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Ca 2+-Activated K + Channels and the Regulation of the Uteroplacental Circulation. Int J Mol Sci 2023; 24:ijms24021349. [PMID: 36674858 PMCID: PMC9867535 DOI: 10.3390/ijms24021349] [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: 12/14/2022] [Revised: 01/06/2023] [Accepted: 01/08/2023] [Indexed: 01/13/2023] Open
Abstract
Adequate uteroplacental blood supply is essential for the development and growth of the placenta and fetus during pregnancy. Aberrant uteroplacental perfusion is associated with pregnancy complications such as preeclampsia, fetal growth restriction (FGR), and gestational diabetes. The regulation of uteroplacental blood flow is thus vital to the well-being of the mother and fetus. Ca2+-activated K+ (KCa) channels of small, intermediate, and large conductance participate in setting and regulating the resting membrane potential of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) and play a critical role in controlling vascular tone and blood pressure. KCa channels are important mediators of estrogen/pregnancy-induced adaptive changes in the uteroplacental circulation. Activation of the channels hyperpolarizes uteroplacental VSMCs/ECs, leading to attenuated vascular tone, blunted vasopressor responses, and increased uteroplacental blood flow. However, the regulation of uteroplacental vascular function by KCa channels is compromised in pregnancy complications. This review intends to provide a comprehensive overview of roles of KCa channels in the regulation of the uteroplacental circulation under physiological and pathophysiological conditions.
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Hirunpattarasilp C, Barkaway A, Davis H, Pfeiffer T, Sethi H, Attwell D. Hyperoxia evokes pericyte-mediated capillary constriction. J Cereb Blood Flow Metab 2022; 42:2032-2047. [PMID: 35786054 PMCID: PMC9580167 DOI: 10.1177/0271678x221111598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Oxygen supplementation is regularly prescribed to patients to treat or prevent hypoxia. However, excess oxygenation can lead to reduced cerebral blood flow (CBF) in healthy subjects and worsen the neurological outcome of critically ill patients. Most studies on the vascular effects of hyperoxia focus on arteries but there is no research on the effects on cerebral capillary pericytes, which are major regulators of CBF. Here, we used bright-field imaging of cerebral capillaries and modeling of CBF to show that hyperoxia (95% superfused O2) led to an increase in intracellular calcium level in pericytes and a significant capillary constriction, sufficient to cause an estimated 25% decrease in CBF. Although hyperoxia is reported to cause vascular smooth muscle cell contraction via generation of reactive oxygen species (ROS), endothelin-1 and 20-HETE, we found that increased cytosolic and mitochondrial ROS levels and endothelin release were not involved in the pericyte-mediated capillary constriction. However, a 20-HETE synthesis blocker greatly reduced the hyperoxia-evoked capillary constriction. Our findings establish pericytes as regulators of CBF in hyperoxia and 20-HETE synthesis as an oxygen sensor in CBF regulation. The results also provide a mechanism by which clinically administered oxygen can lead to a worse neurological outcome.
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Affiliation(s)
- Chanawee Hirunpattarasilp
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, UK.,Princess Srisavangavadhana College of Medicine, Chulabhorn Royal Academy, Bangkok, Thailand
| | - Anna Barkaway
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, UK.,Princess Srisavangavadhana College of Medicine, Chulabhorn Royal Academy, Bangkok, Thailand
| | - Harvey Davis
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, UK.,Princess Srisavangavadhana College of Medicine, Chulabhorn Royal Academy, Bangkok, Thailand
| | - Thomas Pfeiffer
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, UK
| | - Huma Sethi
- Division of Neurosurgery, UCL Queen Square Institute of Neurology, Queen Square, London, UK
| | - David Attwell
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, UK
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Yi X, Zhou Q, Qing T, Ming B, Lin J, Li J, Lin J. 20-hydroxyeiscosatetraenoic acid may be as a predictor of malignant middle cerebral artery infarction in patients with massive middle cerebral artery infarction. BMC Neurol 2021; 21:437. [PMID: 34753429 PMCID: PMC8576932 DOI: 10.1186/s12883-021-02456-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 10/20/2021] [Indexed: 11/10/2022] Open
Abstract
Background Early identification of massive middle cerebral artery infarction (MCAI) at risk for malignant MCAI (m-MCAI) may be useful in selecting patients for aggressive therapies. The aim of this study was to determine whether CYP metabolites may help to predict impending m-MCAI. Methods This is a prospective, two-center observational study in 256 patients with acute massive MCAI. Plasma levels of 20-hydroxyeicosatetraenoic acid (20-HETE), epoxyeicosatrienoic acids, and dihydroxyeicosatrienoic acids were measured at admission. Brain computed tomography (CT) was performed at admission and repeated between day 3 and 7, or earlier if there was neurological deterioration. The primary outcome was m-MCAI. The m-MCAI was diagnosed when follow-up brain CT detected a more than two-thirds space-occupying MCAI with midline shift, compression of the basal cisterns, and neurological worsening. Results In total of 256 enrolled patients, 77 (30.1%) patients developed m-MCAI. Among the 77 patients with m-MCAI, 60 (77.9%) patients died during 3 months of stroke onset. 20-HETE level on admission was significantly higher in patients with m-MCAI than those without m-MCAI. There was an increase in the risk of m-MCAI with increase of 20-HETE levels. The third and fourth quartiles of 20-HETE levels were independent predictors of m-MCAI (OR: 2.86; 95% CI: 1.16 – 6.68; P = 0.025, and OR: 4.23; 95% CI: 1.35 – 8.26; P = 0.002, respectively). Conclusions Incidence of m-MCAI was high in patients with massive MCAI and the prognosis of m-MCAI is very poor. Elevated plasma 20-HETE may be as a predictor for m-MCAI in acute massive MCAI, and it might useful in clinical practice in therapeutic decision making.
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Affiliation(s)
- Xingyang Yi
- Department of Neurology, People's Hospital of Deyang City, Deyang, 618000, Sichuan, China
| | - Qiang Zhou
- Department of Neurology, the Third Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325200, Zhejiang, China
| | - Ting Qing
- Department of Neurology, People's Hospital of Deyang City, Deyang, 618000, Sichuan, China
| | - Bing Ming
- Department of Radiology, People's Hospital of Deyang City, Deyang, 618000, Sichuan, China
| | - Jing Lin
- Department of Neurology, the Third Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325200, Zhejiang, China
| | - Jie Li
- Department of Neurology, People's Hospital of Deyang City, Deyang, 618000, Sichuan, China
| | - Jie Lin
- Department of PET/CT, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, China.
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Stackhouse TL, Mishra A. Neurovascular Coupling in Development and Disease: Focus on Astrocytes. Front Cell Dev Biol 2021; 9:702832. [PMID: 34327206 PMCID: PMC8313501 DOI: 10.3389/fcell.2021.702832] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 06/09/2021] [Indexed: 12/14/2022] Open
Abstract
Neurovascular coupling is a crucial mechanism that matches the high energy demand of the brain with a supply of energy substrates from the blood. Signaling within the neurovascular unit is responsible for activity-dependent changes in cerebral blood flow. The strength and reliability of neurovascular coupling form the basis of non-invasive human neuroimaging techniques, including blood oxygen level dependent (BOLD) functional magnetic resonance imaging. Interestingly, BOLD signals are negative in infants, indicating a mismatch between metabolism and blood flow upon neural activation; this response is the opposite of that observed in healthy adults where activity evokes a large oversupply of blood flow. Negative neurovascular coupling has also been observed in rodents at early postnatal stages, further implying that this is a process that matures during development. This rationale is consistent with the morphological maturation of the neurovascular unit, which occurs over a similar time frame. While neurons differentiate before birth, astrocytes differentiate postnatally in rodents and the maturation of their complex morphology during the first few weeks of life links them with synapses and the vasculature. The vascular network is also incomplete in neonates and matures in parallel with astrocytes. Here, we review the timeline of the structural maturation of the neurovascular unit with special emphasis on astrocytes and the vascular tree and what it implies for functional maturation of neurovascular coupling. We also discuss similarities between immature astrocytes during development and reactive astrocytes in disease, which are relevant to neurovascular coupling. Finally, we close by pointing out current gaps in knowledge that must be addressed to fully elucidate the mechanisms underlying neurovascular coupling maturation, with the expectation that this may also clarify astrocyte-dependent mechanisms of cerebrovascular impairment in neurodegenerative conditions in which reduced or negative neurovascular coupling is noted, such as stroke and Alzheimer’s disease.
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Affiliation(s)
- Teresa L Stackhouse
- Department of Neurology, Jungers Center for Neurosciences Research, Oregon Health & Science University, Portland, OR, United States
| | - Anusha Mishra
- Department of Neurology, Jungers Center for Neurosciences Research, Oregon Health & Science University, Portland, OR, United States.,Knight Cardiovascular Institute, Oregon Health & Sciences University, Portland, OR, United States
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5
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Price BR, Johnson LA, Norris CM. Reactive astrocytes: The nexus of pathological and clinical hallmarks of Alzheimer's disease. Ageing Res Rev 2021; 68:101335. [PMID: 33812051 PMCID: PMC8168445 DOI: 10.1016/j.arr.2021.101335] [Citation(s) in RCA: 62] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 01/21/2021] [Accepted: 03/20/2021] [Indexed: 02/06/2023]
Abstract
Astrocyte reactivity is a hallmark of neuroinflammation that arises with Alzheimer’s disease (AD) and nearly every other neurodegenerative condition. While astrocytes certainly contribute to classic inflammatory processes (e.g. cytokine release, waste clearance, and tissue repair), newly emerging technologies for measuring and targeting cell specific activities in the brain have uncovered essential roles for astrocytes in synapse function, brain metabolism, neurovascular coupling, and sleep/wake patterns. In this review, we use a holistic approach to incorporate, and expand upon, classic neuroinflammatory concepts to consider how astrocyte dysfunction/reactivity modulates multiple pathological and clinical hallmarks of AD. Our ever-evolving understanding of astrocyte signaling in neurodegeneration is not only revealing new drug targets and treatments for dementia but is suggesting we reimagine AD pathophysiological mechanisms.
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Affiliation(s)
- Brittani R Price
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA, 02111, USA
| | - Lance A Johnson
- Sanders-Brown Center on Aging, University of Kentucky, 800 S. Limestone St., Lexington, KY, 40356, USA; Department of Physiology, University of Kentucky, College of Medicine, UK Medical Center MN 150, Lexington, KY, 40536, USA
| | - Christopher M Norris
- Sanders-Brown Center on Aging, University of Kentucky, 800 S. Limestone St., Lexington, KY, 40356, USA; Department of Pharmacology and Nutritional Sciences, University of Kentucky, College of Medicine, UK Medical Center MN 150, Lexington, KY, 40536, USA.
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6
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Kursun O, Karatas H, Bariskaner H, Ozturk S. Arachidonic Acid Metabolites in Neurologic Disorders. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2021; 21:150-159. [PMID: 33982658 DOI: 10.2174/1871527320666210512013648] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 11/23/2020] [Accepted: 12/07/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND & OBJECTIVE Arachidonic acid (ARA) is essential for the fluidity, selective permeability, and flexibility of the cell membrane. It is an important factor for the function of all cells, particularly in the nervous system, immune system, and vascular endothelium. ARA, after docosahexaenoic acid, is the second most common polyunsaturated fatty acid in the phospholipids of the nerve cell membrane. ARA metabolites have many kinds of physiologic roles. The major action of ARA metabolites is the promotion of the acute inflammatory response, mediated by the production of pro-inflammatory mediators such as PGE2 and PGI2, followed by the formation of lipid mediators, which have pro-resolving effects. Another important action of ARA derivatives, especially COX, is the regulation of vascular reactivity through PGs and TXA2. There is significant involvement of ARA metabolites in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and neuropsychiatric disorders. ARA derivatives also make an important contribution to acute stroke, global ischemia, subarachnoid hemorrhage, and anticoagulation- related hemorrhagic transformation. CONCLUSION In this review, we discuss experimental and human study results of neurologic disorders related to ARA and its metabolites in line with treatment options.
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Affiliation(s)
- Oguzhan Kursun
- Ankara City Hospital, Neurology Clinic, Neurointensive Care Unit, Neurology, Turkey
| | - Hulya Karatas
- Hacettepe University, Institute of Neurological Sciences and Psychiatry Neurology, Turkey
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Ottolini M, Sonkusare SK. The Calcium Signaling Mechanisms in Arterial Smooth Muscle and Endothelial Cells. Compr Physiol 2021; 11:1831-1869. [PMID: 33792900 PMCID: PMC10388069 DOI: 10.1002/cphy.c200030] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The contractile state of resistance arteries and arterioles is a crucial determinant of blood pressure and blood flow. Physiological regulation of arterial contractility requires constant communication between endothelial and smooth muscle cells. Various Ca2+ signals and Ca2+ -sensitive targets ensure dynamic control of intercellular communications in the vascular wall. The functional effect of a Ca2+ signal on arterial contractility depends on the type of Ca2+ -sensitive target engaged by that signal. Recent studies using advanced imaging methods have identified the spatiotemporal signatures of individual Ca2+ signals that control arterial and arteriolar contractility. Broadly speaking, intracellular Ca2+ is increased by ion channels and transporters on the plasma membrane and endoplasmic reticular membrane. Physiological roles for many vascular Ca2+ signals have already been confirmed, while further investigation is needed for other Ca2+ signals. This article focuses on endothelial and smooth muscle Ca2+ signaling mechanisms in resistance arteries and arterioles. We discuss the Ca2+ entry pathways at the plasma membrane, Ca2+ release signals from the intracellular stores, the functional and physiological relevance of Ca2+ signals, and their regulatory mechanisms. Finally, we describe the contribution of abnormal endothelial and smooth muscle Ca2+ signals to the pathogenesis of vascular disorders. © 2021 American Physiological Society. Compr Physiol 11:1831-1869, 2021.
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Affiliation(s)
- Matteo Ottolini
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia, USA
| | - Swapnil K Sonkusare
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia, USA.,Department of Molecular Physiology & Biological Physics, University of Virginia, Charlottesville, Virginia, USA.,Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia, USA
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8
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Abstract
The blood-brain barrier (BBB) protects the vertebrate central nervous system from harmful blood-borne, endogenous and exogenous substances to ensure proper neuronal function. The BBB describes a function that is established by endothelial cells of CNS vessels in conjunction with pericytes, astrocytes, neurons and microglia, together forming the neurovascular unit (NVU). Endothelial barrier function is crucially induced and maintained by the Wnt/β-catenin pathway and requires intact NVU for proper functionality. The BBB and the NVU are characterized by a specialized assortment of molecular specializations, providing the basis for tightening, transport and immune response functionality.The present chapter introduces state-of-the-art knowledge of BBB structure and function and highlights current research topics, aiming to understanding in more depth the cellular and molecular interactions at the NVU, determining functionality of the BBB in health and disease, and providing novel potential targets for therapeutic BBB modulation. Moreover, we highlight recent advances in understanding BBB and NVU heterogeneity within the CNS as well as their contribution to CNS physiology, such as neurovascular coupling, and pathophysiology, is discussed. Finally, we give an outlook onto new avenues of BBB research.
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Affiliation(s)
- Fabienne Benz
- Institute of Neurology (Edinger Institute), University Hospital, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Stefan Liebner
- Institute of Neurology (Edinger Institute), University Hospital, Goethe University Frankfurt, Frankfurt am Main, Germany.
- Excellence Cluster Cardio Pulmonary System (CPI), Partner Site Frankfurt, Frankfurt, Germany.
- German Center for Cardiovascular Research (DZHK), Partner Site Frankfurt/Mainz, Frankfurt, Germany.
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9
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Zeigler M, Whittington D, Sotoodehnia N, Lemaitre RN, Totah RA. A sensitive and improved throughput UPLC-MS/MS quantitation method of total cytochrome P450 mediated arachidonic acid metabolites that can separate regio-isomers and cis/trans-EETs from human plasma. Chem Phys Lipids 2018; 216:162-170. [PMID: 30201384 PMCID: PMC6269592 DOI: 10.1016/j.chemphyslip.2018.09.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 08/21/2018] [Accepted: 09/05/2018] [Indexed: 12/19/2022]
Abstract
A method for the detection and quantification of hydroxyl and epoxy arachidonic acid (AA) metabolites in human plasma was developed using liquid-liquid extraction, phospholipid saponification followed by derivatization of the acid moiety and liquid chromatographic tandem mass spectrometric detection. Derivatization with a pyridinium analog allowed for detection in the positive ion mode, greatly improving sensitivity and the stability of the more labile AA metabolites. The entire method utilizes a 96-well plate format, increasing sample throughput, and was optimized to measure 5-, 8-, 9-, 11-, 12-, 15-, 19-, and 20- hydroxyeicosatetraenoic acid (HETE), 5,6-, 8,9-, 11,12-, and 14,15- dihydroxyeicosatrienoic acid (DHET), and the regio- and cis-/ trans- isomers of 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid (EET). The method was validated for its applicability over the FA concentration range found in human plasma. Using 100 μL aliquots of pooled human plasma, EET levels, particularly 5,6-EET, were observed to be higher than previously reported, with measured concentrations of 23.6 ng/ml for 5,6-EET, 5.6 ng/mL for 5,6-trans-EET, 8.0 ng/mL for 8,9-EET, 1.9 ng/mL for 8,9-trans-EET, 8.8 ng/mL for 11,12-EET, 3.4 ng/mL for 11,12-trans-EET, 10.7 ng/mL for 14,15-EET, and 1.7 ng/mL 14,15-trans- EET. This method is suitable for large population studies to elucidate the complex interactions between the eicosanoids and various disease states and may be used for quantitation of a wide variety of fattyacids beyond eicosanoids from small volumes of human plasma.
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Affiliation(s)
- Maxwell Zeigler
- Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, WA 98195, USA.
| | - Dale Whittington
- Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, WA 98195, USA.
| | - Nona Sotoodehnia
- Cardiovascular Health Research Unit, Department of Medicine, University of Washington, 1730 Minor Ave, Suite 1360, Seattle, WA 98101, USA; Division of Cardiology, University of Washington, Box 356422, Seattle, WA 98195, USA.
| | - Rozenn N Lemaitre
- Cardiovascular Health Research Unit, Department of Medicine, University of Washington, 1730 Minor Ave, Suite 1360, Seattle, WA 98101, USA.
| | - Rheem A Totah
- Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, WA 98195, USA.
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10
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Stevenson ME, Lensmire NA, Swain RA. Astrocytes and radial glia-like cells, but not neurons, display a nonapoptotic increase in caspase-3 expression following exercise. Brain Behav 2018; 8:e01110. [PMID: 30240148 PMCID: PMC6192401 DOI: 10.1002/brb3.1110] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/18/2018] [Accepted: 08/05/2018] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Exercise induces plasticity in the hippocampus, which includes increases in neurogenesis, the proliferation of new neurons, and angiogenesis, the sprouting of new capillaries from preexisting blood vessels. Following exercise, astrocytes also undergo morphological changes that parallel the events occurring in the neurovascular system. Interestingly, there have also been reports of apoptosis in the hippocampus following aerobic exercise. This experiment aimed to identify which population of hippocampal cells undergoes apoptosis after an acute bout of exercise. METHODS Cleaved caspase-3, a terminal protein in the apoptotic cascade, was initially used to identify apoptotic cells in the hippocampus after rats completed an acute bout of exercise. Next, the proportion of immature neurons, adult neurons, astrocytes, or radial glia-like cells expressing cleaved caspase-3 was quantified. TUNEL staining was completed as a second measure of apoptosis. RESULTS Following exercise, cleaved caspase-3 expression was increased in the CA1 and DG regions of the hippocampus. Cleaved caspase-3 was not highly expressed in neuronal populations, and expression was not increased in these cells postexercise. Instead, cleaved caspase-3 was predominantly expressed in astrocytes. Following exercise, there was an increased number of cleaved caspase-3 positive astrocytes in DG and CA1, and cleaved caspase-3 positive radial glia-like cells located in the subgranular zone. To determine whether cleaved caspase-3 expression in these glial cells was associated with apoptosis, a TUNEL assay was completed. TUNEL staining was negligible in all groups and did not mirror the pattern of caspase-3 labeling. CONCLUSIONS Cleaved caspase-3 expression was detected largely in non-neuronal cell populations, and the pattern of cleaved caspase-3 expression did not match that of TUNEL. This suggests that after exercise, cleaved caspase-3 expression may serve a nonapoptotic role in these hippocampal astrocytes and radial glia-like cells. It will be important to identify the function of exercise-induced cleaved caspase-3 expression in the future experiments.
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Affiliation(s)
| | - Nicole A. Lensmire
- Department of PsychologyUniversity of Wisconsin‐MilwaukeeMilwaukeeWisconsin
| | - Rodney A. Swain
- Department of PsychologyUniversity of Wisconsin‐MilwaukeeMilwaukeeWisconsin
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11
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Liu Z, Khalil RA. Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease. Biochem Pharmacol 2018; 153:91-122. [PMID: 29452094 PMCID: PMC5959760 DOI: 10.1016/j.bcp.2018.02.012] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 02/12/2018] [Indexed: 12/11/2022]
Abstract
Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.
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Affiliation(s)
- Zhongwei Liu
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA
| | - Raouf A Khalil
- Vascular Surgery Research Laboratories, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA.
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12
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Costa TJ, Ceravolo GS, Echem C, Hashimoto CM, Costa BP, Santos-Eichler RA, Oliveira MA, Jiménez-Altayó F, Akamine EH, Dantas AP, Carvalho MHC. Detrimental Effects of Testosterone Addition to Estrogen Therapy Involve Cytochrome P-450-Induced 20-HETE Synthesis in Aorta of Ovariectomized Spontaneously Hypertensive Rat (SHR), a Model of Postmenopausal Hypertension. Front Physiol 2018; 9:490. [PMID: 29867542 PMCID: PMC5952044 DOI: 10.3389/fphys.2018.00490] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 04/17/2018] [Indexed: 12/02/2022] Open
Abstract
Postmenopausal period has been associated to different symptoms such as hot flashes, vulvovaginal atrophy, hypoactive sexual desire disorder (HSDD) and others. Clinical studies have described postmenopausal women presenting HSDD can benefit from the association of testosterone to conventional hormonal therapy. Testosterone has been linked to development of cardiovascular diseases including hypertension and it also increases cytochrome P-450-induced 20-HETE synthesis which in turn results in vascular dysfunction. However, the effect of testosterone plus estrogen in the cardiovascular system is still very poorly studied. The aim of the present study is to evaluate the role of cytochrome P-450 pathway in a postmenopausal hypertensive female treated with testosterone plus estrogen. For that, hypertensive ovariectomized rats (OVX-SHR) were used as a model of postmenopausal hypertension and four groups were created: SHAM-operated (SHAM), ovariectomized SHR (OVX), OVX treated for 15 days with conjugated equine estrogens [(CEE) 9.6 μg/Kg/day/po] or CEE associated to testosterone [(CEE+T) 2.85 mg/kg/weekly/im]. Phenylephrine-induced contraction and generation of reactive oxygen species (ROS) were markedly increased in aortic rings from OVX-SHR compared to SHAM rats which were restored by CEE treatment. On the other hand, CEE+T abolished vascular effects by CEE and augmented both systolic and diastolic blood pressure of SHR. Treatment of aortic rings with the CYP/20-HETE synthesis inhibitor HET0016 (1 μM) reduced phenylephrine hyperreactivity and the augmented ROS generation in the CEE+T group. These results are paralleled by the increased CYP4F3 protein expression and activity in aortas of CEE+T. In conclusion, we showed that association of testosterone to estrogen therapy produces detrimental effects in cardiovascular system of ovariectomized hypertensive females via CYP4F3/20-HETE pathway. Therefore, our findings support the standpoint that the CYP/20-HETE pathway is an important therapeutic target for the prevention of cardiovascular disease in menopausal women in the presence of high levels of testosterone.
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Affiliation(s)
- Tiago J Costa
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.,Facultat de Medicina, Departament de Farmacologia, Terapèutica i Toxicologia, Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Spain.,Group of Atherosclerosis and Coronary Disease, Institut Clinic del Torax, Institut d'Investigacions Biomédiques August Pi I Sunyer, Barcelona, Spain
| | - Graziela S Ceravolo
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.,Department of Physiological Sciences, State University of Londrina, Londrina, Brazil
| | - Cinthya Echem
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Carolina M Hashimoto
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Beatriz P Costa
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Rosangela A Santos-Eichler
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Maria Aparecida Oliveira
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Francesc Jiménez-Altayó
- Facultat de Medicina, Departament de Farmacologia, Terapèutica i Toxicologia, Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Eliana H Akamine
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Ana Paula Dantas
- Group of Atherosclerosis and Coronary Disease, Institut Clinic del Torax, Institut d'Investigacions Biomédiques August Pi I Sunyer, Barcelona, Spain
| | - Maria Helena C Carvalho
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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13
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Kubacka M, Kotańska M, Kazek G, Waszkielewicz AM, Marona H, Filipek B, Mogilski S. Involvement of the NO/sGC/cGMP/K + channels pathway in vascular relaxation evoked by two non-quinazoline α 1-adrenoceptor antagonists. Biomed Pharmacother 2018; 103:157-166. [PMID: 29653360 DOI: 10.1016/j.biopha.2018.04.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 04/04/2018] [Accepted: 04/05/2018] [Indexed: 02/06/2023] Open
Abstract
The aim of this study was to explore the α1-adrenoceptor-independent mechanisms involved in the vasorelaxant properties of two non-quinazoline α1-adrenoceptors antagonists (MH-76 and MH-79). Endothelium intact and endothelium denuded rat aorta was contracted with 1 μM phenylephrine to plateau, and the vasodilatory effect of MH-76 and MH-79 was examined in the absence or presence of inhibitors of the different signal transduction pathways. cGMP concetration was measured in rat aorta (enzyme immunoassay kit). In human aortic endothelial cells (HAEC) NO production was examined using a DAF-FM DA fluorescent indicator, whereas in human aortic smooth muscle cells the influence of the title compounds on K+ efflux was evaluated. The vasorelaxant effect of MH-76 and MH-79 was attenuated by endothelium removal, Nω-Nitro-l-arginine methyl ester (L-NAME) and 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) pretreatment to the level characteristic for α1-adrenoreceptor blocking activity. In addition, the MH-76 and MH-79 induced relaxation was reduced by K+ channels blockers. In endothelium intact rat aorta, MH-76 and MH-79 caused an increase in cGMP level, whereas in HAEC they increased NO generation. In contrast, the reference, quinazoline based α1-antagonist prazosin, did not influence NO production. Our findings suggest that the mechanisms underlying the vasodilatory properties of non-quinazoline based α1-adrenoceptors antagonists MH-76 and MH-79 involve not only α1-adrenoceptor blocking activity but also the activation of the endothelial NO-cGMP signalling pathway and the subsequent opening of K+ channels. Our studies show that such double mechanism of action is superior to pure α1-adrenoceptor blockade, and may be considered as a promising alternative for the prevention and treatment of cardiovascular diseases.
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Affiliation(s)
- Monika Kubacka
- Department of Pharmacodynamics, Faculty of Pharmacy, Medical College, Jagiellonian University, Medyczna 9, 30-688, Kraków, Poland.
| | - Magdalena Kotańska
- Department of Pharmacodynamics, Faculty of Pharmacy, Medical College, Jagiellonian University, Medyczna 9, 30-688, Kraków, Poland
| | - Grzegorz Kazek
- Department of Pharmacological Screening, Chair of Pharmacodynamics, Faculty of Pharmacy, Medical College, Jagiellonian University, Medyczna 9, 30-688, Kraków, Poland
| | - Anna Maria Waszkielewicz
- Department of Bioorganic Chemistry, Chair of Organic Chemistry, Faculty of Pharmacy, Medical College, Jagiellonian University, Medyczna 9, 30-688, Kraków, Poland
| | - Henryk Marona
- Department of Bioorganic Chemistry, Chair of Organic Chemistry, Faculty of Pharmacy, Medical College, Jagiellonian University, Medyczna 9, 30-688, Kraków, Poland
| | - Barbara Filipek
- Department of Pharmacodynamics, Faculty of Pharmacy, Medical College, Jagiellonian University, Medyczna 9, 30-688, Kraków, Poland
| | - Szczepan Mogilski
- Department of Pharmacodynamics, Faculty of Pharmacy, Medical College, Jagiellonian University, Medyczna 9, 30-688, Kraków, Poland
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14
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Abstract
Cytochrome P450 eicosanoids play important roles in brain function and disease through their complementary actions on cell-cell communications within the neurovascular unit (NVU) and mechanisms of brain injury. Epoxy- and hydroxyeicosanoids, respectively formed by cytochrome P450 epoxygenases and ω-hydroxylases, play opposing roles in cerebrovascular function and in pathological processes underlying neural injury, including ischemia, neuroinflammation and oxidative injury. P450 eicosanoids also contribute to cerebrovascular disease risk factors, including hypertension and diabetes. We summarize studies investigating the roles P450 eicosanoids in cerebrovascular physiology and disease to highlight the existing balance between these important lipid signaling molecules, as well as their roles in maintaining neurovascular homeostasis and in acute and chronic neurovascular and neurodegenerative disorders.
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Affiliation(s)
- Catherine M Davis
- Department of Anesthesiology & Perioperative Medicine, Oregon Health & Science University, Portland, OR 97239, United States; The Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR 97239, United States
| | - Xuehong Liu
- The Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR 97239, United States
| | - Nabil J Alkayed
- Department of Anesthesiology & Perioperative Medicine, Oregon Health & Science University, Portland, OR 97239, United States; The Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR 97239, United States.
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15
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Anthonymuthu TS, Kenny EM, Amoscato AA, Lewis J, Kochanek PM, Kagan VE, Bayır H. Global assessment of oxidized free fatty acids in brain reveals an enzymatic predominance to oxidative signaling after trauma. Biochim Biophys Acta Mol Basis Dis 2017; 1863:2601-2613. [PMID: 28347845 PMCID: PMC5612836 DOI: 10.1016/j.bbadis.2017.03.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/15/2017] [Accepted: 03/23/2017] [Indexed: 12/31/2022]
Abstract
Traumatic brain injury (TBI) is a major health problem associated with significant morbidity and mortality. The pathophysiology of TBI is complex involving signaling through multiple cascades, including lipid peroxidation. Oxidized free fatty acids, a prominent product of lipid peroxidation, are potent cellular mediators involved in induction and resolution of inflammation and modulation of vasomotor tone. While previous studies have assessed lipid peroxidation after TBI, to our knowledge no studies have used a systematic approach to quantify the global oxidative changes in free fatty acids. In this study, we identified and quantified 244 free fatty acid oxidation products using a newly developed global liquid chromatography tandem-mass spectrometry (LC-MS/MS) method. This methodology was used to follow the time course of these lipid species in the contusional cortex of our pediatric rat model of TBI. We show that oxidation peaked at 1h after controlled cortical impact and was progressively attenuated at 4 and 24h time points. While enzymatic and non-enzymatic pathways were activated at 1h post-TBI, enzymatic lipid peroxidation was the predominant mechanism with 15-lipoxygenase (LOX) contributing to the majority of total oxidized fatty acid content. Pro-inflammatory lipid mediators were significantly increased at 1 and 4h after TBI with return to basal levels by 24h. Anti-inflammatory lipid mediators remained significantly increased across all three time points, indicating an elevated and sustained anti-inflammatory response following TBI.
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Affiliation(s)
- Tamil S Anthonymuthu
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA 15261, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA 15224, United States; Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA 15219, United States
| | - Elizabeth M Kenny
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA 15261, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA 15224, United States; Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA 15219, United States
| | - Andrew A Amoscato
- Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219, United States
| | - Jesse Lewis
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA 15261, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA 15224, United States; Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA 15219, United States
| | - Patrick M Kochanek
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA 15261, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA 15224, United States; Children's Hospital of Pittsburgh of UPMC, University of Pittsburgh, Pittsburgh, PA 15224, United States
| | - Valerian E Kagan
- Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA 15219, United States; Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219, United States
| | - Hülya Bayır
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA 15261, United States; Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA 15224, United States; Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA 15219, United States; Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219, United States; Children's Hospital of Pittsburgh of UPMC, University of Pittsburgh, Pittsburgh, PA 15224, United States.
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16
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Salomonsson M, Brasen JC, Sorensen CM. Role of renal vascular potassium channels in physiology and pathophysiology. Acta Physiol (Oxf) 2017; 221:14-31. [PMID: 28371470 DOI: 10.1111/apha.12882] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/10/2016] [Accepted: 03/22/2017] [Indexed: 12/31/2022]
Abstract
The control of renal vascular tone is important for the regulation of salt and water balance, blood pressure and the protection against damaging elevated glomerular pressure. The K+ conductance is a major factor in the regulation of the membrane potential (Vm ) in vascular smooth muscle (VSMC) and endothelial cells (EC). The vascular tone is controlled by Vm via its effect on the opening probability of voltage-operated Ca2+ channels (VOCC) in VSMC. When K+ conductance increases Vm becomes more negative and vasodilation follows, while deactivation of K+ channels leads to depolarization and vasoconstriction. K+ channels in EC indirectly participate in the control of vascular tone by endothelium-derived vasodilation. Therefore, by regulating the tone of renal resistance vessels, K+ channels have a potential role in the control of fluid homoeostasis and blood pressure as well as in the protection of the renal parenchyma. The main classes of K+ channels (calcium activated (KCa ), inward rectifier (Kir ), voltage activated (Kv ) and ATP sensitive (KATP )) have been found in the renal vessels. In this review, we summarize results available in the literature and our own studies in the field. We compare the ambiguous in vitro and in vivo results. We discuss the role of single types of K+ channels and the integrated function of several classes. We also deal with the possible role of renal vascular K+ channels in the pathophysiology of hypertension, diabetes mellitus and sepsis.
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Affiliation(s)
| | - J. C. Brasen
- Department of Electrical Engineering; Technical University of Denmark; Kgs. Lyngby Denmark
| | - C. M. Sorensen
- Department of Biomedical Sciences; Division of Renal and Vascular Physiology; University of Copenhagen; Copenhagen Denmark
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17
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Sten S, Lundengård K, Witt S, Cedersund G, Elinder F, Engström M. Neural inhibition can explain negative BOLD responses: A mechanistic modelling and fMRI study. Neuroimage 2017; 158:219-231. [DOI: 10.1016/j.neuroimage.2017.07.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 06/03/2017] [Accepted: 07/02/2017] [Indexed: 12/13/2022] Open
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18
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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: 222] [Impact Index Per Article: 31.7] [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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19
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Elshenawy OH, Shoieb SM, Mohamed A, El-Kadi AOS. Clinical Implications of 20-Hydroxyeicosatetraenoic Acid in the Kidney, Liver, Lung and Brain: An Emerging Therapeutic Target. Pharmaceutics 2017; 9:pharmaceutics9010009. [PMID: 28230738 PMCID: PMC5374375 DOI: 10.3390/pharmaceutics9010009] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 02/15/2017] [Indexed: 12/30/2022] Open
Abstract
Cytochrome P450-mediated metabolism of arachidonic acid (AA) is an important pathway for the formation of eicosanoids. The ω-hydroxylation of AA generates significant levels of 20-hydroxyeicosatetraenoic acid (20-HETE) in various tissues. In the current review, we discussed the role of 20-HETE in the kidney, liver, lung, and brain during physiological and pathophysiological states. Moreover, we discussed the role of 20-HETE in tumor formation, metabolic syndrome and diabetes. In the kidney, 20-HETE is involved in modulation of preglomerular vascular tone and tubular ion transport. Furthermore, 20-HETE is involved in renal ischemia/reperfusion (I/R) injury and polycystic kidney diseases. The role of 20-HETE in the liver is not clearly understood although it represents 50%-75% of liver CYP-dependent AA metabolism, and it is associated with liver cirrhotic ascites. In the respiratory system, 20-HETE plays a role in pulmonary cell survival, pulmonary vascular tone and tone of the airways. As for the brain, 20-HETE is involved in cerebral I/R injury. Moreover, 20-HETE has angiogenic and mitogenic properties and thus helps in tumor promotion. Several inhibitors and inducers of the synthesis of 20-HETE as well as 20-HETE analogues and antagonists are recently available and could be promising therapeutic options for the treatment of many disease states in the future.
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Affiliation(s)
- Osama H Elshenawy
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
| | - Sherif M Shoieb
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
| | - Anwar Mohamed
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
- Department of Basic Medical Sciences, College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates.
| | - Ayman O S El-Kadi
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
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20
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Yum V, Carlisle RE, Lu C, Brimble E, Chahal J, Upagupta C, Ask K, Dickhout JG. Endoplasmic reticulum stress inhibition limits the progression of chronic kidney disease in the Dahl salt-sensitive rat. Am J Physiol Renal Physiol 2017; 312:F230-F244. [DOI: 10.1152/ajprenal.00119.2016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 11/01/2016] [Accepted: 11/07/2016] [Indexed: 11/22/2022] Open
Abstract
Proteinuria is one of the primary risk factors for the progression of chronic kidney disease (CKD) and has been implicated in the induction of endoplasmic reticulum (ER) stress. We hypothesized that the suppression of ER stress with a low molecular weight chemical chaperone, 4-phenylbutyric acid (4-PBA), would reduce the severity of CKD and proteinuria in the Dahl salt-sensitive (SS) hypertensive rat. To induce hypertension and CKD, 12-wk-old male rats were placed on a high-salt (HS) diet for 4 wk with or without 4-PBA treatment. We assessed blood pressure and markers of CKD, including proteinuria, albuminuria, and renal pathology. Furthermore, we determined if HS feeding resulted in an impaired myogenic response, subsequent to ER stress. 4-PBA treatment reduced salt-induced hypertension, proteinuria, and albuminuria and preserved myogenic constriction. Furthermore, renal pathology was reduced with 4-PBA treatment, as indicated by lowered expression of profibrotic markers and fewer intratubular protein casts. In addition, ER stress in the glomerulus was reduced, and the integrity of the glomerular filtration barrier was preserved. These results suggest that 4-PBA treatment protects against proteinuria in the SS rat by preserving the myogenic response and by preventing ER stress, which led to a breakdown in the glomerular filtration barrier. As such, alleviating ER stress serves as a viable therapeutic strategy to preserve kidney function and to delay the progression of CKD in the animal model under study.
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Affiliation(s)
- Victoria Yum
- Department of Medicine, Division of Nephrology, McMaster University and St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and
| | - Rachel E. Carlisle
- Department of Medicine, Division of Nephrology, McMaster University and St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and
| | - Chao Lu
- Department of Medicine, Division of Nephrology, McMaster University and St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and
| | - Elise Brimble
- Department of Medicine, Division of Nephrology, McMaster University and St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and
| | - Jasmine Chahal
- Department of Medicine, Division of Nephrology, McMaster University and St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and
| | - Chandak Upagupta
- Department of Medicine, Division of Nephrology, McMaster University and St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and
| | - Kjetil Ask
- Department of Medicine, Division of Respirology, McMaster University, St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada
| | - Jeffrey G. Dickhout
- Department of Medicine, Division of Nephrology, McMaster University and St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada; and
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21
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Abstract
Heme oxygenases are composed of two isozymes, Hmox1 and Hmox2, that catalyze the degradation of heme to carbon monoxide (CO), ferrous iron, and biliverdin, the latter of which is subsequently converted to bilirubin. While initially considered to be waste products, CO and biliverdin/bilirubin have been shown over the last 20 years to modulate key cellular processes, such as inflammation, cell proliferation, and apoptosis, as well as antioxidant defense. This shift in paradigm has led to the importance of heme oxygenases and their products in cell physiology now being well accepted. The identification of the two human cases thus far of heme oxygenase deficiency and the generation of mice deficient in Hmox1 or Hmox2 have reiterated a role for these enzymes in both normal cell function and disease pathogenesis, especially in the context of cardiovascular disease. This review covers the current knowledge on the function of both Hmox1 and Hmox2 at both a cellular and tissue level in the cardiovascular system. Initially, the roles of heme oxygenases in vascular health and the regulation of processes central to vascular diseases are outlined, followed by an evaluation of the role(s) of Hmox1 and Hmox2 in various diseases such as atherosclerosis, intimal hyperplasia, myocardial infarction, and angiogenesis. Finally, the therapeutic potential of heme oxygenases and their products are examined in a cardiovascular disease context, with a focus on how the knowledge we have gained on these enzymes may be capitalized in future clinical studies.
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Affiliation(s)
- Anita Ayer
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, Australia; and Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham Veterans Administration Medical Center, Birmingham, Alabama
| | - Abolfazl Zarjou
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, Australia; and Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham Veterans Administration Medical Center, Birmingham, Alabama
| | - Anupam Agarwal
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, Australia; and Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham Veterans Administration Medical Center, Birmingham, Alabama
| | - Roland Stocker
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, Australia; and Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham Veterans Administration Medical Center, Birmingham, Alabama
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22
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Jackson WF. Arteriolar oxygen reactivity: where is the sensor and what is the mechanism of action? J Physiol 2016; 594:5055-77. [PMID: 27324312 PMCID: PMC5023707 DOI: 10.1113/jp270192] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 06/13/2016] [Indexed: 01/02/2023] Open
Abstract
Arterioles in the peripheral microcirculation are exquisitely sensitive to changes in PO2 in their environment: increases in PO2 cause vasoconstriction while decreases in PO2 result in vasodilatation. However, the cell type that senses O2 (the O2 sensor) and the signalling pathway that couples changes in PO2 to changes in arteriolar tone (the mechanism of action) remain unclear. Many (but not all) ex vivo studies of isolated cannulated resistance arteries and large, first-order arterioles support the hypothesis that these vessels are intrinsically sensitive to PO2 with the smooth muscle, endothelial cells, or red blood cells serving as the O2 sensor. However, in situ studies testing these hypotheses in downstream arterioles have failed to find evidence of intrinsic O2 sensitivity, and instead have supported the idea that extravascular cells sense O2 . Similarly, ex vivo studies of isolated, cannulated resistance arteries and large first-order arterioles support the hypotheses that O2 -dependent inhibition of production of vasodilator cyclooxygenase products or O2 -dependent destruction of nitric oxide mediates O2 reactivity of these upstream vessels. In contrast, most in vivo studies of downstream arterioles have disproved these hypotheses and instead have provided evidence supporting the idea that O2 -dependent production of vasoconstrictors mediates arteriolar O2 reactivity, with significant regional heterogeneity in the specific vasoconstrictor involved. Oxygen-induced vasoconstriction may serve as a protective mechanism to reduce the oxidative burden to which a tissue is exposed, a process that is superimposed on top of the local mechanisms which regulate tissue blood flow to meet a tissue's metabolic demand.
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Affiliation(s)
- William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, 48824, USA.
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23
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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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24
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Ringvold HC, Khalil RA. Protein Kinase C as Regulator of Vascular Smooth Muscle Function and Potential Target in Vascular Disorders. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 78:203-301. [PMID: 28212798 PMCID: PMC5319769 DOI: 10.1016/bs.apha.2016.06.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Vascular smooth muscle (VSM) plays an important role in maintaining vascular tone. In addition to Ca2+-dependent myosin light chain (MLC) phosphorylation, protein kinase C (PKC) is a major regulator of VSM function. PKC is a family of conventional Ca2+-dependent α, β, and γ, novel Ca2+-independent δ, ɛ, θ, and η, and atypical ξ, and ι/λ isoforms. Inactive PKC is mainly cytosolic, and upon activation it undergoes phosphorylation, maturation, and translocation to the surface membrane, the nucleus, endoplasmic reticulum, and other cell organelles; a process facilitated by scaffold proteins such as RACKs. Activated PKC phosphorylates different substrates including ion channels, pumps, and nuclear proteins. PKC also phosphorylates CPI-17 leading to inhibition of MLC phosphatase, increased MLC phosphorylation, and enhanced VSM contraction. PKC could also initiate a cascade of protein kinases leading to phosphorylation of the actin-binding proteins calponin and caldesmon, increased actin-myosin interaction, and VSM contraction. Increased PKC activity has been associated with vascular disorders including ischemia-reperfusion injury, coronary artery disease, hypertension, and diabetic vasculopathy. PKC inhibitors could test the role of PKC in different systems and could reduce PKC hyperactivity in vascular disorders. First-generation PKC inhibitors such as staurosporine and chelerythrine are not very specific. Isoform-specific PKC inhibitors such as ruboxistaurin have been tested in clinical trials. Target delivery of PKC pseudosubstrate inhibitory peptides and PKC siRNA may be useful in localized vascular disease. Further studies of PKC and its role in VSM should help design isoform-specific PKC modulators that are experimentally potent and clinically safe to target PKC in vascular disease.
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Affiliation(s)
- H C Ringvold
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States
| | - R A Khalil
- Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States.
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25
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Gebremedhin D, Zhang DX, Carver KA, Rau N, Rarick KR, Roman RJ, Harder DR. Expression of CYP 4A ω-hydroxylase and formation of 20-hydroxyeicosatetreanoic acid (20-HETE) in cultured rat brain astrocytes. Prostaglandins Other Lipid Mediat 2016; 124:16-26. [PMID: 27174801 DOI: 10.1016/j.prostaglandins.2016.04.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Revised: 04/19/2016] [Accepted: 04/27/2016] [Indexed: 02/07/2023]
Abstract
Astrocytes secrete vasodilator and vasoconstrictor factors via end feet processes, altering blood flow to meet neuronal metabolic demand. Compared to what is known about the ability of astrocytes to release factors that dilate local cerebral vasculature, very little is known regarding the source and identity of astrocyte derived constricting factors. The present study investigated if astrocytes express CYP 4A ω-hydroxylase and metabolize arachidonic acid (AA) to 20-hydroxyeicotetraenoic acid (20-HETE) that regulates KCa channel activity in astrocytes and cerebral arterial myocyte contractility. Here we report that cultured astrocytes express CYP 4A2/3 ω-hydroxylase mRNA and CYP 4A protein and produce 20-HETE and the CYP epoxygenase metabolites epoxyeicosatrienoic acids (EETs) when incubated with AA. The production of 20-HETE and EETs was enhanced following stimulation of metabotropic glutamate receptors (mGluR) on the astrocytes. Exogenous application of 20-HETE attenuated, whereas inhibition of 20-HETE production with HET-0016 increased the open state probabilities (NPo) of 71pS and 161pS KCa single-channel currents recorded from astrocytes. Exposure of isolated cerebral arterial myocytes to conditioned media from cultured astrocytes caused shortening of the length of freshly isolated cerebral arterial myocytes that was not evident following inhibition of astrocyte 20-HETE synthesis and action. These findings suggest that astrocytes not only release vasodilator EETs in response to mGluR stimulation but also synthetize and release the cerebral arterial myocyte constrictor 20-HETE that also functions as an endogenous inhibitor of the activity of two types of KCa channel currents found in astrocytes.
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Affiliation(s)
- Debebe Gebremedhin
- Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - David X Zhang
- Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - Koryn A Carver
- Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - Nicole Rau
- Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - Kevin R Rarick
- Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States
| | - Richard J Roman
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS 39216, United States
| | - David R Harder
- Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States; Clement Zablocki VA Medical Center, Milwaukee, WI 53226, United States.
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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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Berg RMG. Myogenic and metabolic feedback in cerebral autoregulation: Putative involvement of arachidonic acid-dependent pathways. Med Hypotheses 2016; 92:12-7. [PMID: 27241246 DOI: 10.1016/j.mehy.2016.04.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/09/2016] [Accepted: 04/13/2016] [Indexed: 01/20/2023]
Abstract
The present paper presents a mechanistic model of cerebral autoregulation, in which the dual effects of the arachidonic acid metabolites 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) on vascular smooth muscle mediate the cerebrovascular adjustments to a change in cerebral perfusion pressure (CPP). 20-HETE signalling in vascular smooth muscle mediates myogenic feedback to changes in vessel wall stretch, which may be modulated by metabolic feedback through EETs released from astrocytes and endothelial cells in response to changes in brain tissue oxygen tension. The metabolic feedback pathway is much faster than 20-HETE-dependent myogenic feedback, and the former thus initiates the cerebral autoregulatory response, while myogenic feedback comprises a relatively slower mechanism that functions to set the basal cerebrovascular tone. Therefore, assessments of dynamic cerebral autoregulation, which may provide information on the response time of the cerebrovasculature, may specifically be used to yield information on metabolic feedback mechanisms, while data based on assessments of static cerebral autoregulation represent the integrated functionality of myogenic and metabolic feedback.
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Affiliation(s)
- Ronan M G Berg
- Department of Clinical Physiology & Nuclear Medicine, Frederiksberg and Bispebjerg Hospitals, Frederiksberg, Denmark.
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Liao D, Yi X, Zhang B, Zhou Q, Lin J. Interaction Between CYP4F2 rs2108622 and CPY4A11 rs9333025 Variants Is Significantly Correlated with Susceptibility to Ischemic Stroke and 20-Hydroxyeicosatetraenoic Acid Level. Genet Test Mol Biomarkers 2016; 20:223-8. [PMID: 26959478 DOI: 10.1089/gtmb.2015.0205] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
AIMS To investigate the association of four variants of two CYP ω-hydroxylase genes and 20-hydroxyeicosatetraenoic acid (HETE) levels with ischemic stroke (IS) and whether gene-gene interactions between these genes increase the risk of IS. METHODS Three hundred ninety-six patients with IS and 378 controls were genotyped for rs2269231, rs9333025, rs2108622, and rs3093135. Gene-gene interactions were analyzed using generalized multifactor dimensionality reduction (GMDR) methods. The 20-HETE levels was measured in 218 IS patients and 126 controls. RESULTS The frequency of the GG genotype of rs9333025 was significantly higher in IS patients than in controls (p < 0.001). The GMDR analysis showed a significant gene-gene interaction between rs9333025 and rs2108622 (p = 0.0116). This gene-gene interaction predicted a significantly higher risk of IS in individuals carrying the genotypes of rs9333025 GG and rs2108622 GG (odds ratio = 1.92, 95% confidence interval = 1.12-4.26, p = 0.007). The plasma levels of 20-HETE were significantly higher in IS patients than in controls, and IS patients carrying the genotype combination of rs9333025 GG and rs2108622 GG had higher 20-HETE levels than IS patients with other combinations of the two variants. CONCLUSION CYP4A1l rs9333025 GG and CYP4F2 rs2108622 GG two-loci interaction significantly increases the risk for IS and an elevated 20-HETE level.
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Affiliation(s)
- Duanxiu Liao
- 1 Department of Neurology, People's Hospital of Deyang City , Deyang, China
| | - Xingyang Yi
- 1 Department of Neurology, People's Hospital of Deyang City , Deyang, China
| | - Biao Zhang
- 1 Department of Neurology, People's Hospital of Deyang City , Deyang, China
| | - Qiang Zhou
- 2 Department of Neurology, Third Affiliated Hospital of Wenzhou Medical College , Zhejiang, China
| | - Jing Lin
- 2 Department of Neurology, Third Affiliated Hospital of Wenzhou Medical College , Zhejiang, China
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Gordon GRJ, Howarth C, MacVicar BA. Bidirectional Control of Blood Flow by Astrocytes: A Role for Tissue Oxygen and Other Metabolic Factors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 903:209-19. [PMID: 27343099 DOI: 10.1007/978-1-4899-7678-9_15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Altering cerebral blood flow through the control of cerebral vessel diameter is critical so that the delivery of molecules important for proper brain functioning is matched to the activity level of neurons. Although the close relationship of brain glia known as astrocytes with cerebral blood vessels has long been recognized, it is only recently that these cells have been demonstrated to translate information on the activity level and energy demands of neurons to the vasculature. In particular, astrocytes respond to elevations in extracellular glutamate as a consequence of synaptic transmission through the activation of group 1 metabotropic glutamate receptors. These Gq-protein coupled receptors elevate intracellular calcium via IP3 signaling. A close examination of astrocyte endfeet calcium signals has been shown to cause either vasoconstriction or vasodilation. Common to both vasomotor responses is the generation of arachidonic acid in astrocytes by calcium sensitive phospholipase A2. Vasoconstriction ensues from the conversion of arachidonic acid to 20-hydroxyeicosatetraenoic acid, while vasodilation ensues from the production of epoxyeicosatrienoic acids or prostaglandins. Factors that determine whether constrictor or dilatory pathways predominate include brain oxygen, lactate, adenosine as well as nitric oxide. Changing the oxygen level itself leads to many downstream changes that facilitate the switch from vasoconstriction at high oxygen to vasodilation at low oxygen. These findings highlight the importance of astrocytes as sensors of neural activity and metabolism to coordinate the delivery of essential nutrients via the blood to the working cells.
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Affiliation(s)
- Grant R J Gordon
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada.
| | - Clare Howarth
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
| | - Brian A MacVicar
- Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
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30
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Calcium-Activated Potassium Channels: Potential Target for Cardiovascular Diseases. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2015; 104:233-261. [PMID: 27038376 DOI: 10.1016/bs.apcsb.2015.11.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Ca(2+)-activated K(+) channels (KCa) are classified into three subtypes: big conductance (BKCa), intermediate conductance (IKCa), and small conductance (SKCa) KCa channels. The three types of KCa channels have distinct physiological or pathological functions in cardiovascular system. BKCa channels are mainly expressed in vascular smooth muscle cells (VSMCs) and inner mitochondrial membrane of cardiomyocytes, activation of BKCa channels in these locations results in vasodilation and cardioprotection against cardiac ischemia. IKCa channels are expressed in VSMCs, endothelial cells, and cardiac fibroblasts and involved in vascular smooth muscle proliferation, migration, vessel dilation, and cardiac fibrosis. SKCa channels are widely expressed in nervous and cardiovascular system, and activation of SKCa channels mainly contributes membrane hyperpolarization. In this chapter, we summarize the physiological and pathological roles of the three types of KCa channels in cardiovascular system and put forward the possibility of KCa channels as potential target for cardiovascular diseases.
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Shaik JSB, Poloyac SM, Kochanek PM, Alexander H, Tudorascu DL, Clark RS, Manole MD. 20-Hydroxyeicosatetraenoic Acid Inhibition by HET0016 Offers Neuroprotection, Decreases Edema, and Increases Cortical Cerebral Blood Flow in a Pediatric Asphyxial Cardiac Arrest Model in Rats. J Cereb Blood Flow Metab 2015; 35:1757-63. [PMID: 26058691 PMCID: PMC4635230 DOI: 10.1038/jcbfm.2015.117] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 03/24/2015] [Accepted: 04/17/2015] [Indexed: 12/28/2022]
Abstract
Vasoconstrictive and vasodilatory eicosanoids generated after cardiac arrest (CA) may contribute to cerebral vasomotor disturbances and neurodegeneration. We evaluated the balance of vasodilator/vasoconstrictor eicosanoids produced by cytochrome P450 (CYP) metabolism, and determined their role on cortical perfusion, functional outcome, and neurodegeneration after pediatric asphyxial CA. Cardiac arrest of 9 and 12 minutes was induced in 16- to 18-day-old rats. At 5 and 120 minutes after CA, we quantified the concentration of CYP eicosanoids in the cortex and subcortical areas. In separate rats, we inhibited 20-hydroxyeicosatetraenoic acid (20-HETE) synthesis after CA and assessed cortical cerebral blood flow (CBF), neurologic deficit score, neurodegeneration, and edema. After 9 minutes of CA, vasodilator eicosanoids markedly increased versus sham. Conversely, after 12 minutes of CA, vasoconstrictor eicosanoid 20-HETE increased versus sham, without compensatory increases in vasodilator eicosanoids. Inhibition of 20-HETE synthesis after 12 minutes of CA decreased cortical 20-HETE levels, increased CBF, reduced neurologic deficits at 3 hours, and reduced neurodegeneration and edema at 48 hours versus vehicle-treated rats. In conclusion, cerebral vasoconstrictor eicosanoids increased after a pediatric CA of 12 minutes. Inhibition of 20-HETE synthesis improved cortical perfusion and short-term neurologic outcome. These results suggest that alterations in CYP eicosanoids have a role in cerebral hypoperfusion and neurodegeneration after CA and may represent important therapeutic targets.
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Affiliation(s)
- Jafar Sadik B Shaik
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Samuel M Poloyac
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Patrick M Kochanek
- Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Henry Alexander
- Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Dana L Tudorascu
- Department of Internal Medicine, Department of Psychiatry, and Department of Biostatistics, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Robert Sb Clark
- Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Mioara D Manole
- Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Pediatrics, Division of Pediatric Emergency Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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32
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Burke M, Pabbidi MR, Farley J, Roman RJ. Molecular mechanisms of renal blood flow autoregulation. Curr Vasc Pharmacol 2015; 12:845-58. [PMID: 24066938 PMCID: PMC4416696 DOI: 10.2174/15701611113116660149] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 12/18/2011] [Accepted: 07/02/2013] [Indexed: 01/10/2023]
Abstract
Diabetes and hypertension are the leading causes of chronic kidney disease and their incidence is increasing at
an alarming rate. Both are associated with impairments in the autoregulation of renal blood flow (RBF) and greater transmission
of fluctuations in arterial pressure to the glomerular capillaries. The ability of the kidney to maintain relatively
constant blood flow, glomerular filtration rate (GFR) and glomerular capillary pressure is mediated by the myogenic response
of afferent arterioles working in concert with tubuloglomerular feedback that adjusts the tone of the afferent arteriole
in response to changes in the delivery of sodium chloride to the macula densa. Despite intensive investigation, the factors
initiating the myogenic response and the signaling pathways involved in the myogenic response and tubuloglomerular
feedback remain uncertain. This review focuses on current thought regarding the molecular mechanisms underlying myogenic
control of renal vascular tone, the interrelationships between the myogenic response and tubuloglomerular feedback,
the evidence that alterations in autoregulation of RBF contributes to hypertension and diabetes-induced nephropathy and
the identification of vascular therapeutic targets for improved renoprotection in hypertensive and diabetic patients.
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Affiliation(s)
| | | | | | - Richard J Roman
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA.
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Wang J, Li H, He J, Li B, Bao Q, Zhang X, Lv Z, Zhang Y, Han J, Ai D, Zhu Y. 20-Hydroxyeicosatetraenoic acid involved in endothelial activation and thrombosis. Am J Physiol Heart Circ Physiol 2015; 308:H1359-67. [DOI: 10.1152/ajpheart.00802.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 03/04/2015] [Indexed: 12/27/2022]
Abstract
Endothelial cells play an important role in the process of coagulation and the function of platelets. We have previously reported that 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite of arachidonic acid, increased platelet aggregation and induced hemostasis. The purpose of the present study is to investigate whether 20-HETE-mediated endothelial activation has effect on the coagulation and platelet aggregation. C57Bl/6 mice were treated with PBS or 20-HETE (20 μg/kg) for 2 h, and then we performed a carotid artery or femoral artery thrombosis model by FeCl3. Detection of blood flow indicated that 20-HETE pretreatment accelerated formation of thrombus in both common carotid artery and femoral artery. In vitro, the secretion and expression of von Willebrand factor (vWF) in cultured human umbilical vein endothelial cells (HUVECs) with 20-HETE stimulation were increased, subsequently. The protein level of vWF in HUVECs was decreased at 1 h but increased with prolonged treatment with 20-HETE (>4 h). In contrast, vWF in the culture medium was increased under administration of 20-HETE at 1 h. As a result, adhesion of platelets on HUVECs was significantly increased by 20-HETE. In HUVECs, the extracellular signal-regulated kinase (ERK) pathway was activated by 20-HETE in a dose-dependent manner, and the inhibitors of ERK and L-type Ca2+channel blocked the release of vWF mediated by 20-HETE. In conclusion, 20-HETE instigates endothelial activation and induces the expression and secretion of vWF via the activation of ERK and calcium channel and therefore triggers thrombosis.
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Affiliation(s)
- Jiaxing Wang
- Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, China
| | - Hua Li
- Department of Pharmacology, College of Pharmacy, Dalian Medical University, Dalian, Liaoning, China
| | - Jinlong He
- Collaborative Innovation Center of Tianjin for Medical Epigenetics and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China
| | - Bochuan Li
- Collaborative Innovation Center of Tianjin for Medical Epigenetics and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China
| | - Qiankun Bao
- Collaborative Innovation Center of Tianjin for Medical Epigenetics and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China
| | - Xu Zhang
- Collaborative Innovation Center of Tianjin for Medical Epigenetics and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China
| | - Zhizhen Lv
- Institute of Vascular Medicine of Peking University Third Hospital, Key Laboratory of Molecular Cardiovascular Sciences of Ministry of Education, Beijing, China; and
| | - Youyi Zhang
- Institute of Vascular Medicine of Peking University Third Hospital, Key Laboratory of Molecular Cardiovascular Sciences of Ministry of Education, Beijing, China; and
| | - Jingyan Han
- Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing, China
| | - Ding Ai
- Collaborative Innovation Center of Tianjin for Medical Epigenetics and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China
| | - Yi Zhu
- Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, China
- Collaborative Innovation Center of Tianjin for Medical Epigenetics and Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China
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Zhang B, Yi X, Wang C, Liao D, Lin J, Chi L. Cytochrome 4A11 Genetic Polymorphisms Increase Susceptibility to Ischemic Stroke and Associate with Atherothrombotic Events After Stroke in Chinese. Genet Test Mol Biomarkers 2015; 19:235-41. [PMID: 25734770 DOI: 10.1089/gtmb.2014.0305] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To evaluate the associations between four single-nucleotide polymorphisms (SNPs) in CYP4A11 and CYP4F2 and ischemic stroke (IS), and between these variants and atherothrombotic events after stroke. IS patients (n=396) and controls (n=378) were genotyped for two CYP4A11 SNPs (rs2269231 and rs9333025) and two CYP4F2 SNPs (rs2108622 and rs3093135). Patients were followed up for 12 months after the stroke for the atherothrombotic events. The frequency of the rs9333025 GG genotype was significantly higher in IS patients than in controls. Logistic regression analysis showed that the presence of rs9333025 GG in patients was associated with significantly higher risk of IS. Cox regression analysis revealed that the rs9333025 GG genotype was an independent risk factor for atherothrombotic events after stroke. The rs9333025 GG genotype increases patients' susceptibility to IS and is associated with high frequencies of atherothrombotic events in stroke patients.
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Affiliation(s)
- Biao Zhang
- 1 Department of Neurology, People's Hospital of Deyang City , Deyang, Sichuan, China
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35
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Yi X, Liao D, Fu X, Zhang B, Wang C. Interaction among CYP2C8, EPHX2, and CYP4A11 Gene Variants Significantly Increases the Risk for Ischemic Stroke in Chinese Populations. J Atheroscler Thromb 2015; 22:1148-57. [DOI: 10.5551/jat.29025] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Xingyang Yi
- Department of Neurology, People's Hospital of Deyang City
| | - Duanxiu Liao
- Department of Neurology, People's Hospital of Deyang City
| | - Xiuquan Fu
- Department of Neurology, People's Hospital of Deyang City
| | - Biao Zhang
- Department of Neurology, People's Hospital of Deyang City
| | - Chun Wang
- Department of Neurology, People's Hospital of Deyang City
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36
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Fan F, Geurts AM, Murphy SR, Pabbidi MR, Jacob HJ, Roman RJ. Impaired myogenic response and autoregulation of cerebral blood flow is rescued in CYP4A1 transgenic Dahl salt-sensitive rat. Am J Physiol Regul Integr Comp Physiol 2014; 308:R379-90. [PMID: 25540098 DOI: 10.1152/ajpregu.00256.2014] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have reported that a reduction in renal production of 20-HETE contributes to development of hypertension in Dahl salt-sensitive (SS) rats. The present study examined whether 20-HETE production is also reduced in the cerebral vasculature of SS rats and whether this impairs the myogenic response and autoregulation of cerebral blood flow (CBF). The production of 20-HETE, the myogenic response of middle cerebral arteries (MCA), and autoregulation of CBF were compared in SS, SS-5(BN) rats and a newly generated CYP4A1 transgenic rat. 20-HETE production was 6-fold higher in cerebral arteries of CYP4A1 and SS-5(BN) than in SS rats. The diameter of the MCA decreased to 70 ± 3% to 65 ± 6% in CYP4A1 and SS-5(BN) rats when pressure was increased from 40 to 140 mmHg. In contrast, the myogenic response of MCA isolated from SS rats did not constrict. Administration of a 20-HETE synthesis inhibitor, HET0016, abolished the myogenic response of MCA in CYP4A1 and SS-5(BN) rats but had no effect in SS rats. Autoregulation of CBF was impaired in SS rats compared with CYP4A1 and SS-5(BN) rats. Blood-brain barrier leakage was 5-fold higher in the brain of SS rats than in SS-5(BN) and SS.CYP4A1 rats. These findings indicate that a genetic deficiency in the formation of 20-HETE contributes to an impaired myogenic response in MCA and autoregulation of CBF in SS rats and this may contribute to vascular remodeling and cerebral injury following the onset of hypertension.
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Affiliation(s)
- Fan Fan
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Aron M Geurts
- Human and Molecular Genetics Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Sydney R Murphy
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Mallikarjuna R Pabbidi
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi; and
| | - Howard J Jacob
- Human and Molecular Genetics Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Richard J Roman
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi; and
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Howarth C. The contribution of astrocytes to the regulation of cerebral blood flow. Front Neurosci 2014; 8:103. [PMID: 24847203 PMCID: PMC4023041 DOI: 10.3389/fnins.2014.00103] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 04/18/2014] [Indexed: 12/31/2022] Open
Abstract
In order to maintain normal brain function, it is critical that cerebral blood flow (CBF) is matched to neuronal metabolic needs. Accordingly, blood flow is increased to areas where neurons are more active (a response termed functional hyperemia). The tight relationships between neuronal activation, glial cell activity, cerebral energy metabolism, and the cerebral vasculature, known as neurometabolic and neurovascular coupling, underpin functional MRI (fMRI) signals but are incompletely understood. As functional imaging techniques, particularly BOLD fMRI, become more widely used, their utility hinges on our ability to accurately and reliably interpret the findings. A growing body of data demonstrates that astrocytes can serve as a "bridge," relaying information on the level of neural activity to blood vessels in order to coordinate oxygen and glucose delivery with the energy demands of the tissue. It is widely assumed that calcium-dependent release of vasoactive substances by astrocytes results in arteriole dilation and the increased blood flow which accompanies neuronal activity. However, the signaling molecules responsible for this communication between astrocytes and blood vessels are yet to be definitively confirmed. Indeed, there is controversy over whether activity-induced changes in astrocyte calcium are widespread and fast enough to elicit such functional hyperemia responses. In this review, I will summarize the evidence which has convincingly demonstrated that astrocytes are able to modify the diameter of cerebral arterioles. I will discuss the prevalence, presence, and timing of stimulus-induced astrocyte calcium transients and describe the evidence for and against the role of calcium-dependent formation and release of vasoactive substances by astrocytes. I will also review alternative mechanisms of astrocyte-evoked changes in arteriole diameter and consider the questions which remain to be answered in this exciting area of research.
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Affiliation(s)
- Clare Howarth
- Department of Psychology, University of Sheffield Sheffield, UK
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38
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Adenosine A1 receptors link to smooth muscle contraction via CYP4a, protein kinase C-α, and ERK1/2. J Cardiovasc Pharmacol 2013; 62:78-83. [PMID: 23519140 DOI: 10.1097/fjc.0b013e3182919591] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Adenosine A1 receptor (A1AR) activation contracts smooth muscle, although signaling mechanisms are not thoroughly understood. Activation of A1AR leads to metabolism of arachidonic acid, including the production of 20-hydroxyeicosatetraenoic acid (20-HETE) by cytochrome P4504a (CYP4a). The 20-HETE can activate protein kinase C-α (PKC-α), which crosstalks with extracellular signal-regulated kinase (ERK1/2) pathway. Both these pathways can regulate smooth muscle contraction, we tested the hypothesis that A1AR contracts smooth muscle through a pathway involving CYP4a, PKC-α, and ERK1/2. Experiments included isometric tension recordings of aortic contraction and Western blots of signaling molecules in wild type (WT) and A1AR knockout (A1KO) mice. Contraction to the A1-selective agonist 2-chloro-N cyclopentyladenosine (CCPA) was absent in A1KO mice aortae, indicating the contractile role of A1AR. Inhibition of CYP4a (HET0016) abolished 2-chloro-N cyclopentyladenosine-induced contraction in WT aortae, indicating a critical role for 20-HETE. Both WT and A1KO mice aortae contracted in response to exogenous 20-HETE. Inhibition of PKC-α (Gö6976) or ERK1/2 (PD98059) attenuated 20-HETE-induced contraction equally, suggesting that ERK1/2 is downstream of PKC-α. Contractions to exogenous 20-HETE were significantly less in A1KO mice; reduced protein levels of PKC-α, p-ERK1/2, and total ERK1/2 supported this observation. Our data indicate that A1AR mediates smooth muscle contraction via CYP4a and a PKC-α-ERK1/2 pathway.
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Toth P, Csiszar A, Tucsek Z, Sosnowska D, Gautam T, Koller A, Schwartzman ML, Sonntag WE, Ungvari Z. Role of 20-HETE, TRPC channels, and BKCa in dysregulation of pressure-induced Ca2+ signaling and myogenic constriction of cerebral arteries in aged hypertensive mice. Am J Physiol Heart Circ Physiol 2013; 305:H1698-708. [PMID: 24097425 DOI: 10.1152/ajpheart.00377.2013] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hypertension in the elderly substantially increases the risk of stroke and vascular cognitive impairment in part due to an impaired functional adaptation of aged cerebral arteries to high blood pressure. To elucidate the mechanisms underlying impaired autoregulatory protection in aging, hypertension was induced in young (3 mo) and aged (24 mo) C57BL/6 mice by chronic infusion of angiotensin II and pressure-induced changes in smooth muscle cell (SMC) intracellular Ca(2+) concentration ([Ca(2+)]i) and myogenic constriction of middle cerebral arteries (MCA) were assessed. In MCAs from young hypertensive mice, pressure-induced increases in vascular SMC [Ca(2+)]i and myogenic tone were increased, and these adaptive responses were inhibited by the cytochrome P-450 ω-hydroxylase inhibitor HET0016 and the transient receptor potential (TRP) channel blocker SKF96365. Administration of 20- hydroxyeicosatetraenoic acid (HETE) increased SMC [Ca(2+)]i and constricted MCAs, and these responses were inhibited by SKF96365. MCAs from aged hypertensive mice did not show adaptive increases in pressure-induced calcium signal and myogenic tone and responses to HET0016 and SKF96365 were blunted. Inhibition of large-conductance Ca(2+)-activated K(+) (BK) channels by iberiotoxin enhanced SMC [Ca(2+)]i and myogenic constriction in MCAs of young normotensive animals, whereas it was without effect in MCAs of young hypertensive mice. Iberiotoxin did not restore myogenic adaptation in MCAs of aged hypertensive mice. Thus functional maladaptation of aged cerebral arteries to hypertension is due to the dysregulation of pressure-induced 20-HETE and TRP channel-mediated SMC calcium signaling, whereas overactivation of BK channels is unlikely to play a role in this phenomenon.
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Affiliation(s)
- Peter Toth
- Reynolds Oklahoma Center on Aging, Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
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Kunduri S, Dick G, Nayeem M, Mustafa S. Adenosine A 1 receptor signaling inhibits BK channels through a PKCα-dependent mechanism in mouse aortic smooth muscle. Physiol Rep 2013; 1. [PMID: 23977428 PMCID: PMC3747964 DOI: 10.1002/phy2.37] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Adenosine receptors (AR; A1, A2A, A2B, and A3) contract and relax smooth muscle through different signaling mechanisms. Deciphering these complex responses remains difficult because relationships between AR subtypes and various end-effectors (e.g., enzymes and ion channels) remain to be identified. A1AR stimulation is associated with the production of 20–hydroxyeicosatetraenoic acid (20–HETE) and activation of protein kinase C (PKC). 20–HETE and PKC can inhibit large conductance Ca2+/voltage-sensitive K+ (BK) channels that regulate smooth muscle contraction. We tested the hypothesis that activation of A1AR inhibits BK channels via a PKC-dependent mechanism. Patch clamp recordings and Western blots were performed using aortae of wild type (WT) and A1AR knockout (A1KO) mice. There were no differences in whole-cell K+ current or α and β1 subunits expression between WT and A1KO. 20–HETE (100 nmol/L) inhibited BK current similarly in WT and A1KO mice. NECA (5′–N–ethylcarboxamidoadenosine; 10 μmol/L), a nonselective AR agonist, increased BK current in myocytes from both WT and A1KO mice, but the increase was greater in A1KO (52 ± 15 vs. 17 ± 3%; P < 0.05). This suggests that A1AR signaling negatively regulates BK channel activity. Accordingly, CCPA (2–chloro–N(6)-cyclopentyladenosine; 100 nmol/L), an A1AR-selective agonist, inhibited BK current in myocytes from WT but not A1KO mice (81 ± 4 vs. 100 ± 7% of control; P < 0.05). Gö6976 (100 nmol/L), a PKCα inhibitor, abolished the effect of CCPA to inhibit BK current (99 ± 3% of control). These data lead us to conclude that, in aortic smooth muscle, A1AR inhibits BK channel activity and that this occurs via a mechanism involving PKCα.
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Affiliation(s)
- Ss Kunduri
- Department of Physiology & Pharmacology, West Virginia University School of Medicine ; Center for Cardiovascular and Respiratory Sciences, West Virginia University School of Medicine
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Roman RJ, Renic M, Dunn KMJ, Takeuchi K, Hacein-Bey L. Evidence that 20-HETE contributes to the development of acute and delayed cerebral vasospasm. Neurol Res 2013; 28:738-49. [PMID: 17164037 DOI: 10.1179/016164106x152016] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Recent studies have indicated that arachidonic acid (AA) is metabolized by the cytochrome P450 4A (CYP4A) enzymes in cerebral arteries to produce 20-hydroxyeicosatetraenoic acid (20-HETE) and that this compound has effects on cerebral vascular tone that mimic those seen following subarachnoid hemorrhage (SAH). In this regard, 20-HETE is a potent constrictor of cerebral arteries that decreases the open state probability of Ca(2+)-activated K(+) channels through activation of protein kinase C (PKC). It increases the sensitivity of the contractile apparatus to Ca(2+) by activating PKC and rho kinase. The formation of 20-HETE is stimulated by angiotensin II (AII), endothelin, adenosine triphosphate (ATP) and serotonin, and inhibited by NO, CO and superoxide radicals. Inhibitors of the formation of 20-HETE block the myogenic response of cerebral arterioles to elevations in transmural pressure in vitro and autoregulation of cerebral blood flow (CBF) in vivo. 20-HETE also plays an important role in modulating the cerebral vascular responses to vasodilators (NO and CO) and vasoconstrictors (AII, endothelin, serotonin). Recent studies have indicated that the levels of 20-HETE in cerebrospinal fluid (CSF) increase in rats, dogs and human patients following SAH and that inhibitors of the synthesis of 20-HETE prevent the acute fall in CBF in rats and reverse delayed vasospasm in both dogs and rats. This review examines the evidence that an elevation in the production of 20-HETE contributes to the initial fall in CBF following SAH and the later development of delayed vasospasm.
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Affiliation(s)
- Richard J Roman
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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Bubb KJ, Wen H, Panayiotou CM, Finsterbusch M, Khan FJ, Chan MV, Priestley JV, Baker MD, Ahluwalia A. Activation of neuronal transient receptor potential vanilloid 1 channel underlies 20-hydroxyeicosatetraenoic acid-induced vasoactivity: role for protein kinase A. Hypertension 2013; 62:426-33. [PMID: 23753406 DOI: 10.1161/hypertensionaha.111.00942] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A rise in intraluminal pressure triggers vasoconstriction in resistance arteries, which is associated with local generation of the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE). Importantly, dysregulation of 20-HETE synthesis and activity has been implicated in several cardiovascular disease states, including ischemic disease, hypertension, and stroke; however, the exact molecular pathways involved in mediating 20-HETE bioactivity are uncertain. We investigated whether 20-HETE activates the transient receptor potential vanilloid 1 (TRPV1) and thereby regulates vascular function and blood pressure. We demonstrate that 20-HETE causes dose-dependent increases in blood pressure, coronary perfusion pressure (isolated Langendorff), and pressure-induced constriction of resistance arteries (perfusion myography) that is substantially attenuated in TRPV1 knockout mice and by treatment with the neurokinin 1 receptor antagonist RP67580. Furthermore, we show that both channel activation (via patch-clamping of dorsal root ganglion neurons) and vessel constriction are enhanced under inflammatory conditions, and our findings indicate a predominant role for protein kinase A-mediated sensitization of TRPV1 in these phenomena. Finally, we identify a prominence of these pathway in males compared with females, an effect we relate to reduced protein kinase A-induced phosphorylation of TRPV1. 20-HETE-induced activation of TRPV1, in part, mediates pressure-induced myogenic constriction and underlies 20-HETE-induced elevations in blood pressure and coronary resistance. Our findings identify a novel vasoconstrictor 20-HETE/TRPV1 pathway that may offer potential for therapeutic targeting in cardiovascular diseases associated with elevated 20-HETE implicated in dysregulated organ blood flow, such as stroke or hypertension.
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Affiliation(s)
- Kristen J Bubb
- Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Sq, London EC1M 6BQ, UK
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Ge Y, Murphy SR, Lu Y, Falck J, Liu R, Roman RJ. Endogenously produced 20-HETE modulates myogenic and TGF response in microperfused afferent arterioles. Prostaglandins Other Lipid Mediat 2013; 102-103:42-8. [PMID: 23500064 DOI: 10.1016/j.prostaglandins.2013.03.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 03/01/2013] [Accepted: 03/04/2013] [Indexed: 01/13/2023]
Abstract
Previous studies have indicated that 20-hydroxyeicosatetraeonic acid (20-HETE) modulates vascular tone in large cerebral and renal arteries through inhibition of the large conductance, calcium sensitive potassium (BK) channel activity. However, the role of 20-HETE in modulating tubuloglomerular feedback (TGF) and the myogenic response in the afferent arteriole (Af-Art) is unknown. The present study examined the effects of inhibitors of the synthesis and action of 20-HETE on the myogenic and TGF responses of isolated rabbit and mouse Af-Arts. Luminal diameter decreased by 9.2±0.5% in mice and 8.9±1.3% in rabbit Af-Art when the perfusion pressure was increased from 60 to 120 mmHg. Administration of a 20-HETE synthesis inhibitor, HET0016 (1 μM), or a selective 20-HETE antagonist, 6, 15-20-hydroxyeicosadienoic acid (6, 15-20-HEDE, 10 μM) completely blocked the myogenic response of both rabbit and mouse Af-Art, while addition of 5, 14-20-HEDE (10 μM), a 20-HETE agonist, restored the myogenic response in vessels treated with HET0016. Increases in NaCl concentration from 10 to 80 mM of the solution perfusing the macula densa constricted the Af-Art of rabbits by 6.0±1.4 μm (n=5). Addition of a 20-HETE agonist to the tubular perfusate potentiated the TGF-mediated vasoconstrictor response. This response was blocked by addition of a 20-HETE antagonist (6, 15-20-HEDE, 10 μM) to the vascular perfusate. These studies indicate that locally produced 20-HETE plays an important role in modulating the myogenic and TGF responsiveness of the Af-Art and may help explain how deficiencies in the renal formation of 20-HETE could promote the development of hypertension induced glomerular injury.
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Affiliation(s)
- Ying Ge
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
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Wickramasekera NT, Gebremedhin D, Carver KA, Vakeel P, Ramchandran R, Schuett A, Harder DR. Role of dual-specificity protein phosphatase-5 in modulating the myogenic response in rat cerebral arteries. J Appl Physiol (1985) 2012; 114:252-61. [PMID: 23172031 DOI: 10.1152/japplphysiol.01026.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The present study examined the role of the dual-specificity protein phosphatase-5 (DUSP-5) in the pressure-induced myogenic responses of organ-cultured cerebral arterial segments. In these studies, we initially compared freshly isolated and organ-cultured cerebral arterial segments with respect to responses to step increases in intravascular pressure, vasodilator and vasoconstrictor stimuli, activities of the large-conductance arterial Ca(2+)-activated K(+) (K(Ca)) single-channel current, and stable protein expression of DUSP-5 enzyme. The results demonstrate maintained pressure-dependent myogenic vasoconstriction, DUSP-5 protein expression, endothelium-dependent and -independent dilations, agonist-induced constriction, and unitary K(Ca) channel conductance in organ-cultured cerebral arterial segments similar to that in freshly isolated cerebral arteries. Furthermore, using a permeabilization transfection technique in organ-cultured cerebral arterial segments, gene-specific small interfering RNA (siRNA) induced knockdown of DUSP-5 mRNA and protein, which were associated with enhanced pressure-dependent cerebral arterial myogenic constriction and increased phosphorylation of PKC-βII. In addition, siRNA knockdown of DUSP-5 reduced levels of phosphorylated ROCK and ERK1 with no change in the level of phosphorylated ERK2. Pharmacological inhibition of ERK1/2 phosphorylation significantly attenuated pressure-induced myogenic constriction in cerebral arteries. The findings within the present studies illustrate that DUSP-5, native in cerebral arterial muscle cells, appears to regulate signaling of pressure-dependent myogenic cerebral arterial constriction, which is crucial for the maintenance of constant cerebral blood flow to the brain.
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Affiliation(s)
- Nadi T Wickramasekera
- Department of Physiology and Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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Pabbidi MR, Juncos J, Juncos L, Renic M, Tullos HJ, Lazar J, Jacob HJ, Harder DR, Roman RJ. Identification of a region of rat chromosome 1 that impairs the myogenic response and autoregulation of cerebral blood flow in fawn-hooded hypertensive rats. Am J Physiol Heart Circ Physiol 2012; 304:H311-7. [PMID: 23144316 DOI: 10.1152/ajpheart.00622.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the effects of transfer of a 2.4-Mbp region of rat chromosome 1 (RNO1) from Brown Norway (BN) into fawn-hooded hypertensive (FHH) rats on autoregulation (AR) of cerebral blood flow (CBF) and the myogenic response of middle cerebral arteries (MCAs). AR of CBF was poor in FHH and FHH.1(BN) AR(-) congenic strains that excluded the critical 2.4-Mbp region. In contrast, AR was restored in FHH.1(BN) AR(+) congenic strains that included this region. The diameter of MCAs of FHH rats increased from 140 ± 14 to 157 ± 18 μm when transmural pressure was increased from 40 to 140 mmHg, but it decreased from 137 ± 5 to 94 ± 7 μm in FHH.1(BN) AR(+) congenic strains. Transient occlusion of MCAs reduced CBF by 80% in all strains. However, the hyperemic response following ischemia was significantly greater in FHH and AR(-) rats than that seen in AR(+) congenic strains (AR(-), 173 ± 11% vs. AR(+), 124 ± 5%). Infarct size and edema formation were also significantly greater in an AR(-) strain (38.6 ± 2.6 and 12.1 ± 2%) than in AR(+) congenic strains (27.6 ± 1.8 and 6.5 ± 0.9%). These results indicate that there is a gene in the 2.4-Mbp region of RNO1 that alters the development of myogenic tone in cerebral arteries. Transfer of this region from BN to FHH rats restores AR of CBF and vascular reactivity and reduces cerebral injury after transient occlusion and reperfusion of the MCA.
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Gleim S, Stitham J, Tang WH, Martin KA, Hwa J. An eicosanoid-centric view of atherothrombotic risk factors. Cell Mol Life Sci 2012; 69:3361-80. [PMID: 22491820 PMCID: PMC3691514 DOI: 10.1007/s00018-012-0982-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 03/22/2012] [Accepted: 03/26/2012] [Indexed: 02/06/2023]
Abstract
Cardiovascular disease is the foremost cause of morbidity and mortality in the Western world. Atherosclerosis followed by thrombosis (atherothrombosis) is the pathological process underlying most myocardial, cerebral, and peripheral vascular events. Atherothrombosis is a complex and heterogeneous inflammatory process that involves interactions between many cell types (including vascular smooth muscle cells, endothelial cells, macrophages, and platelets) and processes (including migration, proliferation, and activation). Despite a wealth of knowledge from many recent studies using knockout mouse and human genetic studies (GWAS and candidate approach) identifying genes and proteins directly involved in these processes, traditional cardiovascular risk factors (hyperlipidemia, hypertension, smoking, diabetes mellitus, sex, and age) remain the most useful predictor of disease. Eicosanoids (20 carbon polyunsaturated fatty acid derivatives of arachidonic acid and other essential fatty acids) are emerging as important regulators of cardiovascular disease processes. Drugs indirectly modulating these signals, including COX-1/COX-2 inhibitors, have proven to play major roles in the atherothrombotic process. However, the complexity of their roles and regulation by opposing eicosanoid signaling, have contributed to the lack of therapies directed at the eicosanoid receptors themselves. This is likely to change, as our understanding of the structure, signaling, and function of the eicosanoid receptors improves. Indeed, a major advance is emerging from the characterization of dysfunctional naturally occurring mutations of the eicosanoid receptors. In light of the proven and continuing importance of risk factors, we have elected to focus on the relationship between eicosanoids and cardiovascular risk factors.
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Affiliation(s)
- Scott Gleim
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511
| | - Jeremiah Stitham
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511
| | - Wai Ho Tang
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511
| | - Kathleen A. Martin
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511
| | - John Hwa
- Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511
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Tunctan B, Sari AN, Kacan M, Unsal D, Buharalioglu CK, Sahan-Firat S, Korkmaz B, Falck JR, Malik KU. NS-398 reverses hypotension in endotoxemic rats: contribution of eicosanoids, NO, and peroxynitrite. Prostaglandins Other Lipid Mediat 2012; 104-105:93-108. [PMID: 22975359 DOI: 10.1016/j.prostaglandins.2012.08.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 08/22/2012] [Accepted: 08/23/2012] [Indexed: 01/09/2023]
Abstract
We have previously demonstrated that inhibition of vasodilator prostanoids, PGI2 and PGE2, and nitric oxide (NO) synthesis by a selective cyclooxygenase-2 (COX-2) inhibitor, NS-398, restores blood pressure as a result of increased systemic and renal levels of 20-hydroxyeicosatetraenoic acid (20-HETE) in endotoxemic rats. The aim of this study was to further investigate the effects of NS-398 on the changes in expression and/or activity of COX-2, cytochrome P450 4A1 (CYP4A1), inducible NO synthase (iNOS), and peroxynitrite formation in serum, renal, cardiac, and/or vascular tissues of lipopolysaccharide (LPS)-treated rats. LPS (10mg/kg, i.p.)-induced decrease in blood pressure was associated with increased protein levels of COX-2, iNOS, and nitrotyrosine in kidney, heart, thoracic aorta, and superior mesenteric artery. The activities of COX-2 and iNOS as well as levels of PGI2, PGE2, and nitrotyrosine were also increased in the systemic circulation and renal, cardiac, and vascular tissues of LPS-treated rats. In contrast, renal, cardiac, and vascular CYP4A1 protein expression as well as systemic and tissue levels of 20-HETE were decreased in endotoxemic rats. These effects of LPS, except COX-2 protein expression, were prevented by NS-398 (10 mg/kg, i.p.), given 1h after injection of LPS. These data suggest that COX-2-derived vasodilator prostanoids, PGI2 and PGE2, produced during endotoxemia increase iNOS protein expression and activity as well as peroxynitrite formation resulting in decreased CYP4A1 protein expression and 20-HETE synthesis. Taken together, we concluded that an increase in 20-HETE levels associated with a decrease in the production of vasodilator prostanoids and NO participates in the effect of NS-398 to prevent hypotension in the rat model of septic shock.
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Affiliation(s)
- Bahar Tunctan
- Department of Pharmacology, Faculty of Pharmacy, Mersin University, Mersin, Turkey.
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Hu XQ, Zhang L. Function and regulation of large conductance Ca(2+)-activated K+ channel in vascular smooth muscle cells. Drug Discov Today 2012; 17:974-87. [PMID: 22521666 PMCID: PMC3414640 DOI: 10.1016/j.drudis.2012.04.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 03/06/2012] [Accepted: 04/05/2012] [Indexed: 12/23/2022]
Abstract
Large conductance Ca(2+)-activated K(+) (BK(Ca)) channels are abundantly expressed in vascular smooth muscle cells. Activation of BK(Ca) channels leads to hyperpolarization of cell membrane, which in turn counteracts vasoconstriction. Therefore, BK(Ca) channels have an important role in regulation of vascular tone and blood pressure. The activity of BK(Ca) channels is subject to modulation by various factors. Furthermore, the function of BK(Ca) channels are altered in both physiological and pathophysiological conditions, such as pregnancy, hypertension and diabetes, which has dramatic impacts on vascular tone and hemodynamics. Consequently, compounds and genetic manipulation that alter activity and expression of the channel might be of therapeutic interest.
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Affiliation(s)
- Xiang-Qun Hu
- Center for Perinatal Biology, Division of Pharmacology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA.
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Duchemin S, Boily M, Sadekova N, Girouard H. The complex contribution of NOS interneurons in the physiology of cerebrovascular regulation. Front Neural Circuits 2012; 6:51. [PMID: 22907993 PMCID: PMC3414732 DOI: 10.3389/fncir.2012.00051] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Accepted: 07/19/2012] [Indexed: 12/23/2022] Open
Abstract
Following the discovery of the vasorelaxant properties of nitric oxide (NO) by Furchgott and Ignarro, the finding by Bredt and coll. of a constitutively expressed NO synthase in neurons (nNOS) led to the presumption that neuronal NO may control cerebrovascular functions. Consequently, numerous studies have sought to determine whether neuraly-derived NO is involved in the regulation of cerebral blood flow (CBF). Anatomically, axons, dendrites, or somata of NO neurons have been found to contact the basement membrane of blood vessels or perivascular astrocytes in all segments of the cortical microcirculation. Functionally, various experimental approaches support a role of neuronal NO in the maintenance of resting CBF as well as in the vascular response to neuronal activity. Since decades, it has been assumed that neuronal NO simply diffuses to the local blood vessels and produce vasodilation through a cGMP-PKG dependent mechanism. However, NO is not the sole mediator of vasodilation in the cerebral microcirculation and is known to interact with a myriad of signaling pathways also involved in vascular control. In addition, cerebrovascular regulation is the result of a complex orchestration between all components of the neurovascular unit (i.e., neuronal, glial, and vascular cells) also known to produce NO. In this review article, the role of NO interneuron in the regulation of cortical microcirculation will be discussed in the context of the neurovascular unit.
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Affiliation(s)
- Sonia Duchemin
- Department of Pharmacology, Université de Montréal Montreal, QC, Canada
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Koller A, Toth P. Contribution of flow-dependent vasomotor mechanisms to the autoregulation of cerebral blood flow. J Vasc Res 2012; 49:375-89. [PMID: 22739136 PMCID: PMC3586555 DOI: 10.1159/000338747] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 04/04/2012] [Indexed: 11/19/2022] Open
Abstract
Regulation of cerebral blood flow (CBF) is the result of multilevel mechanisms to maintain the appropriate blood supply to the brain while having to comply with the limited space available in the cranium. The latter requirement is ensured by the autoregulation of CBF, in which the pressure-sensitive myogenic response is known to play a pivotal role. However, in vivo increases in pressure are accompanied by increases in flow; yet the effects of flow on the vasomotor tone of cerebral vessels are less known. Earlier studies showed flow-sensitive dilation and/or constriction or both, but no clear picture emerged. Recently, the important role of flow-sensitive mechanism(s) eliciting the constriction of cerebral vessels has been demonstrated. This review focuses on the effect of hemodynamic forces (especially intraluminal flow) on the vasomotor tone of cerebral vessels and the underlying cellular and molecular mechanisms. A novel concept of autoregulation of CBF is proposed, suggesting that (in certain areas of the cerebrovascular tree) pressure- and flow-induced constrictions together maintain an effective autoregulation, and that alterations in these mechanisms may contribute to the development of cerebrovascular disorders. Future studies are warranted to explore the signals, the details of signaling processes and the in vivo importance of these mechanisms.
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Affiliation(s)
- Akos Koller
- Department of Pathophysiology and Gerontology, Medical School, University of Pécs, Pécs, Hungary.
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