calyculin-a and Liver-Neoplasms

Topics: Animals; Antifungal Agents; Carcinogens; Ethers, Cyclic; Liver Neoplasms; Marine Toxins; Mice; Molecular Structure; Okadaic Acid; Oxazoles; Peptides, Cyclic; Pyrans; Rats; Skin Neoplasms; Spiro Compounds; Stomach Neoplasms; Structure-Activity Relationship

K(+)-Cl(-)-cotransport (KCC) is ubiquitously present in all cells, and plays an essential role in ion and volume regulation. In this study we investigated the role of reactive oxygen species (ROS) in regulation of KCC in HepG2 human hepatoblastoma cells. N-ethylmaleimide (NEM), a KCC activator, induced Cl(-)-dependent K+ efflux, which was markedly prevented by KCC inhibitors (calyculin-A, genistein and BaCl2), indicating that KCC is activated by NEM in the HepG2 cells. Treatment with NEM also induced a sustained increase in the level of intracellular ROS assessed by 2',7'-dichlorofluorescein fluorescence. Antioxidants, N-acetyl cysteine or N,N'-diphenyl-p-phenylenediamine significantly inhibited both ROS generation and KCC activation induced by NEM. The NEM-induced ROS production was significantly suppressed by inhibitors of NADPH oxidase (diphenylene iodonium, apocynin and neopterine). These inhibitors also significantly inhibited the NEM-induced KCC activation. Taken together, these results suggest that ROS generated by NADPH oxidase may mediate the NEM-induced activation of KCC in human hepatoma cells.

Topics: Carcinoma, Hepatocellular; Chlorides; Enzyme Inhibitors; Ethylmaleimide; Genistein; Humans; K Cl- Cotransporters; Liver Neoplasms; Marine Toxins; NADPH Oxidases; Oxazoles; Potassium; Reactive Oxygen Species; Symporters; Tumor Cells, Cultured