. These exocrine secretions are watery fluids containing electrolytes, and a mixture of proteins, and can be stimulated by a number of agonists. Since water movement is involved in exocrine secretion, aquaporins (AQPs) have been hypothesised to contribute to fluid production in exocrine glands. This chapter will focus on the expression, localisation and function of AQPs in salivary and lacrimal glands and pancreas. The role of multiple water and ion transporters and channels in exocrine fluid secretion will also be reviewed. Finally, this chapter will address the potential role of AQPs in Sjögren's syndrome.

Identification of possible candidate genes regulating Sjögren's syndrome-associated autoimmunity: a potential role for TNFSF4 in autoimmune exocrinopathy

Introduction

Sjögren syndrome (SjS) is a systemic autoimmune disease in which an immunological attack primarily against the salivary and lacrimal glands results in the loss of acinar cell tissue and function, leading to stomatitis sicca and keratoconjunctivitis sicca. In recent years, two genetic regions, one on chromosome 1 (designated autoimmune exocrinopathy 2 or Aec2) and the second on chromosome 3 (designated autoimmune exocrinopathy 1 or Aec1) derived from nonobese diabetic (NOD) mice, have been shown to be necessary and sufficient to replicate SjS-like disease in nonsusceptible C57BL/6 mice.

Methods

Starting with the SjS-susceptible C57BL/6-derived mouse, referred to as C57BL/6.NOD-Aec1Aec2, we generated a large set of recombinant inbred (RI) lines containing portions of Aec2 as a means of identifying more precisely the genetic elements of chromosome 1 responsible for disease development.

Results

Disease profiling of these RI lines has revealed that the SjS susceptibility genes of Aec2 lie within a region located at approximately 79 ± 5 cM distal to the centromere, as defined by microsatellite markers. This chromosomal region contains several sets of genes known to correlate with various immunopathological features of SjS as well as disease susceptibility genes for both type 1 diabetes and systemic lupus erythematosus in mice. One gene in particular, tumor necrosis factor (ligand) superfamily member 4 (or Ox40 ligand), encoding a product whose biological functions correlate with both physiological homeostasis and immune regulations, could be a potential candidate SjS susceptibility gene.

Conclusions

These new RI lines represent the first step not only in fine mapping SjS susceptibility loci but also in identifying potential candidate SjS susceptibility genes. Identification of possible candidate genes permits construction of models describing underlying molecular pathogenic mechanisms in this model of SjS and establishes a basis for construction of specific gene knockout mice.

Differential gene expressions in the lacrimal gland during development and onset of keratoconjunctivitis sicca in Sjögren's syndrome (SJS)-like disease of the C57BL/6.NOD-Aec1Aec2 mouse

Recently, we reported development of the C57BL/6.NOD-Aec1Aec2 mouse carrying two genetic intervals derived from the NOD mouse. These two genetic regions confer Sjögren's syndrome (SjS)-like disease in SjS-non-susceptible C57BL/6 mice. In an attempt to define the molecular bases underlying onset of dacryoadenitis and subsequently keratoconjunctivitis sicca (or xerophthalmia) in the C57BL/6.NOD-Aec1Aec2 mouse model, we have carried out a study utilizing microarray technology. Using oligonucleotide microarrays, gene expression profiles of lacrimal glands at 4, 8, 12, 16 and 20weeks of age were generated for C57BL/6.NOD-Aec1Aec2 male mice. Analyses using Linear Models for Microarray Analysis package and B-statistics, 552 genes were identified as being differentially expressed (adjusted p-value <0.01 and B <1.5) during the development of SjS-like disease. These 552 genes could be arranged into four clusters, with each cluster defining a unique pattern of temporal expression, while the individual genes within each cluster could be grouped according to related function. Using a pair-wise analysis, temporal changes in gene expressions provided profiles indicating that individual genes were differentially expressed at specific time points during development of SjS. In addition, multiple genes that have been reported to show, either in humans or mouse models, an association with autoimmunity and/or SjS, e.g., ApoE, Baff, Clu, Ctla4, Fas/Fasl, Irf5, Lyzs, Nfkb, Socs3, Stat4, Tap2, Tgfbeta1, Tnfa, and Vcam1 were also found to exhibit differential expressions, both quantitatively and temporally. Selecting a few families of genes, e.g., cystatins, cathepsins, metalloproteinases, lipocalins, complement, kallikreins, carbonic anhydrases and tumor necrosis factors, it was noted that only a limited number of family members showed differential expressions, suggesting a restricted glandular expression. Utilizing these genes, pathways of inter-reactive genes have been constructed for apoptosis and fatty acid homeostasis, leading to modeling of possible underlying events inducing disease. Thus, these different approaches to analyze microarray data permit identification of multiple sets of genes of interest whose expressions and expression profiles may correlate with molecular mechanisms, signaling pathways and/or immunological processes involved in the development and onset of SjS in this mouse model, thereby providing new insight into the underlying cause or regulation of this disease.

Inhibition of experimental Sjögren's syndrome through immunization with HSP60 and its peptide amino acids 437-460

OBJECTIVE

To investigate a potential immunomodulatory effect of the 60-kd heat-shock protein (Hsp60) on experimental spontaneous Sjögren's syndrome (SS).

METHODS

Seven-week-old nonobese diabetic (NOD) mice were immunized with eukaryotic Hsp60 or an Hsp60-derived peptide (amino acid residue [aa] 437-460). At 21 weeks of age, nondiabetic mice were investigated for salivary gland inflammation, exocrine function, and extraglandular disease manifestations. In addition, biomarker profiles comprising 87 analytes in serum and 75 in saliva were analyzed.

RESULTS

In mice immunized with Hsp60 and aa 437-460, SS-related histopathologic features were significantly reduced compared with NOD controls. In addition, 50% of Hsp60-injected mice and 33% of aa 437-460-injected mice retained normal exocrine function. Both treatments induced similar changes in biomarker profiles. Notably, levels of circulating interferon-gamma-inducible 10-kd protein (IP-10) and eotaxin were decreased significantly after treatment. Anti-type 3 muscarinic acetylcholine receptor (anti-M3R) IgG1, interleukin-10, and leptin discriminated best between the different treatment groups. Successful prevention of hyposalivation was accompanied by quantitative alterations in 36 biomarkers, of which 19 mediators of inflammation declined to levels comparable with those found in BALB/c mice. Low secreted vascular endothelial growth factor A was the most accurate predictor of successful prevention of hyposalivation. Low salivary granulocyte chemotactic protein 2 was identified as the best predictor of normal secretory function across the strains.

CONCLUSION

Immunization with Hsp60 and its peptide aa 437-460 led to inhibition of SS in NOD mice. Comprehensive analyses revealed specific biomarker signatures capable of predicting treatment group and treatment outcome. Molecules involved in inflammatory chemotaxis, neovascularization, and regulatory pathways caused the differences displayed by the biomarker profiles.

Effects of oral consumption of the green tea polyphenol EGCG in a murine model for human Sjogren's syndrome, an autoimmune disease

SIGNIFICANCE

Protection of glandular cells from autoimmune-induced damage would be of significant clinical benefit to Sjogren's syndrome (SS) patients. Epigallocatechin-3-gallate (EGCG) possesses anti-apoptotic, anti-inflammatory, and autoantigen-inhibitory properties.

AIMS

To investigate if EGCG protects against certain autoimmune-induced pathological changes in the salivary glands of the non-obese diabetic (NOD) mouse model for SS.

MAIN METHODS

Animals were provided with either water or water containing 0.2% EGCG. At the age of 8, 16 and 22 weeks, submandibular salivary gland tissue and serum samples were collected for pathological and serological analysis.

KEY FINDINGS

Significant lymphocyte infiltration was observed in the salivary glands of the water-fed group at the age of 16 weeks, while the EGCG group showed reduced lymphocyte infiltration. By 22 weeks of age, water-fed animals demonstrated elevated levels of apoptotic activity within the lymphocytic infiltrates, and high levels of serum total anti-nuclear antibody, compared to EGCG-fed animals. Remarkably, proliferating cell nuclear antigen (PCNA) and Ki-67 levels in the salivary glands of water-fed NOD mice were significantly elevated in comparison to BALB/c control mice; in contrast, PCNA and Ki-67 levels in EGCG-fed NOD animals were similar to BALB/c mice. These results indicate that EGCG protects the NOD mouse submandibular glands from autoimmune-induced inflammation, and reduces serum autoantibody levels. Abnormal proliferation, rather than apoptosis, appears to be a characteristic of the NOD mouse gland that is normalized by EGCG. The evidence suggests that EGCG could be useful in delaying or managing SS-like autoimmune disorders.

Biomarker profiles in serum and saliva of experimental Sjögren's syndrome: associations with specific autoimmune manifestations

INTRODUCTION

Sjögren's syndrome (SS) is a systemic autoimmune disease that mainly targets the exocrine glands. The aim of this study was to investigate the involvement of 87 proteins measured in serum and 75 proteins analyzed in saliva in spontaneous experimental SS. In addition, we intended to compute a model of the immunological situation representing the overt disease stage of SS.

METHODS

Nondiabetic, nonobese diabetic (NOD) mice aged 21 weeks were evaluated for salivary gland function, salivary gland inflammation and extraglandular disease manifestations. The analytes, comprising chemokines, cytokines, growth factors, autoantibodies and other biomarkers, were quantified using multi-analyte profile technology and fluorescence-activated cell sorting. Age-matched and sex-matched Balb/c mice served as a reference.

RESULTS

We found NOD mice to exhibit impaired salivary flow, glandular inflammation and increased secretory SSB (anti-La) levels. Thirty-eight biomarkers in serum and 34 in saliva obtained from NOD mice were significantly different from those in Balb/c mice. Eighteen biomarkers in serum and three chemokines measured in saliva could predict strain membership with 80% to 100% accuracy. Factor analyses identified principal components mostly correlating with one clinical aspect of SS and having distinct associations with components extracted from other families of proteins.

CONCLUSION

Autoimmune manifestations of SS are greatly independent and associated with various immunological processes. However, CD40, CD40 ligand, IL-18, granulocyte chemotactic protein-2 and anti-muscarinic M3 receptor IgG3 may connect the different aspects of SS. Processes related to the adaptive immune system appear to promote SS with a strong involvement of T-helper-2 related proteins in hyposalivation. This approach further established saliva as an attractive biofluid for biomarker analyses in SS and provides a basis for the comparison and selection of potential drug targets and diagnostic markers.

Identification of a quantitative trait locus regulating B cell-dominant infiltration into autoimmune sialitis lesions of the IQI mouse model of primary Sjögren's syndrome

Sjögren's syndrome (SS) is caused by an autoimmune sialodacryoadenitis, and up to 5% of patients with SS develop malignant B cell growth. The IQI mouse is a spontaneous model of primary SS in which B cells are the dominant cellular subpopulation among mononuclear infiltrates in sialitis lesions. Understanding the genetic control of aberrant B cell growth in IQI mice may help elucidate the genetic mechanisms involved in B-lineage hyperplasia leading to malignant transformation in human SS. B cell-dominant infiltration in the submandibular glands of 6-month-old IQI and C57BL/6 (B6) mice and their F1 and F2 progenies was quantified as B-lymphocytic sialitis score, and a genome-wide scan of 179 (IQI x B6) F2 females was performed to identify a quantitative trait locus (QTL) controlling this phenotype. A QTL significantly associated with variance in B-lymphocytic sialitis score was mapped to the D6Mit138 marker (position of 0.68cM) on proximal chromosome 6, with a logarithm of odds score of 4.3 (p = 0.00005). This QTL, named autoimmune sialitis in IQI mice, associated locus 1 (Asq1), colocalized with Islet cell autoantigen 1 (Ica1), which encodes a target protein of the immune processes that define the pathogenesis of primary SS in humans and in the nonobese diabetic mouse model.

Development of Sjogren's syndrome in nonobese diabetic-derived autoimmune-prone C57BL/6.NOD-Aec1Aec2 mice is dependent on complement component-3

The role of complement in the etiology of Sjögren's syndrome (SjS), a human autoimmune disease manifested primarily by salivary and lacrimal gland dysfunction resulting in dry mouth/dry eye syndrome, remains ill-defined. In the present study, we examined the role of complement component-3 (C3) using a newly constructed C3-gene knockout mouse, C57BL/6.NOD-Aec1Aec2.C3(-/-). Inactivation of C3 in the parental C57BL/6.NOD-Aec1Aec2 strain, a model of primary SjS, resulted in a diminished or total absence of both preclinical and clinical manifestations during development and onset of disease, including reduced acinar cell apoptosis, reduced levels of caspase-3, lack of leukocyte infiltration of submandibular glands, reduced synthesis of disease-associated autoantibodies, maintenance of normal glandular architecture, and retention of normal saliva secretion. In addition, C57BL/6-NOD.Aec1Aec2.C3(-/-) mice did not exhibit increased numbers of marginal zone B cells, a feature of SjS-prone C57BL/6-NOD.Aec1Aec2 mice. Interestingly, C57BL/6-NOD.Aec1Aec2.C3(-/-) mice retained some early pathological manifestations, including activation of serine kinases with proteolytic activity for parotid secretory protein. This improvement in the clinical manifestations of SjS-like disease in C57BL/6.NOD-Aec1Aec2.C3(-/-) mice, apparently a direct consequence of C3 deficiency, supports a much more important role for complement in the adaptive autoimmune response than previously recognized, possibly implicating an essential role for innate immunity.

Autoimmune dacryoadenitis of NOD/LtJ mice and its subsequent effects on tear protein composition

Sjögren's syndrome (SjS) is a human autoimmune disease characterized by exocrine dysfunction resulting from chronic autoimmune attack primarily against the lacrimal and/or salivary glands. Although, we previously established a good correlation between SjS in humans and autoimmune exocrinopathy in NOD/LtJ mice an in-depth evaluation of lacrimal gland disease in the NOD/LtJ mouse has remained limited. This leaves a major gap in our understanding of the dacryoadenitis/keratoconjunctivitis sicca in this model. Here we characterize the development of the autoimmune dacryoadenitis in NOD/LtJ and NOD.B10-H2(b) mice in comparison with age- and sex-matched nonautoimmune CD1 mice. We observed a decline in tear production beginning at 8 weeks of age in both NOD/LtJ and NOD.B10-H2(b) mice, continuing throughout the 40 to 46 weeks studied. This correlated with a quantifiable increase in mixed T- and B-lymphocyte infiltrations in the extraorbital lacrimal glands. In addition, temporal differences in tear protein expression between NOD/LtJ and CD1 mice were identified using two-dimensional gel electrophoresis and tandem mass spectrometry. Thus, using this model we can identify potentially important pathophysiological mechanisms of the autoimmune attack and possible diagnostic markers for development of SjS-associated dacryoadenitis.

Human chorionic gonadotropin prevents Sjögren's syndrome-like exocrinopathy in mice

OBJECTIVE

Results of recent studies suggest that human chorionic gonadotropin (HCG), a placental glycoprotein hormone required for the maintenance of pregnancy, may have immunomodulatory properties. Primary Sjögren's syndrome (SS), a chronic autoimmune disorder of unknown etiology, affects multiple exocrine glands including the salivary and lacrimal glands. The purpose of the present study was to determine whether HCG could prevent the development of salivary gland exocrinopathy in NOD mice, an experimental model of Sjögren's-like syndrome.

METHODS

Female NOD mice were treated with HCG from 6 weeks of age to 12 weeks of age. At 14 weeks, tissue samples were evaluated for inflammatory lesions and cytokine messenger RNA by real-time polymerase chain reaction. At 18 weeks, the salivary flow rate was measured.

RESULTS

Treatment with HCG resulted in a significant decrease in lymphocyte infiltration and parenchymal cell damage in the submandibular salivary glands. Messenger RNA levels of interferon-gamma, tumor necrosis factor alpha, interleukin-1beta, and interleukin-10, as well as inducible nitric oxide synthase and matrix metalloproteinase 9, were significantly decreased. Function studies revealed a marked increase in the salivary flow rate in HCG-treated mice compared with that in phosphate buffered saline-treated mice.

CONCLUSION

In NOD mice, HCG acts as an immune modulator and prevents the development of salivary gland exocrinopathy. These findings suggest that HCG, a naturally occurring reproductive hormone, may be useful in the treatment of Sjögren's syndrome and other human autoimmune diseases.

Inflammation in dry eye

Dry eye is a condition of altered tear composition that results from a diseased or dysfunctional lacrimal functional unit. Evidence suggests that inflammation causes structural alterations and/or functional paralysis of the tear-secreting glands. Changes in tear composition resulting from lacrimal dysfunction, increased evaporation and/or poor clearance have pro-inflammatory effects on the ocular surface. This inflammation is responsible in part for the irritation symptoms, ocular surface epithelial disease, and altered corneal epithelial barrier function in dry eye. Anti-inflammatory therapies for dry eye target one or more of the inflammatory mediators/pathways that have been identified in dry eye.

Usefulness of mouse models to study the pathogenesis of Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disorder characterized by ocular and oral dryness as well as systemic manifestations. The immunopathogenesis of SS is complex with different intricate factors. Because of the delay in the appearance of symptoms and due to ethical issues it is very difficult to study the wide array of factors intervening in the pathogenesis of SS in human patients. To circumvent this problem, different animal models have been elaborated for studying the different subsets of the aspects of the physiopathology of this disease. In this review, we focus on the mouse models that have been established to deepen our insight into the immunopathogenesis of SS.

IL-4-STAT6 signal transduction-dependent induction of the clinical phase of Sjögren's syndrome-like disease of the nonobese diabetic mouse

NOD.B10-H2(b) and NOD/LtJ mice manifest, respectively, many features of primary and secondary Sjögren's syndrome (SjS), an autoimmune disease affecting primarily the salivary and lacrimal glands leading to xerostomia (dry mouth) and xerophthalmia (dry eyes). B lymphocytes play a central role in the onset of SjS with clinical manifestations dependent on the appearance of autoantibodies reactive to multiple components of acinar cells. Previous studies with NOD.IL4(-/-) and NOD.B10-H2(b).IL4(-/-) mice suggest that the Th2 cytokine, IL-4, plays a vital role in the development and onset of SjS-like disease in the NOD mouse model. To investigate the molecular mechanisms by which IL-4 controls SjS development, a Stat6 gene knockout mouse, NOD.B10-H2(b).C-Stat6(-/-), was constructed and its disease profile was defined and compared with that of NOD.B10-H2(b).C-Stat6(+/+) mice. As the NOD.B10-H2(b).C-Stat6(-/-) mice aged from 4 to 24 wk, they exhibited leukocyte infiltration of the exocrine glands, produced anti-nuclear autoantibodies, and showed loss and gain of saliva-associated proteolytic enzymes, similar to NOD.B10-H2(b).C-Stat6(+/+) mice. In contrast, NOD.B10-H2(b).C-Stat6(-/-) mice failed to develop glandular dysfunction, maintaining normal saliva flow rates. NOD.B10-H2(b).C-Stat6(-/-) mice were found to lack IgG1 isotype-specific anti-muscarinic acetylcholine type-3 receptor autoantibodies. Furthermore, the IgG fractions from NOD.B10-H2(b).C-Stat6(-/-) sera were unable to induce glandular dysfunction when injected into naive recipient C57BL/6 mice. NOD.B10-H2(b).C-Stat6(-/-) mice, like NOD.B10-H2(b).IL4(-/-) mice, are unable to synthesize IgG1 Abs, an observation that correlates with an inability to develop end-stage clinical SjS-like disease. These data imply a requirement for the IL-4/STAT6-pathway for onset of the clinical phase of SjS-like disease in the NOD mouse model.

Reduced tear production in three canine endocrinopathies

OBJECTIVES

Previous reports have suggested that hypothyroid and diabetic patients can be predisposed to keratoconjunctivitis sicca. This study aimed to measure tear production in dogs with diabetes, hypothyroidism and hyperadrenocorticism using the Schirmer tear test and to compare these results with Schirmer tear test values for a group of normal dogs.

METHODS

Schirmer tear tests were performed on 16 dogs with hyperadrenocorticism, 18 with diabetes and 12 with hypothyroidism together with 100 control dogs. Corneal sensitivity was also measured in 12 of the 18 diabetic dogs with a Cochet Bonnet aesthesiometer and compared with age- and breed-matched normal dogs.

RESULTS

Schirmer tear test values in dogs with hypothyroidism, hyperadrenocorticism and diabetes were 12.3+/-3.2, 14.0+/-4.0 and 12.3+/-5.3 mm/minutes, respectively. Schirmer tear test values were significantly lower than that for the control group (19.6+/-4.2 mm/minutes) in all dogs with an endocrinopathy. Only in two hypothyroid dogs and three diabetics, this was manifested as profound keratoconjunctivitis sicca with Schirmer tear test value lower than 5 mm/minutes. Diabetic dogs had significantly reduced corneal sensitivity compared with a matched set of control dogs.

CLINICAL SIGNIFICANCE

This study shows a significant reduction in tear production in animals with diabetes mellitus, hypothyroidism and hyperadrenocorticism. Further research is needed to elucidate the mechanisms by which this reduction in tear production occurs. Assessment of tear production should be undertaken in animals diagnosed with these endocrinopathies, as these animals may progress to clinical keratoconjunctivitis sicca.

Early pathogenic events associated with Sjögren's syndrome (SjS)-like disease of the NOD mouse using microarray analysis

Recently, we reported development of the C57BL/6.NOD-Aec1Aec2 mouse carrying two genetic intervals derived from the NOD mouse. These two genetic regions confer full Sjögren's syndrome (SjS)-like disease in SjS-non-susceptible C57BL/6 mice. The current study was undertaken to apply microarray technology to define the molecular basis underlying onset of SjS-disease in C57BL/6.NOD-Aec1Aec2 mice. Using oligonucleotide microarrays, gene expression profiles of submandibular glands derived from 8- to 12-week-old C57BL/6.NOD-Aec1Aec2 mice and 8-week-old C57BL/6 mice were performed for comparison. Significant differential expressions were determined using the Mann-Whitney U test. Hybridizations using submandibular cDNA probes revealed 75 differentially expressed genes at 8 weeks and 105 differentially expressed genes at 12 weeks of age in C57BL/6.NOD-Aec1Aec2 mice compared to 8-week-old C57BL/6 mice. These genes were related generally to basic cellular activities such as transcription, translation, DNA replication, and protein folding. During the predisease phase, genes upregulated encode proteins associated with the IFN-gamma signal-transduction-pathway (Jak/Stat1), TLR-3 (Irf3 and Traf6) and apoptosis (casp11 and casp3), indicative of chronic proinflammatory stimuli, especially IL-1. Between 8 and 12 weeks of age, sets of clustered genes were upregulated that are associated with adaptive immune responses, especially B cell activation, proliferation and differentiation (Baffr, Taci, Bcma, Blys, April, CD70, CD40L, Traf1, Traf3, Pax5, c-Jun, Elk1 and Nf-kB), and neural receptors (Taj/Troy). Altered gene expressions of TLR3 and TNF-superfamily-receptors and ligands during this early phase of SjS suggest a possible viral etiology in the altered glandular homeostasis with an upregulated, possibly overstimulated, B-lymphocyte activation in the early autoimmune response present in the submandibular glands. The importance of NF-kappaB as a critical signal transduction pathway is also suggested but its link is not yet clear.

Experience with experimental biological treatment and local gene therapy in Sjogren's syndrome: implications for exocrine pathogenesis and treatment

Sjögren's syndrome is an autoimmune exocrinopathy, mainly affecting the lacrimal and salivary glands, and resulting in ocular and oral dryness (keratoconjunctivitis sicca and xerostomia). The aetiology and pathogenesis are largely unknown, and only palliative treatment is currently available. Data obtained from experimental animal and human studies using biological agents or gene therapeutics can offer insight into the disease process of Sjögren's syndrome. This article reviews the current literature on these approaches and assesses the lessons learnt about the pathogenesis of Sjögren's syndrome.

NOD mouse model for Sjögren's syndrome: lack of longitudinal stability

OBJECTIVES

The non-obese diabetic (NOD) mouse is not only a widely used model for diabetes mellitus type I, but also for the chronic autoimmune disease Sjögren's syndrome (SS), mainly affecting salivary and lacrimal glands. We studied the efficacy of local recombinant serotype 2 adeno-associated viral (rAAV2) vector transfer of immunomodulatory transgenes to alter the SS-like disease in NOD mice. Data collected over a 2-year period indicated a changing SS phenotype in these mice and this phenomenon was investigated.

METHODS

10(10) particles rAAV2LacZ/gland were delivered to both submandibular glands (SMGs) of NOD/LtJ mice at 8 weeks (before sialadenitis onset) of age. Salivary flow rates were determined at 8 weeks and time of killing. Blood glucose levels and body weights were measured weekly. After killing, saliva and SMGs were harvested. Analyses of salivary output, inflammatory infiltrates (focus score), SMG cytokine profile, body weight, and diabetes mellitus status were performed. Data from six different experimental studies over 2 years were analyzed and compared.

RESULTS

Salivary flow rate, focus score, and SMG cytokines interleukin (IL)-2, IL-4, IL-6, IL-10, IL-12(p70), tumor necrosis factor-alpha and IFNgamma showed changes over time. There were no differences for body weight, diabetes mellitus prevalence, or blood glucose level of non-diabetic mice.

CONCLUSION

This retrospective report is the first to describe longitudinal variability in the NOD mouse as a model for SS. We advise other investigators to continuously monitor the SS phenotype parameters and include appropriate controls when studying this disease in NOD mice.

Sjögren's syndrome-like disease of C57BL/6.NOD-Aec1 Aec2 mice: gender differences in keratoconjunctivitis sicca defined by a cross-over in the chromosome 3 Aec1 locus

Sjögren's syndrome (SjS) is a systemic autoimmune disease in which an immunological attack primarily against the salivary and lacrimal glands results in loss of acinar cell tissue and function leading to stomatitis sicca and keratoconjunctivitis sicca. In recent years, the NOD mouse has become an accepted model of SjS, exhibiting a spontaneously developing disease that strongly mimics the human condition. Two genetic regions, one on chromosome 1 (designated Aec2) and the second on chromosome 3 (designated Aec1) of NOD mice, have been shown to be necessary and sufficient to recapitulate SjS-like disease in non-susceptible C57BL/6 mice. Here we describe a newly derived strain, C57BL/6.NOD-Aec1R1Aec2, in which a recombination in Aec1 has resulted in reducing this genetic region to less than 20 cM from 48.5 cM. Profiling of this recombinant inbred strain has revealed that male mice maintain a full SjS-like disease, whereas female mice exhibit stomatitis sicca in the absence of detectable keratoconjunctivitis sicca. These data suggest SjS-like disease in the NOD mouse shows gender-specific regulation determined by autosomal genes.

Distribution and roles of aquaporins in salivary glands

Salivary glands are involved in secretion of saliva, which is known to participate in the protection and hydratation of mucosal structures within the oral cavity, oropharynx and oesophagus, the initiation of digestion, some antimicrobial defence, and the protection from chemical and mechanical stress. Saliva secretion is a watery fluid containing electrolytes and a mixture of proteins and can be stimulated by muscarinic and adrenergic agonists. Since water movement is involved in saliva secretion, the expression, localization and function of aquaporins (AQPs) have been studied in salivary glands. This review will focus on the expression, localization and functional roles of the AQPs identified in salivary glands. The presence of AQP1, AQP5 and AQP8 has been generally accepted by many, while the presence of AQP3, AQP4, AQP6 and AQP7 still remains controversial. Functionally, AQP5 seems to be the only AQP thus far to be clearly playing a major role in the salivary secretion process. Modifications in AQPs expression and/or distribution have been reported in xerostomic conditions.

Effect of human vasoactive intestinal peptide gene transfer in a murine model of Sjogren's syndrome

BACKGROUND

Sjögren's syndrome (SS), an autoimmune exocrinopathy mainly affecting lachrymal and salivary glands, results in ocular and oral dryness (keratoconjunctivitis sicca and xerostomia). The aetiology and pathogenesis are largely unknown; currently, only palliative treatment is available.

OBJECTIVE

To determine whether gene transfer of vasoactive intestinal peptide (VIP), based on its immunomodulatory properties, might be useful in the management of SS.

METHODS

A recombinant serotype 2 adeno-associated virus encoding the human VIP transgene (rAAV2hVIP) was constructed and its efficacy tested in the female non-obese diabetic (NOD) mouse model for SS after retrograde instillation in submandibular glands (SMGs). 10(10) particles/gland of rAAV2hVIP or rAAV2LacZ (encoding beta-galactosidase; control vector) were administered at 8 weeks of age (before sialadenitis onset). Salivary flow rates were determined before vector delivery and at time of death (16 weeks). After death, saliva, serum, and SMGs were harvested. Salivary output, inflammatory infiltrates (focus scores), VIP protein expression, cytokine profile, and serum anti-VIP antibodies were analysed.

RESULTS

rAAV2hVIP significantly improved the salivary flow, increased SMG and serum expression of VIP, and reduced SMG cytokines interleukin (IL) 2, IL10, IL12 (p70), and tumour necrosis factor alpha, and serum RANTES, compared with the control vector. No difference in focus scores or apoptotic rates was found; neutralising antibodies were not detected.

CONCLUSIONS

Local delivery of rAAV2hVIP can have disease modifying and immunosuppressive effects in SMGs of the NOD mouse model of SS. The new strategy of employing VIP prophylactically may be useful for both understanding and managing the salivary component of SS.

Sjögren's syndrome in the NOD mouse model is an interleukin-4 time-dependent, antibody isotype-specific autoimmune disease

NOD.B10-H2b and NOD/LtJ mice manifest many features of primary and secondary Sjögren's syndrome (SjS), respectively, an autoimmune disease affecting primarily the salivary and lacrimal glands leading to xerostomia (dry mouth) and xerophthalmia (dry eyes). A previous study suggested that the T(H2) cytokine, interleukin (IL)-4, plays an integral role in the development and onset of SjS-like disease in the NOD mouse model. To define further the role of IL-4 in onset of murine SjS-like disease, we have examined two IL4 gene knockout (KO) mouse strains, NOD.IL4-/- and NOD.B10-H2b.IL4-/-. Unlike NOD.IL4-/- mice, NOD.B10-H2b.IL4-/- mice are resistant to development of diabetes. The presence of a dysfunctional IL4 gene did not impede leukocyte infiltration of the salivary glands, yet prevented development of secretory dysfunction. Whereas NOD.B10-H2b.IL4-/- mice exhibited many pathophysiological manifestations of SjS-like disease common to the parental strains, these mice failed to produce anti-muscarinic acetylcholine type-3 receptor (M3R) autoantibodies of the IgG1 isotype. Cytokine mRNA expression profiles and adoptive transfers of T lymphocytes from NOD.B10-H2b.Gfp mice into NOD.B10-H2b.IL4-/- mice at different ages suggest IL-4 is required during the pre-clinical disease stage (around 12 weeks of age) to initiate clinical xerostomia. The results of this study indicate that the failure of NOD.IL4-/- and NOD.B10-H2b.IL4-/- mice to synthesize anti-M3R autoantibodies of the IgG1 isotype apparently explains why these mice fail to develop exocrine gland dysfunction, despite exhibiting pre-clinical manifestations of SjS-like disease.

Role of complement and B lymphocytes in Sjögren's syndrome-like autoimmune exocrinopathy of NOD.B10-H2b mice

Sjögren's syndrome (SjS) is a human autoimmune disease characterized by the loss of exocrine function as a result of a chronic immune attack directed primarily against the salivary and lacrimal glands leading to xerostomia (dry mouth) and xerophthalmia (dry eyes). NOD.B10-H2b mice manifest many features of SjS, exhibiting exocrine gland dysfunction concomitant with leukocyte infiltration of the salivary and lacrimal glands. Recent studies have shown that both SjS patients and NOD.B10-H2b mice exhibit increased B lymphocyte survival, B cell hyper-reactivity and hyper-gammaglobulinemia with high production of autoantibodies. To study the possible influence of complement on the development and expression of SjS-like disease of the NOD.B10-H2b, we have utilized a prophylactic treatment with CVF known to interfere with the action of complement C3 factor. NOD.B10-H2b mice, injected with CVF starting at 10 weeks of age, a time when leukocyte infiltration is expected to begin, failed to develop salivary dysfunction out to 24 weeks of age, a time when reduced salivary flow rates are known to occur in non-treated animals. Concomitant with retention of salivary exocrine function, CVF-treated mice showed reduced levels of leukocytic infiltration, reduction of anti-nuclear autoantibodies and major alterations in the B lymphocyte profiles while maintaining general pathophysiological measures of disease. These data suggest that C3 plays a significant role in development and onset of SjS-like disease, yet additional studies need to be carried out to identify the precise mode of action.

Detection of anti-type 3 muscarinic acetylcholine receptor autoantibodies in the sera of Sjögren's syndrome patients by use of a transfected cell line assay

OBJECTIVE

Sjögren's syndrome (SS) is an autoimmune disease affecting primarily the salivary and lacrimal glands, leading to dry mouth and dry eyes. Recent studies have suggested that autoantibodies reactive with the type 3 muscarinic acetylcholine receptors (M3Rs) expressed on salivary and lacrimal gland cells may be highly specific for SS. To test this hypothesis, we constructed a cell line expressing the human M3R gene in order to screen for anti-M3R autoantibodies in sera from SS patients.

METHODS

Complementary DNA encoding the open-reading frame (ORF) of the human M3R gene was amplified, ligated into the pcDNA5/FRT/V5-His-TOPO TA vector, and then used to transform Escherichia coli bacteria. Plasmid DNA containing the M3R ORF with the correct orientation was transfected into Flp-In Chinese hamster ovary (CHO) cells using Flp recombinase-mediated site-specific recombination. An M3R-transfected CHO cell line, selected and propagated in hygromycin, was used to detect anti-M3R autoantibodies in SS patient and healthy control sera by flow cytometry.

RESULTS

Testing of sera for the presence of anti-M3R autoantibodies bound to CHO-transfected cells revealed the presence of anti-M3R autoantibodies in SS patients (9 of 11) but not in healthy controls (0 of 11). Although the anti-M3R autoantibodies detected in patient sera were of multiple isotypes, the most consistently detected were IgG1, IgG3, and IgA.

CONCLUSION

Using a newly constructed cell line expressing human M3R, anti-M3R autoantibodies were easily detected in sera from SS patients. These autoantibodies were skewed toward the IgG1, IgG3, and IgA isotypes, probably recognizing a tertiary epitope created by extracellular domains of the receptor protein. Anti-M3R autoantibodies represent a highly promising clinical marker for the identification of SS.

Recent advances in understanding molecular mechanisms in the pathogenesis and antibody profile of Sjögren's syndrome

Sjögren's syndrome is a chronic autoimmune and rheumatic disorder of the mucous membranes caused by a lack of proper exocrine secretions, with prominent sicca complaints. The molecular mechanisms of the pathogenesis are virtually unknown, although progress has been made with regard to chemokines, B cell activating factor, and apoptosis. A large number of autoantibodies have been reported in Sjögren's syndrome, some of which relate to impairment of glandular function. Sjögren's syndrome is a female-dominant disease with a late age of onset; most patients contract the disease at the age of 40 to 50 years. Lately, attention has been drawn to the effects of adrenopause in Sjögren's syndrome and on dehydroepiandrosterone and its intracrine metabolism in target tissues. This can influence the maintenance and remodeling of exocrine glands and may explain, in part, another important disease symptom--fatigue.