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Szabo K, Lako E, Juhasz T, Rosengarten B, Csiba L, Olah L. Hypocapnia induced vasoconstriction significantly inhibits the neurovascular coupling in humans. J Neurol Sci 2011; 309:58-62. [PMID: 21831399 DOI: 10.1016/j.jns.2011.07.026] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 07/14/2011] [Accepted: 07/18/2011] [Indexed: 11/25/2022]
Abstract
BACKGROUND/AIMS Previous studies proved that vasodilation, caused by hypercapnia or acetazolamide, does not inhibit the visually evoked flow velocity changes in the posterior cerebral arteries. Our aim was to determine whether vasoconstriction induced by hypocapnia affects the neurovascular coupling. METHODS By using a visual cortex stimulation paradigm, visually evoked flow velocity changes were detected by transcranial Doppler sonography in both posterior cerebral arteries of fourteen young healthy adults. The control measurement was followed by the examination under hyperventilation. Visual-evoked-potentials were also recorded during the control and hyperventilation phases. RESULTS The breathing frequency increased from 16 ± 2 to 37 ± 3/min during hyperventilation, resulting in a decrease of the end-tidal CO(2) from 37 ± 3 to 25 ± 3 mm Hg and decrease of resting peak systolic flow velocity from 58 ± 11 to 48 ± 11 cm/s (p<0.01). To allow comparisons between volunteers, relative flow velocity was calculated in relation to baseline. Repeated measures analysis of variance revealed significant difference between the relative flow velocity time courses during hyper- and normoventilation (p<0.001). The maximum changes of visually evoked relative flow velocities were 26 ± 7% and 12 ± 5% during normoventilation and hyperventilation, respectively (p<0.01). Visual-evoked-potentials did not differ in the control and hyperventilation phases. CONCLUSION The significantly lower visually evoked flow velocity changes but preserved visual-evoked-potential during hyperventilation indicates that the hypocapnia induced vasoconstriction significantly inhibits the neuronal activity evoked flow response.
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Affiliation(s)
- Katalin Szabo
- Department of Neurology, University of Debrecen, Debrecen, Hungary
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252
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Vetri F, Xu H, Mao L, Paisansathan C, Pelligrino DA. ATP hydrolysis pathways and their contributions to pial arteriolar dilation in rats. Am J Physiol Heart Circ Physiol 2011; 301:H1369-77. [PMID: 21803949 DOI: 10.1152/ajpheart.00556.2011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
ATP is thought to be released to the extracellular compartment by neurons and astrocytes during neural activation. We examined whether ATP exerts its effect of promoting pial arteriolar dilation (PAD) directly or upon conversion (via ecto-nucleotidase action) to AMP and adenosine. Blockade of extracellular direct ATP to AMP conversion, with ARL-67156, significantly reduced sciatic nerve stimulation-evoked PADs by 68%. We then monitored PADs during suffusions of ATP, ADP, AMP, and adenosine in the presence and absence of the following: 1) the ecto-5'-nucleotidase inhibitor α,β-methylene adenosine 5'-diphosphate (AOPCP), 2) the A(2) receptor blocker ZM 241385, 3) the ADP P2Y(1) receptor antagonist MRS 2179, and 4) ARL-67156. Vasodilations induced by 1 and 10 μM, but not 100 μM, ATP were markedly attenuated by ZM 241385, AOPCP, and ARL-67156. Substantial loss of reactivity to 100 μM ATP required coapplications of ZM 241385 and MRS 2179. Dilations induced by ADP were blocked by MRS 2179 but were not affected by either ZM 241385 or AOPCP. AMP-elicited dilation was partially inhibited by AOPCP and completely abolished by ZM 241385. Collectively, these and previous results indicate that extracellular ATP-derived adenosine and AMP, via A(2) receptors, play key roles in neural activation-evoked PAD. However, at high extracellular ATP levels, some conversion to ADP may occur and contribute to PAD through P2Y(1) activation.
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Affiliation(s)
- Francesco Vetri
- Neuroanesthesia Research, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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253
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Choi M, Yoon J, Ku T, Choi K, Choi C. Label-free optical activation of astrocyte in vivo. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:075003. [PMID: 21806260 DOI: 10.1117/1.3600774] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
As the most abundant cell type in the central nervous system, astrocyte has been one of main research topics in neuroscience. Although various tools have been developed, at present, there is no tool that allows noninvasive activation of astrocyte in vivo without genetic or pharmacological perturbation. Here we report a noninvasive label-free optical method for physiological astrocyte activation in vivo using a femtosecond pulsed laser. We showed the laser stimulation robustly induced astrocytic calcium activation in vivo and further verified physiological relevance of the calcium increase by demonstrating astrocyte mediated vasodilation in the brain. This novel optical method will facilitate noninvasive physiological study on astrocyte function.
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Affiliation(s)
- Myunghwan Choi
- KAIST, Department of Bio and Brain Engineering, Cell Signaling and Bioimaging Laboratory, 335 Gwahak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
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Ulrich F, Ma LH, Baker RG, Torres-Vázquez J. Neurovascular development in the embryonic zebrafish hindbrain. Dev Biol 2011; 357:134-51. [PMID: 21745463 DOI: 10.1016/j.ydbio.2011.06.037] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 06/10/2011] [Accepted: 06/13/2011] [Indexed: 01/05/2023]
Abstract
The brain is made of billions of highly metabolically active neurons whose activities provide the seat for cognitive, affective, sensory and motor functions. The cerebral vasculature meets the brain's unusually high demand for oxygen and glucose by providing it with the largest blood supply of any organ. Accordingly, disorders of the cerebral vasculature, such as congenital vascular malformations, stroke and tumors, compromise neuronal function and survival and often have crippling or fatal consequences. Yet, the assembly of the cerebral vasculature is a process that remains poorly understood. Here we exploit the physical and optical accessibility of the zebrafish embryo to characterize cerebral vascular development within the embryonic hindbrain. We find that this process is primarily driven by endothelial cell migration and follows a two-step sequence. First, perineural vessels with stereotypical anatomies are formed along the ventro-lateral surface of the neuroectoderm. Second, angiogenic sprouts derived from a subset of perineural vessels migrate into the hindbrain to form the intraneural vasculature. We find that these angiogenic sprouts reproducibly penetrate into the hindbrain via the rhombomere centers, where differentiated neurons reside, and that specific rhombomeres are invariably vascularized first. While the anatomy of intraneural vessels is variable from animal to animal, some aspects of the connectivity of perineural and intraneural vessels occur reproducibly within particular hindbrain locales. Using a chemical inhibitor of VEGF signaling we determine stage-specific requirements for this pathway in the formation of the hindbrain vasculature. Finally, we show that a subset of hindbrain vessels is aligned and/or in very close proximity to stereotypical neuron clusters and axon tracts. Using endothelium-deficient cloche mutants we show that the endothelium is dispensable for the organization and maintenance of these stereotypical neuron clusters and axon tracts in the early hindbrain. However, the cerebellum's upper rhombic lip and the optic tectum are abnormal in clo. Overall, this study provides a detailed, multi-stage characterization of early zebrafish hindbrain neurovascular development with cellular resolution up to the third day of age. This work thus serves as a useful reference for the neurovascular characterization of mutants, morphants and drug-treated embryos.
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Affiliation(s)
- Florian Ulrich
- Department of Developmental Genetics, Skirball Institute of Molecular Medicine, New York City, New York 10016, USA.
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255
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Pfrieger FW, Ungerer N. Cholesterol metabolism in neurons and astrocytes. Prog Lipid Res 2011; 50:357-71. [PMID: 21741992 DOI: 10.1016/j.plipres.2011.06.002] [Citation(s) in RCA: 325] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 06/11/2011] [Accepted: 06/22/2011] [Indexed: 12/20/2022]
Abstract
Cells in the mammalian body must accurately maintain their content of cholesterol, which is an essential membrane component and precursor for vital signalling molecules. Outside the brain, cholesterol homeostasis is guaranteed by a lipoprotein shuttle between the liver, intestine and other organs via the blood circulation. Cells inside the brain are cut off from this circuit by the blood-brain barrier and must regulate their cholesterol content in a different manner. Here, we review how this is accomplished by neurons and astrocytes, two cell types of the central nervous system, whose cooperation is essential for normal brain development and function. The key observation is a remarkable cell-specific distribution of proteins that mediate different steps of cholesterol metabolism. This form of metabolic compartmentalization identifies astrocytes as net producers of cholesterol and neurons as consumers with unique means to prevent cholesterol overload. The idea that cholesterol turnover in neurons depends on close cooperation with astrocytes raises new questions that need to be addressed by new experimental approaches to monitor and manipulate cholesterol homeostasis in a cell-specific manner. We conclude that an understanding of cholesterol metabolism in the brain and its role in disease requires a close look at individual cell types.
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Affiliation(s)
- Frank W Pfrieger
- CNRS UPR 3212, University of Strasbourg, Institute of Cellular and Integrative Neurosciences (INCI), 67084 Strasbourg Cedex, France.
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256
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Chadwick W, Boyle JP, Zhou Y, Wang L, Park SS, Martin B, Wang R, Becker KG, Wood WH, Zhang Y, Peers C, Maudsley S. Multiple oxygen tension environments reveal diverse patterns of transcriptional regulation in primary astrocytes. PLoS One 2011; 6:e21638. [PMID: 21738745 PMCID: PMC3124552 DOI: 10.1371/journal.pone.0021638] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 06/04/2011] [Indexed: 01/28/2023] Open
Abstract
The central nervous system normally functions at O2 levels which would be regarded as hypoxic by most other tissues. However, most in vitro studies of neurons and astrocytes are conducted under hyperoxic conditions without consideration of O2-dependent cellular adaptation. We analyzed the reactivity of astrocytes to 1, 4 and 9% O2 tensions compared to the cell culture standard of 20% O2, to investigate their ability to sense and translate this O2 information to transcriptional activity. Variance of ambient O2 tension for rat astrocytes resulted in profound changes in ribosomal activity, cytoskeletal and energy-regulatory mechanisms and cytokine-related signaling. Clustering of transcriptional regulation patterns revealed four distinct response pattern groups that directionally pivoted around the 4% O2 tension, or demonstrated coherent ascending/decreasing gene expression patterns in response to diverse oxygen tensions. Immune response and cell cycle/cancer-related signaling pathway transcriptomic subsets were significantly activated with increasing hypoxia, whilst hemostatic and cardiovascular signaling mechanisms were attenuated with increasing hypoxia. Our data indicate that variant O2 tensions induce specific and physiologically-focused transcript regulation patterns that may underpin important physiological mechanisms that connect higher neurological activity to astrocytic function and ambient oxygen environments. These strongly defined patterns demonstrate a strong bias for physiological transcript programs to pivot around the 4% O2 tension, while uni-modal programs that do not, appear more related to pathological actions. The functional interaction of these transcriptional ‘programs’ may serve to regulate the dynamic vascular responsivity of the central nervous system during periods of stress or heightened activity.
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Affiliation(s)
- Wayne Chadwick
- Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - John P. Boyle
- Institute for Cardiovascular Research, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, West Yorkshire, United Kingdom
| | - Yu Zhou
- Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Liyun Wang
- Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Sung-Soo Park
- Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Bronwen Martin
- Metabolism Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Rui Wang
- Metabolism Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Kevin G. Becker
- Gene Expression and Genomics Unit, Research Resources Branch, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - William H. Wood
- Gene Expression and Genomics Unit, Research Resources Branch, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Yongqing Zhang
- Gene Expression and Genomics Unit, Research Resources Branch, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Chris Peers
- Institute for Cardiovascular Research, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, West Yorkshire, United Kingdom
- * E-mail: (SM); (CP)
| | - Stuart Maudsley
- Receptor Pharmacology Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail: (SM); (CP)
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Heni M, Hennige AM, Peter A, Siegel-Axel D, Ordelheide AM, Krebs N, Machicao F, Fritsche A, Häring HU, Staiger H. Insulin promotes glycogen storage and cell proliferation in primary human astrocytes. PLoS One 2011; 6:e21594. [PMID: 21738722 PMCID: PMC3124526 DOI: 10.1371/journal.pone.0021594] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Accepted: 06/06/2011] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION In the human brain, there are at least as many astrocytes as neurons. Astrocytes are known to modulate neuronal function in several ways. Thus, they may also contribute to cerebral insulin actions. Therefore, we examined whether primary human astrocytes are insulin-responsive and whether their metabolic functions are affected by the hormone. METHODS Commercially available Normal Human Astrocytes were grown in the recommended medium. Major players in the insulin signaling pathway were detected by real-time RT-PCR and Western blotting. Phosphorylation events were detected by phospho-specific antibodies. Glucose uptake and glycogen synthesis were assessed using radio-labeled glucose. Glycogen content was assessed by histochemistry. Lactate levels were measured enzymatically. Cell proliferation was assessed by WST-1 assay. RESULTS We detected expression of key proteins for insulin signaling, such as insulin receptor β-subunit, insulin receptor substrat-1, Akt/protein kinase B and glycogen synthase kinase 3, in human astrocytes. Akt was phosphorylated and PI-3 kinase activity increased following insulin stimulation in a dose-dependent manner. Neither increased glucose uptake nor lactate secretion after insulin stimulation could be evidenced in this cell type. However, we found increased insulin-dependent glucose incorporation into glycogen. Furthermore, cell numbers increased dose-dependently upon insulin treatment. DISCUSSION This study demonstrated that human astrocytes are insulin-responsive at the molecular level. We identified glycogen synthesis and cell proliferation as biological responses of insulin signaling in these brain cells. Hence, this cell type may contribute to the effects of insulin in the human brain.
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Affiliation(s)
- Martin Heni
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Anita M. Hennige
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Andreas Peter
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Dorothea Siegel-Axel
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Anna-Maria Ordelheide
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Norbert Krebs
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Fausto Machicao
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Andreas Fritsche
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
| | - Hans-Ulrich Häring
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
- * E-mail:
| | - Harald Staiger
- Division of Endocrinology, Diabetology, Angiology, Nephrology and Clinical Chemistry, Department of Internal Medicine, Member of the German Center for Diabetes Research (DZD), Eberhard Karls University Tübingen, Tübingen, Germany
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258
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Barreto GE, Gonzalez J, Torres Y, Morales L. Astrocytic-neuronal crosstalk: implications for neuroprotection from brain injury. Neurosci Res 2011; 71:107-13. [PMID: 21693140 DOI: 10.1016/j.neures.2011.06.004] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 04/28/2011] [Accepted: 05/16/2011] [Indexed: 10/18/2022]
Abstract
The older neurocentric view of the central nervous system (CNS) has changed radically with the growing understanding of the many essential functions of astrocytes. Advances in our understanding of astrocytes include new observations about their structure, organization, function and supportive actions to other cells. Although the contribution of astrocytes to the process of brain injury has not been clearly defined, it is thought that their ability to provide support to neurons after cerebral damage is critical. Astrocytes play a fundamental role in the pathogenesis of brain injury-associated neuronal death, and this secondary injury is primarily a consequence of the failure of astrocytes to support the essential metabolic needs of neurons. These needs include K+ buffering, glutamate clearance, brain antioxidant defense, close metabolic coupling with neurons, and the modulation of neuronal excitability. In this review, we will focus on astrocytic activities that can both protect and endanger neurons, and discuss how manipulating these functions provides a novel and important strategy to enhance neuronal survival and improve the outcome following brain injury.
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Affiliation(s)
- George E Barreto
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá DC, Colombia.
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259
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Halliday GM, Stevens CH. Glia: initiators and progressors of pathology in Parkinson's disease. Mov Disord 2011; 26:6-17. [PMID: 21322014 DOI: 10.1002/mds.23455] [Citation(s) in RCA: 310] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
BACKGROUND Glia are traditionally known as support cells for neurons, and their role in neurodegeneration has been largely considered secondary to neuronal dysfunction. We review newer concepts on glial function and assess glial changes in Parkinson's disease (PD) at the time of disease initiation when α-synuclein is accumulating in brain tissue but there is limited neuronal loss, and also as the disease progresses and neuronal loss is evident. RESULTS Of the two main types of astrocytes, only protoplasmic astrocytes are involved in PD, where they become nonreactive and accumulate α-synuclein. Experimental evidence has shown that astrocytic α-synuclein deposition initiates the noncell autonomous killing of neurons through microglial signaling. As the disease progresses, more protoplasmic astrocytes are affected by the disease with an increasing microglial response. Although there is still controversy on the role microglia play in neurodegeneration, there is evidence that microglia are activated early in PD and possibly assist with the clearance of extracellular α-synuclein at this time. Microglia transform to phagocytes and target neurons as the disease progresses but appear to become dysfunctional with increasing amounts of ingested debris. Only nonmyelinating oligodendroglial cells are affected in PD, and only late in the disease process. CONCLUSIONS Glial cells are responsible for the progression of PD and play an important role in initiating the early tissue response. In particular, early dysfunction and α-synuclein accumulation in astrocytes causes recruitment of phagocytic microglia that attack selected neurons in restricted brain regions causing the clinical symptoms of PD.
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Abstract
The ability of the brain to locally augment glucose delivery and blood flow during neuronal activation, termed neurometabolic and neurovascular coupling, respectively, is compromised in Alzheimer's disease (AD). Since perfusion deficits may hasten clinical deterioration and have been correlated with negative treatment outcome, strategies to improve the cerebral circulation should form an integral element of AD therapeutic efforts. These efforts have yielded several experimental models, some of which constitute AD models proper, others which specifically recapture the AD cerebrovascular pathology, characterized by anatomical alterations in brain vessel structure, as well as molecular changes within vascular smooth muscle cells and endothelial cells forming the blood-brain barrier. The following paper will present the elements of AD neurovascular dysfunction and review the in vitro and in vivo model systems that have served to deepen our understanding of it. It will also critically evaluate selected groups of compounds, the FDA-approved cholinesterase inhibitors and thiazolidinediones, for their ability to correct neurovascular dysfunction in AD patients and models. These and several others are emerging as compounds with pleiotropic actions that may positively impact dysfunctional cerebrovascular, glial, and neuronal networks in AD.
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261
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Glial dysfunction in the pathogenesis of α-synucleinopathies: emerging concepts. Acta Neuropathol 2011; 121:675-93. [PMID: 21562886 DOI: 10.1007/s00401-011-0833-z] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 05/04/2011] [Accepted: 05/04/2011] [Indexed: 12/18/2022]
Abstract
Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) are adult onset neurodegenerative disorders characterised by prominent intracellular α-synuclein aggregates (α-synucleinopathies). The glial contribution to neurodegeneration in α-synucleinopathies was largely underestimated until recently. However, brains of PD and DLB patients exhibit not only neuronal inclusions such as Lewy bodies or Lewy neurites but also glial α-synuclein aggregates. Accumulating experimental evidence in PD models suggests that astrogliosis and microgliosis act as important mediators of neurodegeneration playing a pivotal role in both disease initiation and progression. In MSA, oligodendrocytes are intriguingly affected by aberrant cytoplasmic accumulation of α-synuclein (glial cytoplasmic inclusions, Papp-Lantos bodies). Converging evidence from human postmortem studies and transgenic MSA models suggests that oligodendroglial dysfunction both triggers and exacerbates neuronal degeneration. This review summarises the wide range of responsibilities of astroglia, microglia and oligodendroglia in the healthy brain and the changes in glial function associated with ageing. We then provide a critical analysis of the role of glia in α-synucleinopathies including putative mechanisms promoting a chronically diseased glial microenvironment which can lead to detrimental neuronal changes, including cell loss. Finally, major therapeutic strategies targeting glial pathology in α-synucleinopathies as well as current pitfalls for disease-modification in clinical trials are discussed.
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262
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Pan H, Epstein J, Silbersweig DA, Stern E. New and emerging imaging techniques for mapping brain circuitry. ACTA ACUST UNITED AC 2011; 67:226-51. [DOI: 10.1016/j.brainresrev.2011.02.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 02/17/2011] [Accepted: 02/17/2011] [Indexed: 12/20/2022]
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Abstract
Astrocytes were identified about 150 years ago, and, for the longest time, were considered to be supporting cells in the brain providing trophic, metabolic, and structural support for neural networks. Research in the last 2 decades has uncovered many novel molecules in astrocytes and the finding that astrocytes communicate with neurons via Ca2+ signaling, which leads to release of chemical transmitters, termed gliotransmitters, has led to renewed interest in their biology. This chapter will briefly review the unique morphology and molecular properties of astrocytes. The reader will be introduced to the role of astrocytes in blood-brain barrier (BBB) maintenance, in Ca2+ signaling, in synaptic transmission, in CNS synaptogenesis, and as neural progenitor cells. Mention is also made of the diseases in which astrocyte dysfunction has a role.
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Affiliation(s)
- Sukriti Nag
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
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264
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Dai M, Shi X. Fibro-vascular coupling in the control of cochlear blood flow. PLoS One 2011; 6:e20652. [PMID: 21673815 PMCID: PMC3106013 DOI: 10.1371/journal.pone.0020652] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 05/06/2011] [Indexed: 12/20/2022] Open
Abstract
Background Transduction of sound in the cochlea is metabolically demanding. The lateral
wall and hair cells are critically vulnerable to hypoxia, especially at high
sound levels, and tight control over cochlear blood flow (CBF) is a
physiological necessity. Yet despite the importance of CBF for hearing,
consensus on what mechanisms are involved has not been obtained. Methodology/Principal Findings We report on a local control mechanism for regulating inner ear blood flow
involving fibrocyte signaling. Fibrocytes in the super-strial region are
spatially distributed near pre-capillaries of the spiral ligament of the
albino guinea pig cochlear lateral wall, as demonstrably shown in
transmission electron microscope and confocal images. Immunohistochemical
techniques reveal the inter-connected fibrocytes to be positive for
Na+/K+ ATPase β1 and S100. The connected fibrocytes display
more Ca2+ signaling than other cells in the cochlear lateral
wall as indicated by fluorescence of a Ca2+ sensor, fluo-4.
Elevation of Ca2+ in fibrocytes, induced by photolytic
uncaging of the divalent ion chelator o-nitrophenyl EGTA,
results in propagation of a Ca2+ signal to neighboring
vascular cells and vasodilation in capillaries. Of more physiological
significance, fibrocyte to vascular cell coupled signaling was found to
mediate the sound stimulated increase in cochlear blood flow (CBF).
Cyclooxygenase-1 (COX-1) was required for capillary dilation. Conclusions/Significance The findings provide the first evidence that signaling between fibrocytes and
vascular cells modulates CBF and is a key mechanism for meeting the cellular
metabolic demand of increased sound activity.
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Affiliation(s)
- Min Dai
- Oregon Hearing Research Center, Department of Otolaryngology/Head and
Neck Surgery, Oregon Health & Science University, Portland, Oregon, United
States of America
| | - Xiaorui Shi
- Oregon Hearing Research Center, Department of Otolaryngology/Head and
Neck Surgery, Oregon Health & Science University, Portland, Oregon, United
States of America
- The Institute of Microcirculation, Chinese Academy of Medical Sciences
and Peking Union Medical College, Beijing, China
- Department of Otolaryngology, Renji Hospital, Shanghai Jiao Tong
University, Shanghai, China
- * E-mail:
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265
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Schachtrup C, Le Moan N, Passino MA, Akassoglou K. Hepatic stellate cells and astrocytes: Stars of scar formation and tissue repair. Cell Cycle 2011; 10:1764-71. [PMID: 21555919 DOI: 10.4161/cc.10.11.15828] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Scar formation inhibits tissue repair and regeneration in the liver and central nervous system. Activation of hepatic stellate cells (HSCs) after liver injury or of astrocytes after nervous system damage is considered to drive scar formation. HSCs are the fibrotic cells of the liver, as they undergo activation and acquire fibrogenic properties after liver injury. HSC activation has been compared to reactive gliosis of astrocytes, which acquire a reactive phenotype and contribute to scar formation after nervous system injury, much like HSCs after liver injury. It is intriguing that a wide range of neuroglia-related molecules are expressed by HSCs. We identified an unexpected role for the p75 neurotrophin receptor in regulating HSC activation and liver repair. Here we discuss the molecular mechanisms that regulate HSC activation and reactive gliosis and their contributions to scar formation and tissue repair. Juxtaposing key mechanistic and functional similarities in HSC and astrocyte activation might provide novel insight into liver regeneration and nervous system repair.
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Liu X, Li C, Gebremedhin D, Hwang SH, Hammock BD, Falck JR, Roman RJ, Harder DR, Koehler RC. Epoxyeicosatrienoic acid-dependent cerebral vasodilation evoked by metabotropic glutamate receptor activation in vivo. Am J Physiol Heart Circ Physiol 2011; 301:H373-81. [PMID: 21602473 DOI: 10.1152/ajpheart.00745.2010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Group I metabotropic glutamate receptors (mGluR) on astrocytes have been shown to participate in cerebral vasodilation to neuronal activation in brain slices. Pharmacological stimulation of mGluR in brain slices can produce arteriolar constriction or dilation depending on the initial degree of vascular tone. Here, we examined whether pharmacological stimulation of mGluR in vivo increases cerebral blood flow. A 1-mM solution of the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) superfused at 5 μl/min over the cortical surface of anesthetized rats produced a 30 ± 2% (±SE) increase in blood flow measured by laser-Doppler flowmetry after 15-20 min. The response was completely blocked by superfusion of group I mGluR antagonists and attenuated by superfusion of an epoxyeicosatrienoic acid (EET) antagonist (5 ± 4%), an EET synthesis inhibitor (11 ± 3%), and a cyclooxygenase-2 inhibitor (15 ± 3%). The peak blood flow response was not significantly affected by administration of inhibitors of cyclooxygenase-1, neuronal nitric oxide synthase, heme oxygenase, adenosine A(2B) receptors, or an inhibitor of the synthesis of 20-hydroxyeicosatetraenoic acid (20-HETE). The blood flow response gradually waned following 30-60 min of DHPG superfusion. This loss of the flow response was attenuated by a 20-HETE synthesis inhibitor and was prevented by superfusion of an inhibitor of epoxide hydrolase, which hydrolyzes EETs. These results indicate that pharmacological stimulation of mGluR in vivo increases cerebral blood flow and that the response depends on the release of EETs and a metabolite of cyclooxygenase-2. Epoxide hydrolase activity and 20-HETE synthesis limit the duration of the response to prolonged mGluR activation.
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Affiliation(s)
- Xiaoguang Liu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland, USA
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267
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Prospects for quantitative fMRI: investigating the effects of caffeine on baseline oxygen metabolism and the response to a visual stimulus in humans. Neuroimage 2011; 57:809-16. [PMID: 21586328 DOI: 10.1016/j.neuroimage.2011.04.064] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 04/08/2011] [Accepted: 04/29/2011] [Indexed: 11/20/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) provides an indirect reflection of neural activity change in the working brain through detection of blood oxygenation level dependent (BOLD) signal changes. Although widely used to map patterns of brain activation, fMRI has not yet met its potential for clinical and pharmacological studies due to difficulties in quantitatively interpreting the BOLD signal. This difficulty is due to the BOLD response being strongly modulated by two physiological factors in addition to the level of neural activity: the amount of deoxyhemoglobin present in the baseline state and the coupling ratio, n, of evoked changes in blood flow and oxygen metabolism. In this study, we used a quantitative fMRI approach with dual measurement of blood flow and BOLD responses to overcome these limitations and show that these two sources of modulation work in opposite directions following caffeine administration in healthy human subjects. A strong 27% reduction in baseline blood flow and a 22% increase in baseline oxygen metabolism after caffeine consumption led to a decrease in baseline blood oxygenation and were expected to increase the subsequent BOLD response to the visual stimulus. Opposing this, caffeine reduced n through a strong 61% increase in the evoked oxygen metabolism response to the visual stimulus. The combined effect was that BOLD responses pre- and post-caffeine were similar despite large underlying physiological changes, indicating that the magnitude of the BOLD response alone should not be interpreted as a direct measure of underlying neurophysiological changes. Instead, a quantitative methodology based on dual-echo measurement of blood flow and BOLD responses is a promising tool for applying fMRI to disease and drug studies in which both baseline conditions and the coupling of blood flow and oxygen metabolism responses to a stimulus may be altered.
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268
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Garrecht M, Austin DW. The plausibility of a role for mercury in the etiology of autism: a cellular perspective. TOXICOLOGICAL AND ENVIRONMENTAL CHEMISTRY 2011; 93:1251-1273. [PMID: 22163375 PMCID: PMC3173748 DOI: 10.1080/02772248.2011.580588] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 04/10/2011] [Indexed: 05/23/2023]
Abstract
Autism is defined by a behavioral set of stereotypic and repetitious behavioral patterns in combination with social and communication deficits. There is emerging evidence supporting the hypothesis that autism may result from a combination of genetic susceptibility and exposure to environmental toxins at critical moments in development. Mercury (Hg) is recognized as a ubiquitous environmental neurotoxin and there is mounting evidence linking it to neurodevelopmental disorders, including autism. Of course, the evidence is not derived from experimental trials with humans but rather from methods focusing on biomarkers of Hg damage, measurements of Hg exposure, epidemiological data, and animal studies. For ethical reasons, controlled Hg exposure in humans will never be conducted. Therefore, to properly evaluate the Hg-autism etiological hypothesis, it is essential to first establish the biological plausibility of the hypothesis. This review examines the plausibility of Hg as the primary etiological agent driving the cellular mechanisms by which Hg-induced neurotoxicity may result in the physiological attributes of autism. Key areas of focus include: (1) route and cellular mechanisms of Hg exposure in autism; (2) current research and examples of possible genetic variables that are linked to both Hg sensitivity and autism; (3) the role Hg may play as an environmental toxin fueling the oxidative stress found in autism; (4) role of mitochondrial dysfunction; and (5) possible role of Hg in abnormal neuroexcitory and excitotoxity that may play a role in the immune dysregulation found in autism. Future research directions that would assist in addressing the gaps in our knowledge are proposed.
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Affiliation(s)
- Matthew Garrecht
- Swinburne Autism Bio-Research Initiative, Faculty of Life and Social Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
| | - David W. Austin
- Swinburne Autism Bio-Research Initiative, Faculty of Life and Social Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
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269
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The physiology of developmental changes in BOLD functional imaging signals. Dev Cogn Neurosci 2011; 1:199-216. [PMID: 22436508 DOI: 10.1016/j.dcn.2011.04.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 04/18/2011] [Accepted: 04/19/2011] [Indexed: 12/14/2022] Open
Abstract
BOLD fMRI (blood oxygenation level dependent functional magnetic resonance imaging) is increasingly used to detect developmental changes of human brain function that are hypothesized to underlie the maturation of cognitive processes. BOLD signals depend on neuronal activity increasing cerebral blood flow, and are reduced by neural oxygen consumption. Thus, developmental changes of BOLD signals may not reflect altered information processing if there are concomitant changes in neurovascular coupling (the mechanism by which neuronal activity increases blood flow) or neural energy use (and hence oxygen consumption). We review how BOLD signals are generated, and explain the signalling pathways which convert neuronal activity into increased blood flow. We then summarize in broad terms the developmental changes that the brain's neural circuitry undergoes during growth from childhood through adolescence to adulthood, and present the changes in neurovascular coupling mechanisms and energy use which occur over the same period. This information provides a framework for assessing whether the BOLD changes observed during human development reflect altered cognitive processing or changes in neurovascular coupling and energy use.
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270
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Longden TA, Dunn KM, Draheim HJ, Nelson MT, Weston AH, Edwards G. Intermediate-conductance calcium-activated potassium channels participate in neurovascular coupling. Br J Pharmacol 2011. [PMID: 21506954 DOI: 10.1111/j.1476‐5381.2011.01447.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Controlling vascular tone involves K(+) efflux through endothelial cell small- and intermediate-conductance calcium-activated potassium channels (K(Ca)2.3 and K(Ca)3.1, respectively). We investigated the expression of these channels in astrocytes and the possibility that, by a similar mechanism, they might contribute to neurovascular coupling. EXPERIMENTAL APPROACH Transgenic mice expressing enhanced green fluorescent protein (eGFP) in astrocytes were used to assess K(Ca)2.3 and K(Ca)3.1 expression by immunohistochemistry and RT-PCR. K(Ca) currents in eGFP-positive astrocytes were determined in situ using whole-cell patch clamp electrophysiology. The contribution of K(Ca)3.1 to neurovascular coupling was investigated in pharmacological experiments using electrical field stimulation (EFS) to evoke parenchymal arteriole dilatation in FVB/NJ mouse brain slices and whisker stimulation to evoke changes in cerebral blood flow in vivo, measured by laser Doppler flowmetry. KEY RESULTS K(Ca)3.1 immunoreactivity was restricted to astrocyte processes and endfeet and RT-PCR confirmed astrocytic K(Ca)2.3 and K(Ca)3.1 mRNA expression. With 200 nM [Ca(2+)](i) , the K(Ca)2.1-2.3/K(Ca)3.1 opener NS309 increased whole-cell currents. CyPPA, a K(Ca)2.2/K(Ca)2.3 opener, was without effect. With 1 µM [Ca(2+)](i) , the K(Ca)3.1 inhibitor TRAM-34 reduced currents whereas apamin (K(Ca)2.1-2.3 blocker) had no effect. CyPPA also inhibited currents evoked by NS309 in HEK293 cells expressing K(Ca)3.1. EFS-evoked Fluo-4 fluorescence confirmed astrocyte endfoot recruitment into neurovascular coupling. TRAM-34 inhibited EFS-evoked arteriolar dilatation by 50% whereas charybdotoxin, a blocker of K(Ca)3.1 and the large-conductance K(Ca) channel, K(Ca)1.1, inhibited dilatation by 82%. TRAM-34 reduced the cortical hyperaemic response to whisker stimulation by 40%. CONCLUSION AND IMPLICATIONS Astrocytes express functional K(Ca)3.1 channels, and these contribute to neurovascular coupling.
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Affiliation(s)
- T A Longden
- Faculty of Life Sciences, University of Manchester, UK.
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271
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The role of spreading depression, spreading depolarization and spreading ischemia in neurological disease. Nat Med 2011; 17:439-47. [PMID: 21475241 DOI: 10.1038/nm.2333] [Citation(s) in RCA: 788] [Impact Index Per Article: 60.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The term spreading depolarization describes a wave in the gray matter of the central nervous system characterized by swelling of neurons, distortion of dendritic spines, a large change of the slow electrical potential and silencing of brain electrical activity (spreading depression). In the clinic, unequivocal electrophysiological evidence now exists that spreading depolarizations occur abundantly in individuals with aneurismal subarachnoid hemorrhage, delayed ischemic stroke after subarachnoid hemorrhage, malignant hemispheric stroke, spontaneous intracerebral hemorrhage or traumatic brain injury. Spreading depolarization is induced experimentally by various noxious conditions including chemicals such as potassium, glutamate, inhibitors of the sodium pump, status epilepticus, hypoxia, hypoglycemia and ischemia, but it can can also invade healthy, naive tissue. Resistance vessels respond to it with tone alterations, causing either transient hyperperfusion (physiological hemodynamic response) in healthy tissue or severe hypoperfusion (inverse hemodynamic response, or spreading ischemia) in tissue at risk for progressive damage, which contributes to lesion progression. Therapies that target spreading depolarization or the inverse hemodynamic response may potentially treat these neurological conditions.
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272
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Okubo Y, Kanemaru K, Iino M. Imaging of Ca2+ and related signaling molecules and investigation of their functions in the brain. Antioxid Redox Signal 2011; 14:1303-14. [PMID: 20615120 DOI: 10.1089/ars.2010.3367] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Intracellular Ca(2+) signaling, and related mechanisms involving inositol 1,4,5-trisphosphate (IP(3)), nitric oxide, and the excitatory neurotransmitter glutamate, play a major role in the regulation of cellular function in the brain. Due to the complex morphology of central neurons, the correct spatiotemporal distribution of signaling molecules is essential. Thus, imaging studies have been particularly useful in elucidating the functions of these signaling molecules. The advancement of imaging methods, together with the development of a new method for the specific inhibition of intracellular IP(3) signaling, have made it possible to identify pathways that are regulated by Ca(2+) signals in the brain, including Ca(2+)-dependent synaptic maintenance and glial cell-dependent neurite growth. Further investigation of Ca(2+)-related signaling is expected to increase our understanding of brain function in the future.
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Affiliation(s)
- Yohei Okubo
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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273
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Influences of negative BOLD responses on positive BOLD responses. Neuroimage 2011; 55:1709-15. [DOI: 10.1016/j.neuroimage.2011.01.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 01/07/2011] [Accepted: 01/11/2011] [Indexed: 11/23/2022] Open
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274
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Abstract
The eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs), which are generated from the metabolism of arachidonic acid by cytochrome P450 (CYP) enzymes, possess a wide array of biological actions, including the regulation of blood flow to organs. 20-HETE and EETs are generated in various cell types in the brain and cerebral blood vessels, and contribute significantly to cerebral blood flow autoregulation and the coupling of regional brain blood flow to neuronal activity (neurovascular coupling). Investigations are beginning to unravel the molecular and cellular mechanisms by which these CYP eicosanoids regulate cerebral vascular function and the changes that occur in pathological states. Intriguingly, 20-HETE and the soluble epoxide hydrolase (sEH) enzyme that regulates EET levels have been explored as molecular therapeutic targets for cerebral vascular diseases. Inhibition of 20-HETE, or increasing EET levels by inhibiting the sEH enzyme, decreases cerebral damage following stroke. The improved outcome following cerebral ischaemia is a consequence of improving cerebral vascular structure or function and protecting neurons from cell death. Thus, the CYP eicosanoids are key regulators of cerebral vascular function and novel therapeutic targets for cardiovascular diseases and neurological disorders.
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275
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Neuwelt EA, Bauer B, Fahlke C, Fricker G, Iadecola C, Janigro D, Leybaert L, Molnar Z, O’Donnell M, Povlishock J, Saunders N, Sharp F, Stanimirovic D, Watts R, Drewes L. Engaging neuroscience to advance translational research in brain barrier biology. Nat Rev Neurosci 2011; 12:169-82. [PMID: 21331083 PMCID: PMC3335275 DOI: 10.1038/nrn2995] [Citation(s) in RCA: 392] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The delivery of many potentially therapeutic and diagnostic compounds to specific areas of the brain is restricted by brain barriers, of which the most well known are the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier. Recent studies have shown numerous additional roles of these barriers, including an involvement in neurodevelopment, in the control of cerebral blood flow, and--when barrier integrity is impaired--in the pathology of many common CNS disorders such as Alzheimer's disease, Parkinson's disease and stroke.
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Affiliation(s)
- Edward A. Neuwelt
- Oregon Health & Science University, Portland, Oregon
- Portland Veterans Affairs Medical Center, Portland, Oregon
| | | | | | | | | | | | | | | | | | | | | | - Frank Sharp
- University of California at Davis, Davis, California
| | | | - Ryan Watts
- Genentech, Inc., South San Francisco, California
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276
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In vivo 3D morphology of astrocyte-vasculature interactions in the somatosensory cortex: implications for neurovascular coupling. J Cereb Blood Flow Metab 2011; 31:795-806. [PMID: 21139630 PMCID: PMC3063633 DOI: 10.1038/jcbfm.2010.204] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Astrocytes are increasingly believed to play an important role in neurovascular coupling. Recent in vivo studies have shown that intracellular calcium levels in astrocytes correlate with reactivity in adjacent diving arterioles. However, the hemodynamic response to stimulation involves a complex orchestration of vessel dilations and constrictions that spread rapidly over wide distances. In this work, we study the three-dimensional cytoarchitecture of astrocytes and their interrelations with blood vessels down through layer IV of the mouse somatosensory cortex using in vivo two-photon microscopy. Vessels and astrocytes were visualized through intravenous dextran-conjugated fluorescein and cortically applied sulforhodamine 101 (SR101), respectively. In addition to exploring astrocyte density, vascular proximity, and microvascular density, we found that sheathing of subpial vessels by astrocyte processes was continuous along all capillaries, arterioles, and veins, comprising a highly interconnected pathway through which signals could feasibly be relayed over long distances via gap junctions. An inner SR101-positive sheath noted along pial and diving arterioles was determined to be nonastrocytic, and appears to represent selective SR101 staining of arterial endothelial cells. Our findings underscore the intimate relationship between astrocytes and all cortical blood vessels, and suggest that astrocytes could influence neurovascular regulation at a range of sites, including the capillary bed and pial arterioles.
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277
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Carbon dioxide influence on nitric oxide production in endothelial cells and astrocytes: cellular mechanisms. Brain Res 2011; 1386:50-7. [PMID: 21362408 DOI: 10.1016/j.brainres.2011.02.066] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Revised: 01/19/2011] [Accepted: 02/21/2011] [Indexed: 11/21/2022]
Abstract
Cerebral vessels may regulate cerebral blood flow by responding to changes in carbon dioxide (CO(2)) through nitric oxide (NO) production. To better determine the role of NO production by human adult cerebral microvascular endothelial cells and human fetal astrocytes under different CO(2) conditions, we studied endothelial cell and astrocyte production of NO under hypo-, normo- and hypercapnic conditions. Human cerebral endothelial cell and fetal astrocyte cultures were exposed to hypocapnic (pCO(2) 21.7±6.7mmHg), normocapnic (pCO(2) 40.1±0.9mmHg) and hypercapnic (pCO(2) 56.3±8.7mmHg) conditions. NO production was recorded continuously over 24hours with stable pH. N-nitro-l-arginine [NLA; a nitric oxide synthase (NOS) inhibitor] and l-arginine (substrate for NO production via NOS) were used to further define the role of NOS in chemoregulation. NO levels in endothelial cells increased during hypercapnia by 36% in 8hours and remained 25% above baseline. NO increase in astrocytes was 30% after 1hour but returned to baseline at 8hours. NLA blocked NO increase in endothelial cells under hypercapnia. During hypocapnia, NO levels in the endothelial cells decreased by 30% at 8hours but were unchanged in astrocytes. l-arginine prevented NO decrease in endothelial cells under hypocapnia. NO changes in the endothelial cells correlated with changes in pCO(2) (R=0.99) and were independent of pH. This study suggests that cerebral endothelial cells and astrocytes release NO under normocapnic conditions and NO production is increased during hypercapnia and decreased during hypocapnia independent of pH. Further, this demonstrates that endothelial cells may play a pivotal role in chemoregulation by modulating NOS activity.
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278
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Papadopoulos P, Ongali B, Hamel E. Selective in vivo antagonism of endothelin receptors in transforming growth factor-beta1 transgenic mice that mimic the vascular pathology of Alzheimer's disease. Can J Physiol Pharmacol 2011; 88:652-60. [PMID: 20628431 DOI: 10.1139/y10-042] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Increased levels of transforming growth factor-beta1 (TGF-beta1) induce a vascular pathology that shares similarities with that seen in Alzheimer's disease, and which possibly contributes to the cognitive decline. In aged transgenic mice that overexpress TGF-beta1 (TGF mice), we previously found reduced dilatory function and selectively impaired endothelin-1 (ET-1)-induced contraction. Here we studied the effects of chronic treatments with selective ETA (ABT-627) or ETB (A-192621) receptor antagonist on cerebrovascular reactivity, cerebral perfusion, or memory performance. The dilatory deficit of TGF mice was not improved by either treatment, but both ET-1 contraction and basal nitric oxide (NO) production were distinctly altered. Although ABT-627 was devoid of any effect in TGF mice, it virtually abolished the ET-1-induced contraction and NO release in wild-type (WT) littermates. In contrast, A-192621 only acted upon TGF mice with full recovery of ET-1 contraction and baseline NO synthesis. TGF mice, treated or not, had no cognitive deficit in the Morris water maze, nor did ABT-627-treated WT controls despite severely impaired vasoreactivity. These findings confirm that ETA receptors primarily mediate the ET-1-induced contraction. Further, they suggest that ETB receptors play a detrimental role in conditions of increased TGF-beta1 and that vascular dysfunction does not inevitably lead to cognitive deficit.
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Affiliation(s)
- Panayiota Papadopoulos
- Laboratory of Cerebrovascular Research, Montreal Neurological Institute, McGill University, Montréal, QC H3A 2B4, Canada
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279
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Pelligrino DA, Vetri F, Xu HL. Purinergic mechanisms in gliovascular coupling. Semin Cell Dev Biol 2011; 22:229-36. [PMID: 21329762 DOI: 10.1016/j.semcdb.2011.02.010] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 01/11/2011] [Accepted: 02/07/2011] [Indexed: 01/23/2023]
Abstract
Regional elevations in cerebral blood flow (CBF) often occur in response to localized increases in cerebral neuronal activity. An ever expanding literature has linked this neurovascular coupling process to specific signaling pathways involving neuronal synapses, astrocytes and cerebral arteries and arterioles. Collectively, these structures are termed the "neurovascular unit" (NVU). Astrocytes are thought to be the cornerstone of the NVU. Thus, not only do astrocytes "detect" increased synaptic activity, they can transmit that information to proximal and remote astrocytic sites often through a Ca(2+)- and ATP-related signaling process. At the vascular end of the NVU, a Ca(2+)-dependent formation and release of vasodilators, or substances linked to vasodilation, can occur. The latter category includes ATP, which upon its appearance in the extracellular compartment, can be rapidly converted to the potent vasodilator, adenosine, via the action of ecto-nucleotidases. In the present review, we give consideration to experimental model-specific variations in purinergic influences on gliovascular signaling mechanisms, focusing on the cerebral cortex. In that discussion, we compare findings obtained using in vitro (rodent brain slice) models and multiple in vivo models (2-photon imaging; somatosensory stimulation-evoked cortical hyperemia; and sciatic nerve stimulation-evoked pial arteriolar dilation). Additional attention is given to the importance of upstream (remote) vasodilation; the key role played by extracellular ATP hydrolysis (via ecto-nucleotidases) in gliovascular coupling; and interactions among multiple signaling pathways.
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Affiliation(s)
- Dale A Pelligrino
- Neuroanesthesia Research Laboratory, University of Illinois at Chicago, Chicago, IL 60612, USA.
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280
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Figley CR, Stroman PW. The role(s) of astrocytes and astrocyte activity in neurometabolism, neurovascular coupling, and the production of functional neuroimaging signals. Eur J Neurosci 2011; 33:577-88. [DOI: 10.1111/j.1460-9568.2010.07584.x] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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281
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Knierim E, Leisle L, Wagner C, Weschke B, Lucke B, Bohner G, Dreier JP, Schuelke M. Recurrent Stroke Due to a Novel Voltage Sensor Mutation in Ca
v
2.1 Responds to Verapamil. Stroke 2011; 42:e14-7. [DOI: 10.1161/strokeaha.110.600023] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Ellen Knierim
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
| | - Lilia Leisle
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
| | - Christiane Wagner
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
| | - Bernhard Weschke
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
| | - Barbara Lucke
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
| | - Georg Bohner
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
| | - Jens P. Dreier
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
| | - Markus Schuelke
- From the Department of Neuropediatrics (E.K., C.W., B.W., B.L., M.S.), the NeuroCure Clinical Research Center (E.K., B.L., M.S.), the Department of Neuroradiology (G.B.), and the Center for Stroke Research (J.P.D.), Charité Universitätsmedizin Berlin, Berlin, Germany; and the Leibniz-Institute for Molecular Pharmacology and Max-Delbrueck-Center for Molecular Medicine (L.L.), Berlin, Germany
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282
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Mulligan MK, Rhodes JS, Crabbe JC, Mayfield RD, Harris RA, Ponomarev I. Molecular profiles of drinking alcohol to intoxication in C57BL/6J mice. Alcohol Clin Exp Res 2011; 35:659-70. [PMID: 21223303 DOI: 10.1111/j.1530-0277.2010.01384.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Alcohol addiction develops through a series of stages, and mechanistic studies are needed to understand the transition from initial drug use to sustained controlled alcohol consumption followed by abuse and physical dependence. The focus of this study was to examine the effects of voluntary alcohol consumption on brain gene expression profiles using a mouse model of binge drinking. The main goal was to identify alcohol-responsive genes and functional categories after a single episode of drinking to intoxication. METHODS We used a modification of a "Drinking In the Dark" (DID) procedure (Rhodes et al., 2005) that allows mice to experience physiologically relevant amounts of alcohol in a non-stressful environment and also allows for detection of alcohol-sensitive molecular changes in a dose-dependent manner. C57BL/6J male mice were exposed to either 20% ethanol solution or water (single bottle) starting 3 hours after lights off for 4 hours and brains were harvested immediately after the drinking session. cDNA microarrays were used to assess the effects of voluntary drinking on global gene expression in 6 brain regions. We employed three statistical approaches to analyze microarray data. RESULTS A commonly used approach that applies a strict statistical threshold identified the eight top statistically significant genes whose expression was significantly correlated with blood ethanol concentration (BEC) in one of the brain regions. We then used a systems network approach to examine brain region-specific transcriptomes and identify modules of co-expressed (correlated) genes. In each brain region, we identified alcohol-responsive modules, i.e., modules significantly enriched for genes whose expression was correlated with BEC. A functional over-representation analysis was then applied to examine the organizing principles of alcohol-responsive modules. Genes were clustered into modules according to their roles in different physiological processes, functional groups, and cell types, including blood circulation, signal transduction, cell-cell communication, and striatal neurons. Finally, a meta-analysis across all brain regions suggested a global role of increasing alcohol dose in coordination of brain blood circulation and reaction of astrocytes. CONCLUSIONS This study showed that acute drinking resulted in small but consistent changes in brain gene expression which occurred in a dose-dependent manner. We identified both general and region-specific changes, some of which represent adaptive changes in response to increasing alcohol dose, which may play a role in alcohol-related behaviours, such as tolerance and consumption. Our systems approach allowed us to estimate the functional values of individual genes in the context of their genetic networks and formulate new refined hypotheses. An integrative analysis including other alcohol studies suggested several top candidates for functional validation, including Mt2, Gstm1, Scn4b, Prkcz, and Park7.
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Affiliation(s)
- Megan K Mulligan
- University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, Texas, USA
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283
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Lenti L, Domoki F, Gáspár T, Snipes JA, Bari F, Busija DW. N-methyl-D-aspartate induces cortical hyperemia through cortical spreading depression-dependent and -independent mechanisms in rats. Microcirculation 2011; 16:629-39. [PMID: 19657965 DOI: 10.1080/10739680903131510] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
OBJECTIVE N-methyl-d-aspartate (NMDA) is a powerful cerebrovascular dilator in vivo. Cortical spreading depression (CSD) has recently been shown to contribute to the pial arteriolar dilation in mice. Our main aim was to examine the participation of CSD in the overall cerebrovascular response to NMDA in the rat. METHODS Anesthetized Wistar rats (eight weeks old) were equipped with a closed cranial window to allow topical application of NMDA (10(-5)-10(-3) M) to the parietal cortex. Cortical blood flow (CoBF) under and outside the cranial window was simultaneously monitored by using a two-channel laser-Doppler flowmeter. CSDs were detected by recording the changes in the cortical DC potential. RESULTS Concentrations of 10(-4) and 10(-3) M of NMDA evoked single CSDs associated with rapid, transient hyperemia, followed by a sustained, but reduced, increase in CoBF. The latency and magnitude of the CoBF responses were dose dependent. The higher dose resulted in shorter latency (100+/-5* vs. 146+/-11 seconds, *P<0.05; mean+/-standard error of the mean) and larger overall flow response (77+/-12* vs. 28+/-3% from baseline) under, but not outside, the cranial window. CONCLUSIONS NMDA elicits dose-dependent increases in CoBF that are composed of CSD-dependent and -independent components in rats.
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Affiliation(s)
- Laura Lenti
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, North Carolina, USA.
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284
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Mishra A, Newman EA. Inhibition of inducible nitric oxide synthase reverses the loss of functional hyperemia in diabetic retinopathy. Glia 2011; 58:1996-2004. [PMID: 20830810 DOI: 10.1002/glia.21068] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Neuronal activity leads to arteriole dilation and increased blood flow in retinal vessels. This response, termed functional hyperemia, is diminished in the retinas of diabetic patients, possibly contributing to the development of diabetic retinopathy. The mechanism responsible for this loss is unknown. Here we show that light-evoked arteriole dilation was reduced by 58% in a streptozotocin-induced rat model of type 1 diabetes. Functional hyperemia is believed to be mediated by glial cells and we found that glial-evoked vasodilation was reduced by 60% in diabetic animals. The diabetic retinas showed neither a decrease in the thickness of the retinal layers nor an increase in neuronal loss, although signs of early glial reactivity and an upregulation of inducible nitric oxide synthase (iNOS) were detected. Inhibition of iNOS restored both light- and glial-evoked dilations to control levels. These findings suggest that high NO levels resulting from iNOS upregulation alters glial control of vessel diameter and may underlie the loss of functional hyperemia observed in diabetic retinopathy. Restoring functional hyperemia by iNOS inhibition may limit the progression of retinopathy in diabetic patients.
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Affiliation(s)
- Anusha Mishra
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA
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285
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Drouin A, Bolduc V, Thorin-Trescases N, Bélanger É, Fernandes P, Baraghis E, Lesage F, Gillis MA, Villeneuve L, Hamel E, Ferland G, Thorin E. Catechin treatment improves cerebrovascular flow-mediated dilation and learning abilities in atherosclerotic mice. Am J Physiol Heart Circ Physiol 2010; 300:H1032-43. [PMID: 21186270 DOI: 10.1152/ajpheart.00410.2010] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Severe dyslipidemia and the associated oxidative stress could accelerate the age-related decline in cerebrovascular endothelial function and cerebral blood flow (CBF), leading to neuronal loss and impaired learning abilities. We hypothesized that a chronic treatment with the polyphenol catechin would prevent endothelial dysfunction, maintain CBF responses, and protect learning abilities in atherosclerotic (ATX) mice. We treated ATX (C57Bl/6-LDLR(-/-)hApoB(+/+); 3 mo old) mice with catechin (30 mg · kg(-1) · day(-1)) for 3 mo, and C57Bl/6 [wild type (WT), 3 and 6 mo old] mice were used as controls. ACh- and flow-mediated dilations (FMD) were recorded in pressurized cerebral arteries. Basal CBF and increases in CBF induced by whisker stimulation were measured by optical coherence tomography and Doppler, respectively. Learning capacities were evaluated with the Morris water maze test. Compared with 6-mo-old WT mice, cerebral arteries from 6-mo-old ATX mice displayed a higher myogenic tone, lower responses to ACh and FMD, and were insensitive to NOS inhibition (P < 0.05), suggesting endothelial dysfunction. Basal and increases in CBF were lower in 6-mo-old ATX than WT mice (P < 0.05). A decline in the learning capabilities was also observed in ATX mice (P < 0.05). Catechin 1) reduced cerebral superoxide staining (P < 0.05) in ATX mice, 2) restored endothelial function by reducing myogenic tone, improving ACh- and FMD and restoring the sensitivity to nitric oxide synthase inhibition (P < 0.05), 3) increased the changes in CBF during stimulation but not basal CBF, and 4) prevented the decline in learning abilities (P < 0.05). In conclusion, catechin treatment of ATX mice prevents cerebrovascular dysfunctions and the associated decline in learning capacities.
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Affiliation(s)
- Annick Drouin
- Department of Surgery, Montreal Heart Institute Research Center, Université de Montréal, Montreal, Quebec, Canada.
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286
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Vangilder RL, Rosen CL, Barr TL, Huber JD. Targeting the neurovascular unit for treatment of neurological disorders. Pharmacol Ther 2010; 130:239-47. [PMID: 21172386 DOI: 10.1016/j.pharmthera.2010.12.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Accepted: 11/22/2010] [Indexed: 12/17/2022]
Abstract
Drug discovery for CNS disorders has been restricted by the inability for therapeutic agents to cross the blood-brain barrier (BBB). Moreover, current drugs aim to correct neuron cell signaling, thereby neglecting pathophysiological changes affecting other cell types of the neurovascular unit (NVU). Components of the NVU (pericytes, microglia, astrocytes, and neurons, and basal lamina) act as an intricate network to maintain the neuronal homeostatic microenvironment. Consequently, disruptions to this intricate cell network lead to neuron malfunction and symptoms characteristic of CNS diseases. A lack of understanding in NVU signaling cascades may explain why current treatments for CNS diseases are not curative. Current therapies treat symptoms by maintaining neuron function. Refocusing drug discovery to sustain NVU function may provide a better method of treatment by promoting neuron survival. In this review, we will examine current therapeutics for common CNS diseases, describe the importance of the NVU in cerebral homeostasis and discuss new possible drug targets and technologies that aim to improve treatment and drug delivery to the diseased brain.
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Affiliation(s)
- Reyna L Vangilder
- Department of Health Restoration, West Virginia University School of Nursing, Morgantown WV, USA
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287
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Chen JJ, Rosas HD, Salat DH. Age-associated reductions in cerebral blood flow are independent from regional atrophy. Neuroimage 2010; 55:468-78. [PMID: 21167947 DOI: 10.1016/j.neuroimage.2010.12.032] [Citation(s) in RCA: 258] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 12/07/2010] [Accepted: 12/09/2010] [Indexed: 01/19/2023] Open
Abstract
Prior studies have demonstrated decreasing cerebral blood flow (CBF) in normal aging, but the full spatial pattern and potential mechanism of changes in CBF remain to be elucidated. Specifically, existing data have not been entirely consistent regarding the spatial distribution of such changes, potentially a result of neglecting the effect of age-related tissue atrophy in CBF measurements. In this work, we use pulsed arterial-spin labelling to quantify regional CBF in 86 cognitively and physically healthy adults, aged 23 to 88 years. Surface-based analyses were utilized to map regional decline in CBF and cortical thickness with advancing age, and to examine the spatial associations and dissociations between these metrics. Our results demonstrate regionally selective age-related reductions in cortical perfusion, involving the superior-frontal, orbito-frontal, superior-parietal, middle-inferior temporal, insular, precuneus, supramarginal, lateral-occipital and cingulate regions, while subcortical CBF was relatively preserved in aging. Regional effects of age on CBF differed from that of grey-matter atrophy. In addition, the pattern of CBF associations with age displays an interesting similarity with the default-mode network. These findings demonstrate the dissociation between regional CBF and structural alterations specific to normal aging, and augment our understanding of mechanisms of pathology in older adults.
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Affiliation(s)
- J Jean Chen
- MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
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288
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Qiu Y, Pan J, Li Y, Li X, Li M, Abukhousa I, Wang Y. Relationship between activated astrocytes and hypoxic cerebral tissue in a rat model of cerebral ischemia/reperfusion. Int J Neurosci 2010; 121:1-7. [PMID: 21110698 DOI: 10.3109/00207454.2010.535933] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Following cerebral infarction, hypoxic tissues remains in the ischemic cortex for long periods of time. Glial fibrillary acidic protein (GFAP) is a specific marker of astrocytes, which is thought to be essential for neuronal survival. We aimed to clarify the relationship between hypoxic tissue and astrocytes following cerebral infarction. Rats with middle cerebral artery occlusion were randomly divided into a 1.5-hour ischemia-reperfusion(1.5-hour IR) group and a permanent ischemia (PI) group. Hypoxic tissue and GFAP fluorescence intensity in the ischemic cortex were observed postoperatively on days 1, 3, 7, and 14. Results showed that hypoxic tissue was present from day 1 to 14 in the 1.5-hour IR group and on days 1 and 3 in the PI group. The GFAP fluorescence intensity in the 1.5-hour IR group was stronger than that in the PI group at the same time point of observation. Over time, GFAP expression increased and peaked at 7 days in each group, followed by a decrease in signal. In hypoxic tissue, the GFAP fluorescence intensity was stronger than that in the surrounding tissue at all observation time points. These data indicate that astrocytes were strongly activated in hypoxic tissue induced by temporary ischemia followed by reperfusion. The activation of astrocytes may partially contribute to the survival and repair of hypoxic tissue following brain ischemia.
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Affiliation(s)
- Yu Qiu
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
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289
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Hahn T, Heinzel S, Plichta MM, Reif A, Lesch KP, Fallgatter AJ. Neurovascular Coupling in the Human Visual Cortex Is Modulated by Cyclooxygenase-1 (COX-1) Gene Variant. Cereb Cortex 2010; 21:1659-66. [DOI: 10.1093/cercor/bhq236] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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290
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Abd-El-Basset EM, Abd-El-Barr MM. Effect of interleukin-1β on the expression of actin isoforms in cultured mouse astroglia. Anat Rec (Hoboken) 2010; 294:16-23. [PMID: 21157913 DOI: 10.1002/ar.21303] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 09/27/2010] [Indexed: 12/20/2022]
Abstract
Cytokines are soluble mediators that are thought to act as communication signals between astroglia and neighboring neural cells. They are both released by, and act on, astroglia. It is hypothesized that it is this effect on astroglia that may be important in widespread phenomena including traumatic brain injury, inflammation, and scar formation. In this article, we examine the effect of mouse recombinant interleukin-1β (IL-1β) on the morphology, organization, and expression of glial fibrillary acidic protein (GFAP) and actin isoforms in cultured mouse astroglia. This study shows that the majority of the astroglia treated with IL-1β acquire long processes. Immunofluorescence staining shows that there are no remarkable changes in the organization of GFAP, F-actin, α-smooth muscle (α-sm) actin, and β-actin isoforms. In fluorescent microplate assay, the short-term treated astroglia (range, 1-2 days) show an increase in the intensity of GFAP and β-actin isoform over the level observed in untreated control, whereas no remarkable changes are observed in the intensity of α-sm actin isoform. In the case of long-term treatment (range, 4-8 days), the intensity of GFAP and α-sm actin isoform progressively decreases below the level of untreated control. In addition, the intensity of β-actin isoform increases above the control level. These results have been confirmed by immunoblotting experiments. The upregulation of β-actin isoform may be important in limiting the noxious effects of an inflammatory reaction. This gives credence to the hypothesis that it might be possible to modulate astroglial effects on neuronal inflammation and scar formation with appropriate therapies.
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Affiliation(s)
- E M Abd-El-Basset
- Department of Anatomy, Faculty of Medicine, Kuwait University, Kuwait.
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291
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Lu Y, Iandiev I, Hollborn M, Körber N, Ulbricht E, Hirrlinger PG, Pannicke T, Wei E, Bringmann A, Wolburg H, Wilhelmsson U, Pekny M, Wiedemann P, Reichenbach A, Käs JA. Reactive glial cells: increased stiffness correlates with increased intermediate filament expression. FASEB J 2010; 25:624-31. [DOI: 10.1096/fj.10-163790] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yun‐Bi Lu
- Division of Soft Matter PhysicsDepartment of PhysicsUniversität LeipzigLeipzigGermany
- Paul Flechsig Institute of Brain ResearchUniversität LeipzigLeipzigGermany
- Department of PharmacologySchool of MedicineZhejiang UniversityHang ZhouChina
| | - Ianors Iandiev
- Department of OphthalmologyUniversität LeipzigLeipzigGermany
| | | | - Nicole Körber
- Paul Flechsig Institute of Brain ResearchUniversität LeipzigLeipzigGermany
- Translational Centre for Regenerative MedicineLeipzigGermany
| | - Elke Ulbricht
- Paul Flechsig Institute of Brain ResearchUniversität LeipzigLeipzigGermany
| | | | - Thomas Pannicke
- Paul Flechsig Institute of Brain ResearchUniversität LeipzigLeipzigGermany
| | - Er‐Qing Wei
- Department of PharmacologySchool of MedicineZhejiang UniversityHang ZhouChina
| | | | | | - Ulrika Wilhelmsson
- Center for Brain Repair and RehabilitationDepartment of Clinical Neuroscience and RehabilitationInstitute of Neuroscience and PhysiologySahlgrenska AcademyUniversity of GothenburgGothenburgSweden
| | - Milos Pekny
- Center for Brain Repair and RehabilitationDepartment of Clinical Neuroscience and RehabilitationInstitute of Neuroscience and PhysiologySahlgrenska AcademyUniversity of GothenburgGothenburgSweden
| | - Peter Wiedemann
- Department of OphthalmologyUniversität LeipzigLeipzigGermany
| | | | - Josef A. Käs
- Division of Soft Matter PhysicsDepartment of PhysicsUniversität LeipzigLeipzigGermany
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292
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Hamby ME, Sofroniew MV. Reactive astrocytes as therapeutic targets for CNS disorders. Neurotherapeutics 2010; 7:494-506. [PMID: 20880511 PMCID: PMC2952540 DOI: 10.1016/j.nurt.2010.07.003] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Revised: 07/19/2010] [Accepted: 07/20/2010] [Indexed: 12/30/2022] Open
Abstract
Reactive astrogliosis has long been recognized as a ubiquitous feature of CNS pathologies. Although its roles in CNS pathology are only beginning to be defined, genetic tools are enabling molecular dissection of the functions and mechanisms of reactive astrogliosis in vivo. It is now clear that reactive astrogliosis is not simply an all-or-nothing phenomenon but, rather, is a finely gradated continuum of molecular, cellular, and functional changes that range from subtle alterations in gene expression to scar formation. These changes can exert both beneficial and detrimental effects in a context-dependent manner determined by specific molecular signaling cascades. Dysfunction of either astrocytes or the process of reactive astrogliosis is emerging as an important potential source of mechanisms that might contribute to, or play primary roles in, a host of CNS disorders via loss of normal or gain of abnormal astrocyte activities. A rapidly growing understanding of the mechanisms underlying astrocyte signaling and reactive astrogliosis has the potential to open doors to identifying many molecules that might serve as novel therapeutic targets for a wide range of neurological disorders. This review considers general principles and examines selected examples regarding the potential of targeting specific molecular aspects of reactive astrogliosis for therapeutic manipulations, including regulation of glutamate, reactive oxygen species, and cytokines.
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Affiliation(s)
- Mary E. Hamby
- grid.19006.3e0000000096326718Department of Neurobiology, David Geffen School of Medicine, University of California, 90095 Los Angeles, California
| | - Michael V. Sofroniew
- grid.19006.3e0000000096326718Department of Neurobiology, David Geffen School of Medicine, University of California, 90095 Los Angeles, California
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293
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Vargas MR, Johnson JA. Astrogliosis in amyotrophic lateral sclerosis: role and therapeutic potential of astrocytes. Neurotherapeutics 2010; 7:471-81. [PMID: 20880509 PMCID: PMC2967019 DOI: 10.1016/j.nurt.2010.05.012] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Revised: 04/29/2010] [Accepted: 05/10/2010] [Indexed: 12/12/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal disorder characterized by the progressive loss of motor neurons. Although the molecular mechanism underlying motor neuron degeneration remains unknown; non-neuronal cells (including astrocytes) shape motor neuron survival in ALS. Astrocytes closely interact with neurons to provide an optimized environment for neuronal function and respond to all forms of injury in a typical manner known as reactive astrogliosis. A strong reactive astrogliosis surrounds degenerating motor neurons in ALS patients and ALS-animal models. Although reactive astrogliosis in ALS is probably both primary and secondary to motor neuron degeneration; astrocytes are not passive observers and they can influence motor neuron fate. Due to the important functions that astrocytes perform in the central nervous system; it is of key importance to understand how these functions are altered when astrocytes become reactive in ALS. Here; we review the current evidences supporting a potential toxic role of astrocytes and their viability as therapeutic targets to alter motor neuron degeneration in ALS.
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Affiliation(s)
- Marcelo R. Vargas
- grid.14003.360000000099041312Division of Pharmaceutical Sciences, University of Wisconsin, 53705 Madison, Wisconsin
| | - Jeffrey A. Johnson
- grid.14003.360000000099041312Division of Pharmaceutical Sciences, University of Wisconsin, 53705 Madison, Wisconsin
- grid.14003.360000000099041312Waisman Center, University of Wisconsin, 53705 Madison, Wisconsin
- grid.14003.360000000099041312Molecular and Environmental Toxicology Center, University of Wisconsin, 53705 Madison, Wisconsin
- grid.14003.360000000099041312Center for Neuroscience, University of Wisconsin, 53705 Madison, Wisconsin
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294
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Kimelberg HK, Nedergaard M. Functions of astrocytes and their potential as therapeutic targets. Neurotherapeutics 2010; 7:338-53. [PMID: 20880499 PMCID: PMC2982258 DOI: 10.1016/j.nurt.2010.07.006] [Citation(s) in RCA: 278] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 07/27/2010] [Indexed: 12/28/2022] Open
Abstract
Astrocytes are often referred to, and historically have been regarded as, support cells of the mammalian CNS. Work over the last decade suggests otherwise-that astrocytes may in fact play a more active role in higher neural processing than previously recognized. Because astrocytes can potentially serve as novel therapeutic targets, it is critical to understand how astrocytes execute their diverse supportive tasks while maintaining neuronal health. To that end, this review focuses on the supportive roles of astrocytes, a line of study relevant to essentially all acute and chronic neurological diseases, and critically re-evaluates our concepts of the functional properties of astrocytes and relates these functions and properties to the intricate morphology of these cells.
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Affiliation(s)
| | - Maiken Nedergaard
- grid.16416.340000000419369174Center for Translational Neuromedicine, Department of Neurosurgery, University of Prochester Medical School, 601 Elmwood Avenue, 114642 Rochester, New York
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295
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Paisansathan C, Xu H, Vetri F, Hernandez M, Pelligrino DA. Interactions between adenosine and K+ channel-related pathways in the coupling of somatosensory activation and pial arteriolar dilation. Am J Physiol Heart Circ Physiol 2010; 299:H2009-17. [PMID: 20889844 DOI: 10.1152/ajpheart.00702.2010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Multiple, perhaps interactive, mechanisms participate in the linkage between increased neural activity and cerebral vasodilation. In the present study, we assessed whether neural activation-related pial arteriolar dilation (PAD) involved interactions among adenosine (Ado) A(2) receptors (A(2)Rs), large-conductance Ca(2+)-operated K(+) (BK(Ca)) channels, and inward rectifier K(+) (K(ir)) channels. In rats with closed cranial windows, we monitored sciatic nerve stimulation (SNS)-induced PAD in the absence or presence of pharmacological blockade of A(2)Rs (ZM-241385), ecto-5'-nucleotidase (α,β-methylene-adenosine diphosphate), BK(Ca) channels (paxilline), and K(ir) channels (BaCl(2)). Individually, these interventions led to 53-66% reductions in SNS-induced PADs. Combined applications of these blockers led to little or no further repression of SNS-induced PADs, suggesting interactions among A(2)Rs and K(+) channels. In the absence of SNS, BaCl(2) blockade of K(ir) channels produced 52-80% reductions in Ado and NS-1619 (BK(Ca) channel activator)-induced PADs. In contrast, paxilline blockade of BK(Ca) channels was without effect on dilations elicited by KCl (K(ir) channel activator) and Ado suffusions, indicating that Ado- and NS-1619-associated PADs involved K(ir) channels. In addition, targeted ablation of the superficial glia limitans was associated with a selective 60-80% loss of NS-1619 responses, suggesting that the BK(Ca) channel participation (and paxilline sensitivity) derived largely from channels within the glia limitans. Additionally, blockade of either PKA or adenylyl cyclase caused markedly attenuated pial arteriolar responses to SNS and, in the absence of SNS, responses to Ado, KCl, and NS-1619. These findings suggested a key, possibly permissive, role for A(2)R-linked cAMP generation and PKA-induced K(+) channel phosphorylation in somatosensory activation-evoked PAD.
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Affiliation(s)
- Chanannait Paisansathan
- Neuroanesthesia Research Laboratory, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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296
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Higashimori H, Blanco VM, Tuniki VR, Falck JR, Filosa JA. Role of epoxyeicosatrienoic acids as autocrine metabolites in glutamate-mediated K+ signaling in perivascular astrocytes. Am J Physiol Cell Physiol 2010; 299:C1068-78. [PMID: 20844244 DOI: 10.1152/ajpcell.00225.2010] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Epoxyeicosatrienoic acids (EETs), synthesized and released by astrocytes in response to glutamate, are known to play a pivotal role in neurovascular coupling. In vascular smooth muscle cells (VSMC), EETs activate large-conductance, Ca(2+)-activated K(+) (BK) channels resulting in hyperpolarization and vasodilation. However, the functional role and mechanism of action for glial-derived EETs are still to be determined. In this study, we evaluated the effect of the synthetic EET analog 11-nonyloxy-undec-8(Z)-enoic acid (NUD-GA) on outward K(+) currents mediated by calcium-activated K(+) channels. Addition of NUD-GA significantly increased intracellular Ca(2+) and outward K(+) currents in perivascular astrocytes. NUD-GA-induced currents were significantly inhibited by BK channel blockers paxilline and tetraethylammonium (TEA) (23.4 ± 2.4%; P < 0.0005). Similarly, NUD-GA-induced currents were also significantly inhibited in the presence of the small-conductance Ca(2+)-activated K(+) channel inhibitor apamin along with a combination of blockers against glutamate receptors (12.8 ± 2.70%; P < 0.05). No changes in outward currents were observed in the presence of the channel blocker for intermediate-conductance K(+) channels TRAM-34. Blockade of the endogenous production of EETs with N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH) significantly blunted (dl)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD)-induced outward K(+) currents (P < 0.05; n = 6). Both NUD-GA and t-ACPD significantly increased BK channel single open probability; the later was blocked following MS-PPOH incubation. Our data supports the idea that EETs are potent K(+) channel modulators in cortical perivascular astrocytes and further suggest that these metabolites may participate in NVC by modulating the levels of K(+) released at the gliovascular space.
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Affiliation(s)
- Haruki Higashimori
- Department of Physiology, Medical College of Georgia, Augusta, Georgia 30912, USA
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297
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Pelligrino DA, Xu HL, Vetri F. Caffeine and the control of cerebral hemodynamics. J Alzheimers Dis 2010; 20 Suppl 1:S51-62. [PMID: 20182032 DOI: 10.3233/jad-2010-091261] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
While the influence of caffeine on the regulation of brain perfusion has been the subject of multiple publications, the mechanisms involved in that regulation remain unclear. To some extent, that uncertainty is a function of a complex interplay of processes arising from multiple targets of caffeine located on a variety of different cells, many of which have influence, either directly or indirectly, on cerebral vascular smooth muscle tone. Adding to that complexity are the target-specific functional changes that may occur when comparing acute and chronic caffeine exposure. In the present review, we discuss some of the mechanisms behind caffeine influences on cerebrovascular function. The major effects of caffeine on the cerebral circulation can largely be ascribed to its inhibitory effects on adenosine receptors. Herein, we focus mostly on the A1, A2A, and A2B subtypes located in cells comprising the neurovascular unit (neurons, astrocytes, vascular smooth muscle); their roles in the coupling of increased neuronal (synaptic) activity to vasodilation; how caffeine, through blockade of these receptors, may interfere with the "neurovascular coupling" process; and receptor-linked changes that may occur in cerebrovascular regulation when comparing acute to chronic caffeine intake.
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Affiliation(s)
- Dale A Pelligrino
- Neuroanesthesia Research Laboratory, University of Illinois at Chicago, Chicago, IL 60612, USA.
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Filosa JA. Vascular tone and neurovascular coupling: considerations toward an improved in vitro model. FRONTIERS IN NEUROENERGETICS 2010; 2:16. [PMID: 20802803 PMCID: PMC2928708 DOI: 10.3389/fnene.2010.00016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 06/28/2010] [Indexed: 11/13/2022]
Abstract
Neurovascular research has made significant strides toward understanding how the brain neurovascular unit accomplishes rapid and spatial increases in blood flow following neuronal activation. Among the experimental models used, the in vitro brain slice preparation provides unique information revealing the potential signals and cellular mechanisms involved in functional hyperemia. The most crucial limitation of this model, however, is the lack of intraluminal pressure and flow in the vessels being studied. Moreover, differences in basal vascular tone have led to varied interpretations regarding the polarity of vascular responses following neuron-to-glial stimulation. Given the complexity of astrocyte-induced neurovascular responses, we propose the use of a modified in vitro brain slice preparation, where intraluminal arteriolar pressure and flow are retained. Throughout this review, we discuss the advantages and disadvantages to be considered when using brain slices for neurovascular studies. Potential ways to overcome the current limitations are proposed.
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Affiliation(s)
- Jessica A. Filosa
- Department of Physiology, Medical College of GeorgiaAugusta, GA, USA
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Buxton RB. Interpreting oxygenation-based neuroimaging signals: the importance and the challenge of understanding brain oxygen metabolism. FRONTIERS IN NEUROENERGETICS 2010; 2:8. [PMID: 20616882 PMCID: PMC2899519 DOI: 10.3389/fnene.2010.00008] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 05/21/2010] [Indexed: 01/09/2023]
Abstract
Functional magnetic resonance imaging is widely used to map patterns of brain activation based on blood oxygenation level dependent (BOLD) signal changes associated with changes in neural activity. However, because oxygenation changes depend on the relative changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO(2)), a quantitative interpretation of BOLD signals, and also other functional neuroimaging signals related to blood or tissue oxygenation, is fundamentally limited until we better understand brain oxygen metabolism and how it is related to blood flow. However, the positive side of the complexity of oxygenation signals is that when combined with dynamic CBF measurements they potentially provide the best tool currently available for investigating the dynamics of CMRO(2). This review focuses on the problem of interpreting oxygenation-based signals, the challenges involved in measuring CMRO(2) in general, and what is needed to put oxygenation-based estimates of CMRO(2) on a firm foundation. The importance of developing a solid theoretical framework is emphasized, both as an essential tool for analyzing oxygenation-based multimodal measurements, and also potentially as a way to better understand the physiological phenomena themselves. The existing data, integrated within a simple theoretical framework of O(2) transport, suggests the hypothesis that an important functional role of the mismatch of CBF and CMRO(2) changes with neural activation is to prevent a fall of tissue pO(2). Future directions for better understanding brain oxygen metabolism are discussed.
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Affiliation(s)
- Richard B Buxton
- Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, USA
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