Reduction of brain beta-amyloid (Abeta) by fluvastatin, a hydroxymethylglutaryl-CoA reductase inhibitor, through increase in degradation of amyloid precursor protein C-terminal fragments (APP-CTFs) and Abeta clearance

Blood-Brain Barrier (BBB) Dysfunction in CNS Diseases: Paying Attention to Pericytes

BACKGROUND

Dysfunction of the blood-brain barrier (BBB) is an important pathological mechanism in central nervous system (CNS) diseases and can trigger a series of pathological reactions, such as neuroinflammatory responses, oxidative stress, immune infiltration, etc., thereby worsening brain damage. However, pericytes are often overlooked by researchers, and no review research has yet summarized the mechanism by which pericytes contribute to BBB dysfunction in CNS diseases.

RESULTS

Therefore, this review explores the pathophysiology of BBB dysfunction in CNS diseases and provides a detailed account of the biological characteristics of pericytes, especially the controversy over their biomarkers. Subsequently, we review the role of pericytes in CNS diseases such as Alzheimer's disease, vascular dementia, multiple sclerosis, ischemic stroke, and hemorrhagic stroke, with a particular focus on the role of pericytes in BBB dysfunction. In addition, we also discuss treatments based on pericytes, such as regenerative medicine that induces pericyte differentiation and Pericyte-Extracellular Vesicles.

CONCLUSIONS

This review aims to provide a more comprehensive understanding and guidance on the role of pericytes in BBB dysfunction in CNS diseases and serve clinical treatment.

The blood-brain barrier as a treatment target for neurodegenerative disorders

INTRODUCTION

The blood-brain barrier (BBB) is a vascular endothelial membrane which restricts entry of toxins, cells, and microorganisms into the brain. At the same time, the BBB supplies the brain with nutrients, key substrates for DNA and RNA synthesis, and regulatory molecules, and removes metabolic waste products from brain to blood. BBB breakdown and/or dysfunction have been shown in neurogenerative disorders including Alzheimer's disease (AD). Current data suggests that these BBB changes may initiate and/or contribute to neuronal, synaptic, and cognitive dysfunction, and possibly other aspects of neurodegenerative processes.

AREAS COVERED

We first briefly review recent studies uncovering molecular composition of brain microvasculature and examine the BBB as a possible therapeutic target in neurodegenerative disorders with a focus on AD. Current strategies aimed at protecting and/or restoring altered BBB functions are considered. The relevance of BBB-directed approaches to improve neuronal and synaptic function, and to slow progression of neurodegenerative processes are also discussed. Lastly, we review recent advancements in drug delivery across the BBB.

EXPERT OPINION

BBB breakdown and/or dysfunction can significantly affect neuronal and synaptic function and neurodegenerative processes. More attention should focus on therapeutics to preserve or restore BBB functions when considering treatments of neurodegenerative diseases and AD.

Unraveling the Role of LRP1 in Alzheimer's Disease: A Focus on Aβ Clearance and the Liver-Brain Axis

Alzheimer's disease (AD) is the most prevalent form of dementia, significantly contributing to the global health burden. The progressive accumulation of amyloid-beta (Aβ) plaques and tau tangles triggers neuroinflammation, oxidative stress, and neuronal damage, highlighting the critical need for effective clearance mechanisms. Recent research has identified low-density lipoprotein receptor-related protein 1 (LRP1) as a key factor in the regulation of Aβ clearance, neuroinflammation, and blood-brain barrier integrity, particularly in relation to the liver-brain axis. This review provides a comprehensive examination of the role of LRP1 in AD, focusing on its expression in the brain and liver, its contribution to Aβ metabolism, and its potential as a therapeutic target. Using a systematic literature review, LRP1's multifaceted roles across various biological processes were explored, including its involvement in Aβ transport, clearance via the liver, and modulation of neuroinflammation. Additionally, the impact of physical exercise, pharmacological interventions, and dietary factors on LRP1 expression levels was investigated, elucidating how these approaches may enhance Aβ clearance. The findings demonstrate that LRP1 expression decreases progressively as AD advances, and that augmenting LRP1 activity-particularly through exercise and drug therapies-can improve Aβ clearance and reduce neuroinflammatory responses. Furthermore, LRP1's involvement in the liver-brain axis reveals its broader systemic role in AD pathology. In conclusion, targeting LRP1 offers a promising avenue for AD prevention and treatment, providing new insights into the therapeutic potential of enhancing Aβ clearance pathways through the liver-brain axis.

The Cross-Talk Between the Peripheral and Brain Cholesterol Metabolisms

Cholesterol is an essential element for the development and normal function of the central nervous system. While peripheral cholesterol is influenced by liver metabolism and diet, brain cholesterol metabolism takes place in an isolated system due to the impermeability of the blood-brain barrier (BBB). However, cross-talk occurs between the brain and periphery, specifically through metabolites such as oxysterols that play key roles in regulating cholesterol balance. Several neurodegenerative conditions such as Alzheimer's disease or Parkinson's disease are considered to be affected by the loss of this balance. Also, the treatment of hypercholesterolemia needs to consider these discrete interferences between brain and peripheral cholesterol and the possible implications of each therapeutic approach. This is particularly important because of 27-hydroxycholesterol and 24-hydroxycholesterol, which can cross the BBB and are involved in cholesterol metabolism. This paper examines the metabolic pathways of cholesterol metabolism in the brain and periphery and focuses on the complex cross-talk between these metabolisms. Also, we emphasize the regulatory role of the BBB and the need for an integrated approach to cholesterol management.

Lipidome disruption in Alzheimer's disease brain: detection, pathological mechanisms, and therapeutic implications

Alzheimer's disease (AD) is among the most devastating neurodegenerative disorders with limited treatment options. Emerging evidence points to the involvement of lipid dysregulation in the development of AD. Nevertheless, the precise lipidomic landscape and the mechanistic roles of lipids in disease pathology remain poorly understood. This review aims to highlight the significance of lipidomics and lipid-targeting approaches in the diagnosis and treatment of AD. We summarized the connection between lipid dysregulation in the human brain and AD at both genetic and lipid species levels. We briefly introduced lipidomics technologies and discussed potential challenges and areas of future advancements in the lipidomics field for AD research. To elucidate the central role of lipids in converging multiple pathological aspects of AD, we reviewed the current knowledge on the interplay between lipids and major AD features, including amyloid beta, tau, and neuroinflammation. Finally, we assessed the progresses and obstacles in lipid-based therapeutics and proposed potential strategies for leveraging lipidomics in the treatment of AD.

Amyloid-beta metabolism in age-related neurocardiovascular diseases

Epidemiological evidence suggests the presence of common risk factors for the development and prognosis of both cardio- and cerebrovascular diseases, including stroke, Alzheimer's disease, vascular dementia, heart, and peripheral vascular diseases. Accumulation of harmful blood signals may induce organotypic endothelial dysfunction affecting blood-brain barrier function and vascular health in age-related diseases. Genetic-, age-, lifestyle- or cardiovascular therapy-associated imbalance of amyloid-beta (Aβ) peptide metabolism in the brain and periphery may be the missing link between age-related neurocardiovascular diseases. Genetic polymorphisms of genes related to Aβ metabolism, lifestyle modifications, drugs used in clinical practice, and Aβ-specific treatments may modulate Aβ levels, affecting brain, vascular, and cardiac diseases. This narrative review elaborates on the effects of interventions on Aβ metabolism in the brain, cerebrospinal fluid, blood, and peripheral heart or vascular tissues. Implications for clinical applicability, gaps in knowledge, and future perspectives of Aβ as the link among age-related neurocardiovascular diseases are also discussed.

Unraveling APOE4's Role in Alzheimer's Disease: Pathologies and Therapeutic Strategies

Alzheimer's disease (AD), the most common kind of dementia worldwide, is characterized by elevated levels of the amyloid-β (Aβ) peptide and hyperphosphorylated tau protein in the neurons. The complexity of AD makes the development of treatments infamously challenging. Apolipoprotein E (APOE) genes's ε4 allele is one of the main genetic risk factors for AD. While the APOE gene's ε4 allele considerably increases the chance of developing AD, the ε2 allele is protective compared to the prevalent ε3 variant. It is fiercely discussed how APOE affects the development and course of disease since it has a variety of activities that influence both neuronal and non-neuronal cells. ApoE4 contributes to the formation of tau tangles, deposition of Aβ, neuroinflammation, and other processes. Four decades of research have provided a significant understanding of the structure of APOE and how this may affect the neuropathology and pathogenesis of AD. APOE is a crucial lipid transporter essential for the growth of the central nervous system (CNS), upkeep, and repair. The mechanisms by which APOE contributes to the pathophysiology of AD are still up for discussion, though. Evidence suggests that APOE affects the brain's clearance and deposition of Aβ. Additionally, APOE has Aβ-independent pathways in AD, which has led to the identification of new functions for APOE, including mitochondrial dysfunction. This study summarizes important studies that describe how APOE4 affects well-known AD pathologies, including tau pathology, Aβ, neuroinflammation, and dysfunction of neural networks. This study also envisions some of the therapeutic approaches being used to target APOE4 in the hopes of preventing or treating AD.

Low-Density Lipoprotein Receptor-Related Protein 1 as a Potential Therapeutic Target in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease impacting the lives of millions of people worldwide. The formation of amyloid β (Aβ) plagues in the brain is the main pathological hallmark of AD. The Aβ deposits are formed due to the imbalance between the production and Aβ clearance in the brain and across the blood-brain barrier (BBB). In this respect, low-density lipoprotein receptor-related protein 1 (LRP1) plays a significant role by mediating both brain Aβ production and clearance. Due to its important role in AD pathogenesis, LRP1 is considered an attractive drug target for AD therapies. In the present review, we summarize the current knowledge about the role of LRP1 in AD pathogenesis as well as recent findings on changes in LRP1 expression and function in AD. Finally, we discuss the advances in utilizing LRP1 as a drug target for AD treatments as well as future perspectives on LRP1 research.

Targeting dysregulated lipid metabolism for the treatment of Alzheimer's disease and Parkinson's disease: Current advancements and future prospects

Alzheimer's and Parkinson's diseases are two of the most frequent neurological diseases. The clinical features of AD are memory decline and cognitive dysfunction, while PD mainly manifests as motor dysfunction such as limb tremors, muscle rigidity abnormalities, and slow gait. Abnormalities in cholesterol, sphingolipid, and glycerophospholipid metabolism have been demonstrated to directly exacerbate the progression of AD by stimulating Aβ deposition and tau protein tangles. Indirectly, abnormal lipids can increase the burden on brain vasculature, induce insulin resistance, and affect the structure of neuronal cell membranes. Abnormal lipid metabolism leads to PD through inducing accumulation of α-syn, dysfunction of mitochondria and endoplasmic reticulum, and ferroptosis. Great progress has been made in targeting lipid metabolism abnormalities for the treatment of AD and PD in recent years, like metformin, insulin, peroxisome proliferator-activated receptors (PPARs) agonists, and monoclonal antibodies targeting apolipoprotein E (ApoE). This review comprehensively summarizes the involvement of dysregulated lipid metabolism in the pathogenesis of AD and PD, the application of Lipid Monitoring, and emerging lipid regulatory drug targets. A better understanding of the lipidological bases of AD and PD may pave the way for developing effective prevention and treatment methods for neurodegenerative disorders.

Glymphatic pathway: An emerging perspective in the pathophysiology of neurodegenerative diseases

The central nervous system (CNS) is widely recognized as the only organ system without lymphatic capillaries to promote the removal of interstitial metabolic by-products. Thus, the newly identified glymphatic system which provides a pseudolymphatic activity in the nervous system has been focus of latest research in neurosciences. Also, findings reported that, sleep stimulates the elimination actions of glymphatic system and is linked to normal brain homeostatis. The CNS is cleared of potentially hazardous compounds via the glymphatic system, particularly during sleep. Any age-related alterations in brain functioning and pathophysiology of various neurodegenerative illnesses indicates the disturbance of the brain's glymphatic system. In this context, β-amyloid as well as tau leaves the CNS through the glymphatic system, it's functioning and CSF discharge markedly altered in elderly brains as per many findings. Thus, glymphatic failure may have a potential mechanism which may be therapeutically targetable in several neurodegenerative and age-associated cognitive diseases. Therefore, there is an urge to focus for more research into the connection among glymphatic system and several potential brain related diseases. Here, in our current review paper, we reviewed current research on the glymphatic system's involvement in a number of prevalent neurodegenerative and neuropsychiatric diseases and, we also discussed several therapeutic approaches, diet and life style modifications which might be used to acquire a more thorough performance and purpose of the glymphatic system to decipher novel prospects for clinical applicability for the management of these diseases.

Lipid rafts disruption by statins negatively impacts the interaction between SARS-CoV-2 S1 subunit and ACE2 in intestinal epithelial cells

The causative agent of the COVID-19 pandemic, SARS-CoV-2, is a virus that targets mainly the upper respiratory tract. However, it can affect other systems such as the gastrointestinal (GI) tract. Therapeutic strategies for this virus are still inconclusive and understanding its entry mechanism is important for finding effective treatments. Cholesterol is an important constituent in the structure of cellular membranes that plays a crucial role in a variety of cellular events. In addition, it is important for the infectivity and pathogenicity of several viruses. ACE2, the main receptor of SARS-CoV-2, is associated with lipid rafts which are microdomains composed of cholesterol and sphingolipids. In this study, we investigate the role of statins, lipid-lowering drugs, on the trafficking of ACE2 and the impact of cholesterol modulation on the interaction of this receptor with S1 in Caco-2 cells. The data show that fluvastatin and simvastatin reduce the expression of ACE2 to variable extents, impair its association with lipid rafts and sorting to the brush border membrane resulting in substantial reduction of its interaction with the S1 subunit of the spike protein. By virtue of the substantial effects of statins demonstrated in our study, these molecules, particularly fluvastatin, represent a promising therapeutic intervention that can be used off-label to treat SARS-CoV-2.

Does statin use affect amyloid beta deposition and brain metabolism?

BACKGROUND

There are contradictory findings regarding the effect of statin drugs on amyloid β (Aβ) deposition as one of the main hallmarks of Alzheimer's disease (AD), along with tau pathology. We aimed to longitudinally investigate the therapeutic and preventive role of statin drugs by examining the brain Aβ deposition and metabolism rate in AD, mild cognitive impairment (MCI), and healthy controls (HC).

METHODS

The data of 828 subjects including 178 HC, 492 MCI, and 158 AD individuals were obtained from ADNI. The baseline and longitudinal [18 F] AV45 and 18-fluorodeoxyglucose (FDG) PET standard uptake value ratio (SUVR) measures were investigated among statin users and non-users.

RESULTS

Our results showed that there is no significant difference in baseline Aβ deposition and metabolism rate between statin users and non-users among HC, MCI, and AD subjects. While there was no significant effect of statin on metabolism rate, there was a significant difference in Aβ deposition change after 4 years (from baseline) between statin users and non-users within HC subjects (p = 0.011). The change of Aβ deposition at 4 years from baseline was -2.0 ± 6.3% for statin users and 1.4 ± 4.7% for non-users. There was no significant association between statin duration use with baseline and longitudinal Aβ deposition and metabolism rate. However, statin dosage was significantly associated with Aβ deposition in 2 years (r = -0.412, p = 0.021) in the HC group. Moreover, our analysis showed a significant correlation between total statin exposure (duration×dosage) and Aβ deposition in 2 years visit (r = -0.198, p = 0.037) in HC subjects. Furthermore, we investigated the longitudinal changes within each group of statin users and non-users separately in linear mixed models. Our findings showed that there are no significant changes in AV45 and FDG SUVR among both groups.

CONCLUSION

The present longitudinal analysis revealed that using statins might be beneficial in slowing down or stabilizing the Aβ deposition due to aging in subjects without cognitive impairment. However, once the clinical symptoms of cognitive impairment appear, statins fail to slow down Aβ deposition. Overall, our findings revealed that statin users might have slower Aβ aggregation than non-users.

Nucleic acid drug vectors for diagnosis and treatment of brain diseases

Nucleic acid drugs have the advantages of rich target selection, simple in design, good and enduring effect. They have been demonstrated to have irreplaceable superiority in brain disease treatment, while vectors are a decisive factor in therapeutic efficacy. Strict physiological barriers, such as degradation and clearance in circulation, blood-brain barrier, cellular uptake, endosome/lysosome barriers, release, obstruct the delivery of nucleic acid drugs to the brain by the vectors. Nucleic acid drugs against a single target are inefficient in treating brain diseases of complex pathogenesis. Differences between individual patients lead to severe uncertainties in brain disease treatment with nucleic acid drugs. In this Review, we briefly summarize the classification of nucleic acid drugs. Next, we discuss physiological barriers during drug delivery and universal coping strategies and introduce the application methods of these universal strategies to nucleic acid drug vectors. Subsequently, we explore nucleic acid drug-based multidrug regimens for the combination treatment of brain diseases and the construction of the corresponding vectors. In the following, we address the feasibility of patient stratification and personalized therapy through diagnostic information from medical imaging and the manner of introducing contrast agents into vectors. Finally, we take a perspective on the future feasibility and remaining challenges of vector-based integrated diagnosis and gene therapy for brain diseases.

Reconsidering the role of blood-brain barrier in Alzheimer's disease: From delivery to target

The existence of a selective blood-brain barrier (BBB) and neurovascular coupling are two unique central nervous system vasculature features that result in an intimate relationship between neurons, glia, and blood vessels. This leads to a significant pathophysiological overlap between neurodegenerative and cerebrovascular diseases. Alzheimer's disease (AD) is the most prevalent neurodegenerative disease whose pathogenesis is still to be unveiled but has mostly been explored under the light of the amyloid-cascade hypothesis. Either as a trigger, bystander, or consequence of neurodegeneration, vascular dysfunction is an early component of the pathological conundrum of AD. The anatomical and functional substrate of this neurovascular degeneration is the BBB, a dynamic and semi-permeable interface between blood and the central nervous system that has consistently been shown to be defective. Several molecular and genetic changes have been demonstrated to mediate vascular dysfunction and BBB disruption in AD. The isoform ε4 of Apolipoprotein E is at the same time the strongest genetic risk factor for AD and a known promoter of BBB dysfunction. Low-density lipoprotein receptor-related protein 1 (LRP-1), P-glycoprotein, and receptor for advanced glycation end products (RAGE) are examples of BBB transporters implicated in its pathogenesis due to their role in the trafficking of amyloid-β. This disease is currently devoid of strategies that change the natural course of this burdening illness. This unsuccess may partly be explained by our misunderstanding of the disease pathogenesis and our inability to develop drugs that are effectively delivered to the brain. BBB may represent a therapeutic opportunity as a target itself or as a therapeutic vehicle. In this review, we aim to explore the role of BBB in the pathogenesis of AD including the genetic background and detail how it can be targeted in future therapeutic research.

Targeting Alzheimer's Disease: The Critical Crosstalk between the Liver and Brain

Alzheimer's disease (AD), an age-related neurodegenerative disorder, is currently incurable. Imbalanced amyloid-beta (Aβ) generation and clearance are thought to play a pivotal role in the pathogenesis of AD. Historically, strategies targeting Aβ clearance have typically focused on central clearance, but with limited clinical success. Recently, the contribution of peripheral systems, particularly the liver, to Aβ clearance has sparked an increased interest. In addition, AD presents pathological features similar to those of metabolic syndrome, and the critical involvement of brain energy metabolic disturbances in this disease has been recognized. More importantly, the liver may be a key regulator in these abnormalities, far beyond our past understanding. Here, we review recent animal and clinical findings indicating that liver dysfunction represents an early event in AD pathophysiology. We further propose that compromised peripheral Aβ clearance by the liver and aberrant hepatic physiological processes may contribute to AD neurodegeneration. The role of a hepatic synthesis product, fibroblast growth factor 21 (FGF21), in the management of AD is also discussed. A deeper understanding of the communication between the liver and brain may lead to new opportunities for the early diagnosis and treatment of AD.

Draft genome of Gongronella butleri reveals the genes contributing to its biodegradation potential

BACKGROUND

Gongronella butleri is a fungus with many industrial applications including the composting of solid biowaste. Kerala Agricultural University, India, has developed a microbial consortium of which GbKAU strain of G. butleri is a major component. Even with great industrial significance, genome of this fungus is not published, and the genes and pathways contributing to the applications are not understood. This study had the objective to demonstrate the solid biowaste decomposing capability of the strain, to sequence and annotate the genome, and to reveal the genes and pathways contributing to its biodegradation potential.

RESULTS

Strain GbKAU of G. butleri isolated and purified from the organic compost was found to produce higher levels of laccase and amylase, compared to Bacillus subtilis which is being widely used in biosolid waste management. Both were shown to be equally efficient in the in vivo composting capabilities. Whole genome sequencing has given ~11 million paired-end good quality reads. De novo assembly using dual-fold approach has yielded 44,639 scaffolds with draft genome size of 29.8 Mb. A total of 11,428 genes were predicted and classified into 359 groups involved in diverse pathways, of which 14 belonged to the enzymes involved in the degradation of macromolecules. Seven previously sequenced strains of the fungus were assembled and annotated. A direct comparison showed that the number of genes present in those strains was comparable to our strain, while all the important biodegrading genes were conserved across the genomes. Gene Ontology analysis had classified the genes according to their molecular function, biological process, and cellular component. A total of 104,718 SSRs were mined and classified to mono- to hexa-nucleotide repeats. The variant analysis in comparison with the closely related genus Cunninghamella has revealed 1156 variants.

CONCLUSIONS

Apart from demonstrating the biodegradation capabilities of the GbKAU strain of G. butleri, the genome of this industrially important fungus was sequenced, de novo assembled, and annotated. GO analysis has classified the genes based on their functions, and the genes involved in biodegradation were revealed. Biodegradation potential, genome features in comparison with other strains, and the functions of the identified genes are discussed.

Perspectives on the Role of APOE4 as a Therapeutic Target for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease that is coupled with chronic cognitive dysfunction. AD cases are mostly late onset, and genetic risk factors like the Apolipoprotein E (APOE) play a key role in this process. APOE ɛ2, APOE ɛ3, and APOE ɛ4 are three key alleles in the human APOE gene. For late onset, APOE ɛ4 has the most potent risk factor while APOE ɛ2 plays a defensive role. Several studies suggests that APOE ɛ4 causes AD via different processes like neurofibrillary tangle formation by amyloid-β accumulation, exacerbated neuroinflammation, cerebrovascular disease, and synaptic loss. But the pathway is still unclear that which actions of APOE ɛ4 lead to AD development. Since APOE was found to contribute to many AD pathways, targeting APOE ɛ4 can lead to a hopeful plan of action in development of new drugs to target AD. In this review, we focus on recent studies and perspectives, focusing on APOE ɛ4 as a key molecule in therapeutic strategies.

An evidence-based review of neuronal cholesterol role in dementia and statins as a pharmacotherapy in reducing risk of dementia

INTRODUCTION

Dementia is a progressive neurodegenerative disorder impairing memory and cognition. Alzheimer's Disease, followed by vascular dementia - the most typical form. Risk factors for vascular dementia include diabetes, cardiovascular disease, hyperlipidemia. Lipids' levels are significantly associated with vascular changes in the brain.

AREAS COVERED

The present article reviews the cholesterol metabolism in the brain, which includes: the synthesis, transport, storage, and elimination process. Additionally, it reviews the role of cholesterol in the pathogenesis of dementia and statin as a therapeutic intervention in dementia. In addition to the above, it further reviews evidence in support of as well as against statin therapy in dementia, recent updates of statin pharmacology, and demerits of use of statin pharmacotherapy.

EXPERT OPINION

Amyloid-β peptides and intraneuronal neurofibrillary tangles are markers of Alzheimer's disease. Evidence shows cholesterol modulates the functioning of enzymes associated with Amyloid-β peptide processing and synthesis. Lowering cholesterol using statin may help prevent or delay the progression of dementia. This paper reviews the role of statin in dementia and recommends extensive future studies, including genetic research, to obtain a precise medication approach for patients with dementia.

Interactions of Lipids, Lipoproteins, and Apolipoproteins with the Blood-Brain Barrier

Lipids and lipoproteins are a diverse group of substances and their interactions with the blood-brain barrier (BBB) is similarly diverse. Some lipoproteins such as high density lipoprotein (HDL), apolipoprotein (apo) A-I, apoJ, some free fatty acids, and triglycerides cross the BBB whereas others such as apoE do not. Some forms of cholesterol can cross the BBB and others do not. Lipids can have effects on BBB preservation and function: HDL may protect the BBB during multiple sclerosis, cholesterol can disrupt the BBB, and triglycerides inhibit the transport of leptin across the BBB and the activation of the hypothalamic leptin receptor. ApoE is associated with many effects on the BBB, with the specific isoform apoE4 having detrimental effects. In summary, the diverse ways in which lipids, lipoproteins, and apolipoproteins interact with the BBB is important in both health and disease.

Hyperbaric oxygen therapy alleviates vascular dysfunction and amyloid burden in an Alzheimer's disease mouse model and in elderly patients

Vascular dysfunction is entwined with aging and in the pathogenesis of Alzheimer's disease (AD) and contributes to reduced cerebral blood flow (CBF) and consequently, hypoxia. Hyperbaric oxygen therapy (HBOT) is in clinical use for a wide range of medical conditions. In the current study, we exposed 5XFAD mice, a well-studied AD model that presents impaired cognitive abilities, to HBOT and then investigated the therapeutical effects using two-photon live animal imaging, behavioral tasks, and biochemical and histological analysis. HBOT increased arteriolar luminal diameter and elevated CBF, thus contributing to reduced hypoxia. Furthermore, HBOT reduced amyloid burden by reducing the volume of pre-existing plaques and attenuating the formation of new ones. This was associated with changes in amyloid precursor protein processing, elevated degradation and clearance of Aß protein and improved behavior of 5XFAD mice. Hence, our findings are consistent with the effects of HBOT being mediated partially through a persistent structural change in blood vessels that reduces brain hypoxia. Motivated by these findings, we exposed elderly patients with significant memory loss at baseline to HBOT and observed an increase in CBF and improvement in cognitive performances. This study demonstrates HBOT efficacy in hypoxia-related neurological conditions, particularly in AD and aging.

Traceable Nano-Biohybrid Complexes by One-Step Synthesis as CRISPR-Chem Vectors for Neurodegenerative Diseases Synergistic Treatment

Abnormal protein aggregations are essential pathological features of neurodegenerative diseases. Eliminating while inhibiting the regeneration of these protein aggregates is considered an effective treatment strategy. Herein, the CRISPR/Cas9 gene-editing tool is employed to inhibit the regeneration of disease-related proteins, while chemical drugs are applied to eliminate the proteins that are produced. To efficiently deliver CRISPR-chem drugs into brain lesions, traceable nano-biohybrid complexes (F-TBIO) are constructed by one-step synthesis and CRISPR/Cas9 plasmids (CF-TBIO) are loaded in a controllable manner. CF-TBIO can knock out the BACE1 gene and reduce the burden of amyloid-β, and thereby significantly improve the cognitive abilities of 2xTg-AD mice. In particular, by prolonging the dosing interval, the pathological damage and behavioral abilities of 2xTg-AD mice are still significantly improved. During the therapeutic process, CF-TBIO with a high relaxation rate provides accurate imaging signals in the complex brain physiological environment. The finding shows that CF-TBIO has great potential to serve as a CRISPR-chem drug-delivery platform for neurodegenerative diseases therapy.

Environmental Risk Factors for Progressive Supranuclear Palsy

Typically, progressive supranuclear palsy (PSP) is clinically characterized by slow vertical saccades or supranuclear gaze palsy, levodopa-resistant parkinsonism with predominant axial symptoms, and cognitive executive impairment. Over the past decades, various PSP phenotypes, including PSP with predominant parkinsonism, PSP with corticobasal syndrome, PSP with progressive gait freezing, and PSP with predominant frontal dysfunction, have been identified from pathologically confirmed cases. Expanding knowledge led to new diagnostic criteria for PSP that with increased disease awareness led to increased PSP prevalence estimates. The identification of environmental and modifiable risk factors creates an opportunity to intervene and delay the onset of PSP or slow disease progression. To date, despite the increasing number of publications assessing risk factors for PSP, few articles have focused on environmental and lifestyle risk factors for this disorder. In this article, we reviewed the literature investigating the relationship between PSP and several environmental and other modifiable lifestyle risk factors. In our review, we found that exposures to toxins related to diet, metals, well water, and hypertension were associated with increased PSP risk. In contrast, higher education and statins may be protective. Further case-control studies are encouraged to determine the exact role of these factors in the etiopathogenesis of PSP, which in turn would inform strategies to prevent and reduce the burden of PSP.

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.

Effect of statins on amyloidosis in the rodent models of Alzheimer's disease: Evidence from the preclinical meta-analysis

INTRODUCTION

Previous studies have shown contrasting results in determining efficacy of statins against amyloid beta accumulation. The aim of this study was to assess the impact of statin in AD.

METHOD

We searched PubMed and Embase for relevant preclinical studies. A meta-analysis of the statin's efficacy on amyloidosis and cognitive impairment was performed. Also, stratified analysis was performed on several covariates including the type of statin used, gender and age of rodents and duration of statin therapy, to account for the reported heterogeneity in the results obtained. The study protocol was registered in PROSPERO (CRD42018102557).

RESULT

17 studies including 22 comparisons, containing a sample size of 446 rodents, participated in the meta-analysis of statin's effect on overall Aβ deposition. Although the effect of statin on overall Aβ deposition was found to be protective (p < 0.00001) but as we categorized the efficacy of statin on different Aβ species (soluble and insoluble Aβ40/42) and Aβ plaque load, we found that significance in the protection decreased. A stratified meta-analysis demonstrated a significant role in the duration of statin supplements and rodent's age on the heterogeneity of the results. Statin administered to rodents for the longest duration (>6 months) and younger rodents (<6 months of age) demonstrated significant efficacy of statin on Aβ deposition.

CONCLUSION

Statin showed reduction in Aβ level but stratified analysis revealed that this effect of statin was dependent on rodent's age and duration of the treatment.

The Alzheimer's Disease Amyloid-Beta Hypothesis in Cardiovascular Aging and Disease: JACC Focus Seminar

Aging-related cellular and molecular processes including low-grade inflammation are major players in the pathogenesis of cardiovascular disease (CVD) and Alzheimer's disease (AD). Epidemiological studies report an independent interaction between the development of dementia and the incidence of CVD in several populations, suggesting the presence of overlapping molecular mechanisms. Accumulating experimental and clinical evidence suggests that amyloid-beta (Aβ) peptides may function as a link among aging, CVD, and AD. Aging-related vascular and cardiac deposition of Αβ induces tissue inflammation and organ dysfunction, both important components of the Alzheimer's disease amyloid hypothesis. In this review, the authors describe the determinants of Aβ metabolism, summarize the effects of Aβ on atherothrombosis and cardiac dysfunction, discuss the clinical value of Αβ1-40 in CVD prognosis and patient risk stratification, and present the therapeutic interventions that may alter Aβ metabolism in humans.

Draft genome of Meyerozyma guilliermondii strain vka1: a yeast strain with composting potential

Background

Meyerozyma guilliermondii is a yeast which could be isolated from a variety of environments. The vka1 strain isolated and purified from the organic compost was found to have composting potential. To better understand the genes assisting the composting potential in this yeast, whole genome sequencing and sequence annotation were performed.

Results

The genome of M. guilliermondii vka1 strain was sequenced using a hybrid approach, on Illumina Hiseq-2500 platform at 100× coverage followed by Nanopore platform at 20× coverage. The de novo assembly using dual-fold approach had given draft genome of 10.8 Mb size. The genome was found to contain 5385 genes. The annotation of the genes was performed, and the enzymes identified to have roles in the degradation of macromolecules are discussed in relation to its composting potential. Annotation of the genome assembly of the related strains had revealed the unique biodegradation related genes in this strain. Phylogenetic analysis using the rDNA region has confirmed the position of this strain in the Ascomycota family. Raw reads are made public, and the genome wide proteome profile is presented to facilitate further studies on this organism.

Conclusions

Meyerozyma guilliermondii vka1 strain was sequenced through hybrid approach and the reads were de novo assembled. Draft genome size and the number of genes in the strain were assessed and discussed in relation to the related strains. Scientific insights into the composting potential of this strain are also presented in relation to the unique genes identified in this strain.

Rosuvastatin Improves Cognitive Function of Chronic Hypertensive Rats by Attenuating White Matter Lesions and Beta-Amyloid Deposits

Hypertensive white matter lesion (WML) is one of common causes of vascular cognitive impairment. In this study, we aimed to investigate the effect of rosuvastatin on cognitive impairment and its underlying mechanisms in chronic hypertensive rats. From the 8^th week after establishment of stroke-prone renovascular hypertensive rats (RHRSPs), rosuvastatin (10 mg/kg) or saline as a control was administrated once daily for consecutive 12 weeks by gastric gavage. Cognitive function was assessed with the Morris water maze test and novel object recognition test. WML was observed by Luxol fast blue staining. Aβ deposits, Claudin-5, Occludin, and ZO-1 were determined by immunofluorescence. After rosuvastatin treatment, the escape latencies were decreased and the time of crossing the hidden platform was increased in the Morris water maze, compared with the vehicle-treated RHRSP group. In a novel object recognition test, the recognition index in the rosuvastatin-treated RHRSP group was significantly larger than that in the vehicle-treated RHRSP group. Rosuvastatin treatment presented with the effects of lower WML grades, higher expression of tight junction proteins Claudin-5, Occludin, and ZO-1 in the corpus callosum, and less Aβ deposits in the cortex and hippocampus. The data suggested that rosuvastatin improved the cognitive function of chronic hypertensive rats partly by attenuating WML and reducing Aβ burden.

Molecular Insight into the Therapeutic Promise of Targeting APOE4 for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that causes chronic cognitive dysfunction. Most of the AD cases are late onset, and the apolipoprotein E (APOE) isoform is a key genetic risk factor. The APOE gene has 3 key alleles in humans including APOE2, APOE3, and APOE4. Among them, APOE4 is the most potent genetic risk factor for late-onset AD (LOAD), while APOE2 has a defensive effect. Research data suggest that APOE4 leads to the pathogenesis of AD through various processes such as accelerated beta-amyloid aggregations that raised neurofibrillary tangle formation, cerebrovascular diseases, aggravated neuroinflammation, and synaptic loss. However, the precise mode of actions regarding in what way APOE4 leads to AD pathology remains unclear. Since APOE contributes to several pathological pathways of AD, targeting APOE4 might serve as a promising strategy for the development of novel drugs to combat AD. In this review, we focus on the recent studies about APOE4-targeted therapeutic strategies that have been advanced in animal models and are being prepared for use in humans for the management of AD.

Neurovascular Unit Dysfunction and Neurodegenerative Disorders

The neurovascular unit (NVU), composed of vascular cells, glial cells, and neurons, is the minimal functional unit of the brain. The NVU maintains integrity of the blood–brain barrier (BBB) and regulates supply of the cerebral blood flow (CBF), both of which are keys to maintaining normal brain function. BBB dysfunction and a decreased CBF are early pathophysiological changes in neurodegenerative disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS). In this review, we primarily focus on the NVU in AD as much research has been performed on the connection between NVU dysfunction and AD. We also discuss the role of NVU dysfunction in the pathophysiological mechanisms of PD and ALS. As most neurodegenerative diseases are difficult to treat, we discuss several potential drug targets that focus on the NVU that may inform novel vascular-targeted therapies for AD, PD, and ALS.

Increased levels of Aβ42 decrease the lifespan of ob/ob mice with dysregulation of microglia and astrocytes

Clinical studies have indicated that obesity and diabetes are associated with Alzheimer's disease (AD) and neurodegeneration. Although the mechanisms underlying these associations remain elusive, the bidirectional interactions between obesity/diabetes and Alzheimer's disease (AD) may be involved in them. Both obesity/diabetes and AD significantly reduce life expectancy. We generated App^NL-F/wt knock-in; ob/ob mice by crossing App^NL-F/wt knock-in mice and ob/ob mice to investigate whether amyloid-β (Aβ) affects the lifespan of ob/ob mice. App^NL-F/wt knock-in; ob/ob mice displayed the shortest lifespan compared to wild-type mice, App^NL-F/wt knock-in mice, and ob/ob mice. Notably, the Aβ42 levels were increased at minimum levels before deposition in App^NL-F/wt knock-in mice and App^NL-F/wt knock-in; ob/ob mice at 18 months of age. No differences in the levels of several neuronal markers were observed between mice at this age. However, we observed increased levels of glial fibrillary acidic protein (GFAP), an astrocyte marker, in App^NL-F/wt knock-in; ob/ob mice, while the levels of several microglial markers, including CD11b, TREM2, and DAP12, were decreased in both ob/ob mice and App^NL-F/wt knock-in; ob/ob mice. The increase in GFAP levels was not observed in young App^NL-F/wt knock-in; ob/ob mice. Thus, the increased Aβ42 levels may decrease the lifespan of ob/ob mice, which is associated with the dysregulation of microglia and astrocytes in an age-dependent manner. Based on these findings, the imbalance in these neuroinflammatory cells may provide a clue to the mechanisms by which the interaction between obesity/diabetes and early AD reduces life expectancy.

Amyloid-β-independent regulators of tau pathology in Alzheimer disease

The global epidemic of Alzheimer disease (AD) is worsening, and no approved treatment can revert or arrest progression of this disease. AD pathology is characterized by the accumulation of amyloid-β (Aβ) plaques and tau neurofibrillary tangles in the brain. Genetic data, as well as autopsy and neuroimaging studies in patients with AD, indicate that Aβ plaque deposition precedes cortical tau pathology. Because Aβ accumulation has been considered the initial insult that drives both the accumulation of tau pathology and tau-mediated neurodegeneration in AD, the development of AD therapeutics has focused mostly on removing Aβ from the brain. However, striking preclinical evidence from AD mouse models and patient-derived human induced pluripotent stem cell models indicates that tau pathology can progress independently of Aβ accumulation and arises downstream of genetic risk factors for AD and aberrant metabolic pathways. This Review outlines novel insights from preclinical research that implicate apolipoprotein E, the endocytic system, cholesterol metabolism and microglial activation as Aβ-independent regulators of tau pathology. These factors are discussed in the context of emerging findings from clinical pathology, functional neuroimaging and other approaches in humans. Finally, we discuss the implications of these new insights for current Aβ-targeted strategies and highlight the emergence of novel therapeutic strategies that target processes upstream of both Aβ and tau.

Apolipoprotein E and Alzheimer disease: pathobiology and targeting strategies

Polymorphism in the apolipoprotein E (APOE) gene is a major genetic risk determinant of late-onset Alzheimer disease (AD), with the APOE*ε4 allele conferring an increased risk and the APOE*ε2 allele conferring a decreased risk relative to the common APOE*ε3 allele. Strong evidence from clinical and basic research suggests that a major pathway by which APOE4 increases the risk of AD is by driving earlier and more abundant amyloid pathology in the brains of APOE*ε4 carriers. The number of amyloid-β (Aβ)-dependent and Aβ-independent pathways that are known to be differentially modulated by APOE isoforms is increasing. For example, evidence is accumulating that APOE influences tau pathology, tau-mediated neurodegeneration and microglial responses to AD-related pathologies. In addition, APOE4 is either pathogenic or shows reduced efficiency in multiple brain homeostatic pathways, including lipid transport, synaptic integrity and plasticity, glucose metabolism and cerebrovascular function. Here, we review the recent progress in clinical and basic research into the role of APOE in AD pathogenesis. We also discuss how APOE can be targeted for AD therapy using a precision medicine approach.

Vascular Dysfunction in Alzheimer's Disease: A Prelude to the Pathological Process or a Consequence of It?

Alzheimer's disease (AD) is the most prevalent form of dementia. Despite decades of research following several theoretical and clinical lines, all existing treatments for the disorder are purely symptomatic. AD research has traditionally been focused on neuronal and glial dysfunction. Although there is a wealth of evidence pointing to a significant vascular component in the disease, this angle has been relatively poorly explored. In this review, we consider the various aspects of vascular dysfunction in AD, which has a significant impact on brain metabolism and homeostasis and the clearance of β-amyloid and other toxic metabolites. This may potentially precede the onset of the hallmark pathophysiological and cognitive symptoms of the disease. Pathological changes in vessel haemodynamics, angiogenesis, vascular cell function, vascular coverage, blood-brain barrier permeability and immune cell migration may be related to amyloid toxicity, oxidative stress and apolipoprotein E (APOE) genotype. These vascular deficits may in turn contribute to parenchymal amyloid deposition, neurotoxicity, glial activation and metabolic dysfunction in multiple cell types. A vicious feedback cycle ensues, with progressively worsening neuronal and vascular pathology through the course of the disease. Thus, a better appreciation for the importance of vascular dysfunction in AD may open new avenues for research and therapy.

Low-dose pioglitazone can ameliorate learning and memory impairment in a mouse model of dementia by increasing LRP1 expression in the hippocampus

Amyloid-β (Aβ) accumulation in the brain is a pathological feature of Alzheimer's disease (AD) and enhancing Aβ clearance is a potential therapeutic strategy. Pioglitazone is a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist and is widely used to treat type 2 diabetes. We previously reported that low-dose pioglitazone increased the expression of low-density lipoprotein receptor-related protein 1 (LRP1), which upregulates the clearance of Aβ, using human brain microvascular endothelial cells. We investigated whether low-dose pioglitazone can rescue the pathological phenotype and memory impairment in senescence-accelerated mouse prone-8 (SAMP8) mice by increasing LRP1 levels. SAMP8 mice were treated with vehicle or pioglitazone in dosages of 2 or 5 mg/kg/day for 7 weeks. In the water maze test, 2 mg/kg/day of pioglitazone significantly attenuated the increased escape latency in SAMP8 mice (p = 0.026), while 5 mg/kg/day of treatment did not. Compared with vehicle treatment, the hippocampi of SAMP8 mice with 2 mg/kg/day of pioglitazone exhibited fewer Aβ deposits and reduced Aβ_1-40 levels, along with elevated LRP1 expression (p = 0.005). Collectively, our results proposed that a new therapeutic application of the PPAR-γ agonist for AD treatment should be considered at a lower dose than the conventional dose used to treat diabetes.

Intracellular metalloprotease activity controls intraneuronal Aβ aggregation and limits secretion of Aβ via exosomes

Accumulating evidence suggests that the abnormal aggregation of amyloid-β (Αβ) peptide in Alzheimer's disease (AD) begins intraneuronally, within vesicles of the endosomal-lysosomal pathway where Aβ is both generated and degraded. Metalloproteases, including endothelin-converting enzyme (ECE)-1 and -2, reside within these vesicles and normally limit the accumulation of intraneuronally produced Aβ. In this study, we determined whether disruption of Aβ catabolism could trigger Aβ aggregation within neurons and increase the amount of Aβ associated with exosomes, small extracellular vesicles derived from endosomal multivesicular bodies. Using cultured cell lines, primary neurons, and organotypic brain slices from an AD mouse model, we found that pharmacological inhibition of the ECE family of metalloproteases increased intracellular and extracellular Aβ levels and promoted the intracellular formation of Aβ oligomers, a process that did not require internalization of secreted Aβ. In vivo, the accumulation of intraneuronal Aβ aggregates was accompanied by increased levels of both extracellular and exosome-associated Aβ, including oligomeric species. Neuronal exosomes were found to contain both ECE-1 and -2 activities, suggesting that multivesicular bodies are intracellular sites of Aβ degradation by these enzymes. ECE dysfunction could lead to the accumulation of intraneuronal Aβ aggregates and their subsequent release into the extracellular space via exosomes.-Pacheco-Quinto, J., Clausen, D., Pérez-González, R., Peng, H., Meszaros, A., Eckman, C. B., Levy, E., Eckman, E. A. Intracellular metalloprotease activity controls intraneuronal Aβ aggregation and limits secretion of Aβ via exosomes.

Role of Rab GTPases in Alzheimer's Disease

Alzheimer's disease (AD) comprises two major pathological hallmarks: extraneuronal deposition of β-amyloid (Aβ) peptides ("senile plaques") and intraneuronal aggregation of the microtubule-associated protein tau ("neurofibrillary tangles"). Aβ is derived from sequential cleavage of the β-amyloid precursor protein by β- and γ-secretases, while aggregated tau is hyperphosphorylated in AD. Mounting evidence suggests that dysregulated trafficking of these AD-related proteins contributes to AD pathogenesis. Rab proteins are small GTPases that function as master regulators of vesicular transport and membrane trafficking. Multiple Rab GTPases have been implicated in AD-related protein trafficking, and their expression has been observed to be altered in postmortem AD brain. Here we review current implicated roles of Rab GTPase dysregulation in AD pathogenesis. Further elucidation of the pathophysiological role of Rab GTPases will likely reveal novel targets for AD therapeutics.

Role of simvastatin and insulin in memory protection in a rat model of diabetes mellitus and dementia

OBJECTIVES

The memory protective role of simvastatin and/or insulin, in a rat model of diabetes mellitus (DM) and dementia was examined.

METHODS

DM was induced by an intraperitoneal injection of streptozotocin. Diabetic rats were divided into untreated; insulin treated; simvastatin treated with 10 and 20 mg/kg/day; and combined insulin plus simvastatin treatment in the previous doses. Treatment started after blood glucose elevation and persisted for 6 weeks. Morris water maze and Y maze tests were held to detect behavioral changes. Serum glucose, cholesterol and insulin levels, the hippocampi insulin, amyloid beta (Aß) 1-42 and oxidative stress markers were measured.

RESULTS

Insulin increased the time spent in the target quadrant in the Morris water maze test and the percentage of alternations in the Y maze test, despite the mild improvements in brain parameters demonstrated by amyloid beta 1-42, malondialdehyde and reduced glutathione levels; while simvastatin in both doses improved brain parameters with no positive impact on behavioral tests. Insulin combined with simvastatin 20 mg/kg/day was effective in enhancing the behavioral tests and the measured brain parameters.

CONCLUSIONS

Treatment with insulin and simvastatin could provide a promising memory protective effect in diabetics.

Possible Clues for Brain Energy Translation via Endolysosomal Trafficking of APP-CTFs in Alzheimer's Disease

Vascular dysfunctions, hypometabolism, and insulin resistance are high and early risk factors for Alzheimer's disease (AD), a leading neurological disease associated with memory decline and cognitive dysfunctions. Early defects in glucose transporters and glycolysis occur during the course of AD progression. Hypometabolism begins well before the onset of early AD symptoms; this timing implicates the vulnerability of hypometabolic brain regions to beta-secretase 1 (BACE-1) upregulation, oxidative stress, inflammation, synaptic failure, and cell death. Despite the fact that ketone bodies, astrocyte-neuron lactate shuttle, pentose phosphate pathway (PPP), and glycogenolysis compensate to provide energy to the starving AD brain, a considerable energy crisis still persists and increases during disease progression. Studies that track brain energy metabolism in humans, animal models of AD, and in vitro studies reveal striking upregulation of beta-amyloid precursor protein (β-APP) and carboxy-terminal fragments (CTFs). Currently, the precise role of CTFs is unclear, but evidence supports increased endosomal-lysosomal trafficking of β-APP and CTFs through autophagy through a vague mechanism. While intracellular accumulation of Aβ is attributed as both the cause and consequence of a defective endolysosomal-autophagic system, much remains to be explored about the other β-APP cleavage products. Many recent works report altered amino acid catabolism and expression of several urea cycle enzymes in AD brains, but the precise cause for this dysregulation is not fully explained. In this paper, we try to connect the role of CTFs in the energy translation process in AD brain based on recent findings.

Promoting the clearance of neurotoxic proteins in neurodegenerative disorders of ageing

Neurodegenerative disorders of ageing (NDAs) such as Alzheimer disease, Parkinson disease, frontotemporal dementia, Huntington disease and amyotrophic lateral sclerosis represent a major socio-economic challenge in view of their high prevalence yet poor treatment. They are often called 'proteinopathies' owing to the presence of misfolded and aggregated proteins that lose their physiological roles and acquire neurotoxic properties. One reason underlying the accumulation and spread of oligomeric forms of neurotoxic proteins is insufficient clearance by the autophagic-lysosomal network. Several other clearance pathways are also compromised in NDAs: chaperone-mediated autophagy, the ubiquitin-proteasome system, extracellular clearance by proteases and extrusion into the circulation via the blood-brain barrier and glymphatic system. This article focuses on emerging mechanisms for promoting the clearance of neurotoxic proteins, a strategy that may curtail the onset and slow the progression of NDAs.

APOE and Alzheimer's Disease: Evidence Mounts that Targeting APOE4 may Combat Alzheimer's Pathogenesis

Alzheimer's disease (AD) is an immutable neurodegenerative disease featured by the two hallmark brain pathologies that are the extracellular amyloid ß (Aß) and intraneuronal tau protein. People carrying the APOE4 allele are at high risk of AD concerning the ones carrying the ε3 allele, while the ε2 allele abates risk. ApoE isoforms exert a central role in controlling the transport of brain lipid, neuronal signaling, mitochondrial function, glucose metabolism, and neuroinflammation. Regardless of widespread indispensable studies, the appropriate function of APOE in AD etiology stays ambiguous. Existing proof recommends that the disparate outcomes of ApoE isoforms on Aβ accretion and clearance have a distinct function in AD pathogenesis. ApoE-lipoproteins combine diverse cell-surface receptors to transport lipids and moreover to lipophilic Aβ peptide, that is believed to begin deadly events that generate neurodegeneration in the AD. ApoE has great influence in tau pathogenesis, tau-mediated neurodegeneration, and neuroinflammation, as well as α-synucleinopathy, lipid metabolism, and synaptic plasticity despite the presence of Aβ pathology. ApoE4 shows the deleterious effect for AD while the lack of ApoE4 is defensive. Therapeutic strategies primarily depend on APOE suggest to lessen the noxious effects of ApoE4 and reestablish the protective aptitudes of ApoE. This appraisal represents the critical interactions of APOE and AD pathology, existing facts on ApoE levels in the central nervous system (CNS), and the credible active stratagems for AD therapy by aiming ApoE. This review also highlighted utmost ApoE targeting therapeutic tactics that are crucial for controlling Alzheimer's pathogenesis.

Interaction between amyloidogenic proteins and biomembranes in protein misfolding diseases: Mechanisms, contributors, and therapy

The toxic deposition of misfolded amyloidogenic proteins is associated with more than fifty protein misfolding diseases (PMDs), including Alzheimer's disease, Parkinson's disease and type 2 diabetes mellitus. Protein deposition is a multi-step process modulated by a variety of factors, in particular by membrane-protein interaction. The interaction results in permeabilization of biomembranes contributing to the cytotoxicity that leads to PMDs. Different biological and physiochemical factors, such as protein sequence, lipid composition, and chaperones, are known to affect the membrane-protein interaction. Here, we provide a comprehensive review of the mechanisms and contributing factors of the interaction between biomembranes and amyloidogenic proteins, and a summary of the therapeutic approaches to PMDs that target this interaction. This article is part of a Special Issue entitled: Protein Aggregation and Misfolding at the Cell Membrane Interface edited by Ayyalusamy Ramamoorthy.

Neuroprotective effects of statins against amyloid β-induced neurotoxicity

A growing body of evidence suggests that disruption of the homeostasis of lipid metabolism affects the pathogenesis of Alzheimer's disease (AD). In particular, dysregulation of cholesterol homeostasis in the brain has been reported to considerably increase the risk of developing AD. Thus, dysregulation of lipid homeostasis may increase the amyloid β (Aβ) levels by affecting amyloid precursor protein (APP) cleavage, which is the most important risk factor involved in the pathogenesis of AD. Previous research demonstrated that Aβ can trigger neuronal insulin resistance, which plays an important role in response to Aβ-induced neurotoxicity in AD. Epidemiological studies also suggested that statin use is associated with a decreased incidence of AD. Therefore, statins are believed to be a good candidate for conferring neuroprotective effects against AD. Statins may play a beneficial role in reducing Aβ-induced neurotoxicity. Their effect involves a putative mechanism beyond its cholesterol-lowering effects in preventing Aβ-induced neurotoxicity. However, the underlying molecular mechanisms of the protective effect of statins have not been clearly determined in Aβ-induced neurotoxicity. Given that statins may provide benefits beyond the inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, these drugs may also improve the brain. Thus, statins may have beneficial effects on impaired insulin signaling by activating AMP-activated protein kinase (AMPK) in neuronal cells. They play a potential therapeutic role in targeting Aβ-mediated neurotoxicity.

Antidiabetic Polypill Improves Central Pathology and Cognitive Impairment in a Mixed Model of Alzheimer's Disease and Type 2 Diabetes

Type 2 diabetes (T2D) is an important risk factor to suffer dementia, being Alzheimer's disease (AD) as the most common form. Both AD and T2D are closely related to aging and with a growing elderly population it might be of relevance to explore new therapeutic approaches that may slow or prevent central complications associated with metabolic disorders. Therefore, we propose the use of the antidiabetic polypill (PP), a pharmacological cocktail, commonly used by T2D patients that include metformin, aspirin, simvastatin, and an angiotensin-converting enzyme inhibitor. In order to test the effects of PP at the central level, we have long-term treated a new mixed model of AD-T2D, the APP/PS1xdb/db mouse. We have analyzed AD pathological features and the underlying specific characteristics that relate AD and T2D. As expected, metabolic alterations were ameliorated after PP treatment in diabetic mice, supporting a role for PP in maintaining pancreatic activity. At central level, PP reduced T2D-associated brain atrophy, showing both neuronal and synaptic preservation. Tau and amyloid pathologies were also reduced after PP treatment. Furthermore, we observed a reduction of spontaneous central bleeding and inflammation after PP treatment in diabetic mice. As consequence, learning and memory processes were improved after PP treatment in AD, T2D, and AD-T2D mice. Our data provide the basis to further analyze the role of PP, as an alternative or adjuvant, to slow down or delay the central complications associated with T2D and AD.

Endothelial LRP1 - A Potential Target for the Treatment of Alzheimer's Disease : Theme: Drug Discovery, Development and Delivery in Alzheimer's Disease Guest Editor: Davide Brambilla

The accumulation of the neurotoxin beta-amyloid (Aβ) is a major hallmark in Alzheimer's disease (AD). Aβ homeostasis in the brain is governed by its production and various clearance mechanisms. Both pathways are influenced by the ubiquitously expressed low-density lipoprotein receptor-related protein 1 (LRP1). In cerebral blood vessels, LRP1 is an important mediator for the rapid removal of Aβ from brain via transport across the blood-brain barrier (BBB). Here, we summarize recent findings on LRP1 function and discuss the targeting of LRP1 as a modulator for AD pathology and drug delivery into the brain.

Blood-Brain Barrier Dysfunction and the Pathogenesis of Alzheimer's Disease

Brain capillary endothelial cells form the blood-brain barrier (BBB), which is covered with basement membranes and is also surrounded by pericytes and astrocyte end-feet in the neurovascular unit. The BBB tightly regulates the molecular exchange between the blood flow and brain parenchyma, thereby regulating the homeostasis of the central nervous system (CNS). Thus, dysfunction of the BBB is likely involved in the pathogenesis of several neurological diseases, including Alzheimer’s disease (AD). While amyloid-β (Aβ) deposition and neurofibrillary tangle formation in the brain are central pathological hallmarks in AD, cerebrovascular lesions and BBB alteration have also been shown to frequently coexist. Although further clinical studies should clarify whether BBB disruption is a specific feature of AD pathogenesis, increasing evidence indicates that each component of the neurovascular unit is significantly affected in the presence of AD-related pathologies in animal models and human patients. Conversely, since some portions of Aβ are eliminated along the neurovascular unit and across the BBB, disturbing the pathways may result in exacerbated Aβ accumulation in the brain. Thus, current evidence suggests that BBB dysfunction may causatively and consequently contribute to AD pathogenesis, forming a vicious cycle between brain Aβ accumulation and neurovascular unit impairments during disease progression.

The role of amyloid beta clearance in cerebral amyloid angiopathy: more potential therapeutic targets

Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid β-protein (Aβ) in the leptomeningeal and cortical blood vessels, which is an age-dependent risk factor for intracerebral hemorrhage (ICH), ischemic stroke and contributes to cerebrovascular dysfunction leading to cognitive impairment. However clinical prevention and treatment of the disease is very difficult because of its occult onset and severity of the symptoms. In recent years, many anti-amyloid β immunotherapies have not demonstrated clinical efficacy in subjects with Alzheimer’s disease (AD), and the failure may be due to the deposition of Aβ in the cerebrovascular export pathway resulting in further damage to blood vessels and aggravating CAA. So decreased clearance of Aβ in blood vessels plays a crucial role in the development of CAA and AD, and identification of the molecular pathways involved will provide new targets for treatment. In this review, we mainly describe the mechanisms of Aβ clearance through vessels, especially in terms of some proteins and receptors involved in this process.

Role of Vitamin D in Amyloid clearance via LRP-1 upregulation in Alzheimer's disease: A potential therapeutic target?

Amyloid beta (Aβ) deposition is considered to be one of the primary reason to trigger Alzheimer's disease (AD). Literature clearly suggests decline in Aβ clearance to be accountable for progression of late onset AD as compared to augmented Aβ production. There may be several pathways for Aβ clearance out of which one of the major pathway is the vascular-mediated removal of Aβ from the brain across the blood-brain barrier (BBB) via efflux pumps or receptors. Among Aβ scavenger receptors, low density lipoprotein receptor related protein (LRP-1) has been most extensively studied. LRP-1, is highly expressed in neurons and located on abluminal side of the brain capillaries whose expression decreases in AD patients which give rise to increased cerebral Aβ deposition. Recent evidences reveal that post 1,25-(OH)₂D₃ treatment, LRP1 expression increases significantly for both in-vivo and in-vitro studies, since Vitamin D receptors (VDR) are broadly expressed in brain. Biological actions of Vitamin D are mediated via its nuclear hormone receptor vitamin D receptor (VDR) and is found to regulate many genes. Several lines of evidence suggest that VDR deficiency/inhibition can be a potential risk factor for AD and sufficient Vitamin D supplementation is beneficial to prevent AD onset/pathology or slow down the progression of disease. The present review establishes a strong correlation between Vitamin D and LRP-1 and their possible involvement in Aβ clearance and thereby emerging as new therapeutic target.