RESUMEN
In a previous study, regional reductions in cerebral glucose metabolism have been demonstrated in the tauopathy mouse model rTg4510 (Endepols et al., 2022). Notably, glucose hypometabolism was present in some brain regions without co-localized synaptic degeneration measured with [18F]UCB-H. We hypothesized that in those regions hypometabolism may reflect reduced functional connectivity rather than synaptic damage. To test this hypothesis, we performed seed-based metabolic connectivity analyses using [18F]FDG-PET data in this mouse model. Eight rTg4510 mice at the age of seven months and 8 non-transgenic littermates were injected intraperitoneally with 11.1 ± 0.8 MBq [18F]FDG and spent a 35-min uptake period awake in single cages. Subsequently, they were anesthetized and measured in a small animal PET scanner for 30 min. Three seed-based connectivity analyses were performed per group. Seeds were selected for apparent mismatch between [18F]FDG and [18F]UCB-H. A seed was placed either in the medial orbitofrontal cortex, dorsal hippocampus or dorsal thalamus, and correlated with all other voxels of the brain across animals. In the control group, the emerging correlative pattern was strongly overlapping for all three seed locations, indicating a uniform fronto-thalamo-hippocampal resting state network. In contrast, rTg4510 mice showed three distinct networks with minimal overlap. Frontal and thalamic networks were greatly diminished. The hippocampus, however, formed a new network with the whole parietal cortex. We conclude that resting-state functional networks are fragmented in the brain of rTg4510 mice. Thus, hypometabolism can be explained by reduced functional connectivity of brain areas devoid of tau-related pathology, such as the thalamus.
Asunto(s)
Fluorodesoxiglucosa F18 , Tomografía de Emisión de Positrones , Animales , Ratones , Fluorodesoxiglucosa F18/metabolismo , Ratones Transgénicos , Encéfalo/metabolismo , Mapeo Encefálico , Modelos Animales de Enfermedad , Imagen por Resonancia MagnéticaRESUMEN
The stereotypical progression of Tau pathology during Alzheimer disease has been attributed to trans-neuronal spreading of misfolded Tau proteins, followed by prion-like templated aggregation of Tau. The nature of Tau and the cellular mechanisms of Tau spreading are still under debate. We hypothesized that Tau's propensity for aggregation would correlate with its ability to spread across synapses and propagate pathology. To study the progressive propagation of Tau proteins in brain regions relevant for Alzheimer disease, we used mice expressing near-physiological levels of full-length human Tau protein carrying pro-aggregant (TauΔK280, TauΔK) or anti-aggregant (TauΔK280-PP, TauΔK-PP) mutations in the entorhinal cortex (EC). To enhance Tau expression in the EC, we performed EC injections of adeno-associated virus (AAV) particles encoding TauΔK or TauΔK-PP. The brains of injected and non-injected EC/TauΔK and EC/TauΔK-PP mice were studied by immunohistological and biochemical techniques to detect Tau propagation to dentate gyrus (DG) neurons and Tau-induced pathological changes. Pro- and anti-aggregant mice had comparable low transgene expression (~0.2 times endogenous mouse Tau). They accumulated human Tau at similar rates and only in expressing EC neurons, including their axonal projections of the perforant path and presynaptic terminals in the molecular layer of the DG. Pro-aggregant EC/TauΔK mice showed misfolded Tau and synaptic protein alterations in EC neurons, not observed in anti-aggregant EC/TauΔK-PP mice. Additional AAV-mediated expression of TauΔK or TauΔK-PP in EC/TauΔK or EC/TauΔK-PP mice, respectively, increased the human Tau expression to ~0.65 times endogenous mouse Tau, with comparable spreading of TauΔK and TauΔK-PP throughout the EC. There was a low level of transcellular propagation of Tau protein, without pathological phosphorylation or misfolding, as judged by diagnostic antibodies. Additionally, TauΔK but not TauΔK-PP expression induced hippocampal astrogliosis. Low levels of pro- or anti-aggregant full-length Tau show equivalent distributions in EC neurons, independent of their aggregation propensity. Increasing the expression via AAV induce local Tau misfolding in the EC neurons, synaptotoxicity, and astrogliosis and lead to a low level of detectable trans-neuronal spreading of Tau. This depends on its concentration in the EC, but, contrary to expectations, does not depend on Tau's aggregation propensity/misfolding and does not lead to templated misfolding in recipient neurons.
Asunto(s)
Enfermedad de Alzheimer , Tauopatías , Ratones , Animales , Humanos , Proteínas tau/genética , Proteínas tau/metabolismo , Enfermedad de Alzheimer/genética , Tauopatías/metabolismo , Gliosis , Hipocampo/metabolismo , Modelos Animales de Enfermedad , Ratones TransgénicosRESUMEN
The accumulation of tau is a hallmark of several neurodegenerative diseases and is associated with neuronal hypoactivity and presynaptic dysfunction. Oral administration of the adenosine A1 receptor antagonist rolofylline (KW-3902) has previously been shown to reverse spatial memory deficits and to normalize the basic synaptic transmission in a mouse line expressing full-length pro-aggregant tau (TauΔK) at low levels, with late onset of disease. However, the efficacy of treatment remained to be explored for cases of more aggressive tauopathy. Using a combination of behavioral assays, imaging with several PET-tracers, and analysis of brain tissue, we compared the curative reversal of tau pathology by blocking adenosine A1 receptors in three mouse models expressing different types and levels of tau and tau mutants. We show through positron emission tomography using the tracer [18F]CPFPX (a selective A1 receptor ligand) that intravenous injection of rolofylline effectively blocks A1 receptors in the brain. Moreover, when administered to TauΔK mice, rolofylline can reverse tau pathology and synaptic decay. The beneficial effects are also observed in a line with more aggressive tau pathology, expressing the amyloidogenic repeat domain of tau (TauRDΔK) with higher aggregation propensity. Both models develop a progressive tau pathology with missorting, phosphorylation, accumulation of tau, loss of synapses, and cognitive decline. TauRDΔK causes pronounced neurofibrillary tangle assembly concomitant with neuronal death, whereas TauΔK accumulates only to tau pretangles without overt neuronal loss. A third model tested, the rTg4510 line, has a high expression of mutant TauP301L and hence a very aggressive phenotype starting at ~3 months of age. This line failed to reverse pathology upon rolofylline treatment, consistent with a higher accumulation of tau-specific PET tracers and inflammation. In conclusion, blocking adenosine A1 receptors by rolofylline can reverse pathology if the pathological potential of tau remains below a threshold value that depends on concentration and aggregation propensity.
Asunto(s)
Receptor de Adenosina A1 , Tauopatías , Ratones , Animales , Ratones Transgénicos , Receptor de Adenosina A1/genética , Receptor de Adenosina A1/metabolismo , Proteínas tau/genética , Proteínas tau/metabolismo , Hipocampo/metabolismo , Tauopatías/tratamiento farmacológico , Tauopatías/genética , Tauopatías/metabolismo , Cognición , Modelos Animales de EnfermedadRESUMEN
Cerebral glucose hypometabolism is a typical hallmark of Alzheimer's disease (AD), usually associated with ongoing neurodegeneration and neuronal dysfunction. However, underlying pathological processes are not fully understood and reproducibility in animal models is not well established. The aim of the present study was to investigate the regional interrelation of glucose hypometabolism measured by [18F]FDG positron emission tomography (PET) with various molecular targets of AD pathophysiology using the PET tracers [18F]PI-2620 for tau deposition, [18F]DPA-714 for TSPO expression associated with neuroinflammation, and [18F]UCB-H for synaptic density in a transgenic tauopathy mouse model. Seven-month-old rTg4510 mice (n = 8) and non-transgenic littermates (n = 8) were examined in a small animal PET scanner with the tracers listed above. Hypometabolism was observed throughout the forebrain of rTg4510 mice. Tau pathology, increased TSPO expression, and synaptic loss were co-localized in the cortex and hippocampus and correlated with hypometabolism. In the thalamus, however, hypometabolism occurred in the absence of tau-related pathology. Thus, cerebral hypometabolism was associated with two regionally distinct forms of molecular pathology: (1) characteristic neuropathology of the Alzheimer-type including synaptic degeneration and neuroinflammation co-localized with tau deposition in the cerebral cortex, and (2) pathological changes in the thalamus in the absence of other markers of AD pathophysiology, possibly reflecting downstream or remote adaptive processes which may affect functional connectivity. Our study demonstrates the feasibility of a multitracer approach to explore complex interactions of distinct AD-pathomechanisms in vivo in a small animal model. The observations demonstrate that multiple, spatially heterogeneous pathomechanisms can contribute to hypometabolism observed in AD mouse models and they motivate future longitudinal studies as well as the investigation of possibly comparable pathomechanisms in human patients.
Asunto(s)
Enfermedad de Alzheimer , Tauopatías , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/metabolismo , Animales , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Glucosa , Humanos , Ratones , Ratones Transgénicos , Tomografía de Emisión de Positrones/métodos , Receptores de GABA/metabolismo , Reproducibilidad de los Resultados , Tauopatías/diagnóstico por imagen , Tauopatías/metabolismo , Proteínas tau/metabolismoRESUMEN
BACKGROUND: One of the major hallmarks of Alzheimer's disease (AD)is the aberrant modification and aggregation of the microtubule-associated protein Tau . The extent of Tau pathology correlates with cognitive decline, strongly implicating Tau in the pathogenesis of the disease. Because the inhibition of Tau aggregation may be a promising therapeutic target, we tested the efficacy of BSc3094, an inhibitor of Tau aggregation, in reducing Tau pathology and ameliorating the disease symptoms in transgenic mice. METHODS: Mice expressing human Tau with the P301L mutation (line rTg4510) were infused with BSc3094 into the lateral ventricle using Alzet osmotic pumps connected to a cannula that was placed on the skull of the mice, thus bypassing the blood-brain barrier (BBB) . The drug treatment lasted for 2 months, and the effect of BSc3094 on cognition and on reversing hallmarks of Tau pathology was assessed. RESULTS: BSc3094 significantly reduced the levels of Tau phosphorylation and sarkosyl-insoluble Tau. In addition, the drug improved cognition in different behavioral tasks and reduced anxiety-like behavior in the transgenic mice used in the study. CONCLUSIONS: Our in vivo investigations demonstrated that BSc3094 is capable of partially reducing the pathological hallmarks typically observed in Tau transgenic mice, highlighting BSc3094 as a promising compound for a future therapeutic approach for AD.
RESUMEN
RTP801/REDD1 is a stress-regulated protein whose upregulation is necessary and sufficient to trigger neuronal death. Its downregulation in Parkinson's and Huntington's disease models ameliorates the pathological phenotypes. In the context of Alzheimer's disease (AD), the coding gene for RTP801, DDIT4, is responsive to Aß and modulates its cytotoxicity in vitro. Also, RTP801 mRNA levels are increased in AD patients' lymphocytes. However, the involvement of RTP801 in the pathophysiology of AD has not been yet tested. Here, we demonstrate that RTP801 levels are increased in postmortem hippocampal samples from AD patients. Interestingly, RTP801 protein levels correlated with both Braak and Thal stages of the disease and with GFAP expression. RTP801 levels are also upregulated in hippocampal synaptosomal fractions obtained from murine 5xFAD and rTg4510 mice models of the disease. A local RTP801 knockdown in the 5xFAD hippocampal neurons with shRNA-containing AAV particles ameliorates cognitive deficits in 7-month-old animals. Upon RTP801 silencing in the 5xFAD mice, no major changes were detected in hippocampal synaptic markers or spine density. Importantly, we found an unanticipated recovery of several gliosis hallmarks and inflammasome key proteins upon neuronal RTP801 downregulation in the 5xFAD mice. Altogether our results suggest that RTP801 could be a potential future target for theranostic studies since it could be a biomarker of neuroinflammation and neurotoxicity severity of the disease and, at the same time, a promising therapeutic target in the treatment of AD.
Asunto(s)
Enfermedad de Alzheimer/genética , Encefalitis/genética , Trastornos de la Memoria/genética , Factores de Transcripción/fisiología , Enfermedad de Alzheimer/complicaciones , Enfermedad de Alzheimer/patología , Animales , Estudios de Casos y Controles , Modelos Animales de Enfermedad , Encefalitis/etiología , Encefalitis/patología , Femenino , Humanos , Masculino , Trastornos de la Memoria/etiología , Trastornos de la Memoria/patología , Ratones , Ratones Transgénicos , Neuroinmunomodulación/genética , Síndromes de Neurotoxicidad/etiología , Síndromes de Neurotoxicidad/genética , Síndromes de Neurotoxicidad/patología , Índice de Severidad de la EnfermedadRESUMEN
BACKGROUND: Aggregation of tau proteins is a distinct hallmark of tauopathies and has been a focus of research and clinical trials for Alzheimer's Disease. Recent reports have pointed towards a toxic effect of soluble or oligomeric tau in the spreading of tau pathology in Alzheimer's disease. Here we investigated the effects of expressing human tau repeat domain (tauRD) with pro- or anti-aggregant mutations in regulatable transgenic mouse models of Alzheimer's Disease on the functional neuronal networks and the structural connectivity strength. METHODS: Pro-aggregant and anti-aggregant mice were studied when their mutant tauRD was switched on for 12 months to reach the stage where pro-aggregant mice show cognitive impairment, whereas anti-aggregant mice remained cognitively normal. Then, mutant tauRD was switched off by doxycycline treatment for 8 weeks so that soluble transgenic tau disappeared and cognition recovered in the pro-aggregant mice, although some aggregates remained. At these two time points, at baseline after 12 months of mutant tau expression and after 8 weeks of doxycycline treatment, resting state fMRI and diffusion MRI were used to determine functional neuronal networks and fiber connectivities. Results of the transgenic mice were compared with wildtype littermates. RESULTS: Functional connectivity was strongly reduced in transgenic animals during mutant tauRD expression, in relation to WT mice. Interestingly, transgenic mice with the non-aggregant tau mutant showed identical functional deficits as the pro-aggregant mice, even though in this case there was no cognitive decline by behavioral testing. Upon 8 weeks doxycycline treatment and transgene switch-off, functional connectivity in both transgenic groups presented complete normalization of functional connectivity strength, equivalent to the situation in WT littermates. Structural connectivity was found only marginally sensitive to mutant tau expression (both pro- and anti-aggregant tauRD) and by doxycycline treatment. CONCLUSIONS: Our in vivo investigations unravel for the first time a strong reduction of functional neuronal networks by the presence of increased soluble rather than fibrillary tau, independent of its intrinsic propensity of aggregation, which is reversible by switching tau off. Our functional MRI study thus is an unexpected in vivo validation of a novel property of tau, while previous results pointed to a role of aggregation propensity for a pathological state by histopathology and cognitive decline. Our results present further evidence for early tauopathy biomarkers or a potential early stage drug target by functional networks analysis.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Modelos Animales de Enfermedad , Memoria/fisiología , Proteínas tau/metabolismo , Animales , Cognición/fisiología , Hipocampo/metabolismo , Ratones , Red Nerviosa/fisiopatología , Neuronas/metabolismo , Sinapsis/metabolismo , Tauopatías/metabolismoRESUMEN
BACKGROUND: The microtubule-associated protein Tau plays a role in neurodegeneration as well as neurogenesis. Previous work has shown that the expression of the pro-aggregant mutant Tau repeat domain causes strong aggregation and pronounced neuronal loss in the hippocampus whereas the anti-aggregant form has no deleterious effects. These two proteins differ mainly in their propensity to form ß structure and hence to aggregate. METHODS: To elucidate the basis of these contrasting effects, we analyzed organotypic hippocampal slice cultures (OHSCs) from transgenic mice expressing the repeat domain (RD) of Tau with the anti-aggregant mutation (TauRDΔKPP) and compared them with slices containing pro-aggregant TauRDΔK. Transgene expression in the hippocampus was monitored via a sensitive bioluminescence reporter gene assay (luciferase). RESULTS: The expression of the anti-aggregant TauRDΔKPP leads to a larger volume of the hippocampus at a young age due to enhanced neurogenesis, resulting in an increase in neuronal number. There were no signs of activation of microglia and astrocytes, indicating the absence of an inflammatory reaction. Investigation of signaling pathways showed that Wnt-5a was strongly decreased whereas Wnt3 was increased. A pronounced increase in hippocampal stem cell proliferation (seen by BrdU) was observed as early as P8, in the CA regions where neurogenesis is normally not observed. The increase in neurons persisted up to 16 months of age. CONCLUSION: The data suggest that the expression of anti-aggregant TauRDΔKPP enhances hippocampal neurogenesis mediated by the canonical Wnt signaling pathway, without an inflammatory reaction. This study points to a role of tau in brain development and neurogenesis, in contrast to its detrimental role in neurodegeneration at later age.
Asunto(s)
Neurogénesis , Agregación Patológica de Proteínas/fisiopatología , Proteínas tau/química , Proteínas tau/genética , Secuencias de Aminoácidos , Animales , Astrocitos/citología , Astrocitos/patología , Hipocampo/crecimiento & desarrollo , Humanos , Ratones , Ratones Transgénicos , Microglía/citología , Microglía/metabolismo , Microglía/patología , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Células-Madre Neurales/metabolismo , Prolina , Agregación Patológica de Proteínas/metabolismo , Conformación Proteica , Conformación Proteica en Lámina beta , Dominios Proteicos , Secuencias Repetitivas de Aminoácido , Tauopatías/fisiopatología , Proteínas tau/metabolismoRESUMEN
Huntington's disease (HD) is a fatal neurodegenerative disease with motor, cognitive and psychiatric impairment. Dysfunctions in HD models have been related to reduced levels of striatal brain-derived neurotrophic factor (BDNF) and imbalance between its receptors TrkB and p75(NTR). Thus, molecules with activity on the BDNF/TrkB/p75 system can have therapeutic potential. 7,8-Dihydroxyflavone (7,8-DHF) was described as a TrkB agonist in several models of neuro-degenerative diseases, however, its TrkB activation profile needs further investigation due to its pleiotropic properties and divergence from BDNF effect. To investigate this, we used in vitro and in vivo models of HD to dissect TrkB activation upon 7,8-DHF treatment. 7,8-DHF treatment in primary cultures showed phosphorylation of TrkBY816 but not TrkBY515 with activation of the PLCγ1 pathway leading to morphological and functional improvements. Chronic administration of 7,8-DHF delayed motor deficits in R6/1 mice and reversed deficits on the Novel Object Recognition Test (NORT) at 17 weeks. Morphological and biochemical analyses revealed improved striatal levels of enkephalin, and prevention of striatal volume loss. We found a TrkBY816 but not TrkBY515 phosphorylation recovery in striatum concordant with in vitro results. Additionally, 7,8-DHF normalized striatal levels of induced and neuronal nitric oxide synthase (iNOS and nNOS, respectively) and ameliorated the imbalance of p75/TrkB. Our results provide new insights into the mechanism of action of 7,8-DHF suggesting that its effect through the TrkB receptor in striatum is via selective phosphorylation of its Y816 residue and activation of PLCγ1 pathway, but pleiotropic effects of the drug also contribute to its therapeutic potential.
Asunto(s)
Flavonas/metabolismo , Flavonas/uso terapéutico , Enfermedad de Huntington/metabolismo , Animales , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Cognición/efectos de los fármacos , Cuerpo Estriado/metabolismo , Modelos Animales de Enfermedad , Flavonas/farmacología , Hipocampo/metabolismo , Enfermedad de Huntington/tratamiento farmacológico , Ratones , Ratones Transgénicos , Neuronas Motoras/efectos de los fármacos , Fosfolipasa C gamma/efectos de los fármacos , Fosfolipasa C gamma/metabolismo , Fosforilación , Receptor trkB/metabolismo , Transducción de Señal/efectos de los fármacosRESUMEN
Accumulation of Tau is a characteristic hallmark of several neurodegenerative diseases but the mode of toxic action of Tau is poorly understood. Here, we show that the Tau protein is toxic due to its aggregation propensity, whereas phosphorylation and/or missorting is not sufficient to cause neuronal dysfunction. Aggregate-prone Tau accumulates, when expressed in vitro at near-endogenous levels, in axons as spindle-shaped grains. These axonal grains contain Tau that is folded in a pathological (MC-1) conformation. Proaggregant Tau induces a reduction of neuronal ATP, concomitant with loss of dendritic spines. Counterintuitively, axonal grains of Tau are not targeted for degradation and do not induce a molecular stress response. Proaggregant Tau causes neuronal and astrocytic hypoactivity and presynaptic dysfunction instead. Here, we show that the adenosine A1 receptor antagonist rolofylline (KW-3902) is alleviating the presynaptic dysfunction and restores neuronal activity as well as dendritic spine levels in vitro. Oral administration of rolofylline for 2-wk to 14-mo-old proaggregant Tau transgenic mice restores the spatial memory deficits and normalizes the basic synaptic transmission. These findings make rolofylline an interesting candidate to combat the hypometabolism and neuronal dysfunction associated with Tau-induced neurodegenerative diseases.
Asunto(s)
Antagonistas del Receptor de Adenosina A1/farmacología , Axones/metabolismo , Eliminación de Secuencia , Xantinas/farmacología , Proteínas tau/genética , Adenosina Trifosfato/metabolismo , Animales , Espinas Dendríticas/efectos de los fármacos , Modelos Animales de Enfermedad , Técnica del Anticuerpo Fluorescente , Expresión Génica , Hipocampo/metabolismo , Hipocampo/patología , Humanos , Memoria a Largo Plazo/efectos de los fármacos , Ratones , Ratones Transgénicos , Mitocondrias/metabolismo , Neuronas/metabolismo , Neuronas/patología , Fosforilación , Agregado de Proteínas , Agregación Patológica de Proteínas/genética , Agregación Patológica de Proteínas/metabolismo , Transmisión Sináptica/efectos de los fármacos , Tauopatías/tratamiento farmacológico , Tauopatías/genética , Tauopatías/metabolismo , Tauopatías/patologíaRESUMEN
Huntington's disease (HD) is characterized by motor dysfunction due to the expression of mutant huntingtin that promotes degeneration of striatal GABAergic medium-sized spiny neurons. Here we explore the role of the 90-kDa ribosomal S6 kinase (Rsk) in the physiopathology of HD. First, we show a reduction of Rsk1 and 2 protein levels in the striatum of two HD mouse models, R6/1 and Hdh(Q7/Q111) knock-in mice, at ages when they suffer from motor disturbances. Interestingly, the analysis of post-mortem samples from HD patients revealed a significant reduction of both Rsk forms in the putamen and caudate, but not in the cortex. Rsk1 and 2 levels were also reduced in the striatum of BDNF heterozygous mice, and upon BDNF neutralization in striatal cultures, suggesting that striatal loss of BDNF could be involved in the decrease of Rsk levels. Finally, we injected recombinant adeno-associated-virus (AAV5)-Rsk in the striatum of R6/1 mice at the onset of motor symptoms. Four weeks later, we found higher Rsk levels in the striatum accompanied by improvements in motor coordination, enhanced expression of synaptic markers and increased expression of genes related to synaptic plasticity, such as cfos and egr1. Altogether, we identified Rsk as a key factor in striatal alterations associated with motor deficits in HD.
Asunto(s)
Regulación hacia Abajo , Enfermedad de Huntington/genética , Enfermedad de Huntington/fisiopatología , Proteínas Quinasas S6 Ribosómicas 90-kDa/genética , Animales , Factor Neurotrófico Derivado del Encéfalo/genética , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Células Cultivadas , Cuerpo Estriado/metabolismo , Cuerpo Estriado/fisiopatología , Modelos Animales de Enfermedad , Femenino , Regulación de la Expresión Génica , Técnicas de Sustitución del Gen , Humanos , Proteína Huntingtina/genética , Enfermedad de Huntington/metabolismo , Masculino , Ratones Endogámicos C57BL , Actividad Motora , Mutación , Proteínas Quinasas S6 Ribosómicas 90-kDa/metabolismo , Sinapsis/genética , Sinapsis/metabolismo , Sinapsis/patología , Activación TranscripcionalRESUMEN
Huntington's disease (HD) patients and mouse models show learning and memory impairment even before the onset of motor symptoms. Deficits in hippocampal synaptic plasticity have been involved in the HD memory impairment. Several studies show that prostaglandin E2 (PGE2) EP2 receptor stimulates synaptic plasticity and memory formation. However, this role was not explored in neurodegenerative diseases. Here, we investigated the capacity of PGE2 EP2 receptor to promote synaptic plasticity and memory improvements in a model of HD, the R6/1 mice, by administration of the agonist misoprostol. We found that misoprostol increases dendritic branching in cultured hippocampal neurons in a brain-derived neurotrophic factor (BDNF)-dependent manner. Then, we implanted an osmotic mini-pump system to chronically administrate misoprostol to R6/1 mice from 14 to 18weeks of age. We observed that misoprostol treatment ameliorates the R6/1 long-term memory deficits as analyzed by the T-maze spontaneous alternation task and the novel object recognition test. Importantly, administration of misoprostol promoted the expression of hippocampal BDNF. Moreover, the treatment with misoprostol in R6/1 mice blocked the reduction in the number of PSD-95 and VGluT-1 positive particles observed in hippocampus of vehicle-R6/1 mice. In addition, we observed an increase of cAMP levels in the dentate ` of WT and R6/1 mice treated with misoprostol. Accordingly, we showed a reduction in the number of mutant huntingtin nuclear inclusions in the dentate gyrus of R6/1 mice. Altogether, these results suggest a putative therapeutic effect of PGE2 EP2 receptor in reducing cognitive deficits in HD.
Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/metabolismo , Enfermedad de Huntington/fisiopatología , Trastornos de la Memoria/fisiopatología , Memoria/fisiología , Plasticidad Neuronal/fisiología , Subtipo EP2 de Receptores de Prostaglandina E/metabolismo , Animales , Trastornos del Conocimiento/metabolismo , Dinoprostona/metabolismo , Modelos Animales de Enfermedad , Hipocampo/metabolismo , Enfermedad de Huntington/metabolismo , Trastornos de la Memoria/tratamiento farmacológico , Ratones TransgénicosRESUMEN
In this study, we evaluated the potential beneficial effects of antagonizing prostaglandin E2 (PGE2) EP1 receptor on motor and memory deficits in Huntington's disease (HD). To this aim, we implanted an osmotic mini-pump system to chronically administrate an EP1 receptor antagonist (SC-51089) in the R6/1 mouse model of HD, from 13 to 18 weeks of age, and used different paradigms to assess motor and memory function. SC-51089 administration ameliorated motor coordination and balance dysfunction in R6/1 mice as analyzed by rotarod, balance beam, and vertical pole tasks. Long-term memory deficit was also rescued after EP1 receptor antagonism as assessed by the T-maze spontaneous alternation and the novel object recognition tests. Additionally, treatment with SC-51089 improved the expression of specific synaptic markers and reduced the number of huntingtin nuclear inclusions in the striatum and hippocampus of 18-week-old R6/1 mice. Moreover, electrophysiological studies showed that hippocampal long-term potentiation was significantly recovered in R6/1 mice after EP1 receptor antagonism. Altogether, these results show that the antagonism of PGE2 EP1 receptor has a strong therapeutic effect on R6/1 mice and point out a new therapeutic candidate to treat motor and memory deficits in HD.
Asunto(s)
Modelos Animales de Enfermedad , Enfermedad de Huntington/metabolismo , Trastornos de la Memoria/metabolismo , Trastornos de la Destreza Motora/metabolismo , Subtipo EP1 de Receptores de Prostaglandina E/antagonistas & inhibidores , Subtipo EP1 de Receptores de Prostaglandina E/metabolismo , Animales , Enfermedad de Huntington/tratamiento farmacológico , Enfermedad de Huntington/genética , Hidrazinas/administración & dosificación , Masculino , Trastornos de la Memoria/tratamiento farmacológico , Trastornos de la Memoria/genética , Ratones , Ratones Endogámicos CBA , Ratones Transgénicos , Trastornos de la Destreza Motora/tratamiento farmacológico , Trastornos de la Destreza Motora/genética , Oxazepinas/administración & dosificación , Subtipo EP1 de Receptores de Prostaglandina E/genéticaRESUMEN
The role of peroxisome proliferator activator receptor (PPAR)ß/δ in the pathogenesis of Alzheimer's disease has only recently been explored through the use of PPARß/δ agonists. Here we evaluated the effects of PPARß/δ deficiency on the amyloidogenic pathway and tau hyperphosphorylation. PPARß/δ-null mice showed cognitive impairment in the object recognition task, accompanied by enhanced DNA-binding activity of NF-κB in the cortex and increased expression of IL-6. In addition, two NF-κB-target genes involved in ß-amyloid (Aß) synthesis and deposition, the ß site APP cleaving enzyme 1 (Bace1) and the receptor for advanced glycation endproducts (Rage), respectively, increased in PPARß/δ-null mice compared to wild type animals. The protein levels of glial fibrillary acidic protein (GFAP) increased in the cortex of PPARß/δ-null mice, which would suggest the presence of astrogliosis. Finally, tau hyperphosphorylation at Ser199 and enhanced levels of PHF-tau were associated with increased levels of the tau kinases CDK5 and phospho-ERK1/2 in the cortex of PPARß/δ(-/-) mice. Collectively, our findings indicate that PPARß/δ deficiency results in cognitive impairment associated with enhanced inflammation, astrogliosis and tau hyperphosphorylation in the cortex.
Asunto(s)
Secretasas de la Proteína Precursora del Amiloide/metabolismo , Ácido Aspártico Endopeptidasas/metabolismo , Corteza Cerebral/metabolismo , PPAR-beta/deficiencia , Receptores Inmunológicos/metabolismo , Proteínas tau/metabolismo , Secretasas de la Proteína Precursora del Amiloide/genética , Péptidos beta-Amiloides/genética , Péptidos beta-Amiloides/metabolismo , Animales , Ácido Aspártico Endopeptidasas/genética , Cognición/fisiología , Disfunción Cognitiva/genética , Disfunción Cognitiva/metabolismo , Quinasa 5 Dependiente de la Ciclina/genética , Quinasa 5 Dependiente de la Ciclina/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Proteína Ácida Fibrilar de la Glía , Inflamación , Interleucina-6/genética , Interleucina-6/metabolismo , Sistema de Señalización de MAP Quinasas/genética , Masculino , Ratones , Ratones Endogámicos C57BL , FN-kappa B/genética , FN-kappa B/metabolismo , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , PPAR-beta/genética , PPAR-beta/metabolismo , Fosforilación , Receptor para Productos Finales de Glicación Avanzada , Receptores Inmunológicos/genética , Proteínas tau/genéticaRESUMEN
The transcription factor Elk-1 has been revealed as neuroprotective against toxic stimuli. In this study, we explored the neuroprotective capacity of Elk-1 in Huntington's disease. To this aim, we used two exon-1 mutant huntingtin (mhtt) mouse models (R6/1 and R6/2), and a full-length mhtt striatal cell model (STHdh(Q111/Q111) ). Analysis of Elk-1 and pElk-1(Ser383) in the striatum of R6 mice revealed increased levels during the disease progression. Similarly, Elk-1 and pElk-1(Ser383) levels were increased in STHdh(Q111/Q111) cells when compared with wild-type cells. In addition, we observed a predominant nuclear localization of Elk-1 in STHdh(Q111/Q111) cells, and in the striatum of 30-week-old R6/1 mice. Nuclear Elk-1 did not colocalize with mhtt aggregates, suggesting a higher transcriptional activity. In agreement, the knock-down of Elk-1 decreased immediate early genes expression in STHdh(Q111/Q111) cells, but not in wild-type cells. Interestingly, reduction of Elk-1 levels by siRNAs transfection promoted cell death and caspase 3 cleavage in STHdh(Q111/Q111) cells, but not in wild-type cells. In summary, we propose that increased protein levels, phosphorylation and nuclear localization of Elk-1 observed in exon-1 and full-length Huntington's disease models could be a compensatory mechanism activated by striatal cells in response to the presence of mhtt that contributes to neuroprotection.
Asunto(s)
Enfermedad de Huntington/genética , Enfermedad de Huntington/patología , Proteína Elk-1 con Dominio ets/metabolismo , Animales , Apoptosis/fisiología , Biotransformación/fisiología , Western Blotting , Núcleo Celular/metabolismo , Cuerpo Estriado/citología , Cuerpo Estriado/fisiología , Citosol/metabolismo , Progresión de la Enfermedad , Proteína 2 de la Respuesta de Crecimiento Precoz/genética , Genes fos/efectos de los fármacos , Humanos , Inmunohistoquímica , Masculino , Ratones , Ratones Transgénicos , Microscopía Confocal , Mutación/fisiología , Fosforilación , Reacción en Cadena de la Polimerasa , ARN Interferente Pequeño/farmacología , Proteínas de Transporte de Serotonina en la Membrana Plasmática/genética , Proteínas de Transporte de Serotonina en la Membrana Plasmática/metabolismo , Fracciones Subcelulares/metabolismo , TransfecciónRESUMEN
BACKGROUND: The 90-kDa ribosomal S6 kinase (Rsk) family is involved in cell survival. Rsk activation is regulated by sequential phosphorylations controlled by extracellular signal-regulated kinase (ERK) 1/2 and 3-phosphoinositide-dependent protein kinase 1 (PDK1). Altered ERK1/2 and PDK1 phosphorylation have been described in Huntington's disease (HD), characterized by the expression of mutant huntingtin (mhtt) and striatal degeneration. However, the role of Rsk in this neurodegenerative disease remains unknown. Here, we analyzed the protein levels, activity and role of Rsk in in vivo and in vitro HD models. RESULTS: We observed increased protein levels of Rsk1 and Rsk2 in the striatum of Hdh(Q111/Q111) and R6/1 mice, STHdh(Q111/Q111) cells and striatal cells transfected with full-length mhtt. Analysis of the phosphorylation of Rsk in Hdh mice and STHdh cells showed reduced levels of phospho Ser-380 (dependent on ERK1/2), whereas phosphorylation at Ser-221 (dependent on PDK1) was increased. Moreover, we found that elevated Rsk activity in STHdh(Q111/Q111) cells was mainly due to PDK1 activity, as assessed by transfection with Rsk mutant constructs. The increase of Rsk in STHdh(Q111/Q111) cells occurred in the cytosol and in the nucleus, which results in enhanced phosphorylation of both cytosolic and nuclear Rsk targets. Finally, pharmacological inhibition of Rsk, knock-down and overexpression experiments indicated that Rsk activity exerts a protective effect against mhtt-induced cell death in STHdh(Q7/Q7) cells transfected with mhtt. CONCLUSION: The increase of Rsk levels and activity would act as a compensatory mechanism with capacity to prevent mhtt-mediated cell death. We propose Rsk as a good target for neuroprotective therapies in HD.