Abstract
Sodium arsenite (SA), a well defined carcinogen, will cause various cell damages but the exactly mechanism remains unknown. In this study, sodium arsenite decreased the activity of glutathione peroxidase and survival fraction in human fibroblasts (HF). Survival fraction of HF was 50 % while the cells were treated with 40 mM sodium arsenite for 4 h. Under the same SA, the antioxidant Gpx activity in HF was no difference comparing to control cells, while catalase activity was increased 1.1-fold of control.Immediately after cotreatment with 40 mM sodium arsenite and 2 mM 3-aminotriazole (3-AT, inhibitor of catalase), Gpx activity in HF was increased 30 % than those cells after 4 h treatment with 40 mM SA alone. This indicated that Gpx function was partially replaced by catalase. Cells in same SA treatment and time with or without 3-AT co-treatment following a postincubation in drug-free medium for 12 h had 30 % higher Gpx activity than those from cells without any treatment. However, HF after (a) SA treatment or (b) SA plus 3-AT treatment in similar protocol following a postincubation in drug-free medium for 24 h had only (a) 70 % or (b) 80 % Gpx activity of those from control cells, respectively. On the other hand, glutathione (GSH) content in cells responded to 4 h treatment with 40 mM SA and followed in drug-free medium for 12 h was significantly elevated form those of control cells. GSH content returned to normal level as control in similar SA-treated cells following a postincubation in drug-free medium for 24 h. These different Gpx activity and GSH content in SA-treated HF following 12 or 24 h postincubation may be resulted from the disturbance of regular cell cycle progression in cells after SA treatment, or from the production of reactive oxygen species in cells even after the removal of SA treatment. However, it required more experimental evidences to support.In the presence or absence of 2 mM 3-AT, gpx mRNA expression in HF after 40 mM SA for 4 h was increased about 40 % of those in control cells. Gpx mRNA in HF after 40 mM SA treatment for 4 h and followed a postincubation in drug-free medium for 12 or 24 h was only 70 % or 80 % of those in control cells.Treatment with 100 mM DL-buthionine-[S,R]-sulfoximine (BSO) for 4 h decrease glutathione (GSH) content in HF. Co-treatment cells with 100 mM BSO and 40 mM SA for 4 h would decrease SRB detected survival fraction to 25 % of those from untreated cells. Without BSO treatment, a 50 % survival fraction was resulted in cells after 40 mM SA treatment in the presence or absence of 2 mM 3-AT for 4 h. It was suggested that Gpx might play more important role than catalase to protect cells during SA treatment.Treatment of 40 mM SA in cells for 4 h apparently increased (about 2-fold of that in control sample) the nitrite content released in cell cultured medium, indicating the elevated level of NO. In addition, cells immediately after cotreatment with 3.2 mM NO inhibitor, Nw-nitro-L-arginine methyl ester (NAME), and 40 mM SA, the released nitrite in cultured medium was reduced to the level of control cells. Under the same treatment, Gpx from SA and NAME co-treated cells increased 20 % of those from control. These indicated that the change of Gpx activity in cells after SA treatment may be mediated from the SA-induced NO formation, causing reducing Gpx activity.