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Feng L, Gao L. The role of neurovascular coupling dysfunction in cognitive decline of diabetes patients. Front Neurosci 2024; 18:1375908. [PMID: 38576869 PMCID: PMC10991808 DOI: 10.3389/fnins.2024.1375908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 03/05/2024] [Indexed: 04/06/2024] Open
Abstract
Neurovascular coupling (NVC) is an important mechanism to ensure adequate blood supply to active neurons in the brain. NVC damage can lead to chronic impairment of neuronal function. Diabetes is characterized by high blood sugar and is considered an important risk factor for cognitive impairment. In this review, we provide fMRI evidence of NVC damage in diabetic patients with cognitive decline. Combined with the exploration of the major mechanisms and signaling pathways of NVC, we discuss the effects of chronic hyperglycemia on the cellular structure of NVC signaling, including key receptors, ion channels, and intercellular connections. Studying these diabetes-related changes in cell structure will help us understand the underlying causes behind diabetes-induced NVC damage and early cognitive decline, ultimately helping to identify the most effective drug targets for treatment.
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Affiliation(s)
| | - Ling Gao
- Department of Endocrinology, Renmin Hospital of Wuhan University, Wuhan, China
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2
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Daniel JM, Lindsey SH, Mostany R, Schrader LA, Zsombok A. Cardiometabolic health, menopausal estrogen therapy and the brain: How effects of estrogens diverge in healthy and unhealthy preclinical models of aging. Front Neuroendocrinol 2023; 70:101068. [PMID: 37061205 PMCID: PMC10725785 DOI: 10.1016/j.yfrne.2023.101068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 03/23/2023] [Accepted: 04/10/2023] [Indexed: 04/17/2023]
Abstract
Research in preclinical models indicates that estrogens are neuroprotective and positively impact cognitive aging. However, clinical data are equivocal as to the benefits of menopausal estrogen therapy to the brain and cognition. Pre-existing cardiometabolic disease may modulate mechanisms by which estrogens act, potentially reducing or reversing protections they provide against cognitive decline. In the current review we propose mechanisms by which cardiometabolic disease may alter estrogen effects, including both alterations in actions directly on brain memory systems and actions on cardiometabolic systems, which in turn impact brain memory systems. Consideration of mechanisms by which estrogen administration can exert differential effects dependent upon health phenotype is consistent with the move towards precision or personalized medicine, which aims to determine which treatment interventions will work for which individuals. Understanding effects of estrogens in both healthy and unhealthy models of aging is critical to optimizing the translational link between preclinical and clinical research.
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Affiliation(s)
- Jill M Daniel
- Department of Psychology and Brain Institute, Tulane University, New Orleans, LA, United States.
| | - Sarah H Lindsey
- Department of Pharmacology and Brain Institute, Tulane University, New Orleans, LA, United States
| | - Ricardo Mostany
- Department of Pharmacology and Brain Institute, Tulane University, New Orleans, LA, United States
| | - Laura A Schrader
- Department of Cell & Molecular Biology and Brain Institute, Tulane University, New Orleans, LA, United States
| | - Andrea Zsombok
- Department of Physiology and Brain Institute, Tulane University, New Orleans, LA, United States
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3
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Varga BT, Gáspár A, Ernyey AJ, Hutka B, Tajti BT, Zádori ZS, Gyertyán I. Introduction of a pharmacological neurovascular uncoupling model in rats based on results of mice. Physiol Int 2022. [PMID: 36057105 DOI: 10.1556/2060.2022.00226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 05/02/2022] [Accepted: 05/19/2022] [Indexed: 02/18/2024]
Abstract
Our aim was to establish a pharmacologically induced neurovascular uncoupling (NVU) method in rats as a model of human cognitive decline. Pharmacologically induced NVU with subsequent neurological and cognitive defects was described in mice, but not in rats so far. We used 32 male Hannover Wistar rats. NVU was induced by intraperitoneal administration of a pharmacological "cocktail" consisting of N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MSPPOH, a specific inhibitor of epoxyeicosatrienoic acid-producing epoxidases, 5 mg kg-1), L-NG-nitroarginine methyl ester (L-NAME, a nitric oxide synthase inhibitor, 10 mg kg-1) and indomethacin (a nonselective inhibitor of cyclooxygenases, 1 mg kg-1) and injected twice daily for 8 consecutive days. Cognitive performance was tested in the Morris water-maze and fear-conditioning assays. We also monitored blood pressure. In a terminal operation a laser Doppler probe was used to detect changes in blood-flow (CBF) in the barrel cortex while the contralateral whisker pad was stimulated. Brain and small intestine tissue samples were collected post mortem and examined for prostaglandin E2 (PGE2) level. Animals treated with the "cocktail" showed no impairment in their performance in any of the cognitive tasks. They had higher blood pressure and showed cca. 50% decrease in CBF. Intestinal bleeding and ulcers were found in some animals with significantly decreased levels of PGE2 in the brain and small intestine. Although we could evoke NVU by the applied mixture of pharmacons, it also induced adverse side effects such as hypertension and intestinal malformations while the treatment did not cause cognitive impairment. Thus, further refinements are still required for the development of an applicable model.
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Affiliation(s)
- Bence Tamás Varga
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Attila Gáspár
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Aliz Judit Ernyey
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Barbara Hutka
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Brigitta Tekla Tajti
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Zoltán Sándor Zádori
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - István Gyertyán
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
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Barloese MCJ, Bauer C, Petersen ET, Hansen CS, Madsbad S, Siebner HR. Neurovascular Coupling in Type 2 Diabetes With Cognitive Decline. A Narrative Review of Neuroimaging Findings and Their Pathophysiological Implications. Front Endocrinol (Lausanne) 2022; 13:874007. [PMID: 35860697 PMCID: PMC9289474 DOI: 10.3389/fendo.2022.874007] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 05/17/2022] [Indexed: 01/21/2023] Open
Abstract
Type 2 diabetes causes substantial long-term damage in several organs including the brain. Cognitive decline is receiving increased attention as diabetes has been established as an independent risk factor along with the identification of several other pathophysiological mechanisms. Early detection of detrimental changes in cerebral blood flow regulation may represent a useful clinical marker for development of cognitive decline for at-risk persons. Technically, reliable evaluation of neurovascular coupling is possible with several caveats but needs further development before it is clinically convenient. Different modalities including ultrasound, positron emission tomography and magnetic resonance are used preclinically to shed light on the many influences on vascular supply to the brain. In this narrative review, we focus on the complex link between type 2 diabetes, cognition, and neurovascular coupling and discuss how the disease-related pathology changes neurovascular coupling in the brain from the organ to the cellular level. Different modalities and their respective pitfalls are covered, and future directions suggested.
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Affiliation(s)
- Mads C. J. Barloese
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
- Department of Clinical Physiology and Nuclear Imaging, Center for Functional and Diagnostic Imaging, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
| | - Christian Bauer
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
- Radiography, Department of Technology, University College Copenhagen, Copenhagen, Denmark
| | - Esben Thade Petersen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
- Center for Magnetic Resonance, Department of Electrical Engineering, Technical University of Denmark, Lyngby, Denmark
| | | | - Sten Madsbad
- Department of Endocrinology, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hartwig Roman Siebner
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Neurology, Copenhagen University Hospital - Bispebjerg and Fredriksberg, Copenhagen, Denmark
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5
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Lacalle-Aurioles M, Trigiani LJ, Bourourou M, Lecrux C, Hamel E. Alzheimer's disease and cerebrovascular pathology alter brain endothelial inward rectifier potassium (K IR 2.1) channels. Br J Pharmacol 2021; 179:2259-2274. [PMID: 34820829 PMCID: PMC9304142 DOI: 10.1111/bph.15751] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 11/03/2021] [Accepted: 11/08/2021] [Indexed: 11/27/2022] Open
Abstract
Background and Purpose Inward rectifier potassium (KIR) channels are key effectors of vasodilatation in neurovascular coupling (NVC). KIR channels expressed in cerebral endothelial cells (ECs) have been confirmed as essential modulators of NVC. Alzheimer's disease (AD) and cerebrovascular disease (CVD) impact on EC‐KIR channel function, but whether oxidative stress or inflammation explains this impairment remains elusive. Experimental Approach We evaluated KIR channel function in intact and EC‐denuded pial arteries of wild‐type (WT) and transgenic mice overexpressing a mutated form of the human amyloid precursor protein (APP mice, recapitulating amyloid β‐induced oxidative stress seen in AD) or a constitutively active form of TGF‐β1 (TGF mice, recapitulating inflammation seen in cerebrovascular pathology). The benefits of antioxidant (catalase) or anti‐inflammatory (indomethacin) drugs also were investigated. Vascular and neuronal components of NVC were assessed in vivo. Key Results Our findings show that (i) KIR channel‐mediated maximal vasodilatation in APP and TGF mice reaches only 37% and 10%, respectively, of the response seen in WT mice; (ii) KIR channel dysfunction results from KIR2.1 subunit impairment; (iii) about 50% of K+‐induced artery dilatation is mediated by EC‐KIR channels; (iv) oxidative stress and inflammation impair KIR channel function, which can be restored by antioxidant and anti‐inflammatory drugs; and (v) inflammation induces KIR2.1 overexpression and impairs NVC in TGF mice. Conclusion and Implications Therapies targeting both oxidative stress and inflammation are necessary for full recovery of KIR2.1 channel function in cerebrovascular pathology caused by AD and CVD.
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Affiliation(s)
- María Lacalle-Aurioles
- Laboratory of Cerebrovascular Research, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
| | - Lianne J Trigiani
- Laboratory of Cerebrovascular Research, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
| | - Miled Bourourou
- Laboratory of Cerebrovascular Research, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
| | - Clotilde Lecrux
- Laboratory of Cerebrovascular Research, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
| | - Edith Hamel
- Laboratory of Cerebrovascular Research, Montreal Neurological Institute, McGill University, Montréal, QC, Canada
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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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7
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Sharma S, Brown CE. Microvascular basis of cognitive impairment in type 1 diabetes. Pharmacol Ther 2021; 229:107929. [PMID: 34171341 DOI: 10.1016/j.pharmthera.2021.107929] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/23/2021] [Accepted: 05/19/2021] [Indexed: 02/07/2023]
Abstract
The complex computations of the brain require a constant supply of blood flow to meet its immense metabolic needs. Perturbations in blood supply, even in the smallest vascular networks, can have a profound effect on neuronal function and cognition. Type 1 diabetes is a prevalent and insidious metabolic disorder that progressively and heterogeneously disrupts vascular signalling and function in the brain. As a result, it is associated with an array of adverse vascular changes such as impaired regulation of vascular tone, pathological neovascularization and vasoregression, capillary plugging and blood brain barrier disruption. In this review, we highlight the link between microvascular dysfunction and cognitive impairment that is commonly associated with type 1 diabetes, with the aim of synthesizing current knowledge in this field.
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Affiliation(s)
- Sorabh Sharma
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
| | - Craig E Brown
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada; Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada.
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8
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Hariharan A, Weir N, Robertson C, He L, Betsholtz C, Longden TA. The Ion Channel and GPCR Toolkit of Brain Capillary Pericytes. Front Cell Neurosci 2020; 14:601324. [PMID: 33390906 PMCID: PMC7775489 DOI: 10.3389/fncel.2020.601324] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/13/2020] [Indexed: 12/14/2022] Open
Abstract
Brain pericytes reside on the abluminal surface of capillaries, and their processes cover ~90% of the length of the capillary bed. These cells were first described almost 150 years ago (Eberth, 1871; Rouget, 1873) and have been the subject of intense experimental scrutiny in recent years, but their physiological roles remain uncertain and little is known of the complement of signaling elements that they employ to carry out their functions. In this review, we synthesize functional data with single-cell RNAseq screens to explore the ion channel and G protein-coupled receptor (GPCR) toolkit of mesh and thin-strand pericytes of the brain, with the aim of providing a framework for deeper explorations of the molecular mechanisms that govern pericyte physiology. We argue that their complement of channels and receptors ideally positions capillary pericytes to play a central role in adapting blood flow to meet the challenge of satisfying neuronal energy requirements from deep within the capillary bed, by enabling dynamic regulation of their membrane potential to influence the electrical output of the cell. In particular, we outline how genetic and functional evidence suggest an important role for Gs-coupled GPCRs and ATP-sensitive potassium (KATP) channels in this context. We put forth a predictive model for long-range hyperpolarizing electrical signaling from pericytes to upstream arterioles, and detail the TRP and Ca2+ channels and Gq, Gi/o, and G12/13 signaling processes that counterbalance this. We underscore critical questions that need to be addressed to further advance our understanding of the signaling topology of capillary pericytes, and how this contributes to their physiological roles and their dysfunction in disease.
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Affiliation(s)
- Ashwini Hariharan
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Nick Weir
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Colin Robertson
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Liqun He
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Christer Betsholtz
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.,Department of Medicine Huddinge (MedH), Karolinska Institutet & Integrated Cardio Metabolic Centre, Huddinge, Sweden
| | - Thomas A Longden
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
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Zhang YS, Mucollari I, Kwan CC, Dingillo G, Amar J, Schwartz GW, Fawzi AA. Reversed Neurovascular Coupling on Optical Coherence Tomography Angiography Is the Earliest Detectable Abnormality before Clinical Diabetic Retinopathy. J Clin Med 2020; 9:jcm9113523. [PMID: 33142724 PMCID: PMC7692675 DOI: 10.3390/jcm9113523] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Revised: 10/21/2020] [Accepted: 10/27/2020] [Indexed: 12/20/2022] Open
Abstract
Diabetic retinopathy (DR) has traditionally been viewed as either a microvasculopathy or a neuropathy, though neurovascular coupling deficits have also been reported and could potentially be the earliest derangement in DR. To better understand neurovascular coupling in the diabetic retina, we investigated retinal hemodynamics by optical coherence tomography angiography (OCTA) in individuals with diabetes mellitus (DM) but without DR (DM no DR) and mild non-proliferative DR (mild NPDR) compared to healthy eyes. Using an experimental design to monitor the capillary responses during transition from dark adaptation to light, we examined 19 healthy, 14 DM no DR and 11 mild NPDR individuals. We found that the only structural vascular abnormality in the DM no DR group was increased superficial capillary plexus (SCP) vessel density (VD) compared to healthy eyes, while mild NPDR eyes showed significant vessel loss in the SCP at baseline. There was no significant difference in inner retinal thickness between the groups. During dark adaptation, the deep capillary plexus (DCP) VD was lower in mild NPDR individuals compared to the other two groups, which may leave the photoreceptors more susceptible to ischemia in the dark. When transitioning from dark to ambient light, both diabetic groups showed a qualitative reversal of VD trends in the SCP and middle capillary plexus (MCP), with significantly decreased SCP at 5 min and increased MCP VD at 50 s compared to healthy eyes, which may impede metabolic supply to the inner retina during light adaptation. Mild NPDR eyes also demonstrated DCP dilation at 50 s and 5 min and decreased adjusted flow index at 5 min in light. Our results show altered neurovascular responses in all three macular vascular plexuses in diabetic subjects in the absence of structural neuronal changes on high resolution imaging, suggesting that neurovascular uncoupling may be a key mechanism in the early pathogenesis of DR, well before the clinical appearance of vascular or neuronal loss.
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Affiliation(s)
- Yi Stephanie Zhang
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (Y.S.Z.); (I.M.); (C.C.K.); (G.D.); (J.A.); (G.W.S.)
| | - Ilda Mucollari
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (Y.S.Z.); (I.M.); (C.C.K.); (G.D.); (J.A.); (G.W.S.)
| | - Changyow C. Kwan
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (Y.S.Z.); (I.M.); (C.C.K.); (G.D.); (J.A.); (G.W.S.)
| | - Gianna Dingillo
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (Y.S.Z.); (I.M.); (C.C.K.); (G.D.); (J.A.); (G.W.S.)
| | - Jaspreet Amar
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (Y.S.Z.); (I.M.); (C.C.K.); (G.D.); (J.A.); (G.W.S.)
| | - Gregory W. Schwartz
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (Y.S.Z.); (I.M.); (C.C.K.); (G.D.); (J.A.); (G.W.S.)
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Amani A. Fawzi
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (Y.S.Z.); (I.M.); (C.C.K.); (G.D.); (J.A.); (G.W.S.)
- Correspondence:
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10
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Abstract
Blood flow in the retina increases in response to light-evoked neuronal activity, ensuring that retinal neurons receive an adequate supply of oxygen and nutrients as metabolic demands vary. This response, termed "functional hyperemia," is disrupted in diabetic retinopathy. The reduction in functional hyperemia may result in retinal hypoxia and contribute to the development of retinopathy. This review will discuss the neurovascular coupling signaling mechanisms that generate the functional hyperemia response in the retina, the changes to neurovascular coupling that occur in diabetic retinopathy, possible treatments for restoring functional hyperemia and retinal oxygen levels, and changes to functional hyperemia that occur in the diabetic brain.
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11
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Samora M, Vianna LC, Carmo JC, Macedo V, Dawes M, Phillips AA, Paton JFR, Fisher JP. Neurovascular coupling is not influenced by lower body negative pressure in humans. Am J Physiol Heart Circ Physiol 2020; 319:H22-H31. [PMID: 32442032 DOI: 10.1152/ajpheart.00076.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cerebral blood flow is tightly coupled with local neuronal activation and metabolism, i.e., neurovascular coupling (NVC). Studies suggest a role of sympathetic nervous system in the regulation of cerebral blood flow. However, this is controversial, and the sympathetic regulation of NVC in humans remains unclear. Since impaired NVC has been identified in several chronic diseases associated with a heightened sympathetic activity, we aimed to determine whether reflex-mediated sympathetic activation via lower body negative pressure (LBNP) attenuates NVC in humans. NVC was assessed using a visual stimulation protocol (5 cycles of 30 s eyes closed and 30 s of reading) in 11 healthy participants (aged 24 ± 3 yr). NVC assessments were made under control conditions and during LBNP at -20 and -40 mmHg. Posterior (PCA) and middle (MCA) cerebral artery mean blood velocity (Vmean) and vertebral artery blood flow (VAflow) were simultaneously determined with cardiorespiratory variables. Under control conditions, the visual stimulation evoked a robust increase in PCAVmean (∆18.0 ± 4.5%), a moderate rise in VAflow (∆9.6 ± 4.3%), and a modest increase in MCAVmean (∆3.0 ± 1.9%). The magnitude of NVC response was not affected by mild-to-moderate LBNP (all P > 0.05 for repeated-measures ANOVA). Given the small change that occurred in partial pressure of end-tidal CO2 during LBNP, this hypocapnia condition was matched via voluntary hyperventilation in absence of LBNP in a subgroup of participants (n = 8). The mild hypocapnia during LBNP did not exert a confounding influence on the NVC response. These findings indicate that the NVC is not influenced by LBNP or mild hypocapnia in humans.NEW & NOTEWORTHY Visual stimulation evoked a robust increase in posterior cerebral artery velocity and a modest increase in vertebral artery blood flow, i.e., neurovascular coupling (NVC), which was unaffected by lower body negative pressure (LBNP) in humans. In addition, although LBNP induced a mild hypocapnia, this degree of hypocapnia in the absence of LBNP failed to modify the NVC response.
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Affiliation(s)
- Milena Samora
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Lauro C Vianna
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Jake C Carmo
- Biomechanics and Biological Signal Processing Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Victor Macedo
- Biomechanics and Biological Signal Processing Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Matthew Dawes
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Aaron A Phillips
- Departments of Physiology, Pharmacology, and Clinical Neurosciences, Libin Cardiovascular Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - James P Fisher
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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12
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Zhu YR, Jiang XX, Ye P, Wang ZM, Zheng Y, Liu Z, Chen SL, Zhang DM. Knockout of AKAP150 improves impaired BK channel-mediated vascular dysfunction through the Akt/GSK3β signalling pathway in diabetes mellitus. J Cell Mol Med 2020; 24:4716-4725. [PMID: 32163656 PMCID: PMC7176888 DOI: 10.1111/jcmm.15143] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 02/05/2020] [Accepted: 02/19/2020] [Indexed: 12/15/2022] Open
Abstract
Vascular dysfunction resulting from diabetes is an important factor in arteriosclerosis. Previous studies have shown that during hyperglycaemia and diabetes, AKAP150 promotes vascular tone enhancement by intensifying the remodelling of the BK channel. However, the interaction between AKAP150 and the BK channel remains open to discussion. In this study, we investigated the regulation of impaired BK channel‐mediated vascular dysfunction in diabetes mellitus. Using AKAP150 null mice (AKAP150−/−) and wild‐type (WT) control mice (C57BL/6J), diabetes was induced by intraperitoneal injection of streptozotocin. We found that knockout of AKAP150 reversed vascular remodelling and fibrosis in mice with diabetes and in AKAP150−/− diabetic mice. Impaired Akt/GSK3β signalling contributed to decreased BK‐β1 expression in aortas from diabetic mice, and the silencing of AKAP150 increased Akt phosphorylation and BK‐β1 expression in MOVAS cells treated with HG medium. The inhibition of Akt activity caused a decrease in BK‐β1 expression, and treatment with AKAP150 siRNA suppressed GSK3β expression in the nuclei of MOVAS cells treated with HG. Knockout of AKAP150 reverses impaired BK channel‐mediated vascular dysfunction through the Akt/GSK3β signalling pathway in diabetes mellitus.
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Affiliation(s)
- Yan-Rong Zhu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Xiao-Xin Jiang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Peng Ye
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Zhi-Mei Wang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Yaguo Zheng
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Zhizhong Liu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Shao-Liang Chen
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Dai-Min Zhang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
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13
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Chhabria K, Plant K, Bandmann O, Wilkinson RN, Martin C, Kugler E, Armitage PA, Santoscoy PL, Cunliffe VT, Huisken J, McGown A, Ramesh T, Chico TJ, Howarth C. The effect of hyperglycemia on neurovascular coupling and cerebrovascular patterning in zebrafish. J Cereb Blood Flow Metab 2020; 40:298-313. [PMID: 30398083 PMCID: PMC6985997 DOI: 10.1177/0271678x18810615] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Neurovascular coupling (through which local cerebral blood flow changes in response to neural activation are mediated) is impaired in many diseases including diabetes. Current preclinical rodent models of neurovascular coupling rely on invasive surgery and instrumentation, but transgenic zebrafish coupled with advances in imaging techniques allow non-invasive quantification of cerebrovascular anatomy, neural activation, and cerebral vessel haemodynamics. We therefore established a novel non-invasive, non-anaesthetised zebrafish larval model of neurovascular coupling, in which visual stimulus evokes neuronal activation in the optic tectum that is associated with a specific increase in red blood cell speed in tectal blood vessels. We applied this model to the examination of the effect of glucose exposure on cerebrovascular patterning and neurovascular coupling. We found that chronic exposure of zebrafish to glucose impaired tectal blood vessel patterning and neurovascular coupling. The nitric oxide donor sodium nitroprusside rescued all these adverse effects of glucose exposure on cerebrovascular patterning and function. Our results establish the first non-mammalian model of neurovascular coupling, offering the potential to perform more rapid genetic modifications and high-throughput screening than is currently possible using rodents. Furthermore, using this zebrafish model, we reveal a potential strategy to ameliorate the effects of hyperglycemia on cerebrovascular function.
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Affiliation(s)
- Karishma Chhabria
- Neuroimaging in Cardiovascular Disease (NICAD) Network, University of Sheffield, Sheffield, UK.,Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Medical School, Sheffield, UK.,The Bateson Centre, University of Sheffield, Sheffield, UK
| | - Karen Plant
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Medical School, Sheffield, UK.,The Bateson Centre, University of Sheffield, Sheffield, UK
| | - Oliver Bandmann
- The Bateson Centre, University of Sheffield, Sheffield, UK.,Department of Neuroscience, University of Sheffield Medical School, Sheffield, UK
| | - Robert N Wilkinson
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Medical School, Sheffield, UK.,The Bateson Centre, University of Sheffield, Sheffield, UK
| | - Chris Martin
- Neuroimaging in Cardiovascular Disease (NICAD) Network, University of Sheffield, Sheffield, UK.,Department of Psychology, University of Sheffield, Sheffield, UK
| | - Elisabeth Kugler
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Medical School, Sheffield, UK.,The Bateson Centre, University of Sheffield, Sheffield, UK
| | - Paul A Armitage
- Neuroimaging in Cardiovascular Disease (NICAD) Network, University of Sheffield, Sheffield, UK.,Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Medical School, Sheffield, UK
| | - Paola Lm Santoscoy
- The Bateson Centre, University of Sheffield, Sheffield, UK.,Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Vincent T Cunliffe
- The Bateson Centre, University of Sheffield, Sheffield, UK.,Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Jan Huisken
- Morgridge Institute for Research, Madison, WI, USA
| | - Alexander McGown
- The Bateson Centre, University of Sheffield, Sheffield, UK.,Department of Neuroscience, University of Sheffield Medical School, Sheffield, UK
| | - Tennore Ramesh
- The Bateson Centre, University of Sheffield, Sheffield, UK.,Department of Neuroscience, University of Sheffield Medical School, Sheffield, UK
| | - Tim Ja Chico
- Neuroimaging in Cardiovascular Disease (NICAD) Network, University of Sheffield, Sheffield, UK.,Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield Medical School, Sheffield, UK.,The Bateson Centre, University of Sheffield, Sheffield, UK
| | - Clare Howarth
- Neuroimaging in Cardiovascular Disease (NICAD) Network, University of Sheffield, Sheffield, UK.,Department of Psychology, University of Sheffield, Sheffield, UK
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14
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Disturbed neurovascular coupling in type 2 diabetes mellitus patients: Evidence from a comprehensive fMRI analysis. NEUROIMAGE-CLINICAL 2019; 22:101802. [PMID: 30991623 PMCID: PMC6447740 DOI: 10.1016/j.nicl.2019.101802] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 03/12/2019] [Accepted: 03/26/2019] [Indexed: 02/08/2023]
Abstract
Background Previous studies presumed that the disturbed neurovascular coupling to be a critical risk factor of cognitive impairments in type 2 diabetes mellitus (T2DM), but distinct clinical manifestations were lacked. Consequently, we decided to investigate the neurovascular coupling in T2DM patients by exploring the MRI relationship between neuronal activity and the corresponding cerebral blood perfusion. Methods Degree centrality (DC) map and amplitude of low-frequency fluctuation (ALFF) map were used to represent neuronal activity. Cerebral blood flow (CBF) map was used to represent cerebral blood perfusion. Correlation coefficients were calculated to reflect the relationship between neuronal activity and cerebral blood perfusion. Results At the whole gray matter level, the manifestation of neurovascular coupling was investigated by using 4 neurovascular biomarkers. We compared these biomarkers and found no significant changes. However, at the brain region level, neurovascular biomarkers in T2DM patients were significantly decreased in 10 brain regions. ALFF-CBF in left hippocampus and fractional ALFF-CBF in left amygdala were positively associated with the executive function, while ALFF-CBF in right fusiform gyrus was negatively related to the executive function. The disease severity was negatively related to the memory and executive function. The longer duration of T2DM was related to the milder depression, which suggests T2DM-related depression may not be a physiological condition but be a psychological condition. Conclusion Correlations between neuronal activity and cerebral perfusion maps may be a method for detecting neurovascular coupling abnormalities, which could be used for diagnosis in the future. Trial registry number: This study has been registered in ClinicalTrials.gov (NCT02420470) on April 2, 2015 and published on July 29, 2015. Multi-modal MRI is a method to reflect neurovascular coupling condition. Neurovascular coupling dysfunction was found in diabetics. The memory, executive function and emotion were disrupted in diabetics. The limbic system, basal ganglia, and prefrontal lobe was damaged in diabetics.
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15
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Hendrikx D, Smits A, Lavanga M, De Wel O, Thewissen L, Jansen K, Caicedo A, Van Huffel S, Naulaers G. Measurement of Neurovascular Coupling in Neonates. Front Physiol 2019; 10:65. [PMID: 30833901 PMCID: PMC6387909 DOI: 10.3389/fphys.2019.00065] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 01/21/2019] [Indexed: 01/01/2023] Open
Abstract
Neurovascular coupling refers to the mechanism that links the transient neural activity to the subsequent change in cerebral blood flow, which is regulated by both chemical signals and mechanical effects. Recent studies suggest that neurovascular coupling in neonates and preterm born infants is different compared to adults. The hemodynamic response after a stimulus is later and less pronounced and the stimulus might even result in a negative (hypoxic) signal. In addition, studies both in animals and neonates confirm the presence of a short hypoxic period after a stimulus in preterm infants. In clinical practice, different methodologies exist to study neurovascular coupling. The combination of functional magnetic resonance imaging or functional near-infrared spectroscopy (brain hemodynamics) with EEG (brain function) is most commonly used in neonates. Especially near-infrared spectroscopy is of interest, since it is a non-invasive method that can be integrated easily in clinical care and is able to provide results concerning longer periods of time. Therefore, near-infrared spectroscopy can be used to develop a continuous non-invasive measurement system, that could be used to study neonates in different clinical settings, or neonates with different pathologies. The main challenge for the development of a continuous marker for neurovascular coupling is how the coupling between the signals can be described. In practice, a wide range of signal interaction measures exist. Moreover, biomedical signals often operate on different time scales. In a more general setting, other variables also have to be taken into account, such as oxygen saturation, carbon dioxide and blood pressure in order to describe neurovascular coupling in a concise manner. Recently, new mathematical techniques were developed to give an answer to these questions. This review discusses these recent developments.
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Affiliation(s)
- Dries Hendrikx
- Department of Electrical Engineering, KU Leuven, Leuven, Belgium
- imec, Leuven, Belgium
| | - Anne Smits
- Department of Development and Regeneration, KU Leuven, Leuven, Belgium
- Neonatal Intensive Care Unit, University Hospitals Leuven, Leuven, Belgium
| | - Mario Lavanga
- Department of Electrical Engineering, KU Leuven, Leuven, Belgium
- imec, Leuven, Belgium
| | - Ofelie De Wel
- Department of Electrical Engineering, KU Leuven, Leuven, Belgium
- imec, Leuven, Belgium
| | - Liesbeth Thewissen
- Department of Development and Regeneration, KU Leuven, Leuven, Belgium
- Neonatal Intensive Care Unit, University Hospitals Leuven, Leuven, Belgium
| | - Katrien Jansen
- Department of Development and Regeneration, KU Leuven, Leuven, Belgium
- Neonatal Intensive Care Unit, University Hospitals Leuven, Leuven, Belgium
- Child Neurology, University Hospitals Leuven, Leuven, Belgium
| | - Alexander Caicedo
- Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Bogotá, Colombia
| | - Sabine Van Huffel
- Department of Electrical Engineering, KU Leuven, Leuven, Belgium
- imec, Leuven, Belgium
| | - Gunnar Naulaers
- Department of Development and Regeneration, KU Leuven, Leuven, Belgium
- Neonatal Intensive Care Unit, University Hospitals Leuven, Leuven, Belgium
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16
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Li W, Abdul Y, Ward R, Ergul A. Endothelin and diabetic complications: a brain-centric view. Physiol Res 2018; 67:S83-S94. [PMID: 29947530 DOI: 10.33549/physiolres.933833] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The global epidemic of diabetes is of significant concern. Diabetes associated vascular disease signifies the principal cause of morbidity and mortality in diabetic patients. It is also the most rapidly increasing risk factor for cognitive impairment, a silent disease that causes loss of creativity, productivity, and quality of life. Small vessel disease in the cerebral vasculature plays a major role in the pathogenesis of cognitive impairment in diabetes. Endothelin system, including endothelin-1 (ET-1) and the receptors (ET(A) and ET(B)), is a likely candidate that may be involved in many aspects of the diabetes cerebrovascular disease. In this review, we took a brain-centric approach and discussed the role of the ET system in cerebrovascular and cognitive dysfunction in diabetes.
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Affiliation(s)
- W Li
- Charlie Norwood Veterans Affairs Medical Center, Augusta, Georgia, USA, Department of Physiology, Augusta University, Augusta, Georgia, USA.
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17
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Zhu Y, Ye P, Chen SL, Zhang DM. Functional regulation of large conductance Ca 2+-activated K + channels in vascular diseases. Metabolism 2018; 83:75-80. [PMID: 29373813 DOI: 10.1016/j.metabol.2018.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Revised: 01/03/2018] [Accepted: 01/18/2018] [Indexed: 12/17/2022]
Abstract
The large conductance Ca2+-activated potassium channels, the BK channels, is widely expressed in various tissues and activated in a Ca2+- and voltage-dependent manner. The activation of BK channels hyperpolarizes vascular smooth muscle cell membrane potential, resulting in vasodilation. Under pathophysiological conditions, such as diabetes mellitus and hypertension, impaired BK channel function exacerbates vascular vasodilation and leads to organ ischemia. The vascular BK channel is composed of 4 pore-forming subunits, BK-α together with 4 auxiliary subunits: β1 subunits (BK-β1) or γ1 subunits (BK-γ1). Recent studies have shown that down-regulation of the BK β1 subunit in diabetes mellitus induced vascular dysfunction; however, the molecular mechanism of these vascular diseases is not well understood. In this review, we summarize the potential mechanisms regarding BK channelopathy and the potential therapeutic targets of BK channels for vascular diseases.
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Affiliation(s)
- Yanrong Zhu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Peng Ye
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Shao-Liang Chen
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Dai-Min Zhang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China.
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18
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Coucha M, Abdelsaid M, Ward R, Abdul Y, Ergul A. Impact of Metabolic Diseases on Cerebral Circulation: Structural and Functional Consequences. Compr Physiol 2018; 8:773-799. [PMID: 29687902 DOI: 10.1002/cphy.c170019] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Metabolic diseases including obesity, insulin resistance, and diabetes have profound effects on cerebral circulation. These diseases not only affect the architecture of cerebral blood arteries causing adverse remodeling, pathological neovascularization, and vasoregression but also alter the physiology of blood vessels resulting in compromised myogenic reactivity, neurovascular uncoupling, and endothelial dysfunction. Coupled with the disruption of blood brain barrier (BBB) integrity, changes in blood flow and microbleeds into the brain rapidly occur. This overview is organized into sections describing cerebrovascular architecture, physiology, and BBB in these diseases. In each section, we review these properties starting with larger arteries moving into smaller vessels. Where information is available, we review in the order of obesity, insulin resistance, and diabetes. We also tried to include information on biological variables such as the sex of the animal models noted since most of the information summarized was obtained using male animals. © 2018 American Physiological Society. Compr Physiol 8:773-799, 2018.
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Affiliation(s)
- Maha Coucha
- South University, School of Pharmacy, Savannah, Georgia, USA
| | | | - Rebecca Ward
- Department of Neuroscience & Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Yasir Abdul
- Charlie Norwood VA Medical Center, Augusta, Georgia, USA.,Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Adviye Ergul
- Charlie Norwood VA Medical Center, Augusta, Georgia, USA.,Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
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19
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Long-term diet-induced hypertension in rats is associated with reduced expression and function of small artery SKCa, IKCa, and Kir2.1 channels. Clin Sci (Lond) 2018; 132:461-474. [DOI: 10.1042/cs20171408] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 01/24/2018] [Accepted: 02/01/2018] [Indexed: 02/07/2023]
Abstract
Abdominal obesity and/or a high intake of fructose may cause hypertension. K+ channels, Na/K-ATPase, and voltage-gated Ca2+ channels are crucial determinants of resistance artery tone and thus the control of blood pressure. Limited information is available on the role of K+ transporters in long-term diet-induced hypertension in rats. We hypothesized that a 28-week diet rich in fat, fructose, or both, will lead to changes in K+ transporter expression and function, which is associated with increased blood pressure and decreased arterial function. Male Sprague–Dawley (SD) rats received a diet containing normal chow (Control), high-fat chow (High Fat), high-fructose in drinking water (High Fructose), or a combination of high-fat and high-fructose diet (High Fat/Fruc) for 28 weeks from the age of 4 weeks. Measurements included body weight (BW), systolic blood pressure (SBP), mRNA expression of vascular K+ transporters, and vessel myography in small mesenteric arteries (SMAs). BW was increased in the High Fat and High Fat/Fruc groups, and SBP was increased in the High Fat/Fruc group. mRNA expression of small conductance calcium-activated K+ channel (SKCa), intermediate conductance calcium-activated K+ (IKCa), and Kir2.1 inward rectifier K+ channels were reduced in the High Fat/Fruc group. Reduced endothelium-derived hyperpolarization (EDH)-type relaxation to acetylcholine (ACh) was seen in the High Fat and High Fat/Fruc groups. Ba2+-sensitive dilatation to extracellular K+ was impaired in all the experimental diet groups. In conclusion, reduced expression and function of SKCa, IKCa, and Kir2.1 channels are associated with elevated blood pressure in rats fed a long-term High Fat/Fruc. Rats fed a 28-week High Fat/Fruc provide a relevant model of diet-induced hypertension.
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20
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Ma YG, Liang L, Zhang YB, Wang BF, Bai YG, Dai ZJ, Xie MJ, Wang ZW. Berberine reduced blood pressure and improved vasodilation in diabetic rats. J Mol Endocrinol 2017; 59:191-204. [PMID: 28515053 DOI: 10.1530/jme-17-0014] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 05/17/2017] [Indexed: 12/14/2022]
Abstract
Hyperglycemia and hypertension are considered to be the two leading risk factors for vascular disease in diabetic patients. However, few pharmacologic agents could provide a combinational therapy for controlling hyperglycemia and hypertension at the same time in diabetes. The objectives of this study are to investigate whether berberine treatment could directly reduce blood pressure and identify the molecular mechanism underlying the vascular protection of berberine in diabetic rats. Berberine was intragastrically administered with different dosages of 50, 100 and 200 mg/kg/day to diabetic rats for 8 weeks since the injection of streptozotocin. The endothelium-dependent/-independent relaxation in middle cerebral arteries was investigated. The activity of large-conductance Ca2+-activated K+ channel (BKCa) was investigated by recording whole-cell currents, analyzing single-channel activities and assessing the expressions of α- and β1-subunit at protein or mRNA levels. Results of the study suggest that chronic administration of 100 mg/kg/day berberine not only lowered blood glucose but also reduced blood pressure and improved vasodilation in diabetic rats. Furthermore, berberine markedly increased the function and expression of BKCa β1-subunit in cerebral vascular smooth muscle cells (VSMCs) isolated from diabetic rats or when exposed to hyperglycemia condition. The present study provided initial evidences that berberine reduced blood pressure and improved vasodilation in diabetic rats by activation of BKCa channel in VSMCs, which suggested that berberine might provide a combinational therapy for controlling hyperglycemia and blood pressure in diabetes. Furthermore, our work indicated that activation of BKCa channel might be the underlying mechanism responsible for the vascular protection of berberine in diabetes.
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Affiliation(s)
- Yu-Guang Ma
- Department of OncologyThe Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi Province, China
| | - Liang Liang
- Department of OncologyThe Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi Province, China
| | - Yin-Bin Zhang
- Department of OncologyThe Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi Province, China
| | - Bao-Feng Wang
- Department of OncologyThe Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi Province, China
| | - Yun-Gang Bai
- Department of OncologyThe Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi Province, China
| | - Zhi-Jun Dai
- Department of OncologyThe Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi Province, China
| | - Man-Jiang Xie
- Department of Aerospace PhysiologyKey Laboratory of Aerospace Medicine of Ministry of Education, Fourth Military Medical University, Xi'an, Shaanxi Province, China
| | - Zhong-Wei Wang
- Department of OncologyThe Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi Province, China
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21
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Capillary K +-sensing initiates retrograde hyperpolarization to increase local cerebral blood flow. Nat Neurosci 2017; 20:717-726. [PMID: 28319610 PMCID: PMC5404963 DOI: 10.1038/nn.4533] [Citation(s) in RCA: 326] [Impact Index Per Article: 46.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 02/19/2017] [Indexed: 12/21/2022]
Abstract
Blood flow into the brain is dynamically regulated to satisfy the changing metabolic requirements of neurons, but how this is accomplished has remained unclear. Here, we demonstrate a central role for capillary endothelial cells in sensing neural activity and communicating it to upstream arterioles in the form of an electrical vasodilatory signal. We further demonstrate that this signal is initiated by extracellular potassium (K+)—a byproduct of neural activity—which activates capillary endothelial cell inward-rectifier K+ (KIR2.1) channels to produce a rapidly propagating retrograde hyperpolarization that causes upstream arteriolar dilation, increasing blood flow into the capillary bed. Our results establish brain capillaries as an active sensory web that converts changes in external K+ into rapid, ‘inside-out’ electrical signaling to direct blood flow to active brain regions.
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22
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 212] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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23
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Vetri F, Qi M, Xu H, Oberholzer J, Paisansathan C. Impairment of neurovascular coupling in Type 1 Diabetes Mellitus in rats is prevented by pancreatic islet transplantation and reversed by a semi-selective PKC inhibitor. Brain Res 2016; 1655:48-54. [PMID: 27865779 DOI: 10.1016/j.brainres.2016.11.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 11/07/2016] [Accepted: 11/09/2016] [Indexed: 12/15/2022]
Abstract
Streptozotocin (STZ)-induced chronic hyperglycemia has a detrimental effect on neurovascular coupling, linked to increased PKC-mediated phosphorylation and PKC isoform expression changes. Here, we sought to determine whether: 1) selective PKC-α/β/γ inhibitor, GF109203X, could reverse the effects of chronic hyperglycemia on cerebrovascular reactivity; 2) pancreatic islet transplantation could prevent the development of cerebrovascular impairment seen in a rat model of Type 1 Diabetes. We studied the effect of GF109203X in diabetic (DM), non-diabetic (ND), and transplanted (TR) Lewis rats during either sciatic nerve stimulation (SNS) or the topical applications of the large-conductance Ca2+-operated K+(BKCa) channel opener, NS1619, or the K+ inward rectifier (Kir) channel agonist, KCl. Pial arteriole diameter changes were monitored using a closed cranial window in vivo microscopy technique. The pial arteriole dilatory response associated with SNS was decreased by ~45%, when comparing DM vs either ND or TR rats. Also, pial arteriolar dilations to topical KCl and NS1619 were largely attenuated in DM rats, but not in ND or TR animals. These responses were completely restored by the acute application of GF109203X to the brain surface. The PKC inhibitor had no effect on vascular responses in normoglycemic and TR animals. In conclusion, DM-associated chronic impairment of neurovascular coupling may be readily reversed by a PKC-α/β/γ inhibitor or prevented via pancreatic islet transplantation. We believe that specific PCK isoforms (α/β/γ) are mechanistically linked to the neurovascular uncoupling seen with hyperglycemia.
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Key Words
- BKCa, large-conductance Ca2+-operated K+ channel
- DM, diabetic
- Diabetes mellitus type 1
- GF109203X
- Kir, K+ inward rectifier channel
- ND, non-diabetic
- NVC, neurovascular coupling
- Neurovascular coupling
- PKC
- PKC, protein kinase C
- Pancreatic islet transplantation
- Potassium channels
- SEPs, somatosensory evoked potentials
- STZ, streptozotocin
- TR, transplanted rats
- aCSF, artificial cerebrospinal fluid
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Affiliation(s)
- Francesco Vetri
- Department of Anesthesiology, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA.
| | - Meirigeng Qi
- Division of Transplantation, Department of Surgery, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
| | - Haoliang Xu
- Department of Anesthesiology, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
| | - Jose Oberholzer
- Division of Transplantation, Department of Surgery, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
| | - Chanannait Paisansathan
- Department of Anesthesiology, University of Illinois at Chicago, 1740 W Taylor St, Chicago 60612, IL, USA
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Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 78:89-144. [PMID: 28212804 DOI: 10.1016/bs.apha.2016.07.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Potassium channels importantly contribute to the regulation of vascular smooth muscle (VSM) contraction and growth. They are the dominant ion conductance of the VSM cell membrane and importantly determine and regulate membrane potential. Membrane potential, in turn, regulates the open-state probability of voltage-gated Ca2+ channels (VGCC), Ca2+ influx through VGCC, intracellular Ca2+, and VSM contraction. Membrane potential also affects release of Ca2+ from internal stores and the Ca2+ sensitivity of the contractile machinery such that K+ channels participate in all aspects of regulation of VSM contraction. Potassium channels also regulate proliferation of VSM cells through membrane potential-dependent and membrane potential-independent mechanisms. VSM cells express multiple isoforms of at least five classes of K+ channels that contribute to the regulation of contraction and cell proliferation (growth). This review will examine the structure, expression, and function of large conductance, Ca2+-activated K+ (BKCa) channels, intermediate-conductance Ca2+-activated K+ (KCa3.1) channels, multiple isoforms of voltage-gated K+ (KV) channels, ATP-sensitive K+ (KATP) channels, and inward-rectifier K+ (KIR) channels in both contractile and proliferating VSM cells.
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25
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Krishnamoorthy-Natarajan G, Koide M. BK Channels in the Vascular System. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:401-38. [PMID: 27238270 DOI: 10.1016/bs.irn.2016.03.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Autoregulation of blood flow is essential for the preservation of organ function to ensure continuous supply of oxygen and essential nutrients and removal of metabolic waste. This is achieved by controlling the diameter of muscular arteries and arterioles that exhibit a myogenic response to changes in arterial blood pressure, nerve activity and tissue metabolism. Large-conductance voltage and Ca(2+)-dependent K(+) channels (BK channels), expressed exclusively in smooth muscle cells (SMCs) in the vascular wall of healthy arteries, play a critical role in regulating the myogenic response. Activation of BK channels by intracellular, local, and transient ryanodine receptor-mediated "Ca(2+) sparks," provides a hyperpolarizing influence on the SMC membrane potential thereby decreasing the activity of voltage-dependent Ca(2+) channels and limiting Ca(2+) influx to promote SMC relaxation and vasodilation. The BK channel α subunit, a large tetrameric protein with each monomer consisting of seven-transmembrane domains, a long intracellular C-terminal tail and an extracellular N-terminus, associates with the β1 and γ subunits in vascular SMCs. The BK channel is regulated by factors originating within the SMC or from the endothelium, perivascular nerves and circulating blood, that significantly alter channel gating properties, Ca(2+) sensitivity and expression of the α and/or β1 subunit. The BK channel thus serves as a central receiving dock that relays the effects of the changes in several such concomitant autocrine and paracrine factors and influences cardiovascular health. This chapter describes the primary mechanism of regulation of myogenic response by BK channels and the alterations to this mechanism wrought by different vasoactive mediators.
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Affiliation(s)
| | - M Koide
- University of Vermont, Burlington, VT, United States
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26
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Phillips AA, Chan FH, Zheng MMZ, Krassioukov AV, Ainslie PN. Neurovascular coupling in humans: Physiology, methodological advances and clinical implications. J Cereb Blood Flow Metab 2016; 36:647-64. [PMID: 26661243 PMCID: PMC4821024 DOI: 10.1177/0271678x15617954] [Citation(s) in RCA: 256] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 10/22/2015] [Accepted: 10/23/2015] [Indexed: 12/16/2022]
Abstract
Neurovascular coupling reflects the close temporal and regional linkage between neural activity and cerebral blood flow. Although providing mechanistic insight, our understanding of neurovascular coupling is largely limited to non-physiologicalex vivopreparations and non-human models using sedatives/anesthetics with confounding cerebrovascular implications. Herein, with particular focus on humans, we review the present mechanistic understanding of neurovascular coupling and highlight current approaches to assess these responses and the application in health and disease. Moreover, we present new guidelines for standardizing the assessment of neurovascular coupling in humans. To improve the reliability of measurement and related interpretation, the utility of new automated software for neurovascular coupling is demonstrated, which provides the capacity for coalescing repetitive trials and time intervals into single contours and extracting numerous metrics (e.g., conductance and pulsatility, critical closing pressure, etc.) according to patterns of interest (e.g., peak/minimum response, time of response, etc.). This versatile software also permits the normalization of neurovascular coupling metrics to dynamic changes in arterial blood gases, potentially influencing the hyperemic response. It is hoped that these guidelines, combined with the newly developed and openly available software, will help to propel the understanding of neurovascular coupling in humans and also lead to improved clinical management of this critical physiological function.
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Affiliation(s)
- Aaron A Phillips
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada International Collaboration on Repair Discoveries (ICORD), UBC, Vancouver, Canada Experimental Medicine Program, Faculty of Medicine, UBC, Vancouver, Canada
| | - Franco Hn Chan
- International Collaboration on Repair Discoveries (ICORD), UBC, Vancouver, Canada
| | - Mei Mu Zi Zheng
- International Collaboration on Repair Discoveries (ICORD), UBC, Vancouver, Canada Experimental Medicine Program, Faculty of Medicine, UBC, Vancouver, Canada
| | - Andrei V Krassioukov
- International Collaboration on Repair Discoveries (ICORD), UBC, Vancouver, Canada Experimental Medicine Program, Faculty of Medicine, UBC, Vancouver, Canada Department of Physical Therapy, UBC, Vancouver, Canada GF Strong Rehabilitation Center, Vancouver, Canada Department of Medicine, Division of Physical Medicine and Rehabilitation, UBC, Vancouver, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
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Microvascular Dysfunction and Cognitive Impairment. Cell Mol Neurobiol 2016; 36:241-58. [PMID: 26988697 DOI: 10.1007/s10571-015-0308-1] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 11/19/2015] [Indexed: 12/18/2022]
Abstract
The impact of vascular risk factors on cognitive function has garnered much interest in recent years. The appropriate distribution of oxygen, glucose, and other nutrients by the cerebral vasculature is critical for proper cognitive performance. The cerebral microvasculature is a key site of vascular resistance and a preferential target for small vessel disease. While deleterious effects of vascular risk factors on microvascular function are known, the contribution of this dysfunction to cognitive deficits is less clear. In this review, we summarize current evidence for microvascular dysfunction in brain. We highlight effects of select vascular risk factors (hypertension, diabetes, and hyperhomocysteinemia) on the pial and parenchymal circulation. Lastly, we discuss potential links between microvascular disease and cognitive function, highlighting current gaps in our understanding.
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28
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Rooijackers HMM, Wiegers EC, Tack CJ, van der Graaf M, de Galan BE. Brain glucose metabolism during hypoglycemia in type 1 diabetes: insights from functional and metabolic neuroimaging studies. Cell Mol Life Sci 2016; 73:705-22. [PMID: 26521082 PMCID: PMC4735263 DOI: 10.1007/s00018-015-2079-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 10/16/2015] [Accepted: 10/20/2015] [Indexed: 12/30/2022]
Abstract
Hypoglycemia is the most frequent complication of insulin therapy in patients with type 1 diabetes. Since the brain is reliant on circulating glucose as its main source of energy, hypoglycemia poses a threat for normal brain function. Paradoxically, although hypoglycemia commonly induces immediate decline in cognitive function, long-lasting changes in brain structure and cognitive function are uncommon in patients with type 1 diabetes. In fact, recurrent hypoglycemia initiates a process of habituation that suppresses hormonal responses to and impairs awareness of subsequent hypoglycemia, which has been attributed to adaptations in the brain. These observations sparked great scientific interest into the brain's handling of glucose during (recurrent) hypoglycemia. Various neuroimaging techniques have been employed to study brain (glucose) metabolism, including PET, fMRI, MRS and ASL. This review discusses what is currently known about cerebral metabolism during hypoglycemia, and how findings obtained by functional and metabolic neuroimaging techniques contributed to this knowledge.
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Affiliation(s)
- Hanne M M Rooijackers
- Department of Internal Medicine 463, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - Evita C Wiegers
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Cees J Tack
- Department of Internal Medicine 463, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Marinette van der Graaf
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Pediatrics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bastiaan E de Galan
- Department of Internal Medicine 463, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
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29
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Longden TA, Nelson MT. Vascular inward rectifier K+ channels as external K+ sensors in the control of cerebral blood flow. Microcirculation 2015; 22:183-96. [PMID: 25641345 PMCID: PMC4404517 DOI: 10.1111/micc.12190] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/16/2015] [Indexed: 12/25/2022]
Abstract
For decades it has been known that external K(+) ions are rapid and potent vasodilators that increase CBF. Recent studies have implicated the local release of K(+) from astrocytic endfeet-which encase the entirety of the parenchymal vasculature-in the dynamic regulation of local CBF during NVC. It has been proposed that the activation of KIR channels in the vascular wall by external K(+) is a central component of these hyperemic responses; however, a number of significant gaps in our knowledge remain. Here, we explore the concept that vascular KIR channels are the major extracellular K(+) sensors in the control of CBF. We propose that K(+) is an ideal mediator of NVC, and discuss KIR channels as effectors that produce rapid hyperpolarization and robust vasodilation of cerebral arterioles. We provide evidence that KIR channels, of the KIR 2 subtype in particular, are present in both the endothelial and SM cells of parenchymal arterioles and propose that this dual positioning of KIR 2 channels increases the robustness of the vasodilation to external K(+), enables the endothelium to be actively engaged in NVC, and permits electrical signaling through the endothelial syncytium to promote upstream vasodilation to modulate CBF.
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Affiliation(s)
- Thomas A Longden
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA
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30
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Abstract
SIGNIFICANCE The brain has high energetic requirements and is therefore highly dependent on adequate cerebral blood supply. To compensate for dangerous fluctuations in cerebral perfusion, the circulation of the brain has evolved intrinsic safeguarding measures. RECENT ADVANCES AND CRITICAL ISSUES The vascular network of the brain incorporates a high degree of redundancy, allowing the redirection and redistribution of blood flow in the event of vascular occlusion. Furthermore, active responses such as cerebral autoregulation, which acts to maintain constant cerebral blood flow in response to changing blood pressure, and functional hyperemia, which couples blood supply with synaptic activity, allow the brain to maintain adequate cerebral perfusion in the face of varying supply or demand. In the presence of stroke risk factors, such as hypertension and diabetes, these protective processes are impaired and the susceptibility of the brain to ischemic injury is increased. One potential mechanism for the increased injury is that collateral flow arising from the normally perfused brain and supplying blood flow to the ischemic region is suppressed, resulting in more severe ischemia. FUTURE DIRECTIONS Approaches to support collateral flow may ameliorate the outcome of focal cerebral ischemia by rescuing cerebral perfusion in potentially viable regions of the ischemic territory.
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Affiliation(s)
- Katherine Jackman
- Brain and Mind Research Institute, Weill Cornell Medical College , New York, New York
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Samways DSK. Applications for mass spectrometry in the study of ion channel structure and function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 806:237-61. [PMID: 24952185 DOI: 10.1007/978-3-319-06068-2_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Ion channels are intrinsic membrane proteins that form gated ion-permeable pores across biological membranes. Depending on the type, ion channels exhibit sensitivities to a diverse range of stimuli including changes in membrane potential, binding by diffusible ligands, changes in temperature and direct mechanical force. The purpose of these proteins is to facilitate the passive diffusion of ions down their respective electrochemical gradients into and out of the cell, and between intracellular compartments. In doing so, ion channels can affect transmembrane potentials and regulate the intracellular homeostasis of the important second messenger, Ca(2+). The ion channels of the plasma membrane are of particular clinical interest due to their regulation of cell excitability and cytosolic Ca(2+) levels, and the fact that they are most amenable to manipulation by exogenously applied drugs and toxins. A critical step in improving the pharmacopeia of chemicals available that influence the activity of ion channels is understanding how their three-dimensional structure imparts function. Here, progress has been slow relative to that for soluble protein structures in large part due to the limitations of applying conventional structure determination methods, such as X-ray crystallography, nuclear magnetic resonance imaging, and mass spectrometry, to membrane proteins. Although still an underutilized technique in the assessment of membrane protein structure, recent advances have pushed mass spectrometry to the fore as an important complementary approach to studying the structure and function of ion channels. In addition to revealing the subtle conformational changes in ion channel structure that accompany gating and permeation, mass spectrometry is already being used effectively for identifying tissue-specific posttranslational modifications and mRNA splice variants. Furthermore, the use of mass spectrometry for high-throughput proteomics analysis, which has proven so successful for soluble proteins, is already providing valuable insight into the functional interactions of ion channels within the context of the macromolecular-signaling complexes that they inhabit in vivo. In this chapter, the potential for mass spectrometry as a complementary approach to the study of ion channel structure and function will be reviewed with examples of its application.
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Affiliation(s)
- Damien S K Samways
- Department of Biology, Clarkson University, 8 Clarkson Avenue, Potsdam, NY, 13699, USA,
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Vetri F, Chavez R, Xu HL, Paisansathan C, Pelligrino DA. Complex modulation of the expression of PKC isoforms in the rat brain during chronic type 1 diabetes mellitus. Brain Res 2012; 1490:202-9. [PMID: 23103504 DOI: 10.1016/j.brainres.2012.10.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 10/06/2012] [Accepted: 10/16/2012] [Indexed: 10/27/2022]
Abstract
We previously demonstrated that chronic hyperglycemia has a detrimental influence on neurovascular coupling in the brain-an effect linked to an alteration in the protein kinase C (PKC)-mediated phosphorylation pattern. Moreover, the activity of PKC was increased, in diabetic rat brain, in a tissue fraction composed primarily of the superficial glia limitans and pial vessels, but trended toward a decrease in cerebral cortical gray matter. However, that study did not examine the expression patterns of PKC isoforms in the rat brain. Thus, in a rat model of streptozotocin (STZ)-induced chronic type 1 diabetes mellitus (T1DM), and in non-diabetic (ND) controls, two hypotheses were addressed. First, chronic T1DM is accompanied by changes in the expression of PKC-α, βII, γ, δ, and ε Second, those changes differ when comparing cerebral cortex and glio-pial tissue. In addition, we analyzed the expression of a form of PKC-γ, phosphorylated on threonine 514 (pT514-PKC-γ), as well as the receptor for activated C kinase 1 (RACK1). The expression pattern of different PKC isoforms was altered in a complex and tissue-specific manner during chronic hyperglycemia. Notably, in the gray matter, PKC-α expression significantly decreased, while pT514-PKC-γ expression increased. However, PKC-βII, -γ, -δ, -ε, and RACK1 expressions did not change. Conversely, in glio-pial tissue, PKC-α and RACK1 were upregulated, whereas PKC-γ, pT514-PKC-γ, and PKC-ε were downregulated. PKC-βII, and PKC-δ, were unchanged. These findings suggest that the PKC activity increase previously seen in the glio-pial tissue of diabetic rats may be due to the selective upregulation of PKC-α, and ultimately lead to the impairment of neurovascular coupling.
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Affiliation(s)
- Francesco Vetri
- Neuroanesthesia Research Laboratory, Department of Anesthesiology, University of Illinois, Chicago, IL 60612, USA.
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