RESUMEN
Aerobic physical exercise (EX) and controlling cardiovascular risk factors in midlife can improve and protect cognitive function in healthy individuals and are considered to be effective at reducing late-onset dementia incidence. By investigating commonalities between these preventative approaches, we sought to identify possible targets for effective interventions. We compared the efficacy of EX and simvastatin (SV) pharmacotherapy to counteract cognitive deficits induced by a high-cholesterol diet (2%, HCD) in mice overexpressing TGF-ß1 (TGF mice), a model of vascular cognitive impairment and dementia. Cognitive deficits were found in hypercholesterolemic mice for object recognition memory, and both SV and EX prevented this decline. EX improved stimulus-evoked cerebral blood flow responses and was as effective as SV in normalizing endothelium-dependent vasodilatory responses in cerebral arteries. The up-regulation of galectin-3-positive microglial cells in white matter (WM) of HCD-fed TGF mice with cognitive deficits was significantly reduced by both SV and EX concurrently with cognitive recovery. Altered hippocampal neurogenesis, gray matter astrogliosis, or microgliosis did not correlate with cognitive deficits or benefits. Overall, results indicate that SV and EX prevented cognitive decline in hypercholesterolemic mice and that they share common sites of action in preventing endothelial cell dysfunction and reducing WM inflammation.-Trigiani, L. J., Royea, J., Tong, X.-K., Hamel, E. Comparative benefits of simvastatin and exercise in a mouse model of vascular cognitive impairment and dementia.
Asunto(s)
Disfunción Cognitiva/tratamiento farmacológico , Disfunción Cognitiva/terapia , Demencia/tratamiento farmacológico , Demencia/terapia , Condicionamiento Físico Animal/métodos , Simvastatina/uso terapéutico , Animales , Circulación Cerebrovascular/efectos de los fármacos , Modelos Animales de Enfermedad , Inflamación/tratamiento farmacológico , Inflamación/terapia , Ratones , Microglía/efectos de los fármacos , Microglía/metabolismoRESUMEN
The use of angiotensin receptor blockers (ARBs) correlates with reduced onset and progression of Alzheimer's disease (AD). The mechanism depicting how ARBs such as losartan restore cerebrovascular and cognitive deficits in AD is unknown. Here, we propose a mechanism underlying losartan's benefits by selectively blocking the effects of angiotensin IV (AngIV) at its receptor (AT4R) with divalinal in mice overexpressing the AD-related Swedish and Indiana mutations of the human amyloid precursor protein (APP mice) and WT mice. Young (3-month-old) mice were treated with losartan (â¼10 mg/kg/d, 4 months), followed by intracerebroventricular administration of vehicle or divalinal in the final month of treatment. Spatial learning and memory were assessed using Morris water mazes at 3 and 4 months of losartan treatment. Cerebrovascular reactivity and whisker-evoked neurovascular coupling responses were measured at end point (â¼7 months of age), together with biomarkers related to neuronal and vascular oxidative stress (superoxide dismutase-2), neuroinflammation (astroglial and microglial activation), neurogenesis (BrdU-labeled newborn cells), and amyloidosis [soluble amyloid-ß (Aß) species and Aß plaque load]. Divalinal countered losartan's capacity to rescue spatial learning and memory and blocked losartan's benefits on dilatory function and baseline nitric oxide bioavailability. Divalinal reverted losartan's anti-inflammatory effects, but failed to modify losartan-mediated reductions in oxidative stress. Neither losartan nor divalinal affected arterial blood pressure or significantly altered the amyloid pathology in APP mice. Our findings identify activation of the AngIV/AT4R cascade as the underlying mechanism in losartan's benefits and a target that could restore Aß-related cognitive and cerebrovascular deficits in AD.SIGNIFICANCE STATEMENT Antihypertensive medications that target the renin angiotensin system, such as angiotensin receptor blockers (ARBs), have been associated with lower incidence and progression of Alzheimer's disease (AD) in cohort studies. However, the manner by which ARBs mediate their beneficial effects is unknown. Here, the angiotensin IV receptor (AT4R) was identified as mediating the cognitive and cerebrovascular rescue of losartan, a commonly prescribed ARB, in a mouse model of AD. The AT4R was further implicated in mediating anti-inflammatory benefits. AT4R-mediated effects were independent from changes in blood pressure, amyloidosis, and oxidative stress. Overall, our results implicate the angiotensin IV/AT4R cascade as a promising candidate for AD intervention.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/fisiopatología , Circulación Cerebrovascular/efectos de los fármacos , Trastornos del Conocimiento/tratamiento farmacológico , Trastornos del Conocimiento/fisiopatología , Losartán/administración & dosificación , Receptores de Angiotensina/metabolismo , Bloqueadores del Receptor Tipo 1 de Angiotensina II/administración & dosificación , Animales , Cognición/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Aprendizaje Espacial/efectos de los fármacos , Memoria Espacial/efectos de los fármacosRESUMEN
Brain imaging techniques that use vascular signals to map changes in neuronal activity rely on the coupling between electrophysiology and hemodynamics, a phenomenon referred to as "neurovascular coupling" (NVC). It is unknown whether this relationship remains reliable under altered brain states associated with acetylcholine (ACh) levels, such as attention and arousal and in pathological conditions such as Alzheimer's disease. We therefore assessed the effects of varying ACh tone on whisker-evoked NVC responses in rat barrel cortex, measured by cerebral blood flow (CBF) and neurophysiological recordings (local field potentials, LFPs). We found that acutely enhanced ACh tone significantly potentiated whisker-evoked CBF responses through muscarinic ACh receptors and concurrently facilitated neuronal responses, as illustrated by increases in the amplitude and power in high frequencies of the evoked LFPs. However, the cellular identity of the activated neuronal network within the responsive barrel was unchanged, as characterized by c-Fos upregulation in pyramidal cells and GABA interneurons coexpressing vasoactive intestinal polypeptide. In contrast, chronic ACh deprivation hindered whisker-evoked CBF responses and the amplitude and power in most frequency bands of the evoked LFPs and reduced the rostrocaudal extent and area of the activated barrel without altering its identity. Correlations between LFP power and CBF, used to estimate NVC, were enhanced under high ACh tone and disturbed significantly by ACh depletion. We conclude that ACh is not only a facilitator but also a prerequisite for the full expression of sensory-evoked NVC responses, indicating that ACh may alter the fidelity of hemodynamic signals in assessing changes in evoked neuronal activity.SIGNIFICANCE STATEMENT Neurovascular coupling, defined as the tight relationship between activated neurons and hemodynamic responses, is a fundamental brain function that underlies hemodynamic-based functional brain imaging techniques. However, the impact of altered brain states on this relationship is largely unknown. We therefore investigated how acetylcholine (ACh), known to drive brain states of attention and arousal and to be deficient in pathologies such as Alzheimer's disease, would alter neurovascular coupling responses to sensory stimulation. Whereas acutely increased ACh enhanced neuronal responses and the resulting hemodynamic signals, chronic loss of cholinergic input resulted in dramatic impairments in both types of sensory-evoked signals. We conclude that ACh is not only a potent modulator but also a requirement for the full expression of sensory-evoked neurovascular coupling responses.
Asunto(s)
Acetilcolina/fisiología , Circulación Cerebrovascular/fisiología , Acoplamiento Neurovascular/fisiología , Receptores Nicotínicos/fisiología , Vibrisas/fisiología , Animales , Corteza Cerebral/irrigación sanguínea , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/fisiología , Circulación Cerebrovascular/efectos de los fármacos , Masculino , Acoplamiento Neurovascular/efectos de los fármacos , Antagonistas Nicotínicos/farmacología , Estimulación Física/métodos , Ratas , Ratas Sprague-Dawley , Vibrisas/efectos de los fármacosRESUMEN
Transgenic mice constitutively overexpressing the cytokine transforming growth factor-ß1 (TGF-ß1) (TGF mice) display cerebrovascular alterations as seen in Alzheimer's disease (AD) and vascular cognitive impairment and dementia (VCID), but no or only subtle cognitive deficits. TGF-ß1 may exert part of its deleterious effects through interactions with angiotensin II (AngII) type 1 receptor (AT1R) signaling pathways. We test such interactions in the brain and cerebral vessels of TGF mice by measuring cerebrovascular reactivity, levels of protein markers of vascular fibrosis, nitric oxide synthase activity, astrogliosis, and mnemonic performance in mice treated (6 months) with the AT1R blocker losartan (10 mg/kg per day) or the angiotensin converting enzyme inhibitor enalapril (3 mg/kg per day). Both treatments restored the severely impaired cerebrovascular reactivity to acetylcholine, calcitonin gene-related peptide, endothelin-1, and the baseline availability of nitric oxide in aged TGF mice. Losartan, but not enalapril, significantly reduced astrogliosis and cerebrovascular levels of profibrotic protein connective tissue growth factor while raising levels of antifibrotic enzyme matrix metallopeptidase-9. Memory was unaffected by aging and treatments. The results suggest a pivotal role for AngII in TGF-ß1-induced cerebrovascular dysfunction and neuroinflammation through AT1R-mediated mechanisms. Further, they suggest that AngII blockers could be appropriate against vasculopathies and astrogliosis associated with AD and VCID.
Asunto(s)
Encéfalo/irrigación sanguínea , Gliosis/patología , Gliosis/fisiopatología , Receptor de Angiotensina Tipo 1/metabolismo , Transducción de Señal , Factor de Crecimiento Transformador beta1/metabolismo , Animales , Encéfalo/efectos de los fármacos , Enalapril/farmacología , Enalapril/uso terapéutico , Femenino , Fibrosis , Gliosis/metabolismo , Losartán/farmacología , Losartán/uso terapéutico , Masculino , Ratones , Ratones Transgénicos , Transducción de Señal/efectos de los fármacosRESUMEN
Alzheimer's disease (AD) is a multifactorial and multifaceted disease for which we currently have very little to offer since there is no curative therapy, with only limited disease-modifying drugs. Recent studies in AD mouse models that recapitulate the amyloid-ß (Aß) pathology converge to demonstrate that it is possible to salvage cerebrovascular function with a variety of drugs and, particularly, therapies used to treat cardiovascular diseases such as hypercholesterolemia and hypertension. These drugs can reestablish dilatory function mediated by various endothelial and smooth muscle ion channels as well as nitric oxide availability, benefits that result in normalized brain perfusion. These cerebrovascular benefits would favor brain perfusion, which may help maintain neuronal function and, possibly, delay cognitive failure. However, restoring cerebrovascular function in AD mouse models was not necessarily accompanied by rescue of cognitive deficits related to spatial learning and memory. The results with cardiovascular therapies rather suggest that drugs originally designed to treat cardiovascular diseases that concurrently restore cerebrovascular and cognitive function do so through their pleiotropic effects. Specifically, recent findings suggest that these drugs act directly on brain cells and neuronal pathways involved in memory formation, hence, working simultaneously albeit independently on neuronal and vascular targets. These findings may help select medications for patients with cardiovascular diseases at risk of developing AD with increasing age. Further, they may identify molecular targets for recovering memory pathways that bear potential for new therapeutic avenues.
Asunto(s)
Enfermedad de Alzheimer/terapia , Encéfalo/irrigación sanguínea , Encéfalo/patología , Trastornos del Conocimiento/terapia , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/fisiopatología , Péptidos beta-Amiloides/metabolismo , Animales , Trastornos del Conocimiento/fisiopatología , Humanos , Losartán/uso terapéutico , Simvastatina/uso terapéuticoRESUMEN
Angiotensin II (AngII) receptor blockers that bind selectively AngII type 1 (AT1) receptors may protect from Alzheimer's disease (AD). We studied the ability of the AT1 receptor antagonist losartan to cure or prevent AD hallmarks in aged (~18months at endpoint, 3months treatment) or adult (~12months at endpoint, 10months treatment) human amyloid precursor protein (APP) transgenic mice. We tested learning and memory with the Morris water maze, and evaluated neurometabolic and neurovascular coupling using [(18)F]fluoro-2-deoxy-D-glucose-PET and laser Doppler flowmetry responses to whisker stimulation. Cerebrovascular reactivity was assessed with on-line videomicroscopy. We measured protein levels of oxidative stress enzymes (superoxide dismutases SOD1, SOD2 and NADPH oxidase subunit p67phox), and quantified soluble and deposited amyloid-ß (Aß) peptide, glial fibrillary acidic protein (GFAP), AngII receptors AT1 and AT2, angiotensin IV receptor AT4, and cortical cholinergic innervation. In aged APP mice, losartan did not improve learning but it consolidated memory acquisition and recall, and rescued neurovascular and neurometabolic coupling and cerebrovascular dilatory capacity. Losartan normalized cerebrovascular p67phox and SOD2 protein levels and up-regulated those of SOD1. Losartan attenuated astrogliosis, normalized AT1 and AT4 receptor levels, but failed to rescue the cholinergic deficit and the Aß pathology. Given preventively, losartan protected cognitive function, cerebrovascular reactivity, and AT4 receptor levels. Like in aged APP mice, these benefits occurred without a decrease in soluble Aß species or plaque load. We conclude that losartan exerts potent preventive and restorative effects on AD hallmarks, possibly by mitigating AT1-initiated oxidative stress and normalizing memory-related AT4 receptors.
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Bloqueadores del Receptor Tipo 1 de Angiotensina II/uso terapéutico , Circulación Cerebrovascular/efectos de los fármacos , Trastornos del Conocimiento/tratamiento farmacológico , Trastornos del Conocimiento/etiología , Losartán/uso terapéutico , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Animales , Arginina/análogos & derivados , Arginina/farmacología , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/genética , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Encéfalo/patología , Trastornos del Conocimiento/patología , Modelos Animales de Enfermedad , Endotelina-1/farmacología , Inhibidores Enzimáticos/farmacología , Femenino , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Losartán/farmacología , Masculino , Ratones , Ratones Transgénicos , Mutación/genéticaRESUMEN
Alzheimer's disease (AD) is now established as a progressive compromise not only of the neurons but also of the cerebral vasculature. Increasing evidence also indicates that cerebrovascular dysfunction may be a key or an aggravating pathogenic factor in AD, emphasizing the importance to properly control this deficit when aiming for effective therapy. Here, we report that simvastatin (3-6 months, 40 mg/kg/d) completely rescued cerebrovascular reactivity, basal endothelial nitric oxide synthesis, and activity-induced neurometabolic and neurovascular coupling in adult (6 months) and aged (12 months) transgenic mice overexpressing the Swedish and Indiana mutations of the human amyloid precursor protein (AD mice). Remarkably, simvastatin fully restored short- and long-term memory in adult, but not in aged AD mice. These beneficial effects occurred without any decreasing effect of simvastatin on brain amyloid-ß (Aß) levels or plaque load. However, in AD mice with recovered memory, protein levels of the learning- and memory-related immediate early genes c-Fos and Egr-1 were normalized or upregulated in hippocampal CA1 neurons, indicative of restored neuronal function. In contrast, the levels of phospholipase A2, enkephalin, PSD-95, synaptophysin, or glutamate NMDA receptor subunit type 2B were either unaltered in AD mice or unaffected by treatment. These findings disclose new sites of action for statins against Aß-induced neuronal and cerebrovascular deficits that could be predictive of therapeutic benefit in AD patients. They further indicate that simvastatin and, possibly, other brain penetrant statins bear high therapeutic promise in early AD and in patients with vascular diseases who are at risk of developing AD.
Asunto(s)
Envejecimiento/efectos de los fármacos , Enfermedad de Alzheimer/tratamiento farmacológico , Trastornos Cerebrovasculares/tratamiento farmacológico , Trastornos de la Memoria/tratamiento farmacológico , Simvastatina/uso terapéutico , Envejecimiento/fisiología , Enfermedad de Alzheimer/fisiopatología , Animales , Circulación Cerebrovascular/efectos de los fármacos , Circulación Cerebrovascular/fisiología , Trastornos Cerebrovasculares/fisiopatología , Femenino , Humanos , Masculino , Trastornos de la Memoria/fisiopatología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Simvastatina/farmacologíaRESUMEN
Delineation of key molecules that act epigenetically to transduce diverse stressors into established patterns of disease would facilitate the advent of preventive and disease-modifying therapeutics for a host of neurological disorders. Herein, we demonstrate that selective overexpression of the stress protein heme oxygenase-1 (HO-1) in astrocytes of novel GFAP.HMOX1 transgenic mice results in subcortical oxidative stress and mitochondrial damage/autophagy; diminished neuronal reelin content (males); induction of Nurr1 and Pitx3 with attendant suppression of their targeting miRNAs, 145 and 133b; increased tyrosine hydroxylase and α-synuclein expression with downregulation of the targeting miR-7b of the latter; augmented dopamine and serotonin levels in basal ganglia; reduced D1 receptor binding in nucleus accumbens; axodendritic pathology and altered hippocampal cytoarchitectonics; impaired neurovascular coupling; attenuated prepulse inhibition (males); and hyperkinetic behavior. The GFAP.HMOX1 neurophenotype bears resemblances to human schizophrenia and other neurodevelopmental conditions and implicates glial HO-1 as a prime transducer of inimical (endogenous and environmental) influences on the development of monoaminergic circuitry. Containment of the glial HO-1 response to noxious stimuli at strategic points of the life cycle may afford novel opportunities for the effective management of human neurodevelopmental and neurodegenerative conditions.
Asunto(s)
Astrocitos/metabolismo , Encéfalo/patología , Regulación del Desarrollo de la Expresión Génica/genética , Hemo-Oxigenasa 1/metabolismo , Esquizofrenia/genética , Esquizofrenia/patología , Estimulación Acústica , Factores de Edad , Análisis de Varianza , Animales , Animales Recién Nacidos , Astrocitos/ultraestructura , Benzamidas/farmacocinética , Benzazepinas/farmacocinética , Monoaminas Biogénicas/metabolismo , Cromatografía Líquida de Alta Presión , Modelos Animales de Enfermedad , Dopaminérgicos/farmacocinética , Embrión de Mamíferos , Ensayo de Inmunoadsorción Enzimática , Trastornos Neurológicos de la Marcha/etiología , Trastornos Neurológicos de la Marcha/genética , Proteína Ácida Fibrilar de la Glía/genética , Proteína Ácida Fibrilar de la Glía/metabolismo , Hemo-Oxigenasa 1/genética , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Humanos , Inhibición Psicológica , Flujometría por Láser-Doppler , Ratones , Ratones Transgénicos , MicroARNs/genética , MicroARNs/metabolismo , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares/genética , Miembro 2 del Grupo A de la Subfamilia 4 de Receptores Nucleares/metabolismo , Unión Proteica/efectos de los fármacos , Unión Proteica/genética , ARN Mensajero/metabolismo , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo , Proteína Reelina , Esquizofrenia/fisiopatología , Filtrado Sensorial/genética , Superóxido Dismutasa/genética , Superóxido Dismutasa/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Tritio/farmacocinética , Tirosina 3-Monooxigenasa/genética , Tirosina 3-Monooxigenasa/metabolismo , alfa-Sinucleína/genética , alfa-Sinucleína/metabolismoRESUMEN
BACKGROUND: Recent evidence suggests that the inducible kinin B1 receptor (B1R) contributes to pathogenic neuroinflammation induced by amyloid-beta (Aß) peptide. The present study aims at identifying the cellular distribution and potentially detrimental role of B1R on cognitive and cerebrovascular functions in a mouse model of Alzheimer's disease (AD). METHODS: Transgenic mice overexpressing a mutated form of the human amyloid precursor protein (APPSwe,Ind, line J20) were treated with a selective and brain penetrant B1R antagonist (SSR240612, 10 mg/kg/day for 5 or 10 weeks) or vehicle. The impact of B1R blockade was measured on i) spatial learning and memory performance in the Morris water maze, ii) cerebral blood flow (CBF) responses to sensory stimulation using laser Doppler flowmetry, and iii) reactivity of isolated cerebral arteries using online videomicroscopy. Aß burden was quantified by ELISA and immunostaining, while other AD landmarks were measured by western blot and immunohistochemistry. RESULTS: B1R protein levels were increased in APP mouse hippocampus and, prominently, in reactive astrocytes surrounding Aß plaques. In APP mice, B1R antagonism with SSR240612 improved spatial learning, memory and normalized protein levels of the memory-related early gene Egr-1 in the dentate gyrus of the hippocampus. B1R antagonism restored sensory-evoked CBF responses, endothelium-dependent dilations, and normalized cerebrovascular protein levels of endothelial nitric oxide synthase and B2R. In addition, SSR240612 reduced (approximately 50%) microglial, but not astroglial, activation, brain levels of soluble Aß1-42, diffuse and dense-core Aß plaques, and it increased protein levels of the Aß brain efflux transporter lipoprotein receptor-related protein-1 in cerebral microvessels. CONCLUSION: These findings show a selective upregulation of astroglial B1R in the APP mouse brain, and the capacity of the B1R antagonist to abrogate amyloidosis, cerebrovascular and memory deficits. Collectively, these findings provide convincing evidence for a role of B1R in AD pathogenesis.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Antagonistas del Receptor de Bradiquinina B1 , Circulación Cerebrovascular/efectos de los fármacos , Cognición/efectos de los fármacos , Dioxoles/uso terapéutico , Sulfonamidas/uso terapéutico , Enfermedad de Alzheimer/fisiopatología , Enfermedad de Alzheimer/psicología , Secuencia de Aminoácidos , Precursor de Proteína beta-Amiloide/genética , Animales , Astrocitos/metabolismo , Western Blotting , Proteína 1 de la Respuesta de Crecimiento Precoz/metabolismo , Humanos , Inmunohistoquímica , Flujometría por Láser-Doppler , Proteína 1 Relacionada con Receptor de Lipoproteína de Baja Densidad/metabolismo , Metaloproteinasa 9 de la Matriz/metabolismo , Aprendizaje por Laberinto/efectos de los fármacos , Memoria/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Datos de Secuencia Molecular , Placa Amiloide/tratamiento farmacológico , Placa Amiloide/patología , Receptor de Bradiquinina B1/metabolismoRESUMEN
We previously showed that simvastatin (SV) restored memory in a mouse model of Alzheimer disease (AD) concomitantly with normalization in protein levels of memory-related immediate early genes in hippocampal CA1 neurons. Here, we investigated age-related changes in the hippocampal memory pathway, and whether the beneficial effects of SV could be related to enhanced neurogenesis and signaling in the Wnt/ß-catenin pathway. APP mice and wild-type (WT) littermate controls showed comparable number of proliferating (Ki67-positive nuclei) and immature (doublecortin (DCX)-positive) granule cells in the dentate gyrus until 3 months of age. At 4 months, Ki67 or DCX positive cells decreased sharply and remained less numerous until the endpoint (6 months) in both SV-treated and untreated APP mice. In 6 month-old APP mice, dendritic extensions of DCX immature neurons in the molecular layer were shorter, a deficit fully normalized by SV. Similarly, whereas mature granule cells (calbindin-immunopositive) were decreased in APP mice and not restored by SV, their dendritic arborizations were normalized to control levels by SV treatment. SV increased Prox1 protein levels (↑67.7%, p < 0.01), a Wnt/ß-catenin signaling target, while significantly decreasing (↓61.2%, p < 0.05) the upregulated levels of the ß-catenin-dependent Wnt pathway inhibitor DKK1 seen in APP mice. In APP mice, SV benefits were recapitulated by treatment with the Wnt/ß-catenin specific agonist WAY-262611, whereas they were fully abolished in mice that received the Wnt/ß-catenin pathway inhibitor XAV939 during the last month of SV treatment. Our results indicate that activation of the Wnt-ß-catenin pathway through downregulation of DKK1 underlies SV neuronal and cognitive benefits.
Asunto(s)
Enfermedad de Alzheimer , Vía de Señalización Wnt , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/metabolismo , Animales , Modelos Animales de Enfermedad , Hipocampo/metabolismo , Antígeno Ki-67/metabolismo , Ratones , Neurogénesis/fisiología , Neuronas/metabolismo , Simvastatina/farmacología , Simvastatina/uso terapéutico , beta Catenina/metabolismoRESUMEN
In the central nervous system, the nerve growth factor (NGF) receptor TrkA is expressed primarily in cholinergic neurons that are implicated in spatial learning and memory, whereas the NGF receptor p75(NTR) is expressed in many neuronal populations and glia. We asked whether selective TrkA activation may have a different impact on learning, short-term memory, and long-term memory. We also asked whether TrkA activation might affect cognition differently in wild-type mice versus mice with cognitive deficits due to transgenic overexpression of mutant amyloid-precursor protein (APP mice). Mice were treated with wild-type NGF (a ligand of TrkA and p75(NTR)) or with selective pharmacological agonists of TrkA that do not bind to p75(NTR). In APP mice, the selective TrkA agonists significantly improved learning and short-term memory. These improvements are associated with a reduction of soluble Aß levels in the cortex and AKT activation in the cortex and hippocampus. However, this improved phenotype did not translate into improved long-term memory. In normal wild-type mice, none of the treatments affected learning or short-term memory, but a TrkA-selective agonist caused persistent deficits in long-term memory. The deficit in wild-type mice was associated temporally, in the hippocampus, with increased AKT activity, increased brain-derived neurotrophic factor precursor, increased neurotrophin receptor homolog-2 (p75-related protein), and long-term depression. Together, these data indicate that selective TrkA activation affects cognition but does so differently in impaired APP mice versus normal wild-type mice. Understanding mechanisms that govern learning and memory is important for better treatment of cognitive disorders.
Asunto(s)
Aprendizaje/fisiología , Memoria a Largo Plazo/fisiología , Receptor trkA/fisiología , Animales , Western Blotting , Ensayo de Inmunoadsorción Enzimática , Ligandos , Ratones , Ratones TransgénicosRESUMEN
High brain levels of amyloid-ß (Aß) and transforming growth factor-ß1 (TGF-ß1) have been implicated in the cognitive and cerebrovascular alterations of Alzheimer's disease (AD). We sought to investigate the impact of combined increases in Aß and TGF-ß1 on cerebrovascular, neuronal, and mnemonic function using transgenic mice overproducing these peptides (A/T mice). In particular, we measured cerebrovascular reactivity, evoked cerebral blood flow and glucose uptake during brain activation, cholinergic status, and spatial memory, along with cerebrovascular fibrosis, amyloidosis, and astrogliosis, and their evolution with age. An assessment of perfusion and metabolic responses was considered timely, given ongoing efforts for their validation as AD biomarkers. Relative to wild-type littermates, A/T mice displayed an early progressive decline in cerebrovascular dilatory ability, preserved contractility, and reduction in constitutive nitric oxide synthesis that establishes resting vessel tone. Altered levels of vasodilator-synthesizing enzymes and fibrotic proteins, resistance to antioxidant treatment, and unchanged levels of the antioxidant enzyme, superoxide dismutase-2, accompanied these impairments. A/T mice featured deficient neurovascular and neurometabolic coupling to whisker stimulation, cholinergic denervation, cerebral and cerebrovascular Aß deposition, astrocyte activation, and impaired Morris water maze performance, which gained severity with age. The combined Aß- and TGF-ß1-driven pathology recapitulates salient cerebrovascular, neuronal, and cognitive AD landmarks and yields a versatile model toward highly anticipated diagnostic and therapeutic tools for patients featuring Aß and TGF-ß1 increments.
Asunto(s)
Enfermedad de Alzheimer/fisiopatología , Enfermedad de Alzheimer/psicología , Precursor de Proteína beta-Amiloide/genética , Circulación Cerebrovascular/fisiología , Cognición/fisiología , Factor de Crecimiento Transformador beta1/genética , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Biomarcadores/análisis , Circulación Cerebrovascular/genética , Modelos Animales de Enfermedad , Femenino , Humanos , Masculino , Aprendizaje por Laberinto/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Natación , Factor de Crecimiento Transformador beta1/metabolismo , Estudios de Validación como AsuntoRESUMEN
Alzheimer's disease (AD), the most common form of dementia, is characterized by neuronal degeneration and cerebrovascular dysfunction. Increasing evidence indicates that cerebrovascular dysfunction may be a key or an aggravating pathogenic factor in AD. This emphasizes the importance to investigate the tight coupling between neuronal activity and cerebral blood flow (CBF) termed neurovascular coupling (NVC). NVC depends on all cell types of the neurovascular unit within which astrocytes are important players in the progression of AD. Hence, the objective of this study was to characterize the hippocampal NVC in a mouse model of AD. Hippocampal NVC was studied in 6-month-old amyloid-beta precursor protein (APP) transgenic mice and their corresponding wild-type littermates using in vivo laser Doppler flowmetry to measure CBF in area CA1 of the hippocampus in response to Schaffer collaterals stimulation. Ex vivo two-photon microscopy experiments were performed to determine astrocytic Ca2+ and vascular responses to electrical field stimulation (EFS) or caged Ca2+ photolysis in hippocampal slices. Neuronal synaptic transmission, astrocytic endfeet Ca2+ in correlation with reactive oxygen species (ROS), and vascular reactivity in the presence or absence of Tempol, a mimetic of superoxide dismutase, were further investigated using electrophysiological, caged Ca2+ photolysis or pharmacological approaches. Whisker stimulation evoked-CBF increases and ex vivo vascular responses to EFS were impaired in APP mice compared with their age-matched controls. APP mice were also characterized by decreased basal synaptic transmission, a shorter astrocytic Ca2+ increase, and altered vascular response to elevated perivascular K+. However, long-term potentiation, astrocytic Ca2+ amplitude in response to EFS, together with vascular responses to nitric oxide remained unchanged. Importantly, we found a significantly increased Ca2+ uncaging-induced ROS production in APP mice. Tempol prevented the vascular response impairment while normalizing astrocytic Ca2+ in APP mice. These findings suggest that NVC is altered at many levels in APP mice, at least in part through oxidative stress. This points out that therapies against AD should include an antioxidative component to protect the neurovascular unit.
RESUMEN
Accumulating evidence suggests that cerebrovascular dysfunction is an important factor in the pathogenesis of Alzheimer's disease (AD). Using aged ( approximately 16 months) amyloid precursor protein (APP) transgenic mice that exhibit increased production of the amyloid-beta (Abeta) peptide and severe cerebrovascular and memory deficits, we examined the capacity of in vivo treatments with the antioxidants N-acetyl-L-cysteine (NAC) and tempol, or the peroxisome proliferator-activated receptor gamma agonist pioglitazone to rescue cerebrovascular function and selected markers of AD neuropathology. Additionally, we tested the ability of pioglitazone to normalize the impaired increases in cerebral blood flow (CBF) and glucose uptake (CGU) induced by whisker stimulation, and to reverse spatial memory deficits in the Morris water maze. All compounds fully restored cerebrovascular reactivity of isolated cerebral arteries concomitantly with changes in proteins regulating oxidative stress, without reducing brain Abeta levels or Abeta plaque load. Pioglitazone, but not NAC, significantly attenuated astroglial activation and improved, albeit nonsignificantly, the reduced cortical cholinergic innervation. Furthermore, pioglitazone completely normalized the CBF and CGU responses to increased neuronal activity, but it failed to improve spatial memory. Our results are the first to demonstrate that late pharmacological intervention with pioglitazone not only overcomes cerebrovascular dysfunction and altered neurometabolic coupling in aged APP mice, but also counteracts cerebral oxidative stress, glial activation, and, partly, cholinergic denervation. Although early or combined therapy may be warranted to improve cognition, these findings unequivocally point to pioglitazone as a most promising strategy for restoring cerebrovascular function and counteracting several AD markers detrimental to neuronal function.
Asunto(s)
Acetilcisteína/uso terapéutico , Envejecimiento , Antioxidantes/uso terapéutico , Trastornos Cerebrovasculares/tratamiento farmacológico , Hipoglucemiantes/uso terapéutico , Tiazolidinedionas/uso terapéutico , Acetilcolina/metabolismo , Enfermedad de Alzheimer/complicaciones , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Conducta Animal/efectos de los fármacos , Trastornos Cerebrovasculares/etiología , Trastornos Cerebrovasculares/genética , Modelos Animales de Enfermedad , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Memoria/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mutación/genética , Proteínas del Tejido Nervioso/metabolismo , Óxido Nítrico Sintasa/metabolismo , PPAR gamma/agonistas , Fragmentos de Péptidos/metabolismo , Pioglitazona , Superóxido Dismutasa/metabolismoRESUMEN
Cerebrovascular dysfunctions appear to contribute to Alzheimer's disease (AD) pathogenesis and the associated cognitive decline. Recently, it has been suggested that statins could be beneficial to AD patients independently from their cholesterol-lowering effects. Using 10 month-old amyloid precursor protein transgenic mice (APP mice), we sought to reverse cerebrovascular, neuronal and memory impairments with simvastatin (20 mg/kg/day, 8 weeks). Simvastatin improved reactivity of cerebral arteries, rescued the blood flow response to neuronal activation, attenuated oxidative stress and inflammation, and reduced cortical soluble amyloid-beta (Abeta) levels and the number of Abeta plaque-related dystrophic neurites. However, at such an advanced stage of the pathology, it failed to reduce Abeta plaque load and normalize cholinergic and memory deficits. These findings demonstrate that low-dose simvastatin treatment in aged APP mice largely salvages cerebrovascular function and has benefits on several AD landmarks, which could explain some of the positive effects of statins reported in AD patients.
Asunto(s)
Enfermedad de Alzheimer/tratamiento farmacológico , Péptidos beta-Amiloides/metabolismo , Circulación Cerebrovascular/efectos de los fármacos , Encefalitis/tratamiento farmacológico , Fármacos Neuroprotectores/uso terapéutico , Estrés Oxidativo/efectos de los fármacos , Simvastatina/uso terapéutico , Envejecimiento , Enfermedad de Alzheimer/fisiopatología , Péptidos beta-Amiloides/genética , Precursor de Proteína beta-Amiloide/genética , Animales , Encéfalo/irrigación sanguínea , Encéfalo/efectos de los fármacos , Encéfalo/inmunología , Modelos Animales de Enfermedad , Humanos , Discapacidades para el Aprendizaje/tratamiento farmacológico , Trastornos de la Memoria/tratamiento farmacológico , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Neuroinmunomodulación/efectos de los fármacos , Neuronas/efectos de los fármacos , Neuronas/fisiología , Fármacos Neuroprotectores/administración & dosificación , Placa Amiloide/efectos de los fármacos , Nexinas de Proteasas , Receptores de Superficie Celular/genética , Simvastatina/administración & dosificación , Percepción Espacial/efectos de los fármacosRESUMEN
Transgenic mice overexpressing transforming growth factor-ß1 (TGF mice) display impaired cerebrovascular reactivity, cerebral hypoperfusion and neurovascular uncoupling, but no overt cognitive deficits until old age. Cardiovascular diseases are a major risk factor for vascular cognitive impairment and dementia (VCID). We investigated the impact of a high cholesterol diet (HCD) on cerebrovascular and cognitive function in adult (6 months) and aged (12 months) TGF mice, together with the potential benefit of simvastatin (SV), an anti-cholesterol drug with pleiotropic effects, in adult mice. HCD increased blood, but not brain, cholesterol levels in treated mice, which SV did not reduce. In WT mice, HCD induced small, albeit significant, impairment in endothelium-dependent dilatory function. In TGF mice, HCD worsened the established brain vessel dilatory dysfunction in an age-dependent manner and increased the number of string vessels in the white matter (WM), alterations respectively normalized and significantly countered by SV. HCD triggered cognitive decline only in TGF mice at both ages, a deficit prevented by SV. Concurrently, HCD upregulated galectin-3 immunoreactivity in WM microglial cells, a response significantly reduced in SV-treated TGF mice. Grey matter astrogliosis and microgliosis were not affected by HCD or SV. In the subventricular zone of adult HCD-treated TGF mice, SV promoted oligogenesis and migration of oligodendrocyte progenitor cells. The results demonstrate that an underlying cerebrovascular pathology increases vulnerability to cognitive failure when combined to another risk factor for dementia, and that WM alterations are associated with this loss of function. The results further indicate that myelin repair mechanisms, as triggered by SV, may bear promise in preventing or delaying cognitive decline related to VCID.
Asunto(s)
Trastornos Cerebrovasculares/etiología , Trastornos del Conocimiento/etiología , Hipercolesterolemia/complicaciones , Hipercolesterolemia/tratamiento farmacológico , Simvastatina/uso terapéutico , Animales , Trastornos Cerebrovasculares/patología , Trastornos del Conocimiento/patología , Modelos Animales de Enfermedad , Hipercolesterolemia/patología , Masculino , Ratones , Ratones Transgénicos , Simvastatina/farmacología , Sustancia Blanca/patologíaRESUMEN
The P2X(1) receptor-channels activated by extracellular ATP contribute to the neurogenic component of smooth muscle contraction in vascular beds and genitourinary tracts of rodents and humans. In the present study, we investigated the interactions of plasma membrane phosphoinositides with P2X(1) ATP receptors and their physiological consequences. In an isolated rat mesenteric artery preparation, we observed a strong inhibition of P2X(1)-mediated constrictive responses by depletion of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] with the phosphatidylinositol 4-kinase inhibitor wortmannin. Using the Xenopus laevis oocyte expression system, we provided electrophysiological evidence that lowering PI(4,5)P(2) levels with wortmannin significantly decreases P2X(1) current amplitude and recovery. Previously reported modulation of recovery of desensitized P2X(1) currents by phospholipase C-coupled 5-hydroxytryptamine(2A) metabotropic receptors was also found to be wortmannin-sensitive. Treatment with wortmannin alters the kinetics of P2X(1) activation and inactivation without changing its sensitivity to ATP. The functional impact of wortmannin on P2X(1) currents could be reversed by addition of intracellular PI(4,5)P(2), but not phosphatidylinositol 3,4,5-trisphosphate, and direct application of PI(4,5)P(2) to excised inside-out macropatches rescued P2X(1) currents from rundown. We showed that the proximal region of the intracellular C terminus of P2X(1) subunit directly binds to PI(4,5)P(2) and other anionic phospholipids, and we identified the basic residue Lys(364) as a critical determinant for phospholipid binding and sensitivity to wortmannin. Overall, these results indicate that PI(4,5)P(2) plays a key role in the expression of full native and heterologous P2X(1) function by regulating the amplitude, recovery, and kinetics of ionotropic ATP responses through direct receptor-lipid interactions.
Asunto(s)
Activación del Canal Iónico/efectos de los fármacos , Fosfatidilinositol 4,5-Difosfato/farmacología , Receptores Purinérgicos P2/metabolismo , Adenosina Trifosfato/farmacología , Secuencia de Aminoácidos , Androstadienos/farmacología , Animales , Electrofisiología , Técnicas In Vitro , Cinética , Lisina/metabolismo , Arterias Mesentéricas/efectos de los fármacos , Arterias Mesentéricas/fisiología , Datos de Secuencia Molecular , Oocitos/efectos de los fármacos , Estructura Terciaria de Proteína , Subunidades de Proteína/química , Subunidades de Proteína/metabolismo , Ratas , Receptor de Serotonina 5-HT2A/metabolismo , Receptores Purinérgicos P2/química , Receptores Purinérgicos P2X , Proteínas Recombinantes/metabolismo , Vasoconstricción/efectos de los fármacos , Wortmanina , XenopusRESUMEN
Neurovascular coupling, or the tight coupling between neuronal activity and regional cerebral blood flow (CBF), seems largely driven by the local processing of incoming afferent signals within the activated area. To test if cortical gamma-aminobutyric acid (GABA) interneurons-the local integrators of cortical activity-are involved in this coupling, we stimulated the basalocortical pathway in vivo, monitored cortical CBF, and identified the activated interneurons (c-Fos-immunopositive) and the neuromediators involved in this response. Basal forebrain (BF) stimulation induced ipsilateral increases in CBF and selective activation of layers II to VI somatostatin- and/or neuropeptide Y-containing, as well as layer I GABA interneurons. Nitric oxide synthase interneurons displayed weak bilateral activation, whereas vasoactive intestinal polypeptide- or acetylcholine (ACh)-containing GABA interneurons were not activated. Selective cholinergic deafferentation indicated that ACh released from stimulated BF afferents triggered the CBF response, but the latter was mediated, in part, by the local release of GABA from cholinoceptive cortical interneurons, and through GABA-A receptor-mediated transmission. These data show that activation of specific subsets of GABA interneurons and their GABA-A-mediated effects on neuronal, vascular, and/or astroglial targets are necessary for the full expression of the hemodynamic response to BF stimulation. Further, these findings highlight the importance of understanding the cellular networks and circuitry that underlie hemodynamic signals, as only specific subsets of neurons may be activated by a given stimulus, depending on the afferent inputs they receive and integrate.
Asunto(s)
Vasos Sanguíneos/fisiología , Corteza Cerebral/irrigación sanguínea , Corteza Cerebral/fisiología , Circulación Cerebrovascular/fisiología , Interneuronas/fisiología , Prosencéfalo/irrigación sanguínea , Prosencéfalo/fisiología , Ácido gamma-Aminobutírico/fisiología , Acetilcolina/fisiología , Animales , Astrocitos/efectos de los fármacos , Astrocitos/fisiología , Vasos Sanguíneos/inervación , Capilares/metabolismo , Corteza Cerebral/efectos de los fármacos , Circulación Cerebrovascular/efectos de los fármacos , Desnervación , Estimulación Eléctrica , Electrofisiología , Agonistas de Receptores de GABA-A , Antagonistas de Receptores de GABA-A , Inmunohistoquímica , Interneuronas/efectos de los fármacos , Masculino , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/fisiología , Óxido Nítrico Sintasa de Tipo III/metabolismo , Óxido Nítrico Sintasa de Tipo III/fisiología , Sistema Nervioso Parasimpático/fisiología , Prosencéfalo/efectos de los fármacos , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Ratas , Ratas Sprague-Dawley , Receptores de GABA-A/fisiología , Somatostatina/metabolismoRESUMEN
Mice heterozygous for targeted disruption of Pthrp exhibit, by 3 months of age, diminished bone volume and skeletal microarchitectural changes indicative of advanced osteoporosis. Impaired bone formation arising from decreased BM precursor cell recruitment and increased apoptotic death of osteoblastic cells was identified as the underlying mechanism for low bone mass. The osteoporotic phenotype was recapitulated in mice with osteoblast-specific targeted disruption of Pthrp, generated using Cre-LoxP technology, and defective bone formation was reaffirmed as the underlying etiology. Daily administration of the 1-34 amino-terminal fragment of parathyroid hormone (PTH 1-34) to Pthrp+/- mice resulted in profound improvement in all parameters of skeletal microarchitecture, surpassing the improvement observed in treated WT littermates. These findings establish a pivotal role for osteoblast-derived PTH-related protein (PTHrP) as a potent endogenous bone anabolic factor that potentiates bone formation by altering osteoblast recruitment and survival and whose level of expression in the bone microenvironment influences the therapeutic efficacy of exogenous PTH 1-34.
Asunto(s)
Huesos , Osteoblastos/metabolismo , Osteogénesis/fisiología , Proteína Relacionada con la Hormona Paratiroidea/metabolismo , Hormona Paratiroidea/metabolismo , Fragmentos de Péptidos/metabolismo , Animales , Apoptosis/fisiología , Densidad Ósea , Enfermedades Óseas Metabólicas/genética , Enfermedades Óseas Metabólicas/patología , Huesos/anatomía & histología , Huesos/citología , Huesos/metabolismo , Marcación de Gen , Masculino , Ratones , Ratones Noqueados , Ratones Transgénicos , Osteoblastos/citología , Osteoporosis/patología , Osteoporosis/fisiopatología , Hormona Paratiroidea/administración & dosificación , Hormona Paratiroidea/genética , Hormona Paratiroidea/uso terapéutico , Proteína Relacionada con la Hormona Paratiroidea/genética , Fragmentos de Péptidos/administración & dosificación , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/uso terapéuticoRESUMEN
The angiotensin receptor blocker losartan mitigated cerebrovascular and cognitive deficits in mouse models of Alzheimer disease, in line with some clinical evidence of reduced onset and progression to Alzheimer disease. We investigated whether these benefits apply to another angiotensin receptor blocker, namely candesartan. Adult transgenic mice overexpressing a mutated form of the human APP (amyloid precursor protein) and wild-type controls were treated with vehicle or candesartan (cohort 1: 2 months, 1 mg/kg per day, osmotic subcutaneous minipumps; cohort 2: 5 months, 10 mg/kg per day in drinking water). Candesartan largely restored endothelial and smooth muscle function and reduced neuroinflammation in both cohorts, without improving sensory evoked cerebral blood flow responses. Candesartan exerted restorative effects on the reduced number of Ki67-immunopositive proliferating cells in the granule cell layer of the hippocampus but not on that of DCX (doublecortin)-positive immature granule cells, despite normalizing the length of their dendritic projections in the molecular layer. Amyloid plaque load and impaired cognitive function were unaltered by candesartan, and blood pressure was decreased in treated APP and wild-type mice. Overall, findings show that candesartan shared several advantages reported previously for losartan, but it exhibited limited cognitive benefits and stronger blood pressure lowering effects. The choice of angiotensin receptor blocker may thus be critical for therapeutic efficacy in patients with vascular diseases at high risk of developing Alzheimer disease.