Progressive loss of cortical acetylcholinesterase activity in association with cognitive decline in Alzheimer's disease: A positron emission tomography study

Cholinergic changes in Lewy body disease: implications for presentation, progression and subtypes

Cholinergic degeneration is significant in Lewy body disease, including Parkinson's disease, dementia with Lewy bodies, and isolated REM sleep behaviour disorder. Extensive research has demonstrated cholinergic alterations in the CNS of these disorders. More recently, studies have revealed cholinergic denervation in organs that receive parasympathetic denervation. This enables a comprehensive review of cholinergic changes in Lewy body disease, encompassing both central and peripheral regions, various disease stages and diagnostic categories. Across studies, brain regions affected in Lewy body dementia show equal or greater levels of cholinergic impairment compared to the brain regions affected in Lewy body disease without dementia. This observation suggests a continuum of cholinergic alterations between these disorders. Patients without dementia exhibit relative sparing of limbic regions, whereas occipital and superior temporal regions appear to be affected to a similar extent in patients with and without dementia. This implies that posterior cholinergic cell groups in the basal forebrain are affected in the early stages of Lewy body disorders, while more anterior regions are typically affected later in the disease progression. The topographical changes observed in patients affected by comorbid Alzheimer pathology may reflect a combination of changes seen in pure forms of Lewy body disease and those seen in Alzheimer's disease. This suggests that Alzheimer co-pathology is important to understand cholinergic degeneration in Lewy body disease. Thalamic cholinergic innervation is more affected in Lewy body patients with dementia compared to those without dementia, and this may contribute to the distinct clinical presentations observed in these groups. In patients with Alzheimer's disease, the thalamus is variably affected, suggesting a different sequential involvement of cholinergic cell groups in Alzheimer's disease compared to Lewy body disease. Patients with isolated REM sleep behaviour disorder demonstrate cholinergic denervation in abdominal organs that receive parasympathetic innervation from the dorsal motor nucleus of the vagus, similar to patients who experienced this sleep disorder in their prodrome. This implies that REM sleep behaviour disorder is important for understanding peripheral cholinergic changes in both prodromal and manifest phases of Lewy body disease. In conclusion, cholinergic changes in Lewy body disease carry implications for understanding phenotypes and the influence of Alzheimer co-pathology, delineating subtypes and pathological spreading routes, and for developing tailored treatments targeting the cholinergic system.

Astragaloside IV as a Memory-Enhancing Agent: In Silico Studies with In Vivo Analysis and Post Mortem ADME-Tox Profiling in Mice

Many people around the world suffer from neurodegenerative diseases associated with cognitive impairment. As life expectancy increases, this number is steadily rising. Therefore, it is extremely important to search for new treatment strategies and to discover new substances with potential neuroprotective and/or cognition-enhancing effects. This study focuses on investigating the potential of astragaloside IV (AIV), a triterpenoid saponin with proven acetylcholinesterase (AChE)-inhibiting activity naturally occurring in the root of Astragalus mongholicus, to attenuate memory impairment. Scopolamine (SCOP), an antagonist of muscarinic cholinergic receptors, and lipopolysaccharide (LPS), a trigger of neuroinflammation, were used to impair memory processes in the passive avoidance (PA) test in mice. This memory impairment in SCOP-treated mice was attenuated by prior intraperitoneal (ip) administration of AIV at a dose of 25 mg/kg. The attenuation of memory impairment by LPS was not observed. It can therefore be assumed that AIV does not reverse memory impairment by anti-inflammatory mechanisms, although this needs to be further verified. All doses of AIV tested did not affect baseline locomotor activity in mice. In the post mortem analysis by mass spectrometry of the body tissue of the mice, the highest content of AIV was found in the kidneys, then in the spleen and liver, and the lowest in the brain.

Clinical characteristics of early-onset versus late-onset Alzheimer's disease: a systematic review and meta-analysis

OBJECTIVES

A number of studies have compared Alzheimer's disease (AD), the commonest form of dementia, based on their age of onset, i.e. before the age of 65 years (early-onset AD, EO-AD) to those developing after 65 years of age (late-onset AD, LO-AD), but the differences are not clear. We performed a systematic review and meta-analysis to compare clinical characteristics between EO-AD and LO-AD.

DESIGN, MEASUREMENTS, AND PARTICIPANTS

Medline, Embase, PsycINFO, and CINAHL databases were systematically searched for studies comparing time to diagnosis, cognitive scores, annual cognitive decline, activities of daily living (ADLs), neuropsychiatric symptoms (NPS), quality of life (QoL), and survival time for EO-AD and LO-AD patients.

RESULTS

Forty-two studies were included (EO-AD participants n = 5,544; LO-AD participants n = 16,042). An inverse variance method with random effects models was used to calculate overall effect estimates for each outcome. People with EO-AD had significantly poorer baseline cognitive performance and faster cognitive decline but longer survival times than people with LO-AD. There was no evidence that EO-AD patients differ from people with LO-AD in terms of symptom onset to diagnosis time, ADLs, and NPS. There were insufficient data to estimate overall effects of differences in QoL in EO-AD compared to LO-AD.

CONCLUSIONS

Our findings suggest that EO-AD differs from LO-AD in baseline cognition, cognitive decline, and survival time but otherwise has similar clinical characteristics to LO-AD. Larger studies using standardized questionnaires focusing on the clinical presentations are needed to better understand the impact of age of onset in AD.

Ultrasensitivity Detecting AChE through "Covalent Assembly" and Signal Amplification Strategic Approaches and Applied to Screen Its Inhibitor

An ultrasensitivity detecting assay for acetylcholinesterase (AChE) activity was developed based on "covalent assembly" and signal amplification strategic approaches. After hydrolyzing thioacetylcholine by AChE and participation of thiol in a self-inducing cascade accelerated by the Meldrum acid derivatives of 2-[bis(methylthio) methylene] malonitrile (CA-2), mercaptans triggered an intramolecular cyclization assembly by the probe of 2-(2,2-dicyanovinyl)-5-(diethylamino) phenyl 2,4-dinitrobenzenesulfonate (Sd-I) to produce strong fluorescence. The limit of detection for AChE activity was as low as 0.0048 mU/mL. The detection system also had a good detecting effect on AChE activity in human serum and could also be used to screen its inhibitors. By constructing a Sd-I@agarose hydrogel with a smartphone, a point-of-care detection of AChE activity was achieved again.

Progression of regional cortical cholinergic denervation in Parkinson's disease

Cortical cholinergic deficits contribute to cognitive decline and other deficits in Parkinson's disease. Cross-sectional imaging studies suggest a stereotyped pattern of posterior-to-anterior cortical cholinergic denervation accompanying disease progression in Parkinson's disease. We used serial acetylcholinesterase PET ligand imaging to characterize the trajectory of regional cholinergic synapse deficits in Parkinson's disease, testing the hypothesis of posterior-to-anterior progression of cortical cholinergic deficits. The 16 Parkinson's disease subjects (4 females/12 males; mean age: 64.4 ± 6.7 years; disease duration: 5.5 ± 4.2 years; Hoehn & Yahr stage: 2.3 ± 0.6 at entry) completed serial 11C-methyl-4-piperidinyl propionate acetylcholinesterase PET scans over a 4-8 year period (median 5 years). Three-dimensional stereotactic cortical surface projections and volume-of-interest analyses were performed. Cholinergic synapse integrity was assessed by the magnitude, k 3, of acetylcholinesterase hydrolysis of 11C-methyl-4-piperidinyl propionate. Based on normative data, we generated Z-score maps for both the k 3 and the k 1 parameters, the latter as a proxy for regional cerebral blood flow. Compared with control subjects, baseline scans showed predominantly posterior cortical k 3 deficits in Parkinson's disease subjects. Interval change analyses showed evidence of posterior-to-anterior progression of cholinergic cortical deficits in the posterior cortices. In frontal cortices, an opposite gradient of anterior-to-posterior progression of cholinergic deficits was found. The topography of k 3 changes exhibited regionally specific disconnection from k 1 changes. Interval-change analysis based on k 3/k 1 ratio images (k 3 adjustment for regional cerebral blood flow changes) showed interval reductions (up to 20%) in ventral frontal, anterior cingulate and Brodmann area 6 cortices. In contrast, interval k 3 reductions in the posterior cortices, especially Brodmann areas 17-19, were largely proportional to k 1 changes. Our results partially support the hypothesis of progressive posterior-to-cortical cholinergic denervation in Parkinson's disease. This pattern appears characteristic of posterior cortices. In frontal cortices, an opposite pattern of anterior-to-posterior progression of cholinergic deficits was found. The progressive decline of posterior cortical acetylcholinesterase activity was largely proportional to declining regional cerebral blood flow, suggesting that posterior cortical cholinergic synapse deficits are part of a generalized loss of synapses. The disproportionate decline in regional frontal cortical acetylcholinesterase activity relative to regional cerebral blood flow suggests preferential loss or dysregulation of cholinergic synapses in these regions. Our observations suggest that cortical cholinergic synapse vulnerability in Parkinson's disease is mediated by both diffuse processes affecting cortical synapses and processes specific to subpopulations of cortical cholinergic afferents.

Association between Cerebral Coordination Functions and Clinical Outcomes of Alzheimer's Dementia

Background: Alzheimer’s dementia (AD) is a degenerative disease that impairs cognitive function, initially, and then motor or other function, eventually. Motor coordination function impairment usually accompanies cognition impairment but it is seldom examined whether it can reflect the clinical outcomes of AD. Methods: 113 clinically diagnosed AD patients with a mean age of 78.9 ± 6.9 years underwent an annual neuropsychological assessment using the Mini-Mental State Examination (MMSE), the Cognitive Abilities Screening Instrument (CASI), the Sum of Boxes of Clinical Dementia Rating (CDR-SB), and the CDR. The cerebral coordination function was evaluated through correlations among 15 joints with a kinetic depth sensor annually. An intra-individual comparison of both cognitive and motor coordination functions was performed to examine their correlations. Results: The changes in coordination function in the lower limbs can significantly reflect the clinical outcomes, MMSE (p < 0.001), CASI (p = 0.006), CDR (p < 0.001), and CDR-SB (p < 0.001), but the changes in upper limbs can only reflect the clinical outcome in CDR (p < 0.001). Conclusions: The use of a kinetic depth sensor to determine the coordination between joints, especially in lower limbs, can significantly reflect the global functional and cognitive outcomes in AD. Such evaluations could be another biomarker used to evaluate non-cognitive outcomes in AD for clinical and research purposes.

Dramatic impacts on brain pathology, anxiety, and cognitive function in the knock-in APPNL-G-F mouse model of Alzheimer disease following long-term voluntary exercise

Background

An active lifestyle is associated with improved cognitive functions in aged people and may prevent or slow down the progression of various neurodegenerative diseases including Alzheimer’s disease (AD). To investigate these protective effects, male APP^NL-G-F mice were exposed to long-term voluntary exercise.

Methods

Three-month-old AD mice were housed in a cage supplemented with a running wheel for 9 months for long-term exercise. At the age of 12 months, behavioral tests were completed for all groups. After completing behavioral testing, their brains were assessed for amyloid pathology, microgliosis, and cholinergic cells.

Results

The results showed that APP^NL-G-F mice allowed to voluntarily exercise showed an improvement in cognitive functions. Furthermore, long-term exercise also improved anxiety in APP^NL-G-F mice as assessed by measuring thigmotaxis in the Morris water task. We also found reductions in amyloid load and microgliosis, and a preservation of cholinergic cells in the brain of APP^NL-G-F mice allowed to exercise in their home cages. These profound reductions in brain pathology associated with AD are likely responsible for the observed improvement of learning and memory functions following extensive and regular exercise.

Conclusion

These findings suggest the potential of physical exercise to mitigate the cognitive deficits in AD.

Comparative study of rivastigmine and galantamine on the transgenic Drosophila model of Alzheimer's disease

Alzheimer's Disease (AD) is characterized as a progressive neurodegenerative disease most commonly associated with memory deficits and cognitive decline. The formation of amyloid plaques and neurofibrillary tangles are important pathological markers of AD. The accumulation of amyloid plaques and neurofibrillary tangles leads to the loss of neurons including the cholinergic neurons thus decreasing the levels of acetylcholine (a neurotransmitter). To reduce the AD symptoms cholinesterase inhibitors are widely used to decrease the hydrolysis of acetylcholine released from presynaptic neurons. In the present study we have studied the effect of rivastigmine and galantamine (commonly used cholinesterase inhibitors) on the transgenic Drosophila model of AD expressing human Aβ-42 in the neurons. The effect of similar doses of rivastigmine and galantamine (i.e. 0.1,1 and 10 ​mM) was studied on the climbing ability, lifespan, oxidative stress markers, caspase 9 and 3, acetylcholinesterase activity and on the formation of Aβ-42 aggregates. The results suggest that the rivastigmine is more potent in reducing the oxidative stress and improving climbing ability of AD flies. Both the drugs were found to be effective in increasing the lifespan of AD flies. Galantamine was found to be a more potent inhibitor of acetylcholinesterase compared to rivastigmine. Galantamine prevents the formation of Aβ-42 aggregates more effectively compared to rivastigmine.

PET Imaging of Cholinergic Neurotransmission in Neurodegenerative Disorders

As a neuromodulator, the neurotransmitter acetylcholine plays an important role in cognitive, mood, locomotor, sleep/wake, and olfactory functions. In the pathophysiology of most neurodegenerative diseases, such as Alzheimer disease (AD) or Lewy body disorder (LBD), cholinergic receptors, transporters, or enzymes are involved and relevant as imaging targets. The aim of this review is to summarize current knowledge on PET imaging of cholinergic neurotransmission in neurodegenerative diseases. For PET imaging of presynaptic vesicular acetylcholine transporters (VAChT), (-)-¹⁸F-fluoroethoxybenzovesamicol (¹⁸F-FEOBV) was the first PET ligand that could be successfully translated to clinical application. Since then, the number of ¹⁸F-FEOBV PET investigations on patients with AD or LBD has grown rapidly and provided novel, important findings concerning the pathophysiology of AD and LBD. Regarding the α4β2 nicotinic acetylcholine receptors (nAChRs), various second-generation PET ligands, such as ¹⁸F-nifene, ¹⁸F-AZAN, ¹⁸F-XTRA, (-)-¹⁸F-flubatine, and (+)-¹⁸F-flubatine, were developed and successfully translated to human application. In neurodegenerative diseases such as AD and LBD, PET imaging of α4β2 nAChRs is of special value for monitoring disease progression and drugs directed to α4β2 nAChRs. For PET of α7 nAChR, ¹⁸F-ASEM and ¹¹C-MeQAA were successfully applied in mild cognitive impairment and AD, respectively. The highest potential for α7 nAChR PET is seen in staging, in evaluating disease progression, and in therapy monitoring. PET of selective muscarinic acetylcholine receptors (mAChRs) is still in an early stage, as the development of subtype-selective radioligands is complicated. Promising radioligands to image mAChR subtypes M1 (¹¹C-LSN3172176), M2 (¹⁸F-FP-TZTP), and M4 (¹¹C-MK-6884) were developed and successfully translated to humans. PET imaging of mAChRs is relevant for the assessment and monitoring of therapies in AD and LBD. PET of acetylcholine esterase activity has been investigated since the 1990s. Many PET studies with ¹¹C-PMP and ¹¹C-MP4A demonstrated cortical cholinergic dysfunction in dementia associated with AD and LBD. Recent studies indicated a solid relationship between subcortical and cortical cholinergic dysfunction and noncognitive dysfunctions such as balance and gait in LBD. Taken together, PET of distinct components of cholinergic neurotransmission is of great interest for diagnosis, disease monitoring, and therapy monitoring and to gain insight into the pathophysiology of different neurodegenerative disorders.

Acetylcholinesterase Inhibitors in the Treatment of Neurodegenerative Diseases and the Role of Acetylcholinesterase in their Pathogenesis

Acetylcholinesterase (AChE) plays an important role in the pathogenesis of neurodegenerative diseases by influencing the inflammatory response, apoptosis, oxidative stress and aggregation of pathological proteins. There is a search for new compounds that can prevent the occurrence of neurodegenerative diseases and slow down their course. The aim of this review is to present the role of AChE in the pathomechanism of neurodegenerative diseases. In addition, this review aims to reveal the benefits of using AChE inhibitors to treat these diseases. The selected new AChE inhibitors were also assessed in terms of their potential use in the described disease entities. Designing and searching for new drugs targeting AChE may in the future allow the discovery of therapies that will be effective in the treatment of neurodegenerative diseases.

Nicotine and Cognition in Cognitively Normal Older Adults

The cholinergic system has been shown to be the primary neurotransmitter system which is responsible for the cognitive symptoms associated with dementia; its role in healthy non-demented older adults remains a gap in the literature. Understanding the effects of age-related functional changes on the nicotinic system will address this knowledge gap. As the older adult population grows and hence the importance of understanding cognitive changes that impact functional abilities and everyday life. In this article we examine the benefits of using nicotine as a method for improving cognition in non-demented healthy older adults which may have the potential for slowing neurodegeneration in aging. Furthermore, we discuss how nicotine can play a crucial role in maintaining cognitive abilities throughout normal cognitive aging.

The potential involvement of cholinergic system in finasteride induced cognitive dysfunction

OBJECTIVE

Neurosteroids are known to exert diverse functions in the brain. 5α-reductase (5α-R), a rate-limiting enzyme involved in the biosynthesis of neurosteroids is inhibited by finasteride. Clinical studies suggest that administration of finasteride causes the emergence of affective symptoms and cognitive dysfunction. Modeling this in rats would provide an opportunity to understand the mechanisms. Accordingly, in the present study, we evaluated the effects of repeated finasteride administration on spatial learning and memory in the partially baited radial arm maze task (RAM) and social cognitive behavior in the social interaction test. Further, to initiate the quest to understand the mechanisms underlying the effects of finasteride, in a separate group of animals, acetylcholinesterase (AChE) activity in the frontal cortex, hippocampus, septum and striatum was estimated.

METHODS

2 months old male Wistar rats were trained to learn a partially baited radial arm maze task (four trials per day till they reach a choice accuracy of 80 %). Following this, rats were administered with either vehicle (HPβCD) or finasteride (30 or 100 mg/Kg, s.c.) for 7 days and then subjected to retention test on the eighth day. To evaluate the social cognition, finasteride was administered for 7 days, followed by social interaction test on the eighth day. All the sessions were video-recorded and analyzed using Noldus Ethovision XT™ software. Following finasteride administration, on the eighth day, rats were euthanized, and AChE activity was estimated by modified Ellman's method.

RESULTS

Finasteride (100 mg/Kg, s.c.) administration decreased the percent correct choice during the retention trial of the RAM task. This was paralleled by an increase in the number of total number of errors and reference memory errors. In the social interaction test, finasteride (100 mg/Kg, s.c.) administration decreased the time spent with the rat compared to the object, implying decreased sociability and diminished social preference evidenced by similar time spent with the novel and familiar rat. Reduced AChE activity was observed in the frontal cortex, hippocampus and septum.

CONCLUSION

Our study provides evidence that repeated administration of finasteride decreases social interaction and results in cognitive deficits, potentially through a cholinergic mechanism. Further studies are required to understand the exact link between the cognitive effects and the cholinergic system. A deeper probe of the current findings holds promise for the development of novel neurosteroid-based therapeutics to treat affective and cognitive disorders.

Will temperature rise change the biochemical alterations induced in Mytilus galloprovincialis by cerium oxide nanoparticles and mercury?

It is known that, for marine coastal ecosystems, pollution and global warming are among the most threatening factors. Among emerging pollutants, nanoparticles (NPs) deserve particular attention as their possible adverse effects are significantly influenced by environmental factors such as salinity, pH and temperature, as well as by their ability to interact with other contaminants. In this framework, the present study aimed to evaluate the potential interactions between CeO₂ NPs and the toxic classic metal mercury (Hg), under current and warming conditions. The marine bivalve Mytilus galloprovincialis was used as biological model and exposed to CeO₂ NPs and Hg, either alone or in combination, for 28 day at 17 °C and 22 °C. A suite of biomarkers related to energetic metabolism, oxidative stress/damage, redox balance, and neurotoxicity was applied in exposed and non-exposed (control) mussels. The Hg and Ce accumulation was also assessed. Results showed that the exposure to CeO₂ NPs alone did not induce toxic effects in M. galloprovincialis. On the contrary, Hg exposure determined a significant loss of energetic metabolism and a general impairment in biochemical performances. Hg accumulation in mussels was not modified by the presence of CeO₂ NPs, while the biochemical alterations induced by Hg alone were partially canceled upon co-exposure with CeO₂ NPs. The temperature increase induced loss of metabolic and biochemical functions and the effects of temperature prevailed on mussels exposed to pollutants acting alone or combined.

Efficacy of THN201, a Combination of Donepezil and Mefloquine, to Reverse Neurocognitive Deficits in Alzheimer's Disease

Donepezil (DPZ) is an acetylcholinesterase inhibitor used in Alzheimer’s disease to restore cognitive functions but is endowed with limited efficacy. Recent studies pointed out the implication of astroglial networks in cognitive processes, notably via astrocyte connexins (Cxs), proteins involved in gap junction intercellular communications. Hence, we investigated the impact on cognition of pharmacological or genetic modulations of those astrocyte Cxs during DPZ challenge in two rodent models of Alzheimer’s disease–like memory deficits. We demonstrated that the Cx modulator mefloquine (MEF) significantly enhanced the procognitive effect of DPZ in both models. In parallel, we determined that MEF potentiated DPZ-induced release of acetylcholine in hippocampus. Finally, local genetic silencing of astrocyte Cxs in the hippocampus was also found to enhance the procognitive effect of DPZ, pointing out the importance of Cx-dependent astrocyte networks in memory processes.

Cholinergic and inflammatory phenotypes in transgenic tau mouse models of Alzheimer's disease and frontotemporal lobar degeneration

An early and sizeable loss of basal forebrain cholinergic neurons is a well-characterized feature associated with measurable deficits in spatial learning and cognitive impairment in patients with Alzheimer’s disease. In addition, pro-inflammatory glial cells such as astrocytes and microglia may play a key role in the neurodegenerative cascade of Alzheimer’s disease and tauopathies. We recently presented two mouse models: Line 1, expressing the truncated tau fragment identified as the core of the Alzheimer’s paired helical filament, and Line 66, expressing full-length human tau carrying a double mutation (P301S and G335D). Line 1 mice have a pathology that is akin to Alzheimer’s, whilst Line 66 resembles frontotemporal lobar degeneration. However, their cholinergic and inflammatory phenotypes remain elusive. We performed histological evaluation of choline acetyltransferase, acetylcholinesterase, p75 neurotrophin receptor, microglial ionized calcium binding adaptor molecule 1 and astrocytic glial fibrillary acidic protein in the basal forebrain, hippocampus and cortex of these models. A significant lowering of choline acetyltransferase-positive neurons and p75-positive neurons in the basal forebrain of Line 1 at 3, 6 and 9 months was observed in two independent studies, alongside a significant decrease in acetylcholinesterase staining in the cortex and hippocampus. The reductions in choline acetyltransferase positivity varied between 30% and 50% at an age when Line 1 mice show spatial learning impairments. Furthermore, an increase in microglial ionized calcium binding adaptor molecule 1 staining was observed in the basal forebrain, hippocampus and entorhinal cortex of Line 1 at 6 months. Line 66 mice displayed an intact cholinergic basal forebrain, and no difference in p75-positive neurons at 3 or 9 months. In addition, Line 66 exhibited significant microglial ionized calcium binding adaptor molecule 1 increase in the basal forebrain and hippocampus, suggesting a prominent neuroinflammatory profile. Increased concentrations of microglial interleukin-1β and astrocytic complement 3 were also seen in the hippocampus of both Line 1 and Line 66. The cholinergic deficit in Line 1 mice confirms the Alzheimer’s disease-like phenotype in Line 1 mice, whilst Line 66 revealed no measurable change in total cholinergic expression, a phenotypic trait of frontotemporal lobar degeneration. These two transgenic lines are therefore suitable for discriminating mechanistic underpinnings between the Alzheimer’s and frontotemporal lobar degeneration-like phenotypes of these mice.

Combining antioxidant astaxantin and cholinesterase inhibitor huperzine A boosts neuroprotection

Oxidative stress is a pathophysiological condition resulting in neurotoxicity, which is possibly associated with neurodegenerative disorders. In this study, the antioxidative effects of the antioxidant astaxanthin (AXT) in combination with huperzine A (HupA), which is used as a cholinesterase inhibitor for the treatment of Alzheimer's disease, were investigated. PC12 cells were treated with either tert-butyl hydroperoxide (TBHP), or with the toxic version of β-amyloid, Aβ_25–35, to induce oxidative stress and neurotoxicity. Cell viability, morphology, lactate dehydrogenase (LDH) release, intracellular accumulation of reactive oxygen species (ROS), superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were determined, while neuroprotection was also monitored using an MTT assay. It was found that combining AXT with HupA significantly increased the viability of PC12 cells, prevented membrane damage (as measured by LDH release), attenuated intracellular ROS formation, increased SOD activity and decreased the level of MDA after TBHP exposure when compared to these drugs administered alone. Pretreatment with HupA and AXT decreased toxic damage produced by Aβ_25–35. These data indicated that combining an antioxidant with a cholinesterase inhibitor increases the degree of neuroprotection; with future investigation this could be a potential therapy used to decrease neurotoxicity in the brain.

Voxel-Based Acetylcholinesterase PET Study in Early and Late Onset Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by chronic progressive cognitive decline and displays underlying brain cholinergic dysfunction, providing a rationale for treatment with cholinomimetic medication. The clinical presentations and courses of AD patients may differ by age of onset.

OBJECTIVE

The objective of the present study was to illustrate the regional differences of brain acetylcholinesterase (AChE) activity as quantified by N-[11C]methylpiperidinyl-4-acetate ([11C]MP4A) and PET using parametric whole brain analysis and clarify those differences as a function of age.

METHODS

22 early onset AD (EOAD) with age at onset under 65, the remaining 26 as late onset AD (LOAD), and 16 healthy controls (HC) were enrolled. Voxel-based AChE activity estimation of [11C]MP4A PET images was conducted by arterial input and unconstrained nonlinear least-squares method with subsequent parametrical analyses. Statistical threshold was set as Family Wise Error corrected, p-value <0.05 on cluster-level and cluster extent over 30 voxels.

RESULTS

Voxel-based group comparison showed that, compared to HC, both EOAD and LOAD showed cortical AChE decrement in parietal, temporal, and occipital cortices, with wider and stringent cortical involvement in the EOAD group, most prominently demonstrated in the temporal region. There was no significant correlation between age and regional cerebral AChE activity except for a small left superior temporal region in the AD group (Brodmann's area 22, Zmax = 5.13, 396 voxels), whereas no significant cluster was found in the HC counterpart.

CONCLUSION

Difference in cortical cholinergic dysfunction between EOAD and LOAD may shed some light on the cholinomimetic drug efficacy in AD.

Salivary biomarkers for the diagnosis and monitoring of neurological diseases

Current research efforts on neurological diseases are focused on identifying novel disease biomarkers to aid in diagnosis, provide accurate prognostic information and monitor disease progression. With advances in detection and quantification methods in genomics, proteomics and metabolomics, saliva has emerged as a good source of samples for detection of disease biomarkers. Obtaining a sample of saliva offers multiple advantages over the currently tested biological fluids as it is a non-invasive, painless and simple procedure that does not require expert training or harbour undesirable side effects for the patients. Here, we review the existing literature on salivary biomarkers and examine their validity in diagnosing and monitoring neurodegenerative and neuropsychiatric disorders such as autism and Alzheimer's, Parkinson's and Huntington's disease. Based on the available research, amyloid beta peptide, tau protein, lactoferrin, alpha-synuclein, DJ-1 protein, chromogranin A, huntingtin protein, DNA methylation disruptions, and micro-RNA profiles provide display a reliable degree of consistency and validity as disease biomarkers.

Structural and Functional Brain Patterns of Non-Motor Syndromes in Parkinson's Disease

Parkinson’s disease (PD) is a common, progressive and multisystem neurodegenerative disorder characterized by motor and non-motor symptoms. Advanced magnetic resonance imaging, positron emission tomography, and functional magnetic resonance imaging can render the view toward understanding the neural basis of these non-motor syndromes, as they help to understand the underlying pathophysiological abnormalities. This review provides an up-to-date description of structural and functional brain alterations in patients with PD with cognitive deficits, visual hallucinations, fatigue, impulsive behavior disorders, sleep disorders, and pain.

Amyloid-Beta and Phosphorylated Tau Accumulations Cause Abnormalities at Synapses of Alzheimer's disease Neurons

Amyloid-beta (Aβ) and hyperphosphorylated tau are hallmark lesions of Alzheimer's disease (AD). However, the loss of synapses and dysfunctions of neurotransmission are more directly tied to disease severity. The role of these lesions in the pathoetiological progression of the disease remains contested. Biochemical, cellular, molecular, and pathological studies provided several lines of evidence and improved our understanding of how Aβ and hyperphosphorylated tau accumulation may directly harm synapses and alter neurotransmission. In vitro evidence suggests that Aβ and hyperphosphorylated tau have both direct and indirect cytotoxic effects that affect neurotransmission, axonal transport, signaling cascades, organelle function, and immune response in ways that lead to synaptic loss and dysfunctions in neurotransmitter release. Observations in preclinical models and autopsy studies support these findings, suggesting that while the pathoetiology of positive lesions remains elusive, their removal may reduce disease severity and progression. The purpose of this article is to highlight the need for further investigation of the role of tau in disease progression and its interactions with Aβ and neurotransmitters alike.

[The activity of blood serum cholinesterases and neprilysin as potential biomarkers of mild-cognitive impairment and Alzheimer's disease]

OBJECTIVE

To analyze the activity of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and neprilysin (NEP) in the blood serum in elderly people with different types of cognitive impairment and evaluate the effect of ceraxon on the biochemical parameters.

MATERIAL AND METHODS

Three groups of patients: without cognitive disorders (controls--CG), with amnestic mild cognitive impairment (а-MCI) and with Alzheimer's disease (AD were studied).

RESULTS AND CONCLUSION

The activity of AChE, BChE and NEP was reduced in the blood serum of patients with a-MCI and, to the greater extent, in patients with AD compared to CG and correlated with the level of cognitive dysfunction evaluated by MMSE, ADAS-cog, and other tests. For the first time, it has been shown that treatment of a-MCI patients with ceraxon (citicolin) results in an increase of the activity of blood serum AChE, BChE and NEP to the values observed in the CG. Thus, the activities of blood serum AChE, BChE and NEP reflect the level of cognitive dysfunction and can be used as prognostic biomarkers of the level of dementia progression in patients with impaired memory.

Basal forebrain control of wakefulness and cortical rhythms

Wakefulness, along with fast cortical rhythms and associated cognition, depend on the basal forebrain (BF). BF cholinergic cell loss in dementia and the sedative effect of anti-cholinergic drugs have long implicated these neurons as important for cognition and wakefulness. The BF also contains intermingled inhibitory GABAergic and excitatory glutamatergic cell groups whose exact neurobiological roles are unclear. Here we show that genetically targeted chemogenetic activation of BF cholinergic or glutamatergic neurons in behaving mice produced significant effects on state consolidation and/or the electroencephalogram but had no effect on total wake. Similar activation of BF GABAergic neurons produced sustained wakefulness and high-frequency cortical rhythms, whereas chemogenetic inhibition increased sleep. Our findings reveal a major contribution of BF GABAergic neurons to wakefulness and the fast cortical rhythms associated with cognition. These findings may be clinically applicable to manipulations aimed at increasing forebrain activation in dementia and the minimally conscious state.

The mammalian basal forebrain controls cortical rhythm and wake-sleep. Anaclet et al. use genetically-targeted chemogenetic systems to activate or inhibit cholinergic, glutamatergic or GABAergic neurons in this region, and reveal their contributions to behavioral and electrocortical arousal in behaving mice.

Dementia with Lewy bodies can be well-differentiated from Alzheimer's disease by measurement of brain acetylcholinesterase activity-a [11C]MP4A PET study

OBJECTIVE

To investigate the diagnostic performance of brain acetylcholinesterase (AChE) activity measurement using N-[(11) C]-methyl-4-piperidyl acetate (MP4A) and PET in patients with dementia with Lewy bodies (DLB) and Alzheimer's disease (AD).

METHODS

Participants were 14 DLB patients, 25 AD patients and 18 age-matched healthy controls (HC). All subjects underwent PET scans and MP4A to measure regional brain AChE activity. We performed anatomical standardization of each brain image, and k3 values, an index of AChE activity, in each voxel were estimated by nonlinear least squares analysis. Volumes of interest (VOIs) were identified on parametric k3 images in frontal, temporal, parietal and occipital cortices, and in anterior and posterior cingulate gyri (ACG and PCG). In each VOI, the differential diagnostic performance between AD and DLB of k3 values was assessed by area under the curve (AUC) of the receiver-operating characteristic. Voxel-based statistical analyses were also performed.

RESULTS

Mean cortical AChE activities in AD patients (-8.2% compared with normal mean) and DLB patients (-27.8%) were lower than HCs (p < 0.05, p < 0.001, respectively). There was a significant difference in mean cortical AChE activities between AD and DLB patients (p < 0.001). All regional brain AChE activities of defined VOIs except ACG were able to well discriminate DLB from AD, and notably performance was the most significant in PCG (AUC = 0.989, 95% CI: 0.965-1.000).

CONCLUSIONS

Brain cholinergic deficit is consistently prominent in DLB compared with AD. PET measurement of brain AChE activity may be useful for the differential diagnosis between DLB and AD.

Cellular and molecular mechanisms of the restoration of human APP transgenic mouse cognitive dysfunction after transplant of human iPS cell-derived neural cells

Cholinergic neuronal loss is a common finding in patients with Alzheimer's disease (AD) and AD model mice. We previously transplanted neurons derived from human induced pluripotent stem (iPS) cells into the hippocampus of human amyloid precursor protein transgenic AD model mice. In the present study, we examined the cellular and molecular mechanisms involved in the alleviation of cognitive dysfunction in transplanted mice. After transplant, mice showed improvement in cognitive function, confirming our previous findings. Human choline acetyltransferase (ChAT)-positive cholinergic neurons were distributed throughout the cortex of the grafted mice. Human and mouse ChAT-positive neurons and alpha7 nicotinic acetylcholine receptor (α7nAChR)-positive neurons were significantly increased in the cortex and hippocampus of the grafted mice compared with the vehicle-injected mice. In addition, human and mouse vesicular GABA transporter (VGAT)-positive neurons were located mainly in the hippocampus and, though the number was small, human VGAT-positive neurons were observed in the cortex. In the grafted mouse cortex, the number of GABA receptor (GABAR)-positive neurons of both human origin and mouse origin were significantly increased compared with those in the vehicle-injected mouse cortex. The α7nAChR-positive and GABAR-positive neurons expressed phosphorylated Akt and c-fos in the cortex, suggesting that these receptor-expressing neurons were possibly activated by the neurotransmitters secreted from the grafted neurons. Collectively, the grafted and host neurons may form positive feedback loops via neurotransmitter secretion in both the cerebral cortex and hippocampus, leading to alleviation of cognitive dysfunction in dementia model mice.

Motor cortex excitability changes in mild Alzheimer's disease are reversed by donepezil

BACKGROUND

Recent neuroimaging studies in humans support the clinical observations that the motor cortex is affected early in the course of Alzheimer's disease (AD).

METHODS

We used transcranial magnetic stimulation to measure the active cortical motor threshold (ACMT) in AD patients in the very early stage of the disease, and we explored whether and in which way the pharmacologic manipulation of the cholinergic system could have a direct effect on the excitability of the motor cortex.

RESULTS

An increase of the ACMT was observed in AD patients in the early stage in comparison to controls. After 2 months of treatment with donepezil, the threshold did not differ significantly from normal subjects.

CONCLUSIONS

The results suggest an early functional impairment of cholinergic neurotransmission in AD, which is associated to early changes in the excitability of the motor system.

Neuronal AChE splice variants and their non-hydrolytic functions: redefining a target of AChE inhibitors?

AChE enzymatic inhibition is a core focus of pharmacological intervention in Alzheimer's disease (AD). Yet, AChE has also been ascribed non-hydrolytic functions, which seem related to its appearance in various isoforms. Neuronal AChE presents as a tailed form (AChE-T) predominantly found on the neuronal synapse, and a facultatively expressed readthough form (AChE-R), which exerts short to medium-term protective effects. Notably, this latter form is also found in the periphery. While these non-hydrolytic functions of AChE are most controversially discussed, there is evidence for them being additional targets of AChE inhibitors. This review aims to provide clarification as to the role of these AChE splice variants and their interplay with other cholinergic parameters and their being targets of AChE inhibition: AChE-R is particularly involved in the mediation of (anti-)apoptotic events in cholinergic cells, involving adaptation of various cholinergic parameters and a time-dependent link to the expression of neuroprotective factors. The AChE-T C-terminus is central to AChE activity regulation, while isolated AChE-T C-terminal fragments mediate toxic effects via the α7 nicotinic acetylcholine receptor. There is direct evidence for roles of AChE-T and AChE-R in neurodegeneration and neuroprotection, with these roles involving AChE as a key modulator of the cholinergic system: in vivo data further encourages the use of AChE inhibitors in the treatment of neurodegenerative conditions such as AD since effects on both enzymatic activity and the enzyme's non-hydrolytic functions can be postulated. It also suggests that novel AChE inhibitors should enhance protective AChE-R, while avoiding the concomitant up-regulation of AChE-T.

The integrity of the cholinergic system determines memory performance in healthy elderly

The cholinergic system plays a central role in episodic memory-related processes in health and disease. Cerebral acetylcholinesterase (AChE) activity, a measure of the integrity of the cholinergic system, can be assessed in vivo using positron emission tomography (PET) and [(11)C]N-methyl-4-piperidyl acetate (MP4A). A close relationship between the kinetic constant k3 of MP4A and mnestic functions has been demonstrated for patients suffering from amnestic mild cognitive impairment and Alzheimer's disease. Under the hypothesis that AChE activity and memory are intimately linked in older age, we obtained MP4A-PET and structural magnetic resonance images as well as neuropsychological data from fourteen healthy older adults. Multiple regression analysis revealed that AChE activity in areas previously implicated in mnestic functions predicted episodic memory performance irrespective of cortical atrophy. Data suggest that in older adults the integrity of the cholinergic system underlies inter-individual variability in memory function.

Chronic neuroinflammation in Alzheimer's disease: new perspectives on animal models and promising candidate drugs

Chronic neuroinflammation is now considered one of the major factors in the pathogenesis of Alzheimer's disease (AD). However, the most widely used transgenic AD models (overexpressing mutated forms of amyloid precursor protein, presenilin, and/or tau) do not demonstrate the degree of inflammation, neurodegeneration (particularly of the cholinergic system), and cognitive decline that is comparable with the human disease. Hence a more suitable animal model is needed to more closely mimic the resulting cognitive decline and memory loss in humans in order to investigate the effects of neuroinflammation on neurodegeneration. One of these models is the glial fibrillary acidic protein-interleukin 6 (GFAP-IL6) mouse, in which chronic neuroinflammation triggered constitutive expression of the cytokine interleukin-6 (IL-6) in astrocytes. These transgenic mice show substantial and progressive neurodegeneration as well as a decline in motor skills and cognitive function, starting from 6 months of age. This animal model could serve as an excellent tool for drug discovery and validation in vivo. In this review, we have also selected three potential anti-inflammatory drugs, curcumin, apigenin, and tenilsetam, as candidate drugs, which could be tested in this model.

Basal forebrain moderates the magnitude of task-dependent amygdala functional connectivity

Animal studies reveal that the amygdala promotes attention and emotional memory, in part, by driving activity in downstream target regions including the prefrontal cortex (PFC) and hippocampus. Prior work has demonstrated that the amygdala influences these regions directly through monosynaptic glutamatergic signaling, and indirectly by driving activity of the cholinergic basal forebrain and subsequent downstream acetylcholine release. Yet to date, no work has addressed the functional relevance of the cholinergic basal forebrain in facilitating signaling from the amygdala in humans. We set out to determine how blood oxygen level-dependent signal within the amygdala and cholinergic basal forebrain interact to predict neural responses within downstream targets. Here, we use functional connectivity analyses to demonstrate that the cholinergic basal forebrain moderates increased amygdala connectivity with both the PFC and the hippocampus during the processing of biologically salient stimuli in humans. We further demonstrate that functional variation within the choline transporter gene predicts the magnitude of this modulatory effect. Collectively, our results provide novel evidence for the importance of cholinergic signaling in modulating neural pathways supporting arousal, attention and memory in humans. Further, our results may shed light on prior association studies linking functional variation within the choline transporter gene and diagnoses of major depression and attention-deficit hyperactivity disorder.

Acetylcholinergic neurotransmission and the β-amyloid cascade: implications for Alzheimer’s disease

Alzheimer's disease is characterized by both decreases in acetylcholinergic neurotransmission and increases in beta-amyloid accumulation. Currently, available clinical psychopharmacologic treatment is focused on increasing acetylcholinergic neurotransmission, whereas no clinical treatments to directly reduce beta-amyloid accumulation are available. Cholinesterase inhibitors improve cognition, certain neuropsychiatric symptoms and functional impairment in patients with mild-to-moderate Alzheimer's disease, and it is believed that this is mainly symptomatic treatment. However, this review discusses various levels of interaction between acetylcholinergic neurotransmission and the beta-amyloid cascade, which suggest that some specific acetylcholinergic treatments may reduce beta-amyloid accumulation, and therefore may slow disease progression over the long term. Various suggestions are made on how such potential disease-modifying effects could be studied in the future.

Neuronal damage, central cholinergic dysfunction and oxidative damage correlate with cognitive deficits in rats with chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion has been identified to be a risk factor for cognitive decline in aging, vascular dementia, and Alzheimer's disease. Substantial evidence has shown that chronic cerebral hypoperfusion may cause cognitive impairment, but the underlying neurobiological mechanism is poorly understood so far. In this study, we used a rat model of chronic cerebral hypoperfusion by permanent bilateral common carotid artery occlusion (BCCAO) to investigate the alterations of neuronal damage, glial activation oxidative stress and central cholinergic dysfunction, and their causal relationship with the cognitive deficits induced by chronic cerebral hypoperfusion. We found that BCCAO rats exhibited spatial learning and memory impairments and working memory dysfunction 12 weeks after BCCAO compared with sham-operated rats, simultaneously accompanied by significantly increased neuronal damage and glial cell activation in the cerebral cortex and hippocampus. Twelve weeks of BCCAO treatment in rats resulted in central cholinergic dysfunction and increased oxidative damage compared with sham-operated rats. Correlational analyses revealed that spatial learning and memory impairments and working memory dysfunction were significantly correlated with the measures of neuronal damage, central cholinergic dysfunction and oxidative damage in the cerebral cortex and hippocampus of rats with BCCAO. Moreover, the measures of neuronal damage and central cholinergic dysfunction were significantly correlated with the indexes of oxidative damage in rats with BCCAO. Collectively, this study provides novel evidence that neuronal damage and central cholinergic dysfunction is likely due to increased oxidative stress under the condition of chronic cerebral hypoperfusion. Furthermore, the results of the present study suggest that neuronal damage, central cholinergic dysfunction and oxidative damage in the brain following the reduction of cerebral blood flow could be involved in cognitive deficits induced by chronic cerebral hypoperfusion.

Cholinergic Depletion in Alzheimer's Disease Shown by [ (18) F]FEOBV Autoradiography

Rationale. Alzheimer's Disease (AD) is a neurodegenerative condition characterized in part by deficits in cholinergic basalocortical and septohippocampal pathways. [¹⁸F]Fluoroethoxybenzovesamicol ([¹⁸F]FEOBV), a Positron Emission Tomography ligand for the vesicular acetylcholine transporter (VAChT), is a potential molecular agent to investigate brain diseases associated with presynaptic cholinergic losses. Purpose. To demonstrate this potential, we carried out an [¹⁸F]FEOBV autoradiography study to compare postmortem brain tissues from AD patients to those of age-matched controls. Methods. [¹⁸F]FEOBV autoradiography binding, defined as the ratio between regional grey and white matter, was estimated in the hippocampus (13 controls, 8 AD) and prefrontal cortex (13 controls, 11 AD). Results. [¹⁸F]FEOBV binding was decreased by 33% in prefrontal cortex, 25% in CA3, and 20% in CA1. No changes were detected in the dentate gyrus of the hippocampus, possibly because of sprouting or upregulation toward the resilient glutamatergic neurons of the dentate gyrus. Conclusion. This is the first demonstration of [¹⁸F]FEOBV focal binding changes in cholinergic projections to the cortex and hippocampus in AD. Such cholinergic synaptic (and more specifically VAChT) alterations, in line with the selective basalocortical and septohippocampal cholinergic losses documented in AD, indicate that [¹⁸F]FEOBV is indeed a promising ligand to explore cholinergic abnormalities in vivo.

Associations between a neurophysiological marker of central cholinergic activity and cognitive functions in young and older adults

Background

The deterioration of the central cholinergic system in aging is hypothesized to underlie declines in several cognitive domains, including memory and executive functions. However, there is surprisingly little direct evidence regarding acetylcholine’s specific role(s) in normal human cognitive aging.

Methods

We used short-latency afferent inhibition (SAI) with transcranial magnetic stimulation (TMS) as a putative marker of cholinergic activity in vivo in young (n = 24) and older adults (n = 31).

Results

We found a significant age difference in SAI, concordant with other evidence of cholinergic decline in normal aging. We also found clear age differences on several of the memory and one of the executive function measures. Individual differences in SAI levels predicted memory but not executive functions.

Conclusion

Individual differences in SAI levels were better predictors of memory than executive functions. We discuss cases in which the relations between SAI and cognition might be even stronger, and refer to other age-related biological changes that may interact with cholinergic activity in cognitive aging.

Early memory deficits precede plaque deposition in APPswe/PS1dE9 mice: involvement of oxidative stress and cholinergic dysfunction

A large body of evidence has shown that cognitive deficits occur early, before amyloid plaque deposition, suggesting that soluble amyloid-β protein (Aβ) contributes to the development of early cognitive dysfunction in Alzheimer disease (AD). However, the underlying mechanism(s) through which soluble Aβ exerts its neurotoxicity responsible for cognitive dysfunction in the early stage of AD remains unclear so far. In this study, we used preplaque APPswe/PS1dE9 mice ages 2.5 and 3.5 months to examine alterations in cognitive function, oxidative stress, and cholinergic function. We found that only soluble Aβ, not insoluble Aβ, was detected in these preplaque APPswe/PS1dE9 mice. APPswe/PS1dE9 mice 2.5 months of age did not show any significant changes in the measures of cognitive function, oxidative stress, and cholinergic function, whereas 3.5-month-old APPswe/PS1dE9 mice exhibited spatial memory impairment in the Morris water maze, accompanied by significantly decreased acetylcholine (ACh), choline acetyltransferase (ChAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-px) as well as increased malondialdehyde (MDA) and protein carbonyls. In 3.5-month-old preplaque APPswe/PS1dE9 mice, correlational analyses revealed that the performance of impaired spatial memory was inversely correlated with soluble Aβ, MDA, and protein carbonyls, as well as being positively correlated with ACh, ChAT, SOD, and GSH-px; soluble Aβ level was inversely correlated with ACh, ChAT, SOD, and GSH-px, as well as being positively correlated with MDA and protein carbonyls; ACh level showed a significant positive correlation with ChAT, SOD, and GSH-px, as well as a significant inverse correlation with MDA and protein carbonyls. Collectively, this study provides direct evidence that increased oxidative damage and cholinergic dysfunction may be early pathological responses to soluble Aβ and involved in early memory deficits in the preplaque stage of AD. These findings suggest that early antioxidant therapy and improving cholinergic function may be a promising strategy to prevent or delay the onset and progression of AD.

Altered expression of brain acetylcholinesterase in FTDP-17 human tau transgenic mice

Pathological hyperphosphorylation and aggregation of the tau protein is associated with dementia and can be the central cause of neurodegeneration. Here, we examined potential alterations in the level of the cholinergic enzyme acetylcholinesterase (AChE) in the brain of transgenic mice (Tg-VLW) expressing human tau mutations. Overexpression of mutant hyperphosphorylated tau (P-tau) led to an increase in the activity of AChE in the brain of Tg-VLW mice, paralleled by an increase in AChE protein and transcripts; whereas the levels of the enzyme choline acetyltransferase remained unaffected. VLW tau overexpression in SH-SY5Y cells also increased AChE activity levels. All major molecular forms of AChE were increased in the Tg-VLW mice, including tetrameric AChE, which is the major species involved in hydrolysis of acetylcholine in the brain. Colocalization of human P-tau and AChE supports the conclusion that P-tau can act to increase AChE. This study is the first direct evidence of a modulatory effect of P-tau on brain AChE expression.

Cholinergic system function and cognition in mild cognitive impairment

Evidence for cholinergic dysfunction in very early stages of neurodegeneration like mild cognitive impairment (MCI) is inconclusive. Previous positron emission tomography (PET) studies based on small samples investigated if it is related to memory impairment. We examined whether cortical acetylcholine esterase (AChE) activity is reduced at this stage and correlated with cognitive function. N-[(11)C]-methyl-4-piperidyl acetate ([11C]MP4A), a positron emission tomography tracer for measuring cerebral AChE activity in vivo, was applied in 21 controls and 17 MCI patients. Parametric images of AChE activity were analyzed using standard atlas regions. Principal components analysis (PCA) of regional values of AChE activity and correlation analysis with neuropsychological test results was performed. Cortical AChE activity showed a significant decline in MCI patients compared with controls which was most pronounced in temporal regions. They formed the main part of a principal component that was related significantly to verbal and nonverbal memory, language comprehension and executive function. Cholinergic dysfunction is an early hallmark even before onset of dementia at the clinical stage of MCI. Its impact especially on temporal neocortex is associated with impaired neuropsychological function.

Cholinergic imaging in corticobasal syndrome, progressive supranuclear palsy and frontotemporal dementia

Corticobasal syndrome, progressive supranuclear palsy and frontotemporal dementia are all part of a disease spectrum that includes common cognitive impairment and movement disorders. The aim of this study was to characterize brain cholinergic deficits in these disorders. We measured brain acetylcholinesterase activity by [11C] N-methylpiperidin-4-yl acetate and positron emission tomography in seven patients with corticobasal syndrome (67.6+/-5.9 years), 12 with progressive supranuclear palsy (68.5+/-4.1 years), eight with frontotemporal dementia (59.8+/-6.9 years) and 16 healthy controls (61.2+/-8.5 years). Two-tissue compartment three-parameter model and non-linear least squares analysis with arterial input function were performed. k3 value, an index of acetylcholinesterase activity, was calculated voxel-by-voxel in the brain of each subject. The k3 images in each disease group were compared with the control group by using Statistical Parametric Mapping 2. Volume of interest analysis was performed on spatially normalized k3 images. The corticobasal syndrome group showed decreased acetylcholinesterase activity (k3 values) in the paracentral region, frontal, parietal and occipital cortices (P<0.05, cluster corrected). The group with progressive supranuclear palsy had reduced acetylcholinesterase activity in the paracentral region and thalamus (P<0.05, cluster corrected). The frontotemporal dementia group showed no significant differences in acetylcholinesterase activity. Volume of interest analysis showed mean cortical acetylcholinesterase activity to be reduced by 17.5% in corticobasal syndrome (P<0.001), 9.4% in progressive supranuclear palsy (P<0.05) and 4.4% in frontotemporal dementia (non-significant), when compared with the control group. Thalamic acetylcholinesterase activity was reduced by 6.4% in corticobasal syndrome (non-significant), 24.0% in progressive supranuclear palsy (P<0.03) and increased by 3.3% in frontotemporal dementia (non-significant). Both corticobasal syndrome and progressive supranuclear palsy showed brain cholinergic deficits, but their distribution differed somewhat. Significant brain cholinergic deficits were not seen in frontotemporal dementia, which may explain the unresponsiveness of this condition to cholinergic modulation therapy.