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Daoud HAS, Kokoti L, Al-Karagholi MAM. K ATP channels in cerebral hemodynamics: a systematic review of preclinical and clinical studies. Front Neurol 2024; 15:1417421. [PMID: 39022739 PMCID: PMC11252034 DOI: 10.3389/fneur.2024.1417421] [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: 04/14/2024] [Accepted: 06/14/2024] [Indexed: 07/20/2024] Open
Abstract
Cumulative evidence suggests that ATP-sensitive potassium (KATP) channels act as a key regulator of cerebral blood flow (CBF). This implication seems to be complicated, since KATP channels are expressed in several vascular-related structures such as smooth muscle cells, endothelial cells and pericytes. In this systematic review, we searched PubMed and EMBASE for preclinical and clinical studies addressing the involvement of KATP channels in CBF regulation. A total of 216 studies were screened by title and abstract. Of these, 45 preclinical and 6 clinical studies were included. Preclinical data showed that KATP channel openers (KCOs) caused dilation of several cerebral arteries including pial arteries, the middle cerebral artery and basilar artery, and KATP channel inhibitor (KCI) glibenclamide, reversed the dilation. Glibenclamide affected neither the baseline CBF nor the baseline vascular tone. Endothelium removal from cerebral arterioles resulted in an impaired response to KCO/KCI. Clinical studies showed that KCOs dilated cerebral arteries and increased CBF, however, glibenclamide failed to attenuate these vascular changes. Endothelial KATP channels played a major role in CBF regulation. More studies investigating the role of KATP channels in CBF-related structures are needed to further elucidate their actual role in cerebral hemodynamics in humans. Systematic review registration: Prospero: CRD42023339278 (preclinical data) and CRD42022339152 (clinical data).
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Affiliation(s)
- Hassan Ali Suleiman Daoud
- Department of Neurology, Danish Headache Center, Copenhagen University Hospital- Rigshospitalet, Copenhagen, Denmark
| | - Lili Kokoti
- Department of Neurology, Danish Headache Center, Copenhagen University Hospital- Rigshospitalet, Copenhagen, Denmark
| | - Mohammad Al-Mahdi Al-Karagholi
- Department of Neurology, Danish Headache Center, Copenhagen University Hospital- Rigshospitalet, Copenhagen, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Neurology, Nordsjaellands Hospital- Hilleroed, Hilleroed, Denmark
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2
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Lindquist BE. Spreading depolarizations pose critical energy challenges in acute brain injury. J Neurochem 2024; 168:868-887. [PMID: 37787065 PMCID: PMC10987398 DOI: 10.1111/jnc.15966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 08/08/2023] [Accepted: 09/10/2023] [Indexed: 10/04/2023]
Abstract
Spreading depolarization (SD) is an electrochemical wave of neuronal depolarization mediated by extracellular K+ and glutamate, interacting with voltage-gated and ligand-gated ion channels. SD is increasingly recognized as a major cause of injury progression in stroke and brain trauma, where the mechanisms of SD-induced neuronal injury are intimately linked to energetic status and metabolic impairment. Here, I review the established working model of SD initiation and propagation. Then, I summarize the historical and recent evidence for the metabolic impact of SD, transitioning from a descriptive to a mechanistic working model of metabolic signaling and its potential to promote neuronal survival and resilience. I quantify the energetic cost of restoring ionic gradients eroded during SD, and the extent to which ion pumping impacts high-energy phosphate pools and the energy charge of affected tissue. I link energy deficits to adaptive increases in the utilization of glucose and O2, and the resulting accumulation of lactic acid and CO2 downstream of catabolic metabolic activity. Finally, I discuss the neuromodulatory and vasoactive paracrine signaling mediated by adenosine and acidosis, highlighting these metabolites' potential to protect vulnerable tissue in the context of high-frequency SD clusters.
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Affiliation(s)
- Britta E Lindquist
- Department of Neurology, University of California, San Francisco, California, USA
- Gladstone Institute of Neurological Diseases, San Francisco, California, USA
- Zuckerberg San Francisco General Hospital and Trauma Center, San Francisco, California, USA
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3
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Aleksandrowicz M, Kozniewska E. Compromised regulation of the rat brain parenchymal arterioles in vasopressin-associated acute hyponatremia. Microcirculation 2020; 27:e12644. [PMID: 32603523 DOI: 10.1111/micc.12644] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 05/21/2020] [Accepted: 06/18/2020] [Indexed: 12/12/2022]
Abstract
OBJECTIVE In this study, we examined the effect of acute hyponatremia associated with vasopressin (AVP) on the responses of the isolated rat's MCAs and PAs to acidosis, nitric oxide donor (SNAP) and to endothelium-dependent vasodilator ATP. METHODS The studies were performed on isolated, perfused and pressurized MCAs and PAs in control conditions and during AVP-associated hyponatremia. Hyponatremia was induced in vitro by lowering Na+ concentration from 144 to 121 mmol/L in intra- and extravascular fluid in the presence of AVP. RESULTS Parenchymal arterioles showed greater response to an increase in H+ and K+ ions concentration and to ATP in comparison with MCAs in control normonatremic conditions. Both PAs and MCAs constricted in response to acute hyponatremia associated with AVP. Interestingly, disordered regulation of vascular tone was observed in PAs but not in MCAs. The abnormalities in the regulation comprised a significant reduction of PA response to acidosis and the absence of the response to the administration of SNAP or ATP. CONCLUSIONS Arginine vasopressin-associated hyponatremia leads to constriction and dysregulation of PAs which may impair neurovascular coupling.
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Affiliation(s)
- Marta Aleksandrowicz
- Laboratory of Experimental and Clinical Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Ewa Kozniewska
- Laboratory of Experimental and Clinical Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
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Abutarboush R, Gu M, Kawoos U, Mullah SH, Chen Y, Goodrich SY, Lashof-Sullivan M, McCarron RM, Statz JK, Bell RS, Stone JR, Ahlers ST. Exposure to Blast Overpressure Impairs Cerebral Microvascular Responses and Alters Vascular and Astrocytic Structure. J Neurotrauma 2019; 36:3138-3157. [PMID: 31210096 PMCID: PMC6818492 DOI: 10.1089/neu.2019.6423] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Exposure to blast overpressure may result in cerebrovascular impairment, including cerebral vasospasm. The mechanisms contributing to this vascular response are unclear. The aim of this study was to evaluate the relationship between blast and functional alterations of the cerebral microcirculation and to investigate potential underlying changes in vascular microstructure. Cerebrovascular responses were assessed in sham- and blast-exposed male rats at multiple time points from 2 h through 28 days after a single 130-kPa (18.9-psi) exposure. Pial microcirculation was assessed through a cranial window created in the parietal bone of anesthetized rats. Pial arteriolar reactivity was evaluated in vivo using hypercapnia, barium chloride, and serotonin. We found that exposure to blast leads to impairment of arteriolar reactivity >24 h after blast exposure, suggesting delayed injury mechanisms that are not simply attributed to direct mechanical deformation. Observed vascular impairment included a reduction in hypercapnia-induced vasodilation, increase in barium-induced constriction, and reversal of the serotonin effect from constriction to dilation. A reduction in vascular smooth muscle contractile proteins consistent with vascular wall proliferation was observed, as well as delayed reduction in nitric oxide synthase and increase in endothelin-1 B receptors, mainly in astrocytes. Collectively, the data show that exposure to blast results in delayed and prolonged alterations in cerebrovascular reactivity that are associated with changes in the microarchitecture of the vessel wall and astrocytes. These changes may contribute to long-term pathologies involving dysfunction of the neurovascular unit, including cerebral vasospasm.
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Affiliation(s)
- Rania Abutarboush
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Ming Gu
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Usmah Kawoos
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Saad H Mullah
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Ye Chen
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Samantha Y Goodrich
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Margaret Lashof-Sullivan
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Richard M McCarron
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Jonathan K Statz
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Randy S Bell
- Neurosurgery Department, Walter Reed National Military Medical Center, Bethesda, Maryland
| | - James R Stone
- Department of Radiology and Medical Imaging, University of Virginia Medical Center, Charlottesville, Virginia
| | - Stephen T Ahlers
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland
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5
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Charter ME, Lamb IR, Murrant CL. Arteriolar and capillary responses to CO2and H+in hamster skeletal muscle microvasculature: Implications for active hyperemia. Microcirculation 2018; 25:e12494. [DOI: 10.1111/micc.12494] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 06/21/2018] [Accepted: 07/18/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Mackenzie E. Charter
- Department of Human Health and Nutritional Sciences; University of Guelph; Guelph Ontario Canada
| | - Iain R. Lamb
- Department of Human Health and Nutritional Sciences; University of Guelph; Guelph Ontario Canada
| | - Coral L. Murrant
- Department of Human Health and Nutritional Sciences; University of Guelph; Guelph Ontario Canada
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6
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Boedtkjer E. Acid-base regulation and sensing: Accelerators and brakes in metabolic regulation of cerebrovascular tone. J Cereb Blood Flow Metab 2018; 38:588-602. [PMID: 28984162 PMCID: PMC5888856 DOI: 10.1177/0271678x17733868] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 08/10/2017] [Accepted: 09/06/2017] [Indexed: 12/29/2022]
Abstract
Metabolic regulation of cerebrovascular tone directs blood flow to areas of increased neuronal activity and during disease states partially compensates for insufficient perfusion by enhancing blood flow in collateral blood vessels. Acid-base disturbances frequently occur as result of enhanced metabolism or insufficient blood supply, but despite definitive evidence that acid-base disturbances alter arterial tone, effects of individual acid-base equivalents and the underlying signaling mechanisms are still being debated. H+ is an important intra- and extracellular messenger that modifies cerebrovascular tone. In addition, low extracellular [HCO3-] promotes cerebrovascular contraction through an endothelium-dependent mechanism. CO2 alters arterial tone development via changes in intra- and extracellular pH but it is still controversial whether CO2 also has direct vasomotor effects. Vasocontractile responses to low extracellular [HCO3-] and acute CO2-induced decreases in intracellular pH can counteract H+-mediated vasorelaxation during metabolic and respiratory acidosis, respectively, and may thereby reduce the risk of capillary damage and cerebral edema that could be consequences of unopposed vasodilation. In this review, the signaling mechanisms for acid-base equivalents in cerebral arteries and the mechanisms of intracellular pH control in the arterial wall are discussed in the context of metabolic regulation of cerebrovascular tone and local perfusion.
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Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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7
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Aleksandrowicz M, Dworakowska B, Dolowy K, Kozniewska E. Restoration of the response of the middle cerebral artery of the rat to acidosis in hyposmotic hyponatremia by the opener of large-conductance calcium sensitive potassium channels (BK Ca). J Cereb Blood Flow Metab 2017; 37:3219-3230. [PMID: 28058990 PMCID: PMC5584697 DOI: 10.1177/0271678x16685575] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Hyposmotic hyponatremia (the decrease of extracellular concentration of sodium ions from 145 to 121 mM and the decrease of hyposmolality from 300 to 250 mOsm/kg H2O) impairs response of the middle cerebral artery (MCA) to acetylcholine and NO donor (S-nitroso-N-acetyl-DL-penicillamine). Since acidosis activates a similar intracellular signaling pathway, the present study was designed to verify the hypothesis that the response of the MCA to acidosis is impaired during acute hyposmotic hyponatremia due to abnormal NO-related signal transduction in vascular smooth muscle cells. Studies performed on isolated, cannulated, and pressurized rat MCA revealed that hyposmotic hyponatremia impaired the response of the MCA to acidosis and this was associated with hyposmolality rather than with decreased sodium ion concentration. Response to acidosis was restored by the BKCa but not by the KATP channel activator. Patch-clamp electrophysiology performed on myocytes freshly isolated from MCAs, demonstrated that hyposmotic hyponatremia does not affect BKCa currents but decreases the voltage-dependency of the activation of the BKCa channels in the presence of a specific opener of these channels. Our study suggests that reduced sensitivity of BKCa channels in the MCA to agonists results in the lack of response of this artery to acidosis during acute hyposmotic hyponatremia.
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Affiliation(s)
- Marta Aleksandrowicz
- 1 Department of Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Beata Dworakowska
- 2 Department of Biophysics, Warsaw University of Life Sciences, Warsaw, Poland
| | - Krzysztof Dolowy
- 2 Department of Biophysics, Warsaw University of Life Sciences, Warsaw, Poland
| | - Ewa Kozniewska
- 1 Department of Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.,3 Department of Experimental and Clinical Physiology, Medical University of Warsaw, Warsaw, Poland
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8
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Celotto AC, Capellini VK, Albuquerque AAS, Ferreira LG, Silveira APC, de Nadai TR, Evora PRB. High conductance potassium channels activation by acid exposure in rat aorta is endothelium-dependent. BMC Res Notes 2015; 8:462. [PMID: 26386955 PMCID: PMC4575783 DOI: 10.1186/s13104-015-1422-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 09/07/2015] [Indexed: 11/13/2022] Open
Abstract
Background We investigated, previously, the mechanism by which extracellular acidification promotes relaxation in rat thoracic aorta. These studies suggested that extracellular acidosis promotes vasodilation mediated by NO, KATP and SKCa, and maybe other K+ channels in isolated rat thoracic aorta. This study was carried out to investigate the paxilline-mediated hyperpolarization induced by acid exposure. Results The relaxation response to HCl-induced extracellular acidification (7.4–6.5) was measured in rat aortic rings pre-contracted with phenylephrine (PE, 10−6 M). The vascular reactivity experiments were performed in endothelium-intact and denuded rings, in the presence of paxilline (10−6 M), which is an inhibitor of high calcium conductance potassium BKCa channels. In rings with endothelium, paxilline inhibits relaxation, triggered by acidification at all pH values lower than 7.2 and had no effect on rings without endothelium, showing that the activation of BKCa is endothelium-dependent. Conclusion High conductance potassium channel activation induced by acid exposure is endothelium-dependent.
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Affiliation(s)
- Andrea Carla Celotto
- Department of Surgery and Anatomy, Laboratory of Endothelial Function, School of Medicine, University of São Paulo, Av. Café, 3000, Ribeirão Preto, SP, Brazil.
| | - Verena Kise Capellini
- Department of Surgery and Anatomy, Laboratory of Endothelial Function, School of Medicine, University of São Paulo, Av. Café, 3000, Ribeirão Preto, SP, Brazil.
| | - Agnes Afrodite Sumarelli Albuquerque
- Department of Surgery and Anatomy, Laboratory of Endothelial Function, School of Medicine, University of São Paulo, Av. Café, 3000, Ribeirão Preto, SP, Brazil.
| | - Luciana Garros Ferreira
- Department of Surgery and Anatomy, Laboratory of Endothelial Function, School of Medicine, University of São Paulo, Av. Café, 3000, Ribeirão Preto, SP, Brazil.
| | - Ana Paula Cassiano Silveira
- Department of Surgery and Anatomy, Laboratory of Endothelial Function, School of Medicine, University of São Paulo, Av. Café, 3000, Ribeirão Preto, SP, Brazil.
| | - Tales Rubens de Nadai
- Department of Surgery and Anatomy, Laboratory of Endothelial Function, School of Medicine, University of São Paulo, Av. Café, 3000, Ribeirão Preto, SP, Brazil.
| | - Paulo Roberto Barbosa Evora
- Department of Surgery and Anatomy, Laboratory of Endothelial Function, School of Medicine, University of São Paulo, Av. Café, 3000, Ribeirão Preto, SP, Brazil. .,, Av. Bandeirantes, 3900, HC-FMRP, 9o. andar, Ribeirão Preto, SP, 14.049-900, Brazil.
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9
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Ali TY, Broughton Pipkin F, Khan RN. The effect of pH and ion channel modulators on human placental arteries. PLoS One 2014; 9:e114405. [PMID: 25490401 PMCID: PMC4260857 DOI: 10.1371/journal.pone.0114405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2014] [Accepted: 11/06/2014] [Indexed: 12/31/2022] Open
Abstract
Chorionic plate arteries (CPA) are located at the maternofetal interface where they are able to respond to local metabolic changes. Unlike many other types of vasculature, the placenta lacks nervous control and requires autoregulation for controlling blood flow. The placental circulation, which is of low-resistance, may become hypoxic easily leading to fetal acidosis and fetal distress however the role of the ion channels in these circumstances is not well-understood. Active potassium channel conductances that are subject to local physicochemical modulation may serve as pathways through which such signals are transduced. The aim of this study was to investigate the modulation of CPA by pH and the channels implicated in these responses using wire myography. CPA were isolated from healthy placentae and pre-contracted with U46619 before testing the effects of extracellular pH using 1 M lactic acid over the pH range 7.4 - 6.4 in the presence of a variety of ion channel modulators. A change from pH 7.4 to 7.2 produced a 29±3% (n = 9) relaxation of CPA which increased to 61±4% at the lowest pH of 6.4. In vessels isolated from placentae of women with pre-eclampsia (n = 6), pH responses were attenuated. L-methionine increased the relaxation to 67±7% (n = 6; p<0.001) at pH 6.4. Similarly the TASK 1/3 blocker zinc chloride (1 mM) gave a maximum relaxation of 72±5% (n = 8; p<0.01) which compared with the relaxation produced by the TREK-1 opener riluzole (75±5%; n = 6). Several other modulators induced no significant changes in vascular responses. Our study confirmed expression of several ion channel subtypes in CPA with our results indicating that extracellular pH within the physiological range has an important role in controlling vasodilatation in the human term placenta.
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Affiliation(s)
- Tayyba Y Ali
- Division of Medical Sciences & Graduate Entry Medicine, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Uttoxeter Road, Derby DE22 3DT, United Kingdom
| | - Fiona Broughton Pipkin
- Division of Medical Sciences & Graduate Entry Medicine, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Uttoxeter Road, Derby DE22 3DT, United Kingdom
| | - Raheela N Khan
- Division of Medical Sciences & Graduate Entry Medicine, School of Medicine, University of Nottingham, Royal Derby Hospital Centre, Uttoxeter Road, Derby DE22 3DT, United Kingdom
- * E-mail:
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10
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Namgung B, Liang LH, Kim S. Physiological Significance of Cell-Free Layer and Experimental Determination of its Width in Microcirculatory Vessels. VISUALIZATION AND SIMULATION OF COMPLEX FLOWS IN BIOMEDICAL ENGINEERING 2014. [DOI: 10.1007/978-94-007-7769-9_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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11
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Naranjo D, Arkuszewski M, Rudzinski W, Melhem ER, Krejza J. Brain ischemia in patients with intracranial hemorrhage: pathophysiological reasoning for aggressive diagnostic management. Neuroradiol J 2013; 26:610-28. [PMID: 24355179 PMCID: PMC4202872 DOI: 10.1177/197140091302600603] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 10/15/2013] [Indexed: 11/15/2022] Open
Abstract
Patients with intracranial hemorrhage have to be managed aggressively to avoid or minimize secondary brain damage due to ischemia, which contributes to high morbidity and mortality. The risk of brain ischemia, however, is not the same in every patient. The risk of complications associated with an aggressive prophylactic therapy in patients with a low risk of brain ischemia can outweigh the benefits of therapy. Accurate and timely identification of patients at highest risk is a diagnostic challenge. Despite the availability of many diagnostic tools, stroke is common in this population, mostly because the pathogenesis of stroke is frequently multifactorial whereas diagnosticians tend to focus on one or two risk factors. The pathophysiological mechanisms of brain ischemia in patients with intracranial hemorrhage are not yet fully elucidated and there are several important areas of ongoing research. Therefore, this review describes physiological and pathophysiological aspects associated with the development of brain ischemia such as the mechanism of oxygen and carbon dioxide effects on the cerebrovascular system, neurovascular coupling and respiratory and cardiovascular factors influencing cerebral hemodynamics. Consequently, we review investigations of cerebral blood flow disturbances relevant to various hemodynamic states associated with high intracranial pressure, cerebral embolism, and cerebral vasospasm along with current treatment options.
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Affiliation(s)
- Daniel Naranjo
- Department of Diagnostic Radiology of the University of Maryland, Division of Clinical Research; Baltimore, Maryland, USA
| | - Michal Arkuszewski
- Department of Neurology, Medical University of Silesia, Central University Hospital; Katowice, Poland
| | - Wojciech Rudzinski
- Department of Cardiology, Robert Packer Hospital; Sayre, Pennsylvania USA
| | - Elias R. Melhem
- Department of Diagnostic Radiology of the University of Maryland, Division of Clinical Research; Baltimore, Maryland, USA
| | - Jaroslaw Krejza
- Department of Diagnostic Radiology of the University of Maryland, Division of Clinical Research; Baltimore, Maryland, USA
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Institoris A, Lenti L, Domoki F, Wappler E, Gáspár T, Katakam PV, Bari F, Busija DW. Cerebral microcirculatory responses of insulin-resistant rats are preserved to physiological and pharmacological stimuli. Microcirculation 2013; 19:749-56. [PMID: 22845548 DOI: 10.1111/j.1549-8719.2012.00213.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 07/23/2012] [Indexed: 01/21/2023]
Abstract
OBJECTIVE Previously, we have shown that IR impairs the vascular reactivity of the major cerebral arteries of ZO rats prior to the occurrence of Type-II diabetes mellitus. However, the functional state of the microcirculation in the cerebral cortex is still being explored. METHODS We tested the local CoBF responses of 11-13-week-old ZO (n = 31) and control ZL (n = 32) rats to several stimuli measured by LDF using a closed cranial window setup. RESULTS The topical application of 1-100 μm bradykinin elicited the same degree of CoBF elevation in both ZL and ZO groups. There was no significant difference in the incidence, latency, and amplitude of the NMDA-induced CSD-related hyperemia between the ZO and ZL groups. Hypercapnic CoBF response to 5% carbon-dioxide ventilation did not significantly change in the ZO compared with the ZL. Topical bicuculline-induced cortical seizure was accompanied by the same increase of CoBF in both the ZO and ZL at all bicuculline doses. CONCLUSIONS CoBF responses of the microcirculation are preserved in the early period of the metabolic syndrome, which creates an opportunity for intervention to prevent and restore the function of the major cerebral vascular beds.
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Affiliation(s)
- Adam Institoris
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, North Carolina, USA.
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13
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Bor-Seng-Shu E, Kita WS, Figueiredo EG, Paiva WS, Fonoff ET, Teixeira MJ, Panerai RB. Cerebral hemodynamics: concepts of clinical importance. ARQUIVOS DE NEURO-PSIQUIATRIA 2012; 70:352-6. [PMID: 22618788 DOI: 10.1590/s0004-282x2012000500010] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 12/06/2011] [Indexed: 11/22/2022]
Abstract
Cerebral hemodynamics and metabolism are frequently impaired in a wide range of neurological diseases, including traumatic brain injury and stroke, with several pathophysiological mechanisms of injury. The resultant uncoupling of cerebral blood flow and metabolism can trigger secondary brain lesions, particularly in early phases, consequently worsening the patient's outcome. Cerebral blood flow regulation is influenced by blood gas content, blood viscosity, body temperature, cardiac output, altitude, cerebrovascular autoregulation, and neurovascular coupling, mediated by chemical agents such as nitric oxide (NO), carbon monoxide (CO), eicosanoid products, oxygen-derived free radicals, endothelins, K+, H+, and adenosine. A better understanding of these factors is valuable for the management of neurocritical care patients. The assessment of both cerebral hemodynamics and metabolism in the acute phase of neurocritical care conditions may contribute to a more effective planning of therapeutic strategies for reducing secondary brain lesions. In this review, the authors have discussed concepts of cerebral hemodynamics, considering aspects of clinical importance.
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Affiliation(s)
- Edson Bor-Seng-Shu
- Division of Neurological Surgery, Hospital das Clínicas, University of São Paulo School of Medicine, São Paulo, SP, Brazil.
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14
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Yoon S, Zuccarello M, Rapoport RM. pCO(2) and pH regulation of cerebral blood flow. Front Physiol 2012; 3:365. [PMID: 23049512 PMCID: PMC3442265 DOI: 10.3389/fphys.2012.00365] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Accepted: 08/24/2012] [Indexed: 11/13/2022] Open
Abstract
CO2 serves as one of the fundamental regulators of cerebral blood flow (CBF). It is widely considered that this regulation occurs through pCO2-driven changes in pH of the cerebral spinal fluid (CSF), with elevated and lowered pH causing direct relaxation and contraction of the smooth muscle, respectively. However, some findings also suggest that pCO2 acts independently of and/or in conjunction with altered pH. This action may be due to a direct effect of CSF pCO2 on the smooth muscle as well as on the endothelium, nerves, and astrocytes. Findings may also point to an action of arterial pCO2 on the endothelium to regulate smooth muscle contractility. Thus, the effects of pH and pCO2 may be influenced by the absence/presence of different cell types in the various experimental preparations. Results may also be influenced by experimental parameters including myogenic tone as well as solutions containing significantly altered HCO3− concentrations, i.e., solutions routinely employed to differentiate the effects of pH from pCO2. In sum, it appears that pCO2, independently and in conjunction with pH, may regulate CBF.
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Affiliation(s)
- Seonghun Yoon
- Research Service, Department of Pharmacology and Cell Biophysics, Veterans Affairs Medical Center, University of Cincinnati College of Medicine Cincinnati, OH, USA
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15
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Impact of COPD exacerbation on cerebral blood flow. Clin Imaging 2012; 36:185-90. [PMID: 22542376 DOI: 10.1016/j.clinimag.2011.08.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Revised: 07/12/2011] [Accepted: 08/26/2011] [Indexed: 11/24/2022]
Abstract
We aimed to investigate the impact of chronic obstructive pulmonary disease (COPD) exacerbation on cerebral blood flow (CBF). In 21 COPD patients - in both exacerbation and stable phases -Doppler ultrasonographies of internal carotid artery (ICA) and vertebral artery (VA) were performed. There were significant differences in total, anterior and posterior CBF, ICA and VA flow volumes in exacerbated COPD compared to stable COPD. Total CBF was correlated with cross-sectional areas of left and right ICA, whereas independent predictor of total CBF was cross-sectional area of right ICA. Increased CBF might indicate cerebral autoregulation-mediated vasodilatation to overcome COPD exacerbation induced hypoxia.
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Gómez-Gonzalo M, Losi G, Brondi M, Uva L, Sato SS, de Curtis M, Ratto GM, Carmignoto G. Ictal but not interictal epileptic discharges activate astrocyte endfeet and elicit cerebral arteriole responses. Front Cell Neurosci 2011; 5:8. [PMID: 21747758 PMCID: PMC3128928 DOI: 10.3389/fncel.2011.00008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 06/06/2011] [Indexed: 12/03/2022] Open
Abstract
Activation of astrocytes by neuronal signals plays a central role in the control of neuronal activity-dependent blood flow changes in the normal brain. The cellular pathways that mediate neurovascular coupling in the epileptic brain remain, however, poorly defined. In a cortical slice model of epilepsy, we found that the ictal, seizure-like discharge, and only to a minor extent the interictal discharge, evokes both a Ca2+ increase in astrocyte endfeet and a vasomotor response. We also observed that rapid ictal discharge-induced arteriole responses were regularly preceded by Ca2+ elevations in endfeet and were abolished by pharmacological inhibition of Ca2+ signals in these astrocyte processes. Under these latter conditions, arterioles exhibited after the ictal discharge only slowly developing vasodilations. The poor efficacy of interictal discharges, compared with ictal discharges, to activate endfeet was confirmed also in the intact in vitro isolated guinea pig brain. Although the possibility of a direct contribution of neurons, in particular in the late response of cerebral blood vessels to epileptic discharges, should be taken into account, our study supports the view that astrocytes are central for neurovascular coupling also in the epileptic brain. The massive endfeet Ca2+ elevations evoked by ictal discharges and the poor response to interictal events represent new information potentially relevant to interpret data from diagnostic brain imaging techniques, such as functional magnetic resonance, utilized in the clinic to localize neural activity and to optimize neurosurgery of untreatable epilepsies.
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Celotto AC, Restini CBA, Capellini VK, Bendhack LM, Evora PRB. Acidosis induces relaxation mediated by nitric oxide and potassium channels in rat thoracic aorta. Eur J Pharmacol 2011; 656:88-93. [PMID: 21300058 DOI: 10.1016/j.ejphar.2011.01.053] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 01/05/2011] [Accepted: 01/25/2011] [Indexed: 10/18/2022]
Abstract
We investigated the mechanism by which extracellular acidification promotes relaxation in rat thoracic aorta. The relaxation response to HCl-induced extracellular acidification (7.4 to 6.5) was measured in aortic rings pre-contracted with phenylephrine (Phe, 10(-6) M) or KCl (45mM). The vascular reactivity experiments were performed in endothelium-intact and denuded rings, in the presence or absence of indomethacin (10(-5) M), L-NAME (10(-4) M), apamin (10(-6) M), and glibenclamide (10(-5) M). The effect of extracellular acidosis (pH 7.0 and 6.5) on nitric oxide (NO) production was evaluated in isolated endothelial cells loaded with diaminofluorescein-FM diacetate (DAF-FM DA, 5μM). The extracellular acidosis failed to induce any changes in the vascular tone of aortic rings pre-contracted with KCl, however, it caused endothelium-dependent and independent relaxation in rings pre-contracted with Phe. This acidosis induced-relaxation was inhibited by L-NAME, apamin, and glibenclamide, but not by indomethacin. The acidosis (pH 7.0 and 6.5) also promoted a time-dependent increase in the NO production by the isolated endothelial cells. These results suggest that extracellular acidosis promotes vasodilation mediated by NO, K(ATP) and SK(Ca), and maybe other K(+) channels in isolated rat thoracic aorta.
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Affiliation(s)
- Andréa C Celotto
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
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Li Y, Horiuchi T, Murata T, Hongo K. Mechanism of alkalosis-induced constriction of rat cerebral penetrating arterioles. Neurosci Res 2011; 70:98-103. [PMID: 21256899 DOI: 10.1016/j.neures.2011.01.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Revised: 12/22/2010] [Accepted: 01/11/2011] [Indexed: 10/18/2022]
Abstract
Cerebral arterioles are in close contact with the supplied tissue and are strong regulators of cerebrovascular tone. Transient ischemia can cause brain intracellular alkalosis producing vasoconstriction. However, the mechanisms of alkalosis-induced cerebral arteriolar constriction are poorly understood. Here, we determined the vascular responses to alkalosis under different conditions by monitoring the internal diameter of pressurized penetrating arterioles isolated from the rat cerebrum with an operating microscope. The roles of Na+/H+ exchanger (NHE), Na+/Ca²+ exchanger (NCX), Na+/K+-adenosine triphosphatase (NKA), and potassium (K+) channels during alkalosis were examined using specific inhibitors. Our results indicated that the extent of constriction of the penetrating arterioles was dependent on alkaline pH. Moreover, the alkalosis-induced vasoconstriction was significantly attenuated by inhibitors of NHE, NCX, and NKA, but not K+ channel inhibitors. Therefore, we concluded that NHE, NKA, and NCX are important regulators involved in alkalosis-induced vasoconstriction of rat cerebral penetrating arterioles.
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Affiliation(s)
- Yuhui Li
- Department of Neurosurgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan
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Choi SS. Effect of pH Change on Vascular Smooth Muscle Contractility in Rat Superior Mesenteric Artery and Its Branches. THE KOREAN JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2010. [DOI: 10.5090/kjtcs.2010.43.4.345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Soo Seung Choi
- Department of Thoracic and Cardiovascular Surgery, Ewha Womans University School of Medicine
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20
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Celotto AC, Capellini VK, Restini CBA, Baldo CF, Bendhack LM, Evora PRB. Extracellular alkalinization induces endothelium-derived nitric oxide dependent relaxation in rat thoracic aorta. Nitric Oxide 2010; 23:269-74. [PMID: 20682356 DOI: 10.1016/j.niox.2010.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 07/10/2010] [Accepted: 07/29/2010] [Indexed: 10/19/2022]
Abstract
AIM To investigate the mechanism through which the extracellular alkalinization promotes relaxation in rat thoracic aorta. METHODS The relaxation response to NaOH-induced extracellular alkalinization (7.4-8.5) was measured in aortic rings pre-contracted with phenylephrine (Phe, 10(-6) M). The vascular reactivity experiments were performed in endothelium-intact and -denuded rings, in the presence or and absence of indomethacin (10(-5) M), NG-nitro-l-arginine methyl ester (L-NAME, 10(-4) M), N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide/HCl (W-7, 10(-7) M), 2,5-dimethylbenzimidazole (DMB, 2×10(-5) M) and methyl-β-cyclodextrin (10(-2) M). In addition, the effects of NaOH-induced extracellular alkalinization (pH 8.0 and 8.5) on the intracellular nitric oxide (NO) concentration was evaluated in isolated endothelial cells loaded with diaminofluorescein-FM diacetate (DAF-FM DA, 5 μM), in the presence and absence of DMB (2×10(-5) M). RESULTS The extracellular alkalinization failed to induce any change in vascular tone in aortic rings pre-contracted with KCl. In rings pre-contracted with Phe, the extracellular alkalinization caused relaxation in the endothelium-intact rings only, and this relaxation was maintained after cyclooxygenase inhibition; completely abolished by the inhibition of nitric oxide synthase (NOS), Ca(2+)/calmodulin and Na(+)/Ca(2+) exchanger (NCX), and partially blunted by the caveolae disassembly. CONCLUSIONS These results suggest that, in rat thoracic aorta, that extracellular alkalinization with NaOH activates the NCX reverse mode of endothelial cells in rat thoracic aorta, thereby the intracellular Ca(2+) concentration and activating the Ca(2+)/calmodulin-dependent NOS. In turn, NO is released promoting relaxation.
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Affiliation(s)
- A C Celotto
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil
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Effect of cell-free layer variation on arteriolar wall shear stress. Ann Biomed Eng 2010; 39:359-66. [PMID: 20652744 PMCID: PMC3010219 DOI: 10.1007/s10439-010-0130-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 07/12/2010] [Indexed: 12/31/2022]
Abstract
Relationship between a cell-free layer and wall shear stress (WSS) in small arterioles has been of interest in microcirculatory research. However, influence of temporal variation in the cell-free layer width on the WSS in vivo has not been fully elucidated. In this study, we tested the hypothesis that the layer variation would increase the WSS, and this effect would be enhanced by red blood cell aggregation. The cell-free layer width in arterioles (29.5–67.1 μm ID) in rat cremaster muscles were obtained with a high-speed video camera, and the layer width data were introduced into WSS estimation. Dextran 500 was administrated to elevate the aggregation level of red blood cells to those seen in normal human blood. The variation of the layer was quantified by the variability (coefficient of variation), and its effect on WSS was studied under normal and reduced flow conditions. We found that the dextran-induced red blood cell aggregation significantly elevated the variability (p < 0.01) at low pseudoshear rates of 9.2 ± 0.6 s−1. The WSS estimated without taking account of the variability showed underestimation of its value than that of with consideration of the variability under all flow conditions, and this effect became more pronounced with increasing the variability. The variation of the cell-free layer should, therefore, be considered in the determination of the WSS particularly in the presence of red blood cell aggregation under reduced flow condition.
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Wu GB, Zhou EX, Qing DX. Tanshinone IIA elicited vasodilation in rat coronary arteriole: Roles of nitric oxide and potassium channels. Eur J Pharmacol 2009; 617:102-7. [DOI: 10.1016/j.ejphar.2009.06.046] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 06/15/2009] [Accepted: 06/17/2009] [Indexed: 12/28/2022]
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Differential responses of porcine anterior spinal and middle cerebral arteries to carbon dioxide and pH. Crit Care Med 2009; 37:987-92. [PMID: 19237908 DOI: 10.1097/ccm.0b013e3181961330] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Dysfunction of the anterior spinal arteries (ASAs) may induce paresis or paraplegia after thoracoabdominal aortic aneurysm or spine surgery. However, there have been no reports of the effects of CO2 and pH on ASAs. Information on these effects on ASAs might contribute to the perioperative management or critical care of spinal cord function. Thus, we investigated the effects of CO2 and pH on the vasomotor tone of ASAs and the third branch of the middle cerebral artery (bMCA). DESIGN Prospective study of the effects of CO2 and pH on vasomotor response of porcine ASA and bMCA in vitro. SETTING University laboratories. SUBJECTS Porcine heads and spinal cords obtained from a slaughterhouse. INTERVENTION ASAs and bMCAs were isolated, and changes in the intraluminal region of these pressurized arteries ( approximately 80 mm Hg) were observed for 30 minutes after perfusion with a solution saturated with various concentrations of CO2 and pH. MEASUREMENTS AND MAIN RESULTS Respiratory acidosis (pH/Pco2 approximately 7.10-7.15/ approximately 60-80 mm Hg) constricted the ASAs, followed by a partial but gradual decrease in tone, whereas the bMCAs were exclusively dilated. The respiratory alkalosis (pH/Pco2 approximately 7.60/ approximately 20 mm Hg) did not influence ASA tone. Vasoconstriction of the ASAs induced by respiratory acidosis was abolished by removal of the endothelium, but not by N-nitro-L-arginine (1 microM). Respiratory acidosis dilated the ASAs in all preparations treated with ONO-3708 (1 microM), a specific thromboxane A2 receptor antagonist, and OKY-046 (1 microM), a specific thromboxane synthase inhibitor. Metabolic acidosis (pH/Pco2 approximately 7.10/ approximately 40 mm Hg) caused dilation of both bMCAs and ASAs, which was abolished by glibenclamide (1 microM). CONCLUSIONS CO2-induced endothelium-dependent constriction in porcine ASAs through releasing thromboxane A2-like substance(s). Thus, hypercarbia might not be favorable for the perioperative or critical care management of spinal cord function during thoracoabdominal aortic aneurysm and spine surgery.
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Toda N, Ayajiki K, Okamura T. Cerebral Blood Flow Regulation by Nitric Oxide: Recent Advances. Pharmacol Rev 2009; 61:62-97. [DOI: 10.1124/pr.108.000547] [Citation(s) in RCA: 268] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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Mizuno R, Watanabe S, Ohhashi T. NT-702, a selective phosphodiesterase 3 inhibitor, dilates rabbit spinal arterioles via endothelium-dependent and endothelium-independent mechanisms. J Physiol Sci 2008; 58:229-37. [PMID: 18558016 DOI: 10.2170/physiolsci.rp003808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 06/16/2008] [Indexed: 11/05/2022]
Abstract
We investigated the effects of NT-702, a selective phosphodiesterase (PDE) 3 inhibitor, on arterioles isolated from rabbit lumbar spinal cords. NT-702 caused a dose-dependent dilation of the isolated spinal arterioles. The disruption of endothelium produced a significant reduction of higher concentrations (10(-7) and 10(-6) M), but not lower concentrations (less than 10(-8) M), of NT-702-induced vasodilation. The NT-702-induced vasodilation of the arterioles with endothelium was not affected by pretreatment with an inhibitor of nitric oxide, cyclooxygenase, or cytochrome P-450 monooxygenase. In contrast, catalase reduced significantly the higher concentrations of NT-702-induced vasodilation only. Tetraethylammonium (TEA) completely reduced the lower concentrations of NT-702-induced vasodilation, but decreased only partially the higher concentrations of NT-702-induced vasodilation of the arterioles with endothelium. Hydrogen peroxide dilated significantly the isolated arterioles with endothelium, the response of which was reduced significantly by TEA. KT5720 (a selective protein kinase inhibitor) significantly decreased both the lower and higher concentrations of NT-702-induced vasodilation of the arterioles with endothelium. The findings suggest that NT-702 dose-dependently dilated the isolated spinal arterioles of rabbits via endothelium-dependent and endothelium-independent mechanisms. Protein kinase A (PKA)- and TEA-sensitive K(+) channels may be involved in the NT-702-induced vasodilation. Moreover, hydrogen peroxide may contribute in part to the endothelium-dependent higher concentrations of NT-702-induced vasodilation.
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Affiliation(s)
- Risuke Mizuno
- Department of Physiology, Shinshu University School of Medicine, Matsumoto, 390-8621 Japan
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26
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Moore S, David T. A model of autoregulated blood flow in the cerebral vasculature. Proc Inst Mech Eng H 2008; 222:513-30. [DOI: 10.1243/09544119jeim298] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The circle of Willis is a ring-like arterial structure located in the base of the brain, and is responsible for the distribution of oxygenated blood throughout the cerebral mass. Among the general population, approximately 50 per cent have a complete circle of Willis; for the others a multitude of possible anatomical variations are present, with absent or hypoplastic vessels being common. Certain conditions such as a build-up of atherosclerotic plaque on the arterial wall can result in ischaemic damage and stroke-like symptoms. A three-dimensional computer model has been developed based on the results of magnetic resonance imaging data, incorporating a numerical algorithm to simulate the body's autoregulation mechanism, such that oxygen delivery to the cerebral territories can be predicted in response events, leading to a reduction in cerebral blood flow. Sample results are presented for combinations of occlusion and stenosis.
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Affiliation(s)
- S Moore
- Centre for Bioengineering, Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
| | - T David
- Centre for Bioengineering, Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
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Celotto A, Capellini V, Baldo C, Dalio M, Rodrigues A, Evora P. Effects of acid-base imbalance on vascular reactivity. Braz J Med Biol Res 2008; 41:439-45. [DOI: 10.1590/s0100-879x2008005000026] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Accepted: 05/29/2008] [Indexed: 11/22/2022] Open
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Cankar K, Strucl M. The effect of glibenclamide on cutaneous laser-Doppler flux. Microvasc Res 2008; 75:97-103. [PMID: 17675187 DOI: 10.1016/j.mvr.2007.06.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Revised: 05/28/2007] [Accepted: 06/15/2007] [Indexed: 11/26/2022]
Abstract
The K(ATP) channels play a crucial role in regulation of vascular tone in conditions of hypoxia. Whether they contribute to peripheral blood flow regulation in human cutaneous microcirculation during a non-hypoxic state is the matter of conflicting in vivo studies that have used plethysmographic method. Our aim was therefore to elucidate the role of K(ATP) channels in human skin microcirculation in three different conditions that evoke different interplays of vascular mechanisms; during resting conditions, during the postocclusive vasodilatation and in the vasoconstriction response to local cold exposure. The laser-Doppler (LD) skin response was monitored in 12 healthy volunteers on the skin of the fingertips of both hands at rest, after the release of an 8-min digital arteries occlusion, and during local cooling of one hand at 15 degrees C. We compared the direct (at the measuring site) and the indirect (at the contralateral non-cooled hand) LD flux response after intradermal microinjection of saline solution (1 mul) and after a microinjection of the K(ATP) channel blocker glibenclamide (8 muM saturated solution) at the measuring site after obtaining the dose-dependent effect of glibenclamide. The effect of the saline solution was used as a reference value. There was a statistically significant lower resting LD flux after the microinjection of glibenclamide 273.6+/-36 PU when compared to the values obtained after the application of the saline solution 375.8+/-31 PU (paired t-test, p=0.016). Glibenclamide also significantly reduced the relative area under the LD flux curve during the PRH response 14551+/-2508 PU*s vs. 6402+/-1476 PU*s (paired t-test, p=0.01) and increased the principal frequency of postocclusive PRH oscillations 0.0931+/-0.01 Hz vs. 0.1309+/-0.02 Hz (p=0.01). In addition, glibenclamide significantly decreased the LD flux during both the direct and indirect response to local cold exposure when compared to the application of saline solution (paired t-test, p<0.01). Our results support the conjecture that ATP sensitive K(+) channels are importantly involved in blood flow regulation of human skin microcirculation in PRH response, in resting conditions as well as in microvascular local cold response.
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Affiliation(s)
- Ksenija Cankar
- Institute of Physiology, School of Medicine, Zaloska 4, 1000 Ljubljana, Slovenia.
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29
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Sun H, Zhao H, Sharpe GM, Arrick DM, Mayhan WG. Influence of chronic alcohol consumption on inward rectifier potassium channels in cerebral arterioles. Microvasc Res 2007; 75:367-72. [PMID: 18191159 DOI: 10.1016/j.mvr.2007.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 10/23/2007] [Accepted: 11/26/2007] [Indexed: 11/17/2022]
Abstract
Inward rectifier potassium (K(IR)) channels appear to play an important role in the regulation of cerebral blood flow. Our goal was to examine the influence of chronic alcohol exposure on K(IR) channels in cerebral arterioles. Sprague-Dawley rats were fed liquid diets with or without alcohol for 8-12 weeks. Using intravital microscope, we measured diameter of pial arterioles in response to an inhibitor, BaCl(2), and an activator, KCl, of K(IR) channels in the absence and presence of a scavenger of reactive oxygen species, tempol, or an inhibitor of NAD(P)H oxidase, apocynin. Application of BaCl(2) (30 and 100 microM) produced dose-related vasoconstriction in non-alcohol-fed, but not in alcohol-fed rats. In addition, application of KCl (3, 10, and 30 mM) produced dose-related dilation in non-alcohol-fed and alcohol-fed rats, but the magnitude of vasodilatation was less in alcohol-fed rats. In contrast, nitroglycerin-induced vasodilation was similar in non-alcohol-fed and alcohol-fed rats. Superfusion of cranial window with tempol (0.1 mM) or apocynin (1 mM) did not alter baseline diameter and nitroglycerin-induced dilation of pial arterioles in non-alcohol-fed and alcohol-fed rats but significantly improved impaired KCl-induced dilation in alcohol-fed rats. Our findings suggest that chronic alcohol consumption impairs the role of K(IR) channels in basal tone and KCl-induced dilation of cerebral arterioles. In addition, impaired KCl-induced dilation of cerebral arterioles during alcohol consumption may be related to enhanced release of oxygen-derived free radicals via NAD(P)H oxidase.
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Affiliation(s)
- Hong Sun
- Department of Cellular and Integrative Physiology 985850, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA.
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30
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Abstract
The construction of a computational model of the human brain circulation is described. We combine an existing model of the biophysics of the circulatory system, a basic model of brain metabolic biochemistry, and a model of the functioning of vascular smooth muscle (VSM) into a single model. This represents a first attempt to understand how the numerous different feedback pathways by which cerebral blood flow is controlled interact with each other. The present work comprises the following: Descriptions of the physiology underlying the model; general comments on the processes by which this physiology is translated into mathematics; comments on parameter setting; and some simulation results. The simulations presented are preliminary, but show qualitative agreement between model behaviour and experimental results.
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Affiliation(s)
- Murad Banaji
- Department of Medical Physics and Bioengineering, University College London, Gower Street, London WC1E 6BT, UK.
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31
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Kim MY, Liang GH, Kim JA, Park SH, Hah JS, Suh SH. Contribution of Na+-K+ pump and KIR currents to extracellular pH-dependent changes of contractility in rat superior mesenteric artery. Am J Physiol Heart Circ Physiol 2005; 289:H792-800. [PMID: 15833810 DOI: 10.1152/ajpheart.00050.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We compared the branches and trunk of rat superior mesenteric artery (SMA) with respect to extracellular pH (pHo)-dependent changes in vascular contractility. Decreases in pHo from 7.8 to 6.4 significantly reduced apparent affinity (pD2) to norepinephrine (NE) and maximal contraction by NE, which were more prominent in larger-diameter arteries. On the other hand, decreases in pHo significantly reduced Ba2+-sensitive K+-induced relaxation (which was evoked by elevation of extracellular K+ concentration from 6 to 12 mM) in the first branch and inhibited inwardly rectifying K+ (KIR) currents in cultured smooth muscle cells (SMCs) of SMA. RT-PCR revealed transcripts for Kir2.1 in the SMCs. Real-time PCR analysis revealed 6.1-, 3.3-, and 2.2-fold increases in the Kir2.1 mRNA-to-β-actin mRNA ratios of SMCs of the third, second, and first branches, respectively, vs. the corresponding relative levels of trunk SMCs. The magnitudes of K+-induced relaxation were significantly greater in smaller-diameter arteries, and there was a strong correlation between the transcript levels of Kir2.1 and K+-induced relaxation. A decrease in pHo reduced ouabain-sensitive K+-induced relaxation and ouabain-induced contraction. A decrease in pHo from 7.4 to 6.4 depolarized membrane potential of the cultured SMCs. From these results, we conclude that an increase in pHo activates KIR currents and the Na+-K+ pump, which then reduces vascular contractility. Inasmuch as KIR channel densities are significantly greater in smaller-diameter arteries, the reduction in vascular contractility on increasing pHo is more pronounced in smaller-diameter arteries.
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Affiliation(s)
- Moon Young Kim
- Department of Physiology and Medical Research Institute, College of Medicine, Ewha Women's Univ., 911-1 Mok-6-dong, Yang Chun-gu, Seoul, Republic of Korea, 158-710
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Sun H, Fang Q, Mayhan WG. Inward Rectifier Potassium Channels in the Basilar Artery During Chronic Alcohol Consumption. Alcohol Clin Exp Res 2004; 28:1557-61. [PMID: 15597089 DOI: 10.1097/01.alc.0000141807.81798.b0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The goals of this study were to determine whether chronic alcohol consumption alters potassium channel-mediated reactivity in the basilar artery and to determine a potential mechanism that might account for the effects of alcohol on the basilar artery. METHODS Sprague-Dawley rats were fed liquid diets with or without alcohol for 2 to 3 months. We measured diameter of the basilar artery in response to potassium channel inhibitors and activators. Protein level of inward rectifier potassium channel subunit Kir2.1 in the basilar artery was determined by Western blot. RESULTS Topical application of glibenclamide (1 and 10 microM) significantly constricted the basilar artery at high dose; iberiotoxin (10 and 100 nM), 4-AP (0.1 and 1 mM), and BaCl2 (1 and 10 microM) produced dose-related constriction in both non-alcohol-fed and alcohol-fed rats. However, the magnitude of constriction in response to BaCl2 was significantly less in alcohol-fed rats compared with non-alcohol-fed rats. Topical application of KCl (1 and 3 mM), cromakalim (0.1 and 0.3 microM), and NS1619 (10 and 30 microM) induced dose-related dilation in non-alcohol-fed and alcohol-fed rats. However, the magnitude of vasodilation in response to KCl was significantly less in alcohol-fed rats compared with non-alcohol-fed rats. In addition, Kir2.1 protein level in the basilar artery was significantly reduced in alcohol-fed compared with non-alcohol-fed rats. CONCLUSIONS These findings suggest that chronic alcohol consumption reduces expression of inward rectifier potassium channels and inhibits KIR channel-mediated dilation in the basilar artery.
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Affiliation(s)
- Hong Sun
- Department of Physiology and Biophysics, University of Nebraska Medical Center, Omaha, Nebraska 68198-5850, USA.
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Rosenblum WI, Wei EP, Kontos HA. Vasodilation of brain surface arterioles by blockade of Na–H+ antiport and its inhibition by inhibitors of KATP channel openers. Brain Res 2004; 1005:77-83. [PMID: 15044067 DOI: 10.1016/j.brainres.2004.01.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/28/2004] [Indexed: 11/19/2022]
Abstract
Pial artrioles of rats were monitored in vivo and found to dilate in dose-dependent fashion upon application of either benzamil or ethyl isopropyl amiloride, both of which are inhibitors of the sodium-hydrogen antiport. Antiport blockade is known to decrease the internal pH of vascular smooth muscle (VSM). The dilation was blocked by 1 microm glibenclamide, which in that dose is a selective inhibitor of ATP sensitive potassium channels (K(ATP)). The nitric oxide synthase inhibitor nitro-l arginine (l-NNA) also blocked the response. Previous studies of this preparation under the same experimental conditions showed that l-NNA inhibited dilation by K(ATP) openers and that nitric oxide had no permissive action in this setting. Moreover, one study by others has demonstrated a pH sensitive site on the internal surface of K(ATP) while another study by others has demonstrated that sodium propionate, a direct acidifier of the cell, dilates rat basilar artery in K(ATP)-dependent fashion. Therefore, the present data support the following conclusions: decrease of internal pH dilates brain arterioles; the response is K(ATP) dependent; in some situations, inhibitors of nitric oxide synthase can inhibit K(ATP) and K(ATP)-dependent dilations including those produced by decrease of internal pH.
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Affiliation(s)
- William I Rosenblum
- Department of Pathology (Neuropathology), Virginia Commonwealth University Medical Center-Medical College of Virginia Campus, Richmond VA 23298-0017, USA.
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Lindauer U, Vogt J, Schuh-Hofer S, Dreier JP, Dirnagl U. Cerebrovascular vasodilation to extraluminal acidosis occurs via combined activation of ATP-sensitive and Ca2+-activated potassium channels. J Cereb Blood Flow Metab 2003; 23:1227-38. [PMID: 14526233 DOI: 10.1097/01.wcb.0000088764.02615.b7] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Albeit controversial, it has been suggested by several authors that nitric oxide (NO) serves as a permissive factor in the cerebral blood flow response to systemic hypercapnia. Potassium channels are important regulators of cerebrovascular tone and may be modulated by a basal perivascular NO level. To elucidate the functional targets of the proposed NO modulation during hypercapnia-induced vasodilation, the authors performed experiments in isolated, cannulated, and pressurized rat middle cerebral arteries (MCA). Extracellular pH was reduced from 7.4 to 7.0 in the extraluminal bath to induce NO dependent vasodilation. Acidosis increased vessel diameter by 35 +/- 10%. In separate experiments, ATP-sensitive potassium channels (KATP) were blocked by extraluminal application of glibenclamide (Glib), Ca2+-activated potassium channels (KCa) by tetraethylammonium (TEA), voltage-gated potassium channels (Kv) by 4-aminopyridine, and inward rectifier potassium channels (KIR) by BaCl2. Na+-K+-ATP-ase was inhibited by ouabain. Application of TEA slightly constricted the arteries at pH 7.4 and slightly but significantly attenuated the vasodilation to acidosis. Inhibition of the other potassium channels or Na+-K+-ATP-ase had no effect. Combined blockade of KATP and KCa channels further reduced resting diameter, and abolished acidosis induced vasodilation. The authors conclude that mainly KCa channels are active under resting conditions. KATP and KCa channels are responsible for vasodilation to acidosis. Activity of one of these potassium channel families is sufficient for vasodilation to acidosis, and only combined inhibition completely abolishes vasodilation. During NO synthase inhibition, dilation to the KATP channel opener pinacidil or the KCa channel opener NS1619 was attenuated or abolished, respectively. The authors suggest that a basal perivascular NO level is necessary for physiologic KATP and KCa channel function in rat MCA. Future studies have to elucidate whether this NO dependent effect on KATP and KCa channel function is a principle mechanism of NO induced modulation of cerebrovascular reactivity and whether the variability of findings in the literature concerning a modulatory role of NO can be explained by different levels of vascular NO/cGMP concentrations within the cerebrovascular tree.
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Affiliation(s)
- Ute Lindauer
- Experimental Neurology, Charité, Humboldt-Universität, Berlin, Germany.
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