Aβ Cytotoxicity Research Articles

Suppressors of amyloid-β toxicity improve recombinant protein production in yeast by reducing oxidative stress and tuning cellular metabolism

High-level production of recombinant proteins in industrial microorganisms is often limited by the formation of misfolded proteins or protein aggregates, which consequently induce cellular stress responses. We hypothesized that in a yeast Alzheimer's disease (AD) model overexpression of amyloid-β peptides (Aβ42), one of the main peptides relevant for AD pathologies, induces similar phenotypes of cellular stress. Using this humanized AD model, we previously identified suppressors of Aβ42 cytotoxicity. Here we hypothesize that these suppressors could be used as metabolic engineering targets to alleviate cellular stress and improve recombinant protein production in the yeast Saccharomyces cerevisiae. Forty-six candidate genes were individually deleted and twenty were individually overexpressed. The positive targets that increased recombinant α-amylase production were further combined leading to an 18.7-fold increased recombinant protein production. These target genes are involved in multiple cellular networks including RNA processing, transcription, ER-mitochondrial complex, and protein unfolding. By using transcriptomics and proteomics analyses, combined with reverse metabolic engineering, we showed that reduced oxidative stress, increased membrane lipid biosynthesis and repressed arginine and sulfur amino acid biosynthesis are significant pathways for increased recombinant protein production. Our findings provide new insights towards developing synthetic yeast cell factories for biosynthesis of valuable proteins.

Linking Alzheimer's Disease and Type 2 Diabetes: Characterization and Inhibition of Cytotoxic Aβ and IAPP Hetero-Aggregates.

The cytotoxic self-aggregation of β-amyloid (Aβ) peptide and islet amyloid polypeptide (IAPP) is implicated in the pathogenesis of Alzheimer’s disease (AD) and Type 2 diabetes (T2D), respectively. Increasing evidence, particularly the co-deposition of Aβ and IAPP in both brain and pancreatic tissues, suggests that Aβ and IAPP cross-interaction may be responsible for a pathological link between AD and T2D. Here, we examined the nature of IAPP-Aβ40 co-aggregation and its inhibition by small molecules. In specific, we characterized the kinetic profiles, morphologies, secondary structures and toxicities of IAPP-Aβ40 hetero-assemblies and compared them to those formed by their homo-assemblies. We demonstrated that monomeric IAPP and Aβ40 form stable hetero-dimers and hetero-assemblies that further aggregate into β-sheet-rich hetero-aggregates that are toxic (cell viability <50%) to both PC-12 cells, a neuronal cell model, and RIN-m5F cells, a pancreatic cell model for β-cells. We then selected polyphenolic candidates to inhibit IAPP or Aβ40 self-aggregation and examined the inhibitory effect of the most potent candidate on IAPP-Aβ40 co-aggregation. We demonstrated that epigallocatechin gallate (EGCG) form inter-molecular hydrogen bonds with each of IAPP and Aβ40. We also showed that EGCG reduced hetero-aggregate formation and resulted in lower β-sheets content and higher unordered structures in IAPP-Aβ40-EGCG samples. Importantly, we showed that EGCG is highly effective in reducing the toxicity of IAPP-Aβ40 hetero-aggregates on both cell models, specifically at concentrations that are equivalent to or are 2.5-fold higher than the mixed peptide concentrations. To the best of our knowledge, this is the first study to report the inhibition of IAPP-Aβ40 co-aggregation by small molecules. We conclude that EGCG is a promising candidate to prevent co-aggregation and cytotoxicity of IAPP-Aβ40, which in turn, contribute to the pathological link between AD and T2D.

Callistephin inhibits amyloid-β protein aggregation and determined cytotoxicity against cerebrovascular smooth muscle cells as an in vitro model of cerebral amyloid angiopathy

It has been indicated that amyloid β (Aβ) plaques can be accumulated within the basement membranes of cerebrovascular smooth muscle cells (CVSMCs) and stimulate the induction of cerebral amyloid angiopathy (CAA). However, the exact mechanism(s) of which small molecules including callistephin mitigate the formation of Aβ aggregation and associated CAA is not well-understood. Therefore, in the present study, Aβ 1–42 samples in the aggregation buffer were co-incubated for 36 h without or with of callistephin and the protein aggregation features along with the associated cytotoxicity against CVSMCs as the core components of cerebral arterial wall were explored by different biochemical and cellular methods. Fluorescence (ThT, Nile red) and CD techniques indicated the inhibition of Aβ 1–42 fibrillization in the presence of callistephin. Cellular assays revealed that cytotoxicity of Aβ 1–42 samples aged in the aggregation buffer with callistephin was much less against CVSMCs than Aβ 1–42 amyloid alone through regulation of membrane leakage and downregulation of TNF-α and IL-6 at protein level. In conclusion, these data may provide useful information about the possible mechanisms by which callistephin can show its protective effect against CAA.

Synthesis of carbon quantum dots for application of alleviating amyloid-β mediated neurotoxicity

Alzheimer’s disease (AD) has been an intractable neurodegenerative disease among the elderly in the worldwide. One of the important pathogenic factors in AD is the aggregation of amyloid-β 1-42 (Aβ42) in AD patients’ brain. Inhibition of Aβ peptide aggregation is considered as one of the effective approaches against AD. Herein, a pulsed laser ablation (PLA) method is used to fabricate ultra-small carbon quantum dots (C-QDs) with uniform size. The reduced Aβ42 aggregation by the C-QDs was confirmed by transmission electron microscopy (TEM), thioflavin T assay and circular dichroism (CD) spectroscopy. The results of cell viability experiments showed that the presence of the C-QDs could significantly reduce the cytotoxicity of Aβ42. Furthermore, in vivo studies demonstrate that C-QDs can decrease Aβ42 deposits and promote the biological activity of an AD model of Caenorhabditis elegans CL2006. This work demonstrates the viability of using ultrasmall C-QDs to inhibit amyloid-β aggregation and alleviate amyloid-β mediated neurotoxicity.

Native Ion Mobility-Mass Spectrometry-Enabled Fast Structural Interrogation of Labile Protein Surface Modifications at the Intact Protein Level.

Protein sialylation has been closely linked to many diseases including Alzheimer's disease (AD). It is also broadly implicated in therapeutics operating in a pattern-dependent (e.g., Neu5Ac vs Neu5Gc) manner. However, how the sialylation pattern affects the AD-associated, transferrin-assisted iron/Aβ cellular uptake process remains largely ill-defined. Herein, we report the use of native ion mobility-mass spectrometry (IM-MS)-based fast structural probing methodology, enabling well-controlled, synergistic, and in situ manipulation of mature glycoproteins and attached sialic acids. IM-MS-centered experiments enable the combinatorial interrogation of sialylation effects on Aβ cytotoxicity and the chemical, conformational, and topological stabilities of transferrin. Cell viability experiments suggest that Neu5Gc replacement enhances the transferrin-assisted, iron loading-associated Aβ cytotoxicity. Native gel electrophoresis and IM-MS reveal that sialylation stabilizes transferrin conformation but inhibits its dimerization. Collectively, IM-MS is adapted to capture key sialylation intermediates involved in fine-tuning AD-associated glycoprotein structural microheterogeneity. Our results provide the molecular basis for the importance of sustaining moderate TF sialylation levels, especially Neu5Ac, in promoting iron cellular transportation and rescuing iron-enhanced Aβ cytotoxicity.

Two statins and cromolyn as possible drugs against the cytotoxicity of Aβ(31-35) and Aβ(25-35) peptides: a comparative study by advanced computer simulation methods.

In this work, possible effective mechanisms of cromolyn, atorvastatin and lovastatin on the cytotoxicity of Aβ(31–35) and Aβ(25–35) peptides were investigated by classical molecular dynamics and well-tempered metadynamics simulations. The results demonstrate that all the drugs affect the behavior of the peptides, such as their ability to aggregate, and alter their secondary structures and their affinity to a particular drug. Our findings from the computed properties suggest that the best drug candidate is lovastatin. This medicine inhibits peptide aggregation, adsorbs the peptides on the surface of the drug clusters, changes the secondary structure and binds to MET35, which has been seen as the reason for the toxicity of the studied peptide sequences. Moreover, lovastatin is the drug which previously has demonstrated the strongest ability to penetrate the blood–brain barrier and makes lovastatin the most promising medicine among the three investigated drugs. Atorvastatin is also seen as a potential candidate if its penetration through the blood–brain barrier could be improved. Otherwise, its properties are even better than the ones demonstrated by lovastatin. Cromolyn appears to be less interesting as an anti-aggregant from the computational data, in comparison to the two statins.

The Dynamics of β-Amyloid Proteoforms Accumulation in the Brain of a 5xFAD Mouse Model of Alzheimer's Disease.

Alzheimer’s disease (AD) is the leading cause of dementia among the elderly. Neuropathologically, AD is characterized by the deposition of a 39- to 42-amino acid long β-amyloid (Aβ) peptide in the form of senile plaques. Several post-translational modifications (PTMs) in the N-terminal domain have been shown to increase the aggregation and cytotoxicity of Aβ, and specific Aβ proteoforms (e.g., Aβ with isomerized D7 (isoD7-Aβ)) are abundant in the senile plaques of AD patients. Animal models are indispensable tools for the study of disease pathogenesis, as well as preclinical testing. In the presented work, the accumulation dynamics of Aβ proteoforms in the brain of one of the most widely used amyloid-based mouse models (the 5xFAD line) was monitored. Mass spectrometry (MS) approaches, based on ion mobility separation and the characteristic fragment ion formation, were applied. The results indicated a gradual increase in the Aβ fraction of isoD7-Aβ, starting from approximately 8% at 7 months to approximately 30% by 23 months of age. Other specific PTMs, in particular, pyroglutamylation, deamidation, and oxidation, as well as phosphorylation, were also monitored. The results for mice of different ages demonstrated that the accumulation of Aβ proteoforms correlate with the formation of Aβ deposits. Although the mouse model cannot be a complete analogue of the processes occurring in the human brain in AD, and several of the observed parameters differ significantly from human values supposedly due to the limited lifespan of the model animals, this dynamic study provides evidence on at least one of the possible mechanisms that can trigger amyloidosis in AD, i.e., the hypothesis on the relationship between the accumulation of isoD7-Aβ and the progression of AD-like pathology.

Functional Gallic Acid-Based Dendrimers as Synthetic Nanotools to Remodel Amyloid-β-42 into Noncytotoxic Forms.

The self-assembly of amyloid-β (Aβ) generates cytotoxic oligomers linked to the onset and progression of Alzheimer’s disease (AD). As many fundamental molecular pathways that control Aβ aggregation are yet to be unraveled, an important strategy to control Aβ cytotoxicity is the development of bioactive synthetic nanotools capable of interacting with the heterogeneous ensemble of Aβ species and remodel them into noncytotoxic forms. Herein, the synthesis of nanosized, functional gallic acid (Ga)-based dendrimers with a precise number of Ga at their surface is described. It is shown that these Ga-terminated dendrimers interact by H-bonding with monomeric/oligomeric Aβ species at their Glu, Ala, and Asp residues, promoting their remodeling into noncytotoxic aggregates in a process controlled by the Ga units. The multivalent presentation of Ga on the dendrimer surface enhances their ability to interact with Aβ, inhibiting the primary and secondary nucleation of Aβ fibrillization and disrupting the Aβ preformed fibrils.

Increased ERb expression during ageing could be neuroprotective against Alzheimer's disease development in the male but not the female brain.

Age is the biggest risk factor for Alzheimer's disease (AD) with cases doubling every 5 years after 65 years. Increased risk is also associated with being female. This gender difference in AD incidence could be partly explained by menopause-related hormone deficiencies during ageing. Clinical studies concluded that the age when hormone replacement therapy was started, especially after the menopause, was critical in delaying AD development. Deposition of b-amyloid (Ab) in the hippocampus and cortex is the key pathological feature in AD. Much evidence has demonstrated that oestrogen activation of oestrogen receptors (ER) in neurones decreases Ab accumulation and antagonizes its cytotoxic effects in AD. ERb is an ER subtype highly expressed in the nervous system. In vivo studies reported that ERb activation reduces the cytotoxic effect of Ab through the Akt pathway and improves learning and memory capacity in AD models. However, this finding has not yet been investigated in the clinic. We hypothesised that the increased risk of AD in women could be partly explained by alterations in the levels of oestrogen, its receptors and downstream signalling pathways in the female brain during ageing affecting the expression of AD biomarkers. Levels of ERb, phosphorylated and total Akt, APP, its secretases and metabolites were measured using immunoblotting and ELISA in frontal cortical brain samples from young (20-30), middle-aged (45-55) and old (70-90) men and women with no history of dementia. In female brains significant age-related increases in APP and the secretases were observed but were not seen in male samples. bCTF and the Aβ42:40 ratio also showed age-related increases only in women. Aβ42 levels were higher in elderly female samples compared to male. In contrast, significant age-related increases in ERb and pAkt:total Akt were only seen in male samples. We demonstrate for the first time a sex difference in the expression of AD biomarkers with ageing with a novel age-related increase in APP in the ageing female brain. The increase in ERb expression in male but not female samples could result in a neuroprotective effect against Aβ cytotoxicity. Our findings could partly explain female vulnerability for AD development.

Cytotoxic Aβ Protofilaments Are Generated in the Process of Aβ Fibril Disaggregation

Significant research on Alzheimer’s disease (AD) has demonstrated that amyloid β (Aβ) oligomers are toxic molecules against neural cells. Thus, determining the generation mechanism of toxic Aβ oligomers is crucial for understanding AD pathogenesis. Aβ fibrils were reported to be disaggregated by treatment with small compounds, such as epigallocatechin gallate (EGCG) and dopamine (DA), and a loss of fibril shape and decrease in cytotoxicity were observed. However, the characteristics of intermediate products during the fibril disaggregation process are poorly understood. In this study, we found that cytotoxic Aβ aggregates are generated during a moderate disaggregation process of Aβ fibrils. A cytotoxicity assay revealed that Aβ fibrils incubated with a low concentration of EGCG and DA showed higher cytotoxicity than Aβ fibrils alone. Atomic force microscopy imaging and circular dichroism spectrometry showed that short and narrow protofilaments, which were highly stable in the β-sheet structure, were abundant in these moderately disaggregated samples. These results indicate that toxic Aβ protofilaments are generated during disaggregation from amyloid fibrils, suggesting that disaggregation of Aβ fibrils by small compounds may be one of the possible mechanisms for the generation of toxic Aβ aggregates in the brain.

All-d-Enantiomeric Peptide D3 Designed for Alzheimer's Disease Treatment Dynamically Interacts with Membrane-Bound Amyloid-β Precursors.

Alzheimer's disease (AD) is a severe neurodegenerative pathology with no effective treatment known. Toxic amyloid-β peptide (Aβ) oligomers play a crucial role in AD pathogenesis. All-d-Enantiomeric peptide D3 and its derivatives were developed to disassemble and destroy cytotoxic Aβ aggregates. One of the D3-like compounds is approaching phase II clinical trials; however, high-resolution details of its disease-preventing or pharmacological actions are not completely clear. We demonstrate that peptide D3 stabilizing Aβ monomer dynamically interacts with the extracellular juxtamembrane region of a membrane-bound fragment of an amyloid precursor protein containing the Aβ sequence. MD simulations based on NMR measurement results suggest that D3 targets the amyloidogenic region, not compromising its α-helicity and preventing intermolecular hydrogen bonding, thus creating prerequisites for inhibition of early steps of Aβ conversion into β-conformation and its toxic oligomerization. An enhanced understanding of the D3 action molecular mechanism facilitates development of effective AD treatment and prevention strategies.

A Galantamine-Curcumin Hybrid Decreases the Cytotoxicity of Amyloid-Beta Peptide on SH-SY5Y Cells.

Misfolded amyloid beta (Aβ) peptides aggregate and form neurotoxic oligomers. Membrane and mitochondrial damages, calcium dysregulation, oxidative stress, and fibril deposits are among the possible mechanisms of Aβ cytotoxicity. Galantamine (GAL) prevents apoptosis induced by Aβ mainly through the ability to stimulate allosterically the α7 nAChRs and to regulate the calcium cytosolic concentration. Here, we examined the cytoprotective effects of two GAL derivatives, namely compounds 4b and 8, against Aβ cytotoxicity on the human neuroblastoma cell line SH-SY5Y. The protective effects were tested at simultaneous administration, pre-incubation and post-incubation, with Aβ. GAL and curcumin (CU) were used in the study as reference compounds. It was found that 4b protects cells in a similar mode as GAL, while compound 8 and CU potentiate the toxic effects of Aβ. Allosteric stimulation of α7 nAChRs is suggested as a possible mechanism of the cytoprotectivity of 4b. These and previous findings characterize 4b as a prospective non-toxic multi-target agent against neurodegenerative disorders with inhibitory activity on acetylcholinesterase, antioxidant, and cytoprotective properties.

Molecular dynamics study of water channels in natural and synthetic amyloid-β fibrils.

We compared all-atom explicit solvent molecular dynamics simulations of three types of Aβ(1-40) fibrils: brain-seeded fibrils (2M4J, with a threefold axial symmetry) and the other two, all-synthetic fibril polymorphs (2LMN and 2LMP, made under different fibrillization conditions). Fibril models were constructed using either a finite or an infinite number of layers made using periodic images. These studies yielded four conclusions. First, finite fibrils tend to unravel in a manner reminiscent of fibril dissolution, while infinite fibrils were more stable during simulations. Second, salt bridges in these fibrils remained stable in those fibrils that contained them initially, and those without salt bridges did not develop them over the time course of the simulations. Third, all fibrils tended to develop a "stagger" or register shift of β-strands along the fibril axis. Fourth and most importantly, the brain-seeded, 2M4J, infinite fibrils allowed bidirectional transport of water in and out of the central longitudinal core of the fibril by rapidly developing gaps at the fibril vertices. 2LMP fibrils also showed this behavior, although to a lesser extent. The diffusion of water molecules in the fibril core region involved two dynamical states: a localized state and directed diffusion in the presence of obstacles. These observations provided support for the hypothesis that Aβ fibrils could act as nanotubes. At least some Aβ oligomers resembled fibrils structurally in having parallel, in-register β-sheets and a sheet-turn-sheet motif. Thus, our findings could have implications for Aβ cytotoxicity, which may occur through the ability of oligomers to form abnormal water and ion channels in cell membranes.

Polymorphic SERPINA3-R124C reduces pathogenesis of its wild type by shortening the lifetime of oligomeric Aβ.

Amyloid beta (Aβ) 42 peptide accumulated in Alzheimer disease (AD) patients' brain, often colocalized with serine protease inhibitor family A member 3 (SERPINA3). Being a chaperon, SERPINA3 accelerated Aβ42 fibrillization. While analyzing chaperon activity of human SERPINA3 polymorphisms, we found SERPINA3-R124C played a role in protecting cells from Aβ42 cytotoxicity. SH-SY5Y cells exposed to Aβ42 preincubated with wild-type SERPINA3 (SERPINA3-WT) resulted in extended toxicity leading cell death whereas Aβ42 with SERPINA3-R124C resulted in less cytotoxicity. Transmission electron microscope and thioflavin T assay revealed that SERPINA3-R124C shortened lifetime of small soluble oligomer and maintained β-sheet rich protofibril-like aggregates for longer time compared to that of with SERPINA3-WT. Western blot assay confirmed that SERPINA3-R124C converted Aβ42 mostly into high molecular aggregates. Here, we demonstrate first time that polymorphic SERPINA3 acts as a benign chaperon by modulating the transition states of Aβ42, which may contribute to the reduction of AD risk.

Inhibitory Effects of Sulfated Polysaccharides from the Sea Cucumber Cucumaria Frondosa against Aβ40 Aggregation and Cytotoxicity.

Abnormal aggregation and deposition of Aβ is one of the causative agents for Alzheimer's disease. The development of inhibitors for Aβ aggregation has been considered a possible method to prevent and treat Alzheimer's disease. Edible sea cucumbers contain many bioactive molecules, including saponins, phospholipids, peptides, and polysaccharides. Herein, we report that polysaccharides extracted from sea cucumber Cucumaria frondosa could reduce the aggregation and cytotoxicity of Aβ40. By utilizing multiple biochemical and biophysical instruments, we found that the polysaccharides could inhibit the aggregation of Aβ40. A chemical kinetics analysis further suggested that the major inhibitory effects of the polysaccharides were achieved by disassembling mature fibrils, which in turn reduced the cytotoxicity of Aβ. These results suggested that the polysaccharides extracted from sea cucumber could be used as an effective inhibitor for Aβ.

A Systematic Screening of Traditional Chinese Medicine Identifies Two Novel Inhibitors Against the Cytotoxic Aggregation of Amyloid Beta.

The toxic aggregates of amyloid beta (Aβ) disrupt the cell membrane, induce oxidative stress and mitochondrial dysfunction, and eventually lead to Alzheimer’s disease (AD). Intervening with this cytotoxic aggregation process has been suggested as a potential therapeutic approach for AD and other protein misfolding diseases. Traditional Chinese Medicine (TCM) has been used to treat AD and related cognitive impairment for centuries with obvious efficacy. Extracts or active ingredients of TCMs have been reported to inhibit the aggregation and cytotoxicity of Aβ. However, there is a lack of systematic research on the anti-Aβ aggregation effects of TCM components. In this study, we performed a systematic screening to identify the active ingredients of TCM against the cytotoxic aggregation of Aβ42. Through a literature and database survey, we selected 19 TCM herbals frequently used in the treatment of AD, from which 76 major active chemicals without known anti-amyloid effects were further screened. This took place through two rounds of MTT-based screening detection of the cytotoxicity of these chemicals and their effects on Aβ42-induced cytotoxicity, respectively. Tetrahydroxystilbene-2-O-β-D-glucoside (TSG) and sinapic acid (SA) were found to be less toxic, and they inhibited the cytotoxicity of Aβ42. Further studies demonstrated that TSG and SA concentration-dependently attenuated the amyloidosis and membrane disruption ability of Aβ42. Thus, we identified two novel chemicals (TSG and SA) against the cytotoxic aggregation of Aβ42. Nonetheless, further exploration of their therapeutic potential is warranted.

Current Management and Therapeutic Strategies for Cerebral Amyloid Angiopathy.

Cerebral amyloid angiopathy (CAA) is characterized by accumulation of amyloid β (Aβ) in walls of leptomeningeal vessels and cortical capillaries in the brain. The loss of integrity of these vessels caused by cerebrovascular Aβ deposits results in fragile vessels and lobar intracerebral hemorrhages. CAA also manifests with progressive cognitive impairment or transient focal neurological symptoms. Although development of therapeutics for CAA is urgently needed, the pathogenesis of CAA remains to be fully elucidated. In this review, we summarize the epidemiology, pathology, clinical and radiological features, and perspectives for future research directions in CAA therapeutics. Recent advances in mass spectrometric methodology combined with vascular isolation techniques have aided understanding of the cerebrovascular proteome. In this paper, we describe several potential key CAA-associated molecules that have been identified by proteomic analyses (apolipoprotein E, clusterin, SRPX1 (sushi repeat-containing protein X-linked 1), TIMP3 (tissue inhibitor of metalloproteinases 3), and HTRA1 (HtrA serine peptidase 1)), and their pivotal roles in Aβ cytotoxicity, Aβ fibril formation, and vessel wall remodeling. Understanding the interactions between cerebrovascular Aβ deposits and molecules that accumulate with Aβ may lead to discovery of effective CAA therapeutics and to the identification of biomarkers for early diagnosis.

Molecular Mechanism of Vitamin K2 Protection against Amyloid-β-Induced Cytotoxicity.

The pathological role of vitamin K2 in Alzheimer’s disease (AD) involves a definite link between impaired cognitive functions and decreased serum vitamin K levels. Vitamin K2 supplementation may have a protective effect on AD. However, the mechanism underlying vitamin K2 protection has not been elucidated. With the amyloid-β (Aβ) cascade hypothesis, we constructed a clone containing the C-terminal fragment of amyloid precursor protein (β-CTF/APP), transfected in astroglioma C6 cells and used this cell model (β-CTF/C6) to study the protective effect of vitamin K2 against Aβ cytotoxicity. Both cellular and biochemical assays, including cell viability and reactive oxygen species (ROS), assays assay, and Western blot and caspase activity analyses, were used to characterize and unveil the protective role and mechanism of vitamin K2 protecting against Aβ-induced cytotoxicity. Vitamin K2 treatment dose-dependently decreased the death of neural cells. The protective effect of vitamin K2 could be abolished by adding warfarin, a vitamin K2 antagonist. The addition of vitamin K2 reduced the ROS formation and inhibited the caspase-3 mediated apoptosis induced by Aβ peptides, indicating that the mechanism underlying the vitamin K2 protection is likely against Aβ-mediated apoptosis. Inhibitor assay and Western blot analyses revealed that the possible mechanism of vitamin K2 protection against Aβ-mediated apoptosis might be via regulating phosphatidylinositol 3-kinase (PI3K) associated-signaling pathway and inhibiting caspase-3-mediated apoptosis. Our study demonstrates that vitamin K2 can protect neural cells against Aβ toxicity.

Component of Cannabis, Cannabidiol, as a Possible Drug against the Cytotoxicity of Aβ(31-35) and Aβ(25-35) Peptides: An Investigation by Molecular Dynamics and Well-Tempered Metadynamics Simulations.

In this work cannabidiol (CBD) was investigated as a possible drug against the cytotoxicity of Aβ(31–35) and Aβ(25–35) peptides with the help of atomistic molecular dynamics (MD) and well-tempered metadynamics simulations. Four interrelated mechanisms of possible actions of CBD are proposed from our computations. This implies that one mechanism can be a cause or/and a consequence of another. CBD is able to decrease the aggregation of peptides at certain concentrations of compounds in water. This particular action is more prominent for Aβ(25–35), since originally Aβ(31–35) did not exhibit aggregation properties in aqueous solutions. Interactions of CBD with the peptides affect secondary structures of the latter ones. Clusters of CBD are seen as possible adsorbents of Aβ(31–35) and Aβ(25–35) since peptides are tending to aggregate around them. And last but not least, CBD exhibits binding to MET35. All four mechanisms of actions can possibly inhibit the Aβ-cytotoxicity as discussed in this paper. Moreover, the amount of water also played a role in peptide clustering: with a growing concentration of peptides in water without a drug, the aggregation of both Aβ(31–35) and Aβ(25–35) increased. The number of hydrogen bonds between peptides and water was significantly higher for simulations with Aβ(25–35) at the higher concentration of peptides, while for Aβ(31–35) that difference was rather insignificant. The presence of CBD did not substantially affect the number of hydrogen bonds in the simulated systems.

REDD1 Is Involved in Amyloid β-Induced Synaptic Dysfunction and Memory Impairment.

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by neurological dysfunction, including memory impairment, attributed to the accumulation of amyloid β (Aβ) in the brain. Although several studies reported possible mechanisms involved in Aβ pathology, much remains unknown. Previous findings suggested that a protein regulated in development and DNA damage response 1 (REDD1), a stress-coping regulator, is an Aβ-responsive gene involved in Aβ cytotoxicity. However, we still do not know how Aβ increases the level of REDD1 and whether REDD1 mediates Aβ-induced synaptic dysfunction. To elucidate this, we examined the effect of Aβ on REDD1-expression using acute hippocampal slices from mice, and the effect of REDD1 short hairpin RNA (shRNA) on Aβ-induced synaptic dysfunction. Lastly, we observed the effect of REDD1 shRNA on memory deficit in an AD-like mouse model. Through the experiments, we found that Aβ-incubated acute hippocampal slices showed increased REDD1 levels. Moreover, Aβ injection into the lateral ventricle increased REDD1 levels in the hippocampus. Anisomycin, but not actinomycin D, blocked Aβ-induced increase in REDD1 levels in the acute hippocampal slices, suggesting that Aβ may increase REDD1 translation rather than transcription. Aβ activated Fyn/ERK/S6 cascade, and inhibitors for Fyn/ERK/S6 or mGluR5 blocked Aβ-induced REDD1 upregulation. REDD1 inducer, a transcriptional activator, and Aβ blocked synaptic plasticity in the acute hippocampal slices. REDD1 inducer inhibited mTOR/Akt signaling. REDD1 shRNA blocked Aβ-induced synaptic deficits. REDD1 shRNA also blocked Aβ-induced memory deficits in passive-avoidance and object-recognition tests. Collectively, these results demonstrate that REDD1 participates in Aβ pathology and could be a target for AD therapy.