Parkinson's disease, Alzheimer's disease and motor neurone disease: identifying a common mechanism

A Novel Bioactive Peptide, T14, Selectively Activates mTORC1 Signalling: Therapeutic Implications for Neurodegeneration and Other Rapamycin-Sensitive Applications

T14 modulates calcium influx via the α-7 nicotinic acetylcholine receptor to regulate cell growth. Inappropriate triggering of this process has been implicated in Alzheimer's disease (AD) and cancer, whereas T14 blockade has proven therapeutic potential in in vitro, ex vivo and in vivo models of these pathologies. Mammalian target of rapamycin complex 1 (mTORC1) is critical for growth, however its hyperactivation is implicated in AD and cancer. T14 is a product of the longer 30mer-T30. Recent work shows that T30 drives neurite growth in the human SH-SY5Y cell line via the mTOR pathway. Here, we demonstrate that T30 induces an increase in mTORC1 in PC12 cells, and ex vivo rat brain slices containing substantia nigra, but not mTORC2. The increase in mTORC1 by T30 in PC12 cells is attenuated by its blocker, NBP14. Moreover, in post-mortem human midbrain, T14 levels correlate significantly with mTORC1. Silencing mTORC1 reverses the effects of T30 on PC12 cells measured via AChE release in undifferentiated PC12 cells, whilst silencing mTORC2 does not. This suggests that T14 acts selectively via mTORC1. T14 blockade offers a preferable alternative to currently available blockers of mTOR as it would enable selective blockade of mTORC1, thereby reducing side effects associated with generalised mTOR blockade.

Characterization of a Bioactive Peptide T14 in the Human and Rodent Substantia Nigra: Implications for Neurodegenerative Disease

The substantia nigra is generally considered to show significant cell loss not only in Parkinson's but also in Alzheimer's disease, conditions that share several neuropathological traits. An interesting feature of this nucleus is that the pars compacta dopaminergic neurons contain acetylcholinesterase (AChE). Independent of its enzymatic role, this protein is released from pars reticulata dendrites, with effects that have been observed in vitro, ex vivo and in vivo. The part of the molecule responsible for these actions has been identified as a 14-mer peptide, T14, cleaved from the AChE C-terminus and acting at an allosteric site on alpha-7 nicotinic receptors, with consequences implicated in neurodegeneration. Here, we show that free T14 is co-localized with tyrosine hydroxylase in rodent pars compacta neurons. In brains with Alzheimer's pathology, the T14 immunoreactivity in these neurons increases in density as their number decreases with the progression of the disease. To explore the functional implications of raised T14 levels in the substantia nigra, the effect of exogenous peptide on electrically evoked neuronal activation was tested in rat brain slices using optical imaging with a voltage-sensitive dye (Di-4-ANEPPS). A significant reduction in the activation response was observed; this was blocked by the cyclized variant of T14, NBP14. In contrast, no such effect of the peptide was seen in the striatum, a region lacking the T14 target, alpha-7 receptors. These findings add to the accumulating evidence that T14 is a key signaling molecule in neurodegenerative disorders and that its antagonist NBP14 has therapeutic potential.

When a trophic process turns toxic: Alzheimer's disease as an aberrant recapitulation of a developmental mechanism

Here we review the idea that Alzheimer's disease (AD) results from aberrant activation of a normal developmental mechanism. This process operates in primarily vulnerable, subcortical nuclei with a distinguishing embryological provenance: the basal rather than the alar plate. All cells are dependent for growth on calcium influx yet these neurons retain a sensitivity to trophic factors into maturity. However, as the brain matures this action becomes detrimental such that the trophic process could turn toxic if triggered in adult brain, in retaliation to an initial insult. The signalling molecule driving this trophic-toxic mechanism is a 14mer peptide (T14) that acts on the alpha-7 receptor to enhance calcium entry, inducing excitotoxicity and proliferation of the receptor, perpetuating a feedforward cycle of neurodegeneration including production of beta-amyloid and p-tau. The T14 system has been previously unrecognised as a basic biological process, yet its pharmaceutical manipulation could have valuable clinical applications.

Regulation of acetylcholinesterase during the lipopolysaccharide-induced inflammatory responses in microglial cells

The non-classical function of acetylcholine (ACh) has been reported in neuroinflammation that represents the modulating factor in immune responses via activation of α7 nicotinic acetylcholine receptor (α7 nAChR), i.e., a cholinergic anti-inflammatory pathway (CAP). Acetylcholinesterase (AChE), an enzyme for ACh hydrolysis, has been proposed to have a non-classical function in immune cells. However, the involvement of AChE in neuroinflammation is unclear. Here, cultured BV2 cell, a microglial cell line, and primary microglia from rats were treated with lipopolysaccharide (LPS) to induce inflammation and to explore the regulation of AChE during this process. The expression profiles of AChE, α7 nAChR, and choline acetyltransferase (ChAT) were revealed in BV2 cells. The expression of AChE (G4 form) was induced significantly in LPS-treated BV2 cells: the induction was triggered by NF-κB and cAMP signaling. Moreover, ACh or α7 nAChR agonist suppressed the LPS-induced production of pro-inflammatory cytokines, as well as the phagocytosis of microglia, by activating α7 nAChR and followed by the regulation of NF-κB and CREB signaling. The ACh-induced suppression of inflammation was abolished in AChE overexpressed cells, but did not show a significant change in AChE mutant (enzymatic activity knockout) transfected cells. These results indicate that the neuroinflammation-regulated function of AChE may be mediated by controlling the ACh level in the brain system.

A novel process driving Alzheimer's disease validated in a mouse model: Therapeutic potential

Introduction

The neuronal mechanism driving Alzheimer's disease (AD) is incompletely understood.

Methods

Immunohistochemistry, pharmacology, biochemistry, and behavioral testing are employed in two pathological contexts—AD and a transgenic mouse model—to investigate T14, a 14mer peptide, as a key signaling molecule in the neuropathology.

Results

T14 increases in AD brains as the disease progresses and is conspicuous in 5XFAD mice, where its immunoreactivity corresponds to that seen in AD: neurons immunoreactive for T14 in proximity to T14‐immunoreactive plaques. NBP14 is a cyclized version of T14, which dose‐dependently displaces binding of its linear counterpart to alpha‐7 nicotinic receptors in AD brains. In 5XFAD mice, intranasal NBP14 for 14 weeks decreases brain amyloid and restores novel object recognition to that in wild‐types.

Discussion

These findings indicate that the T14 system, for which the signaling pathway is described here, contributes to the neuropathological process and that NBP14 warrants consideration for its therapeutic potential.

Unraveling Targetable Systemic and Cell-Type-Specific Molecular Phenotypes of Alzheimer's and Parkinson's Brains With Digital Cytometry

Alzheimer's disease (AD) and Parkinson's disease (PD) are the two most common neurodegenerative disorders worldwide, with age being their major risk factor. The increasing worldwide life expectancy, together with the scarcity of available treatment choices, makes it thus pressing to find the molecular basis of AD and PD so that the causing mechanisms can be targeted. To study these mechanisms, gene expression profiles have been compared between diseased and control brain tissues. However, this approach is limited by mRNA expression profiles derived for brain tissues highly reflecting their degeneration in cellular composition but not necessarily disease-related molecular states. We therefore propose to account for cell type composition when comparing transcriptomes of healthy and diseased brain samples, so that the loss of neurons can be decoupled from pathology-associated molecular effects. This approach allowed us to identify genes and pathways putatively altered systemically and in a cell-type-dependent manner in AD and PD brains. Moreover, using chemical perturbagen data, we computationally identified candidate small molecules for specifically targeting the profiled AD/PD-associated molecular alterations. Our approach therefore not only brings new insights into the disease-specific and common molecular etiologies of AD and PD but also, in these realms, foster the discovery of more specific targets for functional and therapeutic exploration.

Potent Acetylcholinesterase Inhibitors: Potential Drugs for Alzheimer's Disease

Alzheimer's disease (AD) is one of the cognitive or memory-related impairments occurring with advancing age. Since its exact mechanism is not known, the full therapy has still not been found. Acetylcholinesterase (AChE) has been reported to be a viable therapeutic target for the treatment of AD and other dementias. To this end, acetylcholinesterase inhibitors (AChEIs) are commonly used. AChE is a member of the hydrolase enzyme family. A hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond. AChE is useful for the development of novel and mechanism-based inhibitors. It has a role in the breakdown of acetylcholine (ACh) neurotransmitters, such as acetylcholinemediated neurotransmission. AChEIs are the most effective approaches to treat AD. AChE hydrolyzes ACh to acetate and choline, as an important neurotransmitter substance. Recently, Gülçin and his group explored new AChEIs. The most suggested mechanism for AD is the deficiency of ACh, which is an important neurotransmitter. In this regard, AChEIs are commonly used for the symptomatic treatment of AD. They act in different ways, such as by inhibiting AChE, protecting cells from free radical toxicity and β-amyloid-induced injury or inhibiting the release of cytokines from microglia and monocytes. This review focuses on the role of AChEIs in AD using commonly available drugs. Also, the aim of this review is to research and discuss the role of AChEIs in AD using commonly available drugs. Therefore, in our review, related topics like AD and AChEIs are highlighted. Also, the latest work related to AChEIs is compiled. In recent research studies, novel natural and synthetic AChEIs, used for AD, are quite noteworthy. These studies can be very promising in detecting potent drugs against AD.

Acetylcholinesterase: The "Hub" for Neurodegenerative Diseases and Chemical Weapons Convention

This article describes acetylcholinesterase (AChE), an enzyme involved in parasympathetic neurotransmission, its activity, and how its inhibition can be pharmacologically useful for treating dementia, caused by Alzheimer’s disease, or as a warfare method due to the action of nerve agents. The chemical concepts related to the irreversible inhibition of AChE, its reactivation, and aging are discussed, along with a relationship to the current international legislation on chemical weapons.

A Multidisciplinary Approach Reveals an Age-Dependent Expression of a Novel Bioactive Peptide, Already Involved in Neurodegeneration, in the Postnatal Rat Forebrain

The basal forebrain has received much attention due to its involvement in multiple cognitive functions, but little is known about the basic neuronal mechanisms underlying its development, nor those mediating its primary role in Alzheimer’s disease. We have previously suggested that a novel 14-mer peptide, ‘T14’, could play a pivotal role in Alzheimer’s disease, via reactivation of a developmental signaling pathway. In this study, we have characterized T14 in the context of post-natal rat brain development, using a combination of different techniques. Ex-vivo rat brain slices containing the basal forebrain, at different stages of development, were used to investigate large-scale neuronal network activity in real time with voltage-sensitive dye imaging. Subsequent Western blot analysis revealed the expression profile of endogenous T14, its target alpha7 nicotinic receptor and the familiar markers of Alzheimer’s: amyloid beta and phosphorylated Tau. Results indicated maximal neuronal activity at the earliest ages during development, reflected in a concomitant profile of T14 peptide levels and related proteins. In conclusion, these findings show that the peptide, already implicated in neurodegenerative events, has an age-dependent expression, suggesting a possible contribution to the physiological mechanisms underlying brain maturation.

Modulatory Effects of a Novel Cyclized Peptide in Reducing the Expression of Markers Linked to Alzheimer's Disease

Despite many studies attempt to identify the primary mechanisms underlying neurodegeneration in Alzheimer's disease (AD), the key events still remain elusive. We have previously shown that a peptide cleaved from the acetylcholinesterase (AChE) C-terminus (T14) can play a pivotal role as a signaling molecule in neurodegeneration, via its interaction with the α7 nicotinic acetylcholine receptor. The main goal of this study is to determine whether a cyclized variant (NBP14) of the toxic AChE-derived peptide can antagonize the effects of its linear counterpart, T14, in modulating well-known markers linked to neurodegeneration. We investigate this hypothesis applying NBP14 on ex-vivo rat brain slices containing the basal forebrain. Western blot analysis revealed an inhibitory action of NBP14 on naturally occurring T14 peptide, as well as on endogenous amyloid beta, whereas the expression of the nicotinic receptor and phosphorylated Tau was relatively unaffected. These results further confirm the neurotoxic properties of the AChE-peptide and show for the first time in an ex-vivo preparation the possible neuroprotective activity of NBP14, over a protracted period of hours, indicating that T14 pathway may offer a new prospect for therapeutic intervention in AD pathobiology.

An Alternative Approach to Study Primary Events in Neurodegeneration Using Ex Vivo Rat Brain Slices

Despite numerous studies that attempt to develop reliable animal models which reflecting the primary processes underlying neurodegeneration, very few have been widely accepted. Here, we propose a new procedure adapted from the well-known ex vivo brain slice technique, which offers a closer in vivo-like scenario than in vitro preparations, for investigating the early events triggering cell degeneration, as observed in Alzheimer's disease (AD). This variation consists of simple and easily reproducible steps, which enable preservation of the anatomical cytoarchitecture of the selected brain region and its local functionality in a physiological milieu. Different anatomical areas can be obtained from the same brain, providing the opportunity to perform multiple experiments with the treatments in question in a site-, dose-, and time-dependent manner. Potential limitations which could affect the outcomes related to this methodology are related to the conservation of the tissue, i.e., the maintenance of its anatomical integrity during the slicing and incubation steps and the section thickness, which can influence the biochemical and immunohistochemical analysis. This approach can be employed for different purposes, such as exploring molecular mechanisms involved in physiological or pathological conditions, drug screening, or dose-response assays. Finally, this protocol could also reduce the number of animals employed in behavioral studies. The application reported here has been recently described and tested for the first time on ex vivo rat brain slices containing the basal forebrain (BF), which is one of the cerebral regions primarily affected in AD. Specifically, it has been demonstrated that the administration of a toxic peptide derived from the C-terminus of acetylcholinesterase (AChE) could prompt an AD-like profile, triggering, along the antero-posterior axis of the BF, a differential expression of proteins altered in AD, such as the alpha7 nicotinic receptor (α7-nAChR), phosphorylated Tau (p-Tau), and amyloid beta (Aβ).

Glioprotective Effects of Lingonberry Extract Against Altered Cellular Viability, Acetylcholinesterase Activity, and Oxidative Stress in Lipopolysaccharide-Treated Astrocytes

Altered astrocytic function is a contributing factor to the development of neurological diseases and neurodegeneration. Berry fruits exert neuroprotective effects by modulating pathways involved in inflammation, neurotransmission, and oxidative stress. The aim of this study was to examine the effects of the lingonberry extract on cellular viability and oxidative stress in astrocytes exposed to lipopolysaccharide (LPS). In the reversal protocol, primary astrocytic cultures were first exposed to 1 µg/mL LPS for 3 h and subsequently treated with lingonberry extract (10, 30, 50, and 100 μg/mL) for 24 and 48 h. In the prevention protocol, exposure to the lingonberry extract was performed before treatment with LPS. In both reversal and prevention protocols, the lingonberry extracts, from 10 to 100 μg/mL, attenuated LPS-induced increase in reactive oxygen species (around 55 and 45%, respectively, P < 0.01), nitrite levels (around 50 and 45%, respectively, P < 0.05), and acetylcholinesterase activity (around 45 and 60%, respectively, P < 0.05) in astrocytic cultures at 24 and 48 h. Also, in both reversal and prevention protocols, the lingonberry extract also prevented and reversed the LPS-induced decreased cellular viability (around 45 and 90%, respectively, P < 0.05), thiol content (around 55 and 70%, respectively, P < 0.05), and superoxide dismutase activity (around 50 and 145%, respectively, P < 0.05), in astrocytes at both 24 and 48 h. Our findings suggested that the lingonberry extract exerted a glioprotective effect through an anti-oxidative mechanism against LPS-induced astrocytic damage.

Meta-Analysis of Parkinson's Disease and Alzheimer's Disease Revealed Commonly Impaired Pathways and Dysregulation of NRF2-Dependent Genes

Many lines of evidence suggest that Parkinson's disease (PD) and Alzheimer's disease (AD) have common characteristics, such as mitochondrial dysfunction and oxidative stress. As the underlying molecular mechanisms are unclear, we perform a meta-analysis with 9 microarray datasets of PD studies and 7 of AD studies to explore it. Functional enrichment analysis revealed that PD and AD both showed dysfunction in the synaptic vesicle cycle, GABAergic synapses, phagosomes, oxidative phosphorylation, and TCA cycle pathways, and AD had more enriched genes. Comparing the differentially expressed genes between AD and PD, we identified 54 common genes shared by more than six tissues. Among them, 31 downregulated genes contained the antioxidant response element (ARE) consensus sequence bound by NRF2. NRF2 is a transcription factor, which protects cells against oxidative stress through coordinated upregulation of ARE-driven genes. To our surprise, although NRF2 was upregulated, its target genes were all downregulated. Further exploration found that MAFF was upregulated in all tissues and significantly negatively correlated with the 31 NRF2-dependent genes in diseased conditions. Previous studies have demonstrated over-expressed small MAFs can form homodimers and act as transcriptional repressors. Therefore, MAFF might play an important role in dysfunction of NRF2 regulatory network in PD and AD.

Dementia and Pressure Ulcers: Is There a Close Pathophysiological Interrelation?

The current theoretical investigation aimed to explore common pathophysiological mechanisms underlying dementia and pressure ulcers (PU). Along with the increased longevity, especially in frail elderly patients, there is a higher rate of functional and cognitive impairment with dementia coinciding with immobility, which results in a higher rate of PU. Understanding common etiological paths resulting in pressure ulcers and dementia is likely to produce new treatment strategies that could lead to the prevention of comorbid complications. Data collected from elderly dementia patients indicate a deterioration of several neurophysiological subsystems associated with motor, sensory, autonomic, cognitive, or behavioral pathways, supporting a "close pathophysiological interrelation" perspective linking PU with dementia progression. Overall, the authors' theoretical systemic-model of disease progression and PU comorbidity proposes that increased clinician awareness to PU in mild to moderate dementia may suppress the accelerated development of PU, resulting in less patient suffering, reduced long-term care hospitalization, and hopefully PU prevention.

A Novel Ex Vivo Model to Investigate the Underlying Mechanisms in Alzheimer's Disease

Currently there is no widely accepted animal model reproducing the full pathological profile of Alzheimer's disease (AD), since the basic mechanisms of neurodegeneration are still poorly understood. We have proposed that the interaction between the α7 nicotinic acetylcholine receptor (α7-nAChR) and a recently discovered toxic peptide, cleaved from the acetylcholinesterase (AChE) C-terminus, could account for the aberrant processes occurring in AD. In this article we describe a new application on ex vivo model procedure, which combines the advantages of both in vivo and in vitro preparations, to study the effects of the AChE-derived peptide on the rat basal forebrain (BF). Western blot analysis showed that the levels of α7-nAChR, p-Tau and Aβ are differentially expressed upon the AChE-peptide administration, in a selective site-dependent manner. In conclusion, this methodology demonstrates the action of a novel peptide in triggering an AD-like phenotype and proposes a new ex vivo approach for manipulating and monitoring neurochemical processes contributing to neurodegeneration, in a time-dependent and site-specific manner.

Optical imaging of the rat brain suggests a previously missing link between top-down and bottom-up nervous system function

Optical imaging with voltage-sensitive dyes enables the visualization of extensive yet highly transient coalitions of neurons (assemblies) operating throughout the brain on a subsecond time scale. We suggest that operating at the mesoscale level of brain organization, neuronal assemblies may provide a functional link between "bottom-up" cellular mechanisms and "top-down" cognitive ones within anatomically defined regions. We demonstrate in ex vivo rat brain slices how varying spatiotemporal dynamics of assemblies reveal differences not previously appreciated between: different stages of development in cortical versus subcortical brain areas, different sensory modalities (hearing versus vision), different classes of psychoactive drugs (anesthetics versus analgesics), different effects of anesthesia linked to hyperbaric conditions and, in vivo, depths of anesthesia. The strategy of voltage-sensitive dye imaging is therefore as powerful as it is versatile and as such can now be applied to the evaluation of neurochemical signaling systems and the screening of related new drugs, as well as to mathematical modeling and, eventually, even theories of consciousness.

A Review on Potential Mechanisms of Terminalia chebula in Alzheimer's Disease

The current management of Alzheimer's disease (AD) focuses on acetylcholinesterase inhibitors (AChEIs) and NMDA receptor antagonists, although outcomes are not completely favorable. Hence, novel agents found in herbal plants are gaining attention as possible therapeutic alternatives. The Terminalia chebula (Family: Combretaceae) is a medicinal plant with a wide spectrum of medicinal properties and is reported to contain various biochemicals such as hydrolysable tannins, phenolic compounds, and flavonoids, so it may prove to be a good therapeutic alternative. In this research, we reviewed published scientific literature found in various databases: PubMed, Science Direct, Scopus, Web of Science, Scirus, and Google Scholar, with the keywords: T. chebula, AD, neuroprotection, medicinal plant, antioxidant, ellagitannin, gallotannin, gallic acid, chebulagic acid, and chebulinic acid. This review shows that T. chebula extracts and its constituents have AChEI and antioxidant and anti-inflammatory effects, all of which are currently relevant to the treatment of Alzheimer's disease.

(II) Physiological profiling of an endogenous peptide in the basal forebrain: Age-related bioactivity and blockade with a novel modulator

Previous studies have suggested that neurodegeneration is an aberrant form of development, mediated by a novel peptide from the C-terminus of acetylcholinesterase (AChE). Using voltage-sensitive dye imaging we have investigated the effects of a synthetic version of this peptide in the in vitro rat basal forebrain, a key site of degeneration in Alzheimer's disease. The brain slice preparation enables direct visualisation in real-time of sub-second meso-scale neuronal coalitions ('Neuronal Assemblies') that serve as a powerful index of brain functional activity. Here we show that (1) assemblies are site-specific in their activity profile with the cortex displaying a significantly more extensive network activity than the sub-cortical basal forebrain; (2) there is an age-dependency, in both cortical and sub-cortical sites, with the younger brain (p14 rats) exhibiting more conspicuous assemblies over space and time compared to their older counterparts (p35-40 rats). (3) AChE-derived peptide significantly modulates the dynamics of neuronal assemblies in the basal forebrain of the p14 rat with the degree of modulation negatively correlated with age, (4) the differential in assembly size with age parallels the level of endogenous peptide in the brain, which also declines with maturity, and (5) this effect is completely reversed by a cyclised variant of AChE-peptide, 'NBP14'. These observations are attributed to an enhanced calcium entry that, according to developmental stage, could be either trophic or toxic, and as such may provide insight into the basic neurodegenerative process as well as an eventual therapeutic intervention.

In silico target fishing and pharmacological profiling for the isoquinoline alkaloids of Macleaya cordata (Bo Luo Hui)

Background

Some isoquinoline alkaloids from Macleaya cordata (Willd). R. Br. (Bo Luo Hui) exhibited antibacterial, antiparasitic, antitumor, and analgesic effects. The targets of these isoquinoline alkaloids are undefined. This study aims to investigate the compound–target interaction network and potential pharmacological actions of isoquinoline alkaloids of M. cordata by reverse pharmacophore database screening.

Methods

The targets of 26 isoquinoline alkaloids identified from M. cordata were predicted by a pharmacophore-based target fishing approach. Discovery Studio 3.5 and two pharmacophore databases (PharmaDB and HypoDB) were employed for the target profiling. A compound–target interaction network of M. cordata was constructed and analyzed by Cytoscape 3.0.

Results

Thirteen of the 65 predicted targets identified by PharmaDB were confirmed as targets by HypoDB screening. The targets in the interaction network of M. cordata were involved in cancer (31 targets), microorganisms (12 targets), neurodegeneration (10 targets), inflammation and autoimmunity (8 targets), parasitosis (5 targets), injury (4 targets), and pain (3 targets). Dihydrochelerythrine (C6) was found to hit 23 fitting targets. Macrophage migration inhibitory factor (MIF) hits 15 alkaloids (C1–2, C11–16, C19–25) was the most promising target related to cancer.

Conclusion

Through in silico target fishing, the anticancer, anti-inflammatory, and analgesic effects of M. cordata were the most significant among many possible activities. The possible anticancer effects were mainly contributed by the isoquinoline alkaloids as active components.

Systems pharmacology-based drug discovery for marine resources: an example using sea cucumber (Holothurians)

ETHNOPHARMACOLOGICAL RELEVANCE

Sea cucumber, a kind of marine animal, have long been utilized as tonic and traditional remedies in the Middle East and Asia because of its effectiveness against hypertension, asthma, rheumatism, cuts and burns, impotence, and constipation. In this study, an overall study performed on sea cucumber was used as an example to show drug discovery from marine resource by using systems pharmacology model. The value of marine natural resources has been extensively considered because these resources can be potentially used to treat and prevent human diseases. However, the discovery of drugs from oceans is difficult, because of complex environments in terms of composition and active mechanisms. Thus, a comprehensive systems approach which could discover active constituents and their targets from marine resource, understand the biological basis for their pharmacological properties is necessary.

MATERIALS AND METHODS

In this study, a feasible pharmacological model based on systems pharmacology was established to investigate marine medicine by incorporating active compound screening, target identification, and network and pathway analysis.

RESULTS

As a result, 106 candidate components of sea cucumber and 26 potential targets were identified. Furthermore, the functions of sea cucumber in health improvement and disease treatment were elucidated in a holistic way based on the established compound-target and target-disease networks, and incorporated pathways.

CONCLUSIONS

This study established a novel strategy that could be used to explore specific active mechanisms and discover new drugs from marine sources.

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.

Presymptomatic treatment with acetylcholinesterase antisense oligonucleotides prolongs survival in ALS (G93A-SOD1) mice

Objective. Previous research suggests that acetylcholinesterase (AChE) may be involved in ALS pathogenesis. AChE enzyme inhibitors can upregulate AChE transcription which in certain contexts can have deleterious (noncatalytic) effects, making them theoretically harmful in ALS, whilst AChE antisense-oligonucleotides (mEN101), which downregulate AChE may be beneficial. Our aim was to investigate whether downregulation of AChE using mEN101 is beneficial in an ALS mouse model. Methods. ALS (G93A-SOD1) mice received saline, mEN101, inverse-EN101, or neostigmine. Treatments were administered from 5 weeks. Disease-onset and survival were recorded. Additional mice were sacrificed for pathological analysis at 15 weeks of age. In a follow-up experiment treatment was started at the symptomatic stage at a higher dose. Results. mEN101 given at the presymptomatic (but not symptomatic) stage prolonged survival and attenuated motor-neuron loss in ALS mice. In contrast, neostigmine exacerbated the clinical parameters. Conclusions. These results suggest that AChE may be involved in ALS pathogenesis. The accelerated disease course with neostigmine suggests that any beneficial effects of mEN101 occur through a non-catalytic rather than cholinergic mechanism.

Modulation of nitrergic signalling pathway by American ginseng attenuates chronic unpredictable stress-induced cognitive impairment, neuroinflammation, and biochemical alterations

Prolonged stress causes extensive loss of neurons leading to deficits in cognitive performance. Increasing evidence indicates that accumulation of intercellular messenger, nitric oxide (NO), plays a crucial role in the pathogenesis of memory disorders. American ginseng (AG) is known to show protection in different animal models of neurological diseases; however, its exact mechanism of action is not clearly understood. Therefore, the current study was designed to investigate the interaction of AG against chronic unpredictable stress (CUS)-associated behavioral and biochemical alterations and the probable role of nitrergic pathway in this effect. Male Laca mice were exposed to a series of stressors along with drug/vehicle treatment daily for 28 days. CUS paradigm caused significant impairment in both acquisition and retention memory as measured in Morris water maze and elevated plus maze task. This was coupled with alterations in oxidative stress markers, mitochondrial enzyme complex activities, pro-inflammatory cytokine (TNF-α), and acetylcholinesterase levels in the hippocampus as compared with naïve group. Besides, there was a marked increase in serum corticosterone levels. AG (100, 200 mg/kg; p.o.) treatment significantly improved cognitive impairment; reduced TNF-α, acetylcholinesterase, and corticosterone levels; and attenuated oxidative-nitrergic stress. Furthermore, pre-treatment of L-arginine (100 mg/kg; i.p.), a nitric oxide donor, with subeffective dose of AG (100 mg/kg; p.o.) reversed its protective effects. However, L-NAME (10 mg/kg, i.p.), a non-specific NO synthase inhibitor, potentiated the effects of AG. Our findings suggest that modulation of nitrergic signalling cascade is involved in the protective effects of AG against CUS-induced cognitive dysfunction, oxidative stress, and neuroinflammation.

Target- and mechanism-based therapeutics for neurodegenerative diseases: strength in numbers

The development of new therapeutics for the treatment of neurodegenerative pathophysiologies currently stands at a crossroads. This presents an opportunity to transition future drug discovery efforts to target disease modification, an area in which much still remains unknown. In this Perspective we examine recent progress in the areas of neurodegenerative drug discovery, focusing on some of the most common targets and mechanisms: N-methyl-d-aspartic acid (NMDA) receptors, voltage gated calcium channels (VGCCs), neuronal nitric oxide synthase (nNOS), oxidative stress from reactive oxygen species, and protein aggregation. These represent the key players identified in neurodegeneration and are part of a complex, intertwined signaling cascade. The synergistic delivery of two or more compounds directed against these targets, along with the design of small molecules with multiple modes of action, should be explored in pursuit of more effective clinical treatments for neurodegenerative diseases.

Additive toxicity of β-amyloid by a novel bioactive peptide in vitro: possible implications for Alzheimer's disease

Background

β-amyloid is regarded as a significant factor in Alzheimer’s disease: but inefficient therapies based on this rationale suggests that additional signalling molecules or intermediary mechanisms must be involved in the actual initiation of the characteristic degeneration of neurons. One clue could be that acetylcholinesterase, also present in amyloid plaques, is aberrant in peripheral tissues such as blood and adrenal medulla that can be implicated in Alzheimer’s disease. The aim of this study was to assess the bioactivity of a fragment of acetylcholinesterase responsible for its non-enzymatic functions, a thirty amino acid peptide (“T30”) which has homologies with β-amyloid.

Methods

Cell viability was measured by sulforhodamine B assay and also lactate dehydrogenase assay: meanwhile, changes in the status of living cells was monitored by measuring release of acetylcholinesterase in cell perfusates using the Ellman reagent.

Findings

T30 peptide and β-amyloid each have toxic effects on PC12 cells, comparable to hydrogen peroxide_. However only the two peptides selectively then evoke a subsequent, enhanced release in acetylcholinesterase that could only be derived from the extant cells. Moreover, unlike hydrogen peroxide, the T30 peptide selectively shifted a sub-threshold dose of β-amyloid to a toxic effect, which also resulted in a comparable enhanced release of acetylcholinesterase.

Interpretation

This is the first study comparing directly the bioactivity of β-amyloid with a peptide derived from acetylcholinesterase: the similarity in action suggests that the sequence homology between the two compounds might have a functional and/or pathological relevance. The subsequent enhanced release of acetylcholinesterase from the extant cells could reflect a primary ‘compensatory’ response of cells prone to degeneration, paradoxically providing further availability of the toxic C-terminal peptide to modulate the potency of β-amyloid. Such a cycle of events may provide new insights into the mechanism of continuing selective cell loss in Alzheimer’s disease and related degenerative disorders.

Galantamine potentiates the protective effect of rofecoxib and caffeic acid against intrahippocampal Kainic acid-induced cognitive dysfunction in rat

Role of neuroinflammatory mediators particularly cyclooxygenase (COX), lipoxygenase (LOX), have been well suggested in the pathophysiology of neurodegenerative disorders. Rofecoxib is a selective cyclooxygenase 2 enzymes belongs to non-steroidal anti-inflammatory drug, commonly called as coxibs. Whereas, caffeic acid (3,4-dihydroxycinnamic acid) is one of the natural phenolic compounds and reported to inhibit 5-lipoxygenase (5-LOX) activity as one of mechanisms. Present study has been designed to investigate the effects of rofecoxib, caffeic acid and its potentiation by galantamine against intrahippocampal kainic acid-induced cognitive impairment, oxidative damage and mitochondrial respiratory enzyme alterations in rats. Kainic acid (KA) was administrated in the hippocampus region of rat brain. Various behavioral (locomotor activity and memory performances were assessed by using actophotometer and Morris water maze respectively) followed by oxidative stress, mitochondrial enzyme complex were assessed. Intrahippocampal administration of KA significantly impaired locomotor activity, memory performance, mitochondrial enzyme complexes and caused oxidative stress as compared to sham treatment. Rofecoxib (5 and 10mg/kg), caffeic acid (5 and 10mg/kg), Gal (2.5 and 5mg/kg) treatment for 14 days significantly improved locomotor activity, memory retention and oxidative defense (as evidenced by decrease lipid peroxidation, nitrite, increased superoxide dismutase activity and redox ratio) in hippocampus. Besides, alterations in the levels of mitochondrial enzymes and acetylcholine esterase enzyme were significantly restored by rofecoxib and caffeic acid as compared to control. Further, combination of rofecoxib (5mg/kg) with caffeic acid (5mg/kg) and lower dose of gal (2.5mg/kg) with rofecoxib (5mg/kg) treatments significantly potentiated their protective effect which was significant as compared to their effect per se. The results of the present study suggest that galantamine potentiates the protective effect of rofecoxib and caffeic acid against kainic acid induced cognitive impairment and associated oxidative damage.

Conformational preferences of a 14-residue fibrillogenic peptide from acetylcholinesterase

A 14-residue fragment from near the C-terminus of the enzyme acetylcholinesterase (AChE) is believed to have a neurotoxic/neurotrophic effect acting via an unknown pathway. While the peptide is α-helical in the full-length enzyme, the structure and association mechanism of the fragment are unknown. Using multiple molecular dynamics simulations, starting from a tetrameric complex of the association domain of AChE and systematically disassembled subsets that include the peptide fragment, we show that the fragment is incapable of retaining its helicity in solution. Extensive replica exchange Monte Carlo folding and unfolding simulations in implicit solvent with capped and uncapped termini failed to converge to any consistent cluster of structures, suggesting that the fragment remains largely unstructured in solution under the conditions considered. Furthermore, extended molecular dynamics simulations of two steric zipper models show that the peptide is likely to form a zipper with antiparallel sheets and that peptides with mutations known to prevent fibril formation likely do so by interfering with this packing. The results demonstrate how the local environment of a peptide can stabilize a particular conformation.

Upregulation of alpha7 Nicotinic Receptors by Acetylcholinesterase C-Terminal Peptides

Background

The alpha-7 nicotinic acetylcholine receptor (α7-nAChR) is well known as a potent calcium ionophore that, in the brain, has been implicated in excitotoxicity and hence in the underlying mechanisms of neurodegenerative disorders such as Alzheimer's disease. Previous research implied that the activity of this receptor may be modified by exposure to a peptide fragment derived from the C-terminal region of the enzyme acetylcholinesterase. This investigation was undertaken to determine if the functional changes observed could be attributed to peptide binding interaction with the α7-nAChR, or peptide modulation of receptor expression.

Methodology/Principal Findings

This study provides evidence that two peptides derived from the C-terminus of acetylcholinesterase, not only selectively displace specific bungarotoxin binding at the α7-nAChR, but also alter receptor binding properties for its familiar ligands, including the alternative endogenous agonist choline. Of more long-term significance, these peptides also induce upregulation of α7-nAChR mRNA and protein expression, as well as enhancing receptor trafficking to the plasma membrane.

Conclusions/Significance

The results reported here demonstrate a hitherto unknown relationship between the α7-nAChR and the non-enzymatic functions of acetylcholinesterase, mediated independently by its C-terminal domain. Such an interaction may prove valuable as a pharmacological tool, prompting new approaches for understanding, and combating, the process of neurodegeneration.

Respective roles of the catalytic domains and C-terminal tail peptides in the oligomerization and secretory trafficking of human acetylcholinesterase and butyrylcholinesterase

Butyrylcholinesterase (BChE) and the T splice variant of acetylcholinesterase that is predominant in mammalian brain and muscles (AChE(T)) possess a characteristic C-terminal tail (t) peptide. This t peptide allows their assembly into tetramers associated with the anchoring proteins ColQ and PRiMA. Although the t peptides of all vertebrate cholinesterases are remarkably similar and, in particular, contain seven strictly conserved aromatic residues, these enzymes differ in some of their oligomerization properties. To explore these differences, we studied human AChE (Aa) and BChE (Bb), and chimeras in which the t peptides (a and b) were exchanged (Ab and Ba). We found that secretion was increased by deletion of the t peptides, and that it was more efficient with a than with b. The patterns of oligomers were similar for Aa and Ab, as well as for Ba and Bb, indicating a predominant influence of the catalytic domains. However, addition of a cysteine within the aromatic-rich segment of the t peptides modified the oligomeric patterns: with a cysteine at position 19, the proportion of tetramers was markedly increased for Aa(S19C) and Ba(S19C), and to a lesser extent for Bb(N19C); the Ab(N19C) mutant produced all oligomeric forms, from monomers to hexamers. These results indicate that both the catalytic domains and the C-terminal t peptides contribute to the capacity of cholinesterases to form and secrete various oligomers. Sequence comparisons show that the differences between the t peptides of AChE and BChE are remarkably conserved among all vertebrates, suggesting that they reflect distinct functional adaptations.

Morphoregulation by acetylcholinesterase in fibroblasts and astrocytes

Acetylcholinesterase (AChE) terminates neurotransmission at cholinergic synapses by hydrolysing acetylcholine, but also has non-enzymatic morphoregulatory effects on neurons such as stimulation of neurite outgrowth. It is widely expressed outside the nervous system, but its function in non-neuronal cells is unclear. Here we have investigated the distribution and function of AChE in fibroblasts and astrocytes. We show that these cells express high levels of AChE protein that co-migrates with recombinant AChE but contains little catalytic activity. Fibroblasts express transcripts encoding the synaptic AChE-T isoform and its membrane anchoring peptide PRiMA-I. AChE is strikingly distributed in arcs, rings and patches at the leading edge of spreading and migrating fibroblasts and astrocytes, close to the cell-substratum interface, and in neuronal growth cones. During in vivo healing of mouse skin, AChE becomes highly expressed in re-epithelialising epidermal keratinocytes 1 day after wounding. AChE appears to be functionally important for polarised cell migration, since an AChE antibody reduces substratum adhesion of fibroblasts, and slows wound healing in vitro as effectively as a beta1-integrin antibody. Moreover, elevation of AChE expression increases fibroblast wound healing independently of catalytic activity. Interestingly, AChE surface patches precisely co-localise with amyloid precursor protein and the extracellular matrix protein perlecan, but not focal adhesions or alpha-dystroglycan, and contain a high concentration of tyrosine phosphorylated proteins in spreading cells. These findings suggest that cell surface AChE, possibly in a novel signalling complex containing APP and perlecan, contributes to a generalised mechanism for polarised membrane protrusion and migration in all adherent cells.

Amyloid peptides and proteins in review

Amyloids are filamentous protein deposits ranging in size from nanometres to microns and composed of aggregated peptide beta-sheets formed from parallel or anti-parallel alignments of peptide beta-strands. Amyloid-forming proteins have attracted a great deal of recent attention because of their association with over 30 diseases, notably neurodegenerative conditions like Alzheimer's, Huntington's, Parkinson's, Creutzfeldt-Jacob and prion disorders, but also systemic diseases such as amyotrophic lateral sclerosis (Lou Gehrig's disease) and type II diabetes. These diseases are all thought to involve important conformational changes in proteins, sometimes termed misfolding, that usually produce beta-sheet structures with a strong tendency to aggregate into water-insoluble fibrous polymers. Reasons for such conformational changes in vivo are still unclear. Intermediate aggregated state(s), rather than precipitated insoluble polymeric aggregates, have recently been implicated in cellular toxicity and may be the source of aberrant pathology in amyloid diseases. Numerous in vitro studies of short and medium length peptides that form amyloids have provided some clues to amyloid formation, with an alpha-helix to beta-sheet folding transition sometimes implicated as an intermediary step leading to amyloid formation. More recently, quite a few non-pathological amyloidogenic proteins have also been identified and physiological properties have been ascribed, challenging previous implications that amyloids were always disease causing. This article summarises a great deal of current knowledge on the occurrence, structure, folding pathways, chemistry and biology associated with amyloidogenic peptides and proteins and highlights some key factors that have been found to influence amyloidogenesis.

Selective enhancement of the activity of C-terminally truncated, but not intact, acetylcholinesterase

Acetylcholinesterase (AChE) is one of the fastest enzymes approaching the catalytic limit of enzyme activity. The enzyme is involved in the terminal breakdown of the neurotransmitter acetylcholine, but non-enzymatic roles have also been described for the entire AChE molecule and its isolated C-terminal sequences. These non-cholinergic functions have been attributed to both the developmental and degenerative situation: the major form of AChE present in these conditions is monomeric. Moreover, AChE has been shown to lose its typical characteristic of substrate inhibition in both development and degeneration. This study characterizes a form of AChE truncated after amino acid 548 (T548-AChE), whose truncation site is homologue to that of a physiological form of T-AChE detected in fetal bovine serum that has lost its C-terminal moiety supposedly due to proteolytic cleavage. Peptide sequences covered by this C-terminal sequence have been shown to be crucially involved in both developmental and degenerative mechanisms in vitro. Numerous studies have addressed the structure-function relationship of the AChE C-terminus with T548-AChE representing one of the most frequently studied forms of truncated AChE. In this study, we provide new insight into the understanding of the functional characteristics that T548-AChE acquires in solution: T548-AChE is incubated with agents of varying net charge and molecular weight. Together with kinetic studies and an analysis of different molecular forms and aggregation states of T548-AChE, we show that the enzymatic activity of T548-AChE, an enzyme verging at its catalytic limit is, nonetheless, apparently enhanced by up to 800%. We demonstrate, first, how the activity of T548-AChE can be enhanced through agents that contain highly positive charged moieties. Moreover, the un-competitive mechanism of activity enhancement most likely involves the peripheral anionic site of AChE that is reflected in delayed substrate inhibition being observed for activity enhanced T548-AChE. The data provides evidence towards a mechanistic and functional link between the form of AChE unique to both development and degeneration and a C-terminal peptide of T-AChE acting under those conditions.

The psychomotor theory of human mind

This study presents a new theory to explain the neural origins of human mind. This is the psychomotor theory. The author briefly analyzed the historical development of the mind-brain theories. The close relations between psychological and motor systems were subjected to a rather detailed analysis, using psychiatric and neurological examples. The feedback circuits between mind, brain, and body were shown to occur within the mind-brain-body triad, in normal states, and psycho-neural diseases. It was stated that psychiatric signs and symptoms are coupled with motor disturbances; neurological diseases are coupled with psychological disturbances; changes in cortico-spinal motor-system activity may influence mind-brain-body triad, and vice versa. Accordingly, a psychomotor theory was created to explain the psychomotor coupling in health and disease, stating that, not the mind-brain duality or unity, but the mind-brain-body triad as a functional unit may be essential in health and disease, because mind does not end in the brain, but further controls movements, in a reciprocal manner; mental and motor events share the same neural substrate, cortical, and spinal motoneurons; mental events emerging from the motoneuronal system expressed by the human language may be closely coupled with the unity of the mind-brain-body triad. So, the psychomotor theory rejects the mind-brain duality and instead advances the unity of the psychomotor system, which will have important consequences in understanding and improving the human mind, brain, and body in health and disease.

Multiple cascade effects of oxidative stress on astroglia

Many neurodegenerative diseases share common underlying features, most prominent of which are dysregulation of calcium homeostasis and reactive astrogliosis, ultimately triggered by oxidative stress. Interestingly, an additional feature of the early response to stress conditions is the upregulation and release of acetylcholinesterase (AChE). This study therefore investigates the link between oxidative stress, calcium influx, gene expression, protein synthesis, and AChE release. We report that, in astroglia and in an immortalized cell line, GH4-halpha7, acute oxidative stress causes influx of extracellular calcium through L-type voltage-gated calcium channels (L-VGCC), followed by increased release of AChE into the extracellular medium. Moreover, rapid and sustained changes in mRNA expression of AChE, L-VGCC, and melastatin-like transient receptor potential 2 (TRPM2) accompany profound suppression of global protein synthesis. Application of L-VGCC blockers selectively reduces stress-induced calcium influx and AChE release, mitigates changes in gene expression, and facilitates recovery from protein synthesis suppression. Although glia exhibit greater sensitivity in their responses, the results are comparable in astroglia and GH4-halpha7 cells, and suggest a generalized and integrated cellular response to stress conditions that characterizes changes observed in neurodegeneration.

Astroglia up-regulate transcription and secretion of 'readthrough' acetylcholinesterase following oxidative stress

Novel and diverse functions of glial cells are currently the focus of much attention [A. Volterra and J. Meldolesi (2005) Nature Rev. 6, 626-640]. Here we present evidence that rat astroglia release acetylcholinesterase (AChE) as part of their response to hypoxic damage. Exposure of astroglia to tert-butyl hydroperoxide, and hence oxidative stress, subsequently leads to a switching in mRNA from the classical membrane-bound T-AChE to a preferential increase in the splice variant for a soluble form, R-AChE, This change in expression is reflected in increased perinuclear and reduced cytoplasmic AChE staining of the insulted glial cells, with a concomitant and marked increase in extracellular secretion that peaks at 1 h post-treatment. An analogous increase in R-AChE, over a similar time scale, occurs in response to psychological stress [D. Kaufer et al. (1998) Nature 93, 373-377], as well as to head injury and stroke [E. Shohami et al. (1999) J. Neurotrauma 6, 365-76]. The data presented here suggest that glial cells may be key chemical intermediaries in such situations and, perhaps more generally in pathological conditions involving oxidative stress, such as neurodegeneration.

Molecular, biochemical and histochemical characterization of two acetylcholinesterase cDNAs from the German cockroach Blattella germanica

Full length cDNAs encoding two acetylcholinesterases (AChEs; Bgace1 and Bgace2) were cloned and characterized from the German cockroach, Blattella germanica. Sequence analyses showed that both genes possess all the typical features of ace, and that Bgace1 is orthologous to the insect ace1 whereas Bgace2 is to the insect ace2. Transcript level of Bgace1 was significantly higher (c. 10 fold) than that of Bgace2 in all 11 tissues examined, suggesting that Bgace1 likely encodes a predominant AChE. Multiple AChE bands were identified by native polyacrylamide gel electrophoresis and isoelectricfocusing from various tissue preparations, among which ganglia produced distinct two major and two minor AChE bands, indicative of the presence of at least two active AChEs. B. germanica AChEs appeared to be mainly localized in the central nervous system as demonstrated by histochemical activity staining, together with quantitative analysis of Bgace transcripts. Fluorescence in situ hybridization of the 1st thoracic ganglion confirmed that Bgace1 is predominantly transcribed and further showed that its transcript is found in almost entire region of inter or motor neurones including the cell bodies and axonal/dendritic branches. Bgace2 transcript is found only in the subset of neurones, particularly in the cell body. In addition, certain neurones were observed to express Bgace1 only.

An acetylcholinesterase-derived peptide inhibits endocytic membrane activity in a human metastatic breast cancer cell line

Acetylcholinesterase (AChE) is well established as having non-cholinergic functions and is also expressed in breast tumours where its function(s) is not known. Recently, a candidate peptide sequence towards the C-terminal of the AChE molecule has been identified, as the salient site remote from normal catalysis in neurons, and possibly other cells. The main aim of this study was to explore the possibility that 'AChE-peptide' might also affect human breast cancer cells. Uptake of the non-cytotoxic tracer horseradish peroxidase (HRP) was used as an index of endocytosis, a key component of the metastatic cascade, representing exocytosis/secretory membrane activity and/or plasma membrane protein turnover. AChE-peptide had no affect on the weakly metastatic MCF-7 human breast cancer cell line. By contrast, application of AChE-peptide to the strongly metastatic MDA-MB-231 cells resulted in a dose-dependent inhibition of HRP uptake; treatment with a scrambled variant of the peptide of comparable amino acid length was ineffective. The action of AChE-peptide was suppressed by lowering the extracellular Ca2+ concentration and co-applying a selective antagonist of alpha7, but not alpha4/beta2, nicotinic receptor. The results suggest that AChE-peptide has a novel, selective bioactivity on breast cancer cells and can potentiate metastatic cell behaviour.

A peptide derived from acetylcholinesterase is a pivotal signalling molecule in neurodegeneration

It is now widely accepted that acetylcholinesterase (AChE) also displays non-cholinergic functions, completely independent of cholinergic transmission. Indeed, AChE has been implicated in a variety of trophic and toxic actions in a range of different systems. However, it is still uncertain what part of the AChE molecule may be responsible for these actions, and indeed via what receptor. Recent work has identified a peptide towards the C-terminus of the AChE molecule that appears to have very similar effects to non-cholinergic AChE itself. This action is to enhance calcium entry, in acute and chronic preparations across a trophic-toxic spectrum, depending on concentration applied and/or duration of exposure.

Acetylcholinesterase in Hirschsprung's disease

The association between the congenital absence of colonic ganglion cells and an increased acetylcholinesterase (AChE) expression in the affected tissue is of diagnostic importance in Hirschsprung's disease (HSCR). Investigation of AChE's function in development may also help unravel some of the complex pathophysiology in HSCR. Normal nerves do not stain for AChE, but increased AChE expression is associated with the hypertrophied extrinsic nerve fibres of the aganglionic segment in HSCR. Although a high degree of histochemical diagnostic accuracy exists, results are not always uniform, and false positives and false negatives are reported. False negative results are primarily related to age, and an absence of AChE reaction does not exclude HSCR in neonates within the first 3 weeks after birth. AChE staining results may lack uniformity, resulting in a number of technical modifications that have been made to improve standardization of AChE staining. At least two distinct histological patterns are described, types A and B. The interpretation of increased AChE staining patterns in ganglionated bowel at the time of surgical pull-through remains a problem in patients with HSCR. The development of rapid staining techniques has helped to identify normal ganglionated bowel with greater certainty. The presence of fine AChE neurofibrils in the ganglionated segment has contributed to the debate surrounding intestinal neuronal dysplasia. Quantitative assay of cholinesterase activity confirms the pattern of histochemical staining. AChE is particularly increased in relation to butrylcholinesterase, with one molecular form, the G4 tetrameric form, predominating. It is likely that the raised levels of AChE in aganglionic tissue are the transcriptional consequence of the abnormalities in signalling molecules that characterize HSCR. Evidence suggests that this AChE is functioning in a nonenzymatic capacity to promote cell adhesion and differentiation and that the hypertrophied nerves and neurofibrils may be the result of this increased AChE expression.

A preclinical view of cholinesterase inhibitors in neuroprotection: do they provide more than symptomatic benefits in Alzheimer's disease?

The prevalence of Alzheimer's disease (AD), a neurodegenerative condition whose greatest risk factor is old age, is expected to rise dramatically during the next five decades, along with the trend for increased longevity. Early diagnosis and intervention with therapies that halt or slow disease progress are likely to represent an important component of effective treatment. Although much progress has been made in this area, there are currently no clinically approved interventions for AD that are classed as disease modifying or neuroprotective. Cholinesterase inhibitors are a drug class used for the symptomatic treatment of AD. Recent evidence from preclinical studies indicates that these agents can attenuate neuronal damage and death from cytotoxic insults, and therefore might affect AD pathogenesis. The mechanisms by which these actions are mediated might or might not be directly related to their primary mode of action.

Acetylcholinesterase interaction with Alzheimer amyloid beta

Acetylcholinesterase (AChE) is an enzyme involved in cholinergic and non-cholinergic functions in both the central and peripheral nervous system, most of the AChE is found as a tetrameric form bound to neuronal membranes. Early cytochemical studies have demonstrated that the AChE associated with senile plaques differs enzymatically from the AChE associated with neurons in several respects. Biochemical studies indicated that AChE induces amyloid fibril formation and form highly toxic AChE-Abeta complexes. A 3.5 kDa peptide containing a tryptophan of the enzyme peripheral binding site (PAS) mimics the effect of the whole enzyme on amyloid formation. The neurotoxicity induced by AChE-Abeta complexes indicated that they trigger more neurodegeneration than those of the Abeta peptide alone, both in vitro (hippocampal neurons) and in vivo (rats injected in the dorsal hippocampus as a model of Alzheimer). The fact that AChE is able to accelerate amyloid formation and that such effect is sensitive to drugs that block PAS of the enzyme, suggests that specific and new AChE inhibitors may well provide an attractive possibility for treating Alzheimer's disease.

Biotechnology, the brain and the future

Several new approaches to illness, inspired by recent advances in molecular biology, informatics and nanoscience, are readily applicable to diseases of the central nervous system. Novel classes of drugs will widen the scope of therapeutic action beyond merely modifying transmitter function and stem cell and gene therapies could offer an even more selective mode of targeting. Further into the future, nanotechnology has the potential to allow development of new medicines and novel access routes via miniaturized monitoring and screening devices: these systems, together with increasing use of carbon-silicon interfacing, will challenge traditional neuropharmacology. As the 21(st) century unfolds, the structure and function of the brain, which is incomparable with any other organ, will present unique technological and ethical questions.

Bioactivity of a peptide derived from acetylcholinesterase: involvement of an ivermectin-sensitive site on the alpha 7 nicotinic receptor

A peptide fragment of 14 amino acids, derived from the C-terminus of acetylcholinesterase (AChE), might underlie the now well-established noncholinergic effects of the enzyme. This peptide is bioactive in a variety of systems including acute (brain slices) and chronic (organotypic culture) preparations of hippocampus, a pivotal area in Alzheimer's disease (AD); invariably, the action of the peptide is mediated specifically via an as yet unknown receptor. In this study, the allosteric alpha 7 agent, ivermectin (IVM), had a modest inhibitory effect, whilst that of the peptide was significantly more marked. However, ivermectin rendered ineffective the toxicity of high doses of the peptide, that is, when the two were co-applied, only the smaller effects of ivermectin were seen. Ivermectin, therefore, is presumably acting at a site that is identical to, or at least strongly interactive with, the normal binding site for AChE-peptide. This observation could have important implications for eventual therapeutic targeting of the action of AChE-peptide, in neurodegeneration.

A peptide derived from the C-terminal region of acetylcholinesterase modulates extracellular concentrations of acetylcholinesterase in the rat substantia nigra

It is well established that acetylcholinesterase (AChE) has 'non-classical' functions independent of cholinergic transmission. A region of AChE distinct from the catalytic site may be responsible for these actions via a 14-residue peptide located between residues 586-599 at the C-terminus of human AChE. This AChE-peptide possesses a high amino acid sequence homology with a region of amyloid precursor protein and shares many biophysical and physiological characteristics. In this study, the effect of AChE-peptide (AEFHRWSSYMVHWK) on the extracellular levels of endogenous AChE was examined in rat substantia nigra in vitro. A chemiluminescent assay was used to continuously measure the soluble AChE concentration from tissue punches of the substantia nigra. Application of NMDA evoked an increase in extracellular AChE levels consistent with previous results obtained from in vivo models. AChE-peptide, when applied alone, had no effect on AChE release: however, when co-applied with NMDA, AChE-peptide reduced the effectiveness of NMDA to evoke release of AChE. These results indicate, in a region of the brain central to the aetiology of Parkinson's disease, that an AChE-peptide fragment derived from AChE displays a bioactivity that could involve regulation of Ca(2+) availability and hence the release of AChE.