ABSTRACT
OBJECTIVE: To assess the extent to which spiritual well-being moderates the relationship between anxiety and physical well-being in a diverse, community-based cohort of newly diagnosed cancer survivors. METHODS: Data originated from the Measuring Your Health (MY-Health) study cohort (n = 5506), comprising people assessed within 6-13 months of cancer diagnosis. Life meaning/peace was assessed using the 8-item subscale of the Spiritual Well-Being Scale (FACIT-Sp-12). Anxiety was measured with an 11-item PROMIS Anxiety short form, and physical well-being was assessed using the 7-item FACT-G subscale. Multiple linear regression models were used to assess relationships among variables. RESULTS: Life meaning and peace was negatively associated with anxiety, b = -0.56 (P < .001) and positively associated with physical well-being, b = 0.43 (P = <.001) after adjusting for race, education, income, and age. A significant interaction between life meaning/peace and anxiety emerged (P < .001) indicating that spiritual well-being moderates the relationship between anxiety and physical well-being. Specifically, for cancer survivors high in anxiety, physical well-being was dependent on levels of life meaning/peace, b = 0.19, P < .001. For those low in anxiety, physical well-being was not associated with levels of life meaning/peace, b = 0.01, P = .541. Differences in cancer clinical factors (cancer stage at diagnosis, cancer type) did not significantly impact results. CONCLUSIONS: Further research is needed to assess how spiritual well-being may buffer the negative effect of anxiety on physical well-being. A clinical focus on spiritual well-being topics such as peace and life meaning may help cancer survivors of all types as they transition into follow-up care.
Subject(s)
Cancer Survivors/psychology , Neoplasms/psychology , Quality of Life/psychology , Spirituality , Adult , Aged , Anxiety , Female , Humans , Male , Middle Aged , Neoplasms/diagnosisABSTRACT
PURPOSE: To evaluate factors associated with compliance to the National Comprehensive Cancer Network (NCCN) guidelines for BRCA1/2 testing and identify groups who are at risk of under- and over-use of BRCA1/2 testing. METHODS: Data included 20,758 women from Dr. Susan Love Research Foundation's The Health of Women (HOW) Study®. Multinomial logistic regression was used to examine the association of socioeconomic and demographic characteristics with whether the woman was over-, under-, or appropriately tested for BRCA1/2 mutations, per 2015 NCCN guidelines. RESULTS: 3894 women (18.8%) reported BRCA1/2 testing. 5628 (27.1%) women who met NCCN criteria for testing were not tested. Among women with a history of breast cancer, those without health insurance were more likely to be under-tested (OR 2.04, 95% CI 1.15-3.60) than those with managed care insurance, and higher education was associated with a lower likelihood of under-testing (Graduate/professional degree OR 0.71, 95% CI 0.55-0.91). CONCLUSION: Almost 30% of women were under-tested, indicating that many high-risk women who may benefit from genetic testing are currently being missed. Without appropriate testing, providers are unable to tailor screening recommendations to those carrying mutations who are at highest risk. Patient and healthcare provider education and outreach targeted to low-income and under-served populations may assist in reducing under-testing.
Subject(s)
Breast Neoplasms/epidemiology , Breast Neoplasms/genetics , Genes, BRCA1 , Genes, BRCA2 , Women's Health , Breast Neoplasms/diagnosis , Female , Genetic Testing , Humans , Male , Middle Aged , Odds Ratio , Practice Guidelines as Topic , Risk FactorsABSTRACT
BACKGROUND: To understand whether patient-reported experiences with lung cancer may create teachable moments (TM) for their relatives as evidenced by shifts in their risk perceptions, affective response, and self-image and in turn, motivation to quit smoking. METHODS: Patients at a comprehensive cancer center (n = 152) completed a survey within 6 months of lung cancer diagnosis to assess their cancer-related symptoms and openness and enumerated relatives who were smokers. Relative smokers (n = 218) then completed a survey assessing their risk perceptions, affective response, and self-image as a smoker related to the patient's diagnosis (TM mechanisms), and their motivation to quit smoking. Cross-sectional mediation and moderation analyses were conducted to explore the links between patient-reported experiences, and relatives' TM mechanisms, and motivation to quit smoking. RESULTS: Relative-reported affect was a significant mediator of the association between patient-reported symptoms and relative smoker's desire to quit. Relatives' self-image was a significant moderator of the association between patient-reported symptoms and relative smoker's desire to quit, such that patients' reported symptoms were associated with relatives' desire to quit only when the relative smoker reported a generally positive self-image as a smoker. No evidence was found for moderated mediation. However, the link between symptoms and negative affect was moderated by perceptions of risk. CONCLUSION: Whether smokers experience a family member's lung cancer as a TM is influenced by multiple interrelated cognitive and affective factors that warrant further exploration. Clearer understanding of these factors could inform how to re-invigorate and sustain this motivation to promote concrete actions toward smoking cessation. Copyright © 2015 John Wiley & Sons, Ltd.
Subject(s)
Attitude to Health , Family Health , Lung Neoplasms/diagnosis , Smoking Cessation/psychology , Smoking/psychology , Adult , Cross-Sectional Studies , Family , Female , Humans , Male , Middle Aged , Motivation , Surveys and QuestionnairesABSTRACT
Health behaviors often co-occur and have common determinants at multiple levels (e.g., individual, relational, environmental). Nevertheless, research programs often examine single health behaviors without a systematic attempt to integrate knowledge across behaviors. This paper highlights the significant potential of cross-cutting behavioral research to advance our understanding of the mechanisms and causal factors that shape health behaviors. It also offers suggestions for how researchers could develop more effective interventions. We highlight barriers to such an integrative science along with potential steps that can be taken to address these barriers. With a more nuanced understanding of health behavior, redundancies in research can be minimized, and a stronger evidence base for the development of health behavior interventions can be realized.
Subject(s)
Delivery of Health Care, Integrated/organization & administration , Health Behavior , Knowledge , Science/methods , Environment , Health Knowledge, Attitudes, Practice , Health Promotion , Humans , Models, Theoretical , United StatesABSTRACT
Amyloid-ß, tau, and α-synuclein, or more specifically their soluble oligomers, are the aetiologic molecules in Alzheimer's disease, tauopathies, and α-synucleinopathies, respectively. These proteins have been shown to interact to accelerate each other's pathology. Clinical studies of amyloid-ß-targeting therapies in Alzheimer's disease have revealed that the treatments after disease onset have little benefit on patient cognition. These findings prompted us to explore a preventive medicine which is orally available, has few adverse effects, and is effective at reducing neurotoxic oligomers with a broad spectrum. We initially tested five candidate compounds: rifampicin, curcumin, epigallocatechin-3-gallate, myricetin, and scyllo-inositol, in cells expressing amyloid precursor protein (APP) with the Osaka (E693Δ) mutation, which promotes amyloid-ß oligomerization. Among these compounds, rifampicin, a well-known antibiotic, showed the strongest activities against the accumulation and toxicity (i.e. cytochrome c release from mitochondria) of intracellular amyloid-ß oligomers. Under cell-free conditions, rifampicin inhibited oligomer formation of amyloid-ß, tau, and α-synuclein, indicating its broad spectrum. The inhibitory effects of rifampicin against amyloid-ß and tau oligomers were evaluated in APPOSK mice (amyloid-ß oligomer model), Tg2576 mice (Alzheimer's disease model), and tau609 mice (tauopathy model). When orally administered to 17-month-old APPOSK mice at 0.5 and 1 mg/day for 1 month, rifampicin reduced the accumulation of amyloid-ß oligomers as well as tau hyperphosphorylation, synapse loss, and microglial activation in a dose-dependent manner. In the Morris water maze, rifampicin at 1 mg/day improved memory of the mice to a level similar to that in non-transgenic littermates. Rifampicin also inhibited cytochrome c release from the mitochondria and caspase 3 activation in the hippocampus. In 13-month-old Tg2576 mice, oral rifampicin at 0.5 mg/day for 1 month decreased amyloid-ß oligomer accumulation, tau hyperphosphorylation, synapse loss, and microglial activation, but not amyloid deposition. Rifampicin treatment to 14-15-month-old tau609 mice at 0.5 and 1 mg/day for 1 month also reduced tau oligomer accumulation, tau hyperphosphorylation, synapse loss, and microglial activation in a dose-dependent fashion, and improved the memory almost completely at 1 mg/day. In addition, rifampicin decreased the level of p62/sequestosome-1 in the brain without affecting the increased levels of LC3 (microtubule-associated protein light chain 3) conversion, suggesting the restoration of autophagy-lysosomal function. Considering its prescribed dose and safety in humans, these results indicate that rifampicin could be a promising, ready-to-use medicine for the prevention of Alzheimer's disease and other neurodegenerative diseases.
Subject(s)
Alzheimer Disease/prevention & control , Amyloid beta-Peptides/drug effects , Rifampin/pharmacology , Rifampin/therapeutic use , Tauopathies/prevention & control , tau Proteins/drug effects , Alzheimer Disease/complications , Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Animals , Caspase 3/metabolism , Cells, Cultured , Cytochromes c/metabolism , Dose-Response Relationship, Drug , Female , Hippocampus/metabolism , Maze Learning/drug effects , Memory Disorders/complications , Memory Disorders/drug therapy , Mice , Mice, Transgenic , Microglia/drug effects , Microtubule-Associated Proteins/metabolism , Neuroprotective Agents/pharmacology , Neuroprotective Agents/therapeutic use , Phosphorylation/drug effects , Sequestosome-1 Protein/metabolism , Synapses/drug effects , Synucleins/drug effects , Synucleins/metabolism , Tauopathies/complications , Tauopathies/metabolism , tau Proteins/metabolismABSTRACT
Alzheimer's disease (AD) is associated with peripheral metabolic disorders. Clinical/epidemiological data indicate increased risk of diabetes in AD patients. Here, we show that intracerebroventricular infusion of AD-associated Aß oligomers (AßOs) in mice triggered peripheral glucose intolerance, a phenomenon further verified in two transgenic mouse models of AD. Systemically injected AßOs failed to induce glucose intolerance, suggesting AßOs target brain regions involved in peripheral metabolic control. Accordingly, we show that AßOs affected hypothalamic neurons in culture, inducing eukaryotic translation initiation factor 2α phosphorylation (eIF2α-P). AßOs further induced eIF2α-P and activated pro-inflammatory IKKß/NF-κB signaling in the hypothalamus of mice and macaques. AßOs failed to trigger peripheral glucose intolerance in tumor necrosis factor-α (TNF-α) receptor 1 knockout mice. Pharmacological inhibition of brain inflammation and endoplasmic reticulum stress prevented glucose intolerance in mice, indicating that AßOs act via a central route to affect peripheral glucose homeostasis. While the hypothalamus has been largely ignored in the AD field, our findings indicate that AßOs affect this brain region and reveal novel shared molecular mechanisms between hypothalamic dysfunction in metabolic disorders and AD.
Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Hypothalamus/metabolism , Oligonucleotides/metabolism , Peripheral Nerves/metabolism , Alzheimer Disease/genetics , Amyloid beta-Peptides/genetics , Animals , Female , Glucose/metabolism , Humans , Macaca , Male , Mice , Mice, Inbred C57BL , NF-kappa B/genetics , NF-kappa B/metabolism , Neurons/metabolism , Oligonucleotides/genetics , Rats , Signal Transduction , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/metabolismABSTRACT
Numerous studies have implicated the abnormal accumulation of intraneuronal amyloid-ß (Aß) as an important contributor to Alzheimer's disease (AD) pathology, capable of triggering neuroinflammation, tau hyperphosphorylation and cognitive deficits. However, the occurrence and pathological relevance of intracellular Aß remain a matter of controversial debate. In this study, we have used a multidimensional approach including high-magnification and super-resolution microscopy, cerebro-spinal fluid (CSF) mass spectrometry analysis and ELISA to investigate the Aß pathology and its associated cognitive impairments, in a novel transgenic rat model overexpressing human APP. Our microscopy studies with quantitative co-localization analysis revealed the presence of intraneuronal Aß in transgenic rats, with an immunological signal that was clearly distinguished from that of the amyloid precursor protein (APP) and its C-terminal fragments (CTFs). The early intraneuronal pathology was accompanied by a significant elevation of soluble Aß42 peptides that paralleled the presence and progression of early cognitive deficits, several months prior to amyloid plaque deposition. Aß38, Aß39, Aß40 and Aß42 peptides were detected in the rat CSF by MALDI-MS analysis even at the plaque-free stages; suggesting that a combination of intracellular and soluble extracellular Aß may be responsible for impairing cognition at early time points. Taken together, our results demonstrate that the intraneuronal development of AD-like amyloid pathology includes a mixture of molecular species (Aß, APP and CTFs) of which a considerable component is Aß; and that the early presence of these species within neurons has deleterious effects in the CNS, even before the development of full-blown AD-like pathology.
Subject(s)
Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/metabolism , Brain/pathology , Cognition Disorders , Intracellular Fluid/metabolism , Peptide Fragments/metabolism , Acoustic Stimulation/adverse effects , Amyloid Precursor Protein Secretases/metabolism , Amyloid beta-Protein Precursor/genetics , Animals , Brain/metabolism , Cognition Disorders/cerebrospinal fluid , Cognition Disorders/genetics , Cognition Disorders/metabolism , Cognition Disorders/pathology , Conditioning, Psychological/physiology , Disease Models, Animal , Fear , Gene Expression Regulation/genetics , Humans , Mutation/genetics , Pain Measurement , Rats , Rats, Transgenic , Recognition, Psychology/physiology , Regression AnalysisSubject(s)
Continuity of Patient Care , Delivery of Health Care, Integrated , Health Services Research , Models, Statistical , Neoplasms , Quality of Health Care , Research Design , Cancer Care Facilities , Continuity of Patient Care/standards , Continuity of Patient Care/trends , Delivery of Health Care, Integrated/standards , Delivery of Health Care, Integrated/trends , Health Behavior , Health Services Research/methods , Health Services Research/trends , Humans , Interdisciplinary Communication , Neoplasms/diagnosis , Neoplasms/therapy , Patient Care Team/standards , Patient Care Team/trends , Quality of Health Care/standards , Quality of Health Care/trendsABSTRACT
Heat shock response, mediated by heat shock proteins, is a highly conserved physiological process in multicellular organisms for reestablishment of cellular homeostasis. Expression of heat shock factors and subsequent heat shock protein plays a role in protection against proteotoxicity in invertebrate and vertebrate models. Proteotoxicity due to beta-amyloid peptide (Abeta) oligomerization has been linked to the pathogenesis of Alzheimer's disease. Previously, we demonstrated that progressive paralysis induced by expression of human Abeta(1-42) in transgenic Caenorhabditis elegans was alleviated by Abeta oligomer inhibitors Ginkgo biloba extract and its constituents [Wu, Y., Wu, Z., Butko, P., Christen, Y., Lambert, M.P., Klein, W.L., Link, C.D., Luo, Y., 2006. Amyloid-beta-induced pathological behaviors are suppressed by Ginkgo biloba extract EGb 761 and ginkgolides in transgenic Caenorhabditis elegans. J. Neurosci. 26(50): 13102-13113]. In this study, we apply a protective heat shock to the transgenic C. elegans and demonstrate: (1) a delay in paralysis, (2) increased expression of small heat shock protein HSP16.2, and (3) significant reduction of Abeta oligomers in a heat shock time-dependent manner. These results suggest that transient heat shock lessens Abeta toxicity by diminishing Abeta oligomerization, which provides a link between up regulation of endogenous chaperone proteins and protection against Abeta proteotoxicity in vivo.
Subject(s)
Amyloid beta-Peptides/toxicity , Behavior, Animal/drug effects , Heat-Shock Response/physiology , Paralysis/chemically induced , Paralysis/prevention & control , Aging/physiology , Amyloid beta-Peptides/genetics , Amyloid beta-Peptides/metabolism , Animals , Animals, Genetically Modified , Antioxidants/therapeutic use , Caenorhabditis elegans , Disease Models, Animal , Ginkgo biloba , Heat-Shock Proteins/genetics , Heat-Shock Proteins/metabolism , Hot Temperature , Humans , Hydrogen Peroxide/metabolism , Molecular Weight , Paralysis/genetics , Peptide Fragments/genetics , Peptide Fragments/metabolism , Phytotherapy/methods , Plant Extracts/therapeutic use , Time FactorsABSTRACT
Loss of synapses has been correlated with dementia in Alzheimer's disease (AD) as an early event during the disease progression. Hence, synaptogenesis and neurogenesis in adulthood could serve as a therapeutic target for the prevention and treatment of AD. Recently, we have demonstrated enhanced hippocampal neurogenesis by oral administration of Ginkgo biloba extract (EGb 761) to a mouse model of AD. This study aims to identify the constituents that contribute to EGb 761-induced neurogenesis. Among the constituents tested, bilobalide and quercetin significantly increased cell proliferation in the hippocampal neurons in a dose-dependent manner. Bilobalide and quercetin also enhanced phosphorylation of cyclic-AMP Response Element Binding Protein (CREB) in these cells, and elevated the levels of pCREB and, brain-derived neurotrophic factor in mice brain. Immunofluorescence staining of synaptic markers shows remarkable dendritic processes in hippocampal neurons treated with either quercetin or bilobalide. Furthermore, both constituents restored amyloid-beta oligomers (also known as ADDL)-induced synaptic loss and phosphorylation of CREB. The present findings suggest that enhanced neurogenesis and synaptogenesis by bilobalide and quercetin may share a common final signaling pathway mediated by phosphorylation of CREB. Despite a recent report showing that EGb 761 was insufficient in prevent dementia, its constituents still warrant future investigation.
Subject(s)
Alzheimer Disease/physiopathology , Cyclopentanes/pharmacology , Furans/pharmacology , Ginkgolides/pharmacology , Hippocampus/drug effects , Neurogenesis/drug effects , Plant Extracts/pharmacology , Quercetin/pharmacology , Alzheimer Disease/drug therapy , Alzheimer Disease/metabolism , Animals , Blotting, Western , Cyclic AMP Response Element-Binding Protein/drug effects , Cyclic AMP Response Element-Binding Protein/metabolism , Dose-Response Relationship, Drug , Ginkgo biloba , Hippocampus/metabolism , Mice , Phosphorylation , Rats , Rats, Sprague-Dawley , Synapses/drug effectsABSTRACT
We examined the effects of ibuprofen on cognitive deficits, Abeta and tau accumulation in young triple transgenic (3xTg-AD) mice. 3xTg-AD mice were fed ibuprofen-supplemented chow between 1 and 6 months. Untreated 3xTg-AD mice showed significant impairment in the ability to learn the Morris water maze (MWM) task compared to age-matched wild-type (WT) mice. The performance of 3xTg-AD mice was significantly improved with ibuprofen treatment compared to untreated 3xTg-AD mice. Ibuprofen-treated transgenic mice showed a significant decrease in intraneuronal oligomeric Abeta and hyperphosphorylated tau (AT8) immunoreactivity in the hippocampus. Confocal microscopy demonstrated co-localization of conformationally altered (MC1) and early phosphorylated tau (CP-13) with oligomeric Abeta, and less co-localization of oligomeric Abeta and later forms of phosphorylated tau (AT8 and PHF-1) in untreated 3xTg-AD mice. Our findings show that prophylactic treatment of young 3xTg-AD mice with ibuprofen reduces intraneuronal oligomeric Abeta, reduces cognitive deficits, and prevents hyperphosphorylated tau immunoreactivity. These findings provide further support for intraneuronal Abeta as a cause of cognitive impairment, and suggest that pathological alterations of tau are associated with intraneuronal oligomeric Abeta accumulation.
Subject(s)
Alzheimer Disease/complications , Amyloid beta-Peptides/metabolism , Cyclooxygenase Inhibitors/therapeutic use , Ibuprofen/therapeutic use , Memory Disorders , tau Proteins/metabolism , Adenosine Triphosphatases/metabolism , Alzheimer Disease/drug therapy , Alzheimer Disease/genetics , Amyloid beta-Protein Precursor/genetics , Animals , DNA-Binding Proteins/metabolism , Disease Models, Animal , Humans , Indoles , Maze Learning/drug effects , Memory Disorders/drug therapy , Memory Disorders/etiology , Memory Disorders/metabolism , Mice , Mice, Transgenic , Mutation/physiology , Phosphorylation/drug effects , Presenilin-1/genetics , tau Proteins/geneticsABSTRACT
One of the major pathological features of Alzheimer's disease (AD) is the appearance of senile plaques characterized by extracellular aggregation of amyloid beta-peptide (Abeta) fibrils. Inhibition of Abeta fibril aggregation is therefore viewed as one possible method to halt the progression of AD. Salvianolic acid B (Sal B) is an active ingredient isolated from Salvia miltiorrhiza, a Chinese herbal medicine commonly used for the treatment of cardiovascular and cerebrovascular disorders. Recent findings show that Sal B prevents Abeta-induced cytotoxicity in a rat neural cell line. To understand the mechanism of Sal B-mediated neuroprotection, its effects on the inhibition of Abeta1-40 fibril formation and destabilization of the preformed Abeta1-40 fibrils were studied. The results were obtained using Thioflavin T fluorescence assay and Abeta aggregating immunoassay. We found that Sal B can inhibit fibril aggregation (IC(50): 1.54-5.37 microM) as well as destabilize preformed Abeta fibril (IC(50): 5.00-5.19 microM) in a dose- and time-dependent manner. Sal B is a better aggregation inhibitor than ferulic acid but less active than curcumin in the inhibition of Abeta1-40 aggregation. In electron microscope study, Sal B-treated Abeta1-40 fibrils are seen in various stages of shortening or wrinkling with numerous deformed aggregates of amorphous structure. Circular dichroism data indicate that Sal B dose dependently prevents the formation of beta-structured aggregates of Abeta1-40. Addition of preincubated Sal B with Abeta1-42 significantly reduces its cytotoxic effects on human neuroblastoma SH-SY5Y cells. These results suggest that Sal B has therapeutic potential in the treatment of AD, and warrant its study in animal models.
Subject(s)
Amyloid beta-Peptides/antagonists & inhibitors , Amyloid beta-Peptides/toxicity , Antioxidants/pharmacology , Benzofurans/pharmacology , Microfibrils/drug effects , Amyloid beta-Peptides/biosynthesis , Benzothiazoles , Cell Aggregation/drug effects , Cell Line, Tumor , Circular Dichroism , Data Interpretation, Statistical , Enzyme-Linked Immunosorbent Assay , Humans , Microfibrils/ultrastructure , Microscopy, Electron , Tetrazolium Salts , Thiazoles/pharmacologyABSTRACT
Amyloid-beta (Abeta) toxicity has been postulated to initiate synaptic loss and subsequent neuronal degeneration seen in Alzheimer's disease (AD). We previously demonstrated that the standardized Ginkgo biloba extract EGb 761, commonly used to enhance memory and by AD patients for dementia, inhibits Abeta-induced apoptosis in neuroblastoma cells. In this study, we use EGb 761 and its single constituents to associate Abeta species with Abeta-induced pathological behaviors in a model organism, Caenorhabditis elegans. We report that EGb 761 and one of its components, ginkgolide A, alleviates Abeta-induced pathological behaviors, including paralysis, and reduces chemotaxis behavior and 5-HT hypersensitivity in a transgenic C. elegans. We also show that EGb 761 inhibits Abeta oligomerization and Abeta deposits in the worms. Moreover, reducing oxidative stress is not the mechanism by which EGb 761 and ginkgolide A suppress Abeta-induced paralysis because the antioxidant L-ascorbic acid reduced intracellular levels of hydrogen peroxide to the same extent as EGb 761, but was not nearly as effective in suppressing paralysis in the transgenic C. elegans. These findings suggest that (1) EGb 761 suppresses Abeta-related pathological behaviors, (2) the protection against Abeta toxicity by EGb 761 is mediated primarily by modulating Abeta oligomeric species, and (3) ginkgolide A has therapeutic potential for prevention and treatment of AD.
Subject(s)
Amyloid beta-Peptides/toxicity , Behavior, Animal/drug effects , Caenorhabditis elegans/drug effects , Caenorhabditis elegans/genetics , Ginkgolides/pharmacology , Plant Extracts/pharmacology , Animals , Animals, Genetically Modified , Behavior, Animal/physiology , Caenorhabditis elegans/physiology , Chemotaxis/drug effects , Chemotaxis/physiology , Ginkgo biloba , Paresis/chemically induced , Paresis/prevention & controlABSTRACT
Amyloid beta 1-42 (Abeta(1-42)) is a self-associating peptide that becomes neurotoxic upon aggregation. Toxicity originally was attributed to the presence of large, readily formed Abeta fibrils, but a variety of other toxic species are now known. The current study shows that Abeta(1-42) can self-assemble into small, stable globular assemblies free of fibrils and protofibrils. Absence of large molecules was verified by atomic force microscopy (AFM) and nondenaturing gel electrophoresis. Denaturing electrophoresis revealed that the globular assemblies comprised oligomers ranging from trimers to 24mers. Oligomers prepared at 4 degrees C stayed fibril-free for days and remained so when shifted to 37 degrees C, although the spectrum of sizes shifted toward larger oligomers at the higher temperature. The soluble, globular Abeta(1-42) oligomers were toxic to PC12 cells, impairing reduction of MTT and interfering with ERK and Rac signal transduction. Occasionally, oligomers were neither toxic nor recognized by toxicity-neutralizing antibodies, suggesting that oligomers could assume alternative conformations. Tests for oligomerization-blocking activity were carried out by dot-blot immunoassays and showed that neuroprotective extracts of Ginkgo biloba could inhibit oligomer formation at very low doses. The observed neurotoxicity, structure, and stability of synthetic Abeta(1-42) globular assemblies support the hypothesis that Abeta(1-42) oligomers play a role in triggering nerve cell dysfunction and death in Alzheimer's disease.
Subject(s)
Amyloid beta-Peptides/chemistry , Amyloid beta-Peptides/toxicity , Neurotoxins/chemistry , Neurotoxins/toxicity , Peptide Fragments/chemistry , Peptide Fragments/toxicity , Amyloid beta-Peptides/antagonists & inhibitors , Amyloid beta-Peptides/isolation & purification , Animals , Body Temperature , Cell Survival/drug effects , Diffusion , Epitopes/chemistry , Ginkgo biloba , Humans , Ligands , Neuroprotective Agents/chemistry , Neurotoxins/antagonists & inhibitors , Neurotoxins/isolation & purification , Nitroblue Tetrazolium/chemistry , PC12 Cells , Peptide Fragments/antagonists & inhibitors , Peptide Fragments/isolation & purification , Plant Extracts/chemistry , Protein Conformation , RatsABSTRACT
Alzheimer's disease (AD) is a fatal, progressive dementia for which there is no cure and for which a molecular basis has yet to be established. However, considerable evidence suggests that AD is linked to neurotoxic assemblies of the 42-amino-acid peptide amyloid beta (Abeta). There is now a clear body of evidence that shows this neurotoxicity resides not only in insoluble fibrils of Abeta but also in soluble Abeta ADDLs (Abeta-derived diffusible ligands) and larger protofibrils. Further, anti-Abeta antibodies have been reported to reverse memory failure in human amyloid precursor protein (hAPP)-expressed transgenic mice in a manner that suggests symptom reversal is attributable to targeting of ADDLs. Clearly, a search for drugs targeting the assembly of these soluble Abeta species represents a new and potentially important approach to the treatment of AD. In this work we describe the development of a dot-blot immunoassay to measure ADDL at the femtomole level, its use in defining the time course of ADDL formation, and its use in determining the presence of ADDLs in the hAPP transgenic mouse brain. Discussion of a protocol to screen agents for inhibition of neurotoxic ADDLformation both in vivo and in vitro is also presented. The methods are suitable for screening combinatorial libraries and, importantly, provide the potential for simultaneous information on candidate transport across the blood-brain barrier.