The multiphasic TNF-α-induced compromise of Calu-3 airway epithelial barrier function

Area of Science:

• Cell Biology
• Immunology
• Respiratory Medicine

Background:

• Airway epithelial barrier integrity is crucial for respiratory health.
• Proinflammatory cytokines, like TNF-α, disrupt this barrier, contributing to various lung diseases.
• Understanding TNF-α's precise effects on airway epithelium is vital for developing targeted therapies.

Purpose of the Study:

• To investigate the impact of TNF-α on the human airway epithelial Calu-3 model.
• To characterize the temporal dynamics of TNF-α-induced barrier dysfunction.
• To identify the molecular mechanisms and signaling pathways involved in TNF-α mediated barrier compromise.

Main Methods:

• Utilized Transepithelial Electrical Resistance (TER) to assess barrier function.
• Measured paracellular permeability using radiolabeled probes (14C-D-mannitol, 14C-inulin).
• Analyzed tight junctional (TJ) protein expression via Western immunoblotting and investigated the role of the ERK signaling pathway.

Main Results:

• TNF-α induced a biphasic disruption of the airway epithelial barrier, with initial leak at 2-4 hours and a sustained leak from 48 hours onwards.
• Significant alterations in TJ proteins, including increased claudins and decreased occludin, were observed at 72 hours.
• Both early and late TNF-α-induced leaks were mediated by the ERK signaling pathway.

Conclusions:

• TNF-α elicits a multiphasic transepithelial leak in airway epithelial cells.
• The ERK pathway and alterations in tight junction proteins are key mediators of TNF-α's effects.
• Micronutrients retinoic acid and calcitriol demonstrated efficacy in reducing TNF-α-induced barrier compromise, offering potential therapeutic avenues for airway diseases, including COVID-19.