Potential therapies in aging and senile dementias

Effect of cholinergic signaling on neuronal cell bioenergetics

Alzheimer's disease (AD) patients have reduced brain acetylcholine and reversing this deficit yields clinical benefits. In this study we explored how increased cholinergic tone impacts cell bioenergetics, which are also perturbed in AD. We treated SH-SY5Y neuroblastoma cells with carbachol, a cholinergic agonist, and tested for bioenergetic flux and bioenergetic infrastructure changes. Carbachol rapidly increased both oxidative phosphorylation and glycolysis fluxes. ATP levels rose slightly, as did cell energy demand, and AMPK phosphorylation occurred. At least some of these effects depended on muscarinic receptor activation, ER calcium release, and ER calcium re-uptake. Our data show that increasing cholinergic signaling enhances cell bioenergetics, and reveal mechanisms that mediate this effect. Phenomena we observed could potentially explain why cholinesterase inhibitor therapy increases AD brain glucose utilization and N-acetyl aspartate levels. The question of whether cholinesterase inhibitors have a disease modifying effect in AD has long been debated; our data suggest a theoretical mechanism through which such an effect could potentially arise.

Multicenter trial of naloxone in Alzheimer's disease

In a double-blind, placebo-controlled, crossover study of intravenously administered naloxone hydrochloride, 54 subjects with clinically ascertained Alzheimer's disease tested at three university centers showed no significant improvement in neuropsychological performance after 1-mg or 10-mg doses; 15 patients at 1 center were similarly unimproved after receiving 30 mg naloxone (single blind). Findings fail to support claims that naloxone monotherapy ameliorates cognitive impairments of Alzheimer's disease.

Lymphopenia in primary degenerative dementia

The central nervous and immune systems share a number of common properties, e.g. neurotransmitter receptors. In contrast to age matched healthy and/or hypertensive controls, the total lymphocyte count in 25 carefully diagnosed and staged patients with primary degenerative dementia were significantly reduced and also correlated with the severity of their dementia. Subjects' age, age of dementia onset, or duration of illness were unrelated. Total leukocyte counts were similar between groups. Nutritional status, ACTH, or plasma cortisol in dementia cohort were also not explanatory of their lymphopenia. These results are potentially significant in light of an immune hypothesis for primary degenerative dementia: Alzheimer's type and/or that population's high concomitant risk of infection.

Effect of acute arecoline, tacrine and arecoline + tacrine post-training administration on retention in old mice

The amnesias characteristic of Alzheimer's disease and other age-related dementias are refractory to conventional pharmacotherapy. A recent treatment strategy is to combine drugs to improve their memory enhancing effect. We previously reported that in young weakly trained mice, the combination of arecoline and tacrine was more effective on a mg/kg basis than either drug administered alone. This was true whether the route of administration was intracerebroventricular, subcutaneous or oral. We now report that 24 month old mice trained to avoid footshock in a T-maze show poor retention when tested one week later. Subcutaneous administration of arecoline, tacrine (also referred to as tetrahydroaminoacridine, THA) and arecoline plus tacrine administered immediately after T-maze footshock avoidance training enhanced retention of 24 month old mice compared to the saline-injected control. Since the combination was as effective as the single drug treatments even though 96% less arecoline and 99.7% less tacrine was administered, the combination showed marked potentiation of drug action of memory processing.

Tissue coenzyme Q (ubiquinone) and protein concentrations over the life span of the laboratory rat

The coenzyme Q (ubiquinone) concentrations of a number of tissues have been determined over the life span of the male laboratory rat. Coenzyme Q increased between 2 and 18 months and decreased significantly at 25 months in the heart and kidney, and the gastrocnemius, oblique and deep aspect (red) vastus lateralis muscles. The coenzyme Q concentration of liver increased over the life span, while it remained relatively constant in brain, lung, and the superficial aspect (white) of the vastus lateralis muscle. Data are also included for organ weights and protein contents of tissues over the life span. The various roles of coenzyme Q in cellular electron transfer and its regulation, energy conservation in oxidative phosphorylation, and its clinical efficacy in diseases of energy metabolism are discussed. It is hypothesized that coenzyme Q serves as a free radical quencher in the mitochondrion, a major site of free radical formation, in addition to its other roles in cellular energy metabolism, and that its cellular diminution may contribute to the loss of cellular function accompanying ageing.