Transthyretin binds amyloid beta peptides, Abeta1-42 and Abeta1-40 to form complex in the autopsied human kidney - possible role of transthyretin for abeta sequestration

Ginkgo biloba extract mitigates the neurotoxicity of AlCl3 in alzheimer rat's model: role of apolipoprotein E4 and clusterin genes in stimulating ROS generation and apoptosis

PURPOSE

Alzheimer's disease (AD) appears as a result of an increase in the accumulation of amyloid beta peptide (Aβ) and a decrease in neurotransmitters (acetylcholine) within the brain cells which may be due to increase in acetylcholinesterase (AchE) activity and change in expression of Apolipoprotein E4 (ApoE4) and Clusterin (Clu) genes. The aim of the present study was using natural products such as Ginkgo biloba (G. biloba) extract that has the potential to reduce Aβ formation and increase AchE inhibition with its ability to save neuronal DNA from damage.

METHODS

Sixty male aged rats were divided into six experimental groups exposed to AlCl3 to induce AD model and were treated with G. biloba extract. Collected brain tissues were used to assess the apoptosis rate, reactive oxygen species (ROS) generation, AchE inhibitory activity, expression alteration in ApoE4 and Clu genes, DNA fragmentations and gutathione peroxidase (GPx) activity.Results: The results exhibited that rats exposed to AlCl3 increased significantly rate of apoptosis, ROS formation, DNA fragmentation, up-regulation of ApoE4 and Clu genes as well as decrease of AchE inhibitory activity and GPx activity compared with those in control rats. However, treatment of AlCl3-rats with G. biloba extract improved the above neurotoxicity results induced by AlCl3 exposure.

CONCLUSIONS

It is therefore likely that G. biloba extract's protective properties against AD are due to its ability to activate the response against oxidative stress.

Transthyretin-Penetratin: A Potent Fusion Protein Inhibitor against Alzheimer's Amyloid-β Fibrillogenesis with High Blood Brain Barrier Crossing Capability

The design of a potent amyloid-β protein (Aβ) inhibitor plays a pivotal role in the prevention and treatment of Alzheimer's disease (AD). Despite endogenous transthyretin (TTR) being recognized as an Aβ inhibitor, the weak inhibitory and blood brain barrier (BBB) crossing capabilities hinder it for Aβ aggregation inhibition and transport. Therefore, we have herein designed a recombinant TTR by conjugating a cationic cell penetrating peptide (penetratin, Pen), which not only enabled the fusion protein, TTR-Pen (TP), to present high BBB penetration but also greatly enhanced the potency of Aβ inhibition. Namely, the protein fusion made TP positively charged, leading to a potent suppression of Aβ40 fibrillization at a low concentration (1.5 μM), while a TTR concentration as high as 12.5 μM was required to gain a similar function. Moreover, TP could mitigate Aβ-induced neuronal death, increase cultured cell viability from 72% to 92% at 2.5 μM, and extend the lifespan of AD nematodes from 14 to 18 d. Thermodynamic studies revealed that TP, enriched in positive charges, presented extensive electrostatic interactions with Aβ40. Importantly, TP showed excellent BBB penetration performance, with a 10 times higher BBB permeability than TTR, which would allow TP to enter the brain of AD patients and participate in the transport of Aβ species out of the brain. Thus, it is expected that the fusion protein has great potential for drug development in AD treatment.

Traversing through half a century research timeline on Ginkgo biloba, in transforming a botanical rarity into an active functional food ingredient

Neurodegenerative diseases and various other chronic ailments have gradually transformed into public-health issues. Neurodegenerative disorders are a range of progressive neural abnormalities characterized by cellular dysfunctions, neuronal structure, and function loss. Among many chronic disorders, oxidative stress, inflammation, mitochondrial dysregulation, and cellular alterations in the human body are considered the most prevalent diagnostic symptoms. They have a profound impact on patients' health and wellbeing. The disease's poor curability, high healthcare costs, and lethality are the principal reasons for approaching and exploring the conventional treatment's phytotherapeutic alternatives. Ginkgo biloba (Maidenhair tree) is a well-known and widely used herbal plant in the Ginkgoaceae family. Its phytochemical constituents, Flavonoids, and terpenes, have been identified as the primary ingredients of Ginkgo biloba leaf extracts. It has been widely used due to its therapeutic properties, including its neuroprotective, anti-dementia, antioxidant, anti-inflammatory, vasoactive, anti-psychotic, anti-neoplastic, and anti-platelet activity. In recent decades, plenty of Ginkgo-derived substances has been researched and elucidated to have significant therapeutic effects in numerous disease models. This review aims to provide a thorough understanding of the botanical basis for Ginkgo biloba, its usage as herbal medicine, and its pivotal role in functional foods. Additionally, the clinical significance of Ginkgo biloba, as observed in various research works and clinical investigations, is also emphasized, facilitating a better understanding of their molecular basis and application in many chronic diseases.

Waste Clearance in the Brain and Neuroinflammation: A Novel Perspective on Biomarker and Drug Target Discovery in Alzheimer's Disease

Alzheimer’s disease (AD) is a multifactorial disease with a heterogeneous etiology. The pathology of Alzheimer’s disease is characterized by amyloid-beta and hyperphosphorylated tau, which are necessary for disease progression. Many clinical trials on disease-modifying drugs for AD have failed to indicate their clinical benefits. Recent advances in fundamental research have indicated that neuroinflammation plays an important pathological role in AD. Damage- and pathogen-associated molecular patterns in the brain induce neuroinflammation and inflammasome activation, causing caspase-1-dependent glial and neuronal cell death. These waste products in the brain are eliminated by the glymphatic system via perivascular spaces, the blood-brain barrier, and the blood–cerebrospinal fluid barrier. Age-related vascular dysfunction is associated with an impairment of clearance and barrier functions, leading to neuroinflammation. The proteins involved in waste clearance in the brain and peripheral circulation may be potential biomarkers and drug targets in the early stages of cognitive impairment. This short review focuses on waste clearance dysfunction in AD pathobiology and discusses the improvement of waste clearance as an early intervention in prodromal AD and preclinical stages of dementia.

Review on Alzheimer's disease: Inhibition of amyloid beta and tau tangle formation

It is reported that approximately 40 million people are suffering from dementia, globally. Dementia is a group of symptoms that affect neurons and cause some mental disorders, such as losing memory. Alzheimer's disease (AD) which is known as the most common cause of dementia, is one of the top medical care concerns across the world. Although the exact sources of the disease are not understood, is it believed that aggregation of amyloid-beta (Aβ) outside of neuron cells and tau aggregation or neurofibrillary tangles (NFTs) formation inside the cell may play crucial roles. In this paper, we are going to review studies that targeted inhibition of amyloid plaque and tau protein tangle formation, to suppress or postpone AD.

Elucidation of the Molecular Mechanism Underlying Lippia citriodora(Lim.)-Induced Relaxation and Anti-Depression

Lippia citriodora ethanolic extract (VEE) and verbascoside (Vs), a phenypropanoid glycoside, have been demonstrated to exert relaxant and anxiolytic properties. However, the molecular mechanisms behind their effects are still unclear. In this work, we studied the effects and action mechanisms of VEE and Vs in vivo and in vitro, on human neurotypic SH-SY5Y cells.TST was conducted on mice treated orally with VEE (25, 50 and 100 mg/Kg), Vs (2.5 and 5 mg/Kg), Bupropion (20 mg/Kg) and Milli-Q water. Higher dose of VEE-treated mice showed an increase of immobility time compared to control groups, indicating an induction of relaxation. This effect was found to be induced by regulation of genes playing key roles in calcium homeostasis (calcium channels), cyclic AMP (cAMP) production and energy metabolism. On the other hand, low doses of VEE and Vs showed an antidepressant-like effect and was confirmed by serotonin, noradrenalin, dopamine and BDNF expressions. Finally, VEE and Vsenhancedcell viability, mitochondrial activity and calcium uptake in vitro confirming in vivo findings. Our results showed induction of relaxation and antidepressant-like effects depending on the administered dose of VEE and Vs, through modulation of cAMP and calcium.

Neuroprotective and Antioxidant Effect of Ginkgo biloba Extract Against AD and Other Neurological Disorders

Alzheimer's disease (AD) is the most common progressive human neurodegenerative disorder affecting elderly population worldwide. Hence, prevention of AD has been a priority of AD research worldwide. Based on understanding of disease mechanism, different therapeutic strategies involving synthetic and herbal approaches are being used against AD. Among the herbal extract, Ginkgo biloba extract (GBE) is one of the most investigated herbal remedy for cognitive disorders and Alzheimer's disease (AD). Standardized extract of Ginkgo biloba is a popular dietary supplement taken by the elderly population to improve memory and age-related loss of cognitive function. Nevertheless, its efficacy in the prevention and treatment of dementia remains controversial. Specifically, the added effects of GBE in subjects already receiving "conventional" anti-dementia treatments have been to date very scarcely investigated. This review summarizes recent advancements in our understanding of the potential use of Ginkgo biloba extract in the prevention of AD including its antioxidant property. A better understanding of the mechanisms of action of GBE against AD will be important for designing therapeutic strategies, for basic understanding of the underlying neurodegenerative processes, and for a better understanding of the effectiveness and complexity of this herbal medicine.

Human mitochondrial transcriptional factor A breaks the mitochondria-mediated vicious cycle in Alzheimer's disease

In the mitochondria-mediated vicious cycle of Alzheimer’s disease (AD), intracellular amyloid β (Aβ) induces mitochondrial dysfunction and reactive oxygen species, which further accelerate Aβ accumulation. This vicious cycle is thought to play a pivotal role in the development of AD, although the molecular mechanism remains unclear. Here, we examined the effects of human mitochondrial transcriptional factor A (hTFAM) on the pathology of a mouse model of AD (3xTg-AD), because TFAM is known to protect mitochondria from oxidative stress through maintenance of mitochondrial DNA (mtDNA). Expression of hTFAM significantly improved cognitive function, reducing accumulation of both 8-oxoguanine, an oxidized form of guanine, in mtDNA and intracellular Aβ in 3xTg-AD mice and increasing expression of transthyretin, known to inhibit Aβ aggregation. Next, we found that AD model neurons derived from human induced pluripotent stem cells carrying a mutant PSEN1_(P117L) gene, exhibited mitochondrial dysfunction, accumulation of 8-oxoguanine and single-strand breaks in mtDNA, and impaired neuritogenesis with a decreased expression of transthyretin, which is known to be downregulated by oxidative stress. Extracellular treatment with recombinant hTFAM effectively suppressed these deleterious outcomes. Moreover, the treatment increased expression of transthyretin, accompanied by reduction of intracellular Aβ. These results provide new insights into potential novel therapeutic targets.

Hippocampal Gene Expression Is Highly Responsive to Estradiol Replacement in Middle-Aged Female Rats

In the hippocampus, estrogens are powerful modulators of neurotransmission, synaptic plasticity and neurogenesis. In women, menopause is associated with increased risk of memory disturbances, which can be attenuated by timely estrogen therapy. In animal models of menopause, 17β-estradiol (E2) replacement improves hippocampus-dependent spatial memory. Here, we explored the effect of E2 replacement on hippocampal gene expression in a rat menopause model. Middle-aged ovariectomized female rats were treated continuously for 29 days with E2, and then, the hippocampal transcriptome was investigated with Affymetrix expression arrays. Microarray data were analyzed by Bioconductor packages and web-based softwares, and verified with quantitative PCR. At standard fold change selection criterion, 156 genes responded to E2. All alterations but 4 were transcriptional activation. Robust activation (fold change > 10) occurred in the case of transthyretin, klotho, claudin 2, prolactin receptor, ectodin, coagulation factor V, Igf2, Igfbp2, and sodium/sulfate symporter. Classification of the 156 genes revealed major groups, including signaling (35 genes), metabolism (31 genes), extracellular matrix (17 genes), and transcription (16 genes). We selected 33 genes for further studies, and all changes were confirmed by real-time PCR. The results suggest that E2 promotes retinoid, growth factor, homeoprotein, neurohormone, and neurotransmitter signaling, changes metabolism, extracellular matrix composition, and transcription, and induces protective mechanisms via genomic effects. We propose that these mechanisms contribute to effects of E2 on neurogenesis, neural plasticity, and memory functions. Our findings provide further support for the rationale to develop safe estrogen receptor ligands for the maintenance of cognitive performance in postmenopausal women.

Amyloid-clearing proteins and their epigenetic regulation as a therapeutic target in Alzheimer's disease

Abnormal elevation of amyloid β-peptide (Aβ) levels in the brain is the primary trigger for neuronal cell death specific to Alzheimer’s disease (AD). It is now evident that Aβ levels in the brain are manipulable due to a dynamic equilibrium between its production from the amyloid precursor protein (APP) and removal by amyloid clearance proteins. Clearance can be either enzymic or non-enzymic (binding/transport proteins). Intriguingly several of the main amyloid-degrading enzymes (ADEs) are members of the M13 peptidase family (neprilysin (NEP), NEP2 and the endothelin converting enzymes (ECE-1 and -2)). A distinct metallopeptidase, insulin-degrading enzyme (IDE), also contributes to Aβ degradation in the brain. The ADE family currently embraces more than 20 members, both membrane-bound and soluble, and of differing cellular locations. NEP plays an important role in brain function terminating neuropeptide signals. Its decrease in specific brain areas with age or after hypoxia, ischaemia or stroke contribute significantly to the development of AD pathology. The recently discovered mechanism of epigenetic regulation of NEP (and other genes) by the APP intracellular domain (AICD) and its dependence on the cell type and APP isoform expression suggest possibilities for selective manipulation of NEP gene expression in neuronal cells. We have also observed that another amyloid-clearing protein, namely transthyretin (TTR), is also regulated in the neuronal cell by a mechanism similar to NEP. Dependence of amyloid clearance proteins on histone deacetylases and the ability of HDAC inhibitors to up-regulate their expression in the brain opens new avenues for developing preventive strategies in AD.

The Aβ-clearance protein transthyretin, like neprilysin, is epigenetically regulated by the amyloid precursor protein intracellular domain

Proteolytic cleavage of the amyloid precursor protein (APP) by the successive actions of β- and γ-secretases generates several biologically active metabolites including the amyloid β-peptide (Aβ) and the APP intracellular domain (AICD). By analogy with the Notch signalling pathway, AICD has been proposed to play a role in transcriptional regulation. Among the cohort of genes regulated by AICD is the Aβ-degrading enzyme neprilysin (NEP). AICD binds to the NEP promoter causing transcriptional activation by competitive replacement with histone deacetylases (HDACs) leading to increased levels of NEP activity and hence increased Aβ clearance. We now show that the Aβ-clearance protein transthyretin (TTR) is also epigenetically up-regulated by AICD. Like NEP regulation, AICD derived specifically from the neuronal APP isoform, APP695 , binds directly to the TTR promoter displacing HDAC1 and HDAC3. Cell treatment with the tyrosine kinase inhibitor Gleevec (imatinib) or with the alkalizing agent NH4 Cl causes an accumulation of 'functional' AICD capable of up-regulating both TTR and NEP, leading to a reduction in total cellular Aβ levels. Pharmacological regulation of both NEP and TTR might represent a viable therapeutic target in Alzheimer's disease.

Resveratrol increases cerebral glycogen synthase kinase phosphorylation as well as protein levels of drebrin and transthyretin in mice: an exploratory study

Alzheimer's disease (AD) is characterized by intraneuronal β-amyloid plaques and hyperphosphorylated tau, leading to neuronal cell death and progressive memory losses. This exploratory work investigates if dietary resveratrol, previously shown to have broad anti-aging effects and improve AD pathology in vivo, leads to neuroprotective changes in specific protein targets in the mouse brain. Both wild-type and APP/PS1 mice, a transgenic AD mouse model, received control AIN-93G diet or AIN-93G supplemented with resveratrol. Pathology parameters and AD risk were assessed via measurements on plaque burden, levels of phosphorylated glycogen synthase kinase 3-β (GSK3-β), tau, transthyretin and drebrin. Dietary resveratrol treatment did not decrease plaque burden in APP/PS1 mice. However, resveratrol-fed mice demonstrated increases in GSK3-β phosphorylation, a 3.8-fold increase in protein levels of transthyretin, and a 2.2-fold increase in drebrin. This study broadens our understanding of specific mechanisms and targets whereby resveratrol provides neuroprotection.

Neuroprotective effect of natural products against Alzheimer's disease

Nature has gifted mankind with a plethora of flora-bearing fruits, vegetables and nuts. The diverse array of bioactive nutrients present in these natural products plays a pivotal role in prevention and cure of various neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease and other neuronal dysfunctions. Accumulated evidence suggests that naturally occurring phyto-compounds, such as polyphenolic antioxidants found in fruits, vegetables, herbs and nuts, may potentially hinder neurodegeneration, and improve memory and cognitive function. Nuts such as walnut have also demonstrated neuroprotective effect against AD. The molecular mechanisms behind the curative effects rely mainly on the action of phytonutrients on distinct signalling pathways associated with protein folding and neuroinflammation. The neuroprotective effects of various naturally occurring compounds in AD is evaluating in this review.

Transthyretin and the brain re-visited: is neuronal synthesis of transthyretin protective in Alzheimer's disease?

Since the mid-1990's a trickle of publications from scattered independent laboratories have presented data suggesting that the systemic amyloid precursor transthyretin (TTR) could interact with the amyloidogenic β-amyloid (Aβ) peptide of Alzheimer's disease (AD). The notion that one amyloid precursor could actually inhibit amyloid fibril formation by another seemed quite far-fetched. Further it seemed clear that within the CNS, TTR was only produced in choroid plexus epithelial cells, not in neurons. The most enthusiastic of the authors proclaimed that TTR sequestered Aβ in vivo resulting in a lowered TTR level in the cerebrospinal fluid (CSF) of AD patients and that the relationship was salutary. More circumspect investigators merely showed in vitro interaction between the two molecules. A single in vivo study in Caenorhabditis elegans suggested that wild type human TTR could suppress the abnormalities seen when Aβ was expressed in the muscle cells of the worm. Subsequent studies in human Aβ transgenic mice, including those from our laboratory, also suggested that the interaction reduced the Aβ deposition phenotype. We have reviewed the literature analyzing the relationship including recent data examining potential mechanisms that could explain the effect. We have proposed a model which is consistent with most of the published data and current notions of AD pathogenesis and can serve as a hypothesis which can be tested.

Ginkgo biloba extract in Alzheimer's disease: from action mechanisms to medical practice

Standardized extract from the leaves of the Ginkgo biloba tree, labeled EGb761, is one of the most popular herbal supplements. Numerous preclinical studies have shown the neuroprotective effects of EGb761 and support the notion that it may be effective in the treatment and prevention of neurodegenerative disorders such as Alzheimer’s disease (AD). Despite the preclinical promise, the clinical efficacy of this drug remains elusive. In this review, possible mechanisms underlying neuroprotective actions of EGb761 are described in detail, together with a brief discussion of the problem of studying this herb clinically to verify its efficacy in the treatment and prevention of AD. Moreover, various parameters e.g., the dosage and the permeability of the blood brain barrier (BBB), impacting the outcome of the clinical effectiveness of the extract are also discussed. Overall, the findings summarized in this review suggest that, a better understanding of the neuroprotective mechanisms of EGb761 may contribute to better understanding of the effectiveness and complexity of this herb and may also be helpful for design of therapeutic strategies in future clinical practice. Therefore, in future clinical studies, different factors that could interfere with the effect of EGb761 should be considered.

Seasonal differences of gene expression profiles in song sparrow (Melospiza melodia) hypothalamus in relation to territorial aggression

Background

Male song sparrows (Melospiza melodia) are territorial year-round; however, neuroendocrine responses to simulated territorial intrusion (STI) differ between breeding (spring) and non-breeding seasons (autumn). In spring, exposure to STI leads to increases in luteinizing hormone and testosterone, but not in autumn. These observations suggest that there are fundamental differences in the mechanisms driving neuroendocrine responses to STI between seasons. Microarrays, spotted with EST cDNA clones of zebra finch, were used to explore gene expression profiles in the hypothalamus after territorial aggression in two different seasons.

Methodology/Principal Findings

Free-living territorial male song sparrows were exposed to either conspecific or heterospecific (control) males in an STI in spring and autumn. Behavioral data were recorded, whole hypothalami were collected, and microarray hybridizations were performed. Quantitative PCR was performed for validation. Our results show 262 cDNAs were differentially expressed between spring and autumn in the control birds. There were 173 cDNAs significantly affected by STI in autumn; however, only 67 were significantly affected by STI in spring. There were 88 cDNAs that showed significant interactions in both season and STI.

Conclusions/Significance

Results suggest that STI drives differential genomic responses in the hypothalamus in the spring vs. autumn. The number of cDNAs differentially expressed in relation to season was greater than in relation to social interactions, suggesting major underlying seasonal effects in the hypothalamus which may determine the differential response upon social interaction. Functional pathway analyses implicated genes that regulate thyroid hormone action and neuroplasticity as targets of this neuroendocrine regulation.

Gene Regulatory Effects of Ginkgo biloba Extract and Its Flavonol and Terpenelactone Fractions in Mouse Brain

The standardised Ginkgo biloba extract EGb761 is known for its potential beneficial effects in the prevention and therapy of neurodegenerative disorders including Alzheimer’s disease (AD). However, the molecular mechanisms and the specific role of its constituents are largely unknown. The aim of the present feeding trial was to investigate the effects of EGb761 and its major constituents on the expression of genes encoding for proteins involved in the pathogenesis of AD in mouse brain. Six month old C57B6 mice were fed semi synthetic diets enriched with either EGb761 or one of its main fractions, flavonols and terpenelactones, respectively, over a period of 4 weeks. Thereafter, mRNA of α-secretase, neprilysin, amyloid precursor protein (App), App binding protein-1 and acetylcholine esterase was quantified in hippocampus and cortex. EGb761 and its flavonol fraction had no effects on relative mRNA levels of the respective genes in mouse brain. However, the terpenelactone fraction significantly decreased the mRNA levels of App in the hippocampus. Taken together, a 4 week dietary treatment with EGb761 or its main fractions had only moderate effects on mRNA levels of AD related genes in cortex and hippocampus of mice.

Biomarkers of Alzheimer's disease

Although a battery of neuropsychological tests is often used in making a clinical diagnosis of Alzheimer's disease (AD), definitive diagnosis still relies on pathological evaluation at autopsy. The identification of AD biomarkers may allow for a less invasive and more accurate diagnosis as well as serve as a predictor of future disease progression and treatment response. Importantly, biomarkers may also allow for the identification of individuals who are already developing the underlying pathology of AD such as plaques and tangles yet who are not yet demented, i.e. "preclinical" AD. Attempts to identify biomarkers have included fluid and imaging studies, with a number of candidate markers showing significant potential. More recently, better reagent availability and novel methods of assessment have further spurred the search for biomarkers of AD. This review will discuss promising fluid and imaging markers to date.

Transthyretin binding to A-Beta peptide--impact on A-Beta fibrillogenesis and toxicity

It has been suggested that transthyretin (TTR) is involved in preventing A-Beta fibrillization in Alzheimer's disease (AD). Here, we characterized the TTR/A-Beta interaction by competition binding assays. TTR binds to different A-Beta peptide species: soluble (Kd, 28 nM), oligomers and fibrils; diverse TTR variants bind differentially to A-Beta. Transmission electron microscopy (TEM) analysis demonstrated that TTR is capable of interfering with A-Beta fibrillization by both inhibiting and disrupting fibril formation. Co-incubation of the two molecules resulted in the abolishment of A-Beta toxicity. Our results confirmed TTR as an A-Beta ligand and indicated the inhibition/disruption of A-Beta fibrils as a possible mechanism underlying the protective role of TTR in AD.

Enrichment improves cognition in AD mice by amyloid-related and unrelated mechanisms

Lifelong cognitive stimulation is associated with a lower risk of Alzheimer's disease (AD), but causality is difficult to prove. We therefore sought to investigate the preventative potential of environmental enrichment (EE) using mice expressing both human mutant presenilin-1 and the amyloid precursor protein (PS1/PDAPP). At weaning, mice were placed into either an enriched or standard housing environment. Behavioral testing at 4.5-6 months showed that environmentally enriched PS1/PDAPP mice outperformed mice in standard housing, and were behaviorally indistinguishable from non-transgenic mice across multiple cognitive domains. PS1/PDAPP mice exposed to both environmental enrichment and behavioral testing, but not to EE alone, showed 50% less brain beta-amyloid without improved dendritic morphology. Microarray analysis revealed large enrichment-induced changes in hippocampal expression of genes/proteins related to Abeta sequestration and synaptic plasticity. These results indicate that EE protects against cognitive impairment in AD transgenic mice through a dual mechanism, including both amyloid dependent and independent mechanisms.

Dietary docosahexaenoic acid and docosapentaenoic acid ameliorate amyloid-beta and tau pathology via a mechanism involving presenilin 1 levels

The underlying cause of sporadic Alzheimer disease (AD) is unknown, but a number of environmental and genetic factors are likely to be involved. One environmental factor that is increasingly being recognized as contributing to brain aging is diet, which has evolved markedly over modern history. Here we show that dietary supplementation with docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, in the 3xTg-AD mouse model of AD reduced the intraneuronal accumulation of both amyloid-beta (Abeta) and tau. In contrast, combining DHA with n-6 fatty acids, either arachidonic acid or docosapentaenoic acid (DPAn-6), diminished the efficacy of DHA over a 12 month period. Here we report the novel finding that the mechanism accounting for the reduction in soluble Abeta was attributable to a decrease in steady-state levels of presenilin 1, and not to altered processing of the amyloid precursor protein by either the alpha- or beta-secretase. Furthermore, the presence of DPAn-6 in the diet reduced levels of early-stage phospho-tau epitopes, which correlated with a reduction in phosphorylated c-Jun N-terminal kinase, a putative tau kinase. Collectively, these results suggest that DHA and DPAn-6 supplementations could be a beneficial natural therapy for AD.

Neuroprotective effects of natural products: interaction with intracellular kinases, amyloid peptides and a possible role for transthyretin

Various studies reported on the neuroprotective effects of natural products, particularly polyphenols, widely present in food and beverages. For example, we have shown that resveratrol, a polyphenol contained present in red wine and other foods, activates the phosphorylation of protein kinase C (PKC), this effect being involved in its neuroprotective action against Ass-induced toxicity. Moreover, tea-derived catechin gallate esters inhibit the formation Ass oligomers/fibrils, suggesting that this action likely contributes to their neuroprotective effects. Interestingly, the effects of polyphenols may be attributable, at least in part, to the presence of specific binding sites. Autoradiographic studies revealed that these binding sites are particularly enriched in choroids plexus in the rat brain. Interestingly, the choroid plexus secretes transthyretin, a protein that has been shown to prevent Abeta aggregation and that may be critical to the maintenance of normal learning capacities in aging. Taken together, these data suggest that polyphenols target multiple enzymes/proteins leading to their neuroprotective actions.

Inhibition of familial cerebral amyloid angiopathy mutant amyloid beta-protein fibril assembly by myelin basic protein

Deposition of fibrillar amyloid beta-protein (Abeta) in the brain is a prominent pathological feature of Alzheimer disease and related disorders, including familial forms of cerebral amyloid angiopathy (CAA). Mutant forms of Abeta, including Dutch- and Iowa-type Abeta, which are responsible for familial CAA, deposit primarily as fibrillar amyloid along the cerebral vasculature and are either absent or present only as diffuse non-fibrillar plaques in the brain parenchyma. Despite the lack of parenchymal fibril formation in vivo, these CAA mutant Abeta peptides exhibit a markedly increased rate and extent of fibril formation in vitro compared with wild-type Abeta. Based on these conflicting observations, we sought to determine whether brain parenchymal factors that selectively interact with and modulate CAA mutant Abeta fibril assembly exist. Using a combination of immunoaffinity chromatography and mass spectrometry, we identified myelin basic protein (MBP) as a prominent brain parenchymal factor that preferentially binds to CAA mutant Abeta compared with wild-type Abeta. Surface plasmon resonance measurements confirmed that MBP bound more tightly to Dutch/Iowa CAA double mutant Abeta than to wild-type Abeta. Using a combination of biochemical and ultrastructural techniques, we found that MBP inhibited the fibril assembly of CAA mutant Abeta. Together, these findings suggest a possible role for MBP in regulating parenchymal fibrillar Abeta deposition in familial CAA.

Comparative proteomics of cerebrospinal fluid in neuropathologically-confirmed Alzheimer's disease and non-demented elderly subjects

OBJECTIVES

Diagnostic tests able to reveal Alzheimer's disease (AD) in living patients before cognitive ability is destroyed are urgently needed. Such tests must distinguish AD from other dementia causes, as well as differentiate subtle changes associated with normal aging from true pathology emergence. A single biomarker offering such diagnostic and prognostic capacities has eluded identification. Therefore, a valuable test for AD is likely to be based on a specific pattern of change in a set of proteins, rather than a single protein.

METHODS

We examined pooled cerebrospinal fluid (CSF) samples obtained from neuropathologically-confirmed AD (n=43) and non-demented control subjects (n=43) using 2-dimensional gel electrophoresis (2DE) proteomic methodology to detect differentially expressed proteins. Proteins exhibiting expression level differences between the pools were recovered and identified using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry.

RESULTS

Five differentially-expressed proteins with potential roles in amyloid-beta metabolism and vascular and brain physiology [apolipoprotein A-1 (Apo A-1), cathepsin D (CatD), hemopexin (HPX), transthyretin (TTR), and two pigment epithelium-derived factor (PEDF) isoforms] were identified. Apo A-1, CatD and TTR were significantly reduced in the AD pool sample, while HPX and the PEDF isoforms were increased in AD CSF.

DISCUSSION

These results suggest that multi-factor proteomic pattern analysis of the CSF may provide a means to diagnose and assess AD.

Specific Plasma Membrane Binding Sites for Polyphenols, Including Resveratrol, in the Rat Brain

Using [3H]resveratrol (3,5,4'-trihydroxy-trans-stilbene) as radioligand, we investigated the possible existence of specific polyphenol binding sites at the level of the cellular plasma membrane in rat brain. Specific [3H]resveratrol binding sites were found to be enriched in the plasma membrane pellet with lower levels in the nuclear and cell debris fraction. Specific [3H]resveratrol binding to the plasma membrane fraction was sensitive to trypsin digestion and protein denaturation but not to DNase and RNase treatment. Saturation binding experiments revealed that specific [3H]resveratrol recognized a single class of sites with an apparent affinity (KD) of 220+/-45 nM and a maximal capacity (Bmax) of 1060+/-120 fmol/mg protein. Various polyphenols and resveratrol derivatives competed against specific [3H]resveratrol binding in rat brain plasma membrane homogenates with the tea catechin gallates (epigallocatechin gallate and epicatechin gallate) displaying the highest affinities (Ki=25-45 nM) followed by resveratrol (Ki=102 nM). Quantitative autoradiographic studies revealed that specific [3H]resveratrol binding sites are broadly distributed in the rat brain, with highest levels of labeling seen in the choroid plexus and subfornical organ. Finally, the potency of various polyphenols and resveratrol analogs in protecting hippocampal cells against beta-amyloid-induced toxicity correlated well (r=0.74) with their apparent affinity in the [3H]resveratrol binding assay. Taken together, these results suggest that the neuroprotective action of various polyphenols and resveratrol analogs could be mediated by the activation of common "receptor" binding sites particularly enriched at the level of the cellular plasma membrane in the rat brain.

Transthyretin inhibition of amyloid beta aggregation and toxicity

OBJECTIVES

The aim of this study was to investigate transthyretin (prealbumin) effects on Abeta25-35-induced cytotoxicity.

DESIGN AND METHODS

In view of the well-recognized literature data demonstrating that Abeta25-35 fibrillar aggregates cause in vitro cytotoxicity to human red blood cells and apoptotic changes to SK-N-BE neuroblastoma cells in cultures (ultrastructural evidence), we tested transthyretin effects on these two experimental models.

RESULTS

Incubation of Abeta25-35 with transthyretin (at transthyretin concentrations equal to CSF physiological levels) demonstrated both inhibition of red blood cells lysis and neutralization of SK-N-BE neuroblastoma cells ultrastructural apoptotic changes. Moreover, transthyretin was shown to be able to inhibit the formation of fibrillar macroaggregates of Abeta25-35.

CONCLUSIONS

The findings imply that experimental systems investigating Abeta-induced cytotoxicity consider the protective interaction of transthyretin with Abeta; an interaction to be considered also in vivo in view of the fact that transthyretin immunoreactivity has been previously demonstrated in amyloid plaques of brains from Alzheimer's disease patients.

Neutralization of transthyretin reverses the neuroprotective effects of secreted amyloid precursor protein (APP) in APPSW mice resulting in tau phosphorylation and loss of hippocampal neurons: support for the amyloid hypothesis

Alzheimer's disease (AD) may be caused by the abnormal processing of the amyloid precursor protein (APP) and the accumulation of beta-amyloid (Abeta). The amyloid precursor protein can be proteolytically cleaved into multiple fragments, many of which have distinct biological actions. Although a high level of Abeta can be toxic, the alpha-secretase cleaved APP (sAPPalpha) is neuroprotective. However, the mechanism of sAPPalpha protection is unknown. Here, we show that sAPPalpha increases the expression levels of several neuroprotective genes and protects organotypic hippocampal cultures from Abeta-induced tau phosphorylation and neuronal death. Antibody interference and small interfering RNA knock-down demonstrate that the sAPPalpha-driven expression of transthyretin and insulin-like growth factor 2 is necessary for protection against Abeta-induced neuronal death. Mice overexpressing mutant APP possess high levels of sAPPalpha and transthyretin and do not develop the tau phosphorylation or neuronal loss characteristic of human AD. Chronic infusion of an antibody against transthyretin into the hippocampus of mice overexpressing APP with the Swedish mutation (APP(Sw)) leads to increased Abeta, tau phosphorylation, and neuronal loss and apoptosis within the CA1 neuronal field. Therefore, the elevated expression of transthyretin is mediated by sAPPalpha and protects APP(Sw) mice from developing many of the neuropathologies observed in AD.

Effects of dietary omega-3 polyunsaturated fatty acids on brain gene expression

Polyunsaturated fatty acids (PUFA) are essential structural components of the central nervous system. Their role in controlling learning and memory has been well documented. A nutrigenomic approach with high-density microarrays was used to reveal brain gene-expression changes in response to different PUFA-enriched diets in rats. In aged rats fed throughout life with PUFA-enriched diets, genes with altered expressions included transthyretin, alpha-synuclein, and calmodulins, which play important roles in synaptic plasticity and learning. The effect of perinatal omega-3 PUFA supply on gene expression later in life also was studied. Several genes showed similar changes in expression in rats fed omega-3-deficient diets in the perinatal period, regardless of whether they or their mothers were fed omega-3 PUFA-sufficient diets after giving birth. In this experiment, among the down-regulated genes were a kainate glutamate receptor and a DEAD-box polypeptide. Among the up-regulated genes were a chemokine-like factor, a tumor necrosis factor receptor, and cytochrome c. The possible involvement of the genes with altered expression attributable to different diets in different brain regions in young and aged rats and the possible mode of regulatory action of PUFA also are discussed. We conclude that PUFA-enriched diets lead to significant changes in expression of several genes in the central nervous tissue, and these effects appear to be mainly independent of their effects on membrane composition. The direct effects of PUFA on transcriptional modulators, the downstream developmentally and tissue-specifically activated elements might be one of the clues to understanding the beneficial effects of the omega-3 PUFA on the nervous system.

Hippocampal and striated skeletal muscle changes in fatty acid composition induced by ethanol in alcohol-preferring rats

Chronic ethanol intake affects various organ systems of the body. The present study evaluated modifications of fatty acid concentrations both in brain and striated skeletal muscles of rats genetically selected for voluntary high ethanol intake. Three groups of rats were tracked for 10 weeks of access to ethanol only as fluid (group 1) to free choice of ethanol and water (group 2) or to water only (group 3). At the end of the period, the animals were sacrificed and their brain hippocampus and striated skeletal muscles were removed and fatty acid content of these tissues was determined. Long-chain fatty acid content increased in the hippocampus while it decreased in the striated skeletal muscles. Short chain fatty acid content decreased in the hippocampus while short chain fatty acid content increased in the striated skeletal muscles. The data show that brain and striated skeletal muscles differently modulate fatty acid content perhaps because these areas utilize different cell membrane functionality regulation systems.

Response of the brain to oligemia: gene expression, c-Fos, and Nrf2 localization

Oligemia is blood flow reduction without acute tissue damage that occurs in shock, migraine, and stroke penumbra. We developed a mouse model of oligemia by lowering mean arterial pressure to 30-40 mm Hg, resulting in a 50% reduction in cerebral blood flow as measured by laser Doppler, and reperfusing the blood after 30 min. Control experiments included anesthesia-only and surgery without blood withdrawal. Using immunohistochemistry, we localized the transcription factors Nrf2, which regulates expression of antioxidant and detoxification protein, and c-Fos, a marker of neuronal activation. Nrf2 was found only in oligemia mice and was localized in neurons of the cingulate cortex and cerebellar Purkinje cells. By contrast, c-Fos was found widely expressed in both groups and was localized in neurons in regions associated with response to stress, immunomodulation, and fluid homeostasis, including the periaqueductal gray and periventricular nucleus. These data indicate that c-Fos expression occurs as a result of surgical stress, but Nrf-2 upregulation is specific to oligemia. The CLONTECH Atlas 1.2 Mouse Array was used to assess genes that were up or down-regulated in oligemia versus surgery controls. Of 1176 genes, 29 differed between oligemia and surgery groups. Upregulation of oxidative stress induced (OSI) protein, heat shock protein (HSP) 84 and transthyretin (TTR) precursor in the oligemia group was confirmed with RT-PCR. The expression of HSP 84, transthyretin precursor, and OSI genes adds further evidence that oligemia induces an oxidative stress response in the brain.

Amyloidogenic and anti-amyloidogenic properties of recombinant transthyretin variants

Most transthyretin (TTR) mutations lead to TTR amyloid depositions in patients with familial amyloidotic polyneuropathy and familial amyloidotic cardiomyopathy. However, though an amyloidogenic protein itself, TTR inhibits aggregation of Alzheimer's amyloid beta protein (A beta) in vitro and in vivo. The pathogenic relationship between two amyloidogenic processes remains unclear. To understand how TTR mutations influence the ability of TTR to inhibit A beta amyloidosis, forty-seven recombinant TTR variants were produced and analyzed. We showed that all recombinant proteins formed tetramers and were functional in thyroxine binding. Acid denaturation at pH 3.8 resulted in aggregation and fibril formation of all TTR variants. However, only TTR G42 and TTR P55 formed fibrils at pH 6.8. Most TTR variants bound to A beta and inhibited A beta aggregation in vitro. TTR variants S64, A71, Q89, V107, H114 and I122 revealed decreased binding to A beta and decreased inhibition of A beta aggregation. Only TTR G42 and TTR P55 completely failed to bind A beta and to inhibit A beta aggregation. We suggest that TTR variants characterized by decreased binding to A beta or by decreased inhibition of A beta aggregation in vitro may contribute to A beta amyloid formation in vivo. These TTR variants might be important targets for epidemiological studies in Alzheimer's disease.

Characterization of beta amyloid assemblies in drusen: the deposits associated with aging and age-related macular degeneration

PURPOSE

Recent studies strongly suggest that drusen, the extracellular deposits associated with age-related macular degeneration (AMD), are a manifestation of local inflammatory events. New evidence indicates that substructural elements within drusen contain activated complement components as well as amyloid beta (Abeta), a major pro-inflammatory component of Alzheimer's disease plaques. We characterized the ultrastructural organization and histochemical staining properties of these Abeta-containing elements in order to further assess their significance in drusen formation and AMD pathogenesis.

METHODS

We used differential interference contrast optics, laser scanning confocal immunofluorescence, and immunogold electron microscopy to characterize the structural properties and molecular composition of Abeta-containing elements in drusen. We obtained estimates of their frequency from montages of electron micrographs gathered from 152 human donor eyes ranging from 9 to 91 years of age.

RESULTS

Spherical Abeta-containing elements, which are typically organized as concentric ring-like structures, are common substructural components of drusen. They stain with thioflavin T, but are not stained by Congo red; nor do they bind cationic, lipophilic, or nucleic acid-binding fluorescent dyes. Ultrastructurally, they are composed of a central core, one or more concentric inner rings with intervening electron lucent layers, and an electron dense outer shell. Immunogold labeling indicates that most Abeta immunoreactivity is associated with the outer layers that consist of densely-packed spherical subunits. No longitudinally-oriented fibril arrays, characteristic of aggregated amyloid fibrils in the brain, are evident. Other prominent drusen-associated proteins including the terminal complement complex C5b-9, vitronectin, apolipoprotein E, serum amyloid P component, and ubiquitin are excluded from the spheres.Conclusions. These structures embedded in drusen appear to represent a new type of macromolecular assembly that contains Abeta as well as activated complement components. The presence of Abeta in these extracellular deposits is an additional indication that some of the pathogenic pathways that give rise to drusen and AMD may be shared with other neurodegenerative diseases characterized by misfolded protein deposition and aggregation.

Pancreatic beta-cell granule peptides form heteromolecular complexes which inhibit islet amyloid polypeptide fibril formation

Islet amyloid polypeptide (IAPP), or 'amylin', is co-stored with insulin in secretory granules of pancreatic islet beta-cells. In Type 2 diabetes, IAPP converts into a beta-sheet conformation and oligomerizes to form amyloid fibrils and islet deposits. Granule components, including insulin, inhibit spontaneous IAPP fibril formation in vitro. To determine the mechanism of this inhibition, molecular interactions of insulin with human IAPP (hIAPP), rat IAPP (rIAPP) and other peptides were examined using surface plasmon resonance (BIAcore), CD and transmission electron microscopy (EM). hIAPP and rIAPP complexed with insulin, and this reaction was concentration-dependent. rIAPP and insulin, but not pro-insulin, bound to hIAPP. Insulin with a truncated B-chain, to prevent dimerization, also bound hIAPP. In the presence of insulin, hIAPP did not spontaneously develop beta-sheet secondary structure or form fibrils. Insulin interacted with pre-formed IAPP fibrils in a regular repeating pattern, as demonstrated by immunoEM, suggesting that the binding sites for insulin remain exposed in hIAPP fibrils. Since rIAPP and hIAPP form complexes with insulin (and each other), this could explain the lack of amyloid fibrils in transgenic mice expressing hIAPP. It is likely that IAPP fibrillogenesis is inhibited in secretory granules (where the hIAPP concentration is in the millimolar range) by heteromolecular complex formation with insulin. Alterations in the proportions of insulin and IAPP in granules could disrupt the stability of the peptide. The increase in the proportion of unprocessed pro-insulin produced in Type 2 diabetes could be a major factor in destabilization of hIAPP and induction of fibril formation.

Gene expression and molecular composition of phospholipids in rat brain in relation to dietary n-6 to n-3 fatty acid ratio

Rats were fed from conception till adulthood either with normal rat chow with a linoleic (LA) to linolenic acid (LNA) ratio of 8.2:1 or a rat chow supplemented with a mixture of perilla and soy bean oil giving a ratio of LA to LNA of 4.7:1. Fat content of the feed was 5%. Fatty acid and molecular species composition of ethanolamine phosphoglyceride was determined. Effect of this diet on gene expression was also studied. There was an accumulation of docosahexaenoic (DHA) and arachidonic acids (AA) in brains of the experimental animals. Changes in the ratio sn-1 saturated, sn-2 docosahexaenoic to sn-1 monounsaturated, sn-2 docosahexaenoic were observed. Twenty genes were found overexpressed in response to the 4.7:1 mixture diet and four were found down-regulated compared to normal rat chow. Among them were the genes related to energy household, lipid metabolism and respiration. The degree of up-regulation exceeded that observed with perilla with a ratio of LA to LNA 8.2:1 [Proc. Natl. Acad. Sci. U. S. A. 99 (2002) 2619]. It was concluded that brain sensitively reacts to the fatty acid composition of the diet. It was suggested that alteration in membrane architecture and function coupled with alterations in gene expression profiles may contribute to the observed beneficial impact of n-3 type polyunsaturated fatty acids on cognitive functions.

A homozygous and a heterozygous defect of the winged helix DNA-binding domain of the fork head (FH) gene in tailless and tailed rat siblings: resultant lymphocyte-rich thymoma connected with renal tubule amyloid beta (Abeta) deposits

OBJECTIVE

To investigate the cause of thymoma connected with renal amyloid beta (Abeta) overproduction.

DESIGN AND METHODS

Pathologic, immune-fluorescence analyses, flow cytometry (FCM) analyses, polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR were applied for tailless and tailed Lewis/Sea rat siblings at the age of 6 months.

RESULTS

A homozygous defect of the winged helix DNA-binding domain of the fork head (FH) gene was detected in the RT-PCR of the tailless rat kidney and liver. Lymphocyte-rich thymoma was found in both rats, but was more prominent in the tailless rat. FCM showed that CD4+ and CD8a+ cells constituted of more than 90% of the thymus lymphocytes in both rats. Abeta deposits in the renal tubules of both rats were shown by positive staining with antihuman Abeta (11-28) antibody (Ab) together with the activation of the kidney presenilin (PSEN) genes. The mRNA level of transthyretin (TTR) was suppressed moderately with age by the homozygous FH1 gene defect.

CONCLUSIONS

Both homozygous and heterozygous defects of the DNA-binding domain of the FH gene caused lymphocyte-rich thymoma and renal Abeta overproduction.

Short-term administration of omega 3 fatty acids from fish oil results in increased transthyretin transcription in old rat hippocampus

Reduced brain levels of long chain polyunsaturated fatty acids [arachidonic acid and docosahexanoic acid (DHA)] are observed in elderly subjects and patients with Alzheimer's disease. To determine the effects of n-3 fatty acids on aged rat brain, 2-year-old rats were fed fish oil (27% DHA content) for 1 month, and gene expression analysis and fatty acid and molecular species composition of the major phospholipid species were assessed. No significant alteration could be observed in the fatty acid composition of ethanolamine phosphoglycerides and phosphatidylserines with the exception of DHA, which was slightly higher in brains of rats receiving fish oil. However, a drastic reduction in arachidonic acid in phosphatidylinositoles was observed. The expression of 23 genes was altered in response to fish oil feeding in the hippocampus. The transcription of transthyretin (TTR) was induced by 10-fold as evidenced by microarray analysis and confirmed by real-time quantitative RT-PCR. Expression of IL-1 and NO synthase, which has been implicated in the prevention of neurological diseases, was unaltered. TTR is an amyloid beta protein scavenger, so an increase in its expression could prevent amyloid aggregate formation. We believe the beneficial effects of fish oil might be common to other agents, i.e., induce TTR expression, like nicotine and Ginkgo biloba extract.

Beta-amyloid production, aggregation, and clearance as targets for therapy in Alzheimer's disease

1. Despite major efforts aimed at elucidating the molecular basis and physiopathology of Alzheimer's disease (AD), there is still no effective treatment available for this devastating disorder. The biological mechanisms underlying the development of AD are complex, as multiple factors appear to modulate (either positively or negatively) the progression of neurodegeneration in the brains of AD patients. Not surprisingly, a number of different therapeutic approaches aimed at distinct aspects of the disease are currently being pursued. Given its central role in the neuropathology of AD, the beta-amyloid peptide (Abeta) is the focus of many such approaches. 2. In this review, we discuss recent developments along three major lines of investigation: (i) identification and characterization of inhibitors of the enzymes involved in proteolytic processing of the amyloid precursor protein and production of Abeta; (ii) identification of the pathways involved in cerebral degradation and clearance of Abeta; and (iii) characterization of small-molecule inhibitors of amyloid aggregation that prevent cerebral amyloid deposition and neurotoxicity. 3. Significant progress has been achieved in these directions, opening up new perspectives toward the development of effective approaches for the treatment or prevention of AD.

Inhibition of amyloid-beta aggregation and caspase-3 activation by the Ginkgo biloba extract EGb761

Standardized extract from the leaves of the Ginkgo biloba tree, labeled EGb761, has been used in clinical trials for its beneficial effects on brain functions, particularly in connection with age-related dementias and Alzheimer's disease (AD). Substantial experimental evidence indicates that EGb761 protects against neuronal damage from a variety of insults, but its cellular and molecular mechanisms remain unknown. Using a neuroblastoma cell line stably expressing an AD-associated double mutation, we report that EGb761 inhibits formation of amyloid-beta (Abeta) fibrils, which are the diagnostic, and possibly causative, feature of AD. The decreased Abeta fibrillogenesis in the presence of EGb761 was observed both in the conditioned medium of this Abeta-secreting cell line and in solution in vitro. In the cells, EGb761 significantly attenuated mitochondrion-initiated apoptosis and decreased the activity of caspase 3, a key enzyme in the apoptosis cell-signaling cascade. These results suggest that (i) neuronal damage in AD might be due to two factors: a direct Abeta toxicity and the apoptosis initiated by the mitochondria; and (ii) multiple cellular and molecular neuroprotective mechanisms, including attenuation of apoptosis and direct inhibition of Abeta aggregation, underlie the neuroprotective effects of EGb761.

Altered expression of novel genes in the cerebral cortex following experimental brain injury

Damage to the cerebral cortex results in neurological impairments such as motor, attention, memory and executive dysfunctions. To examine the molecular mechanisms contributing to these deficits, mRNA expression was profiled using high-density cDNA microarray hybridization after experimental cortical impact injury in mice. The mRNA levels at 2 h, 6 h, 24 h, 3 days and 14 days after injury were compared with those of control animals. This revealed 86 annotated genes and 24 expression sequence tags (ESTs) as being differentially expressed with a 1.5-fold or greater change. Quantitative real-time PCR analysis was used to independently verify these results for selected genes. Seven functional classes of genes were found to be altered following injury, including transcription factors, signal transduction genes and inflammatory proteins. While a few of these genes have been previously reported to be differentially regulated following injury, the most of the genes have not been previously implicated in traumatic brain injury (TBI) pathophysiology. For example, consistent with previous reports, the transcription factor c-jun and the neurotrophic factor bdnf mRNA levels were altered as a result of TBI. Among the novel genes, the mRNA levels for the high mobility group protein 1 (hmg-1), the regulator of G-protein signaling 2 (rgs-2), the transforming growth factor beta inducible early growth response (tieg), the inhibitor of DNA binding 3 (id3), and the heterogeneous nuclear ribonucleoprotein H (hnrnp h) were changed following injury. The functional significance of these genes in neurite outgrowth, neuronal regeneration, and plasticity following injury are discussed.

Proteome analysis of cerebrospinal fluid proteins in Alzheimer patients

By comparing the CSF proteome between Alzheimer disease (AD) patients and controls it may be possible to identify proteins that play a role in the disease process and thus to study the pathogenesis of AD. We used mini-gel technology in a two-dimensional electrophoresis procedure, sensitive SYPRO Ruby staining and mass spectrometry for clinical screening of disease-influenced CSF proteins in 15 AD patients and 12 controls. The levels of six proteins and their isoforms, including proapolipoprotein, apolipoprotein E, beta-2 microglobulin, retinol-binding protein, transthyretin, and ubiquitin, were significantly altered in CSF of AD patients. The most prominently altered proteins were the apolipoproteins, especially proapolipoprotein.

The in vivo neuromodulatory effects of the herbal medicine ginkgo biloba

Extracts of Ginkgo biloba leaves are consumed as dietary supplements to counteract chronic, age-related neurological disorders. We have applied high-density oligonucleotide microarrays to define the transcriptional effects in the cortex and hippocampus of mice whose diets were supplemented with the herbal extract. Gene expression analysis focused on the mRNAs that showed a more than 3-fold change in their expression. In the cortex, mRNAs for neuronal tyrosine/threonine phosphatase 1, and microtubule-associated tau were significantly enhanced. Hyperphosphorylated tau is the major constituent of the neurofibrillary tangles in the brains of Alzheimer's disease patients. The expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-2, calcium and chloride channels, prolactin, and growth hormone (GH), all of which are associated with brain function, were also up-regulated. In the hippocampus, only transthyretin mRNA was upregulated. Transthyretin plays a role in hormone transport in the brain and possibly a neuroprotective role by amyloid-beta sequestration. This study reveals that diets supplemented with Ginkgo biloba extract have notable neuromodulatory effects in vivo and illustrates the utility of genome-wide expression monitoring to investigate the biological actions of complex extracts.