(-)-Epigallocatechin-3-gallate attenuates cognitive deterioration in Alzheimer's disease model mice by upregulating neprilysin expression.

Epigenetic changes are involved in learning and memory, and histone deacetylase (HDAC) inhibitors are considered potential therapeutic agents for Alzheimer's disease (AD). We previously reported that (-)-epigallocatechin-3-gallate (EGCG) acts as an HDAC inhibitor. Here, we demonstrate that EGCG reduced ß-amyloid (Aß) accumulation in vitro and rescued cognitive deterioration in senescence-accelerated mice P8 (SAMP8) via intragastric administration of low- and high-dose EGCG (5 and 15 mg/kg, respectively) for 60 days. The AD brain has decreased levels of the rate-limiting degradation enzyme of Aß, neprilysin (NEP). We found an association between EGCG-induced reduction in Aß accumulation and elevated NEP expression. Further, NEP silencing prevented the EGCG-induced Aß downregulation. Our findings suggest that EGCG might be effective for treating AD.

A strategy focused on MAPT, APP, NCSTN and BACE1 to build blood classifiers for Alzheimer's disease.

BACKGROUND: Although Alzheimer's disease (AD) is a brain disorder, a number of peripheral alterations have been found in these patients, including differences in leukocyte gene expression; however, the key genes involved in plaque and tangle formation have shown a relatively small potential as diagnostic markers. We focused on MAPT, APP, NCSTN and BACE1 as the basis to build and compare blood classifiers for AD. METHODS: We used a combined model to build disease classifiers, using measures of blood pressure and serum glucose, cholesterol and triglyceride levels as well as RT-PCR expression levels of APP, NCSTN and BACE1 in peripheral blood mononuclear cells (PBMCs) from an independent cohort of 36 individuals of cognitively-normal controls, AD and other neuropathologies. Also, a set of genes was carefully selected by molecular interactions with MAPT, APP, NCSTN and BACE1 to test an expression-based classifier in a public microarray dataset of 40 samples (AD and controls). A series of discriminant analyses and classification and regression trees (C&RTs) were used to perform classification tasks. RESULTS: Using C&RTs, the combined model showed potential to differentially diagnose AD with up to 94.4% accuracy and 100% specificity for our independent sample. Furthermore, a subset of 16 genes showed the best diagnostic potential using a minimum number of expression variables, correctly classifying up to 100% of samples in the public dataset. CONCLUSIONS: Our unique method of variable selection proves that even elements showing no significant differences between controls and AD, but that have somehow been linked to AD or AD-related elements, still hold a potential to be used in its diagnosis. Sample size and inherent methodological limitations of this study need to be kept in mind. Our classifiers require careful further testing in larger cohorts. Nonetheless, we believe these results provide evidence for the utility of our innovative method, which contributes a different approach to generate promising diagnostic tools for neuropsychiatric disorders.

Identification and expression analysis of the zebrafish orthologues of the mammalian MAP1LC3 gene family.

Autophagy is the principle pathway within cells involved in clearing damaged proteins and organelles. Therefore autophagy is necessary to maintain the turnover balance of peptides and homoeostasis. Autophagy occurs at basal levels under normal conditions but can be upregulated by chemical inducers or stress conditions. The zebrafish (Danio rerio) serves as a versatile tool to understand the functions of genes implicated in autophagy. We report the identification of the zebrafish orthologues of mammalian genes MAP1LC3A (map1lc3a) and MAP1LC3B (map1lc3b) by phylogenetic and conserved synteny analysis and we examine their expression during embryonic development. The zebrafish map1lc3a and map1lc3b genes both show maternally contributed transcripts in early embryogenesis. However, levels of map1lc3a transcript steadily increase until at least 120h post-fertilisation while the levels of map1lc3b show a more variable pattern across developmental time. We have also validated the LC3I ratio/LC3I immunoblot autophagy assay in the presence of chloroquine (a lysosomal proteolysis inhibitor). We found that the LC3II/LC3I ratio is significantly increased in the presence of sodium azide with chloroquine supporting that hypoxia induces autophagy in zebrafish. This was supported by our qPCR assay that showed increased map1lc3a transcript levels in the presence of sodium azide. In contrast, levels of map1lc3b transcripts were reduced in the presence of rapamycin but the decrease in the presence of sodium azide did not reach statistical significance. Our study supports the use of zebrafish for analysing the interplay between hypoxia, development and autophagy.

Small interfering RNA delivery to the neurons near the amyloid plaques for improved treatment of Alzheimer׳s disease.

Gene therapy represents a promising treatment for the Alzheimer׳s disease (AD). However, gene delivery specific to brain lesions through systemic administration remains big challenge. In our previous work, we have developed an siRNA nanocomplex able to be specifically delivered to the amyloid plaques through surface modification with both CGN peptide for the blood-brain barrier (BBB) penetration and QSH peptide for ß-amyloid binding. But, whether the as-designed nanocomplex could indeed improve the gene accumulation in the impaired neuron cells and ameliorate AD-associated symptoms remains further study. Herein, we prepared the nanocomplexes with an siRNA against ß-site amyloid precursor protein-cleaving enzyme 1 (BACE1), the rate-limiting enzyme of Aß production, as the therapeutic siRNA of AD. The nanocomplexes exhibited high distribution in the Aß deposits-enriched hippocampus, especially in the neurons near the amyloid plaques after intravenous administration. In APP/PS1 transgenic mice, the nanocomplexes down-regulated BACE1 in both mRNA and protein levels, as well as Aß and amyloid plaques to the level of wild-type mice. Moreover, the nanocomplexes significantly increased the level of synaptophysin and rescued memory loss of the AD transgenic mice without hematological or histological toxicity. Taken together, this work presented direct evidences that the design of precise gene delivery to the AD lesions markedly improves the therapeutic outcome.

Data on COA-Cl administration to the APP/PS2 double-transgenic mouse model of Alzheimer׳s disease: Improved hippocampus-dependent learning and unchanged spontaneous physical activity.

We herein present behavioral data regarding whether COA-Cl, a novel adenosine-like nucleic acid analog that promotes angiogenesis and features neuroprotective roles, improves cognitive and behavioral deficits in a murine model for Alzheimer׳s disease (AD). COA-Cl induced significant spatial memory improvement in the amyloid precursor protein/presenilin 2 double-transgenic mouse model of AD (PS2Tg2576 mice). Correspondingly, non-spatial novel object cognition test performance also significantly improved in COA-Cl-treated PS2Tg2576 mice; however, these mice demonstrated no significant changes in physical activity or motor performance. COA-Cl did not change the spontaneous activities and cognitive ability in the wild-type mice.

Mitochondria-targeting drug conjugates for cytotoxic, anti-oxidizing and sensing purposes: current strategies and future perspectives.

Mitochondrial targeting is a promising approach for solving current issues in clinical application of chemotherapy and diagnosis of several disorders. Here, we discuss direct conjugation of mitochondrial-targeting moieties to anticancer drugs, antioxidants and sensor molecules. Among them, the most widely applied mitochondrial targeting moiety is triphenylphosphonium (TPP), which is a delocalized cationic lipid that readily accumulates and penetrates through the mitochondrial membrane due to the highly negative mitochondrial membrane potential. Other moieties, including short peptides, dequalinium, guanidine, rhodamine, and F16, are also known to be promising mitochondrial targeting agents. Direct conjugation of mitochondrial targeting moieties to anticancer drugs, antioxidants and sensors results in increased cytotoxicity, anti-oxidizing activity and sensing activity, respectively, compared with their non-targeting counterparts, especially in drug-resistant cells. Although many mitochondria-targeted anticancer drug conjugates have been investigated in vitro and in vivo, further clinical studies are still needed. On the other hand, several mitochondria-targeting antioxidants have been analyzed in clinical phases I, II and III trials, and one conjugate has been approved for treating eye disease in Russia. There are numerous ongoing studies of mitochondria-targeted sensors.

Induced pluripotent stem cells as a discovery tool for Alzheimer׳s disease.

The ability to accurately and systematically evaluate the cellular mechanisms underlying human neurodegenerative disorders such as Alzheimer׳s disease (AD) should lead to advancements in therapeutics. Recent developments in human induced pluripotent stem cells (iPSCs) have afforded the opportunity to use human neurons and glia to study cellular changes involved in neurological diseases. iPSCs have the potential to be differentiated into AD-relevant cell types, including forebrain neurons, astrocytes, and microglia. This permits the evaluation of individual cell types in isolation or in concert, thus modeling the interdependence of cell types within the brain. When discussing the potential of modeling AD with iPSCs, it is important to remember that the umbrella diagnosis of "Alzheimer׳s disease" represents a disease that is heterogeneous in terms of age of onset, underlying causes, and at times precise pathology. The ability of iPSCs to be derived from an array of AD patients allows for a closer examination of the mechanism of disease progression in particular subsets of subjects, who may have different mutations and allelic variants affecting their risk for disease. Disease mechanisms can be probed both by the genetic manipulation of iPSCs and by modifications to the cellular environment by chemical treatment. These studies may lead not only to the refinement of known pathways implicated in AD, but also to the identification of novel pathways heretofore unaffiliated with disease pathology. In this review, we describe the potential of iPSC models to transform our understanding of AD and to lead to valuable advancements in therapeutics. This article is part of a Special Issue entitled SI: Exploiting human neurons.

Exposure of isoflurane-treated cells to hyperoxia decreases cell viability and activates the mitochondrial apoptotic pathway.

Isoflurane has either neuroprotective or neurotoxic effects. High-dose oxygen is frequently used throughout the perioperative period. We hypothesized that hyperoxia will affect cell viability of rat pheochromocytoma (PC12) cells that were exposed to isoflurane and reactive oxygen species (ROS) may be involved. PC12 cells were exposed to 1.2% or 2.4% isoflurane for 6 or 24h respectively, and cell viability was evaluated. To investigate the effects of hyperoxia, PC12 cells were treated with 21%, 50%, or 95% oxygen and 2.4% isoflurane for 6h, and cell viability, TUNEL staining, ROS production, and expression of B-cell lymphoma 2 (BCL-2), BCL2-associated X protein (BAX), caspase-3 and beta-site APP cleaving enzyme (BACE) were measured. ROS involvement was evaluated using the ROS scavenger 2-mercaptopropiopylglycine (MPG). The viability of cells exposed to 2.4% isoflurane was lower than that of cells exposed to 1.2% isoflurane. Prolonged exposure (6h vs. 24h) to 2.4% isoflurane resulted in a profound reduction in cell viability. Treatment with 95% (but not 50%) oxygen enhanced the decrease in cell viability induced by 2.4% isoflurane alone. Levels of ROS, Bax, caspase-3 and BACE were increased, whereas expression of Bcl-2 was decreased, in cells treated with 95% oxygen plus 2.4% isoflurane compared with the control and 2.4% isoflurane plus air groups. MPG attenuated the effects of oxygen and isoflurane. In conclusion, isoflurane affects cell viability in a dose- and time-dependent manner. This effect is augmented by hyperoxia and may involve ROS, the mitochondrial apoptotic signaling pathway, and ß-amyloid protein.

Regulation of neurological and neuropsychiatric phenotypes by locus coeruleus-derived galanin.

Decades of research confirm that noradrenergic locus coeruleus (LC) neurons are essential for arousal, attention, motivation, and stress responses. While most studies on LC transmission focused unsurprisingly on norepinephrine (NE), adrenergic signaling cannot account for all the consequences of LC activation. Galanin coexists with NE in the vast majority of LC neurons, yet the precise function of this neuropeptide has proved to be surprisingly elusive given our solid understanding of the LC system. To elucidate the contribution of galanin to LC physiology, here we briefly summarize the nature of stimuli that drive LC activity from a neuroanatomical perspective. We go on to describe the LC pathways in which galanin most likely exerts its effects on behavior, with a focus on addiction, depression, epilepsy, stress, and Alzheimer׳s disease. We propose a model in which LC-derived galanin has two distinct functions: as a neuromodulator, primarily acting via the galanin 1 receptor (GAL1), and as a trophic factor, primarily acting via galanin receptor 2 (GAL2). Finally, we discuss how the recent advances in neuropeptide detection, optogenetics and chemical genetics, and galanin receptor pharmacology can be harnessed to identify the roles of LC-derived galanin definitively. This article is part of a Special Issue entitled SI: Noradrenergic System.

Dataset for the role of sustained attention in memory formation of transgenic mice for Alzheimer׳s disease.

Weekly submission of rats to active avoidance apparatus can be considered a neurostimulation strategy, once it can improve memory and can increase the density of receptors from different neurotransmitter systems in brain areas related to memory. These benefits were observed in rats chronically infused with amyloid-ß peptide. In the present work it is presented that the same benefit for memory was observed in five months old transgenic mice for Alzheimer's disease (TG-PDGFB-APPSw,Ind). However, at this age, no change in density of nicotinic receptors was observed.

Potential contribution of the Alzheimer's disease risk locus BIN1 to episodic memory performance in cognitively normal Type 2 diabetes elderly.

In recent years, several promising susceptibility loci for late-onset Alzheimer's disease (AD) were discovered, by implementing genome-wide association studies (GWAS) approach. Recent GWAS meta-analysis has demonstrated the association of 19 loci (in addition to the APOE locus) with AD in the European ancestry population at genome-wide significance level. Since Type 2 Diabetes (T2D) is a substantial risk factor for cognitive decline and dementia, the 19 single nucleotide polymorphisms (SNPs) that represent the 19 AD loci were studied for association with performance in episodic memory, a primary cognitive domain affected by AD, in a sample of 848 cognitively normal elderly Israeli Jewish T2D patients. We found a suggestive association of SNP rs6733839, located near the bridging integrator 1 (BIN1) gene, with this phenotype. Controlling for demographic (age, sex, education, disease duration and ancestry) covariates, carriers of two copies of the AD risk allele T (TT genotype) performed significantly worse (p=0.00576; p=0.00127 among Ashkenazi origin sub-sample) in episodic memory compared to carriers of the C allele (CT+CC genotypes). When including additional potential covariates (clinical and APOE genotype), results remained significant (p=0.00769; p=0.00148 among Ashkenazi). Interestingly, as validated in multiple large studies, BIN1 is one of the most established AD risk loci, with a high odds ratio. Although preliminary and require further replications, our findings support a contribution of BIN1 to individual differences in episodic memory performance among T2D patients.

4'-Chlorodiazepam is neuroprotective against amyloid-beta through the modulation of survivin and bax protein expression in vitro.

The translocator protein of 18kDa (TSPO) is located in the outer mitochondrial membrane and is involved in the cholesterol transport into the mitochondria and in the regulation of steroidogenesis, mitochondrial permeability transition pore opening and apoptosis. TSPO ligands have been investigated as therapeutic agents that promote neuroprotective effects in experimental models of brain injury and neurodegenerative diseases. The aim of this study was to identify the neuroprotective effects of 4'-chlorodiazepam (4'-CD), a ligand of TSPO, against amyloid-beta (Aß) in SHSY-5Y neuroblastoma cells and its mechanisms of action. Aß decreased the viability of SHSY-5Y neuroblastoma cells, while 4'-CD had a neuroprotective effect at the doses of 1nM and 10nM. The neuroprotective effects of 4'-CD against Aß were associated with the inhibition of Aß-induced upregulation of Bax and downregulation of survivin. In summary, our findings indicate that 4'-CD is neuroprotective against Aß-induced neurotoxicity by a mechanism that may involve the regulation of Bax and survivin expression.

Reprint of: From the 90׳s to now: A brief historical perspective on more than two decades of estrogen neuroprotection.

UNLABELLED: Historical perspective abstract:From the 90׳s to now: a historical perspective on more than two decades of estrogen neuroprotection: In the early 90׳s, estrogens were known to exert organizational and activational effects on reproductive tissues and sexual behavior. As well, the role of sex and gonadal hormones in altering the risk for developing Alzheimer׳s Disease (AD) was only beginning to be elucidated. Preliminary investigations suggested that estrogen-containing therapies typically given for the management of disruptive menopausal symptoms could reduce AD risk, attenuate disease-associated cognitive deficits, and modulate brain substrates known to be dysregulated by the condition, such as the cholingeric system. The findings from our seminal paper demonstrating cognitive benefits and cholinergic impacts with exogenous estrogen treatment in a rodent model of surgical hormone depletion provided initial support for use of estrogen-containing therapies as a treatment for age-related brain disorders. We then went on to demonstrate neuroprotective actions of estrogen in several other in vivo and in vitro models of neurological challenge, including stroke and AD. Further, our findings of the chemical structure requirements for estrogen׳s neuroprotective effects identified a novel approach for optimizing future estrogen-containing hormone therapy options. These early efforts laid the groundwork for later, large-scale clinical investigations into the potential of estrogen-based menopausal hormone therapies for the prevention of a variety of age-related disorders. Although findings of these studies were equivocal, the neuroprotective actions of estrogen, and specifically 17ß-estradiol, identified by early investigations, remain well-documented. Future development of interventions that optimize cognitive aging are crucial and, with proper understanding of the factors that influence the realization of beneficial impacts, estrogen-containing treatments may still be among these. ORIGINAL ARTICLE ABSTRACT: Ovarian steroid deprivation results in a reversible learning impairment and compromised cholinergic function in female Sprague-Dawley rats: We hypothesized that estradiol (E2) serves as a neurotrophomodulatory substance for basal forebrain cholinergic neurons thought to be involved in learning and memory. Learning/memory was assessed using the two-way active avoidance paradigm and the Morris water task. Female Sprague-Dawley rats were either ovariectomized (OVX) or OVX for 3 weeks, followed by s.c. implantation of a Silastic pellet containing 17-ßE2 (E2 pellet), resulting in a replacement of E2 to physiological levels. Ovary-intact (INTACT) animals served as our positive control. Active avoidance behavior and choline acetyltransferase (ChAT) activity in the frontal cortex and hippocampus were assessed at 5 and 28 weeks postovariectomy while performance on the Morris water task and high-affinity choline uptake (HACU) were measured only at the 5-week time point. At the 5-week time point, E2 replacement caused a significant elevation in the level of active avoidance performance relative to OVX animals. At the 28-week time point, OVX animals demonstrated a significantly lower number of avoidances relative to controls (61%) whereas E2-pellet animals not only demonstrated superior performance relative to OVX animals but also showed an accelerated rate of learning. Morris water task performance, on the other hand, was not significantly affected by estrogenic milieu despite a trend towards better performance in the E2-pellet group. Neurochemical analyses revealed that 5 weeks of ovariectomy was sufficient to reduce HACU in both the frontal cortex and hippocampus by 24 and 34%, respectively, while E2 replacement was successful in elevating HACU relative to OVX animals in both regions. ChAT activity was decreased in the hippocampus but not the frontal cortex of 5-week OVX animals. E2 replacement resulted in a reversal of this effect. At the 28-week time period, an unexpected decrease in ChAT activity was observed across all treatment groups. Interestingly, E2-pellet animals demonstrated the least severe decline in ChAT. This phenomenon was most evident in the frontal cortex where ChAT decreased by 61 and 56% in INTACT and OVX animals, respectively, whereas the decline in E2-pellet animals was only 16% over the same time period, suggesting a previously unreported cytoprotective effect of E2. Taken together, these findings demonstrate important effects of estrogens on cholinergic neurons and support the potential use of estrogen therapy in treatment of dementias in postmenopausal women. © 1994. This article is part of a Special Issue entitled SI:50th Anniversary Issue.

Long-term electromagnetic pulse exposure induces Abeta deposition and cognitive dysfunction through oxidative stress and overexpression of APP and BACE1.

A progressively expanded literature has been devoted in the past years to the noxious or beneficial effects of electromagnetic field (EMF) to Alzheimer׳s disease (AD). This study concerns the relationship between electromagnetic pulse (EMP) exposure and the occurrence of AD in rats and the underlying mechanisms, focusing on the role of oxidative stress (OS). 55 healthy male Sprague Dawley (SD) rats were used and received continuous exposure for 8 months. Morris water maze (MWM) test was conducted to test the ability of cognitive and memory. The level of OS was detected by superoxide dismutase (SOD) activity and glutathione (GSH) content. We found that long-term EMP exposure induced cognitive damage in rats. The content of ß-amyloid (Aß) protein in hippocampus was increased after long-term EMP exposure. OS of hippocampal neuron was detected. Western blotting and immunohistochemistry (IHC) assay showed that the content of Aß protein and its oligomers in EMP-exposed rats were higher than that of sham-exposed rats. The content of Beta Site App Cleaving Enzyme (BACE1) and microtubule-associated protein 1 light chain 3-II (LC3-II) in EMP-exposed rats hippocampus were also higher than that of sham-exposed rats. SOD activity and GSH content in EMP-exposed rats were lower than sham-exposed rats (p<0.05). Several mechanisms were proposed based on EMP exposure-induced OS, including increased amyloid precursor protein (APP) aberrant cleavage. Although further study is needed, the present results suggest that long-term EMP exposure is harmful to cognitive ability in rats and could induce AD-like pathological manifestation.

Effects of an amyloid-beta 1-42 oligomers antibody screened from a phage display library in APP/PS1 transgenic mice.

We screened anti-Aß1-42 antibodies from a human Alzheimer's disease (AD) specific single chain variable fragment (scFv) phage display library and assessed their effects in APP/PS1 transgenic mice. Reverse transcription-PCR was used to construct the scFv phage display library, and screening identified 11A5 as an anti-Aß1-42 antibody. We mixed 11A5 and the monoclonal antibody 6E10 with Aß1-42 and administered the mixture to Sprague-Dawley rats via intracerebroventricular injection. After 30 days, rats injected with the antibody/Aß1-42 mixture and those injected with Aß1-42 alone were tested on the Morris water maze. We also injected 11A5 and 6E10 into APP/PS1 transgenic mice and assessed the concentrations of Aß in brain and peripheral blood by ELISA at 1-month intervals for 3 months. Finally we evaluated behavior changes in the Morris water maze. Rats injected with Aß1-42 and mixed antibodies showed better performance in the Morris water maze than did rats injected with Aß1-42 alone. In APP/PS1 transgenic mice, Aß concentration was lower in the brains of the antibody-treated group than in the control group, but higher in the peripheral blood. The antibody-treated mice also exhibited improved behavioral performance in the Morris water maze. In conclusion, anti-Aß1-42 antibodies (11A5) screened from the human scFv antibody phage display library promoted the efflux or clearance of Aß1-42 and effectively decreased the cerebral Aß burden in an AD mouse model.

Mechanisms of tau and Aß-induced excitotoxicity.

Excitotoxicity was originally postulated to be a late stage side effect of Alzheimer׳s disease (AD)-related neurodegeneration, however more recent studies indicate that it may occur early in AD and contribute to the neurodegenerative process. Tau and amyloid beta (Aß), the main components of neurofibrillary tangles (NFTs) and amyloid plaques, have been implicated in cooperatively and independently facilitating excitotoxicity. Our study investigated the roles of tau and Aß in AD-related excitotoxicity. In vivo studies showed that tau knockout (tau(-/-)) mice were significantly protected from seizures and hippocampal superoxide production induced with the glutamate analog, kainic acid (KA). We hypothesized that tau accomplished this by facilitating KA-induced Ca(2+) influx into neurons, however lentiviral tau knockdown failed to ameliorate KA-induced Ca(2+) influx into primary rat cortical neurons. We further investigated if tau cooperated with Aß to facilitate KA-induced Ca(2+) influx. While Aß biphasically modulated the KA-induced Cacyt(2+) responses, tau knockdown continued to have no effect. Therefore, tau facilitates KA-induced seizures and superoxide production in a manner that does not involve facilitation of Ca(2+) influx through KA receptors (KAR). On the other hand, acute pretreatment with Aß (10 min) enhanced KA-induced Ca(2+) influx, while chronic Aß (24 h) significantly reduced it, regardless of tau knockdown. Given previously published connections between Aß, group 1 metabotropic glutamate receptors (mGluRs), and KAR regulation, we hypothesized that Aß modulates KAR via a G-protein coupled receptor pathway mediated by group 1 mGluRs. We found that Aß did not activate group 1 mGluRs and inhibition of these receptors did not reverse Aß modulation of KA-induced Ca(2+) influx. Therefore, Aß biphasically regulates KAR via a mechanism that does not involve group 1mGluR activation.

From the 90's to now: A brief historical perspective on more than two decades of estrogen neuroprotection.

Historical perspective abstract:From the 90's to now: a historical perspective on more than two decades of estrogen neuroprotection: In the early 90's, estrogens were known to exert organizational and activational effects on reproductive tissues and sexual behavior. As well, the role of sex and gonadal hormones in altering the risk for developing Alzheimer's Disease (AD) was only beginning to be elucidated. Preliminary investigations suggested that estrogen-containing therapies typically given for the management of disruptive menopausal symptoms could reduce AD risk, attenuate disease-associated cognitive deficits, and modulate brain substrates known to be dysregulated by the condition, such as the cholingeric system. The findings from our seminal paper demonstrating cognitive benefits and cholinergic impacts with exogenous estrogen treatment in a rodent model of surgical hormone depletion provided initial support for use of estrogen-containing therapies as a treatment for age-related brain disorders. We then went on to demonstrate neuroprotective actions of estrogen in several other in vivo and in vitro models of neurological challenge, including stroke and AD. Further, our findings of the chemical structure requirements for estrogen's neuroprotective effects identified a novel approach for optimizing future estrogen-containing hormone therapy options. These early efforts laid the groundwork for later, large-scale clinical investigations into the potential of estrogen-based menopausal hormone therapies for the prevention of a variety of age-related disorders. Although findings of these studies were equivocal, the neuroprotective actions of estrogen, and specifically 17ß-estradiol, identified by early investigations, remain well-documented. Future development of interventions that optimize cognitive aging are crucial and, with proper understanding of the factors that influence the realization of beneficial impacts, estrogen-containing treatments may still be among these. ORIGINAL ARTICLE ABSTRACT: Ovarian steroid deprivation results in a reversible learning impairment and compromised cholinergic function in female Sprague-Dawley rats: We hypothesized that estradiol (E2) serves as a neurotrophomodulatory substance for basal forebrain cholinergic neurons thought to be involved in learning and memory. Learning/memory was assessed using the two-way active avoidance paradigm and the Morris water task. Female Sprague-Dawley rats were either ovariectomized (OVX) or OVX for 3 weeks, followed by s.c. implantation of a Silastic pellet containing 17-ßE2 (E2 pellet), resulting in a replacement of E2 to physiological levels. Ovary-intact (INTACT) animals served as our positive control. Active avoidance behavior and choline acetyltransferase (ChAT) activity in the frontal cortex and hippocampus were assessed at 5 and 28 weeks postovariectomy while performance on the Morris water task and high-affinity choline uptake (HACU) were measured only at the 5-week time point. At the 5-week time point, E2 replacement caused a significant elevation in the level of active avoidance performance relative to OVX animals. At the 28-week time point, OVX animals demonstrated a significantly lower number of avoidances relative to controls (61%) whereas E2-pellet animals not only demonstrated superior performance relative to OVX animals but also showed an accelerated rate of learning. Morris water task performance, on the other hand, was not significantly affected by estrogenic milieu despite a trend towards better performance in the E2-pellet group. Neurochemical analyses revealed that 5 weeks of ovariectomy was sufficient to reduce HACU in both the frontal cortex and hippocampus by 24 and 34%, respectively, while E2 replacement was successful in elevating HACU relative to OVX animals in both regions. ChAT activity was decreased in the hippocampus but not the frontal cortex of 5-week OVX animals. E2 replacement resulted in a reversal of this effect. At the 28-week time period, an unexpected decrease in ChAT activity was observed across all treatment groups. Interestingly, E2-pellet animals demonstrated the least severe decline in ChAT. This phenomenon was most evident in the frontal cortex where ChAT decreased by 61 and 56% in INTACT and OVX animals, respectively, whereas the decline in E2-pellet animals was only 16% over the same time period, suggesting a previously unreported cytoprotective effect of E2. Taken together, these findings demonstrate important effects of estrogens on cholinergic neurons and support the potential use of estrogen therapy in treatment of dementias in postmenopausal women. © 1994. This article is part of a Special Issue entitled SI:50th Anniversary Issue.

Single administration of a novel γ-secretase modulator ameliorates cognitive dysfunction in aged C57BL/6J mice.

Mutations in presenilin 1 (PS1) and presenilin 2 (PS2) are known to cause early onset of Alzheimer's disease (AD). These proteins comprise the catalytic domain of γ-secretase, which catalyzes the cleavage of ß-amyloid (Aß) from amyloid precursor protein (APP). In recent reports, PS1 and PS2 were linked to the modulation of intracellular calcium ion (Ca(2+)) dynamics, a key regulator of synaptic function. Ca(2+) dysregulation and synaptic dysfunction are leading hypothesis of cognitive dysfunctions during aging and AD progression. Accordingly, manipulations of presenilins by small molecules may have therapeutic potential for the treatment of cognitive dysfunction. In an accompanying report, we showed that chronic treatment with compound-1, a novel γ-secretase modulator (GSM), reduced Aß production and ameliorated cognitive dysfunction in Tg2576 APP transgenic mice. Accordingly, in the present study we showed that single oral administration of compound-1 at 1 and 3mg/kg ameliorated cognitive dysfunction in aged non-transgenic mice. Moreover, compound-1 enhanced synaptic plasticity in hippocampal slices from aged C57BL/6J mice and increased messenger RNA (mRNA) expression of the immediate early gene c-fos, which has been shown to be related to synaptic plasticity in vivo. Finally, compound-1 modulated Ca(2+) signals through PS1 in mouse embryonic fibroblast cells. Taken together, compound-1 ameliorates both Aß pathology and age-related cognitive dysfunctions. Hence, compound-1 may have potential as an early intervention for the cognitive declines that are commonly diagnosed in aged subjects, such as mild cognitive impairment (MCI) and prodromal AD.

Functional connectivity increase in the default-mode network of patients with Alzheimer's disease after long-term treatment with Galantamine.

Acetylcholinesterase inhibitors (AChEIs) are efficacious for the treatment of mild to moderate forms of Alzheimer's dementia (AD). Default-mode network (DMN) connectivity is considered to be early impaired in AD. Long-term effects of AChEIs on the DMN in AD have not yet been investigated. Twenty-eight AD patients and 11 age-matched healthy volunteers (HC) participated in the prospective study. AD patients were randomly assigned to either a pharmacotherapy arm (Galantamine, AD G) or to a placebo arm (AD P+G) for the period of 6 months followed by open-label Galantamine therapy from month 7-12. All subjects underwent neuropsychological testing, resting-state functional and structural MRI at baseline and after 12 months, AD patients additionally in between after 6 months. Thirteen AD patients completed the treatment trial and underwent all functional MRI follow-up sequences of good quality. Functional connectivity significantly increased within the AD G group in the posterior cingulate cortex and in the Precuneus between baseline and 12 months follow-up (pcorr<0.05). Between-group analyses demonstrated that functional connectivity in the AD G group significantly increased in the posterior cingulate cortex as well as in the Precuneus compared to the HC group and in the anteromedial aspect of the temporal lobes compared to the AD P+G group, respectively, at 12 months follow-up (pcorr<0.05). Cognitive performance remained stable within groups over time indicating that resting-state fMRI may be sensitive for the detection of pharmacologically induced effects on brain function of AD patients.

Electroconvulsive therapy selectively enhances amyloid ß 1-42 in the cerebrospinal fluid of patients with major depression: A prospective pilot study.

A complex interplay between ß-amyloid (Aß), Alzheimer׳s disease (AD) and major depression disorder (MDD) suggests that patients with MDD have an altered cerebral Aß metabolism and an increased risk of developing AD. In order to elucidate the relationship between antidepressant treatment and Aß metabolism in humans, we performed a study on Aß peptides in the cerebrospinal fluid (CSF) in patients with MDD during electroconvulsive therapy (ECT) as an effective antidepressant treatment. We measured the levels of Aß1-42, Aß1-40 and of tau proteins in the CSF in 12 patients with MDD before and after a course of ECT. Aß1-42 was significantly elevated after the ECT treatment compared to baseline, whereas no difference was found for other peptides and proteins such as Aß1-40, Aß ratio, total tau protein or its phosphorylated form. The most salient finding was, that the increase of Aß1-42 after ECT was found in all patients with clinical response to the treatment, but not in those who did not respond. The number of ECT sessions of each responding patient correlated with the increase of Aß1-42 in the CSF. Our data point towards to a specific antidepressant mechanism which is not based on a general increase of Aß, but seems to involve merely Aß1-42, the isoform with highest amyloidogenic potential. We present the first study in humans demonstrating an isolated mobilization of Aß1-42 in the CSF of patients with depression who respond to an ECT treatment.