New epitopes and function of anti-M3 muscarinic acetylcholine receptor antibodies in patients with Sjögren's syndrome

Primary Sjögren's syndrome: new perspectives on salivary gland epithelial cells

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease primarily affecting exocrine glands such as the salivary glands, leading to impaired secretion and sicca symptoms. As the mainstay of salivation, salivary gland epithelial cells (SGECs) have an important role in the pathology of pSS. Emerging evidence suggests that the interplay between immunological factors and SGECs may not be the initial trigger or the sole mechanism responsible for xerostomia in pSS, challenging conventional perceptions. To deepen our understanding, current research regarding SGECs in pSS was reviewed. Among the extensive aberrations in cellular architecture and function, this review highlighted certain alterations of SGECs that were identified to occur independently of or in absence of lymphocytic infiltration. In particular, some of these alterations may serve as upstream factors of immuno-inflammatory responses. These findings underscore the significance of introspecting the pathogenesis of pSS and developing interventions targeting SGECs in the early stages of the disease.

The study of serum muscarinic acetylcholine receptor subtype 3 (m3AChR)-Specific autoantibodies level in rheumatoid arthritis patients with secondary sjogren syndrome

BACKGROUND

Dry eyes and mouth are symptoms of Sjogren syndrome, which can occur on its own and be referred to as primary Sjogren syndrome or in conjunction with other rheumatic diseases like rheumatoid arthritis and be referred to as secondary Sjogren syndrome. Anti-muscarinic type 3 receptors have been linked to neurological issues as well as secretory dysfunction in Sjogren patients. Consequently, the purpose of this study is to determine the serum level of muscarinic acetylcholine receptor subtype 3 (m3AChR)-specific autoantibodies in rheumatoid arthritis (RA) patients and evaluate its relationship to disease activity, functional disability, and to study its role in the development of secondary Sjogren syndrome manifestations in those patients.

METHODS

In this cross-sectional study, 30 RA patients with secondary Sjogren syndrome signs and 30 RA patients without secondary Sjogren syndrome manifestations were included, along with 30 healthy volunteers who were aged, and sex matched as controls. All participants underwent thorough clinical examination, evaluation of disease activity using the DAS28 score, assessment of functional status using the modified health assessment questionnaire (MHAQ), and evaluation of the serum level of (m3AChR) by (ELISA).

RESULTS

When compared to RA patients without secondary Sjogren syndrome and healthy controls (20.09 ± 4.24, 18.36 ± 3.59 ng/ml respectively), the serum level of m3AChR antibodies among 30 RA patients with secondary Sjogren syndrome considerably increased (mean 25.98 ± 4.81 ng/ml).Analysis of the m3AChR's (ROC)-curve revealed that the three groups under study differed significantly (P < 0.001), with the AUC (0.806), cutoff (> 22.63ng/ml), sensitivity (73.33%), and specificity (86.67%) all exceeding the threshold. Additionally, there was a significant positive connection between the serum level of m3AChR and the following variables (P < 0.05): DAS scores, MHAQ score, number of tender & swollen joints, and acute phase reactants.

CONCLUSION

Autoantibodies against m3AChR may be one of the serum components involved in the pathophysiology of secondary Sjogren syndrome in RA patients, and because of their high sensitivity and specificity, they can be utilized as a diagnostic marker in these individuals.

No evidence of increased anti-M3 muscarinic acetylcholine receptor autoantibodies in SSA-positive connective tissue disease patients

Anti-muscarinic type 3 receptor autoantibodies (M3R) and anti-SSA antibodies are both related to salivary secretion. The presence of M3R antibodies in Sjögren's syndrome is previously demonstrated; nevertheless, the relationship between the anti-SSA antibodies and M3R fragment antibodies, namely the N terminal, first, second, and third extracellular loops, remains to be elucidated. In this study, we analyzed the antibodies against the M3R epitopes in healthy controls and anti-SSA antibody-positive connective tissue disease patients through ELISA method. Antibodies against the first, second, and third extracellular loop (M3R211-230 ) were not increased in anti-SSA positive patients compared to healthy controls. Indeed, antibodies against the N terminal (M3R1-33 ) were found to be high in healthy controls. High levels of M3R1-33 in healthy controls are a novel original finding; further research is needed for the clinical significance. There is no significant difference between SSA-positive patients and healthy controls in terms of autoantibodies against the remainder of the linear M3R fragments.

Autoantibodies identify primary Sjögren's syndrome in patients lacking serum IgG specific for Ro/SS-A and La/SS-B

OBJECTIVE

Identify autoantibodies in anti-Ro/SS-A negative primary Sjögren's syndrome (SS).

METHODS

This is a proof-of-concept, case-control study of SS, healthy (HC) and other disease (OD) controls. A discovery dataset of plasma samples (n=30 SS, n=15 HC) was tested on human proteome arrays containing 19 500 proteins. A validation dataset of plasma and stimulated parotid saliva from additional SS cases (n=46 anti-Ro+, n=50 anti-Ro-), HC (n=42) and OD (n=54) was tested on custom arrays containing 74 proteins. For each protein, the mean+3 SD of the HC value defined the positivity threshold. Differences from HC were determined by Fisher's exact test and random forest machine learning using 2/3 of the validation dataset for training and 1/3 for testing. Applicability of the results was explored in an independent rheumatology practice cohort (n=38 Ro+, n=36 Ro-, n=10 HC). Relationships among antigens were explored using Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) interactome analysis.

RESULTS

Ro+ SS parotid saliva contained autoantibodies binding to Ro60, Ro52, La/SS-B and muscarinic receptor 5. SS plasma contained 12 novel autoantibody specificities, 11 of which were detected in both the discovery and validation datasets. Binding to ≥1 of the novel antigens identified 54% of Ro- SS and 37% of Ro+ SS cases, with 100% specificity in both groups. Machine learning identified 30 novel specificities showing receiver operating characteristic area under the curve of 0.79 (95% CI 0.64 to 0.93) for identifying Ro- SS. Sera from Ro- cases of an independent cohort bound 17 of the non-canonical antigens. Antigenic targets in both Ro+ and Ro- SS were part of leukaemia cell, ubiquitin conjugation and antiviral defence pathways.

CONCLUSION

We identified antigenic targets of the autoantibody response in SS that may be useful for identifying up to half of Ro seronegative SS cases.

OC-01 (Varenicline Solution) Nasal Spray for the Treatment of Dry Eye Disease Signs and Symptoms in Subjects with Autoimmune Disease: Integrated Data from ONSET-1 and ONSET-2

Purpose

We evaluate the treatment effect of OC-01 (varenicline solution) nasal spray (VNS) in dry eye disease (DED) subjects from two randomized trials who self-reported autoimmune disease (AID).

Patients and Methods

Post hoc subgroup analysis of subjects reporting a history of AID from the integrated OC-01 VNS 0.03 or 0.06 mg and vehicle control (VC) treatment groups of the ONSET-1 and ONSET-2 trials. Mean change in Schirmer test with anesthesia score (STS, mm) and Eye Dryness Score (EDS) from baseline to 28 days was compared between OC-01 VNS and VC groups. Consistency of treatment effect in subjects with and without AID was evaluated using treatment-subgroup interaction terms in ANCOVA models for mean changes from baseline STS and EDS, and in a logistic regression model for proportion achieving ≥10 mm STS improvement.

Results

Of the 891 participants, 31 reported comorbid AID. In all models, the treatment-subgroup interaction terms were not significant (p>0.05), indicating consistency of therapeutic effect of OC-01 VNS in subjects with and without AID. In subjects with AID, the treatment difference for STS was 11.8 mm and -9.3 for EDS and difference for proportion of subjects with ≥10 mm STS improvement was 61.1%. The most common adverse event was sneeze (82-84%), graded as mild by 98% of subjects.

Conclusion

OC-01 VNS demonstrated consistency in improving both tear production and patient-reported symptoms in subjects with AID, consistent with pivotal ONSET-1 and 2 trial results. Further investigation is warranted, and results may further support use of OC-01 VNS for DED in AID patients.

Autoimmune autonomic nervous system imbalance and conditions: Chronic fatigue syndrome, fibromyalgia, silicone breast implants, COVID and post-COVID syndrome, sick building syndrome, post-orthostatic tachycardia syndrome, autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants

Chronic fatigue syndrome (CFS), fibromyalgia, silicone breast implants syndrome (SBIs), COVID and post-COVID syndrome (PCS), sick building syndrome (SBS), post-orthostatic tachycardia syndrome (POTS), autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants (ASIA) are frequently accompanied by clinical symptoms characteristic for dysautonomia: severe fatigue, dizziness, fogginess, memory loss, dry mouth and eyes, hearing dysfunction, tachycardia etc. The recent discovery of an imbalance of autoantibodies against G protein-coupled receptors (GPCR) in some autoimmune diseases, post-COVID syndrome, SBIs allowed researchers to assume the novel mechanism in these conditions - autoimmune autonomic nervous system imbalance. In this review, all data published on an imbalance of autoantibodies against GPCR, clinical symptoms and pathogenic mechanisms in CFS, Fibromyalgia, SBIs, COVID and PCS, SBS, POTS, and some autoimmune diseases were analyzed. Possible criteria to diagnose the autoimmune autonomic nervous system imbalance were created.

WITHDRAWN: Autoimmune autonomic nervous system imbalance and conditions: Chronic fatigue syndrome, fibromyalgia, silicone breast implants, COVID and post-COVID syndrome, sick building syndrome, post-orthostatic tachycardia syndrome, autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants

The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.autrev.2022.103230. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Evaluation of Inhibitory Antibodies against the Muscarinic Acetylcholine Receptor Type 3 in Patients with Primary Biliary Cholangitis and Primary Sclerosing Cholangitis

Background: Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) constitute rare chronic inflammatory biliary diseases which likely comprise genetic, environmental and autoimmune factors. Specific inhibitory (auto-) antibodies against the muscarinic acetylcholine receptor type 3 (mAChR3 auto-ab) may contribute to the pathogenesis of chronic biliary inflammation by modulating mAChR3− mediated signaling. Aims: The aim of this study was to analyze the prevalence and relevance of inhibitory mAChR3 auto-ab (mAChR3inh+ auto-ab) in a large cohort of PBC patients from two independent tertiary centers in Berlin and Leipzig in comparison to a large PSC cohort. Baseline parameters and response rates to standard treatment with ursodeoxycholic acid (UDCA) were characterized with respect to the individual mAChR3 auto-ab status. Methods: In total, the study population comprised 437 PBC patients, 187 PSC patients and 80 healthy controls. Clinical and laboratory baseline characteristics were retrieved from medical records. The response to ursodeoxycholic acid (UDCA) therapy after 12 months of treatment was available in 176 PBC and 45 PSC patients. Results: The prevalence of mAChR3inh+ auto-ab was significantly higher among PBC patients (11.2%, 49/437; p = 0.008 vs. healthy controls) and PSC patients (33.6%, 63/187; p < 0.0001 vs. healthy controls) compared to healthy controls (2.5%, 2/80), respectively. PBC patients with mAChR3inh+ auto-ab exhibited significantly higher levels of alkaline phosphatase (ALP) and bilirubin, which constitute established parameters for PBC risk stratification. Moreover, mAChR3inh+ PBC patients tended to show decreased response rates to UDCA therapy compared to PBC patients without mAChR3inh+ auto-ab (mAChR3− PBC). In contrast, PSC patients with mAChR3inh+ auto-ab showed no significant differences in laboratory findings compared to mAChR3 auto-ab negative (mAChR3−) PSC patients. Conclusion: MAChR3inh+ auto-ab might be involved in the pathogenesis and treatment response of chronic biliary inflammation in patients with PBC but not in patients with PSC.

Autoantibodies as Endogenous Modulators of GPCR Signaling

Endogenous self-reactive autoantibodies (AAs) recognize a range of G-protein-coupled receptors (GPCRs). They are frequently associated with cardiovascular, neurological, and autoimmune disorders, and in some cases directly impact disease progression. Many GPCR AAs modulate receptor signaling, but molecular details of their modulatory activity are not well understood. Technological advances have provided insight into GPCR biology, which now facilitates deeper understanding of GPCR AA function at the molecular level. Most GPCR AAs are allosteric modulators and exhibit a broad range of pharmacological properties, altering both receptor signaling and trafficking. Understanding GPCR AAs is not only important for defining how these unusual GPCR modulators function in disease, but also provides insight into the potential use and limitations of using therapeutic antibodies to modulate GPCR signaling.

Investigation of the relationship between the pelvic floor and sexual dysfunction in women with Sjögren's syndrome

BACKGROUND AND AIM

Women with Sjögren's syndrome (SS) may have sexual dysfunctions due to vaginal dryness and may also have pelvic floor problems. The aim of this study was to examine the pelvic floor distress of women with SS with a self-reported questionnaire, to compare this group with healthy individuals, and to examine the relationship between pelvic floor problems and sexual dysfunction.

METHODS

The study included 94 women with SS, aged 47.26 ± 7.56 years, and 94 age-matched healthy women, aged 48.15 ± 8.73 years. The Pelvic Floor Disease Inventory (PFDI-20), Pelvic Floor Impact Questionnaire (PFIQ-7), and Female Sexual Function Scale (FSFI) were used for assessment.

RESULTS

The PFDI-20, PFIQ-7, and FSFI scores of the healthy control group were found to be statistically significantly better than those of the primary SS group (Z = -2.69 to -8.03, P = .00). A moderate-high correlation was found between the total and sub-parameters of PFDI-20 and disease duration, the total and sub-parameters of the PFIQ-7 and the pain sub-parameter and total score of the FSFI (r = -0.66 to 0.78, P = .00-.04).

CONCLUSION

According to the study results, as the disease duration increases, the distress increases and this distress has a negative effect on the health-related quality of life of these women. Pelvic floor distress was associated with poor sexual function and pain. From these results, it can be recommended that the methods of pharmacology, education, exercise, relaxation, lifestyle change, and so on for pelvic floor dysfunction and pain in women with SS should be applied together with a multidisciplinary approach.

Significance of anti-Ro/SSA antibodies in the response and retention of abatacept in patients with rheumatoid arthritis: a multicentre cohort study

Objective: To determine whether the positivity of baseline anti-Ro/Sjögren's syndrome antigen A (SSA) antibodies influences the response to abatacept, we compared therapeutic responses between anti-Ro/SSA antibody-negative and -positive patients with rheumatoid arthritis (RA) using a multicentre RA ultrasonography prospective cohort. Method: We reviewed Japanese patients with RA who started abatacept as the first biological disease-modifying anti-rheumatic drug between June 2013 and April 2018. We assessed 28-joint Disease Activity Score-erythrocyte sedimentation rate (DAS28-ESR) change between baseline and 6 or 12 months after treatment in RA patients treated with abatacept, and European League Against Rheumatism (EULAR) response at 6 and 12 months. The Global OMERACT-EULAR Synovitis Score (GLOESS) was calculated at baseline and at 6 and 12 months. Results: Overall, 51 patients were enrolled and divided into anti-Ro/SSA antibody-negative and -positive groups of 35 and 16, respectively. Median age at baseline was significantly higher in the anti-Ro/SSA antibody-negative group (p = 0.04). The retention rate and percentage of EULAR good responders at 12 months were significantly higher in the anti-Ro/SSA antibody-negative group (both p = 0.02). Anti-Ro/SSA antibody-negative patients exhibited larger decreases in both DAS28-ESR and DAS28-C-reactive protein at 12 months than anti-Ro/SSA antibody-positive patients (p = 0.02 and 0.04, respectively). GLOESS decreased significantly at 6 months in anti-Ro/SSA antibody-negative patients (p = 0.03). Multivariate analyses showed that anti-Ro/SSA antibody positivity was an independent factor associated with change in the DAS28-ESR at 6 months (p < 0.05). Conclusion: Anti-Ro/SSA antibody positivity predicts a poor response to abatacept and low retention rate.

M3 muscarinic acetylcholine receptor-reactive Th17 cells in primary Sjögren's syndrome

M3 muscarinic acetylcholine receptor (M3R) is one of the autoantigens associated with Sjögren's syndrome (SS) and is localized in exocrine glands where disease-specific inflammation occurs. The inflammatory lesion is characterized by infiltration of CD4+ T cells, including clonally expanded Th17 cells. We undertook this study to identify circulating M3R-specific Th17 cells and to determine functional properties of those cells. Using the enzyme-linked immunospot assay (ELISpot) method, we identified M3R-reactive Th17 cells in the peripheral blood of patients with primary SS (pSS). Among 10 examined pSS patients, 10 healthy subjects (HS), and 5 IgG4-related disease (IgG4-RD) patients, M3R-reactive IL-17 secreting cells were significantly increased in 5 pSS patients specifically. The most common T cell epitope, which was analyzed and confirmed by coculture of isolated CD4+ T cells with antigen presenting cells plus M3R peptides in vitro, was peptide 83-95 of M3R. Peptide recognition was partly in an HLA-DR-restricted manner, confirmed by blocking assay. M3R-reactive Th17 cells positivity correlated with higher titers of anti-M3R antibodies, whose systemic disease activity score tended to be higher. Our studies highlight the role of tissue-specific autoantigen-derived circulating Th17 cells in pSS, for which further work might lead to antigen-specific targeted therapy.

Antibodies to the Muscarinic Acetylcholine Receptor M3 in Primary Biliary Cholangitis Inhibit Receptor Function on Cholangiocytes

Background and Aims: In primary biliary cholangitis (PBC), antibodies to a peptide of the muscarinic acetylcholine receptor 3 (mAChR3) have been described. Since the mAChR3 is expressed on cholangiocytes and mAChR3-signaling is involved in the pathogenesis of chronic inflammatory biliary diseases, we wanted to investigate whether anti-mAChR3-antibodies influence the function of the receptor and the proliferative response of cholangiocytes. Methods: Immunoglobulins were isolated by ammonium sulfate precipitation using sera from patients with PBC (n = 63) and with other chronic liver disorders (n = 150). All immunoglobulins were analyzed by a luminometric assay using Chinese hamster ovary (CHO) cells overexpressing the mAChR3 and cholangiocytes (TFK-1-cells) expressing the receptor constitutively. Cell proliferation was measured by ³H-thymidine assay. PBC patients were also analyzed in the follow-up. Results: Antibodies inhibiting the mAChR3 were found in 49 and 79% of PBC patients using CHO-cells or TFK-1-cells, respectively, but only in up to 26% of controls (p < 0.01). Stimulatory antibodies were hardly detected. Antibody reactivity only marginally changed during the course of the disease, independently of the choice of treatment (ursodeoxycholic acid, immunosuppressive therapy, or no medication). There was no correlation with laboratory, clinical or histological parameters, but the antibodies were more frequently found in PBC patients with a benign course (96%) than in patients with active disease progressing to late stages within 10 years (57%; p < 0.01). Proliferation of cells was not influenced by immunoglobulins from PBC-patients. Conclusion: Sera from patients with PBC contain inhibitory antibodies to the mAChR3 on cholangiocytes (TFK-1 cells) without influencing TFK-1-cell proliferation. These antibodies were predominantly observed in patients with non-progressing PBC.

Evaluation of muscarinic acetylcholine receptor type 3 gene polymorphisms in patients with primary biliary cholangitis and primary sclerosing cholangitis

AIM

Muscarinic acetylcholine receptor type 3-mediated signaling might be involved in the pathogenesis of chronic inflammatory biliary diseases, such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). The aim of the present study was to investigate the prevalence of five well-characterized specific single-nucleotide polymorphisms within the muscarinic acetylcholine receptor type 3 gene, CHRM3 (rs11578320, rs6690809, rs6429157, rs7548522, and rs4620530), in patients with PBC and PSC. Patients with chronic hepatitis C (CHC) and healthy individuals served as control cohorts. In the PBC cohort, baseline characteristics and response to ursodeoxycholic acid therapy applying established response criteria at 12 months after the initiation of treatment were evaluated according to the underlying CHRM3 genotype.

METHODS

CHRM3 genotyping was carried out in 306 PBC patients, 205 PSC patients, 208 CHC patients, and 240 healthy controls from two independent German tertiary care university centers in Berlin and Leipzig, Germany.

RESULTS

CHRM3 rs4620530 proportions in patients with PBC significantly differed from patients with PSC (P = 0.005), CHC (P = 0.009), and healthy controls (P = 0.008), primarily due to a substantial overrepresentation of the T allele in PBC (49.3% in PBC vs. 39.8% in PSC, 35.7% in CHC, and 40% in healthy controls), indicating a potential association of the rs4620530 T allele with PBC (OR 1.461, 95% CI 1.147-1.861, P = 0.002). Further analysis showed no association of CHRM3 single-nucleotide polymorphism rs4620530 with baseline characteristics and ursodeoxycholic acid treatment response in PBC.

CONCLUSION

CHRM3 single-nucleotide polymorphism rs4620530 might confer an increased genetic risk for the development of PBC.

Transgenic rice seeds expressing altered peptide ligands against the M3 muscarinic acetylcholine receptor suppress experimental sialadenitis-like Sjögren's syndrome

Objective: We previously reported that Rag1^-/- mice inoculated with splenocytes from M3 muscarinic acetylcholine receptor (M3R) knockout mice immunized with an M3R peptide mixture developed sialadenitis-like Sjögren's syndrome (M3R-induced sialadenitis [MIS]). We also found that intravenous administration of altered peptide ligand (APL) of N-terminal 1 (N1), which is one of the T-cell epitopes of M3R, suppressed MIS. In this study, we aimed to evaluate the suppressive ability and its mechanisms of rice seeds expressing N1-APL7 against MIS.Methods: Rice seeds expressing N1 and N1-APL7 were orally administered to MIS mice for 2 weeks. The changes in saliva flow and sialadenitis (salivary gland inflammation) were analyzed. The M3R-specific T-cell response in the spleen and the expression of regulatory molecules in the cervical lymph nodes and mesenteric lymph nodes were also analyzed.Results: Oral administration of N1-APL7-expressing rice seeds significantly recovered reduction in saliva flow and suppressed sialadenitis when compared with treatment with nontransgenic rice seeds and N1 rice seeds. IFNγ production from M3R-reactive T cells tended to decline in the N1-APL7 rice-treated group as compared with those in the other groups. In the N1-APL7 rice-treated group, the mRNA expression levels of Foxp3 in the cervical-lymph-node CD4⁺ T cells were higher than those in the other groups.Conclusion: Oral administration of N1-APL7-expressing rice suppressed MIS via suppression of M3R-specific IFNγ and IL-17 production and via enhancement of regulatory molecule expression.Key messagesWe generated N1-peptide- or N1-APL7-expressing rice seeds. Oral administration of N1-APL7-expressing rice seeds significantly recovered the reduction of saliva flow and suppressed sialadenitis via the suppression of M3R specific IFNγ and IL-17 production and via enhancement of regulatory T (Treg) cells.

Role of NAADP for calcium signaling in the salivary gland

Coordination of intracellular Ca²⁺ signaling in parotid acini is crucial for controlling the secretion of primary saliva. Previous work from our lab has demonstrated acidic-organelle Ca²⁺ release as a participant in agonist-evoked signaling dynamics of the parotid acinar cell. Furthermore, results implicated a potential role for the potent Ca²⁺ releasing second messenger NAADP in these events. The current study interrogated a direct role of NAADP for Ca²⁺ signaling in the parotid salivary gland acinar cell. Use of live-cell Ca²⁺ imaging, patch-clamp methods, and confocal microscopy revealed for the first time NAADP can evoke or enhance Ca²⁺ dynamics in parotid acini. These results were compared with pancreatic acini, a morphologically similar cell type previously shown to display NAADP-dependent Ca²⁺ signals. Findings presented here may be relevant in establishing new therapeutic targets for those suffering from xerostomia produced by hypofunctioning salivary glands.

Upregulation of IL-6 expression in human salivary gland cell line by IL-17 via activation of p38 MAPK, ERK, PI3K/Akt, and NF-κB pathways

BACKGROUND

The human salivary gland (HSG) cell line has so far been used as in vitro models for study of the influence of cytokines and pharmacologic agents on salivary glands, as well as a model system for inflammation in Sjögren's syndrome (SS). This study aimed to determine the effect of IL-17 on IL-6 production and the underlying molecular mechanism regulated by the HSG cell line.

METHODS

Immunofluorescence analyses, RT-PCR, and Western blot were conducted to evaluate the IL-17 receptor (IL-17R) expression in cultured HSG cells. Real-time PCR and ELISA were then utilized to establish the mRNA and protein levels of IL-6 in IL-17-stimulated HSG cells. Western blot, flow cytometry, immunofluorescence, and inhibitor analyses were conducted to elucidate the involved signaling pathways.

RESULTS

The HSG cells reliably expressed the IL-17R mRNA and its encoded surface-bound protein. The expression of IL-6 mRNA and protein was upregulated by stimulation of HSG cells with IL-17; this effect was impeded by IL-17- or IL-17R-neutralizing antibodies. IL-17 stimulation ended up with the fast phosphorylation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), Akt, and translocation of nuclear factor-kappaB (NF-κB) in the HSG cells. p38 MAPK, Akt, and NF-κB inhibitors significantly subdued IL-6 generation in HSG cells stimulated by IL-17. PD98059, an ERK inhibitor, decreased IL-6 generation under low dose of IL-17 but not with high dose.

CONCLUSIONS

The HSG cells expressed IL-17R and reacted to IL-17 to generate IL-6 via the stimulation of ERK, p38 MAPK, Akt, and NF-κB signaling pathways.

Functional autoantibodies targeting G protein-coupled receptors in rheumatic diseases

G protein-coupled receptors (GPCRs) comprise the largest and most diverse family of integral membrane proteins that participate in different physiological processes such as the regulation of the nervous and immune systems. Besides the endogenous ligands of GPCRs, functional autoantibodies are also able to bind GPCRs to trigger or block intracellular signalling pathways, resulting in agonistic or antagonistic effects, respectively. In this Review, the effects of functional GPCR-targeting autoantibodies on the pathogenesis of autoimmune diseases, including rheumatic diseases, are discussed. Autoantibodies targeting β1 and β2 adrenergic receptors, which are expressed by cardiac and airway smooth muscle cells, respectively, have an important role in the development of asthma and cardiovascular diseases. In addition, high levels of autoantibodies against the muscarinic acetylcholine receptor M3 as well as those targeting endothelin receptor type A and type 1 angiotensin II receptor have several implications in the pathogenesis of rheumatic diseases such as Sjögren syndrome and systemic sclerosis. Expanding the knowledge of the pathophysiological roles of autoantibodies against GPCRs will shed light on the biology of these receptors and open avenues for new therapeutic approaches.

RORγt antagonist suppresses M3 muscarinic acetylcholine receptor-induced Sjögren's syndrome-like sialadenitis

We showed recently that M3 muscarinic acetylcholine receptor (M3R)-reactive CD3⁺ T cells play a pathogenic role in the development of murine autoimmune sialadenitis (MIS), which mimics Sjögren's syndrome (SS). The aim of this study was to determine the effectiveness and mechanism of action of retinoic acid-related orphan receptor-gamma t (RORγt) antagonist (A213) in MIS. Splenocytes from M3R knockout (M3R^-/- ) mice immunized with murine M3R peptide mixture were inoculated into recombination-activating gene 1 knockout (Rag-1^-/- ) mice (M3R^-/- →Rag-1^-/- ) with MIS. Immunized M3R^-/- mice (pretransfer treatment) and M3R^-/- →Rag-1^-/- mice (post-transfer treatment) were treated with A213 every 3 days. Salivary volume, severity of sialadenitis and cytokine production from M3R peptide-stimulated splenocytes and lymph node cells were examined. Effects of A213 on cytokine production were analysed by enzyme-linked immunosorbent assay (ELISA) and on T helper type 1 (Th1), Th17 and Th2 differentiation from CD4⁺ T cells by flow cytometry. Pretransfer A213 treatment maintained salivary volume, improved MIS and reduced interferon (IFN)-γ and interleukin (IL)-17 production significantly compared with phosphate-buffered saline (PBS) (P < 0·05). These suppressive effects involved CD4⁺ T cells rather than CD11c⁺ cells. Post-transfer treatment with A213 increased salivary volume (P < 0·05), suppressed MIS (P < 0·005) and reduced IFN-γ and IL-17 production (P < 0·05). In vitro, A213 suppressed IFN-γ and IL-17 production from M3R-stimulated splenocytes and CD4⁺ T cells of immunized M3R^-/- mice (P < 0·05). In contrast with M3R specific responses, A213 suppressed only IL-17 production from Th17 differentiated CD4⁺ T cells without any effect on Th1 and Th2 differentiation in vitro. Our findings suggested that RORγt antagonism is potentially suitable treatment strategy for SS-like sialadenitis through suppression of IL-17 and IFN-γ production by M3R-specific T cells.

Muscarinic type 3 receptor autoantibodies are associated with anti-SSA/Ro autoantibodies in Sjögren's syndrome

Anti-muscarinic type 3 receptor autoantibodies (anti-M3R) are reported as potential inhibitors of saliva secretion in Sjögren's syndrome (SjS). However, despite extensive efforts to establish an anti-M3R detection method, there is no clinical test available for these autoantibodies. The purpose of this study was to propose inclusion of anti-M3R testing for SjS diagnosis through investigation of their prevalence using a modified In-Cell Western (ICW) assay. A stable cell line expressing human M3R tagged with GFP (M3R-GFP) was established to screen unadsorbed and adsorbed plasma from primary SjS (n=24), rheumatoid arthritis (RA, n=18), systemic lupus erythematosus (SLE, n=18), and healthy controls (HC, n=23). Anti-M3R abundance was determined by screening for the intensity of human IgG interacting with M3R-GFP cells by ICW assay, as detected by an anti-human IgG IRDye800-conjugated secondary antibody and normalized to GFP. Method comparisons and receiver-operating-characteristic (ROC)-curve analyses were performed to evaluate the diagnostic value of our current approaches. Furthermore, clinical parameters of SjS were also analyzed in association with anti-M3R. Anti-M3R was significantly elevated in SjS plasma in comparison with HC, SLE, or RA (P<0.01). SjS anti-M3R intensities were greater than two-standard deviations above the HC mean for both unadsorbed (16/24, 66.67%) and adsorbed (18/24, 75%) plasma samples. Furthermore, anti-M3R was associated with anti-SjS-related-antigen A/Ro positivity (P=0.0353). Linear associations for anti-M3R intensity indicated positive associations with focus score (R(2)=0.7186, P<0.01) and negative associations with saliva flow rate (R(2)=0.3052, P<0.05). Our study strongly supports our rationale to propose inclusion of anti-M3R for further testing as a non-invasive serological marker for SjS diagnosis.

Common molecular mechanism of the hepatic lesion and the cardiac parasympathetic regulation in chronic hepatitis C infection: a critical role for the muscarinic receptor type 3

BACKGROUND

The pathophysiological overlapping between Sjorgen's Syndrome (SS) and HCV, presence of anti- muscarinic receptor type 3 (M3R) antibodies in SS, the role that M3R plays in the regulation of the heart rate, has led to the assumption that cardiovagal dysfunction in HCV patients is caused by anti-M3R antibodies elicited by HCV proteins or by their direct interaction with M3R.

RESULTS

To identify HCV protein which possibly is crossreactive with M3R or which binds to this receptor, we performed the Informational Spectrum Method (ISM) analysis of the HCV proteome. This analysis revealed that NS5A protein represents the most probable interactor of M3R or that this viral protein could elicit antibodies which modulate function of this receptor. Further detailed structure/function analysis of NS5A and M3R performed by the ISM method extended with other Digital Signal processing (DSP) approaches revealed domains of these proteins which participate in their crossreactivity or in their direct interaction, representing promising diagnostic and therapeutic targets.

CONCLUSIONS

Application of the ISM with other compatible bioinformatics methods offers new perspectives for identifying diagnostic and therapeutic targets for complicated forms of HCV and other viral infections. We show how the electron-ion interaction potential (EIIP) amino-acid scale used in the ISM combined with a robust, high performance hydrophobicity scale can provide new insights for understanding protein structure/function and protein-protein interactions.

Pelvic floor dysfunction in female Sjögren's syndrome: an 8-year audit

INTRODUCTION AND HYPOTHESIS

The classic triad of dry eyes, mouth and vagina is known to most gynaecologists as pathognomonic of Sjögren's syndrome, but rheumatologists seldom consider vaginal symptoms. Our hypothesis was that women with Sjögren's syndrome would have an increased likelihood of postoperative voiding dysfunction, severe vaginal stenosis or poor response to anticholinergics compared with the general urogynaecology patient.

METHODS

All patients with Sjögren's syndrome were prospectively recorded from July 2007 to June 2015. Presenting complaint, pelvic examination findings, previous/subsequent pelvic surgery, voiding dysfunction and response to anticholinergics were noted. The denominator, all new urogynaecology patients, was prospectively recorded.

RESULTS

Fifteen patients were identified over 8 years (0.5 % of 2794 new presentations). Of the seven patients who had previously undergone surgery elsewhere, all had demonstrable pelvic tissue fibrosis; five had such severe fibrosis that no speculum could be passed. Anticholinergic medications were completely intolerable in 10/11 (91 %) women, and severe postoperative voiding dysfunction occurred in 6/9 (67 %) women. Only 2/15 (13 %) women were unaffected by fibrosis, postoperative voiding dysfunction or intolerance to anticholinergics.

CONCLUSIONS

This audit demonstrates a substantial risk of vaginal stenosis, postoperative voiding dysfunction or severe intolerance to anticholinergics in women with Sjögren's syndrome.

Autoantibodies against the Second Extracellular Loop of M3R Do neither Induce nor Indicate Primary Sjögren's Syndrome

Objectives

Anti-muscarinic acetylcholine type-3 receptor (anti-M3R) autoantibodies have been suggested to be pathogenic for primary Sjögren’s syndrome (pSS), and the second extracellular loop of M3R is suspected to carry a disease-promoting epitope. In this study, we aimed to evaluate the pathogenicity of autoantibodies against peptides derived from the second extracellular loop of M3R in mice and to determine whether those autoantibodies could be used as biomarker for pSS.

Methods

BALB/c mice were immunized with modified linear or cyclic peptides of the second extracellular loop of M3R. The function of exocrine glands was evaluated by measuring the secretion of saliva and tears. The histological evaluations were performed by using H&E staining or direct immunofluorescence staining. Autoantibodies against linear or cyclic peptides of the second extracellular loop of M3R in human and mice were determined using ELISA.

Results

Immunization induced mice to produce autoantibodies against the linear or cyclic peptides of the second extracellular loop of M3R, and those autoantibodies could bind onto salivary glands. However, those mice showed neither impairment in the secretion of tears or saliva nor histological abnormality in the exocrine glands. Furthermore, passive transfer of the IgG isolated from the immunized mice into healthy mice did not induced the dysfunction of the exocrine glands. The prevalence of autoantibodies against the peptides of the second extracellular loop of M3R was low in pSS patients, and it did not differ significantly from that in healthy controls.

Conclusions

Our results suggest that the autoantibodies against peptides of the second extracellular loop of M3R are not pathogenic in vivo and they are not suitable as biomarkers for pSS diagnosis.

Early BAFF receptor blockade mitigates murine Sjögren's syndrome: Concomitant targeting of CXCL13 and the BAFF receptor prevents salivary hypofunction

Sjögren's syndrome (SS) is a debilitating autoimmune disease. Patients with SS may develop xerostomia. This process is progressive, and there are no therapeutics that target disease etiology. We hypothesized BAFF receptor (BAFFR) blockade would mitigate SS disease development, and neutralization of CXCL13 and BAFF signaling would be more efficacious than BAFFR blockade alone. We treated NOD/ShiLtJ SS mice with soluble BAFF receptor (BAFFR-Fc) or anti-CXCL13/BAFFR-Fc in combination, prior to the development of clinical disease. Our results show treatment with BAFFR-Fc reduced peripheral B cell numbers and decreased sialadenitis. In addition, this treatment reduced total serum immunoglobulin as well as IgG and IgM specific anti-nuclear autoantibodies. NOD/ShiLtJ mice treated with BAFFR-Fc and anti-CXCL13 antibody were protected from salivary deficits. Results from this study suggest blockade of CXCL13 and BAFFR together may be an effective therapeutic strategy in preventing salivary hypofunction and reducing autoantibody titers and sialadenitis in patients with SS.

Mimotope mimicking epidermal growth factor receptor alleviates mononuclear cell infiltration in exocrine glands induced by muscarinic acetylcholine 3 receptor

The muscarinic type 3 receptor (M3R) plays a pivotal role in the pathogenesis of Sjögren's syndrome (SS). Characterization of the crosstalk between M3R and EGFR has been investigated in some human malignancies. In the current study, we sought to investigate whether EGFR mimic immunization could alleviate the abnormal immune responses in an experimental SS-like model triggered by M3R peptides. After immunization with the combination of mimotope and M3R peptide, the active immunization targeting EGFR induced by the mimotope could reduce the marked infiltration of mononuclear cells, the high titer of antibodies against M3R and the accumulation of crucial pro-inflammatory cytokines in mice immunized with M3R peptide. Mechanistic analysis showed that mimotope immunization could alleviate the autoimmune response through inhibiting mitochondrion-mediated anti-apoptosis and up-regulating the FAS apoptosis pathway. These results may help to clarify the role of M3R in the pathogenesis of SS and suggested that transactivation of the EGFR signaling pathway may help M3R activate the autoimmune response in the pathogenesis of SS.

The anergy induction of M3 muscarinic acetylcholine receptor-reactive CD4+ T cells suppresses experimental sialadenitis-like Sjögren's syndrome

OBJECTIVE

Autoreactive CD4+ T cells are involved in the pathogenesis of Sjögren's syndrome (SS). The aim of the present study was to clarify the dominant T cell epitopes of M3 muscarinic acetylcholine receptor (M3R) and to establish a new antigen-specific therapy for SS using an experimental mouse model.

METHODS

Production of cytokines from M3R-reactive CD4+ T cells, after culture with various M3R peptides, was analyzed by enzyme-linked immunosorbent assay. Adoptive cell transfer was performed using splenocytes from M3R(-/-) mice that were immunized with M3R peptides or phosphate buffered saline plus H37Ra as a control. Rag1(-/-) mice were inoculated with the splenocytes and examined for the development of sialadenitis. Altered peptide ligands (APLs) of the T cell epitopes, with substitutions in amino acid residues at T cell receptor contact sites, were synthesized, and the ability of the APLs to suppress sialadenitis was evaluated. The mechanisms underlying such effects were assessed.

RESULTS

CD4+ M3R-reactive T cells produced interleukin-17 (IL-17) and interferon-γ (IFNγ) in response to the N-terminal 1 (N1) and 1st extracellular loop peptides of M3R, and Rag1(-/-) mice that received N1- and/or 1st peptide-immunized splenocytes developed sialadenitis. Among the designed APLs, N1-APL7 (N→S at amino acid 15) significantly suppressed IFNγ production in vitro, and also suppressed sialadenitis in vivo. Levels of early growth response 2 in CD4+ T cells from the cervical lymph nodes of N1-APL7-treated mice were significantly higher than those of control mice, and cell proliferation was reversed by administration of exogenous IL-2. Levels of the anergy-related molecules itchy homolog E3 ubiquitin-protein ligase, Casitas B-lineage lymphoma b, gene related to anergy in lymphocytes, and Deltex-1 were significantly higher in CD4+ T cells cultured with N1-APL7.

CONCLUSION

The major T cell epitopes were from the N1 and 1st peptide regions. Moreover, N1-APL7, selected as the antagonistic APL in vitro, also suppressed sialadenitis through the induction of anergy. This is a potentially useful strategy for regulating pathogenic T cell infiltration in SS.

Effect of Antimuscarinic Autoantibodies in Primary Sjögren's Syndrome

The presence of functional autoantibodies against the muscarinic type 3 receptor (M3R) has been reported in primary Sjögren's syndrome (pSS). However, the pathogenic role of these autoantibodies in pSS development remains to be elucidated. In this experiment, we investigated a pathologic role of pSS autoantibodies (pSS IgG) associated with downregulation of the major histocompatibility complex I (MHC I) molecule with M3R through internalization. Anti-M3R autoantibodies in purified control and pSS IgG were detected using 4 synthesized cyclic M3R peptides by enzyme-linked immunosorbent assay. The binding reactivity of pSS IgG to M3R in situ was analyzed by a dual immunostaining method. Surface expression, interaction, and internalization of M3R with MHC I were analyzed by immunofluorescence confocal microscopy and biochemical assays. Synthetic cyclic peptides M3RP(205-221) and M3RP(520-527) showed significantly high reactivity with pSS IgG compared to the control IgG or the other 3 peptides (P < 0.05). Significantly high reactivity of pSS IgG to M3R in situ was observed. PSS IgG increased the interaction of membrane M3R with MHC I and induced their internalization in primary human submandibular gland cells. The pSS IgG-induced internalization of M3R with MHC I was significantly inhibited by the cholesterol-sequestering drug filipin. Our novel finding-namely, strong downregulation of the membrane MHC I with M3R through internalization of the cholesterol-rich microdomain associating with anti-M3R autoantibodies-could be an important mechanism contributing to the impaired salivation seen in pSS and linking secretory hypofunction to autoimmune pathogenesis.

Meta-analysis of anti-muscarinic receptor type 3 antibodies for the diagnosis of Sjögren syndrome

Purpose

To conduct a meta-analysis to evaluate the diagnostic value of anti-muscarinic receptor type 3 (M3R) antibodies in Sjögren syndrome (SS).

Methods

Two databases, PUBMED and the Cochrane Library, were systematically searched. Approximately 2,000 participants from several studies were included in this research. STATA 11.2 software and Meta-DiSc 1.4 was used to conduct the meta-analysis.

Results

Eleven studies were included in the meta-analysis. The pooled DOR was 13.00 (95% CI, 6.00–26.00). The sensitivity was 0.43 (95% CI, 0.28–0.58) and the specificity was 0.95 (95%CI, 0.91–0.97). The LR+ and LR- were 7.90 (95% CI, 4.70–13.40), 0.61 (95% CI, 0.46–0.79), respectively. The AUC was 0.89 (95% CI, 0.86–0.92).

Conclusion

The anti-M3R antibody had high specificity but relatively low sensitivity for the diagnosis of SS.

Anti-M3 muscarinic acetylcholine receptor antibodies in patients with primary biliary cirrhosis

AIM

M3 muscarinic acetylcholine receptor (M3R) is expressed in biliary tracts as well as in exocrine glands. It is reported that some patients with primary biliary cirrhosis (PBC) carry autoantibodies against M3R. The aim of this study is to clarify the presence, potential use as diagnostic marker and clinical roles of anti-M3R antibodies in PBC.

METHODS

We synthesized peptides encoding the extracellular domains of human-M3R, including the N-terminal region, the first, second and third extracellular loops. Antibodies against these regions were examined by peptide-based enzyme-linked immunoassay in sera of 90 patients with PBC and 40 with chronic hepatitis C (CHC), 21 with non-alcoholic steatohepatitis (NASH), 10 with primary sclerosing cholangitis (PSC), 14 with obstructive jaundice, 10 with drug-induced liver injury and 42 healthy controls.

RESULTS

Antibodies to the N-terminal, first, second and third loop were detected in 90.0% (81/90), 73.3% (66/90), 76.7% (69/90) and 66.7% (60/90) of PBC, in 67.5% (27/40), 10.0% (4/40), 67.5% (27/40) and 27.5% (11/40) of CHC, in 85.7% (18/21), 9.5% (2/21), 4.8% (1/21) and 57.1% (12/21) of NASH, in 60.0% (6/10), 20.0% (2/10), 60.0% (6/10) and 60.0% (6/10) of PSC, in 100.0% (14/14), 0% (0/14), 64.3% (9/14) and 78.6% (11/14) of obstructive jaundice, in 100.0% (10/10), 0% (0/10), 30.0% (3/10) and 10.0% (1/10) of drug-induced liver injury, and in 4.8% (2/42), 7.1% (3/42), 2.4% (1/42) and 2.4% (1/42) of the controls, respectively.

CONCLUSION

A high frequency of PBC carried anti-M3R antibodies. Anti-M3R antibodies against the first loop of M3R are a potentially useful diagnostic marker for PBC.

A novel luminescence-based method for the detection of functionally active antibodies to muscarinic acetylcholine receptors of the M3 type (mAchR3) in patients' sera

In different bioassays, functional antibodies reacting with the human muscarinic acetylcholine receptor M3(mAchR3) have been detected in sera from patients with Sjögren's syndrome (SS), and there is strong evidence that those antibodies may have pathogenetic relevance. However, depending on the method of detection, their prevalence varied. Furthermore, those bioassays are difficult to standardize. We report on the development and optimization of a novel test system based on a luminometric method to determine downstream signalling of mAchR3 which produces specific and reproducible results. Chinese hamster ovarian (CHO) cells were transfected with plasmids encoding mAchR3 and a green fluorescence protein (GFP)/aequorin fusion protein. Incubation of cells with carbachol resulted in an increase in intracellular [Ca(2+)], which was detected by measuring light emission with a luminometer, and the effect of incubation with patients' immunoglobulins (Ig) was evaluated. Optimal cell density, Ig preparation and time of incubation with patients' sera were determined. Sera from patients with primary Sjögren's syndrome (pSS; n = 40), systemic sclerosis (SSc; n = 47), myasthenia gravis (MG; n = 133) and 50 blood donors were analysed. Optimal assay conditions were obtained with a cell density of 100 000 cells/ml, isolation of Ig by ammonium sulphate precipitation and short-term incubation. Based on this highly reliable assay, 50% of the pSS patients had antibodies which inhibited carbachol-induced activation of mAchR3; none of the SSc patients, 6% of the patients with MG and 12% of the blood donors had antibodies which reacted with the mAchR3. This method facilitates the determination of functional anti-mAchR3 antibodies in patients' sera, confirmed their high prevalence in pSS patients and may, therefore, help to analyse their pathogenetic and clinical relevance in more detail.

Candidate chromosome 1 disease susceptibility genes for Sjogren's syndrome xerostomia are narrowed by novel NOD.B10 congenic mice

Sjogren's syndrome (SS) is characterized by salivary gland leukocytic infiltrates and impaired salivation (xerostomia). Cox-2 (Ptgs2) is located on chromosome 1 within the span of the Aec2 region. In an attempt to demonstrate that COX-2 drives antibody-dependent hyposalivation, NOD.B10 congenic mice bearing a Cox-2flox gene were generated. A congenic line with non-NOD alleles in Cox-2-flanking genes failed manifest xerostomia. Further backcrossing yielded disease-susceptible NOD.B10 Cox-2flox lines; fine genetic mapping determined that critical Aec2 genes lie within a 1.56 to 2.17Mb span of DNA downstream of Cox-2. Bioinformatics analysis revealed that susceptible and non-susceptible lines exhibit non-synonymous coding SNPs in 8 protein-encoding genes of this region, thereby better delineating candidate Aec2 alleles needed for SS xerostomia.

Th17 cells play a critical role in the development of experimental Sjögren's syndrome

OBJECTIVE

Although Th17 cells have been increasingly recognised as an important effector in various autoimmune diseases, their function in the pathogenesis of Sjögren's syndrome (SS) remains largely uncharacterised. This study aims to determine the role of Th17 cells in the development of experimental SS (ESS).

METHODS

The ESS was induced in wildtype and IL-17A knockout (IL-17 KO) C57BL/6 mice immunised with salivary glands (SG) proteins. Phenotypic analysis of immune cells in the draining cervical lymph nodes (CLN) and SG was performed by flow cytometry and immunofluorescence microscopy. To determine the role of Th17 cells in ESS, immunised IL-17 KO mice were adoptively transferred with in vitro-generated Th17 cells and monitored for SS development. The salivary flow rate was measured, whereas inflammatory infiltration and tissue destruction in SG were assessed by histopathology.

RESULTS

SG protein-immunised mice developed overt SS symptoms with increased Th17 cells detected in CLN and within lymphocytic foci in inflamed SG. Notably, immunised IL-17 KO mice were completely resistant for SS induction, showing no evidence of disease symptoms and histopathological changes in SG. Adoptive transfer of Th17 cells rapidly induced the onset of ESS in immunised IL-17 KO mice with markedly reduced saliva secretion, elevated autoantibody production and pronounced inflammation and tissue damage in SG.

CONCLUSIONS

Our findings have defined a critical role of Th17 cells in the pathogenesis of ESS. Further studies may validate Th17 cell as a potential target for treating SS.

The role of M3 muscarinic acetylcholine receptor reactive T cells in Sjögren's syndrome: a critical review

CD4+ T cells constitute the majority of infiltrating cells in salivary glands and lachrymal glands of patients with Sjögren's syndrome (SS). The pathophysiology of SS involves T cell recognition of antigens through the T cell antigen receptor, which triggers cytokine production and chronic inflammation. The M3 muscarinic acetylcholine receptor (M3R) molecule is expressed in exocrine glands, such as salivary glands and lachrymal glands, and plays an important role in exocrine secretion. Previous studies indicated the presence of M3R reactive T cells in peripheral blood of 40% of patients with SS and autoantibodies against M3R in sera of 9-100% of the same patients. Thus, M3R is considered a candidate receptor for autoantigen recognition by T and B cells. The relationship between B cell epitopes and the function of anti-M3R antibodies has been reported, suggesting the pathogenic role of anti-M3R antibodies in xerostomia commonly seen in SS patients. We generated new experimental mouse model, M3R-induced sialadenitis (MIS), using Rag1(-/-) mice inoculated with splenocytes from M3R(-/-) mice immunized with M3R synthetic peptides. Mice with MIS developed severe SS-like sialadenitis. Cell transfer experiments using M3R(-/-)xIFNγ(-/-) mice and M3R(-/-)xIL-17(-/-) mice showed that IFNγ and IL-17 are key cytokines in the pathogenesis of sialadenitis. These findings indicate the crucial roles of M3R-reactive Th1 and Th17 cells in autoimmune sialadenitis, and suggest that these cells, in addition to anti-M3R antibodies, are potential targets in new treatments for SS.

Effects of muscarinic acetylcholine 3 receptor(208-227) peptide immunization on autoimmune response in nonobese diabetic mice

The second extracellular loop (LFWQYFVGKRTVPPGECFIQFLSEPTITFGTAI, aa 205-237) of muscarinic acetylcholine 3 receptor (M3R) has been reported to be an epitope for autoantibodies generated during certain autoimmune disorders, including Sjögren's syndrome (SS). Autoantibodies against M3R(228-237) have been shown to interfere with the function of M3R. However, few studies have been performed on the M3R(205-227) peptide of the second extracellular loop. In the current study, we sought to investigate the effect of M3R(208-227) peptide immunization on autoimmune response in NOD/LtJ mice. We synthesized the M3R(208-227) peptide and immunized NOD/LtJ mice to investigate whether peptide-specific antibodies could be generated and whether immunization would lead to changes in autoimmune response in NOD/LtJ mice. Our results demonstrate that the secretions of Th-1, Th-2, and Th-17 cytokines are downregulated and lymphocytic infiltration is improved in the salivary glands and lacrimal glands following immunization with M3R(208-227) peptide in NOD/LtJ mice, suggesting that peptide immunotherapy using the M3R(208-227) peptide may represent a potential therapeutic alternative.

Caffeine increases the expression of cystatin SN in human submandibular acinar-like HSG cells

OBJECTIVE

The study aimed at evaluating in vitro the effect of caffeine on expression of cystatin SN, a potential marker of sensitivity to bitterness in humans.

METHODS

Differentiation of human submandibular gland (HSG) cells was induced by culturing cells on Matrigel. Caffeine cytotoxicity was assessed over 3 days by the Resazurin test. Finally, effects of 5, 50 and 100μM caffeine exposure on cystatin SN expression were explored over 3 days by ELISA.

RESULTS

At concentrations relevant to human adult plasma levels (5, 50 and 100μM), caffeine did not affect cell viability whether cells were differentiated or not. Cystatin SN levels were overall higher in differentiated cells and increased with time in both conditions. There was a significant (p<0.001) effect of caffeine on cystatin SN expression specifically in differentiated cells.

CONCLUSIONS

The HSG cell line proved to be a relevant tool to study in vitro the effect of caffeine at concentrations consistent with dietary intake in human subjects. The results suggest that salivary cystatin SN abundance may depend on caffeine intake, with possible consequences on taste sensitivity.

Autoantibodies against muscarinic type 3 receptor in Sjögren's syndrome inhibit aquaporin 5 trafficking

Sjögren's syndrome (SjS) is a chronic autoimmune disease that mainly targets the salivary and lacrimal glands. It has been controversial whether anti-muscarinic type 3 receptor (α-M3R) autoantibodies in patients with SjS inhibit intracellular trafficking of aquaporin-5 (AQP5), water transport protein, leading to secretory dysfunction. To address this issue, GFP-tagged human AQP5 was overexpressed in human salivary gland cells (HSG-hAQP5) and monitored AQP5 trafficking to the plasma membrane following carbachol (CCh, M3R agonist) stimulation. AQP5 trafficking was indeed mediated by M3R stimulation, shown in partial blockage of trafficking by M3R-antagonist 4-DAMP. HSG-hAQP5 pre-incubated with SjS plasma for 24 hours significantly reduced AQP5 trafficking with CCh, compared with HSG-hAQP5 pre-incubated with healthy control (HC) plasma. This inhibition was confirmed by monoclonal α-M3R antibody and pre-absorbed plasma. Interestingly, HSG-hAQP5 pre-incubated with SjS plasma showed no change in cell volume, compared to the cells incubated with HC plasma showing shrinkage by twenty percent after CCh-stimulation. Our findings clearly indicate that binding of anti-M3R autoantibodies to the receptor, which was verified by immunoprecipitation, suppresses AQP5 trafficking to the membrane and contribute to impaired fluid secretion in SjS. Our current study urges further investigations of clinical associations between SjS symptoms, such as degree of secretory dysfunction, cognitive impairment, and/or bladder irritation, and different profiles (titers, isotypes, and/or specificity) of anti-M3R autoantibodies in individuals with SjS.

Association of increased frequencies of HLA-DPB1*05:01 with the presence of anti-Ro/SS-A and anti-La/SS-B antibodies in Japanese rheumatoid arthritis and systemic lupus erythematosus patients

Introduction

Autoantibodies to ribonucleoprotein are associated with a variety of autoimmune diseases, including rheumatoid arthritis (RA). Many studies on associations between human leukocyte antigen (HLA) alleles and RA have been reported, but few have been validated in RA subpopulations with anti-La/SS-B or anti-Ro/SS-A antibodies. Here, we investigated associations of HLA class II alleles with the presence of anti-Ro/SS-A or anti-La/SS-B antibodies in RA.

Methods

An association study was conducted for HLA-DRB1, DQB1, and DPB1 in Japanese RA and systemic lupus erythematosus (SLE) patients that were positive or negative for anti-Ro/SS-A and/or anti-La/SS-B antibodies.

Results

An increased prevalence of certain class II alleles was associated with the presence of anti-Ro/SS-A antibodies as follows: DRB1*08∶03 (Pc = 3.79×10⁻⁵, odds ratio [OR] 3.06, 95% confidence interval [CI] 1.98–4.73), DQB1*06∶01 (Pc = 0.0106, OR 1.70, 95%CI 1.26–2.31), and DPB1*05∶01 (Pc = 0.0040, OR 1.55, 95%CI 1.23–1.96). On the other hand, DRB1*15∶01 (Pc = 0.0470, OR 3.14, 95%CI 1.63–6.05), DQB1*06∶02 (Pc = 0.0252, OR 3.14, 95%CI 1.63–6.05), and DPB1*05∶01 (Pc = 0.0069, OR 2.27, 95% CI 1.44–3.57) were associated with anti-La/SS-B antibodies. The DPB1*05∶01 allele was associated with anti-Ro/SS-A (Pc = 0.0408, OR 1.69, 95% CI 1.19–2.41) and anti-La/SS-B antibodies (Pc = 2.48×10⁻⁵, OR 3.31, 95%CI 2.02–5.43) in SLE patients.

Conclusion

HLA-DPB1*05∶01 was the only allele associated with the presence of both anti-Ro/SS-A and anti-La/SS-B antibodies in Japanese RA and SLE patients.

Neuroimmune interactions in Sjögren's syndrome: relationship of exocrine gland dysfunction with autoantibodies to muscarinic acetylcholine receptor-3 and mental health status parameters

OBJECTIVES

Antimuscarinic acetylcholine receptor-3 (m3AChR) autoantibodies have been described in primary Sjögren's syndrome (pSS). The aim of this study was to compare various methods for their detection and to assess the contributions of anti-m3AChR and other immunological and psychosocial factors to the pathomechanism of secondary SS (sSS).

METHODS

Sixty-five rheumatoid arthritis (RA) patients, 103 systemic lupus erythematosus (SLE) patients, 76 pSS patients and 50 controls were compared. Three immunodominant epitopes of m3AChR were synthesized and used in ELISA. Two extracellular epitopes were also prepared in fusion with glutathione-S-transferase and one in conjugation with bovine serum albumin. Mental health status was assessed with the 36-item Short-Form Health Survey and Functional Assessment of Chronic Illness Therapy fatigue scale. Correlations were evaluated between glandular function and anti-m3AChR positivities and specificities, features of SLE and RA, and mental health parameters.

RESULTS

Fourteen RA and 27 SLE patients had sSS. The autoantibody levels to all epitopes of m3AChR were significantly higher in pSS and SLE patients than in the controls. The fusion protein forms discriminated RA from pSS and SLE; furthermore, the YNIP fusion protein also distinguished pSS from SLE. The prevalence and the mean levels of all autoantibodies did not differ statistically between sicca and non-sicca SLE or RA patients. Glandular dysfunction correlated with higher age in SLE and RA and an impaired health-related quality of life in SLE.

CONCLUSIONS

The second and third extracellular loops of m3AChR are antigenic in pSS. Immunoassays with antigens as fusion peptides demonstrate the best performance. Sicca SLE patients have worse mental health status. Anti-m3AChR antibodies represent a peculiar example of neuroimmune interactions.