Chronic intermittent mechanical stress increases MUC5AC protein expression.

Area of Science:

• Pulmonary Medicine
• Cell Biology
• Biophysics

Background:

• Increased mucin secretory cells characterize asthma and chronic airway diseases.
• Airway constriction involves mechanical stresses that activate epidermal growth factor receptor (EGFR), influencing mucin expression.

Purpose of the Study:

• To determine if chronic, intermittent, short-duration compressive stress increases MUC5AC-positive cells and mucin levels in human bronchial epithelial cells.
• To investigate the role of EGFR and transforming growth factor-beta2 (TGF-β2) in mediating the response to mechanical stress.

Main Methods:

• Human bronchial epithelial cells cultured at an air-liquid interface were subjected to daily compressive stress (30 cm H2O) for 1 hour over 14 days.
• MUC5AC protein expression and cell abundance were assessed using immunohistochemistry, Western blotting, and slot blotting.
• Cells were treated with an EGFR kinase inhibitor (AG1478) and/or a TGF-β2-neutralizing antibody to evaluate pathway involvement.

Main Results:

• Daily compressive stress significantly increased the percentage of MUC5AC-positive cells and intracellular MUC5AC protein levels.
• The effect was dose-dependent, with significant changes observed after as little as 10 minutes of daily stress.
• EGFR inhibition partially attenuated the response, while combined EGFR inhibition and TGF-β2 neutralization, or TGF-β2 neutralization alone, completely blocked the effect.

Conclusions:

• Intermittent mechanical stress, mimicking bronchoconstriction, is sufficient to increase goblet cell numbers and MUC5AC expression in vitro.
• The mechanical environment in asthma may promote a shift towards mucin secretory cell populations.
• EGFR and TGF-β2 signaling pathways are critical mediators of mechanical stress-induced mucin production in airway epithelium.