Effect of tumor necrosis factor-alpha and interferon-gamma on the growth of a human salivary gland cell line

Single nucleotide polymorphisms of GEMIN3 modify the risk of primary Sjögren's syndrome in female patients

BACKGROUND

MicroRNA (miRNA)-processing machinery may modify the risk of primary Sjögren's syndrome (pSS) by altering miRNA expression profiles. Inflammatory cytokines and reactive oxygen species (ROS) are also involved in pSS; however, the role of altered miRNAs expression in its pathogenesis is still unclear. We aimed to evaluate the relationship between single-nucleotide polymorphisms (SNPs) in miRNA processing machinery genes, including XPO5 (rs11077), RAN (rs14035), Dicer (rs3742330), TNRC6B (rs9623117), GEMIN3 (rs197412), and GEMIN4 (rs2740348), and the risk of pSS in female patients. The potential associations of cytokines and ROS with pSS-susceptible SNPs were also evaluated.

MATERIALS AND METHODS

The SNPs confirmed by polymerase chain reaction ligase detection reaction were genotyped in 74 female patients with pSS and 77 controls. The relationship was analyzed by Student's t-test, Wilcoxon rank-sum test, chi-square test, Pearson's correlation test, and binary logistic regression analysis.

RESULTS

For rs197412 of the GEMIN3 gene, the genotype TT carrier was associated with a 2.172-fold increased risk for pSS when compared with that of CT+CC carrier (odds ratio: 2.172, 95% CI, 1.133-4.166, p=0.019). Simultaneously, the pSS-susceptible TT carriers were associated with increased interferon-γ (IFN-γ) (P < 0.001) and tumor necrosis factor-α (TNF-α) (P = 0.003) levels when compared with that of CT+CC genotype carriers in female patients with pSS. The subsequent analysis also showed a weak positive correlation between IFN-γ and TNF-α levels (r=0.271, P = 0.019).

CONCLUSION

The predictors of GEMIN3 SNPs might modify pSS development in females by mediating the expression of miRNAs and therefore regulate the levels of IFN-γ and TNF-α.

JAK Inhibitors and Oxidative Stress Control

Primary Sjögren's syndrome (SjS) is a complex autoimmune epithelitis, with few treatment options, but the use of Janus kinase (JAK) inhibitors is promising because suppression of the JAK/signal transducer and activator of transcription (STAT) pathway improves sicca manifestations. Playing a primary and pathogenic role in disease development, the oxidative stress response is upregulated in activated salivary gland epithelial cells (SGECs) from patients with SjS. Therefore, the aim of this study was to investigate whether JAK inhibitors would suppress SGEC activation in response to an oxidative stress. For this purpose, the human salivary gland (HSG) cell line was used, and cells were treated with the reactive oxygen species (ROS) inducer hydrogen peroxide (H₂O₂) or with interferons (IFN Type I and Type II), used as positive controls, to mimic activated SGECs as observed in SjS patients. Afterward, the levels of the intracellular adhesion molecule-1 (ICAM-1) and the regulatory programmed-death ligand-1 (PD-L1) were measured by real-time PCR and flow cytometry, and the STAT1/3 phosphorylation status was assessed by Western blotting. Using the HSG cell line, our results showed that both ICAM-1 and PD-L1 are induced by ROS through pSTAT3, and that this activation pathway is reversed by the use of JAK inhibitors, AG490 and ruxolitinib, as well as by N-acetylcysteine, which is a direct inhibitor of ROS. These findings open new perspectives regarding the pathogenesis and therapeutic possibilities for SjS.

IFI16 filament formation in salivary epithelial cells shapes the anti-IFI16 immune response in Sjögren's syndrome

IFN-inducible protein 16 (IFI16) is an innate immune sensor that forms filamentous oligomers when activated by double-stranded DNA (dsDNA). Anti-IFI16 autoantibodies occur in patients with Sjögren's syndrome (SS) and associate with severe phenotypic features. We undertook this study to determine whether the structural and functional properties of IFI16 play a role in its status as an SS autoantigen. IFI16 immunostaining in labial salivary glands (LSGs) yielded striking evidence of filamentous IFI16 structures in the cytoplasm of ductal epithelial cells, representing the first microscopic description of IFI16 oligomerization in human tissues, to our knowledge. Transfection of cultured epithelial cells with dsDNA triggered the formation of cytoplasmic IFI16 filaments with similar morphology to those observed in LSGs. We found that a majority of SS anti-IFI16 autoantibodies immunoprecipitate IFI16 more effectively in the oligomeric dsDNA-bound state. Epitopes in the C-terminus of IFI16 are accessible to antibodies in the DNA-bound oligomer and are preferentially targeted by SS sera. Furthermore, cytotoxic lymphocyte granule pathways (highly enriched in the SS gland) induce striking release of IFI16•dsDNA complexes from cultured cells. Our studies reveal that IFI16 is present in a filamentous state in the target tissue of SS and suggest that this property of DNA-induced filament formation contributes to its status as an autoantigen in SS. These studies highlight the role that tissue-specific modifications and immune effector pathways might play in the selection of autoantigens in rheumatic diseases.

Precise probes of type II interferon activity define the origin of interferon signatures in target tissues in rheumatic diseases

Elucidating the molecular pathways active in pathologic tissues has important implications for defining disease subsets, selecting therapy, and monitoring disease activity. The development of therapeutics directed at IFN-α or IFN-γ makes the discovery of probes that report precisely on the activity of different IFN pathways a high priority. We show that, although type I and II IFNs induce the expression of a largely overlapping group of molecules, precise probes of IFN-γ activity can be defined. Used in combination, these probes show prominent IFN-γ effects in Sjögren syndrome (SS) tissues. In contrast, dermatomyositis muscle shows a dominant type I IFN pattern. Interestingly, heterogeneity of IFN signatures exists in patients with SS, with some patients demonstrating a predominant type I pattern. The biochemical patterns largely distinguish the target tissues in patients with SS from those with dermatomyositis and provide a relative weighting of the effects of distinct IFN pathways in specific biopsies. In SS, type I and II IFN effects are localized to the same epithelial cells, surrounded by inflammatory cells expressing IFN-γ-induced proteins, suggesting reinforcing interactions. Precise probes of the different IFN pathways active in tissues of complex rheumatic diseases will be critical to classify disease, elucidate pathogenesis, and select therapy.

Automated analysis of time-lapse imaging of nuclear translocation by retrospective strategy and its application to STAT1 in HeLa cells

Cell-based image analysis of time-lapse imaging is mainly challenged by faint fluorescence and dim boundaries of cellular structures of interest. To resolve these bottlenecks, a novel method was developed based on “retrospective” analysis for cells undergoing minor morphological changes during time-lapse imaging. We fixed and stained the cells with a nuclear dye at the end of the experiment, and processed the time-lapse images using the binary masks obtained by segmenting the nuclear-stained image. This automated method also identifies cells that move during the time-lapse imaging, which is a factor that could influence the kinetics measured for target proteins that are present mostly in the cytoplasm. We then validated the method by measuring interferon gamma (IFNγ) induced signal transducers and activators of transcription 1 (STAT1) nuclear translocation in living HeLa cells. For the first time, automated large-scale analysis of nuclear translocation in living cells was achieved by our novel method. The responses of the cells to IFNγ exhibited a significant drift across the population, but common features of the responses led us to propose a three-stage model of STAT1 import. The simplicity and automation of this method should enable its application in a broad spectrum of time-lapse studies of nuclear-cytoplasmic translocation.

Effect of soluble ICAM-1 on a Sjögren's syndrome-like phenotype in NOD mice is disease stage dependent

Introduction

Intercellular adhesion molecule-1 (ICAM-1) is involved in migration and co-stimulation of T and B cells. Membrane bound ICAM-1 is over expressed in the salivary glands (SG) of Sjögren's syndrome (SS) patients and has therefore been proposed as a potential therapeutic target. To test the utility of ICAM-1 as a therapeutic target, we used local gene therapy in Non Obese Diabetic (NOD) mice to express soluble (s)ICAM-1 to compete with membrane bound ICAM-1 for binding with its receptor. Therapy was given prior to and just after the influx of immune cells into the SG.

Methods

A recombinant serotype 2 adeno associated virus (rAAV2) encoding ICAM-1/Fc was constructed and its efficacy tested in the female NOD mice after retrograde instillation in SG at eight (early treatment) and ten (late treatment) weeks of age. SG inflammation was evaluated by focus score and immunohistochemical quantification of infiltrating cell types. Serum and SG tissue were analyzed for immunoglobulins (Ig).

Results

Early treatment with ICAM-1/Fc resulted in decreased average number of inflammatory foci without changes in T and B cell composition. In contrast, late treated mice did not show any change in focus scores, but immunohistochemical staining showed an increase in the overall number of CD4+ and CD8+ T cells. Moreover, early treated mice showed decreased IgM within the SGs, whereas late treated mice had increased IgM levels, and on average higher IgG and IgA.

Conclusions

Blocking the ICAM-1/LFA-1 interaction with sICAM-1/Fc may result in worsening of a SS like phenotype when infiltrates have already formed within the SG. As a treatment for human SS, caution should be taken targeting the ICAM-1 axis since most patients are diagnosed when inflammation is clearly present within the SG.

Global gene expression profile progression in Gaucher disease mouse models

BACKGROUND

Gaucher disease is caused by defective glucocerebrosidase activity and the consequent accumulation of glucosylceramide. The pathogenic pathways resulting from lipid laden macrophages (Gaucher cells) in visceral organs and their abnormal functions are obscure.

RESULTS

To elucidate this pathogenic pathway, developmental global gene expression analyses were conducted in distinct Gba1 point-mutated mice (V394L/V394L and D409 V/null). About 0.9 to 3% of genes had altered expression patterns (≥ ± 1.8 fold change), representing several categories, but particularly macrophage activation and immune response genes. Time course analyses (12 to 28 wk) of INFγ-regulated pro-inflammatory (13) and IL-4-regulated anti-inflammatory (11) cytokine/mediator networks showed tissue differential profiles in the lung and liver of the Gba1 mutant mice, implying that the lipid-storage macrophages were not functionally inert. The time course alterations of the INFγ and IL-4 pathways were similar, but varied in degree in these tissues and with the Gba1 mutation.

CONCLUSIONS

Biochemical and pathological analyses demonstrated direct relationships between the degree of tissue glucosylceramides and the gene expression profile alterations. These analyses implicate IFNγ-regulated pro-inflammatory and IL-4-regulated anti-inflammatory networks in differential disease progression with implications for understanding the Gaucher disease course and pathophysiology.

Cytokines in Sjögren's syndrome

Cytokines play a central role in the regulation of immunity and are often found to be deregulated in autoimmune diseases. Sjögren's syndrome is a chronic autoimmune disease characterized by inflammation and loss of secretory function of the salivary and lachrymal glands. This review highlights the current knowledge of the expression and the function of pro- and anti-inflammatory cytokines both locally and systemically in Sjögren's syndrome patients. In the salivary glands, saliva and serum of these patients, many pro-inflammatory cytokines are upregulated. Concomitantly, most anti-inflammatory cytokines are not detectable or are expressed at low levels. Besides a role in inflammation, cytokines are also thought to be involved in salivary gland dysfunction by directly interfering with the epithelial cells in the glands. Future research on the role of novel cytokines in Sjögren's syndrome in combination with a better understanding of the effect of cytokines on exocrine dysfunction will aide the identification of the best therapeutic targets for Sjögren's syndrome.

RAGE expression and NF-kappaB activation attenuated by extracellular domain of RAGE in human salivary gland cell line

The receptor for advanced-glycation-end-products (RAGE) has been implicated as a pro-inflammatory factor in chronic inflammatory conditions such as diabetes mellitus and rheumatoid arthritis. The aim of this study was to investigate the inhibitory effect of the soluble-RAGE (sRAGE), the extracellular domain of RAGE, on RAGE expression and NF-kappaB translocation in human-salivary gland-cell-lines (HSG). Cells were stimulated with agonist S100A4, fusion protein of RAGE encompassing the extracellular domain of RAGE (ex-RAGE), ex-RAGE followed by S100A4, or S100A4 followed by ex-RAGE. Our study indicates that RAGE expression was highest at 150 microg/microl of S100A4 and efficiently down-regulated by 1.8-fold (P < 0.05) when ex-RAGE was incubated prior to agonist S100A4. RAGE protein was also consistently down-regulated by 20-40% with pre-incubation of ex-RAGE. More importantly, nuclear translocation of p65 and p52 of NF-kappaB by S100A4 was inhibited in the presence of ex-RAGE, confirming anti-inflammatory function of ex-RAGE. In conclusion, ex-RAGE down-regulates RAGE expression and inhibits p65 and p52 activation in HSG, providing evidence that ex-RAGE functions as a "decoy" to RAGE-ligand interaction and thus potentially dampening inflammatory conditions.

Interferon-gamma sensitizes the human salivary gland cell line, HSG, to tumor necrosis factor-alpha induced activation of dual apoptotic pathways

Activated immune cells secrete proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha), interferon-gamma (IFN-gamma) and Fas ligand (FasL) and these cytokines have been reported to induce apoptosis in numerous cell types. Apoptotic cell death has been associated with the progression of numerous autoimmune diseases. Proinflammatory cytokines are reportedly involved in apoptosis in the salivary glands of patients with Sjögren's syndrome (SS); an autoimmune disorder characterized by the destruction of salivary and lachrymal glands. In this study, we used the HSG cell line to determine if exposure to proinflammatory cytokines induces apoptosis in human salivary gland cells. In addition, we identified the mediators controlling the apoptotic process in response to TNF alpha and IFN gamma. TNF-alpha and IFN-gamma induced apoptosis in HSG cells and resulted in the activation of caspase 8 and the "death receptor" pathway. We further determined that caspase 9 and the "mitochondrial" pathway was also activated. Induction of the intrinsic and extrinsic pathways in HSG cells resulted in substrate cleavage by effector caspases, in particular the cleavage of alpha II spectrin, an autoantigen in Sjögren's syndrome. Our results suggest that HSG cells provide a model system to study processes regulating proinflammatory cytokine-induced apoptotic cell death.

Pathophysiology of Sjögren's syndrome

The term Sjögren's syndrome refers to keratoconjunctivitis sicca and xerostomia due to lymphocytic infiltrates of lachrymal and salivary glands. The current used criteria for diagnosis of primary Sjögren's syndrome is the American-European consensus. Primary Sjögren's syndrome is an autoimmune disorder characterized by lymphocytic infiltrates and destruction of the salivary and lachrymal glands and systemic production of autoantibodies to the ribonucleoprotein particles SS-A/Ro and SS-B/La. The infiltrating cells (T- and B-cells, dendritic cells) interfere with glandular function at several points: destruction of glandular elements by cell-mediated mechanisms; secretion of cytokines that activate pathways bearing the signature of type 1 and 2 interferons; production of autoantibodies that interfere with muscarinic receptors; and secretion of metalloproteinases (MMPs) that interfere with the interaction of the glandular cell with its extracellular matrix, which is necessary for efficient glandular function. As the process progresses, the mucosal surfaces become sites of chronic inflammation and the start of a vicious circle. Despite extensive study of the underlying cause of Sjögren's syndrome, the pathogenesis remains obscure. In broad terms, pathogenesis is multifactorial; environmental factors are thought to trigger inflammation in individuals with a genetic predisposition to the disorder.

Intracellular trafficking and surface expression of SS-A (Ro), SS-B (La), poly(ADP-ribose) polymerase and alpha-fodrin autoantigens during apoptosis in human salivary gland cells induced by tumour necrosis factor-alpha

Autoantibodies directed against nucleic acid and protein complexes present in cell nuclei characterize autoimmune diseases and are employed in diagnosis. The mechanisms by which these autoantigens escape immunological tolerance are largely unknown, but a number of recent observations suggest that modified self-protein generated during apoptosis my play an important part in the development of autoimmunity. To investigate the possibility that autoantibodies in patients with Sjögren's syndrome are induced by apoptosis and presented on the surface of the cell, the internal distribution of autoantigens in apoptotic human salivary gland cells was studied in vitro. Salivary gland cells were treated with tumour necrosis factor-alpha, an apoptosis inducer. At increasing times after induction, cells were homogenized and cytoplasmic, cell surface membrane and nuclear compartments were fractionated using a sucrose density-gradient system. Autoantigens alpha-fodrin, SS-A (Ro), SS-B (La), and the enzyme poly(ADP-ribose) polymerase, were detected by conventional immunofluorescence and confirmed by Western immunoblotting. At increasing times after apoptosis, nuclear proteins SS-A (Ro) and SS-B (La), but not poly(ADP-ribose) polymerase were relocated from the cell nucleus to the cell surface membrane. Fodrin, a cytoplasmic protein, was also translocated to the cell membrane after cleavage of alpha-fodrin. These results show that autoantigens fodrin, SS-A (Ro) and SS-B (La) in human salivary gland cells undergo a striking redistribution during apoptosis and relocate to the cell membrane of apoptotic cells. The appearance of autoantigens on the surface of induced cells could form the basis of a mechanism for autoantigen presentation, processing and autoantibody induction.

Influence of interferon-gamma on radiation-induced apoptosis in normal and ataxia-telangiectasia fibroblast cell lines

Combination of interferon-gamma (IFN-gamma) with radiation, or chemotherapeutic agents, produces different kind of modulatory effects, depending on the cell types and experimental conditions. The objective of the present study was verify the influence of IFN-gamma on the induction of apoptosis by gamma-radiation. Experiments were carried out on human fibroblast cell lines: VH-25 (primary), MRC-5, and AT-5BIVA (SV40-transformed). Exponentially growing cells were irradiated and exposed to IFN-gamma (1,000, 2,000, and 3,000 UI/mL) until in situ cell staining performed at 6, 24, and 48 h. Induction of apoptosis by ionising radiation was not verified in primary VH-25 cells. A significant increase in the frequencies of apoptotic cells was observed in SV-40-transformed cells lines, MRC-5, and AT-5BIVA fibroblasts, which were irradiated with 1.0 Gy, but the frequencies of necrotic cells were similar to the control levels. In MRC-5 cells, combined treatments with radiation and IFN-gamma induced a statistically significant reduction in the frequencies of apoptotic cells detected at 24 and 48 h after cell irradiation, while for AT cells the interaction effect (reduction of apoptosis frequency) was significant even at earlier time collection (6 h) after gamma-irradiation, and higher when compared to MRC-5 cells. The present study demonstrated that IFN-gamma showed an anti-apoptotic activity in SV40-transformed fibroblasts, normal and AT cells, which were irradiated with gamma-rays, thus indicating a mechanism dependent on the cellular type.

Induction of salivary gland epithelial cell injury in Sjogren's syndrome: in vitro assessment of T cell-derived cytokines and Fas protein expression

Sjogren's syndrome (SS) is an exocrinopathy characterized by T cell infiltrates, salivary gland epithelial cell (SGEC) apoptosis and high Fas and FasL expression. To address the participation of T cell-derived cytokines and of Fas apoptotic pathway in SS glandular lesions, we utilized non-neoplastic SGEC lines established from SS patients and controls. Possibly attesting to their intrinsic activation, cell lines derived from SS patients displayed significantly higher constitutive Fas and FasL than controls. Surface co-expression of Fas and FasL was not associated with spontaneous fratricide apoptosis. SGEC were resistant to anti-Fas-mediated apoptosis (possibly owing to the constitutive expression of anti-apoptotic proteins cFLIP and Bcl-2), but became sensitive after protein or RNA synthesis inhibition. IFN-gamma and TNF-alpha were able to upregulate surface Fas and FasL, whereas IL-1beta downregulated surface FasL. IFN-gamma (but not several other cytokines) reduced the survival of SGEC in a dose- and time-dependent manner and induced Fas/FasL-mediated apoptosis, directly and via anoikia. Dexamethasone inhibited the upregulation of Fas and FasL by IFN-gamma and the induction of SGEC apoptosis and detachment by anti-Fas mAb or IFN-gamma. Our findings indicate the injurious role of IFN-gamma for the salivary epithelia of SS patients through the induction of Fas-mediated apoptosis and anoikia.

Integrating anti-tumor necrosis factor therapy in inflammatory bowel disease: current and future perspectives

Crohn's disease and ulcerative colitis are two idiopathic inflammatory disorders of the GI tract. Manifestations of disease can be severe and lead to long term therapy with a variety of medications and/or surgery. Standard medical therapy consists of agents that either treat suppurative complications or modulate the inflammatory cascade in a nonspecific manner. Many specific chemokine and cytokine effectors that promote intestinal inflammation have been identified. Such work has led to experimental clinical trials with a variety of cytokine antagonists. Compounds directed against one such cytokine, tumor necrosis factor alpha (TNF), have demonstrated the greatest clinical efficacy to date. This is consistent with scientific observations that suggest a central role for TNF in the inflammatory cascade. Infliximab is a chimeric monoclonal antibody against TNF that has been demonstrated to be effective for the treatment of Crohn's disease. Infliximab is Food and Drug Administration approved for the treatment of Crohn's disease. There exist several other TNF antagonists in various phases of investigation, including the monoclonal antibody CDP 571, the fusion peptide etanercept, the phosphodiesterase inhibitor oxpentifylline, and thalidomide. The clinical efficacy of these agents and the role of TNF in the pathogenesis of inflammatory bowel disease is reviewed.

Regulation of insulin-like growth factor-I receptor gene expression by tumor necrosis factor-alpha and interferon-gamma

The insulin-like growth factor-I receptor (IGF-l-R) plays a critical role in normal and pathological growth processes. The expression of the IGF-l-R gene is regulated by various stimuli, including hormones and growth factors. We have investigated the molecular mechanisms by which two inhibitory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), regulate IGF-l-R gene expression. TNF-alpha and IFN-gamma reduced the proliferation rates of the osteogenic sarcoma cell line, Saos-2, and the human salivary gland cell line, HSG, in a dose- and time-dependent fashion. This effect was associated with significant reductions in the levels of IGF-l-R mRNA and protein, and with inhibition of IGF-l-R promoter activity, suggesting that TNF-alpha and IFN-gamma affect IGF-l-R gene expression at the transcriptional level. In addition, TNF-alpha significantly decreased IGF-l-R mRNA stability. Combined cytokine treatment inhibited cellular proliferation and promoter activity in an additive manner. Taken together, these results suggest that a novel potential mechanism by which TNF-alpha and IFN-gamma affect cellular proliferation involves suppression of IGF-l-R promoter activity, as well as destabilization of IGF-l-R transcripts.

Glandular and extraglandular expression of costimulatory molecules in patients with Sjögren's syndrome

OBJECTIVES

To investigate the expression and regulation of CD80, CD86, and CD28 costimulatory molecules in sialoadenitis and interstitial nephritis in patients with Sjögren's syndrome (SS).

METHODS

Expression of CD80, CD86, and CD28 molecules was studied by immunohistochemical staining of lip biopsy specimens obtained from patients who had sialoadenitis associated with SS, and renal biopsy specimens obtained from patients who had interstitial nephritis associated with SS. To elucidate the mechanism of de novo expression of CD80 and CD86 antigens, their induction by cytokines in human salivary duct cell line (HSG) and renal cortical epithelial cells (HRCE) by cell enzyme linked immunosorbent assay (ELISA) was quantitatively investigated.

RESULTS

In patients with severe sialoadenitis, CD80 and CD86 were strongly expressed on ductal epithelial cells. In contrast, these antigens were not found in the minor salivary glands of normal subjects or of patients with mild sialoadenitis. Some infiltrating cells expressed CD28. In patients who had interstitial nephritis associated with SS, some tubular epithelial cells expressed CD86 but not the CD80 antigen. Unstimulated HSG cells did not express CD80 or CD86. Interferon gamma (IFNgamma) consistently up regulated levels of CD80 and CD86. In contrast, tumour necrosis factor alpha (TNFalpha), interleukin 1beta (IL1beta), IL2, and IL4 had no effect on either CD80 or CD86 levels. Unstimulated HRCE did not express CD80 or CD86. IFNgamma consistently up regulated CD86 expression. No CD80 expression was found on tubular cells. TNFalpha, IL1beta, IL2, and IL4 had no discernible effects.

CONCLUSIONS

Salivary ductal cells in patients with SS can express CD80 and CD86 costimulatory molecules in response to IFNgamma. Tubular epithelial cells in patients who have interstitial nephritis associated with SS express only CD86 molecules. In patients with SS, salivary ductal cells and tubular epithelial cells may activate infiltrating CD28 positive T lymphocytes by presenting antigens to T cells, potentially leading to tissue destruction.

Interferon-mediated block in cell cycle and altered integrin expression in a differentiated salivary gland cell line (HSG) cultured on Matrigel

Sjögren's syndrome (SS), an idiopathic, autoimmune exocrinopathy, is partly characterized by diminished salivary flow, acinar cell atrophy, and increased expression of several cytokines. Several in vivo characteristics of the sialoadenitis are also evident in a human salivary gland ductal epithelial cell line (HSG) treated with cytokines. HSG cells differentiate to the acinar phenotype when cultured on Matrigel (Becton Dickinson, Bedford, MA), a basement membrane extract. To elucidate mechanisms of salivary gland pathology, the effects of interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) on cell cycle progression and integrin expression were evaluated in HSG acinarlike cells. Flow cytometry experiments showed that cytokine treatment for 2 days arrested cells in G(1) phase of the cell cycle, and this preceded significant morphologic changes and decreased viability. Whereas only modest cytokine-mediated increases in protein expression for the alpha 3 and beta 1 integrin subunits were seen by immunoprecipitation, a form of alpha 3 integrin displaying enhanced electrophoretic mobility was evident after 6 days of cytokine treatment. To our knowledge, this is the first report demonstrating an IFN-mediated alteration in the electrophoretic mobility of integrin subunits. From this study, it was evident that the combination of IFN-gamma and TNF-alpha resulted in a block in G(1) phase for acinar cells before accumulation of the alpha 3 integrin variant or significant degenerative cellular changes. Information from the present and previous studies suggests that cytokines may alter the pattern of integrin expression and block cell cycle progression in salivary gland cells grown in three-dimensional acinarlike clusters. These experiments may provide a new cell culture model to study the effects of cytokines in normal and diseased salivary glands, including SS.

Evidence for antimuscarinic acetylcholine receptor antibody-mediated secretory dysfunction in nod mice

OBJECTIVE

Antibodies directed against general and specific target-organ autoantigens are present in the sera of human patients and animal models with autoimmune disease. The relevance of these autoantibodies to the disease process remains ambiguous in most cases. In autoimmune exocrinopathy (Sjögren's syndrome), autoantibodies to the intracellular nuclear proteins SSA/Ro and SSB/La, as well as the cell surface muscarinic cholinergic receptor (M3) are observed. To evaluate the potential role of these factors in the loss of secretory function of exocrine tissues, a panel of monoclonal and polyclonal antibodies was developed for passive transfer into the NOD animal model.

METHODS

Monoclonal antibodies to mouse SSB/La, rat M3 receptor, and a rabbit polyclonal antiparotid secretory protein antibody were obtained for this study. These antibody reagents were subsequently infused into NOD-scid mice. Saliva flow rates were subsequently monitored over a 72-hour period. Submandibular gland lysates were examined by Western blotting for alteration of the distribution of the water channel protein aquaporin (AQP).

RESULTS

Evaluation of the secretory response indicated that only antibodies directed toward the extracellular domains of the M3 receptor were capable of mediating the exocrine dysfunction aspect of the clinical pathology of the autoimmune disease. In vitro stimulation with a muscarinic agonist of submandibular gland cells isolated from mice treated with anti-M3 antibody, but not saline or the isotype control, failed to translocate AQP to the plasma membrane.

CONCLUSION

These findings define a clear role for the humoral immune response and the targeting of the cell surface M3 signal transduction receptor as primary events in the development of clinical symptoms of autoimmune exocrinopathy. Furthermore, the anti-M3 receptor activity may negatively affect the secretory response through perturbation of normal signal transduction events, leading to translocation of the epithelial cell water channel.

Cytokine-mediated stimulation of laminin expression and cell-growth arrest in a human submandibular gland duct-cell line (HSG)

Increased expression of laminin and various cytokines, including interferon-y (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) has been demonstrated in minor salivary glands from patients with Sjögren's syndrome. Previous reports state that exposure of a human salivary-gland cell line (HSG) to IFN-gamma results in cellular changes similar to those in vivo Sjögren's syndrome. To begin studies of the cause of increased laminin expression in salivary glands in Sjögren's syndrome and laminin's role in the pathological process, the effects of IFN-gamma on laminin expression and growth of HSG cells were examined here. Subconfluent cultures of HSG cells were treated or not with IFN-gamma (1000 units/ml) for 1, 3 or 6 days. Immunoprecipitation showed that the expression of cell-associated laminin was significantly greater in IFN-gamma-treated cells at 3 or 6 days than in untreated cells, while no significant differences in laminin counts precipitated from the media were evident among any of the IFN-gamma-treated or untreated samples. Western blot analysis strongly suggested that this immunoprecipitated product is a dimer of the beta- and gamma-chains of laminin. Intracellular laminin was demonstrated immunocytochemically in a distinct, perinuclear pattern in both cytokine-treated and untreated cells. However, only faint staining for type IV collagen, and no staining for fibronectin were evident in untreated and cytokine-treated cells. An RNase protection assay showed only slight upregulation of the laminin beta-chain mRNA at 3 days, but no significant difference at 6 days of treatment. Taken together, these data suggest enhanced accumulation of a dimer of laminin beta- and gamma-chains in the cytoplasm of cytokine-treated HSG cells. However, mRNA for glyceraldehyde 3-phosphate dehydrogenase was significantly reduced at 6 days of treatment, suggestive of cytokine-mediated metabolic abnormalities. IFN-gamma treatment also resulted in significant reductions in cell numbers over time, in agreement with previous reports. Treatment of HSG cells for 3 days with IFN-gamma (1000 U/ml) and TNF-alpha (20 U/ml) resulted in no significant changes in cell proliferation or laminin protein and/or mRNA species compared to cells treated with IFN-gamma alone. Karyotype analysis of HSG cells revealed human chromosomes with triploid chromosome numbers and rearrangements, characteristic of transformed cells. These data demonstrate that IFN-gamma increases the amount of intracellular laminin beta-gamma dimers while decreasing cell growth. Further studies are required to define an interaction between laminin expression and the growth and viability of HSG cells.

Tumor necrosis factor alpha and interferon gamma--induced cell growth arrest is mediated via insulin-like growth factor binding protein-3

Retinoic acid (RA), and the combination of TNFalpha and Interferon (IFN-gamma) inhibit human salivary gland tumor (HSG) cell growth with the combination of all three being even more inhibitory (P<0. 05). Previous studies have demonstrated that these inhibitory effects of RA, and the combination of TNFalpha and IFN-gamma are associated with increased accumulation of IGFBP-3 in the culture medium of HSG cells. Therefore, we set out to determine if the increase in IGFBP-3 was due to increased production of IGFBP-3 by the cells and whether IGFBP-3 played a causative role in the inhibition of cellular proliferation. TNFalpha and IFN-gamma induced a rise in IGFBP-3 mRNA levels between 4 and 8 h, which returned to control levels after 24 h. IGFBP-3 was shown to inhibit HSG cell growth at concentrations of >/=75 U (P<0.05). When antibodies to IGFBP-3 were used with TNFalpha and IFN-gamma, the inhibitory effect of the cytokines on cell growth was diminished. Retinoic acid with TNFalpha and IFN-gamma had a marked inhibitory effect (P<0.05) which was similarly reversed by increasing concentrations of IGFBP-3 antibody. The present data support the hypothesis that the combination of TNFalpha and IFN-gamma with retinoic acid exert their anti-proliferative effect on HSG cells by reducing the mitogenic effect of IGF-I due to a shift in IGF-I from the free to the IGFBP-3-bound form.

An alternative perspective to the immune response in autoimmune exocrinopathy: induction of functional quiescence rather than destructive autoaggression

Sjögren's syndrome is characterized by dryness of the eyes and the mouth due to mononuclear cell infiltration of the lacrimal and salivary glands. The aetiology is unknown but autoimmunity is considered to play a significant role in the pathogenesis. Recent studies have focused on the fact that tear and salivary flow involves an entire functional system that includes the mucosal surfaces with adnexes (the site of inflammation), efferent nerve signals sent to the midbrain (lacrimal and salivary response region), and afferent neural signals from the brain to the acinar/ductal epithelial structures in the gland. Mononuclear cell infiltration in exocrine glands can lead to glandular destruction, suggested to be mediated through apoptosis. However, the functional impairment of exocrine glands could be regulated by cytokines and/or antibodies against the muscarinic M3 receptor by inhibiting the neural stimulation of the residual glands. This review discusses the possibility that the pathogenesis of Sjögren's syndrome comprises aberrant immune-mediated neuro-hormonal events.

Characterization of a newly established human acinic cell adenocarcinoma cell line (HACC) originating from the salivary gland: morphological features and role of various growth factors on the growth of the HACC cell line

Human acinic cell adenocarcinoma cell (HACC) line was established from the pleural effusion that contains metastatic tumor cells of acinic cell adenocarcinoma of papillary and microcystic type originating from the parotid gland. The HACC cells grew in an adherent monolayer with a doubling time of 66 h. Implanted tumor of SCID mice revealed similar histological findings to that of the primary tumor. The HACC cells produced mucin and expressed epithelial markers as well as alpha1-antitrypsin and lysozyme, whereas salivary peptide P-C was expressed in cultured HACC cells but not in the primary and implanted HACC cell tumors. S-100 protein was also expressed in both the primary tumor and HACC cell line. Neither amplification of common oncogenes nor expression of p53 was observed. The receptor for epidermal growth factor (EGF) was expressed, indicating EGF and transforming growth factor-alpha (TGF-alpha) enhanced the growth of the HACC line. Unexpectedly, tumor necrosis factor-a (TNF-alpha) also enhanced the growth of the HACC line significantly. However, there was no evidence of autocrine growth using these growth factors. In contrast, TGF-beta1 inhibited the growth of the HACC cell line through apoptosis. The HACC cell line has features similar to both acinar and intercalated ductal cells of the salivary gland. Epidermal growth factor, TGF-alpha and TNF-alpha are potential growth factors for the HACC cell line. The HACC cell line may be a good model for studying the biological behavior of salivary gland neoplasms.

Interferon-gamma induces a decrease in the intracellular calcium pump in a human salivary gland cell line

Interferon-gamma (IFN-gamma) +/- tumor necrosis factor-alpha (TNF-alpha) induces antiproliferation and intracellular Ca2+ store depletion in a human submandibular ductal cell line (HSG), which can be reversed on cytokine removal [A. J. Wu, G. C. Chen, B. J. Baum, and I. S. Ambudkar. Am. J. Physiol. 270 (Cell Physiol. 39): C514-C521, 1996]. Here we have examined a possible mechanism for the IFN-gamma-induced intracellular Ca2+ store depletion. There was a time-dependent decrease in thapsigargin-dependent internal Ca2+ release after exposure of the cells to the cytokines. The intracellular Ca2+ pump [sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)] protein in lysates and membranes of cells treated with IFN-gamma +/- TNF-alpha, but not with TNF-alpha alone, showed a similar time-dependent decrease (examined using a SERCA2 antibody). Removal of the cytokines, which resulted in recovery of cell growth and refill of internal Ca2+ stores, also increased the level of SERCA protein. The decrease in SERCA is not a result of decreased cell proliferation, since thapsigargin, 2,5-di-(t-butyl)-1,4-hydroquinone, or serum-free growth conditions induced antiproliferative effects on HSG cells without any corresponding decrease in SERCA. We suggest that the IFN-gamma-induced decrease in the level of SERCA accounts for the depleted state of internal Ca2+ stores in cytokine-treated HSG cells. These data suggest a novel mechanism for the inhibition of HSG cell growth by IFN-gamma.

Interferon-gamma-induced JAK2 and STAT1 signalling in a human salivary gland cell line

We have used a human salivary gland cell line (HSG) as a possible in vitro model to evaluate the effects of IFN-gamma on human salivary gland epithelium (Wu et al., 1994, 1996, 1997). In the present study, we examined the JAK-STAT signal-transduction pathway in IFN-gamma-treated HSG cells. We demonstrate that JAK2 and Stat1 are phosphorylated at tyrosine residues in a time- and concentration-dependent manner following exposure to IFN-gamma. In addition, we show that activation of this signalling pathway is decreased by the addition of a blocking antibody to the IFN-gamma receptor. The same maneuver is also able to reduce by approximately 50-70% the surface expression of two IFN-gamma-induced immunoregulatory molecules: HLA-DR and ICAM-1. These results demonstrate that the JAK2 and Stat1 signalling pathway is active in salivary-derived epithelial cells and may contribute to their immunopathologic destruction.

In human salivary gland cells, overexpression of E2F1 overcomes an interferon-gamma- and tumor necrosis factor-alpha-induced growth arrest but does not result in complete mitosis

Increased levels of cytokines in the salivary glands have been associated with the loss of secretory cells and reduced salivary function. It has been demonstrated that interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) treatment of a human submandibular gland (HSG) cell line causes growth arrest in the G0/G1 phase of the cell cycle, followed by apoptosis. To stimulate DNA synthesis and reverse this growth arrest, we used an adenovirus vector to overexpress the transcription factor E2F1 in HSG cells. Initially, cells were synchronized by a double thymidine block and then infected with recombinant adenovirus (AdE2F1) expressing E2F1. Cells were harvested at intervals and analyzed by flow cytometry. Greater than 50% of synchronized cells infected with AdE2F1 were in S phase by 18 hours postinfection (hpi) compared to 12% of uninfected cells. Similarly, AdE2F1 infection of HSG cells arrested by IFN-gamma and TNF-alpha treatment caused a fivefold increase in S-phase cells by 48 hpi. However, by 72 hpi, AdE2F1-infected cells showed increases in the subdiploid cell population. Forty-one percent of AdE2F1-infected cells labeled positive by TUNEL, compared to fewer than 6% for controls. Additionally, AdE2F1-infected cells (84 hpi) had low forward-angle and high side scatter light characteristics, similar to apoptotic lymphocytes. These results suggest that E2F1 accumulation in growth-arrested salivary gland cells can stimulate DNA synthesis and overcome a G0/G1 block in the cell cycle. However, E2F1 overexpression did not lead to complete mitosis in HSG cells but, rather, diverted cells into an apoptotic pathway.

Modulation of MMP-2 (gelatinase A) and MMP-9 (gelatinase B) by interferon-gamma in a human salivary gland cell line

Gelatinases have been shown to be regulated by many cytokines and growth factors, and have been implicated in the pathogenesis of certain autoimmune diseases via tissue destruction. High levels of several cytokines, including IFN-gamma and TNF-alpha, have been demonstrated in the salivary gland microenvironment of patients with Sjogren's syndrome (SS). How these cytokines may be contributing to the pathogenesis of this disease is not well understood. We hypothesized that IFN-gamma with or without (+/-) TNF-alpha could be playing a role in the pathogenesis of SS via the regulation of matrix metalloproteinase (MMP) levels. This study examined the role of IFN-gamma and (+) TNF-alpha in the regulation of the matrix metalloproteinases, MMP-2 (72 kD gelatinase A) and MMP-9 (92 kD gelatinase B). A human salivary gland cell line (HSG) has been used as a possible in vitro model to study the role of IFN-gamma + TNF-alpha in the pathogenesis of SS. The HSG cell line, in the presence of IFN +/- TNF-alpha, displays increased MMP-2 and MMP-9 gelatinolytic activity, protein and RNA levels. The increase in MMP activity was partially blocked with an antibody against the IFN-gamma receptor, and this was associated with a complete inhibition of the previously described IFN-gamma +/- TNF-alpha antiproliferative effect. However, incubation of IFN-gamma treated HSG cells with the synthetic MMP inhibitor BB94 did not alleviate this antiproliferative effect. In addition, we demonstrate that there are very high levels of MMP-9 in the saliva of patients with SS when compared to healthy control subjects. These data suggest that cytokines could be regulating MMP production by salivary epithelial cells and thus indicate a potential role for these cells in the pathogenesis of SS.

Interferon-gamma induced cell death in a cultured human salivary gland cell line

Increased levels of several cytokines, including interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), have been demonstrated in the salivary gland microenvironment of patients with Sjögren's syndrome (SS). How these cytokines may be contributing to the pathogenesis of the disease is not well understood. This study examined the role of IFN-gamma +/- TNF-alpha on cellular death in a cultured human salivary gland cell line (HSG). Cells treated long-term with IFN-gamma +/- TNF-alpha demonstrate a profound antiproliferative effect with a decrease in cell number to below that initially plated. Treatment of HSG cells with TNF-alpha alone did not have any significant effects on growth but did increase the expression of the IFN-gamma receptor. Cells labelled with propidium iodide and anti-digoxigenin dUTP/dATP were examined by flow cytometry to determine the percentage of cells exhibiting low DNA content and DNA strand breaks. The percentage of cells exhibiting subdiploid DNA and DNA strand breaks increased with increased time of exposure to the cytokines. The maximum percentage of cells exhibiting DNA degradation at 12 days was 58% for cells treated with IFN-gamma + TNF-alpha, 31% for IFN-gamma treated cells, and < 5% for TNF-alpha-treated and untreated cells. The cells with subdiploid ( < 2n) DNA were subsequently demonstrated to represent two populations, both with evidence of increased DNA strand breaks but with differing light scatter characteristics. One population had features of cells undergoing necrosis, whereas the second population exhibited features of apoptosis. These findings were confirmed by transmission electron microscopy. Cells not exposed to cytokines did not exhibit significant evidence of either death process. We conclude that long-term exposure of a human salivary gland epithelial cell line to IFN-gamma +/- TNF-alpha leads to increased DNA degradation and subsequent cell death. This suggests a potential SS disease mechanism and implicates the role of the epithelial cell in this disease as an important area for future study.

Differences of reactivity to interferon gamma in HeLa and CaSki cells: a combined immunocytochemical and flow-cytometric study

We characterized the changes induced by treatment for 48 h with 100 U/ ml interferon gamma (IFN-gamma) on HeLa and CaSki cells, derived from human uterine carcinomas and containing human papillomavirus (HPV) type 16 and HPV type 18 respectively, by studying cell growth, cell morphology, the cell cycle and expression of epidermal growth factor (EGF) receptor, filaggrin-profilaggrin and MHC class II antigen, HLA-DR. The response of the two cell lines to IFN gamma differed in some cases. In both cell lines, the cells remained viable; cell growth was similarly inhibited as shown by cell counts. Signs of morphological changes were essentially observed in HeLa cells. The cell cycle phases, analyzed by flow cytometry were more disturbed in CaSki than in HeLa cells; the proportion of CaSki cells in S phase increased and those in G2 + M decreased. Expression of EGF receptors related to proliferation increased only in CaSki cells while expression of filaggrin-profilaggrin, a marker of differentiation, and HLA-DR, a marker of epithelial cell immune response, was enhanced in both cell lines. The presence of filaggrin-profilaggrin being unexpected in these cells, the specificity of the reaction with the monoclonal antibody AKH1 was confirmed by immunoblotting. In conclusion, our results show that the two cell lines reacted differently to IFN gamma although they are of similar origin and the different antigens studied may be useful to predict the progression of lesions infected with HPV towards malignancy or the reactivity to IFN gamma of such lesions. However, enhanced synthesis of EGF receptors is probably independent of the antiproliferative effect of IFN gamma but an increase in HLA-DR antigen expression by epithelial cells, which corresponds to an immune response favored by IFN gamma, could act synergistically with cell growth inhibition and differentiation to exclude tumoral and/or HPV-infected cells.

Current concepts of autoimmune exocrinopathy: immunologic mechanisms in the salivary pathology of Sjögren's syndrome

Sjögren's syndrome is a systemic autoimmune disorder characterized by symptoms of oral and ocular dryness and a chronic, progressive loss of salivary and lacrimal function. The exocrine involvement is the result of a focal, peri-ductal mononuclear cell infiltrate and the subsequent loss of secretory epithelial cells. The mechanisms of this autoimmune exocrinopathy are not understood fully. Many recent investigations have described alterations in a number of immune mediators within the salivary glands. These studies provide new insights into the immune regulation of normal salivary gland functions and the mechanisms of gland damage in Sjögren's syndrome.