Expressional and Functional Characterization of Intracellular pH Regulators and Effects of Ethanol in Human Oral Epidermoid Carcinoma Cells.

Background/Aims: To functionally characterize intracellular pH (pH(i)) regulating mechanisms, such as Na+-H+ exchanger (NHE) and Na+-HCO3- co-transporter (NBC), and further examine effects of ethanol on the pH(i) regulating mechanism in human oral epidermoid carcinoma (OEC-M1) cells. Methods: OEC-M1 cells were a gift from Tri-Service General Hospital. Changes of pH(i) were detected by microspectrofluroimetry with a pH-sensitive fluorescent dye, BCECF. Isoforms of transporters were examined by Western blot technique. Results: i) the steady-state pH(i) value shifted from alkaline (7.35 similar to 7.49) to acidic (7.0 similar to 7.03) following acid/base impacts; ii) in HEPES-buffer system, pH(i) recovery following induced-acidification was totally blocked by either removing [Na](o)(+) or adding HOE 694 (a NHE1 specific inhibitor), which demonstrates existence of NHE1; iii) in HCO3-/CO2-buffer system, the pH(i) recovery following induced-acidification was entirely blocked by either removing [Na](o)(+) or adding HOE 694 plus DIDS (a NBC specific inhibitor), which suggests existence of Na+- and HCO3--dependent acid-extruder, i.e. NBC; iv) the isoforms of the two acid extruders were NHE1, NBCn1, NBCe1 and NDCBE; v) ethanol (10-1000 mM) showed a biphasic and concentration-dependent effect on resting pH(i) (i.e. increase then decrease) by changing the activity of NHE1 and NBC accordingly; vi) treatment with ethanol for 24 hr (>= 300 mM) significantly inhibited the expression of NHE1, NBCn1 and NDCBE, while up-regulated NBCe1. Conclusions: Ethanol affects pH(i) in a concentration-dependent manner by changing function and expression of NHE1 and NBC isoforms in OEC-M1 cells. (c) 2018 The Author(s) Published by S. Karger AG, Basel