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

Novel neuroprotective 5,6-dihydropyrido[2',1':2,3]imidazo[4,5-c]quinoline derivatives acting through cholinesterase inhibition and CB2 signaling modulation

A novel group of 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines was prepared via a microwave assisted one-pot telescopic approach. The synthetic sequence involves the formation of an amine precursor of imidazo [1,2-a]pyridine via condensation and reduction under microwave irradiation. Subsequently, the Pictet-Spengler cyclisation reaction occurs with ketones (cyclic or acyclic) to obtain substituted 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines in excellent yields. The compounds were tested as neuroprotective agents. Observed protection of neuron-like cells, SH-SY5Y differentiated with ATRA, in Parkinson's and Huntington's disease models inspired further mechanistic studies of protective activity against damage induced by 1-methyl-4-phenylpyridinium (MPP+), a compound causing Parkinson's disease. The novel compounds exhibit similar or higher potency than ebselen, an established drug with antioxidant activity, in the cells against MPP + -induced total cellular superoxide production and cell death. However, they exhibit a significantly higher capacity to reduce mitochondrial superoxide and preserve mitochondrial membrane potential. We also observed marked differences between a selected derivative and ebselen in terms of normalizing MPP + -induced phosphorylation of Akt and ERK1/2. The cytoprotective activity was abrogated when signaling through cannabinoid receptor CB2 was blocked. The compounds also inhibit both acetylcholine and butyrylcholine esterases. Overall the data show that novel 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinoline have a broad cytoprotective activity which is mediated by several mechanisms including mitoprotection.

Synthesis, In Vitro Biological Evaluation and Molecular Modeling of Benzimidazole-Based Pyrrole/Piperidine Hybrids Derivatives as Potential Anti-Alzheimer Agents

Benzimidazole-based pyrrole/piperidine analogs (1-26) were synthesized and then screened for their acetylcholinesterase and butyrylcholinesterase activities. All the analogs showed good to moderate cholinesterase activities. Synthesized compounds (1-13) were screened in cholinesterase enzyme inhibition assays and showed AChE activities in the range of IC50 = 19.44 ± 0.60 µM to 36.05 ± 0.4 µM against allanzanthane (IC50 = 16.11 ± 0.33 µM) and galantamine (IC50 = 19.34 ± 0.62 µM) and varied BuChE inhibitory activities, with IC50 values in the range of 21.57 ± 0.61 µM to 39.55 ± 0.03 µM as compared with standard allanzanthane (IC50 = 18.14 ± 0.05 µM) and galantamine (IC50 = 21.45 ± 0.21 µM). Similarly, synthesized compounds (14-26) were also subjected to tests to determine their in vitro AChE inhibitory activities, and the results obtained corroborated that all the compounds showed varied activities in the range of IC50 = 22.07 ± 0.13 to 42.01 ± 0.02 µM as compared to allanzanthane (IC50 = 20.01 ± 0.12 µM) and galantamine (IC50 = 18.05 ± 0.31 µM) and varied BuChE inhibitory activities, with IC50 values in the range of 26.32 ± 0.13 to 47.03 ± 0.15 µM as compared to standard allanzanthane (IC50 = 18.14 ± 0.05 µM) and galantamine (IC50 = 21.45 ± 0.21 µM). Binding interactions of the most potent analogs were confirmed through molecular docking studies. The active analogs 2, 4, 10 and 13 established numerous interactions with the active sites of targeted enzymes, with docking scores of -10.50, -9.3, -7.73 and -7.8 for AChE and -8.97, -8.2, -8.20 and -7.6 for BuChE, respectively.

The Neuroprotective Activities of the Novel Multi-Target Iron-Chelators in Models of Alzheimer's Disease, Amyotrophic Lateral Sclerosis and Aging

The concept of chelation therapy as a valuable therapeutic approach in neurological disorders led us to develop multi-target, non-toxic, lipophilic, brain-permeable compounds with iron chelation and anti-apoptotic properties for neurodegenerative diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD), age-related dementia and amyotrophic lateral sclerosis (ALS). Herein, we reviewed our two most effective such compounds, M30 and HLA20, based on a multimodal drug design paradigm. The compounds have been tested for their mechanisms of action using animal and cellular models such as APP/PS1 AD transgenic (Tg) mice, G93A-SOD1 mutant ALS Tg mice, C57BL/6 mice, Neuroblastoma × Spinal Cord-34 (NSC-34) hybrid cells, a battery of behavior tests, and various immunohistochemical and biochemical techniques. These novel iron chelators exhibit neuroprotective activities by attenuating relevant neurodegenerative pathology, promoting positive behavior changes, and up-regulating neuroprotective signaling pathways. Taken together, these results suggest that our multifunctional iron-chelating compounds can upregulate several neuroprotective-adaptive mechanisms and pro-survival signaling pathways in the brain and might function as ideal drugs for neurodegenerative disorders, such as PD, AD, ALS, and aging-related cognitive decline, in which oxidative stress and iron-mediated toxicity and dysregulation of iron homeostasis have been implicated.

Study of neuroprotective activity of new acetylcholinesterase inhibitors TVA and TVS in experimental model of Alzheimer’s disease

Introduction: Alzheimer’s disease (AD) is a severe neurodegenerative disease characterized by loss of synaptic connection between neurons of the cortex and subcortical regions. The cholinergic deficit is a consistent and early finding in AD, hence acetylcholinesterase inhibitors (AChEIs) are used for symptomatic improvement of AD. Most of these therapeutic agents are hepatotoxic, leading to liver failure and other complications. Therefore, the study of new AChEIs with less toxic impact and better effectivity is a topical challenge. In view of this, we synthesized novel chemical compounds: TVA and TVS that possess AChEI activity and studied their neuroprotective effect in an experimental AD model.

Materials and methods: Studies were performed on white rats. Acute toxicity studies were performed by Karber’s method. AD was induced via bilateral intracerebroventricular administration of Aβ 25–35. Histopathological examinations were performed in the hippocampus and the entorhinal cortex. Liver tissue was additionally examined to monitor the hepatotoxicity of these compounds.

Results: Studies of the hippocampus showed that compared to control and TVA-treated groups, under the influence of TVS there were few morphological alterations. Experimental groups showed an increase in the glial cell count, compared to the intact animals. In comparison to the AD group, the increase in microglia was not that prominent under the action of the novel compounds. Under the influence of TVA and TVS, the entorhinal cortex was more susceptible to neuronal injury, although TVS protected pyramidal neurons. Also, the group treated with TVA had signs of acute liver damage, while under the influence of TVS there were no signs of liver changes.

Discussion: Histopathological examination showed that the neurodegenerative processes in the hippocampus, as well as in the entorhinal cortex, were significantly reduced under the influence of TVS, compared with the control group. At the same time, TVA had no significant effect on the protection of neuronal cells. Also, TVS was less toxic, and there was no sign of hepatotoxicity during the experiments.

Conclusion: These studies demonstrated that TVS possesses neuroprotective activity and reduces neuronal damage induced by Aβ.

Graphical abstract:

Current druggable targets for therapeutic control of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative brain disorder that has an increasingly large burden on health and social care systems. The pathophysiology involves the accumulation of extracellular amyloid-beta plaques (Aβ) and intracellular neurofibrillary tangles contributing to neuronal death and leading to cognition impairment. However, its cause remains poorly understood, and there is no cure for AD despite extensive research and billions of dollars spent over decades. Currently, there are only four US Food and Drug Administration (FDA) approved drugs and one combination therapy available in the market for the symptomatic relief of AD. Since 2003, no new drug has been approved by the FDA for the treatment of AD. Researchers continue to explore new treatments and therapeutic strategies to treat AD. The need for novel discoveries on therapeutic targets and the development of new therapeutic approaches is imminent when considering the current expectations regarding the increased number of AD cases each year and the huge financial cost amounted to healthcare. This review focused on the current status of drugs in the clinical pipeline targeting β-amyloid, tau phosphorylation, or neurotransmitter dysfunction for therapeutic control of Alzheimer's disease.

Direct reprogramming of terminally differentiated cells into neurons: A novel and promising strategy for Alzheimer's disease treatment

Glial activation is a common pathological process of the central nervous system (CNS) in disorders such as Alzheimer's disease (AD). Several approaches have been used to reduce the number of activated astrocytes and microglia in damaged areas. In recent years, various kinds of fully differentiated cells have been successfully reprogrammed to a desired type of cell in lesion areas. Interestingly, internal glial cells, including astrocytes and NG2 positive cells, were efficiently converted to neuroblasts and neurons by overexpression of some transcription factors (TFs) or microRNAs (miRNAs). Notably, some specific subtypes of neurons have been achieved by in vivo reprogramming and the resulting neurons were successfully integrated into local neuronal circuits. Furthermore, somatic cells from AD patients have been converted to functional neurons. Although direct reprogramming of a patient's own internal cells has revolutionized regenerative medicine, but there are some major obstacles that should be examined before using these induced cells in clinical therapies. In the present review article, we aim to discuss the current studies on in vitro and in vivo reprogramming of somatic cells to neurons using TFs, miRNAs or small molecules in healthy and AD patients.

Association of MS4A6A, CD33, and TREM2 gene polymorphisms with the late-onset Alzheimer's disease

Introduction: Alzheimer’s disease (AD), which is a progressive neurodegenerative disorder, causes structural and functional brain disruption. MS4A6A, TREM2, and CD33 gene polymorphisms loci have been found to be associated with the pathobiology of late-onset AD (LOAD). In the present study, we tested the hypothesis of association of LOAD with rs983392, rs75932628, and rs3865444 polymorphisms in MS4A6A, TREM2, CD33 genes, respectively.

Methods: In the present study, 113 LOAD patients and 100 healthy unrelated age- and gender-matched controls were selected. DNA was extracted from blood samples by the salting-out method and the genotyping was performed by RFLP-PCR. Electrophoresis was carried out on agarose gel. Sequencing was thereafter utilized for the confirmation of the results.

Results: Only CD33 rs3865444 polymorphism revealed a significant difference in the genotypic frequencies of GG (P = 0.001) and GT (P = 0.001), and allelic frequencies of G (P = 0.033) and T (P = 0.03) between LOAD patients and controls.

Conclusion: The evidence from the present study suggests that T allele of CD33 rs3865444 polymorphism is associated with LOAD in the studied Iranian population.

Involvement of Acetylcholine Receptors in Cholinergic Pathway-Mediated Protection Against Autoimmune Diabetes

Type I diabetes (T1D) is a T cell-driven autoimmune disease that results in the killing of pancreatic β-cells and, consequently, loss of insulin production. Using the multiple low-dose streptozotocin (MLD-STZ) model of experimental autoimmune diabetes, we previously reported that pretreatment with a specific acetylcholinesterase inhibitor (AChEI), paraoxon, prevented the development of hyperglycemia in C57BL/6 mice. This correlated with an inhibition of T cell infiltration into the pancreatic islets and a reduction in pro-inflammatory cytokines. The cholinergic anti-inflammatory pathway utilizes nicotinic and muscarinic acetylcholine receptors (nAChRs and mAChRs, respectively) expressed on a variety of cell types. In this study, we carried out a comparative analysis of the effect of specific antagonists of nAChRs or mAChRs on the development of autoimmune diabetes. Co-administration of mecamylamine, a non-selective antagonist of nAChRs maintained the protective effect of AChEI on the development of hyperglycemia. In contrast, co-administration of atropine, a non-selective antagonist of mAChRs, mitigated AChEI-mediated protection. Mice pretreated with mecamylamine had an improved response in glucose tolerance test (GTT) than mice pretreated with atropine. These differential effects of nAChR and mAChR antagonists correlated with the extent of islet cell infiltration and with the structure and functionality of the β-cells. Taken together, our data suggest that mAChRs are essential for the protective effect of cholinergic stimulation in autoimmune diabetes.

Curcumin-loaded self-nanomicellizing solid dispersion system: part II: in vivo safety and efficacy assessment against behavior deficit in Alzheimer disease

Curcumin (CUR), a natural polyphenolic compound, is considered as one of the most potential candidates against Alzheimer disease (AD) by targeting multiple pathologies such as amyloid-beta, tau phosphorylation, and oxidative stress. Poor physicochemical profile and oral bioavailability (BA) are the major contributors to its failure in clinical trials. Lack of success in numerous drug clinical trials for the treatment of AD urges the need of repositioning of CUR. To overcome its limitation and enhance oral BA, Novel CUR Formulation (NCF) was developed using self-nanomicellizing solid dispersion strategy which displayed 117-fold enhancement in oral BA of CUR. NCF was tested using SH-SY5Y695 APP human neuroblastoma cell line against the cytotoxicity induced by copper metal ion, H₂O₂, and Aβ42 oligomer and compared with CUR control. The safety and efficacy of NCF on mice AD-like behavioral deficits (open field, novel objective recognition, Y-maze, and Morris water maze tests) were assessed in transgenic AD (APPSwe/PS1deE9) mice model. In SH-SY5Y695 APP human neuroblastoma cell line, NCF showed better safety and efficacy against the cytotoxicity due to the significantly enhancement of cellular uptake. It not only prevents the deterioration of cognitive functions of the aged APPSwe/PS1deE9 mice during aging but also reverses the cognitive functions to their much younger age which is also better than the currently available approved options. Moreover, NCF was proved as well tolerated with no appearance of any significant toxicity via oral administration. The results of the study demonstrated the potential of NCF to improve the efficacy of CUR without compromising its safety profile, and pave the way for clinical development for AD.

Investigation of salicylanilide and 4-chlorophenol-based N-monosubstituted carbamates as potential inhibitors of acetyl- and butyrylcholinesterase

Based on the presence of carbamate moiety, twenty salicylanilide N-monosubstituted carbamates concomitantly with their parent salicylanilides and five newly prepared 4-chlorophenyl carbamates obtained from isocyanates were investigated using Ellman's method for their in vitro inhibitory activity against acetylcholinesterase (AChE) from electric eel and butyrylcholinesterase (BChE) from equine serum. The carbamates and salicylanilides exhibited mostly a moderate inhibition of both cholinesterase enzymes with IC₅₀ values ranging from 5 to 235 µM. IC₅₀ values for AChE were in a narrower concentration range when compared to BChE, but many of the compounds produced a balanced inhibition of both cholinesterases. The derivatives were comparable or superior to rivastigmine for AChE inhibition, but only a few of carbamates also for BChE. Several structure-activity relationships were identified, e.g., N-phenethylcarbamates produce clearly favourable BChE inhibition. The compounds also share convenient physicochemical properties for CNS penetration.

Characterization of the interactions between coumarin-derivatives and acetylcholinesterase: Examination by NMR and docking simulations

Alzheimer's disease (AD) is one of the most common forms of dementia and a significant threat to the elderly populations, especially in the Western world. The rapid hydrolysis of the principal neurotransmitter into choline and acetate by acetylcholinesterase (AChE) at synapses causes the loss of cognitive response that becomes the real cause of AD. Therefore, inhibition of AChE is the most fundamental therapy among currently available treatments for AD. In this context, we designed and performed molecular recognitions studies of coumarin-based inhibitors towards AChE. STD NMR and Tr-NOESY applications were utilized to evaluate the binding epitope, the dissociation constant (K_D) and bound conformations of these inhibitors within this inhibitor-AChE complex. Compound 1, which has a similar inhibition activity to tacrine (a current drug) led in this study as a stronger binder with K_D = 30 μM ,even greater than tacrine (K_D = 140 μM). Moreover, docking simulations mimic NMR results and provided evidence of synchronizing binding of compound 1 with three sites; the peripheral anionic site, the bottom of the gorge, and the catalytic site. Therefore, we envisioned from our experimental and theoretical results that coumarin-based inhibitors containing a piperidinyl scaffold might be a potential drug candidates for AD in the future.

Standardized extract of Lactuca sativa Linn. and its fractions abrogates scopolamine-induced amnesia in mice: A possible cholinergic and antioxidant mechanism

OBJECTIVES

The present study was designed to evaluate the efficacy of Lactuca sativa (LS) Linn. (Asteraceae) against scopolamine-induced amnesia and to validate its traditional claim as memory enhancer.

METHODS

Ethanol extract of fresh LS leaves (LSEE), standardized on the basis of quercetin content, was successively partitioned using various solvents viz., hexane, ethyl acetate, and n-butanol in increasing order of polarity. LSEE (50, 100, and 200 mg/kg) and its various fractions (at a dose equivalent to dose of LSEE exhibiting maximum activity), administered orally for 14 days, were evaluated for their memory enhancing effect against scopolamine-induced (1 mg/kg, i.p.) amnesia in 3-4 months old male Laca mice (n = 6 in each group). The memory enhancing effect was evaluated using behavioural (elevated plus maze, novel object recognition and Morris water maze tests) and biochemical parameters (acetylcholinesterase activity, malonaldehyde, superoxide dismutase, nitrite, catalase, and reduced gultathione content). The results of the test substances were compared with both scopolamine and donepezil that was used as a standard memory enhancer and acetylcholinesterase inhibitor.

RESULTS

Scopolamine elicit marked deterioration of memory and alteration in biochemical parameters in comparison to the control group. LSEE and its n-butanol and aqueous fractions significantly (P < 0.05) attenuated the scopolamine-induced amnesia that was evident in all the behavioural and biochemical test parameters. LSEE (200 mg/kg) and n-butanol fraction (15 mg/kg) exhibited maximum anti-amnesic effect among various tested dose levels.

DISCUSSION

The results exhibited that LS prophylaxis attenuated scopolamine-induced memory impairment through its acetylcholinesterase inhibitory and antioxidant activity validating its traditional claim.

Behavioural effects of novel multitarget anticholinesterasic derivatives in Alzheimer's disease

The current pharmacological approach to Alzheimer's disease (AD) treatment, mostly based on acetylcholinesterase inhibitors (AChEIs), is being revisited, especially in terms of the temporal frames and the potential benefits of their noncanonic actions, raising the question of whether inhibitors of AChE might also act in a disease-modifying manner. Besides, in the last decades, the pharmacophoric moieties of known AChEIs have been covalently linked to other pharmacophores in the pursuit of multitarget hybrid molecules that are expected to induce long-lasting amelioration of impaired neurotransmission and clinical symptoms but also to exert disease-modifying effects. Our research consortium has synthesized and defined the pharmacological profile of new AChEIs derivatives of potential interest for the treatment of AD. Among these, huprines and derivatives have been characterized successfully. Huprine X, a reversible AChE inhibitor, designed by molecular hybridization of tacrine and huperzine A, has been shown to affect the amyloidogenic process in vitro, and the AD-related neuropathology in vivo in mice models of the disease. More recently, we have shown that a group of donepezil-huprine heterodimers exerts a highly potent and selective inhibitory action on AChE both in vitro and ex vivo, simultaneously interacting with both peripheral and catalytic binding sites, and inhibiting the β-amyloid aggregation, whereas some levetiracetam-huprine hybrids have been shown to reduce epileptiform activity, neuroinflammation and amyloid burden in an animal model of AD. Here, we summarize the behavioural correlates of these noncanonic actions as assessed in three distinct biological scenarios: middle-age, cognitive deficits associated with ageing and AD-like phenotype in mice. Besides the improvement in the hallmark cognitive symptomatology without inducing side effects, these drugs have shown to be able to modulate emotional and anxiety-like behaviours or to reduce spontaneous seizures, all of them related to the so-called 'behavioural and psychological symptoms of dementia'. Overall, the studies show that these novel multitarget anticholinesterasics exert noncanonic actions providing symptomatic and disease-modifying benefits of potential interest for the management of AD.

Huprine X Attenuates The Neurotoxicity Induced by Kainic Acid, Especially Brain Inflammation

Huprine X (HX) is a synthetic anticholinesterasic compound that exerts a potent inhibitory action on acetylcholinesterase (AChE) activity, an agonist effect on cholinergic receptors, neuroprotective activity in different neurotoxicity models in vivo and in vitro and cognition enhancing effects in non-transgenic (C57BL/6) and transgenic (3xTg-AD, APPswe) mice. In this study, we assessed the ability of HX (0.8 mg/kg, 21 days) to prevent the damage induced by kainic acid (KA; 28 mg/kg) regarding apoptosis, glia reactivity and neurogenesis in mouse brain. KA administration significantly modified the levels of pAkt1, Bcl2, pGSK3β, p25/p35, increased the glial cell markers and reduced the neurogenesis process. We also observed that pre-treatment with HX significantly reduced the p25/p35 ratio and increased synaptophysin levels, which suggests a protective effect against apoptosis and an improvement of neuroplasticity. The increase in GFAP (88%) and Iba-1 (72%) induced by KA was totally prevented by HX pre-treatment, underlying a relevant anti-inflammatory action of the anticholinesterasic drug. Our findings highlight the potential of HX, in particular, and of AChEIs, in general, to treat a number of diseases that course with both cognitive deficits and chronic inflammatory processes.

The protective role of plant biophenols in mechanisms of Alzheimer's disease

Self-assembly of amyloid beta peptide (Aβ) into the neurotoxic oligomers followed by fibrillar aggregates is a defining characteristic of Alzheimer's disease (AD). Several lines of proposed hypotheses have suggested the mechanism of AD pathology, though the exact pathophysiological mechanism is not yet elucidated. The poor understanding of AD and multitude of adverse responses reported from the current synthetic drugs are the leading cause of failure in the drug development to treat or halt the progression of AD and mandate the search for safer and more efficient alternatives. A number of natural compounds have shown the ability to prevent the formation of the toxic oligomers and disrupt the aggregates, thus attracted much attention. Referable to the abundancy and multitude of pharmacological activities of the plant active constituents, biophenols that distinguish them from the other phytochemicals as a natural weapon against the neurodegenerative disorders. This review provides a critical assessment of the current literature on in vitro and in vivo mechanistic activities of biophenols associated with the prevention and treatment of AD. We have contended the need for more comprehensive approaches to evaluate the anti-AD activity of biophenols at various pathologic levels and to assess the current evidences. Consequently, we highlighted the various problems and challenges confronting the AD research, and offer recommendations for future research.

Protection from interferon-β-induced neuronal apoptosis through stimulation of muscarinic acetylcholine receptors coupled to ERK1/2 activation

BACKGROUND AND PURPOSE

Although clinically useful for their immunomodulatory, antiproliferative and antiviral properties, type I interferons (IFNs) are involved in the pathogenesis of several neurodegenerative/neuroinflammatory diseases. In the present study, we investigated the ability of cholinergic stimulation to protect from IFN-β-induced neuronal apoptosis.

EXPERIMENTAL APPROACH

The effects of the ACh receptor agonist carbachol (CCh) on IFN-β-induced apoptosis of human SH-SY5Y neuroblastoma cells were examined by using western blots, immunofluorescence and cytofluorimetry. The involvement of muscarinic acetylcholine receptors (mAChRs) was assessed by using selective antagonists and siRNA transfection. Pharmacological inhibitors and overexpression of ERK2 and an ERK2 constitutively active form (ERK2-CA) were employed to study ERK1/2 signalling. The effects of oxotremorine-M (Oxo-M) on IFN-β-induced apoptosis of mouse hippocampal neurons were examined by measuring cleaved caspase 3 expression.

KEY RESULTS

In SH-SY5Y cells, CCh inhibited IFN-β-induced mitochondrial cytochrome c release, activation of caspases 9, 7 and 3, PARP cleavage and DNA fragmentation. The anti-apoptotic effect of CCh was mediated by M3 receptors, blocked by Gq/11 antagonist YM254890 and PKC inhibitor Go 6983, impaired by inhibition of ERK1/2 pathway, potentiated by overexpression of ERK2 and mimicked by ERK2-CA. Blockade of JNK activation enhanced the CCh anti-apoptotic response. IFN-β inhibited JNK activation and up-regulated CCh-induced ERK1/2 signalling. In hippocampal neurons, Oxo-M reduced IFN-β-induced apoptosis; this effect was antagonized by blockade of M1 /M3 receptors and ERK1/2.

CONCLUSIONS AND IMPLICATIONS

Stimulation of mAChRs counteracted IFN-β-induced neuronal apoptosis through the activation of ERK1/2 signalling. The data indicate that activation of ERK1/2-coupled mAChRs may be an effective strategy for preventing IFNs neurotoxicity.

Effects of donepezil on brain morphometric and metabolic changes in patients with Alzheimer's disease: A DARTEL-based VBM and (1)H-MRS

A few studies have performed on the brain morphometric changes over the whole brain structure following donepezil treatment in patients with Alzheimer's disease (AD). We evaluated the gray matter (GM) and white matter (WM) volume alterations and cellular metabolic changes in patients with AD before and after donepezil treatment, and further to reveal the correlations of the scores of various neuropsychological scales with the volumetric and metabolic changes. Twenty-one subjects comprising of 11 patients with AD and 10 age-matched healthy controls participated in this study. All of the patients participated in the follow-up study 24weeks following donepezil treatment. In this study, a combination of voxel-based morphometry (VBM) and proton magnetic resonance spectroscopy ((1)H-MRS) was used to assess the brain morphometric and metabolic alterations in AD. In the GM volumetric analysis, both of the untreated and treated patients with donepezil showed significantly reduced volumes in the hippocampus (Hip), parahippocampal gyrus (PHG), precuneus (PCu) and middle frontal gyrus compared with healthy controls. However, donepezil-treated patients showed significantly increased volumes in the Hip, PCu, fusiform gyrus and caudate nucleus compared to untreated patients. In the WM volumetric analysis, untreated and treated patients showed significant volume reductions in the posterior limb of internal capsule (PLIC), cerebral peduncle of the midbrain and PHG compared to healthy controls. However, there was no significant WM morphological change after donepezil treatment in patients with AD. In MRS study, untreated patients with AD showed decreased N-acetylaspartate/creatine (NAA/Cr) and increased myo-inositol (mI)/Cr compared to healthy controls, while treated patients showed only decreased NAA/Cr in the same comparison. However, the treated patients showed simultaneously increased NAA/Cr and decreased mI/Cr and choline (Cho)/Cr ratios compared to untreated patients. This study shows the regional GM and WM volume changes in combination with metabolic changes following donepezil treatment in AD. These findings would be helpful to aid our understanding of the neuroanatomical mechanisms associated with effects of donepezil on the cognitive function in AD.

Novel Cholinesterase Inhibitors Based on O-Aromatic N,N-Disubstituted Carbamates and Thiocarbamates

Based on the presence of carbamoyl moiety, twenty salicylanilide N,N-disubstituted (thio)carbamates were investigated using Ellman's method for their ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). O-Aromatic (thio)carbamates exhibited weak to moderate inhibition of both cholinesterases with IC50 values within the range of 1.60 to 311.0 µM. IC50 values for BChE were mostly lower than those obtained for AChE; four derivatives showed distinct selectivity for BChE. All of the (thio)carbamates produced a stronger inhibition of AChE than rivastigmine, and five of them inhibited BChE more effectively than both established drugs rivastigmine and galantamine. In general, 5-chloro-2-hydroxy-N-[4-(trifluoromethyl)-phenyl]benzamide, 2-hydroxy-N-phenylbenzamide as well as N-methyl-N-phenyl carbamate derivatives led to the more potent inhibition. O-{4-Chloro-2-[(4-chlorophenyl)carbamoyl]phenyl} dimethylcarbamothioate was identified as the most effective AChE inhibitor (IC50 = 38.98 µM), while 2-(phenylcarbamoyl)phenyl diphenylcarbamate produced the lowest IC50 value for BChE (1.60 µM). Results from molecular docking studies suggest that carbamate compounds, especially N,N-diphenyl substituted representatives with considerable portion of aromatic moieties may work as non-covalent inhibitors displaying many interactions at peripheral anionic sites of both enzymes. Mild cytotoxicity for HepG2 cells and consequent satisfactory calculated selectivity indexes qualify several derivatives for further optimization.

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.

Current Research Therapeutic Strategies for Alzheimer's Disease Treatment

Alzheimer's disease (AD) currently presents one of the biggest healthcare issues in the developed countries. There is no effective treatment capable of slowing down disease progression. In recent years the main focus of research on novel pharmacotherapies was based on the amyloidogenic hypothesis of AD, which posits that the beta amyloid (Aβ) peptide is chiefly responsible for cognitive impairment and neuronal death. The goal of such treatments is (a) to reduce Aβ production through the inhibition of β and γ secretase enzymes and (b) to promote dissolution of existing cerebral Aβ plaques. However, this approach has proven to be only modestly effective. Recent studies suggest an alternative strategy centred on the inhibition of the downstream Aβ signalling, particularly at the synapse. Aβ oligomers may cause aberrant N-methyl-D-aspartate receptor (NMDAR) activation postsynaptically by forming complexes with the cell-surface prion protein (PrPC). PrPC is enriched at the neuronal postsynaptic density, where it interacts with Fyn tyrosine kinase. Fyn activation occurs when Aβ is bound to PrPC-Fyn complex. Fyn causes tyrosine phosphorylation of the NR2B subunit of metabotropic glutamate receptor 5 (mGluR5). Fyn kinase blockers masitinib and saracatinib have proven to be efficacious in treating AD symptoms in experimental mouse models of the disease.

Donepezil Adherence, Persistence and Time to First Discontinuation in a Three-Year Follow-Up of Older People

Background

Donepezil is indicated for the management of mild to moderate dementia, particularly in Alzheimer's disease. Several studies have described low adherence rates with donepezil.

Aim

To examine and measure donepezil adherence, persistence and time to first discontinuation in older New Zealanders.

Methods

An inception cohort of 1,999 new users of donepezil, aged 65 years or older, were identified from the Pharmaceutical Collections and National Minimum Dataset from 1 November 2010 to 31 December 2013. Kaplan-Meier curves and Cox regression analysis were used to estimate the cumulative probability and risk of time to first discontinuation of donepezil therapy.

Results

The mean age of the cohort was 79.5 ± 6.4 years and included 42.7% females. Adherence was high (89.0%), while the proportion of donepezil dispensings (81.0-32.5%) declined between 6 and 36 months. Persistence between the 1st and 6th dispensing visit decreased by 19.0%, and 11.0% of the total cohort had a gap of 31 days or more. The adjusted risk of time to first discontinuation in the non-adherent group was 2.2 times (95% CI 1.9-2.6) that of the adherent group.

Conclusions

The non-adherent new donepezil users, on average, discontinued faster than the adherent group. Time to first discontinuation in this study was higher compared to discontinuation rates observed in clinical trials.

Attenuating effect of standardized lyophilized Cinnamomum zeylanicum bark extract against streptozotocin-induced experimental dementia of Alzheimer's type

BACKGROUND

The Cinnamomum zeylanicum (CZ; family Lauraceae) bark, an important spice, has also been used traditionally for nervous stress, as a nervine tonic, and as a stimulant. Therefore, the present study was designed to evaluate the effect of the standardized lyophilized aqueous extract of CZ bark (LCZE) on learning and memory in rodents at 50, 100, and 200 mg/kg, p.o. dose levels against streptozotocin (STZ)-induced memory impairment.

METHODS

LCZE was standardized based on the cinnamaldehyde content using high-performance thin-layer chromatography (HPTLC). The effect on learning and memory was evaluated using two widely used behavioral models, the Morris water maze (MWM) test and the object recognition test (ORT). The effect of LCZE on the acetylcholinesterase (AChE) activity and oxidative stress parameters in the cerebral cortex and hippocampus of rat brain was also evaluated.

RESULTS

LCZE significantly (p<0.05) and dose-dependently attenuated STZ-induced cognitive deficit in both models in comparison to only STZ-treated animals. In the MWM test, LCZE (100 and 200 mg/kg) significantly decreased the transfer latency and increased the time spent by the animals in target quadrant. Similarly in the ORT, the LCZE-treated animals exhibited an improved discrimination between a familiar object and a novel object, indicating the reversal of STZ-induced memory impairment. LCZE also restored STZ-induced alteration in AChE activity and oxidative stress parameters in both brain parts.

CONCLUSIONS

The results clearly indicate toward the memory-enhancing effect of LCZE, which could be due to the synergistic effect of anti-AChE and antioxidant activities.

A novel role for synaptic acetylcholinesterase as an apoptotic deoxyribonuclease

In addition to terminating neurotransmission by hydrolyzing acetylcholine, synaptic acetylcholinesterase (AChES) has been found to have a pro-apoptotic role. However, the underlying mechanism has rarely been investigated. Here, we report a nuclear translocation-dependent role for AChES as an apoptotic deoxyribonuclease (DNase). AChES polypeptide binds to and cleaves naked DNA at physiological pH in a Ca(2+)-Mg(2+)-dependent manner. It also cleaves chromosomal DNA both in pre-fixed and in apoptotic cells. In the presence of a pan-caspase inhibitor, the cleavage still occurred after nuclear translocation of AChES, implying that AChES-DNase acts in a CAD- and EndoG-independent manner. AChE gene knockout impairs apoptotic DNA cleavage; this impairment is rescued by overexpression of the wild-type but not (aa 32-138)-deleted AChES. Furthermore, in comparison with the nuclear-localized wild-type AChES, (aa 32-138)-deleted AChES loses the capacity to initiate apoptosis. These observations confirm that AChES mediates apoptosis via its DNase activity.

The cognition-enhancing activity of E1R, a novel positive allosteric modulator of sigma-1 receptors

BACKGROUND AND PURPOSE

Here, we describe the in vitro and in vivo effects of (4R,5S)-2-(5-methyl-2-oxo-4-phenyl-pyrrolidin-1-yl)-acetamide (E1R), a novel positive allosteric modulator of sigma-1 receptors.

EXPERIMENTAL APPROACH

E1R was tested for sigma receptor binding activity in a [³H](+)-pentazocine assay, in bradykinin (BK)-induced intracellular Ca²⁺ concentration ([Ca²⁺](i)) assays and in an electrically stimulated rat vas deferens model. E1R's effects on cognitive function were tested using passive avoidance (PA) and Y-maze tests in mice. A selective sigma-1 receptor antagonist (NE-100), was used to study the involvement of the sigma-1 receptor in the effects of E1R. The open-field test was used to detect the effects of E1R on locomotion.

KEY RESULTS

Pretreatment with E1R enhanced the selective sigma-1 receptor agonist PRE-084's stimulating effect during a model study employing electrically stimulated rat vasa deferentia and an assay measuring the BK-induced [Ca²⁺](i) increase. Pretreatment with E1R facilitated PA retention in a dose-related manner. Furthermore, E1R alleviated the scopolamine-induced cognitive impairment during the PA and Y-maze tests in mice. The in vivo and in vitro effects of E1R were blocked by treatment with the selective sigma-1 receptor antagonist NE-100. E1R did not affect locomotor activity.

CONCLUSION AND IMPLICATIONS

E1R is a novel 4,5-disubstituted derivative of piracetam that enhances cognition and demonstrates efficacy against scopolamine-induced cholinergic dysfunction in mice. These effects are attributed to its positive modulatory action on the sigma-1 receptor and this activity may be relevant when developing new drugs for treating cognitive symptoms related to neurodegenerative diseases.

Beyond symptomatic therapy: a re-examination of acetylcholinesterase inhibitors in Alzheimer’s disease

Acetylcholinesterase inhibitors (AChEIs) are generally regarded as palliative treatments for Alzheimer's disease that slow the progression of dementia symptoms without altering Alzheimer's disease's underlying pathogenic mechanisms. This concept is based on inference rather than evidence, and has limited the scope and persistence of AChEI use in clinical practice. Recent preclinical studies demonstrate that AChEIs exhibit a number of biological effects in addition to cholinesterase inhibition. A broader understanding of the possible mechanisms of action of AChEIs in Alzheimer's disease could result in more effective use and assist in the development of new and improved therapies. The available evidence brings into question the prevailing view that AChEIs are exclusively symptomatic treatments and supports the use of these agents persistently throughout the course of Alzheimer's disease.

Experimental sleep deprivation as a tool to test memory deficits in rodents

Paradigms of sleep deprivation (SD) and memory testing in rodents (laboratory rats and mice) are here reviewed. The vast majority of these studies have been aimed at understanding the contribution of sleep to cognition, and in particular to memory. Relatively little attention, instead, has been devoted to SD as a challenge to induce a transient memory impairment, and therefore as a tool to test cognitive enhancers in drug discovery. Studies that have accurately described methodological aspects of the SD protocol are first reviewed, followed by procedures to investigate SD-induced impairment of learning and memory consolidation in order to propose SD protocols that could be employed as cognitive challenge. Thus, a platform of knowledge is provided for laboratory protocols that could be used to assess the efficacy of drugs designed to improve memory performance in rodents, including rodent models of neurodegenerative diseases that cause cognitive deficits, and Alzheimer's disease in particular. Issues in the interpretation of such preclinical data and their predictive value for clinical translation are also discussed.

Blood pro-inflammatory cytokines in Alzheimer's disease in relation to the use of acetylcholinesterase inhibitors

OBJECTIVE

A potential anti-inflammatory role for acetylcholinesterase inhibitors (AChEIs) has been supported by animal studies. As very limited data exist from individuals with Alzheimer's disease (AD), the aim of this study was to assess the potential influence of AChEIs on blood pro-inflammatory cytokines. We hypothesized that pro-inflammatory cytokine concentrations were lower in individuals with AD stabilized on AChEIs.

METHODS

Blood interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha concentrations were assessed using specific enzyme-linked immunosorbent assays in three groups of participants: patients with AD stabilized on a therapeutic dose of an AChEI (n = 42); AChEIs drug naïve patients (n = 24); and a cognitively unimpaired control group (n = 35). Patients in the AChEIs group had received medication for an average of one year.

RESULTS

Patients stabilized on an AChEI did not differ significantly from drug naïve patients in relation to the concentrations of interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha (p = 0.874, 0.225, and 0.978, respectively). Within the group taking AChEIs, the levels of cytokines did not differ between those taking donepezil, rivastigmine, or galantamine (p = 0.368, 0.851, and 0.299, respectively).

CONCLUSIONS

Results from animal studies suggesting a modulatory anti-inflammatory role for AChEIs was not advanced in this study. In individuals with AD, very limited evidence currently exists to support the hypothesis that AChEIs may influence inflammatory blood markers and function beyond the enhancement of neuronal transmission. However, further studies assessing a wider range of inflammatory markers and processes are still needed before this hypothesis can be ruled out.

Profile of gantenerumab and its potential in the treatment of Alzheimer's disease

Alzheimer's disease, which is characterized by gradual cognitive decline associated with deterioration of daily living activities and behavioral disturbances throughout the course of the disease, is estimated to affect 27 million people around the world. It is expected that the illness will affect about 63 million people by 2030, and 114 million by 2050, worldwide. Current Alzheimer's disease medications may ease symptoms for a time but are not capable of slowing down disease progression. Indeed, all currently available therapies, such as cholinesterase inhibitors (donepezil, galantamine, rivastigmine), are primarily considered symptomatic therapies, although recent data also suggest possible disease-modifying effects. Gantenerumab is an investigational fully human anti-amyloid beta monoclonal antibody with a high capacity to bind and remove beta-amyloid plaques in the brain. This compound, currently undergoing Phase II and III clinical trials represents a promising agent with a disease-modifying potential in Alzheimer's disease. Here, we present an overview of gantenerumab ranging from preclinical studies to human clinical trials.

Undifferentiated and differentiated PC12 cells protected by huprines against injury induced by hydrogen peroxide

Oxidative stress is implicated in the pathogenesis of neurodegenerative disorders and hydrogen peroxide (H₂O₂) plays a central role in the stress. Huprines, a group of potent acetylcholinesterase inhibitors (AChEIs), have shown a broad cholinergic pharmacological profile. Recently, it has been observed that huprine X (HX) improves cognition in non transgenic middle aged mice and shows a neuroprotective activity (increased synaptophysin expression) in 3xTg-AD mice. Consequently, in the present experiments the potential neuroprotective effect of huprines (HX, HY, HZ) has been analyzed in two different in vitro conditions: undifferentiated and NGF-differentiated PC12 cells. Cells were subjected to oxidative insult (H₂O₂, 200 µM) and the protective effects of HX, HY and HZ (0.01 µM–1 µM) were analyzed after a pre-incubation period of 24 and 48 hours. All huprines showed protective effects in both undifferentiated and NGF-differentiated cells, however only in differentiated cells the effect was dependent on cholinergic receptors as atropine (muscarinic antagonist, 0.1 µM) and mecamylamine (nicotinic antagonist, 100 µM) reverted the neuroprotection action of huprines. The decrease in SOD activity observed after oxidative insult was overcome in the presence of huprines and this effect was not mediated by muscarinic or nicotinic receptors. In conclusion, huprines displayed neuroprotective properties as previously observed in in vivo studies. In addition, these effects were mediated by cholinergic receptors only in differentiated cells. However, a non-cholinergic mechanism, probably through an increase in SOD activity, seems to be also involved in the neuroprotective effects of huprines.

Acetylcholinesterase inhibitors: structure based design, synthesis, pharmacophore modeling, and virtual screening

Acetylcholinesterase (AChE) is a main drug target, and its inhibitors have demonstrated functionality in the symptomatic treatment of Alzheimer's disease (AD). In this study, a series of novel AChE inhibitors were designed and their inhibitory activity was evaluated with 2D quantitative structure-activity relationship (QSAR) studies using a training set of 20 known compounds for which IC₅₀ values had previously been determined. The QSAR model was calculated based on seven unique descriptors. Model validation was determined by predicting IC₅₀ values for a test set of 20 independent compounds with measured IC₅₀ values. A correlation analysis was carried out comparing the statistics of the measured IC₅₀ values with predicted ones. These selectivity-determining descriptors were interpreted graphically in terms of principal component analyses (PCA). A 3D pharmacophore model was also created based on the activity of the training set. In addition, absorption, distribution, metabolism, and excretion (ADME) descriptors were also determined to evaluate their pharmacokinetic properties. Finally, molecular docking of these novel molecules into the AChE binding domain indicated that three molecules (6c, 7c, and 7h) should have significantly higher affinities and solvation energies than the known standard drug donepezil. The docking studies of 2H-thiazolo[3,2-a]pyrimidines (6a-6j) and 5H-thiazolo[3,2-a] pyrimidines (7a-7j) with human AChE have demonstrated that these ligands bind to the dual sites of the enzyme. Simple and ecofriendly syntheses and diastereomeric crystallizations of 2H-thiazolo [3,2-a]pyrimidines and 5H-thiazolo[3,2-a] pyrimidines are described. The solid-state structures for the HBr salts of compounds 6a, 6e, 7a, and 7i have been determined using single-crystal X-ray diffraction techniques, and X-ray powder patterns were measured for the bulk solid remaining after solvent was removed from solutions containing 6a and 7a. These studies provide valuable insight for designing more potent and selective inhibitors for the treatment of AD.

Synthesis, pharmacological assessment, and molecular modeling of 6-chloro-pyridonepezils: new dual AChE inhibitors as potential drugs for the treatment of Alzheimer's disease

6-Chloro-pyridonepezils are chloropyridine-donepezil hybrids designed by combining the N-benzylpiperidine moiety present in donepezil with the 2-chloropyridine-3,5-dicarbonitrile heterocyclic ring system, both connected by an appropriate polymethylene linker. 6-Chloro-pyridonepezils1-8 were prepared by reaction of 2,6-dichloro-4-phenylpyridine-3,5-dicarbonitrile (13) [or 2,6-dichloropyridine-3,5-dicarbonitrile (14)] with suitable 2-(1-benzylpiperidin-4-yl)alkylamines (9-12). The biological evaluation showed that these new compounds are cholinesterase inhibitors, in the submicromolar range, one of them (6) being a potent hBuChE inhibitor (IC50 = 0.47 ± 0.08 μM). 6-Chloro-pyridonepezils4, 7 and 8 are potent hAChE inhibitors showing IC50 in the 0.013-0.054 μM range. Particularly, 6-chloro-pyridonepezil8 is 625-fold more selective for hAChE than for hBuChE and compared to donepezil is equipotent for the inhibition of hAChE. Molecular modeling investigation on 6-chloro-pyridonepezils4, 6-8 supports its dual AChE inhibitory profile, by binding simultaneously at the catalytic active and at peripheral anionic sites of the enzyme. The in vitro Blood Brain Barrier (BBB) and theoretical ADME analysis of 6-chloro-pyridonepezils1-8 have been carried out. Overall, compound 8, is a permeable potent and selective dual AChEI that can be considered as a good candidate with potential impact for further pharmacological development in Alzheimer's therapy.

Synthesis, pharmacological assessment, and molecular modeling of acetylcholinesterase/butyrylcholinesterase inhibitors: effect against amyloid-β-induced neurotoxicity

The synthesis, molecular modeling, and pharmacological analysis of phenoxyalkylamino-4-phenylnicotinates (2-7), phenoxyalkoxybenzylidenemalononitriles (12, 13), pyridonepezils (14-18), and quinolinodonepezils (19-21) are described. Pyridonepezils 15-18 were found to be selective and moderately potent regarding the inhibition of hAChE, whereas quinolinodonepezils 19-21 were found to be poor inhibitors of hAChE. The most potent and selective hAChE inhibitor was ethyl 6-(4-(1-benzylpiperidin-4-yl)butylamino)-5-cyano-2-methyl-4-phenylnicotinate (18) [IC(50) (hAChE) = 0.25 ± 0.02 μM]. Pyridonepezils 15-18 and quinolinodonepezils 20-21 are more potent selective inhibitors of EeAChE than hAChE. The most potent and selective EeAChE inhibitor was ethyl 6-(2-(1-benzylpiperidin-4-yl)ethylamino)-5-cyano-2-methyl-4-phenylnicotinate (16) [IC(50) (EeAChE) = 0.0167 ± 0.0002 μM], which exhibits the same inhibitory potency as donepezil against hAChE. Compounds 2, 7, 13, 17, 18, 35, and 36 significantly prevented the decrease in cell viability caused by Aβ(1-42). All compounds were effective in preventing the enhancement of AChE activity induced by Aβ(1-42). Compounds 2-7 caused a significant reduction whereas pyridonepezils 17 and 18, and compound 16 also showed some activity. The pyrazolo[3,4-b]quinolines 36 and 38 also prevented the upregulation of AChE induced by Aβ(1-42). Compounds 2, 7, 12, 13, 17, 18, and 36 may act as antagonists of voltage sensitive calcium channels, since they significantly prevented the Ca(2+) influx evoked by KCl depolarization. Docking studies show that compounds 16 and 18 adopted different orientations and conformations inside the active-site gorges of hAChE and hBuChE. The structural and energetic features of the 16-AChE and 18-AChE complexes compared to the 16-BuChE and 18-BuChE complexes account for a higher affinity of the ligand toward AChE. The present data indicate that compounds 2, 7, 17, 18, and 36 may represent attractive multipotent molecules for the potential treatment of Alzheimer's disease.

Ameliorating effect of lyophilized extract of Butea frondosa leaves on scopolamine-induced amnesia in rats

CONTEXT

Butea frondosa (BF) Roxb. & Koen. (syn. B. monosperma Lam.) (Fabaceae) leaves have been used in folklore medicine for the treatment of diabetes, conjunctivitis, gastrointestinal tract, and central nervous system disorders such as anxiety, amnesia, etc.

OBJECTIVE

To evaluate the effect of lyophilized hydroalcoholic extract of BF leaves (BFLE) at 100, 200 and 400 mg/kg, p.o., for its memory enhancing activity against scopolamine-induced amnesia in rats.

MATERIALS AND METHODS

Antiamnesic effect of the BFLE was evaluated using Morris water maze and object recognition test models. The effect of BFLE on acetylcholinesterase activity and malondialdehyde and glutathione levels were also evaluated in brain homogenate.

RESULT

BFLE ameliorates scopolamine-induced amnesia in both the models with maximum effect at 400 mg/kg. BFLE (400 mg/kg) decreased escape latency and increased time spent in target quadrant (24.2 and 42.5 s, respectively) in comparison to scopolamine (82 and 18.2 s, respectively) in the Morris water maze task. In the object recognition test, BFLE produced significant increase in ability to discriminate between novel and familiar objects. The highest investigated dose of BFLE (400 mg/kg), produced a significant decrease in acetylcholinesterase activity and malondialdehyde levels, and improves glutathione levels in comparison to scopolamine. Moreover, this effect of BFLE at 400 mg/kg was comparable to that of standard, donepezil.

CONCLUSION

BFLE exhibited significant antiamnesic activity in rats thereby validating its folklore use.

In vitro inhibitory profile of NDGA against AChE and its in silico structural modifications based on ADME profile

Acetylcholinesterase (AChE) inhibitors are currently in focus for the pharmacotherapy of Alzheimer's disease (AD). These inhibitors increase the level of acetylcholine in the brain and facilitate cholinergic neurotransmission. AChE inhibitors such as rivastigmine, galantamine, physostigmine and huperzine are obtained from plants, indicating that plants can serve as a potential source for novel AChE inhibitors. We have performed a virtual screening of diverse natural products with distinct chemical structure against AChE. NDGA was one among the top scored compounds and was selected for enzyme kinetic studies. The IC(50) of NDGA on AChE was 46.2 μM. However, NDGA showed very poor central nervous system (CNS) activity and blood-brain barrier (BBB) penetration. In silico structural modification on NDGA was carried out in order to obtain derivatives with better CNS activity as well as BBB penetration. The studies revealed that some of the designed compounds can be used as lead molecules for the development of drugs against AD.

Pyridonepezils, new dual AChE inhibitors as potential drugs for the treatment of Alzheimer's disease: synthesis, biological assessment, and molecular modeling

The synthesis, biological assessment and molecular modeling of new pyridonepezils1-8, able to inhibit human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBuChE), are described. The new compounds have been designed as hybrids resulting from a conjunctive approach that combines the N-benzylpiperidine moiety, present in donepezil, and the 2-amino-6-chloropyridine heterocyclic ring system, connected by an appropriate polymethylene linker. Compounds 1-8 were prepared by reaction of 2-amino-6-chloro-4-phenylpyridine-3,5-dicarbonitrile (13) [or 2-amino-6-chloropyridine-3,5-dicarbonitrile (14)] with 2-(1-benzylpiperidin-4-yl)alkylamines (9-12). The biological evaluation of molecules 1-8 showed that compounds 1-6 are potent AChE inhibitors, in the submicromolar, while compounds 7 and 8 are on the nanomolar range, the most potent, 2-amino-6-((3-(1-benzylpiperidin-4-yl)propyl)amino)pyridine-3,5-dicarbonitrile (7), showing a IC(50) (hAChE) = 9.4 ± 0.4 nM. Inhibitors 2-8 are permeable as determined in the PAMPA assay. Compared to donepezil, compound 7 is in the same range of inhibitory activity for hAChE, and 703-fold more selective for hAChE than for hBuChE. Molecular modeling investigation on pyridonepezil7 supports its dual AChE inhibitory profile, binding simultaneously at the catalytic active and at peripheral anionic sites of the enzyme. The theoretical ADME analysis of pyridonepezils1-8 has been carried out. Overall, compound 7, a potent and selective dual AChEI, can be considered as a candidate with potential impact for further pharmacological development in Alzheimer's therapy.

Huprine X and huperzine A improve cognition and regulate some neurochemical processes related with Alzheimer's disease in triple transgenic mice (3xTg-AD)

BACKGROUND

Different studies have established that cholinergic neurodegeneration could be a major pathological feature of Alzheimer's disease (AD). Thus, enhancement of the central cholinergic neurotransmission has been regarded as one of the most promising strategies for the symptomatic treatment of AD, mainly by means of reversible acetylcholinesterase inhibitors (AChEIs). The cognitive-enhancing properties of both huprine X, a new AChEI, and the structurally related huperzine A, as well as their effects on the regulation of several neurochemical processes related to AD have been studied in triple transgenic mice (3xTg-AD).

METHODS

Seven-month-old homozygous 3xTg-AD male mice, which received chronic intraperitoneal treatment with either saline, huprine X (0.12 µmol·kg(-1)) or huperzine A (0.8 µmol·kg(-1)) were subjected to a battery of behavioural tests after 3 weeks of treatment and thereafter the brains were dissected to study the neurochemical effects induced by the two AChEIs.

RESULTS

Treatments with huprine X and huperzine A improved learning and memory in the Morris water maze and some indicators of emotionality without inducing important adverse effects. Moreover, huprine X and huperzine A activate protein kinase C/mitogen-activated protein kinase pathway signalling, α-secretases (ADAM 10 and TACE) and increase the fraction of phospho-glycogen synthase kinase 3-β.

CONCLUSION

Results obtained herein using a sample of 3xTg-AD animals strongly suggest that the treatment with the two AChEIs not only improves the cognitive performance of the animals but also induces some neurochemical changes that could contribute to the beneficial effects observed.

Hybrid compounds: from simple combinations to nanomachines

The combination of two different and independently acting compounds into one covalently linked hybrid compound can convey synergy from the effects of both independently acting moieties to the new composite compound, leading to a pharmacological potency greater than the sum of each individual moiety's potencies. Here, we review a variety of such hybrid compounds, which can consist of various functional parts, molecular recognition or subcellular targeting moieties, or combinations thereof, acting either simultaneously or sequentially. Such moieties within a hybrid compound can consist of a variety of substance classes, including small organic molecules, polypeptides or nucleic acids identified either via rational molecular design or selection from libraries. Precedent for hybrid compounds comes from naturally occurring proteins and small molecules, such as botulinum toxin and bleomycin, which are secreted by micro-organisms. We review the high degree of suitability of hybrid compounds for the treatment of multifactorial diseases by simultaneously hitting several targets along an identified disease pathway. Examples are hybrid compounds against Alzheimer's disease, against the cancer-relevant phosphoinisitide-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) and epidermal growth factor signaling cascade, or in antimalarial therapy via simultaneous hitting of different mechanisms of hemozoin formation. Molecular recognition by peptides or aptamers (recognition-specific RNA or peptide sequences) can be combined with the transport of small molecule β-sheet breakers or toxins, or targeting to ubiquitin-dependent proteolysis. The vision of molecular nanomachines is currently realized in sequentially acting modular nanotransporters, consisting of four modules including a target, a membrane and nuclear translocation sequence, as well as a drug attachment domain. Through the rational combination of existing drugs and the synergy of their effects, a rapid amplification of their potency may be achieved, greatly accelerating drug development. A further enhancement of simultaneous multitarget action is enabled through the design of multifunctional hybrid drugs with sequential effects that make these hybrid molecules resemble intelligent nanomachines.

Acetylcholinesterase is associated with apoptosis in β cells and contributes to insulin-dependent diabetes mellitus pathogenesis

Acetylcholinesterase (AChE) expression is pivotal during apoptosis. Indeed, AChE inhibitors partially protect cells from apoptosis. Insulin-dependent diabetes mellitus (IDDM) is characterized in part by pancreatic β-cell apoptosis. Here, we investigated the role of AChE in the development of IDDM and analyzed protective effects of AChE inhibitors. Multiple low-dose streptozotocin (MLD-STZ) administration resulted in IDDM in a mouse model. Western blot analysis, cytochemical staining, and immunofluorescence staining were used to detect AChE expression in MIN6 cells, primary β cells, and apoptotic pancreatic β cells of MLD-STZ-treated mice. AChE inhibitors were administered intraperitoneally to the MLD-STZ mice for 30 days. Blood glucose, plasma insulin, and creatine levels were measured, and glucose tolerance tests were performed. The effects of AChE inhibitors on MIN6 cells were also evaluated. AChE expression was induced in the apoptotic MIN6 cells and primary β cells in vitro and pancreatic islets in vivo when treated with STZ. Induction and progressive accumulation of AChE in the pancreatic islets were associated with apoptotic β cells during IDDM development. The administration of AChE inhibitors effectively decreased hyperglycemia and incidence of diabetes, and restored plasma insulin levels and plasma creatine clearance in the MLD-STZ mice. AChE inhibitors partially protected MIN6 cells from the damage caused by STZ treatment. Induction and accumulation of AChE in pancreatic islets and the protective effects of AChE inhibitors on the onset and development of IDDM indicate a close relationship between AChE and IDDM.

Alzheimer's therapeutics: translation of preclinical science to clinical drug development

Over the past three decades, significant progress has been made in understanding the neurobiology of Alzheimer's disease. In recent years, the first attempts to implement novel mechanism-based treatments brought rather disappointing results, with low, if any, drug efficacy and significant side effects. A discrepancy between our expectations based on preclinical models and the results of clinical trials calls for a revision of our theoretical views and questions every stage of translation-from how we model the disease to how we run clinical trials. In the following sections, we will use some specific examples of the therapeutics from acetylcholinesterase inhibitors to recent anti-Aβ immunization and γ-secretase inhibition to discuss whether preclinical studies could predict the limitations in efficacy and side effects that we were so disappointed to observe in recent clinical trials. We discuss ways to improve both the predictive validity of mouse models and the translation of knowledge between preclinical and clinical stages of drug development.

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.

Iron-chelating backbone coupled with monoamine oxidase inhibitory moiety as novel pluripotential therapeutic agents for Alzheimer's disease: a tribute to Moussa Youdim

It is for these authors a great privilege to dedicate this review article to Moussa Youdim, who is one of the most imperative pharmacologists and pioneer investigators in the search and development of novel therapeutics for neurodegenerative diseases. 40 years ago, Moussa Youdim has started studying brain iron, catecholamine receptor and monoamine oxidase (MAO)-A and -B functions. Although Moussa Youdim succeeded in exploring the novel anti-Parkinsonian, selective MAO-B inhibitor drug, rasagiline (Azilect, Teva Pharmaceutical Co.), he did not stop searching for superior therapeutic approaches for neurodegenerative disorders. To date, Moussa Youdim and his research group are designing and synthesizing pluripotential drug candidates possessing diverse pharmacological properties that can act on multiple targets and pathological features ascribed to Parkinson's disease, Alzheimer's disease (AD) and amyotrophic lateral sclerosis. One such example is the multimodal non-toxic, brain-permeable iron-chelating compound, M30 (5-[N-methyl-N-propargylaminomethyl]-8-hydroxyquinoline), which amalgamates the propargyl moiety of rasagiline with the backbone of the potent iron chelator, VK28. This review discusses the multiple effects of several leading compounds of this series, concerning their neuroprotective/neurorestorative molecular mechanisms in vivo and in vitro, with a special focus on the pathological features ascribed to AD, including antioxidant and iron chelating activities, regulation of amyloid precursor protein and amyloid β peptide expression processing, activation of pro-survival signaling pathways and regulation of cell cycle and neurite outgrowth.

Cholinesterase inhibitors for Alzheimer disease: do they provide more than symptomatic benefits?

OBJECTIVE

This study aims to examine survival of patients with Alzheimer disease (AD) receiving clinical efficacy of cholinesterase inhibitors (ChEIs) and to compare their survival with those of patients with AD who never received ChEIs and cognitively intact old psychiatric outpatients.

DESIGN, SETTING, AND PARTICIPANTS

The retrospective cohort study used national mortality data provided by the Korean National Statistics Office and electronic database of 15 general hospitals on older patients who began outpatient treatment with psychiatric medications including ChEIs (N = 3,813). The authors controlled for confounding by using multivariate models and propensity scoring methods.

MEASUREMENTS

Mortality rate of patients with AD receiving ChEIs was compared with those of patients with AD who never received ChEIs and cognitively intact old psychiatric outpatients.

RESULTS

Observed additional survival of patients with AD receiving ChEIs (mortality rate: 13.1%), when compared with patients with AD who never received ChEIs (15.4%) was not statistically significant (p = 0.74; hazard ratio [HR]: 1.03, 95% confidence interval [CI]: 0.67-1.59). Patients with AD receiving ChEIs showed higher mortality rate (13.1%) compared with that of cognitively intact old psychiatric outpatients (8.6%) (p <0.001; HR: 1.60, 95% CI: 0.96-2.68).

CONCLUSION

This study does not support that ChEIs increase survival of patients with AD, compared with patients with AD who have never treated with ChEIs. Therefore, all ChEIs should be considered for symptomatic use only and not to be capable of modifying mortality of patients with AD.