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Hatakeyama N, Unekawa M, Murata J, Tomita Y, Suzuki N, Nakahara J, Takuwa H, Kanno I, Matsui K, Tanaka KF, Masamoto K. Differential pial and penetrating arterial responses examined by optogenetic activation of astrocytes and neurons. J Cereb Blood Flow Metab 2021; 41:2676-2689. [PMID: 33899558 PMCID: PMC8504944 DOI: 10.1177/0271678x211010355] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A variety of brain cells participates in neurovascular coupling by transmitting and modulating vasoactive signals. The present study aimed to probe cell type-dependent cerebrovascular (i.e., pial and penetrating arterial) responses with optogenetics in the cortex of anesthetized mice. Two lines of the transgenic mice expressing a step function type of light-gated cation channel (channelrhodopsine-2; ChR2) in either cortical neurons (muscarinic acetylcholine receptors) or astrocytes (Mlc1-positive) were used in the experiments. Photo-activation of ChR2-expressing astrocytes resulted in a widespread increase in cerebral blood flow (CBF), extending to the nonstimulated periphery. In contrast, photo-activation of ChR2-expressing neurons led to a relatively localized increase in CBF. The differences in the spatial extent of the CBF responses are potentially explained by differences in the involvement of the vascular compartments. In vivo imaging of the cerebrovascular responses revealed that ChR2-expressing astrocyte activation led to the dilation of both pial and penetrating arteries, whereas ChR2-expressing neuron activation predominantly caused dilation of the penetrating arterioles. Pharmacological studies showed that cell type-specific signaling mechanisms participate in the optogenetically induced cerebrovascular responses. In conclusion, pial and penetrating arterial vasodilation were differentially evoked by ChR2-expressing astrocytes and neurons.
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Affiliation(s)
- Nao Hatakeyama
- Graduate School of Informatics and Engineering, University of Electro-Communications, Tokyo, Japan
| | - Miyuki Unekawa
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Juri Murata
- Graduate School of Informatics and Engineering, University of Electro-Communications, Tokyo, Japan
| | - Yutaka Tomita
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan.,Tomita Hospital, Aichi, Japan
| | - Norihiro Suzuki
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan.,Shonan Keiiku Hospital, Kanagawa, Japan
| | - Jin Nakahara
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Hiroyuki Takuwa
- Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, Chiba, Japan
| | - Iwao Kanno
- Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, Chiba, Japan
| | - Ko Matsui
- Super-Network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Miyagi, Japan
| | - Kenji F Tanaka
- Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan
| | - Kazuto Masamoto
- Graduate School of Informatics and Engineering, University of Electro-Communications, Tokyo, Japan.,Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, Chiba, Japan.,Center for Neuroscience and Biomedical Engineering, University of Electro-Communications, Tokyo, Japan
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Quelhas P, Baltazar G, Cairrao E. The Neurovascular Unit: Focus on the Regulation of Arterial Smooth Muscle Cells. Curr Neurovasc Res 2020; 16:502-515. [PMID: 31738142 DOI: 10.2174/1567202616666191026122642] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 09/01/2019] [Accepted: 09/20/2019] [Indexed: 02/08/2023]
Abstract
The neurovascular unit is a physiological unit present in the brain, which is constituted by elements of the nervous system (neurons and astrocytes) and the vascular system (endothelial and mural cells). This unit is responsible for the homeostasis and regulation of cerebral blood flow. There are two major types of mural cells in the brain, pericytes and smooth muscle cells. At the arterial level, smooth muscle cells are the main components that wrap around the outside of cerebral blood vessels and the major contributors to basal tone maintenance, blood pressure and blood flow distribution. They present several mechanisms by which they regulate both vasodilation and vasoconstriction of cerebral blood vessels and their regulation becomes even more important in situations of injury or pathology. In this review, we discuss the main regulatory mechanisms of brain smooth muscle cells and their contributions to the correct brain homeostasis.
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Affiliation(s)
- Patrícia Quelhas
- CICS-UBI - Centro de Investigacao em Ciencias da Saude, University of Beira Interior, 6200-506 Covilha, Portugal
| | - Graça Baltazar
- CICS-UBI - Centro de Investigacao em Ciencias da Saude, University of Beira Interior, 6200-506 Covilha, Portugal
| | - Elisa Cairrao
- CICS-UBI - Centro de Investigacao em Ciencias da Saude, University of Beira Interior, 6200-506 Covilha, Portugal
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Andjelkovic AV, Stamatovic SM, Phillips CM, Martinez-Revollar G, Keep RF. Modeling blood-brain barrier pathology in cerebrovascular disease in vitro: current and future paradigms. Fluids Barriers CNS 2020; 17:44. [PMID: 32677965 PMCID: PMC7367394 DOI: 10.1186/s12987-020-00202-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 06/15/2020] [Indexed: 12/16/2022] Open
Abstract
The complexity of the blood-brain barrier (BBB) and neurovascular unit (NVU) was and still is a challenge to bridge. A highly selective, restrictive and dynamic barrier, formed at the interface of blood and brain, the BBB is a "gatekeeper" and guardian of brain homeostasis and it also acts as a "sensor" of pathological events in blood and brain. The majority of brain and cerebrovascular pathologies are associated with BBB dysfunction, where changes at the BBB can lead to or support disease development. Thus, an ultimate goal of BBB research is to develop competent and highly translational models to understand mechanisms of BBB/NVU pathology and enable discovery and development of therapeutic strategies to improve vascular health and for the efficient delivery of drugs. This review article focuses on the progress being made to model BBB injury in cerebrovascular diseases in vitro.
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Affiliation(s)
- Anuska V Andjelkovic
- Department of Pathology, University of Michigan Medical School, 7520 MSRB I, 1150 West Medical Center Dr, Ann Arbor, MI, 48109-5602, USA.
| | - Svetlana M Stamatovic
- Department of Pathology, University of Michigan Medical School, 7520 MSRB I, 1150 West Medical Center Dr, Ann Arbor, MI, 48109-5602, USA
| | - Chelsea M Phillips
- Graduate Program in Neuroscience, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Gabriela Martinez-Revollar
- Department of Pathology, University of Michigan Medical School, 7520 MSRB I, 1150 West Medical Center Dr, Ann Arbor, MI, 48109-5602, USA
| | - Richard F Keep
- Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Molecular Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
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Bordes SJ, Gandhi J, Bauer B, Protas M, Solomon N, Bogdan L, Brummund D, Bass B, Clunes M, Murray IVJ. Using lectures to identify student misconceptions: a study on the paradoxical effects of hyperkalemia on vascular smooth muscle. ADVANCES IN PHYSIOLOGY EDUCATION 2020; 44:15-20. [PMID: 31821033 DOI: 10.1152/advan.00030.2019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Medical students have difficulty understanding the mechanisms underlying hyperkalemia-mediated local control of blood flow. Such control mechanisms are crucial in the brain, kidney, and skeletal muscle vasculature. We aimed to identify medical students' misconceptions via assessment of students' in-class knowledge and, subsequently, improve future teaching of this concept. In-class polling was performed with the TurningPoint clicker response system (n = 860) to gauge students' understanding of three physiological concepts related to hyperkalemia: membrane potential (Vm), conductance, and smooth muscle response. Vm includes the concepts of equilibrium potential (Veq) for specific ions, as well as driving force (DF = Vm - Veq). Students understood the concept of DF (~70% answered correctly), suggesting their understanding of Vm. However, students misunderstood that hyperkalemia results in depolarization (~52% answered correctly) and leads to an increase in potassium conductance (~31% answered correctly). Clarification of the type of smooth muscle as vascular increased the percentage of correct responses (~51 to 73%). The data indicate that students lacked knowledge of specific potassium conductance in various muscle types, resulting in divergent responses, such as the canonical depolarization in skeletal muscle versus hyperpolarization in smooth muscle cells during hyperkalemia. Misunderstanding of this crucial concept of conductance is directly related to the students' performance. Furthermore, we connected the paradoxical effect of hyperkalemia to pathological acute and chronic hyperkalemia clinical scenarios.
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Affiliation(s)
- Stephen J Bordes
- Medical Student Research Institute, St. George's University School of Medicine, St. George's, Grenada
| | - Jason Gandhi
- Medical Student Research Institute, St. George's University School of Medicine, St. George's, Grenada
| | - Blake Bauer
- Medical Student Research Institute, St. George's University School of Medicine, St. George's, Grenada
| | - Matthew Protas
- School of Medicine, State University of New York Upstate Medical University, Syracuse, New York
| | - Nadia Solomon
- Medical Student Research Institute, St. George's University School of Medicine, St. George's, Grenada
| | - Lukasz Bogdan
- Medical Student Research Institute, St. George's University School of Medicine, St. George's, Grenada
| | - Dieter Brummund
- Medical Student Research Institute, St. George's University School of Medicine, St. George's, Grenada
| | - Brittany Bass
- Northwell Health, Lenox Hill Hospital, New York, New York
| | - Mark Clunes
- Department of Neuroscience, Physiology and Behavioral Sciences, St. George's University School of Medicine, St. George's, Grenada
| | - Ian V J Murray
- Department of Neuroscience, Physiology and Behavioral Sciences, St. George's University School of Medicine, St. George's, Grenada
- Department of Biology, University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Physiology, Engineering Medicine, Texas A&M University, Houston, Texas
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Dogan MF, Yildiz O, Arslan SO, Ulusoy KG. Potassium channels in vascular smooth muscle: a pathophysiological and pharmacological perspective. Fundam Clin Pharmacol 2019; 33:504-523. [PMID: 30851197 DOI: 10.1111/fcp.12461] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 02/28/2019] [Accepted: 03/07/2019] [Indexed: 12/23/2022]
Abstract
Potassium (K+ ) ion channel activity is an important determinant of vascular tone by regulating cell membrane potential (MP). Activation of K+ channels leads to membrane hyperpolarization and subsequently vasodilatation, while inhibition of the channels causes membrane depolarization and then vasoconstriction. So far five distinct types of K+ channels have been identified in vascular smooth muscle cells (VSMCs): Ca+2 -activated K+ channels (BKC a ), voltage-dependent K+ channels (KV ), ATP-sensitive K+ channels (KATP ), inward rectifier K+ channels (Kir ), and tandem two-pore K+ channels (K2 P). The activity and expression of vascular K+ channels are changed during major vascular diseases such as hypertension, pulmonary hypertension, hypercholesterolemia, atherosclerosis, and diabetes mellitus. The defective function of K+ channels is commonly associated with impaired vascular responses and is likely to become as a result of changes in K+ channels during vascular diseases. Increased K+ channel function and expression may also help to compensate for increased abnormal vascular tone. There are many pharmacological and genotypic studies which were carried out on the subtypes of K+ channels expressed in variable amounts in different vascular beds. Modulation of K+ channel activity by molecular approaches and selective drug development may be a novel treatment modality for vascular dysfunction in the future. This review presents the basic properties, physiological functions, pathophysiological, and pharmacological roles of the five major classes of K+ channels that have been determined in VSMCs.
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Affiliation(s)
- Muhammed Fatih Dogan
- Department of Pharmacology, Ankara Yildirim Beyazit University, Bilkent, Ankara, 06010, Turkey
| | - Oguzhan Yildiz
- Department of Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, 06170, Turkey
| | - Seyfullah Oktay Arslan
- Department of Pharmacology, Ankara Yildirim Beyazit University, Bilkent, Ankara, 06010, Turkey
| | - Kemal Gokhan Ulusoy
- Department of Pharmacology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, 06170, Turkey
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Nakamura M, Nagamine T. Serum electrolyte levels may be associated with prefrontal hemodynamic responses in near infrared spectroscopy. JOURNAL OF NEAR INFRARED SPECTROSCOPY 2018; 26:229-234. [DOI: 10.1177/0967033518791341] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Neuronal activity is tightly coordinated with blood flow to ensure proper brain function. This is achieved by neurovascular coupling. Although this mechanism is maintained by numerous mediators such as nitric oxide, ion channels, and astrocytes, its signaling process is much more complex. Frontal-temporal brain activity as measured by near infrared (NIR) spectroscopy has been suggested to be decreased or disturbed in many psychiatric disorders. To investigate the relationship between serum electrolyte levels and prefrontal hemodynamic responses, we evaluated psychiatric patients who underwent NIR spectroscopy with a 22-channel topography system and measurement of serum electrolyte levels. Changes in the concentration of oxygenated hemoglobin were evaluated during a verbal fluency test. The data were analyzed to see any significant correlation between NIR spectroscopy indices (integral value: size of an area during activation, centroid value: centroid time of an area throughout the task, and initial value: axis assessed by an initial change) and serum electrolyte levels (sodium, potassium, and chloride) by gender and cortex region. The study population consisted of 102 males (mean age, 42.4 years) and 133 females (mean age, 47.2 years). Sodium levels were significantly positively correlated with integral values at temporal regions in female subjects, while potassium levels were significantly negatively correlated with initial values at frontal regions in male subjects. However, chloride levels showed no correlations. In conclusion, higher serum sodium levels increase and higher serum potassium levels decrease regional cerebral blood flow with gender variances in psychiatry. The effect of extracellular electrolyte concentrations on hemodynamic responses remains unverified. However, our findings suggest that serum electrolytes levels may be involved in vascular smooth muscle contractility via Na+-K+-ATPase pumps that mediate neurovascular coupling.
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Affiliation(s)
- Masaru Nakamura
- Department of Psychiatric Internal Medicine, Kosekai-Kusatsu Hospital, Hiroshima, Japan
| | - Takahiko Nagamine
- Department of Psychiatric Internal Medicine, Sunlight Brain Research Center, Yamaguchi, Japan
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Hotta H. Neurogenic control of parenchymal arterioles in the cerebral cortex. PROGRESS IN BRAIN RESEARCH 2016; 225:3-39. [DOI: 10.1016/bs.pbr.2016.03.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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