Alzheimer disease: BACE1 inhibitors block new Aβ plaque formation

Revealing the mechanisms of blood-brain barrier in chronic neurodegenerative disease: an opportunity for therapeutic intervention

The brain microenvironment is tightly regulated, and the blood-brain barrier (BBB) plays a pivotal role in maintaining the homeostasis of the central nervous system. It effectively safeguards brain tissue from harmful substances in peripheral blood. However, both acute pathological factors and age-related biodegradation have the potential to compromise the integrity of the BBB and are associated with chronic neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), as well as Epilepsy (EP). This association arises due to infiltration of peripheral foreign bodies including microorganisms, immune-inflammatory mediators, and plasma proteins into the central nervous system when the BBB is compromised. Nevertheless, these partial and generalized understandings do not prompt a shift from passive to active treatment approaches. Therefore, it is imperative to acquire a comprehensive and in-depth understanding of the intricate molecular mechanisms underlying vascular disease alterations associated with the onset and progression of chronic neurodegenerative disorders, as well as the subsequent homeostatic changes triggered by BBB impairment. The present article aims to systematically summarize and review recent scientific work with a specific focus on elucidating the fundamental mechanisms underlying BBB damage in AD, PD, and EP as well as their consequential impact on disease progression. These findings not only offer guidance for optimizing the physiological function of the BBB, but also provide valuable insights for developing intervention strategies aimed at early restoration of BBB structural integrity, thereby laying a solid foundation for designing drug delivery strategies centered around the BBB.

Associations between regional blood-brain barrier permeability, aging, and Alzheimer's disease biomarkers in cognitively normal older adults

BACKGROUND

Increased blood-brain barrier permeability (BBBp) has been hypothesized as a feature of aging that may lead to the development of Alzheimer's disease (AD). We sought to identify the brain regions most vulnerable to greater BBBp during aging and examine their regional relationship with neuroimaging biomarkers of AD.

METHODS

We studied 31 cognitively normal older adults (OA) and 10 young adults (YA) from the Berkeley Aging Cohort Study (BACS). Both OA and YA received dynamic contrast-enhanced MRI (DCE-MRI) to quantify Ktrans values, as a measure of BBBp, in 37 brain regions across the cortex. The OA also received Pittsburgh compound B (PiB)-PET to create distribution volume ratios (DVR) images and flortaucipir (FTP)- PET to create partial volume corrected standardized uptake volume ratios (SUVR) images. Repeated measures ANOVA assessed the brain regions where OA showed greater BBBp than YA. In OA, Ktrans values were compared based on sex, Aβ positivity status, and APOE4 carrier status within a composite region across the areas susceptible to aging. We used linear models and sparse canonical correlation analysis (SCCA) to examine the relationship between Ktrans and AD biomarkers.

RESULTS

OA showed greater BBBp than YA predominately in the temporal lobe, with some involvement of parietal, occipital and frontal lobes. Within an averaged ROI of affected regions, there was no difference in Ktrans values based on sex or Aβ positivity, but OA who were APOE4 carriers had significantly higher Ktrans values. There was no direct relationship between averaged Ktrans and global Aβ pathology, but there was a trend for an Ab status by tau interaction on Ktrans in this region. SCCA showed increased Ktrans was associated with increased PiB DVR, mainly in temporal and parietal brain regions. There was not a significant relationship between Ktrans and FTP SUVR.

DISCUSSION

Our findings indicate that the BBB shows regional vulnerability during normal aging that overlaps considerably with the pattern of AD pathology. Greater BBBp in brain regions affected in aging is related to APOE genotype and may also be related to the pathological accumulation of Aβ.

Propane-2-sulfonic acid octadec-9-enyl-amide, a novel PPARα/γ dual agonist, attenuates molecular pathological alterations in learning memory in AD mice

OBJECTIVE

Previous studies have revealed that Propane-2-sulfonic acid octadec-9-enyl-amide(N15) exerts a protective role in the inflammatory response after ischemic stroke and in neuronal damage. However, little is known about N15 in Alzheimer's disease (AD). The aim of this study was to investigate the effects of N15 on AD and explore the underlying molecular mechanism.

METHODS

AD mice model was established by lateral ventricular injection with Aβ25-35. N15 was daily intraperitoneal administered for 28 days. Morris Water Maze was used to evaluate the neurocognitive function of the mice. The expression of PPARα/γ, brain-derived neurotrophic factor (BDNF), Neurotrophin-3 (NT3), ADAM10, PS1 and BACE1 were measured by qPCR. Aβ amyloid in the hippocampus was measured by Congo red assay. Toluidine blue staining was used to detect the neuronal apoptosis. Protein levels of ADAM10, PS1 and BACE1 were determined using immunoblotting.

RESULTS

N15 treatment significantly reduced neurocognitive dysfunction, which also significantly activated the expression of PPARα/γ at an optimal dose of 200 mg/kg. Administration of N15 alleviated the formation of Aβ amyloid in the hippocampus of AD mice, enhanced the BDNF mRNA expression, decreased the mRNA and protein levels of PS1 and BACE1, upregulated ADAM10 mRNA and protein levels.

CONCLUSION

N15 exerts its neuroprotective effects through the activation of PPARα/γ and may be a potential drug for the treatment of AD.

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.

The Emerging Roles of E3 Ligases and DUBs in Neurodegenerative Diseases

Despite annual increases in the incidence and prevalence of neurodegenerative diseases, there is a lack of effective treatment strategies. An increasing number of E3 ubiquitin ligases (E3s) and deubiquitinating enzymes (DUBs) have been observed to participate in the pathogenesis mechanisms of neurodegenerative diseases, on the basis of which we conducted a systematic literature review of the studies. This review will help to explore promising therapeutic targets from highly dynamic ubiquitination modification processes.

In Silico Molecular Docking Analysis of Karanjin against Alzheimer's and Parkinson's Diseases as a Potential Natural Lead Molecule for New Drug Design, Development and Therapy

Parkinson’s disease (PD) and Alzheimer’s disease (AD) are neurodegenerative disorders that have emerged as among the serious health problems of the 21st century. The medications currently available to treat AD and PD have limited efficacy and are associated with side effects. Natural products are one of the most vital and conservative sources of medicines for treating neurological problems. Karanjin is a furanoflavonoid, isolated mainly from Pongamia pinnata with several medicinal plants, and has been reported for numerous health benefits. However, the effect of karanjin on AD and PD has not yet been systematically investigated. To evaluate the neuroprotective effect of karanjin, extensive in silico studies starting with molecular docking against five putative targets for AD and four targets for PD were conducted. The findings were compared with three standard drugs using Auto Dock 4.1 and Molegro Virtual Docker software. Additionally, the physiochemical properties (Lipinski rule of five), drug-likeness and parameters including absorption, distribution, metabolism, elimination and toxicity (ADMET) profiles of karanjin were also studied. The molecular dynamics (MD) simulations were performed with two selective karanjin docking complexes to analyze the dynamic behaviors and binding free energy at 100 ns time scale. In addition, frontier molecular orbitals (FMOs) and density-functional theory (DFT) were also investigated from computational quantum mechanism perspectives using the Avogadro-ORCA 1.2.0 platform. Karanjin complies with all five of Lipinski’s drug-likeness rules with suitable ADMET profiles for therapeutic use. The docking scores (kcal/mol) showed comparatively higher potency against AD and PD associated targets than currently used standard drugs. Overall, the potential binding affinity from molecular docking, static thermodynamics feature from MD-simulation and other multiparametric drug-ability profiles suggest that karanjin could be considered as a suitable therapeutic lead for AD and PD treatment. Furthermore, the present results were strongly correlated with the earlier study on karanjin in an Alzheimer’s animal model. However, necessary in vivo studies, clinical trials, bioavailability, permeability and safe dose administration, etc. must be required to use karanjin as a potential drug against AD and PD treatment, where the in silico results are more helpful to accelerate the drug development.

Relationship Between Amyloid-β Deposition and Blood-Brain Barrier Dysfunction in Alzheimer's Disease

Amyloid-β (Aβ) is the predominant pathologic protein in Alzheimer's disease (AD). The production and deposition of Aβ are important factors affecting AD progression and prognosis. The deposition of neurotoxic Aβ contributes to damage of the blood-brain barrier. However, the BBB is also crucial in maintaining the normal metabolism of Aβ, and dysfunction of the BBB aggravates Aβ deposition. This review characterizes Aβ deposition and BBB damage in AD, summarizes their interactions, and details their respective mechanisms.

The Synaptic Vesicle Protein 2A Interacts With Key Pathogenic Factors in Alzheimer's Disease: Implications for Treatment

Alzheimer’s disease (AD), a serious neurodegenerative disease, is pathologically characterized by synaptic loss and dysfunction. Synaptic vesicle protein 2A (SV2A) is an indispensable vesicular protein specifically expressed in synapses and can be used as a biomarker for synaptic density. We found that the expression of SV2A was down-regulated in the hippocampus of AD patients, yet the relation of SV2A to other hallmarks of AD pathology such as amyloid precursor protein (APP), β-amyloid (Aβ), and Tau protein is not thoroughly clear. In addition, SV2A colocalized with APP and was down-regulated at Aβ deposition. Moreover, we found that SV2A deficiency leads to a simultaneous increase in Aβ and Tau hyperphosphorylation, while SV2A overexpression was associated with downregulation of β-site APP cleaving enzyme 1 and apolipoprotein E genes. In addition, evidence gained in the study points to the phosphatidylinositol 3-kinase signaling pathway as a possible mediator in SV2A regulation influencing the incidence and development of AD. With limited effective diagnostic methods for AD, a close interplay between SV2A and AD-related proteins demonstrated in our study may provide novel and innovative diagnostic and therapeutic opportunities.

Anthocyanins from Lycium ruthenicum Murr. Ameliorated d-Galactose-Induced Memory Impairment, Oxidative Stress, and Neuroinflammation in Adult Rats

Lycium ruthenicum Murr. (LR) is a perennial shrub commonly used as a nutritional food and medicine. Herein, we identified 12 anthocyanins from LR, with petunidin derivatives constituting approximately 97% of the total anthocyanin content. Furthermore, the potential mechanism of anthocyanins exerting neuroprotective effects in d-galactose (d-gal)-treated rats was explored. Behavioral results showed that anthocyanins relieved d-gal-induced memory disorder. Additionally, anthocyanins reduced receptor for advanced glycation end products (RAGE) and suppressed oxidative stress caused by d-gal. Anthocyanins suppressed microgliosis and astrocytosis and reduced the overexpression of nuclear factor kappa B (NF-κB), interleukin-1-β (IL-1β), cyclooxygenase-2 (COX-2), and tumor necrosis factor-α (TNF-α). Moreover, anthocyanins lowered C-jun N-terminal kinase ( p-JNK), caspase-3 levels, and the B-cell lymphoma 2-associated X protein/B-cell lymphoma 2 (Bax/Bcl-2) ratio. Thus, anthocyanins from LR attenuated memory disfunction, neuroinflammation, and neurodegeneration caused by d-gal, possibly through the RAGE/NF-κB/JNK pathway, representing a promising, safe candidate for prevention and therapy of neurodegenerative diseases.

Iron Exposure and the Cellular Mechanisms Linked to Neuron Degeneration in Adult Mice

Although the causal relationship between Alzheimer's disease (AD) and iron overload remains unclear, iron dyshomeostasis or improper transport mechanisms are speculated to lead to the accumulation of this neurotoxic metal in the hippocampal formation and other cerebral areas related to neurodegenerative diseases, resulting in the formation of reactive oxygen species (ROS) and, ultimately, cell death. In this study, exposure to high dietary iron (HDI) revealed no significant difference in the number of iron-positive cells and iron content in the cortex and hippocampal region between wild-type (WT) and APP/PS1 mice; however, compared with the control mice, the HDI-treated mice exhibited upregulated divalent metal transporter 1 (DMT1) and ferroportin (Fpn) expression, and downregulated transferrin receptor (TFR) expression. Importantly, we confirmed that there were significantly fewer NeuN-positive neurons in both APP/PS1 and WT mice given HDI, than in the respective controls. Moreover, this iron-induced neuron loss may involve increased ROS and oxidative mitochondria dysfunction, decreased DNA repair, and exacerbated apoptosis and autophagy. Although HDI administration might trigger protective antioxidant, anti-apoptosis, and autophagy signaling, especially in pathological conditions, these data clearly indicate that chronic iron exposure results in neuronal loss due to apoptosis, autophagy, and ferroptosis, hence increasing the risk for developing AD.

Computational Studies Applied to Flavonoids against Alzheimer's and Parkinson's Diseases

Neurodegenerative diseases, such as Parkinson's and Alzheimer's, are understood as occurring through genetic, cellular, and multifactor pathophysiological mechanisms. Several natural products such as flavonoids have been reported in the literature for having the capacity to cross the blood-brain barrier and slow the progression of such diseases. The present article reports on in silico enzymatic target studies and natural products as inhibitors for the treatment of Parkinson's and Alzheimer's diseases. In this study we evaluated 39 flavonoids using prediction of molecular properties and in silico docking studies, while comparing against 7 standard reference compounds: 4 for Parkinson's and 3 for Alzheimer's. Osiris analysis revealed that most of the flavonoids presented no toxicity and good absorption parameters. The Parkinson's docking results using selected flavonoids as compared to the standards with four proteins revealed similar binding energies, indicating that the compounds 8-prenylnaringenin, europinidin, epicatechin gallate, homoeriodictyol, capensinidin, and rosinidin are potential leads with the necessary pharmacological and structural properties to be drug candidates. The Alzheimer's docking results suggested that seven of the 39 flavonoids studied, being those with the best molecular docking results, presenting no toxicity risks, and having good absorption rates (8-prenylnaringenin, europinidin, epicatechin gallate, homoeriodictyol, aspalathin, butin, and norartocarpetin) for the targets analyzed, are the flavonoids which possess the most adequate pharmacological profiles.

Genomics: New Light on Alzheimer's Disease Research

Alzheimer's disease (AD) is a progressive neurodegenerative disease that represents a major cause of death in many countries. AD is characterized by profound memory loss, disruptions in thinking and reasoning, and changes in personality and behavior followed by malfunctions in various bodily systems. Although AD was first identified over 100 years ago, and tremendous efforts have been made to cure the disease, the precise mechanisms underlying the onset of AD remain unclear. The recent development of next-generation sequencing tools and bioinformatics has enabled us to investigate the role of genetics in the pathogenesis of AD. In this review, we discuss novel discoveries in this area, including the results of genome-wide association studies (GWAS) that have implicated a number of novel genes as risk factors, as well as the identification of epigenetic regulators strongly associated with the onset and progression of AD. We also review how genetic risk factors may interact with age-associated, progressive decreases in cognitive function in patients with AD.