Reduced sialyl-Lewisx on salivary MUC7 from patients with burning mouth syndrome†
We analysed and compared MUC7 O-glycosylation and inflammatory biomarkers in saliva from female patients with burning mouth syndrome (BMS) and gender/age-matched controls. Oligosaccharides from salivary MUC7 from BMS and controls were released. Inflammatory mediators were measured by multiplex proximity extension assay. Presence of sialyl-Lewisx (Si-Lex) epitope on MUC7 was confirmed using Western blot. MUC7 O-glycans and measured inflammatory biomarkers were found to be similar between BMS and controls. However, oligosaccharides sialyl-Lewisx (Si-Lex) was found to be reduced in samples from BMS patients. Positive correlation (combined patients and controls) was found between levels of C–C motif chemokine 19 (CCL-19) and the amount of core-2 oligosaccharides on MUC7 as well as fractalkine (CX3CL1) and level of sialylation. Patients with BMS were shown to represent a heterogeneous group in terms of inflammatory biomarkers. This indicates that BMS patients could be further stratified on the basis of low-level inflammation. The results furthermore indicate that reduced sialylation of MUC7, particularly Si-Lex, may be an important feature in patients with BMS. However, the functional aspects and potential involvement in immune regulation of Si-Lex remains unclear. Our data suggests a chemokine driven alteration of MUC7 glycosylation.