Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 42
Filtrar
Mais filtros

Base de dados
Tipo de documento
País de afiliação
Intervalo de ano de publicação
1.
Alzheimers Dement ; 20(7): 4572-4582, 2024 07.
Artigo em Inglês | MEDLINE | ID: mdl-38899570

RESUMO

INTRODUCTION: Amyloid beta (Aß) impairs the cerebral blood flow (CBF) increase induced by neural activity (functional hyperemia). Tissue plasminogen activator (tPA) is required for functional hyperemia, and in mouse models of Aß accumulation tPA deficiency contributes to neurovascular and cognitive impairment. However, it remains unknown if tPA supplementation can rescue Aß-induced neurovascular and cognitive dysfunction. METHODS: Tg2576 mice and wild-type littermates received intranasal tPA (0.8 mg/kg/day) or vehicle 5 days a week starting at 11 to 12 months of age and were assessed 3 months later. RESULTS: Treatment of Tg2576 mice with tPA restored resting CBF, prevented the attenuation in functional hyperemia, and improved nesting behavior. These effects were associated with reduced cerebral atrophy and cerebral amyloid angiopathy, but not parenchymal amyloid. DISCUSSION: These findings highlight the key role of tPA deficiency in the neurovascular and cognitive dysfunction associated with amyloid pathology, and suggest potential therapeutic strategies involving tPA reconstitution. HIGHLIGHTS: Amyloid beta (Aß) induces neurovascular dysfunction and impairs the increase of cerebral blood flow induced by neural activity (functional hyperemia). Tissue plasminogen activator (tPA) deficiency contributes to the neurovascular and cognitive dysfunction caused by Aß. In mice with florid amyloid pathology intranasal administration of tPA rescues the neurovascular and cognitive dysfunction and reduces brain atrophy and cerebral amyloid angiopathy. tPA deficiency plays a crucial role in neurovascular and cognitive dysfunction induced by Aß and tPA reconstitution may be of therapeutic value.


Assuntos
Peptídeos beta-Amiloides , Circulação Cerebrovascular , Modelos Animais de Doenças , Camundongos Transgênicos , Ativador de Plasminogênio Tecidual , Animais , Ativador de Plasminogênio Tecidual/farmacologia , Camundongos , Circulação Cerebrovascular/efeitos dos fármacos , Circulação Cerebrovascular/fisiologia , Peptídeos beta-Amiloides/metabolismo , Angiopatia Amiloide Cerebral/tratamento farmacológico , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Disfunção Cognitiva/tratamento farmacológico , Cognição/efeitos dos fármacos , Administração Intranasal , Doença de Alzheimer/tratamento farmacológico , Comportamento de Nidação/efeitos dos fármacos , Masculino , Hiperemia/tratamento farmacológico
2.
Mol Psychiatry ; 27(10): 4264-4273, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35764706

RESUMO

Hypoxic-ischemic injury has been linked with increased risk for developing Alzheimer's disease (AD). The underlying mechanism of this association is poorly understood. Here, we report distinct roles for hypoxia-inducible factor-1α (Hif-1α) in the regulation of BACE1 and γ-secretase activity, two proteases involved in the production of amyloid-beta (Aß). We have demonstrated that Hif-1α upregulates both BACE1 and γ-secretase activity for Aß production in brain hypoxia-induced either by cerebral hypoperfusion or breathing 10% O2. Hif-1α binds to γ-secretase, which elevates the amount of active γ-secretase complex without affecting the level of individual subunits in hypoxic-ischemic mouse brains. Additionally, the expression of full length Hif-1α increases BACE1 and γ-secretase activity in primary neuronal culture, whereas a transcriptionally incompetent Hif-1α variant only activates γ-secretase. These findings indicate that Hif-1α transcriptionally upregulates BACE1 and nontranscriptionally activates γ-secretase for Aß production in hypoxic-ischemic conditions. Consequently, Hif-1α-mediated Aß production may be an adaptive response to hypoxic-ischemic injury, subsequently leading to increased risk for AD. Preventing the interaction of Hif-1α with γ-secretase may therefore be a promising therapeutic strategy for AD treatment.


Assuntos
Doença de Alzheimer , Secretases da Proteína Precursora do Amiloide , Subunidade alfa do Fator 1 Induzível por Hipóxia , Animais , Camundongos , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Secretases da Proteína Precursora do Amiloide/metabolismo , Ácido Aspártico Endopeptidases/metabolismo , Hipóxia/complicações , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo
3.
J Neurosci ; 40(42): 8160-8173, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-32928888

RESUMO

The amyloid-ß (Aß) peptide, a key pathogenic factor in Alzheimer's disease, attenuates the increase in cerebral blood flow (CBF) evoked by neural activity (functional hyperemia), a vital homeostatic response in which NMDA receptors (NMDARs) play a role through nitric oxide, and the CBF increase produced by endothelial factors. Tissue plasminogen activator (tPA), which is reduced in Alzheimer's disease and in mouse models of Aß accumulation, is required for the full expression of the NMDAR-dependent component of functional hyperemia. Therefore, we investigated whether tPA is involved in the neurovascular dysfunction of Aß. tPA activity was reduced, and the tPA inhibitor plasminogen inhibitor-1 (PAI-1) was increased in male mice expressing the Swedish mutation of the amyloid precursor protein (tg2576). Counteracting the tPA reduction with exogenous tPA or with pharmacological inhibition or genetic deletion of PAI-1 completely reversed the attenuation of the CBF increase evoked by whisker stimulation but did not ameliorate the response to the endothelium-dependent vasodilator acetylcholine. The tPA deficit attenuated functional hyperemia by suppressing NMDAR-dependent nitric oxide production during neural activity. Pharmacological inhibition of PAI-1 increased tPA activity, prevented neurovascular uncoupling, and ameliorated cognition in 11- to 12-month-old tg2576 mice, effects associated with a reduction of cerebral amyloid angiopathy but not amyloid plaques. The data unveil a selective role of the tPA in the suppression of functional hyperemia induced by Aß and in the mechanisms of cerebral amyloid angiopathy, and support the possibility that modulation of the PAI-1-tPA pathway may be beneficial in diseases associated with amyloid accumulation.SIGNIFICANCE STATEMENT Amyloid-ß (Aß) peptides have profound neurovascular effects that may contribute to cognitive impairment in Alzheimer's disease. We found that Aß attenuates the increases in blood flow evoked by neural activation through a reduction in tissue plasminogen activator (tPA) caused by upregulation of its endogenous inhibitor plasminogen inhibitor-1 (PAI-1). tPA deficiency prevents NMDA receptors from triggering nitric oxide production, thereby attenuating the flow increase evoked by neural activity. PAI-1 inhibition restores tPA activity, rescues neurovascular coupling, reduces amyloid deposition around blood vessels, and improves cognition in a mouse model of Aß accumulation. The findings demonstrate a previously unappreciated role of tPA in Aß-related neurovascular dysfunction and in vascular amyloid deposition. Restoration of tPA activity could be of therapeutic value in diseases associated with amyloid accumulation.


Assuntos
Precursor de Proteína beta-Amiloide/genética , Vasos Sanguíneos/efeitos dos fármacos , Vasos Sanguíneos/fisiopatologia , Angiopatia Amiloide Cerebral/fisiopatologia , Transtornos Cerebrovasculares/fisiopatologia , Neurônios/efeitos dos fármacos , Ativador de Plasminogênio Tecidual/deficiência , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Angiopatia Amiloide Cerebral/genética , Circulação Cerebrovascular , Transtornos Cerebrovasculares/genética , Transtornos Cerebrovasculares/prevenção & controle , Cognição , Humanos , Hiperemia/fisiopatologia , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Óxido Nítrico/biossíntese , Estimulação Física , Receptores de N-Metil-D-Aspartato/metabolismo , Serpina E2/genética , Ativador de Plasminogênio Tecidual/genética , Vibrissas/inervação
4.
Circ Res ; 121(3): 258-269, 2017 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-28515043

RESUMO

RATIONALE: Increasing evidence indicates that alterations of the cerebral microcirculation may play a role in Alzheimer disease, the leading cause of late-life dementia. The amyloid-ß peptide (Aß), a key pathogenic factor in Alzheimer disease, induces profound alterations in neurovascular regulation through the innate immunity receptor CD36 (cluster of differentiation 36), which, in turn, activates a Nox2-containing NADPH oxidase, leading to cerebrovascular oxidative stress. Brain perivascular macrophages (PVM) located in the perivascular space, a major site of brain Aß collection and clearance, are juxtaposed to the wall of intracerebral resistance vessels and are a powerful source of reactive oxygen species. OBJECTIVE: We tested the hypothesis that PVM are the main source of reactive oxygen species responsible for the cerebrovascular actions of Aß and that CD36 and Nox2 in PVM are the molecular substrates of the effect. METHODS AND RESULTS: Selective depletion of PVM using intracerebroventricular injection of clodronate abrogates the reactive oxygen species production and cerebrovascular dysfunction induced by Aß applied directly to the cerebral cortex, administered intravascularly, or overproduced in the brain of transgenic mice expressing mutated forms of the amyloid precursor protein (Tg2576 mice). In addition, using bone marrow chimeras, we demonstrate that PVM are the cells expressing CD36 and Nox2 responsible for the dysfunction. Thus, deletion of CD36 or Nox2 from PVM abrogates the deleterious vascular effects of Aß, whereas wild-type PVM reconstitute the vascular dysfunction in CD36-null mice. CONCLUSIONS: The data identify PVM as a previously unrecognized effector of the damaging neurovascular actions of Aß and unveil a new mechanism by which brain-resident innate immune cells and their receptors may contribute to the pathobiology of Alzheimer disease.


Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Circulação Cerebrovascular/fisiologia , Macrófagos/metabolismo , Córtex Somatossensorial/irrigação sanguínea , Córtex Somatossensorial/metabolismo , Doença de Alzheimer/patologia , Animais , Encéfalo/irrigação sanguínea , Encéfalo/metabolismo , Encéfalo/patologia , Macrófagos/patologia , Masculino , Camundongos , Camundongos Transgênicos , Distribuição Aleatória , Espécies Reativas de Oxigênio/metabolismo
5.
Cell Mol Neurobiol ; 36(2): 155-65, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26328781

RESUMO

Alzheimer's disease (AD) and cerebrovascular diseases share common vascular risk factors that have disastrous effects on cerebrovascular regulation. Endothelial cells, lining inner walls of cerebral blood vessels, form a dynamic interface between the blood and the brain and are critical for the maintenance of neurovascular homeostasis. Accordingly, injury in endothelial cells is regarded as one of the earliest symptoms of impaired vasoregulatory mechanisms. Extracellular buildup of amyloid-ß (Aß) is a central pathogenic factor in AD. Aß exerts potent detrimental effects on cerebral blood vessels and impairs endothelial structure and function. Recent evidence implicates vascular oxidative stress and activation of the non-selective cationic channel transient receptor potential melastatin (TRPM)-2 on endothelial cells in the mechanisms of Aß-induced neurovascular dysfunction. Thus, Aß triggers opening of TRPM2 channels in endothelial cells leading to intracellular Ca(2+) overload and vasomotor dysfunction. The cerebrovascular dysfunction may contribute to AD pathogenesis by reducing the cerebral blood supply, leading to increased susceptibility to vascular insufficiency, and by promoting Aß accumulation. The recent realization that vascular factors contribute to AD pathobiology suggests new targets for the prevention and treatment of this devastating disease.


Assuntos
Peptídeos beta-Amiloides/toxicidade , Encéfalo/irrigação sanguínea , Encéfalo/fisiopatologia , Endotélio Vascular/fisiopatologia , Doença de Alzheimer/patologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Endotélio Vascular/efeitos dos fármacos , Humanos , Estresse Oxidativo/efeitos dos fármacos
6.
Proc Natl Acad Sci U S A ; 110(8): 3089-94, 2013 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-23382216

RESUMO

Deposition of amyloid-ß (Aß) in cerebral arteries, known as cerebral amyloid angiopathy (CAA), occurs both in the setting of Alzheimer's disease and independent of it, and can cause cerebrovascular insufficiency and cognitive deficits. The mechanisms leading to CAA have not been established, and no therapeutic targets have been identified. We investigated the role of CD36, an innate immunity receptor involved in Aß trafficking, in the neurovascular dysfunction, cognitive deficits, and amyloid accumulation that occurs in mice expressing the Swedish mutation of the amyloid precursor protein (Tg2576). We found that Tg2576 mice lacking CD36 have a selective reduction in Aß1-40 and CAA. This reduced vascular amyloid deposition was associated with preservation of the Aß vascular clearance receptor LRP-1, and protection from the deleterious effects of Aß on cerebral arterioles. These beneficial vascular effects were reflected by marked improvements in neurovascular regulation and cognitive performance. Our data suggest that CD36 promotes vascular amyloid deposition and the resulting cerebrovascular damage, leading to neurovascular dysfunction and cognitive deficits. These findings identify a previously unrecognized role of CD36 in the mechanisms of vascular amyloid deposition, and suggest that this scavenger receptor is a putative therapeutic target for CAA and related conditions.


Assuntos
Antígenos CD36/imunologia , Angiopatia Amiloide Cerebral/imunologia , Imunidade Inata , Animais , Vasos Sanguíneos/metabolismo , Antígenos CD36/genética , Circulação Cerebrovascular , Imunofluorescência , Aprendizagem em Labirinto , Camundongos , Camundongos Transgênicos , Pericitos/imunologia , Proteína da Zônula de Oclusão-1/metabolismo
7.
Stroke ; 45(6): 1815-21, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24781082

RESUMO

BACKGROUND AND PURPOSE: Accumulation of amyloid-ß in cerebral blood vessels occurs in familial and sporadic forms of cerebral amyloid angiopathy and is a prominent feature of Alzheimer disease. However, the functional correlates of the vascular pathology induced by cerebral amyloid angiopathy and the mechanisms involved have not been fully established. METHODS: We used male transgenic mice expressing the Swedish, Iowa, and Dutch mutations of the amyloid precursor protein (Tg-SwDI) to examine the effect of cerebral amyloid angiopathy on cerebrovascular structure and function. Somatosensory cortex cerebral blood flow was monitored by laser-Doppler flowmetry in anesthetized Tg-SwDI mice and wild-type littermates equipped with a cranial window. RESULTS: Tg-SwDI mice exhibited reductions in cerebral blood flow responses to whisker stimulation, endothelium-dependent vasodilators, or hypercapnia at 3 months when compared with wild-type mice, whereas the response to adenosine was not attenuated. However, at 18 and 24 months, all cerebrovascular responses were markedly reduced. At this time, there was evidence of cerebrovascular amyloid deposition, smooth muscle fragmentation, and pericyte loss. Neocortical superfusion with the free radical scavenger manganic(I-II)meso-tetrakis(4-benzoic acid) porphyrin rescued endothelium-dependent responses and functional hyperemia completely at 3 months but only partially at 18 months. CONCLUSIONS: Tg-SwDI mice exhibit a profound age-dependent cerebrovascular dysfunction, involving multiple regulatory mechanisms. Early in the disease process, oxidative stress is responsible for most of the vascular dysfunction, but with advancing disease structural alterations of the vasomotor apparatus also play a role. Early therapeutic interventions are likely to have the best chance to counteract the deleterious vascular effects of cerebral amyloid angiopathy.


Assuntos
Peptídeos beta-Amiloides/biossíntese , Angiopatia Amiloide Cerebral/metabolismo , Angiopatia Amiloide Cerebral/fisiopatologia , Circulação Cerebrovascular , Córtex Somatossensorial , Peptídeos beta-Amiloides/genética , Animais , Velocidade do Fluxo Sanguíneo , Angiopatia Amiloide Cerebral/genética , Angiopatia Amiloide Cerebral/patologia , Modelos Animais de Doenças , Masculino , Camundongos , Camundongos Transgênicos , Córtex Somatossensorial/irrigação sanguínea , Córtex Somatossensorial/metabolismo , Córtex Somatossensorial/patologia , Córtex Somatossensorial/fisiopatologia , Fatores de Tempo
8.
Stroke ; 45(4): 1131-8, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24619393

RESUMO

BACKGROUND AND PURPOSE: Prohibitin is a multi-functional protein involved in numerous cellular activities. Prohibitin overexpression protects neurons from injury in vitro, but it is unclear whether prohibitin can protect selectively vulnerable hippocampal CA1 neurons in a clinically relevant injury model in vivo and, if so, whether the salvaged neurons remain functional. METHODS: A mouse model of transient forebrain ischemia that mimics the brain damage produced by cardiac arrest in humans was used to test whether prohibitin expression protects CA1 neurons from injury. Prohibitin-expressing viral vector was microinjected in mouse hippocampus to upregulate prohibitin. RESULTS: Prohibitin overexpression protected CA1 neurons from transient forebrain ischemia. The protection was associated with dampened postischemic reactive oxygen species generation, reduced mitochondrial cytochrome c release, and decreased caspase-3 activation. Importantly, the improvement in CA1 neuronal viability translated into an improvement in hippocampal function: prohibitin expression ameliorated the spatial memory deficit induced by ischemia, assessed by the Y-maze test, and restored postischemic synaptic plasticity assessed by long-term potentiation, indicating that the neurons spared form ischemic damage were functionally competent. CONCLUSIONS: These data demonstrate that prohibitin overexpression protects highly vulnerable CA1 neurons from ischemic injury in vivo and suggest that the effect is mediated by reduction of postischemic reactive oxygen species generation and preservation of mitochondrial outer membrane integrity that prevents activation of apoptosis. Measures to enhance prohibitin expression could have translational value in ischemic brain injury and, possibly, other forms of brain injury associated with mitochondrial dysfunction.


Assuntos
Região CA1 Hipocampal/patologia , Terapia Genética/métodos , Ataque Isquêmico Transitório/patologia , Proteínas Repressoras/genética , Animais , Região CA1 Hipocampal/metabolismo , Região CA1 Hipocampal/fisiopatologia , Contagem de Células , Dependovirus/genética , Modelos Animais de Doenças , Técnicas de Transferência de Genes , Parada Cardíaca/patologia , Ataque Isquêmico Transitório/metabolismo , Ataque Isquêmico Transitório/fisiopatologia , Aprendizagem em Labirinto/fisiologia , Memória de Curto Prazo/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/fisiologia , Neurônios/metabolismo , Neurônios/patologia , Proibitinas , Espécies Reativas de Oxigênio
9.
Proc Natl Acad Sci U S A ; 108(12): 5063-8, 2011 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-21383152

RESUMO

Increasing evidence indicates that cerebrovascular dysfunction plays a pathogenic role in Alzheimer's dementia (AD). Amyloid-ß (Aß), a peptide central to the pathogenesis of AD, has profound vascular effects mediated, for the most part, by reactive oxygen species produced by the enzyme NADPH oxidase. The mechanisms linking Aß to NADPH oxidase-dependent vascular oxidative stress have not been identified, however. We report that the scavenger receptor CD36, a membrane glycoprotein that binds Aß, is essential for the vascular oxidative stress and neurovascular dysfunction induced by Aß1-40. Thus, topical application of Aß1-40 onto the somatosensory cortex attenuates the increase in cerebral blood flow elicited by neural activity or by endothelium-dependent vasodilators in WT mice but not in CD36-null mice (CD36(0/0)). The cerebrovascular effects of infusion of Aß1-40 into cerebral arteries are not observed in mice pretreated with CD36 blocking antibodies or in CD36(0/0) mice. Furthermore, CD36 deficiency prevents the neurovascular dysfunction observed in transgenic mice overexpressing the Swedish mutation of the amyloid precursor protein Tg2576 despite elevated levels of brain Aß1-40. CD36 is also required for the vascular oxidative stress induced by exogenous Aß1-40 or observed in Tg2576 mice. These observations establish CD36 as a key link between Aß1-40 and the NADPH oxidase-dependent vascular oxidative stress underlying the neurovascular dysfunction and suggest that CD36 is a potential therapeutical target to counteract the cerebrovascular dysfunction associated with Aß.


Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Antígenos CD36/metabolismo , Transtornos Cerebrovasculares/metabolismo , Estresse Oxidativo , Fragmentos de Peptídeos/metabolismo , Doença de Alzheimer/genética , Doença de Alzheimer/fisiopatologia , Peptídeos beta-Amiloides/genética , Animais , Anticorpos Neutralizantes/farmacologia , Antígenos CD36/genética , Circulação Cerebrovascular/efeitos dos fármacos , Circulação Cerebrovascular/genética , Transtornos Cerebrovasculares/genética , Transtornos Cerebrovasculares/fisiopatologia , Feminino , Humanos , Masculino , Camundongos , Camundongos Transgênicos , Mutação , NADPH Oxidases/genética , NADPH Oxidases/metabolismo , Fragmentos de Peptídeos/genética , Ligação Proteica , Córtex Somatossensorial/metabolismo , Córtex Somatossensorial/fisiopatologia
10.
Nat Neurosci ; 27(1): 63-77, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38049579

RESUMO

Hypertension (HTN), a disease afflicting over one billion individuals worldwide, is a leading cause of cognitive impairment, the mechanisms of which remain poorly understood. In the present study, in a mouse model of HTN, we find that the neurovascular and cognitive dysfunction depends on interleukin (IL)-17, a cytokine elevated in individuals with HTN. However, neither circulating IL-17 nor brain angiotensin signaling can account for the dysfunction. Rather, IL-17 produced by T cells in the dura mater is the mediator released in the cerebrospinal fluid and activating IL-17 receptors on border-associated macrophages (BAMs). Accordingly, depleting BAMs, deleting IL-17 receptor A in brain macrophages or suppressing meningeal T cells rescues cognitive function without attenuating blood pressure elevation, circulating IL-17 or brain angiotensin signaling. Our data unveil a critical role of meningeal T cells and macrophage IL-17 signaling in the neurovascular and cognitive dysfunction in a mouse model of HTN.


Assuntos
Disfunção Cognitiva , Hipertensão , Camundongos , Animais , Interleucina-17 , Angiotensina II , Linfócitos T , Cloreto de Sódio na Dieta
11.
Nat Neurosci ; 2024 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-39294490

RESUMO

Apolipoprotein E4 (ApoE4), the strongest genetic risk factor for sporadic Alzheimer's disease, is also a risk factor for microvascular pathologies leading to cognitive impairment, particularly subcortical white matter injury. These effects have been attributed to alterations in the regulation of the brain blood supply, but the cellular source of ApoE4 and the underlying mechanisms remain unclear. In mice expressing human ApoE3 or ApoE4, we report that border-associated macrophages (BAMs), myeloid cells closely apposed to neocortical microvessels, are both sources and effectors of ApoE4 mediating the neurovascular dysfunction through reactive oxygen species. ApoE4 in BAMs is solely responsible for the increased susceptibility to oligemic white matter damage in ApoE4 mice and is sufficient to enhance damage in ApoE3 mice. The data unveil a new aspect of BAM pathobiology and highlight a previously unrecognized cell-autonomous role of BAM in the neurovascular dysfunction of ApoE4 with potential therapeutic implications.

12.
Stroke ; 44(1): 198-204, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23204056

RESUMO

BACKGROUND AND PURPOSE: Amyloid-ß (Aß), a peptide that accumulates in the brain and circulates in the blood of patients with Alzheimer disease, alters the regulation of cerebral blood flow and may contribute to the brain dysfunction underlying the dementia. However, the contributions of brain and circulating Aß1-40 to the vascular dysfunction have not been elucidated. METHODS: We used transgenic mice overexpressing mutated forms of the amyloid precursor protein in which Aß1-40 is elevated in blood and brain (Tg-2576) or only in brain (Tg-SwDI). Mice were equipped with a cranial window, and the increase in cerebral blood flow induced by neural activity (whisker stimulation), or by topical application of endothelium-dependent vasodilators, was assessed by laser-Doppler flowmetry. RESULTS: The cerebrovascular dysfunction was observed also in Tg-SwDI mice, but despite ≈40% higher levels of brain Aß1-40, the effect was less marked than in Tg-2576 mice. Intravascular administration of Aß1-40 elevated plasma Aß1-40 and enhanced the dysfunction in Tg-SwDI mice, but not in Tg-2576 mice. CONCLUSIONS: The results provide evidence that Aß1-40 acts on distinct luminal and abluminal vascular targets, the deleterious cerebrovascular effects of which are additive. Furthermore, the findings highlight the importance of circulating Aß1-40 in the cerebrovascular dysfunction and may provide insight into the cerebrovascular alterations in conditions in which elevations in plasma Aß1-40 occur.


Assuntos
Peptídeos beta-Amiloides/biossíntese , Encéfalo/irrigação sanguínea , Encéfalo/fisiopatologia , Circulação Cerebrovascular/fisiologia , Fragmentos de Peptídeos/biossíntese , Sistema Vasomotor/metabolismo , Sistema Vasomotor/fisiopatologia , Peptídeos beta-Amiloides/sangue , Precursor de Proteína beta-Amiloide/biossíntese , Precursor de Proteína beta-Amiloide/genética , Animais , Encéfalo/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fragmentos de Peptídeos/sangue
13.
Nat Med ; 12(2): 225-9, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16432513

RESUMO

Cyclooxygenase-2 (COX-2), a rate-limiting enzyme for prostanoid synthesis, has been implicated in the neurotoxicity resulting from hypoxia-ischemia, and its inhibition has therapeutic potential for ischemic stroke. However, COX-2 inhibitors increase the risk of cardiovascular complications. We therefore sought to identify the downstream effectors of COX-2 neurotoxicity, and found that prostaglandin E(2) EP1 receptors are essential for the neurotoxicity mediated by COX-2-derived prostaglandin E(2). EP1 receptors disrupt Ca(2+) homeostasis by impairing Na(+)-Ca(2+) exchange, a key mechanism by which neurons cope with excess Ca(2+) accumulation after an excitotoxic insult. Thus, EP1 receptors contribute to neurotoxicity by augmenting the Ca(2+) dysregulation underlying excitotoxic neuronal death. Pharmacological inhibition or gene inactivation of EP1 receptors ameliorates brain injury induced by excitotoxicity, oxygen glucose deprivation and middle cerebral artery (MCA) occlusion. An EP1 receptor inhibitor reduces brain injury when administered 6 hours after MCA occlusion, suggesting that EP1 receptor inhibition may be a viable therapeutic option in ischemic stroke.


Assuntos
Encéfalo/metabolismo , Ciclo-Oxigenase 2/metabolismo , Receptores de Prostaglandina E/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Isquemia Encefálica/metabolismo , Isquemia Encefálica/terapia , Cálcio/metabolismo , Morte Celular , Ciclo-Oxigenase 2/deficiência , Ciclo-Oxigenase 2/genética , Dinoprostona/metabolismo , Ácido Caínico/toxicidade , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , N-Metilaspartato/toxicidade , Neurônios/metabolismo , Neurônios/patologia , Neurotoxinas/metabolismo , Receptores de Prostaglandina E/antagonistas & inibidores , Receptores de Prostaglandina E/deficiência , Receptores de Prostaglandina E/genética , Receptores de Prostaglandina E Subtipo EP1
14.
Mol Neurodegener ; 18(1): 73, 2023 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-37789345

RESUMO

BACKGROUND: Cerebral amyloid angiopathy (CAA) is a devastating condition common in patients with Alzheimer's disease but also observed in the general population. Vascular oxidative stress and neurovascular dysfunction have been implicated in CAA but the cellular source of reactive oxygen species (ROS) and related signaling mechanisms remain unclear. We tested the hypothesis that brain border-associated macrophages (BAM), yolk sac-derived myeloid cells closely apposed to parenchymal and leptomeningeal blood vessels, are the source of radicals through the Aß-binding innate immunity receptor CD36, leading to neurovascular dysfunction, CAA, and cognitive impairment. METHODS: Tg2576 mice and WT littermates were transplanted with CD36-/- or CD36+/+ bone marrow at 12-month of age and tested at 15 months. This approach enables the repopulation of perivascular and leptomeningeal compartments with CD36-/- BAM. Neurovascular function was tested in anesthetized mice equipped with a cranial window in which cerebral blood flow was monitored by laser-Doppler flowmetry. Amyloid pathology and cognitive function were also examined. RESULTS: The increase in blood flow evoked by whisker stimulation (functional hyperemia) or by endothelial and smooth muscle vasoactivity was markedly attenuated in WT → Tg2576 chimeras but was fully restored in CD36-/- → Tg2576 chimeras, in which BAM ROS production was suppressed. CAA-associated Aß1-40, but not Aß1-42, was reduced in CD36-/- → Tg2576 chimeras. Similarly, CAA, but not parenchymal plaques, was reduced in CD36-/- → Tg2576 chimeras. These beneficial vascular effects were associated with cognitive improvement. Finally, CD36-/- mice were able to more efficiently clear exogenous Aß1-40 injected into the neocortex or the striatum. CONCLUSIONS: CD36 deletion in BAM suppresses ROS production and rescues the neurovascular dysfunction and damage induced by Aß. CD36 deletion in BAM also reduced brain Aß1-40 and ameliorated CAA without affecting parenchyma plaques. Lack of CD36 enhanced the vascular clearance of exogenous Aß. Restoration of neurovascular function and attenuation of CAA resulted in a near complete rescue of cognitive function. Collectively, these data implicate brain BAM in the pathogenesis of CAA and raise the possibility that targeting BAM CD36 is beneficial in CAA and other conditions associated with vascular Aß deposition and damage.


Assuntos
Doença de Alzheimer , Angiopatia Amiloide Cerebral , Disfunção Cognitiva , Humanos , Camundongos , Animais , Espécies Reativas de Oxigênio , Camundongos Transgênicos , Angiopatia Amiloide Cerebral/patologia , Peptídeos beta-Amiloides/metabolismo , Doença de Alzheimer/patologia , Encéfalo/patologia , Macrófagos/metabolismo , Estresse Oxidativo , Disfunção Cognitiva/patologia
15.
Res Sq ; 2023 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-37577565

RESUMO

Apolipoprotein-E4 (ApoE4), the strongest genetic risk factor for sporadic Alzheimer's disease, is also a risk factor for microvascular pathologies leading to cognitive impairment, particularly subcortical white matter injury. These effects have been attributed to alterations in the regulation of the brain blood supply, but the cellular source of ApoE4 and the underlying mechanisms remain unclear. In mice expressing human ApoE3 or ApoE4 we report that border associated macrophages (BAM), myeloid cells closely apposed to neocortical microvessels, are both the source and the target of the ApoE4 mediating the neurovascular dysfunction through reactive oxygen species. ApoE4 in BAM is solely responsible for the increased susceptibility to oligemic white matter damage in ApoE4 mice and is sufficient to enhance damage in ApoE3 mice. The data unveil a new aspect of BAM pathobiology and highlight a previously unrecognized cell autonomous role of BAM in the neurovascular dysfunction of ApoE4 with potential therapeutic implications.

16.
Front Aging Neurosci ; 15: 1280218, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38035277

RESUMO

Dementia is often characterized by age-dependent cerebrovascular pathology, neuroinflammation, and cognitive deficits with notable sex differences in risk, disease onset, progression and severity. Women bear a disproportionate burden of dementia, and the onset of menopause (i.e., perimenopause) may be a critical period conferring increased susceptibility. However, the contribution of early ovarian decline to the neuroinflammatory processes associated with cerebrovascular dementia risks, particularly at the initial stages of pathology that may be more amenable to proactive intervention, is unknown. To better understand the influence of early ovarian failure on dementia-associated neuroinflammation we developed a model of perimenopausal cerebral amyloid angiopathy (CAA), an important contributor to dementia. For this, accelerated ovarian failure (AOF) was induced by 4-vinylcyclohexene diepoxide (VCD) treatment to isolate early-stage ovarian failure comparable to human perimenopause (termed "peri-AOF") in transgenic SWDI mice expressing human vasculotropic mutant amyloid beta (Aß) precursor protein, that were also tested at an early stage of amyloidosis. We found that peri-AOF SWDI mice showed increased astrocyte activation accompanied by elevated Aß in select regions of the hippocampus, a brain system involved in learning and memory that is severely impacted during dementia. However, although SWDI mice showed signs of increased hippocampal microglial activation and impaired cognitive function, this was not further affected by peri-AOF. In sum, these results suggest that elevated dysfunction of key elements of the neurovascular unit in select hippocampal regions characterizes the brain pathology of mice at early stages of both CAA and AOF. However, neurovascular unit pathology may not yet have passed a threshold that leads to further behavioral compromise at these early periods of cerebral amyloidosis and ovarian failure. These results are consistent with the hypothesis that the hormonal dysregulation associated with perimenopause onset represents a stage of emerging vulnerability to dementia-associated neuropathology, thus providing a selective window of opportunity for therapeutic intervention prior to the development of advanced pathology that has proven difficult to repair or reverse.

17.
Res Sq ; 2023 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-37162996

RESUMO

Background: Cerebral amyloid angiopathy (CAA) is a devastating condition common in patients with Alzheimer's disease but also observed in the general population. Vascular oxidative stress and neurovascular dysfunction have been implicated in CAA but the cellular source of reactive oxygen species (ROS) and related signaling mechanisms remain unclear. We tested the hypothesis that brain border-associated macrophages (BAM), yolk sac-derived myeloid cells closely apposed to parenchymal and leptomeningeal blood vessels, are the source of radicals through the Aß-binding innate immunity receptor CD36, leading to neurovascular dysfunction, CAA, and cognitive impairment. Methods: Tg2576 mice and WT littermates were transplanted with CD36 -/- or CD36 +/+ bone marrow at 12-month of age and tested at 15 months. This approach enables the repopulation of perivascular and leptomeningeal compartments with CD36 -/- BAM. Neurovascular function was tested in anesthetized mice equipped with a cranial window in which cerebral blood flow was monitored by laser-Doppler flowmetry. Amyloid pathology and cognitive function were also examined. Results: The increase in blood flow evoked by whisker stimulation (functional hyperemia) or by endothelial and smooth muscle vasoactivity was markedly attenuated in WT®Tg2576 chimeras but was fully restored in CD36 -/- ®Tg2576 chimeras, in which BAM ROS production was suppressed. CAA-associated Aß 1-40 , but not Aß 1-42 , was reduced in CD36 -/- ®Tg2576 chimeras. Similarly, CAA, but not parenchymal plaques, was reduced in CD36 -/- ®Tg2576 chimeras. These beneficial vascular effects were associated with cognitive improvement. Finally, CD36 -/- mice were able to more efficiently clear exogenous Aß 1-40 injected into the neocortex or the striatum. Conclusions: CD36 deletion in BAM suppresses ROS production and rescues the neurovascular dysfunction and damage induced by Aß. CD36 deletion in BAM also reduced brain Aß 1-40 and ameliorated CAA without affecting parenchyma plaques. Lack of CD36 enhanced the vascular clearance of exogenous Aß. Restoration of neurovascular function and attenuation of CAA resulted in a near complete rescue of cognitive function. Collectively, these data implicate CNS BAM in the pathogenesis of CAA and raise the possibility that targeting BAM CD36 is beneficial in CAA and other conditions associated with vascular Aß deposition and damage.

18.
bioRxiv ; 2023 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-36824768

RESUMO

INTRODUCTION: In this study, we explore the role of oxidative stress produced by NOX2-containing NADPH oxidase as a molecular mechanism causing capillary stalling and cerebral blood flow deficits in the APP/PS1 mouse model of AD. METHODS: We inhibited NOX2 in APP/PS1 mice by administering a 10 mg/kg dose of the peptide inhibitor gp91-ds-tat i.p., for two weeks. We used in vivo two-photon imaging to measure capillary stalling, penetrating arteriole flow, and vascular inflammation. We also characterized short-term memory function and gene expression changes in cerebral microvessels. RESULTS: We found that after NOX2 inhibition capillary stalling, as well as parenchymal and vascular inflammation, were significantly reduced. In addition, we found a significant increase in penetrating arteriole flow, followed by an improvement in short-term memory, and downregulation of inflammatory gene expression pathways. DISCUSSION: Oxidative stress is a major mechanism leading to microvascular dysfunction in AD, and represents an important therapeutic target.

19.
Am J Physiol Regul Integr Comp Physiol ; 302(9): R1076-83, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22378773

RESUMO

The medial region of the nucleus tractus solitarius (mNTS) is a key brain stem site controlling cardiovascular function, wherein ANG II modulates neuronal L-type Ca(2+) currents via activation of ANG II type 1 receptors (AT(1)R) and production of reactive oxygen species (ROS). ANG II type 2 receptors (AT(2)R) induce production of nitric oxide (NO), which may interact with ROS and modulate AT(1)R signaling. We sought to determine whether AT(2)R-mediated NO production occurs in mNTS neurons and, if so, to elucidate the NO source and the functional interaction with AT(1)R-induced ROS or Ca(2+) influx. Electron microscopic (EM) immunolabeling showed that AT(2)R and neuronal NO synthase (nNOS) are coexpressed in neuronal somata and dendrites receiving synapses in the mNTS. In the presence of the AT(1)R antagonist losartan, ANG II increased NO production in isolated mNTS neurons, an effect blocked by the AT(2)R antagonist PD123319, but not the angiotensin (1-7) antagonist D-Ala. Studies in mNTS neurons of nNOS-null or endothelial NOS (eNOS)-null mice established nNOS as the source of NO. ANG II-induced ROS production was enhanced by PD123319, the NOS inhibitor N(G)-nitro-l-arginine (LNNA), or in nNOS-null mice. Moreover, in the presence of losartan, ANG II reduced voltage-gated L-type Ca(2+) current, an effect blocked by PD123319 or LNNA. We conclude that AT(2)R are closely associated and functionally coupled with nNOS in mNTS neurons. The resulting NO production antagonizes AT(1)R-mediated ROS and dampens L-type Ca(2+) currents. The ensuing signaling changes in the NTS may counteract the deleterious effects of AT(1)R on cardiovascular function.


Assuntos
Canais de Cálcio Tipo L/fisiologia , Cálcio/metabolismo , Ativação do Canal Iônico/fisiologia , Óxido Nítrico/biossíntese , Receptores de Angiotensina/metabolismo , Núcleo Solitário/metabolismo , Animais , Células Cultivadas , Radicais Livres/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Ratos , Ratos Sprague-Dawley
20.
J Neurosci ; 30(36): 12103-12, 2010 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-20826673

RESUMO

Chronic intermittent hypoxia (CIH) is a concomitant of sleep apnea that produces a slowly developing chemosensory-dependent blood pressure elevation ascribed in part to NMDA receptor-dependent plasticity and reduced nitric oxide (NO) signaling in the carotid body. The hypothalamic paraventricular nucleus (PVN) is responsive to hypoxic stress and also contains neurons that express NMDA receptors and neuronal nitric oxide synthase (nNOS). We tested the hypothesis that extended (35 d) CIH results in a decrease in the surface/synaptic availability of the essential NMDA NR1 subunit in nNOS-containing neurons and NMDA-induced NO production in the PVN of mice. As compared with controls, the 35 d CIH-exposed mice showed a significant increase in blood pressure and an increased density of NR1 immunogold particles located in the cytoplasm of nNOS-containing dendrites. Neither of these between-group differences was seen after 14 d, even though there was already a reduction in the NR1 plasmalemmal density at this time point. Patch-clamp recording of PVN neurons in slices showed a significant reduction in NMDA currents after either 14 or 35 d exposure to CIH compared with sham controls. In contrast, NO production, as measured by the NO-sensitive fluorescent dye 4-amino-5-methylamino-2',7'-difluorofluorescein, was suppressed only in the 35 d CIH group. We conclude that CIH produces a reduction in the surface/synaptic targeting of NR1 in nNOS neurons and decreases NMDA receptor-mediated currents in the PVN before the emergence of hypertension, the development of which may be enabled by suppression of NO signaling in this brain region.


Assuntos
Hipóxia/patologia , Plasticidade Neuronal/fisiologia , Neurônios/fisiologia , Óxido Nítrico/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Transdução de Sinais/fisiologia , Análise de Variância , Animais , Arginina/farmacologia , Gasometria/métodos , Pressão Sanguínea/fisiologia , Óxidos N-Cíclicos/farmacologia , Maleato de Dizocilpina/farmacologia , Relação Dose-Resposta a Droga , Agonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Sequestradores de Radicais Livres/farmacologia , Concentração de Íons de Hidrogênio/efeitos dos fármacos , Hipóxia/fisiopatologia , Imidazóis/farmacologia , Técnicas In Vitro , Masculino , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Eletrônica de Transmissão/métodos , N-Metilaspartato/farmacologia , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Óxido Nítrico Sintase Tipo I/metabolismo , Óxido Nítrico Sintase Tipo I/ultraestrutura , Núcleo Hipotalâmico Paraventricular/patologia , Núcleo Hipotalâmico Paraventricular/ultraestrutura , Receptores de N-Metil-D-Aspartato/ultraestrutura , S-Nitroso-N-Acetilpenicilamina/farmacologia , Transdução de Sinais/efeitos dos fármacos , Fatores de Tempo , Vasopressinas/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA