Synthesis and biological evaluation of novel aminoquinolines with an n-octyl linker: Impact of halogen substituents on C(7) or a terminal amino group on anticholinesterase and BACE1 activity.

Alzheimer's disease is age-related multifactorial neurodegenerative disease manifested by gradual loss of memory, cognitive decline and changes in personality. Due to rapid and continuous growth of its prevalence, the treatment of Alzheimer's disease calls for development of new and efficacies drugs, especially those that could be able to simultaneously act on more than one of possible targets of action. Aminoquinolines have proven to be a highly promising structural scaffold in the design of such a drug as cholinesterases and ß-secretase 1 inhibitors. In this study, we synthesised twenty-two new 4-aminoquinolines with different halogen atom and its position in the terminal N-benzyl group or with a trifluoromethyl or a chlorine as C(7)-substituents on the quinoline moiety. All compounds were evaluated as multi-target-directedligands by determining their inhibition potency towards human acetylcholinesterase, butyrylcholinesterase and ß-secretase 1. All of the tested derivatives were very potent inhibitors of human acetylcholinesterase and butyrylcholinesterase with inhibition constants (Ki) in the nM to low µM range. Most were estimated to be able to cross the blood-brain barrier by passive transport and were nontoxic toward cells that represented the main models of individual organs.

Edaravone N-benzyl pyridinium derivatives: BACE-1 inhibition, kinetics and in silico binding pose determination.

BACE-1 plays a pivotal role in the production of ß-amyloid (Aß) peptides, implicated in Alzheimer's Disease (AD) pathology. We previously described edaravone N-benzyl pyridinium derivatives (EBPDs) that exhibited multifunctional activity against multiple AD targets. In this study we explored the EBPDs BACE-1 inhibitory activity to potentially enhance the compounds therapeutic profile. The EBPDs exhibited moderate BACE-1 inhibitory activity (IC50 = 44.10 µM - 123.70 µM) and obtained IC50 values between 2.0 and 5.8-fold greater than resveratrol, a known BACE-1 inhibitor (IC50 = 253.20 µM), in this assay. Compound 3 was the most potent inhibitor with an IC50 of 44.10 µM and a Ki of 19.96 µM and a mixed-type mode of inhibition that favored binding in a competitive manner. Molecular docking identified crucial interactions with BACE-1 active site residues, supported by 100 ns MD simulations. The study highlighted the EBPDs therapeutic potential as BACE-1 inhibitors and multifunctional anti-AD therapeutic agents.

Serum Beta-Secretase 1 Activity Is a Potential Marker for the Differential Diagnosis between Alzheimer's Disease and Frontotemporal Dementia: A Pilot Study.

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are the two major neurodegenerative diseases causing dementia. Due to similar clinical phenotypes, differential diagnosis is challenging without specific biomarkers. Beta-site Amyloid Precursor Protein cleaving enzyme 1 (BACE1) is a ß-secretase pivotal in AD pathogenesis. In AD and mild cognitive impairment subjects, BACE1 activity is increased in brain/cerebrospinal fluid, and plasma levels appear to reflect those in the brain. In this study, we aim to evaluate serum BACE1 activity in FTD, since, to date, there is no evidence about its role. The serum of 30 FTD patients and 30 controls was analyzed to evaluate (i) BACE1 activity, using a fluorescent assay, and (ii) Glial Fibrillary Acid Protein (GFAP) and Neurofilament Light chain (NfL) levels, using a Simoa kit. As expected, a significant increase in GFAP and NfL levels was observed in FTD patients compared to controls. Serum BACE1 activity was not altered in FTD patients. A significant increase in serum BACE1 activity was shown in AD vs. FTD and controls. Our results support the hypothesis that serum BACE1 activity is a potential biomarker for the differential diagnosis between AD and FTD.

Could Mushrooms' Secondary Metabolites Ameliorate Alzheimer Disease? A Computational Flexible Docking Investigation.

Herein, we highlight the significance of molecular modeling approaches prior to in vitro and in vivo studies; particularly, in diseases with no recognized treatments such as neurological abnormalities. Alzheimer disease is a neurodegenerative disorder that causes irreversible cognitive decline. Toxicity and ADMET studies were conducted using the Qikprop platform in Maestro software and Discovery Studio 2.0, respectively, to select the promising skeletons from more than 45 reviewed compounds isolated from mushrooms in the last decade. Using rigid and flexible molecular docking approaches such as induced fit docking (IFD) in the binding sites of ß-secretase (BACE1) and acetylcholine esterase (ACHE), promising structures were screened through high precision molecular docking compared with standard drugs donepezil and (2E)-2-imino-3-methyl-5,5-diphenylimidazolidin-4-one (OKK) using Maestro and Cresset Flare platforms. Molecular interactions, binding distances, and RMSD values were measured to reveal key interactions at the binding sites of the two neurodegenerative enzymes. Analysis of IFD results revealed consistent bindings of dictyoquinazol A and gensetin I in the pocket of 4ey7 while inonophenol A, ganomycin, and fornicin fit quite well in 4dju demonstrating binding poses very close to native ligands at ACHE and BACE1. Respective key amino acid contacts manifested the least steric problems according to their Gibbs free binding energies, Glide XP scores, RMSD values, and molecular orientation respect to the key amino acids. Molecular dynamics simulations further confirmed our findings and prospected these compounds to show significant in vitro results in their future pharmacological studies.

BACE1 inhibitors from the fruits of Alpinia oxyphylla have efficacy to treat T2DM-related cognitive disorder.

The fruits of Alpinia oxyphylla (Alpiniae Oxyphyllae Fructus, AOF) are one of the "Four Famous South Medicines" in China. In this study, beta-site amyloid protein precursor cleaving enzyme 1 (BACE1) was applied to explore the active components in AOF responsible for type 2 diabetes mellitus (T2DM)-related cognitive disorder. As a result, 24 compounds including three unreported ones (1, 3, 4) were isolated from AOF. Compound 1 is an unusual carbon­carbon linked diarylheptanoid dimer, and compound 4 is the first case of 3,4-seco-eudesmane sesquiterpenoid with a 5/6-bicyclic skeleton. Four diarylheptanoids (3, 5-7), one flavonoid (9) and two sesquiterpenoids (14 and 20) showed BACE1 inhibitory activity, of which the most active 6 was revealed to be a non-competitive and anti-competitive mixed inhibitor. Docking simulation suggested that OH-4' of 6 played important roles in maintaining activity by forming hydrogen bonds with Ser36 and Ile126 residues. Compounds 3, 5, 9 and 20 displayed neuroprotective effects against amyloid ß (Aß)-induced damage in BV2 cells. Mechanism study revealed that compounds 5 and 20 downregulated the expression of BACE1 and upregulated the expression of Lamp2 to exert effects. Thus, the characteristic diarylheptanoids and sesquiterpenoids in AOF had the efficacy to alleviate T2DM-related cognitive disorder by inhibiting BACE1 activity and reversing Aß-induced neuronal damage.

Proteolytic cleavage of Golgi glycosyltransferases by SPPL3 and other proteases and its implications for cellular glycosylation.

Glycosylation of proteins and lipids is of fundamental importance in multicellular eukaryotes. The vast diversity of glycan structures observed is generated in the Golgi apparatus by the concerted activity of >100 distinct enzymes, which include glycosyltransferases and other glycan-modifying enzymes. Well-known for decades, the majority of these enzymes is released from the Golgi apparatus and subsequently secreted into the extracellular space following endoproteolytic cleavage, but the underlying molecular mechanisms and the physiological implications have remained unexplored. This review will summarize our current knowledge of Golgi enzyme proteolysis and secretion and will discuss its conceptual implications for the regulation of cellular glycosylation and the organization of the Golgi apparatus. A particular focus will lie on the intramembrane protease SPPL3, which recently emerged as key protease facilitating Golgi enzyme release and has since been shown to affect a multitude of glycosylation-dependent physiological processes.

BACE1 inhibitor drugs for the treatment of Alzheimer's disease: Lessons learned, challenges to overcome, and future prospects†.

Alzheimer's disease (AD), first diagnosed over a century ago, remains one of the major healthcare crises around the globe. Currently, there is no cure or effective treatment. The majority of drug development efforts to date have targeted reduction of amyloid-ß peptide (Aß). Drug development through inhibition of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), resulted in promising early clinical studies. However, nearly all small molecule BACE1 inhibitor drugs failed to live up to expectations in later phase clinical trials, due to toxicity and efficacy issues. This commentary aims to provide a brief review of over two decades of BACE1 inhibitor drug development challenges and efforts for treatment of AD and prospects of future BACE1-based drugs.

Beta-Site APP-Cleaving Enzyme-1 Inhibitory Role of Natural Flavonoids in the Treatment of Alzheimer's Disease.

Alzheimer's Disease (AD) is a devastating neurological condition characterized by a progressive decline in cognitive function, including memory loss, reasoning difficulties, and disorientation. Its hallmark features include the formation of neurofibrillary tangles and neuritic plaques in the brain, disrupting normal neuronal function. Neurofibrillary tangles, composed of phosphorylated tau protein and neuritic plaques, containing amyloid-ß protein (Aß) aggregates, contribute to the degenerative process. The discovery of the beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) in 1999 revolutionized our understanding of AD pathogenesis. BACE1 plays a crucial role in the production of Aß, the toxic protein implicated in AD progression. Elevated levels of BACE1 have been observed in AD brains and bodily fluids, underscoring its significance in disease onset and progression. Despite setbacks in clinical trials of BACE1 inhibitors due to efficacy and safety concerns, targeting BACE1 remains a promising therapeutic strategy for early-stage AD. Natural flavonoids have emerged as potential BACE1 inhibitors, demonstrating the ability to reduce Aß production in neuronal cells and inhibit BACE1 activity. In our review, we delve into the pathophysiology of AD, highlighting the central role of BACE1 in Aß production and disease progression. We explore the therapeutic potential of BACE1 inhibitors, including natural flavonoids, in controlling AD symptoms. Additionally, we provide insights into ongoing clinical trials and available patents in this field, shedding light on future directions for AD treatment research.

Astrocytes in Amyloid Generation and Alcohol Metabolism: Implications of Alcohol Use in Neurological Disorder(s).

As per the National Survey on Drug Use and Health, 10.5% of Americans aged 12 years and older are suffering from alcohol use disorder, with a wide range of neurological disorders. Alcohol-mediated neurological disorders can be linked to Alzheimer's-like pathology, which has not been well studied. We hypothesize that alcohol exposure can induce astrocytic amyloidosis, which can be corroborated by the neurological disorders observed in alcohol use disorder. In this study, we demonstrated that the exposure of astrocytes to ethanol resulted in an increase in Alzheimer's disease markers-the amyloid precursor protein, Aß1-42, and the ß-site-cleaving enzyme; an oxidative stress marker-4HNE; proinflammatory cytokines-TNF-α, IL1ß, and IL6; lncRNA BACE1-AS; and alcohol-metabolizing enzymes-alcohol dehydrogenase, aldehyde dehydrogenase-2, and cytochrome P450 2E1. A gene-silencing approach confirmed the regulatory role of lncRNA BACE1-AS in amyloid generation, alcohol metabolism, and neuroinflammation. This report is the first to suggest the involvement of lncRNA BACE1-AS in alcohol-induced astrocytic amyloid generation and alcohol metabolism. These findings will aid in developing therapies targeting astrocyte-mediated neurological disorders and cognitive deficits in alcohol users.

MGST3 regulates BACE1 protein translation and amyloidogenesis by controlling the RGS4-mediated AKT signaling pathway.

Microsomal glutathione transferase 3 (MGST3) regulates eicosanoid and glutathione metabolism. These processes are associated with oxidative stress and apoptosis, suggesting that MGST3 might play a role in the pathophysiology of Alzheimer's disease. Here, we report that knockdown (KD) of MGST3 in cell lines reduced the protein level of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) and the resulting amyloidogenesis. Interestingly, MGST3 KD did not alter intracellular reactive oxygen species level but selectively reduced the expression of apoptosis indicators which could be associated with the receptor of cysteinyl leukotrienes, the downstream metabolites of MGST3 in arachidonic acid pathway. We then showed that the effect of MGST3 on BACE1 was independent of cysteinyl leukotrienes but involved a translational mechanism. Further RNA-seq analysis identified that regulator of G-protein signaling 4 (RGS4) was a target gene of MGST3. Silencing of RGS4 inhibited BACE1 translation and prevented MGST3 KD-mediated reduction of BACE1. The potential mechanism was related to AKT activity, as the protein level of phosphorylated AKT was significantly reduced by silencing of MGST3 and RGS4, and the AKT inhibitor abolished the effect of MGST3/RGS4 on phosphorylated AKT and BACE1. Together, MGST3 regulated amyloidogenesis by controlling BACE1 protein expression, which was mediated by RGS4 and downstream AKT signaling pathway.

Network Models of BACE-1 Inhibitors: Exploring Structural and Biochemical Relationships.

This study investigates the clustering patterns of human ß-secretase 1 (BACE-1) inhibitors using complex network methodologies based on various distance functions, including Euclidean, Tanimoto, Hamming, and Levenshtein distances. Molecular descriptor vectors such as molecular mass, Merck Molecular Force Field (MMFF) energy, Crippen partition coefficient (ClogP), Crippen molar refractivity (MR), eccentricity, Kappa indices, Synthetic Accessibility Score, Topological Polar Surface Area (TPSA), and 2D/3D autocorrelation entropies are employed to capture the diverse properties of these inhibitors. The Euclidean distance network demonstrates the most reliable clustering results, with strong agreement metrics and minimal information loss, indicating its robustness in capturing essential structural and physicochemical properties. Tanimoto and Hamming distance networks yield valuable clustering outcomes, albeit with moderate performance, while the Levenshtein distance network shows significant discrepancies. The analysis of eigenvector centrality across different networks identifies key inhibitors acting as hubs, which are likely critical in biochemical pathways. Community detection results highlight distinct clustering patterns, with well-defined communities providing insights into the functional and structural groupings of BACE-1 inhibitors. The study also conducts non-parametric tests, revealing significant differences in molecular descriptors, validating the clustering methodology. Despite its limitations, including reliance on specific descriptors and computational complexity, this study offers a comprehensive framework for understanding molecular interactions and guiding therapeutic interventions. Future research could integrate additional descriptors, advanced machine learning techniques, and dynamic network analysis to enhance clustering accuracy and applicability.

Exploring the therapeutic potential of steroidal alkaloids in managing Alzheimer's disease.

Steroidal alkaloids are secondary metabolites that are often found in plants, fungi and sponges. These compounds are considered as a source of bioactive compounds for the treatment of chronic diseases, such as neurological disorder like Alzheimer's disease (AD). Some examples of alkaloid derivatives currently used to treat AD symptoms include galantamine, huperzine A, and other alkaloids. AD is a multifactorial disease caused by multiple factors such as inflammation, oxidative stress, and protein aggregation. Based on the various important neuroprotective activities and different pharmacological effects of steroidal alkaloids with polypharmacological modulatory effects, they can lead to the development of new drugs for the treatment of AD. There are limited studies on the involvement of steroidal alkaloids in AD. Therefore, the mechanisms and neuroprotective abilities of these compounds are still poorly understood. The purpose of this review article is to provide an overview of the mechanism, toxicity and neuroprotective benefits of steroidal alkaloids and to discuss future possibilities to improve the application of steroidal alkaloids as anti-AD agents. The therapeutic value and limitations of the steroidal alkaloid are investigated to provide new perspectives for future clinical development studies.

Comprehensive Investigation of Natural Ligands as Inhibitors of ß Secretase to Identify Alzheimer's Disease Therapeutics.

INTRODUCTION: Alzheimer's disease (AD) is an alarmingly prevalent worldwide neurological disorder that affects millions of people and has severe effects on cognitive functions. The amyloid hypothesis, which links AD to Aß (amyloid beta) plaque aggregation, is a well-acknowledged theory. The ß-secretase (BACE1) is the main cause of Aß production, which makes it a possible target for therapy. FDA-approved therapies for AD do exist, but none of them explicitly target BACE1, and their effectiveness is constrained and accompanied by adverse effects. MATERIALS AND METHODS: We determined the essential chemical components of medicinal herbs by conducting a thorough literature research for BACE1. Computational methods like molecular docking, ADMET (Absorption, distribution, metabolism, excretion, toxicity) screening, molecular dynamic simulations, and MMPBSA analysis were performed in order to identify the most promising ligands for ß-secretase. RESULTS: The results suggested that withasomniferol, tinosporide, and curcumin had better binding affinity with BACE1, suggesting their potential as therapeutic candidates against Alzheimer's disease. CONCLUSION: Herbal therapeutics have immense applications in the treatment of chronic diseases like Alzheimer's disease, and there is an urgent need to assess their efficacy as therapeutics.

Associations of CSF BACE1 with amyloid pathology, neurodegeneration, and cognition in Alzheimer's disease.

Β-site amyloid precursor protein (APP) cleaving enzyme (BACE1) is a crucial protease in the production of amyloid-ß (Aß) in Alzheimer's disease (AD) patients. However, the side effects observed in clinical trials of BACE1 inhibitors, including reduction in brain volume and cognitive worsening, suggest that the exact role of BACE1 in AD pathology is not fully understood. To further investigate this, we examined cerebrospinal fluid (CSF) levels of BACE1 and its cleaved product sAPPß that reflects BACE1 activity in the China Aging and Neurodegenerative Disorder Initiative cohort. We found significant correlations between CSF BACE1 or sAPPß levels and CSF Aß40, Aß42, and Aß42/Aß40 ratio, but not with amyloid deposition detected by 18F-Florbetapir PET. Additionally, CSF BACE1 and sAPPß levels were positively associated with cortical thickness in multiple brain regions, and higher levels of sAPPß were linked to increased cortical glucose metabolism in frontal and supramarginal areas. Interestingly, individuals with higher baseline levels of CSF BACE1 exhibited slower rates of brain volume reduction and cognitive worsening over time. This suggests that increased levels and activity of BACE1 may not be the determining factor for amyloid deposition, but instead, may be associated with increased neuronal activity and potentially providing protection against neurodegeneration in AD.

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-ß peptide (Aß) in AD patients. Indeed, evidence from basic research, human genetic and biomarker studies, suggests the accumulation of Aß as a driver of AD pathogenesis and progression. The aspartic protease ß-site AßPP cleaving enzyme (BACE1) is the initiator for Aß 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 Aß 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-ß protein precursor (AßPP). 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.

Targeting key players in Alzheimer's disease: bioactive compounds from Moringa oleifera, Desmodium gangeticum, and Centella asiatica as potential therapeutics.

Alzheimer's Disease (AD) is one of the critical reasons for dementia around the world, with a huge number of cases being reported every year. The breakdown of Amyloid Precursor Protein (APP) plays a crucial role in AD development. The Beta-site APP Cleaving Enzyme 1 (BACE1) is a highly significant proteolytic enzyme found to be critically involved in the APP breakdown process and generates beta-amyloid plaques in the extracellular neuronal membrane. In this study, we have used natural compounds with cognitive and neuroprotective activities from three plants, Centella asiatica, Moringa oleifera, and Desmodium gangeticum to inhibit the activity of BACE1. We have identified nine compounds out of 73 compounds filtered out from the three plants showing high affinity with the catalytic dyad region of BACE1 through molecular docking studies. Interestingly, the 200 ns molecular dynamics simulation study further confirmed the stability of the complexes formed between 9 compounds and the BACE1 protein. Furthermore, the free energy calculations also revealed these complexes possess favorable energies. Astilbin, Delphinidin 3-glucoside, and kaempferol 7-O-glucoside showed good binding affinity and structural stability when compared to other compounds and the control CNP520. Following a preliminary screening, the Astilbin compound was chosen based on the grounds of binding affinity, ADMET Properties, Hbond formation, Molecular Dynamic simulation, and MM-PBSA studies. A subsequent 1microsecond molecular dynamics simulation was conducted for the Astilbin complex. Through microsecond simulation, it was found that Astilbin alters BACE1's behavior and induces conformational rearrangements. Thus, this study opens a gateway to inhibit the activity of BACE1 protein through Astilbin thereby disclosing the possibility of managing Alzheimer's Disease.Communicated by Ramaswamy H. Sarma.

Involvement of Endolysosomes and Aurora Kinase A in the Regulation of Amyloid ß Protein Levels in Neurons.

Aurora kinase A (AURKA) is a serine/threonine-protein kinase that regulates microtubule organization during neuron migration and neurite formation. Decreased activity of AURKA was found in Alzheimer's disease (AD) brain samples, but little is known about the role of AURKA in AD pathogenesis. Here, we demonstrate that AURKA is expressed in primary cultured rat neurons, neurons from adult mouse brains, and neurons in postmortem human AD brains. AURKA phosphorylation, which positively correlates with its activity, is reduced in human AD brains. In SH-SY5Y cells, pharmacological activation of AURKA increased AURKA phosphorylation, acidified endolysosomes, decreased the activity of amyloid beta protein (Aß) generating enzyme ß-site amyloid precursor protein cleaving enzyme (BACE-1), increased the activity of the Aß degrading enzyme cathepsin D, and decreased the intracellular and secreted levels of Aß. Conversely, pharmacological inhibition of AURKA decreased AURKA phosphorylation, de-acidified endolysosomes, decreased the activity of cathepsin D, and increased intracellular and secreted levels of Aß. Thus, reduced AURKA activity in AD may contribute to the development of intraneuronal accumulations of Aß and extracellular amyloid plaque formation.

Beyond Amyloid-ß: Reevaluating Its Physiological Role to Find Safe Therapies Against Alzheimer's Disease.

This commentary critically examines the long-standing emphasis on amyloid-ß (Aß)-based therapies in Alzheimer's disease (AD), despite numerous clinical trial failures. It highlights the urgency to reassess research methodologies and challenges the initiation of anti-Aß trials in preclinical stages of the disease without conclusive proofs of their safety and efficacy. Instead, a comprehensive approach that considers Aß's physiological roles and addresses AD complex nature is suggested, encouraging the idea that clinical trial failures may result from targeting the wrong mechanism. Evidence-based scientific research is needed to advance with AD treatment, moving beyond the current conception of Aß hypothesis.

Heterologous expression of BACE1 and its interaction with Codonopsis pilosula polysaccharides and Lobetyolin.

BACE1, a crucial enzyme in the amyloid-ß deposition theory of Alzheimer's disease (AD), is targeted by Codonopsis pilosula, a traditional tonic believed to impede AD onset. However, the specific active compounds responsible for its effects remain elusive. Our prior network pharmacology research identified C. pilosula polysaccharides (CPPS) and Lobetyolin may serve as potential inhibitors of AD by suppressing amyloidogenesis. Here, we recombinantly expressed BACE1 under varied conditions and assessed its activity using Fluorescence Resonance Energy Transfer technology. Through spectroscopy, molecular docking, and dynamics, we elucidated the interactions of CPPS, Lobetyolin, and BACE1. Optimal BACE1 expression occurred at 22 °C with 0.4 mM IPTG for 6 h, yielding a 72 kDa protein. Enzyme kinetics displayed a maximum rate of 4096 µmol/min and a Michaelis constant of 16 mg/mL for BACE1. Spectroscopic analysis revealed differing binding affinities of the compounds at various temperatures, peaking at 293 K. Lobetyolin exhibited superior binding to BACE1 compared to CPPS, driven by hydrophobic and electrostatic forces. Molecular docking and dynamics highlighted hydrophobic amino acids' role in BACE1 interactions with Lobetyolin and CPPS, with binding energy < -1.2 kcal/mol signifying strong affinities. Notably, Lobetyolin and CPPS showed higher BACE1 affinity than APP, with the Lobetyolin-BACE1 complex being the most stable.

Inhibition of BACE1 affected both its Aß producing and degrading activities and increased Aß42 and Aß40 levels at high-level BACE1 expression.

The beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the predominant ß-secretase, cleaving the amyloid precursor protein (APP) via the amyloidogenic pathway. In addition, BACE1 as an amyloid degrading enzyme (ADE), cleaves Aß to produce the C-terminally truncated non-toxic Aß fragment Aß34 which is an indicator of amyloid clearance. Here, we analyzed the effects of BACE1 inhibitors on its opposing enzymatic functions, i.e., amyloidogenic (Aß producing) and amyloidolytic (Aß degrading) activities, using cell culture models with varying BACE1/APP ratios. Under high-level BACE1 expression, low-dose inhibition unexpectedly yielded a two-fold increase in Aß42 and Aß40 levels. The concomitant decrease in Aß34 and secreted APPß levels suggested that the elevated Aß42 and Aß40 levels were due to the attenuated Aß degrading activity of BACE1. Notably, the amyloidolytic activity of BACE1 was impeded at lower BACE1 inhibitor concentrations compared to its amyloidogenic activity, thereby suggesting that the Aß degrading activity of BACE1 was more sensitive to inhibition than its Aß producing activity. Under endogenous BACE1 and APP levels, "low-dose" BACE1 inhibition affected both the Aß producing and degrading activities of BACE1, i.e., significantly increased Aß42/Aß40 ratio and decreased Aß34 levels, respectively. Further, we incubated recombinant BACE1 with synthetic Aß peptides and found that BACE1 has a higher affinity for Aß substrates over APP. In summary, our results suggest that stimulating BACE1's ADE activity and halting Aß production without decreasing Aß clearance could still be a promising therapeutic approach with new, yet to be developed, BACE1 modulators.