Discovery of novel multifunctional ligands targeting GABA transporters, butyrylcholinesterase, β-secretase, and amyloid β aggregation as potential treatment of Alzheimer's disease

A novel carbamate-based hybrid derivative with anti-neuroinflammatory properties as a selective butyrylcholinesterase inhibitor for Alzheimer's disease therapy

Cholinesterase inhibitors (ChEIs) are widely utilized for the symptomatic management of Alzheimer's disease (AD) by enhancing acetylcholine levels to improve cognitive function. Concurrently, neuroinflammation has emerged as a critical factor in AD progression, necessitating therapies that address this pathology. In this study, we designed and synthesized a novel bifunctional cholinesterase inhibitor, (E)-4-(2-(3-(benzyloxy)-4-oxo-4H-pyran-2-yl) vinyl)-1,2-phenylene bis(ethyl(methyl)carbamate) (D40), which combines potent cholinesterase inhibition with robust anti-neuroinflammatory activity. D40 demonstrated potent inhibition of human butyrylcholinesterase (hBuChE), with an IC₅₀ value of 0.59 ± 0.03 μM, significantly outperforming Rivastigmine (IC₅₀ = 3.70 ± 0.96 μM). Molecular docking and molecular dynamics simulations confirmed a stable and selective binding of D40 to the BuChE active site, underpinning its inhibitory profile. Additionally, D40 exhibited strong anti-inflammatory effects, with an IC₅₀ value of 4.55 ± 0.78 μM for suppressing nitric oxide production and demonstrated excellent blood-brain barrier permeability. In vivo studies in aged 5 × FAD mice revealed that D40 significantly reduced neuroinflammation by suppressing pro-inflammatory cytokines and glial activation. Furthermore, D40 mitigated Aβ deposition, promoted neuronal survival, and improved cognitive deficits, while demonstrating a favorable safety profile in acute toxicity evaluations. These findings highlight D40 as a dual-function ChEI capable of providing symptomatic relief and modulating neuroinflammatory pathways associated with AD. With its enhanced cholinesterase inhibition and anti-inflammatory properties, D40 emerges as a promising candidate for the treatment of advanced stages of AD. Acetylcholine deficiency and neuroinflammation as drivers of Alzheimer's disease dually intervened by Compound D40.

Discovery of new dual butyrylcholinesterase (BuChE) inhibitors and 5-HT7 receptor antagonists as compounds used to treat Alzheimer's disease symptoms

Alzheimer's disease is a neurodegenerative condition with no effective cure, and current therapies, like donepezil, only alleviate symptoms. Research has explored cholinesterase inhibitors and strategies targeting tau protein, often combining inhibitors with 5-HT receptor antagonists, particularly 5-HT6. However, dual-action BuChE inhibitors and 5-HT7 antagonists have not been studied until now. This study evaluated such compounds in an animal model, focusing on two candidates: compound 18 (BuChE IC50 = 4.75 μM; 5-HT7Ki = 7 nM) and compound 50 (BuChE IC50 = 2.53 μM; 5-HT7Ki = 1 nM). Compound 50 showed robust cognitive improvements, enhancing memory consolidation and acquisition, particularly in reversing scopolamine-induced deficits. In contrast, compound 18 exhibited limited or dose-dependent efficacy, potentially limiting its applicability. These findings highlight the strong potential of compound 50 for cognitive enhancement therapies and suggest it warrants further investigation.

Multi-target-directed therapeutic strategies for Alzheimer's disease: controlling amyloid-β aggregation, metal ion homeostasis, and enzyme inhibition

Alzheimer's disease (AD) is the most prevalent neurodegenerative dementia, marked by progressive cognitive decline and memory impairment. Despite advances in therapeutic research, single-target-directed treatments often fall short in addressing the complex, multifactorial nature of AD. This arises from various pathological features, including amyloid-β (Aβ) aggregate deposition, metal ion dysregulation, oxidative stress, impaired neurotransmission, neuroinflammation, mitochondrial dysfunction, and neuronal cell death. This review illustrates their interrelationships, with a particular emphasis on the interplay among Aβ, metal ions, and AD-related enzymes, such as β-site amyloid precursor protein cleaving enzyme 1 (BACE1), matrix metalloproteinase 9 (MMP9), lysyl oxidase-like 2 (LOXL2), acetylcholinesterase (AChE), and monoamine oxidase B (MAOB). We further underscore the potential of therapeutic strategies that simultaneously inhibit Aβ aggregation and address other pathogenic mechanisms. These approaches offer a more comprehensive and effective method for combating AD, overcoming the limitations of conventional therapies.

From Genes to Metabolites: HSP90B1's Role in Alzheimer's Disease and Potential for Therapeutic Intervention

Alzheimer's disease (AD) is a prototypical neurodegenerative disorder, predominantly affecting individuals in the presenile and elderly populations, with an etiology that remains elusive. This investigation aimed to elucidate the alterations in anoikis-related genes (ARGs) in the AD brain, thereby expanding the repertoire of biomarkers for the disease. Using publically available gene expression data for the hippocampus from both healthy and AD subjects, differentially expressed genes (DEGs) were identified. Subsequent intersection with a comprehensive list of 575 ARGs yielded a subset for enrichment analysis. Machine learning algorithms were employed to identify potential biomarker, which was validated in an AD animal model. Additionally, gene set enrichment analysis was conducted on the biomarker and its interacting genes and microRNAs were predicted through online databases. To assess its biological functions, the expression of the marker was suppressed in an in vitro model to examine cell viability and inflammation-related indicators. Furthermore, following treatment with the inhibitor, the dysregulated metabolites in the hippocampus of the model mice were evaluated. Forty-seven ARGs were ultimately identified, with HSP90B1 emerging as a central marker. HSP90B1 was found to be significantly up-regulated in AD hippocampal samples and its inhibition conferred increased cell viability and reduced levels of inflammatory factors in amyloid β-protein (Aβ)-treated cells. A total of 24 differentially expressed metabolites were confidently identified between model mice and those with low HSP90B1 expression, with bioinformatics analysis shedding light on the molecular underpinnings of HSP90B1's involvement in AD. Collectively, these findings may inform novel insights into the pathogenesis, mechanisms, or therapeutic strategies for AD.

Novel anti-neuroinflammatory pyranone-carbamate derivatives as selective butyrylcholinesterase inhibitors for treating Alzheimer's disease

Butyrylcholinesterase (BuChE) and neuroinflammation have recently emerged as promising therapeutic directions for Alzheimer's disease (AD). Herein, we synthesised 19 novel pyranone-carbamate derivatives and evaluated their activities against cholinesterases and neuroinflammation. The optimal compound 7p exhibited balanced BuChE inhibitory activity (eqBuChE IC50 = 4.68 nM; huBuChE IC50 = 9.12 nM) and anti-neuroinflammatory activity (NO inhibition = 28.82% at 10 μM, comparable to hydrocortisone). Enzyme kinetic and docking studies confirmed compound 7p was a mix-type BuChE inhibitor. Additionally, compound 7p displayed favourable drug-likeness properties in silico prediction, and exhibited high BBB permeability in the PAMPA-BBB assay. Compound 7p had good safety in vivo as verified by an acute toxicity assay (LD50 > 1000 mg/kg). Most importantly, compound 7p effectively mitigated cognitive and memory impairments in the scopolamine-induced mouse model, showing comparable effects to Rivastigmine. Therefore, we envisioned that compound 7p could serve as a promising lead compound for treating AD.

Ways of modulating GABA transporters to treat neurological disease

INTRODUCTION

The main inhibitory neurotransmitter in the central nervous system (CNS), γ-aminobutyric acid (GABA), is involved in a multitude of neurological and psychiatric disorders characterized by an imbalance in excitatory and inhibitory signaling. Regulation of extracellular levels of GABA is maintained by the four GABA transporters (GATs; GAT1, GAT2, GAT3, and BGT1), Na+/Cl--coupled transporters of the solute carrier 6 (SLC6) family. Despite mounting evidence for the involvement of the non-GAT1 GABA transporters in diseases, only GAT1 has successfully been translated into clinical practice via the drug tiagabine.

AREAS COVERED

In this review, all four GATs will be described in terms of their involvement in disease, and the most recent data on structure, function, expression, and localization discussed in relation to their potential role as drug targets. This includes an overview of various ways to modulate the GATs in relation to treatment of diseases caused by imbalances in the GABAergic system.

EXPERT OPINION

The recent publication of various GAT1 structures is an important milestone for future development of compounds targeting the GATs. Such information can provide much needed insight into mechanistic aspects of all GAT subtypes and be utilized to design improved ligands for this highly interesting drug target class.

The neurotransmitter puzzle of Alzheimer's: Dissecting mechanisms and exploring therapeutic horizons

Alzheimer's Disease (AD) represents a complex interplay of neurological pathways and molecular mechanisms, with significant impacts on patients' lives. This review synthesizes the latest developments in AD research, focusing on both the scientific advancements and their clinical implications. We examine the role of microglia in AD, highlighting their contribution to the disease's inflammatory aspects. The cholinergic hypothesis, a cornerstone of AD research, is re-evaluated, including the role of Alpha-7 Nicotinic Acetylcholine Receptors in disease progression. This review places particular emphasis on the neurotransmission systems, exploring the therapeutic potential of GABAergic neurotransmitters and the role of NMDA inhibitors in the context of glutamatergic neurotransmission. By analyzing the interactions and implications of neurotransmitter pathways in AD, we aim to shed light on emerging therapeutic strategies. In addition to molecular insights, the review addresses the clinical and personal aspects of AD, underscoring the need for patient-centered approaches in treatment and care. The final section looks at the future directions of AD research and treatment, discussing the integration of scientific innovation with patient care. This review aims to provide a comprehensive update on AD, merging scientific insights with practical considerations, suitable for both specialists and those new to the field.

Synthesis of symmetrical and unsymmetrical tetrahydroxybiphenyls and their evaluation as amyloid-β aggregation inhibitors

Our group recently reported that the polyhydroxy aromatic compound 3,3',4,4'-biphenyltetrol (2a) is a successful inhibitor of amyloid-β peptide (Aβ) aggregation, decreasing Aβ aggregation by 50 % when present in equimolar concentrations. In the present study, several additional biphenyltetrols were prepared and examined for their in vitro activity against aggregation of Aβ, to investigate the effect of the relative positions of hydrogen-bond donors on the aggregation process. Congo red spectral shift assays have shown that, of the eight (8) additional biphenyltetrol compounds prepared, three (3) successfully inhibit association of Aβ monomers - two symmetrical isomers, 2,2',5,5'-biphenyltetrol (2c), and 2,2',3,3'-biphenyltetrol (2d), along with one unsymmetrical isomer, 2,3',4',5-biphenyltetrol (2g). These results, along with previously reported results of 2a, strongly suggest that hydroxyl group position affects the ability of the inhibitor to bind to Aβ assemblies, thus impacting inhibitory efficacy.

BACE1 Inhibitors for Alzheimer's Disease: Current Challenges and Future Perspectives

Disease-modifying therapies (DMT) for Alzheimer's disease (AD) are highly longed-for. In this quest, anti-amyloid therapies take center stage supported by genetic facts that highlight an imbalance between production and clearance of amyloid-β peptide (Aβ) in AD patients. Indeed, evidence from basic research, human genetic and biomarker studies, suggests the accumulation of Aβ as a driver of AD pathogenesis and progression. The aspartic protease β-site AβPP cleaving enzyme (BACE1) is the initiator for Aβ production. Underpinning a critical role for BACE1 in AD pathophysiology are the elevated BACE1 concentration and activity observed in the brain and body fluids of AD patients. Therefore, BACE1 is a prime drug target for reducing Aβ levels in early AD. Small-molecule BACE1 inhibitors have been extensively developed for the last 20 years. However, clinical trials with these molecules have been discontinued for futility or safety reasons. Most of the observed adverse side effects were due to other aspartic proteases cross-inhibition, including the homologue BACE2, and to mechanism-based toxicity since BACE1 has substrates with important roles for synaptic plasticity and synaptic homeostasis besides amyloid-β protein precursor (AβPP). Despite these setbacks, BACE1 persists as a well-validated therapeutic target for which a specific inhibitor with high substrate selectivity may yet to be found. In this review we provide an overview of the evolution in BACE1 inhibitors design pinpointing the molecules that reached advanced phases of clinical trials and the liabilities that precluded adequate trial effects. Finally, we ponder on the challenges that anti-amyloid therapies must overcome to achieve clinical success.