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Jollet M, Tramontana F, Jiang LQ, Borg ML, Savikj M, Kuefner MS, Massart J, de Castro Barbosa T, Mannerås-Holm L, Checa A, Pillon NJ, Chibalin AV, Björnholm M, Zierath JR. Diacylglycerol kinase delta overexpression improves glucose clearance and protects against the development of obesity. Metabolism 2024; 158:155939. [PMID: 38843995 DOI: 10.1016/j.metabol.2024.155939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2024] [Revised: 05/22/2024] [Accepted: 05/28/2024] [Indexed: 07/06/2024]
Abstract
BACKGROUND AND AIM Diacylglycerol kinase (DGK) isoforms catalyze an enzymatic reaction that removes diacylglycerol (DAG) and thereby terminates protein kinase C signaling by converting DAG to phosphatidic acid. DGKδ (type II isozyme) downregulation causes insulin resistance, metabolic inflexibility, and obesity. Here we determined whether DGKδ overexpression prevents these metabolic impairments. METHODS We generated a transgenic mouse model overexpressing human DGKδ2 under the myosin light chain promoter (DGKδ TG). We performed deep metabolic phenotyping of DGKδ TG mice and wild-type littermates fed chow or high-fat diet (HFD). Mice were also provided free access to running wheels to examine the effects of DGKδ overexpression on exercise-induced metabolic outcomes. RESULTS DGKδ TG mice were leaner than wild-type littermates, with improved glucose tolerance and increased skeletal muscle glycogen content. DGKδ TG mice were protected against HFD-induced glucose intolerance and obesity. DGKδ TG mice had reduced epididymal fat and enhanced lipolysis. Strikingly, DGKδ overexpression recapitulated the beneficial effects of exercise on metabolic outcomes. DGKδ overexpression and exercise had a synergistic effect on body weight reduction. Microarray analysis of skeletal muscle revealed common gene ontology signatures of exercise and DGKδ overexpression that were related to lipid storage, extracellular matrix, and glycerophospholipids biosynthesis pathways. CONCLUSION Overexpression of DGKδ induces adaptive changes in both skeletal muscle and adipose tissue, resulting in protection against HFD-induced obesity. DGKδ overexpression recapitulates exercise-induced adaptations on energy homeostasis and skeletal muscle gene expression profiles.
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Affiliation(s)
- Maxence Jollet
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Flavia Tramontana
- Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Lake Q Jiang
- Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Melissa L Borg
- Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Mladen Savikj
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Michael S Kuefner
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Julie Massart
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Thais de Castro Barbosa
- Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Louise Mannerås-Holm
- Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Antonio Checa
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Nicolas J Pillon
- Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Marie Björnholm
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Juleen R Zierath
- Department of Molecular Medicine and Surgery, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden; Department of Physiology and Pharmacology, Section for Integrative Physiology, Karolinska Institutet, Stockholm, Sweden.
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Rajlic S, Treede H, Münzel T, Daiber A, Duerr GD. Early Detection Is the Best Prevention-Characterization of Oxidative Stress in Diabetes Mellitus and Its Consequences on the Cardiovascular System. Cells 2023; 12:583. [PMID: 36831253 PMCID: PMC9954643 DOI: 10.3390/cells12040583] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/05/2023] [Accepted: 02/08/2023] [Indexed: 02/16/2023] Open
Abstract
Previous studies demonstrated an important role of oxidative stress in the pathogenesis of cardiovascular disease (CVD) in diabetic patients due to hyperglycemia. CVD remains the leading cause of premature death in the western world. Therefore, diabetes mellitus-associated oxidative stress and subsequent inflammation should be recognized at the earliest possible stage to start with the appropriate treatment before the onset of the cardiovascular sequelae such as arterial hypertension or coronary artery disease (CAD). The pathophysiology comprises increased reactive oxygen and nitrogen species (RONS) production by enzymatic and non-enzymatic sources, e.g., mitochondria, an uncoupled nitric oxide synthase, xanthine oxidase, and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). Considering that RONS originate from different cellular mechanisms in separate cellular compartments, adequate, sensitive, and compartment-specific methods for their quantification are crucial for early detection. In this review, we provide an overview of these methods with important information for early, appropriate, and effective treatment of these patients and their cardiovascular sequelae.
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Affiliation(s)
- Sanela Rajlic
- Department of Cardiothoracic and Vascular Surgery, University of Medicine Mainz, 55131 Mainz, Germany
| | - Hendrik Treede
- Department of Cardiothoracic and Vascular Surgery, University of Medicine Mainz, 55131 Mainz, Germany
| | - Thomas Münzel
- Center for Cardiology, Department of Cardiology, Molecular Cardiology, University Medical Center, 55131 Mainz, Germany
| | - Andreas Daiber
- Center for Cardiology, Department of Cardiology, Molecular Cardiology, University Medical Center, 55131 Mainz, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Rhine-Main, 55131 Mainz, Germany
| | - Georg Daniel Duerr
- Department of Cardiothoracic and Vascular Surgery, University of Medicine Mainz, 55131 Mainz, Germany
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Mima A. Mitochondria-targeted drugs for diabetic kidney disease. Heliyon 2022; 8:e08878. [PMID: 35265754 PMCID: PMC8899696 DOI: 10.1016/j.heliyon.2022.e08878] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/17/2022] [Accepted: 01/30/2022] [Indexed: 12/15/2022] Open
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Tun S, Spainhower CJ, Cottrill CL, Lakhani HV, Pillai SS, Dilip A, Chaudhry H, Shapiro JI, Sodhi K. Therapeutic Efficacy of Antioxidants in Ameliorating Obesity Phenotype and Associated Comorbidities. Front Pharmacol 2020; 11:1234. [PMID: 32903449 PMCID: PMC7438597 DOI: 10.3389/fphar.2020.01234] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 07/28/2020] [Indexed: 12/13/2022] Open
Abstract
Obesity has been a worldwide epidemic for decades. Despite the abundant increase in knowledge regarding the etiology and pathogenesis of obesity, the prevalence continues to rise with estimates predicting considerably higher numbers by the year 2030. Obesity is characterized by an abnormal lipid accumulation, however, the physiological consequences of obesity are far more concerning. The development of the obesity phenotype constitutes dramatic alterations in adipocytes, along with several other cellular mechanisms which causes substantial increase in systemic oxidative stress mediated by reactive oxygen species (ROS). These alterations promote a chronic state of inflammation in the body caused by the redox imbalance. Together, the systemic oxidative stress and chronic inflammation plays a vital role in maintaining the obese state and exacerbating onset of cardiovascular complications, Type II diabetes mellitus, dyslipidemia, non-alcoholic steatohepatitis, and other conditions where obesity has been linked as a significant risk factor. Because of the apparent role of oxidative stress in the pathogenesis of obesity, there has been a growing interest in attenuating the pro-oxidant state in obesity. Hence, this review aims to highlight the therapeutic role of antioxidants, agents that negate pro-oxidant state of cells, in ameliorating obesity and associated comorbidities. More specifically, this review will explore how various antioxidants target unique and diverse pathways to exhibit an antioxidant defense mechanism.
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Affiliation(s)
- Steven Tun
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Caleb James Spainhower
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Cameron Lee Cottrill
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Hari Vishal Lakhani
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Sneha S Pillai
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Anum Dilip
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Hibba Chaudhry
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Joseph I Shapiro
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
| | - Komal Sodhi
- Departments of Medicine, Surgery and Biomedical Sciences, Marshall University Joan C. Edwards School of Medicine, Huntington, WV, United States
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Ali SF, Woodman OL. Tocomin Restores Endothelium-Dependent Relaxation in the Diabetic Rat Aorta by Increasing NO Bioavailability and Improving the Expression of eNOS. Front Physiol 2019; 10:186. [PMID: 30886586 PMCID: PMC6409301 DOI: 10.3389/fphys.2019.00186] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 02/14/2019] [Indexed: 12/15/2022] Open
Abstract
We aimed to determine whether tocomin, an extract from palm oil that has a high tocotrienol content, was able to prevent diabetes-induced endothelial dysfunction. To induce type 1 diabetes streptozotocin (50 mg/kg) was injected into the tail vein of Wistar rats. Six weeks later the diabetic rats, and normal rats injected with citrate buffer, commenced treatment with tocomin (40 mg/kg/day sc) or its vehicle (peanut oil) for a further 4 weeks. Aortae isolated from diabetic rats had impaired acetylcholine (ACh)-induced endothelium-dependent relaxation compared to normal rat aortae but there was no change in endothelium-independent relaxation in response to sodium nitroprusside. By contrast, responses to ACh in aortae from diabetic rats treated with tocomin were not different to normal rats. In addition to impaired endothelium-dependent relaxation the diabetic aortae had increased expression of the NADPH oxidase Nox2 subunit, increased generation of superoxide and decreased expression of eNOS and all of these effects were prevented by tocomin treatment. Tocomin did not affect plasma glucose levels. The impaired response to ACh in vitro was maintained in the presence of TRAM-34 and apamin, selective inhibitors of calcium-activated potassium (K Ca ) channels, indicating diabetes impaired the contribution of NO to endothelium-dependent relaxation. By contrast, neither diabetes nor tocomin treatment influenced EDH-type relaxation as, in the presence of L-NNA, an inhibitor of eNOS, and ODQ, to inhibit soluble guanylate cyclase, responses to ACh were similar in all treatment groups. Thus tocomin treatment improves NO mediated endothelium dependent relaxation in aortae from diabetic rats associated with a decrease in vascular oxidant stress but without affecting hyperglycaemia.
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6
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Mulberry leaf tea alleviates diabetic nephropathy by inhibiting PKC signaling and modulating intestinal flora. J Funct Foods 2018. [DOI: 10.1016/j.jff.2018.04.040] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
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Nascimento EBM, Mannerås-Holm L, Chibalin AV, Björnholm M, Zierath JR. Diacylglycerol kinase α deficiency alters inflammation markers in adipose tissue in response to a high-fat diet. J Lipid Res 2017; 59:273-282. [PMID: 29233919 DOI: 10.1194/jlr.m079517] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 12/06/2017] [Indexed: 12/20/2022] Open
Abstract
Conversion of diacylglycerol to phosphatidic acid is mediated by diacylglycerol kinases (DGKs), with DGKα specifically linked to adaptive immune responses. We determined the role of DGKα in obesity and inflammatory responses to a high-fat diet (HFD). DGKα KO and WT littermates were either a) chow-fed, b) HFD-fed for 12 weeks (Long-Term HFD), or c) HFD-fed for 3 days (Acute HFD). Body weight/composition, oxygen consumption, food intake, and glucose tolerance was unaltered between chow-fed DGKα KO and WT mice. Insulin concentration during the intraperitoneal glucose tolerance (IPGT) test was elevated in chow-fed DGKα KO mice, suggesting mild insulin resistance. Insulin concentration during the IPGT test was reduced in Long-Term HFD-fed DGKα KO mice, suggesting a mild enhancement in insulin sensitivity. Acute HFD increased hormone sensitive lipase protein abundance and altered expression of interleukin 1β mRNA, an inflammatory marker in perigonadal adipose tissue of DGKα KO mice. In conclusion, DGKα ablation is associated with mild alterations in insulin sensitivity. However, DGKα is dispensable for whole body insulin-mediated glucose uptake, hepatic glucose production, and energy homeostasis. Our results suggest DGKα aids in modulating the early immune response of adipose tissue following an acute exposure to HFD, possibly through modulation of acute T-cell action.
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Affiliation(s)
| | - Louise Mannerås-Holm
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Marie Björnholm
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Juleen R Zierath
- Department of Physiology and Pharmacology Karolinska Institutet, Stockholm, Sweden .,Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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Guardiola-Serrano F, Beteta-Göbel R, Rodríguez-Lorca R, Ibarguren M, López DJ, Terés S, Alvarez R, Alonso-Sande M, Busquets X, Escribá PV. The Novel Anticancer Drug Hydroxytriolein Inhibits Lung Cancer Cell Proliferation via a Protein Kinase Cα- and Extracellular Signal-Regulated Kinase 1/2-Dependent Mechanism. J Pharmacol Exp Ther 2015; 354:213-24. [PMID: 26065701 DOI: 10.1124/jpet.114.222281] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 06/09/2015] [Indexed: 03/08/2025] Open
Abstract
Membrane lipid therapy is a novel approach to rationally design or discover therapeutic molecules that target membrane lipids. This strategy has been used to design synthetic fatty acid analogs that are currently under study in clinical trials for the treatment of cancer. In this context, and with the aim of controlling tumor cell growth, we have designed and synthesized a hydroxylated analog of triolein, hydroxytriolein (HTO). Both triolein and HTO regulate the biophysical properties of model membranes, and they inhibit the growth of non-small-cell lung cancer (NSCLC) cell lines in vitro. The molecular mechanism underlying the antiproliferative effect of HTO involves regulation of the lipid membrane structure, protein kinase C-α and extracellular signal-regulated kinase activation, the production of reactive oxygen species, and autophagy. In vivo studies on a mouse model of NSCLC showed that HTO, but not triolein, impairs tumor growth, which could be associated with the relative resistance of HTO to enzymatic degradation. The data presented explain in part why olive oil (whose main component is the triacylglycerol triolein) is preventive but not therapeutic, and they demonstrate a potent effect of HTO against cancer. HTO shows a good safety profile, it can be administered orally, and it does not induce nontumor cell (fibroblast) death in vitro or side effects in mice, reflecting its specificity for cancer cells. For these reasons, HTO is a good candidate as a drug to combat cancer that acts by regulating lipid structure and function in the cancer cell membrane.
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Affiliation(s)
- Francisca Guardiola-Serrano
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.).
| | - Roberto Beteta-Göbel
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - Raquel Rodríguez-Lorca
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - Maitane Ibarguren
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - David J López
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - Silvia Terés
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - Rafael Alvarez
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - María Alonso-Sande
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - Xavier Busquets
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
| | - Pablo V Escribá
- Laboratory of Molecular Cell Biomedicine, Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain (F.G.-S., R.B.-G., R.R.-L., M.I., D.J.L., S.T., R.A., M.A.-S., X.B., P.V.E.); and Lipopharma Therapeutics S.L., Palma de Mallorca, Spain (M.I., D.J.L., S.T., R.A., M.A.-S.)
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Das L, Dey G, Chakraborty A. Investigation of the structures, potential energy surface, transition states and vibrational frequencies of a vitamin E precursor-chroman in S0 and S1 states: DFT based computational study. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2014.10.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Vetri F, Chavez R, Xu HL, Paisansathan C, Pelligrino DA. Complex modulation of the expression of PKC isoforms in the rat brain during chronic type 1 diabetes mellitus. Brain Res 2012; 1490:202-9. [PMID: 23103504 DOI: 10.1016/j.brainres.2012.10.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 10/06/2012] [Accepted: 10/16/2012] [Indexed: 10/27/2022]
Abstract
We previously demonstrated that chronic hyperglycemia has a detrimental influence on neurovascular coupling in the brain-an effect linked to an alteration in the protein kinase C (PKC)-mediated phosphorylation pattern. Moreover, the activity of PKC was increased, in diabetic rat brain, in a tissue fraction composed primarily of the superficial glia limitans and pial vessels, but trended toward a decrease in cerebral cortical gray matter. However, that study did not examine the expression patterns of PKC isoforms in the rat brain. Thus, in a rat model of streptozotocin (STZ)-induced chronic type 1 diabetes mellitus (T1DM), and in non-diabetic (ND) controls, two hypotheses were addressed. First, chronic T1DM is accompanied by changes in the expression of PKC-α, βII, γ, δ, and ε Second, those changes differ when comparing cerebral cortex and glio-pial tissue. In addition, we analyzed the expression of a form of PKC-γ, phosphorylated on threonine 514 (pT514-PKC-γ), as well as the receptor for activated C kinase 1 (RACK1). The expression pattern of different PKC isoforms was altered in a complex and tissue-specific manner during chronic hyperglycemia. Notably, in the gray matter, PKC-α expression significantly decreased, while pT514-PKC-γ expression increased. However, PKC-βII, -γ, -δ, -ε, and RACK1 expressions did not change. Conversely, in glio-pial tissue, PKC-α and RACK1 were upregulated, whereas PKC-γ, pT514-PKC-γ, and PKC-ε were downregulated. PKC-βII, and PKC-δ, were unchanged. These findings suggest that the PKC activity increase previously seen in the glio-pial tissue of diabetic rats may be due to the selective upregulation of PKC-α, and ultimately lead to the impairment of neurovascular coupling.
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Affiliation(s)
- Francesco Vetri
- Neuroanesthesia Research Laboratory, Department of Anesthesiology, University of Illinois, Chicago, IL 60612, USA.
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11
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Fox TE, Young MM, Pedersen MM, Han X, Gardner TW, Kester M. Diabetes diminishes phosphatidic acid in the retina: a putative mediator for reduced mTOR signaling and increased neuronal cell death. Invest Ophthalmol Vis Sci 2012; 53:7257-67. [PMID: 22952117 DOI: 10.1167/iovs.11-7626] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
PURPOSE We demonstrated previously that pro-survival insulin receptor, PI3K-Akt, and p70 S6K signaling is diminished in models of diabetic retinopathy. As mammalian target of rapamycin (mTOR), an upstream activator of p70 S6Kinase is, in part, regulated by lipid-derived second messengers, such as phosphatidic acid (PA), we sought to determine if diminished mTOR/p70 S6Kinase signaling in diabetic retinas may reflect diminished PA levels. METHODS Alterations in PA mass from retinas of control and streptozotocin-induced diabetic rats were determined by mass spectrometry. The biochemical and biophysical mechanisms underlying the actions of PA on insulin-activated mTOR/p70 S6Kinase signaling were determined using R28 retinal neuronal cells. RESULTS We demonstrate a significant decrease in PA in R28 retinal neuronal cells exposed to hyperglycemia as well as in streptozotocin-induced diabetic rat retinas. Exogenous PA augmented insulin-induced protection from interleukin-1β-induced apoptosis. Moreover, exogenous PA and insulin cooperatively activated mTOR survival pathways in R28 neuronal cultures. Exogenous PA colocalized with activated mTOR/p70 S6kinase signaling elements within lipid microdomains. The biochemical consequences of this biophysical mechanism is reflected by differential phosphorylation of tuberin at threonine 1462 and serine 1798, respectively, by PA and insulin, which reduce this suppressor of mTOR/S6Kinase signaling within lipid microdomains. CONCLUSIONS These results identify PA-enriched microdomains as a putative lipid-based signaling element responsible for mTOR-dependent retinal neuronal survival. Moreover, diabetic retinal neuronal apoptosis may reflect diminished PA mass. Elevating PA concentrations and restoring mTOR signaling may be an effective therapeutic modality to reduce neuronal cell death in diabetic retinopathy.
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Affiliation(s)
- Todd E Fox
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA 17033, USA
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Breviscapine inhibits high glucose-induced proliferation and migration of cultured vascular smooth muscle cells of rats via suppressing the ERK1/2 MAPK signaling pathway. Acta Pharmacol Sin 2012; 33:606-14. [PMID: 22465949 DOI: 10.1038/aps.2012.6] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
AIM To investigate the influences of breviscapine, a flavonoid extracted from Erigeron breviscapus, on the proliferation and migration of vascular smooth muscle cells (VSMCs) cultured in a high glucose medium and the underlying mechanisms. METHODS VSMCs were isolated from thoracic aortas of male Sprague-Dawley rats and cultured in vitro. Cell proliferation was evaluated using Counting Kit-8 cell viability assay. Cell migration was evaluated using transwell migration assay and in vitro scratch assay. The expression and activity of protein kinase C-β2 (PKC-β2), extracellular signal-regulated kinase 1/2 (ERK1/2), p38 mitogen-activated protein kinase (p38), and JNK mitogen-activated protein kinase (JNK) were measured with Western blotting. RESULTS Exposure of VSMCs to a high glucose (25 mmol/L) medium significantly increased the proliferation and migration potential as compared to the control group. Pretreatment with breviscapine (65 μmol/L and 108 μmol/L) attenuated high glucose-enhanced proliferation and migration of VSMCs. Exposure of VSMCs to the high glucose medium activated both the PKC-β2 and ERK1/2 MAPK, but not the p38 and JNK MAPK. Pretreatment with breviscapine (65 μmol/L and 108 μmol/L) blocked high glucose-induced increase of the ERK1/2 activity, but not that of the PKC-β2 activity. CONCLUSION Our study demonstrated that breviscapine ameliorates high glucose-induced proliferation and migration of VSMCs via inhibiting ERK1/2 MAPK signaling.
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Liu YM, Wang X, Nawaz A, Kong ZH, Hong Y, Wang CH, Zhang JJ. Wogonin ameliorates lipotoxicity-induced apoptosis of cultured vascular smooth muscle cells via interfering with DAG-PKC pathway. Acta Pharmacol Sin 2011; 32:1475-1482. [PMID: 21986573 PMCID: PMC4010212 DOI: 10.1038/aps.2011.120] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Accepted: 07/25/2011] [Indexed: 02/08/2023]
Abstract
AIM To investigate the effects of wogonin (5,7-dihydroxy-8-methoxyflavone) extracted from Scutellaria baicalensis Georgi (S baicalensis) on lipotoxicity-induced apoptosis of vascular smooth muscle cells (VSMCs) and the underlying mechanisms. METHODS Cultured VSMCs were used. Apoptosis of VSMCs was induced by palmitate (0.75 mmol/L), and detected using TUNEL assay. The expression levels of protein and phosphorylated protein were measured using Western blot analysis. RESULTS Treatment of VSMCs with wogonin (10, 25 and 50 μmol/L) significantly attenuated the apoptosis and endoplasmic reticulum (ER) stress induced by palmitate in concentration- and time-dependent manners. Wogonin (50 μmol/L) decreased palmitate-induced reactive oxygen species (ROS) generation. The ER stress inhibitor 4-phenyl butyric acid (5 mmol/L) significantly decreased palmitate-induced apoptotic cells, and occluded the anti-apoptotic effect of wogonin (25 μmol/L). Wogonin (10, 25 and 50 μmol/L) significantly reduced the intracellular diacylglycerol (DAG) accumulation and expression levels of phosphorylated PKCs in palmitate-treated VSMCs. CONCLUSION Our results suggest that wogonin inhibits lipotoxicity-induced apoptosis of VSMCs via suppressing the intracellular DAG accumulation and subsequent inhibition of PKC phosphorylation. Wogonin has therapeutic potential for the prevention and treatment of atherosclerosis.
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Affiliation(s)
- Yu-min Liu
- Department of Neurology, Zhongnan Hospital of Wuhan University, Wuhan 430071, China
| | - Xiong Wang
- Department of Pathophysiology, Hubei University of Medicine, Shiyan 442000, China
| | - Ahmed Nawaz
- Department of Pathophysiology, Wuhan University School of Medicine, Wuhan 430070, China
| | - Zhao-hong Kong
- Department of Neurology, Zhongnan Hospital of Wuhan University, Wuhan 430071, China
| | - Yan Hong
- Department of Neurology, Zhongnan Hospital of Wuhan University, Wuhan 430071, China
| | - Chang-hua Wang
- Department of Pathophysiology, Wuhan University School of Medicine, Wuhan 430070, China
| | - Jun-jian Zhang
- Department of Neurology, Zhongnan Hospital of Wuhan University, Wuhan 430071, China
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14
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Macrophage fusion and multinucleated giant cells of inflammation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 713:97-111. [PMID: 21432016 DOI: 10.1007/978-94-007-0763-4_7] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Macrophages undergo fusion with other macrophages to form the hallmark multinucleated giant cells of chronic inflammation. However, neither the existence of distinct morphological types of giant cells, the signaling pathways that induce their formation, the molecular mechanism(s) of macrophage fusion, nor the significance of macrophage multinucleation at chronic inflammatory sites are well understood. Our efforts have been focused on these unknowns, particularly as they relate to the foreign body-type giant cells that form on implanted biomaterials and biomedical devices. We have pursued the discoveries of human macrophage fusion factors (interleukin-4, interleukin-13, α-tocopherol) with emphasis on foreign body giant cells, and identified adhesion receptors and signaling intermediates, as well as an adhesion protein substrate (vitronectin) that supports macrophage fusion. Studies on the molecular mechanism of macrophage fusion have revealed it to be a mannose receptor-mediated phagocytic process with participation of the endoplasmic reticulum. Further phenotypic and functional investigations will foster new perspectives on these remarkable multinucleated cells and their physiological significances in multiple inflammatory processes.
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15
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Muharis SP, Top AGM, Murugan D, Mustafa MR. Palm oil tocotrienol fractions restore endothelium dependent relaxation in aortic rings of streptozotocin-induced diabetic and spontaneously hypertensive rats. Nutr Res 2010; 30:209-16. [DOI: 10.1016/j.nutres.2010.03.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 03/22/2010] [Accepted: 03/24/2010] [Indexed: 02/06/2023]
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16
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17
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Brigelius-Flohé R. Vitamin E: the shrew waiting to be tamed. Free Radic Biol Med 2009; 46:543-54. [PMID: 19133328 DOI: 10.1016/j.freeradbiomed.2008.12.007] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Revised: 11/28/2008] [Accepted: 12/03/2008] [Indexed: 12/16/2022]
Abstract
Vitamin E is the last of all vitamins whose essentiality is not yet understood. Its widely accepted role as a lipophilic antioxidant has been questioned, since proof of its in vivo relevance remained scarce. The influence of vitamin E on biomarkers of oxidative stress in vivo is inconsistent and metabolites of vitamin E having reacted as an antioxidant are hardly detectable. Novel functions of vitamin E include the regulation of enzymes, most of which are membrane bound or activated by membrane recruitment. Also, expression of genes responds to vitamin E. The search for a transcription factor common to all regulated genes failed so far and a receptor that specifically binds vitamin E has not yet been identified. According to microarray data, pathways preferentially affected by the vitamin E status are the inflammatory response and cellular traffic. A role of vitamin E in cellular trafficking could best explain the neurological symptoms seen in vitamin E deficiency. Emerging knowledge on vitamin E is compiled here with the perspective to unravel the molecular mechanisms that could more likely explain the essentiality of the vitamin than its ability to scavenge free radicals.
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Affiliation(s)
- Regina Brigelius-Flohé
- German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Biochemistry of Micronutrients, Nuthetal, Germany.
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18
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19
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Atkinson J, Epand RF, Epand RM. Tocopherols and tocotrienols in membranes: a critical review. Free Radic Biol Med 2008; 44:739-64. [PMID: 18160049 DOI: 10.1016/j.freeradbiomed.2007.11.010] [Citation(s) in RCA: 197] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 11/09/2007] [Accepted: 11/12/2007] [Indexed: 12/14/2022]
Abstract
The familiar role of tocols (tocopherols and tocotrienols) as lipid-soluble chain-terminating inhibitors of lipid peroxidation is currently in the midst of a reinterpretation. New biological activities have been described for tocols that apparently are not dependent on their well-established antioxidant behaviour. These activities could well be real, but there remain large gaps in our understanding of the behaviour of tocols in membranes, especially when it comes to the alpha-, beta-, gamma-, delta-chroman methylation patterns and the seemingly special nature of tocotrienols. It is inappropriate to make conclusions and develop models based on in vivo (or cell culture) results with reference to in vitro measurements of antioxidant activity. When present in biological membranes, tocols will experience a large variation in the local composition of phospholipids and the presence of neutral lipids such as cholesterol, both of which would be expected to change the efficiency of antioxidant action. It is likely that tocols are not homogeneously dispersed in a membrane, but it is still not known whether any specific combination of lipid head group and acyl chains are conferred special protection from peroxidation, nor do we currently appreciate the structural role that tocols play in membranes. Tocols may enhance curvature stress or counteract similar stresses generated by other lipids such as lysolipids. This review will outline what is known about the location and behaviour of tocols in phospholipid bilayers. We will draw mainly from the biophysical literature, but will attempt to extend the discussion to biologically relevant phenomena when appropriate. We hope that it will assist researchers when designing new experiments and when critically assessing the results, in turn providing a more thorough understanding of the biochemistry of tocols.
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Affiliation(s)
- Jeffrey Atkinson
- Department of Chemistry and Centre for Biotechnology, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada.
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20
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Chibalin AV, Leng Y, Vieira E, Krook A, Björnholm M, Long YC, Kotova O, Zhong Z, Sakane F, Steiler T, Nylén C, Wang J, Laakso M, Topham MK, Gilbert M, Wallberg-Henriksson H, Zierath JR. Downregulation of Diacylglycerol Kinase Delta Contributes to Hyperglycemia-Induced Insulin Resistance. Cell 2008; 132:375-86. [DOI: 10.1016/j.cell.2007.12.035] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 10/04/2007] [Accepted: 12/10/2007] [Indexed: 01/12/2023]
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21
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Bohlen HG. Microvascular Consequences of Obesity and Diabetes. Microcirculation 2008. [DOI: 10.1016/b978-0-12-374530-9.00021-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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22
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Engin KN, Engin G, Kucuksahin H, Oncu M, Engin G, Guvener B. Clinical evaluation of the neuroprotective effect of alpha-tocopherol against glaucomatous damage. Eur J Ophthalmol 2007; 17:528-33. [PMID: 17671926 DOI: 10.1177/112067210701700408] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE To evaluate the vasoregulatory effect of antioxidant alpha-tocopherol on retina via protein kinase C pathway. METHODS Thirty glaucomatous patients (60 eyes) were included in this study. The patients were divided into three groups. For patients in Group A, tocopherol was not supplemented in their therapy. Patients in Groups B and C received 300 and 600 mg/day of oral alpha-tocopherol acetate, respectively. The ultimate blood tocopherol levels were confirmed via high-performance liquid chromatography assay. Progression of the disease for each subject was monitored via visual field measurements and color Doppler imaging of ophthalmic and posterior ciliary arteries at the beginning and at the 6th and 12th months of this study. RESULTS The average differences between the pulsatility indexes (PI) and resistivity indexes (RI) of both ophthalmic arteries (OA) and posterior ciliary arteries (PCA) of Groups B and C were significantly lower than those of Group A at months 6 and 12. In trial groups, RI decreases observed in PCAs at months 6 and 12 and PI decreases observed in OAs at the 6th month were statistically significant. Differences of mean deviations with visual fields in Groups B and C were highly significantly lower than that of Group A. CONCLUSIONS Alpha-tocopherol deserves attention beyond its antioxidant properties for protecting retina from glaucomatous damage.
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Affiliation(s)
- K N Engin
- Department of Ophthalmology, V. Gureba Education Hospital, Findikzade, 34270 Istanbul, Turkey.
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23
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McCarty MF. Adjuvant strategies for prevention of glomerulosclerosis. Med Hypotheses 2006; 67:1277-96. [PMID: 16828231 DOI: 10.1016/j.mehy.2004.11.048] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Accepted: 11/29/2004] [Indexed: 12/23/2022]
Abstract
The glomerulosclerosis which frequently complicates diabetes and severe hypertension is mediated primarily by increased mesangial production and activation of transforming growth factor-beta (TGF-beta), which acts on mesangial cells to boost their production of matrix proteins while suppressing extracellular proteolytic activity. Hyperglycemia and glomerular hypertension work in various complementary ways to stimulate superoxide production via NADPH oxidase in mesangial cells; the resulting oxidant stress results in the induction and activation of TFG-beta. Nitric oxide, generated by glomerular capillaries and by mesangial cells themselves, functions physiologically to oppose mesangial TGF-beta overproduction; however, NO bioactivity is compromised by oxidant stress. In addition to low-protein diets and drugs that suppress angiotensin II activity, a variety of other agents and measures may have potential for impeding the process of glomerulosclerosis. These include vitamin E, which blunts the rise in mesangial diacylglycerol levels induced by hyperglycemia; statins and (possibly) policosanol, which down-regulate NADPH oxidase activity by diminishing isoprenylation of Rac1; lipoic acid, whose potent antioxidant activity antagonizes the impact of oxidant stress on TGF-beta expression; pyridoxamine, which inhibits production of advanced glycation endproducts; arginine, high-dose folate, vitamin C, and salt restriction, which may support glomerular production of nitric oxide; and estrogen and soy isoflavones, which may induce nitric oxide synthase in glomerular capillaries while also interfering with TGF-beta signaling. Further research along these lines may enable the development of complex nutraceuticals which have important clinical utility for controlling and preventing glomerulosclerosis and renal failure. Most of these measures may likewise reduce risk for left ventricular hypertrophy in hypertensives, inasmuch as the signaling mechanisms which mediate this disorder appear similar to those involved in glomerulosclerosis.
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Affiliation(s)
- Mark F McCarty
- NutriGuard Research, 1051 Hermes Ave., Encinitas, CA 92024, USA.
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24
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Gallo A, Ceolotto G, Pinton P, Iori E, Murphy E, Rutter GA, Rizzuto R, Semplicini A, Avogaro A. Metformin prevents glucose-induced protein kinase C-beta2 activation in human umbilical vein endothelial cells through an antioxidant mechanism. Diabetes 2005; 54:1123-31. [PMID: 15793252 DOI: 10.2337/diabetes.54.4.1123] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Hyperglycemia determines the vascular complications of diabetes through different mechanisms: one of these is excessive activation of the isoform beta2 of protein kinase C (PKC-beta2). Metformin, a widely used antidiabetic agent, is associated with decreased cardiovascular mortality in obese type 2 diabetic patients. Therefore, we assessed the role of metformin in glucose-induced activation of PKC-beta2 and determined the mechanism of its effect in human umbilical venous endothelial cells grown to either normo- (5 mmol/l) or hyperglycemia (10 mmol/l) and moderately and acutely exposed to 25 mmol/l glucose. We studied PKC-beta2 activation by developing adenovirally expressed chimeras encoding fusion protein between green fluorescent protein (GFP) and conventional beta2 isoform (PKC-beta2-GFP). Glucose (25 mmol/l) induced the translocation of PKC-beta2-GFP from the cytosol to the membrane in cells grown to hyperglycemia but not in those grown in normal glucose medium. Metformin (20 micromol/l) prevented hyperglycemia-induced PKC-beta2-GFP translocation. We also assessed oxidative stress under the same conditions with a 4-((9-acridine-carbonyl)amino)-2,2,6,6-tetramethylpiperidin-oxyl,free radical (TEMPO-9-AC) fluorescent probe. We observed significantly increased radical oxygen species production in cells grown in hyperglycemia medium, and this effect was abolished by metformin. We show that in endothelial cells, metformin inhibits hyperglycemia-induced PKC-beta2 translocation because of a direct antioxidant effect. Our data substantiate the findings of previous large intervention studies on the beneficial effect of this drug in type 2 diabetic patients.
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Affiliation(s)
- Alessandra Gallo
- Department of Clinical and Experimental Medicine, University of Padova, Padova, Italy
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25
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Fukunaga-Takenaka R, Shirai Y, Yagi K, Adachi N, Sakai N, Merino E, Merida I, Saito N. Importance of chroman ring and tyrosine phosphorylation in the subtype-specific translocation and activation of diacylglycerol kinase α by d-α-tocopherol. Genes Cells 2005; 10:311-9. [PMID: 15773894 DOI: 10.1111/j.1365-2443.2005.00842.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Diacylglycerol kinase (DGK) has been suggested to be a pharmacological target of D-alpha-tocopherol for diabetic renal dysfunctions. However, the DGK subtypes involved in the D-alpha-tocopherol-induced improvement of diabetic renal dysfunctions and the activation mechanisms of DGK by D-alpha-tocopherol are still unknown. Therefore, using GFP-tagged DGKalpha, beta, gamma, epsilon and zeta, we analyzed their response to D-alpha-tocopherol and its derivatives. Only DGKalpha was translocated from the cytoplasm to the plasma membrane with elevation of kinase activity. In addition, troglitazone and trolox possessing 'chroman ring' similarly to D-alpha-tocopherol, induced the subtype-specific translocation of DGKalpha. Furthermore, the translocation of DGKalpha was abolished by pretreatment with tyrosine kinase inhibitors or by mutation on Tyr-334 of the kinase (YF mutant). D-alpha-tocopheryl succinate enhanced the Src-mediated tyrosine phosphorylation of wild-type DGKalpha but the same reagent did not enhance that of the YF mutant. These results demonstrate that tyrosine phosphorylation on Tyr-334 and chroman ring are important for the D-alpha-tocopherol-induced translocation of DGKalpha.
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Affiliation(s)
- Rika Fukunaga-Takenaka
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Nadaku, Kobe 657-8501, Japan
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26
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Campbell M, Trimble ER. Modification of PI3K- and MAPK-Dependent Chemotaxis in Aortic Vascular Smooth Muscle Cells by Protein Kinase C
βII. Circ Res 2005; 96:197-206. [PMID: 15591231 DOI: 10.1161/01.res.0000152966.88353.9d] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Hyperglycemia increases expression of platelet-derived growth factor (PDGF)-β receptor and potentiates chemotaxis to PDGF-BB in human aortic vascular smooth muscle cells (VSMCs) via PI3K and ERK/MAPK signaling pathways. The purpose of this study was to determine whether increased activation of protein kinase C (PKC) isoforms had a modulatory effect on the PI3K and ERK/MAPK pathways, control of cell adhesiveness, and movement. All known PKC isoforms were assessed but only PKC
α
and PKC
βII
levels were increased in 25 mmol/L glucose. However, only PKC
βII
inhibition affected (decreased) PI3K pathway and MAPK pathway activities and inhibited PDGF-β receptor upregulation in raised glucose, and specific MAPK inhibition was required to completely block the effect of glucose. In raised glucose conditions, activity of the ERK/MAPK pathway, PI3K pathway, and PKC
βII
were all sensitive to aldose reductase inhibition. Chemotaxis to PDGF-BB (360 pmol/L), absent in 5 mmol/L glucose, was present in raised glucose and could be blocked by PKC
βII
inhibition. Formation of lamellipodia was dependent on PI3K activation and filopodia on MAPK activation; both lamellipodia and filopodia were eliminated when PKC
βII
was inhibited. FAK phosphorylation and cell adhesion were reduced by PI3K inhibition, and although MAPK inhibition prevented chemotaxis, it did not affect FAK phosphorylation or cell adhesiveness. In conclusion, chemotaxis to PDGF-BB in 25 mmol/L glucose is PKC
βII
-dependent and requires activation of both the PI3K and MAPK pathways. Changes in cell adhesion and migration speed are mediated mainly through the PI3K pathway.
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Affiliation(s)
- Malcolm Campbell
- Department of Clinical Biochemistry and Metabolic Medicine, Queen's University Belfast, Institute of Clinical Science, Royal Victoria Hospital, Grosvenor Rd, Belfast BT12 6BJ, UK.
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27
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Muñoz FJ, Solé M, Coma M. The protective role of vitamin E in vascular amyloid beta-mediated damage. Subcell Biochem 2005; 38:147-65. [PMID: 15709477 DOI: 10.1007/0-387-23226-5_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
Amyloid beta peptide (Abeta) accumulation produces the senile plaques in the brain parenchyma characteristic of Alzheimer's Disease (AD) and the vascular deposits of Cerebral Amyloid Angiopathy (CAA). Oxidative stress is directly involved in Abeta-mediated cytotoxicity and antioxidants have been reported as cytoprotective in AD and CAA. Vitamin E has antioxidant and hydrophobic properties that render this molecule as the main antioxidant present in biological membranes, preventing lipid peroxidation, carbonyl formation and inducing intracellular modulation of cell signalling pathways. Accordingly, vascular damage produced by Abeta and prooxidant agents can be decreased or prevented by vitamin E. The protective effect of vitamin E against Abeta cytotoxicity in vascular cells in comparison to the neuronal system is reviewed in this chapter.
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Affiliation(s)
- Francisco José Muñoz
- Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, 08003-Barcelona, Spain
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28
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Asbun J, Manso AM, Villarreal FJ. Profibrotic influence of high glucose concentration on cardiac fibroblast functions: effects of losartan and vitamin E. Am J Physiol Heart Circ Physiol 2005; 288:H227-34. [PMID: 15345478 DOI: 10.1152/ajpheart.00340.2004] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Long-standing diabetes can result in the development of cardiomyopathy, which can be accompanied by myocardial fibrosis. Although exposure of cultured kidney and skin fibroblasts to high glucose (HG) concentration is known to increase collagen synthesis, little is known about cardiac fibroblasts (CFs). Therefore, we determined the influence of HG conditions on CF functions and the effects of losartan and vitamin E in these responses. We cultured rat CFs in either normal glucose (NG; 5.5 mM) or HG (25 mM) media and assessed changes in protein and collagen synthesis, matrix metalloproteinase (MMP) activity, and levels of mRNA for ANG II type 1 (AT1) receptors. Results indicate that HG-level CFs synthesized more protein and collagen, and these effects were not due to changes in osmotic pressure. The addition of ANG II stimulated protein and collagen synthesis in NG-concentration but not HG-concentration CFs. Interestingly, losartan pretreatment blocked the HG- or ANG II-induced increases in both protein and collagen synthesis. HG or ANG II decreased total MMP activity. Decreases in MMP activity were blocked by losartan. AT1 mRNA levels were upregulated with HG concentration. Vitamin E pretreatment blocked the effects of HG on total protein synthesis and stimulated MMP activity. Results suggest that HG levels may promote fibrosis by increasing CF protein and collagen synthesis and decreasing MMP activity. HG levels may cause these effects via the upregulation of AT1 receptors, which can be blocked by losartan. However, vitamin E can alter HG concentration-induced changes in CF functions independently of AT1 mRNA levels.
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Affiliation(s)
- Juan Asbun
- Department of Medicine, University of California at San Diego, La Jolla, USA
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29
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Schrijvers BF, De Vriese AS, Flyvbjerg A. From hyperglycemia to diabetic kidney disease: the role of metabolic, hemodynamic, intracellular factors and growth factors/cytokines. Endocr Rev 2004; 25:971-1010. [PMID: 15583025 DOI: 10.1210/er.2003-0018] [Citation(s) in RCA: 242] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
At present, diabetic kidney disease affects about 15-25% of type 1 and 30-40% of type 2 diabetic patients. Several decades of extensive research has elucidated various pathways to be implicated in the development of diabetic kidney disease. This review focuses on the metabolic factors beyond blood glucose that are involved in the pathogenesis of diabetic kidney disease, i.e., advanced glycation end-products and the aldose reductase system. Furthermore, the contribution of hemodynamic factors, the renin-angiotensin system, the endothelin system, and the nitric oxide system, as well as the prominent role of the intracellular signaling molecule protein kinase C are discussed. Finally, the respective roles of TGF-beta, GH and IGFs, vascular endothelial growth factor, and platelet-derived growth factor are covered. The complex interplay between these different pathways will be highlighted. A brief introduction to each system and description of its expression in the normal kidney is followed by in vitro, experimental, and clinical evidence addressing the role of the system in diabetic kidney disease. Finally, well-known and potential therapeutic strategies targeting each system are discussed, ending with an overall conclusion.
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Affiliation(s)
- Bieke F Schrijvers
- Medical Department M/Medical Research Laboratories, Clinical Institute, Aarhus University Hospital, Nørrebrogade 44, DK-8000 Aarhus C, Denmark
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30
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Beckman JA, Goldfine AB, Gordon MB, Garrett LA, Keaney JF, Creager MA. Oral antioxidant therapy improves endothelial function in Type 1 but not Type 2 diabetes mellitus. Am J Physiol Heart Circ Physiol 2003; 285:H2392-8. [PMID: 12881209 DOI: 10.1152/ajpheart.00403.2003] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Oxidative stress decreases the bioavailability of endothelium-derived nitric oxide in diabetic patients. We investigated whether impaired endothelium-dependent vasodilation (EDV) in diabetes can be improved by long-term administration of oral antioxidants. Forty-nine diabetic subjects [26 Type 1 (T1) and 23 Type 2 (T2)] and 45 matched healthy control subjects were randomized to receive oral vitamin C (1,000 mg) and vitamin E (800 IU) daily or matching placebo for 6 mo. Vascular ultrasonography was used to determine brachial artery EDV and endothelium-independent vasodilation (EIV). EDV was decreased in both T1 (4.9 +/- 0.9%, P = 0.015) and T2 (4.1 +/- 1.0%, P < 0.01) subjects compared with control subjects (7.7 +/- 0.7%). EIV was decreased in T2 (15.0 +/- 1.2%, P < 0.01) but not T1 subjects (18.5 +/- 2.3%, P = 0.3) compared with controls (21.8 +/- 1.8%). Administration of antioxidant vitamins increased EDV in T1 (by 3.4 +/- 1.4%, P = 0.023) but not T2 subjects (by 0.5. +/- 0.4%, P = 0.3). Antioxidant therapy had no significant affect on EIV. Oral antioxidant therapy improves EDV in T1 but not T2 diabetes. These results are consistent with the lack of clinical benefit in studies that have included primarily T2 diabetic patients.
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Affiliation(s)
- Joshua A Beckman
- Cardiovascular Division, Brigham and Women's Hospital, 75 Francis St., Boston, MA 02115, USA
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31
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Schaan BD. O papel da proteína quinase C no desenvolvimento das complicações vasculares do diabetes mellitus. ACTA ACUST UNITED AC 2003. [DOI: 10.1590/s0004-27302003000600006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A mortalidade dos pacientes com diabetes (DM) é maior do que a da população em geral e decorre especialmente das doenças cardiovasculares. Os prováveis mecanismos da aterosclerose acelerada nestes pacientes são os efeitos tóxicos diretos da glicose sobre a vasculatura, a resistência à insulina e a associação do DM a outros fatores de risco para doença cardiovascular. O principal determinante do dano tecidual causado pelo DM é a hiperglicemia, resultando em aumento de glicose intra-celular, aumento de diacilglicerol (DAG) e ativação da proteína quinase C (PKC). Esta revisão tem por objetivo compilar os efeitos da hiperglicemia sobre a via DAG-PKC, a disfunção vascular relacionada a ela, e, finalmente, as novas perspectivas de tratamento das complicações crônicas vasculares do DM baseadas na inibição desta via.
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Affiliation(s)
- Beatriz D. Schaan
- Instituto de Cardiologia do Rio Grande do Sul; Fundação Universitária de Cardiologia
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32
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McNally AK, Anderson JM. Foreign body-type multinucleated giant cell formation is potently induced by alpha-tocopherol and prevented by the diacylglycerol kinase inhibitor R59022. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 163:1147-56. [PMID: 12937156 PMCID: PMC1868253 DOI: 10.1016/s0002-9440(10)63474-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/14/2003] [Indexed: 01/20/2023]
Abstract
Multinucleated foreign body giant cells (FBGCs) form by monocyte-derived macrophage fusion on implanted biomedical devices and are believed to mediate oxidative damage to biomaterial surfaces. Our in vitro system of human macrophage culture and interleukin (IL)-4-induced FBGC formation was developed to study the macrophage fusion mechanism and the physiological significance of FBGCs on implanted biomaterials and at other sites of chronic inflammation. Here, we demonstrate that the antioxidant vitamin E (90% alpha-tocopherol) moderately induces macrophage fusion and increases IL-4-induced FBGC formation. Moreover, purified alpha-tocopherol, but not beta-, gamma-, or delta-tocopherol, most remarkably induces macrophage fusion, leading to cultures of confluent FBGCs below normal plasma concentrations. This is not observed with the similar antioxidants probucol or Trolox, suggesting that the alpha-tocopherol effects on FBGC formation are independent of its antioxidant activity. Consistent with the reported activation of diacylglycerol kinase by alpha-tocopherol, the diacylglycerol kinase inhibitor R59022 completely abrogates FBGC formation. R59022 inhibition of IL-4-induced FBGC formation is reversed by alpha-tocopherol, suggesting that FBGC formation involves diacylglycerol kinase activation. This study suggests a novel role for diacylglycerol kinase in the mechanism of macrophage fusion/FBGC formation at sites of chronic inflammation and reveals that the pleiotropic lipophilic compound, alpha-tocopherol, is a highly potent macrophage fusion factor.
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Affiliation(s)
- Amy K McNally
- Institute of Pathology, Case Western Reserve University, 2085 Adelbert Road, Cleveland, OH 44106, USA
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Eichberg J. Protein kinase C changes in diabetes: is the concept relevant to neuropathy? INTERNATIONAL REVIEW OF NEUROBIOLOGY 2003; 50:61-82. [PMID: 12198821 DOI: 10.1016/s0074-7742(02)50073-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Protein kinase C (PKC) comprises a superfamily of isoenzymes, many of which are activated by 1,2-diacylglycerol (DAG) in the presence of phosphatidylserine. In order to be capable of DAG activation, PKC must first undergo a series of phosphorylation at three conserved sites. PKC isoforms phosphorylate a wide variety of intracellular target proteins and have multiple functions in signal transduction-mediated cellular regulation. An elevation in DAG levels and an increase in composite PKC activity and/or certain isoforms occurs in several nonneural tissues from diabetic animals, including the vasculature. The ability of isoform-specific PKC inhibitors to antagonize diabetes-induced abnormalities has implicated altered PKC beta activity in the onset of several diabetic complications, In contrast to many other tissues, DAG levels fall in diabetic nerve and a consistent pattern of change in PKC activity has not been observed. Treatments that alter PKC activity affect nerve Na+, K+-ATPase activity, but the mechanism involved is not well understood, Inhibition of PKC beta in diabetic rats appears to correct reduced nerve blood flow and decreased nerve conduction velocity. These and other findings indicate that changes in the neurovasculature exert adverse effects during the pathogenesis of diabetic neuropathy. Still unresolved is a clear-cut role for PKC in the development of abnormalities in neural cell metabolism. Further progress will depend on a more complete understanding of the functions of individual PKC isoforms in nerve. Future investigation could focus profitably on biochemical processes in nerve cells that modulate PKC activity and that are altered in diabetes, such as vascular endothelial growth factor levels and production of reactive oxygen species arising from oxidative stress.
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Affiliation(s)
- Joseph Eichberg
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204, USA
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Azzi A. Vitamin E in Cell Signaling. Antioxidants (Basel) 2003. [DOI: 10.1201/9781439822173.ch14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Srivastava AK. Hyperglycemia-induced protein kinase signaling pathways in vascular smooth muscle cells: implications in the pathogenesis of vascular dysfunction in diabetes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 498:311-8. [PMID: 11900384 DOI: 10.1007/978-1-4615-1321-6_39] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- A K Srivastava
- Research Centre, Centre hospitalier de l'Université de Montréal-Hôtel-Dieu, Department of Medicine, University of Montréal, Québec, Canada.
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Nobe K, Sakai Y, Maruyama Y, Momose K. Hyper-reactivity of diacylglycerol kinase is involved in the dysfunction of aortic smooth muscle contractility in streptozotocin-induced diabetic rats. Br J Pharmacol 2002; 136:441-51. [PMID: 12023947 PMCID: PMC1573360 DOI: 10.1038/sj.bjp.0704722] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Dysfunction of vascular contraction in diabetes has been reported; however, the mechanisms are poorly understood. In this study, calcium sensitization involving increases in contraction in streptozotocin-induced diabetic rat aorta was detected. We hypothesize that an alteration in the intracellular signalling system plays a role in the dysfunction of vascular contractility in diabetes. Therefore, diacylglycerol (DG) kinase as a key enzyme of phosphatidylinositol (PI) turnover was investigated. 2. Treatment with norepinephrine (NE) caused time- and dose-dependent activation of DG kinase in control rats. This activation required simultaneous increases in intracellular calcium concentration ([Ca2+]i) and protein kinase C (PKC) activation. I3. n diabetic rats, hyper-reactivity of DG kinase involving inactivation in the resting state and over-activation in NE stimulation was observed. During hyper-reactivity, [Ca2+]i dependency of DG kinase was enhanced. Treatment with 50 mM KCl induced significant escalation in activity; moreover, basal activation of PKC was detected only in diabetes. These results suggested that PKC had been activated in the resting state. In contrast, these conditions were insufficient for DG kinase activation due to the absence of [Ca2+]i elevation. 4. During NE-stimulation, PKC activation was maintained and [Ca2+]i increased. Therefore, DG kinase was activated and an elevation in calcium dependency enhanced this activation. 5. The present study suggested that DG kinase hyper-reactivity in diabetes involved both an increase in [Ca2+]i and basal activation of PKC. This phenomenon may be associated with increased vascular contraction in diabetes mediated by acceleration of PI-turnover.
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Affiliation(s)
- Koji Nobe
- Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku Tokyo, 142-8555 Japan.
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Abstract
Hyperglycaemia appears to be a critical factor in the aetiology of diabetic retinopathy and initiates downstream events including: basement membrane thickening, pericyte drop out and retinal capillary non-perfusion. More recently, focus has been directed to the molecular basis of the disease process in diabetic retinopathy. Of particular importance in the development and progression of diabetic retinopathy is the role of growth factors (eg vascular endothelial growth factor, placenta growth factor and pigment epithelium-derived factor) together with specific receptors and obligate components of the signal transduction pathway needed to support them. Despite these advances there are still a number of important questions that remain to be answered before we can confidently target pathological signals. How does hyperglycaemia regulate retinal vessels? Which growth factors are most important and at what stage of retinopathy do they operate? What is the preferred point in the growth factor signalling cascade for therapeutic intervention? Answers to these questions will provide the basis for new therapeutic interventions in a debilitating ocular condition.
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Affiliation(s)
- J Cai
- Department of Optometry and Vision Sciences, Cardiff University, UK
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Ricciarelli R, Zingg JM, Azzi A. The 80th anniversary of vitamin E: beyond its antioxidant properties. Biol Chem 2002; 383:457-65. [PMID: 12033435 DOI: 10.1515/bc.2002.048] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Molecules provided with an antioxidant function may have additional properties, the latter being sometimes of greater importance than the former. In the last ten years, alpha-tocopherol has revealed precise cellular functions, some of which are independent of its antioxidant/radical scavenging ability. At the posttranslational level, alpha-tocopherol inhibits protein kinase C and 5-lipoxygenase and activates protein phosphatase 2A and diacylglycerol kinase. Some genes (CD36, alpha-TTP, alpha-tropomyosin, and collagenase) are affected by alpha-tocopherol at the transcriptional level. alpha-Tocopherol also induces inhibition of cell proliferation, platelet aggregation and monocyte adhesion. These effects are unrelated to the antioxidant activity of vitamin E, but rather are believed to be a result of specific interactions of vitamin E with components of the cell, e. g. proteins, enzymes and membranes. This review focuses on novel non-antioxidant functions of alpha-tocopherol and discusses the possibility that many of the effects previously attributed to the antioxidant functions can also be explained by non-antioxidant mechanisms.
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Affiliation(s)
- Roberta Ricciarelli
- Institute of Biochemistry and Molecular Biology, University of Berne, Switzerland
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Lin S, Chugh S, Pan X, Wallner EI, Wada J, Kanwar YS. Identification of up-regulated Ras-like GTPase, Rap1b, by suppression subtractive hybridization. Kidney Int 2001; 60:2129-41. [PMID: 11737587 DOI: 10.1046/j.1523-1755.2001.00061.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Diabetic nephropathy accounts for over 30% of the end-stage renal disease (ESRD). A number of defined mechanisms and molecules that are involved in its pathogenesis are known, while others remain to be identified. METHODS Suppression subtraction hybridization (SSH)-polymerase chain reaction (PCR) was employed to search for new genes that may be relevant to the pathogenesis of diabetic nephropathy during embryonic development, the time when the kidney is most susceptible to various forms of stress. A diabetic state was induced in pregnant mice at day-13 of gestation by administration of streptozotocin. The kidneys of newborn mice with blood glucose level> 200 mg/dL were harvested, mRNA isolated and subjected to SSH-PCR. Several differentially expressed cDNA fragments with up-regulated expression were isolated. One of the cDNA fragments had homology with human Ras-like guanine 5'-triphosphate (GTPase), Rap1b gene. By utilizing the lambdaZAP II mouse cDNA library and SMART RACE amplification, a full-length Rap1b cDNA was isolated. A recombinant protein was generated in pET15b bacterial expression system. An anti-Rap1b antibody was raised in rabbits by immunizing them with the fusion protein, and its specificity was confirmed by Western blot analysis. RESULTS Rap1b cDNA had an open reading frame of 552 bp with a predicted putative protein size of approximately 21 kD. In vitro translation verified the authentication of the Rap1b cDNA clone. Northern blot analyses revealed a single approximately 2.3 kb Rap1b mRNA transcript. Its expression was up-regulated in several tissues, including the kidney of newborn diabetic mice. The degree of up-regulation of Rap1b mRNA expression was proportional to the blood glucose levels. Western blot analyses confirmed the hyperglycemia-induced up-regulation of the Rap1b expression. In situ hybridization and immunofluorescence studies revealed that Rap1b was expressed in the inner medullary collecting tubules. During hyperglycemia, its expression was accentuated and extended into the outer medullary and cortical collecting tubules. Similar up-regulation of Rap1b was observed when embryonic kidneys, harvested at day-13 of gestation, were exposed to high glucose ambience. CONCLUSION The data suggest that Rap1b, a GTP-binding protein that plays a critical role in various signaling intracellular events, is another molecule that may be relevant to the pathobiology of diabetic nephropathy.
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Affiliation(s)
- S Lin
- Department of Pathology, Northwestern University Medical School, Chicago, IL 60611, USA
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Abstract
Hyperglycemic control in diabetes is key to preventing the development and progression of vascular complications such as retinopathy, nephropathy and neuropathy. Increased activation of the diacylglycerol (DAG)-protein kinase C (PKC) signal transduction pathway has been identified in vascular tissues from diabetic animals, and in vascular cells exposed to elevated glucose. Vascular abnormalities associated with glucose-induced PKC activation leading to increased synthesis of DAG include altered vascular blood flow, extracellular matrix deposition, basement membrane thickening, increased permeability and neovascularization. Preferential activation of the PKCbeta isoform by elevated glucose is reported to occur in a variety of vascular tissues. This has lead to the development of LY333531, a PKCbeta isoform specific inhibitor, which has shown potential in animal models to be an orally effective and nontoxic therapy able to produce significant improvements in diabetic retinopathy, nephropathy, neuropathy and cardiac dysfunction. Additionally, the antioxidant vitamin E has been identified as an inhibitor of the DAG-PKC pathway, and shows promise in reducing vascular complications in animal models of diabetes. Given the overwhelming evidence indicating a role for PKC activation in contributing to the development of diabetic vascular complications, pharmacological therapies that can modulate this pathway, particularly with PKC isoform selectivity, show great promise for treatment of vascular complications, even in the presence of hyperglycemia.
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Affiliation(s)
- K J Way
- Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA
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Abstract
Since the discovery of vitamin E in 1922, its deficiency has been associated with various disorders, particularly atherosclerosis, ischemic heart disease, and the development of different types of cancer. A neurological syndrome associated with vitamin E deficiency resembling Friedreich ataxia has also been described. Whereas epidemiological studies have indicated the role of vitamin E in preventing the progression of atherosclerosis and cancer, intervention trials have produced contradictory results, indicating strong protection in some cases and no significant effect in others. Although it is commonly believed that phenolic compounds like vitamin E exert only a protective role against free radical damage, antioxidant molecules can exert other biological functions. For instance, the antioxidant activity of 17-beta-estradiol is not related to its role in determining secondary sexual characters, and the antioxidant capacity of all-trans-retinal is distinguished from its role in rhodopsin and vision. Thus, it is not unusual that alpha-tocopherol (the most active form of vitamin E) has properties independent of its antioxidant/radical scavenging ability. The Roman god Janus, shown in ancient coins as having two faces in one body, inspired the designation of 'Janus molecules' for these substances. The new biochemical face of vitamin E was first described in 1991, with an inhibitory effect on cell proliferation and protein kinase C activity. After a decade, this nonantioxidant role of vitamin E is well established, as confirmed by authoritative studies of signal transduction and gene regulation. More recently, a tocopherol binding protein with possible receptor function has been discovered. Despite such important developments in understanding the molecular mechanism and the targets of vitamin E, its new Janus face is not fully elucidated. Greater knowledge of the molecular events related to vitamin E will help in selecting the parameters for clinical intervention studies such as population type, dose response effects, and possible synergism with other compounds.
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Affiliation(s)
- R Ricciarelli
- Institute of Biochemistry and Molecular Biology, University of Bern, 3012 Bern, Switzerland
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Kowluru RA, Kennedy A. Therapeutic potential of anti-oxidants and diabetic retinopathy. Expert Opin Investig Drugs 2001; 10:1665-76. [PMID: 11772276 DOI: 10.1517/13543784.10.9.1665] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Retinopathy, a severely disabling complication of diabetes mellitus, is today the leading cause of acquired blindness among young adults in developed countries. Good glycaemic control can attenuate the development of diabetic retinopathy but such metabolic control is often difficult to achieve and maintain and additional therapies need to be identified by which retinopathy can be prevented or arrested. Hyperglycaemia plays a critical role in the development and progression of retinopathy, but the mechanism by which hyperglycaemia results in the development of retinopathy is not clear. Oxidative stress is increased in the retina in diabetes. The possible sources of increased oxidative stress might include increased generation of free radicals or impaired anti-oxidant defence system. Dietary supplementation with anti-oxidants in animal models of diabetic retinopathy inhibits retinal metabolic abnormalities and retinal histopathology, suggesting that oxidative stress is associated with the development of retinopathy. The mechanism by which anti-oxidants inhibit retinopathy in diabetes warrants further investigation, but animal studies show that increasing the diversity of anti-oxidants provides significantly more protection than using any single anti-oxidant. Thus, supplementation with anti-oxidants represents an achievable adjunct therapy to help preserve vision in diabetic patients.
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Affiliation(s)
- R A Kowluru
- Kresge Eye Institute, Wayne State University, 4717 St. Antoine, Detroit, MI 48201, USA.
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Du X, Jiang Y, Qian W, Lu X, Walsh JP. Fatty acids inhibit growth-factor-induced diacylglycerol kinase alpha activation in vascular smooth-muscle cells. Biochem J 2001; 357:275-82. [PMID: 11415460 PMCID: PMC1221952 DOI: 10.1042/0264-6021:3570275] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have previously shown that unsaturated fatty acids amplify platelet-derived-growth-factor (PDGF)-induced protein kinase C (PKC) activation in vascular smooth-muscle cells (VSMCs). Diacylglycerol-induced PKC activation is normally terminated by diacylglycerol kinases (DGKs). We thus hypothesized that fatty acids act by inhibiting a DGK. Fractionation of VSMC extracts demonstrated that the DGK alpha isoform was the major DGK activity present. PDGF markedly increased the DGK activity of cultured cells. An inhibitor selective for the DGK alpha isoform, R59949 [3-[2-[4-(bis-(4-fluorophenyl)methylene]piperidin-1-yl)ethyl]-2,3-dihydro-2-thioxo-4(1H)-quinazolinone], abolished the growth-factor-induced increase in DGK activity, but had little effect on basal activity. PDGF thus selectively activates DGKalpha. Epidermal growth factor and alpha-thrombin stimulated total DGK activity similarly to PDGF. Activation by epidermal growth factor was sensitive to R59949, again suggesting involvement of DGKalpha. However, the alpha-thrombin-induced activity was unaffected by this agent. Unsaturated fatty acids inhibited growth-factor-induced DGKalpha activation, but had no effect on basal activity. Fatty acids also amplified the PDGF-induced increase in cell diacylglycerol content. These results indicate that inhibition of DGKalpha contributes to fatty-acid-induced amplification of PKC activation. Increased levels of fatty acids in diabetes may thus contribute to chronic PKC activation associated with this disorder.
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Affiliation(s)
- X Du
- Department of Medicine, Indiana University School of Medicine, Roudebush VA Medical Center (111-E), 1481 West Tenth Street, Indianapolis, IN 46202, USA
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Wilson SH, Davis MI, Caballero S, Grant MB. Modulation of retinal endothelial cell behaviour by insulin-like growth factor I and somatostatin analogues: implications for diabetic retinopathy. Growth Horm IGF Res 2001; 11 Suppl A:S53-S59. [PMID: 11527089 DOI: 10.1016/s1096-6374(01)80009-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Evidence suggests the involvement of growth hormone (GH), insulin-like growth factor I (IGF-I) and somatostatin in the pathology associated with diabetic retinopathy. We examined the effect of IGF-I on human retinal endothelial cell (HREC) survival following high glucose exposure and serum starvation, examined the signalling pathways mediating the protective effect of IGF-I on HREC, and characterized somatostatin receptor-induced retinal endothelial cell death. IGF-I (10 ng/ml) protected HREC from apoptosis induced by high glucose and serum starvation. Wortmannin, a specific inhibitor of phosphotidylinositol-3-kinase, blocks the ability of IGF-I to protect HREC from apoptosis. Incubation of HREC in serum-free medium caused a time-dependent increase in c-Jun N-terminal kinase (JNK) activity, and continuous culture of HREC in the presence of IGF-I or vascular endothelial growth factor (VEGF) prevented JNK activation and arrested apoptosis. Activation of tyrosine kinase receptors results in extracellular signal-related kinase (ERK) activation and activation of ERK is required for proliferation. Both IGF-I and VEGF produced a time- and concentration-dependent increase in the activation of ERK. Type 2 and type 3 somatostatin receptors have been implicated in cell-cycle arrest and apoptosis. Activation of the type 3 receptor in HREC resulted in cell death. These studies suggest that IGF-I is critical for HREC survival, and that somatostatin analogues acting through the type 3 receptor have direct effects on retinal endothelial cells. Furthermore, it appears that the therapeutic efficacy of somatostatin analogues lies not only in systemic inhibition of GH, but also in modulating local growth factor effects.
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