Neuroprotective Effects of Cholinesterase Inhibitors: Current Scenario in Therapies for Alzheimer’s Disease and Future Perspectives

Could protein phosphatase 2A and glycogen synthase kinase-3 beta be targeted by natural compounds to ameliorate Alzheimer's pathologies?

Alzheimer's disease (AD) is a progressive neurological disorder that impairs memory and cognitive abilities, primarily in the elderly. The burden of AD extends beyond patients, impacting families and caregivers due to the patients' reliance on assistance for daily tasks. The main features of the pathogenesis of AD are beta-amyloid plaques and neurofibrillary tangles (NFTs), that strongly correlate with oxidative stress and inflammation. NFTs result from misfolded and hyperphosphorylated tau proteins. Various studies have focused on tau phosphorylation, indicating protein phosphatase 2A (PP2A) as the primary tau phosphatase and glycogen synthase kinase-3 beta (GSK-3β) as the leading tau kinase. Experimental evidence suggests that inhibition of PP2A and increased GSK-3β activity contribute to neuroinflammation, oxidative stress, and cognitive impairment. Hence, targeting PP2A and GSK-3β with pharmacological approaches shows promise in treating AD. The use of natural compounds in the drug development for AD have been extensively studied for their antioxidant, anti-inflammatory, anti-cholinesterase, and neuroprotective properties, demonstrating therapeutic advantages in neurological diseases. Alongside the development of PP2A activator and GSK-3β inhibitor drugs, natural compounds are likely to have neuroprotective effects by increasing PP2A activity and decreasing GSK-3β levels. Therefore, based on the preclinical and clinical studies, the potential of PP2A and GSK-3β as therapeutic targets of natural compounds are highlighted in this review.

Disabled-2, a versatile tissue matrix multifunctional scaffold protein with multifaceted signaling: Unveiling its potential in the cancer battle

A multifunctional scaffold protein termed Disabled-2 (Dab2) has recently gained attention in the scientific community and has emerged as a promising candidate in the realm of cancer research. Dab2 protein is involved in a variety of signaling pathways, due to which its significance in the pathogenesis of several carcinomas has drawn considerable attention. Dab2 is essential for controlling the advancement of cancer because it engages in essential signaling pathways such as the Wnt/β-catenin, epidermal growth factor receptor (EGFR), and transforming growth factor-beta (TGF-β) pathways. Dab2 can also repress epithelial-mesenchymal transition (EMT) which is involved in tumor progression with metastatic expansion and adds another layer of significance to its possible impact on cancer spread. Furthermore, the role of Dab2 in processes such as cell growth, differentiation, apoptosis, invasion, and metastasis has been explored in certain investigative studies suggesting its significance. The present review examines the role of Dab2 in the pathogenesis of various cancer subtypes including breast cancer, ovarian cancer, gastric cancer, prostate cancer, and bladder urothelial carcinoma and also sheds some light on its potential to act as a therapeutic target and a prognostic marker in the treatment of various carcinomas. By deciphering this protein's diverse signaling, we hope to provide useful insights that may pave the way for novel therapeutic techniques and tailored treatment approaches in cancer management. Preclinical and clinical trial data on the impact of Dab2 regulation in cancer have also been included, allowing us to delineate role of Dab2 in tumor suppressor function, as well as its correlation with disease stage classification and potential therapy options. However, we observed that there is very scarce data in the form of studies on the evaluation of Dab2 role and treatment function in carcinomas, and further research into this matter could prove beneficial in the generation of novel therapeutic agents for patient-centric and tailored therapy, as well as early prognosis of carcinomas.

A review on traditional Chinese medicine natural products and acupuncture intervention for Alzheimer's disease based on the neuroinflammatory

Alzheimer's disease (AD) is a neurodegenerative disease with insidious onset and progressive development. It is clinically characterized by cognitive impairment, memory impairment and behavioral change. Chinese herbal medicine and acupuncture are important components of traditional Chinese medicine (TCM), and are commonly used in clinical treatment of AD. This paper systematically summarizes the research progress of traditional Chinese medicine natural products and acupuncture treatment of AD, which combined with existing clinical and preclinical evidence, based on a comprehensive review of neuroinflammation, and discusses the efficacy and potential mechanisms of traditional Chinese medicine natural products and acupuncture treatment of AD. Resveratrol, curcumin, kaempferol and other Chinese herbal medicine components can significantly inhibit the neuroinflammation of AD in vivo and in vitro, and are candidates for the treatment of AD. Acupuncture can alleviate the memory and cognitive impairment of AD by improving neuroinflammation, synaptic plasticity, nerve cell apoptosis and reducing the production and aggregation of amyloid β protein (Aβ) in the brain. It has the characteristics of early, safe, effective and benign bidirectional adjustment. The purpose of this paper is to provide a basis for improving the clinical strategies of TCM for the treatment of AD.

The Effect of a Tribulus-Based Formulation in Alleviating Cholinergic System Impairment and Scopolamine-Induced Memory Loss in Zebrafish (Danio rerio): Insights from Molecular Docking and In Vitro/In Vivo Approaches

Tribulus terrestris L. (Tt) has been recently gaining attention for its pharmacological value, including its neuroprotective activities. In this study, we explore the neuroprotective effects of a Tribulus terrestris extract in a zebrafish (Danio rerio) model of scopolamine (SCOP)-induced memory impairment and brain oxidative stress. SCOP, an anticholinergic drug, was employed to replicate fundamental aspects of Alzheimer's disease (AD) in animal models. The fish were treated with ethanolic leaf extract (ELE) from Tt (1, 3, and 6 mg/L) for 15 days. SCOP (100 µM) was administered 30 min before behavioral tests were conducted. Molecular interactions of the major compounds identified via UPLC-PDA/MS in Tt fractions with the active site of acetylcholinesterase (AChE) were explored via molecular docking analyses. Terrestrosin C, protodioscin, rutin, and saponin C exhibited the most stable binding. The spatial memory performance was assessed using the Y-maze test, and memory recognition was examined using a novel object recognition (NOR) test. Tt extract treatment reversed the altered locomotion patterns that were caused by SCOP administration. Biochemical analyses also verified Tt's role in inhibiting AChE, improving antioxidant enzyme activities, and reducing oxidative stress markers. The present findings pave the way for future application of Tt as a natural alternative to treat cognitive disorders.

Intramuscularly Administered PLGA Microparticles for Sustained Release of Rivastigmine: In Vitro, In Vivo and Histological Evaluation

Rivastigmine is an acetylcholinesterase (AchE) and butyrylcholinesterase (BchE) inhibitor drug approved by the US Food and Drug Administration (FDA) for the treatment of mild to moderate dementia of Alzheimer's type. However, its first-pass metabolism and gastrointestinal side effects negatively affect the tolerability and efficacy of oral therapy. These adverse effects could be avoided with the use of a sustained -release formulation as an intramuscular (IM) administration system. The objective of this work was to develop polylactic co-glycolic acid (PLGA) microparticles for the sustained release of rivastigmine and to evaluate its stability during storage, tissue tolerance, in vitro release, and in vivo pharmacokinetics after its IM administration. The microparticles were made by the solvent evaporation emulsion method. A series of formulation parameters (the type of polymer used, the amount of polymer used, the initial amount of rivastigmine, and the volume of PVA 0.1% w/v) were studied to achieve an encapsulation efficiency (EE) and a rivastigmine load of 54.8 ± 0.9% and 3.3 ± 0.1%, respectively. The microparticles, whose size was 56.1 ± 2.8 μm, had a spherical shape and a smooth surface. FT-IR analysis showed that there is no chemical interaction between rivastigmine and the polymer. PLGA microparticles maintain rivastigmine retained and stable under normal (5 ± 3 °C) and accelerated storage (25 ± 2 °C and 60 ± 5 % RH) conditions for at least 6 months. The microparticles behaved as a sustained release system both in vitro and in vivo compared to non-encapsulated rivastigmine. The IM administration of the formulation in rats did not produce significant tissue damage. However, it is necessary to reproduce the experiments with multiple doses to rule out a negative effect in terms of tolerability in chronic treatment. To the best of our knowledge, this study is the only one that has obtained the sustained release of rivastigmine from PLGA microparticles after IM administration in an in vivo model.

Anthocyanins: Molecular Aspects on Their Neuroprotective Activity

Anthocyanins are a type of flavonoids that give plants and fruits their vibrant colors. They are known for their potent antioxidant properties and have been linked to various health benefits. Upon consumption, anthocyanins are quickly absorbed and can penetrate the blood-brain barrier (BBB). Research based on population studies suggests that including anthocyanin-rich sources in the diet lower the risk of neurodegenerative diseases. Anthocyanins exhibit neuroprotective effects that could potentially alleviate symptoms associated with such diseases. In this review, we compiled and discussed a large body of evidence supporting the neuroprotective role of anthocyanins. Our examination encompasses human studies, animal models, and cell cultures. We delve into the connection between anthocyanin bioactivities and the mechanisms underlying neurodegeneration. Our findings highlight how anthocyanins' antioxidant, anti-inflammatory, and anti-apoptotic properties contribute to their neuroprotective effects. These effects are particularly relevant to key signaling pathways implicated in the development of Alzheimer's and Parkinson's diseases. In conclusion, the outcome of this review suggests that integrating anthocyanin-rich foods into human diets could potentially serve as a therapeutic approach for neurological conditions, and we identify promising avenues for further exploration in this area.

The Antioxidant and Neuroprotective Potential of Leaves and Inflorescences Extracts of Selected Hemp Varieties Obtained with scCO2

Cannabis sativa, a versatile plant with numerous varieties, holds promising potential for a wide range of biological activity. As raw materials for research, we chose leaves and inflorescences of hemp varieties such as Białobrzeskie, Henola, and Tygra, which are cultivated mainly for their fibers or seeds. The choice of extraction is a key step in obtaining the selected compositions of active compounds from plant material. Bearing in mind the lipophilic nature of cannabinoids, we performed supercritical carbon dioxide (scCO2) extraction at 50 °C under 2000 (a) and 6000 PSI (b). The cannabinoid contents were determined with the use of the HPLC-DAD method. The antioxidant capabilities were assessed through a series of procedures, including the DPPH, ABTS, CUPRAC, and FRAP methods. The capacity to inhibit enzymes that play a role in the progression of neurodegenerative diseases, such as acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and tyrosinase was also studied. The dominant cannabinoids in the extracts were cannabidiol (CBD) and cannabidiolic acid (CBDA). The highest concentration of eight cannabinoids was detected in the Tygra inflorescences extract (b). The most notable antioxidant properties were provided by the Tygra inflorescences extract (b). Nonetheless, it was the Henola inflorescences extract (b) that demonstrated the most efficient inhibition of AChE and BChE, and tyrosinase was inhibited the most significantly by the Białobrzeskie inflorescences extract (b). Multidimensional comparative analysis enrolled all assays and revealed that the Henola inflorescences extract (b) showed the most substantial neuroprotective potential.

The Role of Dietary Antioxidants and Their Potential Mechanisms in Alzheimer’s Disease Treatment

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with cognitive decline and characterized by amyloid-β plaques and neurofibrillary tau tangles. Although AD’s exact pathophysiology remains unclear, oxidative stress is known to play a role in the neurodegenerative process. Since no curative treatment exists, antioxidants represent a potential treatment for AD due to their ability to modulate oxidative stress. Therefore, this review aims to examine the impact of antioxidant supplementation and its potential mechanisms on cognitive function. The review primarily discusses research articles published between 2012 and 2022 reporting the results of clinical trials involving antioxidant supplementation on cognitive function in individuals with AD. Antioxidant supplementation included probiotics, selenium, melatonin, resveratrol, rosmarinic acid, carotenoids, curcumin, vitamin E, and coenzyme Q. While the studies included in this review did not provide much evidence for the beneficial role of antioxidant supplements on cognitive function in AD, the results varied from antioxidant to antioxidant and among trials examining the same antioxidant. Furthermore, many of the studies’ findings face several limitations, including short trial durations, small sample sizes, and a lack of diversity among study participants. As a result, more research is required to examine the impact of antioxidant supplementation on cognitive function in AD.

Pseudo-irreversible butyrylcholinesterase inhibitors: Structure-activity relationships, computational and crystallographic study of the N-dialkyl O-arylcarbamate warhead

Alongside reversible butyrylcholinesterase inhibitors, a plethora of covalent butyrylcholinesterase inhibitors have been reported in the literature, typically pseudo-irreversible carbamates. For these latter, however, most cases lack full confirmation of their covalent mode of action. Additionally, the available reports regarding the structure-activity relationships of the O-arylcarbamate warhead are incomplete. Therefore, a follow-up on a series of pseudo-irreversible covalent carbamate human butyrylcholinesterase inhibitors and the structure-activity relationships of the N-dialkyl O-arylcarbamate warhead are presented in this study. The covalent mechanism of binding was tested by IC₅₀ time-dependency profiles, and sequentially and increasingly confirmed by kinetic analysis, whole protein LC-MS, and crystallographic analysis. Computational studies provided valuable insights into steric constraints and identified problematic, bulky carbamate warheads that cannot reach and carbamoylate the catalytic Ser198. Quantum mechanical calculations provided further evidence that steric effects appear to be a key factor in determining the covalent binding behaviour of these carbamate cholinesterase inhibitors and their duration of action. Additionally, the introduction of a clickable terminal alkyne moiety into one of the carbamate N-substituents and in situ derivatisation with azide-containing fluorophore enabled fluorescent labelling of plasma human butyrylcholinesterase. This proof-of-concept study highlights the potential of this novel approach and for these compounds to be further developed as clickable molecular probes for investigating tissue localisation and activity of cholinesterases.

Study on Phenolic and Organic Acid Compositions and Antioxidant and Enzyme Inhibition Activities of Agaricomycetes Mushroom Species from Turkey

Mushrooms stand out as one of nature's best gifts among the natural product sources with their diversity, therapeutic values and increasing popularity. In this study, antioxidant (ABTS·+ scavenging, β-carotene-bleaching, cupric-reducing antioxidant capacity (CUPRAC), DPPH· scavenging, and metal chelating assays), and enzyme (buty-rylcholinesterase (BChE) and acetylcholinesterase (AChE), α-amylase and α-glucosidase) inhibition activities of the extracts obtained from Coprinus comatus (O.F. Müll.) Pers., Cerrena unicolor (Bull.) Murrill, Inocutis rheades (Pers.) Fiasson & Niemela and Leptoporus mollis (Pers.) Quél. mushroom species were investigated. The presence of phenolic and organic acid compounds associated with the bioactive properties of the mushroom species was determined by HPLC-DAD. Fumaric acid was found to be prominent compound in C. comatus (43.90 µg/g dw) and C. unicolor (659.9 µg/g dw), vanillin in L. mollis (19.48 µg/g dw), and p-coumaric acid in I. rheades (21.32 µg/g dw). L. mollis methanol extract, as well as higher antioxidant activity than the standards in CUPRAC and β-carotene-bleaching assays, was noted as superior antioxidant active in all assays (except metal chelating). C. comatus possessed the highest inhibition activity on α-amylase (IC50: 0.23 mg/mL for methanol extract), AChE (IC50: 125.50 µg/mL for hexane extract), and BChE (IC50: 61.03 µg/mL for methanol extract). Also, C. comatus methanol (IC50: 0.09 mg/mL) and L. mollis hexane (IC50 : 0.11 mg/ mL) extracts were better α-glucosidase inhibition active than the acarbose (IC50: 0.37 mg/mL). Our study ascertained that the studied mushroom species are particularly sources of biochemically active compounds with therapeutic potential.

Novel Dual AChE and ROCK2 Inhibitor Induces Neurogenesis via PTEN/AKT Pathway in Alzheimer's Disease Model

Alzheimer's disease (AD) is a progressive and complex neurodegenerative disease. Acetylcholinesterase inhibitors (AChEIs) are a major class of drugs used in AD therapy. ROCK2, another promising target for AD, has been associated with the induction of neurogenesis via PTEN/AKT. This study aimed to characterize the therapeutic potential of a novel donepezil-tacrine hybrid compound (TA8Amino) to inhibit AChE and ROCK2 protein, leading to the induction of neurogenesis in SH-SY5Y cells. Experiments were carried out with undifferentiated and neuron-differentiated SH-SY5Y cells submitted to treatments with AChEIs (TA8Amino, donepezil, and tacrine) for 24 h or 7 days. TA8Amino was capable of inhibiting AChE at non-cytotoxic concentrations after 24 h. Following neuronal differentiation for 7 days, TA8Amino and donepezil increased the percentage of neurodifferentiated cells and the length of neurites, as confirmed by β-III-tubulin and MAP2 protein expression. TA8Amino was found to participate in the activation of PTEN/AKT signaling. In silico analysis showed that TA8Amino can stably bind to the active site of ROCK2, and in vitro experiments in SH-SY5Y cells demonstrate that TA8Amino significantly reduced the expression of ROCK2 protein, contrasting with donepezil and tacrine. Therefore, these results provide important information on the mechanism underlying the action of TA8Amino with regard to multi-target activities.

Linking the Amyloid, Tau, and Mitochondrial Hypotheses of Alzheimer's Disease and Identifying Promising Drug Targets

Damage or loss of brain cells and impaired neurochemistry, neurogenesis, and synaptic and nonsynaptic plasticity of the brain lead to dementia in neurodegenerative diseases, such as Alzheimer's disease (AD). Injury to synapses and neurons and accumulation of extracellular amyloid plaques and intracellular neurofibrillary tangles are considered the main morphological and neuropathological features of AD. Age, genetic and epigenetic factors, environmental stressors, and lifestyle contribute to the risk of AD onset and progression. These risk factors are associated with structural and functional changes in the brain, leading to cognitive decline. Biomarkers of AD reflect or cause specific changes in brain function, especially changes in pathways associated with neurotransmission, neuroinflammation, bioenergetics, apoptosis, and oxidative and nitrosative stress. Even in the initial stages, AD is associated with Aβ neurotoxicity, mitochondrial dysfunction, and tau neurotoxicity. The integrative amyloid-tau-mitochondrial hypothesis assumes that the primary cause of AD is the neurotoxicity of Aβ oligomers and tau oligomers, mitochondrial dysfunction, and their mutual synergy. For the development of new efficient AD drugs, targeting the elimination of neurotoxicity, mutual potentiation of effects, and unwanted protein interactions of risk factors and biomarkers (mainly Aβ oligomers, tau oligomers, and mitochondrial dysfunction) in the early stage of the disease seems promising.

Amyloid β, Lipid Metabolism, Basal Cholinergic System, and Therapeutics in Alzheimer’s Disease

The presence of insoluble aggregates of amyloid β (Aβ) in the form of neuritic plaques (NPs) is one of the main features that define Alzheimer’s disease. Studies have suggested that the accumulation of these peptides in the brain significantly contributes to extensive neuronal loss. Furthermore, the content and distribution of cholesterol in the membrane have been shown to have an important effect on the production and subsequent accumulation of Aβ peptides in the plasma membrane, contributing to dysfunction and neuronal death. The monomeric forms of these membrane-bound peptides undergo several conformational changes, ranging from oligomeric forms to beta-sheet structures, each presenting different levels of toxicity. Aβ peptides can be internalized by particular receptors and trigger changes from Tau phosphorylation to alterations in cognitive function, through dysfunction of the cholinergic system. The goal of this review is to summarize the current knowledge on the role of lipids in Alzheimer’s disease and their relationship with the basal cholinergic system, as well as potential disease-modifying therapies.

2-Mercaptobenzimidazole clubbed hydrazone for Alzheimer’s therapy: In vitro, kinetic, in silico, and in vivo potentials

Alzheimer’s is a type of dementia that affects the affected person’s thinking, memory, and behavior. It is a multifactorial disease, developed by the breakdown of the neurotransmitter acetylcholine via acetylcholinesterase (AChE). The present study was designed to evaluate potential inhibitors of acetylcholinesterase that could be used as a therapeutic agent against Alzheimer’s disease (AD). For this course, synthetic compounds of the Schiff bases class of 2-mercaptobenzimidazole hydrazone derivatives (9–14) were determined to be potent acetylcholinesterase inhibitors with IC₅₀ values varying between 37.64 ± 0.2 and 74.76 ± 0.3 μM. The kinetic studies showed that these are non-competitive inhibitors of AChE. Molecular docking studies revealed that all compounds accommodate well in the active site and are stabilized by hydrophobic interactions and hydrogen bonding. Molecular dynamics (MD) simulations of selected potent inhibitors confirm their stability in the active site of the enzyme. Moreover, all compounds showed antispasmodic and Ca²⁺ antagonistic activities. Among the selected compounds of 2-mercaptobenzimidazole hydrazone derivatives, compound 11 exhibited the highest activity on spontaneous and K⁺-induced contractions, followed by compound 13. Therefore, the Ca²⁺ antagonistic, AChE inhibition potential, and safety profile of these compounds in the human neutrophil viability assay make them potential drug candidates against AD in the future.

The "Cerebrospinal Fluid Sink Therapeutic Strategy" in Alzheimer's Disease-From Theory to Design of Applied Systems

Alzheimer’s disease (AD) is a global health problem, with incidence and prevalence considered to increase during the next decades. However, no currently available effective treatment exists despite numerous clinical trials in progress. Moreover, although many hypotheses are accepted regarding the pathophysiological mechanisms of AD onset and evolution, there are still many unknowns about the disorder. A relatively new approach, based on the amyloid-beta dynamics among different biological compartments, is currently intensely discussed, as it seems to offer a promising solution with significant therapeutic impact. Known as the “cerebrospinal-fluid-sink therapeutic strategy”, part of the “three-sink therapeutic strategy”, this theoretical model focuses on the dynamics of amyloid-beta among the three main liquid compartments of the human body, namely blood, cerebrospinal fluid, and the (brain) interstitial fluid. In this context, this article aims to describe in detail the abovementioned hypothesis, by reviewing in the first part the most relevant anatomical and physiological aspects of amyloid-beta dynamics. Subsequently, explored therapeutic strategies based on the clearance of amyloid-beta from the cerebrospinal fluid level are presented, additionally highlighting their limitations. Finally, the originality and novelty of this work rely on the research experience of the authors, who focus on implantable devices and their utility in AD treatment.