ApoE mimetic improves pathology and memory in a model of Alzheimer's disease

Drugs targeting APOE4 that regulate beta-amyloid aggregation in the brain: Therapeutic potential for Alzheimer's disease

Alzheimer's disease is characterized by progressive cognitive decline, and behavioural and psychological symptoms of dementia are common. The APOE ε4 allele, a genetic risk factor, significantly increases susceptibility to the disease. Despite efforts to effectively treat the disease, only seven drugs are approved for its treatment, and only two of these prevent its progression. This highlights the need to identify new pharmacological options. This review focuses on mimetic peptides, small molecule correctors and HAE-4 antibodies that target ApoE. These drugs reduce β-amyloid-induced neurodegeneration in preclinical models. In addition, loop diuretics such as bumetanide and furosemide show the potential to reduce the prevalence of Alzheimer's disease in humans, and antidepressants such as imipramine improve cognitive function in individuals diagnosed with Alzheimer's disease. Consistent with this, both classes of drugs have been shown to exert neuroprotective effects by inhibiting ApoE4-catalysed Aβ aggregation in preclinical models. Moreover, peroxisome proliferator-activated receptor ligands, particularly pioglitazone and rosiglitazone, reduce ApoE4-induced neurodegeneration in animal models. However, they do not prevent the cognitive decline in APOE ε4 allele carriers. Finally, ApoE4 impairs the integrity of the blood-brain barrier and haemostasis. On this basis, ApoE4 modulation is a promising avenue for the treatment of late-onset Alzheimer's disease.

Multifaceted roles of APOE in Alzheimer disease

For the past three decades, apolipoprotein E (APOE) has been known as the single greatest genetic modulator of sporadic Alzheimer disease (AD) risk, influencing both the average age of onset and the lifetime risk of developing AD. The APOEε4 allele significantly increases AD risk, whereas the ε2 allele is protective relative to the most common ε3 allele. However, large differences in effect size exist across ethnoracial groups that are likely to depend on both global genetic ancestry and local genetic ancestry, as well as gene-environment interactions. Although early studies linked APOE to amyloid-β - one of the two culprit aggregation-prone proteins that define AD - in the past decade, mounting work has associated APOE with other neurodegenerative proteinopathies and broader ageing-related brain changes, such as neuroinflammation, energy metabolism failure, loss of myelin integrity and increased blood-brain barrier permeability, with potential implications for longevity and resilience to pathological protein aggregates. Novel mouse models and other technological advances have also enabled a number of therapeutic approaches aimed at either attenuating the APOEε4-linked increased AD risk or enhancing the APOEε2-linked AD protection. This Review summarizes this progress and highlights areas for future research towards the development of APOE-directed therapeutics.

Humanin variant P3S is associated with longevity in APOE4 carriers and resists APOE4-induced brain pathology

The APOE4 allele is recognized as a significant genetic risk factor to Alzheimer's disease (AD) and influences longevity. Nonetheless, some APOE4 carriers exhibit resistance to AD even in advanced age. Humanin, a mitochondrial-derived peptide comprising 24 amino acids, has variants linked to cognitive resilience and longevity. Our research uncovered a unique humanin variant, P3S, specifically enriched in centenarians with the APOE4 allele. Through in silico analyses and subsequent experimental validation, we demonstrated a strong affinity between humanin P3S and APOE4. Utilizing an APOE4-centric mouse model of amyloidosis (APP/PS1/APOE4), we observed that humanin P3S significantly attenuated brain amyloid-beta accumulation compared to the wild-type humanin. Transcriptomic assessments of mice treated with humanin P3S highlighted its potential mechanism involving the enhancement of amyloid beta phagocytosis. Additionally, in vitro studies corroborated humanin P3S's efficacy in promoting amyloid-beta clearance. Notably, in the temporal cortex of APOE4 carriers, humanin expression is correlated with genes associated with phagocytosis. Our findings suggest a role of the rare humanin variant P3S, especially prevalent among individuals of Ashkenazi descent, in mitigating amyloid beta pathology and facilitating phagocytosis in APOE4-linked amyloidosis, underscoring its significance in longevity and cognitive health among APOE4 carriers.

Application of CRISPR/Cas9 System in the Treatment of Alzheimer's Disease and Neurodegenerative Diseases

Alzheimer's, Parkinson's, and Huntington's are some of the most common neurological disorders, which affect millions of people worldwide. Although there have been many treatments for these diseases, there are still no effective treatments to treat or completely stop these disorders. Perhaps the lack of proper treatment for these diseases can be related to various reasons, but the poor results related to recent clinical research also prompted doctors to look for new treatment approaches. In this regard, various researchers from all over the world have provided many new treatments, one of which is CRISPR/Cas9. Today, the CRISPR/Cas9 system is mostly used for genetic modifications in various species. In addition, by using the abilities available in the CRISPR/Cas9 system, researchers can either remove or modify DNA sequences, which in this way can establish a suitable and useful treatment method for the treatment of genetic diseases that have undergone mutations. We conducted a non-systematic review of articles and study results from various databases, including PubMed, Medline, Web of Science, and Scopus, in recent years. and have investigated new treatment methods in neurodegenerative diseases with a focus on Alzheimer's disease. Then, in the following sections, the treatment methods were classified into three groups: anti-tau, anti-amyloid, and anti-APOE regimens. Finally, we discussed various applications of the CRISPR/Cas-9 system in Alzheimer's disease. Today, using CRISPR/Cas-9 technology, scientists create Alzheimer's disease models that have a more realistic phenotype and reveal the processes of pathogenesis; following the screening of defective genes, they establish treatments for this disease.

ApoE Mimic Peptide COG1410 Reduces Aβ Deposition and Improves Cognitive Function by Inducing the Transformation of A1/A2 Reactive Astrocytes and Increasing the BDNF Concentration in Brain of APP/PS1 Double Transgenic Mice

The main clinical manifestation of Alzheimer's disease is progressive cognitive decline, and its pathological features are β-amyloid (Aβ) deposition, neurofibrillary tangles, synaptic dysfunction and neuron death. Neuroinflammation is an important reason for the occurrence and development of AD, which is mainly manifested by the accumulation of activated microglia and reactive astrocytes. Apolipoprotein E (ApoE) is one of the most important apolipoprotein in the brain, which is related to metabolism, aggregation and toxicity of Aβ. However, the underlying mechanism needs to be further explored. In this study, we studied the effect of ApoE mimetic peptide COG1410 on spatial learning and memory functions, deposition of Aβ in the dentate gyrus (DG) of APP/PS1 transgenic mice, and the different effects of A1 and A2 subtypes of reactive astrocytes. Administration of COG1410 effectively improved performance in spatial learning and memory of APP/PS1 mice, reduced Aβ deposition and significantly reverted the ratio of A1/A2 reactive astrocytes, which could be associated with BDNF/TrkB signaling pathway. On the whole, the present findings suggest new possibility of using apolipoprotein E mimetic peptide to treat AD with potential effectiveness.

APOE4 is a Risk Factor and Potential Therapeutic Target for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease, the main pathological hallmark of which is the loss of neurons, resulting in cognitive and memory impairments. Sporadic late-onset AD is a prevalent form of the disease and the apolipoprotein E4 (APOE4) genotype is the strongest predictor of the disease development. The structural variations of APOE isoforms affect their roles in synaptic maintenance, lipid trafficking, energy metabolism, inflammatory response, and BBB integrity. In the context of AD, APOE isoforms variously control the key pathological elements of the disease, including Aβ plaque formation, tau aggregation, and neuroinflammation. Taking into consideration the limited number of therapy choices that can alleviate symptoms and have little impact on the AD etiology and progression to date, the precise research strategies guided by apolipoprotein E (APOE) polymorphisms are required to assess the potential risk of age-related cognitive decline in people carrying APOE4 genotype. In this review, we summarize the evidence implicating the significance of APOE isoforms on brain functions in health and pathology with the aim to identify the possible targets that should be addressed to prevent AD manifestation in individuals with the APOE4 genotype and to explore proper treatment strategies.

Roles of ApoE4 on the Pathogenesis in Alzheimer's Disease and the Potential Therapeutic Approaches

The Apolipoprotein E ε4 (ApoE ε4) allele, encoding ApoE4, is the strongest genetic risk factor for late-onset Alzheimer's disease (LOAD). Emerging epidemiological evidence indicated that ApoE4 contributes to AD through influencing β-amyloid (Aβ) deposition and clearance. However, the molecular mechanisms of ApoE4 involved in AD pathogenesis remains unclear. Here, we introduced the structure and functions of ApoE isoforms, and then we reviewed the potential mechanisms of ApoE4 in the AD pathogenesis, including the effect of ApoE4 on Aβ pathology, and tau phosphorylation, oxidative stress; synaptic function, cholesterol transport, and mitochondrial dysfunction; sleep disturbances and cerebrovascular integrity in the AD brains. Furthermore, we discussed the available strategies for AD treatments that target to ApoE4. In general, this review overviews the potential roles of ApoE4 in the AD development and suggests some therapeutic approaches for AD. ApoE4 is genetic risk of AD. ApoE4 is involved in the AD pathogenesis. Aβ deposition, NFT, oxidative stress, abnormal cholesterol, mitochondrial dysfunction and neuroinflammation could be observed in the brains with ApoE4. Targeting the interaction of ApoE4 with the AD pathology is available strategy for AD treatments.

Does the imbalance in the apolipoprotein E isoforms underlie the pathophysiological process of sporadic Alzheimer's disease?

Human apolipoprotein E (apoE) is a 299-amino acid secreted glycoprotein binding cholesterol and phospholipids, and with three common isoforms (APOE ε2, APOE ε3, and APOE ε4). The exact mechanism by which APOE gene variants increase/decrease Alzheimer's disease (AD) risk is not fully understood, but APOE isoforms differently affect brain homeostasis and neuroinflammation, blood-brain barrier (BBB) permeability, glial function, synaptogenesis, oral/gut microbiota, neural networks, amyloid beta (Aβ) deposition, and tau-mediated neurodegeneration. In this perspective, we propose a comprehensive interpretation of APOE-mediated effects within AD pathophysiology, describing some specific cellular, biochemical, and epigenetic mechanisms and updating the different APOE-targeting approaches being developed as potential AD therapies. Intracisternal adeno-associated viral-mediated delivery of APOE ε2 is being tested in AD APOE ε4/ε4 carriers, while APOE mimetics are being used in subjects with perioperative neurocognitive disorders. Other approaches including APOE ε4 antisense oligonucleotides, anti-APOE ε4 monoclonal antibodies, APOE ε4 structure correctors, and APOE-Aβ interaction inhibitors produced positive results in transgenic AD mouse models.

ApoE in Alzheimer’s disease: pathophysiology and therapeutic strategies

Alzheimer’s disease (AD) is the most common cause of dementia worldwide, and its prevalence is rapidly increasing due to extended lifespans. Among the increasing number of genetic risk factors identified, the apolipoprotein E (APOE) gene remains the strongest and most prevalent, impacting more than half of all AD cases. While the ε4 allele of the APOE gene significantly increases AD risk, the ε2 allele is protective relative to the common ε3 allele. These gene alleles encode three apoE protein isoforms that differ at two amino acid positions. The primary physiological function of apoE is to mediate lipid transport in the brain and periphery; however, additional functions of apoE in diverse biological functions have been recognized. Pathogenically, apoE seeds amyloid-β (Aβ) plaques in the brain with apoE4 driving earlier and more abundant amyloids. ApoE isoforms also have differential effects on multiple Aβ-related or Aβ-independent pathways. The complexity of apoE biology and pathobiology presents challenges to designing effective apoE-targeted therapeutic strategies. This review examines the key pathobiological pathways of apoE and related targeting strategies with a specific focus on the latest technological advances and tools.

HDL-like-Mediated Cell Cholesterol Trafficking in the Central Nervous System and Alzheimer's Disease Pathogenesis

The main aim of this work is to review the mechanisms via which high-density lipoprotein (HDL)-mediated cholesterol trafficking through the central nervous system (CNS) occurs in the context of Alzheimer’s disease (AD). Alzheimer’s disease is characterized by the accumulation of extracellular amyloid beta (Aβ) and abnormally hyperphosphorylated intracellular tau filaments in neurons. Cholesterol metabolism has been extensively implicated in the pathogenesis of AD through biological, epidemiological, and genetic studies, with the APOE gene being the most reproducible genetic risk factor for the development of AD. This manuscript explores how HDL-mediated cholesterol is transported in the CNS, with a special emphasis on its relationship to Aβ peptide accumulation and apolipoprotein E (ApoE)-mediated cholesterol transport. Indeed, we reviewed all existing works exploring HDL-like-mediated cholesterol efflux and cholesterol uptake in the context of AD pathogenesis. Existing data seem to point in the direction of decreased cholesterol efflux and the impaired entry of cholesterol into neurons among patients with AD, which could be related to impaired Aβ clearance and tau protein accumulation. However, most of the reviewed studies have been performed in cells that are not physiologically relevant for CNS pathology, representing a major flaw in this field. The ApoE4 genotype seems to be a disruptive element in HDL-like-mediated cholesterol transport through the brain. Overall, further investigations are needed to clarify the role of cholesterol trafficking in AD pathogenesis.

Tolerability and Pharmacokinetics of Single Escalating and Repeated Doses of CN-105 in Healthy Participants

PURPOSE

CN-105 is an IV, apolipoprotein E-mimetic pentapeptide. Preclinical studies have reported that CN-105 effectively down-regulates neuroinflammatory responses in microglia and mitigates neuronal excitotoxicity following acute brain injury. The CN-105 Phase I and II trials that have been done in the United States have demonstrated that CN-105 was well tolerated in US participants. Thus, the main objective of the present Phase I study was to investigate the tolerability and pharmacokinetic (PK) profiles of CN-105 in healthy Chinese participants.

METHODS

This randomized, double-blind, placebo-controlled, dose-escalation study was performed in healthy participants using sequential 30-minute IV administration of single and multiple doses of CN-105 (four times daily for 13 doses). Forty volunteers were randomly assigned, in an 8:2 ratio, to one of four dosing groups, receiving either CN-105 (0.03, 0.1, 0.3, or 1 mg/kg), or placebo. Serial blood samples were collected for the measurement of plasma concentrations of CN-105. Tolerability was also assessed.

FINDINGS

After single-dose administration, the plasma CN-105 concentration rapidly reached the peak by the end of infusion. The mean elimination half-life of CN-105 ranged from 2.3 to 3.6 hours. During single- and multiple-dosing paradigms, exposure to CN-105 (AUC) exhibited linear dependency on dose. Steady state was reached by the fourth dose, with minimal accumulation. The PK properties of CN-105 with single and multiple dosing were comparable to those observed in US participants. CN-105 was generally well tolerated in Chinese participants. A total of 13 adverse events were reported in 30% of subjects (12/40) at the 0.03 mg/kg (6/8), 0.1 mg/kg (1/8), 0.3 mg/kg (2/8), 1 mg/kg (0/8) doses and with placebo (3/8). All adverse events were mild or moderate in severity and self-limited, with no dose relationship observed.

IMPLICATIONS

CN-105 was well tolerated in these healthy Chinese participants at doses of 0.1 to 1 mg/kg with single and multiple IV administrations. The PK characteristics of CN-105 were comparable among Chinese and Western subjects. A Phase II study in patients with intracranial hemorrhage is being planned in China.

CLINICALTRIALS

gov identifiers: NCT02670824 and NCT03168581; Chinese Clinical Trial Registration identifier: CTR20202397.

Are apolipoprotein E fragments a promising new therapeutic target for Alzheimer’s disease?

Human apolipoprotein E (ApoE) is a 299-amino acid secreted glycoprotein that binds cholesterol and phospholipids. ApoE exists as three common isoforms (ApoE2, ApoE3, and ApoE4) and heterozygous carriers of the ε4 allele of the gene encoding ApoE (APOE) have a fourfold greater risk of developing Alzheimer’s disease (AD). The enzymes thrombin, cathepsin D, α-chymotrypsin-like serine protease, and high-temperature requirement serine protease A1 are responsible for ApoE proteolytic processing resulting in bioactive C-terminal-truncated fragments that vary depending on ApoE isoforms, brain region, aging, and neural injury. The objectives of the present narrative review were to describe ApoE processing, discussing current hypotheses about the potential role of various ApoE fragments in AD pathophysiology, and reviewing the current development status of different anti-ApoE drugs. The exact mechanism by which APOE gene variants increase/decrease AD risk and the role of ApoE fragments in the deposition are not fully understood, but APOE is known to directly affect tau-mediated neurodegeneration. ApoE fragments co-localize with neurofibrillary tangles and amyloid β (Aβ) plaques, and may cause neurodegeneration. Among anti-ApoE approaches, a fascinating strategy may be to therapeutically overexpress ApoE2 in APOE ε4/ε4 carriers through vector administration or liposomal delivery systems. Another approach involves reducing ApoE4 expression by intracerebroventricular antisense oligonucleotides that significantly decreased Aβ pathology in transgenic mice. Differences in the proteolytic processing of distinct ApoE isoforms and the use of ApoE fragments as mimetic peptides in AD treatment are also under investigation. Treatment with peptides that mimic the structural and biological properties of native ApoE may reduce Aβ deposition, tau hyperphosphorylation, and glial activation in mouse models of Aβ pathology. Alternative strategies involve the use of ApoE4 structure correctors, passive immunization to target a certain form of ApoE, conversion of the ApoE4 aminoacid sequence into that of ApoE3 or ApoE2, and inhibition of the ApoE-Aβ interaction.

Remembering your A, B, C's: Alzheimer's disease and ABCA1

The function of ATP binding cassette protein A1 (ABCA1) is central to cholesterol mobilization. Reduced ABCA1 expression or activity is implicated in Alzheimer's disease (AD) and other disorders. Therapeutic approaches to boost ABCA1 activity have yet to be translated successfully to the clinic. The risk factors for AD development and progression, including comorbid disorders such as type 2 diabetes and cardiovascular disease, highlight the intersection of cholesterol transport and inflammation. Upregulation of ABCA1 can positively impact APOE lipidation, insulin sensitivity, peripheral vascular and blood–brain barrier integrity, and anti-inflammatory signaling. Various strategies towards ABCA1-boosting compounds have been described, with a bias toward nuclear hormone receptor (NHR) agonists. These agonists display beneficial preclinical effects; however, important side effects have limited development. In particular, ligands that bind liver X receptor (LXR), the primary NHR that controls ABCA1 expression, have shown positive effects in AD mouse models; however, lipogenesis and unwanted increases in triglyceride production are often observed. The longstanding approach, focusing on LXRβ vs. LXRα selectivity, is over-simplistic and has failed. Novel approaches such as phenotypic screening may lead to small molecule NHR modulators that elevate ABCA1 function without inducing lipogenesis and are clinically translatable.

Emerging role of HDL in brain cholesterol metabolism and neurodegenerative disorders

High-density lipoproteins (HDLs play a key role in cholesterol homeostasis maintenance in the central nervous system (CNS), by carrying newly synthesized cholesterol from astrocytes to neurons, to support their lipid-related physiological functions. As occurs for plasma HDLs, brain lipoproteins are assembled through the activity of membrane cholesterol transporters, undergo remodeling mediated by specific enzymes and transport proteins, and finally deliver cholesterol to neurons by a receptor-mediated internalization process. A growing number of evidences indicates a strong association between alterations of CNS cholesterol homeostasis and neurodegenerative disorders, in particular Alzheimer's disease (AD), and a possible role in this relationship may be played by defects in brain HDL metabolism. In the present review, we summarize and critically examine the current state of knowledge on major modifications of HDL and HDL-mediated brain cholesterol transport in AD, by taking into consideration the individual steps of this process. We also describe potential and encouraging HDL-based therapies that could represent new therapeutic strategies for AD treatment. Finally, we revise the main plasma and brain HDL modifications in other neurodegenerative disorders including Parkinson's disease (PD), Huntington's disease (HD), and frontotemporal dementia (FTD).

Apolipoprotein E and Alzheimer's disease

Genetic variation in apolipoprotein E (APOE) influences Alzheimer's disease (AD) risk. APOE ε4 alleles are the strongest genetic risk factor for late onset sporadic AD. The AD risk is dose dependent, as those carrying one APOE ε4 allele have a 2-3-fold increased risk, while those carrying two ε4 alleles have a 10-15-fold increased risk. Individuals carrying APOE ε2 alleles have lower AD risk and those carrying APOE ε3 alleles have neutral risk. APOE is a lipoprotein which functions in lipid transport, metabolism, and inflammatory modulation. Isoform specific effects of APOE within the brain include alterations to Aβ, tau, neuroinflammation, and metabolism. Here we review the association of APOE with AD, the APOE isoform specific effects within brain and periphery, and potential therapeutics.

MicroRNA-455-5p/CPEB1 pathway mediates Aβ-related learning and memory deficits in a mouse model of Alzheimer's disease

Alzheimer's disease (AD), a common neurodegenerative disease, is the main cause of dementia, with cognitive decline as the core symptom observed during diagnosis. Synaptic loss may be the main cause of early cognitive dysfunction in AD, but the detailed mechanism is still unclear. In this study, we investigated the role of abnormal miR-455-5p/CPEB1 pathway in AD mouse model. We found that miR-455-5p was upregulated, while its downstream target, cytoplasmic polyadenylation element-binding 1 (CPEB1), was downregulated in the hippocampus of APP/PS1 mice at the age of 9 m. Abnormal miR-455-5p/CPEB1 pathway mediated cognitive deficits in APP/PS1 mice through suppressing α-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor expressions. And miR-455-5p suppression, CPEB1 overexpression or application of a peptide disrupting the miR-455-5p/CPEB1 interaction in CA1 of APP/PS1 mice rescued AD-like phenotypes in mice, including deficits in synaptic plasticity and memory. In conclusion, our results indicated that miRNA-455-5p/CPEB1 pathway mediated synaptic and memory deficits in Alzheimer's Disease through targeting on AMPARs, providing a potential therapeutic strategy for AD.

CN-105 in Participants with Acute Supratentorial Intracerebral Hemorrhage (CATCH) Trial

BACKGROUND

Endogenous apolipoprotein (apo) E mediates neuroinflammatory responses and recovery after brain injury. Exogenously administered apoE-mimetic peptides effectively penetrate the central nervous system compartment and downregulate acute inflammation. CN-105 is a novel apoE-mimetic pentapeptide with excellent evidence of functional and histological improvement in preclinical models of intracerebral hemorrhage (ICH). The CN-105 in participants with Acute supraTentorial intraCerebral Hemorrhage (CATCH) trial is a first-in-disease-state multicenter open-label trial evaluating safety and feasability of CN-105 administration in patients with acute primary supratentorial ICH.

METHODS

Eligible patients were aged 30-80 years, had confirmed primary supratentorial ICH, and were able to intiate CN-105 administration (1.0 mg/kg every 6 h for 72 h) within 12 h of symptom onset. A priori defined safety end points, including hematoma volume, pharmacokinetics, and 30-day neurological outcomes, were analyzed. For clinical outcomes, CATCH participants were compared 1:1 with a closely matched contemporary ICH cohort through random selection. Hematoma volumes determined from computed tomography images on days 0, 1, 2, and 5 and ordinal modified Rankin Scale score at 30 days after ICH were compared.

RESULTS

In 38 participants enrolled across six study sites in the United States, adverse events occurred at an expected rate without increase in hematoma expansion or neurological deterioration. CN-105 treatment had an odds ratio (95% confidence interval) of 2.69 (1.31-5.51) for lower 30-day modified Rankin Scale score, after adjustment for ICH score, sex, and race/ethnicity, as compared with a matched contemporary cohort.

CONCLUSIONS

CN-105 administration represents an excellent translational candidate for treatment of acute ICH because of its safety, dosing feasibility, favorable pharmacokinetics, and possible improvement in neurological recovery.

High-density lipoprotein in Alzheimer's disease: From potential biomarkers to therapeutics

The inverse correlation between high-density lipoprotein (HDL) levels in vivo and the risk of Alzheimer's disease (AD) has become an inspiration for HDL-inspired AD therapy, including plain HDL and various intelligent HDL-based drug delivery systems. In this review, we will focus on the two endogenous HDL subtypes in the central nervous system (CNS), apolipoprotein E-based HDL (apoE-HDL) and apolipoprotein A-I-based HDL (apoA-I-HDL), especially their influence on AD pathophysiology to reveal HDL's potential as biomarkers for risk prediction, and summarize the relevant therapeutic mechanisms to propose possible treatment strategies. We will emphasize the latest advances of HDL as therapeutics (plain HDL and HDL-based drug delivery systems) to discuss the potential for AD therapy and review innovative techniques in the preparation of HDL-based nanoplatforms to provide a basis for the rational design and future development of anti-AD drugs.

Some Candidate Drugs for Pharmacotherapy of Alzheimer's Disease

Alzheimer’s disease (AD; progressive neurodegenerative disorder) is associated with cognitive and functional impairment with accompanying neuropsychiatric symptoms. The available pharmacological treatment is of a symptomatic nature and, as such, it does not modify the cause of AD. The currently used drugs to enhance cognition include an N-methyl-d-aspartate receptor antagonist (memantine) and cholinesterase inhibitors. The PUBMED, Medical Subject Heading and Clinical Trials databases were used for searching relevant data. Novel treatments are focused on already approved drugs for other conditions and also searching for innovative drugs encompassing investigational compounds. Among the approved drugs, we investigated, are intranasal insulin (and other antidiabetic drugs: liraglitude, pioglitazone and metformin), bexarotene (an anti-cancer drug and a retinoid X receptor agonist) or antidepressant drugs (citalopram, escitalopram, sertraline, mirtazapine). The latter, especially when combined with antipsychotics (for instance quetiapine or risperidone), were shown to reduce neuropsychiatric symptoms in AD patients. The former enhanced cognition. Procognitive effects may be also expected with dietary antioxidative and anti-inflammatory supplements—curcumin, myricetin, and resveratrol. Considering a close relationship between brain ischemia and AD, they may also reduce post-brain ischemia neurodegeneration. An investigational compound, CN-105 (a lipoprotein E agonist), has a very good profile in AD preclinical studies, and its clinical trial for postoperative dementia is starting soon.

APOE and Alzheimer's Disease: From Lipid Transport to Physiopathology and Therapeutics

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder characterized by extracellular amyloid β (Aβ) and intraneuronal tau protein aggregations. One risk factor for developing AD is the APOE gene coding for the apolipoprotein E protein (apoE). Humans have three versions of APOE gene: ε2, ε3, and ε4 allele. Carrying the ε4 allele is an AD risk factor while carrying the ε2 allele is protective. ApoE is a component of lipoprotein particles in the plasma at the periphery, as well as in the cerebrospinal fluid (CSF) and in the interstitial fluid (ISF) of brain parenchyma in the central nervous system (CNS). ApoE is a major lipid transporter that plays a pivotal role in the development, maintenance, and repair of the CNS, and that regulates multiple important signaling pathways. This review will focus on the critical role of apoE in AD pathogenesis and some of the currently apoE-based therapeutics developed in the treatment of AD.

APOE and Alzheimer's disease: advances in genetics, pathophysiology, and therapeutic approaches

The APOE ε4 allele remains the strongest genetic risk factor for sporadic Alzheimer's disease and the APOE ε2 allele the strongest genetic protective factor after multiple large scale genome-wide association studies and genome-wide association meta-analyses. However, no therapies directed at APOE are currently available. Although initial studies causally linked APOE with amyloid-β peptide aggregation and clearance, over the past 5 years our understanding of APOE pathogenesis has expanded beyond amyloid-β peptide-centric mechanisms to tau neurofibrillary degeneration, microglia and astrocyte responses, and blood-brain barrier disruption. Because all these pathological processes can potentially contribute to cognitive impairment, it is important to use this new knowledge to develop therapies directed at APOE. Several therapeutic approaches have been successful in mouse models expressing human APOE alleles, including increasing or reducing APOE levels, enhancing its lipidation, blocking the interactions between APOE and amyloid-β peptide, and genetically switching APOE4 to APOE3 or APOE2 isoforms, but translation to human clinical trials has proven challenging.

The Role of HDL and HDL Mimetic Peptides as Potential Therapeutics for Alzheimer's Disease

The role of high-density lipoproteins (HDL) in the cardiovascular system has been extensively studied and the cardioprotective effects of HDL are well established. As HDL particles are formed both in the systemic circulation and in the central nervous system, the role of HDL and its associated apolipoproteins in the brain has attracted much research interest in recent years. Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder and the leading cause of dementia worldwide, for which there currently exists no approved disease modifying treatment. Multiple lines of evidence, including a number of large-scale human clinical studies, have shown a robust connection between HDL levels and AD. Low levels of HDL are associated with increased risk and severity of AD, whereas high levels of HDL are correlated with superior cognitive function. Although the mechanisms underlying the protective effects of HDL in the brain are not fully understood, many of the functions of HDL, including reverse lipid/cholesterol transport, anti-inflammation/immune modulation, anti-oxidation, microvessel endothelial protection, and proteopathy modification, are thought to be critical for its beneficial effects. This review describes the current evidence for the role of HDL in AD and the potential of using small peptides mimicking HDL or its associated apolipoproteins (HDL-mimetic peptides) as therapeutics to treat AD.