Reduced expression of neuronal nicotinic acetylcholine receptors during the early stages of damage by oxidative stress in PC12 cells

The mechanism for a large loss of neuronal nicotinic acetylcholine receptors (nAChRs) in brains with neurodegenerative diseases remains unclear. Based on our previous results of [H-3]epibatidine binding influenced by lipid peroxidation, we suggest that nAChR deficit in neurodegenerative diseases might be related to the neurons attacked by free radicals. To further understand how free radicals influence the expression of nAChRs, we detected [I-125]alpha -bungarotoxin binding, nAChR subunit protein and mRNA during the early stage of damage by oxidative stress in PC12 cells in the present study. The results showed that free radical insult (FeSO4) within the concentration range (1-100 muM) used in the study induced dose-dependent increases in lipid peroxidation and toxicity to PC12 cells, but did not result in apoptosis or necrosis. Significant reductions in [I-125]alpha -bungarotoxin binding site, protein level for the alpha3 and alpha7 subunits, and mRNA level for the alpha7 subunit were observed in PC12 cells treated by FeSO4 at the concentrations without inducing cell death compared to control. Pretreatment of cultural cells with antioxidant such as Vitamin E and reduced glutathione prevented the inhibiting effect of free radicals on [I-125]alpha -bungarotoxin and [H-3]epibatidine bindings. The present results further demonstrate that oxidative stress might reduce the number of [I-125]alpha -bungarotoxin binding site and selectively suppress the expression of the nAChR subunits at protein and mRNA levels during the early stages of damage in PC12 cells. J. Neurosci. Res. 66:551-558, 2001. (C) 2001 Wiley-Liss, Inc.