Inhibiting gene expression of α3 nicotinic receptor in SH-SY5Y cells with the effects on APP metabolism and antioxidation in Alzheimer's disease

In order to examine the effects of α3 nicotinic acetylcholine receptor (nAChR) in connection with the pathogenesis of Alzheimer's disease (AD), neuroblastoma (SH-SY5Y) cells were transfected with small interference RNAs (siRNAs) that target specifically towards α3 nAChR. The expressions of α3 nAChR mRNA and protein were measured by real-time PCR and Western blotting, respectively. The levels of the α-form of secreted amyloid precursor protein (αAPPs) and total-APP were determined by Western blotting. SH-SY5Y cells transfected with siRNA were then treated with 1 μM β-amyloid peptide (Aβ)1–42, following which the levels of lipid peroxidation, the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and the reduction rate of MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] were characterized by utilizing spectrophotometric procedures. As compared to controls, SH-SY5Y cells transfected with siRNA expressed the decreases in the levels of α3 nAChR mRNA and protein by 98% and 66% lower levels, respectively; exhibited reduced level of the αAPPs; and demonstrated enhanced lipid peroxidation, decreased rate of MTT reduction, and declined activities of SOD and GSH-Px. Inhibited gene expression of the α3 nAChR enhanced the toxicity exerted by Aβ. These results indicate that α3 nAChR may improve cleavage of APP by α-secretase, enhance antioxidation and inhibit the toxicity of Aβ, suggesting that the receptor might play an important role in AD.