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

Route of Application and Dose Evaluation of Dental Pulp Stem Cells for the Treatment of Sialadenitis Caused by Sjögren's Syndrome: A Preclinical Study

Background: Sjögren's syndrome (SS) is an autoimmune disorder characterized by sicca syndrome and/or systemic manifestations. In this study, non-obese diabetic (NOD) mice were used as an animal model for studying SS, to evaluate the optimal administration route and dose range of dental pulp stem cells (DPSCs) in the treatment of sialadenitis caused by SS. Methods: Different doses of DPSCs were transplanted into the submandibular glands (SMGs) of 14-week-old NOD mice through two different methods: injection or retrograde perfusion through the catheter orifice into the SMG. At 21 weeks of age, the saliva flow rate (SFR), ectopic lymphocytes, and CD4+ T-cell infiltration were measured. Tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) in the glandular tissues were also quantitatively detected. Results: Compared with untreated and PBS-injected controls, different-dose groups of the two administration methods showed an increased saliva flow rate of NOD mice to varying degrees, reduced infiltration of lymphocytes and CD4+ T cells in the SMG, and decreased IFN-γ/TNF-α levels. Finally, we compared these two administration routes and found that the perfusion of 2 × 105 DPSCs presents good therapeutic effects. Conclusions: DPSC perfusion through the catheter orifice is a simple and effective treatment method, which is worthy of further investigation through clinical trials.

Loss of tricellular tight junction tricellulin leads to hyposalivation in Sjögren's syndrome

Tricellulin, a key tricellular tight junction (TJ) protein, is essential for maintaining the barrier integrity of acinar epithelia against macromolecular passage in salivary glands. This study aims to explore the role and regulatory mechanism of tricellulin in the development of salivary gland hypofunction in Sjögren's syndrome (SS). Employing a multifaceted approach involving patient biopsies, non-obese diabetic (NOD) mice as a SS model, salivary gland acinar cell-specific tricellulin conditional knockout (TricCKO) mice, and IFN-γ-stimulated salivary gland epithelial cells, we investigated the role of tricellulin in SS-related hyposalivation. Our data revealed diminished levels of tricellulin in salivary glands of SS patients. Similarly, NOD mice displayed a reduction in tricellulin expression from the onset of the disease, concomitant with hyposecretion and an increase in salivary albumin content. Consistent with these findings, TricCKO mice exhibited both hyposecretion and leakage of macromolecular tracers when compared to control animals. Mechanistically, the JAK/STAT1/miR-145 axis was identified as mediating the IFN-γ-induced downregulation of tricellulin. Treatment with AT1001, a TJ sealer, ameliorated epithelial barrier dysfunction, restored tricellulin expression, and consequently alleviated hyposalivation in NOD mice. Importantly, treatment with miR-145 antagomir to specifically recover the expression of tricellulin in NOD mice significantly alleviated hyposalivation and macromolecular leakage. Collectively, we identified that tricellulin deficiency in salivary glands contributed to hyposalivation in SS. Our findings highlight tricellulin as a potential therapeutic target for hyposecretion, particularly in the context of reinforcing epithelial barrier function through preventing leakage of macromolecules in salivary glands.

Aged regulatory T cells fail to control autoimmune lacrimal gland pathogenic CD4+ T cells

CD25KO mice are a model of Sjögren disease. CD25KO mice have severe inflammation and infiltrating lymphocytes to the lacrimal glands (LG). Whether the pathogenicity of CD25KO CD4+ T cells can be controlled in vivo by Tregs is unknown. Eight-week-old B6 and CD25KO mice LGs were submitted for RNA bulk sequencing. A total of 3481 genes were differentially expressed in CD25KO LG compared to B6. Tear washing analysis identified CD25KO mice had elevated protein levels of TNF, IFN-γ, and CCL5 and decreased protein levels of IL-12p40 and VEGF-A. Co-adoptive transfer of CD25KO CD4+ T cells with either young or aged B6 Tregs was performed in RAG1KO mice. Recipients of CD25KO CD4+ T cells alone had higher LG inflammation than naive mice. However, in recipients of young B6 Tregs plus CD25KO CD4+ T cells, LGs had significantly reduced inflammation. Recipients of CD25KO CD4+ T cells with aged B6 Tregs had more inflamed LGs than young Tregs, suggesting aged Tregs have less suppressive capacity in vivo. Altogether, CD25KO mice have phenotypic and genetic changes resulting in increased inflammation and severe lymphocytic infiltration in the LGs. However, this autoimmunity can be controlled by the addition of young, but not aged, Tregs, suggesting that aging Tregs have dysfunctional suppression.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

A Review of a Breakdown in the Barrier: Tight Junction Dysfunction in Dental Diseases

The tight junction (TJ), a type of cell-cell junction, regulates the permeability of solutes across epithelial and endothelial cellular sheets and is believed to maintain cell polarity. However, recent studies have provided conflicting views on the roles of TJs in epithelial polarity. Membrane proteins, including occludin, claudin, and the junction adhesion molecule, have been identified as TJ components. TJs are predominantly found at the stratum granulosum and stratum corneum. Although it remains unclear whether the disruption of TJs is the cause or consequence of certain dental diseases, evidence suggests that TJ dysfunction may be a crucial factor in gingival epithelial barrier impairment and the progression of oral diseases. Bacterial infection is among the most specific factors we found that may contribute to the breakdown of the epithelial barrier formed by TJs in dental diseases. Bacteria and their products may weaken the epithelial barrier by directly destroying intercellular junctions or altering the expression of junctional proteins. Additionally, they may induce the production of inflammatory cytokines, which could lead to the downregulation of TJ proteins and, consequently, impair the epithelial barrier. This review introduces a novel perspective by exploring, for the first time, the role of TJs dysfunction in the breakdown of the oral epithelial barrier and its potential link to the progression of dental diseases such as gingivitis, periodontitis, Sjӧgren syndrome, and oral squamous cell carcinoma.

Altered characteristics of regulatory T cells in target tissues of Sjögren's syndrome in murine models

Sjӧgren's syndrome (SS), also known as Sjögren's disease, is a chronic autoimmune condition predominantly affecting the salivary and lacrimal glands. The disease is driven by autoimmune responses involving the activation and actions of major innate- and adaptive immune cell subsets. However, the specific characteristics and roles of regulatory T cells (Tregs) in SS remain elusive. This study seeks to clarify the main phenotypic and functional attributes of Tregs in the salivary glands and their draining lymph nodes in murine models of SS. Our flow cytometric analysis revealed that Tregs in the salivary gland-draining lymph nodes of female non-obese diabetic (NOD) mice, a spontaneous model of SS, exhibited a greater proportion of activated Tregs and fewer resting Tregs compared to Balb/c mice. Furthermore, Tregs from the salivary gland-draining lymph nodes of female C57BL/6.NOD-Aec1Aec2 (B6.NOD-Aec) mice, a model for primary SS, demonstrated significantly lower IL-10 production but markedly higher IFNγ- and IL-17 production than their C57BL/6 counterparts. Additionally, treatment of C57BL/6 Tregs with IL-7, a cytokine critical for SS pathogenesis, resulted in diminished IL-10 production and enhanced IFNγ and IL-17 production in these cells. Notably, the alterations in B6.NOD-Aec Tregs also included an increased expression of the immune-inhibitory molecule CTLA-4 compared to the C57BL/6 Tregs. Intriguingly, in vitro co-cultures of Tregs with conventional CD4 T cells and other key immune populations from lymph nodes indicated that Tregs from salivary gland-draining lymph nodes of both B6.NOD-Aec and C57BL/6 strains exhibited comparable and limited immunosuppressive effects on the proliferation and function of conventional CD4 T cells. The ability of B6.NOD-Aec Tregs to directly inflict damages to salivary gland epithelial tissues and contribute to SS pathologies through IFNγ and IL-17 that they produce warrants further investigations. In addition, enhancing the relatively weak immunosuppressive capacities of these Tregs may also serve as a viable strategy to alleviate the SS phenotype in the mouse models and potentially in patients.

Endogenous IL-22 contributes to the pathogenesis of salivary gland dysfunction in the non-obese diabetic model of Sjögren's syndrome

Sjӧgren's syndrome is a systemic autoimmune disease primarily targeting the salivary and lacrimal glands. Our previous investigations have shown that administration of interleukin-22 (IL-22), an IL-10 family cytokine known for its complex and context-dependent effects on tissues, either protective- or detrimental, to salivary glands leads to hypofunction and pathological changes of salivary glands in C57BL/6 mice and in non-obese diabetic (NOD) mice, the latter being a commonly used model of Sjӧgren's syndrome. This study aims to delineate the pathophysiological roles of endogenously produced IL-22 in the development of salivary gland pathologies and dysfunction associated with Sjӧgren's disease in the NOD mouse model. Our results reveal that neutralizing IL-22 offered a protective effect on salivary gland function without significantly affecting the immune cell infiltration of salivary glands or the autoantibody production. Blockade of IL-22 reduced the levels of phosphorylated STAT3 in salivary gland tissues of NOD mice, while its administration to salivary glands had the opposite effect. Correspondingly, the detrimental impact of exogenously applied IL-22 on salivary glands was almost completely abrogated by a specific STAT3 inhibitor. Moreover, IL-22 blockade led to a downregulation of protein amounts of Ten-Eleven-Translocation 2, a methylcytosine dioxygenase critical for mediating interferon-induced responses, in salivary gland epithelial cells. IL-22 neutralization also exerted a protective effect on the salivary gland epithelial cells that express high levels of surface EpCAM and bear the stem cell potential, and IL-22 treatment in vitro hampered the survival/expansion of these salivary gland stem cells, indicating a direct negative impact of IL-22 on these cells. In summary, this study has uncovered a critical pathogenic role of the endogenous IL-22 in the pathogenesis of Sjögren's disease-characteristic salivary gland dysfunction and provided initial evidence that this effect is dependent on STAT3 activation and potentially achieved through fostering Tet2-mediated interferon responses in salivary gland epithelial cells and negatively affecting the EpCAMhigh salivary gland stem cells.

The Mechanism of 540 nm Green Light in Promoting Salivary Secretion

Background: Although low-level laser therapy (LLLT) is a widely used noninvasive treatment because of photobiomodulation effects, its application for xerostomia remained uncertain. Tight junctions (TJs), mainly composed of claudins, occludin, and ZO family members, are crucial structures that determine material transport through paracellular pathway in salivary gland epithelial cells. This work aimed to investigate whether LLLT affected salivary secretion through epithelial TJs. Methods: Transepithelial electrical resistance (TER) measurement and paracellular permeability assay were applied to evaluate paracellular permeability in submandibular gland (SMG)-C6 cells after irradiation with 540 nm green light. Immunofluorescence and western blot were used to detect the expression of TJ proteins. Quantitative phosphoproteomics were performed to explore possible intracellular signals. Results: We found that irradiation with 540 nm green light significantly decreased TER values while increased paracellular transport in SMG-C6 cells. 540 nm green light-induced redistribution of claudin-1, -3, and -4, but not occludin or ZO-1. Moreover, above phenomena were abolished by preincubation with capsazepine, an antagonist of transient receptor potential vanilloid subtype 1. Notably, irradiation with 540 nm green light on the skin covering the whole submandibular gland regions promoted salivary secretion and attenuated lymphocytic infiltration in 21-week-old non-obese diabetic mice (n = 5 per group), a xerostomia animal model for Sjögren's syndrome. Through in-depth bioinformatics analysis and expression verification, ERK1/2 and EphA2 served as potential canonical and noncanonical signals underlying 540 nm green light. Conclusions: Our findings uncovered the novel therapeutic effects of 540 nm green light on xerostomia through regulation on the expression and distribution of TJs.

Advances in cellular and molecular pathways of salivary gland damage in Sjögren's syndrome

Sjögren's Syndrome (SS) is an autoimmune disorder characterized by dysfunction of exocrine glands. Primarily affected are the salivary glands, which exhibit the most frequent pathological changes. The pathogenesis involves susceptibility genes, non-genetic factors such as infections, immune cells-including T and B cells, macrophage, dendritic cells, and salivary gland epithelial cells. Inflammatory mediators such as autoantibodies, cytokines, and chemokines also play a critical role. Key signaling pathways activated include IFN, TLR, BAFF/BAFF-R, PI3K/Akt/mTOR, among others. Comprehensive understanding of these mechanisms is crucial for developing targeted therapeutic interventions. Thus, this study explores the cellular and molecular mechanisms underlying SS-related salivary gland damage, aiming to propose novel targeted therapeutic approaches.

Comparative studies on the intestinal health of wild and cultured ricefield eel (Monopterus albus)

Fish intestinal health under intensive aquaculture mode plays an important role in growth, development, and immune function. The present study was aimed to systematically investigate the differences of intestinal health between wild and cultured Monopterus albus by biochemical parameters, histomorphology, and molecular biology. A total of 15 healthy M. albus per group, with an average body weight of 45 g, were sampled to analyze intestinal health parameters. Compared with wild fish, the cultured M. albus in the foregut had lower trypsin, lipase, SOD, CAT, T-AOC, and GSH-Px activities (P < 0.05) and higher amylase activity and MDA content (P < 0.05). The villus circumference and goblet cells in the cultured group were significantly lower than those in the wild group (P < 0.05). In addition, the cultured fish showed lower relative expression levels of occludin, zo-1, zo-2, claudin-12, claudin-15, mucin5, mucin15, lysozyme, complement 3, il-10, tgf-β1, tgf-β2, and tgf-β3 (P < 0.05) and higher il-1β, il-6, il-8, tnf-a, and ifnγ mRNA expressions than those of wild fish (P < 0.05). In terms of gut microbiota, the cultured group at the phylum level displayed higher percentages of Chlamydiae and Spirochaetes and lower percentages of Firmicutes, Bacteroidetes, Actinobacteria, Cyanobacteria, and Verrucomicrobia compared to the wild group (P < 0.05). At the genus level, higher abundances of Pseudomonadaceae_Pseudomonas and Spironema and lower abundances of Lactococcus and Cetobacterium were observed in the cultured group than in the wild group (P < 0.05). To our knowledge, this is the first investigation of the intestinal health status between wild and cultured M. albus in terms of biochemistry, histology, and molecular biology levels. Overall, the present study showed significant differences in intestinal health between wild and cultured M. albus and the main manifestations that wild M. albus had higher intestinal digestion, antioxidant capacity, and intestinal barrier functions than cultured M. albus. These results would provide theoretical basis for the subsequent upgrading of healthy aquaculture technology and nutrient regulation of intestinal health of cultured M. albus.

Claudin-10 Decrease in the Submandibular Gland Contributes to Xerostomia

Tight junction proteins play a crucial role in paracellular transport in salivary gland epithelia. It is clear that severe xerostomia in patients with HELIX syndrome is caused by mutations in the claudin-10 gene. However, little is known about the expression pattern and role of claudin-10 in saliva secretion in physical and disease conditions. In the present study, we found that only claudin-10b transcript was expressed in human and mouse submandibular gland (SMG) tissues, and claudin-10 protein was dominantly distributed at the apicolateral membranes of acini in human, rat, and mouse SMGs. Overexpression of claudin-10 significantly reduced transepithelial electrical resistance and increased paracellular transport of dextran and Na+ in SMG-C6 cells. In C57BL/6 mice, pilocarpine stimulation promoted secretion and cation concentration in saliva in a dose-dependent increase. Assembly of claudin-10 to the most apicolateral portions in acini of SMGs was observed in the lower pilocarpine (1 mg/kg)-treated group, and this phenomenon was much obvious in the higher pilocarpine (10 mg/kg)-treated group. Furthermore, 7-, 14-, and 21-wk-old nonobese diabetic (NOD) and BALB/c mice were used to mimic the progression of hyposalivation in Sjögren syndrome. Intensity of claudin-10 protein was obviously lower in SMGs of 14- and 21-wk-old NOD mice compared with that of age-matched BALB/c mice. In the cultured mouse SMG tissues, interferon-γ (IFN-γ) downregulated claudin-10 expression. In claudin-10-overexpressed SMG-C6 cells, paracellular permeability was decreased. Furthermore, IFN-γ stimulation increased p-STAT1 level, whereas pretreatment with JAK/STAT1 antagonist significantly alleviated the IFN-γ-induced claudin-10 downregulation. These results indicate that claudin-10 functions as a pore-forming component in acinar epithelia of SMGs, assembly of claudin-10 is required for saliva secretion, and downregulation of claudin-10 induces hyposecretion. These findings may provide new clues to novel therapeutic targets on hyposalivation.

The role and mechanism of tight junctions in the regulation of salivary gland secretion

Tight junctions (TJs) are cell-cell interactions that localize at the most apical portion of epithelial/endothelial cells. One of the predominant functions of TJs is to regulate material transport through paracellular pathway, which serves as a selective barrier. In recent years, the expression and function of TJs in salivary glands has attracted great interest. The characteristics of multiple salivary gland TJ proteins have been identified. During salivation, the activation of muscarinic acetylcholine receptor and transient receptor potential vanilloid subtype 1, as well as other stimuli, promote the opening of acinar TJs by inducing internalization of TJs, thereby contributing to increased paracellular permeability. Besides, endothelial TJs are also redistributed with leakage of blood vessels in cholinergic-stimulated submandibular glands. Furthermore, under pathological conditions, such as Sjögren's syndrome, diabetes mellitus, immunoglobulin G4-related sialadenitis, and autotransplantation, the integrity and barrier function of TJ complex are impaired and may contribute to hyposalivation. Moreover, in submandibular glands of Sjögren's syndrome mouse model and patients, the endothelial barrier is disrupted and involved in hyposecretion and lymphocytic infiltration. These findings enrich our understanding of the secretory mechanisms that link the importance of epithelial and endothelial TJ functions to salivation under both physiological and pathophysiological conditions.

Association Between Salivary Cytokines, Chemokines and Growth Factors and Salivary Gland Function in Children with Chronic Kidney Disease

Introduction

Chronic kidney disease (CKD) is a systemic inflammatory disease that leads to multiple organ complications not only in the kidneys and the cardiovascular system, but also in the oral cavity. CKD children experience reduced saliva secretion (hyposalivation), which leads to increased incidence of dental caries and significant impairment of patients' quality of life. However, the causes of salivary gland dysfunction in children with CKD are unknown. The present study is the first to evaluate the inflammatory and anti-inflammatory profile in the saliva of children with CKD at different stages of renal failure with normal and reduced salivary gland function.

Methods

Thirty children with CKD (age 9-16) and thirty age- and gender-matched healthy children were classified for the study. Salivary inflammatory and anti-inflammatory profile were assayed using the multiplex ELISA assay.

Results

We demonstrated statistically significant changes in salivary pro-inflammatory (↑TNF-α, ↓IL-7), anti-inflammatory (↑IL-10), Th1 (↑INF-γ, ↑IL-15), Th2 (↑IL-4, ↑IL-5, ↑IL-6, ↑IL-9) and Th17 (IL-17) cytokines as well as chemokines (↑MCP-1/CCL-2, ↑MIP-1α/CCL3, ↓MIP-1β/CCL4, ↓EOTAXIN/CCL11) and growth factors (↑G-CSF, ↑FGF) in unstimulated saliva of children with CKD compared to the controls. Although the evaluation of the salivary inflammatory profile does not indicate a particular dominance of any of the branches of the immune system, we observed a statistically significant increase in the concentration of all Th2 cytokines assayed. The multivariate regression analysis showed that the content of salivary cytokines, chemokines and growth factors depends on the secretory function of the salivary glands, ie, salivary flow, total protein concentration and amylase activity in the saliva. Salivary MIP-1α/CCL3 was the most effective to differentiate children with CKD and hyposalivation from patients with normal saliva secretion.

Discussion

Inflammation is involved in salivary gland dysfunction in children with CKD, although further studies on in vitro and in vivo models are necessary to confirm this hypothesis.

Current experimental methods to investigate the impact of specialized pro-resolving lipid mediators on Sjögren's syndrome

Sjögren's syndrome is a chronic inflammatory autoimmune disease characterized by diminished secretory function of the exocrine glands. Although extensive investigation has been done to understand Sjögren's syndrome, the causes of the disease are as yet unknown and treatments remain largely ineffective, with established therapeutic interventions being limited to use of saliva substitutes with modest effectiveness. A primary feature of Sjögren's syndrome is uncontrolled inflammation of exocrine tissues and previous studies have demonstrated that lipid-based specialized pro-resolving mediators reduce inflammation and restores tissue integrity in salivary glands. However, these studies are limited to a single specialized pro-resolving lipid mediator's family member resolvin D1 or RvD1 and its aspirin-triggered epimer, AT-RvD1. Consequently, additional studies are needed to explore the potential benefits of other members of the specialized pro-resolving lipid mediator's family and related molecules (e.g., additional resolvin subtypes as well as lipoxins, maresins and protectins). In support of this goal, the current review aims to briefly describe the range of current experimental methods to investigate the impact of specialized pro-resolving lipid mediators on Sjögren's syndrome, including both strengths and weaknesses of each approach where this information is known. With this article, the possibilities presented by specialized pro-resolving lipid mediators will be introduced to a wider audience in immunology and practical advice is given to researchers who may wish to take up this work.

A combination treatment of low-dose dexamethasone and aspirin-triggered resolvin D1 reduces Sjögren syndrome-like features in a mouse model

Background

Sjögren syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration and diminished secretory function of the salivary glands. Dexamethasone (DEX) resolves dry mouth and lymphocytic infiltration; however, this treatment is difficult to maintain because of multiple adverse effects (eg, osteoporosis and skin thinning); likewise, aspirin-triggered resolvin D1 (AT-RvD1) increases saliva secretion but cannot eliminate lymphocytic infiltration. Previous studies showed that a combination of low-dose DEX with AT-RvD1 before disease onset prevents SS-like features in a mouse model; however, this is not clinically practical because there are no reliable indicators of SS before disease onset. Therefore, the authors applied the combined treatment at disease onset to show its efficacy and comparative lack of adverse effects, so that it may reasonably be maintained over a patient's lifetime.

Methods

NOD/ShiLtJ mice were treated with ethanol (vehicle control), high-dose DEX alone, AT-RvD1 alone, or a combination of low-dose DEX with AT-RvD1 at disease onset for 8 weeks. Then saliva flow rates were measured, and submandibular glands were harvested for histologic analyses.

Results

A combined treatment of low-dose DEX with AT-RvD1 significantly decreased mast cell degranulation and lymphocytic infiltration, increased saliva secretion, and restored apical aquaporin-5 expression in submandibular glands of NOD/ShiLtJ mice.

Conclusions

Low-dose DEX combined with AT-RvD1 reduces the severity of SS-like manifestation and prevents the development of advanced and potentially irreversible damage, all in a form that can reasonably be administered indefinitely without the need to cease treatment because of secondary effects.

Alternate-Day Fasting Ameliorates Newly Established Sjögren's Syndrome-like Sialadenitis in Non-Obese Diabetic Mice

Intermittent fasting confers protections to various diseases including autoimmune disorders, but the specific effects of intermittent fasting on Sjögren's syndrome (SS) remains inconclusive. The present study was undertaken to determine the specific impact of alternate-day fasting (ADF) on newly established SS-like sialadenitis using non-obese diabetic (NOD) mice. Female NOD mice were deprived of food every other day from 10 to 13 weeks of age, the early stage of established SS, and then analyzed for the disease characteristics. Mice in the ADF group had higher salivary flow rate and attenuated submandibular gland (SMG) inflammation, compared to the control mice fed with standard chow ad libitum. The improvements were accompanied with a decrease in the total leukocytes, T and B lymphocytes and activated CD4 and CD8 T cells, and a down-regulation of pro-inflammatory cytokines IFN-γ and IL-17, chemokine receptor CXCR3 and its ligands CXCL9 and CXCL11 in the SMGs. ADF also led to elevated mRNA levels of water channel protein aquaporin 5 and tight junction protein claudin-1, two factors crucial for normal salivary secretion in the SMGs. In addition, ADF reduced the proportion of IFN-γ- and IL-17- expressing CD4 T cells and diminished mRNA levels of IFN-γ, TNF-α, and IL-17 in the total submandibular draining lymph node cells. Taken together, ADF is effective in ameliorating newly established SS-associated salivary gland exocrinopathy in NOD mice.

Interleukin-22 Exerts Detrimental Effects on Salivary Gland Integrity and Function

Interleukin-22 (IL-22) affects epithelial tissue function and integrity in a context-dependent manner. IL-22 levels are elevated in salivary glands of Sjögren’s syndrome (SS) patients, but its role in the pathogenesis of this disease remains unclear. The objective of this study is to elucidate the impact of IL-22 on salivary gland tissue integrity and function in murine models. We showed that IL-22 levels in sera and salivary glands increased progressively in female non-obese diabetic (NOD) mice, accompanying the development of SS. Administration of IL-22 to the submandibular glands of NOD mice prior to the disease onset reduced salivary secretion and induced caspase-3 activation in salivary gland tissues, which were accompanied by alterations in multiple genes controlling tissue integrity and inflammation. Similarly, IL-22 administration to submandibular glands of C57BL/6 mice also induced hyposalivation and caspase-3 activation, whereas blockade of endogenous IL-22 in C57BL/6 mice treated with anti-CD3 antibody mitigated hyposalivation and caspase-3 activation. Finally, IL-22 treatment reduced the number of viable C57BL/6 mouse submandibular gland epithelial cells cultured in vitro, indicating a direct impact of this cytokine on these cells. We conclude that IL-22 exerts a detrimental impact on salivary gland tissues.

Alteration of tight junctions during botulinum toxin type A-inhibited salivary secretion

OBJECTIVES

Tight junctions (TJs) are involved in the regulation of salivary secretion via paracellular pathway. Botulinum toxin type A (BTXA) is widely used for the treatment of hypersecretion diseases such as sialorrhea. This study aimed to investigate the role of TJs in BTXA-inhibited secretion of the submandibular gland (SMG).

MATERIALS AND METHODS

BTXA was injected into the SMGs of rats, and the same amount of saline was injected as a control. Western blot, real-time PCR and immunofluorescence staining were used to detect the expression and distribution of TJ proteins. Paracellular permeability was evaluated using the transepithelial electrical resistance (TER) measurements and fluorescent tracer detection in BTXA-stimulated SMG-C6 cells.

RESULTS

BTXA injection into the SMGs of rats led to increased expression of claudin (Cldn) -1 and Cldn3. Immunofluorescence staining showed no significant changes in the distribution of TJ proteins. In vitro, BTXA increased the TER values and significantly reduced the permeability of fluorescent tracer, suggesting that BTXA decreased the paracellular permeability. The expression levels of Cldn1, Cldn3 and Cldn4 were upregulated after BTXA treatment.

CONCLUSION

The expression of TJ proteins changed in both animal models and SMG-C6 cells after BTXA treatment, which may contribute to the inhibition of salivary secretion.

Mannan Oligosaccharides Application: Multipath Restriction From Aeromonas hydrophila Infection in the Skin Barrier of Grass Carp (Ctenopharyngodon idella)

The objective of this study was to evaluate the efficacy of dietary Mannan oligosaccharides (MOS) supplementation on skin barrier function and the mechanism of on-growing grass carp (Ctenopharyngodon idella). Five hundred forty grass carp were fed for 60 days from the growing stage with six different levels of MOS diets (0, 200, 400, 600, 800, and 1,000 mg kg^-1). At the end of the growth trial, the 14-day Aeromonas hydrophila challenge experiment has proceeded. The obtained data indicate that MOS could (1) decline skin lesion morbidity after being challenged by the pathogenic bacteria; (2) maintain physical barrier function via improving antioxidant ability, inhibiting excessive apoptosis, and strengthening the tight junction between the epithelial cell and the related signaling pathway (Nrf2/Keap1, p38MAPK, and MLCK); and (3) regulate immune barrier function by modulating the production of antimicrobial compound and expression of involved cytokines and the related signaling pathway (TOR and NFκB). Finally, we concluded that MOS supplementation reinforced the disease resistance and protected the fish skin barrier function from Aeromonas hydrophila infection.

A comprehensive review of the influence of Epigallocatechin gallate on Sjögren's syndrome associated molecular regulators of exocytosis (Review)

Sjögren's syndrome (SS) is an autoimmune disorder that affects the salivary glands, leading to reduced secretory functions and oral and ocular dryness. The salivary glands are composed of acinar cells that are responsible for the secretion and production of secretory granules, which contain salivary components, such as amylase, mucins and immunoglobulins. This secretion process involves secretory vesicle trafficking, docking, priming and membrane fusion. A failure during any of the steps in exocytosis in the salivary glands results in the altered secretion of saliva. Soluble N-ethylmaleimide-sensitive-factor attachment protein receptors, actin, tight junctions and aquaporin 5 all serve an important role in the trafficking regulation of secretory vesicles in the secretion of saliva via exocytosis. Alterations in the expression and distribution of these selected proteins leads to salivary gland dysfunction, including SS. Several studies have demonstrated that green tea polyphenols, most notably Epigallocatechin gallate (EGCG), possess both anti-inflammatory and anti-apoptotic properties in normal human cells. Molecular, cellular and animal studies have indicated that EGCG can provide protective effects against autoimmune and inflammatory reactions in salivary glands in diseases such as SS. The aim of the present article is to provide a comprehensive and up-to-date review on the possible therapeutic interactions between EGCG and the selected molecular mechanisms associated with SS.

Sex Differences in Otolaryngology: Focus on the Emerging Role of Estrogens in Inflammatory and Pro-Resolving Responses

Otolaryngology (also known as ear, nose, and throat (ENT)) diseases can be significantly affected by the level of sex hormones, which indicates that sex differences affect the manifestation, pathophysiology, and outcomes of these diseases. Recently, increasing evidence has suggested that proinflammatory responses in ENT diseases are linked to the level of sex hormones. The sex hormone receptors are present on a wide variety of immune cells; therefore, it is evident that they play crucial roles in regulating the immune system and hence affect the disease progression of ENT diseases. In this review, we focus on how sex hormones, particularly estrogens, regulate ENT diseases, such as chronic rhinosinusitis, vocal fold polyps, thyroid cancer, Sjögren’s syndrome, and head and neck cancers, from the perspectives of inflammatory responses and specialized proresolving mediator-driven resolution. This paper aims to clarify why considering sex differences in the field of basic and medical research on otolaryngology is a key component to successful therapy for both males and females in the future.

Tumor Necrosis Factor Alpha Effects on the Porcine Intestinal Epithelial Barrier Include Enhanced Expression of TNF Receptor 1

Tumor necrosis factor alpha (TNFα) has been shown to impair the intestinal barrier, inducing and maintaining inflammatory states of the intestine. The aim of the current study was to analyze functional, molecular and regulatory effects of TNFα in a newly established non-transformed jejunal enterocyte model, namely IPEC-J2 monolayers. Incubation with 1000 U/mL TNFα induced a marked decrease in transepithelial electrical resistance (TEER), and an increase in permeability for the paracellular flux marker [³H]-D-mannitol compared to controls. Immunoblots revealed a significant decrease in tight junction (TJ) proteins occludin, claudin-1 and claudin-3. Moreover, a dose-dependent increase in the TNF receptor (TNFR)-1 was detected, explaining the exponential nature of pro-inflammatory effects, while TNFR-2 remained unchanged. Recovery experiments revealed reversible effects after the removal of the cytokine, excluding apoptosis as a reason for the observed changes. Furthermore, TNFα signaling could be inhibited by the specific myosin light chain kinase (MLCK) blocker ML-7. Results of confocal laser scanning immunofluorescence microscopy were in accordance with all quantitative changes. This study explains the self-enhancing effects of TNFα mediated by MLCK, leading to a differential regulation of TJ proteins resulting in barrier impairment in the intestinal epithelium.

Protective effects of miR-155-5p silencing on IFN-γ-induced apoptosis and inflammation in salivary gland epithelial cells

Previous studies have demonstrated that microRNAs (miRNAs/miRs) serve a vital role in the pathogenesis of Sjögren's syndrome (SS). The present study aimed to investigate the role of miR-155-5p in SS and determine its underlying molecular mechanism. An inflammatory lesion model was established by stimulating salivary gland epithelial cells (SGECs) with interferon-γ (IFN-γ). The apoptosis of SGECs was measured by using flow cytometry. Levels of proinflammatory factors were detected by reverse transcription-quantitative PCR and ELISA, respectively. Immunofluorescence was used for p65 staining. Dual-luciferase reporter assay was performed to verify the interaction between miR-155-5p and arrestin β2 (ARRB2). The protein levels in the NF-κB signaling pathway were assessed by western blotting. The results of the present study demonstrated that treatment with IFN-γ increased miR-155-5p expression, in addition to inducing apoptosis and inflammation in SGECs. Furthermore, overexpression of miR-155-5p promoted IFN-γ-induced apoptosis and inflammation in SGECs. Overexpression of miR-155-5p also increased Bax protein expression, enzyme activities of caspase 3 and caspase 9, release of inflammatory cytokines interleukin-6 and tumor necrosis factor-α, and decreased Bcl-2 protein expression in IFN-γ-treated SGECs. By contrast, all of the effects aforementioned were reversed following miR-155-5p knockdown. These results demonstrated that miR-155-5p activated the NF-κB signaling pathway, where treatment with the NF-κB inhibitor, pyrrolidine dithiocarbamate, reversed the effects of miR-155-5p overexpression on the inflammatory factors in IFN-γ-induced SGECs. miR-155-5p was demonstrated to target ARRB2 and negatively regulated its expression levels, such that overexpression of ARRB2 reversed the effects of miR-155-5p overexpression on the inflammatory response, apoptosis and the NF-κB signaling pathway in IFN-γ-treated SGECs. Collectively, results from the present study suggest that miR-155-5p may activate the NF-κB signaling pathway by negatively regulating ARRB2 to promote salivary gland damage during SS pathogenesis. This suggests that miR-155-5p may serve to be a potential target for the treatment of SS.

MicroRNA-mRNA expression profiles and functional network after injection of botulinum toxin type A into submandibular glands

Botulinum toxin type A (BTXA) is effective for the treatment of sialorrhea. MicroRNAs (miRNAs) have significant functions in salivary diseases, but the role of miRNAs during BTXA-inhibited salivary secretion is not yet clear. A total of 19 differentially expressed (DE) miRNAs and 1072 DE mRNAs were identified following BTXA injected into submandibular glands of rats (n = 4) through miRNA sequencing and microarray analysis. Bioinformatic analysis identified that several pathways may be associated with the inhibition of salivary secretion, such as the MAPK signalling pathway, tight junctions, and cytokine-cytokine receptor interaction. We predicted the target genes of DE miRNAs and established the miRNA-mRNA interaction network. The intersection of DE mRNAs and target genes of DE miRNAs was performed and seven mRNAs were obtained: Egr2, Paqr9, Zkscan1, Usp6n, Cyb561a3, Zfhx4, and Clic5. These findings explore the mechanism of BTXA in inhibiting salivary secretion and probably will provide new ideas for clinical application.

Oral Mucosa as a Potential Site for Diagnosis and Treatment of Allergic and Autoimmune Diseases

Most prevalent food allergies during early childhood are caused by foods with a high allergenic protein content, such as milk, egg, nuts, or fish. In older subjects, some respiratory allergies progressively lead to food-induced allergic reactions, which can be severe, such as urticaria or asthma. Oral mucosa remodeling has been recently proven to be a feature of severe allergic phenotypes and autoimmune diseases. This remodeling process includes epithelial barrier disruption and the release of inflammatory signals. Although little is known about the immune processes taking place in the oral mucosa, there are a few reports describing the oral mucosa-associated immune system. In this review, we will provide an overview of the recent knowledge about the role of the oral mucosa in food-induced allergic reactions, as well as in severe respiratory allergies or food-induced autoimmune diseases, such as celiac disease.

Contact photolithography-free integration of patterned and semi-transparent indium tin oxide stimulation electrodes into polydimethylsiloxane-based heart-on-a-chip devices for streamlining physiological recordings

Controlled electrical stimulation is essential for evaluating the physiology of cardiac tissues engineered in heart-on-a-chip devices. However, existing stimulation techniques, such as external platinum electrodes or opaque microelectrode arrays patterned on glass substrates, have limited throughput, reproducibility, or compatibility with other desirable features of heart-on-a-chip systems, such as the use of tunable culture substrates, imaging accessibility, or enclosure in a microfluidic device. In this study, indium tin oxide (ITO), a conductive, semi-transparent, and biocompatible material, was deposited onto glass and polydimethylsiloxane (PDMS)-coated coverslips as parallel or point stimulation electrodes using laser-cut tape masks. ITO caused substrate discoloration but did not prevent brightfield imaging. ITO-patterned substrates were microcontact printed with arrayed lines of fibronectin and seeded with neonatal rat ventricular myocytes, which assembled into aligned cardiac tissues. ITO deposited as parallel or point electrodes was connected to an external stimulator and used to successfully stimulate micropatterned cardiac tissues to generate calcium transients or propagating calcium waves, respectively. ITO electrodes were also integrated into the cantilever-based muscular thin film (MTF) assay to stimulate and quantify the contraction of micropatterned cardiac tissues. To demonstrate the potential for multiple ITO electrodes to be integrated into larger, multiplexed systems, two sets of ITO electrodes were deposited onto a single substrate and used to stimulate the contraction of distinct micropatterned cardiac tissues independently. Collectively, these approaches for integrating ITO electrodes into heart-on-a-chip devices are relatively facile, modular, and scalable and could have diverse applications in microphysiological systems of excitable tissues.

CD8+ T Lymphocytes: Crucial Players in Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease associated with damage to multiple organs and glands. The most common clinical manifestations are dry eyes, dry mouth, and enlarged salivary glands. Currently, CD4+ T lymphocytes are considered to be key factors in the immunopathogenesis of pSS, but various studies have shown that CD8+ T lymphocytes contribute to acinar injury in the exocrine glands. Therefore, in this review, we discussed the classification and features of CD8+ T lymphocytes, specifically describing the role of CD8+ T lymphocytes in disease pathophysiology. Furthermore, we presented treatment strategies targeting CD8+ T cells to capitalize on the pathogenic and regulatory potential of CD8+ T lymphocytes in SS to provide promising new strategies for this inflammatory disease.

Tumor necrosis factor-α induces claudin-3 upregulation in kidney tubular epithelial cells through NF-κB and CREB1

Claudins are essential for tight junction formation and paracellular transport, and they affect key cellular events including proliferation and migration. The properties of tight junctions are dynamically modulated by a variety of inputs. We previously showed that the inflammatory cytokine tumor necrosis factor-α (TNFα), a major pathogenic factor in kidney disease, alters epithelial permeability by affecting the expression of claudin-1, -2, and -4 in kidney tubular cells. Here, we explored the effect of TNFα on claudin-3 (Cldn-3), a ubiquitous barrier-forming protein. We found that TNFα elevated Cldn-3 protein expression in tubular epithelial cells (LLC-PK1 and IMCD3) as early as 3 h post treatment. Bafilomycin A and bortezomib, inhibitors of lysosomal and proteasomes, respectively, reduced Cldn-3 degradation. However, TNFα caused a strong upregulation of Cldn-3 in the presence of bafilomycin, suggesting an effect independent from lysosomes. Blocking protein synthesis using cycloheximide prevented Cldn-3 upregulation by TNFα, verifying the contribution of de novo Cldn-3 synthesis. Indeed, TNFα elevated Cldn-3 mRNA levels at early time points. Using pharmacological inhibitors and siRNA-mediated silencing, we determined that the effect of TNFα on Cldn-3 was mediated by extracellular signal regulated kinase (ERK)-dependent activation of NF-κB and PKA-induced activation of CREB1. These two pathways were turned on by TNFα in parallel and both were required for the upregulation of Cldn-3. Because Cldn-3 was suggested to modulate cell migration and epithelial-mesenchymal transition (EMT), and TNFα was shown to affect these processes, Cldn-3 upregulation may modulate regeneration of the tubules following injury.

Salivary exosomes as a new therapy to ameliorate diabetes mellitus and combat xerostomia and submandibular salivary glands dysfunction in diabetic rats

Diabetes mellitus (DM) is one of the major metabolic diseases. Xerostomia and salivary gland dysfunction are of its common oral complications. Exosomes, as a new therapeutic potential containing nucleic acids, proteins and lipids, act as effective vehicles for target molecules delivery. Accordingly, their therapeutic use is gaining much interest. Therefore, this work aimed to assess the therapeutic efficacy of salivary exosomes in ameliorating DM and combating xerostomia as a complication of salivary gland dysfunction in diabetic rats. In the current study, salivary exosomes were injected intravenously to rats of group II (Salivary Exo-treated group) one week after diabetes induction. Group I (Diabetic group) was left untreated. Blood sugar level was checked weekly. Water intake, salivary flow rate, salivary amylase and serum nitric oxide were assessed before and after diabetes induction and at the end of the study. After 5 weeks from the beginning of the study, salivary gland tissues were dissected and examined histologically and ultrastructurally. Gene expression of the inflammatory markers NFκB/p65 and TNFα was assessed by polymerase chain reaction. The results showed that salivary exosomes reduced blood glucose levels and enhanced salivary glands' function. This was indicated by a decrease in water intake, salivary amylase and serum nitric oxide in addition to an increase in salivary flow rate. This was confirmed histologically, ultrastructurally and via downregulation of NFκB/p65 and TNFα gene expression. Our results concluded that salivary exosomes could be considered as a novel cell free based therapy in treatment of xerostomia and salivary gland dysfunction in DM.

Trimers Conjugated to Fibrin Hydrogels Promote Salivary Gland Function

New strategies for tissue engineering have great potential for restoring and revitalizing impaired tissues and organs, including the use of smart hydrogels that can be modified to enhance organization and functionality of the salivary glands. For instance, monomers of laminin-111 peptides chemically conjugated to fibrin hydrogel (L_1pM-FH) promote cell cluster formation in vitro and salivary gland regeneration in vivo when compared with fibrin hydrogel (FH) alone; however, L_1pM-FH produce only weak expression of acinar differentiation markers in vivo (e.g., aquaporin-5 and transmembrane protein 16). Since previous studies demonstrated that a greater impact can be achieved when trimeric forms were used as compared with monomeric or dimeric forms, we investigated the extent to which trimers of laminin-111 chemically conjugated to FH (L_1pT-FH) can increase the expression of acinar differentiation markers and elevate saliva secretion. In vitro studies using Par-C10 acinar cells demonstrated that when compared with L_1pM-FH, L_1pT-FH induced similar levels of acinar-like cell clustering, polarization, lumen formation, and calcium signaling. To assess the performance of the trimeric complex in vivo, we compared the ability of L_1pM-FH and L_1pT-FH to increase acinar differentiation markers and restore saliva flow rate in a salivary gland wound model of C57BL/6 mice. Our results show that L_1pT-FH applied to wounded mice significantly improved the expression of the acinar differentiation markers and saliva secretion when compared with the monomeric form. Together, these positive effects of L_1pT-FH warrant its future testing in additional models of hyposalivation with the ultimate goal of applying this technology in humans.

Primary Sjogren Syndrome: Focus on Innate Immune Cells and Inflammation

Primary Sjogren Syndrome (pSS) is a complex, multifactorial rheumatic disease that mainly targets salivary and lacrimal glands, inducing epithelitis. The cause behind the autoimmunity outbreak in pSS is still elusive; however, it seems related to an aberrant reaction to exogenous triggers such as viruses, combined with individual genetic pre-disposition. For a long time, autoantibodies were considered as the hallmarks of this disease; however, more recently the complex interplay between innate and adaptive immunity as well as the consequent inflammatory process have emerged as the main mechanisms of pSS pathogenesis. The present review will focus on innate cells and on the principal mechanisms of inflammation connected. In the first part, an overview of innate cells involved in pSS pathogenesis is provided, stressing in particular the role of Innate Lymphoid Cells (ILCs). Subsequently we have highlighted the main inflammatory pathways, including intra- and extra-cellular players. A better knowledge of such processes could determine the detection of new therapeutic targets that are a major need for pSS.

Predictive modeling of aspirin-triggered resolvin D1 pharmacokinetics for the study of Sjögren's syndrome

OBJECTIVES

Sjögren's syndrome (SS) is an autoimmune disease that causes chronic inflammation of the salivary glands leading to secretory dysfunction. Previous studies demonstrated that aspirin-triggered resolvin D1 (AT-RvD1) reduces inflammation and restores tissue integrity in salivary glands. Specifically, progression of SS-like features in NOD/ShiLtJ mice can be systemically halted using AT-RvD1 prior or after disease onset to downregulate proinflammatory cytokines, upregulate anti-inflammatory molecules, and restore saliva production. Therefore, the goal of this paper was to create a physiologically based pharmacokinetic (PBPK) model to offer a reasonable starting point for required total AT-RvD1 dosage to be administered in future mice and humans thereby eliminating the need for excessive use of animals and humans in preclinical and clinical trials, respectively. Likewise, PBPK modeling was employed to increase the range of testable scenarios for elucidating the mechanisms under consideration.

MATERIALS AND METHODS

Pharmacokinetics following intravenous administration of a 0.1 mg/kg dose of AT-RvD1 in NOD/ShiLtJ were predicted in both plasma and saliva using PBPK modeling with PK-Sim® and MoBi® Version 7.4 software.

RESULTS

The model provides high-value pathways for future validation via in vivo studies in NOD/ShiLtJ to corroborate the findings themselves while also establishing this method as a means to better target drug development and clinical study design.

CONCLUSIONS

Clinical and basic research would benefit from knowledge of the potential offered by computer modeling. Specifically, short-term utility of these pharmacokinetic modeling findings involves improved targeting of in vivo studies as well as longer term prospects for drug development and/or better designs for clinical trials.

Agonist-induced 4-1BB activation prevents the development of Sjӧgren's syndrome-like sialadenitis in non-obese diabetic mice

Activation of costimulatory receptor 4-1BB enhances T helper 1 (Th1) and CD8 T cell responses in protective immunity, and prevents or attenuates several autoimmune diseases by increasing Treg numbers and suppressing Th17 or Th2 effector response. We undertook this study to elucidate the impact of enforced 4-1BB activation on the development of Sjögren's syndrome (SS)-like sialadenitis in non-obese diabetic (NOD) model of this disease. An anti-4-1BB agnostic antibody was intraperitoneally injected to female NOD mice aged 7 weeks, prior to the disease onset that occurs around 10-11 weeks of age, 3 times weekly for 2 weeks, and the mice were analyzed for SS pathologies at age 11 weeks. The salivary flow rate was markedly higher in the anti-4-1BB-treated NOD mice compared to the IgG-treated controls. Anti-4-1BB treatment significantly reduced the leukocyte infiltration of the submandibular glands (SMGs) and the levels of serum antinuclear antibodies. Flow cytometric analysis showed that the percentages of CD4 T cells, Th17 cells and plasmacytoid dendritic cells among SMG leukocytes were markedly reduced by anti-4-1BB treatment, in conjunction with a reduction in SMG IL-23p19 mRNA levels and serum IL-17 concentrations. Although the proportion of Tregs and IL-10 mRNA levels in SMGs were not altered by 4-1BB activation, IL-10 mRNA levels in salivary gland-draining lymph nodes and serum IL-10 concentrations were both markedly increased. While anti-4-1BB treatment did not affect the amount of Th1 cells and IFNγ mRNA in the SMGs, it increased these measurables in salivary gland-draining lymph nodes. Hence, agonistic activation of 4-1BB impedes the development of SS-like sialadenitis and hyposalivation.

Aspirin Triggered Resolvin D1 reduces inflammation and restores saliva secretion in a Sjögren's syndrome mouse model

OBJECTIVES

SS is characterized by chronic inflammation of the salivary glands leading to loss of secretory function, thereby suggesting specialized pro-resolving mediators targeting inflammation to be a viable option for treating SS. Previous studies demonstrated that aspirin-triggered resolvin D1 (AT-RvD1) prevents chronic inflammation and enhances saliva secretion in a SS-like mouse model when applied before disease onset. However, this therapy cannot be used in SS patients given that diagnosis occurs post-disease onset and no reliable screening methods exist. Therefore, we examined whether treatment with AT-RvD1 reduces SS-like features in a mouse model post-disease onset.

METHODS

Tail vein injections were performed in a SS-like mouse model both with and without AT-RvD1 post-disease onset for 8 weeks, with salivary gland function and inflammatory status subsequently determined.

RESULTS

Treatment of a SS-like mouse model with AT-RvD1 post-disease onset restores saliva secretion in both females and males. Moreover, although AT-RvD1 treatment does not reduce the overall submandibular gland lymphocytic infiltration, it does reduce the number of T helper 17 cells within the infiltrates in both sexes. Finally, AT-RvD1 reduces SS-associated pro-inflammatory cytokine gene and protein expression levels in submandibular glands from female but not male mice.

CONCLUSION

AT-RvD1 treatment administered post-disease onset reduces T helper 17 cells and successfully restores salivary gland function in a SS mouse model with variable effects noted by sex, thus warranting further examination of both the causes for the sex differences and the mechanisms responsible for the observed treatment effect.

Rainbow trout slow myoblast cell culture as a model to study slow skeletal muscle, and the characterization of mir-133 and mir-499 families as a case study

Muscle fibres are classified as fast, intermediate and slow. In vitro myoblast cell culture model from fast muscle is a very useful tool to study muscle growth and development; however, similar models for slow muscle do not exist. Owing to the compartmentalization of fish muscle fibres, we have developed a slow myoblast cell culture for rainbow trout (Oncorhynchus mykiss). Slow and fast muscle-derived myoblasts have similar morphology, but with differential expression of slow muscle markers such as slow myhc, sox6 and pgc-1α We also characterized the mir-133 and mir-499 microRNA families in trout slow and fast myoblasts as a case study during myogenesis and in response to electrostimulation. Three mir-133 (a-1a, a-1b and a-2) and four mir-499 (aa, ab, ba and bb) paralogues were identified for rainbow trout and named base on their phylogenetic relationship to zebrafish and Atlantic salmon orthologues. Omy-mir-499ab and omy-mir-499bb had 0.6 and 0.5-fold higher expression in slow myoblasts compared with fast myoblasts, whereas mir-133 duplicates had similar levels in both phenotypes and little variation during development. Slow myoblasts also showed increased expression for omy-mir-499b paralogues in response to chronic electrostimulation (7-fold increase for omy-mir-499ba and 2.5-fold increase for omy-mir-499bb). The higher expression of mir-499 paralogues in slow myoblasts suggests a role in phenotype determination, while the lack of significant differences of mir-133 copies during culture development might indicate a different role in fish compared with mammals. We have also found signs of sub-functionalization of mir-499 paralogues after electrostimulation, with omy-mir-499b copies more responsive to electrical signals.

Disruption of tight junction structure contributes to secretory dysfunction in IgG4-related sialadenitis

IgG4-related sialadenitis (IgG4-RS) is a chronic fibro-inflammatory disease characterized by swelling of salivary glands and varying degrees of xerostomia. Tight junctions (TJs) play an essential role in maintaining secretory function by regulating the paracellular flow of ions and water. However, whether TJs are altered and contribute to the hyposecretion in IgG4-RS is not fully understood. Here, a total of 399 differentially expressed proteins were identified in IgG4-RS submandibular glands (SMGs) and enriched in the regulation of actin cytoskeleton and the salivary secretion. Real-time PCR results showed that the mRNA levels of claudin-3, -4, -6, -7, -8, -10, -12, occludin, and ZO-1 were significantly lower, whereas claudin-1 and -5 were higher in IgG4-RS SMGs. Immunohistochemical and immunofluorescence staining revealed that claudin-1, -3, -4, occludin, and ZO-1 were mainly distributed at apicolateral membranes in acini and ducts of SMGs from controls, whereas claudin-1 protein intensity at apicolateral membrane was elevated, while the staining of claudin-3, -4, and ZO-1 were reduced in IgG4-RS SMGs. Occludin was dispersed into cytoplasm of acini and ducts in SMGs of patients. Among them, claudin-3 and ZO-1 protein levels were positively correlated with saliva flow rate. Furthermore, the decreased fluorescence intensity of F-actin at peri-apicolateral membranes and the loss of ZO-1 staining at the same location were observed in acinar and ductal cells of IgG4-RS SMGs, which might be responsible for disorganization of TJ complex. Taken together, these findings indicate that the integrity of TJ complex of SMGs is impaired and might contribute to hyposalivation of IgG4-RS patients.

Microphysiological sensing platform for an in-situ detection of tissue-secreted cytokines

Understanding the protein-secretion dynamics from single, specific tissues is critical toward the advancement of disease detection and treatments. However, such secretion dynamics remain difficult to measure in vivo due to the uncontrolled contributions from other tissue populations. Here, we describe an integrated platform designed for the reliable, near real-time measurements of cytokines secreted from an in vitro single-tissue model. In our setup, we grow 3D biomimetic tissues to discretize cytokine source, and we separate them from a magnetic microbead-based biosensing system using a Transwell insert. This design integrates physiochemically controlled biological activity, high-sensitivity protein detection (LOD < 20 pg mL-1), and rapid protein diffusion to enable non-invasive, near real-time measurements. To showcase the specificity and sensitivity of the system, we use our setup to probe the inflammatory process related to the protein Interleukine 6 (IL-6) and to the Tumor Necrosis Factor (TNF-α). We show that our setup can monitor the time-dependence profile of IL-6 and TNF-α secretion that results from the electrical and chemical stimulation of 3D skeletal muscle tissues. We demonstrate a novel and affordable methodology for discretizing the secretion kinetics of specific tissues for advancing metabolic-disorder studies and drug-screening applications.

Cell junctions and oral health

The oral cavity and its appendices are exposed to considerable environmental and mechanical stress. Cell junctions play a pivotal role in this context. Among those, gap junctions permit the exchange of compounds between cells, thereby controlling processes such as cell growth and differentiation. Tight junctions restrict paracellular transportation and inhibit movement of integral membrane proteins between the different plasma membrane poles. Adherens junctions attach cells one to another and provide a solid backbone for resisting to mechanistical stress. The integrity of oral mucosa, normal tooth development and saliva secretion depend on the proper function of all these types of cell junctions. Furthermore, deregulation of junctional proteins and/or mutations in their genes can alter tissue functioning and may result in various human disorders, including dental and periodontal problems, salivary gland malfunction, hereditary and infectious diseases as well as tumorigenesis. The present manuscript reviews the role of cell junctions in the (patho)physiology of the oral cavity and its appendices, including salivary glands.

Targeted TNF-α Overexpression Drives Salivary Gland Inflammation

Chronic inflammation of the salivary glands from pathologic conditions such as Sjögren's syndrome can result in glandular destruction and hyposalivation. To understand which molecular factors may play a role in clinical cases of salivary gland hypofunction, we developed an aquaporin 5 (AQP5) Cre mouse line to produce genetic recombination predominantly within the acinar cells of the glands. We then bred these mice with the TNF-αglo transgenic line to develop a mouse model with salivary gland-specific overexpression of TNF-α; which replicates conditions seen in sialadenitis, an inflammation of the salivary glands resulting from infection or autoimmune disorders such as Sjögren's syndrome. The resulting AQP5-Cre/TNF-αglo mice display severe inflammation in the salivary glands with acinar cell atrophy, fibrosis, and dilation of the ducts. AQP5 expression was reduced in the salivary glands, while tight junction integrity appeared to be disrupted. The immune dysregulation in the salivary gland of these mice led to hyposalivation and masticatory dysfunction.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

Disruption of CXCR3 function impedes the development of Sjögren's syndrome-like xerostomia in non-obese diabetic mice

The chemokine receptor CXCR3 plays an important role in T cell recruitment in various immune responses and autoimmune diseases. Expression of CXCR3 ligands, including CXCL9, CXCL10, and CXCL11, is elevated in the salivary glands of patients with Sjögren's syndrome (SS). To elucidate whether interaction between CXCR3 and its ligands is required for the development of SS, we administrated an anti-CXCR3 blocking antibody (CXCR3-173) to the non-obese diabetic (NOD) mice, a well-defined model of SS, during the stage prior to disease onset. Treatment with this anti-CXCR3 antibody significantly improved salivary secretion, indicating a remission of SS clinical manifestation. Anti-CXCR3 treatment did not affect the gross leukocyte infiltration of the submandibular glands (SMGs) as assessed by hematoxylin and eosin staining. However, flow cytometric analysis showed that anti-CXCR3 treatment markedly reduced the percentage of CXCR3⁺CD8 T and CXCR3⁺CD44⁺CD8 T cells, without affecting that of CXCR3⁺CD4 T and CXCR3⁺CD44⁺CD4 T cells in the SMGs and submandibular lymph nodes, suggesting a preferential effect of this anti-CXCR3 treatment on CXCR3-expressing effector CD8 T cells. Meanwhile, SMG expression of inflammatory factor TNF-α was markedly diminished by anti-CXCR3 treatment. In accordance, anti-CXCR3 significantly enhanced SMG expression of tight junction protein claudin-1 and water channel protein aquaporin 5, two molecules that are crucial for normal salivary secretion and can be down-regulated by TNF-α. Taken together, these findings demonstrated that the interaction between the endogenous CXCR3 and its ligands plays a pro-inflammatory and pathogenic role in the development of SS-like xerostomia in the NOD mouse model.

The G-Protein-Coupled Receptor ALX/Fpr2 Regulates Adaptive Immune Responses in Mouse Submandibular Glands

Lipoxin receptor (ALX)/N-formyl peptide receptor (FPR)-2 is a G-protein-coupled receptor that has multiple binding partners, including the endogenous lipid mediators resolvin D1, lipoxin A₄, and the Ca²⁺-dependent phospholipid-binding protein annexin A1. Previous studies have demonstrated that resolvin D1 activates ALX/Fpr2 to resolve salivary gland inflammation in the NOD/ShiLtJ mouse model of Sjögren syndrome. Moreover, mice lacking the ALX/Fpr2 display an exacerbated salivary gland inflammation in response to lipopolysaccharide. Additionally, activation of ALX/Fpr2 has been shown to be important for regulating antibody production in B cells. These previous studies indicate that ALX/Fpr2 promotes resolution of salivary gland inflammation while modulating adaptive immunity, suggesting the need for investigation of the role of ALX/Fpr2 in regulating antibody production and secretory function in mouse salivary glands. Our results indicate that aging female knockout mice lacking ALX/Fpr2 display a significant reduction in saliva flow rates and weight loss, an increased expression of autoimmune-associated genes, an up-regulation of autoantibody production, and increased CD20-positive B-cell population. Although not all effects were noted among the male knockout mice, the results nonetheless indicate that ALX/Fpr2 is clearly involved in the adaptive immunity and secretory function in salivary glands, with further investigation warranted to determine the cause(s) of these between-sex differences.

Anti-IL-7 receptor-α treatment ameliorates newly established Sjögren's-like exocrinopathy in non-obese diabetic mice

The levels of interleukin (IL)-7 and its receptor are elevated in the salivary glands of patients with Sjögren's syndrome (SS). Our previous study indicates that IL-7 plays a critical pathogenic role in the development and onset of SS in a mouse model of this disease. The present study aims at determining whether IL-7 also plays a role in sustaining SS pathologies after the disease onset, by using the non-obese diabetic (NOD) model. Intraperitoneal administration of a blocking antibody against the IL-7 receptor α chain (IL-7Rα) to female NOD mice aged 10 weeks, which exhibited newly onset clinical SS, for the duration of 3 weeks significantly ameliorated characteristic SS pathologies including hyposalivation and leukocyte infiltration of the submandibular glands (SMGs). These changes were accompanied by a decrease in IFN-γ-producing CD4 T- and CD8 T cells, B cells, and lymphocyte chemoattractants CXCL9, -10, -11 and -13 in the SMGs. Anti-IL-7Rα treatment markedly diminished the amount of TNF-α in the SMGs and increased the level of claudin-1 and aquaporin 5, two molecules critical for normal salivary secretion. Furthermore, neutralization of IFN-γ and TNF-α, individually or in combination, considerably improved salivary secretion, reduced leukocyte infiltration and down-regulated CXCL9 and -13 expression in the SMGs. Collectively, the results indicate that endogenous IL-7R signals promote Th1 and Tc1 responses and IFN-γ- and TNF-α production to sustain the persistence of SS-like sialadenitis in NOD mice. These findings suggest that IL-7 and Th1 cytokines could serve as promising therapeutic targets for this prevalent autoimmune disease.

Activation of Stimulator of Interferon Genes (STING) and Sjögren Syndrome

Sjögren syndrome (SS), a chronic autoimmune disorder causing dry mouth, adversely affects the overall oral health in patients. Activation of innate immune responses and excessive production of type I interferons (IFNs) play a critical role in the pathogenesis of this disorder. Recognition of nucleic acids by cytosolic nucleic acid sensors is a major trigger for the induction of type I IFNs. Upon activation, cytosolic DNA sensors can interact with the stimulator of interferon genes (STING) protein, and activation of STING causes increased expression of type I IFNs. The role of STING activation in SS is not known. In this study, to investigate whether the cytosolic DNA sensing pathway influences SS development, female C57BL/6 mice were injected with a STING agonist, dimethylxanthenone-4-acetic acid (DMXAA). Salivary glands (SGs) were studied for gene expression and inflammatory cell infiltration. SG function was evaluated by measuring pilocarpine-induced salivation. Sera were analyzed for cytokines and autoantibodies. Primary SG cells were used to study the expression and activation of STING. Our data show that systemic DMXAA treatment rapidly induced the expression of Ifnb1, Il6, and Tnfa in the SGs, and these cytokines were also elevated in circulation. In contrast, increased Ifng gene expression was dominantly detected in the SGs. The type I innate lymphoid cells present within the SGs were the major source of IFN-γ, and their numbers increased significantly within 3 d of treatment. STING expression in SGs was mainly observed in ductal and interstitial cells. In primary SG cells, DMXAA activated STING and induced IFN-β production. The DMXAA-treated mice developed autoantibodies, sialoadenitis, and glandular hypofunction. Our study demonstrates that activation of the STING pathway holds the potential to initiate SS. Thus, apart from viral infections, conditions that cause cellular perturbations and accumulation of host DNA within the cytosol should also be considered as possible triggers for SS.

Ca2+-CaMKKβ pathway is required for adiponectin-induced secretion in rat submandibular gland

Adiponectin functions as a promoter of saliva secretion in rat submandibular gland via activation of adenosine monophosphate-activated protein kinase (AMPK) and increased paracellular permeability. Ca²⁺ mobilization is the primary signal for fluid secretion in salivary acinar cells. However, whether intracellular Ca²⁺ mobilization is involved in adiponectin-induced salivary secretion is unknown. Here, we found that full-length adiponectin (fAd) increased intracellular Ca²⁺ and saliva secretion in submandibular glands. Pre-perfusion with ethylene glycol-bis (2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) combined with thapsigargin (TG), an endoplasmic reticulum Ca²⁺-ATPase inhibitor, abolished fAd-induced salivary secretion, AMPK phosphorylation, and enlarged tight junction (TJ) width. Furthermore, in cultured SMG-C6 cells, co-pretreatment with EGTA and TG suppressed fAd-decreased transepithelial electrical resistance and increased 4-kDa FITC-dextran flux responses. Moreover, fAd increased phosphorylation of calcium/calmodulin-dependent protein kinase (CaMKKβ), a major kinase that is activated by elevated levels of intracellular Ca²⁺, but not liver kinase B1 phosphorylation. Pre-perfusion of the isolated gland with STO-609, an inhibitor of CaMKKβ, abolished fAd-induced salivary secretion, AMPK activation, and enlarged TJ width. CaMKKβ shRNA suppressed, whereas CaMKKβ re-expression rescued fAd-increased paracellular permeability. Taken together, these results indicate that adiponectin induced Ca²⁺ modulation in rat submandibular gland acinar cells. Ca²⁺-CaMKKβ pathway is required for adiponectin-induced secretion through mediating AMPK activation and increase in paracellular permeability in rat submandibular glands.

AT-RvD1 combined with DEX is highly effective in treating TNF-α-mediated disruption of the salivary gland epithelium

Sjögren's syndrome (SS) is an autoimmune disorder characterized by chronic inflammation and destruction of salivary and lacrimal glands leading to dry mouth and dry eyes, respectively. Currently, the etiology of SS is unknown and the current therapies have no permanent benefit; therefore, new approaches are necessary to effectively treat this condition. Resolvins are highly potent endogenous lipid mediators that are synthesized during the resolution of inflammation to restore tissue homeostasis. Previous studies indicate that the resolvin family member, RvD1, binds to the ALX/FPR2 receptor to block inflammatory signals caused by tumor necrosis factor-alpha (TNF-α) in the salivary epithelium. More recently, the corticosteroid, dexamethasone (DEX), was shown to be effective in reducing salivary gland inflammation. However, DEX, as with other corticosteroids, elicits adverse secondary effects that could be ameliorated when used in smaller doses. Therefore, we investigated whether the more stable aspirin-triggered (AT) epimer, AT-RvD1, combined with reduced doses of DEX is effective in treating TNF-α-mediated disruption of polarized rat parotid gland (Par-C10) epithelial cell clusters. Our results indicate that AT-RvD1 and DEX individually reduced TNF-α-mediated alteration in the salivary epithelium (i.e, maintained cell cluster formation, increased lumen size, reduced apoptosis, and preserved cell survival signaling responses) as compared to untreated cells. Furthermore, AT-RvD1 combined with a reduced dose of DEX produced stronger responses (i.e., robust salivary cell cluster formation, larger lumen sizes, further reduced apoptosis, and sustained survival signaling responses) as compared to those observed with individual treatments. These studies demonstrate that AT-RvD1 combined with DEX is highly effective in treating TNF-α-mediated disruption of salivary gland epithelium.

Estrogen decreases tight junction protein ZO-1 expression in human primary gut tissues

Females have a higher prevalence of most autoimmune diseases; however, the mechanism is unknown. In this study, we examined the expression of tight junction protein zonula occludens 1 (ZO-1) and estrogen receptor (ER)-α/β in human primary gut tissues by immunohistochemistry, immunofluorescence and qPCR. The expression of ZO-1 and ER-β but not ER-α was present in both male and female gut tissues. There was no sex difference in ER-β expression, but ZO-1 expression was decreased in females compared to males. In vitro, estrogen treatment decreased ZO-1 mRNA and protein expression, ZO-1 promoter activity, IL-6 production, and NF-κB activation in human primary gut tissues or the Caco-2 cells, but increased the ER-β expression in Caco-2 cells. Consistently, plasma IL-6 levels in females were reduced relative to males in vivo. Our finding indicates that estrogen may play a role in gut tight junction expression and permeability.

Innate immunity in Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disease of exocrine tissue that primarily affects women. Although patients typically experience xerostomia and xerophthalmia, numerous systemic disease manifestations are seen. Innate immune hyperactivity is integral to many autoimmune diseases, including SS. Results from SS mouse models suggest that innate immune dysregulation drives disease and this is a seminal event in SS pathogenesis. Findings in SS patients corroborate those in mouse models, as innate immune cells and pathways are dysregulated both in exocrine tissue and in peripheral blood. We will review the role of the innate immune system in SS pathogenesis. We will discuss the etiology of SS with an emphasis on innate immune dysfunction. Moreover, we will review the innate cells that mediate inflammation in SS, the pathways implicated in disease, and the potential mechanisms governing their dysregulation. Finally, we will discuss emerging therapeutic approaches to target dysregulated innate immune signaling in SS.

Clinical Efficacy and Safety of Total Glucosides of Paeony for Primary Sjögren's Syndrome: A Systematic Review

OBJECTIVE

To evaluate the clinical efficacy and safety of total glucosides of paeony (TGP) for primary Sjögren's syndrome (pSS).

METHODS

Eight electronic databases were searched from their inception to July 2016. Clinical randomized controlled trials (RCTs) were included. The study quality was evaluated according to the standard suggested in the Cochrane Handbook. RevMan 5.1 was used for statistical analysis.

RESULTS

Seven RCTs involving 443 patients were included. The results showed that TGP combined with an immunosuppressant (IS) showed greater efficacy for improving the saliva flow test of pSS compared to immunosuppressant alone (WMD -6.88, 95% CI -9.02 to -4.74, and P < 0.00001). And the same trend favouring TGP-IS dual combination was found in Schirmer test (WMD 1.63, 95% CI 0.26 to 3.01, and P = 0.02), ESR (WMD 7.33, 95% CI -10.08 to -4.59, and P < 0.00001), CRP (WMD -6.00, 95% CI -7.17 to -4.83, and P < 0.00001), IgM (WMD = -0.42, 95% CI -0.70 to 0.13, and P = 0.004), and IgG (WMD -3.22, 95% CI -4.32 to -2.12, and P < 0.00001) analysis. However, TGP did not affect IgA (WMD 0.53, 95% CI -1.34 to -0.29, and P = 0.20). The adverse events manifested no significant differences between the two groups.

CONCLUSIONS

The TGP-IS combination is superior to IS alone in the treatment of pSS. However, due to the low quality of included studies, high-quality RCTs are needed to confirm the beneficial effects of TGP.