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Sekar J, Attaway AH. The intersection of HIF-1α, O-GlcNAc, and skeletal muscle loss in chronic obstructive pulmonary disease. Glycobiology 2023; 33:873-878. [PMID: 37812446 PMCID: PMC10859630 DOI: 10.1093/glycob/cwad081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 09/29/2023] [Accepted: 10/04/2023] [Indexed: 10/10/2023] Open
Abstract
Sarcopenia, defined as the loss of muscle mass and strength, is a major cause of morbidity and mortality in COPD (chronic obstructive pulmonary disease) patients. However, the molecular mechanisms that cause sarcopenia remain to be determined. In this review, we will highlight the unique molecular and metabolic perturbations that occur in the skeletal muscle of COPD patients in response to hypoxia, and emphasize important areas of future research. In particular, the mechanisms related to the glycolytic shift that occurs in skeletal muscle in response to hypoxia may occur via a hypoxia-inducible factor 1-alpha (HIF-1α)-mediated mechanism. Upregulated glycolysis in skeletal muscle promotes a unique post-translational glycosylation of proteins known as O-GlcNAcylation, which further shifts metabolism toward glycolysis. Molecular changes in the skeletal muscle of COPD patients are associated with fiber-type shifting from Type I (oxidative) muscle fibers to Type II (glycolytic) muscle fibers. The metabolic shift toward glycolysis caused by HIF-1α and O-GlcNAc modified proteins suggests a potential cause for sarcopenia in COPD, which is an emerging area of future research.
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Affiliation(s)
- Jinendiran Sekar
- Division of Infectious Diseases, Harbor-UCLA Medical Center, 1000 West Carson Street, MRL Building, Box 466; Torrance, CA 90502, United States
- The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, 1124 W Carson St, Torrance, CA 90502, United States
| | - Amy H Attaway
- Respiratory Institute, Cleveland Clinic, Cleveland Clinic Main Campus, Mail Code A90, 9500 Euclid Avenue, Cleveland, OH 44195, United States
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Liu G, Feng L, Liu X, Gao P, Wang F. O-GlcNAcylation Inhibition Upregulates Connexin43 Expression in the Endothelium to Protect the Tight Junction Barrier in Diabetic Retinopathy. Invest Ophthalmol Vis Sci 2023; 64:30. [PMID: 37982762 PMCID: PMC10668625 DOI: 10.1167/iovs.64.14.30] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 08/28/2023] [Indexed: 11/21/2023] Open
Abstract
Purpose This study aimed to investigate the effects of O-linked N-acetylglucosamine modification (O-GlcNAcylation) on connexin43 (Cx43) expression and its subsequent effects on tight junction properties in diabetic retinopathy (DR). Methods O-GlcNAcylation levels in primary human retinal vascular endothelial cells (HRVECs) and retinas from rats with diabetes were regulated by treatment with Thiamet G or alloxan. Immunoprecipitation was used to examine the relationship between O-GlcNAcylation and Cx43 expression. Stable overexpression and knockdown of Cx43 in HRVECs were achieved using lentivirus constructs; further, their effects on occludin and zonula occluden-1 (ZO-1) expression and tight junction barrier function were determined. Results O-GlcNAcylation level increased significantly, whereas Cx43 expression decreased in retinas from rats with diabetes and HRVECs cultured under high-glucose conditions. Immunoprecipitation revealed that Cx43 was modified by O-GlcNAcylation and phosphorylation simultaneously. O-GlcNAcylation inhibition negatively regulated both total Cx43 and phosphorylated Cx43 expression, subsequently disrupting tight junction properties. Conversely, Cx43 overexpression reversed the disruption of tight junction properties and downregulated vascular endothelial growth factor expression. Consistently, Cx43 overexpression increased transendothelial electrical resistance values in HRVEC layers. Conclusions O-GlcNAcylation negatively regulated Cx43 expression, contributing to the disruption of the blood retinal barrier. However, O-GlcNAcylation inhibition and Cx43 overexpression could reverse the tight junction disruption. Therefore, O-GlcNAcylation inhibition is a potential target for avoiding tight junction disruption through the Cx43 pathway in DR.
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Affiliation(s)
- Guodong Liu
- Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, P.R. China
- Tongji Eye Institute, Tongji University School of Medicine, Shanghai, China
| | - Le Feng
- Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, P.R. China
- Tongji Eye Institute, Tongji University School of Medicine, Shanghai, China
| | - Xiaoqiang Liu
- Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, P.R. China
- Tongji Eye Institute, Tongji University School of Medicine, Shanghai, China
| | - Peng Gao
- Department of Ophthalmology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, P.R. China
| | - Fang Wang
- Tongji Eye Institute, Tongji University School of Medicine, Shanghai, China
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Starr CR, Zhylkibayev A, Mobley JA, Gorbatyuk MS. Proteomic analysis of diabetic retinas. Front Endocrinol (Lausanne) 2023; 14:1229089. [PMID: 37693346 PMCID: PMC10486886 DOI: 10.3389/fendo.2023.1229089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 07/28/2023] [Indexed: 09/12/2023] Open
Abstract
Introduction As a metabolic disease, diabetes often leads to health complications such as heart failure, nephropathy, neurological disorders, and vision loss. Diabetic retinopathy (DR) affects as many as 100 million people worldwide. The mechanism of DR is complex and known to impact both neural and vascular components in the retina. While recent advances in the field have identified major cellular signaling contributing to DR pathogenesis, little has been reported on the protein post-translational modifications (PTM) - known to define protein localization, function, and activity - in the diabetic retina overall. Protein glycosylation is the enzymatic addition of carbohydrates to proteins, which can influence many protein attributes including folding, stability, function, and subcellular localization. O-linked glycosylation is the addition of sugars to an oxygen atom in amino acids with a free oxygen atom in their side chain (i.e., threonine, serine). To date, more than 100 congenital disorders of glycosylation have been described. However, no studies have identified the retinal O-linked glycoproteome in health or disease. With a critical need to expedite the discovery of PTMomics in diabetic retinas, we identified both global changes in protein levels and the retinal O-glycoproteome of control and diabetic mice. Methods We used liquid chromatography/mass spectrometry-based proteomics and high throughput screening to identify proteins differentially expressed and proteins differentially O-glycosylated in the retinas of wildtype and diabetic mice. Results Changes in both global expression levels of proteins and proteins differentially glycosylated in the retinas of wild-type and diabetic mice have been identified. We provide evidence that diabetes shifts both global expression levels and O-glycosylation of metabolic and synaptic proteins in the retina. Discussion Here we report changes in the retinal proteome of diabetic mice. We highlight alterations in global proteins involved in metabolic processes, maintaining cellular structure, trafficking, and neuronal processes. We then showed changes in O-linked glycosylation of individual proteins in the diabetic retina.
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Affiliation(s)
- Christopher R. Starr
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Assylbek Zhylkibayev
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, United States
| | - James A. Mobley
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Marina S. Gorbatyuk
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, United States
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Starr CR, Gorbatyuk MS. Posttranslational modifications of proteins in diseased retina. Front Cell Neurosci 2023; 17:1150220. [PMID: 37066080 PMCID: PMC10097899 DOI: 10.3389/fncel.2023.1150220] [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: 01/23/2023] [Accepted: 03/13/2023] [Indexed: 04/03/2023] Open
Abstract
Posttranslational modifications (PTMs) are known to constitute a key step in protein biosynthesis and in the regulation of protein functions. Recent breakthroughs in protein purification strategies and current proteome technologies make it possible to identify the proteomics of healthy and diseased retinas. Despite these advantages, the research field identifying sets of posttranslationally modified proteins (PTMomes) related to diseased retinas is significantly lagging, despite knowledge of the major retina PTMome being critical to drug development. In this review, we highlight current updates regarding the PTMomes in three retinal degenerative diseases-namely, diabetic retinopathy (DR), glaucoma, and retinitis pigmentosa (RP). A literature search reveals the necessity to expedite investigations into essential PTMomes in the diseased retina and validate their physiological roles. This knowledge would accelerate the development of treatments for retinal degenerative disorders and the prevention of blindness in affected populations.
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Affiliation(s)
| | - Marina S. Gorbatyuk
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, United States
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O-GlcNAc Modification and Its Role in Diabetic Retinopathy. Metabolites 2022; 12:metabo12080725. [PMID: 36005597 PMCID: PMC9415332 DOI: 10.3390/metabo12080725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/01/2022] [Accepted: 08/03/2022] [Indexed: 11/17/2022] Open
Abstract
Diabetic retinopathy (DR) is a leading complication in type 1 and type 2 diabetes and has emerged as a significant health problem. Currently, there are no effective therapeutic strategies owing to its inconspicuous early lesions and complex pathological mechanisms. Therefore, the mechanism of molecular pathogenesis requires further elucidation to identify potential targets that can aid in the prevention of DR. As a type of protein translational modification, O-linked β-N-acetylglucosamine (O-GlcNAc) modification is involved in many diseases, and increasing evidence suggests that dysregulated O-GlcNAc modification is associated with DR. The present review discusses O-GlcNAc modification and its molecular mechanisms involved in DR. O-GlcNAc modification might represent a novel alternative therapeutic target for DR in the future.
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Dierschke SK, Dennis MD. Retinal Protein O-GlcNAcylation and the Ocular Renin-angiotensin System: Signaling Cross-roads in Diabetic Retinopathy. Curr Diabetes Rev 2022; 18:e011121190177. [PMID: 33430751 PMCID: PMC8272735 DOI: 10.2174/1573399817999210111205933] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 11/14/2020] [Accepted: 11/16/2020] [Indexed: 01/23/2023]
Abstract
It is well established that diabetes and its associated hyperglycemia negatively impact retinal function, yet we know little about the role played by augmented flux through the Hexosamine Biosynthetic Pathway (HBP). This offshoot of the glycolytic pathway produces UDP-Nacetyl- glucosamine, which serves as the substrate for post-translational O-linked modification of proteins in a process referred to as O-GlcNAcylation. HBP flux and subsequent protein O-GlcNAcylation serve as nutrient sensors, enabling cells to integrate metabolic information to appropriately modulate fundamental cellular processes including gene expression. Here we summarize the impact of diabetes on retinal physiology, highlighting recent studies that explore the role of O-GlcNAcylation- induced variation in mRNA translation in retinal dysfunction and the pathogenesis of Diabetic Retinopathy (DR). Augmented O-GlcNAcylation results in wide variation in the selection of mRNAs for translation, in part, due to O-GlcNAcylation of the translational repressor 4E-BP1. Recent studies demonstrate that 4E-BP1 plays a critical role in regulating O-GlcNAcylation-induced changes in the translation of the mRNAs encoding Vascular Endothelial Growth Factor (VEGF), a number of important mitochondrial proteins, and CD40, a key costimulatory molecule involved in diabetes-induced retinal inflammation. Remarkably, 4E-BP1/2 ablation delays the onset of diabetes- induced visual dysfunction in mice. Thus, pharmacological interventions to prevent the impact of O-GlcNAcylation on 4E-BP1 may represent promising therapeutics to address the development and progression of DR. In this regard, we discuss the potential interplay between retinal O-GlcNAcylation and the ocular renin-angiotensin system as a potential therapeutic target of future interventions.
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Affiliation(s)
- Sadie K. Dierschke
- Department of Cellular and Molecular Physiology, Penn State College of Medicine
| | - Michael D. Dennis
- Department of Cellular and Molecular Physiology, Penn State College of Medicine
- Department of Ophthalmology, Penn State College of Medicine
- Address correspondence to this author at the Department of Cellular and Molecular Physiology, H166, Penn State College of Medicine, 500 University Drive Hershey, PA 17033; Tel: (717)531-0003 Ext-282596; Fax: (717)531-7667;
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Liu G, Wang Y, Keyal K, Feng L, Zhang C, Wang H, Wang F. Identification of connexin43 in diabetic retinopathy and its downregulation by O-GlcNAcylation to inhibit the activation of glial cells. Biochim Biophys Acta Gen Subj 2021; 1865:129955. [PMID: 34229069 DOI: 10.1016/j.bbagen.2021.129955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/20/2021] [Accepted: 06/28/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Despite advances in the treatments of diabetic complications, proliferative diabetic retinopathy (PDR) still remains a major cause leading to visual loss, mainly because of the lack of pathological mechanisms and complicated protein expressions in vivo. Current study aimed to investigate the patterns of connexin43 (Cx43) changes and the possible interactions with O-GlcNAcylation in DR. METHODS Clinical samples of vitreous and fibrovascular membranes were acquired from PDR patients during pars plana vitrectomy. Brown Norway rats were used to build diabetic animal models; to investigate the effects of O-GlcNAcylation on Cx43 expressions, total retinal O-GlcNAcylation was changed by intravitreal injections. Levels of protein expressions were examined by immunofluorescence staining and western blot. RESULTS Our results revealed increased Cx43 expressions in a vessel-shape pattern followed by the distribution of glial fibrillary acidic protein (GFAP) in diabetic fibrovascular membranes. Similarly, Cx43 and GFAP expressions were elevated in PDR vitreous and diabetic animal retinas. Retinal O-GlcNAcylation was effectively regulated by intravitreal injections, and the increase of Cx43 and GFAP was significantly suppressed by O-GlcNAcylation inhibition under hyperglycemia conditions. CONCLUSIONS We systemically proved the changes of Cx43 with different retinal cells, and reported the effective methods to regulate retinal O-GlcNAcylation by intravitreal injections, and clearly illustrated the downregulated effects of O-GlcNAcylation inhibition on Cx43 and GFAP expressions. GENERAL SIGNIFICANCE Targeting connexin43 in glial cells reveals a novel mechanism to understand the formation of diabetic fibrovascular membranes and offers a potential therapeutic strategy to interfere the development of PDR.
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Affiliation(s)
- Guodong Liu
- Department of Ophthalmology, Shanghai Tenth People's Hospital affiliated with Tongji University, 301 Middle Yan Chang Road, Shanghai 200072, PR China
| | - Yanliang Wang
- Department of Ophthalmology, Shanghai Tenth People's Hospital affiliated with Tongji University, 301 Middle Yan Chang Road, Shanghai 200072, PR China
| | - Khusbu Keyal
- Department of Ophthalmology, Shanghai Tenth People's Hospital affiliated with Tongji University, 301 Middle Yan Chang Road, Shanghai 200072, PR China
| | - Le Feng
- Department of Ophthalmology, Shanghai Tenth People's Hospital affiliated with Tongji University, 301 Middle Yan Chang Road, Shanghai 200072, PR China
| | - Conghui Zhang
- Department of Ophthalmology, Shanghai Tenth People's Hospital affiliated with Tongji University, 301 Middle Yan Chang Road, Shanghai 200072, PR China
| | - Hao Wang
- Department of Ophthalmology, Shanghai Tenth People's Hospital affiliated with Tongji University, 301 Middle Yan Chang Road, Shanghai 200072, PR China
| | - Fang Wang
- Department of Ophthalmology, Shanghai Tenth People's Hospital affiliated with Tongji University, 301 Middle Yan Chang Road, Shanghai 200072, PR China.
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Nikolaou MA, Drosos Y, Havaki S, Arvanitis D, Sotiriou S, Vassiou K, Zibis A, Arvanitis LD. The O-Linked N-Acetylglucosamine Containing Epitope H (O-GlcNAcH) is Upregulated in the Trophoblastic and Downregulated in the Fibroblastic Cells in Missed Miscarriage Human Chorionic Villi With Simple Hydropic Degeneration. Int J Gynecol Pathol 2021; 40:324-332. [PMID: 32897971 DOI: 10.1097/pgp.0000000000000693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Epitope H contains an O-linked N-acetylglucosamine (O-GlcNAcH) residue in a specific conformation and/or environment recognized by the mouse monoclonal antibody H. O-GlcNAcH is present in several types of cells and in several polypeptides, including cytokeratin 8 and vimentin, on the latter in cells under stress. In the present work, we examined the expression of the O-GlcNAcH in 60 cases of endometrial curettings from missed miscarriage cases containing normal and simple hydropic degenerated chorionic villi in each case, using monoclonal antibody H and indirect immunoperoxidase and Western blot immunoblot. In all cases examined the expression of the O-GlcNAcH was cytoplasmic as follows: (1) syncytiotrophoblastic cells showed very low expression in chorionic villi (CV) with nonhydropic degeneration (NHD) and high expression in hydropic degenerated (HD) CV; (2) cytotrophoblastic cells showed low expression in CV with NHD and high expression in HD CV; (3) fibroblastic cells showed high expression in CV with NHD and very low expression in HD CV; (4) histiocytes showed very low expression in both types of CV; (5) endothelial cells showed high expression in both types of CV. An immunoblot of CV from one case of a legal abortion from a normal first-trimester pregnancy showed 5 polypeptides with 118.5, 106.3, 85, 53, and 36.7 kD bearing the epitope H and the 53 kD corresponded to cytokeratin 8. The expression of the O-GlcNAcH is upregulated in the trophoblastic cells and downregulated in the fibroblastic cells in the HD CV in comparison to the NHD CV.
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Ahmad K, Shaikh S, Lee EJ, Lee YH, Choi I. Consequences of Dicarbonyl Stress on Skeletal Muscle Proteins in Type 2 Diabetes. Curr Protein Pept Sci 2021; 21:878-889. [PMID: 31746292 DOI: 10.2174/1389203720666191119100759] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 05/27/2019] [Accepted: 10/22/2019] [Indexed: 12/15/2022]
Abstract
Skeletal muscle is the largest organ in the body and constitutes almost 40% of body mass. It is also the primary site of insulin-mediated glucose uptake, and skeletal muscle insulin resistance, that is, diminished response to insulin, is characteristic of Type 2 diabetes (T2DM). One of the foremost reasons posited to explain the etiology of T2DM involves the modification of proteins by dicarbonyl stress due to an unbalanced metabolism and accumulations of dicarbonyl metabolites. The elevated concentration of dicarbonyl metabolites (i.e., glyoxal, methylglyoxal, 3-deoxyglucosone) leads to DNA and protein modifications, causing cell/tissue dysfunctions in several metabolic diseases such as T2DM and other age-associated diseases. In this review, we recapitulated reported effects of dicarbonyl stress on skeletal muscle and associated extracellular proteins with emphasis on the impact of T2DM on skeletal muscle and provided a brief introduction to the prevention/inhibition of dicarbonyl stress.
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Affiliation(s)
- Khurshid Ahmad
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan, 38541, Korea
| | - Sibhghatulla Shaikh
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan, 38541, Korea
| | - Eun Ju Lee
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan, 38541, Korea
| | - Yong-Ho Lee
- Department of Biomedical Sciences, Daegu Catholic University, Gyeongsan, 38430, Korea
| | - Inho Choi
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan, 38541, Korea
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Ju Kim E. O‐GlcNAc Transferase: Structural Characteristics, Catalytic Mechanism and Small‐Molecule Inhibitors. Chembiochem 2020; 21:3026-3035. [DOI: 10.1002/cbic.202000194] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 05/07/2020] [Indexed: 12/21/2022]
Affiliation(s)
- Eun Ju Kim
- Department of Science Education-Chemistry Major Daegu University Gyeongsan-si, GyeongBuk 712-714 South Korea
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Masaki N, Feng B, Bretón‐Romero R, Inagaki E, Weisbrod RM, Fetterman JL, Hamburg NM. O-GlcNAcylation Mediates Glucose-Induced Alterations in Endothelial Cell Phenotype in Human Diabetes Mellitus. J Am Heart Assoc 2020; 9:e014046. [PMID: 32508185 PMCID: PMC7429031 DOI: 10.1161/jaha.119.014046] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Background Posttranslational protein modification with O-linked N-acetylglucosamine (O-GlcNAc) is linked to high glucose levels in type 2 diabetes mellitus (T2DM) and may alter cellular function. We sought to elucidate the involvement of O-GlcNAc modification in endothelial dysfunction in patients with T2DM. Methods and Results Freshly isolated endothelial cells obtained by J-wire biopsy from a forearm vein of patients with T2DM (n=18) was compared with controls (n=10). Endothelial O-GlcNAc levels were 1.8-ford higher in T2DM patients than in nondiabetic controls (P=0.003). Higher endothelial O-GlcNAc levels correlated with serum fasting blood glucose level (r=0.433, P=0.024) and hemoglobin A1c (r=0.418, P=0.042). In endothelial cells from patients with T2DM, normal glucose conditions (24 hours at 5 mmol/L) lowered O-GlcNAc levels and restored insulin-mediated activation of endothelial nitric oxide synthase, whereas high glucose conditions (30 mmol/L) maintained both O-GlcNAc levels and impaired insulin action. Treatment of endothelial cells with Thiamet G, an O-GlcNAcase inhibitor, increased O-GlcNAc levels and blunted the improvement of insulin-mediated endothelial nitric oxide synthase phosphorylation by glucose normalization. Conclusions Taken together, our findings indicate a role for O-GlcNAc modification in the dynamic, glucose-induced impairment of endothelial nitric oxide synthase activation in endothelial cells from patients with T2DM. O-GlcNAc protein modification may be a treatment target for vascular dysfunction in T2DM.
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Affiliation(s)
- Nobuyuki Masaki
- The Whitaker Cardiovascular InstituteDepartment of MedicineBoston University School of MedicineBostonMA
| | - Bihua Feng
- The Whitaker Cardiovascular InstituteDepartment of MedicineBoston University School of MedicineBostonMA
| | - Rosa Bretón‐Romero
- The Whitaker Cardiovascular InstituteDepartment of MedicineBoston University School of MedicineBostonMA
| | - Elica Inagaki
- The Whitaker Cardiovascular InstituteDepartment of MedicineBoston University School of MedicineBostonMA
| | - Robert M. Weisbrod
- The Whitaker Cardiovascular InstituteDepartment of MedicineBoston University School of MedicineBostonMA
| | - Jessica L. Fetterman
- The Whitaker Cardiovascular InstituteDepartment of MedicineBoston University School of MedicineBostonMA
| | - Naomi M. Hamburg
- The Whitaker Cardiovascular InstituteDepartment of MedicineBoston University School of MedicineBostonMA
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Dierschke SK, Toro AL, Barber AJ, Arnold AC, Dennis MD. Angiotensin-(1-7) Attenuates Protein O-GlcNAcylation in the Retina by EPAC/Rap1-Dependent Inhibition of O-GlcNAc Transferase. Invest Ophthalmol Vis Sci 2020; 61:24. [PMID: 32068794 PMCID: PMC7326568 DOI: 10.1167/iovs.61.2.24] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Purpose O-GlcNAcylation of cellular proteins contributes to the pathophysiology of diabetes and evidence supports a role for augmented O-GlcNAcylation in diabetic retinopathy. The aim of this study was to investigate the impact of the renin-angiotensin system on retinal protein O-GlcNAcylation. Methods Mice fed a high-fat diet were treated chronically with the angiotensin-converting enzyme inhibitor captopril or captopril plus the angiotensin-(1-7) Mas receptor antagonist A779. Western blotting and quantitative polymerase chain reaction were used to analyze retinal homogenates. Similar analyses were performed on lysates from human MIO-M1 retinal Müller cell cultures exposed to media supplemented with angiotensin-(1-7). Culture conditions were manipulated to influence the hexosamine biosynthetic pathway and/or signaling downstream of the Mas receptor. Results In the retina of mice fed a high-fat diet, captopril attenuated protein O-GlcNAcylation in a manner dependent on Mas receptor activation. In MIO-M1 cells, angiotensin-(1-7) or adenylate cyclase activation were sufficient to enhance cyclic AMP (cAMP) levels and inhibit O-GlcNAcylation. The repressive effect of cAMP on O-GlcNAcylation was dependent on exchange protein activated by cAMP (EPAC), but not protein kinase A, and was recapitulated by a constitutively active variant of the small GTPase Rap1. We provide evidence that cAMP and angiotensin-(1-7) act to suppress O-GlcNAcylation by inhibition of O-GlcNAc transferase (OGT) activity. In cells exposed to an O-GlcNAcase inhibitor or hyperglycemic culture conditions, mitochondrial superoxide levels were elevated; however, angiotensin-(1-7) signaling prevented the effect. Conclusions Angiotensin-(1-7) inhibits retinal protein O-GlcNAcylation via an EPAC/Rap1/OGT signaling axis.
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Affiliation(s)
- Sadie K. Dierschke
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania, United States
| | - Allyson L. Toro
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania, United States
| | - Alistair J. Barber
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania, United States,Department of Ophthalmology, Penn State College of Medicine, Hershey, Pennsylvania, United States,Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania, United States
| | - Amy C. Arnold
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania, United States
| | - Michael D. Dennis
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania, United States,Department of Ophthalmology, Penn State College of Medicine, Hershey, Pennsylvania, United States
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Consumption of a high fat diet promotes protein O-GlcNAcylation in mouse retina via NR4A1-dependent GFAT2 expression. Biochim Biophys Acta Mol Basis Dis 2018; 1864:3568-3576. [PMID: 30254013 DOI: 10.1016/j.bbadis.2018.09.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 08/29/2018] [Accepted: 09/08/2018] [Indexed: 01/30/2023]
Abstract
The incidence of type 2 diabetes, the most common cause of diabetic retinopathy (DR), is rapidly on the rise in developed countries due to overconsumption of calorie rich diets. Using an animal model of diet-induced obesity/pre-diabetes, we evaluated the impact of a diet high in saturated fat (HFD) on O-GlcNAcylation of retinal proteins, as dysregulated O-GlcNAcylation contributes to diabetic complications and evidence supports a role in DR. Protein O-GlcNAcylation was increased in the retina of mice fed a HFD as compared to littermates receiving control chow. Similarly, O-GlcNAcylation was elevated in retinal Müller cells in culture exposed to the saturated fatty acid palmitate or the ceramide analog Cer6. One potential mechanism responsible for elevated O-GlcNAcylation is increased flux through the hexosamine biosynthetic pathway (HBP). Indeed, inhibition of the pathway's rate-limiting enzyme glutamine-fructose-6-phosphate amidotransferase (GFAT) prevented Cer6-induced O-GlcNAcylation. Importantly, expression of the mRNA encoding GFAT2, but not GFAT1 was elevated in both the retina of mice fed a HFD and in retinal cells in culture exposed to palmitate or Cer6. Notably, expression of nuclear receptor subfamily 4 group A member 1 (NR4A1) was increased in the retina of mice fed a HFD and NR4A1 expression was sufficient to promote GFAT2 mRNA expression and O-GlcNAcylation in retinal cells in culture. Whereas palmitate or Cer6 addition to culture medium enhanced NR4A1 and GFAT2 expression, chemical inhibition of NR4A1 transactivation repressed Cer6-induced GFAT2 mRNA expression. Overall, the results support a model wherein HFD increases retinal protein O-GlcNAcylation by promoting NR4A1-dependent GFAT2 expression.
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O-Linked β- N-acetylglucosamine (O-GlcNAc) modification: a new pathway to decode pathogenesis of diabetic retinopathy. Clin Sci (Lond) 2018; 132:185-198. [PMID: 29352075 DOI: 10.1042/cs20171454] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 12/13/2017] [Accepted: 12/18/2017] [Indexed: 01/08/2023]
Abstract
The incidence of diabetes continues to rise among all ages and ethnic groups worldwide. Diabetic retinopathy (DR) is a complication of diabetes that affects the retinal neurovasculature causing serious vision problems, including blindness. Its pathogenesis and severity is directly linked to the chronic exposure to high glucose conditions. No treatments are currently available to stop the development and progression of DR. To develop new and effective therapeutic approaches, it is critical to better understand how hyperglycemia contributes to the pathogenesis of DR at the cellular and molecular levels. We propose alterations in O-GlcNAc modification of target proteins during diabetes contribute to the development and progression of DR. The O-GlcNAc modification is regulated through hexosamine biosynthetic pathway. We showed this pathway is differentially activated in various retinal vascular cells under high glucose conditions perhaps due to their selective metabolic activity. O-GlcNAc modification can alter protein stability, activity, interactions, and localization. By targeting the same amino acid residues (serine and threonine) as phosphorylation, O-GlcNAc modification can either compete or cooperate with phosphorylation. Here we will summarize the effects of hyperglycemia-induced O-GlcNAc modification on the retinal neurovasculature in a cell-specific manner, providing new insight into the role of O-GlcNAc modification in early loss of retinal pericytes and the pathogenesis of DR.
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Kim SJ, Kim MJ, Choi MY, Kim YS, Yoo JM, Hong EK, Ju S, Choi WS. Aralia elata inhibits neurodegeneration by downregulating O-GlcNAcylation of NF-κB in diabetic mice. Int J Ophthalmol 2017; 10:1203-1211. [PMID: 28861343 DOI: 10.18240/ijo.2017.08.03] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 06/12/2017] [Indexed: 02/04/2023] Open
Abstract
AIM To investigate the role of O-GlcNAcylation of nuclear factor-kappa B (NF-κB) in retinal ganglion cell (RGC) death and analysedthe effect of Aralia elata (AE) on neurodegeneration in diabetic mice. METHODS C57BL/6mice with streptozotocin-induced diabetes were fed daily with AE extract or control (CTL) diet at the onset of diabetes mellitus (DM). Two months after injection of streptozotocin or saline, the degree of cell death and the expression of O-GlcNAc transferase (OGT), N-acetyl-b-D-glucosaminidase (OGA), O-GlcNAcylated proteins, and O-GlcNAcylation of NF-κB were examined. RESULTS AE did not affect the metabolic status of diabetic mice. The decrease in the inner retinal thickness (P<0.001 vs CTL, P<0.01 vs DM) and increases in RGCs with terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (P<0.001 vs CTL, P<0.0001 vs DM), glial activation, and active caspase-3 (P<0.0001 vs CTL, P<0.0001 vs DM) were blocked in diabetic retinas of AE extract-fed mice. Expression levels of protein O-GlcNAcylation and OGT were increased in diabetic retinas (P<0.0001 vs CTL), and the level of O-GlcNAcylation of the NF-κB p65 subunit was higher in diabetic retinas than in controls (P<0.0001 vs CTL). AE extract downregulated O-GlcNAcylation of NF-κB and prevented neurodegeneration induced by hyperglycemia (P<0.0001 vs DM). CONCLUSION O-GlcNAcylation of NF-κB is concerned in neuronal degeneration and that AE prevents diabetes-induced RGC apoptosis via downregulation of NF-κB O-GlcNAcylation. Hence, O-GlcNAcylation may be a new object for the treatment of DR, and AE may have therapeutic possibility to prevent diabetes-induced neurodegeneration.
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Affiliation(s)
- Seong-Jae Kim
- Department of Ophthalmology, School of Medicine, Gyeongsang National University, Jinju 52727, Korea
| | - Min-Jun Kim
- Department of Anatomy and Convergence Medical Science, School of Medicine, Gyeongsang National University, Jinju 52727, Korea
| | - Mee-Young Choi
- Department of Anatomy and Convergence Medical Science, School of Medicine, Gyeongsang National University, Jinju 52727, Korea.,Institute of Health Science, Gyeongsang National University, Jinju 52727, Korea
| | - Yoon-Sook Kim
- Department of Anatomy and Convergence Medical Science, School of Medicine, Gyeongsang National University, Jinju 52727, Korea.,Institute of Health Science, Gyeongsang National University, Jinju 52727, Korea
| | - Ji-Myong Yoo
- Department of Ophthalmology, School of Medicine, Gyeongsang National University, Jinju 52727, Korea.,Institute of Health Science, Gyeongsang National University, Jinju 52727, Korea
| | | | - Sunmi Ju
- Division of Pulmonology and Allergy, Department of Internal Medicine, School of Medicine, Gyeongsang National University, Jinju 52727, Korea
| | - Wan-Sung Choi
- Department of Anatomy and Convergence Medical Science, School of Medicine, Gyeongsang National University, Jinju 52727, Korea.,Institute of Health Science, Gyeongsang National University, Jinju 52727, Korea
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[O-GlcNAc glycosylation influences the biological behaviors and etoposide-induced apoptosis of Nalm-6 cells]. ZHONGHUA XUE YE XUE ZA ZHI = ZHONGHUA XUEYEXUE ZAZHI 2017; 38:237-242. [PMID: 28395449 PMCID: PMC7348384 DOI: 10.3760/cma.j.issn.0253-2727.2017.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
目的 研究O连接的N-乙酰葡萄糖胺(O-GlcNAc)糖基化及乙酰氨基葡萄糖转移酶(OGT)对Nalm-6细胞生物学行为及对依托泊苷(Vp16)诱导凋亡的影响。 方法 利用OGT抑制剂Alloxan构建低O-GlcNAc修饰的Nalm-6细胞模型,CCK-8法检测Alloxan对细胞增殖的影响,流式细胞术检测Alloxan对细胞凋亡及细胞周期的影响;以不同浓度的Vp16处理Nalm-6细胞12 h,Western blot检测O-GlcNAc糖基化修饰程度及OGT表达量的变化;以Alloxan处理Nalm-6细胞24 h后再加入Vp16(5 µg/ml)处理12 h,应用流式细胞术检测不同组别细胞凋亡,Western blot检测凋亡相关蛋白Bax和Bcl-2的表达情况。 结果 随着Vp16浓度的增加,Nalm-6细胞O-GlcNAc修饰及OGT表达均逐渐上调(P<0.05);Alloxan可抑制Nalm-6细胞增殖,诱发Nalm-6细胞凋亡[(15.190±2.539)%对(21.910±4.105)%,P=0.007],阻滞细胞周期[G1期:(43.534±4.453)%对(57.322±6.091)%,P=0.003;S期:(50.747±5.937)%对(37.201±4.661)%,P=0.001];Alloxan可抑制Vp16诱导的Nalm-6细胞凋亡[(75.195±13.845)%对(52.741±10.815)%,P=0.011],并伴随Bax表达下调(5.496±1.998对2.950±0.703,P=0.015)、Bcl-2表达上调(0.454±0.125对0.803±0.223,P=0.013)。 结论 通过抑制OGT而改变Nalm-6细胞O-GlcNAc修饰程度可影响其增殖、凋亡、改变细胞周期并抑制Vp16诱导的细胞凋亡。
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Abstract
The O-linked N-acetylglucosamine (O-GlcNAc) post-translational modification (O-GlcNAcylation) is the dynamic and reversible attachment of N-acetylglucosamine to serine and threonine residues of nucleocytoplasmic target proteins. It is abundant in metazoa, involving hundreds of proteins linked to a plethora of biological functions with implications in human diseases. The process is catalysed by two enzymes: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) that add and remove sugar moieties respectively. OGT knockout is embryonic lethal in a range of animal models, hampering the study of the biological role of O-GlcNAc and the dissection of catalytic compared with non-catalytic roles of OGT. Therefore, selective and potent chemical tools are necessary to inhibit OGT activity in the context of biological systems. The present review focuses on the available OGT inhibitors and summarizes advantages, limitations and future challenges.
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18
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Misra J, Kim DK, Jung YS, Kim HB, Kim YH, Yoo EK, Kim BG, Kim S, Lee IK, Harris RA, Kim JS, Lee CH, Cho JW, Choi HS. O-GlcNAcylation of Orphan Nuclear Receptor Estrogen-Related Receptor γ Promotes Hepatic Gluconeogenesis. Diabetes 2016; 65:2835-48. [PMID: 27335230 DOI: 10.2337/db15-1523] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 06/15/2016] [Indexed: 11/13/2022]
Abstract
Estrogen-related receptor γ (ERRγ) is a major positive regulator of hepatic gluconeogenesis. Its transcriptional activity is suppressed by phosphorylation signaled by insulin in the fed state, but whether posttranslational modification alters its gluconeogenic activity in the fasted state is not known. Metabolically active hepatocytes direct a small amount of glucose into the hexosamine biosynthetic pathway, leading to protein O-GlcNAcylation. In this study, we demonstrate that ERRγ is O-GlcNAcylated by O-GlcNAc transferase in the fasted state. This stabilizes the protein by inhibiting proteasome-mediated protein degradation, increasing ERRγ recruitment to gluconeogenic gene promoters. Mass spectrometry identifies two serine residues (S317, S319) present in the ERRγ ligand-binding domain that are O-GlcNAcylated. Mutation of these residues destabilizes ERRγ protein and blocks the ability of ERRγ to induce gluconeogenesis in vivo. The impact of this pathway on gluconeogenesis in vivo was confirmed by the observation that decreasing the amount of O-GlcNAcylated ERRγ by overexpressing the deglycosylating enzyme O-GlcNAcase decreases ERRγ-dependent glucose production in fasted mice. We conclude that O-GlcNAcylation of ERRγ serves as a major signal to promote hepatic gluconeogenesis.
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Affiliation(s)
- Jagannath Misra
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Don-Kyu Kim
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Yoon Seok Jung
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Han Byeol Kim
- Department of Integrated OMICS for Biomedical Science, Yonsei University, Seoul, Republic of Korea
| | - Yong-Hoon Kim
- Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea
| | - Eun-Kyung Yoo
- Department of Internal Medicine, Kyungpook National University School of Medicine, Deagu, Republic of Korea
| | - Byung Gyu Kim
- Leading-edge Research Center for Drug Discovery and Development and Metabolic Disease, Kyungpook National University, Daegu, Korea
| | - Sunghoon Kim
- Medicinal Bioconvergence Research Center Department of Molecular Medicine and Biopharmaceutical Sciences Graduate School of Convergence Science and Technology College of Pharmacy, Seoul National University, Seoul, Korea
| | - In-Kyu Lee
- Department of Internal Medicine, Kyungpook National University School of Medicine, Deagu, Republic of Korea
| | - Robert A Harris
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine and the Roudebush VA Medical Center, Indianapolis, IN
| | - Jeong-Sun Kim
- Department of Chemistry and Institute of Basic Sciences, Chonnam National University, Gwangju, Republic of Korea
| | - Chul-Ho Lee
- Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea
| | - Jin Won Cho
- Department of Integrated OMICS for Biomedical Science, Yonsei University, Seoul, Republic of Korea
| | - Hueng-Sik Choi
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
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Byon CH, Heath JM, Chen Y. Redox signaling in cardiovascular pathophysiology: A focus on hydrogen peroxide and vascular smooth muscle cells. Redox Biol 2016; 9:244-253. [PMID: 27591403 PMCID: PMC5011184 DOI: 10.1016/j.redox.2016.08.015] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 08/23/2016] [Indexed: 02/07/2023] Open
Abstract
Oxidative stress represents excessive intracellular levels of reactive oxygen species (ROS), which plays a major role in the pathogenesis of cardiovascular disease. Besides having a critical impact on the development and progression of vascular pathologies including atherosclerosis and diabetic vasculopathy, oxidative stress also regulates physiological signaling processes. As a cell permeable ROS generated by cellular metabolism involved in intracellular signaling, hydrogen peroxide (H2O2) exerts tremendous impact on cardiovascular pathophysiology. Under pathological conditions, increased oxidase activities and/or impaired antioxidant systems results in uncontrolled production of ROS. In a pro-oxidant environment, vascular smooth muscle cells (VSMC) undergo phenotypic changes which can lead to the development of vascular dysfunction such as vascular inflammation and calcification. Investigations are ongoing to elucidate the mechanisms for cardiovascular disorders induced by oxidative stress. This review mainly focuses on the role of H2O2 in regulating physiological and pathological signals in VSMC.
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Affiliation(s)
| | - Jack M Heath
- Department of Pathology, Birmingham, AL 35294, USA
| | - Yabing Chen
- Department of Pathology, Birmingham, AL 35294, USA; University of Alabama at Birmingham, and the Birmingham Veterans Affairs Medical Center, Birmingham, AL 35294, USA.
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20
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Xie J, Liu X, Li Y, Liu Y, Su G. Validation of RT-qPCR reference genes and determination of Robo4 expression levels in human retinal endothelial cells under hypoxia and/or hyperglycemia. Gene 2016; 585:135-142. [PMID: 27041242 DOI: 10.1016/j.gene.2016.03.047] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/13/2016] [Accepted: 03/26/2016] [Indexed: 12/17/2022]
Abstract
Real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) has become the most common technique to investigate mRNA expression levels of target genes. In order to obtain accurate results, stable reference genes need to be selected for normalization in an experimental study. Human retinal endothelial cells (HREC) cultured in a hypoxic and hyperglycemic environment is a potential cell model to study diabetic retinopathy (DR), but the proper reference genes for RNA analysis have not yet been determined. In the present study, we evaluated the expression levels of 14 candidate housekeeping genes and selected the most suitable reference genes for RT-qPCR for HREC under hypoxic and/or hyperglycemic conditions. The results of the analyses using GeNorm, NormFinder, and BestKeeper software showed that a combination of TBP, PUM1, and ALAS1 was most suitable for this research. Based on these results, mRNA expression levels of Roundabout4 (Robo4) in HREC were determined. The RT-qPCR analysis showed that there was a significant increase in Robo4 expression under hyperglycemic conditions, while there was a decrease in expression under hypoxic and combined hypoxic and hyperglycemic conditions, suggesting that Robo4 might play different roles in various stages of DR.
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Affiliation(s)
- Jia'nan Xie
- Department of Ophthalmology, Second Hospital of Jilin University, 218 Ziqiang Street, Changchun, Jilin, 130021, China
| | - Xin Liu
- Department of Ophthalmology, Second Hospital of Jilin University, 218 Ziqiang Street, Changchun, Jilin, 130021, China
| | - Ying Li
- Department of Ophthalmology, Second Hospital of Jilin University, 218 Ziqiang Street, Changchun, Jilin, 130021, China
| | - Yang Liu
- Department of Ophthalmology, Second Hospital of Jilin University, 218 Ziqiang Street, Changchun, Jilin, 130021, China
| | - Guanfang Su
- Department of Ophthalmology, Second Hospital of Jilin University, 218 Ziqiang Street, Changchun, Jilin, 130021, China.
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El Khoury NB, Gratuze M, Petry F, Papon MA, Julien C, Marcouiller F, Morin F, Nicholls SB, Calon F, Hébert SS, Marette A, Planel E. Hypothermia mediates age-dependent increase of tau phosphorylation in db/db mice. Neurobiol Dis 2016; 88:55-65. [DOI: 10.1016/j.nbd.2016.01.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/26/2015] [Accepted: 01/07/2016] [Indexed: 11/16/2022] Open
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Liu GD, Xu C, Feng L, Wang F. The augmentation of O-GlcNAcylation reduces glyoxal-induced cell injury by attenuating oxidative stress in human retinal microvascular endothelial cells. Int J Mol Med 2015; 36:1019-27. [PMID: 26311324 PMCID: PMC4564096 DOI: 10.3892/ijmm.2015.2319] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Accepted: 08/11/2015] [Indexed: 12/13/2022] Open
Abstract
It has recently been reported that O-linked β-N-acetyl glucosamine (O-GlcNAc) modification (a simple intracellular serine (Ser)/threonine (Thr)-linked monosaccharide) in human retinal microvascular endothelial cells (HRECs) is related to diabetic retinopathy (DR). During O-GlcNAcylation, O-GlcNAc is added to Ser and Thr residues. As the generation of reactive oxygen species (ROS) is one of the characteristics of advanced glycation end product (AGE) injury, and the most important key pathogenic factor of DR, in the present study, we aimed to investigate the association between O-GlcNAcylation and ROS generation in order to ascertain whether O-GlcNAcylation mitigates cellular injury through the generation of ROS. For this purpose, HRECs were divided into 4 groups as follows: HRECs treated with normal glucose (5 mM), HRECs treated with glyoxal (500 µM), glyoxal-treated HRECs also treated with 200 µM PUGNAc, and glyoxal-treated HRECs infected with O-GlcNAc transferase (OGT) siRNA. We detected increased O-GlcNAc levels and increased ROS production in the glyoxal-treated HRECs. The cellular redox status was determined by cellular ROS staining and by measuring the expression levels of the antioxidant genes, superoxide dismutase (SOD) and glutathione peroxidase (GPX). While the augmentation of O-GlcNAcylation following treatment with PUGNAc significantly attenuated the production of ROS (p<0.01) and increased the expression levels of SOD and GPX, the reduction of O-GlcNAcylation following infection with OGT siRNA, exacerbated the production of ROS (p<0.01) and decreased the expression of antioxidant genes. The effects of O-GlcNAcylation on the viability of HRECs were significant (p<0.01), particularly in the hydrogen peroxide (H2O2)-treated HRECs. Treatment with PUGNAc reduced glyoxal-induced cell apoptosis and transfection with OGT siRNA increased HREC apoptosis; these results were confirmed by flow cytometry and by the assessment of mitochondrial membrane potential. The augmentation of O-GlcNAcylation exerted cytoprotective effects on the HRECs by reducing the generation of ROS, increasing the expression of antioxidant genes, preventing the dissipation of mitochondrial membrane potential and preventing HREC apoptosis. Therefore, it can be concluded that O-GlcNAcylation plays a role in the early developmental process of DR.
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Affiliation(s)
- Guo Dong Liu
- Department of Ophthalmology, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, P.R. China
| | - Chong Xu
- Department of Ophthalmology, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, P.R. China
| | - Le Feng
- Department of Ophthalmology, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, P.R. China
| | - Fang Wang
- Department of Ophthalmology, Shanghai Tenth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai 200072, P.R. China
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Coucha M, Elshaer SL, Eldahshan WS, Mysona BA, El-Remessy AB. Molecular mechanisms of diabetic retinopathy: potential therapeutic targets. Middle East Afr J Ophthalmol 2015; 22:135-44. [PMID: 25949069 PMCID: PMC4411608 DOI: 10.4103/0974-9233.154386] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Diabetic retinopathy (DR) is the leading cause of blindness in working-age adults in United States. Research indicates an association between oxidative stress and the development of diabetes complications. However, clinical trials with general antioxidants have failed to prove effective in diabetic patients. Mounting evidence from experimental studies that continue to elucidate the damaging effects of oxidative stress and inflammation in both vascular and neural retina suggest its critical role in the pathogenesis of DR. This review will outline the current management of DR as well as present potential experimental therapeutic interventions, focusing on molecules that link oxidative stress to inflammation to provide potential therapeutic targets for treatment or prevention of DR. Understanding the biochemical changes and the molecular events under diabetic conditions could provide new effective therapeutic tools to combat the disease.
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Affiliation(s)
- Maha Coucha
- Department of Clinical Pharmacy, Program in Clinical and Experimental Therapeutics, University of Georgia, Georgia, USA ; Culver Vision Discovery Institute, Georgia Regents University, Georgia, USA ; Research Service, Charlie Norwood VA Medical Center, Augusta 30912, Georgia, USA
| | - Sally L Elshaer
- Department of Clinical Pharmacy, Program in Clinical and Experimental Therapeutics, University of Georgia, Georgia, USA ; Culver Vision Discovery Institute, Georgia Regents University, Georgia, USA ; Research Service, Charlie Norwood VA Medical Center, Augusta 30912, Georgia, USA
| | - Wael S Eldahshan
- Department of Clinical Pharmacy, Program in Clinical and Experimental Therapeutics, University of Georgia, Georgia, USA ; Culver Vision Discovery Institute, Georgia Regents University, Georgia, USA ; Research Service, Charlie Norwood VA Medical Center, Augusta 30912, Georgia, USA
| | - Barbara A Mysona
- Department of Clinical Pharmacy, Program in Clinical and Experimental Therapeutics, University of Georgia, Georgia, USA ; Culver Vision Discovery Institute, Georgia Regents University, Georgia, USA ; Research Service, Charlie Norwood VA Medical Center, Augusta 30912, Georgia, USA
| | - Azza B El-Remessy
- Department of Clinical Pharmacy, Program in Clinical and Experimental Therapeutics, University of Georgia, Georgia, USA ; Culver Vision Discovery Institute, Georgia Regents University, Georgia, USA ; Research Service, Charlie Norwood VA Medical Center, Augusta 30912, Georgia, USA
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Kim SJ, Yoo WS, Choi M, Chung I, Yoo JM, Choi WS. Increased O-GlcNAcylation of NF-κB Enhances Retinal Ganglion Cell Death in Streptozotocin-induced Diabetic Retinopathy. Curr Eye Res 2015; 41:249-57. [PMID: 25835259 DOI: 10.3109/02713683.2015.1006372] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE Hyperglycemia results in increased flux through the hexoxamine biosynthetic pathway. We examined whether hyperglycemia increases O-GlcNAcylation in the diabetic retina and whether elevated O-GlcNAcylation of nuclear factor (NF)-κB increases apoptosis of retinal ganglion cells (RGCs) in diabetic retinopathy (DR). MATERIALS AND METHODS Diabetes was induced in C57BL/6 mice by five consecutive intraperitoneal injections of 55 mg/kg streptozotocin. All mice were killed 2 months after injections and expression levels of O-GlcNAcylated proteins, O-linked N-acetylglucosamine transferase (OGT), β-d-N-acetylglucosaminidase and NF-κB, and the extent of RGC death were examined. Immunoprecipitations were performed to investigate whether O-GlcNAcylation of NF-κB led to its activation and RGC death in DR. RESULTS The expression levels of O-GlcNAcylated proteins and OGT were markedly higher in diabetic retinas than in control retinas. OGT colocalized with NeuN, a RGC-specific marker, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells in the ganglion cell layer of diabetic retinas. The p65 subunit of NF-κB was O-GlcNAcylated and the level of O-GlcNAcylated p65 was higher in diabetic retinas than in control retinas. CONCLUSION The present data suggest that hyperglycemia increases O-GlcNAcylation in DR and that O-GlcNAcylation of the p65 subunit of NF-κB is involved in hyperglycemia-induced NF-κB activation and RGC death in DR.
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Affiliation(s)
- Seong-Jae Kim
- a Department of Ophthalmology , School of Medicine, Gyeongsang National University , Jinju , Korea .,b Institute of Health Science, Gyeongsang National University , Jinju , South Korea and
| | - Woong-Sun Yoo
- a Department of Ophthalmology , School of Medicine, Gyeongsang National University , Jinju , Korea
| | - Meeyoung Choi
- b Institute of Health Science, Gyeongsang National University , Jinju , South Korea and.,c Department of Anatomy and Neurobiology , School of Medicine, Gyeongsang National University , Jinju , Korea
| | - Inyoung Chung
- a Department of Ophthalmology , School of Medicine, Gyeongsang National University , Jinju , Korea .,b Institute of Health Science, Gyeongsang National University , Jinju , South Korea and
| | - Ji-Myong Yoo
- a Department of Ophthalmology , School of Medicine, Gyeongsang National University , Jinju , Korea .,b Institute of Health Science, Gyeongsang National University , Jinju , South Korea and
| | - Wan-Sung Choi
- b Institute of Health Science, Gyeongsang National University , Jinju , South Korea and.,c Department of Anatomy and Neurobiology , School of Medicine, Gyeongsang National University , Jinju , Korea
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25
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Zhou F, Zhang Y, Chen D, Su Z, Jin L, Wang L, Hu Z, Ke Z, Song Z. Potential role of Cyr61 induced degeneration of human Müller cells in diabetic retinopathy. PLoS One 2014; 9:e109418. [PMID: 25329584 PMCID: PMC4199605 DOI: 10.1371/journal.pone.0109418] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/04/2014] [Indexed: 01/07/2023] Open
Abstract
The degeneration of Müller cells has been recognized to involve in the pathogenesis of diabetic retinopathy. However, the mechanism is not yet clear. This study is to explore the potential role of Cyr61, a secreted signaling protein in extracellular matrix, in inducing human Müller cell degeneration in diabetic retinopathy (DR). Twenty patients with proliferative diabetic retinopathy (PDR) and twelve non-diabetic patients were recruited for this study. Vitreous fluid was collected during vitrectomy surgery for Cyr61 ELISA. Human Müller cell line MIO-M1 were cultured to be subconfluent, and then treated with glucose (0–20 mM) or Cyr61 (0–300 ng/ml). Cyr61 expression induced by increasing concentrations of glucose was evaluated by RT-qPCR and Western blot. Effects of Cyr61 on Müller cells viability, migration and apoptosis were observed by MTT assay, Transwell assay, and TUNEL assay. Vitreous Cyr61 levels were observed to be 8-fold higher in patients with PDR (3576.92±1574.58 pg/mL), compared with non-diabetic controls (436.14±130.69 pg/mL). Interestingly, the active PDR group was significantly higher than the quiescent PDR group (P<0.01). In retinal Müller cells culture, high glucose significantly and dose-dependently elevated Cyr61 expression at both mRNA and protein levels. Cyr61 at high concentrations dose-dependently inhibited the viability and migration of Müller cells. TUNEL assay further revealed that high concentration of Cyr61 significantly promoted the cell apoptosis. In conclusion, these findings demonstrated for the first time that the expression of Cyr61 was elevated by high glucose in Müller cells, and Cyr61 inhibited cell viability and migration while induced apoptosis, suggesting the potential role of Cyr61 in Müller cell degeneration. The elevated Cyr61 levels in vitreous fluid of PDR patients further support its role in diabetic retinopathy (DR).
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Affiliation(s)
- Fen Zhou
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yikui Zhang
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Ding Chen
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhitao Su
- Eye Center, Second Affiliated Hospital, College of Medicine, Zhejiang University, China
| | - Ling Jin
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Lei Wang
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhixiang Hu
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhisheng Ke
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zongming Song
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- * E-mail:
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