Loss of nicotinic receptors induced by beta-amyloid peptides in PC12 cells: Possible mechanism involving lipid peroxidation

The mechanisms involved in the loss of nicotinic acetylcholine receptors (nAChRs), seen in brains of patients with Alzheimer's disease (AD) and in cultured cells treated by beta-amylold peptides (Abetas), remain elusive. We give results to show that lipid peroxiclation induced directly by Abeta might be involved in the deficits of nAChRs. In the study, PC12 cells were treated by addition of 5 muM of Abeta(25-35) and Abeta(1-40), respectively, with or without a antioxidant, vitamin E. Besides significantly decreased MTT (3-(4,5-dimethylthiazol-2-yl)-2,5,diphenyltetrazolium bromide) reduction, an increased lipid peroxiclation was detected in the cells, but no protein oxidation. Significant reductions in [H-3]epibatidine and [I-125]alpha-bungarotoxin binding sites and in the protein levels of the alpha3 and alpha7 nAChR subunits were observed in the cells treated with Abetas. Furthermore, Abeta(25-35) decreased the level of ubiquinone-9 in PC12 cells, but did not change the amount of cholesterol, providing further evidence for lipid peroxiclation. Interestingly, when PC12 cells were pretreated by antioxidant before the addition of Abetas, the lipid peroxiclation and the decreased ubiquinone resulted from Abetas were prohibited. The decreases of nAChR binding sites and subunit proteins resulted from Abetas were mostly prevented by the pretreatment with antioxidant. These findings suggest that lipid peroxiclation stimulated by Abetas might be a mechanism for the loss of nAChRs associated with the pathogenesis of AD. (C) 2002 Wiley-Liss, Inc.