RESUMEN
Since its discovery as a genetic risk factor for Alzheimer's disease, the APOE4 allele has been linked to the majority of the pathological findings associated with the disease progression. These include abnormalities of the endocytic, autophagic, and lysosomal machineries, which begin at the most early stages of Alzheimer's disease development. Considering that these three vesicular systems share common features and, in fact, comprise an interconnected cargo-trafficking and degradation network, some of the effects of APOE4 are interrelated, while others are system-specific. In turn, APOE4-driven impairments of endocytosis, autophagy, and lysosomal activity influence various aspects of Alzheimer's disease pathology, ranging from Aß generation and clearance to neuronal loss and cognitive deficits. This review discusses the detrimental effects of APOE4 on the endocytic-autophagic-lysosomal axis in the context of Alzheimer's disease, as well as the various mechanisms underlying them.
Asunto(s)
Apolipoproteína E4/metabolismo , Autofagia , Endocitosis , Lisosomas/metabolismo , Enfermedad de Alzheimer/patología , Animales , Humanos , Modelos BiológicosRESUMEN
Apolipoprotein E deficient mice have distinct memory deficits and neurochemical derangements and their recovery from closed head injury is impaired. In the present study, we examined the possibility that the neuronal derangements of apolipoprotein E deficient mice are associated with oxidative stress, which in turn affects their ability to recover from close head injury. It was found that brain phospholipid levels in apolipoprotein E deficient mice are lower than those of the controls (55+/-15% of control, P<0. 01), that the cholesterol levels of the two mice groups are similar and that the levels of conjugated dienes of the apolipoprotein E deficient mice are higher than those of control mice (132+/-15% of P<0.01). Brains of apolipoprotein E deficient mice had higher Mn-superoxide dismutase (134+/-7%), catalase (122+/-8%) and glutathione reductase (167+/-7%) activities than control (P<0.01), whereas glutathione peroxidase activity and the levels of reduced glutathione and ascorbic acid were similar in the two mouse groups. Closed head injury increased catalase and glutathione peroxidase activities in both mouse groups, whereas glutathione reductase increased only in control mice. The superoxide dismutase activity was unaffected in both groups. These findings suggest that the antioxidative metabolism of apolipoprotein E deficient mice is altered both prior to and following head injury and that antioxidative mechanisms may play a role in mediating the neuronal maintenance and repair derangements of the apolipoprotein E deficient mice.
Asunto(s)
Apolipoproteínas E/deficiencia , Química Encefálica , Traumatismos Cerrados de la Cabeza/metabolismo , Estrés Oxidativo , Animales , Antioxidantes/análisis , Ácido Ascórbico/análisis , Catalasa/análisis , Glutatión/análisis , Glutatión Peroxidasa/análisis , Glutatión Reductasa/análisis , Glutatión Transferasa/análisis , Masculino , Ratones , Superóxido Dismutasa/análisisRESUMEN
When PC12 cells are deprived of trophic support they undergo apoptosis. We have previously shown that survival of trophic factor-deprived PC12M1 cells can be promoted by activation of the G protein-coupled muscarinic receptors. The mechanism whereby muscarinic receptors inhibit apoptosis is poorly understood. In the present study we investigated this mechanism by examining the effect of muscarinic receptor activation on the serum deprivation-induced activity of key players in apoptosis, the caspases, in PC12M1 cells. The results showed that m1 muscarinic activation inhibits caspase activity induced by serum deprivation. This effect appeared to be caused by the prevention of activation of caspases such as caspase-2 and caspase-3, and not by the inhibition of existing activity. Muscarinic receptor activation also stimulated the mitogen-activated protein kinase/extracellular signaling-regulated kinase (MAPK/ERK) and phosphoinositide (PI) 3-kinase signaling pathways. The PI 3-kinase pathway inhibitors wortmannin and LY294002, as well as the MAPK/ERK pathway PD98059 inhibitor, did not however suppress the inhibitory effect of the muscarinic receptors on caspase activity. The results therefore suggested that the muscarinic survival effect is mediated by a pathway that leads to caspase inhibition by MAPK/ERK- and PI 3-kinase-independent signaling cascades.
Asunto(s)
Apoptosis , Caspasas/metabolismo , Sistema de Señalización de MAP Quinasas , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas , Receptores Muscarínicos/metabolismo , Transducción de Señal , Animales , Atropina/farmacología , Inhibidores de Caspasas , Caspasas/biosíntesis , Extractos Celulares , Medio de Cultivo Libre de Suero , Relación Dosis-Respuesta a Droga , Activación Enzimática , Inhibidores Enzimáticos/farmacología , Quinasas de Proteína Quinasa Activadas por Mitógenos/antagonistas & inhibidores , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Agonistas Muscarínicos/farmacología , Antagonistas Muscarínicos/farmacología , Oxotremorina/farmacología , Células PC12 , Péptido Hidrolasas/metabolismo , Inhibidores de las Quinasa Fosfoinosítidos-3 , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Ratas , Receptor Muscarínico M1RESUMEN
Sera of normal controls and of patients with neurological diseases contain antineurofilament antibodies. Recent studies suggest that biochemically and immunologically distinct subclasses of neurofilaments occur in different types of neurons. Alzheimer's disease (AD), the major cause of dementia, is associated with a marked degeneration of brain cholinergic neurons. In the present work we characterized the repertoire and age dependence of antineurofilament antibodies in normal sera and examined whether the degeneration of cholinergic neurons in AD is associated with serum antibodies directed specifically against the neurofilaments of mammalian cholinergic neurons. This was performed by immunoblot assays utilizing neurofilaments from the purely cholinergic bovine ventral root neurons and from the chemically heterogeneous bovine dorsal root neurons. Antibodies to the heavy neurofilament protein NF-H were detected in normal control sera. Their levels were significantly higher in older (aged 70-79) than in younger (aged 40-59) subjects. These antibodies bound similarly to bovine ventral root and dorsal root NF-H and their NF-H specificity was unchanged during aging. In contrast, the levels of IgG in AD sera that are directed against ventral root cholinergic NF-H were higher than those directed against the chemically heterogeneous dorsal root NF-H. Immunoblot experiments utilizing dephosphorylated ventral root and dorsal root NF-H and chymotryptic fragments of these molecules revealed that AD sera contain a repertoire of antimamalian NF-H IgG. A subpopulation of these antibodies binds to phosphorylated epitopes that are specifically enriched in ventral root cholinergic NF-H and that are located on the carboxy terminal domain of this molecule.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Envejecimiento/inmunología , Enfermedad de Alzheimer/inmunología , Autoanticuerpos/sangre , Proteínas de Neurofilamentos/inmunología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Niño , Humanos , Persona de Mediana EdadRESUMEN
The nature of the intraterminal compartments from which acetylcholine (ACh) is released following presynaptic stimulation was investigated. This was pursued by examining the effects of the anticholinergic drug 2-(4-phenylpiperidino)cyclohexanol (AH5183) on the release of newly synthesized [3H]ACh and of endogenous ACh from purified cholinergic nerve terminals (synaptosomes) which were isolated from the electric organs of Torpedo. Preincubation of the synaptosomes, with AH5183 (1-10 microM), does not affect either the intraterminal synthesis of [3H]ACh or the uptake of its precursors, but results in a marked inhibition (85%) of the release of the newly synthesized [3H]ACh. However, when AH5183 is added following the accumulation of [3H]ACh in the nerve terminals, it does not affect [3H]ACh release. AH5183 also has no effect on the release of preformed endogenous ACh. These findings, together with the previous in vitro demonstrations that AH5183 is a potent inhibitor of ACh uptake into isolated cholinergic vesicles, suggest that most of the synaptosomal ACh is secreted by a vesicular mechanism.
Asunto(s)
Acetilcolina/metabolismo , Piperidinas , Vesículas Sinápticas/metabolismo , Acetatos/metabolismo , Animales , Órgano Eléctrico/metabolismo , Técnicas In Vitro , Fenciclidina/análogos & derivados , Fenciclidina/farmacología , Vesículas Sinápticas/ultraestructura , Sinaptosomas/metabolismo , TorpedoRESUMEN
Incubation of cholinergic synaptic vesicles purified from the electric organ of Torpedo ocellata with radiolabeled [D-Ala2, D-Leu5]-enkephalin results in its accumulation in the vesicles. Kinetic analysis of the initial rates of uptake reveals temperature-dependent saturation kinetics which are best fitted by a single transport system (KT = 12 +/- 2 microM and Vmax = 0.85 +/- 0.24 pmol/mg protein per min). The specific rates and extents of [3H]-[D-Ala2, D-Leu5]-enkephalin uptake, like those of [3H]acetylcholine uptake, are highest in the purified synaptic vesicles fraction. These findings suggest that Torpedo cholinergic synaptic vesicles contain an opioid peptide transporter. The physiological significance of this transporter is discussed in view of the recent observation that Torpedo nerve terminals contain an endogenous enkephalin-like peptide and presynaptic opiate receptors.
Asunto(s)
Acetilcolina/metabolismo , Órgano Eléctrico/ultraestructura , Encefalina Leucina/análogos & derivados , Vesículas Sinápticas/metabolismo , Torpedo , Animales , Transporte Biológico , Encefalina Leucina/metabolismo , Leucina Encefalina-2-Alanina , Cinética , TemperaturaRESUMEN
Activation of Torpedo presynaptic muscarinic acetylcholine (ACh) receptors with the agonist oxotremorine (20 microM) results in the inhibition of Ca2+-dependent release of endogenous ACh from Torpedo synaptosomes. This effect is reversed by the muscarinic antagonist atropine (1 microM) which, by itself, has no effect. In contrast, under the same conditions the amount of newly synthesized radiolabeled [3H]ACh released is not affected by muscarinic ligands. These findings suggest that presynaptic muscarinic inhibition in the Torpedo is due to interference with the mobilization of ACh from a storage pool.
Asunto(s)
Acetilcolina/fisiología , Órgano Eléctrico/fisiología , Receptores Muscarínicos/fisiología , Sinaptosomas/fisiología , Acetilcolina/biosíntesis , Animales , Calcio/farmacología , Colina/metabolismo , Humanos , Cinética , Oxotremorina/farmacología , Potasio/farmacología , Sinapsis/fisiología , Sinaptosomas/efectos de los fármacos , TorpedoRESUMEN
APOE genotype influences the age at onset of some neurodegenerative diseases such as AD and the rate of progression in others such as MS. The authors hypothesize that APOE genotype ubiquitously determines the efficacy of neuronal maintenance and repair in these diseases and that the seemingly divergent clinical effects are due to the stage of disease at which the diagnosis is made. Early diagnosis facilitates the measurement of effects on disease progression rate, whereas late diagnosis results in a marked effect of APOE genotype on disease onset.
Asunto(s)
Apolipoproteínas E/genética , Enfermedades Neurodegenerativas/genética , Edad de Inicio , Progresión de la Enfermedad , Genotipo , Humanos , Enfermedades Neurodegenerativas/fisiopatologíaRESUMEN
Down's syndrome (DS) patients who survive beyond the third decade develop brain lesions characteristic of Alzheimer's disease (AD). Sera of AD patients contain antibodies that bind specifically to the heavy neurofilament protein (NF-H) of Torpedo cholinergic neurons. In the present report, we examined whether the AD-like pathologic changes in DS are associated with the existence of such antibodies. Our findings show that IgG of older DS patients (greater than 30 years) binds to Torpedo cholinergic NF-H more readily than does that of young DS patients (less than 30 years) and age-matched normal controls. In contrast, the extent of binding of IgG from the young and older DS groups to Torpedo and bovine spinal cords NF-H is similar and equal to that of normal controls. These findings suggest that older DS patients, like AD patients, contain anti-NF-H IgG that binds specifically to epitopes highly enriched in Torpedo cholinergic NF-H.
Asunto(s)
Enfermedad de Alzheimer/inmunología , Anticuerpos/inmunología , Colina O-Acetiltransferasa/inmunología , Síndrome de Down/inmunología , Proteínas de Neurofilamentos/inmunología , Adulto , Animales , Femenino , Humanos , Inmunoglobulina G/análisis , Masculino , Persona de Mediana Edad , TorpedoRESUMEN
Cerebral necrosis following stroke exposes brain antigens to the immune system, potentially initiating an antibody response. The authors measured levels of antibodies to specific neuronal antigens, neurofilaments (NF), and a ubiquitous antigen, cardiolipin (CL), in 45 patients following an acute first-ever stroke, within 48 hours, and 1, 3, and 6 months later. The mean levels of anti-NF antibodies were elevated compared with baseline at 1, 3, and 6, months (p = 0.012, 0.002, and 0.003 by paired t-test). Anti-CL levels did not change significantly.
Asunto(s)
Anticuerpos/inmunología , Encéfalo/inmunología , Cardiolipinas/sangre , Proteínas de Neurofilamentos/sangre , Accidente Cerebrovascular/sangre , Accidente Cerebrovascular/inmunología , Enfermedad Aguda , Anciano , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , MasculinoRESUMEN
BACKGROUND AND OBJECTIVE: The authors recently reported that the APOE epsilon4 allele is associated with significantly greater progression of disability in a 2-year follow-up of patients with MS. In this study, these findings are substantiated and extended in a much larger group of patients followed for up to 40 years. METHODS: Two hundred five patients with clinically definite MS who were genotyped for the APOE epsilon4 carrier state were included. Groups of patients with (n = 41) and without (n = 164) APOE epsilon4 alleles were compared for latency to expanded disability status scale (EDSS) scores of 4.0 and 6.0 by Kaplan-Meier analysis with the log rank test. The results were adjusted for age at onset and sex by Cox regression analysis. RESULTS: The APOE epsilon4 allele frequency in patients with MS (0.10) was similar to that in the general Israeli population. There was a significant effect of APOE genotype on the latency to reach EDSS 4.0 and 6.0 (p = 0.0002 and p = 0.0006 by two-tailed log rank test). Median latencies were shorter by 12 and 11 years in the APOE epsilon4 group for these outcomes. These results were significant after adjustment for age at onset and sex. CONCLUSIONS: The APOE epsilon4 allele is associated with significantly faster progression of disability in MS. This is the first genetic factor to be identified with a major impact on the progression of disability in this disease.
Asunto(s)
Apolipoproteínas E/genética , Esclerosis Múltiple/genética , Esclerosis Múltiple/fisiopatología , Adulto , Progresión de la Enfermedad , Femenino , Estudios de Seguimiento , Genotipo , Humanos , Masculino , Factores de TiempoRESUMEN
We determined the levels of antineurofilament antibodies in 29 patients with postpolio syndrome (PPS), 26 stable postpolio (PP) patients, 22 patients with ALS, and 20 normal controls (NCs). Patients with PPS had higher antibody levels to cholinergic neurofilaments than did all other groups. PP patients and those with ALS had antibody levels similar to those of NCs. The antibody binding level showed no relation to the age of the patients, duration of disease, or motor score.
Asunto(s)
Autoanticuerpos/sangre , Proteínas de Neurofilamentos/inmunología , Síndrome Pospoliomielitis/inmunología , Adulto , Esclerosis Amiotrófica Lateral/inmunología , Fibras Colinérgicas/inmunología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Médula Espinal/citología , Médula Espinal/inmunologíaRESUMEN
We have found that Torpedo electric organ readily synthesizes prostaglandin E2 from both exogenous and endogenous arachidonate and that activation of the presynaptic muscarinic acetylcholine receptor increases the rate of prostaglandin E2 synthesis by inducing the release of tissue arachidonate from its phospholipid pools. The incorporation of radiolabeled arachidonate into tissue phospholipids is slow and Ca2+ independent. However, the electric organ slices readily oxidize the externally added, radiolabeled arachidonate via the cyclo-oxygenase pathway, with prostaglandin E2 being the major product (22 +/- 4% of the initial radioactivity). This process is not affected by either Ca2+ or mepacrine. Torpedo electric organ slices also synthesize prostaglandin E2 from endogenous substrates, and release it into the medium. This process, however, is enhanced by Ca2+ and inhibited by mepacrine. Activation of the Torpedo muscarinic acetylcholine receptor by the agonist oxotremorine results in a dose-dependent atropine-sensitive increase in the synthesis of prostaglandin E2 from endogenous tissue substrates and in the concomitant release of arachidonate into the medium. By contrast, oxotremorine has no effect on either the formation of [14C]prostaglandin E2 from exogenous arachidonate, the incorporation of radiolabeled arachidonate into tissue phospholipids or its liberation from prelabeled slices. These results suggest that activation of the muscarinic acetylcholine receptor induces lipolysis which results in the liberation of endogenous arachidonate and its subsequent conversion to prostaglandin E2.
Asunto(s)
Ácidos Araquidónicos/metabolismo , Órgano Eléctrico/fisiología , Prostaglandinas E/biosíntesis , Receptores Muscarínicos/fisiología , Torpedo/fisiología , Animales , Ácido Araquidónico , Atropina/farmacología , Calcio/fisiología , Dinoprostona , Órgano Eléctrico/metabolismo , Técnicas In Vitro , Oxotremorina/farmacología , Fosfolípidos/biosíntesisRESUMEN
Sera of Alzheimer's disease and Down's syndrome patients contain antibodies which bind specifically to the high molecular weight neurofilament protein of Torpedo cholinergic neurons. We have recently shown that prolonged immunization of rats with this antigen results in the accumulation of IgG in neurons in the septum and hippocampus of the immunized rats and in cognitive impairments. This animal model is termed experimental autoimmune dementia. In the present study we examined whether the anti-cholinergic high molecular weight neurofilament subunit immune response of the experimental autoimmune dementia rats affects forebrain cholinergic neurons. This was performed immunohistochemically utilizing a monoclonal antibody to nerve growth factor receptor, a specific marker of cholinergic neurons in the forebrain. The results obtained revealed significant decreases in the density of cholinergic neurons in the medial septal nucleus and diagonal band of the experimental autoimmune dementia rats. These decreases are specific to the anti-cholinergic high molecular weight neurofilament subunit immune response of the experimental autoimmune dementia rats and are not observed in control rats which were immunized with chemically heterogeneous high molecular weight neurofilament subunit. The decrease in density of forebrain cholinergic neurons in experimental autoimmune dementia rats may mimic pathogenic processes in Alzheimer's disease and supports a role for anti-cholinergic high molecular weight neurofilament subunit antibodies in the degeneration of cholinergic neurons in the disease.
Asunto(s)
Enfermedades Autoinmunes/patología , Demencia/inmunología , Proteínas de Neurofilamentos/inmunología , Neuronas/patología , Prosencéfalo/patología , Acetilcolina/metabolismo , Análisis de Varianza , Animales , Anticuerpos Monoclonales , Demencia/patología , Vías Eferentes/inmunología , Inmunización , Inmunoglobulina G/análisis , Inmunoglobulina G/metabolismo , Inmunohistoquímica , Masculino , Neuronas/inmunología , Prosencéfalo/inmunología , Ratas , Ratas Sprague-Dawley , Receptores de Factor de Crecimiento Nervioso/análisis , Médula Espinal/inmunología , TorpedoRESUMEN
Previous studies suggest that traumatic brain injury is associated with increased risk factor for developing Alzheimer's disease. Furthermore, the extent of the risk seems to be most pronounced in Alzheimer's disease patients who carry the epsilon4 allele of apolipoprotein E, suggesting a connection between susceptibility to head trauma and the apolipoprotein E genotype. Apolipoprotein E-deficient mice provide a useful model for investigating the role of this lipoprotein in neuronal maintenance and repair. In the present study apolipoprotein E-deficient mice and a closed head injury experimental paradigm were used to examine the role of apolipoprotein E in brain susceptibility to head trauma and in neuronal repair. Apolipoprotein E-deficient mice were assessed up to 40 days after closed head injury for neurological and cognitive functions, as well as for histopathological changes in the hippocampus. A neurological severity score used for clinical assessment revealed more severe motor and behavioural deficits in the apolipoprotein E-deficient mice than in the controls, the impairment persisting for at least 40 days after injury. Performance in the Morris water maze, which tests spatial memory, showed a marked learning deficit of the apolipoprotein E-deficient mice when compared with injured controls, which was apparent for at least 40 days. At this time, histopathological examination revealed overt neuronal cell death bilaterally in the hippocampus of the injured apolipoprotein E-deficient mice. The finding that apolipoprotein E-deficient mice exhibit an impaired ability to recover from closed head injury suggests that apolipoprotein E plays an important role in neuronal repair following injury and highlights the applicability of this mouse model to the study of the cellular and molecular mechanisms involved.
Asunto(s)
Apolipoproteínas E/deficiencia , Trastornos del Conocimiento/fisiopatología , Traumatismos Cerrados de la Cabeza/fisiopatología , Traumatismos Cerrados de la Cabeza/psicología , Hipocampo/patología , Aprendizaje por Laberinto , Actividad Motora , Enfermedad de Alzheimer/epidemiología , Análisis de Varianza , Animales , Trastornos del Conocimiento/etiología , Traumatismos Cerrados de la Cabeza/patología , Hipocampo/citología , Humanos , Ratones , Ratones Noqueados , Neuronas/citología , Neuronas/patología , Postura , Reflejo , Factores de Riesgo , Factores de TiempoRESUMEN
Apolipoprotein E genotype is an important risk factor of Alzheimer's disease, which is associated with the degeneration of distinct brain neuronal systems. In the present study we employed apolipoprotein E-deficient mice and human apolipoprotein E3 and apolipoprotein E4 transgenic mice on a null mouse apolipoprotein E background, to examine the extent to which distinct brain neuronal systems are affected by apolipoprotein E and the isoform specificity of this effect. This was pursued by histological and autoradiographic measurements utilizing neuron specific presynaptic markers. The results thus obtained revealed significant reductions in the levels of brain cholinergic and noradrenergic nerve terminals in young apolipoprotein E-deficient mice and no changes in brain dopaminergic nerve terminals. These cholinergic and noradrenergic presynaptic derangements were ameliorated similarly in human apolipoprotein E3 and apolipoprotein E4 transgenic mice. In the case of the cholinergic system, this resulted in complete reversal of the presynaptic deficits, whereas in the case of the noradrenergic neurons the amelioration was partial. These findings suggest that brain cholinergic and noradrenergic neurons are markedly more dependent on brain apolipoprotein E than brain dopaminergic neurons and that the isoform specificity of these effects is not apparent at a young age under non-challenged conditions.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Apolipoproteínas E/deficiencia , Fibras Colinérgicas/patología , Terminales Presinápticos/metabolismo , Acetilcolina/metabolismo , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/fisiopatología , Animales , Apolipoproteína E3 , Apolipoproteína E4 , Apolipoproteínas E/genética , Apolipoproteínas E/metabolismo , Fibras Colinérgicas/metabolismo , Dopamina/metabolismo , Humanos , Masculino , Ratones , Ratones Noqueados , Norepinefrina/metabolismo , Terminales Presinápticos/patología , Terminales Presinápticos/ultraestructuraRESUMEN
Experimental autoimmune dementia is a rat model designed to examine the potential role of anti-cholinergic neurons antibodies in neuronal degeneration in dementia and Alzheimer's disease. We have previously shown that sera of patients with Alzheimer's disease contain antibodies which bind specifically to the high molecular weight neurofilament protein of the purely cholinergic electromotor neurons of Torpedo. Production of such antibodies in experimental autoimmune dementia rats by prolonged immunization with the Torpedo cholinergic high molecular weight neurofilament subunit results in accumulation of antibodies in the septum and hippocampus of the immunized rats, in a marked decrease in the density of forebrain cholinergic neurons, and in memory deficits. In the present study we characterized the open-field behavior of experimental autoimmune dementia rats, and examined whether, like in dementia, the spatiotemporal organization of their behavior is impaired. The results obtained revealed that experimental autoimmune dementia rats travel shorter distances; explore a smaller part of the open-field; and perform less round-trips to the key location--the home base--in reference to which their behavior is normally organized. The shrinkage of the explored space and the reduced number of round trips are independent of the amount of locomotion and represent a deterioration in the organization of behavior in time and space. These behavioral changes are specific to the anti-cholinergic immune response of experimental autoimmune dementia rats as they are not observed in rats which were immunized with chemically heterogeneous high molecular weight neurofilament subunit.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Enfermedades Autoinmunes/fisiopatología , Demencia/inmunología , Demencia/fisiopatología , Actividad Motora , Proteínas de Neurofilamentos/inmunología , Vías Aferentes/inmunología , Animales , Inmunización , Masculino , Ratas , Ratas Sprague-Dawley , Médula Espinal/inmunología , TorpedoRESUMEN
Although the etiology and pathogenesis of the cholinergic degeneration in Alzheimer's disease are not known, several reports implicate immunological mechanisms. Recently we have shown that sera of Alzheimer's disease patients contain antibodies which bind specifically to the heavy molecular weight neurofilament protein of Torpedo cholinergic neurons. In the present study we investigated the possibility that such antibodies play a role in neuronal degeneration by examining the behavioral and cellular effects of immunizing rats with the heavy neurofilament protein of Torpedo cholinergic neurons. The immunized rats developed antibodies which were specific to the heavy neurofilament protein of Torpedo cholinergic neurons and which cross-reacted with rat brain neurofilaments. Immunohistochemical studies revealed the accumulation of antibodies in the perikarya and neurites of neurons in the septum and hippocampus of the cholinergic neurofilament immunized rats and in white matter tracts in their forebrains. No such staining was seen in adjuvant immunized control rats. Behavioral tests revealed that rats immunized with the heavy cholinergic neurofilament protein performed significantly worse than controls in a T-maze alternation test and that their performance deteriorated profoundly after the introduction of a 20-s delay in the paradigm, indicating a deficit in short term memory. In contrast, both groups performed similarly in a T-maze discrimination test, indicating that long term reference memory was not affected by immunization with the heavy cholinergic neurofilament protein. Further experiments revealed that the rats immunized with the heavy cholinergic neurofilament protein were also deficient in a reversal of choice paradigm in a position discrimination test.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Enfermedad de Alzheimer/inmunología , Anticuerpos/fisiología , Proteínas de Filamentos Intermediarios/inmunología , Trastornos de la Memoria/inmunología , Proteínas de Neurofilamentos , Animales , Conducta Animal , Encéfalo/metabolismo , Inmunohistoquímica , Masculino , Trastornos de la Memoria/psicología , Ratas , Ratas EndogámicasRESUMEN
Apolipoprotein E (apoE4) and head trauma are important genetic and environmental risk factors for Alzheimer's disease. Furthermore, apoE4 increases both the acute and chronic consequences of head trauma. The latter are associated with the deposition of amyloid-beta, which is particularly elevated in apoE4 subjects. The short-term effects of head injury are associated with transiently increased metabolism of amyloid precursor protein (APP) and its secreted fragment, APPs. In the present study, we examined the possibility that the acute, short-term pathological effects of apoE4 following head trauma and the corresponding neuroprotective effects of apoE3 are related to isoform-specific effects of apoE on APP metabolism. Accordingly, male transgenic mice expressing human apoE3 or apoE4 on a null mouse apoE background and apoE-deficient and control mice were subjected to closed head injury (CHI). The resulting effects on brain APP, and on its secreted products, APPs and secreted product of the alpha-cleavage of APP (APPsalpha) were then determined 24 h following injury. Immunoblotting revealed no significant differences between the basal APP, APPs and APPsalpha levels of the hippocampus or the cortex of the control and the apoE3 and ApoE4 transgenic mice. The apoE-deficient mice also had similar cortical basal levels of APP and its metabolites, whereas their corresponding basal hippocampal APP and APPs levels were lower than those of the other groups. CHI lowered the hipppocampal APPs and APPsalpha levels of the apoE4 transgenic mice, whereas those of the apoE3 transgenic mice and of the control and apoE-deficient mice were not affected by this insult. In contrast, CHI raised the cortical APP and APPs levels of the apoE3 transgenic mice but had no significant effect on those of the other mice groups. These animal model findings suggest that the acute, short-term pathological effects of apoE4 following CHI and the corresponding neuroprotective effects of apoE3 may be mediated by their opposing effects on the expression and cleavage of cortical and hippocampal APP. Similar isoform-specific interactions between apoE and APP may play a role in the acute, short-term effects of head trauma in humans.
Asunto(s)
Precursor de Proteína beta-Amiloide/metabolismo , Apolipoproteínas E/metabolismo , Traumatismos Cerrados de la Cabeza/metabolismo , Animales , Apolipoproteína E3 , Apolipoproteína E4 , Apolipoproteínas E/deficiencia , Química Encefálica , Modelos Animales de Enfermedad , Humanos , Immunoblotting , Masculino , Ratones , Ratones Transgénicos , Fracciones Subcelulares/metabolismoRESUMEN
Apolipoprotein E, the major brain lipid-binding protein, is expressed in humans as three common isoforms (E2, E3 and E4). Previous studies revealed that the allele apolipoprotein E4 is a major genetic risk factor of Alzheimer's disease and that traumatic brain injury is associated with increased risk for developing this disease. Furthermore, it has been suggested that the effects of traumatic head injury and apolipoprotein E4 in Alzheimer's disease are synergistic. To test the hypothesis that the apolipoprotein E genotype affects susceptibility to brain injury, we subjected transgenic mice, expressing either human apolipoprotein E3 or human apolipoprotein E4 on a null mouse apolipoprotein E background and apolipoprotein E-deficient knockouts, to closed head injury and compared mortality, neurological recovery and the extent of brain damage of the survivors. More than 50% of the transgenic mice expressing human apolipoprotein E4 died following closed head injury, whereas only half as many of the transgenic mice expressing human apolipoprotein E3, and of the control and apolipoprotein E-deficient mice died during this period (P<0.02). A neurological severity score used for clinical assessment of the surviving mice up to 11 days after closed head injury revealed that the four mouse groups displayed similar severity of damage at 1h following injury. At three and 11 days post-injury, however, the neurological severity scores of the transgenic mice expressing human apolipoprotein E3 were significantly lower than those of the other three groups whose scores were similar, indicating better recovery of the transgenic mice expressing human apolipoprotein E3. Histopathological examination of the mice performed 11 days post-injury revealed, consistent with the above neurological results, that the size of the damaged brain area of the transgenic mice expressing human apolipoprotein E3 was smaller than that of the other head-injured groups. These findings show that transgenic mice expressing human apolipoprotein E4 are more susceptible than those expressing apolipoprotein E3 to closed head injury. We suggest that this effect is due to both a protective effect of apolipoprotein E3 and an apolipoprotein E4-related pathological function.