Functional expression of the hypo‐osmosensitive channels TRPV4 and TRPM3 in mouse airway epithelium

Abstract

TRPV4 and TRPM3, members of the transient receptor potential channel family, are membrane proteins that mediate Ca2+ entry in cells upon application of hypo‐osmotic solutions. This study aimed at investigating the expression and functionality of these osmosensitive channels in the epithelium of mouse intrapulmonary airways by combining confocal Ca2+ imaging and multilabel immunohistochemistry.Immunostaining revealed that TRPV4 and TRPM3 are colocalized on both ciliated cells and Clara cells, the most common cell types in the mouse airway epithelium, but also that the neuroendocrine cells, grouped as neuroepithelial bodies, are negative. Confocal live cell imaging of precision cut vibratome slices of mouse lungs loaded with Fluo‐4 showed that short term (30s) perfusion with a hypo‐osmotic solution (200 mOsm) results in a clear and reversible rise in intracellular Ca2+ in all Clara and ciliated cells.Both TRPV4 and TRPM3 channels may allow the cells to react to changes in extracellular osmolarity and therefore potentially play a central role in airway epithelial homeostasis by modulating epithelial water transport. The presented approach opens interesting new perspectives for unraveling functional aspects of diverse cell and tissue types in control lungs and disease models.Support: IWT fellowship SB/81162 (R.L); FWO grant G.0081.08 (D.A.); UA grants GOA BOF 2007 (D.A.) and KP BOF 2006 (I.B.)