Aim: Proteasome inhibitors have been found to suppress glioma cell proliferation and induce apoptosis, but the mechanisms are not fully elucidated. In this study we investigated the mechanisms underlying the apoptosis induced by the proteasome inhibitor MG-132 in glioma cells.
Methods: C6 glioma cells were used. MTT assay was used to analyze cell proliferation. Proteasome activity was assayed using Succinyl-LLVY-AMC, and intracellular ROS level was evaluated with the redox-sensitive dye DCFH-DA. Apoptosis was detected using fluorescence and transmission electron microscopy as well as flow cytometry. The expression of apoptosis-related proteins was investigated using Western blot analysis.
Results: MG-132 inhibited C6 glioma cell proliferation in a time-and dose-dependent manner (the IC(50) value at 24 h was 18.5 mu mol/L). MG-132 (18.5 mu mol/L) suppressed the proteasome activity by about 70% at 3 h. It induced apoptosis via down-regulation of antiapoptotic proteins Bcl-2 and XIAP, up-regulation of pro-apoptotic protein Bax and caspase-3, and production of cleaved C-terminal 85 kDa PARP). It also caused a more than 5-fold increase of reactive oxygen species. Tiron (1 mmol/L) effectively blocked oxidative stress induced by MG-132 (18.5 mu mol/L), attenuated proliferation inhibition and apoptosis in C6 glioma cells, and reversed the expression pattern of apoptosis-related proteins.
Conclusion: MG-132 induced apoptosis of C6 glioma cells via the oxidative stress.
[1]Jilin Univ, Dept Neurosurg, Bethune Hosp 1, Changchun 130021, Peoples R China.
[2]Jilin Univ, Tissue Engn Lab, Coll Pharmaceut Sci, Changchun 130021, Peoples R China.
[3]Nihon Univ, Sch Med, Div Canc Genet, Dept Adv Med Sci, Tokyo 1028251, Japan.
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