[Neuroprotective effects of alpha7 neuronal acetylcholine receptor and its roles in the pathogenesis of Alzheimer's disease].
OBJECTIVE
To investigate the neuroprotective function of alpha7 nicotinic receptor (nAChR) and its roles in the pathogenesis of Alzheimer's disease (AD).


METHODS
Specific RNA interference to alpha7 nAChR mRNA expression was performed by gene specific small interference RNA (siRNA). SH-SY5Y cells were transfected with the siRNA or treated with 20 micromol/L 3-[2, 4-dimethoxybenzylidene] anabaseine (DMXB), an alpha7 nAChR agonist. After 48 hrs culture, levels of alpha7 nAChR mRNA and protein were monitored by RT-PCR and Western blotting, respectively. In the second experiment, SH-SYSY cells treated with siRNA or DMXB were exposed to 1 micromol/L Abeta(25-35), followed by protein analysis of alpha-form of secreted beta-amyloid precursor peptide (alphaAPPs), and total APP was assayed by Western blotting. In addition, lipid peroxidation and MTT [3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] reduction were measured by spectrophotometry.


RESULTS
In RNA interference group, as compared with controls, alpha7 nAChR mRNA and protein levels were decreased with inhibitory efficiency by 80% and 69%, respectively, along with a decrease in protein levels of alphaAPP and reduction of MTT. However the product of lipid peroxidation was increased. There was an enhanced gene inhibition of alpha7 nAChR by Abeta. While cells treated with DMXB, the alpha7 nAChR protein was increased by 23% as compared with that of the control, along with decrease of alphaAPP and ERK 1/2 at the protein level. The enhanced expression of alpha7 nAChR reduced the neurotoxic effects resulted from Abeta.


CONCLUSIONS
The findings indicate that alpha7 nAChR may play a significant neuroprotective role by enhancing cleavage of APP, improving antioxidant defenses and limiting the toxicity of Abeta, which has been implied in the pathogenesis of AD.
Qi
Xiao-Lan
XL
Department of Pathology and Molecular Biology, Guiyang Medical College, Guiyang 550004, China.
Guan
Zhi-Zhong
ZZ
D000109:Acetylcholine / Q000494:pharmacology; D000544:Alzheimer Disease / Q000473:pathology* / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000378:metabolism* / Q000633:toxicity; D016564:Amyloid beta-Protein Precursor / Q000494:pharmacology; D002478:Cells, Cultured; D006801:Humans; D015227:Lipid Peroxidation; D009474:Neurons / Q000187:drug effects* / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology*; D058255:Protease Nexins; D034622:RNA Interference; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D011956:Receptors, Cell Surface; D011978:Receptors, Nicotinic / Q000378:metabolism* / Q000502:physiology; D064569:alpha7 Nicotinic Acetylcholine Receptor
C545487:APP protein, human; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; C579167:Chrna7 protein, human; D018696:Neuroprotective Agents; D018722:Nicotinic Agonists; D058255:Protease Nexins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D000109:Acetylcholine