Anti-amyloidogenic activity of cholinergic agents

Overproduction of the peptide amyloid beta (Abeta) is thought to be a critical pathogenic event in Alzheimer's disease (AD), leading to the formation of senile (amyloid) plaques, which in turn lead to neurofibrillary tangles, neuronal and synaptic loss, and dementia. Mendelian inheritance of AD, which occurs in a very small proportion of cases, is caused by mutations in the genes for [beta-amyloid precursor protein (beta-APP), presenilin 1 or presenilin 2; the mutations are thought to be pathogenic because they result in increased Abeta production. The majority of AD is not inherited in a Mendelian fashion, and is therefore termed sporadic. The cause or causes of this common form of AD is unknown, although it is assumed that overproduction of Abeta is also the critical event. Recent animal experiments suggest that Abeta overproduction in aging and sporadic AD may be the result of cortical cholinergic deafferentation, which occurs as part of normal human aging. Decreasing Abeta production may therefore slow or halt the progression of AD, and cholinergic agents may be particularly suitable for this role. In vitro work has indicated that cholinergic muscarinic M1 receptor agonists may reduce the cellular production of Abeta. In vivo experiments have shown that both muscarinic agonists and acetylcholinesterase inhibitors lower central nervous system (CNS) Abeta concentrations. These results suggest that cholinergic agents may be particularly well suited to a preventative role in AD therapy by limiting the initial accumulation of Abeta. (C) 2002 Wiley-Liss, Inc.