Abstract

Background: The mucous barrier of the oropharynx and nasopharynx is a crucial component of the defense of the upper respiratory tract, with its functionality largely determined by the composition of mucins. The gel-forming MUC5AC and the membrane-bound MUC1 play key roles in pathogen entrapment, maintenance of mucociliary clearance, and regulation of epithelial interactions with the microbiota. An imbalance in their ratio may contribute to the development and persistence of inflammatory processes; however, the role of these mucins in the oropharynx and nasopharynx remains insufficiently studied.

Objective: To assess the levels of MUC1 and MUC5AC in swabs from the oropharynx and nasopharynx and to analyze their relationship with clinical symptoms, frequency of recurrences, dietary factors, and probiotic intake.

Materials and Methods: The study included 184 patients stratified by the presence of chronic inflammatory changes, regularity of probiotic intake, and adherence to a diet enriched with fiber and fermented products. Swabs were analyzed using Western blot to determine MUC1 and MUC5AC levels in arbitrary units of optical density. Clinical manifestations were evaluated using standardized scales for symptoms, recurrences, dietary adherence, and probiotic status. Statistical analysis employed the t-test, Mann-Whitney U-test, and Spearman’s correlation.

Results: Patients with chronic inflammation exhibited higher symptom scores, recurrence rates, and inflammation indices compared to controls (p < 0.001). They showed elevated MUC5AC (0.79 ± 0.18 a.u.) and reduced MUC1 (0.52 ± 0.17 a.u.) compared to healthy individuals (0.47 ± 0.16 a.u. and 0.64 ± 0.15 a.u., respectively). Probiotic intake and a diet enriched with fiber and fermented products were associated with decreased MUC5AC and increased MUC1. MUC5AC positively correlated with symptom severity (r = 0.58) and recurrences (r = 0.52), whereas MUC1 showed negative correlation with symptoms (r = –0.41) and positive correlations with diet (r = 0.38) and probiotics (r = 0.46).

Conclusions: Chronic inflammation of the oropharynx is accompanied by mucin imbalance – elevated MUC5AC and reduced MUC1. Diet and probiotics partially normalize these changes, making MUC1 and MUC5AC promising biomarkers of the mucosal barrier status in the upper respiratory tract.

Keywords: MUC1; MUC5AC; oropharynx; nasopharynx; mucous barrier; probiotics; diet; chronic inflammation; mucin; upper respiratory tract.