Amyloid beta protein disruption of cholinergic and growth factor phospholipase C signals could underlie cognitive and neurodegerative aspects of Alzheimer's disease

Pharmacologic management of Alzheimer disease, Part I: Hormonal and emerging investigational drug therapies

OBJECTIVE

To provide information about current genetic research in Alzheimer disease (AD) and potential pharmacologic interventions. Investigational pharmacologic management of AD, including serenics, hormonal therapy, neurotransmitter augmentation, neurobiologic agents, nootropics, and ampakines are also reviewed.

DATA SOURCES

Studies, review articles, and editorials identified from MEDLINE searches (from January 1993 to December 1996), and bibliographies of identified articles.

STUDY SELECTION

Studies, review articles, and editorials addressing current areas of AD pharmacotherapy research, including hormonal therapy and select investigational agents.

DATA EXTRACTION

Pertinent information was selected and the data were synthesized into a review format.

DATA SYNTHESIS

AD is a devastating disease characterized by progressive memory loss, cognitive decline, and behavioral disturbances. The behavioral problems associated with AD can present a difficult clinical challenge. Many patients with AD are intolerant of traditional pharmacologic management, including antipsychotics, antidepressants, and anxiolytics. Hormonal agents, including estrogen, medroxyprogesterone, and cyproterone acetate, may be efficacious therapeutic alternatives in the management of sexual behavioral disturbances in men. Research regarding estrogen's role in AD prevention and effect on cognitive function and behavioral symptoms in women with AD are evaluated. Studies evaluating neurotransmitter augmentation and neurobiologic agents in AD are reviewed.

CONCLUSIONS

Environmental, genetic, neurobiologic, hormonal, and neurotransmitter influences, and their respective roles in AD pathology, are being investigated. Researchers concur that it is imperative to recognize the correlation of these factors in the etiology of AD to design effective prevention and treatment strategies. Additional studies are essential to elucidate the most efficacious treatments for AD and the attendant behavioral disturbances.

Cholinergic activation of phosphoinositide signaling is impaired in Alzheimer's disease brain

The function of the phosphoinositide signal transduction system was compared in membranes from Alzheimer's disease (AD) and control postmortem brain. [3H]Phosphatidylinositol hydrolysis was concentration-dependently stimulated by GTP[S] and this was 40% lower than controls in AD prefrontal cortical membranes. Carbachol induced a response greater than that of GTP[S] alone, and this response was impaired in AD by 45%. Differential analysis of the receptor-coupled and G-protein contributions to the responses indicated that the G-protein deficit in AD had a predominant influence on the lowered responses to cholinergic agonists. Similar deficits were observed in AD in the responses to five additional cholinergic agonists, including acetylcholine with three different acetylcholinesterase inhibitors. Deficits in stimulated phosphoinositide hydrolysis were regionally selective and these deficits did not correlate directly with reductions in choline acetyltransferase activity in AD tissues. These data demonstrate that in AD there is a brain region-selective, large impairment of cholinergic agonist-induced signal transduction mediated by the phosphoinositide system, which we speculate may impact on amyloid precursor protein processing.