51
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Tsokolas G, Tsaousis KT, Diakonis VF, Matsou A, Tyradellis S. Optical Coherence Tomography Angiography in Neurodegenerative Diseases: A Review. Eye Brain 2020; 12:73-87. [PMID: 32765149 PMCID: PMC7368556 DOI: 10.2147/eb.s193026] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 06/25/2020] [Indexed: 12/11/2022] Open
Abstract
Background Optical coherence tomography angiography (OCT-A) has emerged as a novel, fast, safe and non-invasive imaging technique of analyzing the retinal and choroidal microvasculature in vivo. OCT-A captures multiple sequential B-scans performed repeatedly over a specific retinal area at high speed, thus enabling the composition of a vascular map with areas of contrast change (high flow zones) and areas of steady contrast (slow or no flow zones). It therefore provides unique insight into the exact retinal or choroidal layer and location at which abnormal blood flow develops. OCTA has evolved into a useful tool for understanding a number of retinal pathologies such as diabetic retinopathy, age-related macular degeneration, central serous chorioretinopathy, vascular occlusions, macular telangiectasia and choroidal neovascular membranes of other causes. OCT-A technology is also increasingly being used in the evaluation of optic disc perfusion and has been suggested as a valuable tool in the early detection of glaucomatous damage and monitoring progression. Objective To review the existing literature on the applications of optical coherence tomography angiography in neurodegenerative diseases. Summary A meticulous literature was performed until the present day. Google Scholar, PubMed, Mendeley search engines were used for this purpose. We used 123 published manuscripts as our references. OCT-A has been utilized so far to describe abnormalities in multiple sclerosis (MS), Alzheimer’s disease, arteritic and non-arteritic optic neuropathy (AION and NAION), Leber’s hereditary optic neuropathy (LHON) papilloedema, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis (ALS), Wolfram syndrome, migraines, lesions of the visual pathway and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). It appears that OCT-A findings correlate quite well with the severity of the aforementioned diseases. However, OCT-A has its own limitations, namely its lack of wide-field view of the peripheral retina and the inaccurate interpretation due to motion artifacts in uncooperative groups of patients (e.g. children). Larger prospective longitudinal studies will need to be conducted in order to eliminate the aforementioned limitations.
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Affiliation(s)
- Georgios Tsokolas
- Ophthalmology Department, Leicester Royal Infirmary, University Hospitals of Leicester, Leicester, UK
| | - Konstantinos T Tsaousis
- Ophthalmology Department, Leicester Royal Infirmary, University Hospitals of Leicester, Leicester, UK
| | | | - Artemis Matsou
- Ophthalmology Department, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, UK
| | - Straton Tyradellis
- Ophthalmology Department, Leicester Royal Infirmary, University Hospitals of Leicester, Leicester, UK
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52
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Wright WS, Eshaq RS, Lee M, Kaur G, Harris NR. Retinal Physiology and Circulation: Effect of Diabetes. Compr Physiol 2020; 10:933-974. [PMID: 32941691 PMCID: PMC10088460 DOI: 10.1002/cphy.c190021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In this article, we present a discussion of diabetes and its complications, including the macrovascular and microvascular effects, with the latter of consequence to the retina. We will discuss the anatomy and physiology of the retina, including aspects of metabolism and mechanisms of oxygenation, with the latter accomplished via a combination of the retinal and choroidal blood circulations. Both of these vasculatures are altered in diabetes, with the retinal circulation intimately involved in the pathology of diabetic retinopathy. The later stages of diabetic retinopathy involve poorly controlled angiogenesis that is of great concern, but in our discussion, we will focus more on several alterations in the retinal circulation occurring earlier in the progression of disease, including reductions in blood flow and a possible redistribution of perfusion that may leave some areas of the retina ischemic and hypoxic. Finally, we include in this article a more recent area of investigation regarding the diabetic retinal vasculature, that is, the alterations to the endothelial surface layer that normally plays a vital role in maintaining physiological functions. © 2020 American Physiological Society. Compr Physiol 10:933-974, 2020.
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Affiliation(s)
- William S Wright
- Department of Biomedical Sciences, University of South Carolina School of Medicine Greenville, Greenville, South Carolina, USA
| | - Randa S Eshaq
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
| | - Minsup Lee
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
| | - Gaganpreet Kaur
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
| | - Norman R Harris
- Department of Molecular and Cellular Physiology, Louisiana State University Health Shreveport, Shreveport, Louisiana, USA
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53
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Lin J, Hu J, Schlotterer A, Wang J, Kolibabka M, Awwad K, Dietrich N, Breitschopf K, Wohlfart P, Kannt A, Lorenz K, Feng Y, Popp R, Hoffmann S, Fleming I, Hammes HP. Protective effect of Soluble Epoxide Hydrolase Inhibition in Retinal Vasculopathy associated with Polycystic Kidney Disease. Am J Cancer Res 2020; 10:7857-7871. [PMID: 32685025 PMCID: PMC7359083 DOI: 10.7150/thno.43154] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 05/20/2020] [Indexed: 12/14/2022] Open
Abstract
Rationale: Vasoregression secondary to glial activation develops in various retinal diseases, including retinal degeneration and diabetic retinopathy. Photoreceptor degeneration and subsequent retinal vasoregression, characterized by pericyte loss and acellular capillary formation in the absence diabetes, are also seen in transgenic rats expressing the polycystic kidney disease (PKD) gene. Activated Müller glia contributes to retinal vasodegeneration, at least in part via the expression of the soluble epoxide hydrolase (sEH). Given that an increase in sEH expression triggered vascular destabilization in diabetes, and that vasoregression is similar in diabetic mice and PKD rats, the aim of the present study was to determine whether sEH inhibition could prevent retinal vasoregression in the PKD rat. Methods: One-month old male homozygous transgenic PKD rats were randomly allocated to receive vehicle or a sEH inhibitor (sEH-I; Sar5399, 30 mg/kg) for four weeks. Wild-type Sprague-Dawley (SD) littermates received vehicle as controls. Retinal sEH expression and activity were measured by Western blotting and LC-MS, and vasoregression was quantified in retinal digestion preparations. Microglial activation and immune response cytokines were assessed by immunofluorescence and quantitative PCR, respectively. 19,20-dihydroxydocosapentaenoic acid (19,20-DHDP) mediated Notch signaling, microglial activation and migration were assessed in vivo and in vitro. Results: This study demonstrates that sEH expression and activity were increased in PKD retinae, which led to elevated production of 19,20-DHDP and the depression of Notch signaling. The latter changes elicited pericyte loss and the recruitment of CD11b+/CD74+ microglia to the perivascular region. Microglial activation increased the expression of immune-response cytokines, and reduced levels of Notch3 and delta-like ligand 4 (Dll4). Treatment with Sar5399 decreased 19,20-DHDP generation and increased Notch3 expression. Sar5399 also prevented vasoregression by reducing pericyte loss and suppressed microglial activation as well as the expression of immune-response cytokines. Mechanistically, the activation of Notch signaling by Dll4 maintained a quiescent microglial cell phenotype, i.e. reduced both the surface presentation of CD74 and microglial migration. In contrast, in retinal explants, 19,20-DHDP and Notch inhibition both promoted CD74 expression and reversed the Dll4-induced decrease in migration. Conclusions: Our data indicate that 19,20-DHDP-induced alterations in Notch-signaling result in microglia activation and pericyte loss and contribute to retinal vasoregression in polycystic kidney disease. Moreover, sEH inhibition can ameliorate vasoregression through reduced activity of inflammatory microglia. sEH inhibition is thus an attractive new therapeutic approach to prevent retinal vasoregression.
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54
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Effects of Prolonged Type 2 Diabetes on the Inner Retinal Layer and Macular Microvasculature: An Optical Coherence Tomography Angiography Study. J Clin Med 2020; 9:jcm9061849. [PMID: 32545794 PMCID: PMC7355838 DOI: 10.3390/jcm9061849] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 06/10/2020] [Accepted: 06/11/2020] [Indexed: 12/29/2022] Open
Abstract
Purpose: To identify the effects of prolonged type 2 diabetes (T2DM) on macular microcirculation and the inner retinal layer in diabetic eyes without clinical diabetic retinopathy (DR). Methods: 97, 92, and 57 eyes in the control, patients with T2DM < 10 years (DM group one), and patients with T2DM ≥ 10 years (DM group two) were enrolled. The ganglion cell-inner plexiform layer (GC-IPL) thickness and superficial vessel density (VD) were compared. Linear regression analyses were performed to identify factors associated with VD in T2DM patients. Results: GC-IPL thicknesses in the control, DM group one, and DM group two were 84.58 ± 0.89, 83.49 ± 0.70, and 79.04 ± 0.96 μm, respectively (p < 0.001). The VDs of the full area were 20.32 ± 0.15, 19.46 ± 0.17, and 18.46 ± 0.23 mm−1 (p < 0.001). Post-hoc analyses revealed that the VDs of the full area was significantly different in the control vs. DM group one (p = 0.001), control vs. DM group two (p < 0.001), and DM group one vs. DM group two (p = 0.001). Multivariate linear regression analyses revealed that DM duration (p = 0.037), visual acuity (p = 0.013), and GC-IPL thickness (p < 0.001) were significantly associated with the VD of T2DM patients. Conclusions: We confirmed GC-IPL thinning and decreased superficial VD in the macular areas using OCTA in T2DM patients. Patients with T2DM ≥ 10 years exhibited significantly more severe macular microcirculation impairment compared to patients with T2DM < 10 years and normal controls.
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55
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López-Bernal Á, García-Tejera O, Testi L, Villalobos FJ. Genotypic variability in radial resistance to water flow in olive roots and its response to temperature variations. TREE PHYSIOLOGY 2020; 40:445-453. [PMID: 32031664 DOI: 10.1093/treephys/tpaa010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 12/30/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
As radial root resistance (Rp) represents one of the key components of the soil-plant-atmosphere continuum resistance catena modulating water transport, understanding its control is essential for physiologists, modelers and breeders. Reports of Rp, however, are still scarce and scattered in the scientific literature. In this study, we assessed genetic variability in Rp and its dependence on temperature in five widely used olive cultivars. In a first experiment, cultivar differences in Rp at 25 °C were evaluated from flow-pressure measurements in excised roots and subsequent analysis of root traits. In a second experiment, similar determinations were performed continually over a 5-h period in which temperature was gradually increased from 12 to 32 °C, enabling the assessment of Rp response to changing temperature. Despite some variability, our results did not show statistical differences in Rp among cultivars in the first experiment. In the second, cultivar differences in Rp were not significant at 12 °C, but they became so as temperature increased. Furthermore, the changes in Rp between 12 and 32 °C were higher than those expected by the temperature-driven decrease in water viscosity, with the degree of that change differing among cultivars. Also, Rp at 25 °C reached momentarily in the second experiment was consistently higher than in the first at that same, but fixed, temperature. Overall, our results suggest that there is limited variability in Rp among the studied cultivars when plants have been exposed to a given temperature for sufficient time. Temperature-induced variation in Rp might thus be partly explained by changes in membrane permeability that occur slowly, which explains why our values at 25 °C differed between experiments. The observed cultivar differences in Rp with warming also indicate faster acclimation of Rp to temperature changes in some cultivars than others.
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Affiliation(s)
- Á López-Bernal
- Departamento de Agronomía, Universidad de Córdoba, Campus de Rabanales, Edificio C4, 14071 Córdoba, Spain
| | - O García-Tejera
- Efficient Use of Water Program, Institut de Recerca i Tecnologia Agroalimentàries (IRTA), Parc de Gardeny, Edifici Fruitcentre, 25003 Lleida, Spain
| | - L Testi
- Instituto de Agricultura Sostenible (IAS), Consejo Superior de Investigaciones Científicas (CSIC), Av. Menéndez Pidal s/n, 14080 Córdoba, Spain
| | - F J Villalobos
- Departamento de Agronomía, Universidad de Córdoba, Campus de Rabanales, Edificio C4, 14071 Córdoba, Spain
- Instituto de Agricultura Sostenible (IAS), Consejo Superior de Investigaciones Científicas (CSIC), Av. Menéndez Pidal s/n, 14080 Córdoba, Spain
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56
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Ou K, Copland DA, Theodoropoulou S, Mertsch S, Li Y, Liu J, Schrader S, Liu L, Dick AD. Treatment of diabetic retinopathy through neuropeptide Y-mediated enhancement of neurovascular microenvironment. J Cell Mol Med 2020; 24:3958-3970. [PMID: 32141716 PMCID: PMC7171318 DOI: 10.1111/jcmm.15016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 12/02/2019] [Accepted: 12/27/2019] [Indexed: 12/12/2022] Open
Abstract
Diabetic retinopathy (DR) is one of the most severe clinical manifestations of diabetes mellitus and a major cause of blindness. DR is principally a microvascular disease, although the pathogenesis also involves metabolic reactive intermediates which induce neuronal and glial activation resulting in disruption of the neurovascular unit and regulation of the microvasculature. However, the impact of neural/glial activation in DR remains controversial, notwithstanding our understanding as to when neural/glial activation occurs in the course of disease. The objective of this study was to determine a potential protective role of neuropeptide Y (NPY) using an established model of DR permissive to N-methyl-D-aspartate (NMDA)-induced excitotoxic apoptosis of retinal ganglion cells (RGC) and vascular endothelial growth factor (VEGF)-induced vascular leakage. In vitro evaluation using primary retinal endothelial cells demonstrates that NPY promotes vascular integrity, demonstrated by maintained tight junction protein expression and reduced permeability in response to VEGF treatment. Furthermore, ex vivo assessment of retinal tissue explants shows that NPY can protect RGC from excitotoxic-induced apoptosis. In vivo clinical imaging and ex vivo tissue analysis in the diabetic model permitted assessment of NPY treatment in relation to neural and endothelial changes. The neuroprotective effects of NPY were confirmed by attenuating NMDA-induced retinal neural apoptosis and able to maintain inner retinal vascular integrity. These findings could have important clinical implications and offer novel therapeutic approaches for the treatment in the early stages of DR.
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Affiliation(s)
- Kepeng Ou
- College of Pharmacy, National and Local Joint Engineering Research Center of Targeted and Innovative Therapeutics, Chongqing Key Laboratory of Kinase Modulators as Innovative Medicine, Chongqing University of Arts and Sciences, Chongqing, China.,Laboratory for Experimental Ophthalmology, University of Düsseldorf, Düsseldorf, Germany.,Academic Unit of Ophthalmology, Bristol Medical School, University of Bristol, Bristol, UK
| | - David A Copland
- Academic Unit of Ophthalmology, Bristol Medical School, University of Bristol, Bristol, UK
| | - Sofia Theodoropoulou
- Academic Unit of Ophthalmology, Bristol Medical School, University of Bristol, Bristol, UK
| | - Sonja Mertsch
- Laboratory for Experimental Ophthalmology, University of Düsseldorf, Düsseldorf, Germany.,Department of Ophthalmology, Faculty of Medicine and Health Sciences, University of Oldenburg, Oldenburg, Germany
| | - Youjian Li
- College of Pharmacy, National and Local Joint Engineering Research Center of Targeted and Innovative Therapeutics, Chongqing Key Laboratory of Kinase Modulators as Innovative Medicine, Chongqing University of Arts and Sciences, Chongqing, China.,Academic Unit of Ophthalmology, Bristol Medical School, University of Bristol, Bristol, UK
| | - Jian Liu
- Academic Unit of Ophthalmology, Bristol Medical School, University of Bristol, Bristol, UK
| | - Stefan Schrader
- Laboratory for Experimental Ophthalmology, University of Düsseldorf, Düsseldorf, Germany.,Department of Ophthalmology, Faculty of Medicine and Health Sciences, University of Oldenburg, Oldenburg, Germany
| | - Lei Liu
- Academic Unit of Ophthalmology, Bristol Medical School, University of Bristol, Bristol, UK
| | - Andrew D Dick
- Academic Unit of Ophthalmology, Bristol Medical School, University of Bristol, Bristol, UK.,National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital, University College London Institute of Ophthalmology, London, UK
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57
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Pillar S, Moisseiev E, Sokolovska J, Grzybowski A. Recent Developments in Diabetic Retinal Neurodegeneration: A Literature Review. J Diabetes Res 2020; 2020:5728674. [PMID: 34151902 PMCID: PMC7787838 DOI: 10.1155/2020/5728674] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 10/11/2020] [Accepted: 11/24/2020] [Indexed: 02/08/2023] Open
Abstract
Neurodegeneration plays a significant role in the complex pathology of diabetic retinopathy. Evidence suggests the onset of neurodegeneration occurs early on in the disease, and so a greater understanding of the process is essential for prompt detection and targeted therapies. Neurodegeneration is a common pathway of assorted processes, including activation of inflammatory pathways, reduction of neuroprotective factors, DNA damage, and apoptosis. Oxidative stress and formation of advanced glycation end products amplify these processes and are elevated in the setting of hyperglycemia, hyperlipidemia, and glucose variability. These key pathophysiologic mechanisms are discussed, as well as diagnostic modalities and novel therapeutic avenues, with an emphasis on recent discoveries. The aim of this article is to highlight the crucial role of neurodegeneration in diabetic retinopathy and to review the molecular basis for this neuronal dysfunction, its diagnostic features, and the progress currently made in relevant therapeutic interventions.
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Affiliation(s)
- Shani Pillar
- Department of Ophthalmology, Meir Medical Center, Kfar Saba, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Elad Moisseiev
- Department of Ophthalmology, Meir Medical Center, Kfar Saba, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | | | - Andrzej Grzybowski
- Department of Ophthalmology, University of Warmia and Mazury, Olsztyn, Poland
- Institute for Research in Ophthalmology, Foundation for Ophthalmology Development, Poznan, Poland
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58
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Hughes CHK, Bosviel R, Newman JW, Pate JL. Luteal Lipids Regulate Progesterone Production and May Modulate Immune Cell Function During the Estrous Cycle and Pregnancy. Front Endocrinol (Lausanne) 2019; 10:662. [PMID: 31636603 PMCID: PMC6788218 DOI: 10.3389/fendo.2019.00662] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 09/12/2019] [Indexed: 12/11/2022] Open
Abstract
Although the corpus luteum (CL) contains high concentrations of lipid in the form of steroid hormone precursors and prostaglandins, little is known about the abundance or function of other luteal lipid mediators. To address this, 79 lipid mediators were measured in bovine CL, using ultra performance liquid chromatography-tandem mass spectrometry. CL from estrous cycle days 4, 11, and 18 were compared and, separately, CL from days 18 of the estrous cycle and pregnancy were compared. Twenty-three lipids increased as the estrous cycle progressed (P < 0.05), with nine increasing between days 4 and 11 and fourteen increasing between days 4 and 18. Overall, this indicated a general upregulation of lipid mediator synthesis as the estrous cycle progressed, including increases in oxylipins and endocannabinoids. Only 15-KETE was less abundant in the CL of early pregnancy (P < 0.05), with a tendency (P < 0.10) for four others to be less abundant. Notably, 15-KETE also increased between estrous cycle days 4 and 18. Ingenuity Pathway Analysis (IPA, Qiagen) indicated that functions associated with differentially abundant lipids during the estrous cycle included leukocyte activation, cell migration, and cell proliferation. To investigate changes in CL during maternal recognition of pregnancy, this lipid dataset was integrated with a published dataset from mRNA profiling during maternal recognition of pregnancy. This analysis indicated that lipids and mRNA that changed during maternal recognition of pregnancy may regulate some of the same functions, including immune cell chemotaxis and cell-cell communication. To assess effects of these lipid mediators, luteal cells were cultured with 5-KETE or 15-KETE. One ng/mL 5-KETE reduced luteal progesterone on day 1 of culture, only in the absence of luteinizing hormone (LH), while 1 ng/mL 15-KETE induced progesterone only in the presence of LH (10 ng/mL). On day 7 of culture, 0.1 ng/mL 15-KETE reduced prostaglandin (PG)F2A-induced inhibition of LH-stimulated progesterone production, while 1 ng/mL 15-KETE did not have this effect. Overall, these data suggest a role for lipid mediators during luteal development and early pregnancy, as regulators of steroidogenesis, immune cell activation and function, intracellular signaling, and cell survival and death.
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Affiliation(s)
- Camilla H. K. Hughes
- Center for Reproductive Biology and Health, Department of Animal Sciences, Pennsylvania State University, State College, PA, United States
| | - Remy Bosviel
- West Coast Metabolomics Center, Genome Center, University of California, Davis, Davis, CA, United States
| | - John W. Newman
- West Coast Metabolomics Center, Genome Center, University of California, Davis, Davis, CA, United States
- Obesity and Metabolism Research Unit, USDA-ARS-Western Human Nutrition Research Center, Davis, CA, United States
- Department of Nutrition, University of California, Davis, Davis, CA, United States
| | - Joy L. Pate
- Center for Reproductive Biology and Health, Department of Animal Sciences, Pennsylvania State University, State College, PA, United States
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59
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Phipps JA, Dixon MA, Jobling AI, Wang AY, Greferath U, Vessey KA, Fletcher EL. The renin-angiotensin system and the retinal neurovascular unit: A role in vascular regulation and disease. Exp Eye Res 2019; 187:107753. [PMID: 31408629 DOI: 10.1016/j.exer.2019.107753] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/31/2019] [Accepted: 08/05/2019] [Indexed: 01/16/2023]
Abstract
The retina is known to have a local renin-angiotensin system (RAS) and dysfunction in the RAS is often associated with diseases of the retinal vasculature that cause irreversible vision loss. Regulation of the retinal vasculature to meet the metabolic needs of the tissues occurs through a mechanism called neurovascular coupling, which is critical for maintaining homeostatic function and support for neurons. Neurovascular coupling is the process by which support cells, including glia, regulate blood vessel calibre and blood flow in response to neural activity. In retinal vascular diseases, this coupling mechanism is often disrupted. However, the role that angiotensin II (Ang II), the main effector peptide of the RAS, has in regulating both the retinal vasculature and neurovascular coupling is not fully understood. As components of the RAS are located on the principal neurons, glia and blood vessels of the retina, it is possible that Ang II has a role in regulating communication and function between these three cell types, and therefore the capacity to regulate neurovascular coupling. This review focuses on components of the RAS located on the retinal neurovascular unit, and the potential of this system to contribute to blood flow modulation in the healthy and compromised retina.
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Affiliation(s)
- Joanna A Phipps
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Michael A Dixon
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Andrew I Jobling
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Anna Y Wang
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Ursula Greferath
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Kirstan A Vessey
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Erica L Fletcher
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, 3010, Victoria, Australia.
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60
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Lipecz A, Csipo T, Tarantini S, Hand RA, Ngo BTN, Conley S, Nemeth G, Tsorbatzoglou A, Courtney DL, Yabluchanska V, Csiszar A, Ungvari ZI, Yabluchanskiy A. Age-related impairment of neurovascular coupling responses: a dynamic vessel analysis (DVA)-based approach to measure decreased flicker light stimulus-induced retinal arteriolar dilation in healthy older adults. GeroScience 2019; 41:341-349. [PMID: 31209739 DOI: 10.1007/s11357-019-00078-y] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 06/06/2019] [Indexed: 12/21/2022] Open
Abstract
Aging is a major risk factor for vascular cognitive impairment and dementia (VCID). Recent studies demonstrate that cerebromicrovascular dysfunction plays a causal role in the development of age-related cognitive impairment, in part via disruption of neurovascular coupling (NVC) responses. NVC (functional hyperemia) is responsible for adjusting cerebral blood flow to the increased energetic demands of activated neurons, and in preclinical animal models of aging, pharmacological restoration of NVC is associated with improved cognitive performance. To translate these findings, there is an increasing need to develop novel and sensitive tools to assess cerebromicrovascular function and NVC to assess risk for VCID and evaluate treatment efficacy. Due to shared developmental origins, anatomical features, and physiology, assessment of retinal vessel function may serve as an important surrogate outcome measure to study neurovascular dysfunction. The present study was designed to compare NVC responses in young (< 45 years of age; n = 18) and aged (> 65 years of age; n = 11) healthy human subjects by assessing flicker light-induced changes in the diameter of retinal arterioles using a dynamic vessel analyzer (DVA)-based approach. We found that NVC responses in retinal arterioles were significantly decreased in older adults as compared with younger subjects. We propose that the DVA-based approach can be used to assess NVC, as a surrogate cerebromicrovascular outcome measure, to evaluate the effects of therapeutic interventions in older individuals.
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Affiliation(s)
- Agnes Lipecz
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA.,Department of Ophthalmology, Josa Andras Hospital, Nyiregyhaza, Hungary
| | - Tamas Csipo
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA.,Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary.,Department of Cardiology, Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Stefano Tarantini
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA
| | - Rachel A Hand
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA
| | - Bich-Thy N Ngo
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA
| | - Shannon Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Gabor Nemeth
- Department of Ophthalmology, Borsod-Abaúj-Zemplén County Hospital and University Teaching Hospital, Miskolc, Hungary
| | | | - Donald L Courtney
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA
| | - Valeriya Yabluchanska
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA.,Bon Secours St. Francis Family Medicine Center, Midlothian, VA, USA
| | - Anna Csiszar
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA.,Department of Cardiology, Division of Clinical Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zoltan I Ungvari
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA.,Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary.,Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary.,Department of Health Promotion Sciences, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Andriy Yabluchanskiy
- Translational Geroscience Laboratory, Reynolds Oklahoma Center on Aging/Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC 1311, Oklahoma City, OK, 73104, USA.
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Abstract
Autoimmune uveitis is a sight-threatening ocular inflammatory condition in which the retina and uveal tissues become a target of autoreactive immune cells. While microglia have been studied extensively in autoimmune uveitis, their exact function remains uncertain. The objective of the current study was to determine whether resident microglia are necessary and sufficient to initiate and amplify retinal inflammation in autoimmune uveitis. In this study, we clearly demonstrate that microglia are essential for initiating infiltration of immune cells utilizing a murine model of experimental autoimmune uveoretinitis (EAU) and the recently identified microglia-specific marker P2ry12. Initiating disease is the primary function of microglia in EAU, since eliminating microglia during the later stages of EAU had little effect, indicating that the function of circulating leukocytes is to amplify and sustain destructive inflammation once microglia have triggered disease. In the absence of microglia, uveitis does not develop, since leukocytes cannot gain entry through the blood-retinal barrier, illustrating that microglia play a critical role in regulating infiltration of inflammatory cells into the retina.
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63
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Someya E, Akagawa M, Mori A, Morita A, Yui N, Asano D, Sakamoto K, Nakahara T. Role of Neuron⁻Glia Signaling in Regulation of Retinal Vascular Tone in Rats. Int J Mol Sci 2019; 20:ijms20081952. [PMID: 31010057 PMCID: PMC6514555 DOI: 10.3390/ijms20081952] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/17/2019] [Accepted: 04/17/2019] [Indexed: 12/19/2022] Open
Abstract
The interactions between neuronal, glial, and vascular cells play a key role in regulating blood flow in the retina. In the present study, we examined the role of the interactions between neuronal and glial cells in regulating the retinal vascular tone in rats upon stimulation of retinal neuronal cells by intravitreal injection of N-methyl-d-aspartic acid (NMDA). The retinal vascular response was assessed by measuring the diameter of the retinal arterioles in the in vivo fundus images. Intravitreal injection of NMDA produced retinal vasodilation that was significantly diminished following the pharmacological inhibition of nitric oxide (NO) synthase (nNOS), loss of inner retinal neurons, or intravitreal injection of glial toxins. Immunohistochemistry revealed the expression of nNOS in ganglion and calretinin-positive amacrine cells. Moreover, glial toxins significantly prevented the retinal vasodilator response induced by intravitreal injection of NOR3, an NO donor. Mechanistic analysis revealed that NO enhanced the production of vasodilatory prostanoids and epoxyeicosatrienoic acids in glial cells in a ryanodine receptor type 1-dependent manner, subsequently inducing the retinal vasodilator response. These results suggest that the NO released from stimulated neuronal cells acts as a key messenger in neuron–glia signaling, thereby causing neuronal activity-dependent and glial cell-mediated vasodilation in the retina.
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Affiliation(s)
- Eriko Someya
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Mari Akagawa
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Asami Mori
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Akane Morita
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Natsuko Yui
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Daiki Asano
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Kenji Sakamoto
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
| | - Tsutomu Nakahara
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
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64
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Xu Y, Wang X, Zhang Y. Myocardial Infarction-Related Transcripts (MIAT) Participate in Diabetic Optic Nerve Injury by Regulating Heart Shock Protein 5 (HSPA5) via Competitively Binding to MicroRNA-379. Med Sci Monit 2019; 25:2096-2103. [PMID: 30895947 PMCID: PMC6439961 DOI: 10.12659/msm.911930] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Background The aim of this study was to explore the role of MIAT (myocardial infarction related transcripts) in diabetic optic neuropathy and its underlying mechanism. Material/Methods QRT-PCR (quantitative real-time polymerase chain reaction) was performed to detect the mRNA levels of MIAT and HSPA5 (heart shock protein 5) in diabetic rat model and high-glucose cultured Müller cells. After the intracellular MIAT level was increased by lentivirus transfection, the proliferation, cell cycle, and apoptosis of Müller cells were measured using the CCK-8 (Cell Counting Kit-8) assay, flow cytometry, and TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling) assay, respectively. Mechanisms underlying the MIAT-related apoptosis were explored by Western blot analysis. The binding condition of microRNA-379 to MIAT and HSPA5 was confirmed by luciferase reporter gene assay. Results Both MIAT and HSPA5 levels were remarkably increased in high-glucose cultured Müller cells. After transfected with LV (lentivirus)-MIAT, Müller cells showed a decreased proliferation and an enhanced apoptosis with the increased expressions of pro-apoptotic proteins. However, no remarkable changes were observed in cell cycle. Further mechanistic studies found that MIAT regulated HSPA5 expression by directly binding to microRNA-379. Conclusions MIAT was overexpressed in the diabetic optic nerve. MIAT overexpression remarkably promoted the apoptosis of Müller cells by adsorbing microRNA-379 and thus regulating HSPA5, which was a direct target of microRNA-379.
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Affiliation(s)
- Yonggen Xu
- Department of Ophthalmology, Shaoxing People's Hospital, Shaoxing, Zhejiang, China (mainland)
| | - Xiaolan Wang
- Department of General Medical, The Second Hospital of Shaoxing, Shaoxing, Zhejiang, China (mainland)
| | - Yulv Zhang
- Department of Endocrinology, Zhejiang Provincial People's Hospital, Hangzhou, Zhejiang, China (mainland)
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65
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Zafar S, Sachdeva M, Frankfort BJ, Channa R. Retinal Neurodegeneration as an Early Manifestation of Diabetic Eye Disease and Potential Neuroprotective Therapies. Curr Diab Rep 2019; 19:17. [PMID: 30806815 PMCID: PMC7192364 DOI: 10.1007/s11892-019-1134-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PURPOSE OF REVIEW Diabetic retinopathy (DR) is a major cause of visual impairment and blindness throughout the world. Microvascular changes have long been regarded central to disease pathogenesis. In recent years, however, retinal neurodegeneration is increasingly being hypothesized to occur prior to the vascular changes classically associated with DR and contribute to disease pathogenesis. RECENT FINDINGS There is growing structural and functional evidence from human and animal studies that suggests retinal neurodegeneration to be an early component of DR. Identification of new therapeutic targets is an ongoing area of research with several different molecules undergoing testing in animal models for their neuroprotective properties and for possible use in humans. Retinal neurodegeneration may play a central role in DR pathogenesis. As new therapies are developed, it will be important to develop criteria for clinically defining retinal neurodegeneration. A standardization of the methods for monitoring neurodegeneration along with more sensitive means of detecting preclinical damage is also needed.
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Affiliation(s)
- Sidra Zafar
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD 21287, USA
| | - Mira Sachdeva
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD 21287, USA
| | | | - Roomasa Channa
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD 21287, USA
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
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66
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Shih EK, Robinson MB. Role of Astrocytic Mitochondria in Limiting Ischemic Brain Injury? Physiology (Bethesda) 2019; 33:99-112. [PMID: 29412059 DOI: 10.1152/physiol.00038.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Until recently, astrocyte processes were thought to be too small to contain mitochondria. However, it is now clear that mitochondria are found throughout fine astrocyte processes and are mobile with neuronal activity resulting in positioning near synapses. In this review, we discuss evidence that astrocytic mitochondria confer selective resiliency to astrocytes during ischemic insults and the functional significance of these mitochondria for normal brain function.
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Affiliation(s)
- Evelyn K Shih
- Children's Hospital of Philadelphia Research Institute , Philadelphia, Pennsylvania.,Children's Hospital of Philadelphia, Division of Neurology , Philadelphia, Pennsylvania.,Department of Pediatrics, University of Pennsylvania , Philadelphia, Pennsylvania
| | - Michael B Robinson
- Children's Hospital of Philadelphia Research Institute , Philadelphia, Pennsylvania.,Department of Pediatrics, University of Pennsylvania , Philadelphia, Pennsylvania.,Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania , Philadelphia, Pennsylvania
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67
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Chen M, Luo C, Zhao J, Devarajan G, Xu H. Immune regulation in the aging retina. Prog Retin Eye Res 2018; 69:159-172. [PMID: 30352305 DOI: 10.1016/j.preteyeres.2018.10.003] [Citation(s) in RCA: 153] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/13/2018] [Accepted: 10/19/2018] [Indexed: 12/24/2022]
Abstract
The retina is an immune privileged tissue, which is protected from external and internal insults by its blood-retina barriers and immune suppressive microenvironment. Apart from the avoidance and tolerance strategies, the retina is also protected by its own defense system, i.e., microglia and the complement system. The immune privilege and defense mechanisms work together to maintain retinal homeostasis. During aging, the retina is at an increased risk of developing various degenerative diseases such as age-related macular degeneration, diabetic retinopathy, and glaucomatous retinopathy. Previously, we have shown that aging induces a para-inflammatory response in the retina. In this review, we explore the impact of aging on retinal immune regulation and the connection between homeostatic control of retinal immune privilege and para-inflammation under aging conditions and present a view that may explain why aging puts the retina at risk of developing degenerative diseases.
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Affiliation(s)
- Mei Chen
- Centre for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen's University Belfast, UK
| | - Chang Luo
- Centre for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen's University Belfast, UK; Aier Eye Institute, Aier School of Ophthalmology, Central South University, China
| | - Jiawu Zhao
- Centre for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen's University Belfast, UK
| | | | - Heping Xu
- Centre for Experimental Medicine, School of Medicine, Dentistry & Biomedical Sciences, Queen's University Belfast, UK; Aier Eye Institute, Aier School of Ophthalmology, Central South University, China.
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68
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Simó R, Stitt AW, Gardner TW. Neurodegeneration in diabetic retinopathy: does it really matter? Diabetologia 2018; 61:1902-1912. [PMID: 30030554 PMCID: PMC6096638 DOI: 10.1007/s00125-018-4692-1] [Citation(s) in RCA: 334] [Impact Index Per Article: 55.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 06/19/2018] [Indexed: 02/07/2023]
Abstract
The concept of diabetic retinopathy as a microvascular disease has evolved, in that it is now considered a more complex diabetic complication in which neurodegeneration plays a significant role. In this article we provide a critical overview of the role of microvascular abnormalities and neurodegeneration in the pathogenesis of diabetic retinopathy. A special emphasis is placed on the pathophysiology of the neurovascular unit (NVU), including the contributions of microvascular and neural elements. The potential mechanisms linking retinal neurodegeneration and early microvascular impairment, and the effects of neuroprotective drugs are summarised. Additionally, we discuss how the assessment of retinal neurodegeneration could be an important index of cognitive status, thus helping to identify individuals at risk of dementia, which will impact on current procedures for diabetes management. We conclude that glial, neural and microvascular dysfunction are interdependent and essential for the development of diabetic retinopathy. Despite this intricate relationship, retinal neurodegeneration is a critical endpoint and neuroprotection, itself, can be considered a therapeutic target, independently of its potential impact on microvascular disease. In addition, interventional studies targeting pathogenic pathways that impact the NVU are needed. Findings from these studies will be crucial, not only for increasing our understanding of diabetic retinopathy, but also to help to implement a timely and efficient personalised medicine approach for treating this diabetic complication.
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Affiliation(s)
- Rafael Simó
- Diabetes and Metabolism Research Unit, Vall d'Hebron Research Institute, Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III (ISCIII), Universitat Autònoma de Barcelona, Pg. Vall d'Hebron 119-129, 08035, Barcelona, Spain.
| | - Alan W Stitt
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Belfast, UK
| | - Thomas W Gardner
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI, USA
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69
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Chaurasia SS, Lim RR, Parikh BH, Wey YS, Tun BB, Wong TY, Luu CD, Agrawal R, Ghosh A, Mortellaro A, Rackoczy E, Mohan RR, Barathi VA. The NLRP3 Inflammasome May Contribute to Pathologic Neovascularization in the Advanced Stages of Diabetic Retinopathy. Sci Rep 2018; 8:2847. [PMID: 29434227 PMCID: PMC5809448 DOI: 10.1038/s41598-018-21198-z] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 01/29/2018] [Indexed: 12/11/2022] Open
Abstract
Diabetic retinopathy (DR) is a retinal microvascular disease characterized by inflammatory and angiogenic pathways. In this study, we evaluated NLRP3 inflammasome in a double transgenic mouse model, Akimba (Ins2 Akita xVEGF+/-), which demonstrates hyperglycemia, vascular hyperpermeability and neovascularization seen in the proliferative DR. Retinal structural integrity, vascular leakage and function were examined by fundus photography, fluorescein angiography, optical coherence tomography, retinal flat mounts, laser speckle flowgraphy (LSFG), and electroretinography in Akimba and its parental strains, Akita (Ins2 Akita ) and Kimba (trVEGF029) mice. Inflammatory mechanisms involving NLRP3 inflammasome were investigated using real time-PCR, immunohistochemistry, ELISA and western blots. We observed an increased vascular leakage, reduced retinal thickness, and function in Akimba retina. Also, Akimba retina depicts decreased relative flow volume measured by LSFG. Most importantly, high levels of IL-1β along with increased NLRP3, ASC, and Caspase-1 at mRNA and protein levels were observed in Akimba retina. However, the in vivo functional role remains undefined. In conclusion, increased activation of macroglia (GFAP), microglia (Iba-1 and OX-42) and perivascular macrophages (F4/80 and CD14) together with pro-inflammatory (IL-1β and IL-6) and pro-angiogenic markers (PECAM-1, ICAM-1, VEGF, Flt-1, and Flk-1), suggested a critical role for NLRP3 inflammasome in the Akimba mouse model depicting advanced stages of DR pathogenesis.
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Affiliation(s)
- Shyam S Chaurasia
- Ocular Immunology and Angiogenesis Lab, Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, MO, USA.
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA.
- Ophthalmology, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, USA.
| | - Rayne R Lim
- Ocular Immunology and Angiogenesis Lab, Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, MO, USA
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Ophthalmology, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, USA
| | - Bhav H Parikh
- Translational Pre-Clinical Model Platform, Singapore Eye Research Institute, Singapore, Singapore
| | - Yeo Sia Wey
- Translational Pre-Clinical Model Platform, Singapore Eye Research Institute, Singapore, Singapore
| | - Bo Bo Tun
- Translational Pre-Clinical Model Platform, Singapore Eye Research Institute, Singapore, Singapore
| | - Tien Yin Wong
- Translational Pre-Clinical Model Platform, Singapore Eye Research Institute, Singapore, Singapore
- The Ophthalmology & Visual Sciences Academic Clinical Program, DUKE-NUS Graduate Medical School, Singapore, Singapore
| | - Chi D Luu
- Centre for Eye Research Australia, Department of Surgery (Ophthalmology), University of Melbourne, Melbourne, Australia
| | - Rupesh Agrawal
- National Healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore, Singapore
| | | | - Alessandra Mortellaro
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Elizabeth Rackoczy
- Centre for Ophthalmology and Visual Sciences, University of Western Australia, Perth, WA, 6009, Australia
| | - Rajiv R Mohan
- Ocular Immunology and Angiogenesis Lab, Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, MO, USA
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Ophthalmology, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, USA
- Mason Eye Institute, University of Missouri, Columbia, MO, USA
| | - Veluchamy A Barathi
- Translational Pre-Clinical Model Platform, Singapore Eye Research Institute, Singapore, Singapore
- The Ophthalmology & Visual Sciences Academic Clinical Program, DUKE-NUS Graduate Medical School, Singapore, Singapore
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70
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Erchova I, Tumlinson AR, Fergusson J, White N, Drexler W, Sengpiel F, Morgan JE. Optophysiological Characterisation of Inner Retina Responses with High-Resolution Optical Coherence Tomography. Sci Rep 2018; 8:1813. [PMID: 29379036 PMCID: PMC5788978 DOI: 10.1038/s41598-018-19975-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 01/03/2018] [Indexed: 11/18/2022] Open
Abstract
Low coherence laser interferometry has revolutionised quantitative biomedical imaging of optically transparent structures at cellular resolutions. We report the first optical recording of neuronal excitation at cellular resolution in the inner retina by quantifying optically recorded stimulus-evoked responses from the retinal ganglion cell layer and comparing them with an electrophysiological standard. We imaged anaesthetised paralysed tree shrews, gated image acquisition, and used numerical filters to eliminate noise arising from retinal movements during respiratory and cardiac cycles. We observed increases in contrast variability in the retinal ganglion cell layer and nerve fibre layer with flash stimuli and gratings. Regions of interest were subdivided into three-dimensional patches (up to 5–15 μm in diameter) based on response similarity. We hypothesise that these patches correspond to individual cells, or segments of blood vessels within the inner retina. We observed a close correlation between the patch optical responses and mean electrical activity of the visual neurons in afferent pathway. While our data suggest that optical imaging of retinal activity is possible with high resolution OCT, the technical challenges are not trivial.
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Affiliation(s)
- Irina Erchova
- School of Optometry and Visual Sciences, Cardiff University, Cardiff, United Kingdom
| | - Alexandre R Tumlinson
- School of Optometry and Visual Sciences, Cardiff University, Cardiff, United Kingdom.,Zeiss Meditec, Dublin, California, USA
| | - James Fergusson
- School of Optometry and Visual Sciences, Cardiff University, Cardiff, United Kingdom
| | - Nick White
- School of Optometry and Visual Sciences, Cardiff University, Cardiff, United Kingdom
| | - Wolfgang Drexler
- Center for Medical Physics & Biom Eng, Medical University Vienna, Vienna, Austria
| | - Frank Sengpiel
- School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - James E Morgan
- School of Optometry and Visual Sciences, Cardiff University, Cardiff, United Kingdom. .,Ophthalmology, University Hospital of Wales, Cardiff, United Kingdom.
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71
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Houben AJHM, Martens RJH, Stehouwer CDA. Assessing Microvascular Function in Humans from a Chronic Disease Perspective. J Am Soc Nephrol 2017; 28:3461-3472. [PMID: 28904002 DOI: 10.1681/asn.2017020157] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Microvascular dysfunction (MVD) is considered a crucial pathway in the development and progression of cardiometabolic and renal disease and is associated with increased cardiovascular mortality. MVD often coexists with or even precedes macrovascular disease, possibly due to shared mechanisms of vascular damage, such as inflammatory processes and oxidative stress. One of the first events in MVD is endothelial dysfunction. With the use of different physiologic or pharmacologic stimuli, endothelium-dependent (micro)vascular reactivity can be studied. This reactivity depends on the balance between various mediators, including nitric oxide, endothelin, and prostanoids, among others. The measurement of microvascular (endothelial) function is important to understand the pathophysiologic mechanisms that contribute to MVD and the role of MVD in the development and progression of cardiometabolic/renal disease. Here, we review a selection of direct, noninvasive techniques for measuring human microcirculation, with a focus on methods, interpretation, and limitations from the perspective of chronic cardiometabolic and renal disease.
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Affiliation(s)
- Alfons J H M Houben
- Department of Internal Medicine, Maastricht University Medical Center+, Maastricht, The Netherlands; and .,CARIM School for Cardiovascular Diseases and
| | - Remy J H Martens
- Department of Internal Medicine, Maastricht University Medical Center+, Maastricht, The Netherlands; and.,School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Coen D A Stehouwer
- Department of Internal Medicine, Maastricht University Medical Center+, Maastricht, The Netherlands; and.,CARIM School for Cardiovascular Diseases and
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72
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Lynch SK, Abràmoff MD. Diabetic retinopathy is a neurodegenerative disorder. Vision Res 2017; 139:101-107. [PMID: 28408138 DOI: 10.1016/j.visres.2017.03.003] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 03/28/2017] [Accepted: 03/30/2017] [Indexed: 01/20/2023]
Abstract
Since 1875, controversy has ensued over whether ocular diabetic complications are primarily vasculopathic or neuropathic in nature. Here, we discuss the historical context by which diabetic retinopathy (DR) came to be considered a primary vasculopathy, in contrast to more recent data suggesting the importance of diabetic retinal neurodegeneration (DRN) as the primary manifestation of ocular diabetic damage. Unsurprisingly, DRN parallels other diabetic complications related to neuropathy. In general, there are three possible relationships between microvascular DR and DRN: i) microvasculopathy causes neurodegeneration; ii) neurodegeneration causes microvasculopathy or iii) they are mutually independent. The authors' group has recently produced experimental data showing that DRN precedes even the earliest manifestations of DR microvasculopathy. In combination with earlier studies showing that focal implicit time delays predicted future development of DR microvasculopathy in the same location, relationships i) and iii) are unlikely. As such, ii) is the most likely relationship: DRN is a cause of DR. Granted, additional studies are needed to confirm this hypothesis and elucidate the mechanism of diabetes-induced neurodegeneration. We conclude this review by proposing experimental approaches to test the hypothesis that DRN causes DR. If confirmed, this new paradigm may lead to earlier detection of ocular diabetic damage and earlier treatment of early DR, thereby preventing visual loss in people with diabetes.
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Affiliation(s)
- Stephanie K Lynch
- Department of Ophthalmology and Visual Sciences, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, USA
| | - Michael D Abràmoff
- Department of Ophthalmology and Visual Sciences, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, USA; Iowa Institute for Biomedical Imaging, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, USA; Department of Electrical and Computer Engineering, University of Iowa, Iowa City, IA 52242, USA; Department of Veterans Affairs, 601 US-6, Iowa City, IA 52246, USA.
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73
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Iuliano L, Fogliato G, Querques G, Bandello F, Codenotti M. Retinal vascular changes after vitrectomy for idiopathic epiretinal membrane: a pilot study with dynamic vessel analysis. Graefes Arch Clin Exp Ophthalmol 2017; 255:1325-1332. [PMID: 28337547 DOI: 10.1007/s00417-017-3643-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 03/11/2017] [Accepted: 03/15/2017] [Indexed: 11/28/2022] Open
Abstract
PURPOSE To investigate, using the Dynamic Vessel Analyzer (DVA), the retinal vascular changes that may occur after vitrectomy for idiopathic epiretinal membrane (ERM). METHODS Twenty-six eyes of 13 patients affected by unilateral idiopathic ERM were prospectively analyzed. 13 fellow eyes were used as control. The static (central retinal artery and vein equivalents) and dynamic (after flicker light stimulus) DVA analysis was performed at baseline (1 day before surgery) and 6 months after vitrectomy. RESULTS The static DVA analysis did not highlight any significant change between investigational eyes and controls at baseline and 6 months after surgery. The DVA dynamic analysis showed similar arterial flicker response between cases and controls at baseline (p = 0.3396), but disclosed a significant reduction of the arterial flicker response after surgery in the study eyes compared to fellow eyes (p = 0.0024). No significant changes were appreciated in the venous flicker response after surgery between cases and controls, both at baseline (p = 0.3450) and at the follow-up examination (p = 0.4214). CONCLUSIONS The physiological flicker-induced vasoconstriction is reduced after vitrectomy in arteries. The oxygen saturation change occurring after vitrectomy might have a role in the vascular tone modification.
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Affiliation(s)
- Lorenzo Iuliano
- Department of Ophthalmology, San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina, 60 - 20132, Milan, Italy
| | - Giovanni Fogliato
- Department of Ophthalmology, San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina, 60 - 20132, Milan, Italy
| | - Giuseppe Querques
- Department of Ophthalmology, San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina, 60 - 20132, Milan, Italy.
| | - Francesco Bandello
- Department of Ophthalmology, San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina, 60 - 20132, Milan, Italy
| | - Marco Codenotti
- Department of Ophthalmology, San Raffaele Scientific Institute, Vita-Salute University, Via Olgettina, 60 - 20132, Milan, Italy
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74
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Elshenawy OH, Shoieb SM, Mohamed A, El-Kadi AOS. Clinical Implications of 20-Hydroxyeicosatetraenoic Acid in the Kidney, Liver, Lung and Brain: An Emerging Therapeutic Target. Pharmaceutics 2017; 9:pharmaceutics9010009. [PMID: 28230738 PMCID: PMC5374375 DOI: 10.3390/pharmaceutics9010009] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 02/15/2017] [Indexed: 12/30/2022] Open
Abstract
Cytochrome P450-mediated metabolism of arachidonic acid (AA) is an important pathway for the formation of eicosanoids. The ω-hydroxylation of AA generates significant levels of 20-hydroxyeicosatetraenoic acid (20-HETE) in various tissues. In the current review, we discussed the role of 20-HETE in the kidney, liver, lung, and brain during physiological and pathophysiological states. Moreover, we discussed the role of 20-HETE in tumor formation, metabolic syndrome and diabetes. In the kidney, 20-HETE is involved in modulation of preglomerular vascular tone and tubular ion transport. Furthermore, 20-HETE is involved in renal ischemia/reperfusion (I/R) injury and polycystic kidney diseases. The role of 20-HETE in the liver is not clearly understood although it represents 50%-75% of liver CYP-dependent AA metabolism, and it is associated with liver cirrhotic ascites. In the respiratory system, 20-HETE plays a role in pulmonary cell survival, pulmonary vascular tone and tone of the airways. As for the brain, 20-HETE is involved in cerebral I/R injury. Moreover, 20-HETE has angiogenic and mitogenic properties and thus helps in tumor promotion. Several inhibitors and inducers of the synthesis of 20-HETE as well as 20-HETE analogues and antagonists are recently available and could be promising therapeutic options for the treatment of many disease states in the future.
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Affiliation(s)
- Osama H Elshenawy
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
| | - Sherif M Shoieb
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
| | - Anwar Mohamed
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
- Department of Basic Medical Sciences, College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates.
| | - Ayman O S El-Kadi
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton T6G 2E1, AB, Canada.
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Iwona BS. Growth Factors in the Pathogenesis of Retinal Neurodegeneration in Diabetes Mellitus. Curr Neuropharmacol 2017; 14:792-804. [PMID: 27528260 PMCID: PMC5333593 DOI: 10.2174/1570159x14666160813182009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 11/12/2015] [Accepted: 01/06/2015] [Indexed: 12/13/2022] Open
Abstract
Neurodegeneration is an initial process in the development of diabetic retinopathy (DR). High quantities of glutamate, oxidative stress, induction of the renin-angiotensin system (RAS) and elevated levels of RAGE are crucial elements in the retinal neurodegeneration caused by diabetes mellitus. At least, there is emerging proof to indicate that the equilibrium between the neurotoxic and neuroprotective components will affect the state of the retinal neurons. Somatostatin (SST), pigment epithelium-derived factor (PEDF), and erythropoietin (Epo) are endogenous neuroprotective peptides that are decreased in the eye of diabetic persons and play an essential role in retinal homeostasis. On the other hand, insulin-like growth factor 1 (IGF-1), and vascular endothelial growth factor (VEGF) are pivotal proteins which participate in the development of new capillaries and finally cause damage to the retinal neurons. During recent years, our knowledge about the function of growth factors in the pathogenesis of retinal neurodegeneration has increased. However, intensive investigations are needed to clarify the basic processes that contribute to retinal neurodegeneration and its association with damage to the capillary blood vessels. The objective of this review article is to show new insights on the role of neurotransmitters and growth factors in the pathogenesis of diabetic retinopathy. The information contained in this manuscript may provide the basis for novel strategies based on the factors of neurodegeneration to diagnose, prevent and treat DR in its earliest phases.
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Affiliation(s)
- Ben-Skowronek Iwona
- Department Pediatric Endocrinology and Diabetology, Medical University of Lublin, ul. Prof. A. Gebali 6, 20-093 Lublin, Poland
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76
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Srivastav K, Saxena S, Mahdi AA, Shukla RK, Meyer CH, Akduman L, Khanna VK. Increased serum level of homocysteine correlates with retinal nerve fiber layer thinning in diabetic retinopathy. Mol Vis 2016; 22:1352-1360. [PMID: 27994434 PMCID: PMC5135738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 11/30/2016] [Indexed: 11/16/2022] Open
Abstract
PURPOSE To study the correlation between serum levels of vitamin B12, folic acid, and homocysteine and the severity of diabetic retinopathy and the correlation with retinal nerve fiber layer (RNFL) thinning on spectral domain optical coherence tomography (SD-OCT). METHODS In a tertiary care center-based prospective cross-sectional study, 60 consecutive cases and 20 healthy controls in the age group of 40-65 years were included. The eyes of the cases were divided into three groups according to Early Treatment Diabetic Retinopathy Study (ETDRS) classification: diabetes mellitus without retinopathy (n = 20), non-proliferative diabetic retinopathy with macular edema (n = 20), and proliferative diabetic retinopathy with macular edema (n = 20). The serum levels of vitamin B12 and folic acid were measured using a standard protocol. The serum homocysteine assay was performed using an enzyme-linked immunosorbent assay (ELISA) kit. Average RNFL thickness was measured using SD-OCT. Statistical analysis was used to assess the correlations between the study variables. RESULTS Increased severity of diabetic retinopathy was found to correlate with an increase in the serum levels of homocysteine (F = 53.79; p<0.001). The mean serum levels of vitamin B12 and folic acid were found to be within the normal reference range. A positive correlation was found between retinal nerve fiber layer thinning and serum levels of homocysteine (p<0.001). CONCLUSIONS This study, for the first time, demonstrated a correlation between increased homocysteine with a decrease in RNFL thickness and increased severity of diabetic retinopathy.
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Affiliation(s)
- Khushboo Srivastav
- Retina Service, Department of Ophthalmology, King George’s Medical University, Lucknow, India
| | - Sandeep Saxena
- Retina Service, Department of Ophthalmology, King George’s Medical University, Lucknow, India
| | - Abbas A. Mahdi
- Department of Biochemistry, King George’s Medical University, Lucknow, India
| | | | | | - Levent Akduman
- Vitreoretinal and uveitis service, Department of Ophthalmology, Saint Louis University School of Medicine,St. Louis, MO
| | - Vinay K. Khanna
- CSIR - Indian Institute of Toxicology and Research, Lucknow, India
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Gardner TW, Davila JR. The neurovascular unit and the pathophysiologic basis of diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol 2016; 255:1-6. [PMID: 27832340 DOI: 10.1007/s00417-016-3548-y] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 10/25/2016] [Accepted: 10/31/2016] [Indexed: 01/17/2023] Open
Abstract
PURPOSE To relate the concept of the retinal neurovascular unit and its alterations in diabetes to the pathophysiology of diabetic retinopathy. METHODS Case illustrations and conceptual frameworks are presented that illustrate adaptive and maladaptive "dis-integration" of the retinal neurovascular unit with the progression of diabetes. RESULTS Retinopathy treatment should address pathophysiologic processes rather than pathologic lesions as is current practice. CONCLUSIONS Future improvements in the treatment of diabetic retinopathy requires deeper understanding of the cellular and molecular changes induced by diabetes, coupled with the use of quantitative phenotyping methods that assess the pathophysiologic processes.
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Affiliation(s)
- Thomas W Gardner
- Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan Medical School, 1000 Wall St, Ann Arbor, MI, 48105, USA.
| | - Jose R Davila
- Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan Medical School, 1000 Wall St, Ann Arbor, MI, 48105, USA
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Mishra A. Binaural blood flow control by astrocytes: listening to synapses and the vasculature. J Physiol 2016; 595:1885-1902. [PMID: 27619153 DOI: 10.1113/jp270979] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 07/15/2016] [Indexed: 12/28/2022] Open
Abstract
Astrocytes are the most common glial cells in the brain with fine processes and endfeet that intimately contact both neuronal synapses and the cerebral vasculature. They play an important role in mediating neurovascular coupling (NVC) via several astrocytic Ca2+ -dependent signalling pathways such as K+ release through BK channels, and the production and release of arachidonic acid metabolites. They are also involved in maintaining the resting tone of the cerebral vessels by releasing ATP and COX-1 derivatives. Evidence also supports a role for astrocytes in maintaining blood pressure-dependent change in cerebrovascular tone, and perhaps also in blood vessel-to-neuron signalling as posited by the 'hemo-neural hypothesis'. Thus, astrocytes are emerging as new stars in preserving the intricate balance between the high energy demand of active neurons and the supply of oxygen and nutrients from the blood by maintaining both resting blood flow and activity-evoked changes therein. Following neuropathology, astrocytes become reactive and many of their key signalling mechanisms are altered, including those involved in NVC. Furthermore, as they can respond to changes in vascular pressure, cardiovascular diseases might exert previously unknown effects on the central nervous system by altering astrocyte function. This review discusses the role of astrocytes in neurovascular signalling in both physiology and pathology, and the impact of these findings on understanding BOLD-fMRI signals.
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Affiliation(s)
- Anusha Mishra
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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79
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Renin-angiotensin system as a potential therapeutic target in stroke and retinopathy: experimental and clinical evidence. Clin Sci (Lond) 2016; 130:221-38. [PMID: 26769658 DOI: 10.1042/cs20150350] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
As our knowledge expands, it is now clear that the renin-angiotensin (Ang) system (RAS) mediates functions other than regulating blood pressure (BP). The RAS plays a central role in the pathophysiology of different neurovascular unit disorders including stroke and retinopathy. Moreover, the beneficial actions of RAS modulation in brain and retina have been documented in experimental research, but not yet exploited clinically. The RAS is a complex system with distinct yet interconnected components. Understanding the different RAS components and their functions under brain and retinal pathological conditions is crucial to reap their benefits. The aim of the present review is to provide an experimental and clinical update on the role of RAS in the pathophysiology and treatment of stroke and retinopathy. Combining the evidence from both these disorders allows a unique opportunity to move both fields forward.
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80
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Winther AK, Dalsgaard T, Hedegaard ER, Simonsen U. Involvement of hydrogen sulfide in perivascular and hypoxia-induced inhibition of endothelin contraction in porcine retinal arterioles. Nitric Oxide 2015; 50:1-9. [DOI: 10.1016/j.niox.2015.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 06/26/2015] [Accepted: 07/16/2015] [Indexed: 01/14/2023]
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81
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Srivastav K, Saxena S, Mahdi AA, Kruzliak P, Khanna VK. Increased serum urea and creatinine levels correlate with decreased retinal nerve fibre layer thickness in diabetic retinopathy. Biomarkers 2015; 20:470-3. [PMID: 26474118 DOI: 10.3109/1354750x.2015.1094142] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Correlation of increased levels of serum urea and creatinine with retinal nerve fibre layer (RNFL) thinning on spectral domain optical coherence tomography (SD-OCT) was studied in diabetic retinopathy (DR). Sixty consecutive cases and 20 healthy controls were included. Cases were divided into three groups: without DR, non-proliferative DR with macular oedema and proliferative DR with oedema. Serum urea and creatinine were measured using a standard protocol. Average (RNFL) was measured using SD-OCT. Increased severity of DR was associated with decrease in levels of serum urea and serum creatinine levels. RNFL thinning correlated positively with increase in serum urea and creatinine levels.
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Affiliation(s)
| | | | - Abbas A Mahdi
- b Department of Biochemistry , King George's Medical University , Lucknow , India
| | - Peter Kruzliak
- c International Clinical Research Center, St. Anne's University Hospital and Masaryk University , Brno , Czech Republic , and
| | - Vinay K Khanna
- d Indian Institute of Toxicology and Research , Lucknow , India
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82
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The progress in understanding and treatment of diabetic retinopathy. Prog Retin Eye Res 2015; 51:156-86. [PMID: 26297071 DOI: 10.1016/j.preteyeres.2015.08.001] [Citation(s) in RCA: 630] [Impact Index Per Article: 70.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 08/12/2015] [Accepted: 08/13/2015] [Indexed: 12/15/2022]
Abstract
Diabetic retinopathy is the most frequently occurring complication of diabetes mellitus and remains a leading cause of vision loss globally. Its aetiology and pathology have been extensively studied for half a century, yet there are disappointingly few therapeutic options. Although some new treatments have been introduced for diabetic macular oedema (DMO) (e.g. intravitreal vascular endothelial growth factor inhibitors ('anti-VEGFs') and new steroids), up to 50% of patients fail to respond. Furthermore, for people with proliferative diabetic retinopathy (PDR), laser photocoagulation remains a mainstay therapy, even though it is an inherently destructive procedure. This review summarises the clinical features of diabetic retinopathy and its risk factors. It describes details of retinal pathology and how advances in our understanding of pathogenesis have led to identification of new therapeutic targets. We emphasise that although there have been significant advances, there is still a pressing need for a better understanding basic mechanisms enable development of reliable and robust means to identify patients at highest risk, and to intervene effectively before vision loss occurs.
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83
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Jenkins AJ, Joglekar MV, Hardikar AA, Keech AC, O'Neal DN, Januszewski AS. Biomarkers in Diabetic Retinopathy. Rev Diabet Stud 2015; 12:159-95. [PMID: 26676667 DOI: 10.1900/rds.2015.12.159] [Citation(s) in RCA: 174] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
There is a global diabetes epidemic correlating with an increase in obesity. This coincidence may lead to a rise in the prevalence of type 2 diabetes. There is also an as yet unexplained increase in the incidence of type 1 diabetes, which is not related to adiposity. Whilst improved diabetes care has substantially improved diabetes outcomes, the disease remains a common cause of working age adult-onset blindness. Diabetic retinopathy is the most frequently occurring complication of diabetes; it is greatly feared by many diabetes patients. There are multiple risk factors and markers for the onset and progression of diabetic retinopathy, yet residual risk remains. Screening for diabetic retinopathy is recommended to facilitate early detection and treatment. Common biomarkers of diabetic retinopathy and its risk in clinical practice today relate to the visualization of the retinal vasculature and measures of glycemia, lipids, blood pressure, body weight, smoking, and pregnancy status. Greater knowledge of novel biomarkers and mediators of diabetic retinopathy, such as those related to inflammation and angiogenesis, has contributed to the development of additional therapeutics, in particular for late-stage retinopathy, including intra-ocular corticosteroids and intravitreal vascular endothelial growth factor inhibitors ('anti-VEGFs') agents. Unfortunately, in spite of a range of treatments (including laser photocoagulation, intraocular steroids, and anti-VEGF agents, and more recently oral fenofibrate, a PPAR-alpha agonist lipid-lowering drug), many patients with diabetic retinopathy do not respond well to current therapeutics. Therefore, more effective treatments for diabetic retinopathy are necessary. New analytical techniques, in particular those related to molecular markers, are accelerating progress in diabetic retinopathy research. Given the increasing incidence and prevalence of diabetes, and the limited capacity of healthcare systems to screen and treat diabetic retinopathy, there is need to reliably identify and triage people with diabetes. Biomarkers may facilitate a better understanding of diabetic retinopathy, and contribute to the development of novel treatments and new clinical strategies to prevent vision loss in people with diabetes. This article reviews key aspects related to biomarker research, and focuses on some specific biomarkers relevant to diabetic retinopathy.
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Affiliation(s)
- Alicia J Jenkins
- NHMRC Clinical Trials Centre, University of Sydney, Camperdown, Sydney, Australia
| | - Mugdha V Joglekar
- NHMRC Clinical Trials Centre, University of Sydney, Camperdown, Sydney, Australia
| | | | - Anthony C Keech
- NHMRC Clinical Trials Centre, University of Sydney, Camperdown, Sydney, Australia
| | - David N O'Neal
- NHMRC Clinical Trials Centre, University of Sydney, Camperdown, Sydney, Australia
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Kim SJ, Sung MS, Heo H, Lee JH, Park SW. Mangiferin Protects Retinal Ganglion Cells in Ischemic Mouse Retina via SIRT1. Curr Eye Res 2015. [PMID: 26200953 DOI: 10.3109/02713683.2015.1050736] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
PURPOSE To investigate whether mangiferin can increase the viability of retinal ganglion cells (RGCs) in ischemic mouse retina, and to determine the possible mechanism of neuroprotection. METHODS C57BL/6J mice underwent constant elevation of intraocular pressure for 60 min and received saline or mangiferin (30 mg/kg) intraperitoneally once daily until sacrifice. HIF-1α, GFAP and SIRT1 expression was assessed at 1, 4, and 7 days after retinal ischemia. Bax and Bcl-2 expression was also analyzed at 1 and 4 days. RGC survival was assessed by labeling flat-mounted retinas with Brn3a at 2 weeks after retinal ischemia. The effect of co-treatment with mangiferin and sirtinol (SIRT1 inhibitor) was also evaluated. RESULTS The expression of HIF-1α and GFAP was upregulated in saline-treated retinas within 7 days after ischemia. Mangiferin treatment suppressed this upregulation. The expression of SIRT1 was downregulated in saline-treated ischemic retinas. This downregulation was reversed by mangiferin treatment, resulting in a significant difference from saline-treated ischemic retinas. In mangiferin-treated ischemic retinas, Bax expression was downregulated, whereas Bcl-2 expression was upregulated in comparison with saline-treated ischemic retinas. Mangiferin treatment protected ischemic retinas against RGC loss. Treatment of sirtinol decreased the neuroprotective effect of mangiferin. CONCLUSIONS Our findings suggest that mangiferin has a neuroprotective effect on RGC through downregulation of HIF-1a and GFAP, and upregulation of SIRT1 in ischemic mouse retinas. We suggest that mangiferin might be a potential neuroprotective agent against RGC loss under oxidative stress.
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Affiliation(s)
- Soo-Jin Kim
- a Department of Ophthalmology , Chonnam National University Medical School & Hospital , Gwangju , Korea .,c Department of Pathology , Chonnam National University Medical School , Gwangju , Korea
| | - Mi-Sun Sung
- a Department of Ophthalmology , Chonnam National University Medical School & Hospital , Gwangju , Korea
| | - Hwan Heo
- a Department of Ophthalmology , Chonnam National University Medical School & Hospital , Gwangju , Korea
| | - Jae-Hyuk Lee
- b Center for Creative Biomedical Scientists at Chonnam National University, Chonnam National University Medical School , Gwangju , Korea and.,c Department of Pathology , Chonnam National University Medical School , Gwangju , Korea
| | - Sang-Woo Park
- a Department of Ophthalmology , Chonnam National University Medical School & Hospital , Gwangju , Korea .,c Department of Pathology , Chonnam National University Medical School , Gwangju , Korea
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85
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Sasongko MB, Wong TY, Nguyen TT, Cheung CY, Shaw JE, Kawasaki R, Lamoureux EL, Wang JJ. Retinal Vessel Tortuosity and Its Relation to Traditional and Novel Vascular Risk Markers in Persons with Diabetes. Curr Eye Res 2015; 41:551-7. [DOI: 10.3109/02713683.2015.1034371] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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86
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Beyazyildiz Ö, Tirhiş MH, Hekimoğlu ER, Beyazyildiz E, Kaymaz F, Yilmazbaş P, Öztürk F. Histopathological Analysis of Internal Limiting Membrane Surgically Peeled From Eyes with Epiretinal Membrane. Curr Eye Res 2015; 41:258-65. [DOI: 10.3109/02713683.2015.1008642] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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MacVicar BA, Newman EA. Astrocyte regulation of blood flow in the brain. Cold Spring Harb Perspect Biol 2015; 7:cshperspect.a020388. [PMID: 25818565 DOI: 10.1101/cshperspect.a020388] [Citation(s) in RCA: 215] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Neuronal activity results in increased blood flow in the brain, a response named functional hyperemia. Astrocytes play an important role in mediating this response. Neurotransmitters released from active neurons evoke Ca(2+) increases in astrocytes, leading to the release of vasoactive metabolites of arachidonic acid from astrocyte endfeet onto blood vessels. Synthesis of prostaglandin E2 (PGE2) and epoxyeicosatrienoic acids (EETs) dilate blood vessels, whereas 20-hydroxyeicosatetraenoic acid (20-HETE) constricts vessels. The release of K(+) from astrocyte endfeet may also contribute to vasodilation. Oxygen modulates astrocyte regulation of blood flow. Under normoxic conditions, astrocytic Ca(2+) signaling results in vasodilation, whereas under hyperoxic conditions, vasoconstriction is favored. Astrocytes also contribute to the generation of vascular tone. Tonic release of both 20-HETE and ATP from astrocytes constricts vascular smooth muscle cells, generating vessel tone. Under pathological conditions, including Alzheimer's disease and diabetic retinopathy, disruption of normal astrocyte physiology can compromise the regulation of blood flow.
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Affiliation(s)
- Brian A MacVicar
- Djavad Mowafaghian Centre for Brain Health, Department of Psychiatry, University of British Columbia, Vancouver, British Columbia V6T 2B5, Canada
| | - Eric A Newman
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455
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Cuenca N, Fernández-Sánchez L, Campello L, Maneu V, De la Villa P, Lax P, Pinilla I. Cellular responses following retinal injuries and therapeutic approaches for neurodegenerative diseases. Prog Retin Eye Res 2014; 43:17-75. [PMID: 25038518 DOI: 10.1016/j.preteyeres.2014.07.001] [Citation(s) in RCA: 296] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 07/03/2014] [Accepted: 07/07/2014] [Indexed: 01/17/2023]
Abstract
Retinal neurodegenerative diseases like age-related macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa each have a different etiology and pathogenesis. However, at the cellular and molecular level, the response to retinal injury is similar in all of them, and results in morphological and functional impairment of retinal cells. This retinal degeneration may be triggered by gene defects, increased intraocular pressure, high levels of blood glucose, other types of stress or aging, but they all frequently induce a set of cell signals that lead to well-established and similar morphological and functional changes, including controlled cell death and retinal remodeling. Interestingly, an inflammatory response, oxidative stress and activation of apoptotic pathways are common features in all these diseases. Furthermore, it is important to note the relevant role of glial cells, including astrocytes, Müller cells and microglia, because their response to injury is decisive for maintaining the health of the retina or its degeneration. Several therapeutic approaches have been developed to preserve retinal function or restore eyesight in pathological conditions. In this context, neuroprotective compounds, gene therapy, cell transplantation or artificial devices should be applied at the appropriate stage of retinal degeneration to obtain successful results. This review provides an overview of the common and distinctive features of retinal neurodegenerative diseases, including the molecular, anatomical and functional changes caused by the cellular response to damage, in order to establish appropriate treatments for these pathologies.
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Affiliation(s)
- Nicolás Cuenca
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain; Multidisciplinary Institute for Environmental Studies "Ramon Margalef", University of Alicante, Alicante, Spain.
| | - Laura Fernández-Sánchez
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain
| | - Laura Campello
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain
| | - Victoria Maneu
- Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - Pedro De la Villa
- Department of Systems Biology, University of Alcalá, Alcalá de Henares, Spain
| | - Pedro Lax
- Department of Physiology, Genetics and Microbiology, University of Alicante, Alicante, Spain
| | - Isabel Pinilla
- Department of Ophthalmology, Lozano Blesa University Hospital, Aragon Institute of Health Sciences, Zaragoza, Spain
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Abstract
For years, diabetic retinopathy has been defined based on vascular lesions, and neural abnormalities were not regarded as important. This review summarizes evidence that the neural retina has important effects on the retinal vasculature under normal conditions, and the interaction between the retinal neuroglial cells and vascular function is altered in diabetes. Importantly, new evidence raises a possibility that abnormalities within retinal neuroglial cells (notably photoreceptors) might actually be causing or initiating the vascular disease in diabetic retinopathy.
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Affiliation(s)
- Timothy S. Kern
- Department of Medicine, Case Western Reserve University Medicine, Cleveland, OH, USA
- Department of Medicine, Louis Stokes Cleveland Veterans Administration Medical Center, Cleveland, OH, USA
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90
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Jindal V. Neurodegeneration as a primary change and role of neuroprotection in diabetic retinopathy. Mol Neurobiol 2014; 51:878-84. [PMID: 24826918 DOI: 10.1007/s12035-014-8732-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Accepted: 04/29/2014] [Indexed: 02/06/2023]
Abstract
Diabetic retinopathy (DR) was earlier recognized as a vascular disease, but nowadays, it is considered as a neurovascular disorder. Neuronal death is the primary change which leads to various vascular changes which are visible to an ophthalmologist. But these changes are feature of an advanced disease and can affect vision at any moment of time. There are various evidences which suggests that glutamate excitotoxicity, hyperhomocysteinemia, kynurenic acid, and erythro-poietin plays important role in causation of retinal ganglionic cell apoptosis in diabetic patients. Adaptive optics, a new imaging technique, also showed that loss of photoreceptors (specialized neurons) is the early change in diabetic retinopathy. These changes suggest DR as a neurovascular disorder. Neuroprotective agents also showed good results in delaying progression of DR especially memantine, insulin receptor activation, and neurotrophic factors. More research in this field will help us to find novel therapeutic measures for DR, which can delay or even stop progression of DR at a very early stage.
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Affiliation(s)
- Vishal Jindal
- , H. No. 102 GHS 51 sector 20, Panchkula, Haryana, India,
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Moran E, Ding L, Wang Z, Cheng R, Chen Q, Moore R, Takahashi Y, Ma JX. Protective and antioxidant effects of PPARα in the ischemic retina. Invest Ophthalmol Vis Sci 2014; 55:4568-76. [PMID: 24825105 DOI: 10.1167/iovs.13-13127] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Previous studies have demonstrated that peroxisome proliferator-activated receptor-alpha (PPARα) agonists have therapeutic effects in diabetic retinopathy, although the mechanism of action remains incompletely understood. The purpose of this study was to evaluate PPARα's protective effects in the ischemic retina, and to delineate its molecular mechanism of action. METHODS For the oxygen-induced retinopathy (OIR) model, wild-type (WT), and PPARα knockout (PPARα(-/-)) mice were exposed to 75% O₂ from postnatal day 7 (P7) to P12 and treated with the PPARα agonist fenofibric acid (Feno-FA) from P12 to P16. At P17, the effects of Feno-FA on retinal glial fibrillary acidic protein (GFAP) expression, apoptotic DNA cleavage, and TUNEL labeling were analyzed. Cultured retinal cells were exposed to CoCl₂ to induce hypoxia, and TUNEL staining and 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein dye were used to measure apoptosis and reactive oxygen species (ROS) generation. Western blotting was used to measure GFAP levels and cell signaling. RESULTS Feno-FA decreased retinal apoptosis and oxidative stress in WT but not PPARα(-/-) OIR mice. Peroxisome proliferator-activated receptor-alpha knockout OIR mice showed increased retinal cell death and glial activation in comparison to WT OIR mice. Feno-FA treatment and PPARα overexpression protected cultured retinal cells from hypoxic cell death and decreased ROS levels. Nuclear hypoxia-inducible factor-α (HIF-1α) and nicotine adenine dinucleotide phosphate oxidase-4 (Nox 4) were increased in OIR retinas and downregulated by Feno-FA in WT but not in PPARα(-/-) mice. CONCLUSIONS Peroxisome proliferator-activated receptor-alpha has a potent antiapoptotic effect in the ischemic retina. This protective effect may be mediated in part through downregulation of HIF-1α/Nox 4 and consequently alleviation of oxidative stress.
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Affiliation(s)
- Elizabeth Moran
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Lexi Ding
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, China
| | - Zhongxiao Wang
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Rui Cheng
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Qian Chen
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Robert Moore
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Yusuke Takahashi
- Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Jian-xing Ma
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
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92
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Abcouwer SF, Gardner TW. Diabetic retinopathy: loss of neuroretinal adaptation to the diabetic metabolic environment. Ann N Y Acad Sci 2014; 1311:174-90. [PMID: 24673341 DOI: 10.1111/nyas.12412] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Diabetic retinopathy (DR) impairs vision of patients with type 1 and type 2 diabetes, associated with vascular dysfunction and occlusion, retinal edema, hemorrhage, and inappropriate growth of new blood vessels. The recent success of biologic treatments targeting vascular endothelial growth factor (VEGF) demonstrates that treating the vascular aspects in the later stages of the disease can preserve vision in many patients. It would also be highly desirable to prevent the onset of the disease or arrest its progression at a stage preceding the appearance of overt microvascular pathologies. The progression of DR is not necessarily linear but may follow a series of steps that evolve over the course of multiple years. Abundant data suggest that diabetes affects the entire neurovascular unit of the retina, with an early loss of neurovascular coupling, gradual neurodegeneration, gliosis, and neuroinflammation occurring before observable vascular pathologies. In this article, we consider the pathology of DR from the point of view that diabetes causes measurable dysfunctions in the complex integral network of cell types that produce and maintain human vision.
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Affiliation(s)
- Steven F Abcouwer
- Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, Michigan
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93
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Phenotypes and biomarkers of diabetic retinopathy. Prog Retin Eye Res 2014; 41:90-111. [PMID: 24680929 DOI: 10.1016/j.preteyeres.2014.03.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 03/11/2014] [Accepted: 03/18/2014] [Indexed: 12/15/2022]
Abstract
Diabetic retinopathy (DR) remains a major cause of blindness as the prevalence of diabetes is expected to approximately double globally between 2000 and 2030. DR progresses over time at different rates in different individuals with only a limited number developing significant vision loss due to the two major vision-threatening complications, clinically significant macular edema and proliferative retinopathy. Good metabolic control is important to prevent and delay progression, but whereas some patients escape vision loss even with poor control, others develop vision loss despite good metabolic control. Our research group has been able to identify three different DR phenotypes characterized by different dominant retinal alterations and different risks of progression to vision-threatening complications. Microaneurysm turnover has been validated as a prognostic biomarker of development of clinically significant macular edema, whereas subclinical macular edema identified by OCT and mfERG appear to be also good candidates as organ-specific biomarkers of DR. Hemoglobin A1c remains the only confirmed systemic prognostic biomarker of DR progression. The availability of biomarkers of DR progression and the identification of different phenotypes of DR with different risks for development of vision-threatening complications offers new perspectives for understanding DR and for its personalized management.
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94
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Ivanova E, Toychiev AH, Yee CW, Sagdullaev BT. Intersublaminar vascular plexus: the correlation of retinal blood vessels with functional sublaminae of the inner plexiform layer. Invest Ophthalmol Vis Sci 2014; 55:78-86. [PMID: 24346172 DOI: 10.1167/iovs.13-13196] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
PURPOSE Interactions between vasculature and neurons provide important insight into the function of the nervous system, as well as into neurological diseases wherein these interactions are disrupted. This study characterizes a previously unreported retinal vascular plexus and examines potential sites of neurovascular interaction. METHODS Vascular, neuronal, and glial elements were visualized using immunohistochemical markers. The distribution of vascular layers was measured and compared across eccentricities. Intensity profiles were calculated from confocal image reconstructions to reveal the proximity of vasculature to neuronal and glial processes. RESULTS Retinal vasculature forms a plexus that coincides with the dendritic processes of OFF cholinergic amacrine cells within the inner plexiform layer. Across eccentricities, this plexus comprises approximately 8% of the total length of horizontally running blood vessels in the retina. Processes of Müller glia and OFF cholinergic amacrine cells colocalize with the blood vessels that form the intersublaminar plexus. CONCLUSIONS In the retina, vasculature lacks autonomic control, but shows efficient local regulation. Although the source of this regulation is unclear, these results suggest that cholinergic amacrine cells and Müller glia may interact with the intersublaminar plexus to influence vasomotor activity. This may indicate a key role in modulating reciprocal interactions between neuronal activity and blood flow.
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Affiliation(s)
- Elena Ivanova
- Departments of Ophthalmology and Neurology, Weill Medical College of Cornell University, Burke Medical Research Institute, White Plains, New York
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95
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Simó R, Hernández C. Neurodegeneration in the diabetic eye: new insights and therapeutic perspectives. Trends Endocrinol Metab 2014; 25:23-33. [PMID: 24183659 DOI: 10.1016/j.tem.2013.09.005] [Citation(s) in RCA: 324] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 09/02/2013] [Accepted: 09/27/2013] [Indexed: 11/29/2022]
Abstract
Diabetic retinopathy (DR), one of the leading causes of preventable blindness, has been considered a microcirculatory disease of the retina. However, there is emerging evidence to suggest that retinal neurodegeneration is an early event in the pathogenesis of DR, which participates in the development of microvascular abnormalities. Therefore, the study of the underlying mechanisms leading to neurodegeneration and the identification of the mediators in the crosstalk between neurodegeneration and microangiopathy will be essential for the development of new therapeutic strategies. In this review, an updated discussion of the mechanisms involved in neurodegeneration, as well as the link between neurodegeneration and microangiopathy, is presented. Finally, the therapeutic implications and new perspectives based on identifying those patients with retinal neurodegeneration are given.
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Affiliation(s)
- Rafael Simó
- CIBERDEM (CIBER de Diabetes y Enfermedades Metabólicas Asociadas) and Diabetes and Metabolism Research Unit, Vall Hebron Institut de Recerca (VHIR), Universitat Autónoma de Barcelona, 08035 Barcelona, Spain.
| | - Cristina Hernández
- CIBERDEM (CIBER de Diabetes y Enfermedades Metabólicas Asociadas) and Diabetes and Metabolism Research Unit, Vall Hebron Institut de Recerca (VHIR), Universitat Autónoma de Barcelona, 08035 Barcelona, Spain
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96
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Nakahara T, Mori A, Kurauchi Y, Sakamoto K, Ishii K. Neurovascular interactions in the retina: physiological and pathological roles. J Pharmacol Sci 2013; 123:79-84. [PMID: 24067498 DOI: 10.1254/jphs.13r03cp] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Increasing evidence suggests that the complex interactions among multiple cell types including neuronal, glial, and vascular cells, are critical for maintaining adequate cerebral blood flow that is necessary for normal brain function and survival. The disturbance of these interactions contributes to the pathogenesis of central nervous system disorders such as stroke and Alzheimer's disease. The retina is part of the central nervous system, and the properties of vasculature in the retina are similar to those in the brain. The interactions among multiple cell types in the retina also play an important role in the maintenance of tissue homeostasis, and the impairment of interactions can contribute to the onset and/or progression of retinal diseases. In this review, we describe the neurovascular interactions in the retina and alternations of interactions in pathological conditions such as diabetic retinopathy and glaucoma.
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Affiliation(s)
- Tsutomu Nakahara
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Japan
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97
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Lim M, Sasongko MB, Ikram MK, Lamoureux E, Wang JJ, Wong TY, Cheung CY. Systemic Associations of Dynamic Retinal Vessel Analysis: A Review of Current Literature. Microcirculation 2013; 20:257-68. [DOI: 10.1111/micc.12026] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Accepted: 11/07/2012] [Indexed: 01/29/2023]
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98
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Ola MS, Nawaz MI, Khan HA, Alhomida AS. Neurodegeneration and neuroprotection in diabetic retinopathy. Int J Mol Sci 2013; 14:2559-72. [PMID: 23358247 PMCID: PMC3588002 DOI: 10.3390/ijms14022559] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 01/12/2013] [Accepted: 01/17/2013] [Indexed: 02/06/2023] Open
Abstract
Diabetic retinopathy is widely considered to be a neurovascular disease. This is in contrast to its previous identity as solely a vascular disease. Early in the disease progression of diabetes, the major cells in the neuronal component of the retina consist of retinal ganglion cells and glial cells, both of which have been found to be compromised. A number of retinal function tests also indicated a functional deficit in diabetic retina, which further supports dysfunction of neuronal cells. As an endocrinological disorder, diabetes alters metabolism both systemically and locally in several body organs, including the retina. A growing body of evidences indicates increased levels of excitotoxic metabolites, including glutamate, branched chain amino acids and homocysteine in cases of diabetic retinopathy. Also present, early in the disease, are decreased levels of folic acid and vitamin-B12, which are potential metabolites capable of damaging neurons. These altered levels of metabolites are found to activate several metabolic pathways, leading to increases in oxidative stress and decreases in the level of neurotrophic factors. As a consequence, they may damage retinal neurons in diabetic patients. In this review, we have discussed those potential excitotoxic metabolites and their implications in neuronal damage. Possible therapeutic targets to protect neurons are also discussed. However, further research is needed to understand the exact molecular mechanism of neurodegeneration so that effective neuroprotection strategies can be developed. By protecting retinal neurons early in diabetic retinopathy cases, damage of retinal vessels can be protected, thereby helping to ameliorate the progression of diabetic retinopathy, a leading cause of blindness worldwide.
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Affiliation(s)
- Mohammad Shamsul Ola
- Department of Biochemistry, Faculty of Science, King Saud University, Riyadh 11415, Saudi Arabia.
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99
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Leonelli M, Martins DO, Britto LRG. Retinal Cell Death Induced by TRPV1 Activation Involves NMDA Signaling and Upregulation of Nitric Oxide Synthases. Cell Mol Neurobiol 2013; 33:379-92. [DOI: 10.1007/s10571-012-9904-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 12/29/2012] [Indexed: 01/23/2023]
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100
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Abstract
Diabetic retinopathy (DR) has been considered to be a microcirculatory disease of the retina. However, there is emerging evidence to suggest that retinal neurodegeneration is an early event in the pathogenesis of DR, which may antedate, and also participates in, the microcirculatory abnormalities that occur in DR. Therefore, the study of the underlying mechanisms that lead to neurodegeneration will be essential for identifying new therapeutic targets in the early stages of DR. Elevated levels of glutamate, oxidative stress, the overexpression of the renin-angiotensin system and the upregulation of RAGE play an essential role in the retinal neurodegeneration induced by diabetes. Finally, the balance between the neurotoxic and neuroprotective factors is crucial in determining the survival of retinal neurons. In this review we will focus on neurotrophic factors already synthesized by the retina in physiological conditions as a new therapy strategy for neuroprotection.
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Affiliation(s)
- Cristina Hernández
- CIBERDEM and Diabetes and Metabolism Research Unit, Vall Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Spain
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