Acetylcholine esterase activity in mild cognitive impairment and Alzheimer's disease

In-silico Studies and Antioxidant and Neuroprotective Assessment of Microencapsulated Celecoxib against Scopolamine-induced Alzheimer's Disease

BACKGROUND AND OBJECTIVE

Alzheimer's disease (AD) is an enervating and chronic progressive neurodegenerative disorder. Celecoxib (CXB) possesses efficacious antioxidants and has neuroprotective, anti-inflammatory, and immunomodulatory properties. However, the poor bioavailability of CXB limits its therapeutic utility. Thus, this study aimed to evaluate the microencapsulated celecoxib MCXB for neuroprotection.

METHODOLOGY

CXB was screened by molecular docking study using AutoDock (version 5.2), and the following proteins, such as 4EY7, 2HM1, 2Z5X, and 1PBQ were selected for predicting its neuroprotective effect. Scopolamine 20 mg/kg/day for approximately 7 days was administered to albino rats. Pure CXB 100 mg/kg/- day and 200 mg/kg/day, and MCXB 100 mg/kg/day and 200 mg/kg/day were administered, respectively. Further, to assess the oxidative stress, the nitric oxide (NO), superoxide dismutase (SOD), catalase, and lipid peroxidation (LPO) were evaluated using chemical methods. The neurochemical biomarkers like AChE, glutamate, and dopamine were evaluated using the ELISA method. Further, the histopathology of brain cells was carried out to assess the neuro-regeneration and neurodegeneration of the neurons.

RESULTS

There was a significant binding interaction of CXB (score -6.3, -6.5, -5.1, -9.1) and donepezil (score- 5.5, -7.6, -7.0, and -8.6) with AchE (4EY7), β-secretase (2HM1, monoamine oxidase (2Z5X), and glutamate (1PBQ), respectively. MCXB-treated rats (100 mg/kg/day, 200 mg/kg/day) showed increased SOD levels (p < 0.001), whereas NO, catalase, and LPO levels were significantly (p < 0.001) decreased as compared to scopolamine-treated rats. Further, MCXB-treated rats showed a modulatory effect in the level of dopamine and AchE. However, the glutamate level was significantly (p < 0.001) decreased.

CONCLUSION

In addition to that, histopathological examination of the hippocampus part showed remarkable improvement in brain cells. So, the findings of the results revealed that MCXB, in a dose-dependent manner, showed a neuroprotective effect against scopolamine-induced AD. This effect may be attributed to the activation of cholinergic pathways.

Unraveling the mechanistic interplay of mediators orchestrating the neuroprotective potential of harmine

Neurodegenerative diseases (NDDs) encompass a range of conditions characterized by the specific dysfunction and continual decline of neurons, glial cells, and neural networks within the brain and spinal cord. The majority of NDDs exhibit similar underlying causes, including oxidative stress, neuroinflammation, and malfunctioning of mitochondria. Elevated levels of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), alongside decreased expression of brain-derived neurotrophic factor (BDNF) and glutamate transporter subtype 1 (GLT-1), constitute significant factors contributing to the pathogenesis of NDDs. Additionally, the dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) gene has emerged as a significant target for the treatment of NDDs at the preclinical level. It significantly contributes to developmental brain defects, early onset neurodegeneration, neuronal loss, and dementia in Down syndrome. Moreover, an impaired ubiquitin-proteosome system (UPS) also plays a pathological role in NDDs. Malfunctioning of UPS leads to abnormal protein buildup or aggregation of α-synuclein. α-Synuclein is a highly soluble unfolded protein that accumulates in Lewy bodies and Lewy neurites in Parkinson's disease and other synucleinopathies. Recent research highlights the promising potential of natural products in combating NDDs relative to conventional therapies. Alkaloids have emerged as promising candidates in the fight against NDDs. Harmine is a tricyclic β-carboline alkaloid (harmala alkaloid) with one indole nucleus and a six-membered pyrrole ring. It is extracted from Banisteria caapi and Peganum harmala L. and exhibits diverse pharmacological properties, encompassing neuroprotective, antioxidant, anti-inflammatory, antidepressant, etc. Harmine has been reported to mediate its neuroprotective via reducing the level of inflammatory mediators, NADPH oxidase, AChE, BChE and reactive oxygen species (ROS). Whereas, it has been observed to increase the levels of BDNF, GLT-1 and anti-oxidant enzymes, along with protein kinase-A (PKA)-mediated UPS activation. This review aims to discuss the mechanistic interplay of various mediators involved in the neuroprotective effect of harmine.

Screening of Active Substances Regulating Alzheimer's Disease in Ginger and Visualization of the Effectiveness on 6-Gingerol Pathway Targets

Ginger has been reported to potentially treat Alzheimer's disease (AD), but the specific compounds responsible for this biological function and their mechanisms are still unknown. In this study, a combination of network pharmacology, molecular docking, and dynamic simulation technology was used to screen active substances that regulate AD and explore their mechanisms. The TCMSP, GeneCards, OMIM, and DisGeNET databases were utilized to obtain 95 cross-targets related to ginger's active ingredients and AD as key targets. A functional enrichment analysis revealed that the pathways in which ginger's active substances may be involved in regulating AD include response to exogenous stimuli, response to oxidative stress, response to toxic substances, and lipid metabolism, among others. Furthermore, a drug-active ingredient-key target interaction network diagram was constructed, highlighting that 6-Gingerol is associated with 16 key targets. Additionally, a protein-protein interaction (PPI) network was mapped for the key targets, and HUB genes (ALB, ACTB, GAPDH, CASP3, and CAT) were identified. Based on the results of network pharmacology and cell experiments, 6-Gingerol was selected as the active ingredient for further investigation. Molecular docking was performed between 6-Gingerol and its 16 key targets, and the top three proteins with the strongest binding affinities (ACHE, MMP2, and PTGS2) were chosen for molecular dynamics analysis together with the CASP3 protein as the HUB gene. The findings indicate that 6-Gingerol exhibits strong binding ability to these disease targets, suggesting its potential role in regulating AD at the molecular level, as well as in abnormal cholinesterase metabolism and cell apoptosis, among other related regulatory pathways. These results provide a solid theoretical foundation for future in vitro experiments using actual cells and animal experiments to further investigate the application of 6-Gingerol.

Inhibition of Acetylcholinesterase and Amyloid-β Aggregation by Piceatannol and Analogs: Assessing In Vitro and In Vivo Impact on a Murine Model of Scopolamine-Induced Memory Impairment

Currently, no drug is effective in delaying the cognitive impairment of Alzheimer's disease, which ranks as one of the top 10 causes of death worldwide. Hydroxylated stilbenes are active compounds that exist in fruit and herbal plants. Piceatannol (PIC) and gnetol (GNT), which have one extra hydroxyl group in comparison to resveratrol (RSV), and rhapontigenin (RHA) and isorhapontigenin (isoRHA), which were metabolized from PIC in vivo and contain the same number of hydroxyl groups as RSV, were evaluated for their effects on Alzheimer's disease-associated factors in vitro and in animal experiments. Among the five hydroxylated stilbenes, PIC was shown to be the most active in DPPH radical scavenging and in inhibitory activities against acetylcholinesterase and amyloid-β peptide aggregations, with concentrations for half-maximal inhibitions of 40.2, 271.74, and 0.48 μM. The different interactions of the five hydroxylated stilbenes with acetylcholinesterase or amyloid-β were obtained by molecular docking. The scopolamine-induced ICR mice fed with PIC (50 mg/kg) showed an improved learning behavior in the passive avoidance tests and had significant differences (p < 0.05) compared with those in the control group. The RHA and isoRHA at 10 μM were proven to stimulate neurite outgrowths in the SH-SY5Y cell models. These results reveal that nutraceuticals or functional foods containing PIC have the potential for use in the treatment of neurodegenerative disorders.

Nanoparticle approaches for the renin-angiotensin system

The renin-angiotensin system (RAS) is a hormonal cascade that contributes to several disorders: systemic hypertension, heart failure, kidney disease, and neurodegenerative disease. Activation of the RAS can promote inflammation and fibrosis. Drugs that target the RAS can be classified into 3 categories, AT1 angiotensin receptor blockers (ARBs), angiotensin-converting enzyme (ACE) inhibitors, and renin inhibitors. The therapeutic efficacy of current RAS-inhibiting drugs is limited by poor penetration across the blood-brain barrier, low bioavailability, and to some extent, short half-lives. Nanoparticle-mediated drug delivery systems (DDSs) are possible emerging alternatives to overcome such limitations. Nanoparticles are ideally 1-100 nm in size and are considered efficient DDSs mainly due to their unique characteristics, including water dispersity, prolonged half-life in blood circulation, smaller size, and biocompatibility. Nano-scale DDSs can reduce the drug dosage frequency and acute toxicity of drugs while enhancing therapeutic success. Different types of nanoparticles, such as chitosan, polymeric, and nanofibers, have been examined in RAS-related studies, especially in hypertension, cardiovascular disease, and COVID-19. In this review article, we summarize the physical and chemical characteristics of each nanoparticle to elaborate on their potential use in RAS-related nano-drug delivery research and clinical application.

Capsaicin: A Potential Treatment to Improve Cerebrovascular Function and Cognition in Obesity and Ageing

Impaired cognition is the primary symptom of dementia, which can lead to functional disability and reduced quality of life among an increasingly ageing population. Ageing is associated with increased oxidative stress, chronic low-grade systemic inflammation, and endothelial dysfunction, which reduces cerebrovascular function leading to cognitive decline. Chronic low-grade systemic inflammatory conditions, such as obesity, exacerbate this decline beyond normal ageing and predispose individuals to neurodegenerative diseases, such as dementia. Capsaicin, the major pungent molecule of chilli, has recently demonstrated improvements in cognition in animal models via activation of the transient receptor potential vanilloid channel 1 (TRPV1). Capsaicin-induced TRPV1 activation reduces adiposity, chronic low-grade systemic inflammation, and oxidative stress, as well as improves endothelial function, all of which are associated with cerebrovascular function and cognition. This review examines the current literature on capsaicin and Capsimax, a capsaicin supplement associated with reduced gastrointestinal irritation compared to capsaicin. Acute and chronic capsaicin treatment can improve cognition in animals. However, studies adequately assessing the effects of capsaicin on cerebrovascular function, and cognition in humans do not exist. Capsimax may be a potentially safe therapeutic intervention for future clinical trials testing the effects of capsaicin on cerebrovascular function and cognition.

Metal Coordination-Driven Supramolecular Nanozyme as an Effective Colorimetric Biosensor for Neurotransmitters and Organophosphorus Pesticides

Analytical methods for detecting neurotransmitters (NTs) and organophosphorus (OP) pesticides with high sensitivity are vitally necessary for the rapid identification of physical, mental, and neurological illnesses, as well as to ensure food safety and safeguard ecosystems. In this work, we developed a supramolecular self-assembled system (SupraZyme) that exhibits multi-enzymatic activity. SupraZyme possesses the ability to show both oxidase and peroxidase-like activity, which has been employed for biosensing. The peroxidase-like activity was used for the detection of catecholamine NTs, epinephrine (EP), and norepinephrine (NE) with a detection limit of 6.3 µM and 1.8 µM, respectively, while the oxidase-like activity was utilized for the detection of organophosphate pesticides. The detection strategy for OP chemicals was based on the inhibition of acetylcholine esterase (AChE) activity: a key enzyme that is responsible for the hydrolysis of acetylthiocholine (ATCh). The corresponding limit of detection of paraoxon-methyl (POM) and methamidophos (MAP) was measured to be 0.48 ppb and 15.8 ppb, respectively. Overall, we report an efficient supramolecular system with multiple enzyme-like activities that provide a versatile toolbox for the construction of sensing platforms for the colorimetric point-of-care detection of both NTs and OP pesticides.

M1/M4-Preferring Muscarinic Cholinergic Receptor Agonist Xanomeline Reverses Wake and Arousal Deficits in Nonpathologically Aged Mice

Degeneration of the cholinergic basal forebrain is implicated in the development of cognitive deficits and sleep/wake architecture disturbances in mild cognitive impairment (MCI) and Alzheimer's disease (AD). Indirect-acting muscarinic cholinergic receptor agonists, such as acetylcholinesterase inhibitors (AChEIs), remain the only FDA-approved treatments for the cognitive impairments observed in AD that target the cholinergic system. Novel direct-acting muscarinic cholinergic receptor agonists also improve cognitive performance in young and aged preclinical species and are currently under clinical development for AD. However, little is known about the effects of direct-acting muscarinic cholinergic receptor agonists on disruptions of sleep/wake architecture and arousal observed in nonpathologically aged rodents, nonhuman primates, and clinical populations. The purpose of the present study was to provide the first assessment of the effects of the direct-acting M1/M4-preferring muscarinic cholinergic receptor agonist xanomeline on sleep/wake architecture and arousal in young and nonpathologically aged mice, in comparison with the AChEI donepezil, when dosed in either the active or inactive phase of the circadian cycle. Xanomeline produced a robust reversal of both wake fragmentation and disruptions in arousal when dosed in the active phase of nonpathologically aged mice. In contrast, donepezil had no effect on either age-related wake fragmentation or arousal deficits when dosed during the active phase. When dosed in the inactive phase, both xanomeline and donepezil produced increases in wake and arousal and decreases in nonrapid eye movement sleep quality and quantity in nonpathologically aged mice. Collectively, these novel findings suggest that direct-acting muscarinic cholinergic agonists such as xanomeline may provide enhanced wakefulness and arousal in nonpathological aging, MCI, and AD patient populations.

Association of β-Amyloid and Basal Forebrain With Cortical Thickness and Cognition in Alzheimer and Lewy Body Disease Spectra

OBJECTIVE

Cholinergic degeneration and β-amyloid contribute to brain atrophy and cognitive dysfunction in Alzheimer disease (AD) and Lewy body disease (LBD), but their relationship has not been comparatively evaluated.

METHODS

In this cross-sectional study, we recruited 28 normal controls (NC), 55 patients with AD mild cognitive impairment (MCI), 34 patients with AD dementia, 28 patients with LBD MCI, and 51 patients with LBD dementia. Participants underwent cognitive evaluation, brain MRI to measure the basal forebrain (BF) volume and global cortical thickness (CTh), and ¹⁸F-florbetaben (FBB) PET to measure the standardized uptake value ratio (SUVR). Using general linear models and path analyses, we evaluated the association of FBB-SUVR and BF volume with CTh or cognitive dysfunction in the AD spectrum (AD and NC) and LBD spectrum (LBD and NC), respectively. Covariates included age, sex, education, deep and periventricular white matter hyperintensities, intracranial volume, hypertension, diabetes, and hyperlipidemia.

RESULTS

BF volume mediated the association between FBB-SUVR and CTh in both the AD and LBD spectra, while FBB-SUVR was associated with CTh independently of BF volume only in the LBD spectrum. Significant correlation between voxel-wise FBB-SUVR and CTh was observed only in the LBD group. FBB-SUVR was independently associated with widespread cognitive dysfunction in both the AD and LBD spectra, especially in the memory domain (standardized beta [B] for AD spectrum = -0.60, B for LBD spectrum = -0.33). In the AD spectrum, BF volume was associated with memory dysfunction (B = 0.18), and CTh was associated with language (B = 0.21) and executive (B = 0.23) dysfunction. In the LBD spectrum, however, BF volume and CTh were independently associated with widespread cognitive dysfunction.

CONCLUSIONS

There is a common β-amyloid-related degenerative mechanism with or without the mediation of BF in the AD and LBD spectra, while the association of BF atrophy with cognitive dysfunction is more profound and there is localized β-amyloid-cortical atrophy interaction in the LBD spectrum.

Vitisin A, a Resveratrol Tetramer, Improves Scopolamine-Induced Impaired Learning and Memory Functions in Amnesiac ICR Mice

Resveratrol has been reported to exhibit neuroprotective activities in vitro and in vivo. However, little is known about resveratrol tetramers of hopeaphenol, vitisin A, and vitisin B with the same molecular mass in the improvement of degenerative disorders. In this study, two 95% ethanol extracts (95EE) from stem parts of Vitis thunbergii Sieb. & Zucc. (VT-95EE) and from the root (R) parts of Vitis thunbergii var. taiwaniana (VTT-R-95EE) showed comparable acetylcholinesterase (AChE) inhibitory activities. It was found that VT-95EE and VTT-R-95EE showed different distribution patterns of identified resveratrol and resveratrol tetramers of hopeaphenol, vitisin A, and vitisin B based on the analyses of HPLC chromatographic profiles. The hopeaphenol, vitisin A, and vitisin B, showed AChE and monoamine oxidase-B inhibitions in a dose-dependent manner, among which vitisin B and vitisin A exhibited much better activities than those of resveratrol, and had neuroprotective activities against methylglyoxal-induced SH-SY5Y cell deaths. The scopolamine-induced amnesiac ICR mice treated with VT-95EE and its ethyl acetate-partitioned fraction (VT-95EE-EA) at doses of 200 and 400 mg/kg, or vitisin A at a dose of 40 mg/kg, but not vitisin B (40 mg/kg), were shown significantly to improve the impaired learning behaviors by passive avoidance tests compared to those in the control without drug treatments (p < 0.05). Compared to mice in the control group, the brain extracts in the vitisin A-treated mice or donepezil-treated mice showed significant reductions in AChE activities and malondialdehyde levels (p < 0.05), and elevated the reduced protein expressions of brain-derived neurotrophic factor (BDNF) and BDNF receptor, tropomyosin receptor kinase B (TrkB). These results revealed that vitisin A was the active constituent in the VT-95EE and VTT-95EE, and the VT medicinal plant and that the endemic variety of VTT has potential in developing functional foods for an unmet medical need for neurodegenerative disorders.

The Neuroprotective Effect of α-Lipoic Acid and/or Metformin against the Behavioral and Neurochemical Changes Induced by Hypothyroidism in Rat

OBJECTIVE

The present study evaluates the neuroprotective effect of α-lipoic acid (ALA) and/or metformin (MET) on the behavioral and neurochemical changes induced by hypothyroidism.

METHODS

Rats were divided into control, rat model of hypothyroidism induced by propylthiouracil, and rat model of hypothyroidism treated with ALA, MET, or their combination.

RESULTS

Behaviorally, hypothyroid rats revealed impaired memory and reduced motor activity as indicated from the novel object recognition test and open-field test, respectively. Hypothyroidism induced a significant increase in lipid peroxidation (malondialdehyde [MDA]) and a significant decrease in reduced glutathione (GSH) and nitric oxide (NO) in the cortex and hippocampus. These were associated with a significant increase in tumor necrosis factor-α (TNF-α) and a significant decrease in brain-derived neurotrophic factor (BDNF). Hypothyroidism decreased significantly the levels of serotonin (5-HT), norepinephrine (NE), and dopamine (DA) and reduced the activities of acetylcholinesterase (AchE) and Na+, K+-ATPase in the cortex and hippocampus. Treatment of hypothyroid rats with ALA and/or MET showed an improvement in memory function and motor activity. Moreover, ALA and/or MET prevented the increase in MDA and TNF-α, and the decline in GSH, NO, BDNF, 5-HT, NE, and DA. It also restored AchE and Na+, K+-ATPase activities in the studied brain regions.

CONCLUSION

ALA and/or MET has a potential neuroprotective effect against the adverse behavioral and neurochemical changes induced by hypothyroidism in rats.

Hydrolase-Treated Royal Jelly Attenuates H2O2- and Glutamate-Induced SH-SY5Y Cell Damage and Promotes Cognitive Enhancement in a Rat Model of Vascular Dementia

Vascular dementia (VaD) is the second most common type of dementia following Alzheimer's disease, but the therapeutic efficacy is still not effective. This makes the searching for novel neuroprotective agents important. Therefore, we hypothesized that royal jelly, a well-known traditional medicine, could attenuate memory impairment and brain damage in vascular dementia. This study determined the effects of royal jelly hydrolysate (RJH) and possible mechanism of cell damage and cognitive-enhancing effect in animal study. An in vitro study assessed the effects of RJH on acetylcholinesterase inhibitor, cell viability, and cell damage in SH-SY5Y neuroblastoma cells. Then, an in vivo study examined vascular dementia by the occlusion of the right middle cerebral artery (Rt.MCAO); adult male Wistar rats had been orally given RJH at doses ranging from 10, 50, to 100 mg/kg for 14 days before and 14 days after the occlusion of Rt.MCAO to mimic the VaD condition. Rats' spatial memory was evaluated using Morris water maze and radial arm maze every 7 days after Rt.MCAO throughout a 14-day experimental period, and then, they were sacrificed and the acetylcholinesterase (AChE) activity in the hippocampus was determined. The results showed that RJH has no cytotoxic effect with the final concentration up to 500 μg protein/ml and reduces cell death from the H₂O₂- and glutamate-induced cell damage in in vitro neuroblastoma cells. Importantly, RJH significantly improved memory performance in Morris water maze test and radial arm maze and decreased the level of acetyl cholinesterase activity. In conclusion, RJH is the potential neuroprotective agent and cognitive enhancer for VaD.

Taurine and Camel Milk Modulate Neurobehavioral and Biochemical Changes in Aluminum Chloride-Induced Alzheimer's Disease in Rats

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disease associated with deficiency in motor coordination, cognitive impairment, and excessive reactive oxygen species production in the brain.

OBJECTIVE

The study evaluated effects of taurine and camel milk (CM) on neurobehavior, amyloid-beta peptide 1-42 (Aβ) expression, acetylcholinesterase, and superoxide dismutase activities in aluminum chloride (AlCl3) model of Alzheimer's disease in rats.

METHODS

Thirty-five female Wistar rats were divided into seven groups (n = 5): Normal saline (0.2 mL/kg body weight); AlCl3 (100 mg/kg) (AD); CM (33 mL/kg); Taurine (50 mg/kg); AlCl3 (100 mg/kg) + CM (33 mL/kg); AlCl3 (100 mg/kg) + Taurine (50 mg/kg); and AlCl3 (100 mg/kg) + CM (33 mL/kg) + Taurine (50 mg/kg). The administration lasted for eight weeks via oral gavage. After the eighth week, neurobehavior assessments were performed. Rats were sacrificed, and brain and blood samples collected for analysis.

RESULTS

There was a significant (p < 0.0001) increase in the duration of motor endurance in AD + CM rats, compared to AD rats. Duration of forced swimming time was lowest (p < 0.0001) in AlCl3 + Taurine rats, compared to that of AD rats. Concentration of Aβ peptide decreased (p < 0.05) in AD rats, treated with CM and/or combination. In taurine-treated rats, superoxide dismutase activity was significantly (p < 0.05) higher than in AD rats. Treatment with taurine + CM increased (p < 0.05) acetylcholinesterase activity compared to controls.

CONCLUSION

Taurine and CM enhanced cognition and sensorimotor activity by decreasing Aβ peptide concentration and increasing superoxide dismutase and acetylcholinesterase activities in AD rats.

Hydrolysable Tannins Exhibit Acetylcholinesterase Inhibitory and Anti-Glycation Activities In Vitro and Learning and Memory Function Improvements in Scopolamine-Induced Amnesiac Mice

Agricultural waste from the hulls of water caltrop (Trapa taiwanesis Nakai, TT-hull) was extracted by either steeping them in cold 95% ethanol (C95E), refluxing 95E, refluxing 50E, or refluxing hot water (HW) to obtain C95EE, 95EE, 50EE, and HWE, respectively. These four extracts showed acetylcholinesterase (AChE) inhibitory activities and free radical scavenging activities, as well as anti-non-enzymatic protein glycation in vitro. Eight compounds were isolated from TT-hull-50EE and were used to plot the chromatographic fingerprints of the TT-hull extracts, among which tellimagrandin-I, tellimagrandin-II, and 1,2,3,6-tetra-galloylglucose showed the strongest AChE inhibitory activities, and they also exhibited anti-amyloid β peptide aggregations. The scopolamine-induced amnesiac ICR mice that were fed with TT-hull-50EE or TT-hull-HWE (100 and 200 mg/kg) or tellimagrandin-II (100 and 200 mg/kg) showed improved learning behavior when evaluated using passive avoidance or water maze evaluation, and they showed significant differences (p < 0.05) compared to those in the control group. The enriched hydrolysable tannins of the recycled TT-hull may be developed as functional foods for the treatment of degenerative disorders.

The potential involvement of cholinergic system in finasteride induced cognitive dysfunction

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Alzheimer's disease improved through the activity of mitochondrial chain complexes and their gene expression in rats by boswellic acid

The foremost neurodegenerative disease is Alzheimer's (AD), which is characterized as a gradual decrease in memory, cognitive function, and also personal changes occurred. This study aims to assess the role of boswellic bioactive component in control Alzheimer's disease through enhancing mitochondrial electron transport chain complexes in the rat model. Rats were divided into five equal groups: the control group (G1), boswellic acid control group (G2), AD disease group (G3), boswellic acid -pre-treated group (G4) and boswellic acid-treated group (G5). At the end of the experiment, blood glucose level, tau protein, different neurochemicals parameters (dopamine, acetylcholine), L-malondialdehyde (MDA) levels, and superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities was determined. Also, GLUT2 and mitochondrial electron transport chain complexes were evaluated. As a result, an increase in hippocampus glucose, tau protein expression, MDA and GLUT2 in the AD group (G3) compared to control groups (G1 and G2) has been recorded. These parameters were declined after pre (G4) and treated (G5) by boswellic acid. The neurochemicals, antioxidants parameters, four mitochondrial chain complexes activities and their gene expression in the hippocampus of the AD group were decreased compared to the control groups (G1 and G2). In contrast, pre and treated groups by boswellic acid (G4 and G5, respectively) have shown an increase in antioxidants parameters, and the activities of four mitochondrial complexes, with the best improvement in the pre-treated group (G4), then treated group (G5). In conclusion; the boswellic acid improved the antioxidant and mitochondrial complexes in Alzheimer's disease.

Carbon-11: Radiochemistry and Target-Based PET Molecular Imaging Applications in Oncology, Cardiology, and Neurology

The positron emission tomography (PET) molecular imaging technique has gained its universal value as a remarkable tool for medical diagnosis and biomedical research. Carbon-11 is one of the promising radiotracers that can report target-specific information related to its pharmacology and physiology to understand the disease status. Currently, many of the available carbon-11 (t_1/2 = 20.4 min) PET radiotracers are heterocyclic derivatives that have been synthesized using carbon-11 inserted different functional groups obtained from primary and secondary carbon-11 precursors. A spectrum of carbon-11 PET radiotracers has been developed against many of the upregulated and emerging targets for the diagnosis, prognosis, prediction, and therapy in the fields of oncology, cardiology, and neurology. This review focuses on the carbon-11 radiochemistry and various target-specific PET molecular imaging agents used in tumor, heart, brain, and neuroinflammatory disease imaging along with its associated pathology.

Determination and Comparison of Short-Chain Fatty Acids in Serum and Colon Content Samples: Alzheimer's Disease Rat as a Case Study

Short-chain fatty acids (SCFAs) are the main microbial fermentation products from dietary fibers in the colon, and it has been speculated that they play a key role in keeping healthy in the whole-body. However, differences in SCFAs concentration in the serum and colon samples had attracted little attention. In this study, we have optimized the extract and analysis methods for the determination of ten SCFAs in both serum and colon content samples. Methanol and acetonitrile were chosen for extraction of SCFAs from serum and colon content samples, respectively. Biological samples were collected from Alzheimer's disease rats treated by extract of Schisandra chinensis (Turcz.) Baill (SC-extract) were taken as research objects. The results showed that, the relative peak intensities of SCFAs in the colon content from all groups were quite similar, and the trend was identical in the serum samples. Compared with the values in humans, the ratio of ten SCFAs in rat's colon was similar, while the percent of acetate in rat's serum was significantly higher. For therapy of Alzheimer's disease (AD), SC-extract decreased the concentration of butyrate, 3-Methyvalerate, and caproate in the serum samples towards the trend of normal rats. This study may help our understanding of how SCFAs are transported across colonic epithelium in healthy and diseased organisms.

Therapeutic Strategies to Target Calcium Dysregulation in Alzheimer's Disease

Alzheimer’s disease (AD) is the most common form of dementia, affecting millions of people worldwide. Unfortunately, none of the current treatments are effective at improving cognitive function in AD patients and, therefore, there is an urgent need for the development of new therapies that target the early cause(s) of AD. Intracellular calcium (Ca²⁺) regulation is critical for proper cellular and neuronal function. It has been suggested that Ca²⁺ dyshomeostasis is an upstream factor of many neurodegenerative diseases, including AD. For this reason, chemical agents or small molecules aimed at targeting or correcting this Ca²⁺ dysregulation might serve as therapeutic strategies to prevent the development of AD. Moreover, neurons are not alone in exhibiting Ca²⁺ dyshomeostasis, since Ca²⁺ disruption is observed in other cell types in the brain in AD. In this review, we examine the distinct Ca²⁺ channels and compartments involved in the disease mechanisms that could be potential targets in AD.

Multi-Target Drug Candidates for Multifactorial Alzheimer's Disease: AChE and NMDAR as Molecular Targets

Alzheimer's disease (AD) is one of the most common forms of dementia among elder people, which is a progressive neurodegenerative disease that results from a chronic loss of cognitive activities. It has been observed that AD is multifactorial, hence diverse pharmacological targets that could be followed for the treatment of AD. The Food and Drug Administration has approved two types of medications for AD treatment such as cholinesterase inhibitors (ChEIs) and N-methyl-D-aspartic acid receptor (NMDAR) antagonists. Rivastigmine, donepezil, and galantamine are the ChEIs that have been approved to treat AD. On the other hand, memantine is the only non-competitive NMDAR antagonist approved in AD treatment. As compared with placebo, it has been revealed through clinical studies that many single-target therapies are unsuccessful to treat multifactorial Alzheimer's symptoms or disease progression. Therefore, due to the complex nature of AD pathophysiology, diverse pharmacological targets can be hunted. In this article, based on the entwined link of acetylcholinesterase (AChE) and NMDAR, we represent several multifunctional compounds in the rational design of new potential AD medications. This review focus on the significance of privileged scaffolds in the generation of the multi-target lead compound for treating AD, investigating the idea and challenges of multi-target drug design. Furthermore, the most auspicious elementary units for designing as well as synthesizing hybrid drugs are demonstrated as pharmacological probes in the rational design of new potential AD therapeutics.

On the Etiopathogenesis and Pathophysiology of Alzheimer's Disease: A Comprehensive Theoretical Review

Alzheimers' disease (AD) is the most common cause of dementia, with an estimated 5 million new cases occurring annually. Among the elderly, AD shortens life expectancy, results in disability, decreases quality of life, and ultimately, leads to institutionalization. Despite extensive research in the last few decades, its heterogeneous pathophysiology and etiopathogenesis have made it difficult to develop an effective treatment and prevention strategy. Aging is the biggest risk factor for AD and evidence suggest that the total number of older people in the population is going to increase astronomically in the next decades. Also, there is evidence that air pollution and increasing income inequality may result in higher incidence and prevalence of AD. This makes the need for a comprehensive understanding of the etiopathogenesis and pathophysiology of the disease extremely critical. In this paper, a quintuple framework of thyroid dysfunction, vitamin D deficiency, sex hormones, and mitochondria dysfunction and oxidative stress are used to provide a comprehensive description of AD etiopathogenesis and pathophysiology. The individual role of each factor, their synergistic and genetic interactions, as well as the limitations of the framework are discussed.

Evaluation of the pre-treatment effect of Centella asiatica medicinal plants on long-term potentiation (LTP) in rat model of Alzheimer's disease

The present study was aimed to investigate the pre-treatment effect of Centella asiatica (CeA) extract on long-term potentiation (LTP) in a rat model of Alzheimer's disease (AD). A total of 32 male Wistar rats weighing 380 ± 30 g were randomly divided into four groups (n = 8). Group 1 (C: Control): the control group. Group 2 (L: Lesion): The nucleus basalis of Meynert (NBM) of rats' brain was bilaterally destroyed by injection of Ibotenic acid. Group 3 (CeA): Animals in this group received the CeA leaf extract for only a period of six weeks. Group 4 (CeA + L): The NBM of rats was destroyed by Ibotenic acid after six weeks of a diet containing the CeA leaf extract. In all groups, LTP was recorded using the electrophysiological technique and fEPSP after high frequency stimulation (HFS). The results showed that the slope and amplitude of PS as well as the sub-curve level significantly increased in the CeA + L group compared with the L and CeA groups. The CeA extract improved and strengthened the slope, amplitude and sub-curve surface of cumulative waves in animals with NBM lesion. The results showed that administration CeA extract for six weeks before induction of NBM lesion and induction of Alzheimer could enhance memory. In other words, the CeA extract had a preventive or protective role. The present study showed that CeA had a protective role for neurons among rats with NBM lesion.

Oxidative stress in alzheimer's disease: A review on emergent natural polyphenolic therapeutics

OBJECTIVES

The aim of this research was to review the literature on Alzheimer's disease (AD) with a focus on polyphenolics as antioxidant therapeutics.

DESIGN

This review included a search of the literature up to and including September 2019 in PubMed and MEDLINE databases using search terms that included: Alzheimer's Disease, Aβ peptide, tau, oxidative stress, redox, oxidation, therapeutic, antioxidant, natural therapy, polyphenol. Any review articles, case studies, research reports and articles in English were identified and subsequently interrogated. Citations within relevant articles were also examined for consideration in this review.

RESULTS

Alzheimer's disease is a neurodegenerative disorder that is clinically characterised by the progressive deterioration of cognitive functions and drastic changes in behaviour and personality. Due to the significant presence of oxidative damage associated with abnormal Aβ accumulation and neurofibrillary tangle deposition in AD patients' brains, antioxidant drug therapy has been investigated as potential AD treatment. In particular, naturally occurring compounds, such as plant polyphenols, have been suggested to have potential neuroprotective effects against AD due to their diverse array of physiological actions, which includes potent antioxidant effects.

CONCLUSIONS

The impact of oxidative stress and various mechanisms of pathogenesis in AD pathophysiology was demonstrated along with the therapeutic potential of emergent antioxidant drugs to address such mechanism of oxidation.

Role of GPCR signaling and calcium dysregulation in Alzheimer's disease

Alzheimer's disease (AD), a late onset neurodegenerative disorder is characterized by the loss of memory, disordered cognitive function, caused by accumulation of amyloid-β (Aβ) peptide and neurofibrillary tangles (NFTs) in the neocortex and hippocampal brain area. Extensive research has been done on the findings of the disease etiology or pathological causes of aggregation of Aβ and hyperphosphorylation of tau protein without much promising results. Recently, calcium dysregulation has been reported to play an important role in the pathophysiology of AD. Calcium ion acts as one of the major secondary messengers, regulates many signaling pathways involved in cell survival, proliferation, differentiation, transcription and apoptosis. Calcium signaling is one of the major signaling pathways involved in the formation of memory, generation of energy and other physiological functions. It also can modulate function of many proteins upon binding. Dysregulation in calcium homeostasis leads to many physiological changes leading to neurodegenerative diseases including AD. In AD, GPCRs generate secondary messengers which regulate calcium homeostasis inside the cell and is reported to be disturbed in the pathological condition. Calcium channels and receptors present on the plasma membrane and intracellular organelle maintain calcium homeostasis through different signaling mechanisms. In this review, we have summarized the different calcium channels and receptors involved in calcium dysregulation which in turn play a critical role in the pathogenesis of AD. Understanding the role of calcium channels and GPCRs to maintain calcium homeostasis is an attempt to develop effective AD treatments.

Nanoparticle-mediated approaches for Alzheimer's disease pathogenesis, diagnosis, and therapeutics

Alzheimer's disease (AD) is an irreversible and progressive neurodegenerative disorder manifested by memory loss and cognitive impairment. Deposition of the amyloid β plaques has been identified as the most common AD pathology; however, the excessive accumulation of phosphorylated or total tau proteins, reactive oxygen species, and higher acetylcholinesterase activity are also strongly associated with Alzheimer's dementia. Several therapeutic approaches targeting these pathogenic mechanisms have failed in clinical or preclinical trials, partly due to the limited bioavailability, poor cell, and blood-brain barrier penetration, and low drug half-life of current regimens. The nanoparticles (NPs)-mediated drug delivery systems improve drug solubility and bioavailability, thus renders as superior alternatives. Moreover, NPs-mediated approaches facilitate multiple drug loading and targeted drug delivery, thereby increasing drug efficacy. However, certain NPs can cause acute toxicity damaging cellular and tissue architecture, therefore, NP material should be carefully selected. In this review, we summarize the recent NPs-mediated studies that exploit various pathologic mechanisms of AD by labeling, identifying, and treating the affected brain pathologies. The disadvantages of the select NP-based deliveries and the future aspects will also be discussed.

β-Carotene: A Natural Compound Improves Cognitive Impairment and Oxidative Stress in a Mouse Model of Streptozotocin-Induced Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by a cascade of changes in cognitive, behavioral, and social activities. Several areas of the brain are involved in the regulation of memory. Of most importance are the amygdala and hippocampus. Antioxidant therapy is used for the palliative treatment of different degenerative diseases like diabetes, cirrhosis, and Parkinson's, etc. The objective of this study was to assess the effectiveness of exogenous antioxidants, in particular, β carotene (1.02 and 2.05 mg/kg) against intracerebroventricular injected streptozotocin-induced memory impairment in mice. Streptozotocin (3 mg/kg, i.c.v) was administered in two separate doses (on 1st and 3rd days of treatment) for neurodegeneration. Fifty Albino mice (male) were selected in the protocol, and they were classified into five groups (Group I-control, Group II-disease, Group III-standard, Group IV-V-β-carotene-treated) to investigate the cognitive enhancement effect of selected antioxidants. The cognitive performance was observed following the elevated plus-maze, passive avoidance, and open field paradigms. Acetylcholine esterase, β-amyloid protein, and biochemical markers of oxidative stress such as glutathione peroxidase, superoxide dismutase, and catalase were analyzed in brain homogenates. In silico activity against acetylcholinesterase (AChE) was determined by the molecular modeling of β-carotene. β-carotene at a dose of 2.05 mg/kg was found to attenuate the deleterious effects of streptozotocin-induced behavioral and biochemical impairments, including the inhibition of acetylcholinesterase activity. The in silico studies confirmed the binding capacity of β-carotene with the acetylcholinesterase enzyme. The administration of β-carotene attenuated streptozotocin-induced cognitive deficit via its anti-oxidative effects, inhibition of acetylcholinesterase, and the reduction of amyloid β-protein fragments. These results suggest that β-carotene could be useful for the treatment of neurodegenerative diseases such as Alzheimer's disease.

Isomerization of Asp7 in Beta-Amyloid Enhances Inhibition of the α7 Nicotinic Receptor and Promotes Neurotoxicity

Cholinergic dysfunction in Alzheimer’s disease (AD) can be mediated by the neuronal α7 nicotinic acetylcholine receptor (α7nAChR). Beta-amyloid peptide (Aβ) binds to the α7nAChR, disrupting the receptor’s function and causing neurotoxicity. In vivo not only Aβ but also its modified forms can drive AD pathogenesis. One of these forms, iso-Aβ (containing an isomerized Asp7 residue), shows an increased neurotoxicity in vitro and stimulates amyloidogenesis in vivo. We suggested that such effects of iso-Aβ are α7nAChR-dependent. Here, using calcium imaging and electrophysiology, we found that iso-Aβ is a more potent inhibitor of the α7nAChR-mediated calcium current than unmodified Aβ. However, Asp7 isomerization eliminated the ability of Aβ to decrease the α7nAChR levels. These data indicate differences in the interaction of the peptides with the α7nAChR, which we demonstrated using computer modeling. Neither Aβ nor iso-Aβ competed with ¹²⁵I-α-bungarotoxin for binding to the orthosteric site of the receptor, suggesting the allosteric binging mode of the peptides. Further we found that increased neurotoxicity of iso-Aβ was mediated by the α7nAChR. Thus, the isomerization of Asp7 enhances the inhibitory effect of Aβ on the functional activity of the α7nAChR, which may be an important factor in the disruption of the cholinergic system in AD.

Effect of cholinergic treatment depends on cholinergic integrity in early Alzheimer's disease

In early Alzheimer's disease, which initially presents with progressive loss of short-term memory, neurodegeneration especially affects cholinergic neurons of the basal forebrain. Pharmacotherapy of Alzheimer's disease therefore often targets the cholinergic system. In contrast, cholinergic pharmacotherapy of mild cognitive impairment is debated since its efficacy to date remains controversial. We here investigated the relationship between cholinergic treatment effects and the integrity of the cholinergic system in mild cognitive impairment due to Alzheimer's disease. Fourteen patients with high likelihood of mild cognitive impairment due to Alzheimer's disease and 16 age-matched cognitively normal adults performed an episodic memory task during functional magnetic resonance imaging under three conditions: (i) without pharmacotherapy; (ii) with placebo; and (iii) with a single dose of rivastigmine (3 mg). Cortical acetylcholinesterase activity was measured using PET with the tracer 11C-N-methyl-4-piperidyl acetate (MP4A). Cortical acetylcholinesterase activity was significantly decreased in patients relative to controls, especially in the lateral temporal lobes. Without pharmacotherapy, mild cognitive impairment was associated with less memory-related neural activation in the fusiform gyrus and impaired deactivation in the posterior cingulate cortex, relative to controls. These differences were attenuated under cholinergic stimulation with rivastigmine: patients showed increased neural activation in the right fusiform gyrus but enhanced deactivation of the posterior cingulate cortex under rivastigmine, compared to placebo. Conversely, controls showed reduced activation of the fusiform gyrus and reduced deactivation of the posterior cingulate under rivastigmine, compared to placebo. In both groups, the change in neural activation in response to rivastigmine was negatively associated with local acetylcholinesterase activity. At the behavioural level, an analysis of covariance revealed a significant group × treatment interaction in episodic memory performance when accounting for hippocampal grey matter atrophy and function. Our results indicate that rivastigmine differentially affects memory-related neural activity in patients with mild cognitive impairment and cognitively normal, age-matched adults, depending on acetylcholinesterase activity as a marker for the integrity of the cortical cholinergic system. Furthermore, hippocampal integrity showed an independent association with the response of memory performance to acetylcholinesterase inhibition.

Protective Effects of Centella asiatica on Cognitive Deficits Induced by D-gal/AlCl₃ via Inhibition of Oxidative Stress and Attenuation of Acetylcholinesterase Level

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with cholinergic dysfunctions and impaired redox homeostasis. The plant Centella asiatica (CA) is renowned for its nutritional benefits and herbal formulas for promoting health, enhancing cognition, and its neuroprotective effects. The present study aims to investigate the protective role of CA on D-gal/AlCl₃-induced cognitive deficits in rats. The rats were divided into six groups and administered with donepezil 1 mg/kg/day, CA (200, 400, and 800 mg/kg/day) and D-gal 60 mg/kg/day + AlCl₃ 200 mg/kg/day for 10 weeks. The ethology of the rats was evaluated by the Morris water maze test. The levels of acetylcholinesterase (AChE), phosphorylated tau (P-tau), malondialdehyde (MDA) and activities of superoxide dismutase (SOD), in the hippocampus and cerebral cortex were estimated by enzyme-linked immunosorbent assay (ELISA). Additionally, the ultrastructure of the prefrontal cortex of the rats’ was observed using transmission electron microscopy (TEM). Rats administered with D-gal/AlCl₃ exhibited cognitive deficits, decreased activities of SOD, and marked increase in AChE and MDA levels. Further, prominent alterations in the ultrastructure of the prefrontal cortex were observed. Conversely, co-administration of CA with D-gal/AlCl₃ improved cognitive impairment, decreased AChE levels, attenuated the oxidative stress in hippocampus and cerebral cortex, and prevented ultrastructural alteration of neurons in the prefrontal cortex. Irrespective of the dose of CA administered, the protective effects were comparable to donepezil. In conclusion, this study suggests that CA attenuated the cognitive deficits in rats by restoring cholinergic function, attenuating oxidative stress, and preventing the morphological aberrations.

Overview on the Effects of N-Acetylcysteine in Neurodegenerative Diseases

N-acetylcysteine (NAC), which is an acetylated cysteine compound, has aroused scientific interest for decades due to its important medical applications. It also represents a nutritional supplement in the human diet. NAC is a glutathione precursor and shows antioxidant and anti-inflammatory activities. In addition to the uses quoted in the literature, NAC may be considered helpful in therapies to counteract neurodegenerative and mental health diseases. Furthermore, this compound has been evaluated for its neuroprotective potential in the prevention of cognitive aging dementia. NAC is inexpensive, commercially available and no relevant side effects were observed after its administration. The purpose of this paper is to give an overview on the effects and applications of NAC in Parkinson's and Alzheimer's disorders and in neuropathic pain and stroke.

iPSC-derived familial Alzheimer's PSEN2 N141I cholinergic neurons exhibit mutation-dependent molecular pathology corrected by insulin signaling

BACKGROUND

Type 2 diabetes (T2D) is a recognized risk factor for the development of cognitive impairment (CI) and/or dementia, although the exact nature of the molecular pathology of T2D-associated CI remains obscure. One link between T2D and CI might involve decreased insulin signaling in brain and/or neurons in either animal or postmortem human brains as has been reported as a feature of Alzheimer's disease (AD). Here we asked if neuronal insulin resistance is a cell autonomous phenomenon in a familial form of AD.

METHODS

We have applied a newly developed protocol for deriving human basal forebrain cholinergic neurons (BFCN) from skin fibroblasts via induced pluripotent stem cell (iPSC) technology. We generated wildtype and familial AD mutant PSEN2 ^N141I (presenilin 2) BFCNs and assessed if insulin signaling, insulin regulation of the major AD proteins Aβ and/or tau, and/or calcium fluxes is altered by the PSEN2 ^N141I mutation.

RESULTS

We report herein that wildtype, PSEN2 ^N141I and CRISPR/Cas9-corrected iPSC-derived BFCNs (and their precursors) show indistinguishable insulin signaling profiles as determined by the phosphorylation of canonical insulin signaling pathway molecules. Chronic insulin treatment of BFCNs of all genotypes led to a reduction in the Aβ42/40 ratio. Unexpectedly, we found a CRISPR/Cas9-correctable effect of PSEN2 ^N141I on calcium flux, which could be prevented by chronic exposure of BFCNs to insulin.

CONCLUSIONS

Our studies indicate that the familial AD mutation PSEN2 ^N141I does not induce neuronal insulin resistance in a cell autonomous fashion. The ability of insulin to correct calcium fluxes and to lower Aβ42/40 ratio suggests that insulin acts to oppose an AD-pathophysiology. Hence, our results are consistent with a potential physiological role for insulin as a mediator of resilience by counteracting specific metabolic and molecular features of AD.

Targeting Renin-Angiotensin System Against Alzheimer's Disease

Renin Angiotensin System (RAS) is a hormonal system that regulates blood pressure and fluid balance through a coordinated action of renal, cardiovascular, and central nervous systems. In addition to its hemodynamic regulatory role, RAS involves in many brain activities, including memory acquisition and consolidation. This review has summarized the involvement of RAS in the pathology of Alzheimer’s disease (AD), and the outcomes of treatment with RAS inhibitors. We have discussed the effect of brain RAS in the amyloid plaque (Aβ) deposition, oxidative stress, neuroinflammation, and vascular pathology which are directly and indirectly associated with AD. Angiotensin II (AngII) via AT1 receptor is reported to increase brain Aβ level via different mechanisms including increasing amyloid precursor protein (APP) mRNA, β-secretase activity, and presenilin expression. Similarly, it was associated with tau phosphorylation, and reactive oxygen species generation. However, these effects are counterbalanced by Ang II mediated AT2 signaling. The protective effect observed with angiotensin receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs) could be as the result of inhibition of Ang II signaling. ARBs also offer additional benefit by shifting the effect of Ang II toward AT2 receptor. To conclude, targeting RAS in the brain may benefit patients with AD though it still requires further in depth understanding.

Toxicity evaluation of two polyoxotungstates with anti-acetylcholinesterase activity

A toxicity evaluation of two Keggin-type heteropolytungstates, K₇[Ti₂PW₁₀O₄₀]·6H₂O and K₆H[SiV₃W₉O₄₀]·3H₂O, with different inhibitory potencies toward acetylcholinesterase activity (IC₅₀ values of 1.04×10^-6 and 4.80×10^-4mol/L, respectively) was performed. Wistar albino rats were orally treated with single doses (5 and 50mg/kg) of both investigated compounds. The biochemical parameters of renal (serum urea and creatinine) and liver function (direct and total bilirubin, alanine transaminase, and aspartate aminotransferase) were determined after 24h and 14days. A histopathological analysis of liver tissue was carried out 14days after the polyoxotungstate administration. Both applied doses of the investigated compounds did not induce statistically significant alterations of the renal function markers. However, the polyoxotungstate treatment caused an increase in the activities of serum alanine transaminase and aspartate aminotransferase in a time- and concentration-dependent manner, although statistically significant changes in bilirubin concentrations were not observed. Furthermore, the detected hepatotoxic effect was confirmed by histhopathological analysis that suggested some reversible liver tissue damage two weeks after the treatment, especially in the case of K₆H[SiV₃W₉O₄₀]·3H₂O. Accordingly, the toxicity of these two polyoxotungstates with anti-acetylcholinesterase effect cannot be considered as a severe one, but their potential clinical application would require a more complex toxicological study.

Activation of GSK-3 disrupts cholinergic homoeostasis in nucleus basalis of Meynert and frontal cortex of rats

The cholinergic impairment is an early marker in Alzheimer's disease (AD), while the mechanisms are not fully understood. We investigated here the effects of glycogen synthase kinse-3 (GSK-3) activation on the cholinergic homoeostasis in nucleus basalis of Meynert (NBM) and frontal cortex, the cholinergic enriched regions. We activated GSK-3 by lateral ventricular infusion of wortmannin (WT) and GF-109203X (GFX), the inhibitors of phosphoinositol-3 kinase (PI3-K) and protein kinase C (PKC), respectively, and significantly decreased the acetylcholine (ACh) level via inhibiting choline acetyl transferase (ChAT) rather than regulating acetylcholinesterase (AChE). Neuronal axonal transport was disrupted and ChAT accumulation occurred in NBM and frontal cortex accompanied with hyperphosphorylation of tau and neurofilaments. Moreover, ChAT expression decreased in NBM attributing to cleavage of nuclear factor-κB/p100 into p52 for translocation into nucleus to lower ChAT mRNA level. The cholinergic dysfunction could be mimicked by overexpression of GSK-3 and rescued by simultaneous administration of LiCl or SB216763, inhibitors of GSK-3. Our data reveal the molecular mechanism that may underlie the cholinergic impairments in AD patients.

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

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

Nanomedicine in Central Nervous System (CNS) Disorders: A Present and Future Prospective

Purpose: For the past few decades central nervous system disorders were considered as a major strike on human health and social system of developing countries. The natural therapeutic methods for CNS disorders limited for many patients. Moreover, nanotechnology-based drug delivery to the brain may an exciting and promising platform to overcome the problem of BBB crossing. In this review, first we focused on the role of the blood-brain barrier in drug delivery; and second, we summarized synthesis methods of nanomedicine and their role in different CNS disorder. Method: We reviewed the PubMed databases and extracted several kinds of literature on neuro nanomedicines using keywords, CNS disorders, nanomedicine, and nanotechnology. The inclusion criteria included chemical and green synthesis methods for synthesis of nanoparticles encapsulated drugs and, their in-vivo and in-vitro studies. We excluded nanomedicine gene therapy and nanomaterial in brain imaging. Results: In this review, we tried to identify a highly efficient method for nanomedicine synthesis and their efficacy in neuronal disorders. SLN and PNP encapsulated drugs reported highly efficient by easily crossing BBB. Although, these neuro-nanomedicine play significant role in therapeutics but some metallic nanoparticles reported the adverse effect on developing the brain. Conclusion: Although impressive advancement has made via innovative potential drug development, but their efficacy is still moderate due to limited brain permeability. To overcome this constraint,powerful tool in CNS therapeutic intervention provided by nanotechnology-based drug delivery methods. Due to its small and biofunctionalization characteristics, nanomedicine can easily penetrate and facilitate the drug through the barrier. But still, understanding of their toxicity level, optimization and standardization are a long way to go.

Role of insulin resistance in Alzheimer's disease

A critical role of insulin resistance (IR) in Alzheimer's disease (AD) includes beta-amyloid (Aβ) production and accumulation, the formation of neurofibrillary tangles (NFTs), failure of synaptic transmission and neuronal degeneration. Aβ is sequentially cleavaged from APP by two proteolytic enzymes: β-secretase and γ-secretase. IR could regulate Aβ production via enhancing β- and γ-secretase activity. Meanwhile, IR induces oxidative stress and inflammation in the brain which contributes to Aβ and tau pathology. Aβ accumulation can enhance IR through Aβ-mediated inflammation and oxidative stress. IR is a possible linking between amyloid plaques and NFTs pathology via oxidative stress and neuroinflammation. Additionally, IR could disrupt acetylcholine activity, and accelerate axon degeneration and failures in axonal transport, and lead to cognitive impairment in AD. Preclinical and clinical studies have supported that insulin could be useful in the treatment of AD. Thus, an effective measure to inhibit IR may be a novel drug target in AD.

Silibinin inhibits acetylcholinesterase activity and amyloid β peptide aggregation: a dual-target drug for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is characterized by amyloid β (Aβ) peptide aggregation and cholinergic neurodegeneration. Therefore, in this paper, we examined silibinin, a flavonoid extracted from Silybum marianum, to determine its potential as a dual inhibitor of acetylcholinesterase (AChE) and Aβ peptide aggregation for AD treatment. To achieve this, we used molecular docking and molecular dynamics simulations to examine the affinity of silibinin with Aβ and AChE in silico. Next, we used circular dichroism and transmission electron microscopy to study the anti-Aβ aggregation capability of silibinin in vitro. Moreover, a Morris Water Maze test, enzyme-linked immunosorbent assay, immunohistochemistry, 5-bromo-2-deoxyuridine double labeling, and a gene gun experiment were performed on silibinin-treated APP/PS1 transgenic mice. In molecular dynamics simulations, silibinin interacted with Aβ and AChE to form different stable complexes. After the administration of silibinin, AChE activity and Aβ aggregations were down-regulated, and the quantity of AChE also decreased. In addition, silibinin-treated APP/PS1 transgenic mice had greater scores in the Morris Water Maze. Moreover, silibinin could increase the number of newly generated microglia, astrocytes, neurons, and neuronal precursor cells. Taken together, these data suggest that silibinin could act as a dual inhibitor of AChE and Aβ peptide aggregation, therefore suggesting a therapeutic strategy for AD treatment.

Clitoria ternatea ameliorated the intracerebroventricularly injected streptozotocin induced cognitive impairment in rats: behavioral and biochemical evidence

RATIONALE

Clitoria ternatea, commonly known as Aparajita, is used as Medhya rasayana in Ayurveda. The role of C. ternatea in experimental models of cognitive impairment is yet to be explored.

OBJECTIVES

The present study was designed to study the effect of aqueous and hydroalcoholic extracts of C. ternatea on biochemical and behavioral parameters related to cognitive impairment in in vitro and in vivo studies.

METHODS

In vitro free radical scavenging and enzyme-inhibitory (cholinesterase, glycogen synthase kinase-3-β, rho kinase, prolyl endopeptidase, catechol-O-methyl transferase, and lipoxygenase) activities of aqueous and hydroalcoholic extracts of C. ternatea plant were evaluated. Based on in vitro results, hydroalcoholic extract of C. ternatea (100, 300, and 500 mg/kg, p.o.) was selected for evaluation in intracerebroventricularly injected streptozotocin (STZ)-induced cognitive impairment in male Wistar rats. Behavioral assessment was performed at baseline and on the 14th, 21st, and 28th days after STZ injection using elevated plus maze, passive avoidance, Morris water maze, and photoactometer. Oxidative stress parameters (malondialdehyde, reduced glutathione, nitric oxide levels, and superoxide dismutase activity), cholinesterase activity, and rho kinase (ROCK II) expression were studied in cerebral cortex and hippocampus of rats' brain at the end of the study.

RESULTS

The hydroalcoholic extract possessed significantly more in vitro antioxidant and enzyme-inhibitory activities as compared to aqueous extract. The hydroalcoholic extract of C. ternatea prevented STZ-induced cognitive impairment dose dependently by reducing oxidative stress, cholinesterase activity, and ROCK II expression.

CONCLUSION

In vitro and in vivo results suggest the potential of hydroalcoholic extract of C. ternatea for treatment of cognitive deficit in neurological disorders.

Mechanisms and effects of curcumin on spatial learning and memory improvement in APPswe/PS1dE9 mice

Evidence suggests that curcumin, the phytochemical agent in the spice turmeric, might be a potential therapy for Alzheimer's disease (AD). Its antioxidant, anti-inflammatory properties have been investigated extensively. Studies have also shown that curcumin can reduce amyloid pathology in AD. The underlying mechanism, however, is complex and is still being explored. In this study, we used the APPswe/PS1dE9 double transgenic mice, an AD model, to investigate the effects and mechanisms of curcumin in the prevention and treatment of AD. The water maze test indicated that curcumin can improve spatial learning and memory ability in mice. Immunohistochemical staining and Western blot analysis were used to test major proteins in β-amyloid aggregation, β-amyloid production, and β-amyloid clearance. Data showed that, 3 months after administration, curcumin treatment reduced Aβ40 , Aβ42 , and aggregation of Aβ-derived diffusible ligands in the mouse hippocampal CA1 area; reduced the expression of the γ-secretase component presenilin-2; and increased the expression of β-amyloid-degrading enzymes, including insulin-degrading enzymes and neprilysin. This evidence suggests that curcumin, as a potential AD therapeutic method, can reduce β-amyloid pathological aggregation, possibly through mechanisms that prevent its production by inhibiting presenilin-2 and/or by accelerating its clearance by increasing degrading enzymes such as insulin-degrading enzyme and neprilysin.

Oxidative stress precedes mitochondrial dysfunction in gerbil brain after aluminum ingestion

Several studies suggest that aluminum (Al) intake might increase an individual's risk of developing Alzheimer disease. The dynamic of changes in acetylcholinesterase (AChE), cytochrome c oxidase (COX), Complex I, superoxide dismutase (SOD) and catalase (CAT) activities, and the lipid peroxide (MDA), superoxide anion (O₂(-)) and thiol (SH) group levels in gerbil's brain after aluminum ingestion were analyzed. Gerbils that orally received aluminum chloride (LD₂₅ or LD₅₀) were sacrificed 2, 6 or 24 h later. Another group was subacutely treated (21 days; LD10). Controls received saline. Biochemical parameters were measured in cortex, hippocampus, thalamus and nucleus caudatus. Two hours after acute Al exposure AChE activity and SH group content were decreased and MDA and O₂(-) levels were elevated in all investigated brain structures. The changes of COX and CAT were structure specific. SOD was increased after 6 h. Changes of investigated parameters were also seen after subacute Al treatment. These results might suggest the presence of additional source of free radicals in early phase of Al poisoning.

The senescence hypothesis of disease progression in Alzheimer disease: an integrated matrix of disease pathways for FAD and SAD

Alzheimer disease (AD) is a progressive, neurodegenerative disease characterised in life by cognitive decline and behavioural symptoms and post-mortem by the neuropathological hallmarks including the microtubule-associated protein tau-reactive tangles and neuritic plaques and amyloid-beta-protein-reactive senile plaques. Greater than 95 % of AD cases are sporadic (SAD) with a late onset and <5 % of AD cases are familial (FAD) with an early onset. FAD is associated with various genetic mutations in the amyloid precursor protein (APP) and the presenilins (PS)1 and PS2. As yet, no disease pathway has been fully accepted and there are no treatments that prevent, stop or reverse the cognitive decline associated with AD. Here, we review and integrate available environmental and genetic evidence associated with all forms of AD. We present the senescence hypothesis of AD progression, suggesting that factors associated with AD can be seen as partial stressors within the matrix of signalling pathways that underlie cell survival and function. Senescence pathways are triggered when stressors exceed the cells ability to compensate for them. The APP proteolytic system has many interactions with pathways involved in programmed senescence and APP proteolysis can both respond to and be driven by senescence-associated signalling. Disease pathways associated with sporadic disease may be different to those involving familial genetic mutations. The interpretation we provide strongly points to senescence as an additional underlying causal process in dementia progression in both SAD and FAD via multiple disease pathways.

Radiosynthesis and in vivo evaluation of fluorinated huprine derivates as PET radiotracers of acetylcholinesterase

INTRODUCTION

Developing positron emission tomography (PET) radiotracers for non-invasive study of the cholinergic system is crucial to the understanding of neurodegenerative diseases. Although several acetylcholinesterase (AChE) PET tracers radiolabeled with carbon-11 exist, no fluorinated radiotracer is currently used in clinical imaging studies. The purpose of the present study is to describe the first fluorinated PET radiotracer for this brain enzyme.

METHODS

Three structural analogs of huprine, a specific AChE inhibitor presenting high affinity towards AChE in vitro, were synthesized and labeled with fluorine-18 via a mesylate/fluoro-nucleophilic aliphatic substitution: ([(18)F]-FHUa, [(18)F]-FHUb and [(18)F]-FHUc). Initial biological evaluation included in vitro autoradiography in rat with competition with an AChE inhibitor at different concentrations, and microPET-scan on anesthetized rats. In vivo PET studies in anesthetized cat focused on [(18)F]-FHUa.

RESULTS AND CONCLUSIONS

Although radiosynthesis of these huprine analogs was straightforward, they showed poor brain penetration potential, partially reversed after pharmacological inhibition of P-glycoprotein. These results indicated that current huprine analogs are not suitable for PET mapping of brain AChE receptors, but require physicochemical modulation in order to increase brain penetration.