title: Interferon-gamma suppresses Na+ -H+ exchanger in cultured human endolymphatic sac epithelial cells.
abstract: Adequate regulation of endolymphatic pH is essential for maintaining inner ear function. The Na(+)-H(+) exchanger (NHE) is a major determinant of intracellular pH (pH(i)), and facilitates Na(+) and fluid absorption in various epithelia. We determined the functional and molecular expression of NHEs in cultured human endolymphatic sac (ES) epithelial cells and examined the effect of IFN-gamma on NHE function. Serial cultures of human ES epithelial cells were generated from tissue samples. The molecular expression of NHE1, -2, and -3 isoforms was determined by real-time RT-PCR. The functional activity of NHE isoforms was measured microfluorometrically using a pH-sensitive fluorescent dye, 2',7'-bis(carbonylethyl)-5(6)-carboxyfluorescein (BCECF), and a NHE-inhibitor, 3-methylsulfonyl-4-piperidinobenzoyl guanidine methanesulfonate (HOE694). NHE1, -2, and -3 mRNAs were expressed in human ES epithelial cells. Functional activity of NHE1 and -2 was confirmed in the luminal membrane of ES epithelial cells by sequentially suppressing Na(+)-dependent pH(i) recovery from intracellular acidification using different concentrations of HOE694. Treatment with IFN-gamma (50 nM for 24 h) suppressed mRNA expression of NHE1 and -2. IFN-gamma also suppressed functional activity of both NHE1 and -2 in the luminal membrane of ES epithelial cells. This study shows that NHEs are expressed in cultured human ES epithelial cells and that treatment with IFN-gamma suppresses the expression and functional activity of NHE1 and -2.
authors.affiliation: Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Eun Jin
authors.initials: EJ
authors.lastname: Son
authors.forename: In Seok
authors.initials: IS
authors.lastname: Moon
authors.forename: Sung Huhn
authors.initials: SH
authors.lastname: Kim
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Choi
mesh_terms: D000818:Animals; D002021:Buffers; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D004712:Endolymphatic Sac / Q000166:cytology*; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D005786:Gene Expression Regulation / Q000187:drug effects; D006531:HEPES; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007371:Interferon-gamma / Q000494:pharmacology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D000074082:Sodium-Hydrogen Exchanger 1; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D012996:Solutions
chemical_list: D002021:Buffers; D027682:Cation Transport Proteins; D020033:Protein Isoforms; C490998:SLC9A1 protein, human; C081517:SLC9A2 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D012996:Solutions; D007371:Interferon-gamma; D012964:Sodium; D006531:HEPES