Stimulation of aquaporin-5 and transepithelial water permeability in human airway epithelium by hyperosmotic stress
- 174 Downloads
Osmotic water permeability (Pf) was measured in spheroid-shaped human nasal airway epithelial explants pre-exposed to increasing levels of hyperosmotic stress. The fluid-filled spheroids, derived from nasal polyps, were lined by a single cell layer with the ciliated apical cell membrane facing the outside. The Pf was determined from diameter changes of the spheroids in response to changes in bathing medium osmolarity forth and back between 300 and 225 mOsm·l−1. Continuous diameter measurements also allowed determination of spontaneous fluid absorption. Hyperosmotic pretreatment (increase from 300 up to 600 mOsm·l−1) caused a time- and osmolarity-dependent increase (up to ∼1.5 times) in epithelial Pf which was of similar magnitude in cystic fibrosis (CF) and non-CF spheroids. The effect saturated at ∼450 mOsm·l−1 and at ∼24 h. Expression of aquaporin-5 (AQP5), studied by immunofluorescence and confocal microscopy, showed an increase in parallel with the increase in Pf following hyperosmotic stress. The AQP5 was localized both in cytoplasmic vesicles and in apical cell membranes. Spontaneous fluid absorption rates were equal in CF and non-CF spheroids and were not significantly influenced by hyperosmotic stress. The results suggest that hyperosmotic stress is an important activator of AQP-5 in human airway epithelium, leading to significantly increased transepithelial water permeability.
KeywordsHuman airway epithelia Epithelial spheroids Cystic fibrosis Water permeability Fluid absorption Aquaporin-5 Hyperosmotic stress
- 6.Castillon N, Hinnrasky J, Zahm JM, Kaplan H, Bonnet N, Corlieu P, Klossek JM, Taouil K, Avril-Delplanque A, Peault B, Puchelle E (2002) Polarized expression of cystic fibrosis transmembrane conductance regulator and associated epithelial proteins during the regeneration of human airway surface epithelium in three-dimensional culture. Lab Invest 82:989–998PubMedGoogle Scholar
- 15.Gresz V, Kwon T-H, Gong H, Agre P, Steward MC, King L, Nielsen S (2004) Immunolocalization of AQP-5 in rat parotid and submandibular salivary glands after stimulation or inhibition of secretion in vivo. Am J Physiol 287:G151–G161Google Scholar
- 17.Hasler U, Vinciguerra M, Vandewalle A, Martin PY, Feraille E (2005) Dual effects of hypertonicity on aquaporin-2 expression in cultured renal collecting duct principal cells. J Am Soc NephrolGoogle Scholar