RESUMEN
Clinical investigations have highlighted a biological link between reduced brain glucose metabolism and Alzheimer's disease (AD). Previous studies showed that glucose deprivation may influence amyloid beta formation in vivo but no data are available on the effect that this condition might have on tau protein metabolism. In the current paper, we investigated the effect of glucose deficit on tau phosphorylation, memory and learning, and synaptic function in a transgenic mouse model of tauopathy, the h-tau mice. Compared with controls, h-tau mice with brain glucose deficit showed significant memory impairments, reduction of synaptic long-term potentiation, increased tau phosphorylation, which was mediated by the activation of P38 MAPK Kinase pathway. We believe our studies demonstrate for the first time that reduced glucose availability in the central nervous system directly triggers behavioral deficits by promoting the development of tau neuropathology and synaptic dysfunction. Since restoring brain glucose levels and metabolism could afford the opportunity to positively influence the entire AD phenotype, this approach should be considered as a novel and viable therapy for preventing and/or halting the disease progression.
Asunto(s)
Conducta Animal , Encéfalo/metabolismo , Glucosa/metabolismo , Tauopatías/metabolismo , Enfermedad de Alzheimer , Animales , Encéfalo/fisiopatología , Región CA1 Hipocampal/metabolismo , Región CA1 Hipocampal/fisiopatología , Desoxiglucosa , Modelos Animales de Enfermedad , Potenciales Postsinápticos Excitadores/fisiología , Femenino , Aprendizaje/fisiología , Potenciación a Largo Plazo/fisiología , Masculino , Memoria/fisiología , Ratones , Ratones Transgénicos , Neuronas , Fosforilación , Distribución Aleatoria , Sinapsis/metabolismo , Sinapsis/fisiología , Tauopatías/genética , Tauopatías/fisiopatología , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo , Proteínas tau/genéticaRESUMEN
The pathological hallmark of Alzheimer's disease (AD) is accumulation of misfolded amyloid-ß peptides and hyperphosphorylated tau protein in the brain. Increasing evidence suggests that serine-aspartyl proteases-caspases are activated in the AD brain. Previous studies identified a caspase-3 cleavage site within the amyloid-ß precursor protein, and a caspase-3 cleavage of tau as the mechanisms involved in the development of Aß and tau neuropathology, respectively. However, the potential role that caspase-3 could have on tau metabolism remains unknown. In the current studies, we provide experimental evidence that caspase-3 directly and specifically regulates tau phosphorylation, and demonstrate that this effect is mediated by the GSK3ß kinase pathway via a caspase-3-dependent cleavage of the protein kinase B (also known as Akt). In addition, we confirm these results in vivo by using a transgenic mouse model of AD. Collectively, our findings demonstrate a new role for caspase-3 in the neurobiology of tau, and suggest that therapeutic strategies aimed at inhibiting this protease-dependent cleavage of Akt may prove beneficial in preventing tau hyperphosphorylation and subsequent neuropathology in AD and related tauopathies.
Asunto(s)
Caspasa 3/metabolismo , Glucógeno Sintasa Quinasa 3 beta/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Encéfalo/metabolismo , Glucógeno Sintasa Quinasa 3/metabolismo , Humanos , Ratones , Ratones Transgénicos , Neuronas/metabolismo , Proteína Oncogénica v-akt/metabolismo , Fosforilación , Tauopatías/metabolismo , Proteínas tau/metabolismoRESUMEN
Parkinson's disease (PD) is a chronic and progressive neurodegenerative disorder. Although rare genetically linked cases of PD have been reported, most incidences are sporadic in nature. Late-onset, sporadic PD is thought to result from the combined effects of genetic and environmental risk factors exposure. Sleep and circadian rhythm disorders are recurrent among PD patients and appear early in the disease. Although some evidence supports a relationship between circadian disruption (CD) and PD, whether this is secondary to the motor symptoms or, indeed, is a factor that contributes to the pathogenesis of the disease remains to be investigated. In the present paper, we studied the direct consequence of chronic CD on the development of the phenotype in the MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridinen) model of PD. Pre-exposure to CD to mice treated with MPTP resulted in an exacerbation of motor deficit and a significant reduction in the capability of acquiring motor skills. These changes were associated with a greater loss of tyrosine hydroxylase cell content and intense neuroinflammation. Taken together, our findings demonstrate that CD by triggering a robust neuroinflammatory reaction and degeneration of the nigral-dopaminergic neuronal system exacerbates motor deficit. They support the novel hypothesis that circadian rhythm disorder is an environmental risk factor for developing PD.
Asunto(s)
Trastornos Cronobiológicos/complicaciones , Ritmo Circadiano/fisiología , Enfermedad de Parkinson/metabolismo , Animales , Conducta Animal/fisiología , Ritmo Circadiano/efectos de los fármacos , Modelos Animales de Enfermedad , Neuronas Dopaminérgicas/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos C57BL , Actividad Motora/efectos de los fármacos , Degeneración Nerviosa/patología , Fármacos Neuroprotectores/farmacología , Enfermedad de Parkinson/tratamiento farmacológico , Factores de Riesgo , Tirosina 3-Monooxigenasa/metabolismoRESUMEN
Environmental stressor exposure is associated with a variety of age-related diseases including neurodegeneration. Although the initial events of sporadic Parkinson's disease (PD) are not known, consistent evidence supports the hypothesis that the disease results from the combined effect of genetic and environmental risk factors. Among them, behavioral stress has been shown to cause damage and neuronal loss in different areas of the brain, however, its effect on the dopaminergic system and PD pathogenesis remains to be characterized. The C57BL/6 mice underwent chronic restraint/isolation (RI) stress and were then treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), whereas the control mice were treated only with MPTP and the effect on the PD-like phenotype was evaluated. The mice that underwent RI before the administration of MPTP manifested an exaggerated motor deficit and impairment in the acquisition of motor skills, which were associated with a greater loss of neuronal tyrosine hydroxylase and astrocytes activation. By showing that RI influences the onset and progression of the PD-like phenotype, our study underlines the novel pathogenetic role that chronic behavioral stressor has in the disease process by triggering neuroinflammation and degeneration of the nigral dopaminergic system.
Asunto(s)
1-Metil-4-fenil-1,2,3,6-Tetrahidropiridina , Encéfalo/fisiopatología , Inflamación/fisiopatología , Trastornos Motores/fisiopatología , Enfermedad de Parkinson/fisiopatología , Estrés Psicológico/fisiopatología , Animales , Conducta Animal/fisiología , Enfermedad Crónica , Modelos Animales de Enfermedad , Femenino , Inflamación/complicaciones , Inflamación/psicología , Masculino , Ratones , Ratones Endogámicos C57BL , Trastornos Motores/complicaciones , Trastornos Motores/psicología , Enfermedad de Parkinson/complicaciones , Enfermedad de Parkinson/psicología , Estrés Psicológico/complicaciones , Estrés Psicológico/psicologíaRESUMEN
Dysregulation of stress hormones, such as glucocorticoids, in adult life increases the risk to develop Alzheimer's disease (AD). However, the effect of prenatal glucocorticoids exposure on AD development in the offspring remains unknown. We studied how gestational dexamethasone exposure influences the AD-like phenotype in the offspring of triple transgenic AD mice (3 × Tg). To this end, female mice received dexamethasone or vehicle during the entire pregnancy time in the drinking water. Offspring from vehicle-treated 3 × Tg (controls) were compared with offspring from dexamethasone-treated 3 × Tg later in life for their memory, learning ability and brain pathology. Compared with controls, offspring from dexamethasone-treated mothers displayed improvement in their memory as assessed by fear conditioning test, both in the cue and recall phases. The same animals had a significant reduction in the insoluble fraction of tau, which was associated with an increase in autophagy. In addition, they showed an activation of the transcription factor cellular response element-binding protein and an increase in brain-derived neurotrophic factor and c-FOS protein levels, key regulators of synaptic plasticity and memory. We conclude that dexamethasone exposure during pregnancy provides long-lasting protection against the onset and development of the AD-like phenotype by improving cognition and tau pathology.
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Trastornos del Conocimiento/etiología , Trastornos del Conocimiento/prevención & control , Dexametasona/uso terapéutico , Tauopatías/etiología , Tauopatías/prevención & control , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Animales , Modelos Animales de Enfermedad , Femenino , Humanos , Masculino , Exposición Materna , Aprendizaje por Laberinto/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mutación/genética , Embarazo , Presenilina-1/genética , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Proteínas tau/genéticaRESUMEN
FLAP (5-lipoxygenase-activating protein) is a protein widely distributed within the central nervous system whose function is to regulate the activation of the 5-Lipoxygenase enzyme. Although previous works show that pharmacological blockade of FLAP improve the amyloidotic phenotype of the Tg2576, its contribution to tau pathology remains to be investigated. In the present paper, we studied the effect of FLAP pharmacological inhibition on the metabolism of endogenous tau in these mice. Total tau levels in the brains of mice receiving MK-591, a selective and specific FLAP inhibitor, were not changed when compared with controls. By contrast, treated animals had a significant reduction of tau phosphorylation at specific sites: Ser396; Ser396/Ser404; and Thr 231/Ser 235. This reduction was associated with a significant decrease in the activity of glycogen synthase kinase-3 beta, but not other kinases. In addition, MK-591-treated mice had a significant increase in the post-synaptic density protein-95 and the dendritic protein microtubule-associated protein 2. These data establish a novel functional role for FLAP in the metabolism of tau, and together with its known Aß modulatory effect they suggest that its pharmacological inhibition could represent a novel therapeutic opportunity for Alzheimer's disease.