Both calcium and ROS as common signals mediate Na2SeO3-induced apoptosis in SW480 human colonic carcinoma cells

Recent studies have shown that reactive oxygen species (ROS) play a crucial role in Se-induced cell apoptosis. A number of studies have demonstrated that perturbed cellular calcium homeostasis has been implicated in apoptosis. The main objective of this study was to evaluate the role of Ca2+ in NaSeO3-induced apoptosis and the relationship between Ca2+ and ROS in human colonic carcinoma cells SW480. When SW480 cells were exposed to 25-100 muM Na2SeO3, both cell apoptosis and growth inhibition were observed by flow cytometric analysis and 3-[4.5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Na2SeO3 was able to induce increase of [Ca2+], and ROS production and disrupt mitochondrial membrane potential (DeltaPsim) in SW480 cells monitored by using a confocal laser scanning microscope. Ca2+ channel inhibitor CoCl2 and an intracellular Ca2+ chelator o-phtalaidehyde, 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetra-acetic acid acetoxymethyl ester (BAPTA) completely inhibited [Ca2+], increase, but catalase had no effect on Na2SeO3-induced increase of [Ca2+](i). BAPTA-AM, CoCl2, and mitochondrial Ca2+ uptake inhibitor ruthenium red blocked DeltaPsim dissipation. The increase of ROS was also suppressed by CoCl2 BAPTA, ruthenium red, N-acetylcysteine and catalase, respectively. The mitochondrial uncoupler carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) completely inhibited Na2SeO3-induced ROS increase. This showed that ROS increase is due to mitochondrial Ca2+ overload. The Na2SeO3-induced apoptosis of SW480 cells was also inhibited by CoCl2 BAPTA, ruthenium red, N-acetylcysteine, and catalase, respectively. The results mentioned above imply that both calcium and Ca2+-dependent ROS as a signal molecule mediate apoptosis induced by Na2SeO3 in SW480 cells. (C) 2003 Published by Elsevier Inc.