Figure 9

Selective down-regulation of IRF8 by siRNA protects OPCs from IFNγ-induced OPC apoptosis. A, OPCs were transfected by electroporation with IRF8 siRNA and negative conrol siRNA. Cells were cultured with GM for 3 h after transfection, and then treated with GM alone (control) or GM plus IFNγ (100 ng/ml). At 24 or 48 h after treatments, cells were subjected to western blotting. MTT assay, or stained with TMRE and DAPI followed by the flow cytometric analysis as in Figure. 7. B, Protein levels of IRF8 in the OPCs transfected with negative control siRNA (Neg siRNA) or IRF8 siRNA were examined by immunoblotting at 24 h after addition of IFNγ (+IFNγ, 100 ng/ml). The untransfected OPCs (No siRNA) treated with IFNγ (+IFNγ, 100 ng/ml) or medium alone (C) for 24 h were used as positive and negative control for IRF1 expression, respectively. B, Viability of the OPCs transfected with negative control siRNA (control siRNA, open bar) or IRF8 siRNA (closed bar) was measured by MTT assay at 48 h after treatment with GM alone (control) or GM plus IFNγ (100 ng/ml). C, Number of preapoptotic (TMRE^-/DAPI^-) OPCs in the cultures subjected to electroporation with negative control siRNA (control siRNA, open bar) or IRF8 siRNA (closed bar) at 24 h after treatment with IFNγ (100 ng/ml). ** Indicates p < 0.01 (n = 9).