Abnormalities in MUC5AC and MUC5B Protein in Airway Mucus in Asthma

摘要

Gene expression for MUC5AC is increased in airway epithelial cells in asthma, and MUC5B expression is decreased (1, 2), but it is uncertain how this abnormal gene expression for gel-forming mucins contributes to mechanisms of formation of pathologic airway mucus gels in asthma exacerbation and stable asthma. Recent studies in transgenic mice show different functions for MUC5AC and MUC5B in the lung. Whereas MUC5B has physiologic functions in the mucus gel that ensure normal mucus clearance (3), MUC5AC has pathologic roles in mechanisms of allergen-induced airway hyperresponsiveness, mucous metaplasia, and airway mucus plugging (4). Changes in the relative proportions of MUC5AC and MUC5B could also affect eosinophil survival in the airway mucus gel because glycoepitopes in the MUC5B glycan coat interact with Siglec-8 on eosinophils to induce apoptosis (5). Thus, a relative deficiency of MUC5B in airway mucus could create an environment that promotes eosinophil survival.