Blood markers in Alzheimer disease: subnormal acetylcholinesterase and butyrylcholinesterase in lymphocytes and erythrocytes

Blood acetylcholinesterase level is a potential biomarker for the early detection of cerebral amyloid deposition in cognitively normal individuals

Cerebral β-amyloid (cAβ) deposition and cholinergic dysfunction have been considered as major pathological and functional hallmarks of Alzheimer's disease (AD). Acetylcholinesterase (AChE) is one of the major cholinergic enzymes, and there is no report to show the relationship between cAβ accumulation and peripheral AChE alteration in early stage of AD pathogenesis. Recent studies demonstrate that cAβ starts to deposit 15-20 years ahead of symptomatic appearance and this preclinical AD is important for early diagnosis of disease. In this study, we investigated the link between cAβ deposition and the peripheral AChE in cognitively normal (CN) individuals. A total of 407 individuals who underwent Pittsburgh compound B (PiB)-positron emission tomography participated in our study. Lower levels of plasma AChE and its enzymatic activity were detected in CN individuals with cAβ deposition than in those without cAβ. Plasma AChE levels and enzymatic activity were negatively correlated with the degree of cAβ deposition. Our results suggest that blood AChE can be used as a potential blood biomarker for the prediction of cAβ deposition in CN individuals.

Low Plasma Cholinesterase Activities are Associated with Deficits in Spatial Orientation, Reduced Ability to Perform Basic Activities of Daily Living, and Low Body Mass Index in Patients with Progressed Alzheimer's Disease

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder characterized by a central cholinergic deficit. Non-neuronal cholinergic changes are, however, described as well. Here we focused on possible changes in the activity of the plasma cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), in hospitalized AD patients. We analyzed plasma AChE and BChE activities with regards to age, gender, body mass index (BMI), cognitive functions, and ability to perform activities of daily living in AD patients in comparison to healthy subjects. We observed lower AChE activity and trend toward lower BChE activity in AD patients, which both correlated with low BMI. AD patients unable to perform basic activities of daily living (feeding, bathing, dressing, and grooming) showed reduced plasma AChE activities, while worse spatial orientation was linked to lower BChE activities. Three out of four AD patients with the lowest BChE activities died within one year. In conclusion, progressed AD was accompanied by lower plasma AChE activity and trend toward lower BChE activity, which correlated with BMI and deficits in different components of the AD.

Role of diffuse low-level heteroplasmy of mitochondrial DNA in Alzheimer's disease neurodegeneration

Alzheimer’s disease (AD) is the most common form of dementia in the elderly. The vast majority of cases are not linked to a known genetic defect and the molecular mechanisms underlying AD pathogenesis are still elusive. Evidence suggests that mitochondrial dysfunction is a prominent feature of the disease, and that mitochondrial DNA (mtDNA) alterations may represent a possible starting point of the pathophysiological cascade. Although specific mtDNA alterations have been reported in AD patients both in brain and peripheral tissues, such as D-loop mutations, 4977-bp deletion and poly-C tract D310 cytosine insertion, a generalized subtle allelic shift has also been demonstrated. This shift is significant for a few nucleotide positions (nps), but it is also detectable for most nps, although at a lower level. As single allelic substitutions can unlikely be determinant, it is proposed that the combination of all of them could lead to a less efficient oxidative phosphorylation, thus influencing AD development and course.

Therapeutic potential of Gastrodia elata Blume for the treatment of Alzheimer's disease

Several studies have demonstrated that the Chinese herb Gastrodia elata Blume can protect against amyloid beta-peptide (Aβ)-induced cell death. To investigate the possible therapeutic effects of Gastrodia elata Blume on Alzheimer's disease, we established a rat model of Alzheimer's disease by injecting Aβ25-35 into bilateral hippocampi. These rats were intragastrically administered 500 or 1 000 mg/kg Gastrodia elata Blume per day for 52 consecutive days. Morris water maze tests showed that Gastrodia elata Blume treatment significantly improved the spatial memory of Alzheimer's disease rats. Congo red staining revealed that Gastrodia elata Blume significantly reduced the number of amyloid deposits in the hippocampus of these rats. Western blot analysis showed that choline acetyltransferase expression in the medial septum and hippocampus was significantly increased by the treatment of Gastrodia elata Blume, while Ellman method showed significant decrease in the activity of acetylcholinesterase in all three regions (prefrontal cortex, medial septum and hippocampus). These findings suggest that long-term administration of Gastrodia elata Blume has therapeutic potential for Alzheimer's disease.

Interactions of AChE with Aβ Aggregates in Alzheimer's Brain: Therapeutic Relevance of IDN 5706

Acetylcholinesterase (AChE; EC 3.1.1.7) plays a crucial role in the rapid hydrolysis of the neurotransmitter acetylcholine, in the central and peripheral nervous system and might also participate in non-cholinergic mechanism related to neurodegenerative diseases. Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by a progressive deterioration of cognitive abilities, amyloid-β (Aβ) peptide accumulation and synaptic alterations. We have previously shown that AChE is able to accelerate the Aβ peptide assembly into Alzheimer-type aggregates increasing its neurotoxicity. Furthermore, AChE activity is altered in brain and blood of Alzheimer’s patients. The enzyme associated to amyloid plaques changes its enzymatic and pharmacological properties, as well as, increases its resistant to low pH, inhibitors and excess of substrate. Here, we reviewed the effects of IDN 5706, a hyperforin derivative that has potential preventive effects on the development of AD. Our results show that treatment with IDN 5706 for 10 weeks increases brain AChE activity in 7-month-old double transgenic mice (APP_SWE–PS1) and decreases the content of AChE associated with different types of amyloid plaques in this Alzheimer’s model. We concluded that early treatment with IDN 5706 decreases AChE–Aβ interaction and this effect might be of therapeutic interest in the treatment of AD.

Multivariate analysis of differential lymphocyte cell cycle activity in Alzheimer's disease

Mounting evidence suggests cell cycle dysregulation is involved in the pathogenesis of Alzheimer's disease (AD) and that this failure is systemic, affecting not only neurons but also peripheral blood lymphocytes (PBLs). This study analyzed if differences in PBL proliferation activity could be used as a diagnostic biomarker for AD. CD69 and CD28 expressions on PBL T, B, and monocyte cells were measured by flow cytometry with and without mitogenic stimulation in healthy controls (HC), probable AD, and Parkinson's disease dementia (PDD) subjects. Univariate and multivariate scoring models were employed to evaluate the data relative to the clinical diagnoses. Eleven CD expression markers were significantly altered in AD subjects compared with a mixed pool of PDD and HC subjects using univariate models. Using multivariate models, seven CD expression markers were significantly altered in AD subjects compared with PDD subjects. Multivariate scoring demonstrated up to a 91% positive and 92% negative agreement with subject clinical diagnosis and had little correlation with the severity of dementia. Present findings suggest that with further development this analytical and multivariate modeling procedure could aid the current differential diagnosis of Alzheimer's disease.

Effects in vitro of guanidinoacetate on adenine nucleotide hydrolysis and acetylcholinesterase activity in tissues from adult rats

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine metabolism characterized by low plasma creatine concentrations in combination with elevated guanidinoacetate (GAA) concentrations. The aim of this work was to investigate the in vitro effect of guanidinoacetate in NTPDase, 5'-nucleotidase and acetylcholinesterase activities in the synaptosomes, platelets and blood of rats. The results showed that in synaptosomes the NTPDase and 5'-nucleotidase activities were inhibited significantly in the presence of GAA at concentrations of 50, 100, 150 and 200 microM (P < 0.05). However, in platelets GAA at the same concentrations caused a significant increase in the activities of these two enzymes (P < 0.05). In relation to the acetylcholinesterase activity, GAA caused a significant inhibition in the activity of this enzyme in blood at concentrations of 150 and 200 microM (P < 0.05), but did not alter the acetylcholinesterase activity in synaptosomes from the cerebral cortex. Our results suggest that alterations caused by GAA in the activities of these enzymes may contribute to the understanding of the neurological dysfunction of GAMT-deficient patients.

Butyrylcholinesterase, ApoE and Alzheimer's disease in a population from the Canary Islands (Spain)

AIM

Cholinergic dysfunction is a major neurochemical feature in Alzheimer's disease (AD), accountable for many cognitive dysfunctions and some psychiatric symptoms. Butyrylcholinesterase (BChE) is one of the cholinesterases with increased activity in the brain of Alzheimer's patients. Several mutations code for different BChE, such as the K variant, which is the most common and is capable of reducing BChE activity by 30%. We studied the relationship between this K variant and Alzheimer's disease in our population from the Canary Islands (Spain).

PATIENTS AND METHODS

We used DNA PCR-RFLP techniques to compare 282 patients who had been diagnosed with probable Alzheimer's disease--according to NINCS-ADRDA criteria--with 312 control subjects confirmed to be free of cognitive impairment as assessed by using the CAMDEX cognitive subscale CAMCOG.

RESULTS

In our population the K variant of BChE is linked to the age of diagnosis of Alzheimer's disease, since AD individuals with this allele presented the disease at a later stage. No other susceptibility relations are exposed in this study. In addition, the BChE allelic frequencies in our population are higher than those previously reported.

Dopamine transporter immunoreactivity in peripheral blood lymphocytes discriminates Parkinson's disease from essential tremor

Peripheral blood lymphocytes (PBL) provide a model to study the changes of neurotransmitter-receptor systems in neurodegenerative disorders, including Parkinson's disease (PD). In this study, densitometric analysis was applied to measure dopamine transporter (DAT) immunoreactivity in PBL from dopaminergic drug-free patients suffering PD or essential tremor (ET) with respect to healthy subjects. The results showed a significant reduction of DAT immunoreactivity in PBL in PD but not in ET. These finding suggests that DAT immunoreactivity in PBL may discriminate between PD and ET in the early clinical stages.

Peripheral cholinergic disturbances in Alzheimer's disease

The most pronounced neurochemical abnormality in Alzheimer's disease (AD) is cholinergic dysfunction in the central nervous system. Peripheral tissues may also be affected, however, including blood. The present study undertook to determine the activity of acetylcholinesterase (AChE) and its molecular forms in erythrocytes, lymphocytes and platelets of normal elderly subjects and probable AD cases. These samples contained dimeric globular (G2), tetrameric globular (G4) and asymmetric (A12) AChE forms, but no globular monomeric (G1) enzyme. In both lymphocytes and platelets, the major AChE molecular form was G2 (approximately 80%), with G4 and A12 forms accounting for nearly equal portions of the remainder. Total AChE activities and measured sedimentation coefficients were similar in the control and AD samples (from patients with mild and moderately severe cognitive deficiency). However, the groups differed significantly in the proportion of certain AChE molecular forms. Thus, as compared with controls, the amount of A12 AChE in the AD samples was increased 148 and 161% in lymphocytes and platelets, respectively. Genotyping for apolipoprotein E (ApoE) and the butyrylcholinesterase K (BCHE-K) variant, carried out using the polymerase chain reaction, showed that AD patients carried the ApoE4 allele at a significantly higher frequency than the controls. On the other hand there were no significant group differences in the occurrence of the BCHE-K variant and no synergism between ApoE alleles and the BCHE-K variant in our Hungarian AD population.

Blood cells cholinesterase activity in early stage Alzheimer's disease and vascular dementia

Blood acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities have been studied as markers for Alzheimer's disease (AD), but their usefulness as a disease marker is controversial. To determine cholinesterase (ChE) activity during AD progression and whether ChE changes associate to other dementias, ChE activity was measured in lymphocytes, erythrocytes and platelets. Subjects underwent extensive medical and neuropsychological examination. Both early-AD and AD patients had lower AChE activity in lymphocytes compared to control subjects (p < 0.0001). In contrast, erythrocyte AChE activity was higher in patients with vascular dementia (p = 0.004). Low ChE activity in lymphocytes was the best discriminator for AD. Because it was already low at very early stages of AD, ChE could be helpful as an early biomarker of differential diagnosis for the follow-up of patients during their early stages of cognitive impairment before a clinical dementia is established.

Brain cholinesterases: III. Future perspectives of AD research and clinical practice

Alzheimer's disease (AD) is initially and primarily associated with the degeneration and alteration in the metabolism of cholinesterases (ChEs). The use of ChEs inhibitors to treat Alzheimer's condition, on the basis of the cholinergic hypothesis of the disease, is, therefore, without grounds. Most disturbing is the fact that the currently available anti-ChEs are designed to inhibit normal ChEs in the brain and throughout the body, but not the abnormal ones. Based on the acetylcholinesterase (AChE) deficiency theory, treatment should be designed to protect the cranial ChEs system from alteration and/or to help that system fight against degeneration through restoring its homeostatic action for brain structure and function instead. The overlap in the clinical, biochemical, molecular-cellular, and pathological alterations seen in patients with AD and individuals with many other brain disorders, which has bewildered many investigators, may now be explained by the shared underlying mismetabolism of brain ChEs. The abnormal metabolism of ChEs existing in asymptomatic subjects may indicate that the system is "at risk" and deserves serious attention. Future perspectives of ChEs research in vivo and in vitro in connection with AD and clinical diagnosis, prevention and treatment are proposed. Several potentially useful therapeutic and preventive means and pharmacological agents in this regard are identified and discussed, such as physical and intellectual stimulation, and a class of drugs including vitamin E, R-(-)-deprenyl (deprenyl, selegiline), acetyl L-carnitine, cytidine diphosphocholine (CDP-choline), centrophenoxine, L-phenylalanine, naloxone, galactose, and lithium, that have been proven to be able to stimulate AChE activity. Their working mechanisms may be through directly changing the configuration of AChE molecules and/or correcting micro- and overall environmental biological conditions for ChEs.

Increased lymphocyte dopamine beta-hydroxylase immunoreactivity in Alzheimer's disease: compensatory response to cholinergic deficit?

There is growing interest in the characterization of peripheral blood lymphocytes (PBL) as a biological tool with which to investigate changes in the neurotransmitter-receptor system in neurodegenerative disorders. Here we show a slight decrease in acetylcholinesterase (AChE) and a significant increase in dopamine beta-hydroxylase (DBH) immunoreactivity in the PBL of patients with probable Alzheimer's disease (AD). Therapy with AChE inhibitors completely reversed the increase in DBH immunoreactivity. We hypothesize that the increase in DBH immunoreactivity may represent a compensatory response to cholinergic impairment. Our findings suggest that neurochemical interactions between the noradrenergic and cholinergic systems may be measured at a peripheral level in AD.

Alzheimer patients treated with an AchE inhibitor show higher IL-4 and lower IL-1 beta levels and expression in peripheral blood mononuclear cells

The study evaluates the expression and production of cytokines in peripheral blood mononuclear cells of patients with Alzheimer disease treated or not treated with acetylcholinesterase inhibitor, which enhances neuronal transmission. Cytokines associated with brain inflammation such as interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha have been implicated in the regulation of amyloid peptide protein synthesis. The anti-inflammatory cytokine, IL-4, may suppress the activity of IL-1beta. Patients were assessed for clinical and immunologic features at baseline and after 1 month of treatment with Donepezil, an acetylcholinesterase inhibitor. Peripheral blood mononuclear cells were cultured with and without phytohemagglutinin stimulation. IL-1beta and IL-4 levels were measured by enzyme-linked immunosorbent assay. Reverse transcriptase-polymerase chain reaction was used to determine the expression of cytokines in peripheral mononuclear cells. Compared with untreated patients and healthy control subjects, IL-1beta levels and expression decreased in Alzheimer disease patients treated with Donepezil (P < 0.001). In contrast, IL-4 levels and expression were significantly higher in Alzheimer patients treated with the acetylcholinesterase inhibitor. This increment was observed in both unstimulated and phytohemagglutinin-stimulated peripheral blood mononuclear cells.

Expression of peripheral blood lymphocyte muscarinic cholinergic receptor subtypes in airway hyperresponsiveness

The expression of muscarinic cholinergic receptor subtypes was investigated in peripheral blood lymphocytes (PBL) of bronchial asthma patients by a combined kinetic and equilibrium labeling technique for radioligand binding assay of muscarinic cholinergic receptor subtypes and by receptor immunochemistry and immunocytochemistry. An increased expression of M2 and to a lesser extent of M5 receptors and no changes of M4 receptor were observed in PBL of asthmatics compared to control individuals. The increase was related to bronchial hyperresponsiveness detected by methacholine challenge test. Analysis of M3 receptor expression revealed biphasic changes, with a decreased receptor density in patients with normal, mild and moderate responses to methacholine test and a recovery to levels similar to those found in healthy individuals in severe responders to methacholine test. The demonstration of a different expression of lymphocyte muscarinic receptors in asthma suggests that cholinergic system may participate to a molecular framework influencing immune functions in asthma.

Effect of long-term aluminum feeding on kinetics attributes of tissue cholinesterases

Aluminum (Al) is considered a potential etiological factor in Alzheimer's disease (AD). Neurotoxicity from excess brain exposure to Al is documented from both clinical observations and animal experiments. A key role of the acetylcholine system in memory disturbances that characterize AD has been reported. On this basis, we studied the effect of long-term Al feeding on kinetic properties of cholinesterases employing the rat as experimental model. Animals were given prolonged treatment with soluble salts of Al (100mg AlCl(3)/kg body weight mixed with food for 100-115 days), and the kinetic properties of cholinesterases (acetylcholinesterase, AChE, and butyrylcholinesterase, BChE) were determined in different tissues. Prolonged treatment with Al had no effect on the K(m) values of the soluble and membrane-bound forms of AChE in the brain, but V(max) was instead decreased in all the components of soluble and membrane-bound forms of AChE in the brain. In addition, the Al treatment resulted in complete loss of the component II of erythrocyte membrane AChE. Surprisingly, after prolonged treatment with Al, higher V(max) was observed in all the components of soluble and membrane-bound forms of BChE in the heart and liver. Variable effects of Al exposure were observed on temperature kinetic properties of cholinesterases. Altogether these findings indicate that long-term Al feeding results in inhibition of AChE, while an opposite effect is observed on BChE. Decreased V(max) of the brain AChE could represent the mode of action through which Al may contribute to pathological processes in Al-induced neurotoxicity.

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.

Abnormal erythrocyte anion exchange in Alzheimer disease

CONTEXT

Several abnormalities have been described in red blood cells of patients with Alzheimer disease (AD), but to date none of these has been confirmed by a second, independent study. Erythrocyte anion exchange has been reported to be abnormal in AD; we have developed a new technique for measuring anion exchange.

OBJECTIVES

To confirm the abnormality of erythrocyte anion exchange in AD and to determine whether the phenomenon has potential for clinical utility.

DESIGN

Comparison of patients with probable AD to age-matched controls.

SETTING

University hospital and ambulatory clinic.

METHODS

Chloride-bicarbonate exchange was measured in erythrocyte ghosts resealed with a fluorescent probe of chloride concentration.

RESULTS

Erythrocyte anion exchange is abnormal in AD. This difference appears in citrate but not EDTA anticoagulant. Mahalanobis's generalized distance between the 2 populations is 1.7, and a discriminant function derived from our technique classifies 82% of the study population in accordance with the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria. Receiver operating characteristic analysis demonstrates the possibility of choosing cutoffs with high sensitivity and specificity.

CONCLUSIONS

Measurement of red blood cell anion exchange may be useful in classifying patients with AD. The dependence of this phenomenon on anticoagulant suggests the involvement of platelet activation or complement fixation.

Radioligand binding assay of M1-M5 muscarinic cholinergic receptor subtypes in human peripheral blood lymphocytes

Analysis of lymphocyte muscarinic cholinergic receptors using quantitative techniques such as radioligand binding assay is made difficult due to the low density of these sites and the lack of subtype-specific selectivity of most available muscarinic ligands. In this study, a combined kinetic and equilibrium labeling technique recently developed for brain tissue was used for labeling the five muscarinic cholinergic receptor subtypes in intact human peripheral blood lymphocytes. No specific muscarinic M1 receptor binding was detectable in human peripheral blood lymphocytes using [3H]-pirenzepine as a ligand. Labeling of M2-M5 muscarinic receptors using [3H]N-methyl-scopolamine (NMS) by occluding various receptor subtypes with muscarinic antagonist and mamba venom resulted in the labeling of M2-M5 receptors in brain as well as in human peripheral blood lymphocytes. The relative density of different receptor subtypes was M3 > M5 > M4 > M2. The development of a reproducible technique for assaying muscarinic cholinergic receptor subtypes expressed by human peripheral blood lymphocytes may contribute to clarify their role in lymphocyte function.

Recent bacterial and viral infection is a risk factor for cerebrovascular ischemia: clinical and biochemical studies

We performed a case-control study to investigate the role of recent infection as stroke risk factor and to identify pathogenetic pathways linking infection and stroke. We examined 166 consecutive patients with acute cerebrovascular ischemia and 166 patients hospitalized for nonvascular and noninflammatory neurologic diseases. Control subjects were individually matched to patients for sex, age, and season of admission. We assessed special biochemical parameters in subgroups of stroke patients with and without recent infection (n = 21) who were similar with respect to demographic and clinical parameters. Infection within the preceding week was a risk factor for cerebrovascular ischemia in univariate (odds ratio [OR] 3.1; 95% confidence interval (CI), 1.57 to 6.1) and age-adjusted multiple logistic regression analysis (OR 2.9; 95% CI, 1.31 to 6.4). The OR of recent infection and age were inversely related. Both bacterial and viral infection contributed to increased risk. Infection elevated the risk for cardioembolism and tended to increase the risk for arterioarterial embolism. Stroke patients with and without preceding infection were not different with respect to factor VII and factor VIII activity, fibrin monomer, fibrin D-dimer, von Willebrand factor, C4b-binding protein, protein S, anticardiolipin antibodies, interleukin-1 receptor antagonist, soluble tumor necrosis factor-alpha receptor, interleukin-6, interleukin-8, and neopterin. In conclusion, recent infection is an independent risk factor for acute cerebrovascular ischemia. Its role appears to be more important in younger age groups. The pathogenetic linkage between infection and stroke is still insufficiently understood.

Kinetics of the inhibition of acetylcholinesterase from desert cobra (Walterinnesia aegyptia) venom by local anesthetics: procaine and tetracaine

The kinetic parameters of W. aegyptia venom acetylcholinesterase (AChE) inhibition by procaine and tetracaine hydrochloride were investigated in the present study. Procaine and tetracaine reversibly inhibited the AChE activity in a concentration-dependent manner, the IC50 being about 0.28 and 0.04 mM, respectively. The Michaelis-Menten constant (K(m)) for the hydrolysis of acetylthiocholine iodide was found to be 0.051 mM with Vmax 10.2 mumole/min/mg protein. Both K(m) and Vmax were affected by procaine while only Vmax decreased with tetracaine. A Lineweaver-Burk plot and its secondary replot indicated that the nature of the inhibition is of the linear mixed type for procaine which is considered to be a mixture of competitive and noncompetitive types while the inhibition was noncompetitive for tetracaine. The values of Ki(slope) and K(intercept were estimated as 0.133 mM and 0.451 mM for procaine and 7.2 x 10(-3) mM for tetracaine, respectively, by the secondary replots of the Lineweaver-Burk plot.