Figure 1. Neuroprotective effect of selenium against glutamate cytotoxicity.

(A) Concentration-dependent effect of selenium on HT22 cell viability. Selenium was added in the form of sodium selenite (Na₂SeO₃) and cell viability was estimated 24 h after addition. The cells tolerated selenium well up to 200 nM, while selenium at 500 nM concentration reduced cell viability to about 50% of control. ***p<0.001 by one-way ANOVA analysis followed by post hoc Scheffe’s test. (B) A set of representative microgram of HT22 cells exposed to glutamate (4 mM) with or without selenium (100 nM) for 24 h. Selenium preserved cellular morphologies following glutamate exposure. (C) Summarized bar graph showing the effect of selenium on glutamate-induced cell death up to 48 h of glutamate exposure (4 mM). Selenium (100 nM) was added simultaneously with glutamate and the cell viability was measured after 18, 24 26 and 48 h of glutamate exposure using MTT assay. Selenium significantly improved cell survival following glutamate exposure. (D) Bar graph shows selenium post-treatment of HT22 cells at 1, 3 and 8 h after glutamate exposure. Protective effect of selenium post-treatment was assessed after 24 h of glutamate exposure. Selenium was able to protect cells from glutamate-induced cell death when applied even 8 h after glutamate exposure. Data were collected from 3 or more independent experiments conducted in triplicate. Values are means±SD and analyzed by two-way ANOVA test followed by post hoc Bonferroni’s test. ***P<0.001 vs. control and ###p<0.001 vs. non-selenium, glutamate exposed cells. Groups are control (Cont), glutamate exposed (Glu), selenium added (Se+) and non-selenium added (Se-).