Early memory deficits precede plaque deposition in APPswe/PS1dE9 mice: involvement of oxidative stress and cholinergic dysfunction

Modulation of mitochondrial functions contributes to the protection of lamotrigine against Alzheimer's disease

BACKGROUND

Our previous studies have established that the broad-spectrum anti-epileptic drug lamotrigine (LTG) confers protection against cognitive impairments, synapse and nerve cell damage, as well as characteristic neuropathologies in APP/PS1 mice, a mouse model of Alzheimer's disease (AD). However, the precise molecular mechanisms responsible for this protective effect induced by LTG remain largely elusive.

OBJECTIVE

In this study, we aimed to investigate the mechanisms underlying the beneficial effects of LTG against AD.

METHODS

Five-month-old APP/PS1 mice were treated with 30 mg/kg of LTG daily for three consecutive months. Subsequently, high-throughput ribosome profiling sequencing was conducted to identify differentially translated genes (DTGs) rescued by LTG in the brains of these mice. To gain further insights into the potential functions and pathways of these LTG-rescued DTGs, gene ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were performed. RNA expression, protein levels, and translational efficiency were assessed to explore how LTG regulated gene expression processes in AD-related DTGs. Additionally, Aβ42 peptide-stimulated primary neurons were used to uncover the potential mechanisms and signaling pathway by which LTG mitigated oxidative stress under AD context.

RESULTS

For the first time, we reveal that LTG inactivates mitochondrial complexes in the brains of APP/PS1 mice by suppressing the translational efficiency of mitochondrial complexes-related genes. More importantly, we demonstrate that LTG mitigates mitochondrial-mediated oxidative stress in neurons within the context of AD by activation of SIRT6/PGC-1α pathway.

CONCLUSIONS

These findings provide further insights into the mechanisms underlying the protective effects of LTG against AD.

Cerebroprotein hydrolysate-I ameliorates cognitive dysfunction in APP/PS1 mice by inhibiting ferroptosis via the p53/SAT1/ALOX15 signalling pathway

Ferroptosis, an iron-dependent lipid peroxidation-driven cell death pathway, has been linked to the development of Alzheimer's disease (AD). However, the role of ferroptosis in the pathogenesis of AD remains unclear. Cerebroprotein hydrolysate-I (CH-I) is a mixture of peptides with neurotrophic effects that improves cognitive deficits and reduces amyloid burden. The present study investigated the ferroptosis-induced signalling pathways and the neuroprotective effects of CH-I in the brains of AD transgenic mice. Seven-month-old male APPswe/PS1dE9 (APP/PS1) transgenic mice were treated with intraperitoneal injections of CH-I and saline for 28 days. The Morris water maze test was used to assess cognitive function. CH-I significantly improved cognitive deficits and attenuated beta-amyloid (Aβ) aggregation and tau phosphorylation in the hippocampus of APP/PS1 mice. RNA sequencing revealed that multiple genes and pathways, including ferroptosis-related pathways, were involved in the neuroprotective effects of CH-I. The increased levels of lipid peroxidation, ferrous ions, reactive oxygen species (ROS), and altered expression of ferroptosis-related genes (recombinant solute carrier family 7, member 11 (SLC7A11), spermidine/spermine N1-acetyltransferase 1 (SAT1) and glutathione peroxidase 4 (GPX4)) were significantly alleviated after CH-I treatment. Quantitative real-time PCR and western blotting were performed to investigate the expression of key ferroptosis-related genes and the p53/SAT1/arachidonic acid 15-lipoxygenase (ALOX15) signalling pathway. The p53/SAT1/ALOX15 signalling pathway was found to be involved in mediating ferroptosis, and the activation of this pathway was significantly suppressed in AD by CH-I. CH-I demonstrated neuroprotective effects against AD by attenuating ferroptosis and the p53/SAT1/ALOX15 signalling pathway, thus providing new targets for AD treatment.

Quercetin Attenuates Oxidative Stress and Apoptosis in Brain Tissue of APP/PS1 Double Transgenic AD Mice by Regulating Keap1/Nrf2/HO-1 Pathway to Improve Cognitive Impairment

Objective: The objective of the study is to investigate whether quercetin ameliorates Alzheimer's disease (AD)-like pathology in APP/PS1 double transgenic mice and its hypothesized mechanism, contributing to the comprehension of AD pathogenesis. Methods: A total of 30 APP/PS1 transgenic mice were randomized into model group (APP/PS1), quercetin group (APP/PS1+Q), and donepezil hydrochloride group (APP/PS1+DON). Simultaneously, there were 10 C57 mice of the same age served as a control group. Three months posttreatment, the effects of quercetin on AD mice were evaluated using the Morris water maze (MWM) test, Y maze experiment, immunohistochemistry, immunofluorescence, and western blotting. Results: Results from the water maze and Y maze indicated that quercetin significantly improved cognitive impairment in APP/PS1 transgenic AD mice. Additionally, serum enzyme-linked immunosorbent assay (ELISA) results demonstrated that quercetin elevated MDA, superoxide dismutase (SOD), CAT, GSH, acetylcholine (ACh), and acetylcholinesterase (AChE) levels in AD mice. Hematoxylin-eosin (HE) staining, Nissl staining, and hippocampal tissue thioflavine staining revealed that quercetin reduced neuronal damage and Aβ protein accumulation in AD mice. Western blot validated protein expression in the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2)/HO-1 pathway associated with oxidative stress and apoptosis, confirming quercetin's potential molecular mechanism of enhancing AD mouse cognition. Furthermore, western blot findings indicate that quercetin significantly alters protein expression in the Keap1/Nrf2/HO-1 pathway. Moreover, molecular docking analysis suggests that Keap1, NQO1, HO-1, caspase-3, Bcl-2, and Bax proteins in the Keap1/Nrf2/HO-1 pathway may be potential regulatory targets of quercetin. These findings will provide a molecular basis for quercetin's clinical application in AD treatment. Conclusion: Quercetin can improve cognitive impairment and AD-like pathology in APP/PS1 double transgenic mice, potentially related to quercetin's activation of the Keap1/Nrf2/HO-1 pathway and reduction of cell apoptosis.

Caloric restriction leading to attenuation of experimental Alzheimer's disease results from alterations in gut microbiome

BACKGROUND

Caloric restriction (CR) might be effective for alleviating/preventing Alzheimer's disease (AD), but the biological mechanisms remain unclear. In the current study, we explored whether CR caused an alteration of gut microbiome and resulted in the attenuation of cognitive impairment of AD animal model.

METHODS

Thirty-week-old male APP/PS1 transgenic mice were used as AD models (AD mouse). CR was achieved by 30% reduction of daily free feeding (ad libitum, AL) amount. The mice were fed with CR protocol or AL protocol for six consecutive weeks.

RESULTS

We found that with CR treatment, AD mice showed improved ability of learning and spatial memory, and lower levels of Aβ40, Aβ42, IL-1β, TNF-α, and ROS in the brain. By sequencing 16S rDNA, we found that CR treatment resulted in significant diversity in composition and abundance of gut flora. At the phylum level, Deferribacteres (0.04%), Patescibacteria (0.14%), Tenericutes (0.03%), and Verrucomicrobia (0.5%) were significantly decreased in CR-treated AD mice; at the genus level, Dubosiella (10.04%), Faecalibaculum (0.04%), and Coriobacteriaceae UCG-002 (0.01%) were significantly increased in CR-treated AD mice by comparing with AL diet.

CONCLUSIONS

Our results demonstrate that the attenuation of AD following CR treatment in APP/PS1 mice may result from alterations in the gut microbiome. Thus, gut flora could be a new target for AD prevention and therapy.

Long-Term Krill Oil Administration Alleviated Early Mild Cognitive Impairment in APP/PS1 Mice

SCOPE

Alzheimer's disease is an age-dependent neurodegenerative disorder. Mounting studies focus on the improvement of advanced cognitive impairment by dietary nutrients. Krill oil (KO), a rich source of DHA/EPA and astaxanthin, is effective in improving cognitive function. The study mainly investigates the protective effects of long-term KO administration on early cognitive impairment.

METHODS AND RESULTS

Results show that 2 months KO administration (50 and 100 mg kg-1 BW) can dramatically promote learning and memory abilities. Mechanism studies demonstrate that KO reduces amyloid β concentration by regulating the amyloidogenic pathway, inhibits neuro-inflammation via regulating TLR4-NLRP3 signaling pathway, and prevents neuron injure. KO supplementation also enhances gut barrier integrity, reduces serum lipopolysaccharide leakage, and alters the gut microbiota by reducing Helicobacteraceae, Lactobacillaceae proportion, increasing Dubosiella and Akkermansia relative abundance. Particularly, a significant increase of isovaleric acid, propionic acid, and acetic acid levels is observed after KO supplementation. Correlation analysis shows that short-chain fatty acids (SCFAs), gut microbiota, and cognitive function are strongly correlated.

CONCLUSIONS

The results reveal that KO relieves early mild cognitive impairment possibly for its role in mediating the gut microbiome-SCFAs-brain axis. Thus, KO may provide potential intervention strategies to prevent cognitive impairment in the early stages through the microbiota-gut-brain axis.

Impact of Long-Term Dietary High Fat and Eicosapentaenoic Acid on Behavior and Hypothalamic-Pituitary-Adrenal Axis Activity in Amyloidogenic APPswe/PSEN1dE9 Mice

INTRODUCTION

Alzheimer's disease (AD) alters neurocognitive and emotional function and causes dysregulation of multiple homeostatic processes. The leading AD framework pins amyloid beta plaques and tau tangles as primary drivers of dysfunction. However, many additional variables, including diet, stress, sex, age, and pain tolerance, interact in ways that are not fully understood to impact the onset and progression of AD pathophysiology. We asked: (1) does high-fat diet, compared to low-fat diet, exacerbate AD pathophysiology and behavioral decline? And, (2) can supplementation with eicosapentaenoic (EPA)-enriched fish oil prevent high-fat-diet-induced changes?

METHODS

Male and female APPswePSdE9 mice, and their non-transgenic littermates, were randomly assigned to a diet condition (low-fat, high-fat, high-fat with EPA) and followed from 2 to 10 months of age. We assessed baseline corticosterone concentration during aging, pain tolerance, cognitive function, stress coping, and corticosterone response to a stressor.

RESULTS

Transgenic mice were consistently more active than non-transgenic mice but did not perform worse on either cognitive task, even though we recently reported that these same transgenic mice exhibited metabolic changes and had increased amyloid beta. Mice fed high-fat diet had higher baseline and post-stressor corticosterone, but diet did not impact cognition or pain tolerance. Sex had the biggest influence, as female mice were consistently more active and had higher corticosterone than males.

CONCLUSION

Overall, diet, genotype, and sex did not have consistent impacts on outcomes. We found little support for predicted interactions and correlations, suggesting diet impacts metabolic function and amyloid beta levels, but these outcomes do not translate to changes in behaviors measured here.

Antioxidant evaluation and computational prediction of prospective drug-like compounds from polyphenolic-rich extract of Hibiscus cannabinus L. seed as antidiabetic and neuroprotective targets: assessment through in vitro and in silico studies

BACKGROUND

Reports have implicated diabetes mellitus (DM) and Alzheimer's disease (AD) as some of the global persistent health challenges with no lasting solutions, despite of significant inputs of modern-day pharmaceutical firms. This study therefore, aimed to appraise the in vitro antioxidant potential, enzymes inhibitory activities, and as well carry out in silico study on bioactive compounds from polyphenolic-rich extract of Hibiscus cannabinus seed (PEHc).

METHODS

In vitro antioxidant assays were performed on PEHc using standard methods while the identification of phytoconstituents was carried out with high performance liquid chromatography (HPLC). For the in silico molecular docking using Schrodinger's Grid-based ligand docking with energetics software, seven target proteins were retrieved from the database ( https://www.rcsb.org/ ).

RESULTS

HPLC technique identified twelve chemical compounds in PEHc, while antioxidant quantification revealed higher total phenolic contents (243.5 ± 0.71 mg GAE/g) than total flavonoid contents (54.06 ± 0.09 mg QE/g) with a significant (p < 0.05) inhibition of ABTS (IC₅₀ = 218.30 ± 0.87 µg/ml) and 1, 1-diphenyl-2-picrylhydrazyl free radicals (IC₅₀ = 227.79 ± 0.74 µg/ml). In a similar manner, the extract demonstrated a significant (p < 0.05) inhibitory activity against α-amylase (IC₅₀ = 256.88 ± 6.15 µg/ml) and α-glucosidase (IC₅₀ = 183.19 ± 0.23 µg/ml) as well as acetylcholinesterase (IC₅₀ = 262.95 ± 1.47 µg/ml) and butyrylcholinesterase (IC₅₀ = 189.97 ± 0.82 µg/ml), respectively. Furthermore, In silico study showed that hibiscetin (a lead) revealed a very strong binding affinity energies for DPP-4, (PDB ID: 1RWQ) and α-amylase (PDB ID: 1SMD), gamma-tocopherol ( for peptide-1 receptor; PDB ID: 3C59, AChE; PDB ID: 4EY7 and BChE; PDB ID: 7B04), cianidanol for α-glucosidase; PDB ID: 7KBJ and kaempferol for Poly [ADP-ribose] polymerase 1 (PARP-1); PDB ID: 6BHV, respectively. More so, ADMET scores revealed drug-like potentials of the lead compounds identified in PEHc.

CONCLUSION

As a result, the findings of this study point to potential drug-able compounds in PEHc that could be useful for the management of DM and AD.

Oxazolo[5,4-f]quinoxaline-type selective inhibitors of glycogen synthase kinase-3α (GSK-3α): Development and impact on temozolomide treatment of glioblastoma cells

The 2-(3-pyridyl)oxazolo[5,4-f]quinoxalines CD-07 and FL-291 are ATP-competitive GSK-3 kinase inhibitors. Here, we investigated the impact of FL-291 on neuroblastoma cell viability and showed that treatment at 10 μM (i.e. ∼500 times the IC₅₀ against the GSK-3 isoforms) has no significant effect on the viability of NSC-34 motoneuron-like cells. A study performed on primary neurons (non-cancer cells) led to similar results. The structures co-crystallized with GSK-3β revealed similar binding modes for FL-291 and CD-07, with their hinge-oriented planar tricyclic system. Both GSK isoforms show the same orientations for the amino acids at the binding pocket except for Phe130 (α) and Phe67 (β), leading to a larger pocket on the opposite side of the hinge region for the α isoform. Calculations of the thermodynamic properties of the binding pockets highlighted the required features of potential ligands; these should have a hydrophobic core (which could be larger in the case of GSK-3β) surrounded by polar areas (a little more polar in the case of GSK-3α). A library of 27 analogs of FL-291 and CD-07 was thus designed and synthesized by taking advantage of this hypothesis. While the introduction of substituents at different positions of the pyridine ring, the replacement of the pyridine by other heterocyclic moieties, or the replacement of the quinoxaline ring by a quinoline moiety did not lead to any improvement, the replacement of the N-(thio)morpholino of FL-291/CD-07 by a slightly more polar N-thiazolidino led to a significant result. Indeed, the new inhibitor MH-124 showed clear selectivity for the α isoform, with IC₅₀ values of 17 nM and 239 nM on GSK-3α and GSK-3β, respectively. Finally, the efficacy of MH-124 was evaluated on two glioblastoma cell lines. Although MH-124 alone did not have a significant impact on cell survival, its addition to temozolomide (TMZ) significantly reduced the TMZ IC₅₀ values on the cells tested. The use of the Bliss model allowed a synergy to be evidenced at certain concentrations.

Cholinergic Neuron Targeting Nanosystem Delivering Hybrid Peptide for Combinatorial Mitochondrial Therapy in Alzheimer's Disease

Mitochondrial dysfunction in neurons has recently become a promising therapeutic target for Alzheimer's disease (AD). Regulation of dysfunctional mitochondria through multiple pathways rather than antioxidation monotherapy indicates synergistic therapeutic effects. Therefore, we developed a multifunctional hybrid peptide HNSS composed of antioxidant peptide SS31 and neuroprotective peptide S14G-Humanin. However, suitable peptide delivery systems with excellent loading capacity and effective at-site delivery are still absent. Herein, the nanoparticles made of citraconylation-modified poly(ethylene glycol)-poly(trimethylene carbonate) polymer (PEG-PTMC(Cit)) exhibited desirable loading of HNSS peptide through electrostatic interactions. Meanwhile, based on fibroblast growth factor receptor 1(FGFR1) overexpression in both the blood-brain barrier and cholinergic neuron, an FGFR1 ligand-FGL peptide was modified on the nanosystem (FGL-NP(Cit)/HNSS) to achieve 4.8-fold enhanced accumulation in brain with preferred distribution into cholinergic neurons in the diseased region. The acid-sensitive property of the nanosystem facilitated lysosomal escape and intracellular drug release by charge switching, resulting in HNSS enrichment in mitochondria through directing of the SS31 part. FGL-NP(Cit)/HNSS effectively rescued mitochondria dysfunction via the PGC-1α and STAT3 pathways, inhibited Aβ deposition and tau hyperphosphorylation, and ameliorated memory defects and cholinergic neuronal damage in 3xTg-AD mice. The work provides a potential platform for targeted cationic peptide delivery, harboring utility for peptide therapy in other neurodegenerative diseases.

A Class I HDAC Inhibitor Rescues Synaptic Damage and Neuron Loss in APP-Transfected Cells and APP/PS1 Mice through the GRIP1/AMPA Pathway

As a neurodegenerative disease, Alzheimer’s disease (AD) seriously affects the health of older people. Changes in synapses occur first over the course of the disease, perhaps even before the formation of Aβ plaques. Histone deacetylase (HDAC) mediates the damage of Aβ oligomers to dendritic spines. Therefore, we examined the relationship between HDAC activity and synaptic defects using an HDAC inhibitor (HDACI), BG45, in the human neuroblastoma SH-SY5Y cell line with stable overexpression of Swedish mutant APP (APPsw) and in APP/PS1 transgenic mice during this study. The cells were treated with 15 μM BG45 and the APP/PS1 mice were treated with 30 mg/kg BG45. We detected the levels of synapse-related proteins, HDACs, tau phosphorylation, and amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors using Western blotting and immunohistochemistry. We also measured the expression of cytoskeletal proteins in the cell model. The mRNA levels of the glutamate ion receptor alginate subunit 2 (GRIK2), sodium voltage-gated channel beta subunit (SCN3B), synaptophysin (SYP), Grm2 (the gene encoding glutamate receptor subunit 2 (GluR2)), Grid2IP, glutamate receptor interacting protein 1 (GRIP1), and GRIP2 were detected to explore the effects of the HDACI on regulating the expression of synaptic proteins and AMPA receptors. According to our studies, the expressions of HDAC1, HDAC2, and HDAC3 were increased, which were accompanied by the downregulation of the synapse-related proteins SYP, postsynaptic dendritic protein (PSD-95), and spinophilin as early as 24 h after transfection with the APPsw gene. BG45 upregulated the expression of synapse-related proteins and repaired cytoskeletal damage. In vivo, BG45 alleviated the apoptosis-mediated loss of hippocampal neurons, upregulated synapse-related proteins, reduced Aβ deposition and phosphorylation of tau, and increased the levels of the synapse-related genes GRIK2, SCN3B, SYP, Grm2, and Grid2IP. BG45 increased the expression of the AMPA receptor subunits GluA1, GluA2, and GluA3 on APPsw-transfected cells and increased GRIP1 and GRIP2 expression and AMPA receptor phosphorylation in vivo. Based on these results, HDACs are involved in the early process of synaptic defects in AD models, and BG45 may rescue synaptic damage and the loss of hippocampal neurons by specifically inhibiting HDAC1, HDAC2, and HDAC3, thereby modulating AMPA receptor transduction, increasing synapse-related gene expression, and finally enhancing the function of excitatory synapses. BG45 may be considered a potential drug for the treatment of early AD in further studies.

Impact of chronic doxycycline treatment in the APP/PS1 mouse model of Alzheimer's disease

Due to the pathophysiological complexity of Alzheimer's disease, multitarget approaches able to mitigate several pathogenic mechanisms are of interest. Previous studies have pointed to the neuroprotective potential of Doxycycline (Dox), a safe and inexpensive second-generation tetracycline. Dox has been particularly reported to slow down aggregation of misfolded proteins but also to mitigate neuroinflammatory processes. Here, we have evaluated the pre-clinical potential of Dox in the APP/PS1 mouse model of amyloidogenesis. Dox was provided to APP/PS1 mice from the age of 8 months, when animals already exhibit amyloid pathology and memory deficits. Spatial memory was then evaluated from 9 to 10 months of age. Our data demonstrated that Dox moderately improved the spatial memory of APP/PS1 mice without exerting major effect on amyloid lesions. While Dox did not alleviate overall glial reactivity, we could evidence that it rather enhanced the amyloid-dependent upregulation of several neuroinflammatory markers such as CCL3 and CCL4. Finally, Dox exerted differentially regulated the levels of synaptic proteins in the hippocampus and the cortex of APP/PS1 mice. Overall, these observations support that chronic Dox delivery does not provide major pathophysiological improvements in the APP/PS1 mouse model.

Positron Emission Computed Tomography Imaging of Synaptic Vesicle Glycoprotein 2A in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder seen in age-dependent dementia. There is currently no effective treatment for AD, which may be attributed in part to lack of a clear underlying mechanism. Early diagnosis of AD is of great significance to control the development of the disease. Synaptic loss is an important pathology in the early stage of AD, therefore the measurement of synaptic density using molecular imaging technology may be an effective way to early diagnosis of AD. Synaptic vesicle glycoprotein 2A (SV2A) is located in the presynaptic vesicle membrane of virtually all synapses. SV2A Positron Emission Computed Tomography (PET) could provide a way to measure synaptic density quantitatively in living humans and to track changes in synaptic density in AD. In view of the fact that synaptic loss is the pathology of both epilepsy and AD, this review summarizes the potential role of SV2A in the pathogenesis of AD, and suggests that SV2A should be used as an important target molecule of PET imaging agent for the early diagnosis of AD.

Oxidative stress-A direct bridge to central nervous system homeostatic dysfunction and Alzheimer's disease

Neurologists have highly observed a frequent increasing number of elderly patients with Alzheimer's disease (AD) without any relevant evidence of any genetic or known AD-linked predisposing factors in the past few years. Those patients are characterized by continuous and irreversible neuron cells loss along with declined cognitive functions. Numerous studies have suggested that the exaggerated release of reactive oxygen species (ROS) within the brain may develop late-onset neurodegenerative disorders, especially AD-neuroinflammatory type. However, the central nervous system is vitally linked with whole-brain chemical integrity and its related healthy state, the cascade by which ROS may result in AD's development has not been highly justified or even maintained. It is widely known that the brain consumes a vast amount of oxygen and is characterized by being rich in lipid polyunsaturated fatty acids content, explaining why it is a prone region to oxidative stress (OS) and ROS damage. The formed OS-AD cytoskeletal protein aggregates can be considered a main predisposing factor for amyloid-beta (Aβ) hallmarks precipitation. Herein, this review aims to provide a detailed information on how oxidative stress can play a pathogenic role in activating damage-associated molecular patterns (DAMPs)-related toll-like receptor-4 inflammatory (TLR-4) cascades resulting in the deposition of Aβ hallmarks in brain tissues ending with irreversible cognitive dysfunction. It also explains how microglia can be activated via ROS, which may significantly release several pro-inflammatory cascades ending with general brain atrophy. Furthermore, different types of suggested antioxidant therapies will be discussed to combat AD-related pathological disorders and hallmarks.

Scrophularia buergeriana Extract (Brainon) Improves Scopolamine-Induced Neuronal Impairment and Cholinergic Dysfunction in Mice through CREB-BDNF Signaling Pathway

We evaluated the effectiveness of Scrophularia buergeriana extract (Brainon) on cognitive dysfunction and determined its underlying mechanisms in a scopolamine (SCO)-treated mouse model of memory impairment. Brainon treatment for 28 days ameliorated the symptoms of memory impairment as indicated by the results of both passive avoidance performance and the Morris water mazes. Brainon lowered acetylcholinesterase activity and raised acetylcholine levels in the hippocampus. The treatment elevated the protein levels of brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element-binding (CREB). Additionally, the excessive generation of SCO-induced reactive oxygen species (ROS) and subsequent oxidative stress were suppressed by the enhancement of superoxide dismutase (SOD)-1 and SOD-2 proteins. mRNA levels of upregulated interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, as well as the apoptotic protein Bcl-2-associated X protein (Bax), cleaved caspase-9, and cleaved poly adenosine diphosphate-ribose polymerase (PARP) expression after SCO injection were downregulated by Brainon treatment. Collectively, these findings suggested that Brainon possesses anti-amnesic effects through the CREB-BDNF pathway. Moreover, it exerted antioxidant, anti-inflammatory, and anti-apoptotic effects in SCO-induced mice exhibiting cognitive impairment and memory loss.

Plasma and intracerebral pharmacokinetics and pharmacodynamics modeling for the acetylcholine releasing effect of ginsenoside Rg1 in mPFC of Aβ model rats

Ginsenoside Rg1 is a major bioactive component of ginseng. Limited information is available regarding Rg1 concentrations in the central neural system and the corresponding relationship of plasma/intracerebral concentrations, and intracerebral effects of Rg1. Awake Aβ model rats received a single subcutaneous administration of Rg1. Concentrations of unbound Rg1 and acetylcholine in the brain extracellular fluid and Rg1 in plasma were then determined. An E_max-two compartment pharmacokinetic/pharmacodynamics (PK/PD) model without effect compartment was finally obtained by evaluating three mechanism-based models. The corresponding relationship between the plasma PK and PD of Rg1 can be described as E = 119.05•C/(73.42 + C).[Formula: see text].

Neuroprotective effects of the Chrysophyllum perpulchrum extract against an Alzheimer-like rat model of β amyloid1-40 intrahippocampal injection

Objective

Alzheimer’s disease (AD) is a threatening disease for African populations in the upcoming years because of the increase in their expectancy of life. Here, we investigated whether natural products from Chrysophyllum perpulchrum as catechin and two dimeric procyanidins (catechin + hexose) could prevent progression of oxidative stress and cognitive changes using an AD-like rat model induced by Aβ_1-40 injection into the hippocampal CA1 subfield.

Methodology

Adult male Wistar rats were either microinjected with 1% ammonia as a vehicle (10 µL) or aggregated Aβ_1-40 at 10 µg bilateral hippocampus. On the 14th day of post-surgery, some Aβ rats were treated with melatonin (10 mg/kg i.p.) or with the Chrysophyllum perpulchrum extract (300 mg/kg p.o.), and some sham-operated rats received the extract alone. Cognitive abilities were tested with Y-maze, object recognition test and Morris Water Maze. Oxidative stress markers as well as the level of activated microglial cells were assayed in the brain.

Results

Aβ rats exhibited significant deficits of recognition memory and spatial learning. This was associated with an increase of microglia Iba 1 immunoreactivity as well as nitric oxide (NO), malondialdehyde and superoxide dismutase levels but not to the thiol content in the hippocampus, prefrontal cortex and septum of AD-like rats. The Chrysophyllum perpulchrum extract treatment mitigated Aβ-induced cognitive impairments and reversed microglia overactivation and subsequent generation of oxidative stress markers. Interestingly, the neuroprotective actions of the Chrysophyllum perpulchrum extract seem to be comparable to the control drug melatonin used albeit with some more beneficial effects.

Conclusion

These findings are preliminary and should be strengthened by more pharmacological studies of bioactive compounds of Chrysophyllum perpulchrum before being proposed as a promising drug against AD.

Astrocyte hepcidin ameliorates neuronal loss through attenuating brain iron deposition and oxidative stress in APP/PS1 mice

Iron overload in the brain and iron-induced oxidative damage have been considered to play key roles in the pathogenesis of Alzheimer's disease (AD). Hepcidin is a peptide that regulates systemic iron metabolism by interacting with iron exporter ferroportin 1 (FPN1). Studies have indicated that the astrocyte hepcidin could regulate brain iron intake at the blood-brain barrier and injection of hepcidin into brain attenuated iron deposition in the brain. However, whether overexpression of hepcidin in astrocytes of APP/PS1 transgenic mice can alleviate AD symptoms by reducing iron deposition has not been evaluated. In this study, we overexpressed hepcidin in astrocytes of APP/PS1 mice and investigated its effects on β-amyloid (Aβ) aggregation, neuronal loss, iron deposition and iron-induced oxidative damages. Our results showed that the elevated expression of astrocyte hepcidin in APP/PS1 mice significantly improved their cognitive decline, and partially alleviated the formation of Aβ plaques in cortex and hippocampus. Further investigations revealed that overexpression of hepcidin in astrocytes significantly reduced iron levels in cortex and hippocampus of APP/PS1 mice, especially iron content in neurons, which led to the reduction of iron accumulation-induced oxidative stress and neuroinflammation, and finally decreased neuronal cell death in the cortex and hippocampus of APP/PS1 mice. This study demonstrated that overexpression of hepcidin in astrocytes of APP/PS1 mice could partially alleviate AD symptoms and delay the pathological process of AD.

Evaluation of Mitochondrial Oxidative Stress in the Brain of a Transgenic Mouse Model of Alzheimer's Disease by in vitro Electron Paramagnetic Resonance Spectroscopy

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases responsible for progressive dementia. Deposition of amyloid-β (Aβ) in the brain is the most important pathophysiological hallmark of AD. In addition, recent evidence indicates that reactive oxygen species (ROS) derived from mitochondria contribute to progression of AD pathology. We thus hypothesized that Aβ accumulates and oxidative stress increases in the brain mitochondria of a transgenic mouse model of AD (APdE9). We measured the quantity of Aβ and the activity of the antioxidant enzyme superoxide dismutase (SOD) in brain mitochondrial fractions prepared from APdE9 and wild-type (WT) mice aged 6, 9, 15, and 18 months. We also quantified the age-related changes in redox status in the mitochondrial fractions obtained from both APdE9 and WT mouse brains by electron paramagnetic resonance (EPR) spectrometry using a paramagnetic nitroxide "Mito-Tempo" [(2-(2,2,6,6-Tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride monohydrate] as a mitochondria-targeted redox-sensitive probe. In APdE9 mice, Aβ accumulated in brain mitochondria earlier than in the non-mitochondrial fraction of the brain. Furthermore, increased oxidative stress was demonstrated in brain mitochondria of APdE9 mice by in vitro SOD assay as well as EPR spectroscopy. EPR combined with a mitochondria-targeted redox-sensitive nitroxide probe is a potentially powerful tool to elucidate the etiology of AD and facilitate the development of new therapeutic strategies for AD.

Anti-inflammatory and antioxidant effects of muscarinic acetylcholine receptor (mAChR) activation in the rat hippocampus

Recently we found that acute treatment with Oxotremorine (Oxo), a non-selective mAChRs agonist, up-regulates heat shock proteins and activates their transcription factor heat shock factor 1 in the rat hippocampus. Here we aimed to investigate: a) if acute treatment with Oxo may regulate pro-inflammatory or anti-inflammatory cytokines and oxidative stress in the rat hippocampus; b) if chronic restraint stress (CRS) induces inflammatory or oxidative alterations in the hippocampus and whether such alterations may be affected by chronic treatment with Oxo. In the acute experiment, rats were injected with single dose of Oxo (0.4 mg/kg) and sacrificed at 24 h, 48 h and 72 h. In the CRS experiment, the rats were exposed for 21 days to the CRS and then were treated with Oxo (0.2 mg/kg) for further 10 days. The acute Oxo treatment showed an ability to significantly reduce reactive oxygen species (ROS), singlet oxygen (¹O₂), pro-inflammatory cytokines levels (IL-1β and IL-6) and phosphorylated NF-κB-p65. Acute Oxo treatment also increased superoxide dismutase (SOD)-2 protein levels and stimulated SOD activity. No differences were detected in the anti-inflammatory cytokine levels, including IL-10 and TGF-β1. In the group of rats exposed to the CRS were found increased hippocampal IL-1β and IL-6 levels, together with a reduction of SOD activity level. These changes produced by CRS were counteracted by chronic Oxo treatment. In contrast, the upregulation of ROS and ¹O₂ levels in the CRS group was not counteracted by chronic Oxo treatment. The results revealed a hippocampal anti-inflammatory and antioxidant effect of Oxo treatment in both basal conditions and anti-inflammatory in the CRS rat model.

Inhibition of Rac1-dependent forgetting alleviates memory deficits in animal models of Alzheimer's disease

Accelerated forgetting has been identified as a feature of Alzheimer's disease (AD), but the therapeutic efficacy of the manipulation of biological mechanisms of forgetting has not been assessed in AD animal models. Ras-related C3 botulinum toxin substrate 1 (Rac1), a small GTPase, has been shown to regulate active forgetting in Drosophila and mice. Here, we showed that Rac1 activity is aberrantly elevated in the hippocampal tissues of AD patients and AD animal models. Moreover, amyloid-beta 42 could induce Rac1 activation in cultured cells. The elevation of Rac1 activity not only accelerated 6-hour spatial memory decay in 3-month-old APP/PS1 mice, but also significantly contributed to severe memory loss in aged APP/PS1 mice. A similar age-dependent Rac1 activity-based memory loss was also observed in an AD fly model. Moreover, inhibition of Rac1 activity could ameliorate cognitive defects and synaptic plasticity in AD animal models. Finally, two novel compounds, identified through behavioral screening of a randomly selected pool of brain permeable small molecules for their positive effect in rescuing memory loss in both fly and mouse models, were found to be capable of inhibiting Rac1 activity. Thus, multiple lines of evidence corroborate in supporting the idea that inhibition of Rac1 activity is effective for treating AD-related memory loss.

CREB signals as PBMC-based biomarkers of cognitive dysfunction: A novel perspective of the brain-immune axis

To date, there is no reliable biomarker for the assessment or determination of cognitive dysfunction in Alzheimer's disease and related dementia. Such a biomarker would not only aid in diagnostics, but could also serve as a measure of therapeutic efficacy. It is widely acknowledged that the hallmarks of Alzheimer's disease, namely, amyloid deposits and neurofibrillary tangles, as well as their precursors and metabolites, are poorly correlated with cognitive function and disease stage and thus have low diagnostic or prognostic value. A lack of biomarkers is one of the major roadblocks in diagnosing the disease and in assessing the efficacy of potential therapies. The phosphorylation of cAMP Response Element Binding protein (pCREB) plays a major role in memory acquisition and consolidation. In the brain, CREB activation by phosphorylation at Ser133 and the recruitment of transcription cofactors such as CREB binding protein (CBP) is a critical step for the formation of memory. This set of processes is a prerequisite for the transcription of genes thought to be important for synaptic plasticity, such as Egr-1. Interestingly, recent work suggests that the expression of pCREB in peripheral blood mononuclear cells (PBMC) positively correlates with pCREB expression in the postmortem brain of Alzheimer's patients, suggesting not only that pCREB expression in PBMC might serve as a biomarker of cognitive dysfunction, but also that the dysfunction of CREB signaling may not be limited to the brain in AD, and that a link may exist between the regulation of CREB in the blood and in the brain. In this review we consider the evidence suggesting a correlation between the level of CREB signals in the brain and blood, the current knowledge about CREB in PBMC and its association with CREB in the brain, and the implications and mechanisms for a neuro-immune cross talk that may underlie this communication. This Review will discuss the possibility that peripheral dysregulation of CREB is an early event in AD pathogenesis, perhaps as a facet of immune system dysfunction, and that this impairment in peripheral CREB signaling modifies CREB signaling in the brain, thus exacerbating cognitive decline in AD. A more thorough understanding of systemic dysregulation of CREB in AD will facilitate the search for a biomarker of cognitive function in AD, and also aid in the understanding of the mechanisms underlying cognitive decline in AD.

Glutathione-mimetic D609 alleviates memory deficits and reduces amyloid-β deposition in an AβPP/PS1 transgenic mouse model

Excessive extracellular deposition of amyloid-β-peptide (Aβ) in the brain is a pathological hallmark of Alzheimer’s disease (AD). Oxidative stress is associated with the onset and progression of AD and contributes to Aβ generation. Tricyclodecan-9-yl-xanthogenate (D609) is a glutathione (GSH)-mimetic compound. Although the antioxidant properties of D609 have been well-studied, its potential therapeutic significance on AD remains unclear. In the present study, we used a mouse model of AD to investigate the effects and the mechanism of action of D609 on AD. We found that D609 treatment significantly improved the spatial learning and alleviated the memory decline in the mice harboring amyloid precursor protein (APP) and presenilin-1 (PS1) double mutations (AβPP/PS1 mice). D609 treatment also increased GSH level, GSH and oxidative glutathione ratio, and superoxide dismutase activity, whereas decreased malondialdehyde and protein carbonyl levels, suggesting that D609 alleviated oxidative stress in AβPP/PS1 mice. In addition, D609 reduced β-secretase 1 level and decreased amyloidogenic processing of AβPP, consequently reducing Aβ deposition in the mice. Thus, our findings suggest that D609 might produce beneficial effects on the prevention and treatment of AD.

Curcumin Ameliorates Memory Deficits by Enhancing Lactate Content and MCT2 Expression in APP/PS1 Transgenic Mouse Model of Alzheimer's Disease

Curcumin is a natural product with several anti-Alzheimer's disease (AD) neuroprotective properties. This study aimed to investigate the effects of curcumin on memory deficits, lactate content, and monocarboxylate transporter 2 (MCT2) in APP/PS1 mouse model of AD. APP/PS1 transgenic mice and wild-type (WT) C57BL/6J mice were used in the present study. Spatial learning and memory of the mice was detected using Morris water-maze test. Cerebral cortex and hippocampus lactate contents were detected using lactate assay. MCT2 expression in the cerebral cortex and hippocampus was examined by immunohistochemistry and Western blotting. Results showed that spatial learning and memory deficits were improved in curcumin-treated APP/PS1 mouse group compared with those in APP/PS1 mice group. Brain lactate content and MCT2 protein level were increased in curcumin-treated APP/PS1 mice than in APP/PS1 mice. In summary, our findings indicate that curcumin could ameliorate memory impairments in APP/PS1 mouse model of AD. This phenomenon may be at least partially due to its improving effect on the lactate content and MCT2 protein expression in the brain. Anat Rec, 302:332-338, 2019. © 2018 Wiley Periodicals, Inc.

Biothiols and oxidative stress markers and polymorphisms of TOMM40 and APOC1 genes in Alzheimer's disease patients

Alzheimer’s disease (AD) is a progressive disease, with frequently observed improper biothiols turnover, homocysteine (Hcy) and glutathione (GSH). GSH protects cells from oxidative stress and may be determined by 8-oxo-2’-deoxyguanosine (8-oxo2dG) level and its repair enzyme 8-oxoguanine DNA glycosylase (OGG1). The presence of unfavorable alleles, e.g., in APOE cluster, TOMM40 or APOC1 is known to facilitate the dementia onset under oxidative stress.

The aim of the study was to analyze rs1052452, rs2075650 TOMM40 polymorphisms, rs4420638 APOC1, and their correlation with Hcy, GSH, 8-oxo2dG, OGG1 levels in plasma of AD patients and controls.

We recruited 230 individuals: 88 AD, 80 controls without (UC), 62 controls with (RC) positive family history of AD. The TOMM40 genotype was determined by HRM and capillary electrophoresis, while APOC1 by HRM. The concentrations of OGG1, 8-oxo2dG were determined by ELISA, whereas Hcy, GSH by HPLC/EC.

We showed that over 60% of AD patients had increased Hcy levels (p<0.01 vs. UC, p<0.001 vs. RC), while GSH (p<0.01 vs. UC), 8-oxo2dG (p<0.01 vs. UC, p<0.001 vs. RC) were reduced. Minor variants: rs10524523-L, rs4420638-G, rs2075650-G were significantly overrepresented in AD. For rs4420638-G, rs2075650-G variants, the association remained significant in APOE E4 non-carriers. The misbalance of analyzed biothiols, and 8-oxo2dG, OGG1 were more pronounced in carriers of major variants: rs10524523-S/VL, rs4420638-A, rs2075650-A.

We showed, for the first time, that APOC1 and TOMM40 rs2075650 polymorphisms may be independent risk factors of developing AD, whose major variants are accompanied by disruption of biothiols metabolism and inefficient removal of DNA oxidation.

A guide to using functional magnetic resonance imaging to study Alzheimer's disease in animal models

Alzheimer's disease is a leading healthcare challenge facing our society today. Functional magnetic resonance imaging (fMRI) of the brain has played an important role in our efforts to understand how Alzheimer's disease alters brain function. Using fMRI in animal models of Alzheimer's disease has the potential to provide us with a more comprehensive understanding of the observations made in human clinical fMRI studies. However, using fMRI in animal models of Alzheimer's disease presents some unique challenges. Here, we highlight some of these challenges and discuss potential solutions for researchers interested in performing fMRI in animal models. First, we briefly summarize our current understanding of Alzheimer's disease from a mechanistic standpoint. We then overview the wide array of animal models available for studying this disease and how to choose the most appropriate model to study, depending on which aspects of the condition researchers seek to investigate. Finally, we discuss the contributions of fMRI to our understanding of Alzheimer's disease and the issues to consider when designing fMRI studies for animal models, such as differences in brain activity based on anesthetic choice and ways to interrogate more specific questions in rodents beyond those that can be addressed in humans. The goal of this article is to provide information on the utility of fMRI, and approaches to consider when using fMRI, for studies of Alzheimer's disease in animal models.

Dynamic SAP102 expression in the hippocampal subregions of rats and APP/PS1 mice of various ages

The hippocampus is a structurally and functionally complex brain area that plays important and diverse roles in higher brain functions, such as learning and memory, and mounting evidence indicates that different hippocampal subregions play distinctive roles. The hippocampus is also one of the first regions in the brain to suffer damage in Alzheimer's disease (AD). Synaptic dysfunction in the hippocampus, rather than neuronal loss per se, is paralleled by behavioural and functional deficits in AD. The membrane-associated guanylate kinase (MAGUK) family of proteins, including SAP102, PSD-95, PSD-93 and SAP97, have long been recognized as essential components of the postsynaptic density (PSD) at excitatory synapses. Hippocampal spines are the predominant synaptic transmission sites of excitatory glutamatergic synapses. During postnatal brain development, individual MAGUK members show distinct expression patterns. Although SAP102 has been confirmed as the dominant scaffold protein in neonatal synapses, its expression profiles in adult and ageing rodent hippocampi are discrepant. Furthermore, in AD brains, significantly reduced SAP102 protein levels have been found, suggesting that SAP102 may be related to AD progression; however, the precise mechanism underlying this result remains unclear. Herein, we observed distinct SAP102 expression profiles in the hippocampal CA1, CA3 and DG subregions of rats and APPswe/PS1dE9 (APP/PS1) mice at various ages using immunofluorescence. In Wistar rats, SAP102 was not only highly expressed in the hippocampal subregions of neonatal rats but also maintained relatively high expression levels in adult hippocampi and displayed no obvious decreases in the CA1 and DG subregions of aged rats. Surprisingly, we observed abnormally high SAP102 expression levels in the CA1 stratum moleculare and CA3 stratum polymorphum subregions of 2-month-old APP/PS1 mice, but low SAP102 levels in the DG and CA3 subregions of 7-month-old APP/PS1 mice, reflecting the subregion-specific reactivity and vulnerability of AD mouse models in different disease stages. Our findings provide fundamental data to support the functional differences of SAP102 in different hippocampal subregions during postnatal periods and may serve as the basis for additional functional studies on SAP102 in normal physiological conditions and different stages of AD.

Evaluation of Neuropathological Effects of a High-Fat Diet in a Presymptomatic Alzheimer's Disease Stage in APP/PS1 Mice

Alzheimer's disease (AD) is currently an incurable aging-related neurodegenerative disorder. Recent studies give support to the hypotheses that AD should be considered as a metabolic disease. The present study aimed to explore the relationship between hippocampal neuropathological amyloid-β (Aβ) plaque formation and obesity at an early presymptomatic disease stage (3 months of age). For this purpose, we used APPswe/PS1dE9 (APP/PS1) transgenic mice, fed with a high-fat diet (HFD) in order to investigate the potential molecular mechanisms involved in both disorders. The results showed that the hippocampus from APP/PS1 mice fed with a HFD had an early significant decrease in Aβ signaling pathway specifically in the insulin degrading enzyme protein levels, an enzyme involved in (Aβ) metabolism, and α-secretase. These changes were accompanied by a significant increase in the occurrence of plaques in the hippocampus of these mice. Furthermore, APP/PS1 mice showed a significant hippocampal decrease in PGC-1α levels, a cofactor involved in mitochondrial biogenesis. However, HFD does not provoke changes in neither insulin receptors gene expression nor enzymes involved in the signaling pathway. Moreover, there are no changes in any enzymes (kinases) involved in tau phosphorylation, such as CDK5, and neither in brain oxidative stress production. These results suggest that early changes in brains of APP/PS1 mice fed with a HFD are mediated by an increase in Aβ1 ‒ 42, which induces a decrease in PKA levels and alterations in the p-CREB/ NMDA2B /PGC1-α pathway, favoring early AD neuropathology in mice.

Longitudinal investigation of neuroinflammation and metabolite profiles in the APPswe ×PS1Δe9 transgenic mouse model of Alzheimer's disease

There is increasing evidence linking neuroinflammation to many neurological disorders including Alzheimer's disease (AD); however, its exact contribution to disease manifestation and/or progression is poorly understood. Therefore, there is a need to investigate neuroinflammation in both health and disease. Here, we investigate cognitive decline, neuroinflammatory and other pathophysiological changes in the APP_swe×PS1_Δe9 transgenic mouse model of AD. Transgenic (TG) mice were compared to C57BL/6 wild type (WT) mice at 6, 12 and 18 months of age. Neuroinflammation was investigated by [¹⁸F]DPA‐714 positron emission tomography and myo‐inositol levels using ¹H magnetic resonance spectroscopy (MRS) in vivo. Neuronal and cellular dysfunction was investigated by looking at N‐acetylaspartate (NAA), choline‐containing compounds, taurine and glutamate also using MRS. Cognitive decline was first observed at 12 m of age in the TG mice as assessed by working memory tests . A significant increase in [¹⁸F]DPA‐714 uptake was seen in the hippocampus and cortex of 18 m‐old TG mice when compared to age‐matched WT mice and 6 m‐old TG mice. No overall effect of gene was seen on metabolite levels; however, a significant reduction in NAA was observed in 18 m‐old TG mice when compared to WT. In addition, age resulted in a decrease in glutamate and an increase in choline levels. Therefore, we can conclude that increased neuroinflammation and cognitive decline are observed in TG animals, whereas NAA alterations occurring with age are exacerbated in the TG mice. These results support the role of neuroinflammation and metabolite alteration in AD and in ageing.

Dexibuprofen prevents neurodegeneration and cognitive decline in APPswe/PS1dE9 through multiple signaling pathways

The aim of the present study is to elucidate the neuronal pathways associated to NSAIDs causing a reduction of the risk and progression of Alzheimer's disease. The research was developed administering the active enantiomer of ibuprofen, dexibuprofen (DXI), in order to reduce associated gastric toxicity. DXI was administered from three to six-month-old female APPswe/PS1dE9 mice as a model of familial Alzheimer's disease. DXI treatment reduced the activation of glial cells and the cytokine release involved in the neurodegenerative process, especially TNFα. Moreover, DXI reduced soluble β-amyloid (Aβ1-42) plaque deposition by decreasing APP, BACE1 and facilitating Aβ degradation by enhancing insulin-degrading enzyme. DXI also decreased TAU hyperphosphorylation inhibiting c-Abl/CABLES/p-CDK5 activation signal pathway and prevented spatial learning and memory impairment in transgenic mice. Therefore, chronic DXI treatment could constitute a potential AD-modifying drug, both restoring cognitive functions and reversing multiple brain neuropathological hallmarks.

Ginsenoside Rb1 ameliorates cisplatin-induced learning and memory impairments

Background

Ginsenoside Rb1 (Rb1), a dominant component from the extract of Panax ginseng root, exhibits neuroprotective functions in many neurological diseases. This study was intended to investigate whether Rb1 can attenuate cisplatin-induced memory impairments and explore the potential mechanisms.

Methods

Cisplatin was injected intraperitoneally with a dose of 5 mg/kg/wk, and Rb1 was administered in drinking water at the dose of 2 mg/kg/d to rats for 5 consecutive wk. The novel objects recognition task and Morris water maze were used to detect the memory of rats. Nissl staining was used to examine the neuron numbers in the hippocampus. The activities of superoxide dismutase, glutathione peroxidase, cholineacetyltransferase, acetylcholinesterase, and the levels of malondialdehyde, reactive oxygen species, acetylcholine, tumor necrosis factor-α, interleukin-1β, and interleukin-10 were measured by ELISA to assay the oxidative stress, cholinergic function, and neuroinflammation in the hippocampus.

Results

Rb1 administration effectively ameliorates the memory impairments caused by cisplatin in both novel objects recognition task and Morris water maze task. Rb1 also attenuates the neuronal loss induced by cisplatin in the different regions (CA1, CA3, and dentate gyrus) of the hippocampus. Meanwhile, Rb1 is able to rescue the cholinergic neuron function, inhibit the oxidative stress and neuroinflammation in cisplatin-induced rat brain.

Conclusion

Rb1 rescues the cisplatin-induced memory impairment via restoring the neuronal loss by reducing oxidative stress and neuroinflammation and recovering the cholinergic neuron functions.

Intranasal Cerebrolysin Attenuates Learning and Memory Impairments in D-galactose-Induced Senescence in Mice

Neurotrophic factors are currently being considered as pro-cognitive therapeutic approaches for management of cognitive deficits. This study aims to evaluate the effects of intranasal (i.n.) or intraperitoneal (i.p.) administration of Cerebrolysin (CBL) (as a mixture of neurotrophic factors) on the d-galactose-induced oxidative stress, apoptosis and memory as well as learning impairment in mice. For this purpose, CBL (1, 2.5, 5 ml/kg/i.p.) or (1 ml/kg/i.n.), were administrated daily in d-galactose-received (100 mg/kg/subcutaneous (s.c.)) mice model of aging for eight weeks. Spatial and recognition memories were assessed by the Morris water maze and novel object recognition tasks. Brain and blood of animals were analysed for oxidative stress biomarkers including malondialdehyde, total antioxidant capacity, glutathione peroxidase and superoxide dismutase. Apoptosis rate in the hippocampus was evaluated by TUNEL staining of brain tissue. 5 ml/kg/i.p. dose of CBL increased the locomotor activity but, 1 ml/kg/i.p. dose didn't show detectable behavioural or molecular effects on aged mice. Treatment with 2.5 ml/kg/i.p. and 1 ml/kg/i.n. doses attenuated d-galactose-impaired spatial and recognition memories. Results showed an obvious increase in the antioxidant biomarkers and decrease in the malondialdehyde levels both in the blood and brain of aged mice in 2.5 ml/kg/i.p. dose, and only in the brain in 1 ml/kg/i.n. dose of CBL. Anti-apoptotic effects also were seen in the same dose/rout of CBL administration in aged animals. This study proves the usefulness of i.n. CBL administration as a non-invasive and efficient method of drug delivery to the brain to improve aging-induced oxidative stress, apoptosis and learning as well as memory impairment.

Oxidative Stress in Neurodegenerative Diseases

The pathophysiologies of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and Alzheimer's disease (AD), are far from being fully explained. Oxidative stress (OS) has been proposed as one factor that plays a potential role in the pathogenesis of neurodegenerative disorders. Clinical and preclinical studies indicate that neurodegenerative diseases are characterized by higher levels of OS biomarkers and by lower levels of antioxidant defense biomarkers in the brain and peripheral tissues. In this article, we review the current knowledge regarding the involvement of OS in neurodegenerative diseases, based on clinical trials and animal studies. In addition, we analyze the effects of the drug-induced modulation of oxidative balance, and we explore pharmacotherapeutic strategies for OS reduction.

Therapeutic potential of human amniotic membrane-derived mesenchymal stem cells in APP transgenic mice

Growing evidence indicates that the presence of extensive oxidative stress plays an essential role in the initiation and progression of Alzheimer's disease (AD). Amyloid-β (Aβ) aggregation is involved in the elevation of oxidative stress, contributing to mitochondrial dysfunction and lipid peroxidation. In the present study, human placenta amniotic membrane-derived mesenchymal stem cells (hAMMSCs) were intravenously injected into C57BL/6J-APP transgenic mice. hAMMSCs significantly ameliorated spatial learning and memory function, and were associated with a decreased amount of amyloid plaques of the brain. The correlation of oxidative stress with Aβ levels was lower in the hAMMSCs-injected group than in the phosphate-buffered saline (PBS)-injected group, as indicated by the increased level of antioxidative enzymes and the decreased level of lipid peroxidation product. The glutathione (GSH) level and ratio of GSH to glutathione disulfide were higher in the hAMMSC group than in the PBS group. The superoxide dismutase activity and malonaldehyde level were improved significantly as the level of Aβ decreased, but there was no such trend in the PBS group. As a result, our findings represent evidence that hAMMSC treatment might improve the pathology of AD and memory function through the regulation of oxidative stress.

Sex differences between APPswePS1dE9 mice in A-beta accumulation and pancreatic islet function during the development of Alzheimer’s disease

The pathogenesis of Alzheimer’s disease (AD), a type of neurodegenerative disease characterized by learning and memory impairment, is often associated with pathological features, such as amyloid-beta (Aβ) accumulation and insulin resistance. The transgenic mouse, APPswePS1dE9 (APP/PS1), is one of the most commonly used animal models in pathogenesis studies of AD. The purpose of this study is to investigate the sex differences between APP/PS1 mice in the pathogenesis of AD. The impairment of glucose and insulin tolerance was found to develop earlier in male APP/PS1 mice than in females. Plasma insulin levels were significantly decreased in male APP/PS1 mice, while total cholesterol levels in male APP/PS1 mice were higher than those in females. Triglyceride levels in male mice in both the wild-type (WT) and APP/PS1 groups were higher than in their female littermates. Soluble and insoluble Aβ levels in female APP/PS1 mouse brains were higher than those in males. And the learning and memorizing abilities of female APP/PS1 mice were poorer than those of males. Our results concluded that there were sex differences in Aβ formation, pancreatic islet function and insulin sensitivity between male and female APP/PS1 mice during the pathogenesis of AD.

Rutin protects against cognitive deficits and brain damage in rats with chronic cerebral hypoperfusion

BACKGROUND AND PURPOSE

Chronic cerebral hypoperfusion is a critical causative factor for the development of cognitive decline and dementia in the elderly, which involves many pathophysiological processes. Consequently, inhibition of several pathophysiological pathways is an attractive therapeutic strategy for this disorder. Rutin, a biologically active flavonoid, protects the brain against several insults through its antioxidant and anti-inflammatory properties, but its effect on cognitive deficits and brain damage caused by chronic cerebral hypoperfusion remains unknown. Here, we investigated the neuroprotective effect of rutin on cognitive impairments and the potential mechanisms underlying its action in rats with chronic cerebral hypoperfusion.

EXPERIMENTAL APPROACH

We used Sprague-Dawley rats with permanent bilateral common carotid artery occlusion (BCCAO), a well-established model of chronic cerebral hypoperfusion. After rutin treatment for 12 weeks, the neuroprotective effect of rutin in rats was evaluated by behavioural tests, biochemical and histopathological analyses.

KEY RESULTS

BCCAO rats showed marked cognitive deficits, which were improved by rutin treatment. Moreover, BCCAO rats exhibited central cholinergic dysfunction, oxidative damage, inflammatory responses and neuronal damage in the cerebral cortex and hippocampus, compared with sham-operated rats. All these effects were significantly alleviated by treatment with rutin.

CONCLUSION AND IMPLICATIONS

Our results provide new insights into the pharmacological actions of rutin and suggest that rutin has multi-targeted therapeutical potential on cognitive deficits associated with conditions with chronic cerebral hypoperfusion such as vascular dementia and Alzheimer's disease.

Morin reverses neuropathological and cognitive impairments in APPswe/PS1dE9 mice by targeting multiple pathogenic mechanisms

Alzheimer's disease (AD) is the most common form of dementia worldwide, characterized by progressive cognitive impairment and multiple distinct neuropathological features. Currently, there are no available therapies to delay or block the disease progression. Thus, the disease-modifying therapies are urgent for this devastating disorder by simultaneously targeting multiple distinct pathological processes. Morin, a natural bioflavonoid, have been shown to be strongly neuroprotective in vitro and in vivo. In this study, we first investigated the disease-modifying effects of chronic morin administration on the neuropathological and cognitive impairments in APPswe/PS1dE9 double transgenic mice. Our results showed that chronic morin administration prevented spatial learning and memory deficits in the APPswe/PS1dE9 mice. Morin treatment in the APPswe/PS1dE9 mice markedly reduced cerebral Aβ production and Aβ plaque burden via promoting non-amyloidogenic APP processing pathway by increasing ADAM10 expression, inhibiting amyloidogenic APP processing pathway by decreased BACE1 and PS1 expression, and facilitating Aβ degradation by enhancing Aβ-degrading enzyme expression. In addition, we also found that morin treatment in the APPswe/PS1dE9 mice markedly decreased tau hyperphosphorylation via its inhibitory effect on CDK5 signal pathway. Furthermore, morin treatment in the APPswe/PS1dE9 mice markedly reduced the activated glial cells and increased the expression of synaptic markers. Collectively, our findings demonstrate that chronic morin treatment restores cognitive functions and reverses multiple distinct neuropathological AD-like hallmarks in the APPswe/PS1dE9 mice. This study provides novel insights into the neuroprotective actions and neurobiological mechanisms of morin against AD, suggesting that morin is a potently promising disease-modifying agent for treatment of AD.

Diminished CRE-Induced Plasticity is Linked to Memory Deficits in Familial Alzheimer's Disease Mice

The mechanism underlying impaired learning and memory in Alzheimer's disease is not fully elucidated. The phosphorylation of cyclic-AMP response element binding protein (pCREB) in the hippocampus is thought to be a critical initiating step in the formation of long-term memories. Here, we tested CRE-driven gene expression following learning in mice harboring the familial Alzheimer's disease-linked APPswe/PS1ΔE9 mutations using CRE-β galactosidase reporter. We show that young adult APPswe/PS1ΔE9 mice exhibit impaired recognition memory and reduced levels of pCREB, and its cofactors CREB binding protein (CBP) and p-300 following a learning task, compared to their wild type littermate counterparts. Impairments in learning-induced activation of CREB in these mice are manifested by reduced CRE-driven gene transcription. Importantly, expression of the CRE-driven immediate early gene, Egr-1 (Zif268) is decreased in the CA1 region of the hippocampus. These studies implicate defective CREB-dependent plasticity in the mechanism underlying learning and memory deficits in Alzheimer's disease.

The increased potassium intake improves cognitive performance and attenuates histopathological markers in a model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by hallmarks that include an accumulation of amyloid-β peptide (Aβ), inflammation, oxidative stress and synaptic dysfunction, which lead to a decrease in cognitive function. To date, the onset and progression of AD have been associated with pathologies such as hypertension and diabetes. Hypertension, a disease with a high incidence worldwide, is characterized by a chronic increase in blood pressure. Interestingly, this disease has a close relationship to the eating behavior of patients because high Na(+) intake is a significant risk factor for hypertension. In fact, a decrease in Na(+) consumption, along with an increase in K(+) intake, is a primary non-pharmacological approach to preventing hypertension. In the present work, we examined whether an increase in K(+) intake affects the expression of certain neuropathological markers or the cognitive performance of a murine model of AD. We observed that an increase in K(+) intake leads to a change in the aggregation pattern of the Aβ peptide, a partial decrease in some epitopes of tau phosphorylation and improvement in the cognitive performance. The recovery in cognitive performance was correlated with a significant improvement in the generation of long-term potentiation. We also observed a decrease in markers related to inflammation and oxidative stress such as glial fibrillary acidic protein (GFAP), interleukin 6 (IL-6) and 4-hydroxynonenal (4-HNE). Together, our data support the idea that changes in diet, such as an increase in K(+) intake, may be important in the prevention of AD onset as a non-pharmacological therapy.

Learning performances and vulnerability to amyloid toxicity in the butyrylcholinesterase knockout mouse

Butyrylcholinesterase (BChE) is an important enzyme for detoxication and metabolism of ester compounds. It also hydrolyzes the neurotransmitter acetylcholine (ACh) in pathological conditions and may play a role in Alzheimer's disease (AD). We here compared the learning ability and vulnerability to Aβ toxicity in male and female BChE knockout (KO) mice and their 129Sv wild-type (Wt) controls. Animals tested for place learning in the water-maze showed increased acquisition slopes and presence in the training quadrant during the probe test. An increased passive avoidance response was also observed for males. BChE KO mice therefore showed enhanced learning ability in spatial and non-spatial memory tests. Intracerebroventricular (ICV) injection of increasing doses of amyloid-β[25-35] (Aβ25-35) peptide oligomers resulted, in Wt mice, in learning and memory deficits, oxidative stress and decrease in ACh hippocampal content. In BChE KO mice, the Aβ25-35-induced deficit in place learning was attenuated in males and blocked in females. No change in lipid peroxidation or ACh levels was observed after Aβ25-35 treatment in male or female BChE KO mice. These data showed that the genetic invalidation of BChE in mice augmented learning capacities and lowered the vulnerability to Aβ toxicity.

Evaluation of oxidative stress in the brain of a transgenic mouse model of Alzheimer disease by in vivo electron paramagnetic resonance imaging

Alzheimer disease (AD) is a neurodegenerative disease clinically characterized by progressive cognitive dysfunction. Deposition of amyloid-β (Aβ) peptides is the most important pathophysiological hallmark of AD. Oxidative stress induced by reactive oxygen species is prominent in AD, and several reports suggest the relationship between a change in redox status and AD pathology containing progressive Aβ deposition, the activation of glial cells, and mitochondrial dysfunction. Therefore, we performed immunohistochemical analysis using a transgenic mouse model of AD (APdE9) and evaluated the activity of superoxide dismutase in brain tissue homogenates of APdE9 mice in vitro. Together with those analyses, in vivo changes in redox status with age in both wild-type (WT) and APdE9 mouse brains were measured noninvasively by three-dimensional electron paramagnetic resonance (EPR) imaging using nitroxide (3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-yloxy) as a redox-sensitive probe. Both methods found similar changes in redox status with age, and in particular a significant change in redox status in the hippocampus was observed noninvasively by EPR imaging between APdE9 mice and age-matched WT mice from 9 to 18 months of age. EPR imaging clearly visualized the accelerated change in redox status of APdE9 mouse brain compared with WT. The evaluation of the redox status in the brain of AD model rodents by EPR imaging should be useful for diagnostic study of AD.

Adipokine pathways are altered in hippocampus of an experimental mouse model of Alzheimer's disease

A growing body of evidence suggests that β-amyloid peptides (Aβ) are unlikely to be the only factor involved in Alzheimer's disease (AD) aetiology. In fact, a strong correlation has been established between AD patients and patients with type 2 diabetes and/or cholesterol metabolism alterations. In addition, a link between adipose tissue metabolism, leptin signalling in particular, and AD has also been demonstrated. In the present study we analyzed the expression of molecules related to metabolism, with the main focus on leptin and prolactin signalling pathways in an APPswe/PS1dE9 (APP/PS1) transgenic mice model, at 3 and 6 months of age, compared to wild-type controls. We have chosen to study 3 months-old APP/PS1 animals at an age when neither the cognitive deficits nor significant Aβ plaques in the brain are present, and to compare them to the 6 months-old mice, which exhibit elevated levels of Aβ in the hippocampus and memory loss. A significant reduction in both mRNA and protein levels of the prolactin receptor (PRL-R) was detected in the hippocampi of 3 months old APP/PS1 mice, with a decrease in the levels of the leptin receptor (OB-R) first becoming evident at 6 months of age. We proceeded to study the expression of the intracellular signalling molecules downstream of these receptors, including stat (1-5), sos1, kras and socs (1-3). Our data suggest a downregulation in some of these molecules such as stat-5b and socs (1-3), in 3 months-old APP/PS1 brains. Likewise, at the same age, we detected a significant reduction in mRNA levels of lrp1 and cyp46a1, both of which are involved in cholesterol homeostasis. Taken together, these results demonstrate a significative impairment in adipokine receptors signalling and cholesterol regulation pathways in the hippocampus of APP/PS1 mice at an early age, prior to the Aβ plaque formation.

Nutritional supplementation for Alzheimer's disease?

PURPOSE OF REVIEW

Evidence for the benefit of nutrition in Alzheimer's disease continues to accumulate. Many studies with individual vitamins or supplements show marginal, if any, benefit. However, new findings with combinatorial formulations demonstrate improvement in cognitive performance and behavioral difficulties that accompany Alzheimer's disease. Herein, we review some of the most recent clinical advances and summarize supportive preclinical studies.

RECENT FINDINGS

We present novel positive effects on Alzheimer's disease derived from diet, trace elements, vitamins and supplements. We discuss the inherent difficulty in conducting nutritional studies because of the variance in participants' nutritional history, versus pharmacological interventions in which participants are naive to the intervention. We examine the evidence that epigenetics play a role in Alzheimer's disease and how nutritional intervention can modify the key epigenetic events to maintain or improve cognitive performance.

SUMMARY

Overall consideration of the most recent collective evidence suggests that the optimal approach for Alzheimer's disease would seem to combine early, multicomponent nutritional approaches (a Mediterranean-style diet, multivitamins and key combinatorial supplements), along with lifestyle modifications such as social activity and mental and physical exercise, with ultimate addition of pharmacological agents when warranted.