Fas and Fas-mediated effects on a human salivary cell line in vitro: a model for immune-mediated exocrine damage in Sjögren's syndrome

A re-evaluation of anti-NA-14 antibodies in patients with primary Sjögren's syndrome: Significant role of interferon-γ in the production of autoantibodies against NA-14

Novel autoantibodies against nuclear antigen of 14 kDa (NA-14)/Sjögren's syndrome nuclear antigen-1 (SSNA-1) are predominantly recognized in sera of patients with primary Sjögren's syndrome (pSS). However, the detailed characteristics of the anti-NA-14 antibody remain unknown. Here, we sought to clarify the characteristics of anti-SSNA-1/NA-14 antibodies and the mechanisms of autoantibody production using sera from patients with connective tissue diseases (including pSS), autoimmune sera reacting with standard autoantigens (SS-A/Ro and/or SS-B/La, ds DNA, Scl-70 and Jo-1), and normal healthy controls (NHCs). Anti-NA-14 antibodies were predominantly recognized in sera from patients with pSS and in autoimmune sera reacting with thSS-A/Ro and/or -SS-B/Lo. Indirect immunofluorescence analysis showed that NA-14 was strongly expressed in mitotic-phase cells. Patients with pSS having anti-NA-14 antibodies exhibited significant elevation of serum IP-10 and BAFF compared to that in patients with pSS without anti-NA-14 antibodies and NHCs. Thus, our data demonstrated that anti-NA-14 antibodies could be classified as novel autoantibodies reacting with mitosis-related autoantigens predominantly recognized in pSS. Moreover, interferon-γ played an important role in the production of anti-NA-14 autoantibodies as patients with pSS having anti-NA-14 antibodies exhibited increased serum levels of IP-10 and BAFF.

Interferons in Sjögren's Syndrome: Genes, Mechanisms, and Effects

Sjögren’s syndrome (SS) is a common, progressive autoimmune exocrinopathy distinguished by dry eyes and mouth and affects ∼0.7% of the European population. Overexpression of transcripts induced by interferons (IFN), termed as an “IFN signature,” has been found in SS patients. Four microarray studies have been published in SS that identified dysregulated genes within type I IFN signaling in either salivary glands or peripheral blood of SS patients. The mechanism of this type I IFN activation is still obscure, but several possible explanations have been proposed, including virus infection-initiated and immune complex-initiated type I IFN production by plasmacytoid dendritic cells. Genetic predisposition to increased type I IFN signaling is supported by candidate gene studies showing evidence for association of variants within IFN-related genes. Once activated, IFN signaling may contribute to numerous aspects of SS pathophysiology, including lymphocyte infiltration into exocrine glands, autoantibody production, and glandular cell apoptosis. Thus, dysregulation of IFN pathways is an important feature that can be potentially used as a serum biomarker for diagnosis and targeting of new treatments in this complex autoimmune disease.

p38 mitogen-activated protein kinase and nuclear factor-κB facilitate CD40-mediated salivary epithelial cell death

OBJECTIVE

Our previous studies indicated that CD40-mediated Fas-dependent apoptosis is important for the glandular destruction of Sjögren's syndrome (SS), although other immune and nonimmune mechanisms are also involved in exocrine dysfunction. We investigated the roles of p38 mitogen-activated protein kinase (p38MAPK) and nuclear factor-κB (NF-κB) in salivary epithelial cell death in SS.

METHODS

Expression of p38, phosphorylated p38 (pp38), and IκB-α was examined by Western blotting upon CD40 ligation. Activity of NF-κB induced by anti-CD40 monoclonal antibody (mAb) was examined by electrophoretic mobility shift assay (EMSA) and Western blotting. Expression of Fas was analyzed by flow cytometry and Western blotting with or without the p38-specific inhibitor SB203580 or the NF-κB-specific inhibitor caffeic acid phenethyl ester (CAPE). Induction of apoptosis in salivary epithelial cells was examined by DNA fragmentation and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay. Expression of phosphorylated p38MAPK and NF-κB was measured by immunohistochemistry.

RESULTS

pp38MAPK and NF-κB p65 were predominantly expressed in the ductal and acinar epithelium adjacent to lymphoid infiltrates of SS salivary gland by immunohistochemistry. CD40 ligation strongly enhanced p38MAPK and NF-κB activity by EMSA and Western blotting in cultured salivary epithelial cells. Treatment of cells with anti-CD40 mAb resulted in significantly upregulated Fas expression and induction of Fas-dependent apoptosis. Inhibition of p38MAPK and NF-κB activity by SB203580 and/or CAPE reduced Fas expression and apoptosis in salivary epithelial cells, establishing p38MAPK and NF-κB as proapoptotic factors in this context.

CONCLUSION

CD40 ligation plays an important role in activation of p38MAPK, NF-κB, and Fas molecules to initiate proapoptotic signaling. p38MAPK and NF-κB collaborate in regulation of proapoptotic signaling in CD40-mediated Fas-dependent apoptosis in salivary epithelial cells.

Proinflammatory cytokines tumor necrosis factor-alpha and interferon-gamma alter tight junction structure and function in the rat parotid gland Par-C10 cell line

Sjögren's syndrome (SS) is an autoimmune disorder characterized by inflammation and dysfunction of salivary glands, resulting in impaired secretory function. The production of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) is elevated in exocrine glands of patients with SS, although little is known about the effects of these cytokines on salivary epithelial cell functions necessary for saliva secretion, including tight junction (TJ) integrity and the establishment of transepithelial ion gradients. The present study demonstrates that chronic exposure of polarized rat parotid gland (Par-C10) epithelial cell monolayers to TNF-alpha and IFN-gamma decreases transepithelial resistance (TER) and anion secretion, as measured by changes in short-circuit current (I(sc)) induced by carbachol, a muscarinic cholinergic receptor agonist, or UTP, a P2Y(2) nucleotide receptor agonist. In contrast, TNF-alpha and IFN-gamma had no effect on agonist-induced increases in the intracellular calcium concentration [Ca(2+)](i) in Par-C10 cells. Furthermore, treatment of Par-C10 cell monolayers with TNF-alpha and IFN-gamma increased paracellular permeability to normally impermeant proteins, altered cell and TJ morphology, and downregulated the expression of the TJ protein, claudin-1, but not other TJ proteins expressed in Par-C10 cells. The decreases in TER, agonist-induced transepithelial anion secretion, and claudin-1 expression caused by TNF-alpha, but not IFN-gamma, were reversible by incubation of Par-C10 cell monolayers with cytokine-free medium for 24 h, indicating that IFN-gamma causes irreversible inhibition of cellular activities associated with fluid secretion in salivary glands. Our results suggest that cytokine production is an important contributor to secretory dysfunction in SS by disrupting TJ integrity of salivary epithelium.

Fas single nucleotide polymorphisms and risk of thyroid and salivary gland carcinomas: A case-control analysis

BACKGROUND

The purpose of this study was to examine the association between 4 Fas single nucleotide polymorphisms (SNPs) and risk of differentiated thyroid carcinoma (DTC) and salivary gland carcinoma (SGC).

METHODS

We conducted a case-control study including 279 DTC cases, 165 benign thyroid disease (BTD) cases, 154 SGC cases, 61 benign salivary gland disease (BSGD) cases, and 510 controls.

RESULTS

The A744G SNP genotype distribution was significantly different between subjects with SGC or BSGD and controls, while that of the A18272G SNP was significantly different between subjects with DTC or SGC and controls. Risk of SGC was significantly elevated for the 22628 heterozygous CT genotype (odds ratio [OR] = 1.5, p = .050), and risk of BSGD was elevated for the 22628 homozygous TT genotype (OR = 2.9, p = .023).

CONCLUSION

Fas C22628T SNP may be associated with risk of SGC and BSGD, but none of the investigated Fas SNPs was associated with risk of DTC.

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

Sjögren's Syndrome (SS) is a chronic autoimmune disease characterized by histological and functional alterations of salivary and lacrimal glands that result in a severe dryness of the mouth and the eyes. The etiology of SS has remained undefined despite investigators' significant efforts to identify the mechanisms of initiation. Based on histopathology, several animal models are available--such as MRL/lpr, NZW/NZB, NFS/sld, graft vs. host, transgenic mouse expressing viral surface antigen, and the non-obese diabetic (NOD) mouse--for investigation of the etiology of SS. Biochemical and immunological similarities between human SS and autoimmune exocrinopathy (AEC) in the NOD mouse, including the loss of secretory function, establish the NOD mouse as an appropriate model to unravel the underlying pathophysiology of SS. Recently, several NOD congenic partner strains have been developed to investigate the roles of genetic intervals, cytokines, and autoantibodies in the disease pathogenesis. Studies on NOD-scid suggest that the pathogenesis of SS occurs in two phases: an asymptomatic phase, in which epithelial cells of exocrine tissues undergo dedifferentiation accompanied by elevated apoptosis; and a second phase in which autoaggression is mounted against target organ autoantigens, resulting in the activation of T- and B-cells, and the generation of autoantibodies. The presence of autoantibodies on the cell-surface signaling receptor, the muscarinic(3) receptor, in both SS patients and the NOD mice correlates with the hallmark clinical symptom of secretory dysfunction. Additionally, the NOD mouse model provides an important example of how both Th1 and Th2 cytokines, as well as non-immune genetic loci, are involved in the maintenance of and progression to the overt disease state. Ultimately, analysis of these data provides insight into potentially novel therapeutic interventions.

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.

Mechanism of Fas-mediated cell death and its enhancement by TNF-alpha in human salivary gland adenocarcinoma cell line HSG

Fas-mediated cell death in a human salivary gland adenocarcinoma cell line (HSG) was induced by treatment of the cells with agonistic anti-Fas antibody (CH-11), and this cell death was enhanced by pretreatment with tumor necrosis factor alpha (TNF-alpha). The mode of cell death was apoptosis, because it was accompanied by caspase activation and the cleavage of poly(ADP-ribose) polymerase. The TNF-alpha treatment of the cells increased the expression of Fas, which was accompanied by the activation of nuclear factor kappaB (NFkappaB). These results suggest that the enhancement of the apoptosis caused by TNF-alpha resulted from increased sensitivity of the HSG cells to CH-11-mediated apoptosis due to induction of Fas protein by TNF-alpha via the activation of NFkappaB. In order to elucidate the apoptosis signaling pathway, we examined the effect of various caspase inhibitors on the apoptosis induced by CH-11. Fas-mediated apoptosis of HSG cells was slightly inhibited by the caspase-9 inhibitor although it was mainly inhibited by that for caspase-8. Based on this finding, we consider CH-11-induced apoptosis in HSG cells to be mainly mediated by the type I death signaling pathway that is caused by a caspase cascade initiated by the activation of caspase-8 at the death-inducing signaling complex (DISC).

Regulation of apoptotic cell death by cytokines in a human salivary gland cell line: distinct and synergistic mechanisms in apoptosis induced by tumor necrosis factor alpha and interferon gamma

We examined the mechanisms of apoptosis in a human salivary gland (HSG) cell line induced by tumor necrosis factor (TNF) alpha and interferon (IFN) gamma. DNA fragmentation and the activation of caspase-3 were determined in HSG cells cultured with TNF-alpha or IFN-gamma. Mitochondrial dysfunction also appeared to be involved in the process because a disruption of mitochondrial transmembrane potential with the activation of caspase-9 was demonstrated in TNF-alpha- and IFN-gamma-stimulated HSG cells. Activation of caspase-8 was thought to be essential in TNF-alpha--induced apoptosis of HSG cells; however, the activation of caspase-8 was not involved in IFN-gamma-induced apoptosis of HSG cells. In contrast, Bcl-2 appeared to be an indispensable regulatory molecule in IFN-gamma-induced, but not in TNF-alpha-induced, apoptosis of HSG cells because its expression was inhibited in IFN-gamma-stimulated, but not in TNF-alpha-stimulated, cells. The inhibitory effect of IFN-gamma in Bcl-2 expression was enhanced by coadministration of TNF-alpha and, interestingly, apoptosis of HSG cells, as assessed by DNA fragmentation and the activation of caspase-9 and caspase-3, and disruption of mitochondrial transmembrane potential was also synergistically augmented by TNF-alpha and IFN-gamma. Our results suggest that cytokines expressed in the salivary glands of patients with Sjögren syndrome play an important role in regulating apoptosis of acinar-ductal epithelial cells through distinct and synergistic mechanisms, thereby modulating salivary gland function in patients with Sjögren syndrome.

Pathogenetic factors in Sjögren's syndrome: recent developments

The study of pathogenetic factors in Sjögren's syndrome [SS] has been problematic, given the overall paucity of coherent data that integrate basic research with clinical findings. The presumed autoimmune nature of SS suggests T-cells, autoantibodies, and cytokines as possible immune factors in the initiation and progression of SS. Recent work on programmed cell death (apoptosis) in SS and its models suggests this as a fourth potential mechanism of disease. These four areas of SS research are reviewed with an emphasis on the most recent findings related to mechanisms of disease. New findings confirm the potential for antigen presentation to T-cells in the salivary glands, as well as involvement of other adhesion molecules with respect to T-cell functions. Restrictions on the receptor repertoires of infiltrating T-cells are discussed, as are new findings on antigenic specificities of these cells. New findings on the specificities of autoantibodies observed in SS are reviewed with an eye toward potential mechanisms for depression of exocrine secretory capacity. Stimulating new findings concerning cytokine production in salivary and lacrimal gland are noted. Particular points of interest with regard to apoptosis include the wide range of values obtained for apoptotic activity in SS and its models, and potential means of resolving discongruent results and the study of factors influencing apoptosis are discussed.

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.

Treatment of chronic sialadenitis in a murine model of Sjögren's syndrome by local fasL gene transfer

OBJECTIVE

Infection of Fas (Fas/CD95)-mutant C57BL/6 (B6)-lpr/lpr mice with murine cytomegalovirus (MCMV) leads to a chronic sialadenitis similar to that of Sjögren's syndrome (SS). The aim of this study was to evaluate whether chronic sialadenitis would also occur in Fas ligand (FasL/CD95L)-mutant B6-gld/gld mice upon infection with MCMV and whether the expression of FasL by local gene transfer using recombinant adenoviral vectors would be an effective therapeutic strategy.

METHODS

B6-gld/gld mice were infected intraperitoneally with MCMV, and salivary glands were analyzed histologically at different time points. For treatment of sialadenitis, recombinant adenoviral vectors expressing the fasL gene (AdLoxpFasL + AxCANCre) or the lacZ gene (AdCMVLacZ) were locally injected into the salivary glands of MCMV-infected B6-gld/gld mice and uninfected B6-+/+ and B6-gld/gld mice.

RESULTS

Following MCMV infection, B6-gld/gld mice developed an acute and chronic sialadenitis characterized by multiple foci of infiltrating T cells. After local injection of adenoviral vectors, high levels of lacZ or fasL gene expression could be detected in acinar and ductal cells. Treatment of acute and chronic sialadenitis in B6-gld/gld mice with local fasL gene transfer resulted in a significant reduction in the number of inflammatory foci and tissue destruction in salivary glands compared with mice treated with AdCMVLacZ. Despite high levels of FasL expression after injection of recombinant vectors, <5% of ductal and acinar cells were TUNEL positive, demonstrating that, in this model of SS, acinar and ductal cells were not highly sensitive to FasL-mediated apoptosis.

CONCLUSION

Chronic sialadenitis similar to that of SS developed in B6-gld/gld mice after MCMV infection. FasL expression was reconstituted by local gene transfer, resulting in significant reduction of infiltrating mononuclear cells, which indicates that local gene transfer of fasL might be a novel treatment for chronic sialadenitis.

A case of cytophagic histiocytic panniculitis associated with exertional rhabdomyolysis

An 18-year-old man who suffered from panniculitis involving the entire left lower limb after exertional rhabdomyolysis is reported. A high fever (>39 degrees C) and leukocytosis (>20,000/microL) persisted for 1 week, and his general status deteriorated rapidly into pre-disseminated intravascular coagulation, complicated by pleural effusion and prolonged clotting time. His condition was dramatically improved by steroid pulse therapy and he has remained in good health for the 20 months since discharge. Histologic examination of subcutaneous tissue from the swollen left lower limb revealed pleomorphic small, medium or large lymphocytes, macrophages and neutrophils infiltrating the edematous subcutaneous adipose tissue in a lobular panniculitis-like pattern. The majority of inflammatory cells were T lymphocytes, with equal proportions of CD4+ and CD8+ cells. As polymerase chain reaction did not show bands suggesting T cell receptor gamma gene rearrangement, the proliferation of T lymphocytes was considered to be polyclonal. The T lymphocytes also expressed Fas ligand, suggesting the involvement of Fas-mediated cytotoxicity. This case may represent a new category of cytophagic histiocytic panniculitis induced by exertional rhabdomyolysis.