Methylselenol Formed by Spontaneous Methylation of Selenide Is a Superior Selenium Substrate to the Thioredoxin and Glutaredoxin Systems
Figure 6
A–H. Cytotoxicity of selenium compounds in the presence of SAM.
Cell viability was measured by XTT after 24 h incubation with selenium treatment, combined with SAM, DTNB and MSG. Cells were pretreated with MSG (60 mM) followed by treatment with selenium compounds +/− SAM (500 µM) A) Selenite (5 µM), B) GS-Se-SG (5 µM), C) Seleno-DL-cystine (100 µM). D) SAM toxicity was determined by clonogenic assay. Cells were treated for 8 h with 500 µM SAM, washed and re-seeded, in triplicates. After 9 days, clones were stained and counted. E) Viability over time (0–48 h) after pretreatment with MSG followed by addition of selenite +/− SAM. F) Selenium accumulation in ng/mg protein after 24 h treatment (same concentration of all compounds as in E) measured by GF-AAS analysis. G) Comparison of toxicity between selenite (5 µM) +/− SAM and MSA (5 µM) after 24 h of treatment. H) Representative morphological changes associated with the treatments of selenite (5 µM), selenite +/− SAM and MSA (5 µM) for 20 h. In D, Student t-test was performed to verify the statistical significance between two groups. One-way ANOVA (99.9% confidence interval) followed by Tukey-Kramer multiple comparison test was performed to determine statistical significance in A–C, F (**p<0.01 and ***p<0.001 compared to controls, °p<0.01 and °°p<0.001 compared to selenium treated cells). In E, two-way ANOVA (95% confidence interval) was performed, followed by Bonferroni multiple comparison test. (*p<0.05 and ***p<0.001, compared to control at selected time point). In Fig. G, one-way ANOVA was used, followed by Student-Newman-Keuls multiple comparison test (95% confidence interval, *p<0.05 compared to selenite treatment).