Induction of aquaporin 3 by corticosteroid in a human airway epithelial cell line.

Although aquaporin 3 (AQP3) is expressed in many tissues in the kidney, gastrointestinal tract, lung, and other organs, its physiological significance in the body still remains to be clarified. To determine whether AQP3 expression is regulated by dexamethasone in human airway epithelium, we studied mRNA expression, protein expression, and water permeability of the cell membrane in a human airway epithelial cell line (A549 cells). Expression of AQP3 mRNA and protein was studied by Northern blot analysis and immunoblot analysis, and osmotic water permeability (Pf) was measured by a stopped-flow light-scattering method. Expression of AQP3 mRNA and protein was detectable in A549 cells and was stimulated by dexamethasone. Pf in A549 cells after incubation with dexamethasone was approximately 2.5-fold greater than that without dexamethasone. Moreover, this dexamethasone-induced increase in Pf was inhibited after treatment with HgCl2. In conclusion, the present study shows that A549 cells express AQP3 and that dexamethasone upregulates the expression of AQP3 and increases the water permeability of the cell membrane. Dexamethasone-regulated AQP3 expression might be important in certain forms of pulmonary diseases accompanied by airway hypersecretion that are treated by corticosteroid administration.