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1.
Nat Aging ; 2024 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-39147980

RESUMO

Cervical lymphatic vessels (cLVs) have been shown to drain solutes and cerebrospinal fluid (CSF) from the brain. However, their hydrodynamical properties have never been evaluated in vivo. Here, we developed two-photon optical imaging with particle tracking in vivo of CSF tracers (2P-OPTIC) in superficial and deep cLVs of mice, characterizing their flow and showing that the major driver is intrinsic pumping by contraction of the lymphatic vessel wall. Moreover, contraction frequency and flow velocity were reduced in aged mice, which coincided with a reduction in smooth muscle actin expression. Slowed flow in aged mice was rescued using topical application of prostaglandin F2α, a prostanoid that increases smooth muscle contractility, which restored lymphatic function in aged mice and enhanced central nervous system clearance. We show that cLVs are important regulators of CSF drainage and that restoring their function is an effective therapy for improving clearance in aging.

2.
Fluids Barriers CNS ; 21(1): 26, 2024 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-38475818

RESUMO

Glymphatic transport is vital for the physiological homeostasis of the retina and optic nerve. Pathological alterations of ocular glymphatic fluid transport and enlarged perivascular spaces have been described in glaucomatous mice. It remains to be established how diabetic retinopathy, which impairs vision in about 50% of diabetes patients, impacts ocular glymphatic fluid transport. Here, we examined ocular glymphatic transport in chronic hyperglycemic diabetic mice as well as in healthy mice experiencing a daily transient increase in blood glucose. Mice suffering from severe diabetes for two and four months, induced by streptozotocin, exhibited no alterations in ocular glymphatic fluid transport in the optic nerve compared to age-matched, non-diabetic controls. In contrast, transient increases in blood glucose induced by repeated daily glucose injections in healthy, awake, non-diabetic mice accelerated antero- and retrograde ocular glymphatic transport. Structural analysis showed enlarged perivascular spaces in the optic nerves of glucose-treated mice, which were absent in diabetic mice. Thus, transient repeated hyperglycemic events, but not constant hyperglycemia, ultimately enlarge perivascular spaces in the murine optic nerve. These findings indicate that fluid transport in the mouse eye is vulnerable to fluctuating glycemic levels rather than constant hyperglycemia, suggesting that poor glycemic control drives glymphatic malfunction and perivascular enlargement in the optic nerve.


Assuntos
Diabetes Mellitus Experimental , Hiperglicemia , Camundongos , Humanos , Animais , Glicemia , Transporte Biológico
3.
Nature ; 623(7989): 992-1000, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37968397

RESUMO

Cerebral oedema is associated with morbidity and mortality after traumatic brain injury (TBI)1. Noradrenaline levels are increased after TBI2-4, and the amplitude of the increase in noradrenaline predicts both the extent of injury5 and the likelihood of mortality6. Glymphatic impairment is both a feature of and a contributor to brain injury7,8, but its relationship with the injury-associated surge in noradrenaline is unclear. Here we report that acute post-traumatic oedema results from a suppression of glymphatic and lymphatic fluid flow that occurs in response to excessive systemic release of noradrenaline. This post-TBI adrenergic storm was associated with reduced contractility of cervical lymphatic vessels, consistent with diminished return of glymphatic and lymphatic fluid to the systemic circulation. Accordingly, pan-adrenergic receptor inhibition normalized central venous pressure and partly restored glymphatic and cervical lymphatic flow in a mouse model of TBI, and these actions led to substantially reduced brain oedema and improved functional outcomes. Furthermore, post-traumatic inhibition of adrenergic signalling boosted lymphatic export of cellular debris from the traumatic lesion, substantially reducing secondary inflammation and accumulation of phosphorylated tau. These observations suggest that targeting the noradrenergic control of central glymphatic flow may offer a therapeutic approach for treating acute TBI.


Assuntos
Edema Encefálico , Lesões Encefálicas Traumáticas , Sistema Glinfático , Norepinefrina , Animais , Camundongos , Antagonistas Adrenérgicos/farmacologia , Antagonistas Adrenérgicos/uso terapêutico , Edema Encefálico/complicações , Edema Encefálico/tratamento farmacológico , Edema Encefálico/metabolismo , Edema Encefálico/prevenção & controle , Lesões Encefálicas Traumáticas/complicações , Lesões Encefálicas Traumáticas/tratamento farmacológico , Lesões Encefálicas Traumáticas/metabolismo , Modelos Animais de Doenças , Sistema Glinfático/efeitos dos fármacos , Sistema Glinfático/metabolismo , Inflamação/complicações , Inflamação/tratamento farmacológico , Inflamação/metabolismo , Inflamação/prevenção & controle , Vasos Linfáticos/metabolismo , Norepinefrina/metabolismo , Fosforilação , Receptores Adrenérgicos/metabolismo
4.
Neurobiol Dis ; 188: 106322, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37832797

RESUMO

The ocular glymphatic system supports bidirectional fluid transport along the optic nerve, thereby removes metabolic wastes including amyloid-ß. To better understand this biological process, we examined the distributions of intravitreally and intracisternally infused tracers in full-length optic nerves from different age groups of mice. Aging was linked to globally impaired ocular glymphatic fluid transport, similar to what has seen previously in the brain. Aging also reduced the pupillary responsiveness to light stimulation and abolished light-induced facilitation in anterograde ocular glymphatic flow. In contrast to normal aging, in the DBA/2 J model of glaucoma, we found a pathological increase of glymphatic fluid transport to the anterior optic nerve that was associated with dilation of the perivascular spaces. Thus, aging and glaucoma have fundamentally different effects on ocular glymphatic fluid transport. Manipulation of glymphatic fluid transport might therefore present a new target for the treatment of glaucoma.


Assuntos
Glaucoma , Sistema Glinfático , Animais , Camundongos , Camundongos Endogâmicos DBA , Face , Envelhecimento
5.
Nat Commun ; 14(1): 2186, 2023 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-37069258

RESUMO

Despite extensive research on astrocytic Ca2+ in synaptic transmission, its contribution to the modulation of sensory transmission during different brain states remains largely unknown. Here, by using two-photon microscopy and whole-cell recordings, we show two distinct astrocytic Ca2+ signals in the murine barrel cortex: a small, long-lasting Ca2+ increase during sleep and a large, widespread but short-lasting Ca2+ spike when aroused. The large Ca2+ wave in aroused mice was inositol trisphosphate (IP3)-dependent, evoked by the locus coeruleus-norepinephrine system, and enhanced sensory input, contributing to reliable sensory transmission. However, the small Ca2+ transient was IP3-independent and contributed to decreased extracellular K+, hyperpolarization of the neurons, and suppression of sensory transmission. These events respond to different pharmacological inputs and contribute to distinct sleep and arousal functions by modulating the efficacy of sensory transmission. Together, our data demonstrate an important function for astrocytes in sleep and arousal states via astrocytic Ca2+ waves.


Assuntos
Astrócitos , Vigília , Camundongos , Animais , Astrócitos/fisiologia , Sinalização do Cálcio/fisiologia , Nível de Alerta/fisiologia , Sono
6.
Elife ; 122023 02 09.
Artigo em Inglês | MEDLINE | ID: mdl-36757363

RESUMO

The glymphatic system is a fluid transport network of cerebrospinal fluid (CSF) entering the brain along arterial perivascular spaces, exchanging with interstitial fluid (ISF), ultimately establishing directional clearance of interstitial solutes. CSF transport is facilitated by the expression of aquaporin-4 (AQP4) water channels on the perivascular endfeet of astrocytes. Mice with genetic deletion of AQP4 (AQP4 KO) exhibit abnormalities in the brain structure and molecular water transport. Yet, no studies have systematically examined how these abnormalities in structure and water transport correlate with glymphatic function. Here, we used high-resolution 3D magnetic resonance (MR) non-contrast cisternography, diffusion-weighted MR imaging (MR-DWI) along with intravoxel-incoherent motion (IVIM) DWI, while evaluating glymphatic function using a standard dynamic contrast-enhanced MR imaging to better understand how water transport and glymphatic function is disrupted after genetic deletion of AQP4. AQP4 KO mice had larger interstitial spaces and total brain volumes resulting in higher water content and reduced CSF space volumes, despite similar CSF production rates and vascular density compared to wildtype mice. The larger interstitial fluid volume likely resulted in increased slow but not fast MR diffusion measures and coincided with reduced glymphatic influx. This markedly altered brain fluid transport in AQP4 KO mice may result from a reduction in glymphatic clearance, leading to enlargement and stagnation of fluid in the interstitial space. Overall, diffusion MR is a useful tool to evaluate glymphatic function and may serve as valuable translational biomarker to study glymphatics in human disease.


Assuntos
Sistema Glinfático , Camundongos , Humanos , Animais , Sistema Glinfático/diagnóstico por imagem , Sistema Glinfático/metabolismo , Líquido Extracelular/metabolismo , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Aquaporina 4/genética , Aquaporina 4/metabolismo , Água/metabolismo
7.
Brain ; 145(2): 787-797, 2022 04 18.
Artigo em Inglês | MEDLINE | ID: mdl-34581781

RESUMO

Cerebral oedema develops after anoxic brain injury. In two models of asphyxial and asystolic cardiac arrest without resuscitation, we found that oedema develops shortly after anoxia secondary to terminal depolarizations and the abnormal entry of CSF. Oedema severity correlated with the availability of CSF with the age-dependent increase in CSF volume worsening the severity of oedema. Oedema was identified primarily in brain regions bordering CSF compartments in mice and humans. The degree of ex vivo tissue swelling was predicted by an osmotic model suggesting that anoxic brain tissue possesses a high intrinsic osmotic potential. This osmotic process was temperature-dependent, proposing an additional mechanism for the beneficial effect of therapeutic hypothermia. These observations show that CSF is a primary source of oedema fluid in anoxic brain. This novel insight offers a mechanistic basis for the future development of alternative strategies to prevent cerebral oedema formation after cardiac arrest.


Assuntos
Edema Encefálico , Parada Cardíaca , Hipotermia Induzida , Hipóxia Encefálica , Animais , Encéfalo , Edema Encefálico/etiologia , Parada Cardíaca/complicações , Parada Cardíaca/terapia , Humanos , Hipóxia Encefálica/complicações , Camundongos
8.
Science ; 367(6483)2020 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-32001524

RESUMO

Stroke affects millions each year. Poststroke brain edema predicts the severity of eventual stroke damage, yet our concept of how edema develops is incomplete and treatment options remain limited. In early stages, fluid accumulation occurs owing to a net gain of ions, widely thought to enter from the vascular compartment. Here, we used magnetic resonance imaging, radiolabeled tracers, and multiphoton imaging in rodents to show instead that cerebrospinal fluid surrounding the brain enters the tissue within minutes of an ischemic insult along perivascular flow channels. This process was initiated by ischemic spreading depolarizations along with subsequent vasoconstriction, which in turn enlarged the perivascular spaces and doubled glymphatic inflow speeds. Thus, our understanding of poststroke edema needs to be revised, and these findings could provide a conceptual basis for development of alternative treatment strategies.


Assuntos
Edema Encefálico/líquido cefalorraquidiano , Edema Encefálico/etiologia , Sistema Glinfático/fisiopatologia , Acidente Vascular Cerebral/líquido cefalorraquidiano , Acidente Vascular Cerebral/complicações , Animais , Aquaporina 5/metabolismo , Edema Encefálico/diagnóstico por imagem , Imageamento por Ressonância Magnética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Acidente Vascular Cerebral/diagnóstico por imagem , Vasoconstrição
9.
Nat Commun ; 9(1): 4878, 2018 11 19.
Artigo em Inglês | MEDLINE | ID: mdl-30451853

RESUMO

Flow of cerebrospinal fluid (CSF) through perivascular spaces (PVSs) in the brain is important for clearance of metabolic waste. Arterial pulsations are thought to drive flow, but this has never been quantitatively shown. We used particle tracking to quantify CSF flow velocities in PVSs of live mice. CSF flow is pulsatile and driven primarily by the cardiac cycle. The speed of the arterial wall matches that of the CSF, suggesting arterial wall motion is the principal driving mechanism, via a process known as perivascular pumping. Increasing blood pressure leaves the artery diameter unchanged but changes the pulsations of the arterial wall, increasing backflow and thereby reducing net flow in the PVS. Perfusion-fixation alters the normal flow direction and causes a 10-fold reduction in PVS size. We conclude that particle tracking velocimetry enables the study of CSF flow in unprecedented detail and that studying the PVS in vivo avoids fixation artifacts.


Assuntos
Artérias/diagnóstico por imagem , Líquido Cefalorraquidiano/diagnóstico por imagem , Cisterna Magna/diagnóstico por imagem , Sistema Glinfático/diagnóstico por imagem , Análise de Onda de Pulso/métodos , Animais , Artérias/fisiologia , Líquido Cefalorraquidiano/fisiologia , Cisterna Magna/anatomia & histologia , Cisterna Magna/fisiologia , Corantes Fluorescentes/química , Sistema Glinfático/anatomia & histologia , Sistema Glinfático/fisiologia , Frequência Cardíaca/fisiologia , Processamento de Imagem Assistida por Computador , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Confocal , Microscopia de Fluorescência por Excitação Multifotônica/instrumentação , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Microesferas , Tamanho da Partícula , Fluxo Pulsátil/fisiologia , Análise de Onda de Pulso/instrumentação , Reologia/instrumentação , Reologia/métodos
11.
J Cereb Blood Flow Metab ; 37(6): 2112-2124, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27481936

RESUMO

Brain lactate concentration is higher during wakefulness than in sleep. However, it is unknown why arousal is linked to an increase in brain lactate and why lactate declines within minutes of sleep. Here, we show that the glymphatic system is responsible for state-dependent changes in brain lactate concentration. Suppression of glymphatic function via acetazolamide treatment, cisterna magna puncture, aquaporin 4 deletion, or changes in body position reduced the decline in brain lactate normally observed when awake mice transition into sleep or anesthesia. Concurrently, the same manipulations diminished accumulation of lactate in cervical, but not in inguinal lymph nodes when mice were anesthetized. Thus, our study suggests that brain lactate is an excellent biomarker of the sleep-wake cycle and increases further during sleep deprivation, because brain lactate is inversely correlated with glymphatic-lymphatic clearance. This analysis provides fundamental new insight into brain energy metabolism by demonstrating that glucose that is not fully oxidized can be exported as lactate via glymphatic-lymphatic fluid transport.


Assuntos
Encéfalo/metabolismo , Líquido Cefalorraquidiano/metabolismo , Ácido Láctico/metabolismo , Sistema Linfático/metabolismo , Sono/fisiologia , Vigília/fisiologia , Animais , Aquaporina 4/genética , Eletroencefalografia , Feminino , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microdiálise
12.
Mol Neurodegener ; 11(1): 74, 2016 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-27931262

RESUMO

BACKGROUND: Apolipoprotein E (apoE) is a major carrier of cholesterol and essential for synaptic plasticity. In brain, it's expressed by many cells but highly expressed by the choroid plexus and the predominant apolipoprotein in cerebrospinal fluid (CSF). The role of apoE in the CSF is unclear. Recently, the glymphatic system was described as a clearance system whereby CSF and ISF (interstitial fluid) is exchanged via the peri-arterial space and convective flow of ISF clearance is mediated by aquaporin 4 (AQP4), a water channel. We reasoned that this system also serves to distribute essential molecules in CSF into brain. The aim was to establish whether apoE in CSF, secreted by the choroid plexus, is distributed into brain, and whether this distribution pattern was altered by sleep deprivation. METHODS: We used fluorescently labeled lipidated apoE isoforms, lenti-apoE3 delivered to the choroid plexus, immunohistochemistry to map apoE brain distribution, immunolabeled cells and proteins in brain, Western blot analysis and ELISA to determine apoE levels and radiolabeled molecules to quantify CSF inflow into brain and brain clearance in mice. Data were statistically analyzed using ANOVA or Student's t- test. RESULTS: We show that the glymphatic fluid transporting system contributes to the delivery of choroid plexus/CSF-derived human apoE to neurons. CSF-delivered human apoE entered brain via the perivascular space of penetrating arteries and flows radially around arteries, but not veins, in an isoform specific manner (apoE2 > apoE3 > apoE4). Flow of apoE around arteries was facilitated by AQP4, a characteristic feature of the glymphatic system. ApoE3, delivered by lentivirus to the choroid plexus and ependymal layer but not to the parenchymal cells, was present in the CSF, penetrating arteries and neurons. The inflow of CSF, which contains apoE, into brain and its clearance from the interstitium were severely suppressed by sleep deprivation compared to the sleep state. CONCLUSIONS: Thus, choroid plexus/CSF provides an additional source of apoE and the glymphatic fluid transporting system delivers it to brain via the periarterial space. By implication, failure in this essential physiological role of the glymphatic fluid flow and ISF clearance may also contribute to apoE isoform-specific disorders in the long term.


Assuntos
Doença de Alzheimer/metabolismo , Apolipoproteínas E/metabolismo , Encéfalo/metabolismo , Neurônios/metabolismo , Privação do Sono/metabolismo , Animais , Apolipoproteínas E/líquido cefalorraquidiano , Aquaporina 4/metabolismo , Transporte Biológico , Masculino , Camundongos , Isoformas de Proteínas/metabolismo , Privação do Sono/líquido cefalorraquidiano , Fatores de Tempo
13.
Neurobiol Dis ; 93: 215-25, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27234656

RESUMO

Glymphatic transport, defined as cerebrospinal fluid (CSF) peri-arterial inflow into brain, and interstitial fluid (ISF) clearance, is reduced in the aging brain. However, it is unclear whether glymphatic transport affects the distribution of soluble Aß in Alzheimer's disease (AD). In wild type mice, we show that Aß40 (fluorescently labeled Aß40 or unlabeled Aß40), was distributed from CSF to brain, via the peri-arterial space, and associated with neurons. In contrast, Aß42 was mostly restricted to the peri-arterial space due mainly to its greater propensity to oligomerize when compared to Aß40. Interestingly, pretreatment with Aß40 in the CSF, but not Aß42, reduced CSF transport into brain. In APP/PS1 mice, a model of AD, with and without extensive amyloid-ß deposits, glymphatic transport was reduced, due to the accumulation of toxic Aß species, such as soluble oligomers. CSF-derived Aß40 co-localizes with existing endogenous vascular and parenchymal amyloid-ß plaques, and thus, may contribute to the progression of both cerebral amyloid angiopathy and parenchymal Aß accumulation. Importantly, glymphatic failure preceded significant amyloid-ß deposits, and thus, may be an early biomarker of AD. By extension, restoring glymphatic inflow and ISF clearance are potential therapeutic targets to slow the onset and progression of AD.


Assuntos
Doença de Alzheimer/metabolismo , Encéfalo/metabolismo , Neurônios/metabolismo , Placa Amiloide/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Transporte Biológico/fisiologia , Modelos Animais de Doenças , Progressão da Doença , Camundongos Endogâmicos C57BL
14.
J Neurosci ; 35(2): 518-26, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25589747

RESUMO

The nonspecific and variable presentation of traumatic brain injury (TBI) has motivated an intense search for blood-based biomarkers that can objectively predict the severity of injury. However, it is not known how cytosolic proteins released from traumatized brain tissue reach the peripheral blood. Here we show in a murine TBI model that CSF movement through the recently characterized glymphatic pathway transports biomarkers to blood via the cervical lymphatics. Clinically relevant manipulation of glymphatic activity, including sleep deprivation and cisternotomy, suppressed or eliminated TBI-induced increases in serum S100ß, GFAP, and neuron specific enolase. We conclude that routine TBI patient management may limit the clinical utility of blood-based biomarkers because their brain-to-blood transport depends on glymphatic activity.


Assuntos
Lesões Encefálicas/metabolismo , Líquido Extracelular/metabolismo , Taxa de Depuração Metabólica , Animais , Biomarcadores/sangue , Biomarcadores/líquido cefalorraquidiano , Barreira Hematoencefálica/metabolismo , Lesões Encefálicas/sangue , Lesões Encefálicas/líquido cefalorraquidiano , Feminino , Proteína Glial Fibrilar Ácida/sangue , Proteína Glial Fibrilar Ácida/líquido cefalorraquidiano , Camundongos , Camundongos Endogâmicos C57BL , Neuroglia/metabolismo , Subunidade beta da Proteína Ligante de Cálcio S100/sangue , Subunidade beta da Proteína Ligante de Cálcio S100/líquido cefalorraquidiano , Privação do Sono/sangue , Privação do Sono/líquido cefalorraquidiano , Privação do Sono/metabolismo
15.
J Neurosci ; 34(50): 16594-604, 2014 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-25505312

RESUMO

Experimental advances in the study of neuroglia signaling have been greatly accelerated by the generation of transgenic mouse models. In particular, an elegant manipulation that interferes with astrocyte vesicular release of gliotransmitters via overexpression of a dominant-negative domain of vesicular SNARE (dnSNARE) has led to documented astrocytic involvement in processes that were traditionally considered strictly neuronal, including the sleep-wake cycle, LTP, cognition, cortical slow waves, depression, and pain. A key premise leading to these conclusions was that expression of the dnSNARE was specific to astrocytes. Inconsistent with this premise, we report here widespread expression of the dnSNARE transgene in cortical neurons. We further demonstrate that the activity of cortical neurons is reversibly suppressed in dnSNARE mice. These findings highlight the need for independent validation of astrocytic functions identified in dnSNARE mice and thus question critical evidence that astrocytes contribute to neurotransmission through SNARE-dependent vesicular release of gliotransmitters.


Assuntos
Regulação da Expressão Gênica , Neurônios/metabolismo , Proteínas SNARE/biossíntese , Animais , Animais Recém-Nascidos , Células Cultivadas , Eletroencefalografia/métodos , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas SNARE/genética , Fases do Sono/fisiologia
16.
J Neurosci ; 33(44): 17404-12, 2013 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-24174673

RESUMO

Astrocytes in hippocampal slices can dynamically regulate synaptic transmission in a process mediated by increases in intracellular Ca(2+). However, it is debated whether astrocytic Ca(2+) signals result in release of glutamate. We here compared astrocytic Ca(2+) signaling triggered by agonist exposure versus photolysis side by side. Using transgenic mice in which astrocytes selectively express the MrgA1 receptor, we found that receptor-mediated astrocytic Ca(2+) signaling consistently triggered neuronal hyperpolarization and decreased the frequency of miniature excitatory postsynaptic currents (EPSCs). In contrast, photolysis of caged Ca(2+) (o-nitrophenyl-EGTA) in astrocytes led to neuronal depolarization and increased the frequency of mEPSCs through a metabotropic glutamate receptor-mediated pathway. Analysis of transgenic mice in which astrocytic vesicular release is suppressed (dominant-negative SNARE mice) and pharmacological manipulations suggested that glutamate is primarily released by opening of anion channels rather than exocytosis. Combined, these studies show that photolysis but not by agonists induced astrocytic Ca(2+) signaling triggers glutamate release.


Assuntos
Astrócitos/metabolismo , Sinalização do Cálcio/genética , Ácido Glutâmico/metabolismo , Fotólise , Animais , Regulação para Baixo/genética , Potenciais Pós-Sinápticos Excitadores/genética , Feminino , Hipocampo/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Inibição Neural/genética , Técnicas de Cultura de Órgãos , Receptores Acoplados a Proteínas G/agonistas , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Proteínas SNARE/deficiência , Proteínas SNARE/genética
17.
J Cereb Blood Flow Metab ; 33(7): 996-9, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23611872

RESUMO

Using in vivo two-photon imaging, we show that mice deficient in aquaporin-4 (AQP4) display increased fluorescence of nicotinamide adenine dinucleotide (NADH) when subjected to cortical spreading depression. The increased NADH signal, a proxy of tissue hypoxia, was restricted to microwatershed areas remote from the vasculature. Aqp4 deletion had no effects on the hyperemia response, but slowed [K(+)]o recovery. These observations suggest that K(+) uptake is suppressed in Aqp4(-/-) mice as a consequence of decreased oxygen delivery to tissue located furthest away from the vascular source of oxygen, although increased oxygen consumption may also contribute to our observations.


Assuntos
Aquaporina 4/fisiologia , Depressão Alastrante da Atividade Elétrica Cortical/fisiologia , Hipóxia Encefálica/metabolismo , Microscopia de Fluorescência por Excitação Multifotônica/métodos , NAD/metabolismo , Oxigênio/metabolismo , Animais , Aquaporina 4/genética , Circulação Cerebrovascular/efeitos dos fármacos , Circulação Cerebrovascular/fisiologia , Depressão Alastrante da Atividade Elétrica Cortical/efeitos dos fármacos , Depressão Alastrante da Atividade Elétrica Cortical/genética , Feminino , Deleção de Genes , Masculino , Camundongos , Camundongos Knockout , Modelos Biológicos , NAD/química , Consumo de Oxigênio/fisiologia , Cloreto de Potássio/metabolismo , Cloreto de Potássio/farmacologia
18.
Science ; 339(6116): 197-200, 2013 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-23307741

RESUMO

An extensive literature shows that astrocytes exhibit metabotropic glutamate receptor 5 (mGluR5)-dependent increases in cytosolic calcium ions (Ca(2+)) in response to glutamatergic transmission and, in turn, modulate neuronal activity by their Ca(2+)-dependent release of gliotransmitters. These findings, based on studies of young rodents, have led to the concept of the tripartite synapse, in which astrocytes actively participate in neurotransmission. Using genomic analysis, immunoelectron microscopy, and two-photon microscopy of astrocytic Ca(2+) signaling in vivo, we found that astrocytic expression of mGluR5 is developmentally regulated and is undetectable after postnatal week 3. In contrast, mGluR3, whose activation inhibits adenylate cyclase but not calcium signaling, was expressed in astrocytes at all developmental stages. Neuroglial signaling in the adult brain may therefore occur in a manner fundamentally distinct from that exhibited during development.


Assuntos
Envelhecimento , Astrócitos/metabolismo , Sinalização do Cálcio , Córtex Cerebral/metabolismo , Ácido Glutâmico/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Adolescente , Animais , Cálcio/metabolismo , Córtex Cerebral/citologia , Córtex Cerebral/ultraestrutura , Feminino , Hipocampo/citologia , Hipocampo/metabolismo , Hipocampo/ultraestrutura , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Receptor de Glutamato Metabotrópico 5 , Receptores de Glutamato Metabotrópico/agonistas , Transmissão Sináptica
19.
Glia ; 60(11): 1660-70, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22951907

RESUMO

Chronic neuropathic pain is a frequent consequence of spinal cord injury (SCI). Yet despite recent advances, upstream releasing mechanisms and effective therapeutic options remain elusive. Previous studies have demonstrated that SCI results in excessive ATP release to the peritraumatic regions and that purinergic signaling, among glial cells, likely plays an essential role in facilitating inflammatory responses and nociceptive sensitization. We sought to assess the role of connexin 43 (Cx43) as a mediator of CNS inflammation and chronic pain. To determine the extent of Cx43 involvement in chronic pain, a weight-drop SCI was performed on transgenic mice with Cx43/Cx30 deletions. SCI induced robust and persistent neuropathic pain including heat hyperalgesia and mechanical allodynia in wild-type control mice, which developed after 4 weeks and was maintained after 8 weeks. Notably, SCI-induced heat hyperalgesia and mechanical allodynia were prevented in transgenic mice with Cx43/Cx30 deletions, but fully developed in transgenic mice with only Cx30 deletion. SCI-induced gliosis, detected as upregulation of glial fibrillary acidic protein in the spinal cord astrocytes at different stages of the injury, was also reduced in the knockout mice with Cx43/Cx30 deletions, when compared with littermate controls. In comparison, a standard regimen of post-SCI treatment of minocycline attenuated neuropathic pain to a significantly lesser degree than Cx43 deletion. These findings suggest Cx43 is critically linked to the development of central neuropathic pain following acute SCI. Since Cx43/Cx30 is expressed by astrocytes, these findings also support an important role of astrocytes in the development of chronic pain.


Assuntos
Astrócitos/metabolismo , Conexina 43/metabolismo , Junções Comunicantes/metabolismo , Neuralgia/metabolismo , Traumatismos da Medula Espinal/metabolismo , Medula Espinal/metabolismo , Animais , Conexina 43/genética , Modelos Animais de Doenças , Feminino , Proteína Glial Fibrilar Ácida/metabolismo , Hiperalgesia/etiologia , Hiperalgesia/metabolismo , Camundongos , Camundongos Knockout , Neuralgia/etiologia , Medição da Dor , Limiar da Dor/fisiologia , Traumatismos da Medula Espinal/complicações
20.
Sci Transl Med ; 4(147): 147ra111, 2012 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-22896675

RESUMO

Because it lacks a lymphatic circulation, the brain must clear extracellular proteins by an alternative mechanism. The cerebrospinal fluid (CSF) functions as a sink for brain extracellular solutes, but it is not clear how solutes from the brain interstitium move from the parenchyma to the CSF. We demonstrate that a substantial portion of subarachnoid CSF cycles through the brain interstitial space. On the basis of in vivo two-photon imaging of small fluorescent tracers, we showed that CSF enters the parenchyma along paravascular spaces that surround penetrating arteries and that brain interstitial fluid is cleared along paravenous drainage pathways. Animals lacking the water channel aquaporin-4 (AQP4) in astrocytes exhibit slowed CSF influx through this system and a ~70% reduction in interstitial solute clearance, suggesting that the bulk fluid flow between these anatomical influx and efflux routes is supported by astrocytic water transport. Fluorescent-tagged amyloid ß, a peptide thought to be pathogenic in Alzheimer's disease, was transported along this route, and deletion of the Aqp4 gene suppressed the clearance of soluble amyloid ß, suggesting that this pathway may remove amyloid ß from the central nervous system. Clearance through paravenous flow may also regulate extracellular levels of proteins involved with neurodegenerative conditions, its impairment perhaps contributing to the mis-accumulation of soluble proteins.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Líquido Cefalorraquidiano/metabolismo , Líquido Extracelular/metabolismo , Animais , Aquaporina 4/metabolismo , Astrócitos/metabolismo , Transporte Biológico , Ventrículos Cerebrais/metabolismo , Imageamento Tridimensional , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia de Fluorescência por Excitação Multifotônica , Água/metabolismo
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