Highly sensitive GQDs-MnO2 based assay with turn-on fluorescence for monitoring cerebrospinal acetylcholinesterase fluctuation: A biomarker for organophosphorus pesticides poisoning and management

In this study, we demonstrated an assay with turn-on fluorescence for monitoring cerebrospinal acetylcholinesterase (AChE) fluctuation as a biomarker for organophosphorus pesticides (OPs) poisoning and management based on single layer MnO₂ nanosheets with graphene quantum dots (GQDs) as signal readout. Initially, the fluorescence of GQDs was quenched by MnO₂ nanosheets mainly due to the inner filter effect (IFE). However, with the presence of reductive thiocholine (TCh), the enzymatic product, hydrolyzed from acetylthiocholine (ATCh) by AChE, the redox reaction between MnO₂ and TCh occurred, leading to the destruction of the MnO₂ nanosheets, and thereby IFE was diminished gradually. As a consequence, the turn-on fluorescence of GQDs with the changes in the spectrum of the dispersion constituted a new mechanism for sensing of cerebrospinal AChE. With the method developed here, we could monitor cerebrospinal AChE fluctuation of rats exposed to OPs before and after therapy, and could thereby open up the pathway to a new sensing platform for better understanding the mechanism of brain dysfunctions associate with OPs poisoning.

Complement component C3 and butyrylcholinesterase activity are associated with neurodegeneration and clinical disability in multiple sclerosis

Dysregulation of the complement system is evident in many CNS diseases but mechanisms regulating complement activation in the CNS remain unclear. In a recent large rat genome-wide expression profiling and linkage analysis we found co-regulation of complement C3 immediately downstream of butyrylcholinesterase (BuChE), an enzyme hydrolyzing acetylcholine (ACh), a classical neurotransmitter with immunoregulatory effects. We here determined levels of neurofilament-light (NFL), a marker for ongoing nerve injury, C3 and activity of the two main ACh hydrolyzing enzymes, acetylcholinesterase (AChE) and BuChE, in cerebrospinal fluid (CSF) from patients with MS (n = 48) and non-inflammatory controls (n = 18). C3 levels were elevated in MS patients compared to controls and correlated both to disability and NFL. C3 levels were not induced by relapses, but were increased in patients with ≥9 cerebral lesions on magnetic resonance imaging and in patients with progressive disease. BuChE activity did not differ at the group level, but was correlated to both C3 and NFL levels in individual samples. In conclusion, we show that CSF C3 correlates both to a marker for ongoing nerve injury and degree of disease disability. Moreover, our results also suggest a potential link between intrathecal cholinergic activity and complement activation. These results motivate further efforts directed at elucidating the regulation and effector functions of the complement system in MS, and its relation to cholinergic tone.

Cerebrospinal fluid (CSF) 25-hydroxyvitamin D concentration and CSF acetylcholinesterase activity are reduced in patients with Alzheimer's disease

BACKGROUND

Little is known of vitamin D concentration in cerebrospinal fluid (CSF) in Alzheimer's disease (AD) and its relation with CSF acetylcholinesterase (AChE) activity, a marker of cholinergic function.

METHODS

A cross-sectional study of 52 consecutive patients under primary evaluation of cognitive impairment and 17 healthy controls. The patients had AD dementia or mild cognitive impairment (MCI) diagnosed with AD dementia upon follow-up (n = 28), other dementias (n = 12), and stable MCI (SMCI, n = 12). We determined serum and CSF concentrations of calcium, parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), and CSF activities of AChE and butyrylcholinesterase (BuChE).

FINDINGS

CSF 25OHD level was reduced in AD patients (P < 0.05), and CSF AChE activity was decreased both in patients with AD (P < 0.05) and other dementias (P < 0.01) compared to healthy controls. None of the measured variables differed between BuChE K-variant genotypes whereas the participants that were homozygous in terms of the apolipoprotein E (APOE) ε4 allele had decreased CSF AChE activity compared to subjects lacking the APOE ε4 allele (P = 0.01). In AD patients (n=28), CSF AChE activity correlated positively with CSF levels of total tau (T-tau) (r = 0.44, P < 0.05) and phosphorylated tau protein (P-tau) (r = 0.50, P < 0.01), but CSF activities of AChE or BuChE did not correlate with serum or CSF levels of 25OHD.

CONCLUSIONS

In this pilot study, both CSF 25OHD level and CSF AChE activity were reduced in AD patients. However, the lack of correlations between 25OHD levels and CSF activities of AChE or BuChE might suggest different mechanisms of action, which could have implications for treatment trials.

Regulated Extracellular Choline Acetyltransferase Activity- The Plausible Missing Link of the Distant Action of Acetylcholine in the Cholinergic Anti-Inflammatory Pathway

Acetylcholine (ACh), the classical neurotransmitter, also affects a variety of nonexcitable cells, such as endothelia, microglia, astrocytes and lymphocytes in both the nervous system and secondary lymphoid organs. Most of these cells are very distant from cholinergic synapses. The action of ACh on these distant cells is unlikely to occur through diffusion, given that ACh is very short-lived in the presence of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), two extremely efficient ACh-degrading enzymes abundantly present in extracellular fluids. In this study, we show compelling evidence for presence of a high concentration and activity of the ACh-synthesizing enzyme, choline-acetyltransferase (ChAT) in human cerebrospinal fluid (CSF) and plasma. We show that ChAT levels are physiologically balanced to the levels of its counteracting enzymes, AChE and BuChE in the human plasma and CSF. Equilibrium analyses show that soluble ChAT maintains a steady-state ACh level in the presence of physiological levels of fully active ACh-degrading enzymes. We show that ChAT is secreted by cultured human-brain astrocytes, and that activated spleen lymphocytes release ChAT itself rather than ACh. We further report differential CSF levels of ChAT in relation to Alzheimer's disease risk genotypes, as well as in patients with multiple sclerosis, a chronic neuroinflammatory disease, compared to controls. Interestingly, soluble CSF ChAT levels show strong correlation with soluble complement factor levels, supporting a role in inflammatory regulation. This study provides a plausible explanation for the long-distance action of ACh through continuous renewal of ACh in extracellular fluids by the soluble ChAT and thereby maintenance of steady-state equilibrium between hydrolysis and synthesis of this ubiquitous cholinergic signal substance in the brain and peripheral compartments. These findings may have important implications for the role of cholinergic signaling in states of inflammation in general and in neurodegenerative disease, such as Alzheimer's disease and multiple sclerosis in particular.

A highly sensitive gold-nanoparticle-based assay for acetylcholinesterase in cerebrospinal fluid of transgenic mice with Alzheimer's disease

A highly sensitive, selective, and dual-readout (colorimetric and fluorometric) assay for acetylcholinesterase (AChE) based on Rhodamine B-modified gold nanoparticle is reported. Due to its good sensitivity and selectivity, the assay can be used for monitoring AChE levels in the cerebrospinal fluid of transgenic mice with Alzheimer's disease.

Changes in CSF acetyl- and butyrylcholinesterase activity after long-term treatment with AChE inhibitors in Alzheimer's disease

OBJECTIVES

  To measure cerebrospinal fluid (CSF) activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in patients with Alzheimer's disease (AD) participating in randomized clinical trials from three European centers, before and after long-term treatment with different AChE inhibitors (AChEIs).

MATERIALS AND METHODS

  Of the 144 patients included in the study, 104 were treated with donepezil, 15 with galantamine, 16 with rivastigmine, and nine with placebo. CSF AChE and BChE activities were measured at baseline and after 1- year treatment.

RESULTS

Donepezil and galantamine groups showed a significant increase in CSF AChE activity at follow-up, while no changes for BChE activity were observed; in donepezil group, a positive correlation between plasma concentration and AChE activity was documented. Conversely, in rivastigmine group, a decrease in CSF activity of both enzymes was observed. CSF AChE and BChE activities were not correlated with the clinical outcome in any group considered. CSF biomarkers did not show any change after treatment.

CONCLUSIONS

  AChEIs differently influence the activity of target enzymes in CSF independent of their pharmacodynamic effects.

Association between acetylcholinesterase and beta-amyloid peptide in Alzheimer's cerebrospinal fluid

The altered expression of acetylcholinesterase (AChE) in the brains of patients with Alzheimer's disease (AD) has raised much interest of late. Despite an overall decrease in the AD brain, the activity of AChE increases around beta-amyloid plaques and indeed, the beta-amyloid peptide (Abeta) can influence AChE levels. Such evidence stimulated our interest in the possibility that the levels of AChE and amyloid might vary together in AD. We previously found that the different AChE forms present in both the brain and in the cerebrospinal fluid (CSF) of AD patients varied in conjunction with abnormal glycosylation. Thus, the alterations in glycosylation are correlated with the accumulation of a minor subspecies of AChE monomers. We also recently analysed whether long-term exposure to the cholinesterase inhibitor (ChE-I) donepezil influences the AChE species found in AD CSF. The marked increase in CSF-AChE activity in AD patients following long-term treatment with donepezil was not paralleled by a rise in this subset of light variants. Hence, the correlation with the levels of CSF-Abeta is unique to these AChE species in patients receiving such treatment. The aim of this report is to review the links between AChE and beta-amyloid, and to discuss the significance of the responses of the distinct AChE species to ChE-I during the treatment of AD.

Changes in brain 11C-nicotine binding sites in patients with mild Alzheimer's disease following rivastigmine treatment as assessed by PET

RATIONALE

Marked reduction in the cortical nicotinic acetylcholine receptors is observed in the brain of patients suffering from Alzheimer's disease (AD). Although cholinesterase inhibitors are used for symptomatic treatment of mild to moderate AD patients, numerous long-term treatment studies indicate that they might stabilize or halt the progression of the disease by restoring the central cholinergic neurotransmission. Thus, we used positron emission tomography (PET) technique as a sensitive approach to assess longitudinal changes in the nicotine binding sites in the brains of patients with AD.

OBJECTIVE

To evaluate changes in brain nicotinic binding sites in relation to inhibition level of cholinesterases in cerebrospinal fluid (CSF) and plasma and changes in cognitive performance of the patients in different neuropsychological tests after rivastigmine treatment.

MATERIALS AND METHODS

Ten mild AD patients received rivastigmine for 12 months. A dual-tracer PET model with administration of (15)O-water and (S)(-)(11)C-nicotine was used to assess (11)C-nicotine binding sites in the brain at baseline and after 3 and 12 months of the treatment. Cholinesterase activities in CSF and plasma were assessed colorimetrically.

RESULTS

The (11)C-nicotine binding sites were significantly increased 12-19% in several cortical brain regions after 3 months compared with baseline, while the increase was not significant after 12 months of the treatment. After 3 months treatment, low enzyme inhibition in CSF and plasma was correlated with higher cortical (11)C-nicotine binding. The (11)C-nicotine binding positively correlated with attentional task at the 12-month follow-up.

CONCLUSION

Changes in the (11)C-nicotine binding during rivastigmine treatment might represent remodeling of the cholinergic and related neuronal network.

Cerebrospinal fluid acetylcholinesterase changes after treatment with donepezil in patients with Alzheimer's disease

We analyzed whether donepezil differently influences acetylcholinesterase (AChE) variants from cerebrospinal fluid (CSF) in patients with Alzheimer's disease (AD) after long-term treatment. Overall CSF-AChE activity in AD patients before treatment was not different from controls, but the ratio between the major tetrameric form, G(4), and the smaller G(1) and G(2) species was significantly lower. AChE levels at study outset were found to correlate positively with beta-amyloid (1-42) (Abeta42). When patients were re-examined after 12 months treatment with donepezil, there was a remarkable increase in both the G(4) and the lighter species of CSF AChE. As compared with placebo, donepezil caused decreases in the percentage of AChE that failed to bind to the lectin concanavalin A and the antibody AE1. These non-binding species comprised primarily a small subset of G(1) and G(2) forms. In treated patients, these light variants were the only subset of CSF AChE that correlated with CSF-Abeta42 levels. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that a 77-kDa band, attributed in part to inactive AChE, was lower in AD patients than in controls. Unlike enzyme activity, the intensity of this band did not increase after donepezil treatment. The varying responses of different AChE species to ChE-I treatment suggest different modes of regulation, which may have therapeutic implications.

Altered glycosylation of acetylcholinesterase in the Creutzfeldt-Jakob cerebrospinal fluid

Several neurodegenerative disorders present deficiencies in the cholinergic system. Scarce research on prion encephalopathies has examined the levels of cholinergic pathway-related enzymes. Acetylcholinesterase (AChE) is expressed as several molecular forms. The potential importance of these variants is increased by the possibility that AChE has roles other than acetylcholine hydrolysis. We investigated the levels of AChE, its molecular forms, and glycosylation in the cerebrospinal fluid (CSF) from Creutzfeldt-Jakob disease (CJD) patients.

Inhibition of acetylcholinesterase in CSF versus brain assessed by 11C-PMP PET in AD patients treated with galantamine

The relationship between acetylcholinesterase (AChE) activity in the CSF and brain of patients with Alzheimer's disease (AD) was investigated in 18 mild AD patients following galantamine treatment. The first 3 months of the study had a randomized double-blind placebo-controlled design, during which 12 patients received galantamine (16-24 mg/day) and six patients placebo. This was followed by 9 months galantamine treatment in all patients. Activities and protein levels of both the "read-through" AChE (AChE-R) and the synaptic (AChE-S) variants in CSF were assessed in parallel together with the regional brain AChE activity by (11)C-PMP and PET. The AChE-S inhibition was 30-36% in CSF, which correlated well with the in vivo AChE inhibition in the brain. No significant AChE inhibition was observed in the placebo group. The increased level of the AChE-R protein was 16% higher than that of AChE-S. Both the AChE inhibition and the increased level of AChE-R protein positively correlated with the patient's performance in cognitive tests associated with visuospatial ability and attention. In conclusion, AChE levels in CSF closely mirror in vivo brain AChE levels prior to and after treatment with the cholinesterase inhibitors. A positive cognitive response seems to dependent on the AChE inhibition level, which is balanced by an increased protein level of the AChE-R variant in the patients.

Changes in the activity and protein levels of CSF acetylcholinesterases in relation to cognitive function of patients with mild Alzheimer's disease following chronic donepezil treatment

OBJECTIVES

To evaluate long-term changes in acetylcholinesterase (AChE) activity in CSF and blood following donepezil treatment in relation to the concentration of donepezil and cognition in AD patients.

METHODS

CSF or blood (or both) samples of a total of 104 patients with mild AD were used [MMSE score 23 +/- 0.4; age 75 +/- 1 years (mean +/- SEM); n=53 for CSF and n=51 for plasma/red blood cell (RBC) samples]. The patients were treated with 5 or 10 mg/day donepezil and clinically followed for 2 years. The CSF and RBC AChE activities were measured by the Ellman's direct colorimetric assay. Protein levels of two variants of AChE ("read-through" AChE-R and synaptic AChE-S) were determined by an ELISA-like method.

RESULTS

The plasma donepezil concentration was dose-dependent (between 30 and 60 ng/mL in the 5-mg and 10-mg group, respectively). The CSF donepezil concentration was 10 times lower than the plasma level and showed dose- and time-dependent kinetics. The RBC AChE inhibition was moderate (19-29%). CSF AChE-S inhibition was estimated to 30-40% in the 5-mg and 45-55% in the 10-mg group. Positive correlations were observed between the CSF AChE inhibition, an increased protein level of the AChE-R variant and MMSE examination. Patients with high AChE inhibition (>or=45%) showed a stabilized MMSE test result after up to two years, while a significant decline was observed in AD patients with lower AChE inhibition (<or=30%).

CONCLUSIONS

An increase in the protein level of the AChE-R variant corresponded to a high AChE inhibition in CSF and favored less cognitive deterioration.

Similarities between CSF–brain extracellular transfer and neurofibrillary tangle invasion in Alzheimer's disease

Using the in vivo enzyme protection-enzyme inhibition method, we visualized the distribution of the intraventricularly and cisternally (cisterna magna) injected ambenonium chloride (Am) bound reversibly to the extracellular acetylcholinesterase enzyme (AChE) in the rabbit brain in order to describe the extracellular flow pathways from the cerebrospinal fluid (CSF). We found that the distribution of Am-protected AChE (indicating the Am itself) is similar to tracers having no intracerebral binding sites. The topographical distribution after both ways of application indicates a preferential penetration of Am into the limbic structures of the cerebral hemispheres in a predictable topographic sequence starting from the corticoid areas, allo- and periallo cortices followed by the mesocortical regions and then, in a limited extent, to the isocortex. The lentiform nuclei and the central part of diencephalic halves are inaccessible to Am. The hierarchic order in the sequence of diffusion from the CSF into the hemispheric subpial regions and the distribution pattern of Am resemble the stereotypic topographic expansion pattern and the predominantly limbic distribution of neurofibrillary tangles (NFTs) in Alzheimer's disease and related conditions.

Altered glycosylation of acetylcholinesterase in Creutzfeldt-Jakob disease

Changes in the glycosylation pattern of brain proteins have been associated with Creutzfeldt-Jakob disease (CJD). We have investigated the glycosylation status of acetylcholinesterase (AChE) by lectin binding assay. Our data show that in lumbar CSF from definite and probable sporadic CJD cases AChE activity is lower compared with that in age-matched controls. We also show, for the first time, that AChE glycosylation is altered in CJD CSF and brain. Unlike Alzheimer's disease, in which an alteration in both the glycosylation and levels of AChE molecular forms is observed, the abnormal glycosylation of AChE in CJD appears to be unrelated to changes in molecular forms of this enzyme. These findings suggest that altered AChE glycosylation in CJD may be a consequence of the general perturbation of the glycosylation machinery that affects prion protein, as well as other proteins. The diagnostic potential of these changes remains to be explored.

Long-lasting acetylcholinesterase splice variations in anticholinesterase-treated Alzheimer's disease patients

Protein levels of different acetylcholinesterase (AChE) splice variants were explored by a combination of immunoblot techniques, using two different antibodies, directed against the C-terminus of the AChE-R splice variant or the core domain common to all variants. Both AChE-R and AChE-S splice variants as well as several heavier AChE complexes were detected in brain homogenates from the parietal cortex of patients with or without Alzheimer's disease (AD) as well as the cerebrospinal fluid (CSF) of AD patients, compatible with the assumption that CSF AChEs might originate from CNS neurons. Long-term changes in the composition of CSF AChE variants were further pursued in AD patients treated with rivastigmine (n = 11) or tacrine (n = 17) in comparison to untreated AD patients (n = 5). In untreated patients, AChE-R was markedly reduced as compared with the baseline level (37%), whereas the medium size AChE-S complex was increased by 32%. Intriguingly, tacrine produced a general and profound up-regulation of all detected AChE variants (up to 117%), whereas rivastigmine treatment caused a mild and selective up-regulation of AChE-R ( approximately 10%, p < 0.05). Moreover, the change in the ratio of AChE-R to AChE-S (R/S-ratio) strongly and positively correlated with sustained cognition at 12 months (p < 0.0001). Thus, evaluation of changes in the composition of CSF AChE variants may yield important information referring to the therapeutic efficacy and/or development of drug tolerance in AD patients treated with anti-cholinesterases.

Decreased cerebrospinal fluid acetylcholinesterase in patients with subcortical ischemic vascular dementia

The main objective was to investigate the acetylcholinesterase E (AChE) activity in the cerebrospinal fluid (CSF) of patients with three common dementia disorders. We also wanted to investigate the influence of apolipoprotein E (ApoE) epsilon4 allele possession and CSF-tau level on the CSF-AChE activity in these patients. The study included 17 consecutive patients with subcortical vascular dementia (SVD), 39 with Alzheimer's disease (AD), 14 with frontotemporal dementia (FTD) and 12 controls. CSF was obtained by lumbar puncture and CSF-AChE activity was measured by an enzyme antigen immunoassay. CSF-AchE activity was significantly decreased compared to controls only in the SVD group (p = 0.010). The CSF-tau level was increased in the AD group compared to the control (p < 0.01) and FTD groups (p < 0.05). No influence of ApoE epsilon4 allele possession on CSF-AChE activity was found. It is suggested that abnormal CSF-AChE activity in patients with SVD reflects a disturbance in the cholinergic system.

Glycosylation of acetylcholinesterase and butyrylcholinesterase changes as a function of the duration of Alzheimer's disease

The identification of biochemical markers of Alzheimer's disease (AD) may help in the diagnosis of the disease. Previous studies have shown that Abeta(1-42) is decreased, and tau and phospho-tau are increased in AD cerebrospinal fluid (CSF). Our own studies have identified glycosylated isoforms of acetylcholinesterase (Glyc-AChE) and butyrylcholinesterase (Glyc-BuChE) that are increased in AD CSF. Glyc-AChE is increased in APP (SW) Tg2576 transgenic mice prior to amyloid plaque deposition, which suggests that Glyc-AChE may be an early marker of AD. The aim of this study was to determine whether Glyc-AChE or Glyc-BuChE is increased in CSF at early stages of AD and to compare the levels of these markers with those of Abeta(1-42), tau and phospho-tau. Lumbar CSF was obtained ante mortem from 106 non-AD patients, including 15 patients with mild cognitive impairment (MCI), and 102 patients with probable AD. Glyc-AChE, tau and phospho-tau were significantly increased in the CSF of AD patients compared to non-neurological disease (NND) controls. Abeta(1-42) was lower in the AD patients than in NND controls. A positive correlation was found between the levels of Glyc-AChE or Glyc-BuChE and disease duration. However, there was no clear correlation between the levels of tau, phospho-tau or Abeta(1-42) and disease duration. The results suggest that Glyc-AChE and Glyc-BuChE are unlikely to be early markers of AD, although they may have value as markers of disease progression.

Cerebrospinal fluid levels of biomarkers and activity of acetylcholinesterase (AChE) and butyrylcholinesterase in AD patients before and after treatment with different AChE inhibitors

In order to evaluate the biochemical effects of long-term treatment with inhibitors of acetylcholinesterase (AChE) in patients with Alzheimer's disease (AD), we measured the activities of AChE and butyrylcholinesterase (BuChe) and the concentrations of beta-amyloid (1-42), tau and phosphorylated tau proteins in the cerebrospinal fluid (CSF). A total of 91 patients suffering from probable AD of mild to moderate degree were treated for 6 months with donepezil (n=59), galantamine (n=15), rivastigmine (n=10), or placebo (n=7). AChE activity in CSF was significantly increased after treatment with donepezil and galantamine; the opposite was observed in the rivastigmine-treated group. Untreated patients did not show any AChE activity variation. BuChE did not show any change in any of the groups studied. Mean values of beta-amyloid(1-42), total tau and phosphorylated tau also did not vary significantly. We conclude that AChE inhibitors induce different effects on CSF AChE activity, while other CSF biomarkers are not significantly affected by treatment.

Sustained cholinesterase inhibition in AD patients receiving rivastigmine for 12 months

OBJECTIVE

To study the long-term dual inhibitory effects of rivastigmine on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in patients with AD.

METHODS

Eleven patients with mild AD received rivastigmine for 12 months. Cholinesterase (ChE) activities in the CSF and plasma were assessed colorimetrically. Immunoblot analysis was used to evaluate AChE isoforms. Neuropsychiatric tests were performed throughout the study.

RESULTS

At 12 months, the mean dose of rivastigmine was 8.6 mg/d and specific activities of ChE in the CSF were lower than baseline values (by 36% for AChE and 45% for BuChE), correlating with parallel reductions in the plasma (27% for AChE and 33% for BuChE). The reduction of specific activities in the CSF, but not in the plasma, appeared to be dependent on the dose and duration of treatment. Scores of some of the neuropsychological tests associated with memory and attention were correlated with both plasma and CSF AChE and BuChE inhibition for up to 6 months. Immunoblot analysis revealed up-regulation of the "read-through" AChE isoform (AChE-R), whereas levels of the synaptic isoform were unchanged.

CONCLUSIONS

Rivastigmine causes persistent inhibition of AChE and BuChE in CSF as well as plasma. The persistent CSF inhibition contrasts with earlier findings after long-term treatment by the reversible ChE inhibitor tacrine, which demonstrated increased AChE activity in the CSF but not in the blood. Rivastigmine's effects on the preferential up-regulation of the AChE-R isoform may have a favorable effect on disease stabilization.

Inhibition of acetyl- and butyryl-cholinesterase in the cerebrospinal fluid of patients with Alzheimer's disease by rivastigmine: correlation with cognitive benefit

Cholinesterase (ChE) inhibition represents the most efficacious treatment approach for Alzheimer's disease (AD) to date. This multiple-dose study has examined the relationship between inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities in the cerebrospinal fluid (CSF) and cognitive change (measured by the Computerised Neuropsychological Test Battery [CNTB]) following administration of the ChE inhibitor, rivastigmine (Exelon). In 18 patients with mild to moderate AD, CNTB scores, activities of AChE and BuChE in the CSF, and plasma BuChE activity were determined prior to treatment with rivastigmine. Doses of rivastigmine were then titrated (1 mg b.i.d./week) to final doses of 1, 2, 3, 4, 5 or 6 mg b.i.d. (n = 3 per dose). Following treatment with the target dose of rivastigmine for at least 3 days, CNTB scores were re-determined. CSF samples were continuously collected together with plasma samples prior to and for 12 hours after the final dose of rivastigmine, and AChE and BuChE activities determined.AChE in CSF and BuChE in plasma were dose-dependently inhibited by rivastigmine treatment. The inhibition of BuChE in CSF was not clearly dose-dependent. A statistically significant correlation was observed between the change in CNTB summary score and inhibition of AChE activity (r = -0.56, p < 0.05) and BuChE activity (r = -0.65, p < 0.01) in CSF. Improvement in speed-, attention- and memory-related subtests of the CNTB correlated significantly with inhibition of BuChE but not AChE activity in CSF. Weak or absent correlation with change in cognitive performance was noted for inhibition of plasma BuChE. These results indicate that cognitive improvement with rivastigmine in AD is associated with central inhibition of ChEs and support a role for central BuChE in addition to AChE inhibition in modulating cholinergic function in AD.

Changes in molecular isoform distribution of acetylcholinesterase in rat cortex and cerebrospinal fluid after intracerebroventricular administration of amyloid beta-peptide

Previous studies have shown that an abnormal salt-soluble form of G(1) acetylcholinesterase (AChE) is increased in the Alzheimer's disease (AD) brain. The aim of the present study was to examine changes in AChE activity in an in vivo model of beta-amyloid peptide (A beta) administration. Rats received intracerebroventricular injections of A beta(25-35) (20 microg/day for seven days). Levels of AChE were measured in cerebral cortex and cerebrospinal fluid (CSF) after two months. A beta(25-35) administration did not alter total AChE activity in the cerebral cortex or CSF. However, analysis of salt-extractable AChE isoforms revealed an increase in the proportion of G(1) in both cortex and CSF, similar to that previously observed in AD patients. The results support the view that changes in AChE isoform pattern in the AD brain are a direct consequence of A beta accumulation.

[Blood-cerebrospinal fluid barrier function and cholinesterase activity in cerebrospinal fluid in degenerative changes of the lumbar spine]

The objective of this study was to determine whether spinal compression associated with degenerative changes of the lumbar vertebral column induces significant alteration in defined cerebrospinal fluid parameters. Serum and lumbar cerebrospinal fluid were studied in 62 patients and 47 age-matched controls. Patients were grouped according to neurologic status, duration of symptoms, and findings in magnetic resonance imaging. Statistically significant elevations in cerebrospinal fluid/serum albumin ratio, acetylcholinesterase, butyrylcholinesterase activity, and total protein concentration were observed in lumbar cerebrospinal fluid of patients. Patients with neurologic deficits did not exhibit significant differences in cerebrospinal fluid parameters compared with patients lacking neurologic signs. No significant differences were detectable between lateral and medial compression. Acute disk herniation led to practically the same biochemical changes as chronic compression. Biochemical analysis of lumbar cerebrospinal fluid offers additional diagnostic information in patients suffering from back or leg pain associated with degenerative changes of the spine. Pathological damage to meningeal and neural tissues can be demonstrated even if neurologic signs or obvious spinal compression are missing in the radiological examination. An elevated cerebrospinal fluid/serum albumin ratio reflects alteration of the blood/cerebrospinal fluid barrier status. Increased acetylcholinesterase and butyrylcholinesterase activity point to pathophysiological impairment of neural tissues or meninges.

Inositol monophosphatase activity in normal, Down syndrome and dementia of the Alzheimer type CSF

Inositol monophosphatase (IMPase), a cytoplasmic enzyme that hydrolyses inositol monophosphates to produce inositol is also found in the cerebrospinal fluid (CSF). Since levels of inositol have been previously reported to be elevated in Down syndrome (DS) CSF, IMPase activity was measured in CSF of DS subjects to establish whether altered inositol levels may be related to changes in IMPase activity. In addition, and to better understand the regulation of IMPase expression in the CSF, enzyme activity was measured in normal aging, patients with Alzheimer-type or multi-infarct dementia (DAT and MID, respectively) and in CSF obtained by repeat lumbar puncture or from sequential aliquots of CSF from along the rostro-caudal axis. IMPase activity was relatively constant in CSF obtained from repeated lumbar puncture and there was no significant rostro-caudal gradient of activity in either normal or DS subjects, indicating that the enzyme originates from both brain and spinal cord. Compared to respective age-matched normal subjects, CSF IMPase activity was unaltered in DS, DAT and MID. However, in normal volunteers there was a significant positive correlation between age and CSF IMPase activity. Furthermore, there were significant correlations between CSF IMPase activity and acetylcholinesterase and butyrylcholinesterase activities and total protein, suggesting co-regulation of these parameters within the CSF.

Frequent blood-brain barrier disruption in the human cerebral cortex

1. The blood-brain barrier (BBB) protects the brain from circulating xenobiotic agents. The pathophysiology, time span, spatial pattern, and pathophysiological consequences of BBB disruptions are not known. 2. Here, we report the quantification of BBB disruption by measuring enhancement levels in computerized tomography brain images. 3. Pathological diffuse enhancement associated with elevated albumin levels in the cerebrospinal fluid (CSF) was observed in the cerebral cortex of 28 out of 43 patients, but not in controls. Four patients displayed weeks-long focal BBB impairment. In 19 other patients, BBB disruption was significantly associated with elevated blood pressure, body temperature, serum cortisol, and stress-associated CSF 'readthrough" acetylcholinesterase. Multielectrode electroencephalography revealed enhanced slow-wave activities in areas of focal BBB disruption. Thus, quantification of BBB disruption using minimally invasive procedures, demonstrated correlations with molecular, clinical, and physiological stress-associated indices. 4. These sequelae accompany a wide range of neurological disorders, suggesting that persistent, detrimental BBB disruption is considerably more frequent than previously assumed.

Cerebrospinal fluid acetylcholinesterase activity after long-term treatment with donepezil and rivastigmina

At present acetylcholinesterase (AChE) inhibitors (AChEIs) represent the only reliable therapeutic resource for symptomatic treatment of Alzheimer Disease (AD). This study was designed to assess the effects of 6-12 month treatment with AChEIs donepezil and rivastigmine on cerebrospinal fluid (CSF) AChE and butyrylcholinesterase (BuChE) activity in AD patients. The pattern of AChE isoforms (G4, G1, G2) before and after treatment was investigated as well. In AD patients treated with donepezil a significant increase of CFS AChE activity was observed, whereas treatment with rivastigmine induced a significant decrease of AChE activity. Both drugs did not change BuChE activity and tended to restore the physiological pattern of AChE isoform. The possible significance of the influence of AChEIs on CSF AChE activity and isoforms is discussed.

Acetylcholinesterase in Alzheimer's disease

Since the discovery of the cholinergic deficit in Alzheimer disease (AD), acetylcholinesterase (AChE) has been widely investigated in tissues involved in the disease. These studies showed modifications in AChE activity and changes in its polymorphism in brain as well as in cerebro-spinal fluid (CSF) and blood. The co-localization of the enzyme in the senile plaque provided evidence of its anomalous features. It has been also shown that AChE forms a stable complex with senile plaque components through its peripheral anionic site. Moreover, the neurotoxicity of amyloid components is increased by the presence of AChE. The occurrence of an altered glycosylation of some AChE forms in AD is closely related to the presence of amyloid formations. Literature on expression, relationships and modifications in the molecular polymorphism of AChE, in brain, CSF and blood in AD is reviewed.

Pharmacokinetic-pharmacodynamic modeling of rivastigmine, a cholinesterase inhibitor, in patients with Alzheimer's disease

Rivastigmine is a cholinersterase inhibitor approved recently for the treatment of Alzheimer's disease (AD). The objective of this study is to characterize the pharmacokinetics-pharmacodynamics of rivastigmine in patients with AD. Eighteen AD patients received doses ranging from 1 to 6 mg bid for about 11 weeks. Rivastigmine and its active (major) metabolite (ZNS 114-666, also called NAP 226-90), plasma, and cerebrospinal fluid (CSF) concentrations were determined together with the AChE activity and computerized neuropsychological test battery (CNTB) scores. Nonlinear mixed-effects modeling of pharmacokinetic and pharmacodynamic data was conducted using NONMEM. Rivastigmine and its metabolite exhibited dose-disproportional pharmacokinetics. The apparent clearance and volume of distribution (plasma) of rivastigmine were estimated to be 120 L/h and 236 L, respectively. The relative bioavailability at the 6 mg dose was about 140%. The metabolite had a clearance of about 100 L/h and a volume of distribution of 256 L. The kinetics of the parent and metabolite in CSF showed an equilibration half-life of about 0.2 and 0.5 hours, respectively. The metabolite levels in CSF correlated very well with the acetylcholinesterase inhibition, with a ZNS 114-666 concentration of about 5.4 microg/L required for half-maximal inhibition of acetylcholinesterase activity. No statistically significant correlation of the CNTB scores with enzyme inhibition, parent or metabolite concentration (plasma/CSF), or rivastigmine dose could be established. The PK-PD model presented in this study can provide valuable information to optimize the drug development of rivastigmine and other related compounds and also in rationalizing dosing recommendations.

An unusually glycosylated form of acetylcholinesterase is a CSF biomarker for Alzheimer's disease

The identification of a biochemical marker of Alzheimer's disease (AD) is a major research aim of many groups. Abnormal levels of tau and Abeta have been identified in the cerebrospinal fluid (CSF) of AD patients, although the sensitivity and specificity of the changes in these two biomarkers alone is not sufficient to be of diagnostic value. Recently, our group has identified an abnormality in the glycosylation of acetylcholinesterase (AChE). The increase in this glycoform of AChE is very specific for Alzheimer's disease and is not seen in many other neurological diseases including other dementias.

Differential increase in cerebrospinal fluid-acetylcholinesterase after treatment with acetylcholinesterase inhibitors in patients with Alzheimer's disease

The clinical significance and the effects of pharmacological treatment of patients with Alzheimer's disease (AD) were evaluated by measurement of acetylcholinesterase (AChE) in the cerebrospinal fluid (CSF). CSF-AChE of AD patients was lower, not significantly, compared with controls. However, CSF-AChE was significantly increased after treatment of AD patients with AChE inhibitors (donepezil and galantamine). The increase was higher in patients treated with donezepil than in those treated with galantamine, which might be related to different mechanisms for the substances. The increase was also dose-dependent, and was especially marked in patients showing a clinical response. These data suggest that CSF biomarkers are capable not only of identifying a biochemical effect of drugs, but also of differentiating between different compounds in a dose-dependent manner.

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.

Altered glycosylation of acetylcholinesterase in lumbar cerebrospinal fluid of patients with Alzheimer's disease

As clinical diagnosis of Alzheimer's disease is only 80%-90% accurate, there is a need to identify biochemical markers of Alzheimer's disease. Previous studies have shown an abnormality in the glycosylation of acetylcholinesterase (AChE) in the CSF collected postmortem from patients with Alzheimer's disease. This abnormality was very specific for Alzheimer's disease, as it was not detected in other illnesses causing dementia. We report here that the glycosylation of AChE is also altered in lumbar CSF collected antemortem. The altered glycosylation was due to increased concentrations of a minor AChE isoform that does not bind to concanavalin A (Con A). Glycosylation of AChE may eventually be of diagnostic value, especially when used in combination with other CSF markers.

The recovery of cerebrospinal fluid acetylcholinesterase activity in Alzheimer's disease patients after treatment with metrifonate

We investigated the relationship between peripheral and central cholinesterase (ChE) inhibition levels after chronic treatment of Alzheimer's disease (AD) patients with metrifonate (MTF). In a 6-month, double-blind, placebo-controlled trial in AD patients treated with a weekly 2.9 mg/kg MTF dose, we observed 17.15 +/- 23.43, 66.92 +/- 7.30 and 60.80 +/- 12.20% inhibition (n = 6) of cerebrospinal fluid (CSF) and red blood cell (RBC) acetylcholinesterase (AChE) and plasma butyrylcholinesterase (BuChE), respectively. In another study, AD patients were treated with daily MTF to achieve RBC AChE inhibition levels of 85.90%. The CSF AChE inhibition was 67.93 +/- 13.69% (n = 3) at 3-4 h after the last treatment and 6.62 +/- 9.36% (n = 2) at 8 days after dosing. The recovery half time of CSF AChE was 2.21 +/- 1.22 days. These data show that CSF AChE recovers faster than the peripheral plasma and RBC enzymes. Under conditions of chronic weekly dosing with MTF, RBC AChE inhibition does not reflect CSF, and arguably, brain AChE inhibition. Our data do not support continuous central neuronal AChE inhibition as the mechanism for the long-term efficacy of metrifonate for the treatment of AD.

Preferential cerebrospinal fluid acetylcholinesterase inhibition by rivastigmine in humans

This study sought to examine the feasibility of prolonged assessment of acetylcholinesterase (AChE) activity in the cerebrospinal fluid (CSF) of volunteers and to test the hypothesis that rivastigmine (ENA-713; Exelon, Novartis Pharma AG, Basel, Switzerland) selectively inhibits AChE in CSF in humans at a dose producing minimal inhibition of the peripheral enzyme. Lumbar CSF samples were collected continuously (0.1 mL x min(-1)) for 49 hours from eight healthy volunteers who took either placebo or a single oral dose of rivastigmine (3 mg). CSF specimens and samples of blood cells and blood plasma were analyzed at intervals for rivastigmine and its metabolite NAP 226-90 ([-] [3-([1-dimethylaminolethyl)-phenol]), erythrocyte AChE activity, CSF AChE activity, and plasma and CSF butyrylcholinesterase (BuChE) activity. Safety evaluations were performed 23 hours after drug dosing and at the end of the study. Evaluable data were obtained from six subjects. The mean time to maximal rivastigmine plasma concentration (tmax) was 0.83 +/- 0.26 hours, the mean maximal plasma concentration (Cmax) was 4.88 +/- 3.82 ng x mL(-1), the mean plasma area under the concentration versus time curve (AUC0-infinity) was 7.43 +/- 4.74 ng x hr x mL(-1), and the mean plasma t1/2 was 0.85 +/- 0.115 hours. The concentration of rivastigmine in CSF was lower than the quantification limit for assay (0.65 ng x mL(-1)), but NAP 226-90 reached a mean Cmax of 3.14 +/- 0.57 ng x mL(-1). Only minimal inhibition of erythrocyte AChE activity (approximately 3%) was observed. Inhibition of AChE in the CSF after rivastigmine administration was significantly greater than after placebo for up to 8.4 hours after the dose and was maximal (40%) at 2.4 hours. Plasma BuChE activity was significantly lower after rivastigmine than after placebo, but this was not clinically relevant. BuChE activity in CSF was significantly lower after rivastigmine than after placebo for up to 3.6 hours after dosing, but this difference was not sustained. This study confirms the feasibility of using continuous measurement of AChE activity in CSF over prolonged periods, that rivastigmine markedly inhibits CSF AChE after a single oral dose of 3 mg, and that the inhibition of central AChE is substantially greater than that of peripheral AChE or BuChE.

Neurochemistry and delirium

Acute confusional state or delirium is one of the most common organic brain syndromes especially in the elderly. It develops suddenly, within hours or days, and often during a period of hospitalization. In this paper we review the results of our studies on the neurochemistry of delirium.

Cytotoxic activity of serum and cerebrospinal fluid of amyotrophic lateral sclerosis (ALS) patients against acetylcholinesterase

The activity of acetylcholinesterase (AChE) was tested in serum of 20 cases of amyotrophic lateral sclerosis (ALS), 4 "disease controls" and 20 age-matched healthy normals. The AChE activity has been tested also in cerebrospinal fluid (CSF) of 20 ALS patients, 2 "disease controls" and 10 normal subjects. An increase in serum AChE was present in the majority of ALS patients with a mild course of the disease, in the severe ALS group elevated serum AChE activity was a rare finding. Serum ACHE was also increased in multifocal motor neuropathy (MMN). In the majority of mild and severe ALS the CSF AChE activity was decreased. No AChE changes were found in CSF of the "disease controls". Serum and CSF ultrafiltrates of ALS patients and "disease controls" were modifying in vitro the spinal cord AChE activity. In the mild ALS group serum and CSF ultrafiltrates with high molecular weight compounds were decreasing the AChE activity. On the other hand in the severe ALS group serum and CSF ultrafiltrates with low molecular weight compounds were increasing the AChE activity. AChE was modified also in some of the "disease controls", especially in MMN and Guillain-Barré syndrome (GBS) by serum ultrafiltrates containing high molecular weight compounds. The AChE activity in serum and CSF is the consequence of the enzyme leakage from brain, degenerating cholinergic neurons and neuromuscular junctions. We suggest that because of the evoked peripherally divergent changes of the enzyme activity, the AChE values in serum and CSF in ALS do not equal to the degree of the changes in the affected tissues and cannot be taken into account in the prognosis of the disease in particular ALS cases.

[Alterations in neurotransmitter, amino acid and free radical related substances in cerebrospinal fluid in patients with cerebrovascular diseases]

Acetylcholinesterase (AChE), choline, monoamine and its metabolite, amino acid and superoxide dismutase (SOD) levels were measured in cerebrospinal fluid (CSF) in patients with cerebrovascular diseases. Patients were classified into the following four groups; controls: normal subjects without neurological disease, group A: cerebral hemorrhage, group B: cerebral infarction, group C: patients with mental impairment, including those in groups A and B, and a low score on Hasegawa's Dementia Rating Scale. CSF AChE level of groups A, B and C was decreased significantly, while choline concentration from patients showed a increase compared with that of control cases. CSF alanine concentration showed a tendency to increase, while glycine and glutamate tended to decrease. CSF epinephrine, norepinephrine or 3-methoxy-4-hydroxyphenylethylen glycol concentrations of groups A, B and C did not exhibit a significant difference from that in control cases. Some cases with cerebrovascular diseases showed low concentrations of both CSF 5-hydroxyindole acetic acid and homovanillic acid. However, dihydroxyphenyl acetic acid concentration was higher than in control cases. The CSF SOD level was not significantly from that in control cases. The changes in neurochemical substances in the CSF support their use as markers of cerebrovascular disease-related change.

Molecular isoform distribution and glycosylation of acetylcholinesterase are altered in brain and cerebrospinal fluid of patients with Alzheimer's disease

The glycosylation of acetylcholinesterase (AChE) in CSF was analyzed by lectin binding. AChE from Alzheimer's disease (AD) patients was found to bind differently to two lectins, concanavalin A and wheat germ agglutinin, than AChE from controls. As multiple isoforms of AChE are present in both CSF and brain, we examined whether the abnormal glycosylation of AD AChE was due to changes in a specific molecular isoform. Globular amphiphilic dimeric (G2a) and monomeric (G1a) isoforms of AChE were found to be differentially glycosylated in AD CSF. Glycosylation of AChE was also altered in AD frontal cortex but not in cerebellum and was also associated with an increase in the proportion of light (G2 and G1) isoforms. This study demonstrates that the glycosylation of AChE is altered in the AD brain and that changes in AChE glycosylation in AD CSF may reflect changes in the distribution of brain isoforms. The study also suggests that glycosylation of AChE may be a useful diagnostic marker for AD.

An inhibitor-free assay of acetylcholinesterase and butyrylcholinesterase in the cerebrospinal fluid

An inhibitor-free assay for the simultaneous determination of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in the cerebrospinal fluid (CSF) is described. It is based on our finding that the individual activity ratios of BChE on both its substrates acetylthiocholine (ACh) and butyrylthiocholine (BCh) in the CSF and in the parallel serum are identical under conditions of at least 5 mmol/l substrate concentration (Q(BChE)SE = Q(BChe)CSF). Considering that AChE only reacts with ACh as substrate and occurs with negligible activities in the serum, the measured individual activity ratio of BChE in the serum (Q(BChE)SE) and the total hydrolysis rate of ACh and BCh in the CSF do allow a precise calculation of the AChE activity in the cerebrospinal fluid. The derivation of the corresponding formula is demonstrated in detail. The inhibitor-free assay was compared with procedures using cholinesterase inhibitors (BW284c51 for AChE and/or iso-OMPA for BChE). Achieving widely identical results in particular between the procedure using the AChE inhibitor and the inhibitor-free test, the latter has decisive advantages: (1) it avoids the use of highly toxic inhibitors, (2) it minimizes the test volume needed, (3) it characterizes additionally the status of the blood-CSF barrier by means of the BChE activity ratio in the CSF and in the parallel serum.

Cerebrospinal fluid cholinesterases--markers for loss of cholinergic basal forebrain neurons?

The present study was conducted to test the hypothesis that cholinergic basal forebrain neurons are a major source of cerebrospinal fluid (CSF) cholinesterases. To address this question enzyme activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in both CSF and parietal cortex were assayed following selective lesion of basal forebrain cholinergic neurons by a single intracerebroventricular application of the cholinergic immunotoxin 192IgG-saporin. Cholinergic immunolesions led to a dramatic decrease in total AChE activity in parietal cortex, which was due to the specific loss of the G4 molecular form while the activity of the G1 form was increased as compared to nonlesioned animals. In contrast, the total enzyme activity of BChE and its molecular forms were not affected by cholinergic lesion in both parietal cortex and CSF. The data suggest, that cholinergic basal forebrain neurons are seemingly not a major source of cholinesterases in the CSF, and do not provide any evidence for using CSF cholinesterases as a diagnostic marker of basal forebrain cholinergic cell loss in humans.

CSF cholinesterase activity in demented and non-demented subjects

Samples of cerebrospinal fluid (CSF) were examined, looking mainly at total cholinesterase (ChE) and acetyl-cholinesterase (AChE) levels from 139 living subjects. At the completion of the study, 35 of the 139 patients had died and pathological confirmation of the presence of dementia had been obtained. These results, together with results from other laboratories, provide evidence that a low CSF ChE level presenting in demented patients may indicate a depletion of the brain AChE system, and this may confirm a clinical diagnosis of AD as well as other types of dementia which are associated with an alteration of the brain AChE system. The overlap in the levels of CSF biochemical markers between demented and non-demented subjects which has led to many conflicting reports has always disappointed investigators. It is suggested that some 'control' subjects with CSF ChE activity indistinguishable from that in AD patients may have an abnormal ageing process in their brains (brain at risk), although the symptoms of dementia have not yet been detected. Recognition of a pre-clinical or incubation period is very beneficial for explaining discrepancies in biochemistry and pathology in the literature, and must be considered for both the treatment and the prevention of dementia. The long used treatment, which was designed to inhibit AChE, should no longer be used: treatment must be designed to enhance the activity of the neuronal AChE system, or slow its degeneration.

An CSF anamalous molecular form of acetylcholinesterase in demented and non-demented subjects

Analysis of 139 CSF samples from living subjects, using iso-electric focusing in polyacrylamide gels, demonstrated an anomalous molecular form of acetylcholinesterase (AChE). This form was present in 84 of 87 patients with a clinical diagnosis of Alzheimer's disease (AD), 28 of whom have died and in whom histopathological confirmation of AD was obtained. The abnormal AChE form was also present in 22 of 23 patients with clinical dementia not regarded as AD type. In the six patients who died this abnormal AChE form was found in three cases of multi-infarct dementia, one with cerebral glioma with dementia and one with clinical dementia, but no pathology was found based on the Khachaturian criteria for AD. One patient with normal pressure hydrocephalus was negative when tested for the abnormal AChE form. This evidence indicates that the anomalous molecular form of AChE may not be specific for AD, and may possibly be a common indicator for organic dementia. The discovery of this form in 27 of 29 age-matched non-demented controls may indicate that the anomalous molecular form of AChE may not only exist in patients with clinically detectable dementia, but is probably present for a period before the onset of dementia. Recognizing and understanding the existence of pre-clinical dementia would be beneficial in designing a strategy for both the prevention and the treatment of dementia.

Biochemical properties of acetyl- and butyrylcholinesterase in human meningioma

The structural properties of acetyl-(AChE) and butyrylcholinesterase (BuChE) in meningioma and the possible relationship with brain and plasma were investigated. Meningioma ChEs were extracted with saline and saline-Triton X-100 buffers. The tumor ChE forms were identified by sedimentation analysis, and their amphiphilic/hydrophilic behaviour was assessed by Triton X-114 phase-partitioning and hydrophobic chromatography. Meningioma contained amphiphilic globular AChE dimers (G2A) and monomers (G1A), and hydrophilic BuChE tetramers (G4H). The conversion of G2A into G1A AChE by reduction confirmed their structures. In contrast to the meningioma species, brain G1A AChE forms remained amphiphilic after incubation with alkaline hydroxylamine and phosphatidylinositol-specific phospholipase C (PIPLC). Meningioma G1A and PIPLC-converted G1H, and brain G1A AChE showed similar rate constants for thermal inactivation, and this suggested that the thermal stability of AChE subunits was unaffected by the presence or not of phosphatidylinositol residues. AChE in meningioma and brain did not differ in the interaction with the lectins Con A, LCA, WGA and RCA. BuChE in meningioma and brain bound to a similar extent to Con A, LCA and WGA-Agarose, whereas one-half of BuChE in the tumor, all in plasma and little in brain was fixed by RCA. Therefore, meningioma possesses RCA(+)- and RCA(-)-BuChE, the former predominating in brain and the latter in plasma. It remains to be clarified whether the tumor RCA(+)-BuChE is intrinsic or derived from plasma.

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.

Laboratory examinations correlated with severity of dementia

Acetylcholine esterase, alpha 1-antichymotrypsin, homovanillic acid (HVA), 3-methoxy-4-hydroxy-phenylenglycol (MHPG), norepinephrine, dopamine, 5-hydroxy-indolacetic acid (5-HIAA), and gamma-aminobutyric acid (GABA) in the serum and cerebrospinal fluid (CSF) were quantified. Positive wave with the latency about 300 msec (P300) and electroencephalography (EEG) were examined in 10 patients with Alzheimer's disease, 10 patients with vascular dementia, and 10 age-matched healthy controls. Serum alpha 1-antichymotrypsin concentrations were significantly higher in the Alzheimer's disease group than in the vascular dementia and healthy control groups. Homovanillic acid concentrations in CSF were significantly lower in the vascular dementia group than in the Alzheimer's disease and the healthy control groups. A significant positive correlation was present between the mini-mental state examination (MMSE) score (normal range of 24 to 30) and the acetylcholine esterase concentration in the CSF. Significant negative correlations were present between the MMSE score and the P300 latency, between the MMSE score and the MHPG concentration in the CSF, between the MMSE and the norepinephrine concentration in the CSF, and between the MMSE score and the dopamine concentration in the CSF.

Increased acetylcholinesterase activity in the CSF of Alzheimer patients carrying apolipoprotein epsilon4 allele

We measured CSF acetylcholinesterase (AChE) activity in 57 Alzheimer's disease (AD) patients with different apolipoprotein E (apoE) genotypes at the early stage of the disease, and in 11 non-demented controls. The AChE activities of the whole AD group did not differ from those of controls. However, analysis of variance over the AD subgroups with two, one or no epsilon4 alleles and controls showed significant differences (p < 0.0001); the AD patients with two epsilon4 alleles had higher AChE activities than controls and AD patients with one or no epsilon4 and also the AD patients carrying one epsilon4 allele had higher AChE activities than the AD patients without the epsilon4 allele. The study suggests that cholinergic metabolism is altered in proportion to the number of apoE epsilon4 alleles. The different degree of AChE activity in relation to the number of epsilon4 alleles might have an impact on AD patients' responses to cholinesterase inhibitors.