2--7--bis-(2-carboxyethyl)-5(6)-carboxyfluorescein-acetoxymethyl-ester and Bile-Duct-Neoplasms

In cholangiocarcinogenesis, chronic inflammation and oxidative stress play a key role. The Na(+)/H(+) exchanger (NHE) forms a potential link between control of intra- and pericellular pH and tumor development. Therefore, the effects of oxidant stress were determined by the use of tert-butyl hydroperoxide (t-BOOH) on Na(+)/H(+) exchange in a biliary epithelial cancer cell line (Mz-Cha-1). The cells were exposed to the hydroperoxide and the rate of recovery from acidosis was determined by the use of the pH-sensitive fluorochrome 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF/AM). t-BOOH reduced Na(+)/H(+) exchange activity in a dose-dependent manner. At 4 mM t-BOOH, Na(+)/H(+) exchange activity was virtually absent. This was accompanied by an increase in cytotoxicity (MTT assay). Glutathione repletion and intracellular Ca(++) chelation partially restored the Na(+)/H(+) exchange activity. Hydroperoxide seemed neither to alter the intracellular signal transduction pathways (cAMP and Ca(++) oscillations) nor the membrane distribution of the exchanger (immunostaining). Decrease in Na(+)/H(+) exchange activity in this model of oxidant stress may represent an early perturbation of membrane function, and the functional integrity of Na(+)/H(+) exchange could therefore be dependent on the glutathione redox system.

Topics: Acidosis; Bile Duct Neoplasms; Bile Ducts, Intrahepatic; Calcium; Cation Transport Proteins; Cell Line, Tumor; Chelating Agents; Cholangiocarcinoma; Cyclic AMP; Dose-Response Relationship, Drug; Fluoresceins; Glutathione; Humans; Oncogene Proteins, Fusion; Oxidative Stress; Proto-Oncogene Proteins c-myc; Signal Transduction; Sodium-Hydrogen Exchanger 1; Sodium-Hydrogen Exchangers; tert-Butylhydroperoxide