CHOLINESTERASES, A TARGET OF PHARMACOLOGY AND TOXICOLOGY

In Silico Insight into Potential Anti-Alzheimer's Disease Mechanisms of Icariin

Herbal compounds that have notable therapeutic effect upon Alzheimer's disease (AD) have frequently been found, despite the recent failure of late-stage clinical drugs. Icariin, which is isolated from Epimedium brevicornum, is widely reported to exhibit significant anti-AD effects in in vitro and in vivo studies. However, the molecular mechanism remains thus far unclear. In this work, the anti-AD mechanisms of icariin were investigated at a target network level assisted by an in silico target identification program (INVDOCK). The results suggested that the anti-AD effects of icariin may be contributed by: attenuation of hyperphosphorylation of tau protein, anti-inflammation and regulation of Ca²⁺ homeostasis. Our results may provide assistance in understanding the molecular mechanism and further developing icariin into promising anti-AD agents.

Synthetic analogs of stryphnusin isolated from the marine sponge Stryphnus fortis inhibit acetylcholinesterase with no effect on muscle function or neuromuscular transmission

The current study describes the AChE inhibitory effect of natural marine neuroactive compounds.

Behavioural alterations from exposure to Cu, phenanthrene, and Cu-phenanthrene mixtures: linking behaviour to acute toxic mechanisms in the aquatic amphipod, Hyalella azteca

Phenanthrene (PHE) and Cu are two contaminants commonly co-occurring in marine and freshwater environments. Mixtures of PHE and Cu have been reported to induce more-than-additive lethality in the amphipod, Hyalella azteca, a keystone aquatic invertebrate, yet little is understood regarding the interactive toxic mechanisms that mediate more-than-additive toxicity. Understanding the interactions among toxic mechanisms among Cu and PHE will allow for better predictive power in assessing the ecological risks of Cu-PHE mixtures in aquatic environments. Here we use behavioural impairment to help understand the toxic mechanisms of Cu, PHE, and Cu-PHE mixture toxicity in the aquatic amphipod crustacean, Hyalella azteca. Our principal objective was to link alterations in activity and ventilation with respiratory rates, oxidative stress, and neurotoxicity in adult H. azteca. Adult amphipods were used for all toxicity tests. Amphipods were tested at sublethal exposures of 91.8- and 195-μgL(-1) Cu and PHE, respectively, and a Cu-PHE mixture at the same concentrations for 24h. Neurotoxicity was measured as acetylcholinesterase (AChE) activity, where malathion was used as a positive control. Oxidative stress was measured as reactive oxygen species (ROS) production. Phenanthrene-exposed amphipods exhibited severe behavioural impairment, being hyperstimulated to the extent that they were incapable of coordinating muscle movements. In addition, respiration and AChE activity in PHE-exposed amphipods were increased and reduced by 51% and 23% respectively. However, ROS did not increase following exposure to phenanthrene. In contrast, Cu had no effect on amphipod behaviour, respiration or AChE activity, but did lead to an increase in ROS. However, co-exposure to Cu antagonized the PHE-induced reduction in ventilation and negated any increase in respiration. The results suggest that PHE acts like an organophosphate pesticide (e.g., malathion) in H. azteca following 24h sublethal exposures, and that AChE inhibition is the likely mechanism by which PHE alters H. azteca behaviour. However, interactive aspects of neurotoxicity do not account for the previously observed more-than-additive mortality in H. azteca following exposure to Cu-PHE mixtures.

An immobilization multienzyme microfluidic chip for acetylcholinesterase inhibition assay by fluorescence method

A bi-enzyme immobilized microfluidic device was developed for the rapid enzyme inhibition assay by fluorescence detection.

Citrus hystrix-derived 3,7-dimethyloct-6-enal and 3,7-dimethyloct-6-enyl acetate ameliorate acetylcholine deficits

Cholinergic neurotransmission is an affliction in a plethora of neurodegenerative disorders such as Alzheimer’s, Huntington’s and Parkinson’s diseases and some psychiatric disorders like schizophrenia.

Genomic Discoveries and Personalized Medicine in Neurological Diseases

In the past decades, we have witnessed dramatic changes in clinical diagnoses and treatments due to the revolutions of genomics and personalized medicine. Undoubtedly we also met many challenges when we use those advanced technologies in drug discovery and development. In this review, we describe when genomic information is applied in personal healthcare in general. We illustrate some case examples of genomic discoveries and promising personalized medicine applications in the area of neurological disease particular. Available data suggest that individual genomics can be applied to better treat patients in the near future.

Towards the design of organocatalysts for nerve agents remediation: The case of the active hydrolysis of DCNP (a Tabun mimic) catalyzed by simple amine-containing derivatives

We report herein a study of the hydrolysis of Tabun mimic DCNP in the presence of different amines, aminoalcohols and glycols as potential suitable organocatalysts for DCNP degradation. Experiments were performed in CD3CN in the presence of 5% D2O, which is a suitable solvent mixture to follow the DCNP hydrolysis. These studies allowed the definition of different DCNP depletion paths, resulting in the formation of diethylphosphoric acid, tetraethylpyrophosphate and phosphoramide species as final products. Without organocatalysts, DCNP hydrolysis occurred mainly via an autocatalysis path. Addition of tertiary amines in sub-stoichiometric amounts largely enhanced DCNP depletion whereas non-tertiary polyamines reacted even faster. Glycols induced very slight increment in the DCNP hydrolysis, whereas DCNP hydrolysis increased sharply in the presence of certain aminoalcohols especially, 2-(2-aminoethylamino)ethanol. For the latter compound, DCNP depletion occurred ca. 80-fold faster than in the absence of organocatalysts. The kinetic studies revealed that DCNP hydrolysis in the presence of 2-(2-aminoethylamino)ethanol occurred via a catalytic process, in which the aminoalcohol was involved. DCNP hydrolysis generally depended strongly on the structure of the amine, and it was found that the presence of the OHCH2CH2N moiety in the organocatalyst structure seems important to induce a fast degradation of DCNP.

Effects of environmentally-relevant mixtures of four common organophosphorus insecticides on the honey bee (Apis mellifera L.)

We assessed whether exposure to environmentally-relevant mixtures of four organophosphorus insecticides (OPs) exerted adverse effects on honey bees. Adult and worker bees were orally exposed for five days under laboratory conditions to mixtures of four insecticides, diazinon, malathion, profenofos and chlorpyrifos at two concentrations. Concentration in the mixtures tested were equivalent to the median and 95th centile concentrations of the OPs in honey, as reported in the literature. Effects on survival, behavior, activity of acetylcholinesterase (AChE), and expression of genes important in detoxification of xenobiotics and immune response were examined. Survival of worker bees was not affected by exposure to median or 95th centile concentrations of the OPs. Activity of AChE was significantly greater in worker bees exposed to the 95th centile concentration mixture of OPs compared to the median concentration mixture. Expression of genes involved in detoxification of xenobiotics was not affected by treatment, but the abundance of transcripts of the antimicrobial peptide hymenoptaecin was significantly greater in worker honey bees exposed to the median concentration mixture. Results suggest that short-term exposure to environmentally relevant concentrations of a mixture of OPs do not adversely affect worker honey bees.

Acetylcholinesterase from Human Erythrocytes as a Surrogate Biomarker of Lead Induced Neurotoxicity

Lead induced neurotoxicity in the people engaged in different occupations has received wide attention but very little studies have been carried out to monitor occupational neurotoxicity directly due to lead exposure using biochemical methods. In the present paper an endeavour has been made in order to assess the lead mediated neurotoxicity by in vitro assay of the activity of acetylcholinesterase (AChE) from human erythrocytes in presence of different concentrations of lead. The results suggested that the activity of this enzyme was localized in membrane bound fraction and it was found to be highly stable up to 30 days when stored at -20°C in phosphate buffer (50 mM, pH 7.4) containing 0.2% Triton X-100. The erythrocyte's AChE exhibited K m for acetylcholinesterase to be 0.1 mM. Lead caused sharp inhibition of the enzyme and its IC50 value was computed to be 1.34 mM. The inhibition of the enzyme by lead was found to be of uncompetitive type (K i value, 3.6 mM) which negatively influenced both the V max and the enzyme-substrate binding affinity. Taken together, these results indicate that AChE from human erythrocytes could be exploited as a surrogate biomarker of lead induced neurotoxicity particularly in the people occupationally exposed to lead.

Transient Receptor Potential Channel Opening Releases Endogenous Acetylcholine, which Contributes to Endothelium-Dependent Relaxation Induced by Mild Hypothermia in Spontaneously Hypertensive Rat but Not Wistar-Kyoto Rat Arteries

Mild hypothermia causes endothelium-dependent relaxations, which are reduced by the muscarinic receptor antagonist atropine. The present study investigated whether endothelial endogenous acetylcholine contributes to these relaxations. Aortic rings of spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were contracted with prostaglandin F2 α and exposed to progressive mild hypothermia (from 37 to 31°C). Hypothermia induced endothelium-dependent, Nω-nitro-l-arginine methyl ester-sensitive relaxations, which were reduced by atropine, but not by mecamylamine, in SHR but not in WKY rat aortae. The responses in SHR aortae were also reduced by acetylcholinesterase (the enzyme responsible for acetylcholine degradation), bromoacetylcholine (inhibitor of acetylcholine synthesis), hemicholinium-3 (inhibitor of choline uptake), and vesamicol (inhibitor of acetylcholine release). The mild hypothermia-induced relaxations in both SHR and WKY rat aortae were inhibited by AMTB [N-(3-aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl)-benzamide; the transient receptor potential (TRP) M8 inhibitor]; only those in SHR aortae were inhibited by HC-067047 [2-methyl-1-[3-(4-morpholinyl)propyl]-5-phenyl-N-[3-(trifluoromethyl)phenyl]-1H-pyrrole-3-carboxamide; TRPV4 antagonist] while those in WKY rat aortae were reduced by HC-030031 [2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide; TRPA1 antagonist]. The endothelial uptake of extracellular choline and release of cyclic guanosine monophosphate was enhanced by mild hypothermia and inhibited by HC-067047 in SHR but not in WKY rat aortae. Compared with WKY rats, the SHR preparations expressed similar levels of acetylcholinesterase and choline acetyltransferase, but a lesser amount of vesicular acetylcholine transporter, located mainly in the endothelium. Thus, mild hypothermia causes nitric oxide-dependent relaxations by opening TRPA1 channels in WKY rat aortae. By contrast, in SHR aortae, TRPV4 channels are opened, resulting in endothelial production of acetylcholine, which, in an autocrine manner, activates muscarinic receptors on neighboring cells to elicit endothelium-dependent relaxations in response to mild hypothermia.

Perturbation of acyl ghrelin profile after liver transplantation

BACKGROUND

A significant problem to be solved for patients after liver transplantation (LT) is malnutrition with anorexia in the early posttransplant period. We hypothesized that this problem was due to the change in ghrelin metabolism during LT. The aim of this study was to examine the balance of acyl ghrelin (AG) and desacyl ghrelin and the dependence of the regulation mechanism on hepatic-related enzymes in patients during LT.

MATERIALS AND METHODS

AG, desacyl ghrelin, and acyl/total ghrelin (A/T) concentrations in blood samples were measured in 15 patients with liver failure (LF), 15 patients after LT, and 10 controls. The correlations between the participants' ghrelin profiles and hepatic function-related data, including liver enzymes, were evaluated. In vitro assays using synthetic AG for assessment of deacylation activity in serum were performed.

RESULTS

AG and A/T ratio were significantly higher in the LF patients than the patients after LT and controls (AG: 25.9 ± 12.6 versus 16.4 ± 12.6 and 9.8 ± 7.6 fmol/mL, P < 0.05; A/T ratio: 17.4 ± 4.1 versus 12.2 ± 5.5 and 11.8% ± 5.9%, P < 0.05). The serum cholinesterase level was inversely correlated with AG and A/T ratio (P < 0.01). In vitro assays showed that deacylation activity was significantly lower in patients with LF than controls (10.5% versus 42.4%, 90 min; P < 0.01). Degradation of AG was partially suppressed by a cholinesterase inhibitor.

CONCLUSIONS

Deacylation activity was lower in LF patients, which could cause elevation of AG levels. Serum cholinesterase may be responsible for deacylation in humans.

Postponed effect of neostigmine on oxidative homeostasis

Cholinesterases are enzymes able to hydrolyze the neurotransmitter acetylcholine and thus to terminate transmission. Once the enzymes are inhibited, excitotoxicity can appear in the adjacent cells. It is well known that oxidative stress is involved in the toxicity of cholinesterase inhibitors. Commonly, stress follows inhibition of cholinesterases and disappears shortly afterwards. In the present experiment, it was decided to test the impact of an inhibitor, neostigmine, on oxidative stress in BALB/c mice after a longer interval. The animals were sacrificed three days after onset of the experiment and spleens and livers were collected. Reduced glutathione (GSH), glutathione reductase (GR), glutathione S-transferase (GST), thiobarbituric acid reactive substances (TBARS), ferric reducing antioxidant power (FRAP), caspase-3 and activity of acetylcholinesterase (AChE) were assayed. The tested markers were not altered with exceptions of FRAP. The FRAP values indicate accumulation of low molecular weight antioxidants in the examined organs. The role of low molecular weight antioxidants in the toxicity of AChE inhibitors is discussed.

Photography by Cameras Integrated in Smartphones as a Tool for Analytical Chemistry Represented by an Butyrylcholinesterase Activity Assay

Smartphones are popular devices frequently equipped with sensitive sensors and great computational ability. Despite the widespread availability of smartphones, practical uses in analytical chemistry are limited, though some papers have proposed promising applications. In the present paper, a smartphone is used as a tool for the determination of cholinesterasemia i.e., the determination of a biochemical marker butyrylcholinesterase (BChE). The work should demonstrate suitability of a smartphone-integrated camera for analytical purposes. Paper strips soaked with indoxylacetate were used for the determination of BChE activity, while the standard Ellman’s assay was used as a reference measurement. In the smartphone-based assay, BChE converted indoxylacetate to indigo blue and coloration was photographed using the phone’s integrated camera. A RGB color model was analyzed and color values for the individual color channels were determined. The assay was verified using plasma samples and samples containing pure BChE, and validated using Ellmans’s assay. The smartphone assay was proved to be reliable and applicable for routine diagnoses where BChE serves as a marker (liver function tests; some poisonings, etc.). It can be concluded that the assay is expected to be of practical applicability because of the results’ relevance.

Preparation and performance of a colorimetric biosensor using acetylcholinesterase and indoxylacetate for assay of nerve agents and drugs

Different toxic compounds can target the cholinergic nervous system. Acetylcholinesterase (AChE; EC 3.1.1.7) is one of the most crucial components of the cholinergic nervous system and thus many of the toxins interact with this enzyme. As to inhibitors, nerve agents used as chemical warfare, some insecticides, and drugs influencing the cholinergic system are common examples of AChE inhibitors. Once inhibited by a neurotoxic compound, a serious cholinergic crisis can occur. On the other hand, sensitivity of AChE to the inhibition can be used for analytical purposes. In this study, a simple disposable biosensor with AChE as a recognition element was devised. AChE was immobilized onto a cellulose matrix and indoxylacetate was used as a chromogenic substrate. The enzyme reaction was assessed by the naked eye using arbitrary units and pyridostigmine, tacrine, paraoxon, carbofuran, soman and VX were assayed as selected inhibitors. A good stability of the biosensors was found, with no aging over a quarter of a year and minimal sensitivity to the interference of organic solvents. The limit of detection ranged from 10 to 100 nmol/L for the compounds tested with a sample volume of 40 µL.

Evaluation of 2,6-dichlorophenolindophenol acetate as a substrate for acetylcholinesterase activity assay

Ellman's method is a standard protocol for the determination of cholinesterases activity. Though the method is ready for laboratory purposes, it has some drawbacks as well. In the current article, 2,6-dichloroindophenol acetate is performed as a chromogenic substrate suitable for acetylcholinesterase (AChE) activity examination. Michaelis constant and maximal velocity for 2,6-dichloroindophenol acetate were determined (38.0 µM and 244 pkat) and compared to the values for acetythiocholine (K(m) 0.18 mM; V(max) 5.1 nkat). Docking for 2,6-dichloroindophenol acetate and human AChE was done as well. In conclusion, 2,6-dichloroindophenol acetate seems to be suitable chromogenic substrate for AChE and spectrophotometry and based on this it can be easily performed whenever AChE activity should be tested.

Butyrylcholinesterase: K variant, plasma activity, molecular forms and rivastigmine treatment in Alzheimer's disease in a Southern Brazilian population

Alzheimer's disease (AD) is a neurodegenerative disorder in which there is a decline of cholinergic function. The symptomatic AD treatment involves the use of ChEIs (cholinesterase inhibitors) as rivastigimine, a dual inhibitor. The human butyrylcholinesterase (BChE) is an enzyme that has specific roles in cholinergic neurotransmission and it has been associated with AD. In the serum, BChE is found in four main molecular forms: G1 (monomer); G1-ALB (monomer linked to albumin); G2 (dimer); and G4 (tetramer). The interaction between the products of BCHE gene and CHE2 locus results in CHE2 C5+ and CHE2 C5- phenotypes. CHE2 C5+ phenotype and BChE-K are factors that influence on BChE activity. This work aimed to verify the proportions of BChE molecular forms, total and relative activity in 139 AD patients and 139 elderly controls, taking into account K variant, CHE2 locus, rivastigmine treatment and clinical dementia rating (CDR) of AD patients. Phenotypic frequencies of CHE2 C5+ and frequency of the carriers of the K allele were similar between groups. Total BChE activity in plasma was significantly lower in AD patients than in elderly controls. Furthermore, we found that reduction on plasma BChE activity is associated directly with AD progression in AD patients and that rivastigmine treatment has a stronger effect on BChE activity within the CDR2 group. The reduction in BChE activity did not occur proportionally in all molecular forms. Multiple regression analysis results confirmed that AD acts as the main factor in plasma BChE activity reduction and that severe stages are related with an even greater reduction. These findings suggest that the reduction of total plasma BChE and relative BChE molecular forms activity in AD patients is probably associated with a feedback mechanism and provides a future perspective of using this enzyme as a possible plasmatic secondary marker for AD.

Potential of neural stem cell-based therapies for Alzheimer's disease

Alzheimer's disease (AD), known to be a leading cause of dementia that causes heavy social and financial burdens worldwide, is characterized by progressive loss of neurons and synaptic connectivity after depositions of amyloid-β (Aβ) protein. Current therapies for AD patients can only alleviate symptoms but cannot deter the neural degeneration, thus providing no long-term recovery. Neural stem cells (NSCs), capable of self-renewal and of differentiation into functional neurons and glia, have been shown to repair damaged networks and reverse memory and learning deficits in animal studies, providing new hope for curing AD patients by cell transplantation. Under AD pathology, the microenvironment also undergoes great alterations that affect the propagation of NSCs and subsequent therapeutic efficiency, calling for measures to improve the hostile environment for cell transplantation. This article reviews the therapeutic potential of both endogenous and exogenous NSCs in the treatment of AD and the challenges to application of stem cells in AD treatment, particularly those from the microenvironmental alterations, in the hope of providing more information for future research in exploiting stem cell-based therapies for AD. © 2015 Wiley Periodicals, Inc.

A photonic crystal based sensing scheme for acetylcholine and acetylcholinesterase inhibitors

A 2-layer approach towards optical sensing of acetylcholine and detection of an acetylcholinesterase inhibitor using photonic crystal sensor technology.

Determination of acetylcholinesterase and butyrylcholinesterase activity without dilution of biological samples

Two cholinesterases: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), are known. The enzymes are important in the body and alteration of their activity has significant use in the diagnosis of poisoning, liver function, etc. Currently available methods for the determination of cholinesterases have some major drawbacks including various interferences and the inability to be used for decreasing the enzyme activity in the presence of reversible inhibitors due to sample dilution; hence, a method for dilution free assay of cholinesterases is desired. Here, microplates were modified with indoxylacetate (100 μL of 10 mmol L

Biosensors containing acetylcholinesterase and butyrylcholinesterase as recognition tools for detection of various compounds

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are enzymes expressed in the human body under physiological conditions. AChE is an important part of the cholinergic nerves where it hydrolyses neurotransmitter acetylcholine. Both cholinesterases are sensitive to inhibitors acting as neurotoxic compounds. In analytical applications, the enzymes can serve as a biorecognition element in biosensors as well as simple disposable sensors (dipsticks) and be used for assaying the neurotoxic compounds. In the present review, the mechanism of AChE and BChE inhibition by disparate compounds is explained and methods for assaying the enzymes activity are shown. Optical, electrochemical, and piezoelectric biosensors are described. Attention is also given to the application of sol-gel techniques and quantum dots in the biosensors’ construction. Examples of the biosensors are provided and the pros and cons are discussed.

Kolaviron, isolated from Garcinia kola, inhibits acetylcholinesterase activities in the hippocampus and striatum of wistar rats

BACKGROUND

Kolaviron, isolated from seeds of Garcinia kola, have been shown to possess wide pharmacological properties.

PURPOSE

The present study examined the effect of kolaviron on acetylcholinesterase activities in the hippocampus and striatum of adult Wistar rats.

METHODS

In this study, histological and histochemical methods were used to investigate the effects of kolaviron on the histology of the hippocampus and striatum and on acetylcholinesterase activities in these brain regions.

RESULTS

We showed that kolaviron produced no neurodegenerative changes in the hippocampus and striatum. Kolaviron did not significantly alter (p<0.05) neuronal density in these brain regions. Kolaviron significantly reduced (p<0.05) acetylcholinesterase staining intensity, suggesting a likely inhibiting effect on this enzyme.

CONCLUSION

To the best of our knowledge, this study provides the first evidence that kolaviron could act as an acetylcholinesterase inhibitor. Kolaviron may be developed as a herbal-based natural product with therapeutic potential in the management of neurodegenerative disorders associated with disturbed cholinergic neurotransmitter systems.

Alzheimer disease immunotherapeutics: then and now

Dementia is a public health priority and one of the major contributors to morbidity and global non-communicable disease burden, thus necessitating the need for significant health-care interventions. Alzheimer disease (AD) is the most common cause of dementia and may contribute to 60-70% of cases. The cause and progression of AD are not well understood but have been thought to be due at least in part to protein misfolding (proteopathy) manifest as plaque accumulation of abnormally folded β-amyloid and tau proteins in brain. There are about 8 million new cases per year. The total number of people with dementia is projected to almost double every 20 years, to 66 million in 2030 and 115 million in 2050. Immunotherapy in AD aimed at β-amyloid covers 2 types of vaccination: active vaccination against Aβ42 in which patients receive injections of the antigen itself, or passive vaccination in which patients receive injections of monoclonal antibodies (mAb) against Aβ42. Three of the peptide vaccines for active immunizations, CAD106, ACC001, and Affitope, are in phase 2 clinical trials. Three of the mAbs solanezumab, gantenerumab, and crenezumab, are or were in phase 2 and 3 clinical studies. While the phase 3 trials failed, one of these may have shown a benefit at least in mild forms of AD. There is a need for a greater initiative in the development of immunotherapeutics. Several avenues have been explored and still to come.

Butyrylcholinesterase levels and subjective effects of smoked cocaine in healthy cocaine users

BACKGROUND

Butyrylcholinesterase (BChE) is beginning to attract attention as a possible target for cocaine abuse treatment because of its role in metabolizing cocaine.

OBJECTIVE

The purpose of this analysis was to assess whether endogenous BChE levels are associated with the subjective effects of cocaine.

METHODS

Data from 28 participants in five inpatient cocaine self-administration studies were included in the present analysis. Four minutes after each smoked cocaine dose, participants rated their drug-related effects from 0-100 using a computerized self-report Visual Analogue Scale (VAS). The main outcome measures were nine change-in-VAS ratings between a baseline placebo dose and a 25-mg smoked cocaine dose.

RESULTS

After controlling for age, sex, total years of cocaine use, total milligrams of cocaine administered before the 25-mg dose being analyzed, and baseline diastolic blood pressure, endogenous BChE was not significantly associated with any of the nine change-in-VAS ratings.

CONCLUSION

Though BChE appears to be a possible target for cocaine abuse treatment, these data suggest that endogenous levels of BChE may not play a role in modifying the subjective effects of cocaine. Future larger studies of BChE in respect to the subjective effects produced by cocaine are needed to confirm or refute these findings.

Potential therapeutic strategies for Alzheimer's disease targeting or beyond β-amyloid: insights from clinical trials

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with two hallmarks: β-amyloid plagues and neurofibrillary tangles. It is one of the most alarming illnesses to elderly people. No effective drugs and therapies have been developed, while mechanism-based explorations of therapeutic approaches have been intensively investigated. Outcomes of clinical trials suggested several pitfalls in the choice of biomarkers, development of drug candidates, and interaction of drug-targeted molecules; however, they also aroused concerns on the potential deficiency in our understanding of pathogenesis of AD, and ultimately stimulated the advent of novel drug targets tests. The anticipated increase of AD patients in next few decades makes development of better therapy an urgent issue. Here we attempt to summarize and compare putative therapeutic strategies that have completed clinical trials or are currently being tested from various perspectives to provide insights for treatments of Alzheimer's disease.

Xanthenedione derivatives, new promising antioxidant and acetylcholinesterase inhibitor agents

Natural and synthetic xanthone derivatives are well-known for their ability to act as antioxidants and/or enzyme inhibitors. This paper aims to present a successful synthetic methodology towards xanthenedione derivatives and the study of their aromatization to xanthones. Additionally their ability to reduce Fe(III), to scavenge DPPH radicals and to inhibit AChE was evaluated. The results demonstrated that xanthenedione derivative 5e, bearing a catechol unit, showed higher reduction capacity than BHT and similar to quercetin, strong DPPH scavenging activity (EC₅₀ = 3.79 ± 0.06 µM) and it was also showed to be a potent AChEI (IC₅₀ = 31.0 ± 0.09 µM) when compared to galantamine (IC₅₀ = 211.8 ± 9.5 µM).

Inhibitors of acetylcholinesterase and butyrylcholinesterase meet immunity

Acetylcholinesterase (AChE) inhibitors are widely used for the symptomatic treatment of Alzheimer’s disease and other dementias. More recent use is for myasthenia gravis. Many of these inhibitors interact with the second known cholinesterase, butyrylcholinesterase (BChE). Further, evidence shows that acetylcholine plays a role in suppression of cytokine release through a “cholinergic anti-inflammatory pathway” which raises questions about the role of these inhibitors in the immune system. This review covers research and discussion of the role of the inhibitors in modulating the immune response using as examples the commonly available drugs, donepezil, galantamine, huperzine, neostigmine and pyridostigmine. Major attention is given to the cholinergic anti-inflammatory pathway, a well-described link between the central nervous system and terminal effector cells in the immune system.

Recognizing early dementia in the workplace: a case study

A case study of diagnosis of early dementia is presented and recommendations for educating health care professionals to recognize and treat this condition among workers are offered.

ADSC Therapy in Neurodegenerative Disorders

Neurodegenerative disorders, chronic diseases that can severely affect the patient's daily life, include amyotrophic lateral sclerosis, Parkinson's, Alzheimer's, and Huntington's diseases. However, these diseases all have the common characteristic that they are due to degenerative irreversibility, and thus no efficient drugs or therapy methods can mitigate symptoms completely. Stem cell therapy, such as adipose tissue-derived stem cells (ADSCs), is a promising treatment for incurable disorders. In this review, we summarized the previous studies using ADSCs to treat neurodegenerative disorders, as well as their therapeutic mechanisms. We also suggested possible expectations for future human clinical trials involving minimized intracerebroventricular combined with intravenous administration, using different cell lineages to finish complementary therapy as well as change the extracellular matrix to create a homing niche. Depending on successful experiments in relevant neurodegenerative disorders models, this could form the theoretical basis for future human clinical trials.

Isocorilagin, a Cholinesterase Inhibitor from Phyllanthus niruri

Drugs that have dual inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) produce better clinical efficacy against Alzheimer's disease (AD) than those that selectively inhibit one enzyme. A dual cholinesterase inhibitory-guided fractionation of Phyllanthus niruri leaves afforded isocorilagin, a bioactive tannin possessing good inhibitory activities against AChE (IC50: 0.49 μM) and BChE (IC50: 4.20 μM). Interestingly, isocorilagin was relatively 2- to 3-fold more potent than galanthamine, the clinically used inhibitor. The kinetic analyses suggested that isocorilagin was a non-competitive inhibitor for AChE and an uncompetitive inhibitor for BChE, with calculated Ki values of 1.49 μM and 2.86 μM, respectively. In silico molecular docking revealed that isocorilagin effectively blocked the substrate entry by forming hydrogen bonding with residues at the entrance of the AChE active site. With BChE, the compound completely docked inside and occupied the active site of the enzyme. This study demonstrated for the first time the potent cholinesterase inhibitory activities of isocorilagin, a promising lead that is worthy of further investigation.

Sulfur mustard induced oxidative stress and its alteration using asoxime (HI-6)

Sulfur mustard (SM) is a blister agent with cytotoxic mechanism of action. There is no suitable treatment based on administration of an antidote. In this study, Wistar rats were exposed to SM in doses of 0–40 mg/kg body weight and treated with the compound HI-6. The treatment provided no significant effect on ferric reducing antioxidant power of blood and plasma. However, HI-6 caused an increase in the level of thiobarbituric acid reactive substances. This stressogenic response was presumably the cause of the significant elevation of the blood level of both glutathione reductase and reduced glutathione. HI-6 appears to be suitable for enhancing prophylactically oxidative stress protection from small oxidative insult.

AlzPlatform: an Alzheimer's disease domain-specific chemogenomics knowledgebase for polypharmacology and target identification research

Alzheimer’s disease (AD) is one of the most complicated progressive neurodegeneration diseases that involve many genes, proteins, and their complex interactions. No effective medicines or treatments are available yet to stop or reverse the progression of the disease due to its polygenic nature. To facilitate discovery of new AD drugs and better understand the AD neurosignaling pathways involved, we have constructed an Alzheimer’s disease domain-specific chemogenomics knowledgebase, AlzPlatform (www.cbligand.org/AD/) with cloud computing and sourcing functions. AlzPlatform is implemented with powerful computational algorithms, including our established TargetHunter, HTDocking, and BBB Predictor for target identification and polypharmacology analysis for AD research. The platform has assembled various AD-related chemogenomics data records, including 928 genes and 320 proteins related to AD, 194 AD drugs approved or in clinical trials, and 405 188 chemicals associated with 1 023 137 records of reported bioactivities from 38 284 corresponding bioassays and 10 050 references. Furthermore, we have demonstrated the application of the AlzPlatform in three case studies for identification of multitargets and polypharmacology analysis of FDA-approved drugs and also for screening and prediction of new AD active small chemical molecules and potential novel AD drug targets by our established TargetHunter and/or HTDocking programs. The predictions were confirmed by reported bioactivity data and our in vitro experimental validation. Overall, AlzPlatform will enrich our knowledge for AD target identification, drug discovery, and polypharmacology analyses and, also, facilitate the chemogenomics data sharing and information exchange/communications in aid of new anti-AD drug discovery and development.

Review of the validated HPLC and LC-MS/MS methods for determination of drugs used in clinical practice for Alzheimer's disease

Alzheimer's disease (AD) is a neurological disorder and is the most frequent type of dementia among elderly people. Donepezil, rivastigmine, galantamine, tacrine and memantine are the US Food and Drug Administration approved oral drugs used in the treatment of AD. Quantitation of these drugs in various biological matrices and monitoring them in long-term treatment is essential to titer the dose of these drugs and ensure patient compliance. This review provides a comprehensive account of various HPLC and LC-MS/MS assays, which have been successfully employed to measure the drug levels in various biological matrices arising from preclinical and clinical studies. In addition, this review collates various considerations such as internal standard selection, extraction schemes, matrix effect, selectivity evaluation and optimization of mass spectrometric conditions to enable the development of sound bioanalytical methods for quantitation of Alzheimer's drugs. Overall LC-MS/MS methods have proven to be the choice of bioanalytical method for the quantification of Alzheimer's drugs in both preclinical and clinical studies. In conclusion, important features of LC-MS/MS methodology for Alzheimer's drugs include shortened analysis time, increased throughput, selectivity and lower cost of analysis.

Stem-cell challenges in the treatment of Alzheimer's disease: a long way from bench to bedside

Alzheimer's disease (AD) is the most prevalent type of dementia, and its neuropathology is characterized by deposition of insoluble β-amyloid peptides, intracellular neurofibrillary tangles, and the loss of diverse neurons. Current pharmacological treatments for AD relieve symptoms without affecting the major pathological characteristics of the disease. Therefore, it is essential to develop new and effective therapies. Stem-cell types include tissue-specific stem cells, such as neural stem cells and mesenchymal stem cells, embryonic stem cells derived from blastocysts, and induced pluripotent stem cells (iPSCs) reprogrammed from somatic cells. Recent preclinical evidence suggests that stem cells can be used to treat or model AD. The mechanisms of stem cell based therapies for AD include stem cell mediated neuroprotection and trophic actions, antiamyloidogenesis, beneficial immune modulation, and the replacement of the lost neurons. iPSCs have been recently used to model AD, investigate sporadic and familial AD pathogenesis, and screen for anti-AD drugs. Although considerable progress has been achieved, a series of challenges must be overcome before stem cell based cell therapies are used clinically for AD patients. This review highlights the recent experimental and preclinical progress of stem-cell therapies for AD, and discusses the translational challenges of their clinical application.

Copper, aluminum, iron and calcium inhibit human acetylcholinesterase in vitro

Acetylcholinesterase (AChE) is an important part of cholinergic nerves where it participates in termination of neurotransmission. AChE can be inhibited by e.g. some Alzheimer disease drugs, nerve agents, and secondary metabolites. In this work, metal salts aluminum chloride, calcium chloride, cupric chloride, ferric chloride, potassium chloride, magnesium chloride and sodium chloride were tested for their ability to inhibit AChE. Standard Ellman assay based on human recombinant AChE was done and inhibition was measured using Dixon plot. No inhibition was proved for sodium, potassium and magnesium ions. However, aluminum, cupric, ferric and calcium ions were able to inhibit AChE via noncompetitive mechanism of inhibition. Though the inhibition is much weaker when compared to e.g. drugs with noncompetitive mechanism of action, biological relevance of the findings can be anticipated.