Induction of TNF-alpha-converting enzyme-ectodomain shedding by pathogenic autoantibodies

Defective Efferocytosis in a Murine Model of Sjögren's Syndrome Is Mediated by Dysfunctional Mer Tyrosine Kinase Receptor

Sjögren's syndrome (SjS) is a chronic autoimmune disease primarily involving the exocrine glands in which the involvement of the innate immune system is largely uncharacterized. Mer signaling has been found to be protective in several autoimmune diseases but remains unstudied in SjS. Here, we investigated the role of Mer signaling in SjS. Mer knockout (MerKO) mice were examined for SjS disease criteria. SjS-susceptible (SjS^S) C57BL/6.NOD-Aec1Aec2 mice were assessed for defective Mer signaling outcomes, soluble Mer (sMer) levels, A disintegrin and metalloprotease 17 (ADAM17) activity, and Rac1 activation. In addition, SjS patient plasma samples were evaluated for sMer levels via ELISA, and sMer levels were correlated to disease manifestations. MerKO mice developed submandibular gland (SMG) lymphocytic infiltrates, SMG apoptotic cells, anti-nuclear autoantibodies (ANA), and reduced saliva flow. Mer signaling outcomes were observed to be diminished in SjS^S mice, as evidenced by reduced Rac1 activation in SjS^S mice macrophages in response to apoptotic cells and impaired efferocytosis. Increased sMer was also detected in SjS^S mouse sera, coinciding with higher ADAM17 activity, the enzyme responsible for cleavage and inactivation of Mer. sMer levels were elevated in patient plasma and positively correlated with focus scores, ocular staining scores, rheumatoid factors, and anti-Ro60 levels. Our data indicate that Mer plays a protective role in SjS, similar to other autoimmune diseases. Furthermore, we suggest a series of events where enhanced ADAM17 activity increases Mer inactivation and depresses Mer signaling, thus removing protection against the loss of self-tolerance and the onset of autoimmune disease in SjS^S mice.

Injection of CD40 DNA vaccine ameliorates the autoimmune pathology of non-obese diabetic mice with Sjögren's syndrome

BACKGROUND

Overexpression of CD40 has been reported in patients with primary Sjögren's syndrome (pSS). The increased CD40 expression promote autoimmune response and enhance inflammation in pSS. The aim of this study is to block CD40-CD154 interaction with CD40 DNA vaccine to slow the disease progression of SS in non-obese diabetic (NOD) mice.

METHODS

Female NOD mice were treated with CD40 DNA vaccine, empty vector and normal saline. The salivary flow rate was measured, whereas lymphocytes infiltration in the salivary glands was assessed by histopathology. Expression of CD40 and B220 in salivary were examined by immunohistochemistry. Splenic lymphocyte phenotypes were analyzed by flow cytometry. CD40, IL-1β, TNF-α and IL-6 levels in the salivary glands were detected by PCR. Serum anti-CD40 antibody was measured by ELISA. Serum anti-nuclear antibody (ANA) was monitored by immunofluorescence.

RESULTS

NOD mice treated with CD40 DNA vaccine showed higher levels of anti-CD40 antibody compared with the controls. The expression of CD40 in the salivary glands of NOD mice in CD40 DNA vaccine group was decreased. The infiltration of lymphocytes was reduced in the salivary glands and saliva secretion was increased in the treatment group. The expression level of TNF-α and IL-6 in salivary glands were declined. The splenic dendritic cell and plasma cell populations were reduced and the level of ANA was decreased in NOD mice with CD40 DNA vaccine treatment.

CONCLUSIONS

CD40 DNA vaccine inhibits the immune response and reduce inflammation in epithelial tissues SS in non-obese diabetic (NOD) mice, suggesting that CD40 DNA vaccine could be a new therapeutic approach in treatment of pSS.

Interaction between TNF and BmooMP-Alpha-I, a Zinc Metalloprotease Derived from Bothrops moojeni Snake Venom, Promotes Direct Proteolysis of This Cytokine: Molecular Modeling and Docking at a Glance

Tumor necrosis factor (TNF) is a major cytokine in inflammatory processes and its deregulation plays a pivotal role in several diseases. Here, we report that a zinc metalloprotease extracted from Bothrops moojeni venom (BmooMP-alpha-I) inhibits TNF directly by promoting its degradation. This inhibition was demonstrated by both in vitro and in vivo assays, using known TLR ligands. These findings are supported by molecular docking results, which reveal interaction between BmooMP-alpha-I and TNF. The major cluster of interaction between BmooMP-alpha-I and TNF was confirmed by the structural alignment presenting Ligand Root Mean Square Deviation LRMS = 1.05 Å and Interactive Root Mean Square Deviation IRMS = 1.01 Å, this result being compatible with an accurate complex. Additionally, we demonstrated that the effect of this metalloprotease on TNF is independent of cell cytotoxicity and it does not affect other TLR-triggered cytokines, such as IL-12. Together, these results indicate that this zinc metalloprotease is a potential tool to be further investigated for the treatment of inflammatory disorders involving TNF deregulation.

ADAM17 at the interface between inflammation and autoimmunity

The discovery of the disintegrin and metalloproteinase 17 (ADAM17), originally identified as tumor necrosis factor-a converting enzyme (TACE) for its ability as sheddase of TNF-α inspired scientists to attempt to elucidate the molecular mechanisms underlying ADAM17 implication in diseased conditions. In recent years, it has become evident that this protease can modify many non matrix substrates, such as cytokines (e.g. TNF-α), cytokine receptors (e.g. IL-6R and TNF-R), ligands of ErbB (e.g. TGF-α and amphiregulin) and adhesion proteins (e.g. Lselectin and ICAM-1). Several recent studies have described experimental model system to better understand the role of specific signaling molecules, the interplay of different signals and tissue interactions in regulating ADAM17-dependent cleavage of most relevant substrates in inflammatory diseases. The central question is whether ADAM17 can influence the outcome of inflammation and if so, how it performs this regulation in autoimmunity, since inflammatory autoimmune diseases are often characterized by deregulated metalloproteinase activities. This review will explore the latest research on the influence of ADAM17 on the progression of inflammatory processes linked to autoimmunity and its role as modulator of inflammation.

Salivary gland expression level of IκBα regulatory protein in Sjögren's syndrome

Diagnosis and therapeutic strategies in Sjögren's syndrome (SS) might greatly benefit of the present multidisciplinary approach to studying the molecular pathogenesis of the disease. A deregulated inflammatory response has been described in the SS. The research in the last years sheds light on the importance of the NF-κB pathway regulating the pro-inflammatory cytokine production and leukocyte recruitment. These are important contributors to the inflammatory response during the development of SS. In this study we examine the expression of the NF-κB inhibitory protein termed IκBα in salivary glands epithelial cells (SGEC) comparing it with SGEC from healthy controls, to test the hypothesis that an altered expression of IκBα occurs in SGEC from SS biopsies. Real-Time PCR, western blot and immunohistochemistry demonstrated that the expression level of IκBα was significantly lower in SS with respect to healthy controls leading to an increased NF-κB activity. Our results suggest that the analysis of IκBα expression at salivary gland epithelial cell level could be a potential new hallmark of SS progression and sustain a rationale to more deeply investigate the therapeutic potential of specific NF-κB inhibitors in SS.

Sjögren's syndrome pathological neovascularization is regulated by VEGF-A-stimulated TACE-dependent crosstalk between VEGFR2 and NF-κB

We explore the involvement of tumor necrosis factor α (TNF-α)-converting enzyme (TACE) in vascular endothelial growth factor (VEGF) and its receptor 2 (VEGFR2) (VEGF-A/VEGFR2)-mediated angiogenesis in Sjögren's syndrome (SS), one of the most common autoimmune rheumatic diseases. To test the hypothesis that SS autoantibodies (Abs) regulate VEGF-A/VEGFR2 expression by a TACE-dependent nuclear factor-κB (NF-κB) activation pathway, their effects on the expression and activation of the VEGF-A/TACE/VEGFR2/NF-κB pathway were determined in human salivary gland epithelial cells (SGEC). An enhanced angiogenesis in SS salivary gland biopsies was observed, associated with an increased VEGF-A expression and activation of VEGF-A/VEGFR2 signaling. Human cytokine array analysis of the pro-inflammatory and pro-angiogenic protein response in SGEC treated with SS Abs revealed an overexpression of multiple pro-angiogenic factors. TACE RNA knockdown, the use of anti-VEGF-A monoclonal antibody and the inhibition of NF-κB activity significantly abrogated the release of pro-angiogenic factors, demonstrating that VEGF-A/TACE/VEGFR2/NF-κB axis dysfunction may be contributory to pathogenesis and exacerbation of this autoimmune condition.

A failure of TNFAIP3 negative regulation maintains sustained NF-κB activation in Sjögren's syndrome

Sjögren's syndrome (SS) is characterized by the features of systemic autoimmunity and exocrine gland dysfunction and inflammation. Deregulated cytokine production is known to contribute to the etiology of SS but the underlying molecular mechanism is still remains to be unclear. TNF-α-induced protein 3 or TNFAIP3 is involved in the negative feedback regulation of nuclear factor-κB (NF-κB) signaling in response to specific pro-inflammatory stimuli in different cell types. To define the contribution of TNFAIP3 to SS, the levels of TNFAIP3 expression in human salivary gland epithelial cells (SGEC) derived from active primary SS patients were analyzed. Histological analysis was performed on paraffin-embedded human Sjögren's samples and healthy tissues. In separate experiments, immunofluorescence staining, western blot analysis and quantitative real-time PCR for TNFAIP3 was conducted in SGEC from SS and healthy subjects. Our findings clearly demonstrate changes in levels of the protein and gene expression between healthy controls and SS patients, depicting a very weak positivity for TNFAIP3 in SS samples. TNFAIP3 was found down-regulated in SGECs derived from SS patients in comparison with controls, and the cells with down-regulated TNFAIP3 expression exhibited enhanced NF-κB activities. In addition, to investigate the role of TNFAIP3 in the activation of NF-κB, we depleted TNFAIP3 expression by siRNA in healthy SGEC after treatment with or without TNF-α. Intriguingly, the silencing of TNFAIP3 by its siRNA in healthy SGEC increased NF-κB activation that could explain the deregulated cytokines production observed in SS.

RETRACTED: Blockade of TNF-α signaling suppresses the AREG-mediated IL-6 and IL-8 cytokines secretion induced by anti-Ro/SSA autoantibodies

The aim of this study was to analyze the Furin-TNF-α-converting enzyme (TACE)-amphiregulin (AREG)-IL-6/IL-8 secretion pathway in non-neoplastic human salivary gland epithelial cells (SGECs) stimulated with anti-Ro/SSA autoantibodies (Abs). We examined whether anti-Ro/SSA Abs-mediated TACE activation is responsible for AREG activation. As recent studies have demonstrated that AREG could induce proinflammatory cytokines secretion in epithelial cells, we discuss how TACE-mediated AREG shedding, caused by anti-Ro/SSA Abs treatment, could have a critical role in TNF-α-induced IL-6 and IL-8 secretion by SGEC. Furthermore, the effects of TNF-α blockade on AREG expression and TNF-α-AREG-mediated IL-6 and IL-8 secretion were evaluated. We have discovered that the upregulation of AREG occurs through TNF-α produced after anti-Ro/SSA Abs uptake via Fcγ receptors. Biological drug adalimumab and the gene silencing technique were used to study the AREG-IL-6/IL-8 secretion pathway, demonstrating that (i) adalimumab-mediated TNF-α blocking and TNF-α gene silencing provoke a significant decrease of proinflammatory cytokines production and AREG expression in anti-Ro/SSA Abs-treated SGEC; (ii) AREG gene silencing has a potent inhibitory effect on TNF-α-induced IL-6 and IL-8 secretion in SGEC treated with anti-Ro/SSA Abs; (iii) an inspection of the kinetics of cytokine production after exogeni TNF-α and AREG addition, and the use of cycloheximide in the presence of exogenous TNF-α as stimulant, clarified that TNF-α induces IL-6 and IL-8 secretion through AREG.Laboratory Investigation advance online publication, 20 September 2010; doi:10.1038/labinvest.2010.168.

Expression of pro-inflammatory TACE-TNF-α-amphiregulin axis in Sjögren's syndrome salivary glands

The tumor-necrosis-factor-converting-enzyme (TACE)-TNF-α-Amphiregulin (AREG) axis plays an important pathogenic role in inflammatory and autoimmune disorders. However, the pathological roles of these proteins in the chronic autoimmune disease Sjögren's syndrome (SS) remain to be elucidated. It is known that the TACE-AREG axis is clearly part of a larger cascade of signals that starts with the activation of Furin, responsible for maturation of TACE that, in turn, determines the production of active TNF-α, directly involved in the up-regulation of AREG expression. This study showed that Furin, TACE, TNF-α, and AREG proteins, detected in acinar and ductal cells of human salivary glands from SS patients, increased remarkably in comparison with biopsies of labial salivary glands from healthy controls. The changes in Furin, TACE, TNF- α, and AREG proteins' level detected in salivary glands biopsies of SS patients could be responsible for pro-inflammatory cytokines overexpression characterizing Sjögren's syndrome.