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Christensen M, Schiffer TA, Gustafsson H, Krag SP, Nørregaard R, Palm F. Metformin attenuates renal medullary hypoxia in diabetic nephropathy through inhibition uncoupling protein-2. Diabetes Metab Res Rev 2019; 35:e3091. [PMID: 30345618 DOI: 10.1002/dmrr.3091] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 10/03/2018] [Accepted: 10/16/2018] [Indexed: 11/09/2022]
Abstract
BACKGROUND The purpose of the study is to examine the effect of metformin on oxygen metabolism and mitochondrial function in the kidney of an animal model of insulinopenic diabetes in order to isolate any renoprotective effect from any concomitant effect on blood glucose homeostasis. METHODS Sprague-Dawley rats were injected with streptozotocin (STZ) (50 mg kg-1 ) and when stable started on metformin treatment (250 mg kg-1 ) in the drinking water. Rats were prepared for in vivo measurements 25 to 30 days after STZ injection, where renal function, including glomerular filtration rate and sodium transport, was estimated in anesthetized rats. Intrarenal oxygen tension was measured using oxygen sensors. Furthermore, mitochondrial function was assessed in mitochondria isolated from kidney cortex and medulla analysed by high-resolution respirometry, and superoxide production was evaluated using electron paramagnetic resonance. RESULTS Insulinopenic rats chronically treated with metformin for 4 weeks displayed improved medullary tissue oxygen tension despite of no effect of metformin on blood glucose homeostasis. Metformin reduced UCP2-dependent LEAK and differentially affected medullary mitochondrial superoxide radical production in control and diabetic rats. CONCLUSIONS Metformin attenuates diabetes-induced renal medullary tissue hypoxia in an animal model of insulinopenic type 1 diabetes. The results suggest that the mechanistic pathway to attenuate the diabetes-induced medullary hypoxia is independent of blood glucose homeostasis and includes reduced UCP2-mediated mitochondrial proton LEAK.
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Affiliation(s)
| | - Tomas A Schiffer
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Håkan Gustafsson
- Department of Radiology Norrköping and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | | | - Rikke Nørregaard
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Fredrik Palm
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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Chen M, Wang X, Hu BO, Zhou J, Wang X, Wei W, Zhou H. Ursolic acid stimulates UCP2 expression and protects H9c2 cells from hypoxia-reoxygenation injury via p38 signaling. J Biosci 2018; 43:857-865. [PMID: 30541946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Oxidative stress and apoptosis is involved in hypoxia-reoxygenation (H/R) induced myocardial injury. Increased expression of uncoupling protein 2 (UCP2), a cationic carrier protein, has protective effect against H/R injury. The present study aimed to find candidate drugs for H/R induced cardiac damage by identifying compounds regulating UCP2 expression. Here, among six natural compounds, ursolic acid (UA) had the most significant induction effect on UCP2 expression in H9c2 cells under H/R conditions. Subsequently, we found that UA significantly attenuated cell apoptosis and Caspase 3 activity, but increased nitric oxide (NO) release under H/R conditions. Additionally, UA pretreatment also decreased reactive oxygen species (ROS) production and malondialdehyde (MDA) content, but increased superoxide dismutase (SOD) activity. H/R caused a notable increase in the phosphorylation of p38, which was weakened by UA pretreatment. Moreover, p38 inhibitor (SB203580) showed the similar effects on H/R cells as UA pretreatment, while UCP2 knockdown had the reverse biological effects. More importantly, the effects of UA or p38 inhibitor exposure were partially rescued by UCP2 knockdown. Collectively, our data suggested the functions of UA on UCP2 expression and on the protection of H/Rstimulated H9c2 cells may be attributed to p38 signaling pathway.
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Affiliation(s)
- Min Chen
- Department of Cardiovascular Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, China
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Lang H, Xiang Y, Lin N, Ai Z, You Z, Xiao J, Liu D, Yang Y. Identification of a Panel of MiRNAs as Positive Regulators of Insulin Release in Pancreatic Β-Cells. Cell Physiol Biochem 2018; 48:185-193. [PMID: 30007975 DOI: 10.1159/000491717] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 05/04/2018] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS MicroRNAs (miRNAs) are a novel class of small RNAs that participate in a variety of biological processes. Although miRNAs have been linked to insulin synthesis and glucose homeostasis, their role in the targeting of mitochondrial uncoupling protein 2 (UCP2), a negative modulator of insulin secretion, remains unclear. METHODS miRNA levels were determined by real-time quantitative PCR analysis using TaqMan probes, and insulin secretion from isolated islets was quantified by ELISA. Effects of miRNAs on UCP2 expression were checked with a luciferase assay and western blotting analysis. RESULTS An overall change in a set of miRNAs was discovered, with miR-15a, miR-424, miR-497, and miR-185 coinciding with insulin levels in islets maintained under high-glucose conditions. Moreover, experiments in MIN6 cells illustrated that miR-15a, miR-424, miR-497, and miR-185 positively regulated insulin biosynthesis by co-inhibiting UCP2 expression. Furthermore, the four miRNAs were found to post-transcriptionally repress UCP2 expression by directly targeting the 3'UTR of UCP2 mRNA. CONCLUSIONS Thus, our results shed further light on the regulatory network in β-cells consisting of miRNAs, UCP2, and insulin and provide novel therapeutic targets for diabetes.
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Dando I, Pacchiana R, Pozza ED, Cataldo I, Bruno S, Conti P, Cordani M, Grimaldi A, Butera G, Caraglia M, Scarpa A, Palmieri M, Donadelli M. UCP2 inhibition induces ROS/Akt/mTOR axis: Role of GAPDH nuclear translocation in genipin/everolimus anticancer synergism. Free Radic Biol Med 2017; 113:176-189. [PMID: 28962872 DOI: 10.1016/j.freeradbiomed.2017.09.022] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 09/25/2017] [Indexed: 12/20/2022]
Abstract
Several studies indicate that mitochondrial uncoupling protein 2 (UCP2) plays a pivotal role in cancer development by decreasing reactive oxygen species (ROS) produced by mitochondrial metabolism and by sustaining chemoresistance to a plethora of anticancer drugs. Here, we demonstrate that inhibition of UCP2 triggers Akt/mTOR pathway in a ROS-dependent mechanism in pancreatic adenocarcinoma cells. This event reduces the antiproliferative outcome of UCP2 inhibition by genipin, creating the conditions for the synergistic counteraction of cancer cell growth with the mTOR inhibitor everolimus. Inhibition of pancreatic adenocarcinoma cell growth and induction of apoptosis by genipin and everolimus treatment are functionally related to nuclear translocation of the cytosolic glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The synthetic compound (S)-benzyl-2-amino-2-(S)-3-bromo-4,5-dihydroisoxazol-5-yl-acetate (AXP3009), which binds GAPDH at its redox-sensitive Cys152, restores cell viability affected by the combined treatment with genipin and everolimus, suggesting a role for ROS production in the nuclear translocation of GAPDH. Caspase-mediated apoptosis by genipin and everolimus is further potentiated by the autophagy inhibitor 3-methyladenine revealing a protective role for Beclin1-mediated autophagy induced by the treatment. Mice xenograft of pancreatic adenocarcinoma further confirmed the antiproliferative outcome of drug combination without toxic effects for animals. Tumor masses from mice injected with UCP2 and mTOR inhibitors revealed a strong reduction in tumor volume and number of mitosis associated with a marked GAPDH nuclear positivity. Altogether, these results reveal novel mechanisms through which UCP2 promotes cancer cell proliferation and support the combined inhibition of UCP2 and of Akt/mTOR pathway as a novel therapeutic strategy in the treatment of pancreatic adenocarcinoma.
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Affiliation(s)
- Ilaria Dando
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy.
| | - Raffaella Pacchiana
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Elisa Dalla Pozza
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Ivana Cataldo
- Applied Research on Cancer Centre (ARC-Net) and Department of Diagnostics and Public Health, University of Verona, Verona, Italy
| | - Stefano Bruno
- Food and Dug Department, University of Parma, Parma, Italy
| | - Paola Conti
- Department of Pharmaceutical Sciences, University of Milan, Milan, Italy
| | - Marco Cordani
- Biochemistry Department, Universidad Autónoma de Madrid (UAM), Instituto de Investigaciones Biomédicas "Alberto Sols" (CSIC-UAM), IdiPAZ, Madrid, Spain
| | - Anna Grimaldi
- Department of Biochemistry, Biophysics and General Pathology, University of Campania "L. Vanvitelli", Naples, Italy
| | - Giovanna Butera
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Michele Caraglia
- Department of Biochemistry, Biophysics and General Pathology, University of Campania "L. Vanvitelli", Naples, Italy
| | - Aldo Scarpa
- Applied Research on Cancer Centre (ARC-Net) and Department of Diagnostics and Public Health, University of Verona, Verona, Italy
| | - Marta Palmieri
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Massimo Donadelli
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy.
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Hu M, Lin H, Yang L, Cheng Y, Zhang H. Interleukin-22 restored mitochondrial damage and impaired glucose-stimulated insulin secretion through down-regulation of uncoupling protein-2 in INS-1 cells. J Biochem 2017; 161:433-439. [PMID: 28069865 DOI: 10.1093/jb/mvw084] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 11/03/2016] [Indexed: 01/17/2023] Open
Abstract
Defective glucose-stimulated insulin secretion (GSIS) induced by chronic exposure to fatty acids is a hallmark of type 2 diabetes (T2D). Interleukin-22 (IL-22) has been shown to exert beneficial effects on insulin secretion and to protect pancreatic β-cells from stress. Moreover, uncoupling protein-2 (UCP-2) plays a central role in the regulation of GSIS and β-cell dysfunction, whereas the role of UCP-2 in IL-22-enhanced glycemic control under conditions of lipotoxicity remains unclear. In this present study, we investigated the effects of IL-22 on rat insulin-secreting cells (INS-1 cells) and the mechanisms that underlie IL-22 and lipotoxicity-impaired GSIS in vitro. Chronic palmitate (PA) treatment impaired insulin secretion and activated UCP-2 expression in INS-1 cells. Furthermore, in INS-1 cells, both reduced mitochondrial membrane potential (ΔΨm) and impaired GSIS induced by PA treatment were effectively reversed by an inhibitor of UCP-2 (genipin). Additionally, compared with the PA-treated group, INS-1 cells treated with IL-22 down-regulated UCP-2 expression, increased mitochondrial membrane potential, and restored GSIS. Together, our findings indicate that chronic exposure to PA could activate UCP-2, resulting in mitochondrial damage and impaired GSIS in INS-1 cells. We also suggest that IL-22 plays a protective role in this process via the down-regulation of UCP-2.
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Affiliation(s)
- Minling Hu
- Department of Endocrinology, The First Affiliated Hospital of Clinical Medicine of Guangdong Pharmaceutical University, Guangzhou 510080, China
| | - Hanxiao Lin
- Department of Nutrition, Guangzhou First People's Hospital, Guangzhou Medical University, 602 Ren Min Bei Road, Guangzhou 510180, P.R. China
| | - Li Yang
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, S253 Industry Boulevard, Guangzhou 510282, China
| | - Yanzhen Cheng
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, S253 Industry Boulevard, Guangzhou 510282, China
| | - Hua Zhang
- Department of Endocrinology, Zhujiang Hospital, Southern Medical University, S253 Industry Boulevard, Guangzhou 510282, China
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Ge H, Zhang F, Duan P, Zhu N, Zhang J, Ye F, Shan D, Chen H, Lu X, Zhu C, Ge R, Lin Z. Mitochondrial Uncoupling Protein 2 in human cumulus cells is associated with regulating autophagy and apoptosis, maintaining gap junction integrity and progesterone synthesis. Mol Cell Endocrinol 2017; 443:128-137. [PMID: 28089824 DOI: 10.1016/j.mce.2017.01.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 01/24/2023]
Abstract
To explore the roles of mitochondrial Uncoupling Protein 2 (UCP2) in cumulus cells (CCs), human CCs were cultured in vitro, and the UCP2 was inhibited by treatment with Genipin, a special UCP inhibitor, or by RNA interference targeting UCP2. No significant differences in adenosine triphosphate levels and the ratio of ADP/ATP were observed after UCP2 inhibition. UCP2 inhibition caused a significant increase in cellular oxidative damage, which was reflected in alterations to several key parameters, including reactive oxygen species (ROS) and lipid peroxidation levels and the ratio of reduced GSH to GSSG. UCP2 blocking resulted in an obvious increase in active Caspase-3, accompanied by the decline of proactive Caspase-3 and a significant increase in the LC3-II/LC3-I ratio, suggesting that UCP2 inhibition triggered cellular apoptosis and autophagy. The mRNA and protein expression of connexin 43 (Cx43), a gap junction channel protein, were significantly reduced after treatment with Genipin or siRNA. The progesterone level in the culture medium was also significantly decreased after UCP2 inhibition. Our data indicated that UCP2 plays highly important roles in mediating ROS production and regulating apoptosis and autophagy, as well as maintaining gap junction integrity and progesterone synthesis, which suggests that UCP2 is involved in the regulation of follicle development and early embryo implantation and implies that it might serve as a potential biomarker for oocyte quality and competency.
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Affiliation(s)
- Hongshan Ge
- Center for Reproductive Medicine, Department of Obstetrics and Gynaecology, Taizhou People's Hospital, The Fifth Hospital Affiliated Nantong University, Taizhou, Jiangsu Province, 225300, People's Republic of China; The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China.
| | - Fan Zhang
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - Ping Duan
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - Nan Zhu
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - Jiayan Zhang
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - Feijun Ye
- Maternal and Child Health Hospital, Zhoushan Hospital Affiliated Wenzhou Medical University, Zhejiang Province, 316100, People's Republic of China
| | - Dan Shan
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - Hua Chen
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - XiaoSheng Lu
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - ChunFang Zhu
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - Renshan Ge
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China
| | - Zhenkun Lin
- The Second Affiliated Hospital and YuYing Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, 325000, People's Republic of China.
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Brandi J, Cecconi D, Cordani M, Torrens-Mas M, Pacchiana R, Dalla Pozza E, Butera G, Manfredi M, Marengo E, Oliver J, Roca P, Dando I, Donadelli M. The antioxidant uncoupling protein 2 stimulates hnRNPA2/B1, GLUT1 and PKM2 expression and sensitizes pancreas cancer cells to glycolysis inhibition. Free Radic Biol Med 2016; 101:305-316. [PMID: 27989750 DOI: 10.1016/j.freeradbiomed.2016.10.499] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 10/12/2016] [Accepted: 10/24/2016] [Indexed: 01/09/2023]
Abstract
Several evidence indicate that metabolic alterations play a pivotal role in cancer development. Here, we report that the mitochondrial uncoupling protein 2 (UCP2) sustains the metabolic shift from mitochondrial oxidative phosphorylation (mtOXPHOS) to glycolysis in pancreas cancer cells. Indeed, we show that UCP2 sensitizes pancreas cancer cells to the treatment with the glycolytic inhibitor 2-deoxy-D-glucose. Through a bidimensional electrophoresis analysis, we identify 19 protein species differentially expressed after treatment with the UCP2 inhibitor genipin and, by bioinformatic analyses, we show that these proteins are mainly involved in metabolic processes. In particular, we demonstrate that the antioxidant UCP2 induces the expression of hnRNPA2/B1, which is involved in the regulation of both GLUT1 and PKM2 mRNAs, and of lactate dehydrogenase (LDH) increasing the secretion of L-lactic acid. We further demonstrate that the radical scavenger N-acetyl-L-cysteine reverts hnRNPA2/B1 and PKM2 inhibition by genipin indicating a role for reactive oxygen species in the metabolic reprogramming of cancer cells mediated by UCP2. We also observe an UCP2-dependent decrease in mtOXPHOS complex I (NADH dehydrogenase), complex IV (cytochrome c oxidase), complex V (ATPase) and in mitochondrial oxygen consumption, suggesting a role for UCP2 in the counteraction of pancreatic cancer cellular respiration. All these results reveal novel mechanisms through which UCP2 promotes cancer cell proliferation with the concomitant metabolic shift from mtOXPHOS to the glycolytic pathway.
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Affiliation(s)
- Jessica Brandi
- Department of Biotechnology, Proteomics and Mass Spectrometry Laboratory, University of Verona, Verona, Italy
| | - Daniela Cecconi
- Department of Biotechnology, Proteomics and Mass Spectrometry Laboratory, University of Verona, Verona, Italy
| | - Marco Cordani
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Margalida Torrens-Mas
- Physiopathology of Obesity and Nutrition, CIBERobn (CB06/03), Carlos III Health Research Institute (ISCIII), Madrid, Spain; Palma Institute for Health Research (IdISPa), E07010 Palma, Spain; Multidisciplinar Group of Translational Oncology, University Research Institute on Health Sciences (IUNICS), University of the Balearic Islands, E07122 Palma, Spain
| | - Raffaella Pacchiana
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Elisa Dalla Pozza
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Giovanna Butera
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy
| | - Marcello Manfredi
- Department of Sciences and Technological Innovation, University of Eastern Piedmont, Alessandria, Italy; ISALIT, Novara, Italy
| | - Emilio Marengo
- Department of Sciences and Technological Innovation, University of Eastern Piedmont, Alessandria, Italy
| | - Jordi Oliver
- Physiopathology of Obesity and Nutrition, CIBERobn (CB06/03), Carlos III Health Research Institute (ISCIII), Madrid, Spain; Palma Institute for Health Research (IdISPa), E07010 Palma, Spain; Multidisciplinar Group of Translational Oncology, University Research Institute on Health Sciences (IUNICS), University of the Balearic Islands, E07122 Palma, Spain
| | - Pilar Roca
- Physiopathology of Obesity and Nutrition, CIBERobn (CB06/03), Carlos III Health Research Institute (ISCIII), Madrid, Spain; Palma Institute for Health Research (IdISPa), E07010 Palma, Spain; Multidisciplinar Group of Translational Oncology, University Research Institute on Health Sciences (IUNICS), University of the Balearic Islands, E07122 Palma, Spain
| | - Ilaria Dando
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy.
| | - Massimo Donadelli
- Department of Neuroscience, Biomedicine and Movement, Biochemistry Section, University of Verona, Verona, Italy.
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Gerö D, Szabo C. Glucocorticoids Suppress Mitochondrial Oxidant Production via Upregulation of Uncoupling Protein 2 in Hyperglycemic Endothelial Cells. PLoS One 2016; 11:e0154813. [PMID: 27128320 PMCID: PMC4851329 DOI: 10.1371/journal.pone.0154813] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 04/19/2016] [Indexed: 11/19/2022] Open
Abstract
Diabetic complications are the leading cause of morbidity and mortality in diabetic patients. Elevated blood glucose contributes to the development of endothelial and vascular dysfunction, and, consequently, to diabetic micro- and macrovascular complications, because it increases the mitochondrial proton gradient and mitochondrial oxidant production. Therapeutic approaches designed to counteract glucose-induced mitochondrial reactive oxygen species (ROS) production in the vasculature are expected to show efficacy against all diabetic complications, but direct pharmacological targeting (scavenging) of mitochondrial oxidants remains challenging due to the high reactivity of some of these oxidant species. In a recent study, we have conducted a medium-throughput cell-based screening of a focused library of well-annotated pharmacologically active compounds and identified glucocorticoids as inhibitors of mitochondrial superoxide production in microvascular endothelial cells exposed to elevated extracellular glucose. The goal of the current study was to investigate the mechanism of glucocorticoids' action. Our findings show that glucocorticoids induce the expression of the mitochondrial UCP2 protein and decrease the mitochondrial potential. UCP2 silencing prevents the protective effect of the glucocorticoids on ROS production. UCP2 induction also increases the oxygen consumption and the "proton leak" in microvascular endothelial cells. Furthermore, glutamine supplementation augments the effect of glucocorticoids via further enhancing the expression of UCP2 at the translational level. We conclude that UCP2 induction represents a novel experimental therapeutic intervention in diabetic vascular complications. While direct repurposing of glucocorticoids may not be possible for the therapy of diabetic complications due to their significant side effects that develop during chronic administration, the UCP2 pathway may be therapeutically targetable by other, glucocorticoid-independent pharmacological means.
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Affiliation(s)
- Domokos Gerö
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas, United States of America
- University of Exeter Medical School, Exeter, United Kingdom
- * E-mail:
| | - Csaba Szabo
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas, United States of America
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