Cerebrospinal fluid acetylcholinesterase in progressive supranuclear palsy: reduced activity relative to normal subjects and lack of inhibition by oral physostigmine

Neurochemical biomarkers in the differential diagnosis of movement disorders

In recent years, the neurochemical analysis of neuronal proteins in cerebrospinal fluid (CSF) has become increasingly accepted for the diagnosis of neurodegenerative dementia diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease. CSF surrounds the central nervous system, and in the composition of CSF proteins one finds brain-specific proteins that are prioritized from blood-derived proteins. Levels of specific CSF proteins could be very promising biomarkers for central nervous system diseases. We need the development of more easily accessible biomarkers, in the blood. In neurodegenerative diseases with and without dementia, studies on CSF and blood proteins have investigated the usefulness of biomarkers in differential diagnosis. The clinical diagnoses of Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration still rely mainly on clinical symptoms as defined by international classification criteria. In this article, we review CSF biomarkers in these movement disorders and discuss recent published reports on the neurochemical intra vitam diagnosis of neurodegenerative disorders (including recent CSF alpha-synuclein findings).

Treatment of dementia in parkinsonian syndromes with cholinesterase inhibitors

In Parkinsonian syndromes behavioural symptoms and dementia can be even more debilitating than motor symptoms and are an important predictor for nursing home placement and mortality. Neuropathologically, dementia seems to be primarily related to cortical changes rather than to subcortical alterations. Concerning neurotransmitter systems, the cholinergic system has been proposed to play a key role in cognitive disturbances. Based on studies with patients with Alzheimer disease, the application of cholinesterase inhibitors is vividly discussed also for dementia associated with parkinsonian syndromes. This review focuses on the specific symptoms of dementia in different parkinsonian syndromes and critically questions the effect of cholinergic treatment on cognitive functions in patients with extrapyramidal syndromes and dementia. There is evidence that medication with some cholinesterase inhibitors can enhance cognition as well as activities of daily living in dementia with Parkinson's disease and seems to reduce behavioural disturbances in both dementia with Parkinson's disease and dementia with Lewy bodies. The effect of treatment with cholinesterase inhibitors in progressive supranuclear palsy and corticobasal degeneration warrants carefully designed studies including a sufficient number of patients and symptom-adopted dementia scales.

Toward future therapies in progressive supranuclear palsy

There is a stern therapeutic challenge for progressive supranuclear palsy (PSP) that has not yet been met. The lack of randomized, controlled trials and negative outcomes from the vast majority of studies make it impossible to set therapeutic standards, or to give clear recommendations. We review progress to date in this area and briefly consider future potential therapeutic strategies.

Acetylcholinesterase in lumbar and ventricular cerebrospinal fluid

BACKGROUND

Soluble acetylcholinesterase (AChE, E.C. 3.1.1.7.) is released by neurons, glial and meningeal cells into the CSF. AChE activity in cerebrospinal fluid (CSF) is altered in various disorders of the nervous system. The objects of this study are to define a reference range for CSF AChE activity in human lumbar CSF, to prove that the enzyme activity does not depend on the blood/CSF barrier function, and to provide information about AChE in ventricular CSF. In addition, drugs used in neurosurgical care have been examined for their in vitro effects on CSF AChE activity to exclude interference with the test system.

METHODS

We tested the AChE activity in 64 lumbar CSF samples collected from a clinically healthy population and in 169 ventricular CSF samples obtained from 90 neurosurgical patients. AChE activity was assayed with our inhibitor-free test procedure.

RESULTS

The reference range determined for lumbar CSF AChE activity is 9.2-24.4 nmol/min per ml. Lumbar CSF AChE activity does not correlate with parameters characterising the status of the blood/CSF barrier. Ventricular puncture is only justified for underlying pathology making it impossible to provide reference data for ventricular CSF. Most measurements reveal ventricular enzyme activity below 4 nmol/min per ml.

CONCLUSION

The results of this study suggest the utility of lumbar CSF AChE activity as a measure of specific secretory function in enzyme releasing cells of the nervous system.

The significance of the activity of CSF cholinesterases in dementias

This article reviews the significance of changes in the level of cerebrospinal fluid acetylcholinesterase or cholinesterase in patients with Alzheimer's disease or other dementias. Evidence has shown that the methodology of assaying cerebrospinal fluid acetylcholinesterase or cholinesterase is reliable and the activity of the enzyme is stable. Low acetylcholinesterase or cholinesterase levels presenting in cerebrospinal fluid of a demented individual may confirm the clinical diagnosis of Alzheimer's disease or other organic dementia. A low activity of acetylcholinesterase or cholinesterase existing in cerebrospinal fluid of a non-demented individual may indicate a brain at risk, or that the person is in the preclinical stage of dementia. Recognition of the presence of the preclinical stage may be very beneficial for explaining the real meaning of the 'overlap' in the biochemistry and pathology between dementia and non-dementia, and also very important for prevention and treatment. Therefore, the strategy of prevention and of treatment should no longer be designed to inhibit acetylcholinesterase activity. In contrast, it should be designed to enhance the neuronal acetylcholinesterase activity or to delay the degeneration of brain acetylcholinesterase system.

A multiple-dose safety trial of eptastigmine in Alzheimer's disease, with pharmacodynamic observations of red blood cell cholinesterase

A placebo-controlled multiple dose study was conducted to evaluate the safety, tolerability, and pharmacodynamics of multiple dose levels of eptastigmine in 25 patients with probable Alzheimer's disease (AD). Twenty patients (12 M, 8 F; mean age 74, range 57-84) were randomized to receive 12mg (N = 3), 20mg (N = 6), 28mg (N = 6) or placebo (N = 5) tid on a double-blind basis for 14 days, followed by seven days of single blind placebo, in successively rising dose groups. All patients completed the study without intolerable or severe adverse events. All doses significantly (p < 0.001) reduced peak and trough RBC cholinesterase (AChE) activity as compared to baseline. Percent inhibition for Day 14 peak and trough RBC AChE peak and trough values, respectively, appeared proportional to dose: 18% and 21% (12mg); 36% and 35% (20mg); 40% and 44% (28mg). In order to determine the maximum tolerated dose of eptastigmine, an additional single-blind study was performed in five patients (2 M, 3 F; mean age 78, range 72-80) utilizing a rising dose schedule of eptastigmine (N = 4) or placebo (N = 1), starting with the previously tolerated 28mg tid dose and increasing by 4mg tid up to a potential maximum of 56mg tid. Dose-limiting adverse events occurred requiring discontinuation of medication in one patient at 48mg tid and two patients at 52mg tid; RBC AChE inhibition was proportional to dose, with peak values up to 70% inhibition at 48mg tid. The maximum tolerated dose of 48mg tid was identified as a basis for potential Phase II multicenter efficacy trials.

Pharmacological evaluation of the cholinergic system in progressive supranuclear palsy

Severe cholinergic loss occurs in the brains of patients with progressive supranuclear palsy. To evaluate the functional implications of this neuronal deficit, dose-response curves were obtained in patients with progressive supranuclear palsy and normal control subjects undergoing intravenous cholinergic blockade (scopolamine) and stimulation (physostigmine). Physostigmine had no significant neurobehavioral effects at any dose in patients with progressive supranuclear palsy. Scopolamine, at low and medium doses, significantly impaired memory performance of both groups, but worsened the gait of only the patients. High-dose scopolamine, which could not be tolerated by the patients, resulted in gait deterioration among control subjects. Thus, patients with progressive supranuclear palsy have increased sensitivity to cholinergic blockade compared to control subjects. Since loss of cholinergic neurons appears to contribute to the pathogenesis of certain cognitive and motor deficits found in progressive supranuclear palsy, the use of oral anticholinergics should ordinarily be avoided in this disorder. On the other hand, physostigmine at clinically tolerated dose levels seems to be therapeutically ineffective.

Acetylcholinesterase provides deeper insights into Alzheimer's disease

This article reviews the considerable evidence which rejects the cholinergic hypothesis of Alzheimer's disease (AD) and proposes that it is the AChE system of which the lightly stained neurons are located in the entorhinal cortex, the CA1/subiculum of the hippocampus and the amygdala which are the most vulnerable and are the earliest affected in the pathological processes of AD. Changes then spread out to the intermediately stained neurons of the association cortex, until they affect the heavily stained cells of the motor cortex. In general, senile plaque, a hallmark of AD, may be formed from the terminals of AChE-containing neurons. Neurofibrillary tangle, another hallmark of AD, may be formed in the perikarya of AChE-containing cells and bring about the demise of the neuron, thus leading to dementia.

Cholinergic approaches to the treatment of progressive supranuclear palsy

In spite of the severe loss of cholinergic neurons in the brains of patients with progressive supranuclear palsy (PSP), marginal or null benefits are seen in clinical trials after the administration of physostigmine, a cholinesterase inhibitor, or RS-86, a cholinergic agonist. The possible role of cholinergic therapy in PSP is reevaluated.

CSF galanin and neuropeptide Y immunoreactivity in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) has been associated with degenerative changes in cholinergic and dopaminergic neurons in several brain regions. Since acetylcholine is colocalized with the neuropeptide galanin in certain neuronal populations, we measured the concentration of this neuropeptide and neuropeptide Y in cerebrospinal fluid (CSF) of 11 patients with PSP and in 16 age-matched healthy controls. No significant alterations in the CSF levels of galanin or neuropeptide Y were found.