TRPV 4‐Mediated Calcium Influx and Ciliary Activity in Human Native Airway Epithelial Cells

The transient receptor potential vanilloid 4 ( TRPV 4) is a calcium permeable ion channel expressed in airway epithelial cells. Based on studies of cell lines and animals, TRPV 4 has been suggested to play a role in the regulation of ciliary beat frequency ( CBF ). Whether the same is true for human ciliated epithelial cells is not known. Therefore, the aim was to examine the expression and function of TRPV 4 in human native nasal epithelial cells. Expression of TRPV 4 mRNA in nasal epithelial cells and in the cell lines BEAS 2 B and 16 HBE was confirmed by quantitative real‐time PCR . A marked apical TRPV 4 immunoreactivity was observed in nasal epithelial cells using immunocytochemistry. Responses to pharmacological modulation of TRPV 4 were assessed with calcium imaging and CBF measurements. The TRPV 4 agonist GSK 1016790 A produced concentration‐dependent calcium responses in TRPV 4‐expressing HEK 293, BEAS 2 B and 16 HBE cells, and the TRPV 4 antagonist HC 067047 caused a rightward shift of the GSK 1016790 A concentration‐response curves. Nasal epithelial cells responded to the TRPV 4 agonist GSK 1016790 A with increased intracellular calcium signals and increased CBF , followed by cessation of ciliary beating and cell death. These effects were prevented or inhibited by the TRPV 4 antagonist HC 067047, the TRP channel blocker ruthenium red or removal of extracellular calcium. We conclude that TRPV 4 is expressed in human primary nasal epithelial cells and modulates epithelial calcium levels and CBF . Thus, TRPV 4 may participate in mucociliary clearance and airway protection. However, exaggerated activation of TRPV 4 may result in epithelial cell death.