Memantine: a review of its use in Alzheimer's disease

The ketamine chameleon: history, pharmacology, and the contested value of experience

INTRODUCTION

Since its synthesis in 1962, ketamine has been widely used in diverse medical contexts, from anesthesia to treatment-resistant depression. However, interpretations of ketamine's subjective effects remain polarized. Biomedical frameworks typically construe the drug's experiential effects as dissociative or psychotomimetic, while psychedelic paradigms emphasize the potential therapeutic merits of these non-ordinary states.

AREAS COVERED

Ketamine's psychoactive effects have inspired diverse interpretations. In this review, we trace the historical evolution of these perspectives - which we broadly categorize as 'dissociative,' 'dream-like,' and 'psychedelic' - and show how they emerged out of these clinical contexts. We highlight the influence of factors such as language, dose, and environmental context on ketamine's effects and therapeutic outcomes. We discuss potential mechanisms underlying these context-dependent effects and explore the broader clinical and research-related ramifications.

EXPERT OPINION

Ketamine's subjective effects are undeniably powerful, yet their therapeutic significance remains debated. A nuanced, interdisciplinary approach is essential for maximizing ketamine's potential. Future research should focus on how explanatory models, treatment environments, and patient preparation can optimize ketamine's benefits while minimizing distress. We suggest that, rather than being a tiger to be tamed as its creator once described, ketamine may best be understood as a chameleon whose color shifts depending on its context.

Medications and cognitive decline in Alzheimer's disease: Cohort cluster analysis of 15,428 patients

BACKGROUND

Medications for comorbid conditions may affect cognition in Alzheimer's disease (AD).

OBJECTIVE

To explore the association between common medications and cognition, measured with the Mini-Mental State Examination.

METHODS

Cohort study including persons with AD from the Swedish Registry for Cognitive/Dementia Disorders (SveDem). Medications were included if they were used by ≥5% of patients (26 individual drugs). Each follow-up was analyzed independently by performing 100 Monte-Carlo simulations of two steps each 1) k-means clustering of patients according to Mini-Mental State Examination at follow-up and its decline since previous measure, and 2) Identification of medications presenting statistically significant differences in the proportion of users in the different clusters.

RESULTS

15,428 patients (60.38% women) were studied. Four clusters were identified. Medications associated with the best cognition cluster (relative to the worse) were atorvastatin (point estimate 1.44 95% confidence interval [1.15-1.83] at first follow-up, simvastatin (1.41 [1.11-1.78] at second follow-up), warfarin (1.56 [1.22-2.01] first follow-up), zopiclone (1.35 [1.15-1.58], and metformin (2.08 [1.35-3.33] second follow-up. Oxazepam (0.60 [0.50-0.73] first follow-up), paracetamol (0.83 [0.73-0.95] first follow-up), cyanocobalamin, felodipine and furosemide were associated with the worst cluster. Cholinesterase inhibitors were associated with the best cognition clusters, whereas memantine appeared in the worse cognition clusters, consistent with its indication in moderate to severe dementia.

CONCLUSIONS

We performed unsupervised clustering to classify patients based on their current cognition and cognitive decline from previous testing. Atorvastatin, simvastatin, warfarin, metformin, and zopiclone presented a positive and statistically significant associations with cognition, while oxazepam, cyanocobalamin, felodipine, furosemide and paracetamol, were associated with the worst cluster.

Inflammasomes in Alzheimer's Progression: Nrf2 as a Preventive Target

Current knowledge about Alzheimer's disease highlights the accumulation of β-amyloid plaques (Aβ1-42) and neurofibrillary tangles composed of hyperphosphorylated Tau, which lead to the loss of neuronal connections. Microglial activation and the release of inflammatory mediators play a significant role in the progression of Alzheimer's pathology. Recent advances have identified the involvement of inflammasomes, particularly NOD-like receptor NLR family pyrin domain containing 3 (NLRP3), whose activation promotes the release of proinflammatory cytokines and triggers pyroptosis, exacerbating neuroinflammation. Aggregates of Aβ1-42 and hyperphosphorylated Tau have been shown to activate these inflammasomes, while the apoptosis-associated speck-like protein (ASC) components form aggregates that further accelerate Aβ aggregation. Defects in the autophagic clearance of inflammasomes have also been implicated in Alzheimer's disease, contributing to sustained inflammation. This review explores strategies to counteract inflammation in Alzheimer's, emphasizing the degradation of ASC specks and the inhibition of NLRP3 inflammasome activation. Notably, the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor emerges as a promising therapeutic target due to its dual role in mitigating oxidative stress and directly inhibiting NLRP3 inflammasome formation. By reducing inflammasome-driven inflammation, Nrf2 offers significant potential for addressing the neuroinflammatory aspects of Alzheimer's disease.

Sex differences in mitochondrial free-carnitine levels in subjects at-risk and with Alzheimer's disease in two independent study cohorts

A major challenge in the development of more effective therapeutic strategies for Alzheimer's disease (AD) is the identification of molecular mechanisms linked to specific pathophysiological features of the disease. Importantly AD has a two-fold higher incidence in women than men and a protracted prodromal phase characterized by amnestic mild-cognitive impairment (aMCI) suggesting that biological processes occurring early can initiate vulnerability to AD. Here, we used a sample of 125 subjects from two independent study cohorts to determine the levels in plasma (the most accessible specimen) of two essential mitochondrial markers acetyl-L-carnitine (LAC) and its derivative free-carnitine motivated by a mechanistic model in rodents in which targeting mitochondrial metabolism of LAC leads to the amelioration of cognitive function and boosts epigenetic mechanisms of gene expression. We report a sex-specific deficiency in free-carnitine levels in women with aMCI and early-AD compared to cognitively healthy controls; no change was observed in men. We also replicated the prior finding of decreased LAC levels in both women and men with AD, supporting the robustness of the study samples assayed in our new study. The magnitude of the sex-specific free-carnitine deficiency reflected the severity of cognitive dysfunction and held in two study cohorts. Furthermore, patients with the lower free-carnitine levels showed higher β-amyloid(Aβ) accumulation and t-Tau levels assayed in cerebrospinal fluid (CSF). Computational analyses showed that the mitochondrial markers assayed in plasma are at least as accurate as CSF measures to classify disease status. Together with the mechanistic platform in rodents, these translational findings lay the groundwork to create preventive individualized treatments targeting sex-specific changes in mitochondrial metabolism that may be subtle to early cognitive dysfunction of AD risk.

Evaluating Quinolines: Molecular Dynamics Approach to Assess Their Potential as Acetylcholinesterase Inhibitors for Alzheimer's Disease

Quinoline represents a promising scaffold for developing potential drugs because of the wide range of biological and pharmacological activities that it exhibits. In the present study, quinoline derivatives obtained from CADMA-Chem docking protocol were investigated in the mean of molecular dynamics simulations as potential inhibitors of acetylcholinesterase enzyme. The examined species can be partitioned between neutral, dq815 (2,3 dihydroxyl-quinoline-4-carbaldehyde), dq829 (2,3 dihydroxyl-quinoline-8-carboxylic acid methane ester), dq1356 (3,4 dihydroxyl-quinoline-6-carbaldehyde), dq1368 (3,4 dihydroxyl-quinoline-8-carboxylic acid methane ester) and dq2357 (5,6 dihydroxyl-quinoline-8-carboxylic acid methane ester), and deprotonated, dq815_dep, dq829_dep, dq1356_dep and dq2357_dep. Twelve molecular dynamics simulations were performed including those of natural acetylcholine, of the well-known donepezil inhibitor and of the founder quinoline chosen as reference. Key intermolecular interactions were detected and discussed to describe the different dynamic behavior of all the considered species. Binding energies calculation from MMPBSA well accounts for the dynamic behavior observed in the simulation time proposing dq1368 as promising candidate for the inhibition of acetylcholinesterase. Retrosynthetic route for the production of the investigated compounds is also proposed.

Dizocilpine derivatives as neuroprotective NMDA receptor antagonists without psychomimetic side effects

We aimed to prepare novel dibenzo [a,d][7]annulen derivatives that act on N-methyl-d-aspartate (NMDA) receptors with potential neuroprotective effects. Our approach involved modifying the tropane moiety of MK-801, a potent open-channel blocker known for its psychomimetic side effects, by introducing a seven-membered ring with substituted base moieties specifically to alleviate these undesirable effects. Our in silico analyses showed that these derivatives should have high gastrointestinal absorption and cross the blood-brain barrier (BBB). Our pharmacokinetic studies in rats supported this conclusion and confirmed the ability of leading compounds 3l and 6f to penetrate the BBB. Electrophysiological experiments showed that all compounds exhibited different inhibitory activity towards the two major NMDA receptor subtypes, GluN1/GluN2A and GluN1/GluN2B. Of the selected compounds intentionally differing in the inhibitory efficacy, 6f showed high relative inhibition (∼90 % for GluN1/GluN2A), while 3l showed moderate inhibition (∼50 %). An in vivo toxicity study determined that compounds 3l and 6f were safe at 10 mg/kg doses with no adverse effects. Behavioral studies demonstrated that these compounds did not induce hyperlocomotion or impair prepulse inhibition of startle response in rats. Neuroprotective assays using a model of NMDA-induced hippocampal neurodegeneration showed that compound 3l at a concentration of 30 μM significantly reduced hippocampal damage in rats. These results suggest that these novel dibenzo [a,d][7]annulen derivatives are promising candidates for developing NMDA receptor-targeted therapies with minimal psychotomimetic side effects.

Glutamate: Molecular Mechanisms and Signaling Pathway in Alzheimer's Disease, a Potential Therapeutic Target

Gamma-glutamate is an important excitatory neurotransmitter in the central nervous system (CNS), which plays an important role in transmitting synapses, plasticity, and other brain activities. Nevertheless, alterations in the glutamatergic signaling pathway are now accepted as a central element in Alzheimer's disease (AD) pathophysiology. One of the most prevalent types of dementia in older adults is AD, a progressive neurodegenerative illness brought on by a persistent decline in cognitive function. Since AD has been shown to be multifactorial, a variety of pharmaceutical targets may be used to treat the condition. N-methyl-D-aspartic acid receptor (NMDAR) antagonists and acetylcholinesterase inhibitors (AChEIs) are two drug classes that the Food and Drug Administration has authorized for the treatment of AD. The AChEIs approved to treat AD are galantamine, donepezil, and rivastigmine. However, memantine is the only non-competitive NMDAR antagonist that has been authorized for the treatment of AD. This review aims to outline the involvement of glutamate (GLU) at the molecular level and the signaling pathways that are associated with AD to demonstrate the drug target therapeutic potential of glutamate and its receptor. We will also consider the opinion of the leading authorities working in this area, the drawback of the existing therapeutic strategies, and the direction for the further investigation.

GC-MS-employed Phytochemical Characterization and Anticancer, Antidiabetic, and Antioxidant Activity Screening of Lagerstroemia Thorelli

Lagerstroemia thorelli (L. thorelli) is a member of the Lythraceae family and has not been previously researched. Thus, this study aimed to investigate its unexplored potential and identify novel therapeutic prospects. This research evaluated antioxidant, antidiabetic, and cytotoxic potentials along with compound characterization of the ethanolic leaf extract of L. thorelli. The antioxidant potential was assessed using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free radical and hydrogen peroxide (H2O2) scavenging assays, total antioxidant capacity (TAC), total phenolic content (TPC), total flavonoid content (TFC) determination, antidiabetic property was assessed using α-amylase inhibition, and the cytotoxic effect was examined on HeLa and Vero cells using MTT colorimetric assay. Chemical characterization was performed using gas chromatography-mass spectrometry (GC-MS). The findings demonstrated strong antioxidant, strong antidiabetic, and moderate cytotoxic activities. Comprehensive phytochemical analysis revealed its abundance in flavonoids, phenols/phenolics, tannins, glycosides, steroids, resin, etc. GC-MS analysis of the L. thorelli extract identified 80 important compounds including cis-11-eicosenamide, beta-D-glucopyranoside, methyl-, alpha-D-glucopyranoside, methyl-, phthalic acid, gamma-sitosterol, phytol, silicic acid, squalene, butanoic acid, cyclobarbital, etc. which are well-documented for their antioxidant, antidiabetic, and anticancer effects. Thus, it can be inferred that L. thorelli could hold new promises in treating diseases like diabetes and free radical-induced conditions, including neurodegenerative diseases.

Memories and mimics: unveiling the potential of FDG-PET in guiding therapeutic approaches for neurodegenerative cognitive disorders

Fluorodeoxyglucose F18 (FDG) positron emission tomography (PET) imaging can help clinicians pursue the differential diagnosis of various neurodegenerative diseases. It has become an invaluable diagnostic tool in routine clinical practice in conjunction with computed tomography (CT) imaging, magnetic resonance imaging (MRI), and biomarker studies. We present a single-institution case series and systematic literature review, showing how FDG-PET imaging has helped physicians diagnose neurodegenerative diseases and their mimickers and how patient care was amended. A single institution analysis and comprehensive literature search were completed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. These medical subjects' headings (MeSH) terms were used: "FDG-PET" AND "dementia" OR "Alzheimer's" OR "neurodegeneration" OR "frontotemporal dementia" OR "atypical parkinsonian syndrome" OR "primary progressive aphasia" OR "lewy body dementia." The inclusion criteria included studies with uncertain diagnoses of neurocognitive disease resolved with FDG-PET, PET/MRI, or PET/CT hybrid imaging. A literature search resulted in 3,976 articles. After considering inclusion and exclusion criteria, 14 case reports and 1 case series were selected, representing 19 patients. The average age of patients was 70.8 years (range: 54-83 years). Five of the 19 patients were females. Dementia with Lewy bodies (DLB) had the highest propensity for being misidentified as another neurodegenerative disease, followed by Alzheimer's disease (AD) and frontotemporal dementia (FTD). Without accurate molecular imaging, neurodegenerative diseases may be missed or misdiagnosed. Our single-institution case series and literature review demonstrate how FDG-PET brain imaging can be used to correct and clarify preexisting clinical diagnoses of neurodegenerative disease.

In-Silico discovery of 17alpha-hydroxywithanolide-D as potential neuroprotective allosteric modulator of NMDA receptor targeting Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder marked by cognitive decline, memory impairment, and behavioral alterations. The N-methyl-D-aspartate (NMDA) receptor has emerged as a promising target for AD pharmacotherapy due to its role in the disease's pathogenesis. This study leverages advanced computational methods to screen 80 active constituents of Withania somnifera (Ashwagandha), a traditional herb known for its neuroprotective effects, against the NMDA receptor, using FDA-approved Ifenprodil as a reference. Our blind virtual screening results demonstrated that all tested compounds could bind to various domains of the NMDA receptor, with binding energies ranging from - 4.1 to -11.9 kcal/mol, compared to Ifenprodil's -7.8 kcal/mol. Binding preference analysis revealed 7 compounds bound to the A-chain, 37 to the B-chain, 7 to the C-chain, and 29 to the D-chain of the receptor. Notable binding was observed predominantly at the Amino Terminal Domain (ATD) core site, some at the ATD-Ligand Binding Domain (LBD) interface, and a few at the Transmembrane Domain (TMD). Particularly, 17alpha-hydroxywithanolide D, with a binding energy of -11.9 kcal/mol, emerged as a prime candidate for further investigation. Molecular dynamics simulations of this compound revealed key interactions, including direct hydrogen bonding with residues ASP165, ARG431, THR433, LYS466, and TYR476 on the D-chain, as well as additional hydrophobic and water-bridging interactions. These simulations highlighted the compound's influence on dynamic conformational states of the GluN1b-GluN2B receptor complex, modulating interactions between GluN1b Lys178 and GluN2B Asn184. Furthermore, the compound affected the distance between LBD heterodimers and the tension within the LBD-M30 linker, demonstrating its potential to modulate NMDA receptor activity. This comprehensive study not only underscores the therapeutic promise of Withania somnifera derivatives for AD but also provides a detailed molecular basis for their efficacy, offering valuable insights for targeted drug development and innovative therapeutic strategies against Alzheimer's disease.

Alzheimer's Disease as Type 3 Diabetes: Understanding the Link and Implications

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) are two prevalent conditions that present considerable public health issue in aging populations worldwide. Recent research has proposed a novel conceptualization of AD as "type 3 diabetes", highlighting the critical roles of insulin resistance and impaired glucose metabolism in the pathogenesis of the disease. This article examines the implications of this association, exploring potential new avenues for treatment and preventive strategies for AD. Key evidence linking diabetes to AD emphasizes critical metabolic processes that contribute to neurodegeneration, including inflammation, oxidative stress, and alterations in insulin signaling pathways. By framing AD within this metabolic context, we can enhance our understanding of its etiology, which in turn may influence early diagnosis, treatment plans, and preventive measures. Understanding AD as a manifestation of diabetes opens up the possibility of employing novel therapeutic strategies that incorporate lifestyle modifications and the use of antidiabetic medications to mitigate cognitive decline. This integrated approach has the potential to improve patient outcomes and deepen our comprehension of the intricate relationship between neurodegenerative diseases and metabolic disorders.

Profiling aducanumab as a treatment option for Alzheimer's disease: an overview of efficacy, safety and tolerability

INTRODUCTION

Alzheimer's disease is the most common form of dementia worldwide. Aducanumab, a monoclonal antibody targeting amyloid-beta, became the first disease-modifying treatment for mild cognitive impairment due to Alzheimer's disease (AD) and mild AD dementia and suggested that removing amyloid from the brain, especially in early AD, might make a difference in slowing cognitive decline.

AREAS COVERED

In this review, the authors outline aducanumab's clinical efficacy as shown through key clinical trials and discuss its approval by the Food and Drug Administration under the accelerated pathway, which sparked both hope and controversy. We also discuss the importance of amyloid-related imaging abnormalities as a major side effect of aducanumab and all subsequent monoclonal antibodies targeting amyloid-beta.

EXPERT OPINION

Aducanumab, became the first monoclonal antibody that provided at least partial support for the amyloid hypothesis by demonstrating slowed cognitive decline by removing amyloid from the brain, although full FDA approval now seems unlikely due to discontinuation of its development. Its introduction raised awareness of ARIA, highlighted the significant costs and need for informed consent in treatment, and emphasized the importance of long-term, diverse, and combination therapy data for future AD treatments targeting amyloid and tau.

Challenges and Opportunities for Consideration of Efavirenz Drug Repurposing for Alzheimer's Disease Therapeutics

Therapeutic research and development for Alzheimer's disease (AD) has been an area of intense research to alleviate memory loss and neurodegeneration. There is growing interest in drug repositioning and repurposing strategies for FDA-approved medications as potential candidates that may further advance AD therapeutics. The FDA drug efavirenz has been investigated as a candidate drug for repurposing as an AD medication. The proposed mechanism of action of efavirenz (at low doses) is the activation of the neuron-specific enzyme CYP46A1 that converts excess brain cholesterol into 24-hydroxycholesterol (24-HC) that is exported to the periphery. Efavirenz at a low dose was found to improve memory deficit in the 5XFAD model of AD that was accompanied by elevated 24-HC and reduction in Aβ; furthermore, efavirenz reduced pTau and excess cholesterol levels in human iPSC-derived Alzheimer's neurons. The low dose of efavirenz used in the AD mouse model to increase 24-HC contrasts with the use of more than 100-fold higher doses of efavirenz for clinical treatment of human immunodeficiency virus (HIV) through inhibition of reverse transcriptase. Low doses of efavirenz may avoid neurotoxic adverse effects that occur at high efavirenz doses used for HIV treatment. This review evaluates the drug properties of efavirenz with respect to its preclinical data on regulating memory deficit, pharmacokinetics, pharmacodynamics, metabolites, and genetic variabilities in drug metabolism as well as its potential adverse effects. These analyses discuss the challenges and questions that should be addressed in future studies to consider the opportunity for low dose efavirenz as a candidate for AD drug development.

The selective disruption of the JNK2/Syntaxin-1A interaction by JGRi1 protects against NMDA-evoked toxicity in SH-SY5Y cells

N-methyl-D-aspartate (NMDA) receptors are calcium-permeable ion-channel receptors, specifically activated by glutamate, that permit the activation of specific intracellular calcium-dependent pathways. Aberrant NMDA receptor activation leads to a condition known as excitotoxicity, in which excessive calcium inflow induces apoptotic pathways. To date, memantine is the only NMDA receptor antagonist authorized in clinical practice, hence, a better understanding of the NMDA cascade represents a need to discover novel pharmacological targets. We previously reported non-conventional intracellular signaling triggered by which, upon activation, promotes the interaction between JNK2 and STX1A which enhances the rate of vesicular secretion. We developed a cell-permeable peptide, named JGRi1, able to disrupt such interaction, thus reducing vesicular secretion. In this work, to selectively study the effect of JGRi1 in a much simpler system, we employed neuroblastoma cells, SH-SY5Y. We found that SH-SY5Y cells express the components of the NMDA receptor-JNK2 axis and that the NMDA stimulus increases the rate of vesicle release. Both JGRi1 and memantine protected SH-SY5Y cells from NMDA toxicity, but only JGRi1 reduced the interaction between JNK2 and STX1A. Both drugs successfully reduced NMDA-induced vesicle release, although, unlike memantine, JGRi1 did not prevent calcium influx. NMDA treatment induced JNK2 expression, but not JNK1 or JNK3, which was prevented by both JGRi1 and memantine, suggesting that JNK2 may be specifically involved in the response to NMDA. In conclusion, being JGRi1 able to protect cells against NMDA toxicity by interfering with JNK2/STX1A interaction, it could be considered a novel pharmacological tool to counteract excitotoxicity.

Updates in Alzheimer's disease: from basic research to diagnosis and therapies

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized pathologically by extracellular deposition of β-amyloid (Aβ) into senile plaques and intracellular accumulation of hyperphosphorylated tau (pTau) as neurofibrillary tangles. Clinically, AD patients show memory deterioration with varying cognitive dysfunctions. The exact molecular mechanisms underlying AD are still not fully understood, and there are no efficient drugs to stop or reverse the disease progression. In this review, we first provide an update on how the risk factors, including APOE variants, infections and inflammation, contribute to AD; how Aβ and tau become abnormally accumulated and how this accumulation plays a role in AD neurodegeneration. Then we summarize the commonly used experimental models, diagnostic and prediction strategies, and advances in periphery biomarkers from high-risk populations for AD. Finally, we introduce current status of development of disease-modifying drugs, including the newly officially approved Aβ vaccines, as well as novel and promising strategies to target the abnormal pTau. Together, this paper was aimed to update AD research progress from fundamental mechanisms to the clinical diagnosis and therapies.

Potent and reversible open-channel blocker of NMDA receptor derived from dizocilpine with enhanced membrane-to-channel inhibition

N-methyl-D-aspartate receptors (NMDARs) play a significant role in developing several central nervous system (CNS) disorders. Currently, memantine, used for treating Alzheimer's disease, and ketamine, known for its anesthetic and antidepressant properties, are two clinically used NMDAR open-channel blockers. However, despite extensive research into NMDAR modulators, many have shown either harmful side effects or inadequate effectiveness. For instance, dizocilpine (MK-801) is recognized for its powerful psychomimetic effects due to its high-affinity and nearly irreversible inhibition of the GluN1/GluN2 NMDAR subtypes. Unlike ketamine, memantine and MK-801 also act through a unique, low-affinity "membrane-to-channel inhibition" (MCI). We aimed to develop an open-channel blocker based on MK-801 with distinct inhibitory characteristics from memantine and MK-801. Our novel compound, K2060, demonstrated effective voltage-dependent inhibition in the micromolar range at key NMDAR subtypes, GluN1/GluN2A and GluN1/GluN2B, even in the presence of Mg2+. K2060 showed reversible inhibitory dynamics and a partially trapping open-channel blocking mechanism with a significantly stronger MCI than memantine. Using hippocampal slices, 30 µM K2060 inhibited excitatory postsynaptic currents in CA1 hippocampal neurons by ∼51 %, outperforming 30 µM memantine (∼21 % inhibition). K2060 exhibited No Observed Adverse Effect Level (NOAEL) of 15 mg/kg upon intraperitoneal administration in mice. Administering K2060 at a 10 mg/kg dosage resulted in brain concentrations of approximately 2 µM, with peak concentrations (Tmax) achieved within 15 minutes. Finally, applying K2060 with trimedoxime and atropine in mice exposed to tabun improved treatment outcomes. These results underscore K2060's potential as a therapeutic agent for CNS disorders linked to NMDAR dysfunction.

Recent advances in Alzheimer's disease: Mechanisms, clinical trials and new drug development strategies

Alzheimer's disease (AD) stands as the predominant form of dementia, presenting significant and escalating global challenges. Its etiology is intricate and diverse, stemming from a combination of factors such as aging, genetics, and environment. Our current understanding of AD pathologies involves various hypotheses, such as the cholinergic, amyloid, tau protein, inflammatory, oxidative stress, metal ion, glutamate excitotoxicity, microbiota-gut-brain axis, and abnormal autophagy. Nonetheless, unraveling the interplay among these pathological aspects and pinpointing the primary initiators of AD require further elucidation and validation. In the past decades, most clinical drugs have been discontinued due to limited effectiveness or adverse effects. Presently, available drugs primarily offer symptomatic relief and often accompanied by undesirable side effects. However, recent approvals of aducanumab (1) and lecanemab (2) by the Food and Drug Administration (FDA) present the potential in disrease-modifying effects. Nevertheless, the long-term efficacy and safety of these drugs need further validation. Consequently, the quest for safer and more effective AD drugs persists as a formidable and pressing task. This review discusses the current understanding of AD pathogenesis, advances in diagnostic biomarkers, the latest updates of clinical trials, and emerging technologies for AD drug development. We highlight recent progress in the discovery of selective inhibitors, dual-target inhibitors, allosteric modulators, covalent inhibitors, proteolysis-targeting chimeras (PROTACs), and protein-protein interaction (PPI) modulators. Our goal is to provide insights into the prospective development and clinical application of novel AD drugs.

GLP-1-directed NMDA receptor antagonism for obesity treatment

The N-methyl-D-aspartate (NMDA) receptor is a glutamate-activated cation channel that is critical to many processes in the brain. Genome-wide association studies suggest that glutamatergic neurotransmission and NMDA receptor-mediated synaptic plasticity are important for body weight homeostasis1. Here we report the engineering and preclinical development of a bimodal molecule that integrates NMDA receptor antagonism with glucagon-like peptide-1 (GLP-1) receptor agonism to effectively reverse obesity, hyperglycaemia and dyslipidaemia in rodent models of metabolic disease. GLP-1-directed delivery of the NMDA receptor antagonist MK-801 affects neuroplasticity in the hypothalamus and brainstem. Importantly, targeting of MK-801 to GLP-1 receptor-expressing brain regions circumvents adverse physiological and behavioural effects associated with MK-801 monotherapy. In summary, our approach demonstrates the feasibility of using peptide-mediated targeting to achieve cell-specific ionotropic receptor modulation and highlights the therapeutic potential of unimolecular mixed GLP-1 receptor agonism and NMDA receptor antagonism for safe and effective obesity treatment.

Integrative Pharmacology in the Treatment of Substance Use Disorders

The detrimental physical, mental, and socioeconomic effects of substance use disorders (SUDs) have been apparent to the medical community for decades. However, it has become increasingly urgent in recent years to develop novel pharmacotherapies to treat SUDs. Currently, practitioners typically rely on monotherapy. Monotherapy has been shown to be superior to no treatment at all for most substance classes. However, many randomized controlled trials (RCTs) have revealed that monotherapy leads to poorer outcomes when compared with combination treatment in all specialties of medicine. The results of RCTs suggest that monotherapy frequently fails since multiple dysregulated pathways, enzymes, neurotransmitters, and receptors are involved in the pathophysiology of SUDs. As such, research is urgently needed to determine how various neurobiological mechanisms can be targeted by novel combination treatments to create increasingly specific yet exceedingly comprehensive approaches to SUD treatment. This article aims to review the neurobiology that integrates many pathophysiologic mechanisms and discuss integrative pharmacology developments that may ultimately improve clinical outcomes for patients with SUDs. Many neurobiological mechanisms are known to be involved in SUDs including dopaminergic, nicotinic, N-methyl-D-aspartate (NMDA), and kynurenic acid (KYNA) mechanisms. Emerging evidence indicates that KYNA, a tryptophan metabolite, modulates all these major pathophysiologic mechanisms. Therefore, achieving KYNA homeostasis by harmonizing integrative pathophysiology and pharmacology could prove to be a better therapeutic approach for SUDs. We propose KYNA-NMDA-α7nAChRcentric pathophysiology, the "conductor of the orchestra," as a novel approach to treat many SUDs concurrently. KYNA-NMDA-α7nAChR pathophysiology may be the "command center" of neuropsychiatry. To date, extant RCTs have shown equivocal findings across comparison conditions, possibly because investigators targeted single pathophysiologic mechanisms, hit wrong targets in underlying pathophysiologic mechanisms, and tested inadequate monotherapy treatment. We provide examples of potential combination treatments that simultaneously target multiple pathophysiologic mechanisms in addition to KYNA. Kynurenine pathway metabolism demonstrates the greatest potential as a target for neuropsychiatric diseases. The investigational medications with the most evidence include memantine, galantamine, and N-acetylcysteine. Future RCTs are warranted with novel combination treatments for SUDs. Multicenter RCTs with integrative pharmacology offer a promising, potentially fruitful avenue to develop novel therapeutics for the treatment of SUDs.

Role of Biosynthesis and Catabolism of Neurotransmitters in Drug Discovery for Anxiety and Depression

The purpose of this review is to correlate the probable causes of anxiety disorders with the imbalance of neurotransmitters in the brain and also highlight the drugs for these mental disorders that have been discovered based on the biosynthesis and catabolism of these brain chemicals. Peer-reviewed journal's articles, news and books published in English between 1997 and 2023 describing the role of neurotransmitters in anxiety disorders were searched in Google Scholar, Research Gate and PubMed databases. The contents were carefully analyzed by the authors and understood and compiled to build a concise perspective on the role of biosynthesis and catabolism of neurotransmitters in anxiety and depression. Anxiety disorders are reported to be common patterns of psychological symptoms that impact multiple areas of life. Anxiety and depression are prevalent worldwide and are significantly contributing towards the global health burden. Genetic determinants are believed to play an important role in these disorders. According to modern medicine, one of the most important aspects that is known to be crucial for these disorders is the imbalance of neurotransmitters in the brain. The biosynthesis and catabolism of neurotransmitters have been extensively targeted for innovative drug discovery approaches at various steps that have led to the discovery of many drugs for these psychological disorders. The biosynthetic and catabolic reaction cycles of neurotransmitters and the discovery of drugs based on these hypotheses are discussed. To the best of the authors' knowledge, this review compiles already known descriptive knowledge on "relation of neurotransmitter imbalance with anxiety disorders" in a precise way that will provide readers with an overview of the vast literature.

Review of Phytochemical Potency as a Natural Anti-Helicobacter pylori and Neuroprotective Agent

Phytochemicals are plant secondary metabolites that show health benefits for humans due to their bioactivity. There is a huge variety of phytochemicals that have already been identified, and these compounds can act as antimicrobial and neuroprotection agents. Due to their anti-microbial activity and neuroprotection, several phytochemicals might have the potency to be used as natural therapeutic agents, especially for Helicobacter pylori infection and neurodegenerative disease, which have become a global health concern nowadays. According to previous research, there are some connections between H. pylori infection and neurodegenerative diseases, especially Alzheimer's disease. Hence, this comprehensive review examines different kinds of phytochemicals from natural sources as potential therapeutic agents to reduce H. pylori infection and improve neurodegenerative disease. An additional large-scale study is needed to establish the connection between H. pylori infection and neurodegenerative disease and how phytochemicals could improve this condition.

Evaluation of bumetanide as a potential therapeutic agent for Alzheimer's disease

Therapeutics discovery and development for Alzheimer's disease (AD) has been an area of intense research to alleviate memory loss and the underlying pathogenic processes. Recent drug discovery approaches have utilized in silico computational strategies for drug candidate selection which has opened the door to repurposing drugs for AD. Computational analysis of gene expression signatures of patients stratified by the APOE4 risk allele of AD led to the discovery of the FDA-approved drug bumetanide as a top candidate agent that reverses APOE4 transcriptomic brain signatures and improves memory deficits in APOE4 animal models of AD. Bumetanide is a loop diuretic which inhibits the kidney Na+-K+-2Cl- cotransporter isoform, NKCC2, for the treatment of hypertension and edema in cardiovascular, liver, and renal disease. Electronic health record data revealed that patients exposed to bumetanide have lower incidences of AD by 35%-70%. In the brain, bumetanide has been proposed to antagonize the NKCC1 isoform which mediates cellular uptake of chloride ions. Blocking neuronal NKCC1 leads to a decrease in intracellular chloride and thus promotes GABAergic receptor mediated hyperpolarization, which may ameliorate disease conditions associated with GABAergic-mediated depolarization. NKCC1 is expressed in neurons and in all brain cells including glia (oligodendrocytes, microglia, and astrocytes) and the vasculature. In consideration of bumetanide as a repurposed drug for AD, this review evaluates its pharmaceutical properties with respect to its estimated brain levels across doses that can improve neurologic disease deficits of animal models to distinguish between NKCC1 and non-NKCC1 mechanisms. The available data indicate that bumetanide efficacy may occur at brain drug levels that are below those required for inhibition of the NKCC1 transporter which implicates non-NKCC1 brain mechansims for improvement of brain dysfunctions and memory deficits. Alternatively, peripheral bumetanide mechanisms may involve cells outside the central nervous system (e.g., in epithelia and the immune system). Clinical bumetanide doses for improved neurological deficits are reviewed. Regardless of mechanism, the efficacy of bumetanide to improve memory deficits in the APOE4 model of AD and its potential to reduce the incidence of AD provide support for clinical investigation of bumetanide as a repurposed AD therapeutic agent.

The Role of NMDA Receptor Subunits in the Effect of Memantine on the Brain of Healthy Animals

The non-competitive NMDA glutamate receptor antagonist memantine has neuroprotective properties and is the first non-cholinergic drug approved for the treatment of Alzheimer's disease. The purpose of this work was to test the hypothesis that injections of memantine to healthy animals can affect the subunit composition of NMDA receptors in the brain, which may explain the effects of its chronic administration. For this, the expression of subunits GluN1, GluN2A, GluN2B, and GluN2C was studied in the hippocampus and prefrontal cortex of rats after single or five subchronic injections of memantine. The results showed that the GluN2C subunit (GRIN2C) plays an important role in the effects of memantine; against the background of memantine treatment, the expression of this subunit markedly decreased in the prefrontal cortex, but not in the hippocampus, which significantly affected the excitation/inhibition balance in cortical structures.

Virtual brain simulations reveal network-specific parameters in neurodegenerative dementias

Introduction

Neural circuit alterations lay at the core of brain physiopathology, and yet are hard to unveil in living subjects. The Virtual Brain (TVB) modeling, by exploiting structural and functional magnetic resonance imaging (MRI), yields mesoscopic parameters of connectivity and synaptic transmission.

Methods

We used TVB to simulate brain networks, which are key for human brain function, in Alzheimer's disease (AD) and frontotemporal dementia (FTD) patients, whose connectivity and synaptic parameters remain largely unknown; we then compared them to healthy controls, to reveal novel in vivo pathological hallmarks.

Results

The pattern of simulated parameter differed between AD and FTD, shedding light on disease-specific alterations in brain networks. Individual subjects displayed subtle differences in network parameter patterns that significantly correlated with their individual neuropsychological, clinical, and pharmacological profiles.

Discussion

These TVB simulations, by informing about a new personalized set of networks parameters, open new perspectives for understanding dementias mechanisms and design personalized therapeutic approaches.

Memantine, an NMDA receptor antagonist, protected the brain against the long-term consequences of sepsis in mice

AIMS

Long-term neuroinflammation and brain dysfunction have frequently been reported in sepsis survivors. In this study, the protective effect of memantine (an NMDA receptor antagonist) on the long-term consequences of sepsis on the brain was investigated in mice.

MATERIALS AND METHODS

Eighty-five male C57 mice were included. Memantine was administrated through gavage at 5, 10, and 20 mg/kg three days before sepsis and continued for three days after sepsis induction. Sepsis was induced by intraperitoneal injection of 5 mg/kg LPS. A cohort of mice was sacrificed on the 4th day post sepsis to measure NF-κB, TNF-α, and IL-1β mRNA expression and oxidative stress markers in the brain. The second cohort was used for behavioral tests one month after sepsis induction and then sacrificed for oxidative stress markers and acetylcholinesterase (AChE) activity measurement.

KEY FINDINGS

MDA levels and mRNA expression of NF-κB, TNF-α, and IL-1β ameliorated by memantine at the early days of sepsis induction, and total thiol content and SOD activity were increased. Post-septic mice showed significant disruption of recognition memory in novel object recognition (NOR) and depressive and anxiety-like behaviors in tail suspension test, elevated plus maze (EPM), and open field tests one month after sepsis. Memantine at 10 and 20 mg/kg dose-dependently ameliorated behavioral abnormalities, reduced AChE activity and MDA levels, and enhanced SOD activity and thiol content one month after sepsis.

SIGNIFICANCE

These findings suggest that early treatment of septic mice with memantine could ameliorate brain inflammation and oxidative damage and prevent long-term behavioral consequences of sepsis.

Ca2+-Permeable TRPV1 Receptor Mediates Neuroprotective Effects in a Mouse Model of Alzheimer's Disease via BDNF/CREB Signaling Pathway

Transient receptor potential vanilloid 1 (TRPV1) protein is a Ca2+-permeable non-selective cation channel known for its pain modulation pathway. In a previous study, it was discovered that a triple-transgenic Alzheimer's disease (AD) mouse model (3xTg-AD+/+) has anti-AD effects. The expression of proteins in the brain-derived neurotrophic factor (BDNF)/cAMP response element binding protein (CREB) pathway in a 3xTg-AD/TRPV1 transgenic mice model was investigated to better understand the AD regulatory effect of TRPV1 deficiency. The results show that TRPV1 deficiency leads to CREB activation by increasing BDNF levels and promoting phosphorylation of tyrosine receptor kinase B (TrkB), extracellular signal-regulated kinase (ERK), protein kinase B (Akt), and CREB in the hippocampus. Additionally, TRPV1 deficiency-induced CREB activation increases the antiapoptotic factor B-cell lymphoma 2 (Bcl-2) gene, which consequently downregulates Bcl-2-associated X (Bax) expression and decreases cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP), which leads to the prevention of hippocampal apoptosis. In conclusion, TRPV1 deficiency exhibits neuroprotective effects by preventing apoptosis through the BDNF/CREB signal transduction pathway in the hippocampus of 3xTg-AD mice.

Effects of Phytochemicals from Fermented Food Sources in Alzheimer's Disease In Vivo Experimental Models: A Systematic Review

The socioeconomic burden of Alzheimer's Disease (AD) stems from its characteristic multifactorial etiology and, implicitly, the difficulties associated with its treatment. With the increase in life expectancy and health awareness, nutraceuticals and functional foods are filling in the gaps left by the limitation of classical medical treatment in chronic conditions associated with lifestyle factors, such as neurological disorders. Processes, such as fermentation that enhance food phytochemical content are garnering increased attention due to their functional and health-related properties. This systematic review aims to provide an overview of the evidence of phytochemicals from fermented food sources inducing therapeutic outcomes and cognitive benefits from in vivo experimental models of Alzheimer's Disease. The present systematic review was conducted in accordance with PRISMA guidelines. Searches were performed in the following databases: MEDLINE, Embase, Cochrane, Scopus, Google Scholar, and Science Citation Index Expanded (Web of Science) by two independent reviewers. Titles and abstracts yielded by the search were screened for eligibility against the inclusion criteria. The search strategy yielded 1899 titles, encompassing studies from 1948 to 2022. After the removal of duplicates, and screening of titles, abstracts, and full texts, thirty three studies obtained from the original search strategy and seven studies from references satisfied the inclusion criteria and were included in the present systematic review. Several studies have emphasized the potential of fermentation to yield small-molecule phytochemicals that are not present in raw products. When these phytochemicals are combined, their collective strength has demonstrated the ability to exceed the antioxidant, anti-inflammatory, and neuroprotective benefits of individual phytochemicals when given in their pure form. Among the various fermented foods that have been studied, soy isoflavones obtained through fermentation have shown the most substantial evidence of altering phytochemical content and improving outcomes in animal models of AD. While promising in initial results, other fermented foods and traditional medicines require more detailed research in order to establish their effectiveness and proper utilization. As is, many of the experimental designs lacked phytochemical analysis of the used fermented product or comparison with the non-fermented counterpart. This, coupled with proper reporting in animal studies, will significantly raise the quality of performed studies as well as the weight of obtained results.

Drug repositioning targeting glutaminase reveals drug candidates for the treatment of Alzheimer's disease patients

BACKGROUND

Despite numerous clinical trials and decades of endeavour, there is still no effective cure for Alzheimer's disease. Computational drug repositioning approaches may be employed for the development of new treatment strategies for Alzheimer's patients since an extensive amount of omics data has been generated during pre-clinical and clinical studies. However, targeting the most critical pathophysiological mechanisms and determining drugs with proper pharmacodynamics and good efficacy are equally crucial in drug repurposing and often imbalanced in Alzheimer's studies.

METHODS

Here, we investigated central co-expressed genes upregulated in Alzheimer's disease to determine a proper therapeutic target. We backed our reasoning by checking the target gene's estimated non-essentiality for survival in multiple human tissues. We screened transcriptome profiles of various human cell lines perturbed by drug induction (for 6798 compounds) and gene knockout using data available in the Connectivity Map database. Then, we applied a profile-based drug repositioning approach to discover drugs targeting the target gene based on the correlations between these transcriptome profiles. We evaluated the bioavailability, functional enrichment profiles and drug-protein interactions of these repurposed agents and evidenced their cellular viability and efficacy in glial cell culture by experimental assays and Western blotting. Finally, we evaluated their pharmacokinetics to anticipate to which degree their efficacy can be improved.

RESULTS

We identified glutaminase as a promising drug target. Glutaminase overexpression may fuel the glutamate excitotoxicity in neurons, leading to mitochondrial dysfunction and other neurodegeneration hallmark processes. The computational drug repurposing revealed eight drugs: mitoxantrone, bortezomib, parbendazole, crizotinib, withaferin-a, SA-25547 and two unstudied compounds. We demonstrated that the proposed drugs could effectively suppress glutaminase and reduce glutamate production in the diseased brain through multiple neurodegeneration-associated mechanisms, including cytoskeleton and proteostasis. We also estimated the human blood-brain barrier permeability of parbendazole and SA-25547 using the SwissADME tool.

CONCLUSIONS

This study method effectively identified an Alzheimer's disease marker and compounds targeting the marker and interconnected biological processes by use of multiple computational approaches. Our results highlight the importance of synaptic glutamate signalling in Alzheimer's disease progression. We suggest repurposable drugs (like parbendazole) with well-evidenced activities that we linked to glutamate synthesis hereby and novel molecules (SA-25547) with estimated mechanisms for the treatment of Alzheimer's patients.

Pharmacological Modulation of Excitotoxicity through the Combined Use of NMDA Receptor Inhibition and Group III mGlu Activation Reduces TMT-Induced Neurodegeneration in the Rat Hippocampus

We studied the neuroprotective properties of the non-competitive NMDA receptor antagonist memantine, in combination with a positive allosteric modulator of metabotropic glutamate receptors of Group III, VU 0422288. The treatment was started 48 h after the injection of neurotoxic agent trimethyltin (TMT) at 7.5 mg/kg. Three weeks after TMT injection, functional and morphological changes in a rat hippocampus were evaluated, including the expression level of genes characterizing glutamate transmission and neuroinflammation, animal behavior, and hippocampal cell morphology. Significant neuronal cell death occurred in the CA3 and CA4 regions, and to a lesser extent, in the CA1 and CA2 regions. The death of neurons in the CA1 field was significantly reduced in animals with a combined use of memantine and VU 0422288. In the hippocampus of these animals, the level of expression of genes characterizing glutamatergic synaptic transmission (Grin2b, Gria1, EAAT2) did not differ from the level in control animals, as well as the expression of genes characterizing neuroinflammation (IL1b, TGF beta 1, Aif1, and GFAP). However, the expression of genes characterizing neuroinflammation was markedly increased in the hippocampus of animals treated with memantine or VU 0422288 alone after TMT. The results of immunohistochemical studies confirmed a significant activation of microglia in the hippocampus three weeks after TMT injection. In contrast to the hilus, microglia in the CA1 region had an increase in rod-like cells. Moreover, in the CA1 field of the hippocampus of the animals of the MEM + VU group, the amount of such microglia was close to the control. Thus, the short-term modulation of glutamatergic synaptic transmission by memantine and subsequent activation of Group III mGluR significantly affected the dynamics of neurodegeneration in the hippocampus.

Herbal/Natural Compounds Resist Hallmarks of Brain Aging: From Molecular Mechanisms to Therapeutic Strategies

Aging is a complex process of impaired physiological integrity and function, and is associated with increased risk of cardiovascular disease, diabetes, neurodegeneration, and cancer. The cellular environment of the aging brain exhibits perturbed bioenergetics, impaired adaptive neuroplasticity and flexibility, abnormal neuronal network activity, dysregulated neuronal Ca²⁺ homeostasis, accumulation of oxidatively modified molecules and organelles, and clear signs of inflammation. These changes make the aging brain susceptible to age-related diseases, such as Alzheimer's and Parkinson's diseases. In recent years, unprecedented advances have been made in the study of aging, especially the effects of herbal/natural compounds on evolutionarily conserved genetic pathways and biological processes. Here, we provide a comprehensive review of the aging process and age-related diseases, and we discuss the molecular mechanisms underlying the therapeutic properties of herbal/natural compounds against the hallmarks of brain aging.

The Cannabinoids, CBDA and THCA, Rescue Memory Deficits and Reduce Amyloid-Beta and Tau Pathology in an Alzheimer’s Disease-like Mouse Model

Most studies related to hemp are focused on Cannabidiol (CBD) and Tetrahydrocannabinol (THC); however, up to 120 types of phytocannabinoids are present in hemp. Hemp leaves contain large amounts of Cannabidiolic acid (CBDA) and Tetrahydrocannabinolic acid (THCA), which are acidic variants of CBD and THC and account for the largest proportion of CBDA. In recent studies, CBDA exhibited anti-hyperalgesia and anti-inflammatory effects. THCA also showed anti-inflammatory and neuroprotective effects that may be beneficial for treating neurodegenerative diseases. CBDA and THCA can penetrate the blood–brain barrier (BBB) and affect the central nervous system. The purpose of this study was to determine whether CBDA and THCA ameliorate Alzheimer’s disease (AD)-like features in vitro and in vivo. The effect of CBDA and THCA was evaluated in the Aβ1–42-treated mouse model. We observed that Aβ1–42-treated mice had more hippocampal Aβ and p-tau levels, pathological markers of AD, and loss of cognitive function compared with PBS-treated mice. However, CBDA- and THCA-treated mice showed decreased hippocampal Aβ and p-tau and superior cognitive function compared with Aβ1–42-treated mice. In addition, CBDA and THCA lowered Aβ and p-tau levels, alleviated calcium dyshomeostasis, and exhibited neuroprotective effects in primary neurons. Our results suggest that CBDA and THCA have anti-AD effects and mitigate memory loss and resilience to increased hippocampal Ca2+, Aβ, and p-tau levels. Together, CBDA and THCA may be useful therapeutic agents for treating AD.

Neurotransmitter release progressively desynchronizes in induced human neurons during synapse maturation and aging

Rapid release of neurotransmitters in synchrony with action potentials is considered a key hardwired property of synapses. Here, in glutamatergic synapses formed between induced human neurons, we show that action potential-dependent neurotransmitter release becomes progressively desynchronized as synapses mature and age. In this solely excitatory network, the emergence of NMDAR-mediated transmission elicits endoplasmic reticulum (ER) stress leading to downregulation of key presynaptic molecules, synaptotagmin-1 and cysteine string protein α, that synchronize neurotransmitter release. The emergence of asynchronous release with neuronal maturity and subsequent aging is maintained by the high-affinity Ca2+ sensor synaptotagmin-7 and suppressed by the introduction of GABAergic transmission into the network, inhibition of NMDARs, and ER stress. These results suggest that long-term disruption of excitation-inhibition balance affects the synchrony of excitatory neurotransmission in human synapses.

Honey and Alzheimer's Disease-Current Understanding and Future Prospects

Alzheimer's disease (AD), a leading cause of dementia, has been a global concern. AD is associated with the involvement of the central nervous system that causes the characteristic impaired memory, cognitive deficits, and behavioral abnormalities. These abnormalities caused by AD is known to be attributed by extracellular aggregates of amyloid beta plaques and intracellular neurofibrillary tangles. Additionally, genetic factors such as abnormality in the expression of APOE, APP, BACE1, PSEN-1, and PSEN-2 play a role in the disease. As the current treatment aims to treat the symptoms and to slow the disease progression, there has been a continuous search for new nutraceutical agent or medicine to help prevent and cure AD pathology. In this quest, honey has emerged as a powerful nootropic agent. Numerous studies have demonstrated that the high flavonoids and phenolic acids content in honey exerts its antioxidant, anti-inflammatory, and neuroprotective properties. This review summarizes the effect of main flavonoid compounds found in honey on the physiological functioning of the central nervous system, and the effect of honey intake on memory and cognition in various animal model. This review provides a new insight on the potential of honey to prevent AD pathology, as well as to ameliorate the damage in the developed AD.

Memantine as a neuroprotective agent in ischemic stroke: Preclinical and clinical analysis

The primary mechanism for neuron death after an ischemic stroke is excitotoxic injury. Excessive depolarization leads to NMDA-mediated calcium entry to the neuron and, subsequently, cellular death. Therefore, the inhibition of the NMDA channel has been proposed as a neuroprotective measure in ischemic stroke. The high morbimortality associated with stroke warrants new therapies that can improve the functional prognosis of patients. Memantine is a non-competitive NMDA receptor antagonist which has gained attention as a potential drug for ischemic stroke. Here we analyze the available preclinical and clinical evidence concerning the use of memantine following an ischemic stroke. Preclinical evidence shows inhibition of the excitotoxic cascade, as well as improved outcomes in terms of motor and sensory function with the use of memantine. The available clinical trials of high-dose memantine in patients poststroke have found that it can improve patients' NIHSS and Barthel index and help patients with poststroke aphasia and intracranial hemorrhage. These results suggest that memantine has a clinically relevant neuroprotective effect; however, small sample sizes and other study shortcomings limit the impact of these findings. Even so, current studies show promising results that should serve as a basis to promote future research to conclusively determine if memantine does improve the outcomes of patients' post-ischemic stroke. We anticipate that future trials will fill current gaps in knowledge, and these latter results will broaden the therapeutic arsenal for clinicians looking to improve the prognosis of patients poststroke.

Alzheimer's and Parkinson's disease therapies in the clinic

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most prevalent neurodegenerative diseases, affecting millions and costing billions each year in the United States alone. Despite tremendous progress in developing therapeutics that manage the symptoms of these two diseases, the scientific community has yet to develop a treatment that effectively slows down, inhibits, or cures neurodegeneration. To gain a better understanding of the current therapeutic frontier for the treatment of AD and PD, we provide a review on past and present therapeutic strategies for these two major neurodegenerative disorders in the clinical trial process. We briefly recap currently US Food and Drug Administration-approved therapies, and then explore trends in clinical trials across the variables of therapy mechanism of disease intervention, administration route, use of delivery vehicle, and outcome measures, across the clinical phases over time for "Drug" and "Biologic" therapeutics. We then present the success rate of past clinical trials and analyze the intersections in therapeutic approaches for AD and PD, revealing the shift in clinical trials away from therapies targeting neurotransmitter systems that provide symptomatic relief, and towards anti-aggregation, anti-inflammatory, anti-oxidant, and regeneration strategies that aim to inhibit the root causes of disease progression. We also highlight the evolving distribution of the types of "Biologic" therapies investigated, and the slowly increasing yet still severe under-utilization of delivery vehicles for AD and PD therapeutics. We then briefly discuss novel preclinical strategies for treating AD and PD. Overall, this review aims to provide a succinct overview of the clinical landscape of AD and PD therapies to better understand the field's therapeutic strategy in the past and the field's evolution in approach to the present, to better inform how to effectively treat AD and PD in the future.

Advanced molecular therapies for neurological diseases: focus on stroke, alzheimer's disease, and parkinson's disease

Neurological diseases (NDs) are one of the leading causes of disability and the second leading cause of death globally. Among these stroke, Alzheimer's disease (AD), and Parkinson's disease (PD) are the most common NDs. A rise in the absolute number of individuals affected with these diseases indicates that the current treatment strategies in management and prevention of these debilitating diseases are not effective sufficiently. Therefore, novel treatment strategies are being explored to cure these diseases by addressing the causative mechanisms at the molecular level. Advanced therapies like gene therapy (gene editing and gene silencing) and stem cell therapies aim to cure diseases by gene editing, gene silencing and tissue regeneration, respectively. Gene editing results in the deletion of the aberrant gene or insertion of the corrected gene which can be executed using the CRISPR/Cas gene editing tool a promising treatment strategy being explored for many other prevalent diseases. Gene silencing using siRNA silences the gene by inhibiting protein translation, thereby silencing its expression. Stem cell therapy aims to regenerate damaged cells or tissues because of their ability to divide into any type of cell in the human body. Among these approaches, gene editing and gene silencing have currently been applied in vitro and to animal models, while stem cell therapy has reached the clinical trial stage for the treatment of NDs. The current status of these strategies suggests a promising outcome in their clinical translation.

Current Pharmacotherapy and Multi-Target Approaches for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by decreased synaptic transmission and cerebral atrophy with appearance of amyloid plaques and neurofibrillary tangles. Cognitive, functional, and behavioral alterations are commonly associated with the disease. Different pathophysiological pathways of AD have been proposed, some of which interact and influence one another. Current treatment for AD mainly involves the use of therapeutic agents to alleviate the symptoms in AD patients. The conventional single-target treatment approaches do not often cause the desired effect in the disease due to its multifactorial origin. Thus, multi-target strategies have since been undertaken, which aim to simultaneously target multiple targets involved in the development of AD. In this review, we provide an overview of the pathogenesis of AD and the current drug therapies for the disease. Additionally, rationales of the multi-target approaches and examples of multi-target drugs with pharmacological actions against AD are also discussed.

Interventions for preventing and ameliorating cognitive deficits in adults treated with cranial irradiation

BACKGROUND

Cognitive deficits are common in people who have received cranial irradiation and have a serious impact on daily functioning and quality of life. The benefit of pharmacological and non-pharmacological treatment of cognitive deficits in this population is unclear. This is an updated version of the original Cochrane Review published in Issue 12, 2014.

OBJECTIVES

To assess the effectiveness of interventions for preventing or ameliorating cognitive deficits in adults treated with cranial irradiation.

SEARCH METHODS

For this review update we searched the Cochrane Register of Controlled Trials (CENTRAL), MEDLINE via Ovid, Embase via Ovid, and PsycInfo via Ovid to 12 September 2022.

SELECTION CRITERIA

We included randomised controlled (RCTs) trials that evaluated pharmacological or non-pharmacological interventions in cranial irradiated adults, with objective cognitive functioning as a primary or secondary outcome measure.

DATA COLLECTION AND ANALYSIS

Two review authors (MK, JD) independently extracted data from selected studies and carried out a risk of bias assessment. Cognitive function, fatigue and mood outcomes were reported. No data were pooled.

MAIN RESULTS

Eight studies met the inclusion criteria and were included in this updated review. Six were from the original version of the review, and two more were added when the search was updated. Nineteen further studies were assessed as part of this update but did not fulfil the inclusion criteria. Of the eight included studies, four studies investigated "prevention" of cognitive problems (during radiotherapy and follow-up) and four studies investigated "amelioration" (interventions to treat cognitive impairment as a late complication of radiotherapy). There were five pharmacological studies (two studies on prevention and three in amelioration) and three non-pharmacological studies (two on prevention and one in amelioration). Due to differences between studies in the interventions being evaluated, a meta-analysis was not possible.  Studies in early radiotherapy treatment phase (five studies) Pharmacological studies in the "early radiotherapy treatment phase" were designed to prevent or ameliorate cognitive deficits and included drugs used in dementia (memantine) and fatigue (d-threo-methylphenidate hydrochloride). Non-pharmacological studies in the "early radiotherapy treatment phase" included a ketogenic diet and a two-week cognitive rehabilitation and problem-solving programme.  In the memantine study, the primary cognitive outcome of memory at six months did not reach significance, but there was significant improvement in overall cognitive function compared to placebo, with similar adverse events across groups. The d-threo-methylphenidate hydrochloride study found no statistically significant difference between arms, with few adverse events. The study of a calorie-restricted ketogenic diet found no effect, although a lower than expected calorie intake in the control group complicates interpretation of the results.  The study investigating the utility of a rehabilitation program did not carry out a statistical comparison of cognitive performance between groups.  Studies in delayed radiation or late effect phase (four studies) The "amelioration" pharmacological studies to treat cognitive complications of radiotherapy included drugs used in dementia (donepezil) or psychostimulants (methylphenidate and modafinil). Non-pharmacological measures included cognitive rehabilitation and problem solving (Goal Management Training). These studies included patients with cognitive problems at entry who had "stable" brain cancer.  The donepezil study did not find an improvement in the primary cognitive outcome of overall cognitive performance, but did find improvement in an individual test of memory, compared to placebo; adverse events were not reported. A study comparing methylphenidate with modafinil found improvements in cognitive function in both the methylphenidate and modafinil arms; few adverse events were reported. Another  study comparing two different doses of modafinil combined treatment arms and found improvements across all cognitive tests, however, a number of adverse events were reported. Both studies were limited by a small sample size. The Goal Management Training study suggested a benefit of the intervention, a behavioural intervention that combined mindfulness and strategy training, on executive function and processing speed.  There were a number of limitations across studies and few were without high risks of bias.

AUTHORS' CONCLUSIONS

In this update, limited additional evidence was found for the treatment or amelioration of cognitive deficits in adults treated with cranial irradiation. As concluded in the original review, there is supportive evidence that memantine may help prevent cognitive deficits for adults with brain metastases receiving cranial irradiation. There is supportive evidence that donepezil, methylphenidate and modafinil may have a role in treating cognitive deficits in adults with brain tumours who have been treated with cranial irradiation; patient withdrawal affected the statistical power of these studies. Further research that tries to minimise the withdrawal of consent, and subsequently reduce the requirement for imputation procedures, may offer a higher certainty of evidence. There is evidence from only a single small study to support non-pharmacological interventions in the amelioration of cognitive deficits. Further research is required.

Memantine has a nicotinic neuroprotective pathway in acute hippocampal slices after an NMDA insult

Memantine is a non-competitive antagonist with a moderate affinity to the N-methyl-d-Aspartate (NMDA) receptor. The present study assessed memantine's neuroprotective activity using electrophysiology of ex-vivo hippocampal slices. Interestingly, a nicotinic component was necessary for memantine's neuroprotection (NP). Memantine demonstrated a bell-shaped dose-response curve of NP against NMDA. Memantine was neuroprotective at concentrations below 3 μM, but the NP declined at higher concentrations (>3 μM) when memantine inhibits the NMDA receptor. Additional evidence that memantine NP is mediated by an alternate mechanism independent of the inhibition of the NMDA receptor is supported by its ability to protect neurons when applied before or after the NMDA insult and in the presence of D(-)-2-Amino-5-phosphonopentanoic acid (APV), the standard NMDA receptor inhibitor. We found several similarities between the memantine NP mechanism and the neuroprotective nicotinic drug, the 4R cembranoid. Memantine's NP requires the release of acetylcholine, the activation of α4β2, and is independent of MEK/MAPK signaling. Both 4R and memantine require the activation of PI3K/AKT for NP against NMDA-mediated excitotoxicity, although at different concentrations. In conclusion, our studies show memantine is neuroprotective through a nicotinic pathway, similar to the nicotinic drug 4R. This information leads to a better understanding of memantine's mechanisms of action and explains its dose-dependent effectiveness in Alzheimer's and other neurological disorders.

Chemiluminescent Cucurbit[n]uril-Based Chemosensor for the Detection of Drugs in Biofluids

Chemiluminescence-based detection methods offer a superior signal-to-noise ratio and are commonly adopted for biosensors. This work presents the design and implementation of a supramolecular assay based on a chemiluminescent chemosensor. Specifically, an indicator displacement assay (IDA) with the supramolecular host-guest complex of chemiluminescent phenoxy 1,2-dioxetane and cucurbit[8]uril enables the low-micromolar detection of drugs in human urine and human serum samples. Cucurbit[8]uril thereby acts as a non-surfactant chemiluminescence enhancer and a synthetic receptor. Additionally, we show that adding an equimolar amount of cucurbit[8]uril to a commercially available dioxetane used in standard enzymatic chemiluminescence immunoassays enhances the chemiluminescence by more than 15 times. Finally, we demonstrate that a chemiluminescence resonance energy transfer between a unimolecular macrocyclic cucurbit[7]uril-dye conjugate and a phenoxy 1,2-dioxetane can be utilized to detect the herbicide paraquat at a micromolar concentration in aqueous media.

Kinetic and structural studies on the inhibition of acetylcholinesterase and butyrylcholinesterase by a series of multitarget-directed galantamine-peptide derivatives

Complex neurological disorders, including Alzheimer's disease, are one of the major therapeutic areas to which multitarget drug discovery strategies have been applied in the last twenty years. Due to the complex multifactorial etiopathogenesis of Alzheimer's disease, it has been proposed that to be successful the pharmaceutical agents should act on multiple targets in order to restore the complex disease network and to provide disease modifying effects. Here we report on the synthesis and the anticholinergic activity profiles of seven multitarget anti-Alzheimer compounds designed by combining galantamine, a well-known acetylcholinesterase inhibitor, with different peptide fragments endowed with inhibitory activity against BACE-1. A complementary approach based on molecular docking simulations of the galantamine-peptide derivatives in the active sites of acetylcholinesterase and of the related butyrylcholinesterase, as well as on inhibition kinetics, by global fitting of the reaction progress curves, allowed to gain insights into the enzyme-inhibitor mechanism of interaction. The resulting structure-activity relationships pave the way towards the design of more effective pharmacodynamic/pharmacokinetic multitarget inhibitors.

Pharmacotherapy of Alzheimer's disease: an overview of systematic reviews

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disease and the most common cause of dementia. In this umbrella systematic review (SR), we summarized the efficacy of different pharmacological interventions in improving cognitive function in patients with AD.

METHODS

A systematic search was performed through the PubMed, Scopus, Embase, and Cochrane databases for SRs of studies assessing the efficacy of pharmacological interventions versus placebo in improving cognitive function in AD or mild cognitive impairment due to AD. The risk of bias (RoB) was assessed using the Risk of Bias in SRs (ROBIS) tool.

RESULTS

Out of 1748 articles found through the database survey, 33 SR articles were included. These studies assessed effects of immunotherapy, cholinesterase inhibitors (ChEIs), memantine, statins, lithium, nonsteroidal anti-inflammatory drugs (NSAIDs), antidiabetic agents, Cerebrolysin, RAS-targeting antihypertensive drugs (ARBs and ACEIs), psychostimulants, glycogen synthase kinase 3 (GSK-3) inhibitors, melatonin, and herbal medications on cognitive function in AD patients. There was no notable overall RoB in 18 studies (54.5%), the RoB in 14 studies (42.4%) was high, and in one study (3.0%) it was unclear.

CONCLUSIONS

The use of ChEIs, including rivastigmine, galantamine, and donepezil, as well as memantine has demonstrated a positive impact on improving cognitive outcomes of AD patients, but no considerable effects were found for immunotherapies. Melatonin, statins, antihypertensive drugs, antidiabetic agents, Cerebrolysin, psychostimulants, and some herbal drugs such as Danggui-Shaoyao-San and Ginkgo biloba seem to be effective in improving cognitive function of AD patients, but the evidence in this regard is limited.

Promises and Pitfalls of NMDA Receptor Antagonists in Treating Violent Aggression

Treatment options for chronically aggressive individuals remain limited despite recent medical advances. Traditional pharmacological agents used to treat aggression, such as atypical antipsychotics, have limited efficacy and are often replete with dangerous side effects. The non-competitive NMDAR antagonists ketamine and memantine are promising alternatives, but their effects appear to be highly dependent on dosage, context, and personal experience. Importantly, these drugs can increase aggression when combined with substances of abuse or during periods of heightened stress. This is likely due to mechanistic differences operating at specific synapses under different contexts. Previous findings from our lab and others have shown that early life stress, substance abuse, and attack experience promote aggression through NMDAR-dependent synaptic plasticity within aggression-related brain circuits. Ketamine and memantine affect these types of aggression in opposite ways. This has led us to propose that ketamine and memantine oppositely affect aggression brought on by early life stress, substance abuse, or attack experience through opposite effects on NMDAR-dependent synaptic plasticity. This would account for the persistent effects of these drugs on aggression and suggest they could be leveraged as a more long-lasting treatment option. However, a more thorough examination of the effects of ketamine and memantine on cellular and synaptic function will be necessary for responsible administration. Additionally, because the effects of ketamine and memantine are highly dependent on prior drug use, traumatic stress, or a history of aggressive behavior, we propose a more thorough medical evaluation and psychiatric assessment will be necessary to avoid possible adverse interactions with these drugs.

Memantine Disrupts Motor Coordination through Anxiety-like Behavior in CD1 Mice

Memantine is an FDA approved drug for the treatment of Alzheimer’s disease. It reduces neurodegeneration in the hippocampus and cerebral cortex through the inhibition of extrasynaptic NMDA receptors in patients and mouse models. Potentially, it could prevent neurodegeneration in other brain areas and caused by other diseases. We previously used memantine to prevent functional damage and to retain morphology of cerebellar neurons and Bergmann glia in an optogenetic mouse model of spinocerebellar ataxia type-1 (SCA1). However, before suggesting wider use of memantine in clinics, its side effects must be carefully evaluated. Blockers of NMDA receptors are controversial in terms of their effects on anxiety. Here, we investigated the effects of chronic application of memantine over 9 weeks to CD1 mice and examined rotarod performance and anxiety-related behaviors. Memantine-treated mice exhibited an inability to adapt to anxiety-causing conditions which strongly affected their rotarod performance. A tail suspension test revealed increased signs of behavioral despair. These data provide further insights into the potential deleterious effects of memantine which may result from the lack of adaptation to novel, stressful conditions. This effect of memantine may affect the results of tests used to assess motor performance and should be considered during clinical trials of memantine in patients.

Lipid-Based Nanocarriers for Neurological Disorders: A Review of the State-of-the-Art and Therapeutic Success to Date

Neurodegenerative disorders including Alzheimer's, Parkinson's, and dementia are chronic and advanced diseases that are associated with loss of neurons and other related pathologies. Furthermore, these disorders involve structural and functional defections of the blood-brain barrier (BBB). Consequently, advances in medicines and therapeutics have led to a better appreciation of various pathways associated with the development of neurodegenerative disorders, thus focusing on drug discovery and research for targeted drug therapy to the central nervous system (CNS). Although the BBB functions as a shield to prevent toxins in the blood from reaching the brain, drug delivery to the CNS is hindered by its presence. Owing to this, various formulation approaches, including the use of lipid-based nanocarriers, have been proposed to address shortcomings related to BBB permeation in CNS-targeted therapy, thus showing the potential of these carriers for translation into clinical use. Nevertheless, to date, none of these nanocarriers has been granted market authorization following the successful completion of all stages of clinical trials. While the aforementioned benefits of using lipid-based carriers underscores the need to fast-track their translational development into clinical practice, technological advances need to be initiated to achieve appropriate capacity for scale-up and the production of affordable dosage forms.

Insoluble Salt of Memantine with a Unique Fluorescence Phenomenon

Alzheimer's disease is a chronic disease, and the long-term treatment of chronic diseases has always been a concern. Memantine (Mem) is approved by the US Food and Drug Administration for the treatment of moderate to severe Alzheimer's disease. In this study, reactions of memantine (Mem) with pamoic acid (Pam) were carried out to form insoluble salts (Mem-Pam). Four polymorphic forms (Forms I-IV) of Mem-Pam were successfully obtained through polymorphic screening, which were systematically characterized by X-ray powder diffraction (PXRD), thermal analysis (TGA and DSC), single-crystal X-ray diffraction (SXRD), and solid-state fluorescence. Compared with the hydrochloride form, the dissolution and release rates of these four forms are lower. The presence of pamoic acid reduces the release rate of memantine and makes it possible to achieve a sustained release of the drug. Interestingly, because of the presence of memantine, each polymorphic solid crystal of Mem-Pam has unique fluorescence emission. Therefore, memantine and pamoic acid have a synergistic effect on the fluorescence performance and can be expected to be used for real-time monitoring in continuous and controlled release drug delivery systems. In addition, the polymorphic solid crystals also exhibit reversible mechanochromic luminescence under the fumigation of acetonitrile vapor, which has a guiding role in the fluorescence design and synthesis of Pam substances and is expected to be used for information security, visual inspection of organic substances, etc.

Pharmacotherapeutic combinations for the treatment of Alzheimer's disease

INTRODUCTION

Alzheimer's disease (AD) is the most common form of dementia, and four medications are currently available as symptomatic therapies: three cholinesterase inhibitors (ChEI) and memantine. In June 2021, aducanumab was approved in the United States under an accelerated approval pathway as the first novel putative disease-modifying therapy (p-DMT) targeting the β-amyloid (Aβ) cascade in the brain. The combination of several monotherapies to address the multifactorial pathogenesis of neurodegenerative diseases is an anticipated next step.

AREAS COVERED

The cholinergic hypothesis and the amyloid cascade hypothesis have been proposed as explanations for the pathogenesis of AD. Given the limited effectiveness of monotherapies based on these hypotheses, approaches using combination therapy are attempting to address the complexity of AD pathogenesis, including putative causative proteins-related neurodegeneration, neurotransmitters, and neuroinflammation, in a comprehensive manner.

EXPERT OPINION

The efficacy of an initial or add-on combination approach to counteracting neurodegenerative processes and functional deterioration has been investigated. The combination of symptomatic therapies with approved anti-dementia medicines (one ChEI and memantine) has been found to be functionally effective for a moderately severe disease stage. Furthermore, combination strategies involving p-DMTs, symptomatic therapies, and neuro-regeneration may be useful in the future.

Personalised treatment for cognitive impairment in dementia: development and validation of an artificial intelligence model

BACKGROUND

Donepezil, galantamine, rivastigmine and memantine are potentially effective interventions for cognitive impairment in dementia, but the use of these drugs has not been personalised to individual patients yet. We examined whether artificial intelligence-based recommendations can identify the best treatment using routinely collected patient-level information.

METHODS

Six thousand eight hundred four patients aged 59-102 years with a diagnosis of dementia from two National Health Service (NHS) Foundation Trusts in the UK were used for model training/internal validation and external validation, respectively. A personalised prescription model based on the Recurrent Neural Network machine learning architecture was developed to predict the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores post-drug initiation. The drug that resulted in the smallest decline in cognitive scores between prescription and the next visit was selected as the treatment of choice. Change of cognitive scores up to 2 years after treatment initiation was compared for model evaluation.

RESULTS

Overall, 1343 patients with MMSE scores were identified for internal validation and 285 [21.22%] took the drug recommended. After 2 years, the reduction of mean [standard deviation] MMSE score in this group was significantly smaller than the remaining 1058 [78.78%] patients (0.60 [0.26] vs 2.80 [0.28]; P = 0.02). In the external validation cohort (N = 1772), 222 [12.53%] patients took the drug recommended and reported a smaller MMSE reduction compared to the 1550 [87.47%] patients who did not (1.01 [0.49] vs 4.23 [0.60]; P = 0.01). A similar performance gap was seen when testing the model on patients prescribed with AChEIs only.

CONCLUSIONS

It was possible to identify the most effective drug for the real-world treatment of cognitive impairment in dementia at an individual patient level. Routine care patients whose prescribed medications were the best fit according to the model had better cognitive performance after 2 years.