Mitochondria as a promising target for developing novel agents for treating Alzheimer's disease

Cholesterol Oxime Olesoxime Assessed as a Potential Ligand of Human Cholinesterases

Olesoxime, a cholesterol derivative with an oxime group, possesses the ability to cross the blood-brain barrier, and has demonstrated excellent safety and tolerability properties in clinical research. These characteristics indicate it may serve as a centrally active ligand of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), whose disruption of activity with organophosphate compounds (OP) leads to uncontrolled excitation and potentially life-threatening symptoms. To evaluate olesoxime as a binding ligand and reactivator of human AChE and BChE, we conducted in vitro kinetic studies with the active metabolite of insecticide parathion, paraoxon, and the warfare nerve agents sarin, cyclosarin, tabun, and VX. Our results showed that both enzymes possessed a binding affinity for olesoxime in the mid-micromolar range, higher than the antidotes in use (i.e., 2-PAM, HI-6, etc.). While olesoxime showed a weak ability to reactivate AChE, cyclosarin-inhibited BChE was reactivated with an overall reactivation rate constant comparable to that of standard oxime HI-6. Moreover, in combination with the oxime 2-PAM, the reactivation maximum increased by 10-30% for cyclosarin- and sarin-inhibited BChE. Molecular modeling revealed productive interactions between olesoxime and BChE, highlighting olesoxime as a potentially BChE-targeted therapy. Moreover, it might be added to OP poisoning treatment to increase the efficacy of BChE reactivation, and its cholesterol scaffold could provide a basis for the development of novel oxime antidotes.

Mitochondrial complex I density is associated with IQ and cognition in cognitively healthy adults: an in vivo [18F]BCPP-EF PET study

BACKGROUND

Mitochondrial function plays a key role in regulating neurotransmission and may contribute to general intelligence. Mitochondrial complex I (MC-I) is the largest enzyme of the respiratory chain. Recently, it has become possible to measure MC-I distribution in vivo, using a novel positron emission tomography tracer [18F]BCPP-EF, thus, we set out to investigate the association between MC-I distribution and measures of cognitive function in the living healthy brain.

RESULTS

Analyses were performed in a voxel-wise manner and identified significant associations between [18F]BCPP-EF DVRCS-1 in the precentral gyrus and parietal lobes and WAIS-IV predicted IQ, WAIS-IV arithmetic and WAIS-IV symbol-digit substitution scores (voxel-wise Pearson's correlation coefficients transformed to Z-scores, thresholded at Z = 2.3 family-wise cluster correction at p < 0.05, n = 16). Arithmetic scores were associated with middle frontal and post-central gyri tracer uptake, symbol-digit substitution scores were associated with precentral gyrus tracer uptake. RAVLT recognition scores were associated with [18F]BCPP-EF DVRCS-1 in the middle frontal gyrus, post-central gyrus, occipital and parietal regions (n = 20).

CONCLUSIONS

Taken together, our findings support the theory that mitochondrial function may contribute to general intelligence and indicate that interindividual differences in MC-I should be a key consideration for research into mitochondrial dysfunction in conditions with cognitive impairment.

Natural polyphenol: Their pathogenesis-targeting therapeutic potential in Alzheimer's disease

Alzheimer's disease (AD) is a detrimental neurodegenerative disease affecting the elderly. Clinically, it is characterized by progressive memory decline and subsequent loss of broader cognitive functions. Current drugs provide only symptomatic relief but do not have profound disease-modifying effects. There is an unmet need to identify novel pharmacological agents for AD therapy. Neuropathologically, the characteristic hallmarks of the disease are extracellular senile plaques containing amyloid β-peptides and intracellular neurofibrillary tangles containing hyperphosphorylated microtubule-associated protein tau. Simultaneously, oxidative stress, neuroinflammation and mitochondrial dysfunction in specific brain regions are early events during the process of AD pathologic changes and are associated with Aβ/tau toxicity. Here, we first summarized probable pathogenic mechanisms leading to neurodegeneration and hopefully identify pathways that serve as specific targets to improve therapy for AD. We then reviewed the mechanisms that underlie disease-modifying effects of natural polyphenols, with a focus on nuclear factor erythroid 2-related factor 2 activators for AD treatment. Lastly, we discussed challenges in the preclinical to clinical translation of natural polyphenols. In conclusion, there is evidence that natural polyphenols can be therapeutically useful in AD through their multifaceted mechanism of action. However, more clinical studies are needed to confirm these effects.

Mitochondrial Interaction with Serotonin in Neurobiology and Its Implication in Alzheimer's Disease

Alzheimer's disease (AD) is a lethal neurodegenerative disorder characterized by severe brain pathologies and progressive cognitive decline. While the exact cause of this disease remains unknown, emerging evidence suggests that dysregulation of neurotransmitters contributes to the development of AD pathology and symptoms. Serotonin, a critical neurotransmitter in the brain, plays a pivotal role in regulating various brain processes and is implicated in neurological and psychiatric disorders, including AD. Recent studies have shed light on the interplay between mitochondrial function and serotonin regulation in brain physiology. In AD, there is a deficiency of serotonin, along with impairments in mitochondrial function, particularly in serotoninergic neurons. Additionally, altered activity of mitochondrial enzymes, such as monoamine oxidase, may contribute to serotonin dysregulation in AD. Understanding the intricate relationship between mitochondria and serotonin provides valuable insights into the underlying mechanisms of AD and identifies potential therapeutic targets to restore serotonin homeostasis and alleviate AD symptoms. This review summarizes the recent advancements in unraveling the connection between brain mitochondria and serotonin, emphasizing their significance in AD pathogenesis and underscoring the importance of further research in this area. Elucidating the role of mitochondria in serotonin dysfunction will promote the development of therapeutic strategies for the treatment and prevention of this neurodegenerative disorder.

Effects of Redox Homeostasis and Mitochondrial Damage on Alzheimer's Disease

Bioenergetic mitochondrial dysfunction is a common feature of several diseases, including Alzheimer's disease (AD), where redox imbalance also plays an important role in terms of disease development. AD is an age-related disease and begins many years before the appearance of neurodegenerative symptoms. Intracellular tau aggregation, extracellular β-amyloid (Aβ) deposition in the brain, and even the APOE4 genotype contribute to the process of AD by impairing redox homeostasis and mitochondrial dysfunction. This review summarizes the evidence for the redox imbalance and mitochondrial dysfunction in AD and demonstrates the current therapeutic strategies related to mitochondrial maintenance.

Mitochondria and Oxidative Stress as a Link between Alzheimer's Disease and Diabetes Mellitus

This review is devoted to the problems of the common features linking metabolic disorders and type 2 diabetes with the development of Alzheimer's disease. The pathogenesis of Alzheimer's disease closely intersects with the mechanisms of type 2 diabetes development, and an important risk factor for both pathologies is aging. Common pathological mechanisms include both factors in the development of oxidative stress, neuroinflammation, insulin resistance, and amyloidosis, as well as impaired mitochondrial dysfunctions and increasing cell death. The currently available drugs for the treatment of type 2 diabetes and Alzheimer's disease have limited therapeutic efficacy. It is important to note that drugs used to treat Alzheimer's disease, in particular acetylcholinesterase inhibitors, show a positive therapeutic potential in the treatment of type 2 diabetes, while drugs used in the treatment of type 2 diabetes can also prevent a number of pathologies characteristic for Alzheimer's disease. A promising direction in the search for a strategy for the treatment of type 2 diabetes and Alzheimer's disease may be the creation of complex multi-target drugs that have neuroprotective potential and affect specific common targets for type 2 diabetes and Alzheimer's disease.

Current and future therapeutic strategies for Alzheimer's disease: an overview of drug development bottlenecks

Alzheimer's disease (AD) is the most common chronic neurodegenerative disease worldwide. It causes cognitive dysfunction, such as aphasia and agnosia, and mental symptoms, such as behavioral abnormalities; all of which place a significant psychological and economic burden on the patients' families. No specific drugs are currently available for the treatment of AD, and the current drugs for AD only delay disease onset and progression. The pathophysiological basis of AD involves abnormal deposition of beta-amyloid protein (Aβ), abnormal tau protein phosphorylation, decreased activity of acetylcholine content, glutamate toxicity, autophagy, inflammatory reactions, mitochondria-targeting, and multi-targets. The US Food and Drug Administration (FDA) has approved five drugs for clinical use: tacrine, donepezil, carbalatine, galantamine, memantine, and lecanemab. We have focused on the newer drugs that have undergone clinical trials, most of which have not been successful as a result of excessive clinical side effects or poor efficacy. Although aducanumab received rapid approval from the FDA on 7 June 2021, its long-term safety and tolerability require further monitoring and confirmation. In this literature review, we aimed to explore the possible pathophysiological mechanisms underlying the occurrence and development of AD. We focused on anti-Aβ and anti-tau drugs, mitochondria-targeting and multi-targets, commercially available drugs, bottlenecks encountered in drug development, and the possible targets and therapeutic strategies for future drug development. We hope to present new concepts and methods for future drug therapies for AD.

Fluorescence microscopic platforms imaging mitochondrial abnormalities in neurodegenerative diseases

Neurodegenerative diseases (NDs) are progressive disorders that cause the degeneration of neurons. Mitochondrial dysfunction is a common symptom in NDs and plays a crucial role in neuronal loss. Mitochondrial abnormalities can be observed in the early stages of NDs and evolve throughout disease progression. Visualizing mitochondrial abnormalities can help understand ND progression and develop new therapeutic strategies. Fluorescence microscopy is a powerful tool for dynamically imaging mitochondria due to its high sensitivity and spatiotemporal resolution. This review discusses the relationship between mitochondrial dysfunction and ND progression, potential biomarkers for imaging dysfunctional mitochondria, advances in fluorescence microscopy for detecting organelles, the performance of fluorescence probes in visualizing ND-associated mitochondria, and the challenges and opportunities for developing new generations of fluorescence imaging platforms for monitoring mitochondria in NDs.

Role of melatonin and quercetin as countermeasures to the mitochondrial dysfunction induced by titanium dioxide nanoparticles

AIM

Due to the growing commercialization of titanium dioxide nanoparticles (TNPs), it is necessary to use these particles in a manner that is safe, healthy and environmental friendly. Through reactive oxygen species (ROS) generation, it has been discovered that TNPs have a harmful effect on the brain. The aim of this study is to provide valuable insights into the possible mechanisms of TNPs induced mitochondrial dysfunction in brain and its amelioration by nutraceuticals, quercetin (QR) and melatonin (Mel) in in vitro and in vivo conditions.

MATERIALS AND METHODS

Whole brain mitochondrial sample was used for in-vitro evaluation. Pre-treatment of QR (30 μM) and Mel (100 μM) at 25 °C for 1 h was given prior to TNPs (50 μg/ml) exposure. For in-vivo study, male Wistar rats were divided into four groups. Group I was control and group II was exposed to TNPs (5 mg/kg b.wt., i.v.). QR (5 mg/kg b.wt.) and Mel (5 mg/kg b.wt.) were given orally as pre-treatment in groups III and IV, respectively. Biochemical parameters, neurobehavioural paradigms, mitochondrial respiration, neuronal architecture assessment were assessed.

KEY FINDINGS

QR and Mel restored the mitochondrial oxidative stress biomarkers in both the studies. Additionally, these nutraceuticals resuscitated the neurobehavioural alterations and restored the neuronal architecture alterations in TNPs exposed rats. The mitochondrial dysfunction induced by TNPs was also ameliorated by QR and Mel by protecting the mitochondrial complex activity and mitochondrial respiration rate.

SIGNIFICANCE

Results of the study demonstrated that QR and Mel ameliorated mitochondrial mediated neurotoxic effects induced by TNPs exposure.

Molecular mechanisms of Alzheimer's disease: From therapeutic targets to promising drugs

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive impairment so widespread that it interferes with a person's ability to complete daily activities. AD is becoming increasingly common, and it is estimated that the number of patients will reach 152 million by 2050. Current treatment options for AD are symptomatic and have modest benefits. Therefore, considering the human, social, and economic burden of the disease, the development of drugs with the potential to alter disease progression has become a global priority. In this review, the molecular mechanisms involved in the pathology of AD were evaluated as therapeutic targets. The main aim of the review is to focus on new knowledge about mitochondrial dysfunction, oxidative stress, and neuronal transmission in AD, as well as a range of cellular signaling mechanisms and associated treatments. Important molecular interactions leading to AD were described in amyloid cascade and in tau protein function, oxidative stress, mitochondrial dysfunction, cholinergic and glutamatergic neurotransmission, cAMP-regulatory element-binding protein (CREB), the silent mating type information regulation 2 homolog 1 (SIRT-1), neuroinflammation (glial cells), and synaptic alterations. This review summarizes recent experimental and clinical research in AD pathology and analyzes the potential of therapeutic applications based on molecular disease mechanisms.

Small-molecule inhibitors of cyclophilin D as potential therapeutics in mitochondria-related diseases

Cyclophilin D (CypD) is a key regulator of mitochondrial permeability transition pore (mPTP) opening. This pathophysiological phenomenon is associated with the development of several human diseases, including ischemia-reperfusion injury and neurodegeneration. Blocking mPTP opening through CypD inhibition could be a novel and promising therapeutic approach for these conditions. While numerous CypD inhibitors have been discovered to date, none have been introduced into clinical practice, mostly owing to their high toxicity, unfavorable pharmacokinetics, and low selectivity for CypD over other cyclophilins. This review summarizes current knowledge of CypD inhibitors, with a particular focus on small-molecule compounds with regard to their in vitro activity, their selectivity for CypD, and their binding mode within the enzyme's active site. Finally, approaches for improving the molecular design of CypD inhibitors are discussed.

Effect of Tau Protein on Mitochondrial Functions

Alzheimer's disease is the most common age-related progressive neurodegenerative disorder of brain cortex and hippocampus leading to cognitive impairment. Accumulation of extracellular amyloid plaques and intraneuronal neurofibrillary tangles are believed to be the main hallmarks of the disease. Origin of Alzheimer's disease is not totally clear, multiple initiator factors are likely to exist. Intracellular impacts of Alzheimer's disease include mitochondrial dysfunction, oxidative stress, ER-stress, disruption of autophagy, severe metabolic challenges leading to massive neuronal apoptosis. Mitochondria are the key players in all these processes. This formed the basis for the so-called mitochondrial cascade hypothesis. This review provides current data on the molecular mechanisms of the development of Alzheimer's disease associated with mitochondria. Special attention was paid to the interaction between Tau protein and mitochondria, as well as to the promising therapeutic approaches aimed at preventing development of neurodegeneration.

Pharmacological sequestration of mitochondrial calcium uptake protects against dementia and β-amyloid neurotoxicity

All forms of dementia including Alzheimer's disease are currently incurable. Mitochondrial dysfunction and calcium alterations are shown to be involved in the mechanism of neurodegeneration in Alzheimer's disease. Previously we have described the ability of compound Tg-2112x to protect neurons via sequestration of mitochondrial calcium uptake and we suggest that it can also be protective against neurodegeneration and development of dementia. Using primary co-culture neurons and astrocytes we studied the effect of Tg-2112x and its derivative Tg-2113x on β-amyloid-induced changes in calcium signal, mitochondrial membrane potential, mitochondrial calcium, and cell death. We have found that both compounds had no effect on β-amyloid or acetylcholine-induced calcium changes in the cytosol although Tg2113x, but not Tg2112x reduced glutamate-induced calcium signal. Both compounds were able to reduce mitochondrial calcium uptake and protected cells against β-amyloid-induced mitochondrial depolarization and cell death. Behavioral effects of Tg-2113x on learning and memory in fear conditioning were also studied in 3 mouse models of neurodegeneration: aged (16-month-old) C57Bl/6j mice, scopolamine-induced amnesia (3-month-old mice), and 9-month-old 5xFAD mice. It was found that Tg-2113x prevented age-, scopolamine- and cerebral amyloidosis-induced decrease in fear conditioning. In addition, Tg-2113x restored fear extinction of aged mice. Thus, reduction of the mitochondrial calcium uptake protects neurons and astrocytes against β-amyloid-induced cell death and contributes to protection against dementia of different ethology. These compounds could be used as background for the developing of a novel generation of disease-modifying neuroprotective agents.

Dysfunction of Mitochondria in Alzheimer’s Disease: ANT and VDAC Interact with Toxic Proteins and Aid to Determine the Fate of Brain Cells

Alzheimer’s disease (AD), certainly the most widespread proteinopathy, has as classical neuropathological hallmarks, two groups of protein aggregates: senile plaques and neurofibrillary tangles. However, the research interest is rapidly gaining ground in a better understanding of other pathological features, first, of all the mitochondrial dysfunctions. Several pieces of evidence support the hypothesis that abnormal mitochondrial function may trigger aberrant processing of amyloid progenitor protein or tau and thus neurodegeneration. Here, our aim is to emphasize the role played by two ‘bioenergetic’ proteins inserted in the mitochondrial membranes, inner and outer, respectively, that is, the adenine nucleotide translocator (ANT) and the voltage-dependent anion channel (VDAC), in the progression of AD. To perform this, we will magnify the ANT and VDAC defects, which are measurable hallmarks of mitochondrial dysfunction, and collect all the existing information on their interaction with toxic Alzheimer’s proteins. The pathological convergence of tau and amyloid β-peptide (Aβ) on mitochondria may finally explain why the therapeutic strategies used against the toxic forms of Aβ or tau have not given promising results separately. Furthermore, the crucial role of ANT-1 and VDAC impairment in the onset/progression of AD opens a window for new therapeutic strategies aimed at preserving/improving mitochondrial function, which is suspected to be the driving force leading to plaque and tangle deposition in AD.

Unveiling the Multitarget Anti-Alzheimer Drug Discovery Landscape: A Bibliometric Analysis

Multitarget anti-Alzheimer agents are the focus of very intensive research. Through a comprehensive bibliometric analysis of the publications in the period 1990-2020, we have identified trends and potential gaps that might guide future directions. We found that: (i) the number of publications boomed by 2011 and continued ascending in 2020; (ii) the linked-pharmacophore strategy was preferred over design approaches based on fusing or merging pharmacophores or privileged structures; (iii) a significant number of in vivo studies, mainly using the scopolamine-induced amnesia mouse model, have been performed, especially since 2017; (iv) China, Italy and Spain are the countries with the largest total number of publications on this topic, whereas Portugal, Spain and Italy are the countries in whose scientific communities this topic has generated greatest interest; (v) acetylcholinesterase, β-amyloid aggregation, oxidative stress, butyrylcholinesterase, and biometal chelation and the binary combinations thereof have been the most commonly pursued, while combinations based on other key targets, such as tau aggregation, glycogen synthase kinase-3β, NMDA receptors, and more than 70 other targets have been only marginally considered. These results might allow us to spot new design opportunities based on innovative target combinations to expand and diversify the repertoire of multitarget drug candidates and increase the likelihood of finding effective therapies for this devastating disease.

Mechanisms of Acupuncture in Improving Alzheimer's Disease Caused by Mitochondrial Damage

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases among the elderly and it accounts for nearly 80% of all dementias. The pathogenesis of AD is complicated and enigmatic thus far. The mitochondrial cascade hypothesis assumes that mitochondrial damage may mediate, drive, or contribute to a variety of AD pathologies and may be the main factor in late-onset AD. Currently, there are no widely recognized drugs able to attenuate mitochondrial damage in AD. Notably, increasing evidence supports the efficacy of acupuncture for improving the mitochondrial structure and protecting mitochondrial functions in AD. This review reports the mechanisms by which acupuncture regulates mitochondrial dynamics, energy metabolism, calcium homeostasis and apoptosis. In conclusion, these findings suggest that AD mitochondrial dysfunction represents a reasonable therapeutic target and acupuncture could play a significant role in preventing and treating AD.

Recent Advancements in Strategies for Abnormal Protein Clearance in Alzheimer's Disease

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Alzheimer's disease (AD) is a intricate neurodegenerative disease with chronic and progressive development whose typical neuropathological features encompasses senile plaques and neurofibrillary tangles respectively formed by the extracellular deposition of amyloid-beta (Aβ) and the intracellular accumulation of hyperphosphorylated tau protein in the brain, particularly in limbic and cortical regions. The pathological changes are considered to be caused by the loss of Aβ and tau protein clearance mechanisms under pathological conditions, which leads to an imbalance between the rates of clearance and production. Consequently, the main strategies for treating AD aim to reduce the production of Aβ and hyperphosphorylated tau protein in the brain, inhibit their accumulation, or accelerate their clearance. Although drugs utilizing these therapeutic strategies have been studied successively, their therapeutic effects have generally been less than ideal. Fortunately, recent advances have been made in clearance strategies for these abnormally expressed proteins, including immunotherapies and nanomedicines targeting Aβ or tau, which could represent an important breakthrough for treating AD. Here, we review recent development of the strategies for the removal of abnormal proteins and provide new ideas and methods for treating AD.

Role of Bioactive Compounds in the Regulation of Mitochondrial Dysfunctions in Brain and Age-Related Neurodegenerative Diseases

Mitochondria are multifunctional organelles that participate in a wide range of metabolic processes, including energy production and biomolecule synthesis. The morphology and distribution of intracellular mitochondria change dynamically, reflecting a cell’s metabolic activity. Oxidative stress is defined as a mismatch between the body’s ability to neutralise and eliminate reactive oxygen and nitrogen species (ROS and RNS). A determination of mitochondria failure in increasing oxidative stress, as well as its implications in neurodegenerative illnesses and apoptosis, is a significant developmental process of focus in this review. The neuroprotective effects of bioactive compounds linked to neuronal regulation, as well as related neuronal development abnormalities, will be investigated. In conclusion, the study of secondary components and the use of mitochondrial features in the analysis of various neurodevelopmental diseases has enabled the development of a new class of mitochondrial-targeted pharmaceuticals capable of alleviating neurodegenerative disease states and enabling longevity and healthy ageing for the vast majority of people.

The molecular mechanism, targets, and novel molecules in the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurological illness that causes dementia mainly in the elderly. The challenging obstacles related to AD has freaked global healthcare system to encourage scientists in developing novel therapeutic startegies to overcome with the fatal disease. The current treatment therapy of AD provides only symptomatic relief and to some extent disease-modifying effects. The current approach for AD treatment involves designing of cholinergic inhibitors, Aβ disaggregation inducing agents, tau inhibitors and several antioxidants. Hence, extensive research on AD therapy urgently requires a deep understanding of its pathophysiology and exploration of various chemical scaffolds to design and develop a potential drug candidate for the treatment. Various issues linked between disease and therapy need to be considered such as BBB penetration capability, clinical failure and multifaceted pathophisiology requires a proper attention to develop a lead candidate. This review article covers all probable mechanisms including one of the recent areas for investigation i.e., lipid dyshomeostasis, pathogenic involvement of P. gingivalis and neurovascular dysfunction, recently reported molecules and drugs under clinical investigations and approved by FDA for AD treatment. Our summarized information on AD will attract the researchers to understand and explore current status and structural modifications of the recently reported heterocyclic derivatives in drug development for AD therapy.

Two Birds One Stone: The Neuroprotective Effect of Antidiabetic Agents on Parkinson Disease-Focus on Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease affecting more than 1% of the population over 65 years old. The etiology of the disease is unknown and there are only symptomatic managements available with no known disease-modifying treatment. Aging, genes, and environmental factors contribute to PD development and key players involved in the pathophysiology of the disease include oxidative stress, mitochondrial dysfunction, autophagic-lysosomal imbalance, and neuroinflammation. Recent epidemiology studies have shown that type-2 diabetes (T2DM) not only increased the risk for PD, but also is associated with PD clinical severity. A higher rate of insulin resistance has been reported in PD patients and is suggested to be a pathologic driver in this disease. Oral diabetic drugs including sodium-glucose cotransporter 2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and dipeptidyl peptidase-4 (DPP-4) inhibitors have been shown to provide neuroprotective effects in both PD patients and experimental models; additionally, antidiabetic drugs have been demonstrated to lower incidence rates of PD in DM patients. Among these, the most recently developed drugs, SGLT2 inhibitors may provide neuroprotective effects through improving mitochondrial function and antioxidative effects. In this article, we will discuss the involvement of mitochondrial-related oxidative stress in the development of PD and potential benefits provided by antidiabetic agents especially focusing on sglt2 inhibitors.

Conjugation of Aminoadamantane and γ-Carboline Pharmacophores Gives Rise to Unexpected Properties of Multifunctional Ligands

A new series of conjugates of aminoadamantane and γ-carboline, which are basic scaffolds of the known neuroactive agents, memantine and dimebon (Latrepirdine) was synthesized and characterized. Conjugates act simultaneously on several biological structures and processes involved in the pathogenesis of Alzheimer’s disease and some other neurodegenerative disorders. In particular, these compounds inhibit enzymes of the cholinesterase family, exhibiting higher inhibitory activity against butyrylcholinesterase (BChE), but having almost no effect on the activity of carboxylesterase (anti-target). The compounds serve as NMDA-subtype glutamate receptor ligands, show mitoprotective properties by preventing opening of the mitochondrial permeability transition (MPT) pore, and act as microtubule stabilizers, stimulating the polymerization of tubulin and microtubule-associated proteins. Structure–activity relationships were studied, with particular attention to the effect of the spacer on biological activity. The synthesized conjugates showed new properties compared to their prototypes (memantine and dimebon), including the ability to bind to the ifenprodil-binding site of the NMDA receptor and to occupy the peripheral anionic site of acetylcholinesterase (AChE), which indicates that these compounds can act as blockers of AChE-induced β-amyloid aggregation. These new attributes of the conjugates represent improvements to the pharmacological profiles of the separate components by conferring the potential to act as neuroprotectants and cognition enhancers with a multifunctional mode of action.