Epigallocatechin-3-gallate Inhibits LPS/AßO-induced Neuroinflammation in BV2 Cells through Regulating the ROS/TXNIP/NLRP3 Pathway.

Neuroinflammation is a key factor in cognitive dysfunction and neurodegenerative diseases such as Alzheimer's disease (AD), so inhibiting neuroinflammation is considered as a potential treatment for AD. Epigallocatechin-3-gallate (EGCG), a polyhydroxyphenol of green tea, has been found to exhibit anti-oxidative, anti-inflammatory and neuroprotective effects. The aim of this study was to investigate the inhibitory effect of EGCG on inflammation and its mechanism. In this study, BV2 cells were simultaneously exposed to lipopolysaccharides (LPS) and the amyloid-ß oligomer (AßO) to induce inflammatory microenvironments. Inflammatory cytokines and NLRP3 inflammasome-related molecules were detected by RT-PCR and Western Blot. The results show that EGCG inhibits LPS/AßO-induced inflammation in BV2 cells through regulating IL-1ß, IL-6, and TNF-α. Meanwhile, EGCG reduces the activation of the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome and levels of intracellular ROS in BV2 cells treated with LPS/AßO by affecting the mitochondrial membrane potential (MMP). Further research found that EGCG inhibited MMP through regulating thioredoxin-interacting protein (TXNIP) in LPS/AßO-induced neuroinflammation. In conclusion, EGCG may alleviate LPS/AßO-induced microglial neuroinflammation by suppressing the ROS/ TXNIP/ NLRP3 pathway. It may provide a potential mechanism underlying the anti-inflammatory properties of EGCG for alleviating AD.

Hydrophobic C-Terminal Peptide Analog Aß31-41 Protects the Neurons from Aß-Induced Toxicity.

Spontaneous aggregation of amyloid beta (Aß) leads to the formation of neurotoxic senile plaque considered as the most crucial event in Alzheimer's disease (AD) progression. Inhibition or disruption of this deadly aggregate formation is one of the most efficient strategies for the development of potential therapeutics, and extensive research is in progress by various research groups. In this direction, the development of a peptide analogous to that of the native Aß peptide is an attractive strategy. Based on this rationale, ß-sheet breakers were developed from the Aß central hydrophobic core. These peptide derivatives will bind to the full length of the parent Aß and interfere in self-recognition, thereby preventing the folding of the Aß peptide into cross ß-sheet neurotoxic aggregates. However, this approach is effective in the inhibition of fibrillar aggregation, but this strategy is ineffective in the Aß neurotoxic oligomer formation. Therefore, an alternative and efficient approach is to use the Aß peptide analogous to the C-terminal region, which arbitrates fibrillation and oligomerization. Herein, we developed the Aß C-terminal fragment (ACT-1 to ACT-7) for inhibition of oligomerization as well as fibrillar aggregation. Screening of these seven peptides resulted in an efficient anti-Aß peptide aggregative agent (ACT-7), which was evaluated by the ThT assay peptide. The ThT assay reveals complete inhibition and showed significant neuroprotection of PC-12-derived neurons from Aß-induced toxicity and reduced cell apoptosis. Further, analysis using CD and FTIR spectroscopy reveals that the ACT-7 peptide efficiently inhibits the formation of the ß-sheet secondary structure content. HR-TEM microscopic analysis confirmed the inhibition of formation. Therefore, the inhibition of ß-sheet Aß fibrillary aggregation by the protease-stable ACT-7 peptide may provide a beneficial effect on AD treatment to control the Aß aggregates. Finally, we anticipate that our newly designed ACT peptides may also assist as a template molecular scaffold for designing potential anti-AD therapeutics.

Clioquinol rescues yeast cells from Aß42 toxicity via the inhibition of oxidative damage.

Alzheimer's disease (AD), the most common form of dementia, has gotten considerable attention. Previous studies have demonstrated that clioquinol (CQ) as a metal chelator is a potential drug for the treatment of AD. However, the mode of action of CQ in AD is still unclear. In our study, the antioxidant effects of CQ on yeast cells expressing Aß42 were investigated. We found that CQ could reduce Aß42 toxicity by alleviating reactive oxygen species (ROS) generation and lipid peroxidation level in yeast cells. These alterations were mainly attributable to the increased reduced glutathione (GSH) content and independent of activities of superoxide dismutase (SOD) and/or catalase (CAT). CQ could affect antioxidant enzyme activity by altering the transcription level of related genes. Interestingly, it was noted for the first time that CQ could combine with antioxidant enzymes to reduce their enzymatic activities by molecular docking and circular dichroism spectroscopy. In addition, CQ restored Aß42-mediated disruption of GSH homeostasis via regulating YAP1 expression to protect cells against oxidative stress. Our findings not only improve the current understanding of the mechanism of CQ as a potential drug for AD treatment but also provide ideas for subsequent drug research and development.

The selective butyrylcholinesterase inhibitor UW-MD-95 shows symptomatic and neuroprotective effects in a pharmacological mouse model of Alzheimer's disease.

AIMS: Alzheimer's disease (AD) is a devastating dementia characterized by extracellular amyloid-ß (Aß) protein aggregates and intracellular tau protein deposition. Clinically available drugs mainly target acetylcholinesterase (AChE) and indirectly sustain cholinergic neuronal tonus. Butyrylcholinesterase (BChE) also controls acetylcholine (ACh) turnover and is involved in the formation of Aß aggregates and senile plaques. UW-MD-95 is a novel carbamate-based compound acting as a potent pseudo-irreversible BChE inhibitor, with high selectivity versus AChE, and showing promising protective potentials in AD. METHODS: We characterized the neuroprotective activity of UW-MD-95 in mice treated intracerebroventricularly with oligomerized Aß25-35 peptide using behavioral, biochemical, and immunohistochemical approaches. RESULTS: When injected acutely 30 min before the behavioral tests (spontaneous alternation in the Y-maze, object recognition, or passive avoidance), UW-MD-95 (0.3-3 mg/kg) showed anti-amnesic effects in Aß25-35-treated mice. When injected once a day over 7 days, it prevented Aß25-35-induced memory deficits. This effect was lost in BChE knockout mice. Moreover, the compound prevented Aß25-35-induced oxidative stress (assessed by lipid peroxidation or cytochrome c release), neuroinflammation (IL-6 and TNFα levels or GFAP and IBA1 immunoreactivity) in the hippocampus and cortex, and apoptosis (Bax level). Moreover, UW-MD-95 significantly reduced the increase in soluble Aß1-42 level in the hippocampus induced by Aß25-35. CONCLUSION: UW-MD-95 appeared as a potent neuroprotective compound in the Aß25-35 model of AD, with potentially an impact on Aß1-42 accumulation that could suggest a novel mechanism of neuroprotection.

The protective effects of Chromofungin in oligomeric amyloid ß42 (Aß42)-induced toxicity in neurons in Alzheimer's disease.

Oligomeric Aß42 is considered to play a harmful role in the pathophysiology of Alzheimer's disease (AD). Prolonged exposure to oligomeric Aß42 could induce neuronal damage including cellular senescence. Amelioration of Aß42-induced cellular senescence has been considered as a promising strategy for the treatment of AD. Chromofungin, a chromogranin A-derived peptide, has displayed various biological functions in different types of cells and tissues. However, the effects of Chromofungin on oligomeric Aß42-induced cellular senescence have not been previously reported. In the current study, we report a novel function of Chromofungin by showing that treatment with Chromofungin could ameliorate Aß42-induced neurotoxicity in M17 neuronal cells. The Cell Counting Kit-8 (CCK-8) assay and the lactate dehydrogenase (LDH) release experiments revealed that 0.5 and 1 mM are the optimal concentrations of Chromofungin for cell culture in M17 cells. Challenging with oligomeric Aß42 (5 µM) for 7 and 14 days led to a significant decrease in telomerase activity, which was rescued by Chromofungin dose-dependently. Additionally, the senescence-associated ß-galactosidase (SA-ß-gal) staining assay demonstrated that Chromofungin mitigated oligomeric Aß42-induced cellular senescence. Correspondingly, treatment with Chromofungin reversed the gene expression of human telomerase reverse transcriptase (hTERT), telomeric repeat-binding factor 2 (TERF2), and p21 against oligomeric Aß42 in M17 neurons. Interestingly, Chromofungin attenuated oligomeric Aß42-induced oxidative stress (OS) in M17 cells by reducing the production of intracellular reactive oxygen species (ROS) but increasing the levels of intracellular superoxide dismutase (SOD). Importantly, the presence of Chromofungin reduced the expression of cyclooxygenase2 (COX-2) as well as the generation of prostaglandin E2 (PGE2). Transduction with Ad-COX-2 impaired the effects of Chromofungin on telomerase activity and the profile of cellular senescence. Our findings suggest that Chromofungin might act as a potential agent for the treatment of AD.

Cornuside ameliorates cognitive impairments via RAGE/TXNIP/NF-κB signaling in Aß1-42 induced Alzheimer's disease mice.

Cornuside has been discovered to improve learning and memory in AD mice, however, its underlying mechanism was not fully understood. In the present study, we established an AD mice model by intracerebroventricular injection of Aß1-42, which were treated with cornuside (3, 10, 30 mg/kg) for 2 weeks. Cornuside significantly ameliorated cognitive function of AD mice in series of behavioral tests, including Morris water maze test, nest building test, novel object recognition test and step-down test. Additionally, cornuside could attenuate neuronal injury, and promote cholinergic synaptic transmission by restoring the level of acetylcholine (ACh) via inhibiting acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), as well as facilitating choline acetyltransferase (ChAT). Furthermore, cornuside inhibited oxidative stress levels amplified as decreased malondialdehyde (MDA), by inhibiting TXNIP expression, improving total anti-oxidative capacity (TAOC), raising activities of superoxide dismutase (SOD) and catalase (CAT). Cornuside also reduced the activation of microglia and astrocytes, decreased the level of proinflammatory factors TNF-α, IL-6, IL-1ß, iNOS and COX2 via interfering RAGE-mediated IKK-IκB-NF-κB phosphorylation. Similar anti-oxidative and anti-inflammatory effects were also found in LPS-stimulated BV2 cells via hampering RAGE-mediated TXNIP activation and NF-κB nuclear translocation. Virtual docking revealed that cornuside could interact with the active pocket of RAGE V domain directly. In conclusion, cornuside could bind to the RAGE directly impeding the interaction of Aß and RAGE, and cut down the expression of TXNIP inhibiting ROS production and oxidative stress, as well as hamper NF-κB p65 mediated the inflammation.

A Proteomic Approach Identified TFEB as a Key Player in the Protective Action of Novel CB2R Bitopic Ligand FD22a against the Deleterious Effects Induced by ß-Amyloid in Glial Cells.

Neurodegenerative diseases (NDDs) are progressive multifactorial disorders of the nervous system sharing common pathogenic features, including intracellular misfolded protein aggregation, mitochondrial deficit, and inflammation. Taking into consideration the multifaceted nature of NDDs, development of multitarget-directed ligands (MTDLs) has evolved as an attractive therapeutic strategy. Compounds that target the cannabinoid receptor type II (CB2R) are rapidly emerging as novel effective MTDLs against common NDDs, such as Alzheimer's disease (AD). We recently developed the first CB2R bitopic/dualsteric ligand, namely FD22a, which revealed the ability to induce neuroprotection with fewer side effects. To explore the potential of FD22a as a multitarget drug for the treatment of NDDs, we investigated here its ability to prevent the toxic effect of ß-amyloid (Aß25-35 peptide) on human cellular models of neurodegeneration, such as microglia (HMC3) and glioblastoma (U87-MG) cell lines. Our results displayed that FD22a efficiently prevented Aß25-35 cytotoxic and proinflammatory effects in both cell lines and counteracted ß-amyloid-induced depression of autophagy in U87-MG cells. Notably, a quantitative proteomic analysis of U87-MG cells revealed that FD22a was able to potently stimulate the autophagy-lysosomal pathway (ALP) by activating its master transcriptional regulator TFEB, ultimately increasing the potential of this novel CB2R bitopic/dualsteric ligand as a multitarget drug for the treatment of NDDs.

Protection of Si Nanowires against Aß Toxicity by the Inhibition of Aß Aggregation.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by the accumulation of amyloid beta (Aß) plaques in the brain. Aß1-42 is the main component of Aß plaque, which is toxic to neuronal cells. Si nanowires (Si NWs) have the advantages of small particle size, high specific surface area, and good biocompatibility, and have potential application prospects in suppressing Aß aggregation. In this study, we employed the vapor-liquid-solid (VLS) growth mechanism to grow Si NWs using Au nanoparticles as catalysts in a plasma-enhanced chemical vapor deposition (PECVD) system. Subsequently, these Si NWs were transferred to a phosphoric acid buffer solution (PBS). We found that Si NWs significantly reduced cell death in PC12 cells (rat adrenal pheochromocytoma cells) induced by Aß1-42 oligomers via double staining with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and fluorescein diacetate/propyl iodide (FDA/PI). Most importantly, pre-incubated Si NWs largely prevented Aß1-42 oligomer-induced PC12 cell death, suggesting that Si NWs exerts an anti-Aß neuroprotective effect by inhibiting Aß aggregation. The analysis of Fourier Transform Infrared (FTIR) results demonstrates that Si NWs reduce the toxicity of fibrils and oligomers by intervening in the formation of ß-sheet structures, thereby protecting the viability of nerve cells. Our findings suggest that Si NWs may be a potential therapeutic agent for AD by protecting neuronal cells from the toxicity of Aß1-42.

Elucidation of molecular mechanisms by which amyloid ß1-42 fibrils exert cell toxicity.

Abrupt aggregation of amyloid ß1-42 (Aß1-42) peptide in the frontal lobe is the expected underlying cause of Alzheimer's disease (AD). ß-Sheet-rich oligomers and fibrils formed by Aß1-42 exert high cell toxicity. A growing body of evidence indicates that lipids can uniquely alter the secondary structure and toxicity of Aß1-42 aggregates. At the same time, underlying molecular mechanisms that determine this difference in toxicity of amyloid aggregates remain unclear. Using a set of molecular and biophysical assays to determine the molecular mechanism by which Aß1-42 aggregates formed in the presence of cholesterol, cardiolipin, and phosphatidylcholine exert cell toxicity. Our findings demonstrate that rat neuronal cells exposed to Aß1-42 fibrils formed in the presence of lipids with different chemical structure exert drastically different magnitude and dynamic of unfolded protein response (UPR) in the endoplasmic reticulum (ER) and mitochondria (MT). We found that the opposite dynamics of UPR in MT and ER in the cells exposed to Aß1-42: cardiolipin fibrils and Aß1-42 aggregates formed in a lipid-free environment. We also found that Aß1-42: phosphatidylcholine fibrils upregulated ER UPR simultaneously downregulating the UPR response of MT, whereas Aß1-42: cholesterol fibrils suppressed the UPR response of ER and upregulated UPR response of MT. We also observed progressively increasing ROS production that damages mitochondrial membranes and other cell organelles, ultimately leading to cell death.

Polycatechols inhibit ferroptosis and modulate tau liquid-liquid phase separation to mitigate Alzheimer's disease.

Alzheimer's disease (AD) is a complex neurodegenerative disorder that affects learning, memory, and cognition. Current treatments targeting amyloid-ß (Aß) and tau have shown limited effectiveness, necessitating further research on the aggregation and toxicity mechanisms. One of these mechanisms involves the liquid-liquid phase separation (LLPS) of tau, contributing to the formation of pathogenic tau aggregates, although their conformational details remain elusive. Another mechanism is ferroptosis, a type of iron-dependent lipid peroxidation-mediated cell death, which has been implicated in AD. There is a lack of therapeutic strategies that simultaneously target amyloid toxicity and ferroptosis. This study aims to explore the potential of polycatechols, PDP and PLDP, consisting of dopamine and L-Dopa, respectively, as multifunctional agents to modulate the pathological nexus between ferroptosis and AD. Polycatechols were found to sequester the labile iron pool (LIP), inhibit Aß and tau aggregation, scavenge free radicals, protect mitochondria, and prevent ferroptosis, thereby rescuing neuronal cell death. Interestingly, PLDP promotes tau LLPS, and modulates their intermolecular interactions to inhibit the formation of toxic tau aggregates, offering a conceptually innovative approach to tackle tauopathies. This is a first-of-its-kind polymer-based integrative approach that inhibits ferroptosis, counteracts amyloid toxicity, and modulates tau LLPS to mitigate the multifaceted toxicity of AD.

The Co-oligomers of Aß42 and Human Islet Amyloid Polypeptide Exacerbate Neurotoxicity and Alzheimer-like Pathology at Cellular Level.

The Aß hypothesis has long been central to Alzheimer's disease (AD) theory, with a recent surge in attention following drug approvals targeting Aß plaque clearance. Aß42 oligomers (AßO) are key neurotoxins. While ß-amyloid (Aß) buildup is a hallmark of AD, postmortem brain analyses have unveiled human islet amyloid polypeptide (hIAPP) deposition in AD patients, suggesting a potential role in Alzheimer's pathology. This study investigates the neurotoxic effects of co-aggregates of Aß42 and hIAPP, specifically focusing on their impact on cell survival, apoptosis, and AD-like pathology. We analyzed and compared the impact of AßO and Aß42-hIAPP on cell survival in SH-SY5Y cells, apoptosis and inducing AD-like pathology in glutamatergic neurons. Aß42-hIAPP co-oligomers exhibited significantly greater toxicity, causing 2.3-3.5 times higher cell death compared to AßO alone. Furthermore, apoptosis rates were significantly exacerbated in glutamatergic neurons when exposed to Aß42-hIAPP co-oligomers. The study also revealed that Aß42-hIAPP co-oligomers induced typical AD-like pathology in glutamatergic neurons, including the presence of Aß deposits (detected by 6E10 and 4G8 immunofluorescence) and alterations in tau protein (changes in total tau HT7, phosphorylated tau AT8, AT180). Notably, Aß42-hIAPP co-oligomers induced a more severe AD pathology compared to AßO alone. These findings provide compelling evidence for the heightened toxicity of Aß42-hIAPP co-oligomers on neurons and their role in exacerbating AD pathology. The study contributes novel insights into the pathogenesis of Alzheimer's disease, highlighting the potential involvement of hIAPP in AD pathology. Together, these findings offer novel insights into AD pathogenesis and routes for constructing animal models.

NB-02 Protects Neurons and Astrocytes from Oligomeric Amyloid-ß-Mediated Damage.

Alzheimer's disease (AD) is a progressive neurodegenerative disease with limited therapeutic strategies. NB-02 is a novel botanical drug that has shown promise as a protective and therapeutic treatment for AD in an APP/PS1 preclinical mouse model. In this paper, we investigate the underlying mechanisms by which NB-02 provides these therapeutic advantages using in vitro neuron-astrocyte co-cultures. Pretreatment with NB-02 prevented pathological calcium elevations in neurons and astrocytes after application of toxic soluble amyloid-ß (Aß) oligomers. NB-02 also prevented cell death associated with the addition of soluble Aß oligomers suggesting NB-02 is effective at protecting both neurons and astrocytes from Aß-mediated damage.

Protective effect of Ganoderma lucidum-fermented crop extracts against hydrogen peroxide- or ß-amyloid-induced damage in human neuronal SH-SY5Y cells.

BACKGROUND: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of stacked ß-amyloid peptides in the brain and associated with the generation of oxidative stress. So far, there is no cure for AD or a way to stop its progression. Although the neuroprotective effects of Ganoderma lucidum aqueous extract and G. lucidum-derived triterpenoids and polysaccharides have been reported, the influence of G. lucidum-fermented crops on AD still lacks clarity. METHODS: This study aimed to investigate the protective effect of G. lucidum-fermented crop extracts against hydrogen peroxide- or ß-amyloid peptide (Aß25-35)-induced damage in human neuroblastoma SH-SY5Y cells. RESULTS: Various extracts of G. lucidum-fermented crops, including extract A: 10% ethanol extraction using microwave, extract B: 70˚C water extraction, and extract C: 100˚C water extraction followed by ethanol precipitation, were prepared and analyzed. Extract B had the highest triterpenoid content. Extract C had the highest total glucan content, while extract A had the highest gamma-aminobutyric acid (GABA) content. The median inhibitory concentration (IC50, mg/g) for DPPH and ABTS scavenging activity of the fermented crop extracts was significantly lower than that of the unfermented extract. Pretreatment with these extracts significantly increased the cell viability of SH-SY5Y cells damaged by H2O2 or Aß25-35, possibly by reducing cellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels and increasing superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) activities. Moreover, extract B markedly alleviated the activity of acetylcholinesterase (AChE), which is crucial in the pathogenesis of AD. CONCLUSION: These results clearly confirmed the effects of G. lucidum-fermented crop extracts on preventing against H2O2- or Aß25-35-induced neuronal cell death and inhibiting AChE activity, revealing their potential in management of AD.

Lecanemab blocks the effects of the Aß/fibrinogen complex on blood clots and synapse toxicity in organotypic culture.

Proteinaceous brain inclusions, neuroinflammation, and vascular dysfunction are common pathologies in Alzheimer's disease (AD). Vascular deficits include a compromised blood-brain barrier, which can lead to extravasation of blood proteins like fibrinogen into the brain. Fibrinogen's interaction with the amyloid-beta (Aß) peptide is known to worsen thrombotic and cerebrovascular pathways in AD. Lecanemab, an FDA-approved antibody therapy for AD, clears Aß plaque from the brain and slows cognitive decline. Here, we show that lecanemab blocks fibrinogen's binding to Aß protofibrils, preventing Aß/fibrinogen-mediated delayed fibrinolysis and clot abnormalities in vitro and in human plasma. Additionally, we show that lecanemab dissociates the Aß/fibrinogen complex and prevents fibrinogen from exacerbating Aß-induced synaptotoxicity in mouse organotypic hippocampal cultures. These findings reveal a possible protective mechanism by which lecanemab may slow disease progression in AD.

PEDF-derived peptide protects against Amyloid-ß toxicity in vitro and prevents retinal dysfunction in rats.

Amyloid-beta (Aß), a family of aggregation-prone and neurotoxic peptides, has been implicated in the pathophysiology of age-related macular degeneration (AMD). We have previously shown that oligomeric and fibrillar species of Aß42 exerted retinal toxicity in rats, but while the consequences of exposure to amyloid were related to intracellular effects, the mechanism of Aß42 internalization in the retina is not well characterized. In the brain, the 67 kDa laminin receptor (67LR) participates in Aß-related neuronal cell death. A short peptide derived from pigment epithelium-derived factor (PEDF), formerly designated PEDF-335, was found to mitigate experimental models of ischemic retinopathy via targeting of 67LR. In the present study, we hypothesized that 67LR mediates the uptake of pathogenic Aß42 assemblies in the retina, and that targeting of this receptor by PEDF-335 may limit the internalization of Aß, thereby ameliorating its retinotoxicity. To test this assumption ARPE-19 cells in culture were incubated with PEDF-335 before treatment with fibrillar or oligomeric structures of Aß42. Immunostaining confirmed that PEDF-335 treatment substantially prevented amyloid internalization into ARPE-19 cells and maintained their viability in the presence of toxic oligomeric and fibrillar Aß42 entities in vitro. FRET competition assay was performed and confirmed the binding of PEDF-335 to 67LR in RPE-like cells. Wild-type rats were treated with intravitreal PEDF-335 in the experimental eye 2 days prior to administration of retinotoxic Aß42 oligomers or fibrils to both eyes. Retinal function was assessed by electroretinography through 6 weeks post injection. The ERG responses in rats treated with oligomeric or fibrillar Aß42 assemblies were near-normal in eyes previously treated with intravitreal PEDF-335, whereas those measured in the control eyes treated with injection of the Aß42 assemblies alone showed pathologic attenuation of the retinal function through 6 weeks. The retinal presence of 67LR was determined ex vivo by immunostaining and western blotting. Retinal staining demonstrated the constitutional expression of 67LR mainly in the retinal nuclear layers. In the presence of Aß42, the levels of 67LR were increased, although its retinal distribution remained largely unaltered. In contrast, no apparent differences in the retinal expression level of 67LR were noted following exposure to PEDF-335 alone, and its pattern of localization in the retina remained similarly concentrated primarily in the inner and outer nuclear layers. In summary, we found that PEDF-335 confers protection against Aß42-mediated retinal toxicity, with significant effects noted in cells as well as in vivo in rats. The effects of PEDF-335 in the retina are potentially mediated via binding to 67LR and by at least partial inhibition of Aß42 internalization. These results suggest that PEDF-335 may merit further consideration in the development of targeted inhibition of amyloid-related toxicity in the retina. More broadly, our observations provide evidence on the importance of extracellular versus intracellular Aß42 in the retina and suggest concepts on the molecular mechanism of Aß retinal pathogenicity.

Probing the anti-Aß42 aggregation and protective effects of prenylated xanthone against Aß42-induced toxicity in transgenic Caenorhabditis elegans model.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid-ß (Aß) protein aggregates, leading to synaptic dysfunction and neuronal cell death. In this study, we used a comprehensive approach encompassing in vitro assays, computational analyses, and an in vivo Caenorhabditis elegans model to evaluate the inhibitory effects of various xanthones, focusing on Garcinone D (GD), on Aß42 oligomer formation. Dot blot analysis revealed concentration-dependent responses among xanthones, with GD consistently inhibiting Aß42 oligomer formation at low concentrations (0.1 and 0.5 µM, inhibitions of 84.66 ± 2.25% and 85.06 ± 6.57%, respectively). Molecular docking and dynamics simulations provided insights into the molecular interactions between xanthones and Aß42, highlighting the disruption of key residues involved in Aß42 aggregation. The neuroprotective potential of GD was established using transgenic C. elegans GMC101, with substantial delays in paralysis reported at higher concentrations. Our findings show that GD is a potent suppressor of Aß42 oligomer formation, suggesting its potential as a therapeutic candidate for AD. The concentration-dependent effects observed in both in vitro and in vivo models underscore the need for nuanced dose-response assessments. These findings contribute novel insights into the therapeutic landscape of xanthones against AD, emphasizing the multifaceted potential of GD for further translational endeavors in neurodegenerative disorder research.

Natural flavonoid hesperetin blocks amyloid ß-protein fibrillogenesis, depolymerizes preformed fibrils and alleviates cytotoxicity caused by amyloids.

The aggregation of ß-amyloid (Aß) peptides to form amyloid plaques is one of the primary hallmarks for Alzheimer's disease (AD). Dietary flavonoid supplements containing hesperetin have an ability to decline the risk of developing AD, but the molecular mechanism is still unclear. In this work, hesperetin, a flavanone abundant in citrus fruits, has been proven to prevent the formation of Aß aggregates and depolymerized preformed fibrils in a concentration-dependent fashion. Hesperetin inhibited the conformational conversion from the natural structure to a ß-sheet-rich conformation. It was found that hesperetin significantly reduced the cytotoxicity and relieved oxidative stress eventuated by Aß aggregates in a concentration-dependent manner. Additionally, the beneficial effects of hesperetin were confirmed in Caenorhabditis elegans, including the inhibition of the formation and deposition of Aß aggregates and extension of their lifespan. Finally, the results of molecular dynamics simulations showed that hesperetin directly interacted with an Aß42 pentamer mainly through strong non-polar and electrostatic interactions, which destroyed the structural stability of the preformed pentamer. To summarize, hesperetin exhibits great potential as a prospective dietary supplement for preventing and improving AD.

Amyloid Beta-Mediated Neurovascular Toxicity in Alzheimer's Disease.

The brain vascular system receives one-fifth of the total oxygen from the cardiac output, and this transport system is highly dependent on blood-brain barrier (BBB) integrity. The cerebral blood flow is controlled by neurovascular coupling through neurovascular units (NVUs). The NVU includes different types of cells, such as mural cells, astrocytes, pericytes, endothelial cells (ECs), and vascular smooth muscle cells (VSMCs). The cellular composition of NVU varies throughout the vascular tree. Amyloid ß (Aß) is abundantly present in the central nervous system, but the pathological accumulation of misfolded Aß protein causes vascular damage, resulting in neurovascular dysfunction. Aß aggregation can activate the astrocytes and endothelial cells. It is followed by pericyte degeneration which results in dysregulation of cerebral blood flow (CBF), neurovascular uncoupling, and BBB breakdown. Thus, understanding the cellular and molecular mechanisms of Aß-induced neurovascular toxicity is crucial for determining normal and diseased brain function. This chapter discusses the components of NVU, neurovascular uncoupling, Aß-induced cerebrovascular reactivity, and cerebral blood flow reduction in neurodegenerative disorders, with special emphasis on Alzheimer's disease.

Blockage of metallothionein synthesis via adrenaline ß receptor activation invalidates dehydroeffusol-mediated prevention of amyloid ß1-42 toxicity.

Dehydroeffusol, a major phenanthrene in Juncus effusus, protects neurodegeneration induced by intracellular Zn2+ ferried by extracellular amyloid ß1-42 (Aß1-42). Here we focused on adrenaline ß receptor activation and the induction of metallothioneins (MTs), intracellular Zn2+-binding proteins to test the protective mechanism of dehydroeffusol. Isoproterenol, an agonist of adrenergic ß receptors elevated the level of MTs in the dentate granule cell layer 1 day after intracerebroventricular (ICV) injection. When Aß1-42 was injected 1 day after isoproterenol injection, pre-injection of isoproterenol protected Aß1-42 toxicity via reducing the increase in intracellular Zn2+ after ICV injection of Aß1-42. On the basis of the effect of increased MTs by isoproterenol, dehydroeffusol (15 mg/kg body weight) was orally administered to mice once a day for 2 days. On day later, dehydroeffusol elevated the level of MTs and prevented Aß1-42 toxicity via reducing Aß1-42-mediated increase in intracellular Zn2+. In contrast, propranolol, an antagonist of adrenergic ß receptors reduced the level of MTs increased by dehydroeffusol, resulting in invalidating the preventive effect of dehydroeffusol on Aß1-42 toxicity. The present study indicates that blockage of MT synthesis via adrenaline ß receptor activation invalidates dehydroeffusol-mediated prevention of Aß1-42 toxicity. It is likely that MT synthesis via adrenaline ß receptor activation is beneficial to neuroprotection and that oral intake of dehydroeffusol preventively serves against the Aß1-42 toxicity.

The Protective Effects of Ecdysterone on Cognitive Impairment through Regulating Akt/GSK-3ß/Nrf2 Signaling Pathway and Oxidative Stress in Cognitive Mice Model and Aß-Induced Cell Neurotoxicity.

BACKGROUND: Severe neurological condition like Alzheimer's disease (AD) has a significantly negative impact on families and society, wherein there is no proven cure. As one of the principal active constituents of Achyranthes bidentata Blume, ecdysterone (ECR) has demonstrated antioxidant and cognitive dysfunction improvement effects. Nonetheless, the mechanism underlying the improvement of cognitive dysfunction by ECR remains unclear. This study sought to ascertain whether ECR may allebviate cognitive impairment by reducing oxidative stress via activation of the nuclear factor erythroid-2-related factor-2 (Nrf2) antioxidant system through Akt/GSK3ß pathway. METHODS: In terms of the experimental procedure, we determined the neuroprotective benefits of ECR in vivo via a cognitive impairment model of senescence-accelerated mouse prone 8 (SAMP8), we performed procedures such as behavioral testing, biochemical assaying, Nissl and TUNEL stainings, as well as flow cytometry, immunohistochemistry and western blotting. Furthermore, we investigated the underlying mechanistic action of ECR by activating PC12 cells with ß-amyloid peptide fragment 25-35 (Aß25-35). RESULTS: In vivo studies showed that ECR effectively improved cognitive impairment in SAMP8 via enhancement of learning and memory capabilities, but decreased oxidative stress, apoptosis and neuronal damage in the hippocampus. During the in vitro study, we observed that ECR dose-dependently reduced the oxidative stress and apoptosis that were induced in PC12 cells by Aß25-35. Additionally, the use of Akt inhibitors further established the potential of ECR to control Nrf2 through activation of the Akt/GSK3ß pathway and protect the PC12 cells from Aß25-35 induced damage. CONCLUSIONS: These findings offer proof that ECR reduces cognitive impairment by triggering the Nrf2 antioxidant system via the Akt/GSK3ß pathway and offer fresh information on ECR's potential as a promising therapeutic development candidate for AD.