Expression and localization of aquaporin 1, 2, 3, 4, and 5 in human nasal mucosa

Background: Aquaporins (AQPs) are water-specific membrane channel proteins that regulate water homeostasis for cells and organisms. The purpose of this study was to elucidate the role of AQPs 1, 2, 3, 4, and 5 in normal and diseased human nasal mucosa. Methods: Nasal polyps were obtained from eight patients with chronic rhinosinusitis (CRS). Inferior turbinate tissue was obtained from five patients with allergic rhinitis (AR) and from six patients with septal deviation (controls). Expression of AQP1-5 mRNA was examined using reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting, and tissue localization of AQP1-5 was studied by immunohistochemistry. Semiquantitative RT-PCR was used to investigate disease-specific changes in the expression in AQP1, -3, and -5 mRNA. Results: Expression of AQP1, -3, -4, and -5 mRNA and AQP1-5 protein were confirmed in normal human nasal mucosa. Immunohistochemical studies revealed that AQP1 was localized in fibroblasts (especially in the subepithelial area) and endothelial cells of blood vessels, AQP2 was localized in the cytoplasm of epithelial cells and acinar cells, AQP3 was localized in the basolateral sites of epithelial cells and acinar cells, AQP4 was localized in the basolateral sites of acinar cells, and AQP5 was localized in the apical sites of epithelial cells and acinar cells. Semiquantitative RT-PCR revealed that there were no significant differences in the mRNA expression of AQP1, AQP3, and AQP5 among control, AR, and CRS patients. Conclusion: AQP1, -2, -3, -4, and -5 were present in normal human nasal mucosa. mRNA expression of AQP1, -3, and -5 did not change among control, AR, and CRS patients. (Am J Rhinol Allergy 26, 167-171, 2012; doi: 10.2500/ajra.2012.26.3742)