Muc5b is required for airway defence.

Area of Science:

• Respiratory biology
• Immunology
• Mucinology

Background:

• Airway surfaces are constantly exposed to particulates and pathogens.
• Mucociliary clearance (MCC) relies on a mucus barrier to trap and eliminate these threats.
• Mucin glycoproteins, MUC5AC and MUC5B, are key components of airway mucus, and their genetic variants are linked to lung diseases.

Purpose of the Study:

• To investigate the specific roles of MUC5AC and MUC5B in MCC.
• To determine the effects of MUC5B inhibition on airway health and immune function.
• To clarify the contribution of mucins to respiratory diseases like asthma and COPD.

Main Methods:

• Utilized mouse models to study the function of Muc5b and Muc5ac.
• Assessed MCC, infection control, and immune homeostasis in wild-type and gene-deficient mice.
• Analyzed macrophage function and inflammatory responses in Muc5b-deficient and overexpressing mice.

Main Results:

• Mouse Muc5b, but not Muc5ac, is crucial for MCC, airway infection control, and lung immune homeostasis.
• Muc5b deficiency led to mucus accumulation, chronic bacterial infections (including Staphylococcus aureus), and unresolved inflammation.
• Impaired macrophage phagocytosis and reduced IL-23 production were observed in Muc5b-deficient mice, while MUC5B overexpression improved macrophage function.

Conclusions:

• Muc5b plays a critical, specific role in mucociliary clearance and host defense against respiratory infections.
• Muc5ac is dispensable for these functions, challenging existing dogma.
• Findings provide a basis for targeted therapies aimed at controlling mucin secretion and restoring MCC in respiratory diseases.