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Li J, Chen K, Li X, Zhang X, Zhang L, Yang Q, Xia Y, Xie C, Wang X, Tong J, Shen Y. Mechanistic insights into the alterations and regulation of the AKT signaling pathway in diabetic retinopathy. Cell Death Discov 2023; 9:418. [PMID: 37978169 PMCID: PMC10656479 DOI: 10.1038/s41420-023-01717-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 11/05/2023] [Accepted: 11/08/2023] [Indexed: 11/19/2023] Open
Abstract
In the early stages of diabetic retinopathy (DR), diabetes-related hyperglycemia directly inhibits the AKT signaling pathway by increasing oxidative stress or inhibiting growth factor expression, which leads to retinal cell apoptosis, nerve proliferation and fundus microvascular disease. However, due to compensatory vascular hyperplasia in the late stage of DR, the vascular endothelial growth factor (VEGF)/phosphatidylinositol 3 kinase (PI3K)/AKT cascade is activated, resulting in opposite levels of AKT regulation compared with the early stage. Studies have shown that many factors, including insulin, insulin-like growth factor-1 (IGF-1), VEGF and others, can regulate the AKT pathway. Disruption of the insulin pathway decreases AKT activation. IGF-1 downregulation decreases the activation of AKT in DR, which abrogates the neuroprotective effect, upregulates VEGF expression and thus induces neovascularization. Although inhibiting VEGF is the main treatment for neovascularization in DR, excessive inhibition may lead to apoptosis in inner retinal neurons. AKT pathway substrates, including mammalian target of rapamycin (mTOR), forkhead box O (FOXO), glycogen synthase kinase-3 (GSK-3)/nuclear factor erythroid 2-related factor 2 (Nrf2), and nuclear factor kappa-B (NF-κB), are a research focus. mTOR inhibitors can delay or prevent retinal microangiopathy, whereas low mTOR activity can decrease retinal protein synthesis. Inactivated AKT fails to inhibit FOXO and thus causes apoptosis. The GSK-3/Nrf2 cascade regulates oxidation and inflammation in DR. NF-κB is activated in diabetic retinas and is involved in inflammation and apoptosis. Many pathways or vital activities, such as the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and mitogen-activated protein kinase (MAPK) signaling pathways, interact with the AKT pathway to influence DR development. Numerous regulatory methods can simultaneously impact the AKT pathway and other pathways, and it is essential to consider both the connections and interactions between these pathways. In this review, we summarize changes in the AKT signaling pathway in DR and targeted drugs based on these potential sites.
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Affiliation(s)
- Jiayuan Li
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
- Department of Cardiology, The Second Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Kuangqi Chen
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiang Li
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Xuhong Zhang
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Liyue Zhang
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Qianjie Yang
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Yutong Xia
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Chen Xie
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiawei Wang
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China
| | - Jianping Tong
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China.
| | - Ye Shen
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang University, Hangzhou, Zhejiang, China.
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2
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Shan S, Liu F, Ford E, Caldwell RB, Narayanan SP, Somanath PR. Triciribine attenuates pathological neovascularization and vascular permeability in a mouse model of proliferative retinopathy. Biomed Pharmacother 2023; 162:114714. [PMID: 37080089 DOI: 10.1016/j.biopha.2023.114714] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/11/2023] [Accepted: 04/14/2023] [Indexed: 04/22/2023] Open
Abstract
Proliferative retinopathies are the leading cause of irreversible blindness in all ages, and there is a critical need to identify novel therapies. We investigated the impact of triciribine (TCBN), a tricyclic nucleoside analog and a weak Akt inhibitor, on retinal neurovascular injury, vascular permeability, and inflammation in oxygen-induced retinopathy (OIR). Post-natal day 7 (P7) mouse pups were subjected to OIR, and treated (i.p.) with TCBN or vehicle from P14-P16 and compared with age-matched, normoxic, vehicle or TCBN-treated controls. P17 retinas were processed for flat mounts, immunostaining, Western blotting, and qRT-PCR studies. Fluorescein angiography, electroretinography, and spectral domain optical coherence tomography were performed on days P21, P26, and P30, respectively. TCBN treatment significantly reduced pathological neovascularization, vaso-obliteration, and inflammation marked by reduced TNFα, IL6, MCP-1, Iba1, and F4/80 (macrophage/microglia markers) expression compared to the vehicle-treated OIR mouse retinas. Pathological expression of VEGF (vascular endothelial growth factor), and claudin-5 compromised the blood-retinal barrier integrity in the OIR retinas correlating with increased vascular permeability and neovascular tuft formation, which were blunted by TCBN treatment. Of note, there were no changes in the retinal architecture or retinal cell function in response to TCBN in the normoxia or OIR mice. We conclude that TCBN protects against pathological neovascularization, restores blood-retinal barrier homeostasis, and reduces retinal inflammation without adversely affecting the retinal structure and neuronal function in a mouse model of OIR. Our data suggest that TCBN may provide a novel therapeutic option for proliferative retinopathy.
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Affiliation(s)
- Shengshuai Shan
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, 30912, USA; Research Department, Charlie Norwood VA Medical Center, Augusta, GA, 30901, USA; Vascular Biology Center, Augusta University, Augusta, GA, 30912, USA; Culver Vision Discovery Institute, Augusta University, Augusta, GA, 30912, USA
| | - Fang Liu
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, 30912, USA; Research Department, Charlie Norwood VA Medical Center, Augusta, GA, 30901, USA; Vascular Biology Center, Augusta University, Augusta, GA, 30912, USA; Culver Vision Discovery Institute, Augusta University, Augusta, GA, 30912, USA
| | - Edith Ford
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, 30912, USA
| | - Ruth B Caldwell
- Vascular Biology Center, Augusta University, Augusta, GA, 30912, USA; Culver Vision Discovery Institute, Augusta University, Augusta, GA, 30912, USA
| | - S Priya Narayanan
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, 30912, USA; Research Department, Charlie Norwood VA Medical Center, Augusta, GA, 30901, USA; Vascular Biology Center, Augusta University, Augusta, GA, 30912, USA; Culver Vision Discovery Institute, Augusta University, Augusta, GA, 30912, USA.
| | - Payaningal R Somanath
- Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, 30912, USA; Research Department, Charlie Norwood VA Medical Center, Augusta, GA, 30901, USA; Culver Vision Discovery Institute, Augusta University, Augusta, GA, 30912, USA.
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3
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Wang Y, Fung NSK, Lam WC, Lo ACY. mTOR Signalling Pathway: A Potential Therapeutic Target for Ocular Neurodegenerative Diseases. Antioxidants (Basel) 2022; 11:antiox11071304. [PMID: 35883796 PMCID: PMC9311918 DOI: 10.3390/antiox11071304] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/20/2022] [Accepted: 06/20/2022] [Indexed: 02/04/2023] Open
Abstract
Recent advances in the research of the mammalian target of the rapamycin (mTOR) signalling pathway demonstrated that mTOR is a robust therapeutic target for ocular degenerative diseases, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma. Although the exact mechanisms of individual ocular degenerative diseases are unclear, they share several common pathological processes, increased and prolonged oxidative stress in particular, which leads to functional and morphological impairment in photoreceptors, retinal ganglion cells (RGCs), or retinal pigment epithelium (RPE). mTOR not only modulates oxidative stress but is also affected by reactive oxygen species (ROS) activation. It is essential to understand the complicated relationship between the mTOR pathway and oxidative stress before its application in the treatment of retinal degeneration. Indeed, the substantial role of mTOR-mediated autophagy in the pathogenies of ocular degenerative diseases should be noted. In reviewing the latest studies, this article summarised the application of rapamycin, an mTOR signalling pathway inhibitor, in different retinal disease models, providing insight into the mechanism of rapamycin in the treatment of retinal neurodegeneration under oxidative stress. Besides basic research, this review also summarised and updated the results of the latest clinical trials of rapamycin in ocular neurodegenerative diseases. In combining the current basic and clinical research results, we provided a more complete picture of mTOR as a potential therapeutic target for ocular neurodegenerative diseases.
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Lewandowski D, Sander CL, Tworak A, Gao F, Xu Q, Skowronska-Krawczyk D. Dynamic lipid turnover in photoreceptors and retinal pigment epithelium throughout life. Prog Retin Eye Res 2021; 89:101037. [PMID: 34971765 PMCID: PMC10361839 DOI: 10.1016/j.preteyeres.2021.101037] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 12/13/2021] [Accepted: 12/15/2021] [Indexed: 12/13/2022]
Abstract
The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.
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Affiliation(s)
- Dominik Lewandowski
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Christopher L Sander
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Aleksander Tworak
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Fangyuan Gao
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Qianlan Xu
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Dorota Skowronska-Krawczyk
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA.
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5
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Fort PE, Rajendiran TM, Soni T, Byun J, Shan Y, Looker HC, Nelson RG, Kretzler M, Michailidis G, Roger JE, Gardner TW, Abcouwer SF, Pennathur S, Afshinnia F. Diminished retinal complex lipid synthesis and impaired fatty acid β-oxidation associated with human diabetic retinopathy. JCI Insight 2021; 6:e152109. [PMID: 34437304 PMCID: PMC8525591 DOI: 10.1172/jci.insight.152109] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 08/25/2021] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND This study systematically investigated circulating and retinal tissue lipid determinants of human diabetic retinopathy (DR) to identify underlying lipid alterations associated with severity of DR. METHODS Retinal tissues were retrieved from postmortem human eyes, including 19 individuals without diabetes, 20 with diabetes but without DR, and 20 with diabetes and DR, for lipidomic study. In a parallel study, serum samples from 28 American Indians with type 2 diabetes from the Gila River Indian Community, including 12 without DR, 7 with mild nonproliferative DR (NPDR), and 9 with moderate NPDR, were selected. A mass-spectrometry–based lipidomic platform was used to measure serum and tissue lipids. RESULTS In the postmortem retinas, we found a graded decrease of long-chain acylcarnitines and longer-chain fatty acid ester of hydroxyl fatty acids, diacylglycerols, triacylglycerols, phosphatidylcholines, and ceramide(NS) in central retina from individuals with no diabetes to those with diabetes with DR. The American Indians’ sera also exhibited a graded decrease in circulating long-chain acylcarnitines and a graded increase in the intermediate-length saturated and monounsaturated triacylglycerols from no DR to moderate NPDR. CONCLUSION These findings suggest diminished synthesis of complex lipids and impaired mitochondrial β-oxidation of fatty acids in retinal DR, with parallel changes in circulating lipids. TRIAL REGISTRATION ClinicalTrials.gov NCT00340678. FUNDING This work was supported by NIH grants R24 DK082841, K08DK106523, R03DK121941, P30DK089503, P30DK081943, P30DK020572, P30 EY007003; The Thomas Beatson Foundation; and JDRF Center for Excellence (5-COE-2019-861-S-B).
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Affiliation(s)
- Patrice E Fort
- Department of Ophthalmology and Visual Sciences.,Department of Molecular and Integrative Physiology
| | | | | | - Jaeman Byun
- Department of Internal Medicine-Nephrology, University of Michigan, Ann Arbor, Michigan, USA
| | - Yang Shan
- Department of Ophthalmology and Visual Sciences
| | - Helen C Looker
- Chronic Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Phoenix, Arizona, USA
| | - Robert G Nelson
- Chronic Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Phoenix, Arizona, USA
| | - Matthias Kretzler
- Department of Internal Medicine-Nephrology, University of Michigan, Ann Arbor, Michigan, USA
| | - George Michailidis
- Department of Statistics and the Informatics Institute, University of Florida, Gainesville, Florida, USA
| | - Jerome E Roger
- Paris-Saclay Institute of Neuroscience, CERTO-Retina France, CNRS, Université Paris-Saclay, Orsay, France
| | - Thomas W Gardner
- Department of Ophthalmology and Visual Sciences.,Department of Molecular and Integrative Physiology.,Department of Internal Medicine-Metabolism, Endocrinology and Diabetes, and
| | | | - Subramaniam Pennathur
- Department of Molecular and Integrative Physiology.,Department of Internal Medicine-Nephrology, University of Michigan, Ann Arbor, Michigan, USA.,Michigan Regional Comprehensive Metabolomics Resource Core, University of Michigan, Ann Arbor, Michigan, USA
| | - Farsad Afshinnia
- Department of Internal Medicine-Nephrology, University of Michigan, Ann Arbor, Michigan, USA
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6
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Sas KM, Lin J, Rajendiran TM, Soni T, Nair V, Hinder LM, Jagadish HV, Gardner TW, Abcouwer SF, Brosius FC, Feldman EL, Kretzler M, Michailidis G, Pennathur S. Shared and distinct lipid-lipid interactions in plasma and affected tissues in a diabetic mouse model. J Lipid Res 2017; 59:173-183. [PMID: 29237716 DOI: 10.1194/jlr.m077222] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 12/12/2017] [Indexed: 01/17/2023] Open
Abstract
Lipids are ubiquitous metabolites with diverse functions; abnormalities in lipid metabolism appear to be related to complications from multiple diseases, including type 2 diabetes. Through technological advances, the entire lipidome has been characterized and researchers now need computational approaches to better understand lipid network perturbations in different diseases. Using a mouse model of type 2 diabetes with microvascular complications, we examined lipid levels in plasma and in renal, neural, and retinal tissues to identify shared and distinct lipid abnormalities. We used correlation analysis to construct interaction networks in each tissue, to associate changes in lipids with changes in enzymes of lipid metabolism, and to identify overlap of coregulated lipid subclasses between plasma and each tissue to define subclasses of plasma lipids to use as surrogates of tissue lipid metabolism. Lipid metabolism alterations were mostly tissue specific in the kidney, nerve, and retina; no lipid changes correlated between the plasma and all three tissue types. However, alterations in diacylglycerol and in lipids containing arachidonic acid, an inflammatory mediator, were shared among the tissue types, and the highly saturated cholesterol esters were similarly coregulated between plasma and each tissue type in the diabetic mouse. Our results identified several patterns of altered lipid metabolism that may help to identify pathogenic alterations in different tissues and could be used as biomarkers in future research into diabetic microvascular tissue damage.
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Affiliation(s)
- Kelli M Sas
- Division of Nephrology, Departments of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | - Jiahe Lin
- Departments of Statistics, University of Michigan, Ann Arbor, MI 48109
| | - Thekkelnaycke M Rajendiran
- Departments of Pathology, University of Michigan, Ann Arbor, MI 48109.,Michigan Regional Comprehensive Metabolomics Resource Core Ann Arbor, MI 48105
| | - Tanu Soni
- Michigan Regional Comprehensive Metabolomics Resource Core Ann Arbor, MI 48105
| | - Viji Nair
- Division of Nephrology, Departments of Internal Medicine, University of Michigan, Ann Arbor, MI 48109.,Departments of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109
| | - Lucy M Hinder
- Departments of Neurology, University of Michigan, Ann Arbor, MI 48109
| | - Hosagrahar V Jagadish
- Departments of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109
| | - Thomas W Gardner
- Departments of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48109.,Departments of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109
| | - Steven F Abcouwer
- Departments of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48109
| | - Frank C Brosius
- Division of Nephrology, Departments of Internal Medicine, University of Michigan, Ann Arbor, MI 48109.,Departments of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109
| | - Eva L Feldman
- Departments of Neurology, University of Michigan, Ann Arbor, MI 48109
| | - Matthias Kretzler
- Division of Nephrology, Departments of Internal Medicine, University of Michigan, Ann Arbor, MI 48109.,Departments of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109
| | - George Michailidis
- Department of Statistics and Computer and Information Sciences, University of Florida, Gainesville, FL 32611
| | - Subramaniam Pennathur
- Division of Nephrology, Departments of Internal Medicine, University of Michigan, Ann Arbor, MI 48109 .,Michigan Regional Comprehensive Metabolomics Resource Core Ann Arbor, MI 48105.,Departments of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109
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7
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The mTOR Conundrum: Essential for Muscle Function, but Dangerous for Survival. J Am Med Dir Assoc 2016; 17:963-966. [DOI: 10.1016/j.jamda.2016.09.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 09/01/2016] [Indexed: 02/06/2023]
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8
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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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9
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Matsuda S, Nakanishi A, Wada Y, Kitagishi Y. Roles of PI3K/AKT/PTEN Pathway as a Target for Pharmaceutical Therapy. THE OPEN MEDICINAL CHEMISTRY JOURNAL 2013; 7:23-9. [PMID: 24222802 PMCID: PMC3821079 DOI: 10.2174/1874104501307010023] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 09/23/2013] [Accepted: 10/05/2013] [Indexed: 12/11/2022]
Abstract
Multiple enzymes participate in the phosphorylation of a group of phosphoinositide lipids. Because of their important role in signal transduction, the dysregulated metabolism of phosphoinositides represents a key step in many disease settings. Loss of their function has been demonstrated to occur as an early event a wide variety of carcinogenesis and has therefore been suggested as a biomarker for the premalignant disease. In addition, genetic alterations at multiple nodes in the pathway have been implicated in several other diseases. Accordingly, given this pervasive involvement in many diseases, the development of molecules that modulates this pathway has been initiated in studies. They have been the focus of extensive research and drug discovery activities. A better understanding of the molecular connections could uncover new targets for drug development.
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Affiliation(s)
- Satoru Matsuda
- Department of Food Science and Nutrition, Nara Women's University, Kita-Uoya Nishimachi, Nara 630-8506, Japan
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10
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Huang CCY, Ko ML, Ko GYP. A new functional role for mechanistic/mammalian target of rapamycin complex 1 (mTORC1) in the circadian regulation of L-type voltage-gated calcium channels in avian cone photoreceptors. PLoS One 2013; 8:e73315. [PMID: 23977383 PMCID: PMC3747127 DOI: 10.1371/journal.pone.0073315] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 07/19/2013] [Indexed: 01/10/2023] Open
Abstract
In the retina, the L-type voltage-gated calcium channels (L-VGCCs) are responsible for neurotransmitter release from photoreceptors and are under circadian regulation. Both the current densities and protein expression of L-VGCCs are significantly higher at night than during the day. However, the underlying mechanisms of circadian regulation of L-VGCCs in the retina are not completely understood. In this study, we demonstrated that the mechanistic/mammalian target of rapamycin complex (mTORC) signaling pathway participated in the circadian phase-dependent modulation of L-VGCCs. The activities of the mTOR cascade, from mTORC1 to its downstream targets, displayed circadian oscillations throughout the course of a day. Disruption of mTORC1 signaling dampened the L-VGCC current densities, as well as the protein expression of L-VGCCs at night. The decrease of L-VGCCs at night by mTORC1 inhibition was in part due to a reduction of L-VGCCα1 subunit translocation from the cytosol to the plasma membrane. Finally, we showed that mTORC1 was downstream of the phosphatidylionositol 3 kinase-protein kinase B (PI3K-AKT) signaling pathway. Taken together, mTORC1 signaling played a role in the circadian regulation of L-VGCCs, in part through regulation of ion channel trafficking and translocation, which brings to light a new functional role for mTORC1: the modulation of ion channel activities.
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Affiliation(s)
- Cathy Chia-Yu Huang
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Michael Lee Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Gladys Yi-Ping Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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11
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Lai AKW, Lo ACY. Animal models of diabetic retinopathy: summary and comparison. J Diabetes Res 2013; 2013:106594. [PMID: 24286086 PMCID: PMC3826427 DOI: 10.1155/2013/106594] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 09/02/2013] [Accepted: 09/02/2013] [Indexed: 12/16/2022] Open
Abstract
Diabetic retinopathy (DR) is a microvascular complication associated with chronic exposure to hyperglycemia and is a major cause of blindness worldwide. Although clinical assessment and retinal autopsy of diabetic patients provide information on the features and progression of DR, its underlying pathophysiological mechanism cannot be deduced. In order to have a better understanding of the development of DR at the molecular and cellular levels, a variety of animal models have been developed. They include pharmacological induction of hyperglycemia and spontaneous diabetic rodents as well as models of angiogenesis without diabetes (to compensate for the absence of proliferative DR symptoms). In this review, we summarize the existing protocols to induce diabetes using STZ. We also describe and compare the pathological presentations, in both morphological and functional aspects, of the currently available DR animal models. The advantages and disadvantages of using different animals, ranging from zebrafish, rodents to other higher-order mammals, are also discussed. Until now, there is no single model that displays all the clinical features of DR as seen in human. Yet, with the understanding of the pathological findings in these animal models, researchers can select the most suitable models for mechanistic studies or drug screening.
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Affiliation(s)
- Angela Ka Wai Lai
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Amy C. Y. Lo
- Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
- Research Center of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
- *Amy C. Y. Lo:
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