A M1 muscarinic acetylcholine receptor-specific positive allosteric modulator VU0486846 reduces neurogliosis in female Alzheimer's mice

Alzheimer's disease (AD) is the most prevalent type of dementia, disproportionately affecting females, who make up nearly 60% of diagnosed cases. In AD patients, the accumulation of beta-amyloid (Aβ) in the brain triggers a neuroinflammatory response driven by neuroglia, worsening the condition. We have previously demonstrated that VU0486846, an orally available positive allosteric modulator (PAM) targeting M1 muscarinic acetylcholine receptors, enhances cognitive function and reduces Aβ pathology in female APPswe/PSEN1ΔE9 (APP/PS1) mice. However, it remained unclear whether these improvements were linked to a decrease in neuroglial activation. To investigate, we treated nine-month-old APP/PS1 and wildtype mice with VU0486846 for 8 weeks and analyzed brain slices for markers of microglial activation (ionized calcium binding adaptor molecule 1, Iba1) and astrocyte activation (Glial fibrillary acidic protein, GFAP). We find that VU0486846 reduces the presence of Iba1-positive microglia and GFAP-positive astrocytes in the hippocampus of female APP/PS1 mice and limits the recruitment of these cells to remaining Aβ plaques. This study sheds light on an additional mechanism through which novel M1 mAChR PAMs exhibit disease-modifying effects by reducing neuroglial activation and underscore the potential of these ligands for the treatment of AD, especially in females.

Plasma oligomer beta-amyloid is associated with disease severity and cerebral amyloid deposition in Alzheimer's disease spectrum

BACKGROUND

Multimer detection system-oligomeric amyloid-β (MDS-OAβ) is a measure of plasma OAβ, which is associated with Alzheimer's disease (AD) pathology. However, the relationship between MDS-OAβ and disease severity of AD is not clear. We aimed to investigate MDS-OAβ levels in different stages of AD and analyze the association between MDS-OAβ and cerebral Aβ deposition, cognitive function, and cortical thickness in subjects within the AD continuum.

METHODS

In this cross-sectional study, we analyzed a total 126 participants who underwent plasma MDS-OAβ, structural magnetic resonance image of brain, and neurocognitive measures using Korean version of the Consortium to Establish a Registry for Alzheimer's Disease, and cerebral Aβ deposition or amyloid positron emission tomography (A-PET) assessed by [18F] flutemetamol PET. Subjects were divided into 4 groups: N = 39 for normal control (NC), N = 31 for A-PET-negative mild cognitive impairment (MCI) patients, N = 30 for A-PET-positive MCI patients, and N = 22 for AD dementia patients. The severity of cerebral Aβ deposition was expressed as standard uptake value ratio (SUVR).

RESULTS

Compared to the NC (0.803 ± 0.27), MDS-OAβ level was higher in the A-PET-negative MCI group (0.946 ± 0.137) and highest in the A-PET-positive MCI group (1.07 ± 0.17). MDS-OAβ level in the AD dementia group was higher than in the NC, but it fell to that of the A-PET-negative MCI group level (0.958 ± 0.103). There were negative associations between MDS-OAβ and cognitive function and both global and regional cerebral Aβ deposition (SUVR). Cortical thickness of the left fusiform gyrus showed a negative association with MDS-OAβ when we excluded the AD dementia group.

CONCLUSIONS

These findings suggest that MDS-OAβ is not only associated with neurocognitive staging, but also with cerebral Aβ burden in patients along the AD continuum.

Similar brain proteomic signatures in Alzheimer's disease and epilepsy

The prevalence of epilepsy is increased among Alzheimer's Disease (AD) patients and cognitive impairment is common among people with epilepsy. Epilepsy and AD are linked but the shared pathophysiological changes remain poorly defined. We aim to identify protein differences associated with epilepsy and AD using published proteomics datasets. We observed a highly significant overlap in protein differences in epilepsy and AD: 89% (689/777) of proteins altered in the hippocampus of epilepsy patients were significantly altered in advanced AD. Of the proteins altered in both epilepsy and AD, 340 were altered in the same direction, while 216 proteins were altered in the opposite direction. Synapse and mitochondrial proteins were markedly decreased in epilepsy and AD, suggesting common disease mechanisms. In contrast, ribosome proteins were increased in epilepsy but decreased in AD. Notably, many of the proteins altered in epilepsy interact with tau or are regulated by tau expression. This suggests that tau likely mediates common protein changes in epilepsy and AD. Immunohistochemistry for Aβ and multiple phosphorylated tau species (pTau396/404, pTau217, pTau231) showed a trend for increased intraneuronal pTau217 and pTau231 but no phosphorylated tau aggregates or amyloid plaques in epilepsy hippocampal sections. Our results provide insights into common mechanisms in epilepsy and AD and highlights the potential role of tau in mediating common pathological protein changes in epilepsy and AD.

Kamikihito reduces β-amyloid25-35-induced axon damage via neurotrophic factors

The Japanese herbal medicine kamikihito (KKT) is widely used for insomnia, anorexia, anemia, and depression. Recently, the efficacy of KKT against Alzheimer's disease (AD) has been demonstrated in clinical and non-clinical studies. To address the mechanism underlying the effect of KKT on AD, we examined the effects of KKT in β-amyloid (Aβ)25-35-exposed primary cultured neurons. The effects of KKT on Aβ25-35-induced neurotoxicity were assessed by immunocytochemical assays and Sholl analysis of neurites, and the influence of KKT on neurotrophic factor (NF) gene expression was examined using RT-PCR analysis. As a result, Aβ25-35 exposure attenuated the arborization of neurites of single cultured hippocampal neurons, and KKT treatment for 3 days ameliorated the Aβ25-35-induced impairment of tau-positive axon outgrowth. This ameliorative effect of KKT was largely abolished by the Trk inhibitor K252a, and expression of NFs, nerve growth factor (Ngf), brain-derived neurotrophic factor (Bdnf), neurotrophin-3 (NT-3) was significantly increased by KKT. These results indicate that KKT ameliorates axonal atrophy via NFs signaling, providing a mechanistic basis for treatment of AD with KKT.

Protective effects of L-arginine on Alzheimer's disease: Modulating hippocampal nitric oxide levels and memory deficits in aluminum chloride-induced rat model

There is evidence that high daily intake of aluminum (Al) is associated with an increased risk of dementia or cognitive decline. We injected L-arginine into the dorsal hippocampus (DH) of an AlCl3-induced Alzheimer's model and studied memory deficit, β-amyloid (βA) accumulation, neurodegeneration, and molecular changes. Male Wistar rats were cannulated unilaterally in the DH under a stereotaxic apparatus and a dose of AlCl3 (1-200 μg/rat) was injected into the CA1. After recovery, L-arginine and L-NAME (0.05-25 μg/rat) were injected into CA1 and animals were tested in novelty seeking task. One group received βA (2 μg/rat, intra CA1) as a reference group. Control groups received saline (1 μL/rat, intra-CA1) and galantamine (25 μg/rat, intra-CA1), respectively. Finally, rats were anesthetized and hippocampal tissues were isolated on ice. Levels of neuronal NO synthase (nNOS), β-secretase and soluble guanylyl cyclase (sGC) were measured by western blotting. βA formation and the number of CA1 neurons were assessed by Congo red and Nissl staining. NOS activation by NADPH-diaphorase (NADPH-d) was investigated. All data were analyzed using analysis of variance (ANOVA) at α = 0.05 level. Like βA, AlCl3 (25 μg/rat) caused accumulation of βA in the DH and increased stopping of the animal on the novel side (indicating a recall deficit). CA1 neurons decreased, and nNOS and β-secretase, but not sGC, showed a change consistent with Alzheimer's. However, prophylactic intervention of L-arginine at 3-9 μg/rat was protective, probably by nNOS stimulation in DH, as shown by NADPH-d assay. L-arginine may protect against Alzheimer's by increasing hippocampal NO levels.

Alzheimer's disease as a viral disease: Revisiting the infectious hypothesis

Alzheimer's disease (AD) represents the most frequent type of dementia in elderly people. Two major forms of the disease exist: sporadic - the causes of which have not yet been fully understood - and familial - inherited within families from generation to generation, with a clear autosomal dominant transmission of mutations in Presenilin 1 (PSEN1), 2 (PSEN2) or Amyloid Precursors Protein (APP) genes. The main hallmark of AD consists of extracellular deposits of amyloid-beta (Aβ) peptide and intracellular deposits of the hyperphosphorylated form of the tau protein. An ever-growing body of research supports the viral infectious hypothesis of sporadic forms of AD. In particular, it has been shown that several herpes viruses (i.e., HHV-1, HHV-2, HHV-3 or varicella zoster virus, HHV-4 or Epstein Barr virus, HHV-5 or cytomegalovirus, HHV-6A and B, HHV-7), flaviviruses (i.e., Zika virus, Dengue fever virus, Japanese encephalitis virus) as well as Human Immunodeficiency Virus (HIV), hepatitis viruses (HAV, HBV, HCV, HDV, HEV), SARS-CoV2, Ljungan virus (LV), Influenza A virus and Borna disease virus, could increase the risk of AD. Here, we summarized and discussed these results. Based on these findings, significant issues for future studies are also put forward.

Intensity-dependent gamma electrical stimulation regulates microglial activation, reduces beta-amyloid load, and facilitates memory in a mouse model of Alzheimer's disease

BACKGROUND

Gamma sensory stimulation may reduce AD-specific pathology. Yet, the efficacy of alternating electrical current stimulation in animal models of AD is unknown, and prior research has not addressed intensity-dependent effects.

METHODS

The intensity-dependent effect of gamma electrical stimulation (GES) with a sinusoidal alternating current at 40 Hz on Aβ clearance and microglia modulation were assessed in 5xFAD mouse hippocampus and cortex, as well as the behavioral performance of the animals with the Morris Water Maze.

RESULTS

One hour of epidural GES delivered over a month significantly (1) reduced Aβ load in the AD brain, (2) increased microglia cell counts, decreased cell body size, increased length of cellular processes of the Iba1 + cells, and (3) improved behavioral performance (learning & memory). All these effects were most pronounced when a higher stimulation current was applied.

CONCLUSION

The efficacy of GES on the reduction of AD pathology and the intensity-dependent feature provide guidance for the development of this promising therapeutic approach.

Neuronal vulnerability to brain aging and neurodegeneration in cognitively impaired marmoset monkeys (Callithrix jacchus)

The investigation of neurobiological and neuropathological changes that affect synaptic integrity and function with aging is key to understanding why the aging brain is vulnerable to Alzheimer's disease. We investigated the cellular characteristics in the cerebral cortex of behaviorally characterized marmosets, based on their trajectories of cognitive learning as they transitioned to old age. We found increased astrogliosis, increased phagocytic activity of microglial cells and differences in resting and reactive microglial cell phenotypes in cognitively impaired compared to nonimpaired marmosets. Differences in amyloid beta deposition were not related to cognitive trajectory. However, we found age-related changes in density and morphology of dendritic spines in pyramidal neurons of layer 3 in the dorsolateral prefrontal cortex and the CA1 field of the hippocampus between cohorts. Overall, our data suggest that an accelerated aging process, accompanied by neurodegeneration, that takes place in cognitively impaired aged marmosets and affects the plasticity of dendritic spines in cortical areas involved in cognition and points to mechanisms of neuronal vulnerability to aging.

Beta amyloid deposition and cognitive decline in Parkinson's disease: a study of the PPMI cohort

The accumulation of beta amyloid in the brain has a complex and poorly understood impact on the progression of Parkinson's disease pathology and much controversy remains regarding its role, specifically in cognitive decline symptoms. Some studies have found increased beta amyloid burden is associated with worsening cognitive impairment in Parkinson's disease, especially in cases where dementia occurs, while other studies failed to replicate this finding. To better understand this relationship, we examined a cohort of 25 idiopathic Parkinson's disease patients and 30 healthy controls from the Parkinson's Progression Marker Initiative database. These participants underwent [¹⁸F]Florbetaben positron emission tomography scans to quantify beta amyloid deposition in 20 cortical regions. We then analyzed this beta amyloid data alongside the longitudinal Montreal Cognitive Assessment scores across 3 years to see how participant's baseline beta amyloid levels affected their cognitive scores prospectively. The first analysis we performed with these data was a hierarchical cluster analysis to help identify brain regions that shared similarity. We found that beta amyloid clusters differently in Parkinson's disease patients compared to healthy controls. In the Parkinson's disease group, increased beta amyloid burden in cluster 2 was associated with worse cognitive ability, compared to deposition in clusters 1 or 3. We also performed a stepwise linear regression where we found an adjusted R² of 0.495 (49.5%) in a model explaining the Parkinson's disease group's Montreal Cognitive Assessment score 1-year post-scan, encompassing the left gyrus rectus, the left anterior cingulate cortex, and the right parietal cortex. Taken together, these results suggest regional beta amyloid deposition alone has a moderate effect on predicting future cognitive decline in Parkinson's disease patients. The patchwork effect of beta amyloid deposition on cognitive ability may be part of what separates cognitive impairment from cognitive sparing in Parkinson's disease. Thus, we suggest it would be more useful to measure beta amyloid burden in specific brain regions rather than using a whole-brain global beta amyloid composite score and use this information as a tool for determining which Parkinson's disease patients are most at risk for future cognitive decline.

KLVFF oligopeptide-decorated amphiphilic cyclodextrin nanomagnets for selective amyloid beta recognition and fishing

Recognition and capture of amyloid beta (Aβ) is a challenging task for the early diagnosis of neurodegenerative disorders, such as Alzheimer's disease. Here, we report a novel KLVFF-modified nanomagnet based on magnetic nanoparticles (MNP) covered with a non-ionic amphiphilic β-cyclodextrin (SC16OH) and decorated with KLVFF oligopeptide for the self-recognition of the homologous amino-acids sequence of Aβ to collect Aβ (1-42) peptide from aqueous samples. MNP@SC16OH and MNP@SC16OH/Ada-Pep nanoassemblies were fully characterized by complementary techniques both as solid powders and in aqueous dispersions. Single domain MNP@SC16OH/Ada-Pep nanomagnets of 20-40 nm were observed by TEM analysis. DLS and ζ-potential measurements revealed that MNP@SC16OH nanoassemblies owned in aqueous dispersion a hydrodynamic radius of about 150 nm, which was unaffected by Ada-Pep decoration, while the negative ζ-potential of MNP@SC16OH (-40 mV) became less negative (-30 mV) in MNP@SC16OH/Ada-Pep, confirming the exposition of positively charged KLVFF on nanomagnets surface. The ability of MNP@SC16OH/Ada-Pep to recruit Aβ (1-42) in aqueous solution was evaluated by MALDI-TOF and compared with the ineffectiveness of undecorated MNP@SC16OH and VFLKF scrambled peptide-decorated nanoassemblies (MNP@SC16OH/Ada-scPep), pointing out the selectivity of KLVFF-decorated nanohybrid towards Aβ (1-42). Finally, the property of nanomagnets to extract Aβ in conditioned medium of cells over-producing Aβ peptides was investigated as proof of concept of effectiveness of these nanomaterials as potential diagnostic tools.

A M1 muscarinic acetylcholine receptor positive allosteric modulator improves pathology and cognitive deficits in female APPswe/PSEN1ΔE9 mice

BACKGROUND AND PURPOSE

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive decline and women account for 60% of diagnosed cases. Beta-amyloid (Aβ) oligomers is considered the principal neurotoxic species in AD brains. The M1 muscarinic acetylcholine receptor (M1 mAChR) plays a key role in memory and learning. M1 mAChR agonists show pro-cognitive activity but cause many adverse off-target effects. A new orally bioavailable M1 mAChR positive allosteric modulator (PAM), VU0486846, is devoid of direct agonist activity or adverse effects but was not tested for disease-modifying efficacy in female AD mice.

EXPERIMENTAL APPROACH

Nine-month-old female APPswe/PSEN1ΔE9 (APPswe) and wildtype mice were treated with VU0486846 in drinking water (10mg/kg/day) for 4 or 8 weeks. Cognitive function of mice was assessed after treatment and brains were harvested for biochemical and immunohistochemical assessment.

KEY RESULTS

VU0486846 improved cognitive function of APPswe mice when tested in novel object recognition and Morris water maze. This was paralleled by a significant reduction in Aβ oligomers and plaques and neuronal loss in hippocampus. VU0486846 reduced Aβ oligomer production in APPswe mice by increasing M1 mAChR expression and shifting the processing of amyloid precursor protein from amyloidogenic cleavage to non-amyloidogenic cleavage. Specifically, VU0486846 reduced the expression of β-secretase 1 (BACE1), whereas it enhanced the expression of the α-secretase ADAM10 in APPswe hippocampus.

CONCLUSION AND IMPLICATIONS

Using M1 mAChR PAMs can be a viable disease-modifying approach that should be exploited clinically to slow AD in women.

Estimating Progression Rates Across the Spectrum of Alzheimer's Disease for Amyloid-Positive Individuals Using National Alzheimer's Coordinating Center Data

INTRODUCTION

Published estimates of Alzheimer's disease (AD) progression do not capture the full disease continuum. This study provides transition probabilities of individuals with amyloid-β (Aβ+) pathology across the disease continuum.

METHODS

Patient-level longitudinal data from the National Alzheimer's Coordinating Center were used to estimate progression rates. Progression rates through five clinically defined AD stages-asymptomatic, mild cognitive impairment due to AD (MCI-AD), mild AD dementia, moderate AD dementia, severe AD dementia-and death were measured as transition probabilities. Rates were assessed in "incident" patients who recently entered the stage, controlling for covariates. Transition probabilities were generated from multinomial logit regression models that predicted an individual's health state as a function of health state at the previous visit and adjusted for time between initial and follow-up visits, age, sex, years of education, and concomitant symptomatic AD medications.

RESULTS

Annual transition probabilities to more severe dementia stages for surviving incident Aβ+ patients were as follows: asymptomatic to MCI-AD, 40.8%; MCI-AD to mild AD dementia or worse, 21.8%; mild AD dementia to moderate AD dementia or worse, 35.9%; moderate AD dementia to severe AD dementia, 28.6%. Transition probabilities to less severe dementia stages were: 5.3% annual reversion from MCI-AD to asymptomatic, 3.0% mild AD dementia to MCI-AD, 1.8% moderate AD dementia to mild AD dementia, and 1.3% for severe AD dementia to moderate AD dementia.

CONCLUSIONS

These transition probabilities reflect the full continuum of AD progression in Aβ+ individuals and can be used to assess the impact of treatment on expected transitions.

Characterization of monomeric and soluble aggregated Aβ in Down's syndrome and Alzheimer's disease brains

The major characteristics of Alzheimer's disease (AD) are amyloid plaques, consisting of aggregated beta amyloid (Aβ) peptides, together with tau pathology (tangles, neuropil treads and dystrophic neurites surrounding the plaques), in the brain. Down's syndrome (DS) individuals are at increased risk to develop AD-type pathology; most DS individuals have developed substantial pathology already at the age of 40. DS individuals have an extra copy of chromosome 21, harbouring the amyloid precursor protein gene (APP). Our aim was to investigate the Aβ peptide pattern in DS and AD brains to investigate differences in their amyloid deposition and aggregation, respectively. Cortical tissue from patients with DS (with amyloid pathology), sporadic AD and controls were homogenized and fractionated into TBS (water soluble) and formic acid (water insoluble) fractions. Immunoprecipitation (IP) was performed using a variety of antibodies targeting different Aβ species including oligomeric Aβ. Mass spectrometry was then used to evaluate the presence of Aβ species in the different patient groups. A large number of Aβ peptides were identified including Aβ1-X, 2-X, 3-X, 4-X, 5-X, 11-X, and Aβ peptides extended N terminally of the BACE1 cleavage site and ending at amino 15 in the Aβ sequence APP/Aβ(-X to 15), as well as peptides post-translationally modified by pyroglutamate formation. Most Aβ peptides had higher abundance in AD and DS compared to controls, except the APP/Aβ(-X to 15) peptides which were most abundant in DS followed by controls and AD. Furthermore, the abundancies of AβX-40 and AβX-34 were increased in DS compared with AD. Aβ1-40, Aβ1-42, and Aβ4-42 were identified as the main constitutes of protofibrils (IP'd using mAb158) and higher relative Aβ1-42 signals were obtained compared with samples IP'd with 6E10 + 4G8, indicating that the protofibrils/oligomers were enriched with peptides ending at amino acid 42. All Aβ peptides found in AD were also present in DS indicating similar pathways of Aβ peptide production, degradation and accumulation, except for APP/Aβ(-X to 15). Likewise, the Aβ peptides forming protofibrils/oligomers in both AD and DS were similar, implying the possibility that treatment with clinical benefit in sporadic AD might also be beneficial for subjects with DS.

Screening of Synthetic Isoxazolone Derivative Role in Alzheimer's Disease: Computational and Pharmacological Approach

Alzheimer's disease (AD) is age-dependent neurological disorder with progressive loss of cognition and memory. This multifactorial disease is characterized by intracellular neurofibrillary tangles, beta amyloid plaques, neuroinflammation, and increased oxidative stress. The increased cellular manifestations of these markers play a critical role in neurodegeneration and pathogenesis of AD. Therefore, reducing neurodegeneration by decreasing one or more of these markers may provide a potential therapeutic roadmap for the treatment of AD. AD causes a devastating loss of cognition with no conclusive and effective treatment. Many synthetic compound containing isoxazolone nucleus have been reported as neuroprotective agents. The aim of this study was to explore the anti-Alzheimer's potential of a newly synthesized 3,4,5-trimethoxy isoxazolone derivative (TMI) that attenuated the beta amyloid (Aβ1-42) and tau protein levels in streptozotocin (STZ) induced Alzheimer's disease mouse model. Molecular analysis revealed increased beta amyloid (Aβ1-42) protein levels, increased tau protein levels, increased cellular oxidative stress and reduced antioxidant enzymes in STZ exposed mice brains. Furthermore, ELISA and PCR were used to validate the expression of Aβ1-42. Pre-treatment with TMI significantly improved the memory and cognitive behavior along with ameliorated levels of Aβ1-42 proteins. TMI treated mice further showed marked increase in GSH, CAT, SOD levels while decreased levels of acetylcholinesterase inhibitors (AChEI's) and MDA intermediate. The multidimensional nature of isoxazolone derivatives and its versatile affinity towards various targets highpoint its multistep targeting nature. These results indicated the neuroprotective potential of TMI which may be considered for the treatment of neurodegenerative disease specifically in AD.

Do neprilysin inhibitors walk the line? Heart ameliorative but brain threatening!

Sacubitril/valsartan (Entresto™; LCZ696) is the first angiotensin receptor-neprilysin inhibitor (ARNI) drug approved by the US and EU for heart failure (HF) and especially recommended for hypertensive HF (HHF). Sacubitril inhibits the enzyme neprilysin (NEP) which produces both beneficial and adverse effects in the human body. While LCZ696 causes beneficial cardiovascular effects, it may induce memory and cognitive dysfunction, or even exacerbate Alzheimer's disease (AD). This article reviewed data reported by experimental and clinical studies that examined NEP inhibitors and their dementia-related side effects. Based on the literature, LCZ696 increases the risk of memory and cognitive dysfunctions, and clinical trials failed to show compelling evidence for LCZ696 safety for the brain. Together, it was concluded that more experimental and clinical studies with particular focus on LCZ696 side effects on β-amyloid (Aβ) degradation are needed to assess LCZ696 safety for the cognitive function, especially in case of long-term administration.

Biological evaluation and molecular docking of novel 1,3,4-thiadiazole-resorcinol conjugates as multifunctional cholinesterases inhibitors

Two series of novel 1,3,4-thiadiazole-resorcinol conjugates were efficiently synthesized and evaluated as cholinesterases inhibitors. N-Butyl- and N-chlorophenyl-5-amino-1,3,4-thiadiazol-2-yl)benzene-1,3-diols were identified as the most promising compounds of low nanomolar activity against AChE (IC₅₀ = 29-76 nM) and moderate activity against BuChE. The inhibition mechanism studies proved that the compounds are mixed type inhibitors. The docking simulations showed great affinity of the compounds for both enzymes. The modelled amine derivatives exhibited a similar arrangement in the catalytic anionic site of AChE similar to that of tacrine. The thiadiazole ring interacted with Trp84 and the phenyl groups created π-π stacking interactions with the residue - Phe330. The compounds showed better inhibition of the in vitro self-induced Aβ (1-42) aggregation than that compared with curcumin as well as antioxidant properties similar to those of quercetin. They exhibited metal ion chelating properties, acceptable cytotoxicity in vitro and favourable ADMET profile determined in silico.

Conjugates of desferrioxamine and aromatic amines improve markers of iron-dependent neurotoxicity

Alzheimer's Disease (AD) is a complex neurodegenerative disorder associated in some instances with dyshomeostasis of redox-active metal ions, such as copper and iron. In this work, we investigated whether the conjugation of various aromatic amines would improve the pharmacological efficacy of the iron chelator desferrioxamine (DFO). Conjugates of DFO with aniline (DFOANI), benzosulfanylamide (DFOBAN), 2-naphthalenamine (DFONAF) and 6-quinolinamine (DFOQUN) were obtained and their properties examined. DFOQUN had good chelating activity, promoted a significant increase in the inhibition of β-amyloid peptide aggregation when compared to DFO, and also inhibited acetylcholinesterase (AChE) activity both in vitro and in vivo (Caenorhabditis elegans). These data indicate that the covalent conjugation of a strong iron chelator to an AChE inhibitor offers a powerful approach for the amelioration of iron-induced neurotoxicity symptoms.

β-amyloid: The known unknowns

Alzheimer's disease (AD) stands out as a major disease without any form of preventative or disease modifying therapy. This is not for lack of trying. 33 phase 3 clinical trials of drugs targeting amyloid beta (Aβ) have failed to slow cognitive decline in AD. The field is at a cross-roads about whether to continue anti-Aβ therapy or more actively pursue alternative targets. With the burden of this disease to patients, families, and healthcare budgets growing yearly, the need for disease modifying AD therapies has become one of the highest priorities in all of medicine. While pathology, genetic and biochemical data offer a popular narrative for the causative role of Aβ, there are alternative explanations, and dissenting findings that, now more than ever, warrant thorough reanalysis. This review questions the major assumptions about Aβ on which therapies for AD were premised, and invites renewed interrogation into AD pathogenesis.

Abelmoschus esculentus subfractions attenuate Aβ and tau by regulating DPP-4 and insulin resistance signals

Background

Insulin resistance could be associated with the development of Alzheimer disease (AD). The neuropathological hallmarks of AD are beta amyloid (Aβ) produced from sequential cleavage initiated by β-secretase and degraded by insulin degradation enzyme (IDE), as well as hyperphosphorylation of tau (p-tau). Insulin action involves the cascades of insulin receptor substrates (IRS) and phosphatidylinositol 3-kinase (PI3K), while phosphorylation of IRS-1 at ser307 (p-^ser307IRS-1) hinders the response. Our previous report suggested dipeptidyl peptidase-4 (DPP-4) is crucial to insulin resistance, and the subfractions of Abelmoschus esculentus (AE), F1 and F2, attenuate the signaling. Here we aim to investigate whether AE works to reduce Aβ generation via regulating DPP4 and insulin resistance.

Methods

The subfractions F1 and F2 were prepared according to a succession of procedures. F1 was composed by quercetin glycosides and triterpene ester, and F2 contained a large amount of polysaccharides. The in vitro insulin resistance model was established by SK-N-MC cell line treated with palmitate. MTT was used to define the dose range, and thereby Western blot, ELISA, and the activity assay were used to detect the putative markers. One-way ANOVA was performed for the statistical analysis.

Results

Treatment of palmitate induced the level of p-^ser307IRS-1. Both F1 and F2 effectively decrease p-^ser307IRS-1, and recover the expression of p-PI3K. However, the expression of total IRS plunged with 25 μg/mL of F1, while descended steadily with 5 μg/mL of F2. As palmitate increased the levels of Aβ40 and Aβ42, both AE subfractions were effective to reduce Aβ generation of and β-secretase activity, but IDE was not altered in any treatment conditions. The expression of DPP4 was also accompanied with insulin resistance signals. Inhibition of DPP4 attenuated the activity of β-secretase and production of Aβ. Moreover, the present data revealed that both AE subfractions significantly decrease the level of p-Tau.

Conclusions

In conclusion, we demonstrated that AE would be a potential adjuvant to prevent insulin resistance and the associated pathogenesis of AD, and F2 seems more feasible to be developed.

Evaluation of chronic lead effects in the blood brain barrier system by DCE-CT

BACKGROUND

Lead (Pb) is an environmental factor has been suspected of contributing to the dementia including Alzheimer's disease (AD). Our previous studies have shown that Pb exposure at the subtoxic dose increased brain levels of beta-amyloid (Aβ) and amyloid plaques, a pathological hallmark for AD, in amyloid precursor protein (APP) transgenic mice, and is hypothesized to inhibit Aβ clearance in the blood- cerebrospinal fluid (CSF) barrier. However, it remains unclear how different levels of Pb affect Aβ clearance in the whole blood-brain barrier system. This study was designed to investigate whether chronic exposure of Pb affected the permeability of the blood-brain barrier system by using the Dynamic Contrast-Enhanced Computerized Tomography (DCE-CT) method.

METHODS

DEC-CT was used to investigate whether chronic exposure of toxic Pb affected the permeability of the real-time blood brain barrier system.

RESULTS

Data showed that Pb exposure increased permeability surface area product, and also significantly induced brain perfusion. However, Pb exposure did not alter extracellular volumes or fractional blood volumes of mouse brain.

CONCLUSION

Our data suggest that Pb exposure at subtoxic and toxic levels directly targets the brain vasculature and damages the blood brain barrier system.

Amyloid-beta peptide and phosphorylated tau in the frontopolar cerebral cortex and in the cerebellum of toothed whales: aging versus hypoxia

Hypoxia could be a possible risk factor for neurodegenerative alterations in cetaceans' brain. Among toothed whales, the beaked whales are particularly cryptic and routinely dive deeper than 1000 m for about 1 h in order to hunt squids and fishes. Samples of frontal cerebral and cerebellar cortex were collected from nine animals, representing six different species of the suborder Odontoceti. Immunohistochemical analysis employed anti-β-amyloid (Aβ) and anti-neurofibrillary tangle (NFT) antibodies. Six of nine (67%) animals showed positive immunolabeling for Aβ and/or NFT. The most striking findings were intranuclear Aβ immunopositivity in cerebral cortical neurons and NFT immunopositivity in cerebellar Purkinje neurons with granulovacuolar degeneration. Aβ plaques were also observed in one elderly animal. Herein, we present immunohistopathological findings classic of Alzheimer's and other neurodegenerative diseases in humans. Our findings could be linked to hypoxic phenomena, as they were more extensive in beaked whales. Despite their adaptations, cetaceans could be vulnerable to sustained and repetitive brain hypoxia.

Cognitive behavioral therapy for insomnia to enhance cognitive function and reduce the rate of Aβ deposition in older adults with symptoms of insomnia: A single-site randomized pilot clinical trial protocol

Lifestyle interventions to increase exercise and improve diet have been the focus of recent clinical trials to potentially prevent Alzheimer's disease (AD). However, despite the strong links between sleep disruptions, cognitive decline, and AD, sleep enhancement has yet to be targeted as a lifestyle intervention to prevent AD. A recent meta-analysis suggests that approximately 15% of AD may be prevented by an efficacious intervention aimed to reduce sleep disturbances and sleep disorders. Chronic insomnia is the most frequent sleep disorder occurring in at least 40% of older adults. Individuals with insomnia are more likely to be diagnosed with Alzheimer's Disease (AD) and demonstrate decline in cognitive function at long-term follow-up. AD is characterized by the accumulation of amyloid-β (Aβ) plaques and tau tangles in the brain, and growing evidence shows impaired sleep contributes to the accumulation of Aβ. An intervention aimed at improving insomnia may be a critical opportunity for primary prevention to slow cognitive decline and potentially delay the onset of AD. Cognitive behavioral therapy for insomnia (CBT-I) is an efficacious treatment for insomnia, but the use of CBT-I to improve cognitive function and potentially reduce the rate of Aβ accumulation has never been examined. Therefore, the objective of the proposed study is to examine the efficacy of CBT-I on improving cognitive function in older adults with symptoms of insomnia. An exploratory aim is to assess the effect of CBT-I on rate of Aβ accumulation.

Collagen hydrogel confinement of Amyloid-β (Aβ) accelerates aggregation and reduces cytotoxic effects

Alzheimer's disease (AD) is the most common form of dementia and is associated with the accumulation of amyloid-β (Aβ), a peptide whose aggregation has been associated with neurotoxicity. Drugs targeting Aβ have shown great promise in 2D in vitro models and mouse models, yet preclinical and clinical trials for AD have been highly disappointing. We propose that current in vitro culture systems for discovering and developing AD drugs have significant limitations; specifically, that Aβ aggregation is vastly different in these 2D cultures carried out on flat plastic or glass substrates vs. in a 3D environment, such as brain tissue, where Aβ confinement alters aggregation kinetics and thermodynamics. In this work, we identified attenuation of Aβ cytotoxicity in 3D hydrogel culture compared to 2D cell culture. We investigated Aβ structure and aggregation in solution vs. hydrogel using Transmission Electron Microscopy (TEM), Fluorescence Correlation Spectroscopy (FCS), and Thioflavin T (ThT) assays. Our results reveal that the equilibrium is shifted to stable extended β-sheet (ThT positive) aggregates in hydrogels and away from the relatively unstable/unstructured presumed toxic oligomeric Aβ species in solution. Volume exclusion imparted by hydrogel confinement stabilizes unfolded, presumably toxic species, promoting stable extended β-sheet fibrils. STATEMENT OF SIGNIFICANCE: Alzheimer's disease (AD) is a devastating disease and has been studied for over 100 years. Yet, no cure exists and only 5 prescription drugs are FDA-approved to temporarily treat the AD symptoms of declining brain functions related to thinking and memory. Why don't we have more effective treatments to cure AD or relieve AD symptoms? We propose that current culture methods based upon cells cultured on flat, stiff substrates have significant limitations for discovering and developing AD drugs. This study provides strong evidence that AD drugs should be tested in 3D culture systems as a step along the development pathway towards new, more effective drugs to treat AD.

Collagen hydrogel confinement of Amyloid-β (Aβ) accelerates aggregation and reduces cytotoxic effects

Alzheimer's disease (AD) is the most common form of dementia and is associated with the accumulation of amyloid-β (Aβ), a peptide whose aggregation has been associated with neurotoxicity. Drugs targeting Aβ have shown great promise in 2D in vitro models and mouse models, yet preclinical and clinical trials for AD have been highly disappointing. We propose that current in vitro culture systems for discovering and developing AD drugs have significant limitations; specifically, that Aβ aggregation is vastly different in these 2D cultures carried out on flat plastic or glass substrates vs. in a 3D environment, such as brain tissue, where Aβ confinement alters aggregation kinetics and thermodynamics. In this work, we identified attenuation of Aβ cytotoxicity in 3D hydrogel culture compared to 2D cell culture. We investigated Aβ structure and aggregation in solution vs. hydrogel using Transmission Electron Microscopy (TEM), Fluorescence Correlation Spectroscopy (FCS), and Thioflavin T (ThT) assays. Our results reveal that the equilibrium is shifted to stable extended β-sheet (ThT positive) aggregates in hydrogels and away from the relatively unstable/unstructured presumed toxic oligomeric Aβ species in solution. Volume exclusion imparted by hydrogel confinement stabilizes unfolded, presumably toxic species, promoting stable extended β-sheet fibrils. STATEMENT OF SIGNIFICANCE: Alzheimer's disease (AD) is a devastating disease and has been studied for over 100 years. Yet, no cure exists and only 5 prescription drugs are FDA-approved to temporarily treat the AD symptoms of declining brain functions related to thinking and memory. Why don't we have more effective treatments to cure AD or relieve AD symptoms? We propose that current culture methods based upon cells cultured on flat, stiff substrates have significant limitations for discovering and developing AD drugs. This study provides strong evidence that AD drugs should be tested in 3D culture systems as a step along the development pathway towards new, more effective drugs to treat AD.

Chronic Administration of Scopolamine Increased GSK3βP9, Beta Secretase, Amyloid Beta, and Oxidative Stress in the Hippocampus of Wistar Rats

The increase of amyloid beta (Aβ) release and hyperphosphorylation of Tau protein represents the main events related to Alzheimer's disease (AD). Furthermore, the sporadic type represents the most common form of AD. Therefore, the establishment of a non-transgenic animal model that resembles the characteristics of the disease is of particular importance. Scopolamine has been linked to increases in both Aβ production and oxidative stress in rat and mice brains. Thus, the purpose of the present work was to identify changes in biomarkers that are related to AD after chronic administration of scopolamine (2 mg/kg i.p., during 6 and 12 weeks) to male Wistar rats. The results showed increased Aβ deposition at rat hippocampus which could be due to an increase of β-site amyloid-β-protein precursor cleaving enzyme 1 (BACE1) expression and activity. These findings could be related to the increase of glycogen synthase kinase 3 phosphorylated (GSK3βP9) expression. Finally, the establishment of a state of oxidative stress in groups treated with scopolamine was demonstrated by an increase in free radical content and MDA levels. The present study facilitates our understanding of the changes that occur in biomolecules related to AD in Wistar rats after the chronic administration of scopolamine.

Dynamic association between AT(N) profile and cognition mediated by cortical thickness in Alzheimer's continuum

BACKGROUND

The recently-proposed National Institute on Aging and Alzheimer's Association research framework organizes Alzheimer's disease (AD) biomarkers based on amyloid/tau/neurodegeneration (AT(N)). This study investigated the mediating effect of structural change in brain MRI on changes in cognitive function according to initial AT(N) profiles.

METHODS

We included 576 subjects (cognitively unimpaired (N = 136), mild cognitive impairment (N = 294), dementia (N = 146)) from the Alzheimer's disease Neuroimaging Initiative study. The parallel-process latent growth curve model was applied to test the mediational effect of cortical thickness growth trajectory between the initial AT(N) profiles and cognitive growth trajectory.

RESULTS

In Alzheimer's continuum, only the A + T + (N)+ profile showed a mediational effect of the cortical thickness growth trajectory. A + T - (N)- was not sufficient to induce direct or indirect effects on cognitive dysfunction, and A + T + (N)- showed a significant direct path from an altered cortical thickness to cognitive decline.

CONCLUSION

The sequential effect between changes in brain MRI and cognition varied by baseline AT(N) profile, suggesting the dynamic changes in the relationships among biomarkers in the current cascade model.

APOE-amyloid interaction: Therapeutic targets

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that is growing in prevalence globally. It is the only major cause of death without any effective pharmacological means to treat or slow progression. Inheritance of the ε4 allele of the Apolipoprotein (APO) E gene is the strongest genetic risk factor for late-onset AD. The interaction between APOE and amyloid β (Aβ) plays a key role in AD pathogenesis. The APOE-Aβ interaction regulates Aβ aggregation and clearance and therefore directly influences the development of amyloid plaques, congophilic amyloid angiopathy and subsequent tau related pathology. Relatively few AD therapeutic approaches have directly targeted the APOE-Aβ interaction thus far. Here we review the critical role of APOE in the pathogenesis of AD and some of the most promising therapeutic approaches that focus on the APOE-Aβ interaction.

Robust neuroinflammation and perivascular pathology in rTg-DI rats, a novel model of microvascular cerebral amyloid angiopathy

Background

Cerebral amyloid angiopathy (CAA) is a common cerebral small vessel disease of the aged and a prominent comorbidity of Alzheimer’s disease (AD). CAA can promote a variety of vascular-related pathologies including neuroinflammation, cerebral infarction, and hemorrhages, which can all contribute to vascular cognitive impairment and dementia (VCID). Our understanding of the pathogenesis of CAA remains limited and further investigation of this condition requires better preclinical animal models that more accurately reflect the human disease. Recently, we generated a novel transgenic rat model for CAA (rTg-DI) that develops robust and progressive microvascular CAA, consistent microhemorrhages and behavioral deficits.

Methods

In the current study, we investigated perivascular pathological processes that accompany the onset and progressive accumulation of microvascular CAA in this model. Cohorts of rTg-DI rats were aged to 3 months with the onset of CAA and to 12 months with advanced stage disease and then quantitatively analyzed for progression of CAA, perivascular glial activation, inflammatory markers, and perivascular stress.

Results

The rTg-DI rats developed early-onset and robust accumulation of microvascular amyloid. As the disease progressed, rTg-DI rats exhibited increased numbers of astrocytes and activated microglia which were accompanied by expression of a distinct subset of inflammatory markers, perivascular pericyte degeneration, astrocytic caspase 3 activation, and disruption of neuronal axonal integrity.

Conclusions

Taken together, these results demonstrate that rTg-DI rats faithfully mimic numerous aspects of human microvascular CAA and provide new experimental insight into the pathogenesis of neuroinflammation and perivascular stress associated with the onset and progression of this condition, suggesting new potential therapeutic targets for this condition. The rTg-DI rats provide an improved preclinical platform for developing new biomarkers and testing therapeutic strategies for microvascular CAA.

Silymarin encapsulated nanoliquid crystals for improved activity against beta amyloid induced cytotoxicity

Silymarin (SLY) a natural Aβ aggregation inhibitor, antioxidant and act as neuroprotectant. In the present study, we have prepared nano liquid crystals (NLCs) of negatively charged glycerylmonooleate (GMO) loaded with SLY for enhancing activity against Aβ_1-42 induced toxicity. SLY-NLCs are characterized for physicochemical parameters such as particle size, zeta potential, and drug-loading. The average particle size, zeta potential and % DL were found ≤200 nm, -22 mV, and 8.73% respectively. The amorphous form and entrapment of SLY in NLC were confirmed using DSC and FTIR analysis. The cubosomal SLY-NLCs shape was characterized by SEM and TEM. The cumulative drug release of SLY was ~76% at pH 7.4 (cerebrospinal fluid) from lyophilized SLY-NLC in 48 h. In order to understand the Aβ_1-42 aggregation inhibition due to SLY-NLC ThT (Thioflavin T) kinetic binding assay was also performed. The cell viability assessment of SLY-NLC was performed on SHSY5Y cell line that showed the highest viability in comparison to free SLY treated groups. ROS and apoptosis activity study SLY-NLCs reduced the Aβ_1-42 induced free radical with cell death. Cellular uptake study proved enhanced intracellular internalization of FITC tagged NLCs in 24 h. SLY-NLCs can offer great prospects in the field of drug delivery for neuroprotection.

Neural stem cell therapy for neurovascular injury in Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is characterized by progressive neurodegeneration leading to severe cognitive decline and eventual death. AD pathophysiology is complex, but neurotoxic accumulation of amyloid-β (Aβ) and hyperphosphorylation of Tau are believed to be main drivers of neurodegeneration in AD. The formation and deposition of Aβ plaques occurs in the brain parenchyma as well as in the cerebral vasculature. Thus, proper blood-brain barrier (BBB) and cerebrovascular functioning are crucial for clearance of Aβ from the brain, and neurovascular dysfunction may be a critical component of AD development. Further, neuroinflammation and dysfunction of angiogenesis, neurogenesis, and neurorestorative capabilities play a role in AD pathophysiology. Currently, there is no effective treatment to prevent or restore loss of brain tissue and cognitive decline in patients with AD. Based on multifactorial and complex pathophysiological cascades in multiple Alzheimer's disease stages, effective AD therapies need to focus on targeting early AD pathology and preserving cerebrovascular function. Neural stem cells (NSCs) participate extensively in mammalian brain homeostasis and repair and exhibit pleiotropic intrinsic properties that likely make them attractive candidates for the treatment of AD. In the review, we summarize the current advances in knowledge regarding neurovascular aspects of AD-related neurodegeneration and discuss multiple actions of NSCs from preclinical studies of AD to evaluate their potential for future clinical treatment of AD.

Vascular retinal biomarkers improves the detection of the likely cerebral amyloid status from hyperspectral retinal images

Introduction

This study investigates the relationship between retinal image features and β-amyloid (Aβ) burden in the brain with the aim of developing a noninvasive method to predict the deposition of Aβ in the brain of patients with Alzheimer's disease.

Methods

Retinal images from 20 cognitively impaired and 26 cognitively unimpaired cases were acquired (3 images per subject) using a hyperspectral retinal camera. The cerebral amyloid status was determined from binary reads by a panel of 3 expert raters on ¹⁸F-florbetaben positron-emission tomography (PET) studies. Image features from the hyperspectral retinal images were calculated, including vessels tortuosity and diameter and spatial-spectral texture measures in different retinal anatomical regions.

Results

Retinal venules of amyloid-positive subjects (Aβ+) showed a higher mean tortuosity compared with the amyloid-negative (Aβ−) subjects. Arteriolar diameter of Aβ+ subjects was found to be higher than the Aβ− subjects in a zone adjacent to the optical nerve head. Furthermore, a significant difference between texture measures built over retinal arterioles and their adjacent regions were observed in Aβ+ subjects when compared with the Aβ−. A classifier was trained to automatically discriminate subjects combining the extracted features. The classifier could discern Aβ+ subjects from Aβ− subjects with an accuracy of 85%.

Discussion

Significant differences in texture measures were observed in the spectral range 450 to 550 nm which is known as the spectral region known to be affected by scattering from amyloid aggregates in the retina. This study suggests that the inclusion of metrics related to the retinal vasculature and tissue-related textures extracted from vessels and surrounding regions could improve the discrimination performance of the cerebral amyloid status.

Improvement of memory deficits in the rat model of Alzheimer's disease by erythropoietin-loaded solid lipid nanoparticles

Erythropoietin (EPO), a hematopoietic factor, is one of the promising neuroprotective candidates in neurodegenerative disorders such as Alzheimer's disease (AD). Due to the high molecular weight, hydrophilicity and rapid clearance from circulation, EPO could not completely pass the blood-brain barrier in the case of systemic administration. To overcome this limitation, EPO-loaded Solid Lipid Nanoparticle (EPO-SLN) was developed in this study using a double emulsion solvent evaporation method (W₁/O/W₂). Glycerin monostearate (GMS), span®80/span®60, Dichloromethane (DCM) and tween®80 were chosen as lipid, internal phase surfactants, solvent, and external aqueous phase surfactant, respectively. After physicochemical evaluations, the effect of EPO-SLN on the beta-amyloid-induced AD-like animal model was investigated. In vivo evaluations, it was demonstrated that the memory was significantly restored in cognitive deficit rats treated with EPO-SLN compared to the rats treated with native drug using the Morris water maze test. In addition, EPO-SLN reduced the oxidative stress, ADP/ATP ratio, and beta-amyloid plaque deposition in the hippocampus more effectively than the free EPO. Hence, the designed SLN can be regarded as a promising system for safe and effective delivery of EPO in the AD.

Synergism between fornix microstructure and beta amyloid accelerates memory decline in clinically normal older adults

The fornix is the primary efferent white matter tract of the hippocampus and is implicated in episodic memory. In this study, we investigated whether baseline measures of altered fornix microstructure and elevated beta amyloid (Aβ) burden influence prospective cognitive decline. A secondary goal examined whether Aβ burden is negatively associated with fornix microstructure. 253 clinically normal older adults underwent diffusion-weighted imaging and Pittsburgh Compound B positron emission tomography at baseline. We applied a novel streamline tractography protocol to reconstruct a fornix bundle in native space. Cognition was measured annually in domains of episodic memory, executive function, and processing speed (median follow-up = 4.0 ± 1.4 years). After controlling for covariates, linear mixed-effects models demonstrated an interaction of fornix microstructure with Aβ burden on episodic memory, such that combined lower fornix microstructure and higher Aβ burden was associated with accelerated decline. By contrast, associations with executive function and processing speed were not significant. There was no cross-sectional association between Aβ burden and fornix microstructure. In conclusion, altered fornix microstructure may accelerate memory decline in preclinical Alzheimer's disease.

Long-term voluntary wheel running does not alter vascular amyloid burden but reduces neuroinflammation in the Tg-SwDI mouse model of cerebral amyloid angiopathy

BACKGROUND

Cardiovascular exercise (CVE) has been shown to be protective against cognitive decline in aging and the risk for dementias, including Alzheimer's Disease (AD). CVE has also been shown to have several beneficial effects on brain pathology and behavioral impairments in mouse models of AD; however, no studies have specifically examined the effects of CVE on cerebral amyloid angiopathy (CAA), which is the accumulation of amyloid-beta (Aβ) in the cerebral vasculature. CAA may be uniquely susceptible to beneficial effects of CVE interventions due to the location and nature of the pathology. Alternatively, CVE may exacerbate CAA pathology, due to added stress on already compromised cerebral vasculature.

METHODS

In the current study, we examined the effects of CVE over many months in mice, thereby modeling a lifelong commitment to CVE in humans. We assessed this voluntary CVE in Tg-SwDI mice, a transgenic mouse model of CAA that exhibits behavioral deficits, fibrillar vascular Aβ pathology, and significant perivascular neuroinflammation. Various "doses" of exercise intervention (0 h ("Sedentary"), 1 h, 3 h, 12 h access to running wheel) were assessed from ~ 4 to 12 months of age for effects on physiology, behavior/cognitive performance, and pathology.

RESULTS

The 12 h group performed the greatest volume of exercise, whereas the 1 h and 3 h groups showed high levels of exercise intensity, as defined by more frequent and longer duration running bouts. Tg-SwDI mice exhibited significant cerebral vascular Aβ pathology and increased expression of pro-inflammatory cytokines as compared to WT controls. Tg-SwDI mice did not show motor dysfunction or altered levels of anxiety or sociability compared to WT controls, though Tg-SwDI animals did appear to exhibit a reduced tendency to explore novel environments. At all running levels, CAA pathology in Tg-SwDI mice was not significantly altered, but 12-h high-volume exercise showed increased insoluble Aβ burden. However, CVE attenuated the expression of pro-inflammatory cytokines TNF-α and IL-6 and was generally effective at enhancing motor function and reducing anxiety-like behavior in Tg-SwDI mice, though alterations in learning and memory tasks were varied.

CONCLUSIONS

Taken together, these results suggest that CAA can still develop regardless of a lifespan of substantial CVE, although downstream effects on neuroinflammation may be reduced and functional outcomes improved.

Imaging beta amyloid aggregation and iron accumulation in Alzheimer's disease using quantitative susceptibility mapping MRI

Beta amyloid is a protein fragment snipped from the amyloid precursor protein (APP). Aggregation of these peptides into amyloid plaques is one of the hallmarks of Alzheimer's disease. MR imaging of beta amyloid plaques has been attempted using various techniques, notably with T2* contrast. The non-invasive detectability of beta amyloid plaques in MR images has so far been largely attributed to focal iron deposition accompanying the plaques. It is believed that the T2* shortening effects of paramagnetic iron are the primary source of contrast between plaques and surrounding tissue. Amyloid plaque itself has been reported to induce no magnetic susceptibility effect. We hypothesized that aggregations of beta amyloid would increase electron density and induce notable changes in local susceptibility value, large enough to generate contrast relative to surrounding normal tissues that can be visualized by quantitative susceptibility mapping (QSM) MR imaging. To test this hypothesis, we first demonstrated in a phantom that beta amyloid is diamagnetic and can generate strong contrast on susceptibility maps. We then conducted experiments on a transgenic mouse model of Alzheimer's disease that is known to mimic the formation of human beta amyloid but without neurofibrillary tangles or neuronal death. Over a period of 18 months, we showed that QSM can be used to longitudinally monitor beta amyloid accumulation and accompanied iron deposition in vivo. Individual beta amyloid plaque can also be visualized ex vivo in high resolution susceptibility maps. Moreover, the measured negative susceptibility map and positive susceptibility map could provide histology-like image contrast for identifying deposition of beta amyloid plaques and iron. Finally, we demonstrated that the diamagnetic susceptibility of beta amyloid can also be observed in brain specimens of AD patients. The ability to assess beta amyloid aggregation non-invasively with QSM MR imaging may aid the diagnosis of Alzheimer's disease.

Is there a specific memory signature associated with Aβ-PET positivity in patients with amnestic mild cognitive impairment?

Amnestic mild cognitive impairment (aMCI) is a clinical entity with various potential etiologies including but not limited to Alzheimer's disease. We examined whether a positive ([18F]Florbetapir) beta amyloid positron emission tomography scan, supporting underlying Alzheimer's disease pathophysiology, was associated with specific memory deficits in 48 patients with aMCI (33 beta amyloid positive, 15 beta amyloid negative). Memory was evaluated using an autobiographical fluency task and a word-list learning task with 2 different encoding types (shallow/incidental versus deep/intentional). Compared with 40 beta amyloid-negative controls, both aMCI subgroups demonstrated severe deficits in the global memory score and in most subscores of both tasks. Finer-grained analyses of memory tests showed subtle association with beta amyloid status, revealing a stronger impairment of the primacy effect in beta amyloid-positive patients. Structural magnetic resonance imaging showed that both aMCI subgroups exhibited comparable atrophy patterns, with similar degrees of medial temporal volume loss compared with controls. Specifically assessing the primacy effect might complement global memory scores in identifying beta amyloid-positive patients with aMCI.

Prestimulation of Microglia Through TLR4 Pathway Promotes Interferon Beta Expression in a Rat Model of Alzheimer's Disease

Soluble amyloid beta (Aβ) oligomers are the most common forms of Aβ in the early stage of Alzheimer's disease (AD). They are highly toxic to the neurons but their capability to activate microglia remains controversial. Microglia develop two distinct phenotypes, classic (M1) and alternative (M2). Tuning of microglia to the alternative (anti-inflammatory) state is of major interest in treatment of neuroinflammatory disease. This study aimed to assess tuning the microglia to produce interferon beta (IFN-β) as an anti-inflammatory cytokine through TLR4 pathway in a rat model of AD. Microglial BV-2 cells were treated with 1 μg/ml lipopolysaccharides (LPS), Monophosphoryl lipid A (MPL), or vehicles for 24 h, and then incubated with Aβ oligomer. After 24 h, cell pellets were harvested and TIR-domain-containing adapter-inducing interferon-β (TRIF), interferon regulatory factor 3 (IRF3), and IFN-β levels were measured. The ligands/vehicle were microinjected into the right ventricle of male Wistar rats every 3 days. Two weeks later, an osmotic pump filled with oligomeric Aβ/vehicle was implanted in the left ventricle. After 2 weeks, TRIF, IRF3, and IFN-β levels were measured in the hippocampal tissue. TNF-α and IFN-β levels were assessed in the hippocampus using immunohistochemistry. The oligomeric Aβ did not change TRIF, IRF3, and IFN-β levels in both cell culture and hippocampal tissue. However, pretreatment with LPS or MPL increased the level of these proteins. BV-2 cells morphologically express M1 state in presence of higher dose of Aβ oligomer (10 μM). Pretreatment with LPS or MPL decreased the TNF-α and increased the number of IFN-β positive cells in the hippocampus of Aβ-treated rats. In conclusion, pretreatment with low dose TLR4 agonists could induce microglia to produce neuroprotective cytokines including IFN-β which may be considered as a potential strategy to combat neuronal degeneration in AD.

Antidepressant agomelatine attenuates behavioral deficits and concomitant pathology observed in streptozotocin-induced model of Alzheimer's disease in male rats

Experimental findings suggest that the melatonin system has a beneficial role in models of Alzheimer's disease (ADs). The aim of the present study was to explore whether the atypical antidepressant agomelatine (Ago), which is a melatonin MT₁ and MT₂ agonist and 5-HT_2C antagonist, is effective against behavioral, biochemical and histological impairments in streptozotocin (STZ)-induced model of ADs in male rats. Male Sprague Dawley rats were treated intraperitoneally (i.p.) with Ago (40 mg/kg) for 30 days starting three months following the intracerebroventricular (icv) injection of STZ. Chronic Ago treatment reduced anxiety-like behavior of STZ-treated rats in the elevated plus maze, increased the preference to saccharine and corrected the spatial memory impairment in the eight-arm radial arm maze test. This melatonin analogue restored STZ-induced biochemical changes, including an increase of beta amyloid (Aβ) protein, and signal markers of inflammation (TNF-alpha and IL-1 beta). Ago exerted partial neuroprotection, specifically in the temporal CA3b subfield of the dorsal hippocampus and temporal piriform cortex. The ability of Ago to alleviate behavioral symptoms and concomitant neuropathological events observed in a model of sporadic ADs suggests that this melatonin alternative can be considered a promising adjuvant in this disease.

Choroid plexus genes for CSF production and brain homeostasis are altered in Alzheimer's disease

Background

The roles of the choroid plexus (CP) and cerebrospinal fluid (CSF) production have drawn increasing attention in Alzheimer’s disease (AD) research. Specifically, studies document markedly decreased CSF production and turnover in moderate-to-severe AD. Moreover, reduced CP function and CSF turnover lead to impaired clearance of toxic metabolites, likely promote neuroinflammation, and may facilitate neuronal death during AD progression. We analyzed CP gene expression in AD compared with control subjects, specifically considering those genes involved with CSF production and CP structural integrity.

Methods

The Brown-Merck Gene Expression Omnibus (GEO) database (CP transcripts) was mined to examine changes in gene expression in AD compared to controls with a focus on assorted genes thought to play a role in CSF production. Specifically, genes coding for ion transporters in CP epithelium (CPE) and associated enzymes like Na–K-ATPase and carbonic anhydrase, aquaporins, mitochondrial transporters/enzymes, blood–cerebrospinal fluid barrier (BCSFB) stability proteins, and pro-inflammatory mediators were selected for investigation. Data were analyzed using t test p-value and fold-change analysis conducted by the GEO2R feature of the GEO database.

Results

Significant expression changes for several genes were observed in AD CP. These included disruptions to ion transporters (e.g., the solute carrier gene SLC4A5, p = 0.004) and associated enzyme expressions (e.g., carbonic anhydrase CA4, p = 0.0001), along with decreased expression of genes involved in BCSFB integrity (e.g., claudin CLDN5, p = 0.039) and mitochondrial ATP synthesis (e.g., adenosine triphosphate ATP5L, p = 0.0004). Together all changes point to disrupted solute transport at the blood–CSF interface in AD. Increased expression of pro-inflammatory (e.g., interleukin IL1RL1, p = 0.00001) and potential neurodegenerative genes (e.g., amyloid precursor APBA3, p = 0.002) also implicate disturbed CP function.

Conclusions

Because the altered expression of numerous transcripts in AD-CP help explain decreased CSF production in AD, these findings represent a first step towards identifying novel therapeutic targets in AD.

Electronic supplementary material

The online version of this article (10.1186/s12987-018-0120-7) contains supplementary material, which is available to authorized users.

The neuroprotective effect of agmatine against amyloid β-induced apoptosis in primary cultured hippocampal cells involving ERK, Akt/GSK-3β, and TNF-α

β-Amyloid peptide (Aβ), the major element of senile plaques in Alzheimer's disease (AD), has been found to accumulate in brain regions critical for memory and cognition. Deposits of Aβ trigger neurotoxic events which lead to neural apoptotic death. The present study examined whether agmatine, an endogenous polyamine formed by the decarboxylation of L-arginine, possesses a neuroprotective effect against Aβ-induced toxicity. Primary rat hippocampal cells extracted from the brains of 18-19-day-old embryos were exposed to 10 µM of Aβ (25-35) in the absence or presence of agmatine at 150 or 250 µM. Additionally, the involvement of Akt (Protein Kinae B), GSK-3β (glycogen synthase kinase 3-β), ERK (Extracellular Signal-Regulated Kinase) and TNF-α (Tumor necrosis factor-α) in the agmatine protection against Aβ-induced neurotoxicity was investigated. Agmatine significantly prevented the effect of Aβ exposure on cell viability and caspase-3 assays. Furthermore, agmatine considerably restored Aβ-induced decline of phospho-Akt and phospho-GSK and blocked Aβ-induced increase of phospho-ERK and TNF-alpha. Taken together, these findings might shed light on the protective effect of agmatine as a potential therapeutic agent for AD.

Relevance of electroencephalogram assessment in amyloid and tau pathology in rat

In order to contribute to a better knowledge on the relationship between amyloid and tau pathology, and electroencephalography (EEG) disturbances, the aim of this study was to evaluate the effects of injection of beta amyloid Abeta(1-42) peptide, tau (a recombinant AAV (Adeno-Associated Virus) containing the human transgene tau with the P301 L mutation on rats and the combination of both, on the power of brain's rhythm (delta, theta, alpha, beta and gamma waves) during the different sleep/wake states of animals by EEG recording. Currently, no preclinical studies explore the effect of the tau pathology on EEG. The experimentations were performed 3 weeks and 3 months post injections. Beta amyloid deposits and hyperphosphorylated Tau are observed by immunohistofluorescence, only in the hippocampus. Furthermore, using a radial arm water maze, the main effect was observed on working memory which was significantly impaired in Abeta-Tau group only 3 months post injections. However, on EEG, as early as the 3^rd week, an overall decrease of the EEG bands power was observed in the treated groups, particularly the theta waves during the rapid eye movement (REM) sleep. Beta amyloid was mainly involved in these perturbations. Obviously, EEG seems to be an interesting tool in the early diagnostic of amyloid and tau pathologies, with a good sensitivity and the possibility to perform a follow up during a large period.

Salivary beta amyloid protein levels are detectable and differentiate patients with Alzheimer's disease dementia from normal controls: preliminary findings

Background

Peripheral diagnostics for Alzheimer’s disease (AD) continue to be developed. Diagnostics capable of detecting AD before the onset of symptoms are particularly desirable, and, given the fact that early detection is imperative for alleviating long-term symptoms of the disease, methods which enable detection in the earliest stages are urgently needed. Saliva testing is non-invasive, and saliva is easy to acquire. A simple, non-invasive saliva test can potentially be used as an adjunct to diagnose AD during its earliest stages.

Methods

Salivary levels of beta amyloid 42 (Aβ₄₂) were quantitated with enzyme-linked immunosorbent–type assays. Fifteen AD patients (7 men, mean age 77.8 ± 1.8 years, mean Mini-Mental State Examination [MMSE] score 19.0 ± 1.3) and 7 normal controls (2 men, mean age 60.4 ± 4.7 years, mean MMSE 29.0 ± 0.4) were enrolled.

Results

Salivary Aβ₄₂ levels were significantly higher in AD patients than in controls (51.7 ± 1.6 pg/mL for AD and 21.1 ± 0.3 pg/mL for controls, p < 0.001). Based on these results, saliva testing appears to be a promising method for detecting AD during its critical early stages.

Centella asiatica attenuates hippocampal mitochondrial dysfunction and improves memory and executive function in β-amyloid overexpressing mice

Centella asiatica is a medicinal plant used to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) attenuates β-amyloid (Aβ)-induced spatial memory deficits in mice and improves neuronal health. Yet the effect of CAW on other cognitive domains remains unexplored as does its in vivo mechanism of improving Aβ-related cognitive impairment. This study investigates the effects of CAW on learning, memory and executive function as well as mitochondrial function and antioxidant response in the 5xFAD model of Aβ accumulation. Seven month old 5xFAD female mice were treated with CAW (2 mg/mL) in their drinking water for two weeks prior to behavioral testing. Learning, memory and executive function were assessed using the object location memory task (OLM), conditioned fear response (CFR) and odor discrimination reversal learning (ODRL) test. Mitochondrial function was profiled using the Seahorse XF platform in hippocampal mitochondria isolated from these animals and tissue was harvested for assessment of mitochondrial, antioxidant and synaptic proteins. CAW improved performance in all behavioral tests in the 5xFAD but had no effect on WT animals. Hippocampal mitochondrial function was improved and hippocampal and cortical expression of mitochondrial genes was increased in CAW-treated 5xFAD mice. Gene expression of the transcription factor NRF2, as well as its antioxidant target enzymes, was also increased with CAW treatment in both WT and 5xFAD mice. CAW treatment also decreased Aβ-plaque burden in the hippocampus of treated 5xFAD mice but had no effect on plaques in the cortex. These data show that CAW can improve many facets of Aβ-related cognitive impairment in 5xFAD mice. Oral treatment with CAW also attenuates hippocampal mitochondrial dysfunction in these animals. Because mitochondrial dysfunction and oxidative stress accompany cognitive impairment in many pathological conditions beyond Alzheimer's disease, this suggests potentially broad therapeutic utility of CAW.

Alzheimer's disease and late-onset epilepsy of unknown origin: two faces of beta amyloid pathology

Although amyloid pathology plays a role in epilepsy, little is known about the relationship between beta amyloid and progression to Alzheimer's disease (AD) among patients with late-onset epilepsy of unknown origin (LOEU). This multicenter, observational, prospective study enrolled 40 consecutive nondemented adults diagnosed with LOEU, together with 43 age- and sex-matched healthy controls. All patients completed neuropsychological tests, core CSF AD biomarkers assessment (Aβ_1-42, total tau, and phosphorylated tau), and follow-up for a mean of 3 years to verify cognitive decline. Despite age and baseline cognitive performance were similar to healthy controls, patients with LOEU had significant prevalence of CSF pathological Aβ_1-42 (<500 pg/mL; 37.5%), 7.5% displaying an AD-like CSF pattern. Moreover, 17.5% of patients with LOEU converted to AD dementia, versus none among healthy controls (p < 0.005). Patients with LOEU with pathological Aβ_1-42 had a hazard ratio 3.4 (CI 0.665-17.73) for progression to AD dementia at follow-up. Patients with LOEU have a high prevalence of abnormal CSF Aβ_1-42 and progression to AD dementia compared with healthy controls, and therefore should be monitored for cognitive decline.

The effect of amyloid-β peptide on synaptic plasticity and memory is influenced by different isoforms, concentrations, and aggregation status

The increase of oligomeric amyloid-beta (oAβ) has been related to synaptic dysfunction, thought to be the earliest event in Alzheimer's disease pathophysiology. Conversely, the suppression of endogenous Aβ impaired synaptic plasticity and memory, suggesting that the peptide is needed in the healthy brain. However, different species, aggregation forms and concentrations of Aβ might differently influence synaptic function/dysfunction. Here, we have tested the contribution of monomeric and oligomeric Aβ42 and Aβ40 at 200 nM and 200 pM concentrations on hippocampal long-term potentiation and spatial memory. We found that, when at 200 nM, oAβ40, oAβ42, and monomeric Aβ42 impaired long-term potentiation and memory, whereas only oAβ42 200 pM enhanced synaptic plasticity and memory and rescued the detrimental effect due to depletion of endogenous Aβ. Interestingly, quantification of monomer-like and oligomer-like species carried out by transmission electron microscopy revealed an increase of the monomer/oligomer ratio in the oAβ42 200 pM preparation, suggesting that the content of monomers and oligomers depends on the final concentration of the solution.

Incensole acetate prevents beta-amyloid-induced neurotoxicity in human olfactory bulb neural stem cells

β-Amyloid peptide (Aβ) is a potent neurotoxic protein associated with Alzheimer's disease (AD) which causes oxidative damage to neurons. Incensole acetate (IA) is a major constituent of Boswellia carterii resin, which has anti-inflammatory and protective properties against damage of a large verity of neural subtypes. However, this neuroprotective effect was not studied on human olfactory bulb neural stem cells (hOBNSCs). Herein, we evaluated this effect and studied the underlying mechanisms. Exposure to Aβ_25-35 (5 and 10 μM for 24 h) inhibited proliferation (revealed by downregulation of Nestin and Sox2 gene expression), and induced differentiation (marked by increased expression of the immature neuronal marker Map2 and the astrocyte marker Gfap) of hOBNSCs. However, pre-treatment with IA (100 μM for 4 h) stimulated proliferation and differentiation of neuronal, rather than astrocyte, markers. Moreover, IA pretreatment significantly decreased the Aβ_25-35-induced viability loss, apoptotic rate (revealed by decreased caspase 3 activity and protein expression, downregulated expression of Bax, caspase 8, cyto c, caspase3, and upregulated expression of Bcl2 mRNAs and proteins, in addition to elevated mitochondrial membrane potential and lowered intracellular Ca⁺²). IA reduced Aβ-mediated ROS production (revealed by decreased intracellular ROS and MDA level, and increased SOD, CAT, and GPX contents), and inhibited Aβ-induced inflammation (marked by down-regulated expression of IL1b, TNFa, NfKb, and Cox2 genes). IA also significantly upregulated mRNA and protein expression of Erk1/2 and Nrf2. Notably, IA increased the antioxidant enzyme heme oxygenase-1 (HO-1) expression and this effect was reversed by HO-1 inhibitor zinc protoporphyrin (ZnPP) leading to reduction of the neuroprotective effect of IA against Aβ-induced neurotoxicity. These findings clearly show the ability of IA to initiate proliferation and differentiation of neuronal progenitors in hOBNSCs and induce HO-1 expression, thereby protecting the hOBNSCs cells from Aβ_25-35-induced oxidative cell death. Thus, IA may be applicable as a potential preventive agent for AD by its effect on hOBNSCs and could also be used as an adjuvant to hOBNSCs in cellular therapy of neurodegenerative diseases.

Piper sarmentosum Roxb. confers neuroprotection on beta-amyloid (Aβ)-induced microglia-mediated neuroinflammation and attenuates tau hyperphosphorylation in SH-SY5Y cells

ETHNOPHARMACOLOGICAL RELEVANCE

Piper sarmentosum Roxb. (PS), belonging to Piperaceae family, is an edible plant with medicinal properties. It is traditionally used by the Malays to treat headache and boost memory. Pharmacological studies revealed that PS exhibits anti-inflammatory, anti-oxidant, anti-acetylcholinesterase, and anti-depressant-like effects. In view of this, the present study aimed to investigate the anti-inflammatory actions of PS and its potential neuroprotective effects against beta-amyloid (Aβ)-induced microglia-mediated neurotoxicity.

MATERIALS AND METHODS

The inhibitory effects of hexane (L_HXN), dichloromethane (L_DCM), ethyl acetate (L_EA) and methanol (L_MEOH) extracts from leaves of PS on Aβ-induced production and mRNA expression of pro-inflammatory mediators in BV-2 microglial cells were assessed using colorimetric assay with Griess reagent, ELISA kit and real-time RT-PCR respectively. Subsequently, MTT reduction assay was used to evaluate the neuroprotective effects of PS leaf extracts against Aβ-induced microglia-mediated neurotoxicity in SH-SY5Y neuroblastoma cells. The levels of tau proteins phosphorylated at threonine 231 (pT231) and total tau proteins (T-tau) were determined using ELISA kits.

RESULTS

Polar extracts of PS leaves (L_EA and L_MEOH) reduced the Aβ-induced secretion of pro-inflammatory cytokines (IL-1β and TNF-α) in BV-2 cells by downregulating the mRNA expressions of pro-inflammatory cytokines. The inhibition of nitric oxide (NO) production could be due to the free radical scavenging activity of the extracts. In addition, conditioned media from Aβ-induced BV-2 cells pre-treated with L_EA and L_MEOH protected SH-SY5Y cells against microglia-mediated neurotoxicity. Further mechanistic study suggested that the neuroprotective effects were associated with the downregulation of phosphorylated tau proteins.

CONCLUSIONS

The present study suggests that polar extracts of PS leaves confer neuroprotection against Aβ-induced microglia-mediated neurotoxicity in SH-SY5Y cells by attenuating tau hyperphosphorylation through their anti-inflammatory actions and could be a potential therapeutic agent for Alzheimer's disease.

d-galactose and aluminium chloride induced rat model with cognitive impairments

Cognitive impairments and cholinergic dysfunctions have been well reported in old age disorders including Alzheimer's disease (AD). d-galactose (D-gal) has been reported as a senescence agent while aluminium act as a neurotoxic metal, but little is known about their combined effects at different doses. The aim of this study was to establish an animal model with cognitive impairments by comparing the effects of different doses of co-administrated D-gal and aluminium chloride (AlCl₃). In this study male albino wistar rats were administered with D-gal 60 mg/kg.bwt intra peritoneally (I.P) injected and AlCl₃ (100, 200, or 300 mg/kg.bwt.) was orally administered once daily for 10 consecutive weeks. Performance of the rats were evaluated through behavioural assessments; Morris water maze (MWM) and open field tests (OFT); histopathological examination was performed on the hippocampus; moreover biochemical measurements of acetylcholinesterase (AChE) and hyperphosphorylated tau protein (p-tau) were examined. The results of this experiment on rats treated with D-gal 60 + AlCl₃ 200 mg/kg.bwt showed near ideal cognitive impairments. The rats exhibited an obvious memory and learning deficits, marked neuronal loss in hippocampus, showed increase in AChE activities and high expression of p-tau within the tissues of the brain. This study concludes that D-gal 60 + AlCl₃ 200 mg/kg.bwt as the ideal dose for mimicking AD like cognitive impairments in albino wistar rats. It is also crucial to understand the pathogenesis of this neurodegenerative disease and for drug discovery.

Exercise Improves Recognition Memory and Acetylcholinesterase Activity in the Beta Amyloid-Induced Rat Model of Alzheimer's Disease

Objective

A correlation between physical exercise and cognitive improvement has been found in Alzheimer's disease (AD). This study aimed to investigate the effects of aerobic and resistance exercise on the recognition memory and acetylcholinesterase (AChE) activity in beta amyloid (Aβ) model of AD in rat.

Materials and Methods

Fifty male 8-week-old Wistar rats (250-280 g) were divided into 5 groups (n = 10 each) of control, sham surgery, Aβ-received sedentary, Aβ-received with aerobic exercise and Aβ-received with resistance exercise. AD was induced by intracerebroventricular injection of Aβ_25-35 peptide. The sham surgery group received normal saline using the same route and condition. Two groups of Aβ-received animals were trained by treadmill for aerobic exercise and by ladder for strength exercise for 8 weeks (4 days/week). Novel object recognition (NOR) task was used to assess recognitional memory in groups. AChE activity in the brain tissue was assessed using the Spectrophotometry method.

Results

There was no significant difference in memory index and AChE activity between the sham surgery and control groups (p > 0.05). Also, impairment of NOR indices was seen in the Aβ-injected sedentary rats (p < 0.05). However, both aerobic and strength training improved the exploration index in this test (p < 0.05). Further, AChE activity increased in the Aβ-injected sedentary group but declined in the aerobic and resistance exercise groups (p < 0.01).

Conclusion

Aerobic and resistance exercise could improve recognition memory and decrease AChE activity in Aβ-induced AD in rats. The decrease in AChE activity may be one of the mechanisms by which exercise improves cognition and memory in AD.

A cAMP analog attenuates beta-amyloid (1-42)-induced mitochondrial dysfunction and spatial learning and memory deficits

Alzheimer's disease (AD), a neurodegenerative disorder in elderly, is indicated with deposition of Amyloid β (Aβ) in the brain and accompanied with cognitive impairment. Bucladesine, a phosphodiesterase inhibitor, may ameliorate AD's cognitive dysfunctions through mimicking the action of cAMP and raising its intracellular level. Here, we investigated the effects of bucladesine on Aβ-induced memory and learning impairment in a Morris water maze (MWM) model. Rats were injected with bucladesine (1 μl/side from a 100 μM stock solution) and Aβ (1 μl/side from a 100 μM stock solution) intra-hippocampally and after 19 days were trained for 4 successive days. The oxidative stress was evaluated through measurement of thiobarbituric acid (TBARS), thiol groups, and ferric reducing antioxidant power (FRAP). Effect of Aβ and its combination with bucladesine on the mitochondrial function was assessed according to changes in the ROS generation, mitochondrial membrane potential (MMP), mitochondrial swelling, ATP/ADP ratio, mitochondrial outer membrane damage and cytochrome C release. Our results showed a significant elevation in TBARS level after administration of Aβ causing mitochondrial ROS generation, swelling, outer membrane damage, cytochrome C release and also lower thiol, FRAP, and MMP levels. Aβ-induced spatial memory impairment was prevented by pre-treatment with bucladesine and the changed mitochondrial and biochemical indices upon treatment dose were improved. Taken together, we have obtained satisfactory results suggesting protecting effects of bucladesine against the Aβ-mediated memory deficit and implying its plausible beneficial capacity as a therapeutic agent in oxidative stress-associated neurodegenerative diseases.