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OCT-Angiography Findings in Patients with Amblyopia: Comparison between Healthy Controls, Treatment-Responsive, and Treatment-Unresponsive Amblyopic Patients. Diagnostics (Basel) 2021; 11:diagnostics11101751. [PMID: 34679448 PMCID: PMC8534794 DOI: 10.3390/diagnostics11101751] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/13/2021] [Accepted: 09/20/2021] [Indexed: 11/16/2022] Open
Abstract
There is no consensus on whether amblyopia affects the retinal vascular plexus and morphology. Previous studies focused on the differences between amblyopic patients and normal controls without evaluating amblyopic eyes after patching. To evaluate differences in the superficial vascular density of amblyopic eyes, normal eyes, and amblyopic eyes reaching normal BCVA after patch therapy, OCTA was used. All patients underwent a comprehensive ophthalmological examination, including visual acuity, refraction, ocular motility tests, and anterior and posterior segment examination. OCTA was performed by an expert physician using the Zeiss Cirrus 5000-HD-OCT Angioplex (Carl Zeiss, Meditec, Inc., Dublin, OH, USA). OCTA scans were performed using a 3 × 3 mm2 and 6 × 6 mm2 fovea-centered image setting. The mean outer macular vessel density in the previously amblyopic group was 19.15 ± 0.51%. This was statistically significantly higher than in both the amblyopic group (18.70 ± 1.14%) and the normal controls (18.18 ± 1.40%) (p = 0.014). The previously amblyopic group also significantly differed from both normal controls and amblyopic eyes with regards to the inner (p = 0.011), outer (p = 0.006), and full (p = 0.003) macular perfusion. Finally, linear regression analysis revealed that BCVA was linearly correlated to outer perfusion in amblyopic (p = 0.003) and ex amblyopic eyes (p < 0.001). Considering the cross-sectional nature of our study, from our results, we can only hypothesize a possible correlation between light stimulation and retinal vasculature development. However, further longitudinal studies are needed to support this hypothesis.
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Arora S, Surakiatchanukul T, Arora T, Cagini C, Lupidi M, Chhablani J. Sildenafil in ophthalmology: An update. Surv Ophthalmol 2021; 67:463-487. [PMID: 34175342 DOI: 10.1016/j.survophthal.2021.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 06/18/2021] [Accepted: 06/21/2021] [Indexed: 12/14/2022]
Abstract
Sildenafil citrate, a selective oral phosphodiesterase 5 inhibitor, is a widely used drug for erectile dysfunction that acts by elevating cGMP levels and causing smooth muscle relaxation. It also has 10% activity against PDE6, a key enzyme in phototransduction cascade in the retina. Recent ocular imaging developments have further revealed the influence of sildenafil on ocular hemodynamics, particularly choroidal perfusion. Choroidal thickness is increased, and choroidal perfusion is also enhanced by autoregulatory mechanisms that are further dependent on age and microvascular abnormalities. Studies demonstrating high intraocular pressure via a "parallel pathway" from increased choroidal volume and blood flow to the ciliary body have challenged previous concepts. Another new observation is the effect of sildenafil on bipolar cells and cyclic-nucleotide gated channels. We discuss potential deleterious effects (central serous chorioretinopathy, glaucoma, ischemic optic neuropathy, and risks to recessive carriers of retinitis pigmentosa), potential beneficial effects (ameliorate choroidal ischemia, prevent thickening of Bruch membrane, and promote recovery of the ellipsoid zone) in macular degeneration, as well as potential drug interactions of sildenafil.
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Affiliation(s)
- Supriya Arora
- Bahamas Vision Centre and Princess Margaret Hospital, Nassau NP, Bahamas.
| | - Thamolwan Surakiatchanukul
- Department of Ophthalmology, Jamaica Hospital Medical Center, New York Medical College, Jamaica, NY, USA
| | - Tarun Arora
- Bahamas Vision Centre and Princess Margaret Hospital, Nassau NP, Bahamas.
| | - Carlo Cagini
- Department of Biochemical and Surgical Sciences, Section of ophthalmology, University of Perugia, Perugia, Italy
| | - Marco Lupidi
- Department of Biochemical and Surgical Sciences, Section of ophthalmology, University of Perugia, Perugia, Italy
| | - Jay Chhablani
- University of Pittsburgh, UPMC Eye Center, Pittsburgh, PA, USA.
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Bahrami N, Childs SJ. Development of vascular regulation in the zebrafish embryo. Development 2020; 147:147/10/dev183061. [PMID: 32423977 DOI: 10.1242/dev.183061] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 04/07/2020] [Indexed: 01/03/2023]
Abstract
The thin endothelial wall of a newly formed vessel is under enormous stress at the onset of blood flow, rapidly acquiring support from mural cells (pericytes and vascular smooth muscle cells; vSMCs) during development. Mural cells then develop vasoactivity (contraction and relaxation) but we have little information as to when this first develops or the extent to which pericytes and vSMCs contribute. For the first time, we determine the dynamic developmental acquisition of vasoactivity in vivo in the cerebral vasculature of zebrafish. We show that pericyte-covered vessels constrict in response to α1-adrenergic receptor agonists and dilate in response to nitric oxide donors at 4 days postfertilization (dpf) but have heterogeneous responses later, at 6 dpf. In contrast, vSMC-covered vessels constrict at 6 dpf, and dilate at both stages. Using genetic ablation, we demonstrate that vascular constriction and dilation is an active response. Our data suggest that both pericyte- and vSMC-covered vessels regulate their diameter in early development, and that their relative contributions change over developmental time.
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Affiliation(s)
- Nabila Bahrami
- Alberta Children's Hospital Research Institute and Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
| | - Sarah J Childs
- Alberta Children's Hospital Research Institute and Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
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Grünert U, Martin PR. Cell types and cell circuits in human and non-human primate retina. Prog Retin Eye Res 2020; 78:100844. [PMID: 32032773 DOI: 10.1016/j.preteyeres.2020.100844] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/28/2020] [Accepted: 01/31/2020] [Indexed: 12/12/2022]
Abstract
This review summarizes our current knowledge of primate including human retina focusing on bipolar, amacrine and ganglion cells and their connectivity. We have two main motivations in writing. Firstly, recent progress in non-invasive imaging methods to study retinal diseases mean that better understanding of the primate retina is becoming an important goal both for basic and for clinical sciences. Secondly, genetically modified mice are increasingly used as animal models for human retinal diseases. Thus, it is important to understand to which extent the retinas of primates and rodents are comparable. We first compare cell populations in primate and rodent retinas, with emphasis on how the fovea (despite its small size) dominates the neural landscape of primate retina. We next summarise what is known, and what is not known, about the postreceptoral neurone populations in primate retina. The inventories of bipolar and ganglion cells in primates are now nearing completion, comprising ~12 types of bipolar cell and at least 17 types of ganglion cell. Primate ganglion cells show clear differences in dendritic field size across the retina, and their morphology differs clearly from that of mouse retinal ganglion cells. Compared to bipolar and ganglion cells, amacrine cells show even higher morphological diversity: they could comprise over 40 types. Many amacrine types appear conserved between primates and mice, but functions of only a few types are understood in any primate or non-primate retina. Amacrine cells appear as the final frontier for retinal research in monkeys and mice alike.
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Affiliation(s)
- Ulrike Grünert
- The University of Sydney, Save Sight Institute, Faculty of Medicine and Health, Sydney, NSW, 2000, Australia; Australian Research Council Centre of Excellence for Integrative Brain Function, Sydney Node, The University of Sydney, Sydney, NSW, 2000, Australia.
| | - Paul R Martin
- The University of Sydney, Save Sight Institute, Faculty of Medicine and Health, Sydney, NSW, 2000, Australia; Australian Research Council Centre of Excellence for Integrative Brain Function, Sydney Node, The University of Sydney, Sydney, NSW, 2000, Australia
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Blanco S, Hernández R, Franchelli G, Ramos-Álvarez MM, Peinado MÁ. Melatonin influences NO/NOS pathway and reduces oxidative and nitrosative stress in a model of hypoxic-ischemic brain damage. Nitric Oxide 2017; 62:32-43. [DOI: 10.1016/j.niox.2016.12.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 11/28/2016] [Accepted: 12/03/2016] [Indexed: 12/17/2022]
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The Gatekeepers in the Mouse Ophthalmic Artery: Endothelium-Dependent Mechanisms of Cholinergic Vasodilation. Sci Rep 2016; 6:20322. [PMID: 26831940 PMCID: PMC4735817 DOI: 10.1038/srep20322] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 01/04/2016] [Indexed: 01/25/2023] Open
Abstract
Cholinergic regulation of arterial luminal diameter involves intricate network of intercellular communication between the endothelial and smooth muscle cells that is highly dependent on the molecular mediators released by the endothelium. Albeit the well-recognized contribution of nitric oxide (NO) towards vasodilation, the identity of compensatory mechanisms that maintain vasomotor tone when NO synthesis is deranged remain largely unknown in the ophthalmic artery. This is the first study to identify the vasodilatory signalling mechanisms of the ophthalmic artery employing wild type mice. Acetylcholine (ACh)-induced vasodilation was only partially attenuated when NO synthesis was inhibited. Intriguingly, the combined blocking of cytochrome P450 oxygenase (CYP450) and lipoxygenase (LOX), as well as CYP450 and gap junctions, abolished vasodilation; demonstrating that the key compensatory mechanisms comprise arachidonic acid metabolites which, work in concert with gap junctions for downstream signal transmission. Furthermore, the voltage-gated potassium ion channel, Kv1.6, was functionally relevant in mediating vasodilation. Its localization was found exclusively in the smooth muscle. In conclusion, ACh-induced vasodilation of mouse ophthalmic artery is mediated in part by NO and predominantly via arachidonic acid metabolites, with active involvement of gap junctions. Particularly, the Kv1.6 channel represents an attractive therapeutic target in ophthalmopathologies when NO synthesis is compromised.
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Molina F, Rus A, Pedrosa JÁ, del Moral ML. Acute hypoxia-induced depletion of striatal nitric oxide synthase pathway. J Chem Neuroanat 2013; 47:42-9. [DOI: 10.1016/j.jchemneu.2012.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 11/12/2012] [Accepted: 12/12/2012] [Indexed: 11/26/2022]
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Zwain AAMH, Hadi NR, Al-Mudhaffer AM. Sildenafil dilates ophthalmic artery in type 2 diabetic patients. SAGE Open Med 2013; 1:2050312113495195. [PMID: 26770675 PMCID: PMC4687761 DOI: 10.1177/2050312113495195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Background: Conflicting reports exist on the effect of sildenafil on ophthalmic artery blood flow; many visual disturbances due to vascular insult were reported with the use of sildenafil in diabetic patients like nonarteritic ischemic optic neuropathy. Objectives: The present work aimed to investigate whether sildenafil modulates ophthalmic artery vasoreactivity in patients with type 2 diabetes mellitus. Literature reports on this aspect are lacking. Methods: A total of 35 male subjects were enrolled in this study, 18 with type 2 diabetes mellitus matched with 17 normal individuals. Ophthalmic artery was insonated through a transorbital window using colored Doppler equipment with transcranial Doppler facility. Ophthalmic artery reactivity was assessed using breath holding/hyperventilation test, before and after giving 50 mg oral sildenafil. Results: It was found that in both normal subjects and diabetic patients, sildenafil increased baseline control of mean flow velocity of ophthalmic artery significantly (p < 0.05), breath holding caused a decrease of MFVopa (p < 0.05), and subsequent hyperventilation caused increase of MFVopa (p < 0.05). There was no statistically significant change in breath holding index and full range of vasodilatation of ophthalmic artery (p > 0.05) after sildenafil, in normal and diabetic groups. There was a significant increase of resistive index of ophthalmic artery flow in diabetic patients compared with that of normal subject (p < 0.05). Sildenafil decreased resistive index of ophthalmic artery flow significantly only in diabetic patients (p < 0.05). Conclusion: Sildenafil increased MFVopa, but had no significant effect on vasoreactivity of ophthalmic artery; sildenafil decreased resistive index only in type 2 diabetic patients.
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Affiliation(s)
- Akeel AMH Zwain
- Department of Clinical Physiology, Faculty of Medicine, University of Kufa, Najaf, Iraq
| | - Najah R Hadi
- Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Kufa, Najaf, Iraq
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Innervation pattern of the preocular human central retinal artery. Exp Eye Res 2012; 110:142-7. [PMID: 23220730 DOI: 10.1016/j.exer.2012.11.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 11/26/2012] [Accepted: 11/29/2012] [Indexed: 11/23/2022]
Abstract
The central retinal artery (CRA) is the main vessel for inner retinal oxygen and nutrition supply. While the intraocular branches lack autonomic innervation, the innervation pattern of the extra-ocular part of this vessel along its course within the optic nerve is poorly investigated. This part however is essential for maintenance of retinal blood supply, in physiological and pathological conditions. Therefore, the aim of this study was the characterization of the autonomic innervation of the preocular CRA in humans with morphological methods. Meeting the Declaration of Helsinki, eyes of body or cornea donors were processed for single or double immunohistochemistry against tyrosine hydroxilase (TH), dopamine-β-hydroxylase (DBH), choline acetyl-transferase (ChAT), vesicular acetylcholine transporter (VAChT), neuronal nitric oxide synthase (nNOS), calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), and cytochemistry for NADPH-diaphorase (NADPH-d). For documentation, light-, fluorescence-, and confocal laser-scanning microscopy were used. TH and DBH immunoreactive nerve fibres were detected in the CRA vessel wall, although a distinct perivascular plexus was missing. Further, nerve fibres immunoreactive for ChAT and VAChT were found, while CGRP, SP, and VIP were not detected. NADPH-d staining revealed scattered nerve fibres in the adventitia of the CRA and in close vicinity; however, nNOS-immunostaining could not confirm this finding. The CRA receives adrenergic and cholinergic innervations, indicating sympathetic and parasympathetic components, respectively. Remarkably, a peptidergic primary afferent innervation was missing. Since clinical results suggest an autoregulation of intraretinal vessels, further studies are needed to clarify the impact of CRA innervation for retinal perfusion.
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Marçal AC, Leonelli M, Fiamoncini J, Deschamps FC, Rodrigues MAM, Curi R, Carpinelli AR, Britto LRG, Carvalho CRO. Diet-induced obesity impairs AKT signalling in the retina and causes retinal degeneration. Cell Biochem Funct 2012; 31:65-74. [PMID: 22915345 DOI: 10.1002/cbf.2861] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 06/18/2012] [Accepted: 07/05/2012] [Indexed: 11/06/2022]
Abstract
Retinopathy, a common complication of diabetes, is characterized by an unbalanced production of nitric oxide (NO), a process regulated by nitric oxide synthase (NOS). We hypothesized that retinopathy might stem from changes in the insulin receptor substrate (IRS)/PI3K/AKT pathway and/or expression of NOS isoforms. Thus, we analysed the morphology and apoptosis index in retinas of obese rats in whom insulin resistance had been induced by a high-fat diet (HFD). Immunoblotting analysis revealed that the retinal tissue of HFD rats had lower levels of AKT(1) , eNOS and nNOS protein than those of samples taken from control animals. Furthermore, immunohistochemical analyses indicated higher levels of iNOS and 4-hydroxynonenal and a larger number of apoptotic nuclei in HFD rats. Finally, both the inner and outer retinal layers of HFD rats were thinner than those in their control counterparts. When considered alongside previous results, these patterns suggest two major ways in which HFD might impact animals: direct activity of ingested fatty acids and/or via insulin-resistance-induced changes in intracellular pathways. We discuss these possibilities in further detail and advocate the use of this animal model for further understanding relationships between retinopathy, metabolic syndrome and type 2 diabetes.
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Affiliation(s)
- Anderson C Marçal
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas (ICB), Universidade de São Paulo (USP), SP, Brazil.
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May CA. Age-dependent morphology of NADPH diaphorase-positive amacrine cells in the mouse retina. Anat Histol Embryol 2012; 41:476-8. [PMID: 22472000 DOI: 10.1111/j.1439-0264.2012.01152.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Accepted: 03/01/2012] [Indexed: 11/30/2022]
Abstract
NADPH diaphorase-positive amacrine cells (NAC) were studied in retinal whole mount preparation of mice, ranging from 1 day to 30 months of age. Following a peak in number and size during early development at postnatal day 14, their number and distribution remained well preserved up to senescence. Functional considerations include immunological, vascular and neuro-modulating aspects.
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Affiliation(s)
- C-A May
- Department of Anatomy, Medical Faculty Carl Gustav Carus, TU Dresden, Germany.
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Cioni C, Di Patti MCB, Venturini G, Modica MV, Scarpa F, Oliverio M, Toni M. Cellular, biochemical, and molecular characterization of nitric oxide synthase expressed in the nervous system of the prosobranch Stramonita haemastoma (Gastropoda, Neogastropoda). J Comp Neurol 2012; 520:364-83. [PMID: 21800313 DOI: 10.1002/cne.22729] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Nitric oxide synthase (NOS) has been characterized in several opistobranchs and pulmonates but it was much less investigated in prosobranchs, which include more than 20,000 species and account for most of the gastropod diversity. Therefore, new data from this large group are needed for a better knowledge of the molecular evolution of NOS enzymes in molluscs. This study focused on NOS expressed in the nervous system of the prosobranch neogastropod Stramonita haemastoma. In this study we report compelling evidence on the expression of a constitutive Ca(2+) /CaM-dependent neuronal NOS in the central and peripheral nervous system. The prevailing neuronal localization of NADPHd activity was demonstrated by NADPHd histochemistry in both central and peripheral nervous system structures. L-arginine/citrulline assays suggested that Stramonita NOS is a constitutive enzyme which is both cytosolic and membrane-bound. Molecular cloning of the full-length Stramonita NOS (Sh-NOS) by reverse-transcription polymerase chain reaction (RT-PCR) followed by 5' and 3' RACE showed that Sh-NOS is a protein of 1,517 amino acids, containing a PDZ domain at the N-terminus and sharing similar regulatory domains to the mammalian neuronal NOS (nNOS). Regional expression of the Sh-NOS gene was evaluated by RT-PCR. This analysis showed different expression levels in the nerve ring, the osphradium, the cephalic tentacles, the buccal tissues, and the foot, whereas NOS expression was not found in the salivary glands and the gland of Leiblein. The present data provide a solid background for further studies addressing the specific functions of NO in neogastropods.
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Affiliation(s)
- Carla Cioni
- Department of Biology and Biotechnology Charles Darwin, Sapienza University, 00161 Rome, Italy
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Rus A, Molina F, Peinado MÁ, Del Moral ML. Nitric oxide averts hypoxia-induced damage during reoxygenation in rat heart. Microsc Res Tech 2011; 74:1093-103. [PMID: 21538695 DOI: 10.1002/jemt.21000] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 01/28/2011] [Indexed: 01/18/2023]
Abstract
Nitric oxide (NO), synthesized by the hemoproteins NO synthases (NOS), is known to play important roles in physiological and pathological conditions in the heart, including hypoxia/reoxygenation (H/R). This work investigates the role that endogenous NO plays in the cardiac H/R-induced injury. A follow-up study was conducted in Wistar rats subjected to 30 min of hypoxia, with or without prior treatment using the nonselective NOS inhibitor L-NAME (1.5 mM). The rats were studied at 0 h, 12 h, and 5 days of reoxygenation, analysing parameters of cell, and tissue damage (lipid peroxidation, apoptosis, and protein nitration), as well as in situ NOS activity and NO production (NOx). The results showed that after L-NAME administration, in situ NOS activity was almost completely eliminated in all the experimental groups, and consequently, NOx levels fell. Contrarily, the lipid peroxidation level and the percentage of apoptotic cells rose throughout the reoxygenation period. These results reveal that NOS inhibition exacerbates the peroxidative and apoptotic damage observed before the treatment with L-NAME in the hypoxic heart, pointing to a cardioprotective role of NOS-derived NO against H/R-induced injury. These findings could open the possibility of future studies to design new therapies for H/R-dysfunctions based on NO-pharmacology.
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Affiliation(s)
- Alma Rus
- Department of Experimental Biology, University of Jaén, Paraje Las Lagunillas s/n, Jaén 23071, Spain.
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Rus A, Peinado MA, Castro L, Del Moral ML. Lung eNOS and iNOS are reoxygenation time-dependent upregulated after acute hypoxia. Anat Rec (Hoboken) 2010; 293:1089-98. [PMID: 20225207 DOI: 10.1002/ar.21141] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Nitric oxide plays a critical role in many physiological and physiopathological processes in the lung. Changes in the NO/NOS (Nitric Oxide/Nitric Oxide Synthase) system after hypoxia situations remain controversial in this organ, so that the aim of this work is to perform a complete study of this system in the hypoxic lung after different reoxygenation times ranging from 0 h to 5 days posthypoxia. This is a novel follow-up study carried out in Wistar rats submitted for 30 min to acute hypobaric hypoxia. We measured endothelial and inducible NOS (eNOS, iNOS) mRNA and protein expression, location, and in situ NOS activity as well as nitrated protein expression and location. In addition, NO levels were indirectly quantified (NOx) as well as the apoptosis level. Results showed an increase in eNOS mRNA, protein, activity as well as eNOS positive immunostaining at 0 h posthypoxia, coinciding with raised NOx levels. Contrary, iNOS, nitrated protein expression and apoptosis level augmented during the final reoxygenation times. The lung NO/NOS system provokes two responses to the hypoxia/reoxygenation processes: (i) eNOS is responsible of the immediate response, producing NO, which causes vasodilation and bronchodilation, and (ii) iNOS is related to the second late response, which seems to be involved in some of the deleterious consequences that hypoxia induces in the lung.
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Affiliation(s)
- Alma Rus
- Department of Experimental Biology, University of Jaén, Jaén, Spain
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Rus A, Molina F, Peinado MÁ, Del Moral ML. Endogenous nitric oxide can act as beneficial or deleterious in the hypoxic lung depending on the reoxygenation time. Anat Rec (Hoboken) 2010; 293:2193-201. [PMID: 20734424 DOI: 10.1002/ar.21229] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Accepted: 06/01/2010] [Indexed: 12/28/2022]
Abstract
Nitric oxide (NO) has been implicated in many pathophysiological situations in the lung, including hypoxia/reoxygenation. This work seeks to clarify the current controversy concerning the double protective/toxic role of endogenous NO under hypoxia/reoxygenation situations in the lung by using a nitric oxide synthase (NOS) inhibitor, in a novel approach to address the problems raised from assaults under such circumstances. A follow-up study was conducted in Wistar rats submitted to hypoxia/reoxygenation (hypoxia for 30 min; reoxygenation of 0 h, 48 h, and 5 days), with or without prior treatment using the nonselective NOS inhibitor L-NAME (1.5 mM, in drinking water). Lipid peroxidation, apoptosis level, protein nitration, in situ NOS activity and NO production (NOx) were analyzed. This is the first work to focus on the time-course effects of L-NAME in the adult rat lung submitted to hypoxia/reoxygenation. The results showed that after L-NAME administration, in situ NOS activity was almost completely eliminated and consequently, NOx levels fell. Lipid peroxidation and the percentage of apoptotic cells rose at the earliest reoxygenation time (0 h), but decreased in the later period (48 h and 5 days). Also nitrated protein expression decreased at 48 h and 5 days posthypoxia. These results suggest that NOS-derived NO exerts two different effects on lung hypoxia/reoxygenation injury depending on the reoxygenation time: NO has a beneficial role just after the hypoxic stimulus and a deleterious effect in the later reoxygenation times. Moreover, we propose that this dual role of NO depends directly on the producer NOS isoform.
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Affiliation(s)
- Alma Rus
- Department of Experimental Biology, University of Jaén, Jaén, Spain
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Blanco S, Molina FJ, Castro L, Del Moral ML, Hernandez R, Jimenez A, Rus A, Martinez-Lara E, Siles E, Peinado MA. Study of the nitric oxide system in the rat cerebellum during aging. BMC Neurosci 2010; 11:78. [PMID: 20576087 PMCID: PMC2905430 DOI: 10.1186/1471-2202-11-78] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 06/24/2010] [Indexed: 11/30/2022] Open
Abstract
Background The cerebellum is the neural structure with the highest levels of nitric oxide, a neurotransmitter that has been proposed to play a key role in the brain aging, although knowledge concerning its contribution to cerebellar senescence is still unclear, due mainly to absence of integrative studies that jointly evaluate the main factors involved in its cell production and function. Consequently, in the present study, we investigate the expression, location, and activity of nitric oxide synthase isoenzymes; the protein nitration; and the production of nitric oxide in the cerebellum of adult and old rats. Results Our results show no variation in the expression of nitric oxide synthase isoforms with aging, although, we have detected some changes in the cellular distribution pattern of the inducible isoform particularly in the cerebellar nuclei. There is also an increase in nitric oxide synthase activity, as well as greater protein-nitration levels, and maintenance of nitrogen oxides (NOx) levels in the senescent cerebellum. Conclusions The nitric oxide/nitric oxide syntahses system suffers from a number of changes, mainly in the inducible nitric oxide synthase distribution and in overall nitric oxide synthases activity in the senescent cerebellum, which result in an increase of the protein nitration. These changes might be related to the oxidative damage detected with aging in the cerebellum.
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Affiliation(s)
- Santos Blanco
- Department of Experimental Biology, University of Jaen, Campus Las Lagunillas s/n, 23071, Jaén, Spain
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Hamilton NB, Attwell D, Hall CN. Pericyte-mediated regulation of capillary diameter: a component of neurovascular coupling in health and disease. FRONTIERS IN NEUROENERGETICS 2010; 2. [PMID: 20725515 PMCID: PMC2912025 DOI: 10.3389/fnene.2010.00005] [Citation(s) in RCA: 343] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 04/28/2010] [Indexed: 12/18/2022]
Abstract
Because regional blood flow increases in association with the increased metabolic demand generated by localized increases in neural activity, functional imaging researchers often assume that changes in blood flow are an accurate read-out of changes in underlying neural activity. An understanding of the mechanisms that link changes in neural activity to changes in blood flow is crucial for assessing the validity of this assumption, and for understanding the processes that can go wrong during disease states such as ischaemic stroke. Many studies have investigated the mechanisms of neurovascular regulation in arterioles but other evidence suggests that blood flow regulation can also occur in capillaries, because of the presence of contractile cells, pericytes, on the capillary wall. Here we review the evidence that pericytes can modulate capillary diameter in response to neuronal activity and assess the likely importance of neurovascular regulation at the capillary level for functional imaging experiments. We also discuss evidence suggesting that pericytes are particularly sensitive to damage during pathological insults such as ischaemia, Alzheimer's disease and diabetic retinopathy, and consider the potential impact that pericyte dysfunction might have on the development of therapeutic interventions and on the interpretation of functional imaging data in these disorders.
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Affiliation(s)
- Nicola B Hamilton
- Department of Neuroscience, Physiology and Pharmacology, University College London London, UK
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Affiliation(s)
- F Simonelli
- Department of Ophthalmology, Second University of Naples, Napoli, Italy.
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20
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Somatostatin analogues as therapeutics in retinal disease. Pharmacol Ther 2009; 122:324-33. [DOI: 10.1016/j.pharmthera.2009.03.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Accepted: 03/24/2009] [Indexed: 12/30/2022]
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Sun C, Wang JJ, Mackey DA, Wong TY. Retinal Vascular Caliber: Systemic, Environmental, and Genetic Associations. Surv Ophthalmol 2009; 54:74-95. [PMID: 19171211 DOI: 10.1016/j.survophthal.2008.10.003] [Citation(s) in RCA: 277] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Cong Sun
- Centre for Eye Research Australia, University of Melbourne, Victoria, Australia
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Thermos K. Novel signals mediating the functions of somatostatin: the emerging role of NO/cGMP. Mol Cell Endocrinol 2008; 286:49-57. [PMID: 18384933 DOI: 10.1016/j.mce.2008.02.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 02/11/2008] [Accepted: 02/12/2008] [Indexed: 11/16/2022]
Abstract
The neuropeptide somatostatin is a cyclic tetradecapeptide, which is widely distributed in the peripheral and central nervous system. It mediates a plethora of physiological actions and functions as a neurotransmitter, neuromodulator or trophic factor. Somatostatin activates six receptor subtypes that are expressed differentially in different tissues and are coupled to diverse signalling pathways. In order to elucidate the functional role of the individual receptor subtypes, many investigations focused on the assignment of each receptor to a particular signalling pathway. Signalling pathways involving enzyme (adenylate cyclase, phospholipases, phosphatases) and ion channel systems in native and recombinant receptor systems have been extensively studied. A one to one situation (receptor/pathway) has yet to be established, thus justifying the diverse actions of somatostatin. Recently, a NO/cGMP pathway has been shown to mediate the functions of somatostatin and its receptors. This review will present the findings that support the emerging role of NO/cGMP as a novel signal in SRIF's actions in retinal physiology and somatotroph release.
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Affiliation(s)
- Kyriaki Thermos
- University of Crete, Faculty of Medicine, Department of Basic Sciences, Laboratory of Pharmacology, Heraklion, Crete, Greece.
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Abstract
AbstractThe melanopsin positive, intrinsically photosensitive retinal ganglion cells (ipRGCs) of the inner retina have been shown to send wide-ranging projections throughout the brain. To investigate the response of this important cell type during retinal dystrophy, we use the Royal College of Surgeons (RCS) dystrophic rat, a major model of retinal degeneration. We find that ipRGCs exhibit a distinctive molecular profile that remains unaltered during early stages of outer retinal pathology (15 weeks of age). In particular, these cells express βIII tubulin, α-acetylated tubulin, and microtubule-associated proteins (MAPs), while remaining negative for other RGC markers such as neurofilaments, calretinin, and parvalbumin. By 14 months of age, melanopsin positive fibers invade ectopic locations in the dystrophic retina and ipRGC axons/dendrites become distorted (a process that may involve vascular remodeling). The morphological abnormalities in melanopsin processes are associated with elevated immunoreactivity for MAP1b and a reduction in α-acetylated tubulin. Quantification of ipRGCs in whole mounts reveals reduced melanopsin cell number with increasing age. Focusing on the retinal periphery, we find a significant decline in melanopsin cell density contrasted by a stability of melanopsin positive processes. In addition to these findings, we describe for the first time, a distinct plexus of melanopsin processes in the far peripheral retina, a structure that is coincident with a short wavelength opsin cone-enriched rim. We conclude that some ipRGCs are lost in RCS dystrophic rats as the disease progresses and that this loss may involve vascular remodeling. However, a significant number of melanopsin positive cells survive into advanced stages of retinal degeneration and show indications of remodeling in response to pathology. Our findings underline the importance of early intervention in human retinal disease in order to preserve integrity of the inner retinal photoreceptive network.
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Filosa JA, Nelson MT, Gonzalez Bosc LV. Activity-dependent NFATc3 nuclear accumulation in pericytes from cortical parenchymal microvessels. Am J Physiol Cell Physiol 2007; 293:C1797-805. [PMID: 17881610 DOI: 10.1152/ajpcell.00554.2006] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The calcium-dependent transcription factor NFATc3, which is a member of the nuclear factor of activated T cells (NFAT) family of transcription factors, is critical for embryonic vascular development and differentiation. Despite its potential importance, nothing is known about NFATc3 regulation in the brain microcirculation. In the present study, we sought to investigate the role that glutamate, possibly through astrocytic communication, plays in the control of NFATc3 regulation in pericytes from parenchymal microvessels. Coronal cortical slices from neonatal rats were subjected to electrical field stimulation or were treated with the metabotropic glutamate receptor agonist (+/-)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD). NFATc3, glial fibrillary acidic protein (an astrocyte-specific marker), and platelet-derived growth factor-beta-receptor (a pericyte-specific marker) were detected by immunofluorescence. Electrical field stimulation induced NFATc3 nuclear accumulation in pericytes. This response was dependent on neuronal activity and group I metabotropic glutamate receptor (mGluR) activation. In addition, t-ACPD significantly increased NFATc3 nuclear accumulation in both astrocytes and pericytes. NFATc3 nuclear accumulation in pericytes was prevented when astrocytic function was abolished with the gliotoxin L-alpha-aminoadipate or by the inhibition of calcineurin, cyclooxygenase, and nitric oxide synthase. This is the first study to report NFATc3 expression in pericytes from parenchymal microvessels and in astrocytes from native tissue. Our results suggest a model by which glutamate, via mGluR activation, may regulate gene transcription in pluripotent vascular pericytes.
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Affiliation(s)
- Jessica A Filosa
- Department of Psychiatry, University of Cincinnati, Cincinnati, OH 45237, USA.
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Dündar SO, Dayanir Y, Topaloğlu A, Dündar M, Koçak I. Effect of sildenafil on ocular hemodynamics in 3 months regular use. Int J Impot Res 2006; 18:282-6. [PMID: 16292333 DOI: 10.1038/sj.ijir.3901416] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The aim of this study was to evaluate the effect of sildenafil on ocular hemodynamics in a group of men with erectile dysfunction in 3 months regular use. A total of 15 patients with erectile dysfunction were included in this prospective study. All patients received 50 mg doses of sildenafil (Viagra, Pfizer) two times per week regularly for 3 months. The following examinations were performed on both eyes before and after sildenafil treatment: best-corrected visual acuity (BCVA), intraocular pressure (IOP), color vision, anterior segment, and fundus examination. Using color Doppler imaging, we measured hemodynamic variables in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary artery (SPCA). No significant changes in BCVA, color vision and IOP were found after sildenafil treatment. The anterior segment and fundus examinations showed no abnormalities. All Doppler parameters of OA, CRA, and SPCA remained nonsignificant for both eyes after sildenafil treatment. Oral sildenafil in 3 months regular use seems to have no effect on ocular hemodynamics.
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Affiliation(s)
- S O Dündar
- Department of Ophthalmology, Adnan Menderes University Faculty of Medicine, Aydin, Turkey.
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Metea MR, Newman EA. Glial cells dilate and constrict blood vessels: a mechanism of neurovascular coupling. J Neurosci 2006; 26:2862-70. [PMID: 16540563 PMCID: PMC2270788 DOI: 10.1523/jneurosci.4048-05.2006] [Citation(s) in RCA: 439] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuronal activity evokes localized changes in blood flow. Although this response, termed neurovascular coupling, is widely used to monitor human brain function and diagnose pathology, the cellular mechanisms that mediate the response remain unclear. We investigated the contribution of glial cells to neurovascular coupling in the acutely isolated mammalian retina. We found that light stimulation and glial cell stimulation can both evoke dilation or constriction of arterioles. Light-evoked and glial-evoked vasodilations were blocked by inhibitors of cytochrome P450 epoxygenase, the synthetic enzyme for epoxyeicosatrienoic acids. Vasoconstrictions, in contrast, were blocked by an inhibitor of omega-hydroxylase, which synthesizes 20-hydroxyeicosatetraenoic acid. Nitric oxide influenced whether vasodilations or vasoconstrictions were produced in response to light and glial stimulation. Light-evoked vasoactivity was blocked when neuron-to-glia signaling was interrupted by a purinergic antagonist. These results indicate that glial cells contribute to neurovascular coupling and suggest that regulation of blood flow may involve both vasodilating and vasoconstricting components.
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Zhu Y, Ohlemiller KK, McMahan BK, Park TS, Gidday JM. Constitutive nitric oxide synthase activity is required to trigger ischemic tolerance in mouse retina. Exp Eye Res 2005; 82:153-63. [PMID: 16045907 DOI: 10.1016/j.exer.2005.06.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2005] [Revised: 05/16/2005] [Accepted: 06/02/2005] [Indexed: 01/08/2023]
Abstract
Profound morphologic and functional protection against retinal ischemic injury can be achieved if the tissue is 'preconditioned' one day earlier with a brief, noninjurious ischemic challenge. To begin to address the mechanistic basis of this 'ischemic tolerance', we used genetic and pharmacologic approaches to test the hypothesis that nitric oxide (NO) derived from one of the three NO synthase (NOS) isoforms was responsible for triggering the adaptive response to brief preconditioning ischemia. Retinae of adult mice were preconditioned with 5-min preconditioning ischemia and subjected to 45-min injurious ischemia 24 hr later. Some animals were treated with the constitutive NOS inhibitor L-nitroarginine (5 mg/kg, i.p.) 1 hr before preconditioning. Retinal layer thicknesses and cell counts were determined one week postischemia in 5-mum thin sections, and flash electroretinograms were obtained at 1 and 7 days postischemia. We confirmed that ischemic preconditioning afforded morphologic and functional protection in the strains of wild-type mice studied. Histopathologic analyses of inducible NOS (iNOS) knockout mice revealed that ischemic preconditioning was completely effective, whereas ischemic tolerance was not achieved in the retinae of endothelial NOS (eNOS) and neuronal NOS (nNOS) knockout mice. The participation of the constitutive NOS enzymes in preconditioning-induced tolerance was confirmed by the finding that administration of the NOS inhibitor L-NA to wild-type mice prior to ischemic preconditioning blocked the development of ischemic tolerance. These cross-validating genetic and pharmacologic findings indicate that NO derived from both eNOS and nNOS is a required molecular signal in the adaptive response to ischemic preconditioning in the retina.
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Affiliation(s)
- Yanli Zhu
- Department of Neurosurgery, Washington University School of Medicine, Box 8057, 660 S. Euclid Ave., St Louis, MO 63110, USA
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Koksal M, Ozdemir H, Kargi S, Yesilli C, Tomaç S, Mahmutyazicioglu K, Mungan A. The effects of sildenafil on ocular blood flow. ACTA ACUST UNITED AC 2005; 83:355-9. [PMID: 15948790 DOI: 10.1111/j.1600-0420.2005.00422.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
PURPOSE To investigate the effects of sildenafil, a popular new drug in the treatment of erectile dysfunction, on ocular blood flow. METHODS This study was designed as a prospective, double-blind, placebo-controlled study. Twenty participants with erectile dysfunction were given a single oral dose of 100 mg sildenafil, while 10 participants with erectile dysfunction were given placebo. All the participants underwent routine systemic and ophthalmological examinations. Intraocular pressure, systolic and diastolic blood pressure and ocular blood flow (ophthalmic, central retinal, short posterior ciliary arteries) were measured in both eyes before and 1 hour after the dose of sildenafil or placebo. Ocular blood flow measurements were performed using colour Doppler ultrasonography. RESULTS None of the parameters were significantly different between the groups before study drug intake. Although central retinal artery velocities were not changed, ophthalmic artery and short posterior ciliary artery peak systolic velocity, end-diastolic velocity, and mean velocity values were significantly increased 1 hour after drug intake in the sildenafil group compared to the placebo group (p < 0.05). CONCLUSION Sildenafil causes a significant increase in blood flow in these arteries. A possible role of inhibition of phosphodiesterase-5 in vascular smooth muscles by sildenafil is implicated. Further studies are needed to investigate the effects of sildenafil on ocular blood flow in patients with senile macular degeneration, diabetic retinopathy and glaucoma.
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Affiliation(s)
- Murat Koksal
- Ophthalmology Department, Faculty of Medicine, Zonguldak Karaelmas University, Zonguldak, Turkey.
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Palanza L, Jhaveri S, Donati S, Nuzzi R, Vercelli A. Quantitative spatial analysis of the distribution of NADPH-diaphorase-positive neurons in the developing and mature rat retina. Brain Res Bull 2005; 65:349-60. [PMID: 15811601 DOI: 10.1016/j.brainresbull.2005.01.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Revised: 07/26/2004] [Accepted: 01/25/2005] [Indexed: 01/08/2023]
Abstract
NADPH-diaphorase (NADPH-d) histochemistry labels a subpopulation of nitric oxide-synthesizing amacrine cells in the inner nuclear layer of the rat retina. We have studied their morphology and distribution in postnatal and adult rats in whole-mounted retinae. NAPDH-d-positive neurons are detected as early as postnatal day (P)5, especially in the peripheral retina; intense labeling of somata and long lengths of dendrites is obtained between P10 and P18, after which only the somata exhibit NADPH-d activity. The density and number of these cells increase progressively from P7 to P14, with a significantly higher density in the central retina as compared to the periphery. The sociology of these cells was analyzed quantitatively studying the Voronoi domains: a polygon area can be drawn that delineates the territory of the map that is closer to the cell than to any other cell of the map. In addition, we calculated the conformity ratio of Cook, i.e., the mean nearest neighbor distance/standard deviation of all the nearest neighbor distances, in order to reveal whether or not these cells are regularly distributed through the retina. We find that the distribution of the NADPH-d-positive cells tends to be regular throughout the retina: the local coefficient of variation (obtained by comparing the size of each Voronoi polygon area to those of its neighbors) tends to regularity at P14 and remains unaltered through maturity. Therefore, as other cell types, NADPH-d-positive amacrine cells are almost regularly distributed from the time of eye opening and nitric oxide may play a role in the development of retinal circuitry and in the regulation of retinal blood flow.
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Affiliation(s)
- L Palanza
- Department of Anatomy, Pharmacology and Forensic Medicine, University of Turin, Corso M. D'Azeglio 52, 10126 Turin, Italy
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Loeliger M, Rees S. Immunocytochemical development of the guinea pig retina. Exp Eye Res 2005; 80:9-21. [PMID: 15652521 DOI: 10.1016/j.exer.2004.08.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Accepted: 08/03/2004] [Indexed: 10/26/2022]
Abstract
The aim of the present study was to establish the neurochemical profile of amacrine and horizontal cells during ontogeny in the guinea pig, a precocial species where significant retinal development occurs prenatally as opposed to altricial species where development largely occurs postnatally. The expression of neurochemical markers of horizontal cells and specific amacrine cell populations was investigated from 20 days of gestation (dg, term approximately 67 dg) to adulthood. Amacrine cell populations were identified immunohistochemically using antibodies to gamma-amino-butyric acid, cholineacetyltransferase, calbindin, calretinin, neuronal nitric oxide synthetase and tyrosine hydroxylase; horizontal cells were labelled with calbindin. All markers were present at 30 dg and had attained their mature (adult) laminar distribution and expression by 60 dg. Horizontal cells appeared in their final location at 30 dg with amacrine cell populations appearing in their final locations by 45 dg. Thus, in the guinea pig retina, the amacrine and horizontal cell populations investigated in this study are fully mature prior to birth.
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Affiliation(s)
- Michelle Loeliger
- Department of Anatomy and Cell Biology, University of Melbourne, Grattan St, Melbourne, Vic. 3010, Australia.
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Dorner GT, Garhofer G, Kiss B, Polska E, Polak K, Riva CE, Schmetterer L. Nitric oxide regulates retinal vascular tone in humans. Am J Physiol Heart Circ Physiol 2003; 285:H631-6. [PMID: 12750062 DOI: 10.1152/ajpheart.00111.2003] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of the present study was to investigate the contribution of basal nitric oxide (NO) on retinal vascular tone in humans. In addition, we set out to elucidate the role of NO in flicker-induced retinal vasodilation in humans. Twelve healthy young subjects were studied in a three-way crossover design. Subjects received an intravenous infusion of either placebo or NG-monomethyl-L-arginine (L-NMMA; 3 or 6 mg/kg over 5 min), an inhibitor of NO synthase. Thereafter, diffuse luminance flicker was consecutively performed for 16, 32, and 64 s at a frequency of 8 Hz. The effect of L-NMMA on retinal arterial and venous diameter was assessed under resting conditions and during the hyperemic flicker response. Retinal vessel diameter was measured with a Zeiss retinal vessel analyzer. L-NMMA significantly reduced arterial diameter (3 mg/kg: -2%; 6 mg/kg: -4%, P < 0.001) and venous diameter (3 mg/kg: -5%; 6 mg/kg: -8%, P < 0.001). After placebo infusion, flicker induced a significant increase in retinal vessel diameter (P < 0.001). At a flicker duration of 64 s, arterial diameter increased by 4% and venous diameter increased by 3%. L-NMMA did not abolish these hyperemic responses but blunted venous vasodilation (P = 0.017) and arterial vasodilation (P = 0.02) in response to flicker stimulation. Our data indicate that NO contributes to basal retinal vascular tone in humans. In addition, NO appears to play a role in flicker-induced vasodilation of the human retinal vasculature.
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Affiliation(s)
- Guido T Dorner
- Department of Clinical Pharmacology, University of Vienna Medical School, Waehringer Guertel 18-20, Vienna A-1090, Austria
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Tolcos M, Harding R, Loeliger M, Breen S, Cock M, Duncan J, Rees S. The fetal brainstem is relatively spared from injury following intrauterine hypoxemia. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2003; 143:73-81. [PMID: 12763582 DOI: 10.1016/s0165-3806(03)00103-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Our aim was to test the hypothesis that the fetal brainstem is relatively spared, compared to other brain regions, from hypoxia-induced damage. We have used established experimental models of acute and chronic intrauterine compromise in sheep to mimic conditions that can arise in human pregnancy. The acute insult was 12 h of placental insufficiency induced by restricted utero-placental blood flow at 90 days of gestation (term approximately 147 days). Five weeks after this insult (n=7 fetuses) there was no overt damage to the brainstem nor were there alterations to the blood vessel morphology, volume of the medulla or of medullary nuclei compared to controls (n=8). This regimen is known to have significant effects on the forebrain and cerebellum. The chronic insult was induced in five fetuses via embolisation of the umbilico-placental circulation from 120 to 140 days of gestation. An additional three fetuses were found to be spontaneously hypoxemic (SH) immediately after surgery. At 140 days, in brainstems of all chronically hypoxemic fetuses compared to controls (n=8), there was an increase (P<0.05) in the percentage of neuropil occupied by blood vessels and abnormal myelin in the most severely SH fetus but no other morphological or neurochemical alterations. This regimen is known to cause marked damage to the cerebral hemispheres and to a lesser extent to the cerebellum. We suggest that the absence of marked structural or neurochemical alterations in the brainstem is most likely due to the maintenance of oxygen delivery to the brainstem during fetal hypoxemia.
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Affiliation(s)
- Mary Tolcos
- Department of Anatomy and Cell Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
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Toda N, Okamura T. The pharmacology of nitric oxide in the peripheral nervous system of blood vessels. Pharmacol Rev 2003; 55:271-324. [PMID: 12773630 DOI: 10.1124/pr.55.2.3] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Unanticipated, novel hypothesis on nitric oxide (NO) radical, an inorganic, labile, gaseous molecule, as a neurotransmitter first appeared in late 1989 and into the early 1990s, and solid evidences supporting this idea have been accumulated during the last decade of the 20th century. The discovery of nitrergic innervation of vascular smooth muscle has led to a new understanding of the neurogenic control of vascular function. Physiological roles of the nitrergic nerve in vascular smooth muscle include the dominant vasodilator control of cerebral and ocular arteries, the reciprocal regulation with the adrenergic vasoconstrictor nerve in other arteries and veins, and in the initiation and maintenance of penile erection in association with smooth muscle relaxation of the corpus cavernosum. The discovery of autonomic efferent nerves in which NO plays key roles as a neurotransmitter in blood vessels, the physiological roles of this nerve in the control of smooth muscle tone of the artery, vein, and corpus cavernosum, and pharmacological and pathological implications of neurogenic NO have been reviewed. This nerve is a postganglionic parasympathetic nerve. Mechanical responses to stimulation of the nerve, mainly mediated by NO, clearly differ from those to cholinergic nerve stimulation. The naming "nitrergic or nitroxidergic" is therefore proposed to avoid confusion of the term "cholinergic nerve", from which acetylcholine is released as a major neurotransmitter. By establishing functional roles of nitrergic, cholinergic, adrenergic, and other autonomic efferent nerves in the regulation of vascular tone and the interactions of these nerves in vivo, especially in humans, progress in the understanding of cardiovascular dysfunctions and the development of pharmacotherapeutic strategies would be expected in the future.
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Affiliation(s)
- Noboru Toda
- Toyama Institute for Cardiovascular Pharmacology Research, Toyama Bldg., 7-13, 1-Chome, Azuchi-machi, Chuo-ku, Osaka 541-0052, Japan.
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Tsumamoto Y, Yamashita K, Takumida M, Okada K, Mukai S, Shinya M, Yamashita H, Mishima HK. In situ localization of nitric oxide synthase and direct evidence of NO production in rat retinal ganglion cells. Brain Res 2002; 933:118-29. [PMID: 11931856 DOI: 10.1016/s0006-8993(02)02289-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The expression of isoforms of nitric oxide synthase (NOS), enzymes responsible for NO production, and the synthesis of nitric oxide (NO) in rat retinal ganglion cells (RGCs) during synaptogenesis for various phases of the pre- and postnatal developmental periods were investigated. The retinas from prenatal, lactating, young, and adult rats were fixed in paraformaldehyde. The cryosections or paraformaldehyde-fixed ganglion cells purified from rat pups were immunostained for constitutive isoforms of NOS (n and eNOS) and observed with a confocal laser scanning microscope. Synthesis of NO in the RGCs was achieved by in vitro stimulation with glutamate. The intracellular NO levels were measured in real time using diaminofluorescein-2 diacetate, a fluorescence indicator of NO. Immunohistochemical analysis revealed nNOS and eNOS expressed in retinal ganglion cells during the first 2 postnatal weeks. Cultured RGCs also expressed nNOS and eNOS in vitro. Intracellular NO levels in cultured RGCs showed spontaneous fluctuation during a 20-min observation. The presence of both a non-specific NOS inhibitor, L-NAME, and a specific nNOS inhibitor, 7-NI, significantly inhibited (P<0.001) the increase of intracellular NO 6 and 8 min after the introduction of L-arginine and glutamate to the medium. This study revealed that all constitutive NOS isoforms are expressed in RGCs and demonstrated that NO is produced by nNOS mainly through stimulation by glutamate in cultured RGCs.
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Affiliation(s)
- Yuichi Tsumamoto
- Department of Ophthalmology, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan
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Hardy P, Lamireau D, Hou X, Dumont I, Abran D, Nuyt AM, Varma DR, Chemtob S. Major role for neuronal NO synthase in curtailing choroidal blood flow autoregulation in newborn pig. J Appl Physiol (1985) 2001; 91:1655-62. [PMID: 11568147 DOI: 10.1152/jappl.2001.91.4.1655] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined whether nitric oxide (NO) generated from neuronal NO synthase (nNOS) contributes to the reduced ability of the newborn to autoregulate retinal blood flow (RBF) and choroidal blood flow (ChBF) during acute rises in perfusion pressure. In newborn pigs (1-2 days old), RBF (measured by microsphere) is autoregulated over a narrow range of perfusion pressure, whereas ChBF is not autoregulated. N(G)-nitro-L-arginine methyl ester (L-NAME) or specific nNOS inhibitors 7-nitroindazole, 3-bromo-7-nitroindazole, and 1-(2-trifluoromethyl-phenyl)imidazole as well as ganglionic blocker hexamethonium, unveiled a ChBF autoregulation as observed in juvenile (4- to 6-wk old) animals, whereas autoregulation of RBF in the newborn was only enhanced by L-NAME. All NOS inhibitors and hexamethonium prevented the hypertension-induced increase in NO mediator cGMP in the choroid. nNOS mRNA expression and activity were three- to fourfold higher in the choroid of newborn pigs than in tissues of juvenile pigs. It is concluded that increased production of NO from nNOS curtails ChBF autoregulation in the newborn and suggests a role for the autonomic nervous system in this important hemodynamic function, whereas, for RBF autoregulation, endothelial NOS seems to exert a more important contribution in limiting autoregulation.
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Affiliation(s)
- P Hardy
- Department of Pediatrics, Research Center of Hôpital Sainte-Justine, 3175 Côte Sainte-Catherine, Montréal H3T 1C5, Québec, Canada
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Sakagami K, Kawamura H, Wu DM, Puro DG. Nitric oxide/cGMP-induced inhibition of calcium and chloride currents in retinal pericytes. Microvasc Res 2001; 62:196-203. [PMID: 11516249 DOI: 10.1006/mvre.2001.2343] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the CNS, contractile pericytes positioned on endothelium-lined lumens appear to play a role in regulating capillary blood flow. This function may be particularly important in the retina where pericytes are more numerous than in other tissues. Despite the importance of pericytes, knowledge of the effects of vasoactive molecules, such as nitric oxide (NO), on the physiology of these cells is limited. Since it is likely that ion channels play a role in the response of pericytes to signaling molecules from other cells, we used the perforated-patch configuration of the patch-clamp technique to record the whole-cell currents of pericytes located on microvessels freshly isolated from the rat retina. We found that voltage-gated calcium currents and calcium-activated chloride currents were inhibited during exposure to the NO donor, sodium nitroprusside (SNP). 8-Bromo-cyclic guanosine monophosphate (cGMP) mimicked these effects. In contrast, neither SNP nor the cGMP analog significantly affected the potassium or nonspecific cation conductances, which establish the resting membrane potential of retinal pericytes. Consistent with endogenous NO suppressing pericyte channel activity, exposure of isolated microvessels to an inhibitor of NO synthase increased the calcium and chloride currents. Since our experiments indicate that chloride channel activity is dependent, in part, upon the function of voltage-gated calcium channels, we postulate that a NO/cGMP-mediated inhibition of calcium channels reduces calcium influx and, thereby, lessens the opening of the calcium-activated chloride channels. This may be one mechanism by which NO decreases the contractile tone of pericytes.
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Affiliation(s)
- K Sakagami
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan 48105, USA
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Dündar SO, Dündar M, Koçak I, Dayanir Y, Ozkan SB. Effect of sildenafil on ocular haemodynamics. Eye (Lond) 2001; 15:507-10. [PMID: 11767027 DOI: 10.1038/eye.2001.163] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To study the effect of sildenafil, which is an effective agent for the treatment of erectile dysfunction, on ocular haemodynamics. METHODS In this prospective study we examined the effect of a single oral dose of 50 mg sildenafil (Viagra) in a group of healthy young male volunteers, by using colour Doppler ultrasound imaging to measure haemodynamic variables in the central retinal artery (CRA), short temporal posterior ciliary artery (STPCA) and ophthalmic artery (OA). The following examinations were performed on both eyes immediately before and 1 h after a single oral dose of 50 mg sildenafil: visual acuity, intraocular pressure (IOP), colour vision, anterior segment, fundus appearance, resting heart rate, blood pressure and colour Doppler measurements. RESULTS After sildenafil administration, peak systolic velocity, mean velocity and end-diastolic velocity significantly increased in the OA of both eyes. All Dopper indices remained non-significant for the CRA and STPCA of both eyes. Sildenafil did not cause any significant change in IOP, colour vision, visual acuity, systolic blood pressure or diastolic blood pressure. However, heart rate measurements increased significantly after sildenafil administration compared with baseline (p = 0.003). CONCLUSION The increased flow velocity in the ophthalmic artery seems to be due to a vasodilator effect of sildenafil.
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Affiliation(s)
- S O Dündar
- Department of Ophthalmology, Adnan Menderes University, Aydin, Turkey.
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38
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Polak K, Dorner G, Kiss B, Polska E, Findl O, Rainer G, Eichler HG, Schmetterer L. Evaluation of the Zeiss retinal vessel analyser. Br J Ophthalmol 2000; 84:1285-90. [PMID: 11049956 PMCID: PMC1723319 DOI: 10.1136/bjo.84.11.1285] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIM To investigate the reproducibility and sensitivity of the Zeiss retinal vessel analyser, a new method for the online determination of retinal vessel diameters in healthy subjects. METHODS Two model drugs were administered, a peripheral vasoconstrictor (the alpha receptor agonist phenylephrine) and a peripheral vasodilator (the nitric oxide donor sodium nitroprusside) in stepwise increasing doses. Nine healthy young subjects were studied in a placebo controlled double masked three way crossover design. Subjects received intravenous infusions of either placebo or stepwise increasing doses of phenylephrine (0.5, 1, or 2 microg/kg/min) or sodium nitroprusside (0.5, 1, or 2 microg/kg/min). Retinal vessel diameters were measured with the new Zeiss retinal vessel analyser. Retinal leucocyte velocity, flow, and density were measured with the blue field entoptic technique. The reproducibility of measurements was assessed with coefficients of variation and intraclass correlation coefficients. RESULTS Placebo and phenylephrine did not influence retinal haemodynamics, although the alpha receptor antagonist significantly increased blood pressure. Sodium nitroprusside induced a significant increase in retinal venous and arterial diameters (p<0.001 each), leucocyte density (p=0.001), and leucocyte flow (p=0.024) despite lowering blood pressure to a significant degree. For venous and arterial vessel size measurements short term coefficients of variation were 1.3% and 2.6% and intraclass correlation coefficients were 0.98 and 0.96, respectively. The sensitivity was between 3% and 5% for retinal veins and 5% and 7% for retinal arteries. CONCLUSIONS These data indicate that the Zeiss retinal vessel analyser is an accurate system for the assessment of retinal diameters in healthy subjects. In addition, nitric oxide appears to have a strong influence on retinal vascular tone.
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Affiliation(s)
- K Polak
- Department of Clinical Pharmacology, University of Vienna, Vienna, Austria
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39
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Abstract
The development of immunocytochemistry has led to a better understanding of synaptic transmission carried out by neuroactive substances in the mammalian brain, including the retina. In the mammalian retina, nitric oxide (NO) is widely accepted as a neuromodulator. Histochemistry based on NADPH-d and immunocytochemistry based on nitric oxide synthase (NOS) have been used to identify the presence of nitric oxide in the mammalian retina. Certain types of amacrine cells and a class of displaced amacrine cells have been labeled consistently in all mammalian retinae studied to date. Other cell types showing NADPH-d reactivity or NOS immunoreactivity varied between species. NADPH-d reactive or NOS immunoreactive amacrine cells may serve as a source of NO for amacrine, bipolar, and ganglion cells in the inner retina, whereas interplexiform cells, bipolar cells, and horizontal cells may serve as a source of NO for the outer retina of mammals.
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Affiliation(s)
- I B Kim
- Department of Anatomy, College of Medicine, Catholic University of Korea, Seoul, Korea
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40
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Abstract
The neuronal form of nitric oxide synthase (NOS-1) has been localized to several cell types in the retinas of experimental animals; however, localization in the human retina has not been definitive. By using in situ hybridization and immunohistochemistry, we have compared the cellular expression and localization of NOS-1 in the rat and human retinas. In both rat and human retinas, NOS-1 is expressed in the inner segments of photoreceptors, cells in the inner nuclear layer, particularly amacrine cells, and retinal ganglion cells. In human cones, NOS-1 is abundantly present in the outer segments. In the rat, optic nerve transection caused a loss of cells that were positive for NOS-1 in the ganglion cell layer. Although a retinal ganglion cell localization has not been reported consistently in the literature, our data clearly localize NOS-1 to the retinal ganglion cells of the rat and human retinas.
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Affiliation(s)
- A H Neufeld
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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41
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Chapter IV Nitric oxide in the retina. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0924-8196(00)80058-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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42
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Archer DB. Bowman Lecture 1998. Diabetic retinopathy: some cellular, molecular and therapeutic considerations. Eye (Lond) 1999; 13 ( Pt 4):497-523. [PMID: 10692923 DOI: 10.1038/eye.1999.130] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Affiliation(s)
- D B Archer
- Department of Ophthalmology, Royal Victoria Hospital, Belfast, Northern Ireland.
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43
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Cellerino A, Arango-González BA, Kohler K. Effects of brain-derived neurotrophic factor on the development of NADPH-diaphorase/nitric oxide synthase-positive amacrine cells in the rodent retina. Eur J Neurosci 1999; 11:2824-34. [PMID: 10457179 DOI: 10.1046/j.1460-9568.1999.00690.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Amacrine neurons expressing nitric oxide synthase (NOS) contain brain-derived neurotrophic factor (BDNF) receptors and respond to exogenous BDNF [Klöcker, N., Cellerino, A. & Bähr, M. (1998) J. Neurosci., 18, 1038-1046]. We analysed the effects of BDNF on the development of neurons which express NOS in the mouse and rat retina. Rat pups received a total of three intraocular injections of BDNF at intervals of 48 h, starting at postnatal day 16 (P16), and were killed at P22. The retinas were stained for NADPH-diaphorase, a histological marker of NOS. NOS-expressing neurons were found in both the inner nuclear layer (INL) and the ganglion cell layer (GCL). Two classes of NOS-expressing neurons, type I and type II, had already been distinguished in the INL [Koistinaho, J. & Sagar, S.M. (1995) In Osborne, N.N. & Chader, G.J. (eds), Progress in Retinal and Eye Research, Vol. 15. Oxford University Press, pp. 69-87] and a third one in the GCL. Up-regulation of NADPH-diaphorase activity was observed after BDNF treatment. The number of type I neurons remained stable, whereas the number of type II neurons and NOS-positive neurons in the GCL increased significantly (P < 0.001). Type I and type II neurons were significantly larger in BDNF-treated retinas. Double-labelling experiments revealed that BDNF induces NADPH-diaphorase in dopaminergic neurons and amacrine cells displaced to the GCL, but not in retinal ganglion cells. In mice homozygous for a null mutation of the bdnf gene, the intensity of NADPH-diaphorase labelling in both somata and processes was reduced, but the number of labelled neurons was not dramatically reduced. These findings indicate that BDNF regulates the neurotransmitter phenotype of NOS-expressing amacrine neurons under physiological conditions, but is not required for their survival.
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Affiliation(s)
- A Cellerino
- Department of Pathophysiology of Vision and Neuroophthalmology, Division of Experimental Ophthalmology, University Eye Hospital, Tübingen, Germany
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44
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Chen ST, Wang JP, Shen CL, Jen LS. NADPH-diaphorase activity in normally developing and intracranially transplanted retinas. Neurochem Res 1999; 24:1051-7. [PMID: 10478945 DOI: 10.1023/a:1021013011808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The activity and distribution of nicotinamide dinucleotide phosphate diaphorase (NADPH-d), an enzyme that is widely distributed in the central nervous system and involved in the production of the free radical nitric oxide, were investigated histochemically in the normal developing and intracranially transplanted retinas. In the normal rat retina, NADPH-d activity was first detected in cells in the ganglion cells layer (GCL) and blood vessels on the first postnatal day (P0). A small but distinct population of NADPH-d positive cells were observed along the inner border of the inner nuclear layer at P7. NADPH-d positive sublaminae began to appear in the inner plexiform layer during the second postnatal week, and several strongly reactive sublaminae resembling those observed in the adult were observed by the fourth postnatal week. The overall spatio- temporal sequence of development of NADPH-d positive cells in the transplanted retina was similar to that of the normal retina, except a lack of reactive in the inner plexiform layer in more mature transplants as compared with normal retinas of corresponding ages. These results indicate that the time course of development and distribution of NADPH-d cells in early postnatal retina requires signals mainly of intraretinal origin and is independent of influence from the surroundings. While this finding is supportive to the notion that neurons that are rich in NADPH-d are resistant to injury or perturbation, the observation of a lack of well organized NADPH-d reactive sublaminae in the inner plexiform layer in older transplants suggests a possible alteration in the synaptic circuitry in the inner retina with increasing postgrafting survival time.
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Affiliation(s)
- S T Chen
- Department of Anatomy, National Cheng Kung University, Taiwan, ROC.
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45
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Abstract
Nitric oxide generated by three distinct enzyme systems appears to play a critical role in many diverse physiological processes. Using both conventional and immunohistochemical techniques, nitric oxide synthases have been identified throughout the body, including all regions of the eye. A large number of in vitro and in vivo preparations have been utilized showing nitric oxide to have an important role in regulation of regional ocular blood flow. Nitric oxide-mediated control of basal ocular blood flow is demonstrated by vasoconstriction seen in experiments where vascular endothelial cells are removed, or when nitric oxide synthase is inhibited. The endogenous source of nitric oxide in the eye appears to be both endothelial and neural. In addition, administration of drugs that can 'donate' nitric oxide produces vasodilation of the eye vasculature. Local vasodilation in response to illumination of the retina is controlled by generation and release of nitric oxide, whereas most other physiological adjustments of ocular blood flow (i.e., autoregulation and responses to altered blood gas levels) seem to be relatively independent of nitric oxide mechanisms. Nitric oxide is implicated in a variety of ocular pathophysiological states including uveitis, retinal ischemic disease, diabetes and glaucoma.
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Affiliation(s)
- M C Koss
- Department of Cell Biology, University of Oklahoma College of Medicine, Oklahoma City 73190, USA
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46
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Fischer AJ, Stell WK. Nitric oxide synthase-containing cells in the retina, pigmented epithelium, choroid, and sclera of the chick eye. J Comp Neurol 1999; 405:1-14. [PMID: 10022192 DOI: 10.1002/(sici)1096-9861(19990301)405:1<1::aid-cne1>3.0.co;2-u] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Nitric oxide is a nonconventional neurotransmitter that is produced as needed by the enzyme nitric oxide synthase (NOS). NOS has been detected in numerous neural structures, including distinct populations of retinal neurons in a variety of vertebrate species. The purpose of this study was to identify NOS-containing cells in the retina and extraretinal ocular tissues of hatched chicks. NOS was detected in frozen sections by using nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry and antisera to neuronal NOS. In the retina, NADPH-diaphorase and NOS immunolabelling were present in four subtypes of amacrine cells, some ganglion cells, efferent fibers, efferent target cells, and neuronal processes in both plexiform layers, whereas diaphorase alone was detected in photoreceptor ellipsoids and Müller cells. In addition, NADPH-diaphorase and immunoreactive NOS were detected in axon bundles and innervation to vascular smooth muscle in the choroid, whereas stromal and endothelial cells in the choroid, scleral chondrocytes, and the retinal pigmented epithelium contained only NADPH-diaphorase. The excitotoxin quisqualate destroyed all but one subtype of NOS-immunoreactive amacrine cell and caused increased NADPH-diaphorase activity in Müller cells. We conclude that nitric oxide is produced by many different cells in the chick eye, including retinal amacrine and ganglion cells, Müller cells, retinal pigmented epithelium, and cells in the choroid, and likely has a broad range of visual and regulatory functions.
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Affiliation(s)
- A J Fischer
- Lions' Sight Centre and Department of Anatomy, The University of Calgary, Faculty of Medicine, Alberta, Canada.
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47
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Kelly PA, Buckley CH, Ritchie IM, O'Brien C. Possible role for nitric oxide releasing nerves in the regulation of ocular blood flow in the rat. Br J Ophthalmol 1998; 82:1199-202. [PMID: 9924311 PMCID: PMC1722380 DOI: 10.1136/bjo.82.10.1199] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIM To investigate the role of nitrergic nerves in the regulation of ocular blood flow. METHODS Conscious, lightly restrained rats were treated with either the neuronal nitric oxide synthase inhibitor 7-nitroindazole (7-NI), or the nonselective inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), and ocular blood flow was measured ex vivo from tissue samples, using the fully quantitative [14C]-iodoantipyrine technique. RESULTS In the peripheral circulation, L-NAME produced an increase in arterial blood pressure (+22%) while 7-NI had no effect. In contrast, both 7-NI and L-NAME produced significant decreases in ocular blood flow (-31% and -59% respectively). The ocular vascular resistance calculated from ocular blood flow and mean arterial blood pressure increased by 29% following 7-NI, but by 130% following L-NAME. CONCLUSIONS Nitric oxide releasing neurons may play an important contributory role in regulating ocular blood flow.
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Affiliation(s)
- P A Kelly
- Department of Clinical Neurosciences, University of Edinburgh
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48
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Haverkamp S, Eldred WD. Localization of nNOS in photoreceptor, bipolar and horizontal cells in turtle and rat retinas. Neuroreport 1998; 9:2231-5. [PMID: 9694205 DOI: 10.1097/00001756-199807130-00015] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Neuronal nitric oxide synthase (nNOS), an enzyme that synthesizes NO, has been found in the outer retina using light microscopic immunocytochemistry, but its subcellular localization is unknown. We used electron immunocytochemistry to examine nNOS-like immunoreactivity (nNOS-LI) in the outer plexiform layer of turtle and rat retinas. In turtle, nNOS-LI was present in some bipolar and horizontal cell processes at photoreceptor ribbon synapses and at basal junctions between photoreceptors. In rat, nNOS-LI was present in some rod bipolar and B-type horizontal cell axon terminals at rod ribbon synapses. These results indicate that in vertebrates, NO is produced by all of the major nerve cell types in the outer retina at specific synaptic contacts.
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Affiliation(s)
- S Haverkamp
- Boston University, Department of Biology, MA 02215, USA
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49
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Chen Z, Gu Q, Kaufman PL, Cynader MS. Histochemical mapping of NADPH-diaphorase in monkey and human eyes. Curr Eye Res 1998; 17:370-9. [PMID: 9561828 DOI: 10.1080/02713689808951217] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE To localize nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in normal human and monkey eyes. METHODS NADPH-d activity in ocular tissue sections was revealed by histochemical staining. RESULTS NADPH-d staining was found in the anterior and posterior ocular segment of both species. In the anterior segment, reaction product was present in the corneal epithelium and endothelium, iris dilator and sphincter, lens capsule, ciliary muscle, and non-pigmented epithelial cells and stroma of the ciliary processes. Staining density in the longitudinal ciliary muscle was higher than in the other ciliary muscle regions in the human; such regionalization was less apparent in the monkey. The trabecular meshwork stained minimally if at all in both species. In the posterior segment, staining was seen around choroidal blood vessels and choroidal nerves, and in the retinal pigment epithelial, photoreceptor, bipolar, inner plexiform and ganglion cell layers. CONCLUSIONS NADPH-d is widespread in human and monkey eyes, indicating significant and presumably functionally relevant NO production in the various ocular structures.
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Affiliation(s)
- Z Chen
- Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
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Free radical scavenging and inhibition of nitric oxide synthase potentiates the neurotrophic effects of brain-derived neurotrophic factor on axotomized retinal ganglion cells In vivo. J Neurosci 1998. [PMID: 9437024 DOI: 10.1523/jneurosci.18-03-01038.1998] [Citation(s) in RCA: 152] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) partially promotes the survival of axotomized retinal ganglion cells (RGCs). In analogy with in vitro experiments (; ), we tested whether neuroprotection by BDNF is limited by adverse effects as a consequence of excessive free radical formation. First, we investigated whether BDNF and the free radical scavenger N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN) cooperate in protecting RGCs from axotomy-induced death. Although systemic S-PBN treatment alone did not influence RGC survival after axotomy, it potentiated the neuroprotective effects of BDNF significantly. Single BDNF treatment rescued 27% of the RGCs, which otherwise would have died 14 d after optic nerve transection, whereas a combined treatment of BDNF and S-PBN improved this rescue rate up to 68%. We then investigated whether the adverse effects of BDNF could be ascribed to activation of nitric oxide synthase (NOS). We found colocalization of NOS and the BDNF receptor TrkB in the retina. NADPH-diaphorase reactivity, a reliable marker for NOS in the rat retina, increased after chronic BDNF treatment in vivo. Systemic application of the NOS-inhibitor N-omega-nitro-L-arginine-methylester (L-NAME) potentiated the neuroprotective action of BDNF (55% rescue rate). We conclude that activation of NOS is a pathological consequence of BDNF application, which reduces its neuroprotective potential. The observation that this adverse effect can be antagonized by systemic application of free radical scavengers could be of relevance for clinical applications of neurotrophins in human neurodegenerative diseases.
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