Autophagy occurs in lymphocytes infiltrating Sjögren's syndrome minor salivary glands and correlates with histological severity of salivary gland lesions

Histological differences related to autophagy in the minor salivary gland between primary and secondary types of Sjögren's syndrome

Some forms of Sjögren's syndrome (SS) follow a clinical course accompanied by systemic symptoms caused by lymphocyte infiltration and proliferation in the liver, kidneys, and other organs. To better understand the clinical outcomes of SS, here we used minor salivary gland tissues from patients and examine their molecular, biological, and pathological characteristics. A retrospective study was performed, combining clinical data and formalin-fixed paraffin-embedded (FFPE) samples from female patients over 60 years of age who underwent biopsies at Okayama University Hospital. We employed direct digital RNA counting with nCounter® and multiplex immunofluorescence analysis with a PhenoCycler™ on the labial gland biopsies. We compared FFPE samples from SS patients who presented with other connective tissue diseases (secondary SS) with those from stable SS patients with symptoms restricted to the exocrine glands (primary SS). Secondary SS tissues showed enhanced epithelial damage and lymphocytic infiltration accompanied by elevated expression of autophagy marker genes in the immune cells of the labial glands. The close intercellular distance between helper T cells and B cells positive for autophagy-associated molecules suggests accelerated autophagy in these lymphocytes and potential B cell activation by helper T cells. These findings indicate that examination of FFPE samples from labial gland biopsies can be an effective tool for evaluating molecular histological differences between secondary and primary SS through multiplexed analysis of gene expression and tissue imaging.

Research progress of T cell autophagy in autoimmune diseases

T cells, as a major lymphocyte population involved in the adaptive immune response, play an important immunomodulatory role in the early stages of autoimmune diseases. Autophagy is a cellular catabolism mediated by lysosomes. Autophagy maintains cell homeostasis by recycling degraded cytoplasmic components and damaged organelles. Autophagy has a protective effect on cells and plays an important role in regulating T cell development, activation, proliferation and differentiation. Autophagy mediates the participation of T cells in the acquired immune response and plays a key role in antigen processing as well as in the maintenance of T cell homeostasis. In autoimmune diseases, dysregulated autophagy of T cells largely influences the pathological changes. Therefore, it is of great significance to study how T cells play a role in the immune mechanism of autoimmune diseases through autophagy pathway to guide the clinical treatment of diseases.

The Genetic Landscape of Systemic Rheumatic Diseases: A Comprehensive Multigene-Panel Study Identifying Key Gene Polymorphisms

Systemic rheumatic diseases, including conditions such as rheumatoid arthritis, Sjögren's syndrome, systemic sclerosis, and systemic lupus erythematosus, represent a complex array of autoimmune disorders characterized by chronic inflammation and diverse clinical manifestations. This study focuses on unraveling the genetic underpinnings of these diseases by examining polymorphisms in key genes related to their pathology. Utilizing a comprehensive genetic analysis, we have documented the involvement of these genetic variations in the pathogenesis of rheumatic diseases. Our study has identified several key polymorphisms with notable implications in rheumatic diseases. Polymorphism at chr11_112020916 within the IL-18 gene was prevalent across various conditions with a potential protective effect. Concurrently, the same IL18R1 gene polymorphism located at chr2_103010912, coding for the IL-18 receptor, was observed in most rheumatic conditions, reinforcing its potential protective role. Additionally, a further polymorphism in IL18R1 at chr2_103013408 seems to have a protective influence against the rheumatic diseases under investigation. In the context of emerging genes involved in rheumatic diseases, like PARK2, a significant polymorphism at chr6_161990516 was consistently identified across different conditions, exhibiting protective characteristics in these pathological contexts. The findings underscore the complexity of the genetic landscape in rheumatic autoimmune disorders and pave the way for a deeper understanding of their etiology and the possible development of more targeted and effective therapeutic strategies.

Lysosome-Associated Membrane Protein 3 Induces Lysosome-Dependent Cell Death by Impairing Autophagic Caspase 8 Degradation in the Salivary Glands of Individuals With Sjögren's Disease

OBJECTIVE

Lysosome-associated membrane protein 3 (LAMP3) overexpression is implicated in the development and progression of Sjögren's disease (SjD) by inducing lysosomal membrane permeabilization (LMP) and apoptotic cell death in salivary gland epithelium. The aim of this study was to clarify the molecular details of LAMP3-induced lysosome-dependent cell death and to test lysosomal biogenesis as a therapeutic intervention.

METHODS

Human labial minor salivary gland biopsies were analyzed using immunofluorescence staining for LAMP3 expression levels and galectin-3 puncta formation, a marker of LMP. Expression level of caspase 8, an initiator of LMP, was determined by Western blotting in cell culture. Galectin-3 puncta formation and apoptosis were evaluated in cell cultures and a mouse model treated with glucagon-like peptide 1 receptor (GLP-1R) agonists, a known promoter of lysosomal biogenesis.

RESULTS

Galectin-3 puncta formation was more frequent in the salivary glands of SjD patients compared to control glands. The proportion of galectin-3 puncta-positive cells was positively correlated with LAMP3 expression levels in the glands. LAMP3 overexpression increased caspase 8 expression, and knockdown of caspase 8 decreased galectin-3 puncta formation and apoptosis in LAMP3-overexpressing cells. Inhibition of autophagy increased caspase 8 expression, while restoration of lysosomal function using GLP-1R agonists decreased caspase 8 expression, which reduced galectin-3 puncta formation and apoptosis in both LAMP3-overexpressing cells and mice.

CONCLUSION

LAMP3 overexpression induced lysosomal dysfunction, resulting in lysosome-dependent cell death via impaired autophagic caspase 8 degradation, and restoring lysosomal function using GLP-1R agonists could prevent this. These findings suggested that LAMP3-induced lysosomal dysfunction is central to disease development and is a target for therapeutic intervention in SjD.

The Ragulator complex: delving its multifunctional impact on metabolism and beyond

Our understanding of lysosomes has undergone a significant transformation in recent years, from the view that they are static organelles primarily responsible for the disposal and recycling of cellular waste to their recognition as highly dynamic structures. Current research posits that lysosomes function as a signaling hub that integrates both extracellular and intracellular stimuli, thereby regulating cellular homeostasis. The dysregulation of lysosomal function has been linked to a wide range of diseases. Of note, lysosomes contribute to the activation of mammalian target of rapamycin complex 1 (mTORC1), a key regulator of cellular metabolism. The Ragulator complex, a protein complex anchored on the lysosomal membrane, was initially shown to tether the mTORC1 complex to lysosomes. Recent research has substantially expanded our understanding of the roles of the Ragulator complex in lysosomes, including roles in the regulation of metabolism, inflammation, cell death, cell migration, and the maintenance of homeostasis, via interactions with various proteins. This review summarizes our current knowledge on the diverse functions of the Ragulator complex, highlighting important protein interactions.

Genetics and epigenetics of primary Sjögren syndrome: implications for future therapies

In primary Sjögren syndrome (pSS), chronic inflammation of exocrine glands results in tissue destruction and sicca symptoms, primarily of the mouth and eyes. Fatigue, arthralgia and myalgia are also common symptoms, whereas extraglandular manifestations that involve the respiratory, nervous and vascular systems occur in a subset of patients. The disease predominantly affects women, with an estimated female to male ratio of 14 to 1. The aetiology of pSS, however, remains incompletely understood, and effective treatment is lacking. Large-scale genetic and epigenetic investigations have revealed associations between pSS and genes in both innate and adaptive immune pathways. The genetic variants mediate context-dependent effects, and both sex and environmental factors can influence the outcome. As such, genetic and epigenetic studies can provide insight into the dysregulated molecular mechanisms, which in turn might reveal new therapeutic possibilities. This Review discusses the genetic and epigenetic features that have been robustly connected with pSS, putting them into the context of cellular function, carrier sex and environmental challenges. In all, the observations point to several novel opportunities for early detection, treatment development and the pathway towards personalized medicine.

Immunomodulatory effects of umbilical mesenchymal stem cell-derived exosomes on CD4+ T cells in patients with primary Sjögren's syndrome

BACKGROUND

Primary Sjögren's syndrome (pSS) is an autoimmune disease that leads to the destruction of exocrine glands and multisystem lesions. Abnormal proliferation, apoptosis, and differentiation of CD4⁺ T cells are key factors in the pathogenesis of pSS. Autophagy is one of the important mechanisms to maintain immune homeostasis and function of CD4⁺ T cells. Human umbilical cord mesenchymal stem cell-derived exosomes (UCMSC-Exos) may simulate the immunoregulation of MSCs while avoiding the risks of MSCs treatment. However, whether UCMSC-Exos can regulate the functions of CD4⁺ T cells in pSS, and whether the effects via the autophagy pathway remains unclear.

METHODS

The study analyzed retrospectively the peripheral blood lymphocyte subsets in pSS patients, and explored the relationship between lymphocyte subsets and disease activity. Next, peripheral blood CD4⁺ T cells were sorted using immunomagnetic beads. The proliferation, apoptosis, differentiation, and inflammatory factors of CD4⁺ T cells were determined using flow cytometry. Autophagosomes of CD4⁺ T cells were detected using transmission electron microscopy, autophagy-related proteins and genes were detected using western blotting or RT-qPCR.

RESULTS

The study demonstrated that the peripheral blood CD4⁺ T cells decreased in pSS patients, and negatively correlated with disease activity. UCMSC-Exos inhibited excessive proliferation and apoptosis of CD4⁺ T cells in pSS patients, blocked them in the G0/G1 phase, inhibited them from entering the S phase, reduced the Th17 cell ratio, elevated the Treg ratio, inhibited IFN-γ, TNF-α, IL-6, IL-17A, and IL-17F secretion, and promoted IL-10 and TGF-β secretion. UCMSC-Exos reduced the elevated autophagy levels in the peripheral blood CD4⁺ T cells of patients with pSS. Furthermore, UCMSC-Exos regulated CD4⁺ T cell proliferation and early apoptosis, inhibited Th17 cell differentiation, promoted Treg cell differentiation, and restored the Th17/Treg balance in pSS patients through the autophagy pathway.

CONCLUSIONS

The study indicated that UCMSC-Exos exerts an immunomodulatory effect on the CD4⁺ T cells, and maybe as a new treatment for pSS.

The abscopal effect: Implications for drug discovery in autoimmunity

The emergence of novel targeted therapies and the tools that increase the stability and delivery of drugs have greatly improved treatment outcomes in autoimmune diseases (ADs). Recently-developed strategies deplete specific deleterious T- and B-cell subsets, interrupt receptor-ligand interactions, and/or inhibit the secretion or activity of inflammatory mediators linked to tissue damage. Although generally efficient, these lines of intervention have limitations, with documented cases of drug-resistance and undesired side effects. They are also difficult to apply to non-organ-specific ADs, where the trigger and effector antigens are unknown and in which autoimmune activity is widely spread throughout the body. The potential of cellular modulators that act at a distance from the affected site, by abscopal effect, as described in the case of cancer radio- and immuno-therapy might be especially efficient in the context of ADs. Future research to discover small molecule- and peptide-based treatments will need to explore potential drugs with abscopal effects that could elicit potent immune tolerance and clinical quiescence to restore quality of life of affected patients.

The role of lysosomes in metabolic and autoimmune diseases

Lysosomes are catabolic organelles that contribute to the degradation of intracellular constituents through autophagy and of extracellular components through endocytosis, phagocytosis and macropinocytosis. They also have roles in secretory mechanisms, the generation of extracellular vesicles and certain cell death pathways. These functions make lysosomes central organelles in cell homeostasis, metabolic regulation and responses to environment changes including nutrient stresses, endoplasmic reticulum stress and defects in proteostasis. Lysosomes also have important roles in inflammation, antigen presentation and the maintenance of long-lived immune cells. Their functions are tightly regulated by transcriptional modulation via TFEB and TFE3, as well as by major signalling pathways that lead to activation of mTORC1 and mTORC2, lysosome motility and fusion with other compartments. Lysosome dysfunction and alterations in autophagy processes have been identified in a wide variety of diseases, including autoimmune, metabolic and kidney diseases. Deregulation of autophagy can contribute to inflammation, and lysosomal defects in immune cells and/or kidney cells have been reported in inflammatory and autoimmune pathologies with kidney involvement. Defects in lysosomal activity have also been identified in several pathologies with disturbances in proteostasis, including autoimmune and metabolic diseases such as Parkinson disease, diabetes mellitus and lysosomal storage diseases. Targeting lysosomes is therefore a potential therapeutic strategy to regulate inflammation and metabolism in a variety of pathologies.

Melatonin: a potential therapeutic approach for the management of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune disease that primarily affects the exocrine glands and is mainly characterized by sicca symptoms of the eyes and mouth. Approximately 30-50% of pSS patients develop systemic multi-organ disorders including malignant lymphoma. The etiology of pSS is not well understood; growing evidence suggests that uncontrolled immune/inflammatory responses, excessive oxidative stress, defected apoptosis, dysregulated autophagy, exosomes, and exogenous virus infections may participate in the pathogenesis of pSS. There is no ideal therapeutic method for pSS; the management of pSS is mainly palliative, which aims to alleviate sicca symptoms. Melatonin, as the main secretory product of the pineal gland, has been evidenced to show various physiological functions, including effects of immunoregulation, capability of antioxidation, moderation of autophagy, suppressive activities of apoptosis, regulative capacity of exosomes, properties of anti-infection, and improvement of sleep. The beneficial effects of melatonin have been already validated in some autoimmune diseases such as multiple sclerosis (MS), type 1 diabetes mellitus (T1DM), systemic lupus erythematosus (SLE), and inflammatory bowel disease (IBD). However, our previous research firstly revealed that melatonin might inhibit pathogenic responses of peripheral Th17 and double-negative (DN) T cells in pSS. More importantly, melatonin administration alleviated the development of pSS in animal models with reduced infiltrating lymphocytes, improved functional activity of salivary gland, and decreased production of inflammatory factors as well as autoantibodies. Owing to the important biological properties reported in melatonin are characteristics closely related to the treatment of pSS; the potential role and underlying mechanisms of melatonin in the administration of pSS are certainly worth further investigations. Consequently, the aim of this review is to give a deep insight to the therapeutic potency of melatonin for pSS.

JAK/STAT Pathway Targeting in Primary Sjögren Syndrome

Primary Sjögren's syndrome (pSS) is an autoimmune systemic disease mainly affecting exocrine glands and resulting in disabling symptoms, as dry eye and dry mouth. Mechanisms underlying pSS pathogenesis are intricate, involving multiplanar and, at the same time, interlinked levels, e.g., genetic predisposition, epigenetic modifications and the dysregulation of both immune system and glandular-resident cellular pathways, mainly salivary gland epithelial cells. Unravelling the biological and molecular complexity of pSS is still a great challenge but much progress has been made in recent years in basic and translational research field, allowing the identification of potential novel targets for therapy development. Despite such promising novelties, however, none therapy has been specifically approved for pSS treatment until now. In recent years, growing evidence has supported the modulation of Janus kinases (JAK) - signal transducers and activators of transcription (STAT) pathways as treatment strategy immune mediated diseases. JAK-STAT pathway plays a crucial role in autoimmunity and systemic inflammation, being involved in signal pathways of many cytokines. This review aims to report the state-of-the-art about the role of JAK-STAT pathway in pSS, with particular focus on available research and clinical data regarding the use of JAK inhibitors in pSS.

Alterations of m6A RNA methylation regulators contribute to autophagy and immune infiltration in primary Sjögren's syndrome

N6-methyladenosine (m6A) RNA modification is a new epigenetic regulation mechanism on eukaryotic mRNA. Few autoimmune diseases focused on the role of m6A in their pathogenies, and m6A modulation in the pathological process of primary Sjögren's syndrome (pSS) is still unknown. In this work, three microarray datasets of pSS patients were downloaded from the GEO database: datasets #1 and #2 from the whole peripheral blood (PB) samples, dataset #3 from the labial salivary gland tissue samples, as well as a PB cohort collected from our hospital. Six differentially expressed m6A regulators were identified by comparing the PB dataset #1 of pSS and healthy controls using the Wilcox test and logistic regression analysis. Among them, four (ALKBH5, RBMX, RBM15B, and YTHDF1) were confirmed as down-regulated in PB dataset #2 and in our PB cohort by RT-PCR, and four (ALKBH5, METTL3, RBM15B, and YTHDF1) were confirmed as down-regulated in the dataset #3 of the labial gland tissue. In addition, discrepantly expressed m6A regulators accompanied by diverse immunocytes, including dendritic cells (DCs), T cells, and CD56dim natural killer cells, and among the regulators, ALKBH5 and METTL3 were comprehensively linked with the infiltrated immune cells. Notably, the most enriched autophagy mechanism mediated by m6A was observed in pSS using functional annotation analysis. Ten hub genes were identified using a protein-protein interaction network, and their expression in PB dataset #2 and the expression of three genes (PIK3CA, STAT1, and MAPK3) in the labial gland tissue dataset #3 were confirmed. Our study provides evidence that m6A methylation is widely involved in the immune infiltration and autophagy of pSS, thus contributing to the pathogenesis of this disease and potentially representing a novel therapeutic target.

Impaired GATE16-mediated exocytosis in exocrine tissues causes Sjögren's syndrome-like exocrinopathy

Sjögren's syndrome (SjS) is a chronic autoimmune disease characterized by immune cell infiltration of the exocrine glands, mainly the salivary and lacrimal glands. Despite recent advances in the clinical and mechanistic characterization of the disease, its etiology remains largely unknown. Here, we report that mice with a deficiency for either Atg7 or Atg3, which are enzymes involved in the ubiquitin modification pathway, in the salivary glands exhibit a SjS-like phenotype, characterized by immune cell infiltration with autoantibody detection, acinar cell death, and dry mouth. Prior to the onset of the SjS-like phenotype in these null mice, we detected an accumulation of secretory vesicles in the acinar cells of the salivary glands and found that GATE16, an uncharacterized autophagy-related molecule activated by ATG7 (E1-like enzyme) and ATG3 (E2-like enzyme), was highly expressed in these cells. Notably, GATE16 was activated by isoproterenol, an exocytosis inducer, and localized on the secretory vesicles in the acinar cells of the salivary glands. Failure to activate GATE16 was correlated with exocytosis defects in the acinar cells of the salivary glands in Atg7 and Atg3 cKO mice. Taken together, our results show that GATE16 activation regulated by the autophagic machinery is crucial for exocytosis and that defects in this pathway cause SjS.

Autophagy in Rheumatic Diseases: Role in the Pathogenesis and Therapeutic Approaches

Autophagy is a lysosomal pathway for the degradation of damaged proteins and intracellular components that promotes cell survival under specific conditions. Apoptosis is, in contrast, a critical programmed cell death mechanism, and the relationship between these two processes influences cell fate. Recent evidence suggests that autophagy and apoptosis are involved in the self-tolerance promotion and in the regulatory mechanisms contributing to disease susceptibility and immune regulation in rheumatic diseases. The aim of this review is to discuss how the balance between autophagy and apoptosis may be dysregulated in multiple rheumatic diseases and to dissect the role of autophagy in the pathogenesis of rheumatoid arthritis, systemic lupus erythematosus, and Sjögren’s syndrome. Furthermore, to discuss the potential capacity of currently used disease-modifying antirheumatic drugs (DMARDs) to target and modulate autophagic processes.

Tofacitinib Decreases Autophagy of Fibroblast-Like Synoviocytes From Rheumatoid Arthritis Patients

The pathway of Janus tyrosine kinases (JAKs) has a central role in the pathogenesis of Rheumatoid Arthritis (RA) by regulating multiple immune functions and cytokine production. The JAK inhibitor tofacitinib is effective in RA patients not responding to methotrexate or TNF-inhibitors. Since hyperactive autophagy has been associated with impaired apoptosis of RA fibroblast-like synoviocytes (FLS), we aimed to investigate the role of tofacitinib in modulating autophagy and apoptosis in these cells. FLS isolated from RA biopsies were cultured with tofacitinib in presence of autophagy inducer rapamycin and in serum deprivation condition. Levels of autophagy, apoptosis, and citrullinated proteins were analyzed by western blot, flow cytometry, immunocytofluorescence, and Real-Time PCR. Rapamycin induced an increase in RA-FLS autophagy while the levels of autophagy marker LC3-II were reduced after in vitro treatment with tofacitinib. The analysis of autophagic flux by specific fluorescence dye confirmed the reduction of autophagy in RA FLS. The treatment with tofacitinib did not influence apoptosis of RA FLS. Modulation of the autophagic process by tofacitinib did not significantly change citrullination. The results of this study demonstrate that tofacitinib is able to modulate autophagy of FLS contributing to its effectiveness in RA patients.

Targeting lysosomes in human disease: from basic research to clinical applications

In recent years, accumulating evidence has elucidated the role of lysosomes in dynamically regulating cellular and organismal homeostasis. Lysosomal changes and dysfunction have been correlated with the development of numerous diseases. In this review, we interpreted the key biological functions of lysosomes in four areas: cellular metabolism, cell proliferation and differentiation, immunity, and cell death. More importantly, we actively sought to determine the characteristic changes and dysfunction of lysosomes in cells affected by these diseases, the causes of these changes and dysfunction, and their significance to the development and treatment of human disease. Furthermore, we outlined currently available targeting strategies: (1) targeting lysosomal acidification; (2) targeting lysosomal cathepsins; (3) targeting lysosomal membrane permeability and integrity; (4) targeting lysosomal calcium signaling; (5) targeting mTOR signaling; and (6) emerging potential targeting strategies. Moreover, we systematically summarized the corresponding drugs and their application in clinical trials. By integrating basic research with clinical findings, we discussed the current opportunities and challenges of targeting lysosomes in human disease.

Maladaptive autophagy in the pathogenesis of autoimmune epithelitis in Sjӧgren's Syndrome

OBJECTIVE

Salivary gland epithelial cells (SGECs) are key cellular drivers in the pathogenesis of primary Sjӧgren's Syndrome (pSS); however, the mechanisms sustaining SGECs activation in pSS remain undetermined. The aim of this study is to determine the role of autophagy in the survival and activation of SGECs in pSS.

METHODS

Primary SGECs isolated from minor salivary glands (SG) of patients with pSS or sicca syndrome were evaluated by flow-cytometry, immunoblotting, and immunofluorescence to assess autophagy (autophagic-flux, LC3IIB, p62, LC3B+/LAMP1+ staining), apoptosis (annexin V/PI, Caspase-3) and activation (ICAM, VCAM). Focus score and germinal centers presence was assessed in SG from the same patients to correlate with histological severity. Human salivary gland (HSG) cells were stimulated in vitro with PBMCs and serum from pSS patients in the presence or absence of autophagy inhibitors to determine changes in autophagy and epithelial cell activation.

RESULTS

SGECs from pSS patients (n=24) exhibited increased autophagy (autophagic-flux p=0.001; LC3IIB p=0.02; p62 p=0.064; LC3IIB/LAMP1+ staining), increased expression of anti-apoptotic molecules (Bcl2 p=0.006), and reduced apoptosis (Annexin-V/PI p=0.002, Caspase-3 p=0.057) compared to sicca (n=16). Autophagy correlated with histologic disease severity. In vitro experiments on HSG cells stimulated with serum and PBMCs from pSS patients confirmed activation of autophagy and expression of adhesion molecules, which was reverted upon pharmacologic inhibition of autophagy.

CONCLUSIONS

In pSS SGECs, inflammation induces autophagy and pro-survival mechanisms, which promote SGEC activation and mirror histological severity. These findings indicate that autophagy is a central contributor to the pathogenesis of pSS and a new therapeutic target.