Biomedical subjects

William R Markesbery

Publications and source records attributed to William R Markesbery.

49 records · Page 3Linked to original sources

PubMed2003

Head circumference, education and risk of dementia: findings from the Nun Study.

To examine the prevalence of dementia associated with having a smaller brain, lower education or both of these characteristics, 294 Catholic sisters were assessed annually for dementia. Sixty participants died and their brains were evaluated to determine fulfillment of neuropathological criteria for Alzheimer's disease (AD). Lower educational attainment and the interaction of smaller head circumference with lower education were associated with the presence of dementia, controlling for age and the presence of one or more apolipoprotein E-epsilon 4 alleles. By contrast, neither low educational attainment nor head circumference was significantly associated with fulfillment of neuropathological criteria for AD. Individuals having both low education and small head circumference were four times as likely to be demented as the rest of the sample. The findings suggest that higher education and larger head size, alone or in combination, may reduce the risk of expressing dementia in late life.

Aged↗

PubMed2003

Autoantibodies to amyloid beta-peptide (Abeta) are increased in Alzheimer's disease patients and Abeta antibodies can enhance Abeta neurotoxicity: implications for disease pathogenesis and vaccine development.

Studies of amyloid precursor protein transgenic mice suggest that immune responses to amyloid beta peptide (Abeta) may be instrumental in the removal of plaques from the brain, but the initial clinical trial of an Abeta vaccine in patients with Alzheimer s disease (AD) was halted as the result of serious neurological complications in some patients. We now provide evidence that AD patients exhibit an enhanced immune response to Abeta and that, contrary to expectations, Abeta antibodies enhance the neurotoxic activity of the peptide. Serum titers to Abeta were significantly elevated in AD patients and Abeta antibodies were found in association with amyloid plaques in their brains, but there was no evidence of cell-mediated immune responses to Abeta in the patients. Abeta antibodies were detected in the serum of old APP mutant transgenic mice with plaque-like Abeta deposits, but not in the serum of younger transgenic or nontransgenic mice. Serum from APP mutant mice potentiated the neurotoxicity of Abeta. Our data suggest that a humoral immune response to Abeta in AD patients may promote neuronal degeneration, a process with important implications for the future of vaccine-based therapies for AD.

Aged↗

PubMed2003

Protection against amyloid beta peptide and iron/hydrogen peroxide toxicity by alpha lipoic acid.

Current evidence supports the role of oxidative stress in the pathogenesis of neuron degeneration in Alzheimer's disease (AD). alpha-Lipoic acid (LA), an essential cofactor in mitochondrial dehydrogenase reactions, functions as an antioxidant and reduces oxidative stress in aged animals. Here, we describe the effects of LA and its reduced form, dihydrolipoic acid (DHLA), in neuron cultures treated with amyloid beta-peptide (Abeta 25-35) and iron/hydrogen peroxide (Fe/H2O2). Pretreatment of dissociated primary hippocampal cultures with LA significantly protected against Abeta and Fe/H2O2 toxicity. In contrast, concomitant treatment of cultures with LA and Fe/H2O2 significantly potentiated the toxicity. Decreased cell survival in cultures treated concomitantly with LA and Fe/H2O2 correlated with increased free radical production measured by dichlorofluorescein fluorescence. Treatment of cortical neurons with DHLA significantly protected glucose-transport against Fe/H2O2 or beta-mediated decreases although treatment with LA did not provide protection. These data suggest that DHLA, the reduced form of LA, significantly protects against both Abeta and Fe/H2O2 mediated toxicity. The data also suggest that concomitant exposure to LA and Fe/H2O2 significantly potentiates the oxidative stress. Overall, these data suggest that the oxidation state of LA is critical to its function and that in the absence of studies of LA/DHLA equilibria in human brain the use of LA as an antioxidant in disorders where there is increased Fe such as AD is of questionable efficacy.

Alzheimer Disease↗

PubMed2002

Lipid peroxidation in aging brain and Alzheimer's disease.

Lipid peroxidation is one of the major outcomes of free radical-mediated injury that directly damages membranes and generates a number of secondary products, both from fission and endocyclization of oxygenated fatty acids that possess neurotoxic activity. Numerous studies have demonstrated increased lipid peroxidation in brain of patients with Alzheimer's disease (AD) compared with age-matched controls. These data include quantification of fission and endocyclized products such as 4-hydroxy-2-nonenal, acrolein, isoprostanes, and neuroprostanes. Immunohistochemical and biochemical studies have localized the majority of lipid peroxidation products to neurons. A few studies have consistently demonstrated increased cerebrospinal fluid (CSF) levels of isoprostanes in AD patients early in the course of their dementia, and one study has suggested that CSF isoprostanes may improve the laboratory diagnostic accuracy for AD. Similar analyses of control individuals over a wide range of ages indicate that brain lipid peroxidation is not a significant feature of usual aging. Quantification of isoprostanes in plasma and urine of AD patients has yielded inconsistent results. These results indicate that brain lipid peroxidation is a potential therapeutic target in probable AD patients, and that CSF isoprostanes may aid in the assessment of antioxidant experimental therapeutics and the laboratory diagnosis of AD.

Adult↗

PubMed2002

Proteomic identification of oxidatively modified proteins in Alzheimer's disease brain. Part I: creatine kinase BB, glutamine synthase, and ubiquitin carboxy-terminal hydrolase L-1.

Oxidative alterations of proteins by reactive oxygen species (ROS) have been implicated in the progression of aging and age-related neurodegenerative disorders such as Alzheimer's disease (AD). Protein carbonyls, a marker of protein oxidation, are increased in AD brain, indicating that oxidative modification of proteins is relevant in AD. Oxidative damage can lead to several events such as loss in specific protein function, abnormal protein clearance, depletion of the cellular redox-balance and interference with the cell cycle, and, ultimately, to neuronal death. Identification of specific targets of protein oxidation represents a crucial step in establishing a relationship between oxidative modification and neuronal death in AD, and was partially achieved previously in our laboratory through immunochemical detection of creatine kinase BB and beta-actin as specifically oxidized proteins in AD brain versus control brain. However, this process is laborious, requires the availability of specific antibodies, and, most importantly, requires a reasonable guess as to the identity of the protein in the first place. In this study, we present the first proteomics approach to identify specifically oxidized proteins in AD, by coupling 2D fingerprinting with immunological detection of carbonyls and identification of proteins by mass spectrometry. The powerful techniques, emerging from application of proteomics to neurodegenerative disease, reveal the presence of specific targets of protein oxidation in Alzheimer's disease (AD) brain: creatine kinase BB, glutamine synthase, and ubiquitin carboxy-terminal hydrolase L-1. These results are discussed with reference to potential involvement of these oxidatively modified proteins in neurodegeneration in AD brain. Proteomics offers a rapid means of identifying oxidatively modified proteins in aging and age-related neurodegenerative disorders without the limitations of the immunochemical detection method.

Alzheimer Disease↗

PubMed2002

Alzheimer's neurofibrillary pathology and the spectrum of cognitive function: findings from the Nun Study.

The development of interventions designed to delay the onset of dementia highlights the need to determine the neuropathologic characteristics of individuals whose cognitive function ranges from intact to demented, including those with mild cognitive impairments. We used the Braak method of staging Alzheimer's disease pathology in 130 women ages 76-102 years who were participants in the Nun Study, a longitudinal study of aging and Alzheimer's disease. All participants had complete autopsy data and were free from neuropathologic conditions other than Alzheimer's disease lesions that could affect cognitive function. Findings showed a strong relationship between Braak stage and cognitive state. The presence of memory impairment was associated with more severe Alzheimer's disease pathology and higher incidence of conversion to dementia in the groups classified as having mild or global cognitive impairments. In addition to Braak stage, atrophy of the neocortex was significantly related to the presence of dementia. Our data indicate that Alzheimer's neurofibrillary pathology is one of the neuropathologic substrates of mild cognitive impairments. Additional studies are needed to help explain the variability in neuropathologic findings seen in individuals whose cognitive performance falls between intact function and dementia.

Aged↗

PubMed2002

The nitration product 5-nitro-gamma-tocopherol is increased in the Alzheimer brain.

Oxidative stress and quasi-inflammatory processes recently have been recognized as contributing factors in the pathogenesis of Alzheimer's disease (AD). Reactive nitrating species have specifically been implicated in AD based on immunochemical and instrumental detection of nitrotyrosine in AD brain protein. The significance of lipid-phase nitration has not been investigated in AD. This study documents a significant two- to threefold increase in the lipid nitration product 5-nitro-gamma-tocopherol in affected regions of the AD brain as determined by high-performance liquid chromatography with electrochemical detection. In a bioassay to compare the relative potency of alpha-tocopherol and gamma-tocopherol against nitrative stress, rat brain mitochondria were exposed to the peroxynitrite-generating compound SIN-1. The oxidation-sensitive Kreb's cycle enzyme alpha-ketoglutarate dehydrogenase was inactivated by SIN-1, in a manner that could be significantly attenuated by gamma-tocopherol (at <10 microM) but not by alpha-tocopherol. These data indicate that nitric oxide-derived species are significant contributors to lipid oxidation in the AD brain. The findings are discussed in reference to the neuroinflammatory hypothesis of AD and the possible role of gamma-tocopherol as a major lipid-phase scavenger of reactive nitrogen species.

Aged↗

PubMed2002

Proteomic identification of oxidatively modified proteins in Alzheimer's disease brain. Part II: dihydropyrimidinase-related protein 2, alpha-enolase and heat shock cognate 71.

Alzheimer's disease (AD) is a neurodegenerative disorder in which oxidative stress has been implicated as an important event in the progression of the pathology. In particular, it has been shown that protein modification by reactive oxygen species (ROS) occurs to a greater extent in AD than in control brain, suggesting a possible role for oxidation-related decrease in protein function in the process of neurodegeneration. Oxidative damage to proteins, assessed by measuring the protein carbonyl content, is involved in several events such as loss in specific protein function, abnormal protein clearance, depletion of the cellular redox-balance and interference with the cell cycle, and, ultimately, neuronal death. The present investigation represents a further step in understanding the relationship between oxidative modification of protein and neuronal death in AD. Previously, we used our proteomics approach, which successfully substitutes for labor-intensive immunochemical analysis, to detect proteins and identified creatine kinase, glutamine synthase and ubiquitin carboxy-terminal hydrolase L-1 as specifically oxidized proteins in AD brain. In this report we again applied our proteomics approach to identify new targets of protein oxidation in AD inferior parietal lobe (IPL). The dihydropyrimidinase related protein 2 (DRP-2), which is involved in the axonal growth and guidance, showed significantly increased level in protein carbonyls in AD brain, suggesting a role for impaired mechanism of neural network formation in AD. Additionally, the cytosolic enzyme alpha-enolase was identified as a target of protein oxidation and is involved the glycolytic pathway in the pathological events of AD. Finally, the heat shock cognate 71 (HSC-71) revealed increased, but not significant, oxidation in AD brain. These results are discussed with reference to potential involvement of these oxidatively modified proteins in neurodegeneration in AD brain.

Aged↗

PubMed2002

Cerebrovascular pathology and dementia in autopsied Honolulu-Asia Aging Study participants.

Clinicopathologic data from 285 autopsies were analyzed. The decedents were long-standing participants in the Honolulu-Asia Aging Study, a prospective epidemiologic investigation of stroke, neurodegenerative diseases, and aging. We assessed the prevalence at death of four primary neuropathologic processes using specific microscopic lesions as indicators. An algorithm was developed to assign each decedent to one of six subsets, corresponding to pathologic dominance by microvascular lesions (14% of decedents), Alzheimer lesions (12%), hippocampal sclerosis (5%), cortical Lewy bodies (5%), codominance by two or more primary processes (9%), or without a dominant pathologic process recognized (55%). Definite or probable dementia had been identified in 118 of the decedents. The proportions of men in each subset identified as demented were (in the same order) 57%, 53%, 79%, 57%, 76%, and 25%. In this autopsied panel of older Japanese-American men, the importance of microvascular lesions as a likely explanation for dementia was nearly equal to that of Alzheimer lesions. The cerebrovascular lesion type most essentially and inclusively related to dementia was multiple microinfarction.

Aged↗

PubMed2002

Cerebrospinal fluid lipoprotein delivery to human neuronal cells is increased in Alzheimer's disease and is dependent on apoE monomer concentration.

Recent studies of cerebrospinal fluid (CSF) have shown increased oxidation of CSF lipoproteins in Alzheimer's disease (AD) patients, and neurotoxicity from oxidized CSF lipoproteins in culture. Since inheritance of different alleles of the apolipoprotein (apo) E gene is a risk factor for AD and apoE is the major lipoprotein trafficking molecule in brain, we hypothesized that apoE may modify the pathogenesis of AD by directing the delivery of oxidized CSF lipoproteins to neurons. To test this hypothesis, we adapted a method previously used with isolated plasma lipoproteins to specifically label lipid particles in situ in native CSF and quantified their delivery to human SK-N-BE(2)C neuroblastoma cells. CSF lipoproteins were delivered to neuronal cells largely through apoE-dependent processes. Importantly, CSF lipoproteins from AD patients were delivered more efficiently than CSF lipoproteins from age-matched controls; this effect was not associated with apoE genotype or degree of CSF lipoprotein oxidation but was associated with apoE monomer concentration that tended to be lower in AD patients. The inverse relationship between apoE monomer concentration and CSF lipoprotein delivery was duplicated in SK-N-BE(2)C cells, but not human astrocytoma cells, using artificial lipid particles and purified human apoE. These results suggest that lipoproteins in CSF from AD patients are delivered more efficiently to neurons than are CSF lipoproteins from controls, and that this abnormality may be explained largely by variations in CSF apoE concentration.

Alleles↗

PubMedDate not supplied

Use of bomb pulse carbon-14 to age senile plaques and neurofibrillary tangles in Alzheimer's disease.

The time course of formation of neurofibrillary tangles (NFT) and senile plaques (SP) in Alzheimer's disease (AD) brain is unknown. Above ground nuclear weapons testing in the late 1950s and early 1960s led to significantly increased levels of 14C in the atmosphere and carbon cycle. Because the amyloid beta peptide of SP and paired helical filaments of NFT, once formed, are relatively resistant to degradation, 14C levels observed in SP and NFT should reflect their year of formation. The purpose of this study was to develop a method to determine whether 14C levels could be used to define NFT and SP ages. Using accelerator mass spectrometry to measure bomb-pulse 14C levels, we determined the average age of formation of isolated SP and NFT fractions in bulk brain samples of 6 AD subjects. Although preliminary, the results demonstrate that it is possible to use bomb pulse 14C to determine the average year of formation of NFT and SP in the brain in AD. In addition, the data show that these structures, once formed, have a much slower carbon turnover rate than normal brain and are not in a formation/enzymatic degradation equilibrium.

Aged↗

PubMedDate not supplied

F2-isoprostanes in Alzheimer and other neurodegenerative diseases.

Increased free radical-mediated injury to brain is proposed to be an integral component of several neurodegenerative diseases, including Alzheimer's disease (AD). Lipid peroxidation is a major outcome of free radical- mediated injury to brain, where it directly damages membranes and generates a number of oxidized products. F2-Isoprostanes (F2-IsoPs), one group of lipid peroxidation products derived from arachidonic acid, are especially useful as in vivo biomarkers of lipid peroxidation. F2-IsoP concentration is selectively increased in diseased regions of brain from patients who died from advanced AD, where pathologic changes include amyloid beta (Abeta) amyloidogenesis, neurofibrillary tangle formation, and extensive neuron death. Interestingly, cerebral F2-IsoPs are not reproducibly elevated in aged mouse models of cerebral Abeta amyloidogenesis only. There is broad agreement that increased cerebrospinal fluid (CSF) levels of F2-IsoPs also are present in patients with early AD. Demonstrated applications of quantifying CSF F2-IsoPs have improved laboratory diagnostic accuracy of AD and objective assessment of antioxidant therapeutics. In contrast, quantification of F2-IsoPs in plasma and urine of AD patients has produced conflicting data. These results indicate that brain lipid peroxidation is a potential therapeutic target early in the course of AD, and that CSF F2-IsoPs may aid in the assessment of antioxidant experimental therapeutics and laboratory diagnosis of AD.

Alzheimer Disease↗

PubMedDate not supplied

DNA oxidation in Alzheimer's disease.

Oxidative damage to DNA may play an important role in aging and neurodegenerative diseases such as Alzheimer's disease (AD). Attack on DNA by reactive oxygen species, particularly hydroxyl radicals, can lead to strand breaks, DNA-DNA and DNA-protein cross-linking, sister chromatid exchange and translocation, and formation of at least 20 oxidized base adducts. Modification of DNA bases can lead to mutation and altered protein synthesis. In late-stage AD brain, several studies have shown an elevation of the base adducts 8 hydroxyguanine (8-OHG), 8-hydroxyadenine (8-OHA), 5-hydroxycytosine (5-OHC), and 5-hydroxyuracil, a chemical degradation product of cytosine. Several studies have shown a decline in repair of 8-OHG in AD. Most recently, our studies have shown elevated 8-OHG, 8-OHA, and 5,6-diamino-5-formamidopyrimidine in nuclear and mitochondrial DNA in mild cognitive impairment, the earliest detectable form of AD, suggesting that oxidative damage to DNA is an early event in AD and not a secondary phenomenon.

Adenine↗