Novel Therapies For Alzheimer's Disease Research Articles

Novel Therapeutic Approaches in Alzheimer's Disease

Alzheimer's disease (AD) is a neurological condition associated with a decrease in levels of acetylcholine and diminished cholinergic functions. This may be caused by the degeneration of cholinergic neurons in the brain, leading to cognitive deficits. Due to the difficulty and invasiveness of collecting cerebrospinal fluid (CSF) required for assessing conventional biomarkers, researchers are currently exploring less intrusive, less expensive, and more straightforward methods for diagnosing AD. Additionally, conventional interventions such as cholinesterase inhibitors like rivastigmine, donepezil, and galantamine are US FDA-approved drugs that are still effective for managing AD. The goal of this therapy is to increase acetylcholine levels in the brain by inhibiting the enzymes that degrade acetylcholine. Therefore, this therapeutic approach is useful for treating mild-to-moderate AD. However, only symptomatic treatment is currently available, and it can lead to serious adverse effects from conventional therapy. Thus, novel therapies for AD are needed in a growing global population. This manuscript provides information on various biomarkers with possible pathogenesis mechanisms, novel treatment strategies such as microalgae, HupA, cannabinoids, and the beneficial effects of coenzyme Q10, bacterial probiotics, omega-3 fatty acids, vitamin B12, and D3 in memory impairment for managing AD. Non-pharmacological treatments such as music therapy, Electroacupuncture (EA), or manual acupuncture (MA) also play an important role in enhancing the effectiveness of conventional pharmacological treatments for AD.

Effect of sodium channels in Alzheimer’s disease

Alzheimer disease (AD), depicted by the formation of amyloid β-protein plaque(Aβ), has been recognized for dementia and epilepsy. The pathological mechanism of AD is complicated and it remains unclear. Currently, most therapies are focusing on elimination of Aβ plaque and preventing the breakdown of acetylcholine to prevent neuron cell death, however, most of these drugs fail to improve cognitive functions in AD patients. Therefore, the development of novel therapies for AD is in urgent need. Emerging evidences show that cellular sodium (Na+) signals play a significant role in neurol physiology. Aβ oligomer upregulates the expression of Nav1.6, leading to cognition loss, epilepsy, and malfunction of neuron development (shorter neurite length is observed during Aβ-interfered neuron development), indicating that sodium channel may be a target for treating AD. This review summarizes current development of molecular mechanisms linking sodium dysregulation with AD pathologies and discusses potential therapies for AD by correcting Na+ disruption.

MCU knockdown in hippocampal neurons improves memory performance of an Alzheimer's disease mouse model.

Alzheimer's disease (AD) is a progressive and degenerative disorder accompanied by cognitive decline, which could be promoted by mitochondrial dysfunction induced by mitochondrial Ca 2+ (mCa 2+) homeostasis Mitochondrial calcium uniporter (MCU), a key channel of mCa 2+ uptake, may be a target for AD treatment. In the present study, we reveal for the first time that MCU knockdown in hippocampal neurons improves the memory performance of APP/PS1/tau mice through radial arm maze task. Western blot analysis, transmission electron microscopy (TEM), Golgi staining, immunohistochemistry (IHC) and ELISA results demonstrate that MCU knockdown in hippocampal neurons upregulates the levels of postsynaptic density protein 95 (PSD95) and synaptophysin (SYP), and increases the numbers of synapses and dendritic spines. Meanwhile, MCU knockdown in hippocampal neurons decreases the neuroinflammatory response induced by astrogliosis and high levels of IL-1β and TNF-α, and improves the PINK1-Parkin mitophagy signaling pathway and increases the level of Beclin-1 but decreases the level of P62. In addition, MCU knockdown in hippocampal neurons recovers the average volume and number of mitochondria. These data confirm that MCU knockdown in hippocampal neurons improves the memory performance of APP/PS1/tau mice through ameliorating the synapse structure and function, relieving the inflammation response and recovering mitophagy, indicating that MCU inhibition has the potential to be developed as a novel therapy for AD.

Recommendations to address key recruitment challenges of Alzheimer's disease clinical trials.

Clinical trials for Alzheimer's disease (AD) are slower to enroll study participants, take longer to complete, and are more expensive than trials in most other therapeutic areas. The recruitment and retention of a large number of qualified, diverse volunteers to participate in clinical research studies remain among the key barriers to the successful completion of AD clinical trials. An advisory panel of experts from academia, patient-advocacy organizations, philanthropy, non-profit, government, and industry convened in 2020 to assess the critical challenges facing recruitment in Alzheimer's clinical trials and develop a set of recommendations to overcome them. This paper briefly reviews existing challenges in AD clinical research and discusses the feasibility and implications of the panel's recommendations for actionable and inclusive solutions to accelerate the development of novel therapies for AD.

Senegenin Inhibits Aβ1-42-Induced PC12 Cells Apoptosis and Oxidative Stress via Activation of the PI3K/Akt Signaling Pathway.

Background/AimApoptosis and oxidative stress have been considered as key events in the pathogenesis of Alzheimer’s disease (AD). Senegenin (Sen), the major and most effective ingredient of Radix Polygalae, which has anti-apoptotic and anti-oxidative effects. The aim of this study was to investigate the anti-apoptotic and anti-oxidant effects of Sen on Aβ1-42-induced PC12 cells apoptosis and oxidative stress as well as its possible signaling pathway.MethodsRat pheochromocytoma (PC12) cells were treated by 20 μM Aβ1-42 and then divided into 5 different treatment groups (Control; Aβ1-42 20 μM; Aβ1-42 20 μM + Sen 10 μM; Aβ1-42 20 μM + Sen 30 μM; Aβ1-42 20μM + Sen 60 μM). PC12 cells activity was detected by MTT assay. Colony formation assay was performed to assess the clonogenic ability of cells. The cell apoptosis was detected by Annexin-V/PI staining. The pro-apoptotic protein (Bax), anti-apoptotic protein (Bcl-2), anti-oxidative stress factor (HO-1, Nuclear Nrf2, Total Nrf2) and pathway-related protein (Akt, P-Akt, PI3K, P-PI3K) were tested by Western blot. The reactive oxygen species (ROS) level was assessed with a DCFH-DA probe.ResultsThe results indicated that Sen dose-dependently increased cell viability and reduced the number of apoptotic cells. The ratio of P-PI3K/PI3K and P-Akt/Akt increased in a dose-dependent manner under the treatment of Sen, suggesting that Sen might activate the PI3K/Akt signaling pathway. Moreover, Sen upregulates the ratio of Bcl-2/Bax. Further study revealed that Sen can play an antioxidant role in enhancing HO-1, promoting Nrf2 nuclear translocation and reducing ROS accumulation to reduce oxidative stress.ConclusionSen is effective in inhibiting apoptosis and oxidative stress in Aβ1-42-induced PC12 cells, which likely contribute to the development of novel therapies for AD.

Reactive astrocytes as treatment targets in Alzheimer's disease-Systematic review of studies using the APPswePS1dE9 mouse model.

Astrocytes regulate synaptic communication and are essential for proper brain functioning. In Alzheimer's disease (AD) astrocytes become reactive, which is characterized by an increased expression of intermediate filament proteins and cellular hypertrophy. Reactive astrocytes are found in close association with amyloid‐beta (Aβ) deposits. Synaptic communication and neuronal network function could be directly modulated by reactive astrocytes, potentially contributing to cognitive decline in AD. In this review, we focus on reactive astrocytes as treatment targets in AD in the APPswePS1dE9 AD mouse model, a widely used model to study amyloidosis and gliosis. We first give an overview of the model; that is, how it was generated, which cells express the transgenes, and the effect of its genetic background on Aβ pathology. Subsequently, to determine whether modifying reactive astrocytes in AD could influence pathogenesis and cognition, we review studies using this mouse model in which interventions were directly targeted at reactive astrocytes or had an indirect effect on reactive astrocytes. Overall, studies specifically targeting astrocytes to reduce astrogliosis showed beneficial effects on cognition, which indicates that targeting astrocytes should be included in developing novel therapies for AD.

Neurotrophin-3 Promotes the Neuronal Differentiation of BMSCs and Improves Cognitive Function in a Rat Model of Alzheimer's Disease.

Transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) has the potential to be developed into an effective treatment for neurodegenerative diseases such as Alzheimer's disease (AD). However, the therapeutic effects of BMSCs are limited by their low neural differentiation rate. We transfected BMSCs with neurotrophin-3 (NT-3), a neurotrophic factor that promotes neuronal differentiation, and investigated the effects of NT-3 gene overexpression on the differentiation of BMSCs into neurons in vitro and in vivo. We further studied the possible molecular mechanisms. We found that overexpression of NT-3 promoted the differentiation of BMSCs into neurons in vitro and in vivo and improved cognitive function in rats with experimental AD. By contrast, silencing NT-3 inhibited the differentiation of BMSCs and decreased cognitive function in rats with AD. The Wnt/β-catenin signaling pathway was involved in the mechanism by which NT-3 gene modification influenced the neuronal differentiation of BMSCs in vitro and in vivo. Our findings support the prospect of using NT-3-transduced BMSCs for the development of novel therapies for AD.

Targeted Lipidomics Investigation of N‐acylethanolamines in a Transgenic Mouse Model of AD: A Longitudinal Study

In the present work, mice overexpressing mutant amyloid precursor protein (Tg2576), a transgenic model of Alzheimer's disease (AD), are used to investigate a specific lipid profile over the course of disease progression. Using a targeted lipidomic approach, plasma levels of N‐acylethanolamines with different length and unsaturation at presymptomatic, mild‐symptomatic, and symptomatic disease stages are measured. Moreover, N‐acylethanolamines are also assessed in the brain areas most affected in AD. The ethanolamides of palmitic, oleic, arachidonic, eicosapentaenoic, and docosahexaenoic acids do not show any significant alteration in blood of Tg2576 mice at the different stages analyzed, as compared to wild‐type. Except for N‐docosahexaenoylethanolamine, a general tendency to decrease is instead detected for all measured N‐acylethanolamines in the cortex, hippocampus, striatum, and cerebellum of symptomatic Tg2576 mice. Together, the data can help to redefine the range of lipid‐associated signals in Alzheimer pathophysiology.Practical Application: The development of novel therapies for AD is strongly narrowed not only by the lack of a full comprehension of underlying pathophysiological mechanisms but also by the absence of affordable, reliable, and noninvasive biomarkers. Hence, there is the practical necessity to acquire accessible blood biomarkers to provide rapid, cost‐effective, and critical information to timely identify disease stage and implement preventive strategies aimed at slowing down cognitive decline. In this study, a targeted lipidomics investigation of N‐acylethanolamines at different stages of disease progression, clearly indicates that the discovery of innovative blood biomarkers should be refocused on different indices of deranged lipid metabolism for a realistic prediction of the risk of AD.It is investigated that potential alterations of N‐acylethanolamines content during disease development in a transgenic mouse model of Alzheimer's disease (AD). Circulating and central N‐acylethanolamine levels did not show any alteration in Tg2576 mice at different disease stages.

Lixisenatide reduces amyloid plaques, neurofibrillary tangles and neuroinflammation in an APP/PS1/tau mouse model of Alzheimer's disease

Type 2 diabetes mellitus (T2DM) has been identified as a high risk factor for Alzheimer's disease (AD). The impairment of insulin signaling has been found in AD brain. Glucagon-like peptide-1 (GLP-1) is an incretin hormone, normalises insulin signaling and acts as a neuroprotective growth factor. We have previously shown that the long-lasting GLP-1 receptor (GLP-1R) agonist lixisenatide plays an important role in memory formation, synaptic plasticity and cell proliferation of rats. In the follow-up study, we analysed the neuroprotective effect and mechanism of lixisenatide, injected for 60 days at 10 nmol/kg i.p. once daily in APP/PS1/tau female mice and C57BL/6J female mice (as control) aged 12 month. The results showed that lixisenatide could reduce amyloid plaques, neurofibrillary tangles and neuroinflammation in the hippocampi of 12-month-old APP/PS1/tau female mice; activation of PKA-CREB signaling pathway and inhibition of p38-MAPK might be the important mechanisms in the neuroprotective function of lixisenatide. The study demonstrated that GLP-1R agonists such as lixisenatide might have the potential to be developed as a novel therapy for AD.

Novel strategies for Alzheimer's disease treatment: An overview of anti-amyloid beta monoclonal antibodies

Alzheimer's disease (AD) is a multifactorial, progressive neurodegenerative disorder with a poor prognosis, and thus, novel therapies for AD are certainly needed in a growing population of elderly patients or asymptomatic individuals, who are at risk for AD, worldwide. It has been established that some AD biomarkers such as amyloid-beta load in the brain, precede the onset of the disease, by approximately 20 years. Therefore, the therapy to prevent or effectively treat AD has to be initiated before the emergence of symptoms. A goal of this review is to present the results of recent clinical trials on monoclonal antibodies against amyloid beta, used for the treatment of AD and also to address some of the current challenges and emerging strategies to prevent AD. In recent trials, a monoclonal antibody, i.e. solanezumab has shown some beneficial cognitive effects among mild AD patients. Ongoing studies with gantenerumab and crenezumab will examine when exactly the AD treatment, aimed at modifying the disease course has to be started. This review was based on Medline database search for trials on passive anti-AD immunotherapy, for which the main timeframe was set from 2012 to 2015.

Tonic inhibition in dentate gyrus impairs long-term potentiation and memory in an Alzheimer's [corrected] disease model.

SUMMARYAmyloid plaques and tau tangles are common pathological hallmarks for Alzheimer’s disease (AD), however reducing Aβ production failed to relieve the symptoms of AD patients. Here we report a high GABA (γ-aminobutyric acid) content in reactive astrocytes in the dentate gyrus (DG) of a mouse model for AD (5xFAD) that results in increased tonic inhibition and memory deficit. We also confirm in human AD patient brains that dentate astrocytes have a high GABA content, suggesting that high astrocytic GABA level may be a novel biomarker and a potential diagnostic tool for AD. The excessive GABA in 5xFAD astrocytes is released through an astrocyte-specific GABA transporter GAT3/4, and significantly enhanced tonic GABA inhibition in dentate granule cells. Importantly, reducing tonic inhibition in 5xFAD mice rescues the impairment of long-term potentiation (LTP) and memory deficit. Thus, reducing tonic GABA inhibition in the DG may lead to a novel therapy for Alzheimer’s disease.

Alzheimer’s Disease Risk Gene CD33 Inhibits Microglial Uptake of Amyloid Beta

The transmembrane protein CD33 is a sialic acid-binding immunoglobulin-like lectin that regulates innate immunity but has no known functions in the brain. We have previously shown that the CD33 gene is a risk factor for Alzheimer's disease (AD). Here, we observed increased expression of CD33 in microglial cells in AD brain. The minor allele of the CD33 SNP rs3865444, which confers protection against AD, was associated with reductions in both CD33 expression and insoluble amyloid beta 42 (Aβ42) levels in AD brain. Furthermore, the numbers of CD33-immunoreactive microglia were positively correlated with insoluble Aβ42 levels and plaque burden in AD brain. CD33 inhibited uptake and clearance of Aβ42 in microglial cell cultures. Finally, brain levels of insoluble Aβ42 as well as amyloid plaque burden were markedly reduced in APP(Swe)/PS1(ΔE9)/CD33(-/-) mice. Therefore, CD33 inactivation mitigates Aβ pathology and CD33 inhibition could represent a novel therapy for AD.

Macromolecular and small-molecule modulation of intracellular Aβ42 aggregation and associated toxicity

Aβ (amyloid β-peptide) has a central role in AD (Alzheimer's disease) where neuronal toxicity is linked to its extracellular and intracellular accumulation as oligomeric species. Searching for molecules that attenuate Aβ aggregation could uncover novel therapies for AD, but most studies in mammalian cells have inferred aggregation indirectly by assessing levels of secreted Aβ peptide. In the present study we establish a mammalian cell system for the direct visualization of Aβ formation by expression of an Aβ(42)-EGFP (enhanced green fluorescent protein) fusion protein in the human embryonic kidney cell line T-REx293, and use this to identify both macromolecules and small molecules that reduce aggregation and associated cell toxicity. Thus a molecular shield protein AavLEA1 [Aphelenchus avenae LEA (late embryogenesis abundant) protein 1], which limits aggregation of proteins with expanded poly(Q) repeats, is also effective against Aβ(42)-EGFP when co-expressed in T-REx293 cells. A screen of polysaccharide and small organic molecules from medicinal plants and fungi reveals one candidate in each category, PS5 (polysaccharide 5) and ganoderic acid DM respectively, with activity against Aβ. Both PS5 and ganoderic acid DM probably promote Aβ aggregate clearance indirectly through the proteasome. The model is therefore of value to study the effects of intracellular Aβ on cell physiology and to identify reagents that counteract those effects.

Role of RanBP9 on amyloidogenic processing of APP and synaptic protein levels in the mouse brain.

We previously reported that RanBP9 binds low-density lipoprotein receptor-related protein (LRP), amyloid precursor protein (APP), and BACE1 and robustly increased Aβ generation in a variety of cell lines and primary neuronal cultures. To confirm the physiological/ pathological significance of this phenotype in vivo, we successfully generated transgenic mice overexpressing RanBP9 as well as RanBP9-null mice. Here we show that RanBP9 overexpression resulted in >2-fold increase in Aβ40 levels as early as 4 mo of age. A sustained increase in Aβ40 levels was seen at 12 mo of age in both CHAPS-soluble and formic acid (FA)-soluble brain fractions. In addition, Aβ42 levels were also significantly increased in FA-soluble fractions at 12 mo of age. More important, increased Aβ levels were translated to increased deposition of amyloid plaques. In addition, RanBP9 overexpression significantly decreased the levels of synaptophysin and PSD-95 proteins. Conversely, RanBP9-null mice showed increased levels of synaptophysin, PSD-95, and drebrin A protein levels. Given that loss of synapses is the best pathological correlate of cognitive deficits in Alzheimer's disease (AD), increased Aβ levels by RanBP9 observed in the present study provides compelling evidence that RanBP9 may indeed play a key role in the etiology of AD. If so, RanBP9 provides a great opportunity to develop novel therapy for AD.

AMYLOID PRECURSOR PROTEIN PROCESSING IN ALZHEIMER'S DISEASE

How to Cite this Article: Bhadbhade A, Cheng DW. Amyloid Precursor Protein Processing in Alzheimer’s Disease. Iranian Journal of Child Neurology2012;6(1):1-5. Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and a leading cause of dementia. The AD is characterized by presence of intraneuronal tangles and extracellular plaques in the brain. The plaques are composed of dense and mostly insoluble deposits of amyloid beta peptide (Aβ), formed by sequential cleavage of the Amyloid Precursor Protein (APP), by two pathways amyloidogenic and non-amyloidogenic. Tangles are composed of paired helical fragments, which aggregate to form, microtubular protein tau. Although Aβ plaques are established to be the cause of the disease, there exist genetic factors and other pathological identifications in addition to these which are an integral part of the disease. This article gives an overview into the mechanism of APP action, genetic factors and other pathological identifications contributing to Alzheimer’s disease formation. References Brookmeyer R, Gray S, Kawas C. Projections of Alzheimer’s disease in the United States and the public health impact of delaying disease onset. American Journal of Public Health 1998;88(9):1337. Hebert LE, Scherr PA, Bienias JL, Bennett DA, Evans DA. Alzheimer disease in the US population. Arch Neurol 2003;60(8):1119-22. Moller HJ, Graeber M. The case described by Alois Alzheimer in 1911. European Archives of Psychiatry and Clinical Neuroscience 1998:248(3):111-122. Selkoe D J. (2002). Deciphering the genesis and fate of amyloid beta-protein yields novel therapies for Alzheimer disease. J Clinic Investigat 2002;110(10): 1375-82. Wolfe MS. Tau mutations in neurodegenerative diseases. J Biolog Chem 2009;284(10):6021. Selkoe DJ. Alzheimer’s disease: genes, proteins, and therapy. Physiological reviews 2001;81(2):741. Selkoe DJ. The cell biology of [beta]-amyloid precursor protein and presenilin in Alzheimer’s disease. Trends in Cell Biology 1998;8(11):447-453. Thinakaran G, Koo EH. Amyloid precursor protein trafficking, processing, and function. Journal of Biological Chemistry 2008;283(44):29615. Zhang YW, Thompson R, Zhang H, Xu H. APP processing in Alzheimer’s disease. Mol Brain 2011;4:3. doi: 1756- 6606-4-3 [pii] 10.1186/1756-6606-4-3. Nunan J, Small DH. Regulation of APP cleavage by α-,β- and γ-secretases. J Biolog Chem 2000:483(1):6-10. Pearson HA, Peers C. Physiological roles for amyloid peptides. J Physiology 2006;575(1):5-10. Wang Y, Ha Y. The X-ray structure of an antiparallel dimer of the human amyloid precursor protein E2 domain. Molecular Cell 2004;15(3):343-353. Quitschke WW, Goldgaber D. The amyloid b-protein precursor promoter. Journal Biolog Chem 1992;267(24):17362-17368. Vostrov AA, Taheny MJ, Izkhakov N, Quitschke WW. A nuclear factor-binding domain in the 5’-untranslated region of the amyloid precursor protein promoter: implications for the regulation of gene expression. BMC Research Notes 2010;3:4. Ghosala K,Vogta D, Lianga M, Shenb Y, Lamba BT, Sanjay W, Pimplikara SW. Alzheimer’s disease-like pathological features in transgenic mice expressing the APP intracellular domain. Proceedings of National Academy of Sciences 2009;106(43):18367-77.

Surrogate consent for dementia research: a national survey of older Americans.

Research in novel therapies for Alzheimer disease (AD) relies on persons with AD as research subjects. Because AD impairs decisional capacity, informed consent often must come from surrogates, usually close family members. But policies for surrogate consent for research remain unsettled after decades of debate. We designed a survey module for a random subsample (n = 1,515) of the 2006 wave of the Health and Retirement Study, a biennial survey of a nationally representative sample of Americans aged 51 and older. The participants answered questions regarding one of four randomly assigned surrogate-based research (SBR) scenarios: lumbar puncture study, drug randomized control study, vaccine study, and gene transfer study. Each participant answered three questions: whether our society should allow family surrogate consent, whether one would want to participate in the research, and whether one would allow one's surrogate some or complete leeway to override stated personal preferences. Most respondents stated that our society should allow family surrogate consent for SBR (67.5% to 82.5%, depending on the scenario) and would themselves want to participate in SBR (57.4% to 79.7%). Most would also grant some or complete leeway to their surrogates (54.8% to 66.8%), but this was true mainly of those willing to participate. There was a trend toward lower willingness to participate in SBR among those from ethnic or racial minority groups. Family surrogate consent-based dementia research is broadly supported by older Americans. Willingness to allow leeway to future surrogates needs to be studied further for its ethical significance for surrogate-based research policy.

Designing Peptide Inhibitors for Oligomerization and Toxicity of Alzheimer's β-Amyloid Peptide

Convergent biochemical and genetic evidence suggests that the formation of beta-amyloid (Abeta) deposits in the brain is an important and, probably, seminal step in the development of Alzheimer's disease (AD). Recent studies support the hypothesis that Abeta soluble oligomers are the pathogenic species that prompt the disease. Inhibiting Abeta self-oligomerization could, therefore, provide a novel approach to treating the underlying cause of AD. Here, we designed potential peptide-based aggregation inhibitors containing Abeta amino acid sequences (KLVFF) from part of the binding region responsible for Abeta self-association (residues 16-20), with RG-/-GR residues added at their N- and C-terminal ends to aid solubility. Two such peptides (RGKLVFFGR, named OR1, and RGKLVFFGR-NH2, named OR2) were effective inhibitors of Abeta fibril formation, but only one of these peptides (OR2) inhibited Abeta oligomer formation. Interestingly, this same OR2 peptide was the only effective inhibitor of Abeta toxicity toward human neuroblastoma SH-SY5Y cells. Our data support the idea that Abeta oligomers are responsible for the cytotoxic effects of Abeta and identify a potential peptide inhibitor for further development as a novel therapy for AD.

Relationship of fMRI activation to clinical trial memory measures in Alzheimer disease

Functional MRI (fMRI) has shown promise as a tool to characterize altered brain function in Alzheimer disease (AD) and for use in proof of concept clinical trials. FMRI studies of subjects with AD have demonstrated altered hippocampal and neocortical activation while encoding novel stimuli compared to older controls. However, the relationship between fMRI activation and performance on standardized clinical trial memory measures has not been fully investigated. To determine whether patterns of activation during an associative-memory fMRI paradigm correlate with performance on memory measures used in AD clinical trials. Twenty-nine subjects with AD underwent neuropsychological testing, including the AD Assessment Scale (ADAS-Cog), and an associative-encoding fMRI paradigm. Scores were entered as regressors in SPM2 analyses of the differential fMRI activation to novel-vs-repeated (NvR) stimuli. To account for cerebral atrophy, native-space structure-function analyses were performed with subjects' high-resolution structural images. Performance on the ADAS-Cog verbal memory component, and the ADAS-Cog total score, correlated with NvR activation in left superior temporal (p = 0.0003; r = -0.51) and left prefrontal (p = 0.00001; r = -0.63) cortices. In a subgroup with more extensive neuropsychological testing (n = 14), performance on the Free and Cued Selective Reminding Test was correlated with activation in these same regions. fMRI activation remained correlated with performance even when accounting for atrophy. The relationship between functional MRI (fMRI) activation and standardized memory measures supports the potential use of fMRI to investigate regional mechanisms of treatment response in clinical trials of novel therapies for Alzheimer disease. .

A marine-derived acidic oligosaccharide sugar chain specifically inhibits neuronal cell injury mediated by β-amyloid-induced astrocyte activation in vitro

In Alzheimer's disease (AD), β-amyloid (Aβ) plaques are surrounded by activated astrocytes and microglia. A growing body of evidence suggests that these activated astrocytes contribute to neurotoxicity through the induction of inflammatory cytokines and the production of oxidative stress mediators. Thus, a compound inhibiting Aβ-induced activation of astrocytes may lead to a novel therapy for AD. Our current work investigates the roles of acidic oligosaccharide sugar chain (AOSC), derived from brown algae Echlonia Kurome Okam, on Aβ-induced inflammatory responses and cytotoxicity. We observed that AOSC inhibited the toxicity and apoptosis in SH-SY5Y cell line induced by Aβ-stimulated astrocytes conditioned medium. We found that AOSC inhibited the reactive phenotype of astrocytes, blocked cellular oxidative stress, reduced the production of tumor necrosis factor (TNF)-α and interleukin (IL)-6 and prevented the influx of Ca2+. Thus, our results indicate that AOSC might be a potentially therapeutic compound for AD.

RAC1 Inhibition Targets Amyloid Precursor Protein Processing by γ-Secretase and Decreases Aβ Production in Vitro and in Vivo

beta-Amyloid peptides (Abeta) that form the senile plaques of Alzheimer disease consist mainly of 40- and 42-amino acid (Abeta 40 and Abeta 42) peptides generated from the cleavage of the amyloid precursor protein (APP). Generation of Abeta involves beta-secretase and gamma-secretase activities and is regulated by membrane trafficking of the proteins involved in Abeta production. Here we describe a new small molecule, EHT 1864, which blocks the Rac1 signaling pathways. In vitro, EHT 1864 blocks Abeta 40 and Abeta 42 production but does not impact sAPPalpha levels and does not inhibit beta-secretase. Rather, EHT 1864 modulates APP processing at the level of gamma-secretase to prevent Abeta 40 and Abeta 42 generation. This effect does not result from a direct inhibition of the gamma-secretase activity and is specific for APP cleavage, since EHT 1864 does not affect Notch cleavage. In vivo, EHT 1864 significantly reduces Abeta 40 and Abeta 42 levels in guinea pig brains at a threshold that is compatible with delaying plaque accumulation and/or clearing the existing plaque in brain. EHT 1864 is the first derivative of a new chemical series that consists of candidates for inhibiting Abeta formation in the brain of AD patients. Our findings represent the first pharmacological validation of Rac1 signaling as a target for developing novel therapies for Alzheimer disease.