CSF acetylcholinesterase in Parkinson disease: decreased enzyme activity and immunoreactivity in demented patients

Cerebrospinal fluid biochemical studies in patients with Parkinson's disease: toward a potential search for biomarkers for this disease

The blood-brain barrier supplies brain tissues with nutrients and filters certain compounds from the brain back to the bloodstream. In several neurodegenerative diseases, including Parkinson's disease (PD), there are disruptions of the blood-brain barrier. Cerebrospinal fluid (CSF) has been widely investigated in PD and in other parkinsonian syndromes with the aim of establishing useful biomarkers for an accurate differential diagnosis among these syndromes. This review article summarizes the studies reported on CSF levels of many potential biomarkers of PD. The most consistent findings are: (a) the possible role of CSF urate on the progression of the disease; (b) the possible relations of CSF total tau and phosphotau protein with the progression of PD and with the preservation of cognitive function in PD patients; (c) the possible value of CSF beta-amyloid 1-42 as a useful marker of further cognitive decline in PD patients, and (d) the potential usefulness of CSF neurofilament (NFL) protein levels in the differential diagnosis between PD and other parkinsonian syndromes. Future multicentric, longitudinal, prospective studies with long-term follow-up and neuropathological confirmation would be useful in establishing appropriate biomarkers for PD.

Diagnostic cerebrospinal fluid biomarkers for Parkinson's disease: a pathogenetically based approach

The inaccuracy of the early diagnosis of Parkinson's disease (PD) has been a major incentive for studies aimed at the identification of biomarkers. Brain-derived cerebrospinal fluid (CSF) proteins are potential biomarkers considering the major role that proteins play in PD pathogenesis. In this review, we discuss the current hypotheses about the pathogenesis of PD and identify the most promising candidate biomarkers among the CSF proteins studied so far. The list of potential markers includes proteins involved in various pathogenetic processes, such as oxidative stress and protein aggregation. This list will undoubtedly grow in the near future by application of CSF proteomics and subsequent validation of identified proteins. Probably a single biomarker will not suffice to reach high sensitivity and specificity, because PD is pathogenetically heterogeneous and shares etiological factors with other neurodegenerative diseases. Furthermore, identified candidate biomarkers will have to be thoroughly validated before they can be implemented as diagnostic aids.

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).

Acetylcholinesterase assay for cerebrospinal fluid using bupivacaine to inhibit butyrylcholinesterase

BACKGROUND

Most test systems for acetylcholinesterase activity (E.C.3.1.1.7.) are using toxic inhibitors (BW284c51 and iso-OMPA) to distinguish the enzyme from butyrylcholinesterase (E.C.3.1.1.8.) which occurs simultaneously in the cerebrospinal fluid. Applying Ellman's colorimetric method, we were looking for a non-toxic inhibitor to restrain butyrylcholinesterase activity. Based on results of previous in vitro studies bupivacaine emerged to be a suitable inhibitor.

RESULTS

Pharmacokinetic investigations with purified cholinesterases have shown maximum inhibition of butyrylcholinesterase activity and minimal interference with acetylcholinesterase activity at bupivacaine final concentrations between 0.1 and 0.5 mmol/l. Based on detailed analysis of pharmacokinetic data we developed three equations representing enzyme inhibition at bupivacaine concentrations of 0.1, 0.2 and 0.5 mmol/l. These equations allow us to calculate the acetylcholinesterase activity in solutions containing both cholinesterases utilizing the extinction differences measured spectrophotometrically in samples with and without bupivacaine. The accuracy of the bupivacaine-inhibition test could be confirmed by investigations on solutions of both purified cholinesterases and on samples of human cerebrospinal fluid. If butyrylcholinesterase activity has to be assessed simultaneously an independent test using butyrylthiocholine iodide as substrate (final concentration 5 mmol/l) has to be conducted.

CONCLUSIONS

The bupivacaine-inhibition test is a reliable method using spectrophotometrical techniques to measure acetylcholinesterase activity in cerebrospinal fluid. It avoids the use of toxic inhibitors for differentiation of acetylcholinesterase from butyrylcholinesterase in fluids containing both enzymes. Our investigations suggest that bupivacaine concentrations of 0.1, 0.2 or 0.5 mmol/l can be applied with the same effect using 1 mmol/l acetylthiocholine iodide as substrate.

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.

Somatostatin-like immunoreactivity, its molecular forms and monoaminergic metabolites in aged and demented patients with Parkinson's disease--effect of L-Dopa

There is some evidence that Parkinson's disease (PD) seems to be a heterogenous and generalized brain disorder reflecting a degeneration of multiple neuronal networks, including somatostatinergic neurons. Somatostatin-like immunoreactivity (SLI) and its molecular forms, high molecular weight form (HMV-SST), somatostatin-14 (SST-14), somatostatin-25/28 (SST-25/28) and Des-ala-somatostatin (Des-ala-SST), as well as homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were estimated using HPLC and radioimmunoassay in the cerebrospinal fluid (CSF) of 35 aged parkinsonian patients with different stages of intellectual deterioration. The influence of L-dopa-treatment on these neurochemical parameters was evaluated. Without a correlation with dementia scores (p = 0.11), SLI was significantly reduced in PD in comparison to the control group (p < 0.05). The reduction was related to the progression of the disease. Correlations between SLI, HVA and 5-HIAA indicate a heterogenous brain disorder in PD with alterations of several transmitter systems and functions. Complex qualitative and quantitative changes in the molecular pattern of SLI are compatible with a dysregulated synthesis and/or posttranslational processing. L-dopa-treatment was associated with a significant increase of HVA (p < 0.05) and HMV-SST (p < 0.05) and a slight, but insignificant increase of SLI (p = 0.11).