Functional effects of proinflammatory factors present in Sjögren's syndrome salivary microenvironment in an in vitro model of human salivary gland

Experimental apical periodontitis alters salivary biochemical composition and induces local redox state disturbances in the salivary glands of male rats

OBJECTIVES

The objective was to evaluate the effects of experimental apical periodontitis on the inflammatory, functional, biochemical, and redox parameters of the parotid and submandibular glands in rats.

MATERIALS AND METHODS

Twenty 12-week-old male Wistar rats were randomly divided into two groups (n = 10): a control group and apical periodontitis group. After 28 days, the saliva was collected for salivary flow rate and biochemistry composition. Both glands were sampled for quantification of the tumor necrosis factor-alpha (TNF-α) and biochemical analyses of redox state.

RESULTS

TNF-α concentrations were higher in both salivary glands adjacent to the periapical lesions in animals with apical periodontitis and also compared to the control group. The apical periodontitis group increased the salivary amylase, chloride, potassium, calcium, and phosphate. The total oxidant capacity increased in the parotid gland adjacent to the periapical lesions in the same rat and compared to the control group. Conversely, the total antioxidant capacity of the parotid glands on both sides in the apical periodontitis group was lower than that in the control group. Furthermore, glutathione peroxidase activity increased in the submandibular gland adjacent to the apical periodontitis group compared to the control group.

CONCLUSIONS

Experimental apical periodontitis alters salivary biochemical composition, in addition to increasing inflammatory marker and inducing local disturbances in the redox state in the parotid and submandibular glands of male rats.

CLINICAL RELEVANCE

Apical periodontitis could exacerbate the decline in oral health by triggering dysfunction in the salivary glands.

Alterations in histology of the aging salivary gland and correlation with the glandular inflammatory microenvironment

Aging-related salivary dysfunction typically causes reduced saliva volumes, which leads to debilitating consequences, even affecting patient quality of life. Understanding the respective clinicopathological characteristics and molecular mechanisms underlying salivary gland functioning during aging is vital for therapeutic purposes. Here, we provide a detailed atlas of the salivary gland microenvironment during aging, and we identified several phenotypes characteristic of aging salivary glands, including acini atrophy, increased inflammatory cells, altered immune responses, and accumulation of lysosomes and autophagosomes in aging cells, which may reflect progressive degeneration of salivary gland function. Furthermore, our analyses suggested significant enrichment of metabolic pathways in aging glands. Our results revealed complex cellular cross-talk among aging acinar cells, inflammatory factors, and immune responses. A natural aging animal model was established to verify these findings. This study provides mechanistic insights into age-related clinicopathogenesis, important implications for early diagnosis, and identification of new targets for improving salivary gland dysfunction.

Genome-wide association study identifies Sjögren's risk loci with functional implications in immune and glandular cells

Sjögren's disease is a complex autoimmune disease with twelve established susceptibility loci. This genome-wide association study (GWAS) identifies ten novel genome-wide significant (GWS) regions in Sjögren's cases of European ancestry: CD247, NAB1, PTTG1-MIR146A, PRDM1-ATG5, TNFAIP3, XKR6, MAPT-CRHR1, RPTOR-CHMP6-BAIAP6, TYK2, SYNGR1. Polygenic risk scores yield predictability (AUROC = 0.71) and relative risk of 12.08. Interrogation of bioinformatics databases refine the associations, define local regulatory networks of GWS SNPs from the 95% credible set, and expand the implicated gene list to >40. Many GWS SNPs are eQTLs for genes within topologically associated domains in immune cells and/or eQTLs in the main target tissue, salivary glands.

Inflammatory Stratification in Primary Sjögren's Syndrome Reveals Novel Immune Cell Alterations in Patients' Minor Salivary Glands

There is a critical need to deconvolute the heterogeneity displayed by the minor salivary glands of primary Sjögren’s syndrome (pSS) patients. This is challenging primarily because the disease etiology remains unknown. The hypothesis includes that initial events in the disease pathogenesis target the salivary glands, thereby triggering the development of focal infiltrates (≥50 mononuclear cells) and finally germinal center-like structures. However, the proportion of key mononuclear immune cells residing at these sites, in combination with the overall ratio of morphometric tissue atrophy and adipose infiltration within the minor salivary glands (MSG) parenchyma at distinct phases of inflammatory disease establishment and progression have not been quantified in detail. In this cross-sectional study, we intended to address this problem by stratifying 85 patients into mild (S1), moderate (S2), and severe (S3) stages using the Inflammatory severity index. We found that mild (<3%) and marked (≥3%) levels of atrophy were accompanied by the respective levels of adipose infiltration in the non-SS sicca controls (p <0.01), but not in pSS patients. The percentage of adipose infiltration significantly correlated with the age of patients (r = 0.458, p <0.0001) and controls (r = 0.515, p <0.0001). The CD4⁺ T helper cell incidence was reduced in the focal infiltrates of the MSG of S2 patients compared to S1 (p <0.01), and in S2 compared to S1 and S3 combined (p <0.05). CD20⁺ B cells increased from S1 to S3 (p <0.01) and S2 to S3 (p <0.01), meanwhile CD138⁺ plasma cells diminished in S3 patients compared to both S1 and S2 groups combined (p <0.01). The proportion of patients with anti-Ro/SSA⁺, anti-La/SSB⁺, and RF⁺ increased over the course of inflammatory disease progression and they were significantly more common in the S3 group relative to S1 (p <0.05). On the other hand, S2 patients measured a higher mean salivary flow relative to S1 and S3 patients combined (p <0.05). Our results demonstrate how the proposed Inflammatory severity index stratification revealed pathological cell and tissue-associated aberrations in the salivary component over the course of inflammatory progression, and their correlations to clinical outcomes. This could be directly transferred to the optimization of available diagnostic strategies applied for pSS patients.

In vitro effects of curcumin on proinflammatory cytokines and expression of their genes in minor salivary gland tissue of patients with Sjogren's syndrome

Curcumin reduces disease severity and ameliorates lupus-like/Sjögren's Syndrome-like disease in mice model. The immunological basis of these effects is largely unknown. This study examined the effects of curcumin on pro-inflammatory cytokines secreted by minor salivary glands in patients with primary Sjögren's syndrome (pSS). Minor salivary gland (MSG) tissue samples were collected from patients undergoing biopsy for suspected pSS. The tissues were treated with phytohemagglutinin (PHA) alone as well as PHA with curcumin (30 μM) and cultured in RPMI 1640 medium for 48 h at 37 °C in CO₂ incubator. After the incubation period, culture supernatant and tissues were stored in the freezer (-80 °C). IL-6 levels were measured in supernatant by ELISA kit. Gene expressions of pro-inflammatory cytokines, namely IL-6, IL-8, TNF-α, IL-1β, IL-4, IL-10, IL-17, IL-21, and IFN-γ, were measured by qPCR. IL-6 secretion levels and gene expressions were compared statistically between groups by Student's t test. Forty-seven patients were screened. Eight patients satisfied ACR/EULAR criteria for pSS. Seven patients with absent glandular inflammation and negative serology constituted sicca controls. These 15 subjects were included in final analysis. In pSS group, but not in controls, median IL-6 levels in supernatant were less in curcumin-treated as compared to PHA-alone subset [5.5 (0.7-13.34) vs 18.3 (12-32) ng/ml; p = 0.0156]. mRNA expression levels of IL-6 were also lower in curcumin-treated samples as compared to PHA alone, when cases and controls were analyzed together as well as in cases alone (p = 0.0009 and p = 0.0078, respectively); however, mRNA expression of IL-1β was lower in curcumin-treated samples as compared to PHA alone, only when cases and controls were analyzed together (p = 0.0215). There was no difference in other cytokine gene expression levels between the subsets under the in-vitro experimental conditions. In conclusion, curcumin reduced mRNA expression as well as secretion of IL-6 levels by salivary gland tissue of patients with pSS. Curcumin also suppressed PHA-induced mRNA expression levels of IL-6 and IL-1β in MSG tissue of patients with pSS and controls when analyzed together as a combined group.

Comparison of postoperative cytokine and hormone between endoscopically assisted and open parotid tumor resection

OBJECTIVE

Endoscopically assisted extracapsular dissection through a single incision along the cephaloauricular furrow has been adapted as a method of access for operating on benign parotid gland tumors. However, no study has compared the immune and stress responses after surgery between the endoscopic procedure and conventional open surgery.

METHODS

Through a randomized method, 50 patients with benign parotid gland tumors were assigned to undergo either endoscopically assisted extracapsular dissection or open parotidectomy. The postoperative inflammatory changes and hormonal response in the patients were analyzed at serum level during the preoperative period and at 12, 24, and 72 hr after either surgery.

RESULTS

Twenty-three patients received an endoscopic procedure, while 27 underwent open surgery. The size of the incision, amount of intraoperative bleeding, volume of drainage, postoperative pain score, and satisfaction with appearance were all improved in the endoscopic procedure group. Additionally, the serum levels of C-reactive protein, interleukin (IL)-6, IL-10, and cortisol were significantly lower in the endoscopy group in comparison with those in the open surgery group.

CONCLUSION

Endoscopically assisted extracapsular dissection on patients with benign parotid gland tumors is associated with lower inflammatory changes and hormone responses than open surgery, thereby reducing perioperative pathophysiological disturbance and enhancing recovery after surgery.

Current State of Knowledge on Primary Sjögren's Syndrome, an Autoimmune Exocrinopathy

Primary Sjögren's syndrome (pSS) is a chronic systemic autoimmune rheumatic disease characterized by lymphoplasmacytic infiltration of the salivary and lacrimal glands, whereby sicca syndrome and/or systemic manifestations are the clinical hallmarks, associated with a particular autoantibody profile. pSS is the most frequent connective tissue disease after rheumatoid arthritis, affecting 0.3-3% of the population. Women are more prone to develop pSS than men, with a sex ratio of 9:1. Considered in the past as innocent collateral passive victims of autoimmunity, the epithelial cells of the salivary glands are now known to play an active role in the pathogenesis of the disease. The aetiology of the "autoimmune epithelitis" still remains unknown, but certainly involves genetic, environmental and hormonal factors. Later during the disease evolution, the subsequent chronic activation of B cells can lead to the development of systemic manifestations or non-Hodgkin's lymphoma. The aim of the present comprehensive review is to provide the current state of knowledge on pSS. The review addresses the clinical manifestations and complications of the disease, the diagnostic workup, the pathogenic mechanisms and the therapeutic approaches.

Insight into Salivary Gland Aquaporins

The main role of salivary glands (SG) is the production and secretion of saliva, in which aquaporins (AQPs) play a key role by ensuring water flow. The AQPs are transmembrane channel proteins permeable to water to allow water transport across cell membranes according to osmotic gradient. This review gives an insight into SG AQPs. Indeed, it gives a summary of the expression and localization of AQPs in adult human, rat and mouse SG, as well as of their physiological role in SG function. Furthermore, the review provides a comprehensive view of the involvement of AQPs in pathological conditions affecting SG, including Sjögren's syndrome, diabetes, agedness, head and neck cancer radiotherapy and SG cancer. These conditions are characterized by salivary hypofunction resulting in xerostomia. A specific focus is given on current and future therapeutic strategies aiming at AQPs to treat xerostomia. A deeper understanding of the AQPs involvement in molecular mechanisms of saliva secretion and diseases offered new avenues for therapeutic approaches, including drugs, gene therapy and tissue engineering. As such, AQP5 represents a potential therapeutic target in different strategies for the treatment of xerostomia.