Oxidative stress in Alzheimer's disease
TL;DR: This review discusses free radical-mediated damage to the biochemical components involved in the pathology and clinical symptoms of Alzheimer's disease and explains how amyloid beta-protein, microtubule-associated protein tau, presenilins, apolipoprotein E, mitochondria and proteases play a role in increasing oxidative stress in AD.
About: This article is published in Pathophysiology.The article was published on 2006-08-01. It has received 318 citations till now. The article focuses on the topics: Oxidative stress & Neurofibrillary tangle.
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TL;DR: The role of oxidative stress in synaptic dysfunction in AD, innovative therapeutic strategies evolved based on a better understanding of the complexity of molecular mechanisms of AD, and the dual role ROS play in health and disease are discussed.
Abstract: Alzheimer's disease (AD) is a devastating neurodegenerative disorder without a cure. Most AD cases are sporadic where age represents the greatest risk factor. Lack of understanding of the disease mechanism hinders the development of efficacious therapeutic approaches. The loss of synapses in the affected brain regions correlates best with cognitive impairment in AD patients and has been considered as the early mechanism that precedes neuronal loss. Oxidative stress has been recognized as a contributing factor in aging and in the progression of multiple neurodegenerative diseases including AD. Increased production of reactive oxygen species (ROS) associated with age- and disease-dependent loss of mitochondrial function, altered metal homeostasis, and reduced antioxidant defense directly affect synaptic activity and neurotransmission in neurons leading to cognitive dysfunction. In addition, molecular targets affected by ROS include nuclear and mitochondrial DNA, lipids, proteins, calcium homeostasis, mitochondrial dynamics and function, cellular architecture, receptor trafficking and endocytosis, and energy homeostasis. Abnormal cellular metabolism in turn could affect the production and accumulation of amyloid-β (Aβ) and hyperphosphorylated Tau protein, which independently could exacerbate mitochondrial dysfunction and ROS production, thereby contributing to a vicious cycle. While mounting evidence implicates ROS in the AD etiology, clinical trials with antioxidant therapies have not produced consistent results. In this review, we will discuss the role of oxidative stress in synaptic dysfunction in AD, innovative therapeutic strategies evolved based on a better understanding of the complexity of molecular mechanisms of AD, and the dual role ROS play in health and disease.
967 citations
TL;DR: In this article, the authors investigated the role of oxidative stress in the early stages of Alzheimer's disease in a triple-transgenic mouse model and showed that the levels of antioxidants, namely, reduced glutathione and vitamin E, are decreased and the extent of lipid peroxidation is increased.
304 citations
Cites background from "Oxidative stress in Alzheimer's dis..."
...SOD, GPx, and GRd are three enzymes involved in cellular protection against damage induced by oxygen-derived free radicals [14]....
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...Oxidative stress can be due to either an increase in ROS production or a decrease in the activity of the antioxidant enzymes such as SOD and GPx or nonenzymatic antioxidants, namely, vitamin E or GSH [14]....
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...Manganese-SOD detoxifies superoxide anion (O2−) to give H2O2, which is then converted into H2O by either GPx or catalase [14]....
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...Aβ-mediated oxidative stress can be due to either an increase in reactive oxygen species (ROS) production or a decrease in the endogenous antioxidants, namely, in the activity of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) and of nonenzymatic antioxidants such as vitamin E and GSH [14]....
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...GSH is one of the most relevant cellular nonenzymatic antioxidants [14]....
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TL;DR: There was a strong correlation between the reducing power and the total phenolic content of the seaweeds methanolic dry extracts and these seaweeds could be potential rich sources of natural antioxidants.
Abstract: The antioxidant activity of eight edible species of Malaysian North Borneo seaweeds obtained from Sabah waters (Kudat, Tanjung Aru and Semporna) consisting of three red seaweeds (Eucheuma cottonii, E. spinosum and Halymenia durvillaei), two green seaweeds (Caulerpa lentillifera and C. racemosa) and three brown seaweeds (Dictyota dichotoma, Sargassum polycystum and Padina sp.) were determined. Methanol and diethyl ether were used as extraction solvent. The antioxidant activities were determined by two methods, TEAC (trolox equivalent antioxidant capacity) and FRAP (ferric reducing antioxidant power) assays. The total phenolic content of the extract was determined according to the Folin–Ciocalteu method and results were expressed as phloroglucinol equivalents. The methanolic extracts of green seaweeds, C. lentillifera and C. racemosa, and the brown seaweed, S. polycystum showed better radical-scavenging and reducing power ability, and higher phenolic content than the other seaweeds. The TEAC and FRAP assays showed positive and significantly high correlation (R
2 = 0.89). There was a strong correlation (R
2 = 0.96) between the reducing power and the total phenolic content of the seaweeds methanolic dry extracts. These seaweeds could be potential rich sources of natural antioxidants.
297 citations
TL;DR: The data indicate that significant reductions in spatial learning deficits of aged APP/PS1 mice in a Morris Water Maze can be achieved by modulating levels of NRF2 in the brain and suggest that the Nrf2-ARE pathway may represent a potential therapeutic strategy to pursue in AD in humans, particularly in view of the multiple mechanisms by which Nrf1 can exert its protective effects.
Abstract: The amyloid hypothesis of Alzheimer's disease (AD) postulates that amyloid-β (Aβ) deposition and neurotoxicity play a causative role in AD; oxidative injury is thought to be central in the pathogenesis. An endogenous defense system against oxidative stress is induced by binding of the transcription factor nuclear factor E2-related factor 2 (Nrf2) to the antioxidant response element (ARE) enhancer sequence. The Nrf2-ARE pathway is activated in response to reactive oxygen species to trigger the simultaneous expression of numerous protective enzymes and scavengers. To exploit the Nrf2-ARE pathway therapeutically, we delivered Nrf2 bilaterally into the hippocampus of 9-month-old transgenic AD mice (APP/PS1 mice) using a lentiviral vector encoding human Nrf2. The data indicate that significant reductions in spatial learning deficits of aged APP/PS1 mice in a Morris Water Maze can be achieved by modulating levels of Nrf2 in the brain. Memory improvement in APP/PS1 mice after Nrf2 transduction shifts the balance between soluble and insoluble Aβ toward an insoluble Aβ pool without concomitant change in total brain Aβ burden. Nrf2 gene transfer is associated with a robust reduction in astrocytic but not microglial activation and induction of Nrf2 target gene heme oxygenase 1, indicating overall activation of the Nrf2-ARE pathway in hippocampal neurons 6 months after injection. Results warrant further exploration of the Nrf2-ARE pathway for treatment of AD and suggest that the Nrf2-ARE pathway may represent a potential therapeutic strategy to pursue in AD in humans, particularly in view of the multiple mechanisms by which Nrf2 can exert its protective effects.
261 citations
TL;DR: It is shown that treatment with resveratrol prevents the increase in AChE activity and consequently memory impairment in diabetic rats, demonstrating that this compound can modulate cholinergic neurotransmission and consequently improve cognition.
223 citations
Cites background from "Oxidative stress in Alzheimer's dis..."
...…AChE responds to various insults including oxidative stress, an important event that has been related to the pathogenesis and progression of a variety of CNS disorders, such as stroke (Ozkul et al., 2007), Alzheimer's diseases (Chauhan and Chauhan, 2006) and diabetes mellitus (Kuhad et al., 2008)....
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..., 2007), Alzheimer's diseases (Chauhan and Chauhan, 2006) and diabetes mellitus (Kuhad et al....
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References
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TL;DR: It seems possible that one factor in aging may be related to deleterious side attacks of free radicals (which are normally produced in the course of cellular metabolism) on cell constituents.
Abstract: The phenomenon of growth, decline and death—aging—has been the source of considerable speculation (1, 8, 10). This cycle seems to be a more or less direct function of the metabolic rate and this in turn depends on the species (animal or plant) on which are superimposed the factors of heredity and the effects of the stresses and strains of life—which alter the metabolic activity. The universality of this phenomenon suggests that the reactions which cause it are basically the same in all living things. Viewing this process in the light of present day free radical and radiation chemistry and of radiobiology, it seems possible that one factor in aging may be related to deleterious side attacks of free radicals (which are normally produced in the course of cellular metabolism) on cell constituents.* Irradiation of living things induces mutation, cancer, and aging (9). Inasmuch as these also arise spontaneously in nature, it is natural to inquire if the processes might not be similar. It is believed that one mechanism of irradiation effect is through liberation of OH and HO 2 radicals (12). There is evidence, although indirect, that these two highly active free radicals are produced normally in living systems. In the first place, free radicals are present in living cells; this was recently demonstrated in vivo by a paramagnetic resonance absorption method (3). Further, it was shown that the concentration of free radicals increased with increasing metabolic activity in conformity with the postulates set forth some years ago that free radicals were involved in biologic oxidation-reduction reactions (11, 13). Are some of these free radicals OH and/or HO2, or radicals of a similar high order of reactivity, and where might they arise in the cell? The most likely source of OH and HO2 radicals, at least in the animal cell, would be the interaction of the respiratory enzymes involved
7,917 citations
TL;DR: An apparently full-length complementary DNA clone coding for the A4 polypeptide is isolated and sequenced and suggests that the cerebral amyloid deposited in Alzheimer's disease and aged Down's syndrome is caused by aberrant catabolism of a cell-surface receptor.
Abstract: Alzheimer's disease is characterized by a widespread functional disturbance of the human brain. Fibrillar amyloid proteins are deposited inside neurons as neurofibrillary tangles and extracellularly as amyloid plaque cores and in blood vessels. The major protein subunit (A4) of the amyloid fibril of tangles, plaques and blood vessel deposits is an insoluble, highly aggregating small polypeptide of relative molecular mass 4,500. The same polypeptide is also deposited in the brains of aged individuals with trisomy 21 (Down's syndrome). We have argued previously that the A4 protein is of neuronal origin and is the cleavage product of a larger precursor protein. To identify this precursor, we have now isolated and sequenced an apparently full-length complementary DNA clone coding for the A4 polypeptide. The predicted precursor consists of 695 residues and contains features characteristic of glycosylated cell-surface receptors. This sequence, together with the localization of its gene on chromosome 21, suggests that the cerebral amyloid deposited in Alzheimer's disease and aged Down's syndrome is caused by aberrant catabolism of a cell-surface receptor.
4,603 citations
"Oxidative stress in Alzheimer's dis..." refers background in this paper
...[13] J....
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...Butterfield, Amyloid beta-peptide [1-42]-associated free radical-induced oxidative stress and neurodegeneration in Alzheimer’s disease brain: mechanisms and consequences, Curr....
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...F d W r p r A is produced by the proteolytic cleavage of membranessociated -amyloid precursor protein (APP) [13]....
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TL;DR: The shared 4-kDa subunit indicates a common origin for the amyloids of the plaque core and of the congophilic angiopathy of Alzheimer disease and Down syndrome.
Abstract: We have purified and characterized the cerebral amyloid protein that forms the plaque core in Alzheimer disease and in aged individuals with Down syndrome. The protein consists of multimeric aggregates of a polypeptide of about 40 residues (4 kDa). The amino acid composition, molecular mass, and NH2-terminal sequence of this amyloid protein are almost identical to those described for the amyloid deposited in the congophilic angiopathy of Alzheimer disease and Down syndrome, but the plaque core proteins have ragged NH2 termini. The shared 4-kDa subunit indicates a common origin for the amyloids of the plaque core and of the congophilic angiopathy. There are superficial resemblances between the solubility characteristics of the plaque core and some of the properties of scrapie infectivity, but there are no similarities in amino acid sequences between the plaque core and scrapie polypeptides.
4,327 citations
"Oxidative stress in Alzheimer's dis..." refers background in this paper
...[3] C....
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...AD pathology is often observed in adult DS patients [3]....
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...The major amyloid protein in AD and also in adult Down syndrome (DS) is amyloid beta-protein (A ) of 39–43 amino acids [3]....
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...Butterfield, Amyloid beta-peptide [1-42]-associated free radical-induced oxidative stress and neurodegeneration in Alzheimer’s disease brain: mechanisms and consequences, Curr....
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TL;DR: Overexpression of a transmembrane aspartic protease, termed BACE (for beta-site APP-cleaving enzyme) increased the amount of beta-secretase cleavage products, and these were cleaved exactly and only at known beta- secretase positions.
Abstract: Cerebral deposition of amyloid beta peptide (Abeta) is an early and critical feature of Alzheimer's disease. Abeta generation depends on proteolytic cleavage of the amyloid precursor protein (APP) by two unknown proteases: beta-secretase and gamma-secretase. These proteases are prime therapeutic targets. A transmembrane aspartic protease with all the known characteristics of beta-secretase was cloned and characterized. Overexpression of this protease, termed BACE (for beta-site APP-cleaving enzyme) increased the amount of beta-secretase cleavage products, and these were cleaved exactly and only at known beta-secretase positions. Antisense inhibition of endogenous BACE messenger RNA decreased the amount of beta-secretase cleavage products, and purified BACE protein cleaved APP-derived substrates with the same sequence specificity as beta-secretase. Finally, the expression pattern and subcellular localization of BACE were consistent with that expected for beta-secretase. Future development of BACE inhibitors may prove beneficial for the treatment of Alzheimer's disease.
3,879 citations
TL;DR: The APOE∈4 allele represents a major risk factor for AD in all ethnic groups studied, across all ages between 40 and 90 years, and in both men and women.
Abstract: Objective. —To examine more closely the association between apolipoprotein E (APOE) genotype and Alzheimer disease (AD) by age and sex in populations of various ethnic and racial denominations. Data Sources. —Forty research teams contributed data onAPOEgenotype, sex, age at disease onset, and ethnic background for 5930 patients who met criteria for probable or definite AD and 8607 controls without dementia who were recruited from clinical, community, and brain bank sources. Main Outcome Measures. —Odds ratios (ORs) and 95% confidence intervals (Cls) for AD, adjusted for age and study and stratified by major ethnic group (Caucasian, African American, Hispanic, and Japanese) and source, were computed forAPOEgenotypes ∈2/∈2,∈2/∈3,∈2/∈4,∈3/∈4 and ∈4/∈4 relative to the ∈3/∈3 group. The influence of age and sex on the OR for each genotype was assessed using logistic regression procedures. Results. —Among Caucasian subjects from clinic- or autopsy-based studies, the risk of AD was significantly increased for people with genotypes ∈2/∈4 (OR=2.6, 95% Cl=1.6-4.0), ∈3/∈4 (OR=3.2, 95% Cl=2.8-3.8), and ∈4/∈4 (OR=14.9, 95% CI=10.8-20.6); whereas, the ORs were decreased for people with genotypes ∈2/∈2 (OR=0.6, 95% Cl=0.2-2.0) and ∈2/∈3 (OR=0.6, 95% Cl=0.5-0.8). TheAPOE∈4-AD association was weaker among African Americans and Hispanics, but there was significant heterogeneity in ORs among studies of African Americans (P Conclusions. —TheAPOE∈4 allele represents a major risk factor for AD in all ethnic groups studied, across all ages between 40 and 90 years, and in both men and women. The association betweenAPOE∈4 and AD in African Americans requires clarification, and the attenuated effect ofAPOE∈4 in Hispanics should be investigated further.
3,825 citations