Anti-M(3) muscarinic cholinergic autoantibodies from patients with primary Sjögren's syndrome trigger production of matrix metalloproteinase-3 (MMP-3) and prostaglandin E(2) (PGE(2)) from the submandibular glands

Prostaglandin analogues signal detection by data mining in the FDA Adverse Event Reporting System database

OBJECTIVE

This study aims to identify safety signals of ophthalmic prostaglandin analogues through data mining the Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHODS

A data mining search by proportional reporting ratio, reporting OR, Bayesian confidence propagation neural network, information component 0.25 and χ2 for safety signals detection was conducted to the FAERS database for the following ophthalmic medications: latanoprost, travoprost, tafluprost and bimatoprost.

RESULTS

12 preferred terms were statistically associated: diabetes mellitus, n=2; hypoacusis, n=2; malignant mediastinal neoplasm, n=1; blood immunoglobulin E increased, n=1; cataract, n=1; blepharospasm, n=1; full blood count abnormal, n=1; skin exfoliation, n=1; chest discomfort, n=1; and dry mouth, n=1.

LIMITATION OF THE STUDY

The FAERS database's limitations, such as the undetermined causality of cases, under-reporting and the lack of restriction to only health professionals reporting this type of event, could modify the statistical outcomes. These limitations are particularly relevant in the context of ophthalmic drug analysis, as they can affect the accuracy and reliability of the data, potentially leading to biased or incomplete results.

CONCLUSIONS

Our findings have revealed a potential relationship due to the biological plausibility among malignant mediastinal neoplasm, full blood count abnormal, blood immunoglobulin E increased, diabetes mellitus, blepharospasm, cataracts, chest discomfort and dry mouth; therefore, it is relevant to continue investigating the possible drug-event association, whether to refute the safety signal or identify a new risk.

Antibody deposition on vascular endothelial cells contributes to localized inflammation in salivary glands

BACKGROUND

Oral and ocular dryness due to reduced saliva and tear production, exocrine gland inflammation, and autoantibodies to multiple cellular proteins are the cardinal features of Sjögren's Disease. Among the autoantibody specificities, anti-Ro52 is linked with higher disease severity. We have previously reported that mice immunized with recombinant Ro52 developed IgG deposits in salivary and lacrimal glands and showed reduced saliva and tear production. Furthermore, passive transfer of sera from Ro52-immunized mice rapidly induced glandular dysfunction without immune cell infiltration in recipient mice.

METHODS

To identify mechanisms driving antibody-mediated salivary gland dysfunction, hyperimmune rabbit antiserum to mouse Ro52 was passively transferred into NZM2758 female mice, pretreated with alum adjuvant. Alum-pretreated mice given hyperimmune rabbit antiserum to maltose-binding protein served as controls. Antibody deposition and its distribution in the salivary glands were studied by immunofluorescence staining for rabbit IgG, nerve fibers, and endothelial cells. The nCounter inflammation panel was used to determine differentially expressed genes in the salivary gland.

RESULTS

Rabbit IgG deposits were detected in salivary glands of anti-Ro52 immune sera recipients. The rabbit IgG was present on the endothelial cells in small blood vessels, and it did not co-localize with nerve fibers. Ingenuity pathway analysis of the gene expression dataset predicted the canonical vascular endothelial growth factor (VEGF) pathway as the most activated and Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) as the most inhibited pathway in the salivary glands of anti-Ro52 sera recipients.

CONCLUSION

Our study suggests that autoantibody deposition on salivary gland endothelial cells might play a critical role in the pathogenesis of Sjögren's Disease.

The role of the cholinergic anti-inflammatory pathway in autoimmune rheumatic diseases

The cholinergic anti-inflammatory pathway (CAP) is a classic neuroimmune pathway, consisting of the vagus nerve, acetylcholine (ACh)-the pivotal neurotransmitter of the vagus nerve-and its receptors. This pathway can activate and regulate the activities of immune cells, inhibit cell proliferation and differentiation, as well as suppress cytokine release, thereby playing an anti-inflammatory role, and widely involved in the occurrence and development of various diseases; recent studies have demonstrated that the CAP may be a new target for the treatment of autoimmune rheumatic diseases. In this review, we will summarize the latest progress with the view of figuring out the role of the cholinergic pathway and how it interacts with inflammatory reactions in several autoimmune rheumatic diseases, and many advances are results from a wide range of experiments performed in vitro and in vivo.

Sex Bias and Autoimmune Diseases

Sex bias in immune function has been well-described, and women have been shown to counter immunologically stimulating phenomena such as infection, malignancy, and trauma with more protective responses than men. Heightened immunity in women may also result in a predisposition for loss of self-tolerance and development of autoimmunity, reflected by the overwhelming female sex bias of patients with autoimmune diseases. In this review, we discuss the postulated evolutionary etiologies for sexual dimorphism in immunity. We also review the molecular mechanisms underlying divergent immune responses in men and women, including sex hormone effects, X chromosome dosage, and autosomal sex-biased genes. With increasing evidence that autoimmune disease susceptibility is influenced by numerous hormonal and genetic factors, a comprehensive understanding of these topics may facilitate the development of much-needed targeted therapeutics.

Autonomic Nervous System Dysfunction in Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease which primarily affects the exocrine glands, but can also affect other organs, including the nervous system. Many studies have reported evidence of autonomic nervous system (ANS) dysfunction in pSS which may contribute to a wide range of symptoms and functional burden. Symptoms of ANS dysfunction are common and widespread among patients with pSS and are associated with other features of the disease, particularly fatigue. Accumulating data on the inter-relationship between the ANS and the immune system via the vagus nerve have been reported. Vagus nerve stimulation (VNS) has also been associated with improvement in fatigue in patients with pSS. Taken together, these data suggest that the ANS may be a potential treatment target for pSS, in particularly those with fatigue being a predominant symptom. Future research to dissect the link between the ANS, immune dysregulation and clinical manifestations in pSS and to evaluate the potential of VNS as a therapy for pSS is warranted.

A new role for matrix metalloproteinase-3 in the NGF metabolic pathway: Proteolysis of mature NGF and sex-specific differences in the continuum of Alzheimer's pathology

Matrix metalloproteinase-3 (MMP-3) has been associated with risk of Alzheimer's disease (AD). In this study we introduce a novel role for MMP-3 in degrading nerve growth factor (NGF) in vivo and examine its mRNA and protein expression across the continuum of AD pathology. We provide evidence that MMP-3 participates in the degradation of mature NGF in vitro and in vivo and that it is secreted from the rat cerebral cortex in an activity-dependent manner. We show that cortical MMP-3 is upregulated in the McGill-R-Thy1-APP transgenic rat model of AD-like amyloidosis. A similar upregulation was found in AD and MCI brains as well as in cognitively normal individuals with elevated amyloid deposition. We also observed that frontal cortex MMP-3 protein levels are higher in males. MMP-3 protein correlated with more AD neuropathology, markers of NGF metabolism, and lower cognitive scores in males but not in females. These results suggest that MMP-3 upregulation in AD might contribute to NGF dysmetabolism, and therefore to cholinergic atrophy and cognitive deficits, in a sex-specific manner. MMP-3 should be further investigated as a biomarker candidate or as a therapeutic target in AD.

Calcium signaling defects underlying salivary gland dysfunction

Salivary glands secrete saliva, a mixture of proteins and fluids, which plays an extremely important role in the maintenance of oral health. Loss of salivary secretion causes a dry mouth condition, xerostomia, which has numerous deleterious consequences including opportunistic infections within the oral cavity, difficulties in eating and swallowing food, and problems with speech. Saliva secretion is regulated by stimulation of specific signaling mechanisms within the acinar cells of the gland. Neurotransmitter-stimulated increase in cytosolic [Ca²⁺] ([Ca²⁺]_i) in acinar cells is the primary trigger for salivary fluid secretion from salivary glands, the loss of which is a critical factor underlying dry mouth conditions in patients. The increase in [Ca²⁺]_i regulates multiple ion channel and transport activities that together generate the osmotic gradient which drives fluid secretion across the apical membrane. Ca²⁺ entry mediated by the Store-Operated Ca²⁺ Entry (SOCE) mechanism provides the essential [Ca²⁺]_i signals to trigger salivary gland fluid secretion. Under physiological conditions depletion of ER-Ca²⁺ stores is caused by activation of IP3R by IP3 and this provides the stimulus for SOCE. Core components of SOCE in salivary gland acinar cells are the plasma membrane Ca²⁺ channels, Orai1 and TRPC1, and STIM1, a Ca²⁺-sensor protein in the ER, which regulates both channels. In addition, STIM2 likely enhances the sensitivity of cells to ER-Ca²⁺ depletion thereby tuning the cellular response to agonist stimulation. Two major, clinically relevant, conditions which cause irreversible salivary gland dysfunction are radiation treatment for head-and-neck cancers and the autoimmune exocrinopathy, Sjögren's syndrome (pSS). However, the exact mechanism(s) that causes the loss of fluid secretion, in either condition, is not clearly understood. A number of recent studies have identified that defects in critical Ca²⁺ signaling mechanisms underlie salivary gland dysfunction caused by radiation treatment or Sjögren's syndrome (pSS). This chapter will discuss these very interesting and important studies.

Update on Pathogenesis of Sjogren's Syndrome

Sjogren's syndrome is a common autoimmune disease that presents with sicca symptoms and extraglandular features. Sjogren's syndrome is presumably as common as RA; yet it is poorly understood, underdiagnosed and undertreated. From the usual identity as an autoimmune exocrinopathy to its most recent designate as an autoimmune epithelitis - the journey of SS is complex. We herein review some of the most important milestones that have shed light on different aspects of pathogenesis of this enigmatic disease. This includes role of salivary gland epithelial cells, and their interaction with cells of the innate and adaptive immune system. Non-immune factors acting in concert or in parallel with immune factors may also be important. The risk genes identified so far have only weak association, nevertheless advances in genetics have enhanced understanding of disease mechanisms. Role of epigenetic and environmental role factors is also being explored. SS has also some unique features such as congenital heart block and high incidence of lymphoma; disease mechanisms accounting for these manifestations are also reviewed.

Review of autoantigens in Sjögren's syndrome: an update

Primary Sjögren’s syndrome (pSS) is an autoimmune disease characterized by inflammation in exocrine glands, resulting in reduced secretion of tears and saliva, manifesting as xerophthalmia and xerostomia, respectively. It is commonly associated with Sjögren’s syndrome type A (Ro) and Sjögren’s syndrome type B (La) antigens. However, in most patients, the identity of the triggering antigen is not known. Factors such as genetics of histocompatibility, dysregulation of T-cells, B-cells and viral infections have been implicated. Several important studies on autoantigens in pSS have been published since a review in 2012, and the aim of this review is to provide an update on further peer-reviewed original articles in this field. Oxidative damage of Ro60 antigen may explain the epitope spreading during the immune activation in pSS. Immune-mediated destruction of the muscarinic receptor-3-expressing cells has been associated with a reduction in parasympathetic function, which could cause reduced secretory function of exocrine glands. Such a process also activates reactive oxidative species and antioxidants, which are linked to the triggering of inflammatory responses. Elevated levels of kallikrein, yet another antigen present in the lacrimal gland and other tissues, are similarly involved in triggering an autoimmune T-cell response against target glands. Studying additional antigens, the platelet-selectin and vasoactive intestinal peptides, in patients with pSS can help to elucidate the origin and process of autoimmunity, or even lead to potential biomarkers. In conclusion, the understanding of autoantigens has led to exciting major advances in the biology of pSS and may influence diagnosis and management of pSS in future.

Autoantibodies in Sjögren's Syndrome

We compiled information on antibodies in Sjögren syndrome, focusing more on clinical manifestations associated with anti-Ro/SSA and anti-La/SSB antibodies and studies regarding novel antibodies. We reviewed previous as well as most recent studies with the subject heading Sjogren in combination with antibodies and congenital heart block (CHB). Almost half of asymptomatic mothers giving birth to children with CHB ultimately develop Sjögren. We discussed studies concerning the presence of antibodies predating clinical manifestations of disease. Studies in the future are required to ascertain the pathogenic mechanisms associated with these antibodies and the specific clinical manifestation related to new autoantibodies.

Predominant Glandular Cholinergic Dysautonomia in Patients With Primary Sjögren's Syndrome

OBJECTIVE

The autonomic nervous system (ANS) modulates exocrine gland function. Available data show poor correlation between the degree of function and destruction of the exocrine glands in primary Sjögren's syndrome (SS), suggesting that other mechanisms, such as autonomic dysfunction, may be important in these patients. The aim of this study was to perform a comprehensive analysis of sympathoneural and sympathetic cholinergic function in well-characterized patients with primary SS.

METHODS

Twenty-one patients with primary SS (mean ± SEM age 44.2 ± 2.8 years) and 13 healthy control subjects (mean ± SEM age 50.8 ± 1.9 years) were assessed during orthostasis and intravenous injection of edrophonium (10 mg). The postganglionic sympathetic cholinergic system was evaluated by assessing sweat production by means of the Quantitative Sudomotor Axon Reflex Test (QSART). Tests of gastric emptying were used to assess the gastrointestinal ANS in primary SS patients.

RESULTS

The velocity index and the acceleration index were significantly higher (P < 0.05) in patients with primary SS as compared to controls, both before and during the orthostatic and edrophonium tests. Findings of other hemodynamic and neurochemical parameters did not differ between primary SS patients and controls during the orthostasis and edrophonium test; however, the edrophonium-induced saliva increment was lower in primary SS patients (P = 0.002). Abnormally low sweat production was found in 4 primary SS patients but in none of the controls, as determined by the QSART. Gastric empting was delayed in 53% of primary SS patients.

CONCLUSION

We observed subtle differences in several ANS domains, including the gastrointestinal and sympathocholinergic systems, suggesting the presence of a complex ANS dysfunction in primary SS. The impact was greatest on the exocrine glands, with subtle differences in the cardiac parasympathetic function that were independent of glandular inflammation and atrophy, suggesting an alternative mechanism of disease pathogenesis in primary SS.

Action of anti-M₃muscarinic acetylcholine receptor IgG of primary Sjögren's syndrome on the enzymatic antioxidant system in rat submandibular gland

BACKGROUND

We demonstrate that serum immunoglobulin G (IgG) directed against glandular M3 muscarinic acetylcholine receptors (M₃mAChR) and pilocarpine triggers the increment of superoxide dismutase (SOD) and catalase (CAT) and the production of nitric oxide (NO) and prostaglandin E₂(PGE₂).

METHODS

Enzyme-linked immunosorbent assay (ELISA) was performed in the presence of the human M₂mAChR synthetic peptide as antigen to detect in serum of pSS patients the autoantibodies. Further, SOD and CAT specific activity and NO were determined chemically in the presence of anti-M₃mAChR IgG and pilocarpine. The level of PGE₂generation in the presence of autoantibody and pilocarpine was determined by ELISA.

RESULTS

An association between anti-M₂mAChR autoantibodies and pilocarpine given the increment of the specific activity of SOD and CAT in the serum of pSS patients and in the rat submandibular gland was observed. As a result of this action, M₃synthetic peptide and atropine abrogated the stimulatory action. The L-type calcium channel, calcium/calmodulin complex and COX-2 inhibitors selectively blocked the increment of the specific activity of SOD and CAT in the rat submandibular gland. An increased production of NO and PGE₂by the cholinergic autoantibody and pilocarpine was also detected.

CONCLUSION

On the basis of these results, the increment of the specific activity of SOD and CAT in pSS patients as compared to control healthy individuals may be seen as a defensive reaction to the increment of the amount of ROS, which becoming uncontrollable, leads to irreversible cellular and tissue damage.

Primary Sjogrens syndrome is associated with impaired autonomic response to orthostasis and sympathetic failure

BACKGROUND

Symptoms in keeping with autonomic dysfunction are commonly described by primary Sjögrens syndrome patients (pSS); whether objective abnormalities of autonomic function occur is unclear. This study set out to explore dynamic cardiovascular autonomic responses in pSS and their relationship with symptoms and quality of life.

METHODS

Twenty-one people from the UK pSS registry, 21 community controls and 21 patients with the autoimmune liver disease primary biliary cirrhosis (PBC) (matched case-wise for age and sex) attended for assessment of autonomic responses to orthostasis and Valsalva manoeuvre (VM). pSS patients also completed EULAR Sjögrens Syndrome patient-reported index (ESSPRI), EULAR Sjögren's syndrome disease activity index (ESSDAI), fatigue impact scale and EURO-QOL 5-dimension (EQ-5D).

RESULTS

Compared with controls, pSS patients had significantly lower baseline systolic blood pressure (SBP) (114 ± 13 vs. 127 ± 20; P = 0.02), which dropped to a significantly lower value (98 ± 22 vs. 119 ± 24, P = 0.009). When area under the curve (AUC) was calculated for when the SBP was below baseline this was significantly greater in pSS compared to both control groups (pSS vs. control vs. PBC: 153 ± 236 vs. 92 ± 85 vs. 1.2 ± 0.3, P = 0.005). Peak phase IV SBP during the VM was significantly lower in pSS (P = 0.007) indicating early sympathetic failure. Increased heart rate associated with fatigue (P = 0.02; r(2) = 0.2) and EQ-5D. A shift in sympathetic-vagal balance associated with overall symptom burden (ESSPRI) (P = 0.04, r(2) = 0.3) and EULAR sicca score (P = 0.016; r(2) = 0.3), the latter also correlated with baroreceptor effectiveness (P = 0.03; r(2) = 0.2) and diastolic blood pressure variability (P = 0.003; r(2) = 0.4).

CONCLUSION

pSS patients have impaired blood pressure response to standing. Dysautonomia correlates with PSS-associated symptoms and quality of life.

Autonomic symptoms are common and are associated with overall symptom burden and disease activity in primary Sjogren's syndrome

Objectives

To determine the prevalence of autonomic dysfunction (dysautonomia) among patients with primary Sjögren's syndrome (PSS) and the relationships between dysautonomia and other clinical features of PSS.

Methods

Multicentre, prospective, cross-sectional study of a UK cohort of 317 patients with clinically well-characterised PSS. Symptoms of autonomic dysfunction were assessed using a validated instrument, the Composite Autonomic Symptom Scale (COMPASS). The data were compared with an age- and sex-matched cohort of 317 community controls. The relationships between symptoms of dysautonomia and various clinical features of PSS were analysed using regression analysis.

Results

COMPASS scores were significantly higher in patients with PSS than in age- and sex-matched community controls (median (IQR) 35.5 (20.9–46.0) vs 14.8 (4.4–30.2), p<0.0001). Nearly 55% of patients (vs 20% of community controls, p<0.0001) had a COMPASS score >32.5, a cut-off value indicative of autonomic dysfunction. Furthermore, the COMPASS total score correlated independently with EULAR Sjögren's Syndrome Patient Reported Index (a composite measure of the overall burden of symptoms experienced by patients with PSS) (β=0.38, p<0.001) and disease activity measured using the EULAR Sjögren's Syndrome Disease Activity Index (β=0.13, p<0.009).

Conclusions

Autonomic symptoms are common among patients with PSS and may contribute to the overall burden of symptoms and link with systemic disease activity.