The Investigation Of The Proliferative Inhibition And Apoptosis Of K562 Cells Induced By Sodium Selenite

Objective: To investigate the effects of sodium selenite on the cell proliferation and apoptosis of K562 cells and to elucidate its molecular mechanisms.Methods: 1. MTT assay was employed to evaluate the effects of sodium selenite on the proliferative inhibition of K562 cells after they had been treated with various concentrations of sodium selenite for different time. 2. AnnexinⅤ-FITC/PI staining, Electronmicroscope, TUNEL were performed to confirm the apoptosis of K562 cells incubated with sodium selenite for different time. 3. Cell cycle of K562 cells treated with sodium selenite for 24h was assayed by flow cytometry. 4. Colorimetric method were used to measure the activities of caspase-3,-8,-9 of K562 cells incubated with sodium selenite for 48h. 5. RT-PCR was employed to analyze the mRNA expression levels of Bcl-2, Bax, p21 in K562 cells after having been treated with sodium selenite for 48h. 6. Flow cytometry were used to measure the free [Ca2+] of K562 cells incubated with sodium selenite for 6h,12h,24h,36h and 48h. Results: 1. Sodium selenite could inhibit proliferation of K562 cells in a time dependent manner. 2. K562 cells could be induced to undergo apoptosis after 20μmol/L sodium selenite treatment for 48h,the apoptotic rate was (25.93±0.22)%. Compared with the control group, it was significantly higher(P<0.01). A typical apoptotic morphological change and TUNEL cells were observed after K562 cells had been treated with 20μmol/L sodium selenite for 48h. 3. The percentage of S phase cells increased after K562 cells had been treated with sodium selenite for 24h, arrestting cell cycle in S phase. 4. The caspase-3,-8,-9 activities of K562 cells which had been treated with sodium selenite for 48h elevated remarkably. Compared with the control group, the caspase-3,-8,-9 activities of 20μmol/L sodium selenite treated groups were markedly higher(P<0.01). 5. RT-PCR results showed that sodium selenite could decrease the mRNA expression levels of Bcl-2 significantly and increase the mRNA expression levels of Bax and p21 obviously. 6. Flow cytometry results indicated that the free [Ca2+] of K562 cells incubated with sodium selenite for 6h,12h,24h,36h and 48h increased significantly compared with control group(P<0.01).Conclusions: 1. Sodium selenite can inhibit proliferation of K562 cells in a time dependent manner by arresting cell cycle in S phase. 2. The downregulating of mRNA expression level of Bcl-2 and upregulating of mRNA expression level of Bax and p21 might be related to apoptosis of K562 induced by sodium selenite. 3. Sodium selenite can induce K562 cells to undergo apoptosis, and the underlying mechanism might be related to upregulation of caspase-9 activity which subsequently transforms caspase-3 into its active form, and the free [Ca2+], caspase-8 activeity of K562 cells were increased, all of the above indicate the mechanism of apoptosis might be related to chondriosome, death recepter and endoplasmic reticulum pathway.