Possible role of NF-κB in Bcl-XL protection against hydrogen peroxide-induced PC12 cell death

Bcl-X-L, a mitochondrial membrane protein, blocks apoptosis induced by a wide array of death signals. In spite of extensive research, the molecular milieu that characterizes the anti-apoptotic function of Bcl-X-L is complex and not fully clarified. In the present work, we have investigated the role of Bcl-X-L in protecting against oxidative death induced by H2O2 in cultured rat pheochromocytoma (PC12) cells. PC12 cells exposed to H2O2 underwent apoptotic cell death as determined by internucleosomal DNA fragmentation and an increased pro-apoptotic Bax to anti-apoptotic Bcl-X-L ratio. Moreover, stable transfection with the bcl-X-L gene rescued PC12 cells from apoptotic death caused by H2O2. PC12 cells overexpressing bcl-X-L exhibited relatively high constitutive transcriptional as well as DNA binding activities of NF-kappaB, compared with the vector-transfected control cells. Addition of NF-kappaB inhibitors, such as parthenolide and N-tosyl-L-phenylalanine chloromethyl ketone, to the media aggravated H2O2-induced oxidative cell death. PC12 cells transfected with bcl-X-L exhibited higher levels of the heme oxygenase-1, which may confer these cells protection against oxidative stress. These results suggest that the redox-sensitive transcription factor NF-kappaB may play a role in bcl-X-L-mediated protection against oxidative cell death.