RESUMEN
Hyperphosphorylation and accumulation of tau aggregates are prominent features in tauopathies, including Alzheimer's disease, but the impact of loss of tau function on synaptic and cognitive deficits remains poorly understood. We report that old (19-20 months; OKO) but not middle-aged (8-9 months; MKO) tau knock-out mice develop Morris Water Maze (MWM) deficits and loss of hippocampal acetylated α-tubulin and excitatory synaptic proteins. Mild motor deficits and reduction in tyrosine hydroxylase (TH) in the substantia nigra were present by middle age, but did not affect MWM performance, whereas OKO mice showed MWM deficits paralleling hippocampal deficits. Deletion of tau, a microtubule-associated protein (MAP), resulted in increased levels of MAP1A, MAP1B, and MAP2 in MKO, followed by loss of MAP2 and MAP1B in OKO. Hippocampal synaptic deficits in OKO mice were partially corrected with dietary supplementation with docosahexaenoic acid (DHA) and both MWM and synaptic deficits were fully corrected by combining DHA with α-lipoic acid (ALA), which also prevented TH loss. DHA or DHA/ALA restored phosphorylated and total GSK3ß and attenuated hyperactivation of the tau C-Jun N-terminal kinases (JNKs) while increasing MAP1B, dephosphorylated (active) MAP2, and acetylated α-tubulin, suggesting improved microtubule stability and maintenance of active compensatory MAPs. Our results implicate the loss of MAP function in age-associated hippocampal deficits and identify a safe dietary intervention, rescuing both MAP function and TH in OKO mice. Therefore, in addition to microtubule-stabilizing therapeutic drugs, preserving or restoring compensatory MAP function may be a useful new prevention strategy.
Asunto(s)
Envejecimiento/patología , Hipocampo/patología , Aprendizaje por Laberinto/fisiología , Sinapsis/metabolismo , Proteínas tau/deficiencia , Envejecimiento/efectos de los fármacos , Envejecimiento/genética , Enfermedad de Alzheimer/complicaciones , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/patología , Animales , Modelos Animales de Enfermedad , Ácidos Docosahexaenoicos/administración & dosificación , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Hipocampo/efectos de los fármacos , Discapacidades para el Aprendizaje/dietoterapia , Discapacidades para el Aprendizaje/etiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Trastornos del Movimiento/dietoterapia , Trastornos del Movimiento/etiología , Desempeño Psicomotor/fisiología , Tiempo de Reacción/efectos de los fármacos , Sustancia Negra/metabolismo , Sustancia Negra/patología , Sinapsis/efectos de los fármacos , Sinapsis/genética , Ácido Tióctico/administración & dosificaciónRESUMEN
The mechanisms underlying Tau-related synaptic and cognitive deficits and the interrelationships between Tau species, their clearance pathways, and synaptic impairments remain poorly understood. To gain insight into these mechanisms, we examined these interrelationships in aged non-mutant genomic human Tau mice, with established Tau pathology and neuron loss. We also examined how these interrelationships changed with an intervention by feeding mice either a control diet or one containing the brain permeable beta-amyloid and Tau aggregate binding molecule curcumin. Transgene-dependent elevations in soluble and insoluble phospho-Tau monomer and soluble Tau dimers accompanied deficits in behavior, hippocampal excitatory synaptic markers, and molecular chaperones (heat shock proteins (HSPs)) involved in Tau degradation and microtubule stability. In human Tau mice but not control mice, HSP70, HSP70/HSP72, and HSP90 were reduced in membrane-enriched fractions but not in cytosolic fractions. The synaptic proteins PSD95 and NR2B were reduced in dendritic fields and redistributed into perikarya, corresponding to changes observed by immunoblot. Curcumin selectively suppressed levels of soluble Tau dimers, but not of insoluble and monomeric phospho-Tau, while correcting behavioral, synaptic, and HSP deficits. Treatment increased PSD95 co-immunoprecipitating with NR2B and, independent of transgene, increased HSPs implicated in Tau clearance. It elevated HSP90 and HSC70 without increasing HSP mRNAs; that is, without induction of the heat shock response. Instead curcumin differentially impacted HSP90 client kinases, reducing Fyn without reducing Akt. In summary, curcumin reduced soluble Tau and elevated HSPs involved in Tau clearance, showing that even after tangles have formed, Tau-dependent behavioral and synaptic deficits can be corrected.
Asunto(s)
Antiinflamatorios no Esteroideos/farmacocinética , Conducta Animal/efectos de los fármacos , Curcumina/farmacología , Proteínas de Choque Térmico/metabolismo , Multimerización de Proteína/efectos de los fármacos , Sinapsis/metabolismo , Tauopatías/metabolismo , Proteínas tau/metabolismo , Anciano , Anciano de 80 o más Años , Animales , Homólogo 4 de la Proteína Discs Large , Femenino , Proteínas de Choque Térmico/genética , Hipocampo/metabolismo , Hipocampo/patología , Humanos , Péptidos y Proteínas de Señalización Intracelular/genética , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Masculino , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones , Ratones Transgénicos , Multimerización de Proteína/genética , Proteolisis/efectos de los fármacos , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas Proto-Oncogénicas c-fyn/genética , Proteínas Proto-Oncogénicas c-fyn/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Solubilidad/efectos de los fármacos , Sinapsis/genética , Sinapsis/patología , Tauopatías/tratamiento farmacológico , Tauopatías/genética , Tauopatías/patología , Proteínas tau/genéticaRESUMEN
Both insulin resistance (type II diabetes) and beta-amyloid (Abeta) oligomers are implicated in Alzheimer's disease (AD). Here, we investigate the role of Abeta oligomer-induced c-Jun N-terminal kinase (JNK) activation leading to phosphorylation and degradation of the adaptor protein insulin receptor substrate-1 (IRS-1). IRS-1 couples insulin and other trophic factor receptors to downstream kinases and neuroprotective signaling. Increased phospho-IRS-1 is found in AD brain and insulin-resistant tissues from diabetics. Here, we report Abeta oligomers significantly increased active JNK and phosphorylation of IRS-1 (Ser616) and tau (Ser422) in cultured hippocampal neurons, whereas JNK inhibition blocked these responses. The omega-3 fatty acid docosahexaenoic acid (DHA) similarly inhibited JNK and the phosphorylation of IRS-1 and tau in cultured hippocampal neurons. Feeding 3xTg-AD transgenic mice a diet high in saturated and omega-6 fat increased active JNK and phosphorylated IRS-1 and tau. Treatment of the 3xTg-AD mice on high-fat diet with fish oil or curcumin or a combination of both for 4 months reduced phosphorylated JNK, IRS-1, and tau and prevented the degradation of total IRS-1. This was accompanied by improvement in Y-maze performance. Mice fed with fish oil and curcumin for 1 month had more significant effects on Y-maze, and the combination showed more significant inhibition of JNK, IRS-1, and tau phosphorylation. These data indicate JNK mediates Abeta oligomer inactivation of IRS-1 and phospho-tau pathology and that dietary treatment with fish oil/DHA, curcumin, or a combination of both has the potential to improve insulin/trophic signaling and cognitive deficits in AD.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/farmacología , Curcumina/farmacología , Inhibidores Enzimáticos/farmacología , Ácidos Grasos Omega-3/farmacología , Proteínas Sustrato del Receptor de Insulina/metabolismo , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Neuronas/efectos de los fármacos , Fragmentos de Péptidos/farmacología , Transducción de Señal/efectos de los fármacos , Proteínas tau/metabolismo , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/dietoterapia , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/genética , Animales , Conducta Animal , Células Cultivadas , Curcumina/uso terapéutico , Modelos Animales de Enfermedad , Embrión de Mamíferos , Inhibidores Enzimáticos/uso terapéutico , Ácidos Grasos Omega-3/uso terapéutico , Hipocampo/citología , Humanos , Ratones , Ratones Transgénicos , Persona de Mediana Edad , Fosforilación/efectos de los fármacos , Cambios Post Mortem , Presenilina-1/genética , Ratas , Ratas Sprague-Dawley , Serina/metabolismoRESUMEN
BACKGROUND: The sortilin-related receptor SorLA/LR11 (LR11) is a transmembrane neuronal sorting protein that reduces beta-amyloid precursor protein trafficking to secretases, notably BACE1 that generates beta-amyloid, the principal component of senile plaques in Alzheimer disease (AD). LR11 protein is reduced in patients with late-onset AD, and LR11 polymorphisms have been associated with late-onset AD. OBJECTIVE: T o detect soluble LR11 and APP in cerebrospinal fluid (CSF) from patients with AD and control subjects, as (like beta-amyloid precursor protein) LR11 is cleaved near the membrane to release a large N-terminal fragment that is secreted to media from cultured cells. DESIGN: Case-control study. SETTING: Academic research. PARTICIPANTS: Patients with AD and control subjects. MAIN OUTCOME MEASURES: We evaluated CSF LR11, beta-amyloid precursor protein, and apolipoprotein E levels by Western blot in lumbar and postmortem CSF samples. RESULTS: LR11 levels were detectable and stable during 6 months in the CSF of patients with AD. LR11 levels were significantly reduced in lumbar samples from patients with mild to moderate probable AD, as well as in ventricular CSF from patients with autopsy-confirmed AD (predominantly Braak stage III-IV). Bivariate analysis with beta-amyloid 42 and LR11 levels improved diagnostic specificity for AD. Reduced LR11 levels are significantly correlated with soluble beta-amyloid precursor protein but not apolipoprotein E levels. CONCLUSION: Reduced LR11 levels in CSF of patients with AD may have potential as a diagnostic biomarker for patients with LR11 deficits that promote beta-amyloid production or as an index of therapeutic response in late-onset AD.
Asunto(s)
Enfermedad de Alzheimer/líquido cefalorraquídeo , Péptidos beta-Amiloides/líquido cefalorraquídeo , Encéfalo/metabolismo , Proteínas Relacionadas con Receptor de LDL/líquido cefalorraquídeo , Proteínas Relacionadas con Receptor de LDL/genética , Proteínas de Transporte de Membrana/líquido cefalorraquídeo , Proteínas de Transporte de Membrana/genética , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/líquido cefalorraquídeo , Apolipoproteínas E/líquido cefalorraquídeo , Western Blotting , Encéfalo/patología , Estudios de Casos y Controles , Línea Celular , Regulación de la Expresión Génica/genética , Humanos , Ovillos Neurofibrilares/patología , Fragmentos de Péptidos/líquido cefalorraquídeo , Placa Amiloide/patología , Valor Predictivo de las Pruebas , Valores de ReferenciaRESUMEN
The dysregulation of glycogen synthase kinase-3 (GSK3) has been implicated in Alzheimer disease (AD) pathogenesis and in Abeta-induced neurotoxicity, leading us to investigate it as a therapeutic target in an intracerebroventricular Abeta infusion model. Infusion of a specific GSK3 inhibitor SB216763 (SB) reduced a downstream target, phospho-glycogen synthase 39%, and increased glycogen levels 44%, suggesting effective inhibition of enzyme activity. Compared to vehicle, Abeta increased GSK3 activity, and was associated with elevations in levels of ptau, caspase-3, the tau kinase phospho-c-jun N-terminal kinase (pJNK), neuronal DNA fragmentation, and gliosis. Co-infusion of SB corrected all responses to Abeta infusion except the induction of gliosis and behavioral deficits in the Morris water maze. Nevertheless, SB alone was associated with induction of neurodegenerative markers and behavioral deficits. These data support a role for GSK3 hyperactivation in AD pathogenesis, but emphasize the importance of developing inhibitors that do not suppress constitutive activity.
Asunto(s)
Enfermedad de Alzheimer/terapia , Inhibidores Enzimáticos/uso terapéutico , Glucógeno Sintasa Quinasa 3/antagonistas & inhibidores , Indoles/uso terapéutico , Maleimidas/uso terapéutico , Enfermedad de Alzheimer/inducido químicamente , Péptidos beta-Amiloides/farmacología , Animales , Caspasa 3/metabolismo , Células Cultivadas , Fragmentación del ADN , Modelos Animales de Enfermedad , Inhibidores Enzimáticos/efectos adversos , Gliosis/inducido químicamente , Glucógeno/metabolismo , Glucógeno Sintasa Quinasa 3/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/fisiología , Indoles/efectos adversos , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Maleimidas/efectos adversos , Aprendizaje por Laberinto , Degeneración Nerviosa/tratamiento farmacológico , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Fosforilación , Ratas , Ratas Sprague-Dawley , Proteínas tau/metabolismoRESUMEN
The rat amyloid-beta (Abeta) intracerebroventricular infusion can model aspects of Alzheimer's disease (AD) and has predicted efficacy of therapies such as ibuprofen and curcumin in transgenic mouse models. High density lipoprotein (HDL), a normal plasma carrier of Abeta, is used to attenuate Abeta aggregation within the pump, causing Abeta-dependent toxicity and cognitive deficits within 3 months. Our goal was to identify factors that might accelerate onset of Abeta-dependent deficits to improve efficiency and cost-effectiveness of model. We focused on: 1) optimizing HDL-Abeta preparation for maximal toxicity; 2) evaluating the role of copper, a factor typically in water that can impact oligomer stability; and 3) determining impact of insulin resistance (type II diabetes), a risk factor for AD. In vitro studies were performed to determine doses of copper and methods of Abeta-HDL preparation that maximized toxicity. These preparations when infused resulted in earlier onset of cognitive deficits within 6 weeks post-infusion. Induction of insulin resistance did not exacerbate Abeta-dependent cognitive deficits, but did exacerbate synaptic protein loss. In summary, the newly described in vivo infusion model may be useful cost-effective method for screening for new therapeutic drugs for AD.
Asunto(s)
Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/genética , Péptidos beta-Amiloides/metabolismo , Trastornos del Conocimiento/genética , Trastornos del Conocimiento/psicología , Cobre/toxicidad , Resistencia a la Insulina/genética , Proteínas del Tejido Nervioso/metabolismo , Sinapsis/metabolismo , Enfermedad de Alzheimer/patología , Animales , Western Blotting , Células Cultivadas , Trastornos del Conocimiento/patología , Dieta , Fructosa/farmacología , Resistencia a la Insulina/fisiología , Aprendizaje por Laberinto/fisiología , Ósmosis , Ratas , Ratas Sprague-DawleyRESUMEN
Defects in dendritic spines and synapses contribute to cognitive deficits in mental retardation syndromes and, potentially, Alzheimer disease. p21-activated kinases (PAKs) regulate actin filaments and morphogenesis of dendritic spines regulated by the Rho family GTPases Rac and Cdc42. We previously reported that active PAK was markedly reduced in Alzheimer disease cytosol, accompanied by downstream loss of the spine actin-regulatory protein Drebrin. beta-Amyloid (Abeta) oligomer was implicated in PAK defects. Here we demonstrate that PAK is aberrantly activated and translocated from cytosol to membrane in Alzheimer disease brain and in 22-month-old Tg2576 transgenic mice with Alzheimer disease. This active PAK coimmunoprecipitated with the small GTPase Rac and both translocated to granules. Abeta42 oligomer treatment of cultured hippocampal neurons induced similar effects, accompanied by reduction of dendrites that were protected by kinase-active but not kinase-dead PAK. Abeta42 oligomer treatment also significantly reduced N-methyl-d-aspartic acid receptor subunit NR2B phosphotyrosine labeling. The Src family tyrosine kinase inhibitor PP2 significantly blocked the PAK/Rac translocation but not the loss of p-NR2B in Abeta42 oligomer-treated neurons. Src family kinases are known to phosphorylate the Rac activator Tiam1, which has recently been shown to be Abeta-responsive. In addition, anti-oligomer curcumin comparatively suppressed PAK translocation in aged Tg2576 transgenic mice with Alzheimer amyloid pathology and in Abeta42 oligomer-treated cultured hippocampal neurons. Our results implicate aberrant PAK in Abeta oligomer-induced signaling and synaptic deficits in Alzheimer disease.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Quinasas p21 Activadas/química , Péptidos beta-Amiloides/química , Animales , Citosol/metabolismo , GTP Fosfohidrolasas/química , Humanos , Ratones , Ratones Transgénicos , Modelos Biológicos , Neuronas/metabolismo , Transporte de Proteínas , Ratas , Ratas Sprague-Dawley , Proteínas de Unión al GTP rac/metabolismoRESUMEN
Environmental and genetic factors, notably ApoE4, contribute to the etiology of late-onset Alzheimer's disease (LOAD). Reduced mRNA and protein for an apolipoprotein E (ApoE) receptor family member, SorLA (LR11) has been found in LOAD but not early-onset AD, suggesting that LR11 loss is not secondary to pathology. LR11 is a neuronal sorting protein that reduces amyloid precursor protein (APP) trafficking to secretases that generate beta-amyloid (Abeta). Genetic polymorphisms that reduce LR11 expression are associated with increased AD risk. However these polymorphisms account for only a fraction of cases with LR11 deficits, suggesting involvement of environmental factors. Because lipoprotein receptors are typically lipid-regulated, we postulated that LR11 is regulated by docosahexaenoic acid (DHA), an essential omega-3 fatty acid related to reduced AD risk and reduced Abeta accumulation. In this study, we report that DHA significantly increases LR11 in multiple systems, including primary rat neurons, aged non-Tg mice and an aged DHA-depleted APPsw AD mouse model. DHA also increased LR11 in a human neuronal line. In vivo elevation of LR11 was also observed with dietary fish oil in young rats with insulin resistance, a model for type II diabetes, another AD risk factor. These data argue that DHA induction of LR11 does not require DHA-depleting diets and is not age dependent. Because reduced LR11 is known to increase Abeta production and may be a significant genetic cause of LOAD, our results indicate that DHA increases in SorLA/LR11 levels may play an important role in preventing LOAD.
Asunto(s)
Enfermedad de Alzheimer/dietoterapia , Enfermedad de Alzheimer/metabolismo , Ácidos Docosahexaenoicos/administración & dosificación , Regulación de la Expresión Génica/efectos de los fármacos , Proteínas de Transporte de Membrana/metabolismo , Receptores de LDL/metabolismo , Factores de Edad , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/genética , Análisis de Varianza , Animales , Línea Celular Tumoral , Modelos Animales de Enfermedad , Embrión de Mamíferos , Femenino , Humanos , Masculino , Proteínas de Transporte de Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Proteínas del Tejido Nervioso/metabolismo , Neuroblastoma , Ratas , Ratas Sprague-Dawley , Receptores de LDL/genética , Factores de TiempoRESUMEN
Extracellular-signal regulated kinase (ERK) signaling is critical for memory and tightly regulated by acute environmental stimuli. In Alzheimer disease transgenic models, active ERK is shown to first be increased, then later reduced, but whether these baseline changes reflect disruptions in ERK signaling is less clear. We investigated the influence of the familial Alzheimer's disease transgene APPsw and beta-amyloid peptide (Abeta) immunoneutralization on cannulation injury-associated (i.c.v. infusion) ERK activation. At both 12 and 22 months of age, the trauma-associated activation of ERK observed in Tg(-) mice was dramatically attenuated in Tg(+). In cortices of 22-month-old non-infused mice, a reduction in ERK activation was observed in Tg(+), relative to Tg(-) mice. Intracerebroventricular (i.c.v.) anti-Abeta infusion significantly increased phosphorylated ERK, its substrate cAMP-response element-binding protein (CREB) and a downstream target, the NMDA receptor subunit. We also demonstrated that Abeta oligomer decreased active ERK and subsequently active CREB in human neuroblastoma cells, which could be prevented by oligomer immunoneutralization. Abeta oligomers also inhibited active ERK and CREB in primary neurons, in addition to reducing the downstream post-synaptic protein NMDA receptor subunit. These effects were reversed by anti-oligomer. Our data strongly support the existence of an APPsw transgene-dependent and Abeta oligomer-mediated defect in regulation of ERK activation.
Asunto(s)
Enfermedad de Alzheimer/enzimología , Péptidos beta-Amiloides/fisiología , Proteína de Unión a CREB/fisiología , Quinasas MAP Reguladas por Señal Extracelular/fisiología , Sistema de Señalización de MAP Quinasas/genética , Transgenes/fisiología , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Péptidos beta-Amiloides/genética , Animales , Proteína de Unión a CREB/genética , Línea Celular Tumoral , Modelos Animales de Enfermedad , Activación Enzimática/genética , Quinasas MAP Reguladas por Señal Extracelular/genética , Humanos , Ratones , Ratones TransgénicosRESUMEN
Defects in dendritic spines are common to several forms of cognitive deficits, including mental retardation and Alzheimer disease. Because mutation of p21-activated kinase (PAK) can lead to mental retardation and because PAK-cofilin signaling is critical in dendritic spine morphogenesis and actin dynamics, we hypothesized that the PAK pathway is involved in synaptic and cognitive deficits in Alzheimer disease. Here, we show that PAK and its activity are markedly reduced in Alzheimer disease and that this is accompanied by reduced and redistributed phosphoPAK, prominent cofilin pathology and downstream loss of the spine actin-regulatory protein drebrin, which cofilin removes from actin. We found that beta-amyloid (Abeta) was directly involved in PAK signaling deficits and drebrin loss in Abeta oligomer-treated hippocampal neurons and in the Appswe transgenic mouse model bearing a double mutation leading to higher Abeta production. In addition, pharmacological PAK inhibition in adult mice was sufficient to cause similar cofilin pathology, drebrin loss and memory impairment, consistent with a potential causal role of PAK defects in cognitive deficits in Alzheimer disease.
Asunto(s)
Enfermedad de Alzheimer/enzimología , Péptidos beta-Amiloides/metabolismo , Trastornos del Conocimiento/enzimología , Proteínas Serina-Treonina Quinasas/metabolismo , Factores Despolimerizantes de la Actina/metabolismo , Enfermedad de Alzheimer/complicaciones , Enfermedad de Alzheimer/patología , Animales , Células Cultivadas , Trastornos del Conocimiento/etiología , Trastornos del Conocimiento/patología , Espinas Dendríticas/metabolismo , Modelos Animales de Enfermedad , Femenino , Humanos , Masculino , Ratones , Ratones Transgénicos , Neuropéptidos/metabolismo , Ratas , Quinasas p21 ActivadasRESUMEN
Although active and passive immunization against the beta-amyloid peptide (Abeta) of amyloid plaque-bearing transgenic mice markedly reduces amyloid plaque deposition and improves cognition, the mechanisms of neuroprotection and impact on toxic oligomer species are not understood. We demonstrate that compared to control IgG2b, passive immunization with intracerebroventricular (icv) anti-Abeta (1-15) antibody into the AD HuAPPsw (Tg2576) transgenic mouse model reduced specific oligomeric forms of Abeta, including the dodecamers that correlate with cognitive decline. Interestingly, the reduction of soluble Abeta oligomers, but not insoluble Abeta, significantly correlated with reduced tau phosphorylation by glycogen synthase kinase-3beta (GSK-3beta), a major tau kinase implicated previously in mediating Abeta toxicity. A conformationally-directed antibody against amyloid oligomers (larger than tetramer) also reduced Abeta oligomer-induced activation of GSK3beta and protected human neuronal SH-SY5Y cells from Abeta oligomer-induced neurotoxicity, supporting a role for Abeta oligomers in human tau kinase activation. These data suggest that antibodies that are highly specific for toxic oligomer subspecies may reduce toxicity via reduction of GSK-3beta, which could be an important strategy for Alzheimer's disease (AD) therapeutics.
Asunto(s)
Péptidos beta-Amiloides/inmunología , Péptidos beta-Amiloides/metabolismo , Anticuerpos/farmacología , Reactivadores Enzimáticos/farmacología , Glucógeno Sintasa Quinasa 3/metabolismo , Proteínas tau/metabolismo , Precursor de Proteína beta-Amiloide/genética , Análisis de Varianza , Animales , Western Blotting/métodos , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Corteza Cerebral/metabolismo , Corteza Cerebral/patología , Activación Enzimática/efectos de los fármacos , Ensayo de Inmunoadsorción Enzimática/métodos , Femenino , Glucógeno Sintasa Quinasa 3 beta , Humanos , Inmunohistoquímica/métodos , Técnicas In Vitro , Masculino , Ratones , Ratones Transgénicos , Neuroblastoma , Fragmentos de Péptidos/metabolismo , Fosforilación/efectos de los fármacos , Placa Amiloide/patología , Distribución Aleatoria , Tinción con Nitrato de Plata/métodosRESUMEN
Alzheimer's disease (AD) involves amyloid beta (Abeta) accumulation, oxidative damage, and inflammation, and risk is reduced with increased antioxidant and anti-inflammatory consumption. The phenolic yellow curry pigment curcumin has potent anti-inflammatory and antioxidant activities and can suppress oxidative damage, inflammation, cognitive deficits, and amyloid accumulation. Since the molecular structure of curcumin suggested potential Abeta binding, we investigated whether its efficacy in AD models could be explained by effects on Abeta aggregation. Under aggregating conditions in vitro, curcumin inhibited aggregation (IC(50) = 0.8 microM) as well as disaggregated fibrillar Abeta40 (IC(50) = 1 microM), indicating favorable stoichiometry for inhibition. Curcumin was a better Abeta40 aggregation inhibitor than ibuprofen and naproxen, and prevented Abeta42 oligomer formation and toxicity between 0.1 and 1.0 microM. Under EM, curcumin decreased dose dependently Abeta fibril formation beginning with 0.125 microM. The effects of curcumin did not depend on Abeta sequence but on fibril-related conformation. AD and Tg2576 mice brain sections incubated with curcumin revealed preferential labeling of amyloid plaques. In vivo studies showed that curcumin injected peripherally into aged Tg mice crossed the blood-brain barrier and bound plaques. When fed to aged Tg2576 mice with advanced amyloid accumulation, curcumin labeled plaques and reduced amyloid levels and plaque burden. Hence, curcumin directly binds small beta-amyloid species to block aggregation and fibril formation in vitro and in vivo. These data suggest that low dose curcumin effectively disaggregates Abeta as well as prevents fibril and oligomer formation, supporting the rationale for curcumin use in clinical trials preventing or treating AD.
Asunto(s)
Péptidos beta-Amiloides/química , Péptidos beta-Amiloides/metabolismo , Curcumina/metabolismo , Curcumina/farmacología , Placa Amiloide/metabolismo , Placa Amiloide/patología , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/antagonistas & inhibidores , Péptidos beta-Amiloides/toxicidad , Animales , Antiinflamatorios no Esteroideos/metabolismo , Antiinflamatorios no Esteroideos/farmacología , Benzoatos/química , Benzoatos/farmacología , Benzotiazoles , Compuestos de Bifenilo/química , Compuestos de Bifenilo/farmacología , Barrera Hematoencefálica/efectos de los fármacos , Barrera Hematoencefálica/fisiología , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Encéfalo/patología , Línea Celular Tumoral , Rojo Congo , Curcumina/química , Diaminas/química , Diaminas/farmacología , Humanos , Ibuprofeno/farmacología , Ratones , Ratones Transgénicos , Naproxeno/farmacología , Fragmentos de Péptidos/antagonistas & inhibidores , Fragmentos de Péptidos/química , Fragmentos de Péptidos/metabolismo , Fragmentos de Péptidos/toxicidad , Placa Amiloide/química , Placa Amiloide/genética , Unión Proteica/efectos de los fármacos , Desnaturalización Proteica/efectos de los fármacos , Estructura Cuaternaria de Proteína/efectos de los fármacos , Piridazinas/química , Piridazinas/farmacología , Solubilidad , TiazolesRESUMEN
Insulin-degrading enzyme (IDE) is one of the proteins that has been demonstrated to play a key role in degrading beta-amyloid (Abeta) monomer in vitro and in vivo, raising the possibility of upregulating IDE as an approach to reduce Abeta. Little is known, however, about the cellular and molecular regulation of IDE protein. Because one of the main functions of IDE is to degrade insulin, we hypothesized that there is a negative feedback mechanism whereby stimulation of insulin receptor-mediated signaling upregulates IDE to prevent chronic activation of the pathway. We show that treatment of primary hippocampal neurons with insulin increased IDE protein levels by approximately 25%. Insulin treatment also led to phosphatidylinositol-3 (PI3) kinase activation evidenced by Akt phosphorylation, which was blocked by PI3 kinase inhibitors, wortmannin and LY 294002. Inhibition of PI3 kinase abolished the IDE upregulation by insulin, indicating a cause-effect relationship between insulin signaling and IDE upregulation. Further support for this link was provided by the findings that deficient insulin signaling (decreased PI3 kinase subunit P85) was correlated with reduced IDE in Alzheimer's disease (AD) brains and in Tg2576 Swedish amyloid precursor protein transgenic mice fed a safflower oil-enriched ("Bad") diet used to accelerate pathogenesis. Consistent with IDE function in the degradation of Abeta monomer, the IDE decrease in the Bad diet-fed Tg2576 mice was associated with increased Abeta monomer levels. These in vitro and in vivo analyses validate the use of enhanced CNS insulin signaling as a potential strategy for AD intervention to correct the IDE defects occurring in AD.