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Mavridis T, Mavridi A, Karampela E, Galanos A, Gkiokas G, Iacovidou N, Xanthos T. Sovateltide (ILR-1620) Improves Motor Function and Reduces Hyperalgesia in a Rat Model of Spinal Cord Injury. Neurocrit Care 2024:10.1007/s12028-024-01950-2. [PMID: 38443708 DOI: 10.1007/s12028-024-01950-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 01/26/2024] [Indexed: 03/07/2024]
Abstract
BACKGROUND Spinal cord injury (SCI) presents a major global health challenge, with rising incidence rates and substantial disability. Although progress has been made in understanding SCI's pathophysiology and early management, there is still a lack of effective treatments to mitigate long-term consequences. This study investigates the potential of sovateltide, a selective endothelin B receptor agonist, in improving clinical outcomes in an acute SCI rat model. METHODS Thirty male Sprague-Dawley rats underwent sham surgery (group A) or SCI and treated with vehicle (group B) or sovateltide (group C). Clinical tests, including Basso, Beattie, and Bresnahan scoring, inclined plane, and allodynia testing with von Frey hair, were performed at various time points. Statistical analyses assessed treatment effects. RESULTS Sovateltide administration significantly improved motor function, reducing neurological deficits and enhancing locomotor recovery compared with vehicle-treated rats, starting from day 7 post injury. Additionally, the allodynic threshold improved, suggesting antinociceptive properties. Notably, the sovateltide group demonstrated sustained recovery, and even reached preinjury performance levels, whereas the vehicle group plateaued. CONCLUSIONS This study suggests that sovateltide may offer neuroprotective effects, enhancing neurogenesis and angiogenesis. Furthermore, it may possess anti-inflammatory and antinociceptive properties. Future clinical trials are needed to validate these findings, but sovateltide shows promise as a potential therapeutic strategy to improve functional outcomes in SCI. Sovateltide, an endothelin B receptor agonist, exhibits neuroprotective properties, enhancing motor recovery and ameliorating hyperalgesia in a rat SCI model. These findings could pave the way for innovative pharmacological interventions for SCI in clinical settings.
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Affiliation(s)
- Theodoros Mavridis
- First Department of Neurology, Eginition Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
- Department of Neurology, Tallaght University Hospital (TUH)/The Adelaide and Meath Hospital, Dublin, Incorporating the National Children's Hospital (AMNCH), Dublin, Ireland.
| | - Artemis Mavridi
- First Department of Pediatrics, Medical School, Aghia Sophia Children's Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | | | - Antonis Galanos
- Laboratory for Research of the Musculoskeletal System, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
| | - George Gkiokas
- Second Department of Surgery, Aretaieion University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Nicoletta Iacovidou
- Department of Neonatology, Aretaieio Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Theodoros Xanthos
- School of Health and Caring Sciences, University of West Attica, Athens, Greece
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Abutarboush R, Gu M, Kawoos U, Mullah SH, Chen Y, Goodrich SY, Lashof-Sullivan M, McCarron RM, Statz JK, Bell RS, Stone JR, Ahlers ST. Exposure to Blast Overpressure Impairs Cerebral Microvascular Responses and Alters Vascular and Astrocytic Structure. J Neurotrauma 2019; 36:3138-3157. [PMID: 31210096 PMCID: PMC6818492 DOI: 10.1089/neu.2019.6423] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Exposure to blast overpressure may result in cerebrovascular impairment, including cerebral vasospasm. The mechanisms contributing to this vascular response are unclear. The aim of this study was to evaluate the relationship between blast and functional alterations of the cerebral microcirculation and to investigate potential underlying changes in vascular microstructure. Cerebrovascular responses were assessed in sham- and blast-exposed male rats at multiple time points from 2 h through 28 days after a single 130-kPa (18.9-psi) exposure. Pial microcirculation was assessed through a cranial window created in the parietal bone of anesthetized rats. Pial arteriolar reactivity was evaluated in vivo using hypercapnia, barium chloride, and serotonin. We found that exposure to blast leads to impairment of arteriolar reactivity >24 h after blast exposure, suggesting delayed injury mechanisms that are not simply attributed to direct mechanical deformation. Observed vascular impairment included a reduction in hypercapnia-induced vasodilation, increase in barium-induced constriction, and reversal of the serotonin effect from constriction to dilation. A reduction in vascular smooth muscle contractile proteins consistent with vascular wall proliferation was observed, as well as delayed reduction in nitric oxide synthase and increase in endothelin-1 B receptors, mainly in astrocytes. Collectively, the data show that exposure to blast results in delayed and prolonged alterations in cerebrovascular reactivity that are associated with changes in the microarchitecture of the vessel wall and astrocytes. These changes may contribute to long-term pathologies involving dysfunction of the neurovascular unit, including cerebral vasospasm.
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Affiliation(s)
- Rania Abutarboush
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Ming Gu
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Usmah Kawoos
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Saad H Mullah
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Ye Chen
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Samantha Y Goodrich
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Margaret Lashof-Sullivan
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Richard M McCarron
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Jonathan K Statz
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland.,The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc., Bethesda, Maryland
| | - Randy S Bell
- Neurosurgery Department, Walter Reed National Military Medical Center, Bethesda, Maryland
| | - James R Stone
- Department of Radiology and Medical Imaging, University of Virginia Medical Center, Charlottesville, Virginia
| | - Stephen T Ahlers
- Neurotrauma Department, Naval Medical Research Center, Silver Spring, Maryland
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Hirzallah MI, Choi HA. The Monitoring of Brain Edema and Intracranial Hypertension. JOURNAL OF NEUROCRITICAL CARE 2016. [DOI: 10.18700/jnc.160093] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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4
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The pathophysiological role of astrocytic endothelin-1. Prog Neurobiol 2016; 144:88-102. [DOI: 10.1016/j.pneurobio.2016.04.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 03/23/2016] [Accepted: 04/25/2016] [Indexed: 12/13/2022]
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5
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Mayer D, Oevermann A, Seuberlich T, Vandevelde M, Casanova-Nakayama A, Selimovic-Hamza S, Forterre F, Henke D. Endothelin-1 Immunoreactivity and its Association with Intramedullary Hemorrhage and Myelomalacia in Naturally Occurring Disk Extrusion in Dogs. J Vet Intern Med 2016; 30:1099-111. [PMID: 27353293 PMCID: PMC5094511 DOI: 10.1111/jvim.14364] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 03/04/2016] [Accepted: 05/23/2016] [Indexed: 01/28/2023] Open
Abstract
Background The pathophysiology of ascending/descending myelomalacia (ADMM) after canine intervertebral disk (IVD) extrusion remains poorly understood. Vasoactive molecules might contribute. Hypothesis/Objectives To investigate the immunoreactivity of endothelin‐1 (ET‐1) in the uninjured and injured spinal cord of dogs and its potential association with intramedullary hemorrhage and extension of myelomalacia. Animals Eleven normal control and 34 dogs with thoracolumbar IVD extrusion. Methods Spinal cord tissue of dogs retrospectively selected from our histopathologic database was examined histologically at the level of the extrusion (center) and in segments remote from the center. Endothelin‐1 immunoreactivity was examined immunohistochemically and by in situ hybridization. Associations between the immunoreactivity for ET‐1 and the severity of intramedullary hemorrhage or the extension of myelomalacia were examined. Results Endothelin‐1 was expressed by astrocytes, macrophages, and neurons and only rarely by endothelial cells in all dogs. At the center, ET‐1 immunoreactivity was significantly higher in astrocytes (median score 4.02) and lower in neurons (3.21) than in control dogs (3.0 and 4.54) (P < .001; P = .004) irrespective of the grade of hemorrhage or myelomalacia. In both astrocytes and neurons, there was a higher ET‐1 immunoreactivity in spinal cord regions remote from the center (4.58 and 4.15) than in the center itself (P = .013; P = .001). ET‐1 mRNA was present in nearly all neurons with variable intensity, but not in astrocytes. Conclusion and Clinical Importance Enhanced ET‐1 immunoreactivity over multiple spinal cord segments after IVD extrusion might play a role in the pathogenesis of ADMM. More effective quantitative techniques are required.
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Affiliation(s)
- D Mayer
- Division of Neurological Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Division of Clinical Neurology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - A Oevermann
- Division of Neurological Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - T Seuberlich
- Division of Neurological Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - M Vandevelde
- Division of Neurological Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Division of Clinical Neurology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - A Casanova-Nakayama
- Centre for Fish and Wildlife Health, Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - S Selimovic-Hamza
- Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - F Forterre
- Division of Neurological Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Division of Small Animal Surgery, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - D Henke
- Division of Neurological Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Division of Clinical Neurology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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6
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Kumar H, Ropper AE, Lee SH, Han I. Propitious Therapeutic Modulators to Prevent Blood-Spinal Cord Barrier Disruption in Spinal Cord Injury. Mol Neurobiol 2016; 54:3578-3590. [PMID: 27194298 DOI: 10.1007/s12035-016-9910-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 05/03/2016] [Indexed: 01/09/2023]
Abstract
The blood-spinal cord barrier (BSCB) is a specialized protective barrier that regulates the movement of molecules between blood vessels and the spinal cord parenchyma. Analogous to the blood-brain barrier (BBB), the BSCB plays a crucial role in maintaining the homeostasis and internal environmental stability of the central nervous system (CNS). After spinal cord injury (SCI), BSCB disruption leads to inflammatory cell invasion such as neutrophils and macrophages, contributing to permanent neurological disability. In this review, we focus on the major proteins mediating the BSCB disruption or BSCB repair after SCI. This review is composed of three parts. Section 1. SCI and the BSCB of the review describes critical events involved in the pathophysiology of SCI and their correlation with BSCB integrity/disruption. Section 2. Major proteins involved in BSCB disruption in SCI focuses on the actions of matrix metalloproteinases (MMPs), tumor necrosis factor alpha (TNF-α), heme oxygenase-1 (HO-1), angiopoietins (Angs), bradykinin, nitric oxide (NO), and endothelins (ETs) in BSCB disruption and repair. Section 3. Therapeutic approaches discusses the major therapeutic compounds utilized to date for the prevention of BSCB disruption in animal model of SCI through modulation of several proteins.
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Affiliation(s)
- Hemant Kumar
- Department of Neurosurgery, CHA University, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, 13496, Republic of Korea
| | - Alexander E Ropper
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA
| | - Soo-Hong Lee
- Department of Biomedical Science, CHA University, Seongnam-si, Gyeonggi-do, 13488, Republic of Korea.
| | - Inbo Han
- Department of Neurosurgery, CHA University, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, 13496, Republic of Korea.
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Abstract
Na x, which is preferentially expressed in the glial cells of sensory circumventricular organs in the brain, is a sodium channel that is poorly homologous to voltage-gated sodium channels. We previously reported that Na x is a sodium concentration ([Na+])-sensitive, but not a voltage-sensitive channel that is critically involved in body-fluid homeostasis. Nax-knockout mice do not stop ingesting salt even when dehydrated and transiently develop hypernatremia. [Na+] in body fluids is strictly controlled at 135 to 145 mM in mammals. Although the set point must be within this range, Na x was shown to have a threshold value of ~150 mM for extracellular [Na+] ([Na+]o) for activation in vitro. Therefore, the [Na+]o dependency of Na x in vivo is presumably modified by an as yet unidentified mechanism. We recently demonstrated that the [Na+]o dependency of Na x in the subfornical organ was adjusted to the physiological range by endothelin-3. Pharmacological experiments revealed that endothelin receptor B signaling was involved in this modulation of Na x gating through protein kinase C and ERK1/2 activation. In addition, we identified a case of essential hypernatremia caused by autoimmunity to Na x. Occurrence of a ganglioneuroma composed of Schwann-like cells that robustly expressed Na x was likely to induce the autoimmune response in this patient. An intravenous injection of the immunoglobulin fraction of the patient’s serum, which contained anti-Na x antibodies, into mice reproduced the patient’s symptoms. This review provides an overview of the physiological functions of Na x by summarizing our recent studies.
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Affiliation(s)
- Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
- School of Life Science, The Graduate University for Advanced Studies, Okazaki, Japan
| | - Takeshi Y. Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Japan
- School of Life Science, The Graduate University for Advanced Studies, Okazaki, Japan
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8
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Guo J, Li Y, He Z, Zhang B, Li Y, Hu J, Han M, Xu Y, Li Y, Gu J, Dai B, Chen Z. Targeting endothelin receptors A and B attenuates the inflammatory response and improves locomotor function following spinal cord injury in mice. Int J Mol Med 2014; 34:74-82. [PMID: 24756152 PMCID: PMC4072339 DOI: 10.3892/ijmm.2014.1751] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 04/01/2014] [Indexed: 11/06/2022] Open
Abstract
After spinal cord injury (SCI), the disruption of blood-spinal cord barrier by activation of the endothelin (ET) system is a critical event leading to leukocyte infiltration, inflammatory response and oxidative stress, contributing to neurological disability. In the present study, we showed that blockade of ET receptor A (ETAR) and/or ET receptor B (ETBR) prevented early inflammatory responses directly via the inhibition of neutrophil and monocyte diapedesis and inflammatory mediator production following traumatic SCI in mice. Long-term neurological improvement, based on a series of tests of locomotor performance, occurred only in the spinal cord‑injured mice following blockade of ETAR and ETBR. We also examined the post‑traumatic changes of the micro-environment within the injured spinal cord of mice following blockade of ET receptors. Oxidative stress reflects an imbalance between malondialdehyde and superoxide dismutase in spinal cord‑injured mice treated with vehicle, whereas blockade of ETAR and ETBR reversed the oxidation state imbalance. In addition, hemeoxygenase-1, a protective protease involved in early SCI, was increased in spinal cord‑injured mice following the blockade of ETAR and ETBR, or only ETBR. Matrix metalloproteinase-9, a tissue-destructive protease involved in early damage, was decreased in the injured spinal cord of mice following blockade of ETAR, ETBR or a combination thereof. The findings of the present study therefore suggested an association between ETAR and ETBR in regulating early pathogenesis of SCI and determining the outcomes of long‑term neurological recovery.
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Affiliation(s)
- Jian Guo
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Yiqiao Li
- Central Laboratory, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Zhennian He
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Bin Zhang
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Yonghuan Li
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Jianghua Hu
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Mingyuan Han
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Yuanlin Xu
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Yongfu Li
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Jie Gu
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Bo Dai
- Department of Orthopaedic Surgery, Ningbo Beilun People Hospital, Ningbo, Zhejiang 315800, P.R. China
| | - Zhong Chen
- Department of Orthopaedic Surgery, The First Affiliated Hospital of College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310000, P.R. China
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9
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Kleindienst A, Grünbeck F, Buslei R, Emtmann I, Buchfelder M. Intraperitoneal treatment with S100B enhances hippocampal neurogenesis in juvenile mice and after experimental brain injury. Acta Neurochir (Wien) 2013; 155:1351-60. [PMID: 23649988 DOI: 10.1007/s00701-013-1720-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Accepted: 04/08/2013] [Indexed: 11/26/2022]
Abstract
BACKGROUND Neurogenesis is documented in adult mammals including humans, is promoted by neurotrophic factors, and constitutes an innate repair mechanism following brain injury. The glial neurotrophic protein S100B is released following various types of brain injuries, enhances hippocampal neurogenesis and improves cognitive function following brain injury in rats when applied intrathecally. The present study was designed to elucidate whether the beneficial effect of S100B on injury-induced neurogenesis can be confirmed in mice when applied intraperitoneally (i.p.), and whether this effect is dose-dependent. METHODS Male juvenile mice were subjected to a unilateral parietal cryolesion or sham injury, and treated with S100B at 20nM, 200nM or vehicle i.p. once daily. Hippocampal progenitor cell proliferation was quantified following labelling with bromo-deoxyuridine (BrdU, 50 mg/KG i.p.) in the germinative area of the dentate gyrus, the subgranular zone (SGZ), on day 4 as well as on cell survival and migration to the granular cell layer (GCL) on day 28. Progenitor cell differentiation was assessed following colabelling with the glial marker GFAP and the neuronal marker NeuN. RESULTS S100B enhanced significantly the early progenitor cell proliferation in the SGZ as well as cell survival and migration to the GCL, and promoted neuronal differentiation. While these effects were predominately dose-dependent, 200nM S100B failed to enhance the proliferation in the SGZ on day 4 post-injury. CONCLUSION We conclude that S100B participates in hippocampal neurogenesis after injury at lower nanomolar concentrations. Therefore S100B may serve as a potential adjunct treatment to promote neuroregeneration following brain damage.
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Affiliation(s)
- Andrea Kleindienst
- Departments of Neurosurgery and Neuropathology, Friedrich-Alexander University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany.
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10
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Hiyama TY, Yoshida M, Matsumoto M, Suzuki R, Matsuda T, Watanabe E, Noda M. Endothelin-3 expression in the subfornical organ enhances the sensitivity of Na(x), the brain sodium-level sensor, to suppress salt intake. Cell Metab 2013; 17:507-19. [PMID: 23541371 DOI: 10.1016/j.cmet.2013.02.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 01/09/2013] [Accepted: 02/25/2013] [Indexed: 10/27/2022]
Abstract
Salt homeostasis is essential to survival, but brain mechanisms for salt-intake control have not been fully elucidated. Here, we found that the sensitivity of Na(x) channels to [Na(+)](o) is dose-dependently enhanced by endothelin-3 (ET-3). Na(x) channels began to open when [Na(+)](o) exceeded ~150 mM without ET-3, but opened fully at a physiological [Na(+)](o) (135–145 mM) with 1 nM ET-3. Importantly, ET-3 was expressed in the subfornical organ (SFO) along with Nax, and the level was robustly increased by dehydration. Pharmacological experiments revealed that endothelin receptor B (ET(B)R) signaling is involved in this modulation of Na(x) gating through protein kinase C and ERK1/2 activation. ET(B)R agonists increased the firing rate of GABAergic neurons via lactate in the SFO, and an ET(B)R antagonist attenuated salt aversion during dehydration. These results indicate that ET-3 expression in the SFO is tightly coupled with body-fluid homeostasis through modulation of the [Na(+)](o) sensitivity of Na(x).
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Affiliation(s)
- Takeshi Y Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, Okazaki, Aichi 444-8787, Japan
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Maegele M, Wafaisade A, Peiniger S, Braun M. The role of endothelin and endothelin antagonists in traumatic brain injury: a review of the literature. Neurol Res 2012; 33:119-26. [PMID: 21801586 DOI: 10.1179/016164111x12881719352093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVES To date, there is increasing evidence for the role of endothelins in the pathophysiological development of cerebral vasospasms associated with a variety of neurological diseases, e.g., stroke and subarachnoid hemorrhage. In contrast, only little is known regarding the role of endothelins in impaired cerebral hemodynamics after traumatic brain injury. Therapeutic work in blocking the endothelin system has led to the discovery of a number of antagonists potentially useful in restoring cerebral blood flow after traumatic brain injury, potentially reducing the detrimental effects of secondary brain injury. Therefore, the present work provides an overview of background topics such as structures and biosynthesis of endothelins, different types as well as potential mechanisms and sites of action. In addition, the role of age for the effects of endothelins on cerebral hemodynamics after traumatic brain injury is discussed. RESULTS Description of data supporting the role of the endothelins play in a host of neurological deficits. CONCLUSIONS Endothelin antagonists may be effective as novel treatments for various neuropathologies.
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Affiliation(s)
- Marc Maegele
- Department of Trauma and Orthopedic Surgery, University of Witten/Herdecke, Cologne-Merheim Medical Center, Germany.
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12
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Ostrow LW, Suchyna TM, Sachs F. Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs). Biochem Biophys Res Commun 2011; 410:81-6. [PMID: 21640709 DOI: 10.1016/j.bbrc.2011.05.109] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 05/18/2011] [Indexed: 01/23/2023]
Abstract
The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (<20%) of a rubber substrate increased ET-1 secretion, and 4 μM GsMTx-4 (a specific inhibitor of SACs) inhibited secretion by 30%. GsMTx-4 did not alter basal ET-1 levels in the absence of stretch. Decreasing the calcium influx by lowering extracellular calcium also inhibited stretch-induced ET-1 secretion without effecting ET-1 secretion in unstretched controls. Furthermore, inhibiting SACs with the less specific inhibitor streptomycin also inhibited stretch-induced ET-1 secretion. The data can be explained with a simple model in which ET-1 secretion depends on an internal Ca(2+) threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.
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Affiliation(s)
- Lyle W Ostrow
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
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13
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Chatfield DA, Brahmbhatt DH, Sharp T, Perkes IE, Outrim JG, Menon DK. Juguloarterial endothelin-1 gradients after severe traumatic brain injury. Neurocrit Care 2011; 14:55-60. [PMID: 20652766 DOI: 10.1007/s12028-010-9413-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Endothelin-1 (ET-1) is a potent vasoconstrictor and is thought to be responsible for secondary ischemia and vasogenic edema after traumatic brain injury (TBI). Both CSF and plasma concentrations have been shown to be increased after TBI, but there is little evidence to confirm an intracranial site of production. METHODS Using paired arterial and jugular venous bulb sampling, we measured arterial and jugular levels of ET-1 and its precursor, big endothelin (Big ET), and calculated juguloarterial (JA) gradients for the first 5 days post-TBI. RESULTS Arterial levels of both Big ET and ET-1 were maximal on day 1 post-TBI, and decreased thereafter (P < 0.05). Arterial levels of Big ET and ET-1 showed correlation across all 5 days of the study (r(2) = 0.25, P < 0.001). While there was no significant JA gradient for Big ET, significant gradients were observed for ET-1 on days 1-4 post-TBI (P < 0.05). There was no correlation between JA gradients for Big ET and ET-1 (r(2) < 0.1, P > 0.9). These data suggest parenchymal production of ET-1 by brain tissue with spill over into the blood, rather than local intraluminal cleavage of Big ET in the cerebral vasculature. Systemic ET-1 levels and JA gradients of ET-1 were unrelated to the injury severity, APACHE II score, Marshall Grade, the presence of subarachnoid or subdural hemorrhage, or eventual outcome. CONCLUSIONS These findings confirm the synthesis of Big ET and its cleavage to ET-1 within the brain after TBI. More work is needed to elucidate the pathophysiological role and the outcome impact of ET-1 generation after TBI.
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Affiliation(s)
- Doris A Chatfield
- Division of Anaesthesia, Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
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14
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Kobayashi NR, Hawes SM, Crook JM, Pébay A. G-protein coupled receptors in stem cell self-renewal and differentiation. Stem Cell Rev Rep 2010; 6:351-66. [PMID: 20625855 DOI: 10.1007/s12015-010-9167-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Stem cells have great potential for understanding early development, treating human disease, tissue trauma and early phase drug discovery. The factors that control the regulation of stem cell survival, proliferation, migration and differentiation are still emerging. Some evidence now exists demonstrating the potent effects of various G-protein coupled receptor (GPCR) ligands on the biology of stem cells. This review aims to give an overview of the current knowledge of the regulation of embryonic and somatic stem cell maintenance and differentiation by GPCR ligands.
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15
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Brain cellular localization of endothelin receptors A and B in a rodent model of diffuse traumatic brain injury. Neuroscience 2010; 168:820-30. [DOI: 10.1016/j.neuroscience.2010.01.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2008] [Revised: 12/23/2009] [Accepted: 01/11/2010] [Indexed: 01/23/2023]
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16
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Abstract
In the postnatal brain, oligodendrocyte progenitor cells (OPCs) arise from the subventricular zone (SVZ) and migrate into the developing white matter, where they differentiate into oligodendrocytes and myelinate axons. The mechanisms regulating OPC migration and differentiation are not fully defined. The present study demonstrates that endothelin-1 (ET-1) is an astrocyte-derived signal that regulates OPC migration and differentiation. OPCs in vivo and in culture express functional ET(A) and ET(B) receptors, which mediate ET-1-induced ERK (extracellular signal-regulated kinase) and CREB (cAMP response element-binding protein) phosphorylation. ET-1 exerts both chemotactic and chemokinetic effects on OPCs to enhance cell migration; it also prevents lineage progression from the O4(+) to the O1(+) stage without affecting cell proliferation. Astrocyte-conditioned medium stimulates OPC migration in culture through ET receptor activation, whereas multiphoton time-lapse imaging shows that selective ET receptor antagonists or anti-ET-1 antibodies inhibit OPC migration from the SVZ. Inhibition of ET receptor activity also derepresses OPC differentiation in the corpus callosum in slice cultures. Our findings indicate that ET-1 is a soluble astrocyte-derived signal that regulates OPC migration and differentiation during development.
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Vidovic M, Chen MM, Lu QY, Kalloniatis KF, Martin BM, Tan AHY, Lynch C, Croaker GDH, Cass DT, Song ZM. Deficiency in endothelin receptor B reduces proliferation of neuronal progenitors and increases apoptosis in postnatal rat cerebellum. Cell Mol Neurobiol 2008; 28:1129-38. [PMID: 18683040 DOI: 10.1007/s10571-008-9292-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 06/17/2008] [Indexed: 12/19/2022]
Abstract
Endothelins regulate cellular functions in the mammalian brain through the endothelin receptors A and B (EDNRA and EDNRB). In this study, we investigated the role of EDNRB on cell proliferation in the cerebellum by using the spotting lethal (sl) rat, which carries a naturally occurring deletion in the EDNRB gene. Proliferating cells in the three genotypes, wild-type (+/+), heterozygous (+/sl) and homozygous mutant (sl/sl) rats were labelled by intraperitoneal injection of 5-bromo-2'-deoxyuridine (BrdU) at postnatal day 2. The density of BrdU-positive cells (per mm(2)) in the external germinal layer of sl/sl rats (Mean +/- SEM, 977 +/- 388) was significantly reduced compared to +/+ (4915 +/- 631) and +/sl (2304 +/- 557) rats. Subsequently, we examined the effects of EDNRB mutation on neural apoptosis by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labelling assay. This showed that the density of apoptotic cells in the cerebella of sl/sl rats (9.3 +/- 0.5/mm(2)) was significantly more increased than +/+ rats (4 +/- 0.7). The expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) were measured with standard ELISA, but were unchanged in all genotypes. These results suggest that ENDRB mediates neural proliferation and have anti-apoptotic effects in the cerebellum of the postnatal rat, and that these effects are independent of changes in the expression of BDNF and GDNF. Our findings will lead to better understanding of the morphological changes in the cerebellum of Hirschsprung's disease patients with congenital EDNRB mutation.
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Affiliation(s)
- Maria Vidovic
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 0200, Australia
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18
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Lehmann C, Eisner F, Engele J. Role of endothelins as mediators of injury-induced alterations of glial glutamate turnover. J Neurosci Res 2008; 86:660-7. [PMID: 17893916 DOI: 10.1002/jnr.21512] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Astroglia terminate glutamatergic neurotransmission and prevent excitotoxic extracellular glutamate concentration by clearing synaptically released glutamate through the high-affinity, sodium-dependent glutamate transporters GLT-1 and GLAST. Many brain injures are associated with the disturbed expression of glial glutamate transporters and a subsequent increase of extracellular glutamate to neurotoxic levels. We have now followed up initial hints pointing to endothelins, a family of injury-regulated peptides, as mediators of this injury-induced loss of glial glutamate transporter expression. We observed that, in line with such a role, endothelins not only act as potent inhibitors of basal and exogenously (dbcAMP)-induced expression of GLT-1 in cortical astrocytes as shown before, but likewise inhibit expression of GLT-1 or GLAST in astrocytes cultured from the diencephalon, mesencephalon, cerebellum, and spinal cord. We further demonstrate that endothelins equally inhibit GLT-1 expression in cortical slice cultures, a culture system closely resembling the in vivo situation. Although brain injuries are usually associated with an increase in the expression of the glutamate-converting enzyme glutamine synthetase, cultured cortical astrocytes maintained with endothelins showed an almost complete loss of glutamine synthetase. Interestingly, the inhibitory effects of endothelins on the expression of glutamine synthetase, but not of glutamate transporters, was overridden by high extracellular glutamate, indicating that the primarily inhibitory action of endothelins on the various components of glial glutamate turnover dissociates in the injured brain.
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Affiliation(s)
- Claudia Lehmann
- Institute of Anatomy, University of Leipzig, Medical Faculty, Leipzig, Germany
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19
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Vatter H, Konczalla J, Weidauer S, Preibisch C, Raabe A, Zimmermann M, Seifert V. CHARACTERIZATION OF THE ENDOTHELIN-B RECEPTOR EXPRESSION AND VASOMOTOR FUNCTION DURING EXPERIMENTAL CEREBRAL VASOSPASM. Neurosurgery 2007; 60:1100-8; discussion 1108-9. [PMID: 17538385 DOI: 10.1227/01.neu.0000255471.75752.4b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Several investigations suggest a key role of endothelin (ET) in the development of cerebral vasospasm (CVS). In the cerebrovasculature, physiologically ET-dependent constriction is mediated by the ET(A) receptor, whereas activation of the endothelial ET(B) receptor results in relaxation. However, existence of a contractile ET(B) receptor was postulated after subarachnoid hemorrhage (SAH), according to gene expression studies. The aim of the present investigation is, therefore, to characterize the function and the expression of the ET(B) receptor in the cerebrovasculature during CVS. METHODS CVS was induced in the rat double-hemorrhage model and assessed by perfusion-weighted magnetic resonance imaging scans. Rats were sacrificed on Days 3 and 5 after SAH, and immunohistochemical staining for ET(B) receptors was performed. Isometric force of basilar artery ring segments with (E+) and without (E-) endothelial function was measured. Concentration effect curves for the ET(B) receptor agonist, sarafotoxin 6c, were constructed by cumulative application in segments under resting tension and after precontraction. RESULTS Immunoreactivity for the ET(B) receptor was observed exclusively in the endothelium and was not significantly altered after SAH. Under resting tension, sarafotoxin 6c did not induce significant contraction in E+ or E- segments. After precontraction, a significant relaxation was induced by sarafotoxin 6c administration in sham-operated rats (mean maximum effect, 103 +/- 10%), which decreased time dependently after SAH (Day 3, 68 +/- 3%; Day 5, 42 +/- 3%). Endothelium-dependent relaxation induced by acetylcholine, however, was not significantly reduced. CONCLUSION The present investigation provides evidence for the loss of the ET(B) receptor-mediated vasomotor function after SAH. Thus, antagonism of the ET(B) receptor may be undesirable for the treatment of CVS.
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Affiliation(s)
- Hartmut Vatter
- Department of Neurosurgery, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
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20
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Figiel M, Allritz C, Lehmann C, Engele J. Gap junctional control of glial glutamate transporter expression. Mol Cell Neurosci 2007; 35:130-7. [PMID: 17369047 DOI: 10.1016/j.mcn.2007.02.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 02/06/2007] [Accepted: 02/08/2007] [Indexed: 11/24/2022] Open
Abstract
The uptake of glutamate into astroglia is the predominant mechanism to terminate glutamatergic neurotransmission and to prevent neurotoxic extracellular glutamate concentrations. Here, we show that uncoupling cultured cortical astrocytes with the gap junction blocker, propofol, or the Cx43 mimetic peptide, Gap27, inhibits the expression of GLT-1, the major glutamate transporter subtype in the cortex. The dependence of GLT-1 expression on gap junctions was further confirmed by the use of astrocytes in which either the expression of Cx43, the major astrocytic gap junction protein, was inhibited by RNA interference or which were derived from animals carrying an astrocyte-specific deletion of the Cx43 gene. In both cases, reduced astrocytic coupling was associated with a pronounced decline in GLT-1 expression. Finally, a luciferase reporter gene assay demonstrated that blockade of gap junctions/connexins suppressed transcriptional activity of GLT-1 promoter. These observations unravel a previously unrecognized role of gap junctions in the control of glial glutamate transport.
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Affiliation(s)
- Maciej Figiel
- Institute of Anatomy, University of Leipzig, Medical Faculty, Liebigstr. 13, 04103 Leipzig, Germany
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21
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Luo G, Jamali R, Cao YX, Edvinsson L, Xu CB. Vascular endothelin ET(B) receptor-mediated contraction requires phosphorylation of ERK1/2 proteins. Eur J Pharmacol 2006; 538:124-31. [PMID: 16650404 DOI: 10.1016/j.ejphar.2006.03.057] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 03/23/2006] [Accepted: 03/27/2006] [Indexed: 11/16/2022]
Abstract
In cardiovascular diseases, endothelin type B (ET(B)) receptors in arterial smooth muscle cells are upregulated. The present study revealed that organ culture of rat mesenteric artery segments enhanced endothelin ET(B) receptor-mediated contraction paralleled with increase in the receptor mRNA and protein expressions. The endothelin ET(B) receptor-mediated contraction was associated with increase in phosphorylation of extracellular regulation kinase 1 and 2 (ERK1/2) proteins and elevated levels of intracellular calcium. The elevation curve of intracellular calcium consisted of two phases: one rapid and one sustained. Inhibition of ERK1/2 phosphorylation by SB386023 or blockage of calcium channels by nifedipine significantly reduced the endothelin ET(B) receptor-mediated contraction (P<0.05) and decreased the sustained phase of intracellular calcium level, but not the rapid phase. Thus, phosphorylation of ERK1/2 proteins and elevation of intracellular calcium level are required for endothelin ET(B) receptor-mediated contraction in rat mesenteric artery.
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Affiliation(s)
- Guogang Luo
- Neurology Department of the First Hospital, Medical College of Xian Jiaotong University, P. R. China
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22
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Sirén AL, Radyushkin K, Boretius S, Kämmer D, Riechers CC, Natt O, Sargin D, Watanabe T, Sperling S, Michaelis T, Price J, Meyer B, Frahm J, Ehrenreich H. Global brain atrophy after unilateral parietal lesion and its prevention by erythropoietin. ACTA ACUST UNITED AC 2005; 129:480-9. [PMID: 16339796 DOI: 10.1093/brain/awh703] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In humans, neurotrauma is suspected to cause brain atrophy and accelerate slowly progressive neurodegenerative disorders, such as Alzheimer's disease or schizophrenia. However, a direct link between brain injury and subsequent delayed global neurodegeneration has remained elusive. Here we show that juvenile (4-week-old) mice that are given a discrete unilateral lesion of the parietal cortex, develop to adulthood without obvious clinical symptoms. However, when monitored 3 and 9 months after lesioning, using high-resolution three-dimensional MRI and behavioural testing, the same mice display global neurodegenerative changes. Surprisingly, erythropoietin, a haematopoietic growth factor with potent neuroprotective activity, prevents behavioural abnormalities, cognitive dysfunction and brain atrophy when given for 2 weeks after acute brain injury. This demonstrates that a localized brain lesion is a primary cause of delayed global neurodegeneration that can be efficiently counteracted by neuroprotection.
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Affiliation(s)
- Anna-Leena Sirén
- Division of Clinical Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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23
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Abstract
Glutamate is the main excitatory neurotransmitter in the mammalian central nervous system which at high extracellular levels leads to neuronal over-stimulation and subsequent excitotoxic neuronal cell death. Both the termination of glutamatergic neurotransmission and the prevention of neurotoxic extracellular glutamate concentrations are predominantly achieved by the uptake of extracellular glutamate into astroglia through the high-affinity glutamate transporters, excitatory amino acid transporter-2/glutamate transporter-1 (EAAT-2/GLT-1) and EAAT-1/glutamate aspartate transporter (GLAST). Although several injury-induced growth factors such as epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) potently stimulate the expression of glutamate transporters in cultured astroglia, GLT-1 and/or GLAST expression temporarily decreases during acute brain injuries eventually contributing to secondary neuronal cell death. We now demonstrate that the stimulatory influences of these injury-regulated growth factors are overridden by endothelins (ETs), a family of peptides also upregulated in the injured brain. Exposure of cultured cortical astroglia to ET-1, ET-2, and ET-3 resulted in a major loss of basal glutamate transporter expression after 72 hours and the complete prevention of the known stimulatory influences of dibutyryl cyclic (dbc)AMP, pituitary adenylate cyclase-activating polypeptide (PACAP), EGF, and TGFalpha on both GLT-1 and GLAST expression. With all ET isoforms, the inhibitory effects were detectable with similar low nanomolar concentrations and persisted in endothelin B-receptor deficient astroglia, suggesting that the inhibitory action is equally induced by endothelin A and B receptors. In astroglial cultures maintained with endothelins alone or in combination with PACAP, the inhibitory action was remarkably long-lasting and was still detectable after 7 days. In apparent contrast, glutamate transporter expression partially recovered between days 5 and 7 in cultures maintained with a combination of ETs and the injury-regulated growth factors EGF or TGFalpha. These findings point to ETs as major mediators of injury-dependent down-regulation of glial glutamate transporters and subsequent glutamate-induced brain damage.
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Affiliation(s)
- Joanna Rozyczka
- Institute of Anatomy, University of Leipzig, Medical Faculty, Leipzig, Germany
| | - Maciej Figiel
- Institute of Anatomy, University of Leipzig, Medical Faculty, Leipzig, Germany
| | - Jürgen Engele
- Institute of Anatomy, University of Leipzig, Medical Faculty, Leipzig, Germany
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Rozyczka J, Figiel M, Engele J. Chronic endothelin exposure inhibits connexin43 expression in cultured cortical astroglia. J Neurosci Res 2005; 79:303-9. [PMID: 15605384 DOI: 10.1002/jnr.20355] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Severe brain lesions are accompanied by sustained increases in endothelin (ET) levels, which in turn profoundly affect brain microcirculation and neural cell function. A known response of astrocytes to acute increases in ET levels is the rapid and transient closure of gap junctions and the subsequent decrease of gap junction-mediated intercellular communication (GJIC). Because evidence exists that the loss of GJIC alters astrocytic gene expression, we analyzed the effects of chronic ET exposure on astrocytic gap junction coupling. We found that within 24 hr, cultured cortical astrocytes respond to low nanomolar concentrations (2-10 nM) of either ET-1 or ET-3 with a robust inhibition of connexin (Cx)43 expression, the major junctional protein in astrocytes, and a subsequent decline of GIJC. We further observed that in the continuous presence of ETs, Cx43 expression remained inhibited for at least 7 days. In addition, a similar decrease of Cx43 expression occurred in cultured spinal cord astrocytes maintained with ET-1 for 3 days. Applying ETs in combination with the highly selective ETA and ETB receptor antagonists, BQ123 and BQ788, respectively, revealed that the inhibitory influences on astrocytic Cx43 expression depend on activation of ETB receptors. We suggest that the observed ET-dependent inhibition of Cx43 expression and the resulting decline of GJIC might represent a major pathway by which ETs regulate astrocytic gene expression in the injured brain.
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Affiliation(s)
- Joanna Rozyczka
- Institute of Anatomy, University of Leipzig, Medical Faculty, Leipzig, Germany
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25
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Erdös B, Snipes JA, Kis B, Miller AW, Busija DW. Vasoconstrictor mechanisms in the cerebral circulation are unaffected by insulin resistance. Am J Physiol Regul Integr Comp Physiol 2004; 287:R1456-61. [PMID: 15331381 DOI: 10.1152/ajpregu.00279.2004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin-resistance (IR) impairs agonist-induced relaxation in cerebral arteries, but little is known about its effect on constrictor mechanisms. We examined the vascular responses of the basilar artery (BA) and its side branches in anesthetized Zucker lean (ZL) and IR Zucker obese (ZO) rats using a cranial window technique. Endothelin-1 (ET-1) constricted the BAs in both the ZL and ZO rats, but there was no significant difference between the two groups (ZL: 36 ± 8%; ZO: 33 ± 3% at 10−8 M). Inhibition of the ETA receptors by BQ-123 slightly increased the diameters of the BAs, with no difference shown between the ZL (6 ± 1%) and ZO (5 ± 3%) rats. Expressions of the ETA receptors and ET-1 mRNA examined by immunoblot analysis and RT-PCR, respectively, were also similar in the ZL and ZO groups. Phorbol 12,13-dibutyrate (PDBu), an activator of protein kinase C (PKC), and the thromboxane A2 (TxA2) mimetic U-46619 constricted the BAs, but similarly to ET-1, there was no significant difference between the ZL and ZO groups (10−6 M PDBu: ZL: 33 ± 2%; ZO: 32 ± 4%; and 10−7 M U-46619: ZL: 23 ± 1%; ZO: 19 ± 2%). Inhibition of Rho-kinase with Y-27632 induced dilation of the BAs, and these responses were also comparable in the ZL and ZO rats (ZL: 39 ± 4%; ZO: 38 ± 2% at 10−5 M). In contrast, nitric oxide-dependent relaxation to bradykinin was significantly reduced in the ZO rats (10−6 M: 10 ± 3%) compared with ZLs (29 ± 7%, P < 0.01). These findings indicate that vasoconstrictor responses of the BA mediated by ET-1, TxA2, PKC, and Rho-kinase are not affected by IR.
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Affiliation(s)
- Benedek Erdös
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Blvd., Winston-Salem, NC 27157-1083, USA
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26
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Ostrow LW, Sachs F. Mechanosensation and endothelin in astrocytes--hypothetical roles in CNS pathophysiology. ACTA ACUST UNITED AC 2004; 48:488-508. [PMID: 15914254 DOI: 10.1016/j.brainresrev.2004.09.005] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2003] [Revised: 08/19/2004] [Accepted: 09/09/2004] [Indexed: 01/23/2023]
Abstract
Endothelin (ET) is a potent autocrine mitogen produced by reactive and neoplastic astrocytes. ET has been implicated in the induction of astrocyte proliferation and other transformations engendered by brain pathology, and in promoting the malignant behavior of astrocytomas. Reactive astrocytes containing ET are found in the periphery/penumbra of a wide array of CNS pathologies. Virtually all brain pathology deforms the surrounding parenchyma, either by direct mass effect or edema. Mechanical stress is a well established stimulus for ET production and release by other cell types, but has not been well studied in the brain. However, numerous studies have illustrated that astrocytes can sense mechanical stress and translate it into chemical messages. Furthermore, the ubiquitous reticular meshwork formed by interconnected astrocytes provides an ideal morphology for sensing and responding to mechanical disturbances. We have recently demonstrated stretch-induced ET production by astrocytes in vitro. Inspired by this finding, the purpose of this article is to review the literature on (1) astrocyte mechanosensation, and (2) the endothelin system in astrocytes, and to consider the hypothesis that mechanical induction of the ET system may influence astrocyte functioning in CNS pathophysiology. We conclude by discussing evidence supporting future investigations to determine whether specific inhibition of stretch-activated ion channels may represent a novel strategy for treating or preventing CNS disturbances, as well as the relevance to astrocyte-derived tumors.
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Affiliation(s)
- Lyle W Ostrow
- Department of Physiology and Biophysics, S.U.N.Y. at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, NY 14214, USA
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Wang Y, Wang DH. Prevention of endothelin-1-induced increases in blood pressure: role of endogenous CGRP. Am J Physiol Heart Circ Physiol 2004; 287:H1868-74. [PMID: 15205172 DOI: 10.1152/ajpheart.00241.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
To determine the role of endothelin-1 (ET-1) and its receptors in the regulation of calcitonin gene-related peptide (CGRP) release, male Wistar rats were divided into six groups and subjected to the following treatments for 1 wk with or without ABT-627 (an ET(A) receptor antagonist, 5 mg.kg(-1).day(-1) in drinking water) or A-192621 (an ET(B)-receptor antagonist, 30 mg.kg(-1).day(-1) by oral gavage): control (Con), ET-1 (5 ng.kg(-1).min(-1) iv), Con + ABT-627, Con + A-192621, ET-1 + ABT-627, and ET-1 + A-192621. Baseline mean arterial pressure (MAP, mmHg) was higher (P < 0.05) in Con + A-192621 (122 +/- 4) and ET-1 + A-192621 (119 +/- 4) groups compared with Con (104 +/- 6), ET1 (106 +/- 3), Con + ABT-627 (104 +/- 3), and ET1 + ABT-627 (100 +/- 3) groups. Intravenous administration of CGRP(8-37) (a CGRP receptor antagonist, 1 mg/kg) increased MAP (P < 0.05) in ET-1 (13 +/- 1), Con + A-192621 (12 +/- 1), and ET-1 + A-192621 (15 +/- 3) groups compared with Con (4 +/- 1), Con-ABT-627 (4 +/- 1), and ET-1 + ABT-627 (5 +/- 1) groups. Plasma CGRP levels (in pg/ml) were increased (P < 0.05) in ET-1 (57.5 +/- 6.1), Con + A-192621 (53.9 +/- 3.4), and ET-1 + A-192621 (60.4 +/- 3.0) groups compared with Con (40.4 +/- 1.6), Con + ABT-627 (40.0 +/- 2.9), and ET-1 + ABT-627 (42.6 +/- 1.9) groups. Plasma ET-1 levels (in pg/ml) were higher (P < 0.05) in ET-1 (2.8 +/- 0.2), ET-1 + ABT-627 (3.2 +/- 0.4), Con + A-192621 (3.3 +/- 0.4), and ET-1 + A-192621 (4.6 +/- 0.3) groups compared with Con (1.1 +/- 0.2) and Con-ABT-627 (1.3 +/- 0.2) groups. Therefore, our data show that ET-1 infusion leads to increased CGRP release via activation of the ET(A) receptor, which plays a compensatory role in preventing ET-1-induced elevation in blood pressure.
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Affiliation(s)
- Youping Wang
- Dept. of Medicine, B316 Clinical Center, Michigan State University, East Lansing, MI 48824, USA
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Blomstrand F, Venance L, Sirén AL, Ezan P, Hanse E, Glowinski J, Ehrenreich H, Giaume C. Endothelins regulate astrocyte gap junctions in rat hippocampal slices. Eur J Neurosci 2004; 19:1005-15. [PMID: 15009148 DOI: 10.1111/j.0953-816x.2004.03197.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Gap junctional communication (GJC) is a typical feature of astrocytes proposed to contribute to the role played by these glial cells in brain physiology and pathology. In acutely isolated hippocampal slices from rat (P11-P19), intercellular diffusion of biocytin through gap junction channels was shown to occur between hundreds of cells immuno-positive for astrocytic markers studied in the CA1/CA2 region. Single-cell RT-PCR demonstrated astrocytic mRNA expression of several connexin (Cx) subtypes, the molecular constituent of gap junction channels, whereas immunoblotting confirmed that Cx43 and Cx30 are the main gap junction proteins in hippocampal astrocytes. In the brain, astrocytes represent a major target for endothelins (Ets), a vasoactive family of peptides. Our results demonstrate that Ets decrease the expression of phosphorylated Cx43 forms and are potent inhibitors of GJC. The Et-induced effects were investigated using specific Et receptor agonists and antagonists, including Bosentan (Tracleer trade mark ), an EtA/B receptor antagonist, and using hippocampal slices and cultures from EtB-receptor-deficient rats. Interestingly, the pharmacological profile of Ets effects did not follow the classical profile established in cardiovascular systems. The present study therefore identifies Ets as potent endogenous inhibitory regulators of astrocyte networks. As such, the action of these peptides on astrocyte GJC might be involved in the contribution of astrocytes to neuroprotective processes and have a therapeutic potential in neuropathological situations.
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Affiliation(s)
- F Blomstrand
- Neuropharmacologie, INSERM U114, Collège de France, Paris, France.
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29
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Peters CM, Rogers SD, Pomonis JD, Egnaczyk GF, Keyser CP, Schmidt JA, Ghilardi JR, Maggio JE, Mantyh PW, Egnazyck GF. Endothelin receptor expression in the normal and injured spinal cord: potential involvement in injury-induced ischemia and gliosis. Exp Neurol 2003; 180:1-13. [PMID: 12668144 DOI: 10.1016/s0014-4886(02)00023-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The endothelins (ETs) are a family of peptides that exert their biological effects via two distinct receptors, the endothelin A receptor (ET(A)R) and the endothelin B receptor (ET(B)R). To more clearly define the potential actions of ETs following spinal cord injury, we used immunohistochemistry and confocal microscopy to examine the protein expression of ET(A)R and ET(B)R in the normal and injured rat spinal cord. In the normal spinal cord, ET(A)R immunoreactivity (IR) is expressed by vascular smooth muscle cells and a subpopulation of primary afferent nerve fibers. ET(B)R-IR is expressed primarily by radial glia, a small population of gray and white matter astrocytes, ependymal cells, vascular endothelial cells, and to a lesser extent in smooth muscle cells. Fourteen days following compression injury to the spinal cord, there was a significant upregulation in both the immunoexpression and number of astrocytes expressing the ET(B)R in both gray and white matter and a near disappearance of ET(B)R-IR in ependymal cells and ET(A)R-IR in primary afferent fibers. Conversely, the vascular expression of ET(A)R and ET(B)R did not appear to change. As spinal cord injury has been shown to induce an immediate increase in plasma ET levels and a sustained increase in tissue ET levels, ETs would be expected to induce an initial marked vasoconstriction via activation of vascular ET(A)R/ET(B)R and then days later a glial hypertrophy via activation of the ET(B)R expressed by astrocytes. Strategies aimed at blocking vascular ET(A)R/ET(B)R and astrocyte ET(B)Rs following spinal cord injury may reduce the resulting ischemia and astrogliosis and in doing so increase neuronal survival, regeneration, and function.
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MESH Headings
- Animals
- Disease Models, Animal
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/pathology
- Female
- Gliosis/etiology
- Gliosis/pathology
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Neuroglia/metabolism
- Neuroglia/pathology
- Rats
- Rats, Sprague-Dawley
- Receptor, Endothelin A
- Receptor, Endothelin B
- Receptors, Endothelin/biosynthesis
- Spinal Cord/metabolism
- Spinal Cord/pathology
- Spinal Cord Injuries/complications
- Spinal Cord Injuries/metabolism
- Spinal Cord Injuries/pathology
- Spinal Cord Ischemia/etiology
- Spinal Cord Ischemia/pathology
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Affiliation(s)
- Christopher M Peters
- Department of Preventive Science, University of Minnesota, Minneapolis, MN 55455, USA
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30
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Leker RR, Shohami E, Constantini S. Experimental models of head trauma. ACTA NEUROCHIRURGICA. SUPPLEMENT 2003; 83:49-54. [PMID: 12442621 DOI: 10.1007/978-3-7091-6743-4_9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Abstract
Traumatic brain injury is one of the most common causes for chronic disability in young people. Despite this there are currently no widely available modes of therapy that would limit the extent of brain damage secondary to trauma. Therefore, new insights into the pathological mechanisms involved in head trauma possibly leading to the identification of new therapeutic targets are urgently needed. In order to attain these goals adequate animal models for traumatic brain injury are needed. In the following paper the authors will review the various animal models for head trauma and emphasize their potential strengths and weaknesses.
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Affiliation(s)
- R R Leker
- Department of Neurology, Agnes Ginges Center for Human Neurogenetics, Hebrew University-Hadassah Medical School, Hadassah University Hospital, Jerusalem, Israel
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31
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Petrov T, Steiner J, Braun B, Rafols JA. Sources of endothelin-1 in hippocampus and cortex following traumatic brain injury. Neuroscience 2003; 115:275-83. [PMID: 12401340 DOI: 10.1016/s0306-4522(02)00345-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Endothelin 1 (ET-1) exerts normally a powerful vasoconstrictor role in the control of the brain microcirculation. In altered states, such as following traumatic brain injury (TBI), it may contribute to the development of ischemia and/or secondary cell injury. Because little is known of ET-1's cellular compartmentalization and its association to vulnerable neurons after TBI, we assessed its expression (both mRNA and protein) in cerebral cortex and hippocampus using correlative in situ hybridization and immunocytochemical techniques.Sprague-Dawley male rats were killed at 4, 24 or 48 h after TBI (450 g from 2 m, Marmarou's model). Semiquantitative analysis of our in situ hybridization results indicated a 2.5- and a 2.0-fold increase in ET-1 mRNA content in the hippocampus and cortex respectively which persisted up to 48 h post TBI. At 4 and 24 h after TBI enzyme-linked immunosorbent assay showed a tendency for increased ET-1 synthesis. In animals subjected to TBI, qualitative immunocytochemical analysis revealed a shift in ET-1 expression from astrocytes (in control animals) to endothelial cells, macrophages and neurons. Astrocytes and macrophages were identified unequivocally by using double immunofluorescence revealing ET-1 and glial fibrillary acidic protein or ED-1, respectively, the markers being specific for these cellular types. While this redistribution was most prominent at 4 and 24 h post TBI, at 48 h the endothelial cells remained strongly ET-1 immunopositive. The results suggest that cellular types which in the intact animal synthesize little or no ET-1 provide novel sources of the peptide after TBI. These sources may contribute to the sustained cerebrovascular hypoperfusion observed post TBI.
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Affiliation(s)
- Th Petrov
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, 540 East Canfield Avenue, Detroit, MI 48201, USA.
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Rogers SD, Peters CM, Pomonis JD, Hagiwara H, Ghilardi JR, Mantyh PW. Endothelin B receptors are expressed by astrocytes and regulate astrocyte hypertrophy in the normal and injured CNS. Glia 2003; 41:180-90. [PMID: 12509808 DOI: 10.1002/glia.10173] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The ability of mammalian central nervous system (CNS) neurons to survive and/or regenerate following injury is influenced by surrounding glial cells. To identify the factors that control glial cell function following CNS injury, we have focused on the endothelin B receptor (ET(B)R), which we show is expressed by the majority of astrocytes that are immunoreactive for glial acid fibrillary protein (GFAP) in both the normal and crushed rabbit optic nerve. Optic nerve crush induces a marked increase in ET(B)R and GFAP immunoreactivity (IR) without inducing a significant increase in the number of GFAP-IR astrocytes, suggesting that the crush-induced astrogliosis is due primarily to astrocyte hypertrophy. To define the role that endothelins play in driving this astrogliosis, artificial cerebrospinal fluid (CSF), ET-1 (an ET(A)R and ET(B)R agonist), or Bosentan (a mixed ET(A)R and ET(B)R antagonist) were infused via osmotic minipumps into noninjured and crushed optic nerves for 14 days. Infusion of ET-1 induced a hypertrophy of ET(B)R/GFAP-IR astrocytes in the normal optic nerve, with no additional hypertrophy in the crushed nerve, whereas infusion of Bosentan induced a significant decrease in the hypertrophy of ET(B)R/GFAP-IR astrocytes in the crushed but not in the normal optic nerve. These data suggest that pharmacological blockade of astrocyte ET(B)R receptors following CNS injury modulates glial scar formation and may provide a more permissive substrate for neuronal survival and regeneration.
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Affiliation(s)
- Scott D Rogers
- Molecular Neurobiology Laboratory, Veterans Affairs Medical Center, Minneapolis, Minnesota 55455, USA
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Sirén AL, Lewczuk P, Hasselblatt M, Dembowski C, Schilling L, Ehrenreich H. Endothelin B receptor deficiency augments neuronal damage upon exposure to hypoxia-ischemia in vivo. Brain Res 2002; 945:144-9. [PMID: 12113963 DOI: 10.1016/s0006-8993(02)02911-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The role of functional endothelin-B (ETB)-receptors on neuronal survival upon hypoxia-ischemia (HI) has been investigated in 14-day-old ETB-receptor-deficient spotting lethal (sl/sl) and wildtype (+/+) rats. Carotid ligation followed by exposure to 8% oxygen for 2 h produced distinct cortical and hippocampal neuronal damage. Damage severity 24 h after HI was mild to intermediate in +/+ rats whereas large cortical infarcts and profound apoptosis of the hippocampus evolved in sl/sl rats. The number of apoptotic cells in the dentate 24 h after HI amounted to 30 +/- 7 cells/0.1 mm(2) in sl/sl compared to 9 +/- 3 cells/0.1 mm(2) in wildtype rats (mean +/- S.E.M., n=10-11, P=0.0093). In-vitro hypoxia (15 h) resulted in a comparable increase in cell death in primary pure neuronal hippocampal cultures from both groups (49.8 +/- 1.6% in sl/sl, 51.4 +/- 0.9% in +/+, mean +/- S.E.M., n=5, P=0.0560). To conclude, absence of functional ETB receptors is associated with an increased susceptibility to HI in-vivo, which is not intrinsic to neurons. Antagonism of ETB receptors seems not to be desirable in ischemic stroke.
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Affiliation(s)
- Anna-Leena Sirén
- Department of Neurology, Georg-August-University, and Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Strasse 3, D-37075 Göttingen, Germany.
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Abstract
Endothelin is a vasoactive peptide that has been shown to play an important role in vascular homeostasis. Recently, endothelin and its receptors have been found in ocular tissues where it appears to have a regulatory function. Endothelin is found in both the aqueous and vitreous humors and its concentration is elevated in glaucoma patients and in animal models of glaucoma. In the current review, the authors present information about the distribution of endothelin and endothelin receptors in the eye and the ocular actions of endothelins. Specifically, endothelin/aqueous humor dynamics, endothelin/nitric oxide interactions, endothelin and ischemia, and endothelin/optic nerve head effects. Observations concerning the potential role of endothelin in glaucoma pathophysiology is presented and discussed relative to its effects on the optic nerve head and in relation to glaucoma theories.
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Affiliation(s)
- Thomas Yorio
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, North Texas Eye Research Institute, Fort Worth, Texas 76107, USA.
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Leker RR, Shohami E. Cerebral ischemia and trauma-different etiologies yet similar mechanisms: neuroprotective opportunities. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2002; 39:55-73. [PMID: 12086708 DOI: 10.1016/s0165-0173(02)00157-1] [Citation(s) in RCA: 281] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Cerebral ischemia leads to brain damage caused by pathogenetic mechanisms that are also activated by neurotrauma. These mechanisms include among others excitotoxicity, over production of free radicals, inflammation and apoptosis. Furthermore, cerebral ischemia and trauma both trigger similar auto-protective mechanisms including the production of heat shock proteins, anti-inflammatory cytokines and endogenous antioxidants. Neuroprotective therapy aims at minimizing the activation of toxic pathways and at enhancing the activity of endogenous neuroprotective mechanisms. The similarities in the damage-producing and endogenous auto-protective mechanisms may imply that neuroprotective compounds found to be active against one of these conditions may indeed be also protective in the other. This review summarizes the pathogenetic events of ischemic and traumatic brain injury and reviews the neuroprotective strategies employed thus far in each of these conditions with a special emphasize on their clinical relevance and on future directions in the field of neuronal protection.
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Affiliation(s)
- Ronen R Leker
- Department of Neurology and the Agnes Ginges Center for Human Neurogenetics, Hebrew University-Hadassah Medical School and Hadassah University Hospital, Jerusalem, Israel.
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Hasselblatt M, Lewczuk P, Löffler BM, Kamrowski-Kruck H, von Ahsen N, Sirén AL, Ehrenreich H. Role of the astrocytic ET(B) receptor in the regulation of extracellular endothelin-1 during hypoxia. Glia 2001; 34:18-26. [PMID: 11284016 DOI: 10.1002/glia.1036] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Astrocytes are known to possess an effective endothelin (ET) eliminatory system which involves astrocytic ET(A) and ET(B) receptors and may become particularly relevant under pathophysiological conditions. The present study has therefore been designed to explore the effect of standardized hypoxia on extracellular concentrations of endothelin-1 (ET-1) and on endothelin-converting enzyme (ECE) activity in primary rat astrocytes genetically (sl/sl) or experimentally (dexamethasone) deficient in ET(B) receptors. The results revealed (1) a hypoxia-mediated decrease of extracellular ET-1 in wildtype astrocytes (+/+) that was not observed in ET(B)-deficient (sl/sl) cultures; (2) an ET receptor antagonist-induced increase in ET-1 in the media of both genotypes with further elevation upon hypoxia in +/+ cultures only; (3) augmentation of the dexamethasone-induced increase in extracellular ET-1 by hypoxia in +/+, but not in sl/sl cultures; (4) synergistic reduction of ET(B) gene transcription by hypoxia and dexamethasone; and (5) significant increases in endothelin-converting enzyme activity in the presence of hypoxia. To conclude, hypoxia stimulates astrocytic release of mature ET-1. This stimulation is (over)compensated for by increased ET-1 binding to functional ET(B) receptors. ET(B) deficiency, whether genetic or experimentally induced, impairs elimination of extracellular ET-1.
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Affiliation(s)
- M Hasselblatt
- Department of Neurology, Georg-August-University, Göttingen, Germany
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