Effect of Genetic Polymorphisms (SNPs) in CHRNA7 Gene on Response to Acetylcholinesterase Inhibitors (AChEI) in Patients with Alzheimer's Disease

Abstract

Background: Cholinergic transmission loss is one of the major features in Alzheimer's Disease (AD). Acetylcholinesterase inhibitors (AChEI) are moderately active in AD. α7nAChR (alpha-7 nicotinic acetylcholine receptor), encoded by CHRNA7 (Nicotinic Cholinergic Receptor Alpha-7 gene), is involved in the cholinergic neurotransmission and AD pathogenesis. α7nAChR is a putative receptor of amyloid beta (Aβ). The complex α7nAChR-Aβ is found in neuritic plaques and AD cortical neurons. In normal physiologic conditions, α7nAChR-Aβ interaction leads to receptor activation. Genetic polymorphisms (SNPs) of CHRNA7 and/or CHRFAM7A (fusion gene containing CHRNA7 partial duplication) may be a possible susceptibility trait to dementia, potentially useful to identify high risk or responder individuals. CHRFAM7A-2-bp deletion or CHRNA7 SNPs (rs1514246, rs2337506, rs8027814) seem protective factors in different forms of dementia including AD.

Objective: Correlation between(SNPs) of CHRNA7 and/or CHRFAM7A and cholinesterase inhibitors in AD.

Methods: Literature review.

Results: Among the leading AD therapeutics, Donepezil (DP) and galantamine (AChEI) induce upregulation of α7nAChR protein levels, protecting neurons from degeneration. Patients carrying rs8024987 (C/G) or rs6494223 (C/T) respond better to AChEI. In the caucasic population rs6494223 TT subjects are 7-15% of the total. α7nAChR upregulation induced by DP is higher in lymphocytes from TT subjects than in CC or CT as well as calcium uptake.

Conclusion: The correlation between genetic and functionality data may have an impact on several aspects of disease presentation and therapy, helping in prediction pattern of AD presentation and treatment efficacy. As a consequence it may lead to better patients quality of life and longer periods of self- sufficiency. Moreover, it may contribute to clarify AChEI mechanisms of action.

Keywords: AChEI-cognitive response; AD pathogenesis; Acetylcholinesterase inhibitors (AChEI); CHRNA7; cholinergic transmission; donepezil; galantamine; genetic polymorphisms (SNPs).