Design, synthesis and evaluation of bioactivity of peptidomimetics based on chloroalkene dipeptide isosteres.

Ample biologically active peptides have been found, identified and modified for use in drug discovery to date. However, several factors, such as low metabolic stability due to proteolysis and non-specific interactions with multiple off-target molecules, might limit the therapeutic use of peptides. To enhance the stability and/or bioactivity of peptides, the development of "peptidomimetics," which mimick peptide molecules, is considered to be idealistic. Hence, chloroalkene dipeptide isosteres (CADIs) was designed, and their synthetic methods have been developed by us. Briefly, in a CADI an amide bond in peptides is replaced with a chloroalkene structure. CADIs might be superior mimetics of amide bonds because the Van der Waals radii (VDR) and the electronegativity value of a chlorine atom are close to those of the replaced oxygen atom. By a developed method of the "liner synthesis", N-tert-butylsulfonyl protected CADIs can be synthesized via a key reaction involving diastereoselective allylic alkylation using organocopper reagents. On the other hand, by a developed method of the "convergent synthesis", N-fluorenylmethoxycarbonyl (Fmoc)-protected carboxylic acids can be also constructed based on N- and C-terminal analogues from corresponding amino acid starting materials via an Evans syn aldol reaction and the Ichikawa allylcyanate rearrangement reaction involving a [3.3] sigmatropic rearrangement. Notably, CADIs can also be applied for Fmoc-based solid-phase peptide synthesis and therefore introduced into bioactive peptides including as the Arg-Gly-Asp (RGD) peptide and the amyloid ß fragment Lys-Leu-Val-Phe-Phe (KLVFF) peptide, which are correlated with cell attachment and Alzheimer's disease (AD), respectively. These CADI-containing peptidomimetics stabilized the conformation and enhanced the potency of the cyclic RGD peptide and the cyclic KLVFF peptide.

Amyloid particles facilitate surface-catalyzed cross-seeding by acting as promiscuous nanoparticles.

Amyloid seeds are nanometer-sized protein particles that accelerate amyloid assembly as well as propagate and transmit the amyloid protein conformation associated with a wide range of protein misfolding diseases. However, seeded amyloid growth through templated elongation at fibril ends cannot explain the full range of molecular behaviors observed during cross-seeded formation of amyloid by heterologous seeds. Here, we demonstrate that amyloid seeds can accelerate amyloid formation via a surface catalysis mechanism without propagating the specific amyloid conformation associated with the seeds. This type of seeding mechanism is demonstrated through quantitative characterization of the cross-seeded assembly reactions involving two nonhomologous and unrelated proteins: the human Aß42 peptide and the yeast prion-forming protein Sup35NM. Our results demonstrate experimental approaches to differentiate seeding by templated elongation from nontemplated amyloid seeding and rationalize the molecular mechanism of the cross-seeding phenomenon as a manifestation of the aberrant surface activities presented by amyloid seeds as nanoparticles.

GC/MS and LC-ESI-MS analysis of Conocarpus erectus Leaves Extract via Regulating Amyloid-ß-peptide, Tau protein, Neurotransmitters, Inflammation and Oxidative Stress against AlCl3-Induced Alzheimer's Disease in Rats.

This study investigated the therapeutic effect of Conocarpus erectus leaves methanolic extract against AlCl3 -induced Alzheimer's disease (AD) in rats comparing with Donepezil-hydrochloride as a reference drug. The bioactive compounds of C. erectus leaves were isolated and identified by GC/MS and LC-ESI-MS analysis. Malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), amyloid-ß-peptide (Aß-peptide), tau protein, acetylcholinesterase (AChE), serotonin (5-HT), dopamine (DA) and nor-adrenaline (NE) levels were estimated. The neuromuscular strength, memory behavior and histopathological examination of cerebral cortex region were also conducted. Forty-three compounds were characterized from the non-polar fraction of C. erectus L. leaves extract and nineteen compounds were identified from the defatted extract. AlCl3- induction caused significant elevation of brain oxidative stress, Aß-peptide, tau protein, IL-6, TNF-α and AChE levels. A significant decrease in 5-HT, ND and DA levels were noticed. Additionally, AlCl3 reduced neuromuscular strength and compromised memory function. Treatment of AlCl3- induced rats with C. erectuse extract ameliorated these selected parameters by variable degrees. In conclusion, C. erectus protects against AlCl3- induced AD in rats through its antioxidant, anti-inflammatory, and antineutron damage. It could be considered as a new nutraceutical agent for attenuating symptoms associated with Alzheimer's disease.

In Search for Low-Molecular-Weight Ligands of Human Serum Albumin That Affect Its Affinity for Monomeric Amyloid ß Peptide.

An imbalance between production and excretion of amyloid ß peptide (Aß) in the brain tissues of Alzheimer's disease (AD) patients leads to Aß accumulation and the formation of noxious Aß oligomers/plaques. A promising approach to AD prevention is the reduction of free Aß levels by directed enhancement of Aß binding to its natural depot, human serum albumin (HSA). We previously demonstrated the ability of specific low-molecular-weight ligands (LMWLs) in HSA to improve its affinity for Aß. Here we develop this approach through a bioinformatic search for the clinically approved AD-related LMWLs in HSA, followed by classification of the candidates according to the predicted location of their binding sites on the HSA surface, ranking of the candidates, and selective experimental validation of their impact on HSA affinity for Aß. The top 100 candidate LMWLs were classified into five clusters. The specific representatives of the different clusters exhibit dramatically different behavior, with 3- to 13-fold changes in equilibrium dissociation constants for the HSA-Aß40 interaction: prednisone favors HSA-Aß interaction, mefenamic acid shows the opposite effect, and levothyroxine exhibits bidirectional effects. Overall, the LMWLs in HSA chosen here provide a basis for drug repurposing for AD prevention, and for the search of medications promoting AD progression.

Investigation of the Aggregation of Aß Peptide (1-40) in the Presence of κ-Carrageenan-Stabilised Liposomes Loaded with Homotaurine.

The kinetics of amyloid aggregation was studied indirectly by monitoring the changes in the polydispersity of mixed dispersion of amyloid ß peptide (1-40) and composite liposomes. The liposomes were prepared from the 1,2-dioleoyl-sn-glicero-3-phoshocholine (DOPC) phospholipid and stabilised by the electrostatic adsorption of κ-carrageenan. The produced homotaurine-loaded and unloaded liposomes had a highly negative electrokinetic potential and remarkable stability in phosphate buffer (pH 4 and 7.4). For the first time, the appearance and evolution of the aggregation of Aß were presented through the variation in the standard percentile readings (D10, D50, and D90) obtained from the particle size distribution analysis. The kinetic experiments indicated the appearance of the first aggregates almost 30 min after mixing the liposomes and peptide solution. It was observed that by adding unloaded liposomes, the size of 90% of the particles in the dispersion (D90) increased. In contrast, the addition of homotaurine-loaded liposomes had almost minimal impact on the size of the fractions of larger particles during the kinetic experiments. Despite the specific bioactivity of homotaurine in the presence of natural cell membranes, this study reported an additional inhibitory effect of the compound on the amyloid peptide aggregation due to the charge effects and 'molecular crowding'.

Royal jelly improves learning and memory deficits in an amyloid ß-induced model of Alzheimer's disease in male rats: Involvement of oxidative stress.

Alzheimer's disease (AD) as the commonest type of dementia is associated with the cognitive function failure. Oxidative stress performs an essential role in the progression of AD. Royal jelly (RJ) is a natural product of bees with antioxidant and anti-inflammatory properties. The present research aimed to investigate the possible protective effect of RJ on learning and memory in a rat model of Aß-induced AD. Forty male adult Wistar rats were equally distributed into five groups: control, sham-operated, Aß (receiving intracerebroventricular (ICV) injection of amyloid beta (Aß1-40)), Aß + RJ 50 mg/kg, and Aß + RJ 100 mg/kg. RJ was administered daily post-surgery by oral gavage for four weeks. Behavioral learning and memory were examined using the novel object recognition (NOR) and passive avoidance learning (PAL) tests. Also, oxidative stress markers, such as malondialdehyde (MDA), total oxidant status (TOS) and total antioxidant capacity (TAC), were assessed in the hippocampus. Aß reduced step-through latency (STLr) and increased time spent in the dark compartment (TDC) in the PAL task and also decreased discrimination index in the NOR test. Administration of RJ ameliorated the Aß-related memory impairment in both NOR and PAL tasks. Aß decreased TAC and increased MDA and TOS levels in the hippocampus, whereas RJ administration reversed these Aß-induced alterations. Our results indicated that RJ has the potential to ameliorate learning and memory impairment in the Aß model of AD via attenuating oxidative stress.

Alzheimer's Amyloid ß Peptide Induces Angiogenesis in an Alzheimer's Disease Model Mouse through Placental Growth Factor and Angiopoietin 2 Expressions.

Increased angiogenesis, especially the pathological type, has been documented in Alzheimer's disease (AD) brains, and it is considered to be activated due to a vascular dysfunction-mediated hypoxic condition. To understand the role of the amyloid ß (Aß) peptide in angiogenesis, we analyzed its effects on the brains of young APP transgenic AD model mice. Immunostaining results revealed that Aß was mainly localized intracellularly, with very few immunopositive vessels, and there was no extracellular deposition at this age. Solanum tuberosum lectin staining demonstrated that compared to their wild-type littermates, the vessel number was only increased in the cortex of J20 mice. CD105 staining also showed an increased number of new vessels in the cortex, some of which were partially positive for collagen4. Real-time PCR results demonstrated that placental growth factor (PlGF) and angiopoietin 2 (AngII) mRNA were increased in both the cortex and hippocampus of J20 mice compared to their wild-type littermates. However, vascular endothelial growth factor (VEGF) mRNA did not change. Immunofluorescence staining confirmed the increased expression of PlGF and AngII in the cortex of the J20 mice. Neuronal cells were positive for PlGF and AngII. Treatment of a neural stem cell line (NMW7) with synthetic Aß1-42 directly increased the expression of PlGF and AngII, at mRNA levels, and AngII at protein levels. Thus, these pilot data indicate that pathological angiogenesis exists in AD brains due to the direct effects of early Aß accumulation, suggesting that the Aß peptide regulates angiogenesis through PlGF and AngII expression.

Molecular Integrative Analysis of the Inhibitory Effects of Dipeptides on Amyloid ß Peptide 1-42 Polymerization.

The major pathological feature of Alzheimer's disease (AD) is the aggregation of amyloid ß peptide (Aß) in the brain. Inhibition of Aß42 aggregation may prevent the advancement of AD. This study employed molecular dynamics, molecular docking, electron microscopy, circular dichroism, staining of aggregated Aß with ThT, cell viability, and flow cytometry for the detection of reactive oxygen species (ROS) and apoptosis. Aß42 polymerizes into fibrils due to hydrophobic interactions to minimize free energy, adopting a ß-strand structure and forming three hydrophobic areas. Eight dipeptides were screened by molecular docking from a structural database of 20 L-α-amino acids, and the docking was validated by molecular dynamics (MD) analysis of binding stability and interaction potential energy. Among the dipeptides, arginine dipeptide (RR) inhibited Aß42 aggregation the most. The ThT assay and EM revealed that RR reduced Aß42 aggregation, whereas the circular dichroism spectroscopy analysis showed a 62.8% decrease in ß-sheet conformation and a 39.3% increase in random coiling of Aß42 in the presence of RR. RR also significantly reduced the toxicity of Aß42 secreted by SH-SY5Y cells, including cell death, ROS production, and apoptosis. The formation of three hydrophobic regions and polymerization of Aß42 reduced the Gibbs free energy, and RR was the most effective dipeptide at interfering with polymerization.

APP mouse models for Alzheimer's disease preclinical studies.

Animal models of human diseases that accurately recapitulate clinical pathology are indispensable for understanding molecular mechanisms and advancing preclinical studies. The Alzheimer's disease (AD) research community has historically used first-generation transgenic (Tg) mouse models that overexpress proteins linked to familial AD (FAD), mutant amyloid precursor protein (APP), or APP and presenilin (PS). These mice exhibit AD pathology, but the overexpression paradigm may cause additional phenotypes unrelated to AD Second-generation mouse models contain humanized sequences and clinical mutations in the endogenous mouse App gene. These mice show Aß accumulation without phenotypes related to overexpression but are not yet a clinical recapitulation of human AD In this review, we evaluate different APP mouse models of AD, and review recent studies using the second-generation mice. We advise AD researchers to consider the comparative strengths and limitations of each model against the scientific and therapeutic goal of a prospective preclinical study.

Aß monomer induces phosphorylation of Tau at Ser-214 through ß2AR-PKA-JNK signaling pathway.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with synaptic dysfunction, pathological accumulation of ß-amyloid peptide 1-42 (Aß1-42 ), and neuronal loss. The self-association of Aß1-42 monomers (Aß-M) into soluble oligomers seems to be crucial for the development of neurotoxicity. Previous publications have shown that Aß oligomers and dimers might play key roles in inducing AD. The role of Aß-M was rarely investigated and still unclear in AD. To understand the effects of Aß-M on neurons and other cell types in the brain could be the key to understand its function. In our study, we found that Aß-M expression slowly induced cell apoptosis within 48 hours after transfection, ß2 adrenergic receptor (ß2AR) interacted with Aß-M in the pull-down and the yeast two-hybrid assays, and Aß-M played a major role in inducing phosphorylation of Tau at Ser-214, c-Jun N-terminal kinase (JNK) at Thr-183/Tyr-185, p70 ribosomal protein S6 kinase (p70S6K) at Thr-389. We also discovered that ß2AR, G protein-coupled receptor kinase 2 (GRK2), and protein kinase A (PKA) mediated the phosphorylation of Tau and JNK. Aß-M induced phosphorylation of Tau at Ser-214 through both ß2AR-cAMP/PKA-JNK and ß2AR-GRK signaling pathways. Mitogen-activated protein kinase kinase (MEK) mediated the phosphorylation of p70S6K induced by Aß-M.

An Overview of Several Inhibitors for Alzheimer's Disease: Characterization and Failure.

Amyloid beta (Aß) oligomers are the most neurotoxic aggregates causing neuronal death and cognitive damage. A detailed elucidation of the aggregation pathways from oligomers to fibril formation is crucial to develop therapeutic strategies for Alzheimer's disease (AD). Although experimental techniques rely on the measure of time- and space-average properties, they face severe difficulties in the investigation of Aß peptide aggregation due to their intrinsically disorder character. Computer simulation is a tool that allows tracing the molecular motion of molecules; hence it complements Aß experiments, as it allows to explore the binding mechanism between metal ions and Aß oligomers close to the cellular membrane at the atomic resolution. In this context, integrated studies of experiments and computer simulations can assist in mapping the complete pathways of aggregation and toxicity of Aß peptides. Aß oligomers are disordered proteins, and due to a rapid exploration of their intrinsic conformational space in real-time, they are challenging therapeutic targets. Therefore, no good drug candidate could have been identified for clinical use. Our previous investigations identified two small molecules, M30 (2-Octahydroisoquinolin-2(1H)-ylethanamine) and Gabapentin, capable of Aß binding and inhibiting molecular aggregation, synaptotoxicity, intracellular calcium signaling, cellular toxicity and memory losses induced by Aß. Thus, we recommend these molecules as novel candidates to assist anti-AD drug discovery in the near future. This review discusses the most recent research investigations about the Aß dynamics in water, close contact with cell membranes, and several therapeutic strategies to remove plaque formation.

Serotonin Promotes Serum Albumin Interaction with the Monomeric Amyloid ß Peptide.

Prevention of amyloid ß peptide (Aß) deposition via facilitation of Aß binding to its natural depot, human serum albumin (HSA), is a promising approach to preclude Alzheimer's disease (AD) onset and progression. Previously, we demonstrated the ability of natural HSA ligands, fatty acids, to improve the affinity of this protein to monomeric Aß by a factor of 3 (BBRC, 510(2), 248-253). Using plasmon resonance spectroscopy, we show here that another HSA ligand related to AD pathogenesis, serotonin (SRO), increases the affinity of the Aß monomer to HSA by a factor of 7/17 for Aß40/Aß42, respectively. Meanwhile, the structurally homologous SRO precursor, tryptophan (TRP), does not affect HSA's affinity to monomeric Aß, despite slowdown of the association and dissociation processes. Crosslinking with glutaraldehyde and dynamic light scattering experiments reveal that, compared with the TRP-induced effects, SRO binding causes more marked changes in the quaternary structure of HSA. Furthermore, molecular docking reveals distinct structural differences between SRO/TRP complexes with HSA. The disintegration of the serotonergic system during AD pathogenesis may contribute to Aß release from HSA in the central nervous system due to impairment of the SRO-mediated Aß trapping by HSA.

Calcium Dyshomeostasis in Alzheimer's Disease Pathogenesis.

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder that is characterized by amyloid ß-protein deposition in senile plaques, neurofibrillary tangles consisting of abnormally phosphorylated tau protein, and neuronal loss leading to cognitive decline and dementia. Despite extensive research, the exact mechanisms underlying AD remain unknown and effective treatment is not available. Many hypotheses have been proposed to explain AD pathophysiology; however, there is general consensus that the abnormal aggregation of the amyloid ß peptide (Aß) is the initial event triggering a pathogenic cascade of degenerating events in cholinergic neurons. The dysregulation of calcium homeostasis has been studied considerably to clarify the mechanisms of neurodegeneration induced by Aß. Intracellular calcium acts as a second messenger and plays a key role in the regulation of neuronal functions, such as neural growth and differentiation, action potential, and synaptic plasticity. The calcium hypothesis of AD posits that activation of the amyloidogenic pathway affects neuronal Ca2+ homeostasis and the mechanisms responsible for learning and memory. Aß can disrupt Ca2+ signaling through several mechanisms, by increasing the influx of Ca2+ from the extracellular space and by activating its release from intracellular stores. Here, we review the different molecular mechanisms and receptors involved in calcium dysregulation in AD and possible therapeutic strategies for improving the treatment.

[Mechanism of puerarin reversing SH-SY5Y cell injury induced by Aß_(1-42) based on proteomics].

Puerarin has the anti-Alzheimer's disease (AD) activity,which can reverse nerve injury induced by Aßand inhibit neuronal apoptosis.However,its potential pharmacodynamic mechanism still needs to be further researched.The occurrence and development of AD is due to the change of multiple metabolic links in the body,which leads to the destruction of balance.Puerarin may act on multiple targets and multiple metabolic processes to achieve therapeutic purposes.Quantitative proteomic analysis provides a new choice to understand the mechanism as completely as possible.This research adopted SH-SY5Y cells induced by Aß_(1-42)to establish AD cell model,and Aßimmunofluorescence detection showed that Aßdecreased significantly after puerarin intervention.The mechanism of puerarin reversing SH-SY5Y cell injured by Aß_(1-42)was further explored by using label-free non-labeled quantitative technology and Western blot detection based on bioinformatics analysis result.The results showed that most of the differential proteins were related to biological processes such as cellular component organization or biogenesis,cellular component organization and cellular component biogenesis,and they mainly participated in the top ten pathways of P value such as pathogenic Escherichia coli infection,m TOR signaling pathway,regulation of autophagy,regulation of actin cytoskeleton,spliceosome,hepatocellular carcinoma,tight junction,non-small cell lung cancer,apoptosis and gap junction.Annexin V/PI flow cytometry and TUNEL were used to detect apoptosis,and the results showed that Aßdecreased significantly and the rate of apoptosis decreased significantly after puerarin intervention.Western blot analysis found that the protein expression level of autophagy related protein LC3Ⅱwas up-regulated after Aßinduction,and the degree of this up-regulation was further enhanced in puerarin intervention group.The trend of the ratio of LC3Ⅱ/LC3Ⅰamong groups was the same as the protein expression level of LC3Ⅱ，the protein expression level of p62 in the control group,AD model group and puerarin intervention group decreased successively.Protein interaction network analysis showed that CAP1 was correlated with TUBA1B,HSP90AB2P,DNM1L,TUBA1A and ERK1/2,and the correlation between CAP1 and ERK1/2 was the highest among them.Western blot showed that the expressions of p-ERK1/2,Bax and CAP1 were significantly down-regulated and the protein expression level of Bcl-2 was significantly up-regulated after puerarin intervention.Therefore,puerarin might improve the SH-SY5Y cells injured by Aß_(1-42)through the interaction of multiple biological processes and pathways in cells multiple locations,and CAP1 might play an important role among them.

GABAergic dysfunction in excitatory and inhibitory (E/I) imbalance drives the pathogenesis of Alzheimer's disease.

OBJECTIVE: To propose a new hypothesis that GABAergic dysfunction in excitatory and inhibitory (E/I) imbalance drives the pathogenesis of Alzheimer's disease (AD). BACKGROUND: Synaptic dysfunction and E/I imbalance emerge decades before the appearance of cognitive decline in AD patients, which contribute to neurodegeneration. Initially, E/I imbalance was thought to occur first, due to dysfunction of the glutamatergic and cholinergic systems. However, new evidence has demonstrated that the GABAergic system, the counterpart of E/I balance and the major inhibitory neurotransmitter system in the central nervous system, is altered enormously and that this contributes to E/I imbalance and further AD pathogenesis. NEW HYPOTHESIS: Alterations to the GABAergic system, induced by multiple AD pathogenic or risk factors, contribute to E/I imbalance and AD pathogenesis. MAJOR CHALLENGES FOR THE HYPOTHESIS: This GABAergic hypothesis accounts for many critical questions and common challenges confronting a new hypothesis of AD pathogenesis. More specifically, it explains why amyloid beta (Aß), ß-secretase (BACE1), apolipoprotein E4 gene (APOE ε4), hyperactive glia cells, contributes to AD pathogenesis and why age and sex are the risk factors of AD. GABAergic dysfunction promotes the spread of Aß pathology throughout the AD brain and associated cognitive impairments, and the induction of dysfunction induced by these varied risk factors shares this common neurobiology leading to E/I imbalance. In turn, some of these factors exacerbate GABAergic dysfunction and E/I imbalance. Moreover, the GABAergic system modulates various brain functions and thus, the GABAergic hypothesis accounts for nonamnestic manifestations. Furthermore, corrections of E/I balance through manipulation of GABAergic functions have shown positive outcomes in preclinical and clinical studies, suggesting the potential of the GABAergic system as a therapeutic target in AD. LINKAGE TO OTHER MAJOR THEORIES: Dysfunction of the GABAergic system is induced by multiple critical signaling pathways, which include the existing major theories of AD pathogenesis, such as the Aß and neuroinflammation hypotheses. In a new perspective, this GABAergic hypothesis accounts for the E/I imbalance and related excitotoxicity, which contribute to cognitive decline and AD pathogenesis. Therefore, the GABAergic system could be a key target to restore, at least partially, the E/I balance and cognitive function in AD patients.

Molecular Dysfunctions of Mitochondria-Associated Membranes (MAMs) in Alzheimer's Disease.

Alzheimer's disease (AD) is a multifactorial neurodegenerative pathology characterized by a progressive decline of cognitive functions. Alteration of various signaling cascades affecting distinct subcellular compartment functions and their communication likely contribute to AD progression. Among others, the alteration of the physical association between the endoplasmic reticulum (ER) and mitochondria, also reffered as mitochondria-associated membranes (MAMs), impacts various cellular housekeeping functions such as phospholipids-, glucose-, cholesterol-, and fatty-acid-metabolism, as well as calcium signaling, which are all altered in AD. Our review describes the physical and functional proteome crosstalk between the ER and mitochondria and highlights the contribution of distinct molecular components of MAMs to mitochondrial and ER dysfunctions in AD progression. We also discuss potential strategies targeting MAMs to improve mitochondria and ER functions in AD.

MicroRNA-25 aggravates Aß1-42-induced hippocampal neuron injury in Alzheimer's disease by downregulating KLF2 via the Nrf2 signaling pathway in a mouse model.

Recently, numerous microRNAs (miRNAs) have been considered as key players in the regulation of neuronal processes. The purpose of the present study is to explore the effect of miR-25 on hippocampal neuron injury in Alzheimer's disease (AD) induced by amyloid ß (Aß) peptide fragment 1 to 42 (Aß1-42) via Kruppel-like factor 2 (KLF2) through the nuclear factor-E2-related factor 2 (Nrf2) signaling pathway. A mouse model of AD was established through Aß1-42 induction. The underlying regulatory mechanisms of miR-25 were analyzed through treatment of miR-25 mimics, miR-25 inhibitors, or small interfering RNA (siRNA) against KLF2 in hippocampal tissues and cells isolated from AD mice. The targeting relationship between miR-25 and KLF2 was predicted using a target prediction program and verified by luciferase activity determination. MTT assay was used to evaluate the proliferative ability and flow cytometry to detect cell cycle distribution and apoptosis. KLF2 was confirmed as a target gene of miR-25. When the mice were induced by Aß1-42, proliferation was suppressed while apoptosis was promoted in hippocampal neurons as evidenced by lower levels of KLF2, Nrf2, haem oxygenase, glutathione S transferase α1, glutathione, thioredoxin, and B-cell lymphoma-2 along with higher bax level. However, such alternations could be reversed by treatment of miR-25 inhibitors. These findings indicate that miR-25 may inhibit hippocampal neuron proliferation while promoting apoptosis, thereby aggravating hippocampal neuron injury through downregulation of KLF2 via the Nrf2 signaling pathway.

The binding of monomeric amyloid ß peptide to serum albumin is affected by major plasma unsaturated fatty acids.

Human serum albumin (HSA) serves as a natural depot of amyloid ß peptide (Aß). Improvement of Aß binding to HSA should impede Alzheimer's disease (AD). We developed a method for quantitation of the interaction between monomeric Aß40/42 and HSA using surface plasmon resonance spectroscopy. The dissociation constant of HSA complex with recombinant Aß40/42 is 0.2-0.3 µM. Flemish variant of Aß40 has 2.5-10-fold higher affinity to HSA. The parameters of the HSA-Aß interaction are selectively sensitive to HSA binding of major plasma unsaturated fatty acids and Cu2+. Linoleic and arachidonic acids promote the HSA-Aß42 interaction. The developed methodology for quantitation of HSA-Aß interaction may serve as a tool for search of compounds favoring HSA-Aß interaction, thereby preventing AD progression.

Potent Acetylcholinesterase Selective and Reversible Homodimeric Agent Based on Tacrine for Theranostics.

Acetylcholinesterase (AChE) has been an important biomarker for diagnosing Alzheimer's disease (AD), due to reduction in AChE activity in post-mortem brains of AD patients. A potent, selective, and reversible homodimeric inhibitor of AChE, 5-amino- N1, N3-bis(2-(1,2,3,4-tetrahydroacridin-9-ylamino)ethyl)isophthalamide (compound 4), was synthesized by using 9-alkyl(1,2,3,4-tetrahydroacridine) pharmacophore with appended functionality. In the present work, we report the synthesis of this bivalent inhibitor of AChE. The homodimeric ligand structure was designed and studied with molecular docking tools, which revealed its high affinity and interactions with active site gorge of AChE, which includes both catalytic active site (CAS) and peripheral active site (PAS). The IC50 value of this bivalent inhibitor for AChE and BuChE were 0.54 ± 0.06 and 32.49 ± 1.2 nM, respectively, with a selectivity ratio of 60.16 toward AChE. The designed ligand also showed potent inhibitory properties on PAS activity as well as on AChE-induced amyloid aggregation with low cytotoxicity on rat hippocampal neurons. The AFM images further corroborated the Aß1-42 aggregation inhibition by compound 4 to an extent similar to bis(7)-tacrine. Moreover, the bivalent ligand was also proven to be of neurogenic potential due to its ability to induce S-phase post-treatment in rat hippocampal neuronal cells. On the basis of initial results, the agent could be further explored for its theranostic value clinically, which gives the possibility of tracing the AChE levels by molecular imaging techniques in correlation with progression of neurocognitive disorders like AD for better therapy response and patient management.

Ginsenoside compound K ameliorates Alzheimer's disease in HT22 cells by adjusting energy metabolism.

Energy metabolism disorders have been shown to exert detrimental effects on the pathology of Alzheimer's disease (AD). The ginsenoside compound K (CK), a major intestinal metabolite underlying the pharmacological actions of orally administered ginseng, has an ameliorating effect against AD, but the relevant molecular mechanism remains unclear. We hypothesized that the improvement of AD by CK is mediated by the energy metabolism signaling pathway induced by amyloid ß peptide (Aß) and tested this hypothesis in HT22 cells. HT22 cells were incubated with CK and exposed to Aß. Cell viability was analyzed using the MTT assay. Cell growth curves were derived from real-time cell analysis. Apoptosis was determined by flow cytometry, Aß localization and expression by immunofluorescence, and ATP content by a specific assay kit. The expression of proteins related to the energy metabolism signaling pathway was analyzed using Western blotting. CK treatment improved cell viability, cell growth, and apoptosis induced by Aß, and the cellular localization and expression of Aß. Moreover, CK increased ATP content by promoting the activity of glucose transporters (GLUTs). Therefore, the neuroprotective effect of CK against Aß injury was mainly realized through the activation of the energy metabolism signaling pathway. CK treatment inhibits neuronal damage caused by Aß through the activation of the energy metabolism signaling pathway, revealing that CK might be one of the key bioactive ingredients of ginseng in the treatment of Alzheimer's disease and may serve as a preventive or therapeutic agent for Alzheimer's disease.