Activation of nuclear transcription factor kappa B (NF-κB) is essential for dopamine-induced apoptosis in PC12 cells

The etiology of Parkinson's disease is still unknown, though current investigations support the notion of the pivotal involvement of oxidative stress in the process of neuro-degeneration in the substantia nigra (SN). In the present study, we investigated the molecular mechanisms underlying cellular response to a challenge by dopamine, one of the local oxidative stressors in the SN. Based on studies showing that nuclear factor kappa B (NF-κB) is activated by oxidative stress, we studied the involvement of NF-κB in the toxicity of PC12 cells following dopamine exposure. We found that dopamine (0.1-0.5 mμ) treatment increased the phosphorylation of the IκB protein, the inhibitory subunit of NF-κB in the cytoplasm. Immunoblot analysis demonstrated the presence of NF-κB-p65 protein in the nuclear fraction and its disappearance from the cytoplasmic fraction after 2 h of dopamine exposure. Dopamine-induced NF-κB activation was also evidenced by electromobility shift assay using radioactive labeled NF-κB consensus DNA sequence. Cell-permeable NF-κB inhibitor SN-50 rescued the cells from dopamine-induced apoptosis and showed the importance of NF-κB activation to the induction of apoptosis. Furthermore, flow cytometry assay demonstrated a higher level of translocated NF-κB-p65 in the apoptotic nuclei than in the unaffected nuclei. In conclusion, our findings suggest that NF-κB activation is essential to dopamine-induced apoptosis in PC12 cells and it may be involved in nigral neurodegeneration in patients with Parkinson's disease.