hsa-miR-424-5p and hsa-miR-513c-3p dysregulation mediated by IFN-γ is associated with salivary gland dysfunction in Sjögren's syndrome patients

Integrated stress response inhibition restores hsa-miR-145-5p levels after IFN-β stimulation in salivary gland epithelial cells. Association between cellular stress and miRNA biogenesis in Sjögren's disease

Labial salivary glands (LSG) from Sjögren's disease (SjD) patients are characterized by increased levels of pro-inflammatory cytokines, such as type I interferons (IFN-I). These LSG also show activation of the integrated stress response (ISR) with overexpression of protein kinase R (PKR), a known IFN-stimulated gene. In vitro, IFN-I stimulation reproduces the downregulation of hsa-miR-145-5p, which is associated with TLR4 overexpression observed in LSG of SjD patients. MicroRNA levels depend on its biogenesis, which is a multi-step process involving several protein complexes. It is not known whether altered miRNA biogenesis is associated with the activation of the ISR induced by IFN-I in LSG from SjD. The aim of this study was to characterize the expression and localization of components of the miRNA biogenesis machinery in LSG of SjD patients, to assess the effect of pro-inflammatory cytokines on these components, and to test whether inhibition of the IFN-β-induced ISR restores the levels of hsa-miR-145-5p. In LSG from 12 SjD patients and 11 non-SjD sicca controls, we determined mRNA fold changes, relative protein levels, and the localization of the ISR and miRNA biogenesis machinery components by RT-qPCR, Western blot, and immunofluorescence, respectively. Pro-inflammatory cytokines, the ISR inhibitor ISRIB, and the PKR inhibitor C16 were used for in vitro assays. In LSG from SjD patients, PKR and its activator PACT colocalized in the cytoplasm, whereas the PKR inhibitor TRBP was observed in the nuclei. IFN-β activates PKR, increases p-eIF2α and ATF4 levels, and increases PACT and AGO2 detection in stress granules. C16 inhibits PKR phosphorylation but increases ATF4 by activating GCN2. ISRIB restores levels of hsa-miR-145-5p and its target TLR4 mRNA upon IFN-β stimulation. These findings suggest an association between inflammation, cellular stress, and miRNA biogenesis, where modulation of the ISR emerges as a potential strategy to restore cellular homeostasis in LSG from SjD patients.

miR-216a-3p alleviates primary Sjögren's syndrome by regulating the STAT1/JAK signaling pathway

BACKGROUND

Sjögren's syndrome (SS) is a chronic systemic autoimmune It chiefly impacts the exocrine glands, specifically the salivary and lacrimal ones, causing manifestations such as dry mouth and eye. Sjögren's syndrome often coexists with other autoimmune diseases, making it difficult to study its pathogenesis. Mounting evidence suggests that microRNAs (miRNAs) play a pivotal role in the development of autoimmune diseases, yet the precise mechanisms underlying their involvement in SS remain to be fully elucidated.

METHODS

A cohort dataset pertaining to Sjögren's syndrome was procured from the Gene Expression Omnibus (GEO) database and subsequently analyzed using bioinformatics tools. The association between Signal Transducer and Activator of Transcription 1 (STAT1) and Sjögren's syndrome is well-established. To predict miRNAs targeting STAT1, we utilized the TargetScan database, focusing on miR-216a-3p. Furthermore, to model primary Sjögren's syndrome (pSS) in vivo, we employed a rat model established through submandibular gland protein immunization. These pSS model rats were then subjected to injections of either miR-216a-3p mimics or inhibitors. Subsequently, histological analysis was conducted to assess the resulting tissue morphology. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) was employed to determine the expression levels of both STAT1 and miR-216a-3p. Cytokine levels were quantified using enzyme-linked immunosorbent assay (ELISA). To investigate the protein expression of key components of the STAT/JAK signaling pathway, Western blot analysis was performed, targeting Signal Transducer and Activator of Transcription 1 (STAT1), Janus kinase 1 (JAK1), and Janus kinase 2 (JAK2).

RESULTS

Our findings indicate that miR-216a-3p exerts regulatory control over the JAK/STAT signaling pathway by modulating the phosphorylation of STAT1, thereby attenuating the severity of primary Sjögren's syndrome in our model. Moreover, miR-216a-3p was observed to inhibit the secretion of pro-inflammatory cytokines and mitigate B cell hyperactivation. These results collectively suggest a potentially significant role for miR-216a-3p in the pathogenesis of autoimmune diseases, warranting further investigation.

Causal association between Helicobacter pylori infection and Sjogren's syndrome: a bidirectional Mendelian randomization analysis

BACKGROUND

The results of observational studies indicate a potential link between Helicobacter pylori infection and Sjogren's syndrome (SS), but the causal relationship between them remains unknown. This study applied Mendelian randomization (MR) to evaluate this relationship.

METHOD

Genome-wide association study (GWAS) summary statistics on H. pylori infection [sample size=8735 (EBI, https://gwas.mrcieu.ac.uk/ )] and SS [sample size=368,028 (cases=2495, controls=365533) (FinnGen, https://r9.finngen.fi/ )] were analyzed. We used bidirectional MR to evaluate the association between H. pylori infection and SS and identify causation. The major MR analysis method was inverse-variance weighted (IVW) MR, supplemented by MR‒Egger and weighted median approaches. In addition, the stability and reliability of the results were tested using the retention method, heterogeneity test, and horizontal gene pleiotropy test.

RESULTS

Evidence of the impact of H. pylori infection on SS risk was found in the IVW results [odds ratio (OR)=1.6705; 95% confidence interval (CI)=1.0966 to 2.5446; P=0.0168]. Evidence of the impact of SS on H. pylori infection risk was also found (OR=1.0158; 95% CI=1.0033 to 1.0285; P=0.0128).

CONCLUSION

The results of MR analysis support a causal association between H. pylori infection and SS and indicate that SS can lead to a greater risk of H. pylori infection. Our research will support the development of novel approaches for continued H. pylori and SS-related research and therapy that consider the genetic relationship between H. pylori infection and SS.

Role of ncRNAs in the Pathogenesis of Sjögren's Syndrome

Sjögren's syndrome is a multisystemic autoimmune disease that mainly affects the exocrine glands, causing dryness of the eyes and the mouth as the principal symptoms. Non-coding RNAs (ncRNAs), once regarded as genomic "junk", are now appreciated as important molecular regulators of gene expression, not least in Sjögren's syndrome and other autoimmune diseases. Here we review research into the causative roles of microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) on immunological responses, inflammation, and salivary gland epithelial cell function in Sjögren's syndrome patients. These ncRNAs represent promising new therapeutic targets for treating the disease and possibly as biomarkers for early diagnosis.

CD4 T cell-secreted IFN-γ in Sjögren's syndrome induces salivary gland epithelial cell ferroptosis

BACKGROUND

Sjögren's syndrome (SS) is a chronic autoimmune disease that predominantly affects exocrine glands. Previous studies have demonstrated that upregulated interferon-gamma (IFN-γ) in SS triggers ferroptosis in salivary gland epithelial cells (SGECs), resulting in impaired salivary gland secretion. However, the immune cells responsible for secreting IFN-γ remain unclear. Therefore, this study conducted bioinformatics analysis and molecular validation to identify the origin of IFN-γ in SS salivary gland.

METHODS

The 'limma' package in R software was utilized to identify differentially expressed genes (DEGs) in the human SS dataset. Subsequently, the identified DEGs were compared with the ferroptosis database and screened through Cytoscape to determine candidate genes. The cellular localization and expression patterns of candidate genes were further confirmed in the salivary gland single-cell RNA sequence (scRNA-seq) data set from healthy control and SS mice. Furthermore, in vitro and in vivo studies were performed to analyze the effect of CD4 T-secreted IFN-γ on SGECs' ferroptosis and functions.

RESULTS

Upregulated TLR4, IFNG, and IL33 were screened as candidates ferroptosis ferroptosis-inducing genes in SS salivary glands. The association of IFNG and IL33 with CD4 T cells was established through immune infiltration analysis. The expression of IFN-γ on CD4 T cells was robustly higher compared with that of IL33 as evidenced by scRNA-seq and immunofluorescence co-localization. Subsequent experiments conducted on candidate genes consistently demonstrated the potent ability of IFN-γ to induce SGECs' ferroptosis and inhibit AQP5 expression.

CONCLUSIONS

Our findings indicate that CD4 T cell-secreted IFN-γ in SS induces SGECs' ferroptosis and inhibits AQP5 expression.

Role of microRNAs in Immune Regulation with Translational and Clinical Applications

MicroRNAs (miRNAs) are 19-23 nucleotide long, evolutionarily conserved noncoding RNA molecules that regulate gene expression at the post-transcriptional level. In this review, involvement of miRNAs is summarized in the differentiation and function of immune cells, in anti-infective immune responses, immunodeficiencies and autoimmune diseases. Roles of miRNAs in anticancer immunity and in the transplantation of solid organs and hematopoietic stem cells are also discussed. Major focus is put on the translational clinical applications of miRNAs, including the establishment of noninvasive biomarkers for differential diagnosis and prediction of prognosis. Patient selection and response prediction to biological therapy is one of the most promising fields of application. Replacement or inhibition of miRNAs has enormous therapeutic potential, with constantly expanding possibilities. Although important challenges still await solutions, evaluation of miRNA fingerprints may contribute to an increasingly personalized management of immune dysregulation with a remarkable reduction in toxicity and treatment side effects. More detailed knowledge of the molecular effects of physical exercise and nutrition on the immune system may facilitate self-tailored lifestyle recommendations and advances in prevention.

Modes and Mechanisms of Salivary Gland Epithelial Cell Death in Sjogren's Syndrome

Sjogren's syndrome is an autoimmune disease in middle and old-aged women with a dry mucosal surface, which is caused by the dysfunction of secretory glands, such as the oral cavity, eyeballs, and pharynx. Pathologically, Sjogren's syndrome are characterized by lymphocyte infiltration into the exocrine glands and epithelial cell destruction caused by autoantibodies Ro/SSA and La/SSB. At present, the exact pathogenesis of Sjogren's syndrome is unclear. Evidence suggests epithelial cell death and the subsequent dysfunction of salivary glands as the main causes of xerostomia. This review summarizes the modes of salivary gland epithelial cell death and their role in Sjogren's syndrome progression. The molecular mechanisms involved in salivary gland epithelial cell death during Sjogren's syndrome as potential leads to treating the disease are also discussed.