Fungi in Mucoobstructive Airway Diseases.

Area of Science:

• Allergy and immunology
• Pulmonary medicine
• Microbiology

Background:

• Allergic airway diseases, including asthma and chronic rhinosinusitis, cause significant morbidity due to dyspnea and potential fatality.
• Airway hyperresponsiveness and mucus overproduction are key features of asthma, mediated by interleukin-4 (IL-4), interleukin-13 (IL-13), and signal transducer and activator of transcription 6 (STAT6).

Purpose of the Study:

• To review the molecular pathways involved in airway obstruction in allergic airway diseases.
• To investigate the role of a second major signaling pathway in mucus production involving fibrinogen and Toll-like receptor 4 (TLR4).
• To explore the potential link between airway fungal infections and severe allergic airway disease.

Main Methods:

• Analysis of human sputum and paranasal sinus fluid.
• Review of existing research on molecular pathways in airway obstruction.

Main Results:

• A second major pathway for mucus production involves proteinase-cleaved fibrinogen signaling through TLR4.
• Analysis revealed a unique airway fungal infection, termed airway mycosis, pathogenically linked to most cases of severe allergic airway disease.
• Fungal and endogenous proteinases mediate fibrinogenolysis, crucial for TLR4 signaling and fibrin deposition, contributing to airway obstruction alongside mucus.

Conclusions:

• Airway mycosis is a significant, often overlooked, factor in severe allergic airway diseases.
• The fibrinogen/TLR4 pathway, influenced by fungal proteinases, plays a critical role in airway obstruction.
• Understanding these pathways may lead to novel therapeutic strategies for allergic airway diseases.