Matriptase deletion initiates a Sjögren's syndrome-like disease in mice

The role of Th9 CD4+ T cells and IL-9 during primary Sjogren's syndrome

OBJECTIVE

The objective of this study is to investigate the expression levels of Th₉ CD4⁺ T cells and IL-9 secretion in peripheral blood mononuclear cells of patients with primary Sjogren's syndrome. Further, this study aimed to investigate the role of Th₉ cells in the occurrence and development of pSS.

METHODS

A total of 20 pSS patients and 20 healthy people, matched with age and gender, were selected as the experimental and control group, respectively. Flow cytometry and ELISA were used to detect the expression of Th₉ cytokines in peripheral blood mononuclear cells and IL-9 in serum, respectively. These factors were then correlated to other clinical indicators.

RESULTS

The levels of Th₉ CD4⁺ T cells and IL-9 of pSS patients were significantly higher than those of the control group. Th₉ CD4⁺ T cells and IL-9 levels in peripheral blood of pSS patients were negatively correlated with salivary flow rate, while IL-9 level was positively correlated with globulin. The transcription levels of IL-9 and immune-related genes including IL-4, IL-7, IL-17, SMAD3, STAT5 and JAK3 were dramatically increased in serum of pSS patients.

CONCLUSION

The expression levels of Th₉ in peripheral blood and serum IL-9 of patients with pSS were significantly increased, which were correlated with clinical immunological indexes. Together, these data suggest that Th₉ cells and IL-9 may be involved in the pathogenesis of pSS.

ENaC activation by proteases

Proteases are fundamental for a plethora of biological processes, including signalling and tissue remodelling, and dysregulated proteolytic activity can result in pathogenesis. In this review, we focus on a subclass of membrane‐bound and soluble proteases that are defined as channel‐activating proteases (CAPs), since they induce Na⁺ ion transport through an autocrine mechanism when co‐expressed with the highly amiloride‐sensitive epithelial sodium channel (ENaC) in Xenopus oocytes. These experiments first identified CAP1 (channel‐activating protease 1, prostasin) followed by CAP2 (channel‐activating protease 2, TMPRSS4) and CAP3 (channel‐activating protease 3, matriptase) as in vitro mediators of ENaC current. Since then, more serine‐, cysteine‐ and metalloproteases were confirmed as in vitro CAPs that potentially cleave and regulate ENaC, and thus this nomenclature was not further followed, but is accepted as functional term or alias. The precise mechanism of ENaC modulation by proteases has not been fully elucidated. Studies in organ‐specific protease knockout models revealed evidence for their role in increasing ENaC activity, although the proteases responsible for ENaC activation are yet to be identified. We summarize recent findings in animal models of these CAPs with respect to their implication in ENaC activation. We discuss the consequences of dysregulated CAPs underlying epithelial phenotypes in pathophysiological conditions, and the role of selected protease inhibitors. We believe that these proteases may present interesting therapeutic targets for diseases with aberrant sodium homoeostasis.

Sclerosing Sialadenitis Is Associated With Salivary Gland Hypofunction and a Unique Gene Expression Profile in Sjögren's Syndrome

Purpose

To develop a novel method to quantify the amount of fibrosis in the salivary gland and to investigate the relationship between fibrosis and specific symptoms associated with Sjögren’s syndrome (SS) using this method.

Materials and Methods

Paraffin-embedded labial salivary gland (LSG) slides from 20 female SS patients and their clinical and LSG pathology data were obtained from the Sjögren’s International Collaborative Clinical Alliance. Relative interstitial fibrosis area (RIFA) in Masson’s trichrome-stained LSG sections was quantified from digitally scanned slides and used for correlation analysis. Gene expression levels were assessed by microarray analysis. Core promoter accessibility for RIFA-correlated genes was determined using DNase I hypersensitive sites sequencing analysis.

Results

RIFA was significantly correlated with unstimulated whole saliva flow rate in SS patients. Sixteen genes were significantly and positively correlated with RIFA. In a separate analysis, a group of differentially expressed genes was identified by comparing severe and moderate fibrosis groups. This combined set of genes was distinct from differentially expressed genes identified in lung epithelium from idiopathic pulmonary fibrosis patients compared with controls. Single-cell RNA sequencing analysis of salivary glands suggested most of the RIFA-correlated genes are expressed by fibroblasts in the gland and are in a permissive chromatin state.

Conclusion

RIFA quantification is a novel method for assessing interstitial fibrosis and the impact of fibrosis on SS symptoms. Loss of gland function may be associated with salivary gland fibrosis, which is likely to be driven by a unique set of genes that are mainly expressed by fibroblasts.

Membrane-anchored serine proteases as regulators of epithelial function

Cleavage of proteins in the extracellular milieu, including hormones, growth factors and their receptors, ion channels, and various cell adhesion and extracellular matrix molecules, plays a key role in the regulation of cell behavior. Among more than 500 proteolytic enzymes encoded by mammalian genomes, membrane-anchored serine proteases (MASPs), which are expressed on the surface of epithelial cells of all major organs, are excellently suited to mediate signal transduction across the epithelia and are increasingly being recognized as important regulators of epithelial development, function, and disease [ 1-3]. In this minireview, we summarize current knowledge of the in vivo roles of MASPs in acquisition and maintenance of some of the defining functions of epithelial tissues, such as barrier formation, ion transport, and sensory perception.

Inhibition of bone morphogenetic protein 6 receptors ameliorates Sjögren's syndrome in mice

Primary Sjögren’s syndrome (pSS) is a chronic autoimmune disease, with only palliative treatments available. Recent work has suggested that increased bone morphogenetic protein 6 (BMP6) expression could alter cell signaling in the salivary gland (SG) and result in the associated salivary hypofunction. We examined the prevalence of elevated BMP6 expression in a large cohort of pSS patients and tested the therapeutic efficacy of BMP signaling inhibitors in two pSS animal models. Increased BMP6 expression was found in the SGs of 54% of pSS patients, and this increased expression was correlated with low unstimulated whole saliva flow rate. In mouse models of SS, inhibition of BMP6 signaling reduced phosphorylation of SMAD1/5/8 in the mouse submandibular glands, and led to a recovery of SG function and a decrease in inflammatory markers in the mice. The recovery of SG function after inhibition of BMP6 signaling suggests cellular plasticity within the salivary gland and a possibility for therapeutic intervention that can reverse the loss of function in pSS.

Type II transmembrane serine proteases as potential targets for cancer therapy

Carcinogenesis is accompanied by increased protein and activity levels of extracellular cell-surface proteases that are capable of modifying the tumor microenvironment by directly cleaving the extracellular matrix, as well as activating growth factors and proinflammatory mediators involved in proliferation and invasion of cancer cells, and recruitment of inflammatory cells. These complex processes ultimately potentiate neoplastic progression leading to local tumor cell invasion, entry into the vasculature, and metastasis to distal sites. Several members of the type II transmembrane serine protease (TTSP) family have been shown to play critical roles in cancer progression. In this review the knowledge collected over the past two decades about the molecular mechanisms underlying the pro-cancerous properties of selected TTSPs will be summarized. Furthermore, we will discuss how these insights may facilitate the translation into clinical settings in the future by specifically targeting TTSPs as part of novel cancer treatment regimens.

Matriptase zymogen supports epithelial development, homeostasis and regeneration

Background

Matriptase is a membrane serine protease essential for epithelial development, homeostasis, and regeneration, as well as a central orchestrator of pathogenic pericellular signaling in the context of inflammatory and proliferative diseases. Matriptase is an unusual protease in that its zymogen displays measurable enzymatic activity.

Results

Here, we used gain and loss of function genetics to investigate the possible biological functions of zymogen matriptase. Unexpectedly, transgenic mice mis-expressing a zymogen-locked version of matriptase in the epidermis displayed pathologies previously reported for transgenic mice mis-expressing wildtype epidermal matriptase. Equally surprising, mice engineered to express only zymogen-locked endogenous matriptase, unlike matriptase null mice, were viable, developed epithelial barrier function, and regenerated the injured epithelium. Compatible with these observations, wildtype and zymogen-locked matriptase were equipotent activators of PAR-2 inflammatory signaling.

Conclusion

The study demonstrates that the matriptase zymogen is biologically active and is capable of executing developmental and homeostatic functions of the protease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-017-0384-4) contains supplementary material, which is available to authorized users.

Aquaporin gene therapy corrects Sjögren's syndrome phenotype in mice

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease that is estimated to affect 35 million people worldwide. Currently, no effective treatments exist for Sjögren's syndrome, and there is a limited understanding of the physiological mechanisms associated with xerostomia and hyposalivation. The present work revealed that aquaporin 5 expression, a water channel critical for salivary gland fluid secretion, is regulated by bone morphogenetic protein 6. Increased expression of this cytokine is strongly associated with the most common symptom of primary Sjögren's syndrome, the loss of salivary gland function. This finding led us to develop a therapy in the treatment of Sjögren's syndrome by increasing the water permeability of the gland to restore saliva flow. Our study demonstrates that the targeted increase of gland permeability not only resulted in the restoration of secretory gland function but also resolved the hallmark salivary gland inflammation and systemic inflammation associated with disease. Secretory function also increased in the lacrimal gland, suggesting this local therapy could treat the systemic symptoms associated with primary Sjögren's syndrome.

Extracellular: Plasma Membrane Proteases – Serine Proteases

Membrane-anchored serine proteases are a group of extracellular serine proteases tethered directly to plasma membranes, via a C-terminal glycosylphosphatidylinositol linkage (GPI-anchored), a C-terminal transmembrane domain (Type I), or an N-terminal transmembrane domain (Type II). A variety of biochemical, cellular, and in vivo studies have established that these proteases are important pericellular contributors to processes vital for the maintenance of homeostasis, including food digestion, blood pressure regulation, hearing, epithelial permeability, sperm maturation, and iron homeostasis. These enzymes are hijacked by viruses to facilitate infection and propagation, and their misregulation is associated with a wide range of diseases, including cancer malignancy.

Advances in salivary gland gene therapy - oral and systemic implications

INTRODUCTION

Much research demonstrates the feasibility and efficacy of gene transfer to salivary glands. Recently, the first clinical trial targeting a salivary gland was completed, yielding positive safety and efficacy results.

AREAS COVERED

There are two major disorders affecting salivary glands: radiation damage following treatment for head and neck cancers and Sjögren's syndrome (SS). Salivary gland gene transfer has also been employed in preclinical studies using transgenic secretory proteins for exocrine (upper gastrointestinal tract) and endocrine (systemic) applications.

EXPERT OPINION

Salivary gland gene transfer is safe and can be beneficial in humans. Applications to treat and prevent radiation damage show considerable promise. A first-in-human clinical trial for the former was recently successfully completed. Studies on SS suffer from an inadequate understanding of its etiology. Proof of concept in animal models has been shown for exocrine and endocrine disorders. Currently, the most promising exocrine application is for the management of obesity. Endocrine applications are limited, as it is currently impossible to predict if systemically required transgenic proteins will be efficiently secreted into the bloodstream. This results from not understanding how secretory proteins are sorted. Future studies will likely employ ultrasound-assisted and pseudotyped adeno-associated viral vector-mediated gene transfer.