Peroxidase-mediated mucin cross-linking drives pathologic mucus gel formation in IL-13–stimulated airway epithelial cells
Maude A. Liegeois, Margaret Braunreuther, Annabelle R. Charbit, Wilfred W. Raymond, Monica Tang, Prescott G. Woodruff, Stephanie A. Christenson, Mario Castro, Serpil C. Erzurum, Elliot Israel, Nizar N. Jarjour, Bruce D. Levy, Wendy C. Moore, Sally E. Wenzel, Gerald G. Fuller, John V. Fahy
Maude A. Liegeois, Margaret Braunreuther, Annabelle R. Charbit, Wilfred W. Raymond, Monica Tang, Prescott G. Woodruff, Stephanie A. Christenson, Mario Castro, Serpil C. Erzurum, Elliot Israel, Nizar N. Jarjour, Bruce D. Levy, Wendy C. Moore, Sally E. Wenzel, Gerald G. Fuller, John V. Fahy
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Research Article Cell biology Pulmonology

Peroxidase-mediated mucin cross-linking drives pathologic mucus gel formation in IL-13–stimulated airway epithelial cells

Abstract

Mucus plugs occlude airways to obstruct airflow in asthma. Studies in patients and in mouse models show that mucus plugs occur in the context of type 2 inflammation, and studies in human airway epithelial cells (HAECs) show that IL-13–activated cells generate pathologic mucus independently of immune cells. To determine how HAECs autonomously generate pathologic mucus, we used a magnetic microwire rheometer to characterize the viscoelastic properties of mucus secreted under varying conditions. We found that normal HAEC mucus exhibited viscoelastic liquid behavior and that mucus secreted by IL-13–activated HAECs exhibited solid-like behavior caused by mucin cross-linking. In addition, IL-13–activated HAECs shows increased peroxidase activity in apical secretions, and an overlaid thiolated polymer (thiomer) solution shows an increase in solid behavior that was prevented by peroxidase inhibition. Furthermore, gene expression for thyroid peroxidase (TPO), but not lactoperoxidase (LPO), was increased in IL-13–activated HAECs and both TPO and LPO catalyze the formation of oxidant acids that cross-link thiomer solutions. Finally, gene expression for TPO in airway epithelial brushings was increased in patients with asthma with high airway mucus plug scores. Together, our results show that IL-13–activated HAECs autonomously generated pathologic mucus via peroxidase-mediated cross-linking of mucin polymers.

Authors

Maude A. Liegeois, Margaret Braunreuther, Annabelle R. Charbit, Wilfred W. Raymond, Monica Tang, Prescott G. Woodruff, Stephanie A. Christenson, Mario Castro, Serpil C. Erzurum, Elliot Israel, Nizar N. Jarjour, Bruce D. Levy, Wendy C. Moore, Sally E. Wenzel, Gerald G. Fuller, John V. Fahy

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Figure 1

Design of the magnetic microwire rheometer and its application to measure the biophysical properties of mucus gels secreted by human airway epithelial cells grown at air-liquid interface culture.

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Design of the magnetic microwire rheometer and its application to measur...
(A) Photograph and schematic of the magnetic microwire rheometer. (B) Illustration of the measurement of the distance between the microwire placed on top of the mucus gel and the surface of the epithelial cells. The wire position was identified using the bright-field channel of the microscope (white arrow), the cell layer was identified using the CellMask deep red at 647 nm, and the top of the mucus layer was estimated using fluorescent green particles imaged at 488 nm. Scale bar: 100 μm. (C) Plots of the relative intensity of the CellMask deep red signal (647nm), the bright-field signal, and the green particle signal (488 nm) to determine the position of the transwell insert membrane, the cell layer, the microwire, and the mucus layer.