Effect of nerve growth factor on AP-1, NF-κB, and Oct DNA binding activity in apoptotic PC12 cells: Extrinsic and intrinsic elements

Both intrinsic signals, such as serum and neurotrophic factor deprivation, and extrinsic events or agents, such as oxidative stress and glucose deprivation, can induce cell death in pheochromocytoma (PC12) cells. Also, treatment with nerve growth factor (NGF) reduces cell death due to the treatments mentioned. Serumless-induced cell death, as a model of apoptosis, has been intensively investigated in PC12 cells. In the present study, we investigated the molecular components of H₂O₂-induced cell death and compared it with serumless-induced cell death. Exposure of PC12 cells to intermediate concentrations of H₂O₂ (100 μM) induced nuclear condensation and DNA fragmentation, indicating that there is an apoptotic component in H₂O₂-induced cell death. Since transcription factors have been shown to play an essential role in the control of cellular proliferation, differentiation, and survival, we measured changes in the DNA binding activities of the transcription factors activator protein-1 (AP-1), nuclear factor kappa B (NF-κB), and octamer-binding protein (Oct) by electrophoretic mobility shift assay (EMSA) after H₂O₂ treatment and serum deprivation, both in the absence and presence of exogenous NGF in PC12 cells. AP-1 DNA binding activity transiently increased during apoptosis due to serum deprivation, and NGF treatment further stimulated AP-1 DNA binding activity in a more persistent fashion. NF-κB DNA binding activity only increased slightly after serum deprivation, and NGF treatment of PC12 cells decreased NF-κB binding activity in the late stages of serum deprivation. Oct DNA binding activity decreased after serum deprivation, while NGF had an opposite effect. AP-1 DNA binding activity also transiently increased after H₂O₂ treatment, as did NF-κB DNA binding activity. Our results suggest that AP-1 is likely to be a common component of signaling pathways associated with both the induction or suppression of apoptosis induced by intrinsic or extrinsic stimuli.