Regulatory effect of dexamethasone on aquaporin 5 in human middle ear epithelium

Abstract

PurposeTo evaluate the effect of dexamethasone on the expression of aquaporin 5 (AQP5) in cultured human middle ear epithelium cells in vitro, which is related closely with water transports in the middle ear cavityMethodsWith dexamethasone, the expression of AQP5 was assessed by reverse transcriptase and real time PCR. We evaluated it''s protein level using western blot and immunofluorscence methods. Functionally, the absorption of water from the surface treated with texas red was evaluated through special own confocal microscopy methods.ResultsTranscripts for AQP5 were expressed consistently in cultured cells from 3 to 5 days after the treatment of dexamethasone (a 16 fold increase at day 5 compared with day 0). Similar patterns of increase in proteins were demonstrated on western blot (a 2.5 fold increase at day 5 than day 0), too. We visualized the expressions of AQP5 in the surface of dexamethasone treated cells with immunofluorescence, which was not shown in the control cultured cells. Absorption of fluid occurred on the surface of the epithelium cells functionally in the presence of dexamethasone. ConclusionsWith dexamethsone, the expressions of AQP5 in the middle ear epithelium were increased. The role of AQP5 may be related to the absorption of water from the middle ear cavity to subepithelial spaces in otitis media. This is the first study to suggest the pathophysiology and the potential therapeutic effect of dexamethasone on the AQP5 in otitis media.