Down-modulation of Bis senstizes cell depth in C6 glioma cells induced by the oxygen-glucose deprivation through inhibiting NF-kappa B activity

Abstract

[한글]

[영문]Bcl-2 interacting cell death suppressor (Bis) has been implicated in anti-stress and anti-apoptotic pathways. Previous study showed a significant induction of Bis in the reactive astrocytes of rat hippocampus after transient forebrain ischemia. To investigate the significance of its induction in the ischemic injury, the expression of Bis was reduced by si-RNA strategy in C6 glioma cells, which were then exposed to oxygen-glucose deprivation (OGD). Bis knock-down resulted in a decrease in viability after OGD accompanied by ROS accumulation. Among the cellular antioxidants, superoxide dismutase (SOD) activity was significantly perturbed in bis si-RNA treated cells (bis-kd C6). A Subsequent analysis of in-gel reduction ability and quantification of mRNA revealed that induction of SOD1 in response to OGD was impaired at transcriptional levels as a result of bis knock-down. As a candidate for the transcription factor for sod1 gene, the activity of NF-?B was determined using a DNA binding assay and the nuclear translocation of p65 subunit, showing that activation of NF-?B was attenuated in bis si-RNA transfected C6 cells. The treatment of SOD mimetic resulted in the recovery of the viability of C6 cells upon OGD, which is more prominent in bis si-RNA treated C6 cells. Furthermore, the inhibition of NF-?B suppressed the induction of SOD1 transcription and aggravated the cell death, which was potentiated with reduction of Bis, after OGD. The constitutive levels of p65 were decreased by Bis reduction while Bis overexpression increased p65 protein levels, but not mRNA levels. These results suggest that one of the physiological function of Bis is the regulation of p65 protein stability and thereby NF-?B activity which affects the induction of SOD1 after oxidative stress and subsequent cell viability. The critical mechanisms by which Bis control the p65 stability remain to be determined.