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Molecular and functional expression of anion exchangers in cultured normal human nasal epithelial cells
Author(s) -
Shin J.H.,
Son E. J.,
Lee H. S.,
Kim S. J.,
Kim K.,
Choi J. Y.,
Lee M. G.,
Yoon J.H.
Publication year - 2007
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2007.01731.x
Subject(s) - dids , forskolin , western blot , chemistry , microbiology and biotechnology , intracellular , gene expression , immunocytochemistry , extracellular , messenger rna , apical membrane , purinergic receptor , epithelial polarity , biology , receptor , endocrinology , biochemistry , cell , membrane , gene
Abstract Aims: Anions have an important role in the regulation of airway surface liquid (ASL) volume, viscosity and pH. However, functional localization and regulation of anion exchangers (AEs) have not been clearly described. The aim of this study was to investigate the regulation of AE mRNA expression level in accordance with mucociliary differentiation and the functional expression of AEs cultured normal human nasal epithelial (NHNE) cells. Methods: Nasal mucosal specimens from three patients are obtained and serially cultured cells are subjected to morphological examinations, RT‐PCR, Western blot analysis and immunocytochemistry. AE activity is assessed by pHi measurements. Results: Expression of ciliated cells on the apical membrane and expression of MUC5AC, a marker of mucous differentiation, increased with time. AE2 and SLC26A4 mRNA expression decreased as mucociliary differentiation progressed, and AE4, SLC26A7 and SLC26A8 mRNA expression increased on the 14th and 28th day after confluence. Accordingly, AE4 protein expression also progressively increased. AE activity in 100 m m K + buffer solutions was nearly twofold higher than that in 5 m m K + buffer solutions. Moreover, only luminal AE activity increased about fourfold over the control in the presence of 5 μ m forskolin. In the presence of 100 μ m adenosine‐5′‐triphosphate (ATP) which evokes intracellular calcium signalling through activation of purinergic receptors, only luminal AE activity was again significantly increased. On the other hand, 500 μ m 4,4′‐diisothiocyanostilbene‐2,2′‐disulfonic acid (DIDS), an inhibitor of most SLC4 and SLC26AE isoforms, nearly abolished AE activity in both luminal and basolateral membranes. We found that AE activity was affected by intracellular cAMP and calcium signalling in the luminal membrane and was DIDS‐sensitive in both membranes of cultured NHNE cells. Conclusion: Our findings through molecular and functional studies using cultured NHNE cells suggest that AEs may have an important role in the regulation of ASL.