Tight junctions (TJs) play an important role in water, ion, and solute transport through the paracellular pathway of epithelial cells; however, their role in diabetes-induced salivary gland dysfunction remains unknown. Here, we found that the TJ proteins claudin-1 and claudin-3 were significantly increased in the submandibular glands (SMGs) of db/db mice and high glucose (HG)-treated human SMGs. HG decreased paracellular permeability and increased claudin-1 and claudin-3 expression in SMG-C6 cells. Knockdown of claudin-1 or claudin-3 reversed the HG-induced decrease in paracellular permeability. MiR-22-3p was significantly downregulated in diabetic SMGs and HG-treated SMG-C6 cells. A miR-22-3p mimic suppressed claudin-1 and claudin-3 expression and abolished the HG-induced increases in claudin-1 and claudin-3 levels in SMG-C6 cells, whereas a miR-22-3p inhibitor produced the opposite effects. Specificity protein-1 (Sp1) was enhanced in diabetic SMGs and HG-treated SMG-C6 cells, which promoted claudin-1 and claudin-3 transcription through binding to the corresponding promoters. A luciferase reporter assay confirmed that miR-22-3p repressed Sp1 by directly targeting the Sp1 mRNA 3′-untranslated region (3′-UTR). Consistently, the miR-22-3p mimic suppressed, whereas the miR-22-3p inhibitor enhanced, the effects of HG on Sp1 expression. Taken together, our results demonstrate a new regulatory pathway through which HG decreases the paracellular permeability of SMG cells by inhibiting miR-22-3p/Sp1-mediated claudin-1 and claudin-3 expression.

Oral squamous cell carcinoma (OSCC) is a highly aggressive relatively common cancer that poses a serious threat to patient health, leading to significant economic burdens on healthcare systems. This study was designed to investigate the expression levels of disulphidptosis-related genes (DRGs) in OSCC and assess their potential as biomarkers for diagnosis and prognosis. We used in-depth bioinformatics analysis of RNA sequencing data from the public databases, as well as functional enrichment analysis, survival analysis, immune cell infiltration levels and single cell analysis, to assess DRG expression in OSCC samples. Fifteen highly elevated DRGs, including inverted formin 2 (INF2) and destrin (DSTN), were investigated, and their expression in OSCC samples was validated by real-time PCR. The expression of these 15 DRGs correlated with patient survival rates and immune cell infiltration patterns. Functional enrichment analysis revealed that these genes are engaged in the regulation of essential biological processes, including the cytoskeleton and focal adhesion, indicating their importance in tumour development and tumour microenvironment interactions. Furthermore, receiver operating characteristic analysis revealed that the area under the curve for these DRGs ranged between 0.651 and 0.932, indicating their potential as diagnostic and prognostic biomarkers. The mRNA expressions of INF2 and DSTN were increased in OSCC samples. Single-cell RNA sequencing analysis emphasised the predominant expression of DRGs in cancer cells. INF2 and DSTN could serve as valuable biomarkers for the early detection and prognosis of OSCC, potentially impacting future therapeutic strategies. However, further research, including laboratory validation and clinical trials, is essential to explore the therapeutic targeting of INF2 and DSTN and their effects on the immune microenvironment in OSCC. INF2 and DSTN have been shown to be independent predictors of overall survival and progression-free survival in OSCC patients. Integrating tumour node metastasis staging with these DRG features could significantly improve the accuracy of prognosis prediction. This will help clinicians to more accurately assess the risk of recurrence and death in patients, and to guide more individualised plans for postoperative follow-up intensity and frequency.