Current status of antioxidant therapy for Alzheimer's Disease

Metabolic correlates of late midlife cognitive outcomes: findings from the 1946 British Birth Cohort

Investigating associations between metabolites and late midlife cognitive function could reveal potential markers and mechanisms relevant to early dementia. Here, we systematically explored the metabolic correlates of cognitive outcomes measured across the seventh decade of life, while untangling influencing life course factors. Using levels of 1019 metabolites profiled by liquid chromatography-mass spectrometry (age 60-64), we evaluated relationships between metabolites and cognitive outcomes in the British 1946 Birth Cohort (N = 1740). We additionally conducted pathway and network analyses to allow for greater insight into potential mechanisms, and sequentially adjusted for life course factors across four models, including sex and blood collection (Model 1), Model 1 + body mass index and lipid medication (Model 2), Model 2 + social factors and childhood cognition (Model 3) and Model 3 + lifestyle influences (Model 4). After adjusting for multiple tests, 155 metabolites, 10 pathways and 5 network modules were associated with cognitive outcomes. Of the 155, 35 metabolites were highly connected in their network module (termed 'hub' metabolites), presenting as promising marker candidates. Notably, we report relationships between a module comprised of acylcarnitines and processing speed which remained robust to life course adjustment, revealing palmitoylcarnitine (C16) as a hub (Model 4: β = -0.10, 95% confidence interval = -0.15 to -0.052, P = 5.99 × 10-5). Most associations were sensitive to adjustment for social factors and childhood cognition; in the final model, four metabolites remained after multiple testing correction, and 80 at P < 0.05. Two modules demonstrated associations that were partly or largely attenuated by life course factors: one enriched in modified nucleosides and amino acids (overall attenuation = 39.2-55.5%), and another in vitamin A and C metabolites (overall attenuation = 68.6-92.6%). Our other findings, including a module enriched in sphingolipid pathways, were entirely explained by life course factors, particularly childhood cognition and education. Using a large birth cohort study with information across the life course, we highlighted potential metabolic mechanisms associated with cognitive function in late midlife, suggesting marker candidates and life course relationships for further study.

Cannabidiol Inhibits Tau Aggregation In Vitro

A hallmark of Alzheimer’s disease (AD) is the accumulation of tau protein in the brain. Compelling evidence indicates that the presence of tau aggregates causes irreversible neuronal destruction, eventually leading to synaptic loss. So far, the inhibition of tau aggregation has been recognized as one of the most effective therapeutic strategies. Cannabidiol (CBD), a major component found in Cannabis sativa L., has antioxidant activities as well as numerous neuroprotective features. Therefore, we hypothesize that CBD may serve as a potent substance to hamper tau aggregation in AD. In this study, we aim to investigate the CBD effect on the aggregation of recombinant human tau protein 1N/4R isoform using biochemical methods in vitro and in silico. Using Thioflavin T (ThT) assay, circular dichroism (CD), and atomic force microscopy (AFM), we demonstrated that CBD can suppress tau fibrils formation. Moreover, by quenching assay, docking, and job’s plot, we further demonstrated that one molecule of CBD interacts with one molecule of tau protein through a spontaneous binding. Experiments performed by quenching assay, docking, and Thioflavin T assay further established that the main forces are hydrogen Van der Waals and some non-negligible hydrophobic forces, affecting the lag phase of tau protein kinetics. Taken together, this study provides new insights about a natural substance, CBD, for tau therapy which may offer new hope for the treatment of AD.

Esculetin as a Bifunctional Antioxidant Prevents and Counteracts the Oxidative Stress and Neuronal Death Induced by Amyloid Protein in SH-SY5Y Cells

Oxidative stress (OS) appears to be an important determinant during the different stages of progression of Alzheimer’s Disease (AD). In particular, impaired antioxidant defense mechanisms, such as the decrease of glutathione (GSH) and nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), a master regulator of antioxidant genes, including those for GSH, are associated with OS in the human AD brain. Among the neuropathological hallmarks of AD, the soluble oligomers of amyloid beta (Aβ) peptides seem to promote neuronal death through mitochondrial dysfunction and OS. In this regard, bifunctional antioxidants can exert a dual neuroprotective role by scavenging reactive oxygen species (ROS) directly and concomitant induction of antioxidant genes. In this study, among natural coumarins (esculetin, scopoletin, fraxetin and daphnetin), we demonstrated the ability of esculetin (ESC) to prevent and counteract ROS formation in neuronal SH-SY5Y cells, suggesting its profile as a bifunctional antioxidant. In particular, ESC increased the resistance of the SH-SY5Y cells against OS through the activation of Nrf2 and increase of GSH. In similar experimental conditions, ESC could also protect the SH-SY5Y cells from the OS and neuronal death evoked by oligomers of Aβ_1–42 peptides. Further, the use of the inhibitors PD98059 and LY294002 also showed that Erk1/2 and Akt signaling pathways were involved in the neuroprotection mediated by ESC. These results encourage further research in AD models to explore the efficacy and safety profile of ESC as a novel neuroprotective agent.

Redox theory of aging: implications for health and disease

Genetics ultimately defines an individual, yet the phenotype of an adult is extensively determined by the sequence of lifelong exposures, termed the exposome. The redox theory of aging recognizes that animals evolved within an oxygen-rich environment, which created a critical redox interface between an organism and its environment. Advances in redox biology show that redox elements are present throughout metabolic and structural systems and operate as functional networks to support the genome in adaptation to environmental resources and challenges during lifespan. These principles emphasize that physical and functional phenotypes of an adult are determined by gene-environment interactions from early life onward. The principles highlight the critical nature of cumulative exposure memories in defining changes in resilience progressively during life. Both plasma glutathione and cysteine systems become oxidized with aging, and the recent finding that cystine to glutathione ratio in human plasma predicts death in coronary artery disease (CAD) patients suggests this could provide a way to measure resilience of redox networks in aging and disease. The emerging concepts of cumulative gene-environment interactions warrant focused efforts to elucidate central mechanisms by which exposure memory governs health and etiology, onset and progression of disease.

A Novel Peptide from Soybean Protein Isolate Significantly Enhances Resistance of the Organism under Oxidative Stress

Recent studies have indicated that protein hydrolysates have broad biological effects. In the current study we describe a novel antioxidative peptide, FDPAL, from soybean protein isolate (SPI). The aim of this study was to purify and characterize an antioxidative peptide from SPI and determine its antioxidative mechanism. LC–MS/MS was used to isolate and identify the peptide from SPI. The sequence of the peptide was determined to be Phe-Asp-Pro-Ala-Leu (FDPAL, 561 Da). FDPAL can cause significant enhancement of resistance to oxidative stress both in cells as well as simple organisms. In Caenorhabditis elegans (C. elegans), FDPAL can up-regulate the expression of certain genes associated with resistance. The antioxidant activity of this peptide can be attributed to the presence of a specific amino acid sequence. Results from our work suggest that FDPAL can facilitate potential applications of proteins carrying this sequence in the nutraceutical, bioactive material and clinical medicine areas, as well as in cosmetics and health care products.

Are Polyphenols Strong Dietary Agents Against Neurotoxicity and Neurodegeneration?

Life expectancy of most human populations has greatly increased as a result of factors including better hygiene, medical practice, and nutrition. Unfortunately, as humans age, they become more prone to suffer from neurodegenerative diseases and neurotoxicity. Polyphenols can be cheaply and easily obtained as part of a healthy diet. They present a wide range of biological activities, many of which have relevance for human health. Compelling evidence has shown that dietary phytochemicals, particularly polyphenols, have properties that may suppress neuroinflammation and prevent toxic and degenerative effects in the brain. The mechanisms by which polyphenols exert their action are not fully understood, but it is clear that they have a direct effect through their antioxidant activities. They have also been shown to modulate intracellular signaling cascades, including the PI3K-Akt, MAPK, Nrf2, and MEK pathways. Polyphenols also interact with a range of neurotransmitters, illustrating that these compounds can promote their health benefits in the brain through a direct, indirect, or complex action. We discuss whether polyphenols obtained from diet or food supplements are an effective strategy to prevent or treat neurodegeneration. We also discuss the safety, mechanisms of action, and the current and future relevance of polyphenols in clinical treatment of neurodegenerative diseases. As populations age, it is important to discuss the dietary strategies to avoid or counteract the effects of incurable neurodegenerative disorders, which already represent an enormous financial and emotional burden for health care systems, patients, and their families.

Vitamin E: Curse or Benefit in Alzheimer's Disease? A Systematic Investigation of the Impact of α-, γ- and δ-Tocopherol on Aß Generation and Degradation in Neuroblastoma Cells

OBJECTIVES

The E vitamins are a class of lipophilic compounds including tocopherols, which have high antioxidative properties. Because of the elevated lipid peroxidation and increased reactive oxidative species in Alzheimer's disease (AD) many attempts have been made to slow down the progression of AD by utilizing the antioxidative action of vitamin E. Beside the mixed results of these studies nothing is known about the impact of vitamin E on the mechanisms leading to amyloid-β production and degradation being responsible for the plaque formation, one of the characteristic pathological hallmarks in AD. Here we systematically investigate the influence of different tocopherols on Aβ production and degradation in neuronal cell lines.

MEASUREMENTS

Beside amyloid-β level the mechanisms leading to Aβ production and degradation are examined.

RESULTS

Surprisingly, all tocopherols have shown to increase Aβ level by enhancing the Aβ production and decreasing the Aβ degradation. Aβ production is enhanced by an elevated activity of the involved enzymes, the β- and γ-secretase. These secretases are not directly affected, but tocopherols increase their protein level and expression. We could identify significant differences between the single tocopherols; whereas α-tocopherol had only minor effects on Aβ production, δ-tocopherol showed the highest potency to increase Aβ generation. Beside Aβ production, Aβ clearance was decreased by affecting IDE, one of the major Aβ degrading enzymes.

CONCLUSIONS

Our results suggest that beside the beneficial antioxidative effects of vitamin E, tocopherol has in respect to AD also a potency to increase the amyloid-β level, which differ for the analysed tocopherols. We therefore recommend that further studies are needed to clarify the potential role of these various vitamin E species in respect to AD and to identify the form which comprises an antioxidative property without having an amyloidogenic potential.

Alzheimer disease: epidemiology, diagnostic criteria, risk factors and biomarkers

The global prevalence of dementia is as high as 24 million, and has been predicted to quadruple by the year 2050. In the US alone, Alzheimer disease (AD) - the most frequent cause of dementia characterized by a progressive decline in cognitive function in particular the memory domain - causes estimated health-care costs of $ 172 billion per year. Key neuropathological hallmarks of the AD brain are diffuse and neuritic extracellular amyloid plaques - often surrounded by dystrophic neurites - and intracellular neurofibrillary tangles. These pathological changes are frequently accompanied by reactive microgliosis and loss of neurons, white matter and synapses. The etiological mechanisms underlying these neuropathological changes remain unclear, but are probably caused by both environmental and genetic factors. In this review article, we provide an overview of the epidemiology of AD, review the biomarkers that may be used for risk assessment and in diagnosis, and give suggestions for future research.

Modulation of Hippocampal Plasticity and Cognitive Behavior by Short-term Blueberry Supplementation in Aged Rats

During aging, reductions in hippocampal neurogenesis are associated with memory decline indicating a causal relationship. Indeed, insulin-like growth factor-1 (IGF-1), a major activator of the extracellular receptor kinase pathway that is central in learning and memory processes, is also a key modulator of hippocampal neurogenesis. Previously, we showed that age-related declines in spatial memory tasks can be improved by antioxidant-rich diets containing blueberries. In this study, to begin to understand the mechanisms responsible for the beneficial effects of blueberries, we assessed changes in hippocampal plasticity parameters such as hippocampal neurogenesis, extracellular receptor kinase activation, and IGF-1 and IGF-1R levels in blueberry-supplemented aged animals. Our results show that all these parameters of hippocampal neuronal plasticity are increased in supplemented animals and aspects such as proliferation, extracellular receptor kinase activation and IGF-1 and IGF-1R levels correlate with improvements in spatial memory. Therefore, cognitive improvements afforded by polyphenolic-rich fruits such as blueberries appear, in part, to be mediated by their effects on hippocampal plasticity.

Oxidative modification of lipoic acid by HNE in Alzheimer disease brain

Alzheimer disease (AD) is an age-related neurodegenerative disease characterized by the presence of three pathological hallmarks: synapse loss, extracellular senile plaques (SP) and intracellular neurofibrillary tangles (NFTs). The major component of SP is amyloid β-peptide (Aβ), which has been shown to induce oxidative stress. The AD brain shows increased levels of lipid peroxidation products, including 4-hydroxy-2-nonenal (HNE). HNE can react covalently with Cys, His, or Lys residues on proteins, altering structure and function of the latter. In the present study we measured the levels of the HNE-modified lipoic acid in brain of subjects with AD and age-matched controls. Lipoic acid is a key co-factor for a number of proteins including pyruvate dehydrogenase and α-ketoglutarate dehydrogenase, key complexes for cellular energetics. We observed a significant decrease in the levels of HNE-lipoic acid in the AD brain compared to that of age-matched controls. To investigate this phenomenon further, the levels and activity of lipoamide dehydrogenase (LADH) were measured in AD and control brains. Additionally, LADH activities were measured after in-vitro HNE-treatment to mice brains. Both LADH levels and activities were found to be significantly reduced in AD brain compared to age-matched control. HNE-treatment also reduced the LADH activity in mice brain. These data are consistent with a two-hit hypothesis of AD: oxidative stress leads to lipid peroxidation that, in turn, causes oxidative dysfunction of key energy-related complexes in mitochondria, triggering neurodegeneration. This study is consonant with the notion that lipoic acid supplementation could be a potential treatment for the observed loss of cellular energetics in AD and potentiate the antioxidant defense system to prevent or delay the oxidative stress in and progression of this devastating dementing disorder.

Antibacterial activities of Ginkgo biloba L. leaf extracts

The antibacterial activity of methanol, ethanol, chloroform, and hexane extracts of the leaves of Himalayan gymnospermous plant Ginkgo biloba L. was assessed against five animal and plant pathogenic strains (Agrobacterium tumefaciens, Bacillus subtilis, Escherichia coli, Erwinia chrysanthemi, and Xanthomonas phaseoli) employing disc-diffusion and broth-dilution assays. The methanol extract showed the highest activity (zone of inhibition of 15–21 mm) followed by ethanol (14–19 mm), chloroform (15–20 mm), and hexane (14–19 mm) extracts at 250 μg/mL. A minimum inhibitory concentration (MIC) of 7.8 μg/mL was found for the methanol extract against most of the pathogens tested.

Epidemiology of Alzheimer disease

The global prevalence of dementia is estimated to be as high as 24 million, and is predicted to double every 20 years through to 2040, leading to a costly burden of disease. Alzheimer disease (AD) is the leading cause of dementia and is characterized by a progressive decline in cognitive function, which typically begins with deterioration in memory. Before death, individuals with this disorder have usually become dependent on caregivers. The neuropathological hallmarks of the AD brain are diffuse and neuritic extracellular amyloid plaques-which are frequently surrounded by dystrophic neurites-and intracellular neurofibrillary tangles. These hallmark pathologies are often accompanied by the presence of reactive microgliosis and the loss of neurons, white matter and synapses. The etiological mechanisms underlying the neuropathological changes in AD remain unclear, but are probably affected by both environmental and genetic factors. Here, we provide an overview of the criteria used in the diagnosis of AD, highlighting how this disease is related to, but distinct from, normal aging. We also summarize current information relating to AD prevalence, incidence and risk factors, and review the biomarkers that may be used for risk assessment and in diagnosis.

Nanoparticle and iron chelators as a potential novel Alzheimer therapy

Current therapies for Alzheimer disease (AD) such as the acetylcholinesterase inhibitors and the latest NMDA receptor inhibitor, Namenda, provide moderate symptomatic delay at various stages of the disease, but do not arrest the disease progression or bring in meaningful remission. New approaches to the disease management are urgently needed. Although the etiology of AD is largely unknown, oxidative damage mediated by metals is likely a significant contributor since metals such as iron, aluminum, zinc, and copper are dysregulated and/or increased in AD brain tissue and create a pro-oxidative environment. This role of metal ion-induced free radical formation in AD makes chelation therapy an attractive means of dampening the oxidative stress burden in neurons. The chelator desferrioxamine, FDA approved for iron overload, has shown some benefit in AD, but like many chelators, it has a host of adverse effects and substantial obstacles for tissue-specific targeting. Other chelators are under development and have shown various strengths and weaknesses. Here, we propose a novel system of chelation therapy through the use of nanoparticles. Nanoparticles conjugated to chelators show unique ability to cross the blood-brain barrier (BBB), chelate metals, and exit through the BBB with their corresponding complexed metal ions. This method may provide a safer and more effective means of reducing the metal load in neural tissue, thus attenuating the harmful effects of oxidative damage and its sequelae. Experimental procedures are presented in this chapter.

Chronic antioxidant therapy reduces oxidative stress in a mouse model of Alzheimer's disease

Oxidative modifications are a hallmark of oxidative imbalance in the brains of individuals with Alzheimer's, Parkinson's and prion diseases and their respective animal models. While the causes of oxidative stress are relatively well-documented, the effects of chronically reducing oxidative stress on cognition, pathology and biochemistry require further clarification. To address this, young and aged control and amyloid-beta protein precursor-over-expressing mice were fed a diet with added R-alpha lipoic acid for 10 months to determine the effect of chronic antioxidant administration on the cognition and neuropathology and biochemistry of the brain. Both wild type and transgenic mice treated with R-alpha lipoic acid displayed significant reductions in markers of oxidative modifications. On the other hand, R-alpha lipoic acid had little effect on Y-maze performance throughout the study and did not decrease end-point amyloid-beta load. These results suggest that, despite the clear role of oxidative stress in mediating amyloid pathology and cognitive decline in ageing and AbetaPP-transgenic mice, long-term antioxidant therapy, at levels within tolerable nutritional guidelines and which reduce oxidative modifications, have limited benefit.

Cellular and biochemical actions of melatonin which protect against free radicals: role in neurodegenerative disorders

Molecular oxygen is toxic for anaerobic organisms but it is also obvious that oxygen is poisonous to aerobic organisms as well, since oxygen plays an essential role for inducing molecular damage. Molecular oxygen is a triplet radical in its ground-stage (.O-O.) and has two unpaired electrons that can undergoes consecutive reductions of one electron and generates other more reactive forms of oxygen known as free radicals and reactive oxygen species. These reactants (including superoxide radicals, hydroxyl radicals) possess variable degrees of toxicity. Nitric oxide (NO*) contains one unpaired electron and is, therefore, a radical. NO* is generated in biological tissues by specific nitric oxide synthases and acts as an important biological signal. Excessive nitric oxide production, under pathological conditions, leads to detrimental effects of this molecule on tissues, which can be attributed to its diffusion-limited reaction with superoxide to form the powerful and toxic oxidant, peroxynitrite.Reactive oxygen and nitrogen species are molecular "renegades"; these highly unstable products tend to react rapidly with adjacent molecules, donating, abstracting, or even sharing their outer orbital electron(s). This reaction not only changes the target molecule, but often passes the unpaired electron along to the target, generating a second free radical, which can then go on to react with a new target amplifying their effects.This review describes the mechanisms of oxidative damage and its relationship with the most highly studied neurodegenerative diseases and the roles of melatonin as free radical scavenger and neurocytoskeletal protector.

Oxidative stress related changes in the brain of hypercholesterolemic rabbits

In recent years, there has been increasing evidence that cholesterol plays a role in the pathology of Alzheimer disease. Since hypercholesterolemia was reported to increase the levels of reactive oxygen species and Alzheimer disease has clearly involved an oxidative component, it is possible that hypercholesterolemia is via increased oxidant production facilitating the disease development of the neurodegenerative disease. Therefore, we tested in an established model of enhanced cholesterol feed in rabbits the effects of serum cholesterol increase on oxidative stress parameters as well in serum as in the brain. In addition to that we tested the effects of vitamin E on the cholesterol-induced oxidative stress. Since Alzheimer disease is largely connected with increased protein oxidation whereas cholesterol is rather connected with lipid peroxidation processes, we tested both protein carbonyl levels and the formation of malondialdehyde, a marker of lipid peroxidation. We could clearly demonstrate an increase in serum malondialdehyde due to high cholesterol feeding, which is accompanied by an increase in protein oxidation parameters in the brain, especially in the hippocampus. Therefore, we suggest that specific neuropathological changes occur during the feeding of hypercholesterolemic diet.

Diet and Alzheimer's disease

Alzheimer's disease (AD) is increasing in prevalence. There are no known preventive or curative measures. There is evidence that oxidative stress, homo-cysteine-related vitamins, fats, and alcohol have a role in the pathogenesis of AD. Some epidemiologic studies suggest that higher dietary intake of antioxidants, vitamins B(6), B(12), and folate, unsaturated fatty acids, and fish are related to a lower risk of AD, but reports are inconsistent. Modest to moderate alcohol intake, particularly wine, may be related to a lower risk of AD. The Mediterranean diet may also be related to lower AD risk. However, randomized clinical trials of supplements of vitamins E, B(12), B(6), and folate have shown no cognitive benefit, and randomized trials for other nutrients or diets in AD are not available. The existing evidence does not support the recommendation of specific supplements, foods, or diets for the prevention of AD.

Cellular therapy using microglial cells

Recent insights into the function and dysfunction of microglia may inform future therapies to combat neurodegeneration. We hypothesise how different aspects of microglial activity including migration, activation, oxidative response, phagocytosis, proteolysis, and replenishment could be targeted by novel therapeutic approaches. A combined approach is suggested, encompassing opsonization and anti-inflammatory strategies in conjunction with an engineering of microglial precursors. Xenoproteases for bioremediation could be used to enhance intracellular and extracellular proteolytic capacity. The capacity of microglial precursors to cross the blood-brain barrier and to home in on sites of neural damage and inflammation might prove to be particularly useful for future therapeutic strategies.

Hallmarks of protein oxidative damage in neurodegenerative diseases: focus on Alzheimer’s disease

The pathogenesis of several neurodegenerative diseases, including Alzheimer's disease, has been linked to a condition of oxidative and nitrosative stress, arising from the imbalance between increased reactive oxygen species (ROS) and reactive nitrogen species (RNS) production and antioxidant defences or efficiency of repair or removal systems. The effects of free radicals are expressed by the accumulation of oxidative damage to biomolecules: nucleic acids, lipids and proteins. In this review we focused our attention on the large body of evidence of oxidative damage to protein in Alzheimer's disease brain and peripheral cells as well as in their role in signalling pathways. The progress in the understanding of the molecular alterations underlying Alzheimer's disease will be useful in developing successful preventive and therapeutic strategies, since available drugs can only temporarily stabilize the disease, but are not able to block the neurodegenerative process.

Use of herbal preparations in the treatment of oxidant-mediated inflammatory disorders

Complementary and alternative medicine (CAM) use has increased in popularity in recent years and herbal therapy alone is now a billion dollar market. For centuries herbs have been used as food and for medicinal purposes. Various herbs have been identified as possessing anti-inflammatory and antioxidative properties, and they are currently being used to treat inflammatory disorders as well as those caused by reactive oxygen species (ROS). Asthma, Alzheimer's disease, inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and atherogenesis are all disorders where inflammation and ROS are involved in their pathogenesis. This review examines the pathogenesis of the above mentioned ROS-mediated inflammatory disorders, as well as discusses the antioxidant and anti-inflammatory mechanisms of various herbs and the clinical trials where herbs have been used to treat these disorders.

Protective effects of Glycyrrhiza uralensis Fisch. on the cognitive deficits caused by beta-amyloid peptide 25-35 in young mice

Amyloid beta protein (Abeta) may be involved in the progression of Alzheimer's disease (AD), by acting as a neurotoxin and eliciting oxidative stress. This study was designed to determine the effects of Glycyrrhiza uralensis Fisch. water extract (GWE) on the cognitive deficits and oxidative stress induced by the administration of Abeta(25-35) in mice. Mice in two of the four animal groups were fed an experimental diet containing either 0.5 or 1% GWE for the entire 6-week experimental period. Control mice and a further experimental group were fed a non-GWE diet. Abeta(25-35) was administered to the three experimental groups by intracerebroventricular (i.c.v.) injection (10 microg/10 microl/mouse) once per week in weeks 5 and 6 of the experimental period. Behavioral changes were assessed using both a passive avoidance (after the injection of Abeta(25-35) in week 5) and the Morris water-maze tests (after the injection of Abeta(25-35) in week 6). Control animals were administered vehicle alone. The prolonged consumption of a diet containing GWE ameliorated the cognitive deficits caused by the i.c.v. injections of Abeta(25-35). Treatment with Abeta(25-35) led to higher concentrations of thiobarbituric acid reactive substances in the brain, and GWE attenuated this response. There was a decrease in catalase activity in the group provided with 1% GWE. Acetylcholinesterase activity was significantly reduced in the brains of all GWE-treated animals compared to that in the non-GWE-fed experimental group. These results suggest that GWE exerts a protective effect against the cognitive impairments often observed in AD, and that in mice this effect is mediated by antioxidant actions against oxidative stress.

Tocopherol-mediated modulation of age-related changes in microglial cells: turnover of extracellular oxidized protein material

Proteins accumulate during aging and form insoluble protein aggregates. Microglia are responsible for their removal from the brain. During aging, changes within the microglia might play a crucial role in the malfunctioning of these cells. Therefore, we isolated primary microglial cells from adult rats and compared their activation status and their ability to degrade proteins to that of microglial cells isolated from newborn animals. The ability of adult microglial cells to degrade proteins is substantially decreased. However, the preincubation of microglial cells with vitamin E improves significantly the degradation of such modified proteins. The degradation of proteins from apoptotic vesicles is decreased in microglia isolated from adult rats. This might be the result of a suppression of the CD36 receptor due to vitamin E treatment. We concluded that microglial cells isolated from adult organisms have different metabolic properties and seem to be a more valuable model to study age-related diseases.

Nutritional factors, cognitive decline, and dementia

Nutritional factors and nutritional deficiencies have been repeatedly associated with cognitive impairment. Most of the evidence is based on cross-sectional studies, which cannot prove whether a nutritional deficit is the cause or the consequence of an impaired cognitive status. In fact, cognitive impairment, in turn, can determine changes in dietary habits and consequent nutritional deficiencies. We reviewed clinical and epidemiological studies from January 1983 to June 2004. Several cross-sectional and fewer prospective studies reported an association between dietary or supplemental intake of antioxidants and protection from cognitive decline and dementia. There are negative reports as well and some methodological biases might have affected the consistencies across studies. Deficiencies of several B vitamins have been associated with cognitive dysfunction in many observational studies. More recently, deficiencies of folate (B9) and cobalamine (B12) have been studied in relation to hyperhomocysteinemia as potential determinants of cognitive impairment, dementia, and Alzheimer's disease (AD). A small number of studies assessed the association between intake of macronutrients and cognitive function or dementia. Among the others, the intake of fatty acids and cholesterol has received particular attention. Although the results are not always consistent, most studies have reported a protective role of dietary intakes of poly- and mono-unsaturated fatty acids against cognitive decline and AD. We point out that well designed intervention studies are warranted in order to establish specific levels of micro- and macronutrient deficiencies and to set general recommendations for the population.

Effect of vitamin E on memory retention in rats: possible involvement of cholinergic system

This study concerned effects of vitamin E and the cholinergic system on memory retention of passive avoidance learning in rats. Post-training intracerebroventricular (i.c.v.) injections were carried out in all experiments. Administrations of vitamin E (10, 25 and 50 microg/rat), nicotine (0.1 microg/rat) and pilocarpine (0.5 microg/rat), the muscarinic receptor agonist increased memory retention, while mecamylamine (0.01, 0.1 and 0.5 microg/rat), the nicotinic receptor antagonist and scopolamine (0.1, 1 and 5 microg/rat), the muscarinic receptor antagonist decreased memory retention. The combination of vitamin E with nicotine or pilocarpine showed potentiation. Effects of mecamylamine or scopolamine were attenuated by vitamin E. It is concluded that vitamin E has a close interaction with cholinergic system in memory retention process.

Nanoparticle and other metal chelation therapeutics in Alzheimer disease

Current therapies for Alzheimer disease (AD) such as the anticholinesterase inhibitors and the latest NMDA receptor inhibitor, Namenda, provide moderate symptomatic delay at various stages of disease, but do not arrest disease progression or supply meaningful remission. As such, new approaches to disease management are urgently needed. Although the etiology of AD is largely unknown, oxidative damage mediated by metals is likely a significant contributor since metals such as iron, aluminum, zinc, and copper are dysregulated and/or increased in AD brain tissue and create a pro-oxidative environment. This role of metal ion-induced free radical formation in AD makes chelation therapy an attractive means of dampening the oxidative stress burden in neurons. The chelator desferioxamine, FDA approved for iron overload, has shown some benefit in AD, but like many chelators, it has a host of adverse effects and substantial obstacles for tissue-specific targeting. Other chelators are under development and have shown various strengths and weaknesses. In this review, we propose a novel system of chelation therapy through the use of nanoparticles. Nanoparticles conjugated to chelators show a unique ability to cross the blood-brain barrier (BBB), chelate metals, and exit through the BBB with their corresponding complexed metal ions. This method may prove to be a safe and effective means of reducing the metal load in neural tissue thus staving off the harmful effects of oxidative damage and its sequelae.

Is antioxidant use protective of cognitive function in the community-dwelling elderly?

BACKGROUND

The role of oxidative stress in the pathogenesis of diseases such as macular degeneration, certain types of cancer, and Alzheimer's disease has received much attention. Thus, there is considerable interest in the potential contribution of antioxidants to the prevention of these diseases.

OBJECTIVE

The objective of this study was to determine whether use of supplemental antioxidants (vitamins A, C, or E, plus selenium or zinc) was associated with a reduced risk of development of cognitive impairment or cognitive decline in a representative sample of the community-dwelling elderly.

METHODS

The sample consisted of 2082 nonproxy subjects from the Duke Established Populations for Epidemiologic Studies of the Elderly who were not cognitively impaired at the 1989-1990 interview (baseline for the present analysis). Medication use was determined during in-home interviews. Cognitive function was assessed 3 and 7 years from baseline in terms of incident cognitive impairment, as measured on the Short Portable Mental Status Questionnaire (SPMSQ) using specific cut points (number of errors) based on race and education, and cognitive decline, defined as an increase of > or = 2 errors on the SPMSQ. Multivariate analyses were performed using weighted data adjusted for sampling design and controlled for sociodemographic characteristics, health-related behaviors, and health status.

RESULTS

At baseline, 224 (10.8%) subjects were currently taking a supplement containing an antioxidant. During the follow-up period, 24.0% of subjects developed cognitive impairment and 34.5% experienced cognitive decline. Current antioxidant users had a 34.0% lower risk of developing cognitive impairment compared with non-antioxidant users (adjusted relative risk [RR], 0.66; 95% CI, 0.44-1.00) and a 29.0% lower risk of experiencing cognitive decline (adjusted RR, 0.71; 95% CI, 0.49-1.01).

CONCLUSION

The results of this analysis suggest a possible beneficial effect of antioxidant use in terms of reducing cognitive decline among the community-dwelling elderly.

Tocopherol (vitamin E) in Alzheimer's disease and other neurodegenerative disorders

In this article, we review the evidence that tocopherol (vitamin E) may have a role to play in the prevention and treatment of Alzheimer's disease and other neurological diseases. The theoretical rationale for the effectiveness of tocopherol as treatment and/or prevention of Alzheimer's disease is based on its antioxidant properties. Results from animal and in vitro studies provide evidence to support use of tocopherol for prevention and treatment of degenerative neurological diseases. Furthermore, several, but not all, epidemiological, cross-sectional, prospective studies indicate that tocopherol may have protective effects in Alzheimer's disease, although dietary and supplemental forms of the vitamin may differ in their efficacy. Mixed results have been obtained from clinical trials. Evidence of the use of tocopherol as a protective measure or as therapy in neurological diseases other than Alzheimer's disease is less compelling. To date, there are no clear-cut answers as to whether tocopherol is worth prescribing, but current clinical practice favours its use in the treatment of Alzheimer's disease.

Antioxidant treatment in Alzheimer's disease: current state

Accumulating data from experimental and human studies indicate that oxidative stress (OS) plays a major role in the pathogenesis of Alzheimer's disease (AD). The production of reactive oxygen species (ROS), which leads to OS, can occur very early, even before the appearance of symptoms and molecular events (beta-amyloid plaques and neurofibrillary tangles), leading to tissue damage via several different cellular molecular pathways. ROS can cause damage to cardinal cellular components such as lipids, proteins, and nucleic acids (e.g., RNA, DNA), causing cell death by modes of necrosis or apoptosis. The damage can become more widespread because of the weakened cellular antioxidant defense systems. Therefore, treatment with antioxidants might theoretically act to prevent propagation of tissue damage and improve both survival and neurological outcome. Indeed, several studies preformed to date examined whether dietary intake of several antioxidants, mainly vitamins, might prevent or reduce the progression of AD. Although a few of the antioxidants showed some efficacy in these trials, no answer is yet available as to whether antioxidants are truly protective against AD. Reasons for these results might include, in part, blood-brain barrier (BBB) permeability, inappropriate timing of administration, or suboptimal drug levels at the target site in the central nervous system. Thus, antioxidant cocktails or antioxidants combined with other drugs may have more successful synergistic effects. Further, well-designed intervention, as well as observational investigations based on large cohorts studied over a long period of time with several methods for assessing antioxidant exposure, including relation to BBB penetration, are needed to test this hypothesis.

Dietary factors and Alzheimer's disease

Alzheimer's disease (AD) is increasing in prevalence, and environmental risk factors have not been identified with certainty. There is evidence that oxidative stress, homocysteine-related vitamins, fats, and alcohol have a role in the pathogenesis of AD. Few large epidemiological studies have explored the associations between nutrients and AD, and there has been only one trial of vitamin E in the prevention of AD. Some studies suggest that high intake of vitamins C, E, B6, and B12, and folate, unsaturated fatty acids, and fish are related to a low risk of AD, but reports are inconsistent. Modest to moderate alcohol intake, particularly wine, may be related to a low risk of AD. Available data do not permit definitive conclusions regarding diet and AD or specific recommendations on diet modification for the prevention of AD.

Metals in our minds: therapeutic implications for neurodegenerative disorders

BACKGROUND

Abnormal interactions of copper or iron in the brain with metal-binding proteins (such as amyloid-beta peptide [Abeta] or neuromelanin) that lead to oxidative stress have emerged as important potential mechanisms in brain ageing and neurodegenerative disorders. Although a controlled study of desferrioxamine in Alzheimer's disease(AD) had some promising results, concerns about toxicity and brain delivery have limited trials of traditional chelators. The therapeutic significance of metal dysregulation in neurodegenerative disorders has remained difficult to test.

RECENT DEVELOPMENTS

Clioquinol was identified as a prototype metal-protein-attenuating compound (MPAC). In a blinded and controlled 9 week study of a mouse model of AD, oral clioquinol decreased brain Abeta by 49% without systemic toxicity. The concentrations of copper and zinc in the brain rose by about 15% in mice treated with clioquinol. Two other studies in mice showed that the raising of brain copper concentrations through diet or genetics could lower amyloid load and increase survival. A recent placebo-controlled trial in 36 patients with AD showed that clioquinol (250-750 mg daily) reduced plasma concentrations of Abeta(1-42), raised plasma concentrations of zinc, and-in a subset with moderate dementia-slowed cognitive decline over 24 weeks. Two recent experiments also showed the neuroprotective effects of iron chelation in a mouse model of Parkinson's disease. WHERE NEXT?: The experimental and transgenic-animal studies of metal-protein interactions are convincing but do not provide conclusive answers either about causality or whether this strategy will protect against neurodegeneration in human beings. The finding that clioquinol could modulate plasma concentrations of amyloid and cognition in patients with AD needs to be interpreted cautiously, but is an important first step. Clioquinol was withdrawn because of concerns of its association with subacute myelo-optic neuropathy in Japan; therefore, any additional studies with this drug will likely be small and closely monitored proof-of-concept studies. The development of optimal second-generation MPACs is a desirable goal and may permit greater insights into the significance of metal-protein interactions across several neurodegenerative disorders.

Alcohol intake and risk of dementia

OBJECTIVES

To examine the association between intake of alcoholic beverages and risk of Alzheimer's disease (AD) and dementia associated with stroke (DAS) in a cohort of elderly persons from New York City.

DESIGN

Cohort study.

SETTING

The Washington Heights Inwood-Columbia Aging Project.

PARTICIPANTS

Nine hundred eighty community-dwelling individuals aged 65 and older without dementia at baseline and with data on alcohol intake recruited between 1991 and 1996 and followed annually.

MEASUREMENTS

Intake of alcohol was measured using a semiquantitative food frequency questionnaire at baseline. Subjects were followed annually, and incident dementia was diagnosed using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria and classified as AD or DAS.

RESULTS

After 4 years of follow-up, 260 individuals developed dementia (199 AD, 61 DAS). After adjusting for age, sex, apolipoprotein E (APOE)-epsilon 4 status, education, and other alcoholic beverages, only intake of up to three daily servings of wine was associated with a lower risk of AD (hazard ratio=0.55, 95% confidence interval=0.34-0.89). Intake of liquor, beer, and total alcohol was not associated with a lower risk of AD. Stratified analyses by the APOE-epsilon 4 allele revealed that the association between wine consumption and lower risk of AD was confined to individuals without the APOE-epsilon 4 allele.

CONCLUSIONS

Consumption of up to three servings of wine daily is associated with a lower risk of AD in elderly individuals without the APOE epsilon-4 allele.

Ginkgo biloba prevents mobile phone-induced oxidative stress in rat brain

BACKGROUND

The widespread use of mobile phones (MP) in recent years has raised the research activities in many countries to determine the consequences of exposure to the low-intensity electromagnetic radiation (EMR) of mobile phones. Since several experimental studies suggest a role of reactive oxygen species (ROS) in EMR-induced oxidative damage in tissues, in this study, we investigated the effect of Ginkgo biloba (Gb) on MP-induced oxidative damage in brain tissue of rats.

METHODS

Rats (EMR+) were exposed to 900 MHz EMR from MP for 7 days (1 h/day). In the EMR+Gb groups, rats were exposed to EMR and pretreated with Gb. Control and Gb-administrated groups were produced by turning off the mobile phone while the animals were in the same exposure conditions. Subsequently, oxidative stress markers and pathological changes in brain tissue were examined for each groups.

RESULTS

Oxidative damage was evident by the: (i) increase in malondialdehyde (MDA) and nitric oxide (NO) levels in brain tissue, (ii) decrease in brain superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and (iii) increase in brain xanthine oxidase (XO) and adenosine deaminase (ADA) activities. These alterations were prevented by Gb treatment. Furthermore, Gb prevented the MP-induced cellular injury in brain tissue histopathologically.

CONCLUSION

Reactive oxygen species may play a role in the mechanism that has been proposed to explain the biological side effects of MP, and Gb prevents the MP-induced oxidative stress to preserve antioxidant enzymes activity in brain tissue.

Activation of microglia: a neuroinflammatory role for CAP37

Recent evidence suggests that inflammation and immune function in the central nervous system (CNS) may play a considerable role in the progression of many neurodegenerative diseases. It is known that microglia, the CNS equivalent of peripheral blood monocytes, may be instrumental in causing neurotoxicity. However, the mediator(s) that activates microglia to produce toxic substances that orchestrate cell death has yet to be elucidated. We have identified a novel inflammatory molecule, cationic antimicrobial protein of molecular weight 37 kDa (CAP37), to the brains of patients dying from Alzheimer's disease. CAP37 is known to be a potent activator and regulator of monocyte function in the systemic circulation. We hypothesize that CAP37, a mediator previously shown to recruit and activate monocytes in the systemic circulation, may also play a role in CNS inflammation by modulating microglial function. Here we demonstrate that CAP37 is a chemoattractant for microglia and that CAP37-treated microglia express class II major histocompatibility antigens and produce proinflammatory cytokines and chemokines. We conclude that CAP37 has the ability to activate microglial cells and suggest that it has the potential to serve as a neuroinflammatory molecule.

Prodrug and covalent linker strategies for the solubilization of dual-action antioxidants/iron chelators

Water soluble prodrugs of hybrid free radical scavenger/iron chelating molecules, based on 3,5-disubstituted-4-hydroxyphenyl derivatives and 3-hydroxy-2-methyl-4(1H)-pyridinone (deferiprone), have been prepared. Related hybrid molecules containing a covalent poly(ethylene)glycol or an amine linker were also synthesized.

Neuroplasticity in Alzheimer's disease

Ramon y Cajal proclaimed in 1928 that "once development was ended, the founts of growth and regeneration of the axons and dendrites dried up irrevocably. In the adult centers the nerve paths are something fixed, ended and immutable. Everything must die, nothing may be regenerated. It is for the science of the future to change, if possible, this harsh decree." (Ramon y Cajal, 1928). In large part, despite the extensive knowledge gained since then, the latter directive has not yet been achieved by 'modern' science. Although we know now that Ramon y Cajal's observation on CNS plasticity is largely true (for lower brain and primary cortical structures), there are mechanisms for recovery from CNS injury. These mechanisms, however, may contribute to the vulnerability to neurodegenerative disease. They may also be exploited therapeutically to help alleviate the suffering from neurodegenerative conditions.

Antioxidants and Alzheimer's disease: from bench to bedside (and back again)

PURPOSE OF REVIEW

Accumulating evidence from both animal and human studies indicates a major role for oxidative damage in the pathogenesis of Alzheimer's disease, occurring even before symptoms arise and both beta-amyloid-containing plaques and neurofibrillary tangles are formed. This raises the possibility of preventing, or at least slowing down, the progression of Alzheimer's disease by the use of antioxidants. In this review, we present recent studies on the association between oxidative stress and Alzheimer's disease pathology, and on the efficacy of dietary, exogenous antioxidants to prevent or attenuate the progression of Alzheimer's disease.

RECENT FINDINGS

Recent prospective studies have indicated that dietary intake of several exogenous antioxidants is associated with a lower risk for Alzheimer's disease. This suggests that people at risk for developing Alzheimer's disease or being in the early phases of this disease may benefit from intervention with exogenous antioxidants. The clinical studies carried out so far, however, do not provide the final answer to whether antioxidants are truly protective against Alzheimer's disease.

SUMMARY

There is compelling evidence that oxidative stress is involved in Alzheimer's disease pathogenesis, and several lines of evidence indicate that administration of antioxidants may be useful in prevention and treatment of Alzheimer's disease. Further clinical studies, based on larger cohorts studied over a longer period of time, are needed, however, to test this hypothesis. Furthermore, for the future one might expect balanced upregulation of both exogenous and endogenous antioxidants as one of the best treatment strategies for preventing or at least slowing down the progression of Alzheimer's disease.

Cognitive and motor symptoms in dementia: focus on dementia with Lewy bodies

PURPOSE

To describe the clinical syndrome called dementia with Lewy bodies (DLB) and highlight its common and unique characteristics with respect to diagnosis and management.

DATA SOURCES

Review of the scientific literature including psychiatric literature, reports of clinical trials, and clinical practice guidelines.

CONCLUSIONS

DLB is a clinical and histopathologic disease, which is second only to Alzheimer's disease (AD) as a cause of dementia in older adults. The clinical syndrome of DLB includes cognitive and motor deterioration reminiscent of symptoms associated with AD and Parkinson's disease (PD) respectively.

IMPLICATIONS FOR PRACTICE

The late life intersection of cognitive and motor symptoms can present significant challenges in the primary care setting. Recognizing key features of common neurodegenerative disorders is essential to accurately diagnosing and appropriately treating the growing population of older adults who suffer from AD, PD, and DLB.