Interleukin-17 and -22 synergy linking inflammation and EMT-dependent fibrosis in Sjögren's syndrome

G protein-coupled receptor kinase 2 as a novel therapeutic target for gland fibrosis of Sjögren's syndrome

Sjogren's syndrome (SS) is a chronic, progressive autoimmune disorder characterized by gland fibrosis. We previously found a close correlation between gland fibrosis and the expression of G protein-coupled receptor kinase 2 (GRK2). In this study we explored the pathological and therapeutic significance of GRK2 in SS. Submandibular gland (SMG) antigen-induced SS mouse model was established in WT and GRK2+/- mice. We showed that the expression levels of GRK2 were significantly up-regulated in glandular tissue and positively correlated with fibrotic morphology in SS patients and mice. Hemizygous knockout of GRK2 significantly inhibited the gland fibrosis. In mouse salivary gland epithelial cells (SGECs), we demonstrated that GRK2 interacted with Smad2/3 to positively regulate the activation of TGF-β-Smad signaling with a TGF-β-GRK2 positive feedback loop contributing to gland fibrosis. Hemizygous knockout of GRK2 attenuated TGF-β-induced collagen I production in SGECs in vitro and hindered gland fibrosis in murine SS though preventing Smad2/3 nuclear translocation. Around 28 days post immunization with SMG antigen, WT SS mice were treated with a specific GRK2 inhibitor paroxetine (Par, 5 mg·kg-1·d-1, i.g. for 19 days). We found that Par administration significantly attenuated gland fibrosis and alleviated the progression of SS in mice. We conclude that genetic knockdown or pharmacological inhibition of GRK2 significantly attenuates gland fibrosis and alleviates the progression of SS. GRK2 binds to Smad2/3 and positively regulates the activation of TGF-β-Smad signaling. A TGF-β-GRK2 positive feedback loop contributes to gland fibrosis. Our research points out that GRK2 could be a promising therapeutic target for treating SS.

Exploring Salivary Epithelial Dysfunction in Sjögren's Disease

Sjögren's Disease (SjD) is an autoimmune disease of the exocrine tissues. Etiological events result in the loss of epithelial homeostasis alongside extracellular matrix (ECM) destruction within the salivary and lacrimal glands, followed by immune cell infiltration. In this review, we have assessed the current understanding of epithelial-mesenchymal transition (EMT)-associated changes within the salivary epithelium potentially involved in salivary dysfunction and SjD pathogenesis. We performed a PubMed literature review pertaining to the determination of pathogenic events that lead to EMT-related epithelial dysfunction and signaling in SjD. Molecular patterns of epithelial dysfunction in SjD salivary glands share commonalities with EMT mediating wound healing. Pathological changes altering salivary gland integrity and function may precede direct immune involvement while perpetuating MMP9-mediated ECM destruction, inflammatory mediator expression, and eventual immune cell infiltration. Dysregulation of EMT-associated factors is present in the salivary epithelium of SjD and may be significant in initiating and perpetuating the disease. In this review, we further highlight the gap regarding mechanisms that drive epithelial dysfunction in salivary glands in the early or subclinical pre-lymphocytic infiltration stages of SjD.

The role of epithelial cells in fibrosis: Mechanisms and treatment

Fibrosis is a pathological process that affects multiple organs and is considered one of the major causes of morbidity and mortality in multiple diseases, resulting in an enormous disease burden. Current studies have focused on fibroblasts and myofibroblasts, which directly lead to imbalance in generation and degradation of extracellular matrix (ECM). In recent years, an increasing number of studies have focused on the role of epithelial cells in fibrosis. In some cases, epithelial cells are first exposed to external physicochemical stimuli that may directly drive collagen accumulation in the mesenchyme. In other cases, the source of stimulation is mainly immune cells and some cytokines, and epithelial cells are similarly altered in the process. In this review, we will focus on the multiple dynamic alterations involved in epithelial cells after injury and during fibrogenesis, discuss the association among them, and summarize some therapies targeting changed epithelial cells. Especially, epithelial mesenchymal transition (EMT) is the key central step, which is closely linked to other biological behaviors. Meanwhile, we think studies on disruption of epithelial barrier, epithelial cell death and altered basal stem cell populations and stemness in fibrosis are not appreciated. We believe that therapies targeted epithelial cells can prevent the progress of fibrosis, but not reverse it. The epithelial cell targeting therapies will provide a wonderful preventive and delaying action.

Targeting Interleukin-17 as a Novel Treatment Option for Fibrotic Diseases

Fibrosis is the end result of persistent inflammatory responses induced by a variety of stimuli, including chronic infections, autoimmune reactions, and tissue injury. Fibrotic diseases affect all vital organs and are characterized by a high rate of morbidity and mortality in the developed world. Until recently, there were no approved antifibrotic therapies. In recent years, high levels of interleukin-17 (IL-17) have been associated with chronic inflammatory diseases with fibrotic complications that culminate in organ failure. In this review, we provide an update on the role of IL-17 in fibrotic diseases, with particular attention to the most recent lines of research in the therapeutic field represented by the epigenetic mechanisms that control IL-17 levels in fibrosis. A better knowledge of the IL-17 signaling pathway implications in fibrosis could design new strategies for therapeutic benefits.

Extracellular matrix turnover in salivary gland disorders and regenerative therapies: Obstacles and opportunities

Salivary gland (SG) extracellular matrix (ECM) has a major influence on tissue development, homeostasis, and tissue regeneration after injury. During aging, disease, and physical insult, normal remodeling of the SG microenvironment (i.e. ECM) becomes dysregulated, leading to alterations in matrix composition which disrupt tissue architecture/structure, alter cell activity, and negatively impact gland function. Matrix metalloproteinases (MMPs) are a large and diverse family of metalloendopeptidases which play a major role in matrix degradation and are intimately involved in regulating development and cell function; dysregulation of these enzymes leads to the production of a fibrotic matrix. In the SG this altered fibrotic ECM (or cell microenvironment) negatively impacts normal cell function and the effectiveness of gene and stem cell therapies which serve as a foundation for many SG regenerative therapies. For this reason, prospective regenerative strategies should prioritize the maintenance and/or restoration of a healthy SG ECM. Mesenchymal stem cells (MSCs) have great potential for mitigating damage to the SG microenvironment by ameliorating inflammation, reducing fibrosis, and repairing the damaged milieu of extracellular regulatory cues, including the matrix. This review addresses our current understanding of the impact of aging and disease on the SG microenvironment and suggests critical deficiencies and opportunities in ECM-targeted therapeutic interventions.

Interleukin-22 Inhibits Apoptosis of Gingival Epithelial Cells Through TGF-β Signaling Pathway During Periodontitis

Periodontitis is a chronic inflammatory disease characterized by the destruction of tooth-supporting tissues. The gingival epithelium is the first barrier of periodontal tissue against oral pathogens and harmful substances. The structure and function of epithelial lining are essential for maintaining the integrity of the epithelial barrier. Abnormal apoptosis can lead to the decrease of functional keratinocytes and break homeostasis in gingival epithelium. Interleukin-22 is a cytokine that plays an important role in epithelial homeostasis in intestinal epithelium, inducing proliferation and inhibiting apoptosis, but its role in gingival epithelium is poorly understood. In this study, we investigated the effect of interleukin-22 on apoptosis of gingival epithelial cells during periodontitis. Interleukin-22 topical injection and Il22 gene knockout were performed in experimental periodontitis mice. Human gingival epithelial cells were co-cultured with Porphyromonas gingivalis with interleukin-22 treatment. We found that interleukin-22 inhibited apoptosis of gingival epithelial cells during periodontitis in vivo and in vitro, decreasing Bax expression and increasing Bcl-xL expression. As for the underlying mechanisms, we found that interleukin-22 reduced the expression of TGF-β receptor type II and inhibited the phosphorylation of Smad2 in gingival epithelial cells during periodontitis. Blockage of TGF-β receptors attenuated apoptosis induced by Porphyromonas gingivalis and increased Bcl-xL expression stimulated by interleukin-22. These results confirmed the inhibitory effect of interleukin-22 on apoptosis of gingival epithelial cells and revealed the involvement of TGF-β signaling pathway in gingival epithelial cell apoptosis during periodontitis.

Involvement of Epithelial-Mesenchymal Transition (EMT) in Autoimmune Diseases

Epithelial-mesenchymal transition (EMT) is a complex reversible biological process characterized by the loss of epithelial features and the acquisition of mesenchymal features. EMT was initially described in developmental processes and was further associated with pathological conditions including metastatic cascade arising in neoplastic progression and organ fibrosis. Fibrosis is delineated by an excessive number of myofibroblasts, resulting in exuberant production of extracellular matrix (ECM) proteins, thereby compromising organ function and ultimately leading to its failure. It is now well acknowledged that a significant number of myofibroblasts result from the conversion of epithelial cells via EMT. Over the past two decades, evidence has accrued linking fibrosis to many chronic autoimmune and inflammatory diseases, including systemic sclerosis (SSc), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), and inflammatory bowel diseases (IBD). In addition, chronic inflammatory states observed in most autoimmune and inflammatory diseases can act as a potent trigger of EMT, leading to the development of a pathological fibrotic state. In the present review, we aim to describe the current state of knowledge regarding the contribution of EMT to the pathophysiological processes of various rheumatic conditions.

Epithelial-mesenchymal transition in the lacrimal gland morphogenesis, damage and repair

Epithelial-mesenchymal transition (EMT) constitutes an important pathway in organ fibrosis seen in the lungs, liver, eye, and salivary glands. This review summarizes the EMT observed within the lacrimal gland during its development, tissue damage and repair along with possible translational implications. Existing animal and human studies have reported the increased expression of EMT regulators i.e., transcription factors like Snail, TGF-β1 within the lacrimal glands, and a possible role of reactive oxygen species, which might be initiating the cascade of EMT. In these studies, EMT is typically detected by reduced E-cadherin expression in the epithelial cells and increased Vimentin and Snail expression within the lacrimal glands' myoepithelial or ductal epithelial cells. Other than specific markers, electron microscopic evidence of disrupted basal lamina, increased collagen deposition, reorganised cytoskeleton of myoepithelial cells also indicated EMT. Very few studies have shown myoepithelial cells to be the cells transitioning into mesenchymal cells with increased extracellular matrix deposition within the lacrimal glands. EMT in animal models seemed reversible as glands got repaired after damage with IL-1α injection or duct ligation and transiently used the EMT as a means for tissue repair. The EMT cells also expressed nestin, a marker for progenitor cells in a rabbit duct ligation model. However, lacrimal glands of ocular graft versus host disease and IgG4 dacryoadenitis demonstrate irreversible acinar atrophy along with signs of EMT-fibrosis, reduced E-cadherin, and increased Vimentin and Snail expression. Future studies exploring the molecular mechanisms of EMT and thereby developing targeted therapies capable of transforming the mesenchymal cells into epithelial cells or blocking the EMT might help in the restoration of the lacrimal gland function.

The Role of IL-17 in the Pathogenesis of Oral Squamous Cell Carcinoma

Elucidating the inflammatory mechanisms underlying formation and progression of oral squamous cell carcinoma (OSCC) is crucial for discovering new targeted therapeutics. The proinflammatory cytokine IL-17 has proven roles in tumor formation, growth, and metastasis. The presence of IL-17 is demonstrated in both in vitro and in vivo models, and in OSCC patients, is mostly accompanied by enhanced proliferation and invasiveness of cancer cells. Here we review the known facts regarding the role of IL-17 in OSCC pathogenesis, namely the IL-17 mediated production of proinflammatory mediators that mobilize and activate myeloid cells with suppressive and proangiogenic activities and proliferative signals that directly induce proliferation of cancer cells and stem cells. The possibility of a potential IL-17 blockade in OSCC therapy is also discussed.

Primary-Sjögren's-Syndrome-Related Interstitial Lung Disease: A Clinical Review Discussing Current Controversies

Lung involvement, especially interstitial lung disease, is a potentially severe extra-glandular manifestation of Primary Sjogren's Syndrome (pSS-ILD). ILD can manifest either as a late complication of pSS or anticipate sicca symptoms, likely reflecting two different patho-physiological entities. Presence of lung involvement in pSS subjects can remain subclinical for a long time; therefore, patients should be actively screened, and lung ultrasound is currently being investigated as a potential low cost, radiation-free, easily repeatable screening tool for detection of ILD. In contrast, rheumatologic evaluation, serology testing, and minor salivary gland biopsy are crucial for the recognition of pSS in apparently idiopathic ILD patients. Whether the HRCT pattern influences prognosis and treatment response in pSS-ILD is not clear; a UIP pattern associated with a worse prognosis in some studies, but not in others. Many aspects of pSS-ILD, including its actual prevalence, association with specific clinical-serological characteristics, and prognosis, are still debated by the current literature, likely due to poor phenotypic stratification of patients in clinical studies. In the present review, we critically discuss these and other clinically relevant "hot topics" in pSS-ILD. More specifically, after a focused discussion, we compiled a list of questions regarding pSS-ILD that, in our opinion, are not easily answered by the available literature. We subsequently tried to formulate adequate answers on the basis of an extensive literature search and our clinical experience. At the same, we highlighted different issues that require further investigation.

Anti-vimentin antibodies are associated with higher severity of Sjögren's disease

Vimentin is a ubiquitously present Type III intermediate filament protein, often targeted by autoimmune responses in multiple rheumatic disorders. Although previous studies have reported anti-vimentin antibodies in Sjögren's disease (SjD) patients, the clinical significance of such antibodies is unknown. To address this issue, the presence of anti-vimentin antibodies was determined in serum samples from a well-characterized cohort of primary SjD patients, non-SjD Sicca, and healthy controls. The occurrence of anti-vimentin antibodies and their association with different clinical features of the disease were evaluated. Anti-vimentin antibodies were detected in 24% of primary SjD patients, compared to 4% in non-SjD sicca patients and 3% in healthy controls. In primary SjD patients, higher levels of anti-vimentin antibodies were significantly associated with reduced saliva and tear flow and severe ocular surface damage indicators. The anti-vimentin antibody levels did not show significant associations with the presence or absence of other autoantibodies like ANA, RF, and anti-Ro/La. Our data suggest that the anti-vimentin antibody specificity arises in a subset of primary SjD patients and is associated with oral and ocular features of the disease. Anti-vimentin can potentially serve as a novel biomarker for evaluating the severity of salivary and lacrimal gland dysfunction in primary SjD.

The Role of Endothelial Barrier Function in the Fibrosis of Salivary Gland

In the salivary glands, fibrosis occurs in many pathological conditions. Endothelial tight junction (TJ)-based barrier function plays a vital role in maintaining the homeostasis of the salivary glands. However, whether endothelial barrier function is changed and involved in the pathogenesis of glandular fibrosis is unknown. Here, by using a mouse model in which the main excretory duct of the submandibular gland (SMG) was ligated to induce inflammation and fibrosis, endothelial barrier function and TJ protein expression and distribution were examined. Both 4-kDa and 70-kDa fluorescence-labeled dextrans permeated more in the 1-, 3-, and 7-d ligated SMGs. Meanwhile, the mRNA level of claudin-5 was increased with an obvious redistribution from apicolateral membranes to lateral membranes and cytoplasm in the fibrotic glands. Notably, the TJ sealer AT1001 significantly attenuated the disrupted endothelial barrier function and thereby ameliorated the glandular fibrosis. Cytokine array detection showed that monocyte chemoattractant protein-1 (MCP-1) was highly enriched in the 3-d ligated SMGs, and MCP-1 directly impaired barrier function, increased claudin-5 expression, induced the relocalization of claudin-5, and activated p-ERK1/2 in cultured human endothelial cells. Furthermore, the upregulation and disorganization of claudin-5 as well as the elevation of MCP-1 and p-ERK1/2 signaling were also confirmed in fibrotic SMGs from patients with chronic sialadenitis and immunoglobulin G4-related sialadenitis. Altogether, our findings revealed that disrupted endothelial barrier function contributed to the progression of glandular fibrosis, and targeting endothelial TJs might be a promising approach to alleviate salivary gland fibrosis-related diseases.

Oestrogen-induced epithelial-mesenchymal transition (EMT) in endometriosis: Aetiology of vaginal agenesis in Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome

Endometriosis occurs when endometrial-like tissue forms and grows outside the uterus due to oestrogen-induced epithelial-mesenchymal transition in the female reproductive tract. Factors that suppress this event could become potential therapeutic agents against disease occurrence and progression. However, an overview of these studies is still lacking. This review assessed the impact of a number factors on oestrogen-mediated epithelial-mesenchymal transition in the emergence of several diseases in the female reproductive tract, primarily endometriosis. The association between epithelial-mesenchymal transition and Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome was also investigated. Oestrogen, Wnt4 and epithelial-mesenchymal transition were chosen as keywords in Scopus, PubMed, and Web of Science searches performed on 28th June 2021. Study selection was refined to cancer-irrelevant, English, original articles published between years 2011-2021. The full-text assessment was carried out for topic-related articles after title and abstract screening. Included studies were summarised and assessed for their risk of bias using the Office of Health Assessment and Translation tool. In this review, 10 articles investigating oestrogen and epithelial-mesenchymal transition in the female reproductive tract were summarised and classified into two groups: seven studies under 'factor'-modulated epithelial-mesenchymal transition and three studies under 'factor'-manipulated oestrogen-induced epithelial-mesenchymal transition. The current evidence proposes that epithelial-mesenchymal transition is one of the prime causes of reproductive-related disease. This event could be mediated by distinct stimuli, specifically oestrogen and Wnt4 aberration. The results of this review suggest that oestrogen and Wnt4 participate in epithelial-mesenchymal transition in vaginal epithelial cells in MRKH syndrome, adopting from the theories of endometriosis development, which could therefore serve as a foundation for novel target treatment, specifically related to vaginal epithelialisation, to ensure better surgical outcomes.

Molecular Mechanisms Linking Inflammation to Autoimmunity in Sjögren's Syndrome: Identification of New Targets

Sjögren's syndrome (SS) is a systemic autoimmune rheumatic disorder characterized by the lymphocytic infiltration of exocrine glands and the production of autoantibodies to self-antigens. The involvement of the exocrine glands drives the pathognomonic manifestations of dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) that define sicca syndrome. To date, the molecular mechanisms mediating pathological salivary gland dysfunction in SS remain to be elucidated, despite extensive studies investigating the underlying cause of this disease, hampering the development of novel therapeutic strategies. Many researchers have identified a multifactorial pathogenesis of SS, including environmental, genetic, neuroendocrine, and immune factors. In this review, we explore the latest developments in understanding the molecular mechanisms involved in the pathogenesis of SS, which have attracted increasing interest in recent years.

The Expression of Follistatin-like 1 Protein Is Associated with the Activation of the EMT Program in Sjögren’s Syndrome

Background: The activation of the epithelial to mesenchymal transition (EMT) program is a pathological response of the Sjögren’s syndrome (SS) salivary glands epithelial cells (SGEC) to chronic inflammation. Follistatin-like 1 protein (FSTL1) is a secreted glycoprotein induced by transforming growth factor-β1 (TGF-β1), actively involved in the modulation of EMT. However, the role of FSTL1 in the EMT program activation in SS has not yet been investigated. Methods: TGF-β1-stimulated healthy human SGEC, SS SGEC, and SS salivary glands (SGs) biopsies were used to assess the effect of FSTL1 on the activation of the EMT program. FSTL1 gene activity was inhibited by the siRNA gene knockdown technique. Results: Here we reported that FSTL1 is up-regulated in SS SGs tissue in a correlated manner with the inflammatory grade. Blockage of FSTL1 gene expression by siRNA negatively modulates the TGF-β1-induced EMT program in vitro. We discovered that these actions were mediated through the modulation of the SMAD2/3-dependent EMT signaling pathway. Conclusions: Our data suggest that the TGF-β1-FSTL1-SMAD2/3 regulatory circuit plays a key role in the regulation of EMT in SS and targeting FSTL1 may be a strategy for the treatment of SGs EMT-dependent fibrosis.

Composition and regulation of the immune microenvironment of salivary gland in Sjögren’s syndrome

Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease characterized by exocrine gland dysfunction and inflammation. Patients often have dry mouth and dry eye symptoms, which seriously affect their lives. Improving dry mouth and eye symptoms has become a common demand from patients. For this reason, researchers have conducted many studies on external secretory glands. In this paper, we summarize recent studies on the salivary glands of pSS patients from the perspective of the immune microenvironment. These studies showed that hypoxia, senescence, and chronic inflammation are the essential characteristics of the salivary gland immune microenvironment. In the SG of pSS, genes related to lymphocyte chemotaxis, antigen presentation, and lymphocyte activation are upregulated. Interferon (IFN)-related genes, DNA methylation, sRNA downregulation, and mitochondrial-related differentially expressed genes are also involved in forming the immune microenvironment of pSS, while multiple signaling pathways are involved in regulation. We further elucidated the regulation of the salivary gland immune microenvironment in pSS and relevant, targeted treatments.

Mesenchymal stem cell transplantation alleviates Sjögren's syndrome symptoms by modulating Tim-3 expression

Mesenchymal stem cell (MSC) transplantation has been proven to be an effective treatment for Sjögren's syndrome (SS) to improve salivary gland pathology and exocrine function, but the mechanism remains unclear. A recently reported inhibitory receptor, Tim-3, also appears to be closely related to autoimmune diseases. Here, we aimed to explore the roles of Tim-3 in the pathogenesis of SS and MSC treatment. The results showed that Tim-3 was downregulated in T cells of SS patients and nonobese diabetic (NOD) mice, which is correlated with SS pathogenesis. MSC transplantation ameliorated SS-like symptoms and pathological changes in the submandibular glands with modulated Tim-3 expression, resulting in attenuation of localized inflammation, fibrosis, and epithelial-mesenchymal transition. Furthermore, Tim-3 is crucial for the inhibitory effect of MSCs on PBMC proliferation in vitro. Therefore, our work has demonstrated that MSC transplantation effectively mitigates the pathological changes of SS by regulating Tim-3 expression, which provides a novel mechanism of MSC treatment and indicates a brand-new perspective of the combination of inhibitory-receptor-targeted treatment and MSC therapy in SS.

Th17 Activation and Th17/Treg Imbalance in Prolonged Anterior Intraocular Inflammation after Ocular Alkali Burn

Ocular alkali burn (OAB) is a sight-threatening disease with refractory ocular inflammation causing various blinding complications. Th17 lymphocytes account for the pathogeneses of the autoimmune disease and chronic inflammation, but their role in prolonged anterior intraocular inflammation after OAB is still unknown. A rat OAB model was established for this purpose. Anterior intraocular inflammation was observed in both the acute and late phases of OAB, and histological examination confirmed the presence of inflammatory cell infiltration and fibrin exudation in the anterior segment. Luminex xMAP technology and qPCR were used to evaluate the intraocular levels of cytokines. The levels of IL-1β, IL-6, and TNF-α were significantly elevated during the acute phase. The expression of IL-17A gradually increased from day 7 onwards and remained at a relatively high level. Immunofluorescence was performed to identify Th17 cells. CD4 and IL-17A double positive cells were detected in the anterior chamber from days 7 to 28. Flow cytometry showed that the frequency of Th17 cells increased in both lymph nodes and spleen, while the frequency of Treg cells remained unchanged, resulting in an elevated Th17/Treg ratio. The present study suggests that Th17 activation and Th17/Treg imbalance account for prolonged anterior intraocular inflammation after OAB.

Sjögren's Syndrome-Related Organs Fibrosis: Hypotheses and Realities

Sjögren's syndrome (SS) is a systemic chronic autoimmune disorder characterized by lymphoplasmacytic infiltration of salivary glands (SGs) and lacrimal glands, causing glandular damage. The disease shows a combination of dryness symptoms found in the oral cavity, pharynx, larynx, and vagina, representing a systemic disease. Recent advances link chronic inflammation with SG fibrosis, based on a molecular mechanism pointing to the epithelial to mesenchymal transition (EMT). The continued activation of inflammatory-dependent fibrosis is highly detrimental and a common final pathway of numerous disease states. The important question of whether and how fibrosis contributes to SS pathogenesis is currently intensely debated. Here, we collect the recent findings on EMT-dependent fibrosis in SS SGs and explore clinical evidence of multi-organ fibrosis in SS to highlight potential avenues for therapeutic investigation.

Fisetin suppresses cigarette smoke extract-induced epithelial to mesenchymal transition of airway epithelial cells through regulating COX-2/MMPs/β-catenin pathway

Cigarette smoke exposure leads to upregulation of cyclooxygenase-2 (COX-2), an inducible enzyme that synthesizes prostaglandin E2 (PGE2) and promotes airway inflammation. COX-2 overexpression is frequently implicated in inflammation, invasion, metastasis, and epithelial-mesenchymal transition (EMT). However, its detailed molecular mechanism in cigarette smoke induced EMT is not clear. Further, fisetin, a bioflavonoid, exhibits antioxidant and anti-inflammatory properties, but its effect in modulating COX-2-mediated inflammation and downstream sequelae remains unexplored. Therefore, we have investigated the mechanism of cigarette smoke-induced COX-2-mediated EMT in airway epithelial cells and examined the role of fisetin in controlling this aberration. MTT, trypan blue staining, gelatin zymography, Western blotting, invasion, wound healing, and tumor sphere formation assays in cigarette smoke extract (CSE) and/or fisetin treated airway epithelial cells, and in-silico molecular docking studies were performed. Results revealed that CSE exposure increased the expression and activity of COX-2, MMP-2/9, and β-catenin and also enhanced expression of EMT markers leading to higher migration and invasion potential of airway epithelial cells. A specific COX-2 inhibitor NS-398 as well as fisetin treatment reversed the expression of EMT biomarkers, reduced the activity of MMP-2/9, and blocked the migration and invasion potential induced by CSE. Further, PGE2 also increased MMPs activity, invasion, and migration potential similar to CSE, which were significantly reversed by fisetin. In-silico studies showed a high binding affinity of fisetin to key EMT associated proteins, validating its anti-EMT potential. Thus, our study firstly unearths the mechanism of CSE-induced EMT in airway epithelial cells via COX-2/MMP/β-catenin pathway, and secondly, it reveals that fisetin could significantly reverse CSE-induced EMT by inhibiting COX-2, indicating that fisetin could be an effective drug candidate for cigarette smoke-induced lung dysfunction.

Akt Signaling Pathway Is Activated in the Minor Salivary Glands of Patients with Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune exocrinopathy of mainly the salivary and lacrimal glands associated with high prevalence of lymphoma. Akt is a phosphoinositide-dependent serine/threonine kinase, controlling numerous pathological processes, including oncogenesis and autoimmunity. Herein, we sought to examine its implication in pSS pathogenesis and related lymphomagenesis. The expression of the entire and activated forms of Akt (partially and fully activated: phosphorylated at threonine-308 (T308) and serine-473 (S473), respectively), and two of its substrates, the proline-rich Akt-substrate of 40 kDa (PRAS40) and FoxO1 transcription factor has been immunohistochemically examined in minor salivary glands (MSG) of pSS patients (n = 29; including 9 with pSS-associated lymphoma) and sicca-complaining controls (sicca-controls; n = 10). The entire and phosphorylated Akt, PRAS40, and FoxO1 molecules were strongly, uniformly expressed in the MSG epithelia and infiltrating mononuclear cells of pSS patients, but not sicca-controls. Morphometric analysis revealed that the staining intensity of the fully activated phospho-Akt-S473 in pSS patients (with or without lymphoma) was significantly higher than sicca-controls. Akt pathway activation was independent from the extent or proximity of infiltrates, as well as other disease features, including lymphoma. Our findings support that the Akt pathway is specifically activated in MSGs of pSS patients, revealing novel therapeutic targets.

Targeted Therapy for Primary Sjögren's Syndrome: Where are We Now?

Primary Sjögren's syndrome (pSS) is an autoimmune exocrinopathy characterized by dryness symptoms. This review briefly describes recent advances in the targeted therapies for pSS. Biologics evaluated for pSS treatment mainly include B cell-depleting agents, inhibitors of B cell activation, and agents that target co-signaling molecules or proinflammatory cytokines. Small molecule inhibitors that target signaling pathways have also been evaluated. However, current evidence for the efficacy of targeted therapies in pSS is still sparse. Although ianalumab (an anti-B cell-activating factor [BAFF]-receptor antibody) and iscalimab (an anti-CD40 antibody) are promising biologics for pSS, their efficacy still needs to be evaluated in larger clinical trials. For other biologics, clinical trials have found no differences versus placebo in the change from baseline in European League Against Rheumatism Sjögren's Syndrome Disease Activity Index (ESSDAI) score and fatigue score. Possible causes of the disappointing outcomes mainly include the inefficacy of those evaluated biologics in treating pSS, the high heterogeneous nature of pSS, irreversible exocrine glandular failure at advanced disease stages, inappropriate recruitment strategy in clinical trials, and outcome measures. Early diagnosis and glandular function-centered outcome measures may help to improve the current situation in the systemic therapy of pSS.

Molecular Mechanism of Sphingosine-1-Phosphate Receptor 1 Regulating CD4+ Tissue Memory in situ T Cells in Primary Sjogren's Syndrome

Objective

Although extensive research has been carried out on CD4⁺T cells infiltrating the labial glands in patients with primary Sjögren’s Syndrome (pSS), it is still unclear how CD4⁺T cells remain in the labial gland tissue and develop into tissue resident cells. The aim of this study was to investigate the molecular mechanism by which CD4⁺T reside in labial glandular tissue of pSS patients.

Methods

Lymphocyte infiltration in labial salivary glands (LSG) of pSS patients was detected by H&E staining. Expression of sphingosine-1-phosphate receptor 1 (S1PR1) in LSG was examined by Immunohistochemistry. Immunofluorescence analyses were utilized to detect the co-expression of CD4, CD69 and S1PR1 in T cells of LSG of pSS patients. Expression of gene S1pr1 in peripheral blood CD4⁺T cells of healthy controls and pSS patients was detected by quantitative real-time PCR (QPCR). QPCR was used to examine the expression of gene S1pr1, Klf2, and Cd69 in the CD4⁺T cells that were co-cultured in vitro with cytokines TNF-α, TGF-β, and IL-33.

Results

S1PR1 was expressed in the infiltrating monocytes in LSG of pSS patients, and S1PR1 was weakly or even not expressed in cytoplasm of CD4⁺CD69⁺T_RM cells of LSG in patients with pSS. Expression of gene S1pr1 in peripheral blood CD4⁺T cells of pSS patients was about three-fifths of that of healthy controls (P < 0.05). Expression of genes S1pr1 (P < 0.001) and Klf-2 (P < 0.001) was significantly decreased, and the expression of gene Cd69 (P < 0.05) was significantly increased in peripheral blood CD4⁺T cells of pSS patients co-cultured in vitro with cytokines TNF-α, TGF-β, and IL-33.

Conclusion

Our study suggests that the decrease of S1pr1 gene expression may provide a molecular basis for promoting the tissue retention and development of CD4⁺CD69⁺T_RM cells.

The Th17/IL-17 Axis and Kidney Diseases, With Focus on Lupus Nephritis

Systemic lupus erythematosus (SLE) is a disease characterized by dysregulation and hyperreactivity of the immune response at various levels, including hyperactivation of effector cell subtypes, autoantibodies production, immune complex formation, and deposition in tissues. The consequences of hyperreactivity to the self are systemic and local inflammation and tissue damage in multiple organs. Lupus nephritis (LN) is one of the most worrying manifestations of SLE, and most patients have this involvement at some point in the course of the disease. Among the effector cells involved, the Th17, a subtype of T helper cells (CD4+), has shown significant hyperactivation and participates in kidney damage and many other organs. Th17 cells have IL-17A and IL-17F as main cytokines with receptors expressed in most renal cells, being involved in the activation of many proinflammatory and profibrotic pathways. The Th17/IL-17 axis promotes and maintains repetitive tissue damage and maladaptive repair; leading to fibrosis, loss of organ architecture and function. In the podocytes, the Th17/IL-17 axis effects include changes of the cytoskeleton with increased motility, decreased expression of health proteins, increased oxidative stress, and activation of the inflammasome and caspases resulting in podocytes apoptosis. In renal tubular epithelial cells, the Th17/IL-17 axis promotes the activation of profibrotic pathways such as increased TGF-β expression and epithelial-mesenchymal transition (EMT) with consequent increase of extracellular matrix proteins. In addition, the IL-17 promotes a proinflammatory environment by stimulating the synthesis of inflammatory cytokines by intrinsic renal cells and immune cells, and the synthesis of growth factors and chemokines, which together result in granulopoiesis/myelopoiesis, and further recruitment of immune cells to the kidney. The purpose of this work is to present the prognostic and immunopathologic role of the Th17/IL-17 axis in Kidney diseases, with a special focus on LN, including its exploration as a potential immunotherapeutic target in this complication.

IL-17 drives salivary gland dysfunction via inhibiting TRPC1-mediated calcium movement in Sjögren's syndrome

Objectives

This study aims to determine a role of interleukin‐17A (IL‐17) in salivary gland (SG) dysfunction and therapeutic effects of targeting IL‐17 in SG for treating autoimmune sialadenitis in primary Sjögren’s syndrome (pSS).

Methods

Salivary IL‐17 levels and IL‐17‐secreting cells in labial glands of pSS patients were examined. Kinetic changes of IL‐17‐producing cells in SG from mice with experimental Sjögren’s syndrome (ESS) were analysed. To determine a role of IL‐17 in salivary secretion, IL‐17‐deficient mice and constructed chimeric mice with IL‐17 receptor C (IL‐17RC) deficiency in non‐hematopoietic and hematopoietic cells were examined for saliva flow rates during ESS development. Both human and murine primary SG epithelial cells were treated with IL‐17 for measuring cholinergic activation‐induced calcium movement. Moreover, SG functions were assessed in ESS mice with salivary retrograde cannulation of IL‐17 neutralisation antibodies.

Results

Increased salivary IL‐17 levels were negatively correlated with saliva flow rates in pSS patients. Both IL‐17‐deficient mice and chimeric mice with non‐hematopoietic cell‐restricted IL‐17RC deficiency exhibited no obvious salivary reduction while chimeric mice with hematopoietic cell‐restricted IL‐17RC deficiency showed significantly decreased saliva secretion during ESS development. In SG epithelial cells, IL‐17 inhibited acetylcholine‐induced calcium movement and downregulated the expression of transient receptor potential canonical 1 via promoting Nfkbiz mRNA stabilisation. Moreover, local IL‐17 neutralisation in SG markedly attenuated hyposalivation and ameliorated tissue inflammation in ESS mice.

Conclusion

These findings identify a novel function of IL‐17 in driving salivary dysfunction during pSS development and may provide a new therapeutic strategy for targeting SG dysfunction in pSS patients.

SMADS-Mediate Molecular Mechanisms in Sjögren's Syndrome

There is considerable interest in delineating the molecular mechanisms of action of transforming growth factor-β (TGF-β), considered as central player in a plethora of human conditions, including cancer, fibrosis and autoimmune disease. TGF-β elicits its biological effects through membrane bound serine/threonine kinase receptors which transmit their signals via downstream signalling molecules, SMADs, which regulate the transcription of target genes in collaboration with various co-activators and co-repressors. Until now, therapeutic strategy for primary Sjögren’s syndrome (pSS) has been focused on inflammation, but, recently, the involvement of TGF-β/SMADs signalling has been demonstrated in pSS salivary glands (SGs) as mediator of the epithelial-mesenchymal transition (EMT) activation. Although EMT seems to cause pSS SG fibrosis, TGF-β family members have ambiguous effects on the function of pSS SGs. Based on these premises, this review highlights recent advances in unravelling the molecular basis for the multi-faceted functions of TGF-β in pSS that are dictated by orchestrations of SMADs, and describe TGF-β/SMADs value as both disease markers and/or therapeutic target for pSS.

NK Cells in Autoimmune Diseases: Protective or Pathogenic?

Autoimmune diseases generally result from the loss of self-tolerance (i.e., failure of the immune system to distinguish self from non-self), and are characterized by autoantibody production and hyperactivation of T cells, which leads to damage of specific or multiple organs. Thus, autoimmune diseases can be classified as organ-specific or systemic. Genetic and environmental factors contribute to the development of autoimmunity. Recent studies have demonstrated the contribution of innate immunity to the onset of autoimmune diseases. Natural killer (NK) cells, which are key components of the innate immune system, have been implicated in the development of multiple autoimmune diseases such as systemic lupus erythematosus, type I diabetes mellitus, and autoimmune liver disease. However, NK cells have both protective and pathogenic roles in autoimmunity depending on the NK cell subset, microenvironment, and disease type or stage. In this work, we review the current knowledge of the varied roles of NK cell subsets in systemic and organic-specific autoimmune diseases and their clinical potential as therapeutic targets.

Organ Fibrosis and Autoimmunity: The Role of Inflammation in TGFβ-Dependent EMT

Recent advances in our understanding of the molecular pathways that control the link of inflammation with organ fibrosis and autoimmune diseases point to the epithelial to mesenchymal transition (EMT) as the common association in the progression of these diseases characterized by an intense inflammatory response. EMT, a process in which epithelial cells are gradually transformed to mesenchymal cells, is a major contributor to the pathogenesis of fibrosis. Importantly, the chronic inflammatory microenvironment has emerged as a decisive factor in the induction of pathological EMT. Transforming growth factor-β (TGF-β), a multifunctional cytokine, plays a crucial role in the induction of fibrosis, often associated with chronic phases of inflammatory diseases, contributing to marked fibrotic changes that severely impair normal tissue architecture and function. The understanding of molecular mechanisms underlying EMT-dependent fibrosis has both a basic and a translational relevance, since it may be useful to design therapies aimed at counteracting organ deterioration and failure. To this end, we reviewed the recent literature to better elucidate the molecular response to inflammatory/fibrogenic signals in autoimmune diseases in order to further the specific regulation of EMT-dependent fibrosis in more targeted therapies.

Interleukin-22 and connective tissue diseases: emerging role in pathogenesis and therapy

Interleukin-22 (IL-22), a member of the IL-10 family of cytokines, is produced by a number of immune cells involved in the immune microenvironment of the body. IL-22 plays its pivotal roles by binding to the IL-22 receptor complex (IL-22R) and subsequently activating the IL-22R downstream signalling pathway. It has recently been reported that IL-22 also contributes to the pathogenesis of many connective tissue diseases (CTDs). In this review, we will discuss the role of IL-22 in several CTDs, such as system lupus erythematosus, rheumatoid arthritis, Sjögren’s syndrome, systemic sclerosis and dermatomyositis, suggesting that IL-22 may be a potential therapeutic target in CTDs.

Primary Breast Extranodal Marginal Zone Lymphoma in Primary Sjögren Syndrome: Case Presentation and Relevant Literature

The association between autoimmune diseases, mostly rheumatoid arthritis, systemic lupus erythematosus, celiac disease and Sjögren syndrome, and lymphoma, has been widely demonstrated by several epidemiologic studies. By a mechanism which has not yet been entirely elucidated, chronic activation/stimulation of the immune system, along with the administration of specific treatments, may lead to the onset of different types of lymphoma in such patients. Specifically, patients affected by Sjögren syndrome may develop lymphomas many years after the original diagnosis. Several epidemiologic, hematologic, and histological features may anticipate the progression from Sjögren syndrome into lymphoma but, to the best of our knowledge, a definite pathogenetic mechanism for such progression is still missing. In fact, while the association between Sjögren syndrome and non-Hodgkin lymphoma, mostly extranodal marginal zone lymphomas and, less often, diffuse large B-cell, is well established, many other variables, such as time of onset, gender predilection, sites of occurrence, subtype of lymphoma, and predictive factors, still remain unclear. We report on a rare case of primary breast lymphoma occurring three years after the diagnosis of Sjögren syndrome in a 57-year-old patient. The diagnostic work-up, including radiograms, core needle biopsy, and histological examination, is discussed, along with emerging data from the recent literature, thus highlighting the usefulness of breast surveillance in Sjögren syndrome patients.

TGF-β Pathway in Salivary Gland Fibrosis

Fibrosis is presented in various physiologic and pathologic conditions of the salivary gland. Transforming growth factor beta (TGF-β) pathway has a pivotal role in the pathogenesis of fibrosis in several organs, including the salivary glands. Among the TGF-β superfamily members, TGF-β1 and 2 are pro-fibrotic ligands, whereas TGF-β3 and some bone morphogenetic proteins (BMPs) are anti-fibrotic ligands. TGF-β1 is thought to be associated with the pro-fibrotic pathogenesis of sialadenitis, post-radiation salivary gland dysfunction, and Sjögren’s syndrome. Potential therapeutic strategies that target multiple levels in the TGF-β pathway are under preclinical and clinical research for fibrosis. Despite the anti-fibrotic effect of BMPs, their in vivo delivery poses a challenge in terms of adequate clinical efficacy. In this article, we will review the relevance of TGF-β signaling in salivary gland fibrosis and advances of potential therapeutic options in the field.

IL-6 Contributes to the TGF-β1-Mediated Epithelial to Mesenchymal Transition in Human Salivary Gland Epithelial Cells

To determine the role of IL-6 in bringing about the EMT, in SGEC obtained from healthy subjects. Human salivary gland (SGs) epithelial cells (SGEC) from primary Sjögren's syndrome (pSS) are able to synthesize interleukin (IL)-6, which is a critical mediator of the SGs modifications in response to chronic inflammation. Recently, a hypothetical link between epithelial-mesenchymal transition (EMT)-dependent salivary gland fibrosis and chronic inflammatory conditions has been suggested for pSS; the present study was conducted to evaluate this link. Primary cultures of human SGEC from salivary mucoceles were stimulated with increasing concentrations of IL-6 for 24-72 h. Microscopy, RT-PCR, Real-time PCR, immunoblotting and flow cytometry were used to detect morphological changes, mRNA and protein expression of the EMT markers E-Cadherin, Vimentin and Collagen type I following IL-6 stimulation. The data collected demonstrate that IL-6 can induce SGEC to undergo a morphological and phenotypical transition to a mesenchymal phenotype, in a dose-dependent manner. Decreased mRNA levels of E-Cadherin accompanied by higher mRNA levels of Vimentin and Collagen type I were observed in the IL-6-treated cells compared to control cells (all p < 0.05). This was confirmed at the protein level, demonstrating the decreased E-Cadherin expression, while Vimentin and Collagen type I expression was increased in IL-6-treated SGEC compared to controls (all p < 0.05). The results obtained corroborate the hypothesis that dysregulated cytokines IL-6 may contribute to the EMT-dependent fibrosis, offering a more complete understanding of the role of the EMT during SGs fibrosis in pSS.

Interleukin-22 promotes the migration and invasion of oral squamous cell carcinoma cells

The roles of interleukin-22 (IL-22) in carcinogenesis have been proposed in various neoplasms. Increased expression of IL-22 has been observed in oral squamous cell carcinoma (OSCC) lesions as well as in other cancers. OSCC is still associated with poor prognosis and a high mortality rate because of its invasiveness and frequent lymph node metastasis. In the present study, we investigated the effects of IL-22 on OSCC cells. The human OSCC cell lines Ca9-22 and SAS were stimulated with IL-22 (1-10 ng/mL), and their migration abilities were examined using a cell scratch assay. A Matrigel invasion assay was performed to evaluate the invasion abilities of OSCC cells. Signal transducer and activator of transcription 3 (STAT3) phosphorylation, matrix metalloproteinase (MMP) and epithelial-mesenchymal transition (EMT)-related genes and proteins were also examined. IL-22 treatment promoted the migration and invasion abilities of OSCC cells without increasing their viability. IL-22 stimulation also induced STAT3 phosphorylation, MMP-9 activity and EMT-related genes and proteins. Our findings suggest that IL-22 has possible roles in the development of OSCC.

TGFβ1-Smad canonical and -Erk noncanonical pathways participate in interleukin-17-induced epithelial-mesenchymal transition in Sjögren's syndrome

Interleukin-17 (IL-17) is a pleiotropic cytokine that plays a primary role in triggering epithelial-mesenchymal transition (EMT) in many chronic inflammatory diseases. EMT plays a critical role in the progression of salivary gland (SG) fibrosis in primary Sjögren's syndrome (pSS). This study focused on the activation of the canonical TGF-β1/Smad2/3 and noncanonical TGF-β1/Erk1/2 pathways in IL-17-dependent TGFβ1-induced EMT in human SG epithelial cells (SGEC) derived from healthy subjects. The expression of phosphorylated Smad2/3 and Erk1/2 during IL-17 treatment-stimulated EMT was evaluated in healthy SGEC. Cotreatment with IL-17 and specific TGFβ receptor type I kinase inhibitor SB431542, or Erk 1/2 inhibitor U0126, abrogates the corresponding morphological changes and EMT phenotypic markers expression in healthy SGEC. Interestingly, inhibition of canonical TGFβ1/Smad2/3 signal transduction had no effect on activation of the noncanonical TGFβ1/Erk1/2/EMT pathway, suggesting that the two pathways act independently in activating IL-17-dependent EMT in SGEC.

Peptide-Based Vaccination Therapy for Rheumatic Diseases

Rheumatic diseases are extremely heterogeneous diseases with substantial risks of morbidity and mortality, and there is a pressing need in developing more safe and cost-effective treatment strategies. Peptide-based vaccination is a highly desirable strategy in treating noninfection diseases, such as cancer and autoimmune diseases, and has gained increasing attentions. This review is aimed at providing a brief overview of the recent advances in peptide-based vaccination therapy for rheumatic diseases. Tremendous efforts have been made to develop effective peptide-based vaccinations against rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), while studies in other rheumatic diseases are still limited. Peptide-based active vaccination against pathogenic cytokines such as TNF-α and interferon-α (IFN-α) is shown to be promising in treating RA or SLE. Moreover, peptide-based tolerogenic vaccinations also have encouraging results in treating RA or SLE. However, most studies available now have been mainly based on animal models, while evidence from clinical studies is still lacking. The translation of these advances from experimental studies into clinical therapy remains impeded by some obstacles such as species difference in immunity, disease heterogeneity, and lack of safe delivery carriers or adjuvants. Nevertheless, advances in high-throughput technology, bioinformatics, and nanotechnology may help overcome these impediments and facilitate the successful development of peptide-based vaccination therapy for rheumatic diseases.