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Xue R, Xiao H, Kumar V, Lan X, Malhotra A, Singhal PC, Chen J. The Molecular Mechanism of Renal Tubulointerstitial Inflammation Promoting Diabetic Nephropathy. Int J Nephrol Renovasc Dis 2023; 16:241-252. [PMID: 38075191 PMCID: PMC10710217 DOI: 10.2147/ijnrd.s436791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 11/30/2023] [Indexed: 02/12/2024] Open
Abstract
Diabetic nephropathy (DN) is a common complication affecting many diabetic patients, leading to end-stage renal disease. However, its pathogenesis still needs to be fully understood to enhance the effectiveness of treatment methods. Traditional theories are predominantly centered on glomerular injuries and need more explicit explanations of recent clinical observations suggesting that renal tubules equally contribute to renal function and that tubular lesions are early features of DN, even occurring before glomerular lesions. Although the conventional view is that DN is not an inflammatory disease, recent studies indicate that systemic and local inflammation, including tubulointerstitial inflammation, contributes to the development of DN. In patients with DN, intrinsic tubulointerstitial cells produce many proinflammatory factors, leading to medullary inflammatory cell infiltration and activation of inflammatory cells in the interstitial region. Therefore, understanding the molecular mechanism of renal tubulointerstitial inflammation contributing to DN injury is of great significance and will help further identify key factors regulating renal tubulointerstitial inflammation in the high glucose environment. This will aid in developing new targets for DN diagnosis and treatment and expanding new DN treatment methods.
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Affiliation(s)
- Rui Xue
- Affiliated Mental Health Center & Hangzhou Seventh People’s Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310000, People’s Republic of China
| | - Haiting Xiao
- Key Laboratory of Luzhou City for Aging Medicine, Department of Pharmacology, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, 646000, People’s Republic of China
| | - Vinod Kumar
- Department of Dermatology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160012, India
| | - Xiqian Lan
- Key Laboratory of Luzhou City for Aging Medicine, Department of Pharmacology, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, 646000, People’s Republic of China
| | - Ashwani Malhotra
- Feinstein Institute for Medical Research and Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Manhasset, NY, 11030, USA
| | - Pravin C Singhal
- Feinstein Institute for Medical Research and Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Manhasset, NY, 11030, USA
| | - Jianning Chen
- Affiliated Mental Health Center & Hangzhou Seventh People’s Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310000, People’s Republic of China
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Curran CS, Kopp JB. RAGE pathway activation and function in chronic kidney disease and COVID-19. Front Med (Lausanne) 2022; 9:970423. [PMID: 36017003 PMCID: PMC9395689 DOI: 10.3389/fmed.2022.970423] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 07/21/2022] [Indexed: 12/23/2022] Open
Abstract
The multi-ligand receptor for advanced glycation end-products (RAGE) and its ligands are contributing factors in autoimmunity, cancers, and infectious disease. RAGE activation is increased in chronic kidney disease (CKD) and coronavirus disease 2019 (COVID-19). CKD may increase the risk of COVID-19 severity and may also develop in the form of long COVID. RAGE is expressed in essentially all kidney cell types. Increased production of RAGE isoforms and RAGE ligands during CKD and COVID-19 promotes RAGE activity. The downstream effects include cellular dysfunction, tissue injury, fibrosis, and inflammation, which in turn contribute to a decline in kidney function, hypertension, thrombotic disorders, and cognitive impairment. In this review, we discuss the forms and mechanisms of RAGE and RAGE ligands in the kidney and COVID-19. Because various small molecules antagonize RAGE activity in animal models, targeting RAGE, its co-receptors, or its ligands may offer novel therapeutic approaches to slowing or halting progressive kidney disease, for which current therapies are often inadequate.
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Affiliation(s)
- Colleen S. Curran
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Jeffrey B. Kopp
- Kidney Disease Section, NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases), National Institutes of Health, Bethesda, MD, United States
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Rashid G, Luzon AA, Korzets Z, Klein O, Zeltzer E, Bernheim J. The Effect of Advanced Glycation End-Products and Aminoguanidine on Tnfα Production by Rat Peritoneal Macrophages. Perit Dial Int 2020. [DOI: 10.1177/089686080102100203] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
ObjectiveTo evaluate the effect of advanced glycation end-products (AGEs) and the inhibitor of their formation, aminoguanidine, on tumor necrosis factor-α (TNFα) production (as a functional marker) by rat peritoneal macrophages (PMΦ).DesignCharles River rats underwent a daily intraperitoneal injection of peritoneal dialysis solution [(PDS), 4.25 g/dL dextrose; Dialine, Travenol, Ashdod, Israel] for a 2-month period (group E). Another group of rats was subjected to the same protocol with the addition of 25 mg/kg aminoguanidine (group A). Three control groups were utilized: ( 1 ) rats that were injected daily with aminoguanidine only (group AO), ( 2 ) rats that were injected with Dulbecco's phosphate-buffered saline (group D), and ( 3 ) rats in which no intervention was carried out (group C). After 2 months, PMΦ were isolated from rat peritoneal effluent and their TNFα production measured by ELISA in cell-free culture supernatants, in both the basal state and after 24-hour stimulation with lipopolysaccharide (LPS). The concentrations of AGEs in peritoneal effluent were assayed and correlated to TNFα levels. PMΦ obtained from normal rats were then incubated for 24 hours with ( 1 ) the peritoneal effluent of each of the above respective groups, with or without LPS; ( 2 ) increasing concentrations of AGEs (0 - 250 μg/mL); and ( 3 ) increasing concentrations of aminoguanidine (0 - 7.5 mg/mL), and TNFα secretion again determined.ResultsAfter 2 months of daily intraperitoneal injection of PDS, in the basal state, TNFα production was significantly higher in PMΦ isolated from the peritoneal effluent groups (groups E, A, and AO) compared to controls (group C). Following LPS stimulation, a further increase in TNFα secretion was seen, with a significantly greater response in group AO versus groups E, A, and D. Effluent AGEs were markedly elevated only in group E. No correlation was found between TNFα secretion by these PMΦ and the concentration of AGEs. On incubation with the respective peritoneal effluents (groups E, A, and AO), in both the basal and stimulated state, TNFα production by PMΦ from normal rats was significantly enhanced compared to group C. Incubation with increasing concentrations of AGEs or aminoguanidine resulted in an increase of TNFα secretion by these PMΦ.ConclusionsFollowing intermittent intraperitoneal administration of glucose-based PDS, rat PMΦ are chronically activated, as evidenced by increased basal TNFα secretion. The peritoneal effluent of such treated animals is capable of stimulating TNFα production by normal rat PMΦ. These data suggest that glucose-based PDS acts as a primer of PMΦ, which retain their ability to further stimulation by LPS. Although, in vitro, AGEs promote TNFα secretion by normal rat PMΦ, in vivo, their influence is probably modulated by other factors. Aminoguanidine has a specific inducing effect on rat PMΦ, independent of glucose-based PDS.
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Affiliation(s)
- Gloria Rashid
- Department of Nephrology and Hypertension, Sapir Medical Center, Kfar-Saba, and The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ami-Ad Luzon
- Department of Nephrology and Hypertension, Sapir Medical Center, Kfar-Saba, and The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ze'ev Korzets
- Department of Nephrology and Hypertension, Sapir Medical Center, Kfar-Saba, and The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Osnat Klein
- Department of Nephrology and Hypertension, Sapir Medical Center, Kfar-Saba, and The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ella Zeltzer
- Department of Nephrology and Hypertension, Sapir Medical Center, Kfar-Saba, and The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Jacques Bernheim
- Department of Nephrology and Hypertension, Sapir Medical Center, Kfar-Saba, and The Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
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Magdaleno F, Blajszczak CC, Charles-Niño CL, Guadrón-Llanos AM, Vázquez-Álvarez AO, Miranda-Díaz AG, Nieto N, Islas-Carbajal MC, Rincón-Sánchez AR. Aminoguanidine reduces diabetes-associated cardiac fibrosis. Exp Ther Med 2019; 18:3125-3138. [PMID: 31572553 DOI: 10.3892/etm.2019.7921] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 05/31/2019] [Indexed: 02/07/2023] Open
Abstract
Aminoguanidine (AG) inhibits advanced glycation end products (AGEs) and advanced oxidation protein products (AOPP) accumulated as a result of excessive oxidative stress in diabetes. However, the molecular mechanism by which AG reduces AGE-associated damage in diabetes is not well understood. Thus, we investigated whether AG supplementation mitigates oxidative-associated cardiac fibrosis in rats with type 2 diabetes mellitus (T2DM). Forty-five male Wistar rats were divided into three groups: Control, T2DM and T2DM+AG. Rats were fed with a high-fat, high-carbohydrate diet (HFCD) for 2 weeks and rendered diabetic using low-dose streptozotocin (STZ) (20 mg/kg), and one group was treated with AG (20 mg/kg) up to 25 weeks. In vitro experiments were performed in primary rat myofibroblasts to confirm the antioxidant and antifibrotic effects of AG and to determine if blocking the receptor for AGEs (RAGE) prevents the fibrogenic response in myofibroblasts. Diabetic rats exhibited an increase in cardiac fibrosis resulting from HFCD and STZ injections. By contrast, AG treatment significantly reduced cardiac fibrosis, α-smooth muscle actin (αSMA) and oxidative-associated Nox4 and Nos2 mRNA expression. In vitro challenge of myofibroblasts with AG under T2DM conditions reduced intra- and extracellular collagen type I expression and Pdgfb, Tgfβ1 and Col1a1 mRNAs, albeit with similar expression of Tnfα and Il6 mRNAs. This was accompanied by reduced phosphorylation of ERK1/2 and SMAD2/3 but not of AKT1/2/3 and STAT pathways. RAGE blockade further attenuated collagen type I expression in AG-treated myofibroblasts. Thus, AG reduces oxidative stress-associated cardiac fibrosis by reducing pERK1/2, pSMAD2/3 and collagen type I expression via AGE/RAGE signaling in T2DM.
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Affiliation(s)
- Fernando Magdaleno
- Department of Physiology, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico.,Department of Pathology, College of Medicine, University of Illinois at Chicago, IL 60612, USA
| | | | - Claudia Lisette Charles-Niño
- Department of Physiology, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico.,Department of Microbiology and Pathology, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico
| | - Alma Marlene Guadrón-Llanos
- Department of Physiology, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico
| | - Alan Omar Vázquez-Álvarez
- Department of Physiology, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico
| | - Alejandra Guillermina Miranda-Díaz
- Institute of Experimental and Clinical Therapeutics, Department of Physiology, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico
| | - Natalia Nieto
- Department of Pathology, College of Medicine, University of Illinois at Chicago, IL 60612, USA
| | - María Cristina Islas-Carbajal
- Institute of Experimental and Clinical Therapeutics, Department of Physiology, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico
| | - Ana Rosa Rincón-Sánchez
- Institute of Molecular Biology and Gene Therapy, Department of Molecular Biology and Genomics, University Center of Health Sciences, Guadalajara University, Guadalajara, Jalisco 44340, Mexico
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5
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Chen F, Ghosh A, Hu M, Long Y, Sun H, Kong L, Hong H, Tang S. RAGE-NF-κB-PPARγ Signaling is Involved in AGEs-Induced Upregulation of Amyloid-β Influx Transport in an In Vitro BBB Model. Neurotox Res 2017; 33:284-299. [PMID: 28871412 DOI: 10.1007/s12640-017-9784-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 07/04/2017] [Accepted: 07/05/2017] [Indexed: 11/25/2022]
Abstract
The receptor for advanced glycation end products (RAGE) at the blood-brain barrier (BBB) is critical for regulation of amyloid-β (Aβ) homeostasis in the diabetic brain. In this study, we used an in vitro BBB model consisting of mouse brain capillary endothelial cells (MBCECs) to investigate whether advanced glycation end products (AGEs) increase Aβ influx transport across the BBB and the underlying mechanisms. We found that AGEs induced Aβ influx transport across the BBB in concentration- and time-dependent manner, accompanied by increased RAGE expression and nuclear factor-kappa B p65 (NF-κB p65), and decreased nuclear peroxisome proliferator-activated receptor γ (PPARγ). Blockade of RAGE with its antibody and inhibition of NF-κB signaling with PDTC as well as activation of PPARγ with rosiglitazone significantly decreased Aβ transport across the BBB from the periphery to the brain. These treatments also pronouncedly suppressed AGEs-induced increases in RAGE expression and nuclear NF-κB p65 and reversed the decrease in nuclear PPARγ. These results suggest that RAGE-NF-κB-PPARγ signaling is involved in regulation of AGEs-induced influx transport of Aβ across the BBB and targeting the signaling pathway could serve as a novel strategy to modify such Aβ transport.
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Affiliation(s)
- Fang Chen
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China
| | - Arijit Ghosh
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China
- Department of Biomedical Sciences, City University of Hong Kong, HKSAR, China
| | - Mei Hu
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China
| | - Yan Long
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China
| | - Hongbin Sun
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China
| | - Lingyi Kong
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China
| | - Hao Hong
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China.
| | - Susu Tang
- Department of Pharmacology, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 210009, China.
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6
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Braidy N, Izadi M, Sureda A, Jonaidi-Jafari N, Banki A, Nabavi SF, Nabavi SM. Therapeutic relevance of ozone therapy in degenerative diseases: Focus on diabetes and spinal pain. J Cell Physiol 2017; 233:2705-2714. [PMID: 28594115 DOI: 10.1002/jcp.26044] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 06/06/2017] [Accepted: 06/07/2017] [Indexed: 12/18/2022]
Abstract
Ozone, one of the most important air pollutants, is a triatomic molecule containing three atoms of oxygen that results in an unstable form due to its mesomeric structure. It has been well-known that ozone has potent ability to oxidize organic compounds and can induce respiratory irritation. Although ozone has deleterious effects, many therapeutic effects have also been suggested. Since last few decades, the therapeutic potential of ozone has gained much attention through its strong capacity to induce controlled and moderated oxidative stress when administered in precise therapeutic doses. A plethora of scientific evidence showed that the activation of hypoxia inducible factor-1α (HIF-1a), nuclear factor of activated T-cells (NFAT), nuclear factor-erythroid 2-related factor 2-antioxidant response element (Nrf2-ARE), and activated protein-1 (AP-1) pathways are the main molecular mechanisms underlying the therapeutic effects of ozone therapy. Activation of these molecular pathways leads to up-regulation of endogenous antioxidant systems, activation of immune functions as well as suppression of inflammatory processes, which is important for correcting oxidative stress in diabetes and spinal pain. The present study intended to review critically the available scientific evidence concerning the beneficial properties of ozone therapy for treatment of diabetic complications and spinal pain. It finds benefit for integrating the therapy with ozone into pharmacological procedures, instead of a substitutive or additional option to therapy.
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Affiliation(s)
- Nady Braidy
- Centre for Healthy Brain Ageing, School of Psychiatry, University of New South Wales, Sydney, Australia
| | - Morteza Izadi
- Health Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Antoni Sureda
- Grup de Nutrició Comunitària i Estrès Oxidatiu (IUNICS) and CIBEROBN (Physiopathology of Obesity and Nutrition), Universitat de les Illes Balears, Palma de Mallorca, Spain
| | | | - Abdolali Banki
- Department of Neurology, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Seyed F Nabavi
- Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Seyed M Nabavi
- Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
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7
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Lim AI, Chan LYY, Tang SCW, Lai KN, Leung JCK. Albumin and glycated albumin activate KIM-1 release in tubular epithelial cells through distinct kinetics and mechanisms. Inflamm Res 2014; 63:831-9. [DOI: 10.1007/s00011-014-0757-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 07/05/2014] [Accepted: 07/08/2014] [Indexed: 01/06/2023] Open
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Proteome wide reduction in AGE modification in streptozotocin induced diabetic mice by hydralazine mediated transglycation. Sci Rep 2013; 3:2941. [PMID: 24126953 PMCID: PMC3796742 DOI: 10.1038/srep02941] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 09/27/2013] [Indexed: 02/07/2023] Open
Abstract
The non-enzymatic reaction between glucose and protein can be chemically reversed by transglycation. Here we report the transglycation activity of hydralazine using a newly developed MALDI-TOF-MS based assay. Hydralazine mediated transglycation of HbA1c, plasma proteins and kidney proteins was demonstrated in streptozotocin (STZ) induced diabetic mice, as evidenced by decrease in protein glycation, as well as presence of hydralazine-glucose conjugate in urine of diabetic mice treated with hydralazine. Hydralazine down regulated the expression of Receptor for Advanced Glycation End products (RAGE), NADPH oxidase (NOX), and super oxide dismutase (SOD). These findings will provide a new dimension for developing intervention strategies for the treatment of glycation associated diseases such as diabetes complications, atherosclerosis, and aging.
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9
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Abstract
The glomerulus has been at the center of attention as the primary site of injury in diabetic nephropathy (DN). Although there is no question that there are changes seen in the glomerulus, it is also well known that tubulointerstitial changes are a prominent component of the disease, especially in patients with type 2 diabetes. The level of albuminuria and DN disease progression best correlate with tubular degeneration and interstitial fibrosis. Nephrotoxicity studies in animals reveal that albuminuria is a highly sensitive marker of early tubular toxicity even in the absence of glomerular pathology. Urinary biomarker data in human beings support the view that proximal tubule injury contributes in a primary way, rather than in a secondary manner, to the development of early DN. I present a model in which very specific injury to the proximal tubule in vivo in the mouse results in severe inflammation, loss of blood vessels, interstitial fibrosis, and glomerulosclerosis. Increased glucose levels, free glycation adducts, reactive oxygen species, and oxidized lipids result in toxicity to tubule epithelia. This results in loss of cells with a stimulus to repair the epithelium. However, because of sublethal injury there is cell-cycle arrest in epithelial cells attempting to replace damaged cells. This leads to epithelial secretion of both profibrogenic growth factors, collagens, and factors that cause pericytes to proliferate and differentiate into myofibroblasts, leading to endothelial destabilization and capillary rarefaction. Local ischemia ensues with further injury to the tubules, more profibrogenic mediators, matrix protein deposition, fibrosis, and glomerulosclerosis.
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10
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Goodwin M, Herath C, Jia Z, Leung C, Coughlan MT, Forbes J, Angus P. Advanced glycation end products augment experimental hepatic fibrosis. J Gastroenterol Hepatol 2013; 28:369-76. [PMID: 23173780 DOI: 10.1111/jgh.12042] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/02/2012] [Indexed: 01/03/2023]
Abstract
BACKGROUND AND AIMS Advanced glycation end products (AGEs) are nonenzymatic modifications of proteins by reducing sugars. These compounds accumulate in a number of chronic disease states, contributing to tissue injury via several mechanisms, including activation of the receptor for advanced glycation end products (RAGE). We aimed to investigate whether AGEs can exacerbate chronic liver injury and contribute to hepatic fibrosis. METHODS We initially studied the effects of chronic hepatic exposure to high levels of AGEs given intraperitoneally as AGE-rat serum albumin. In a separate experiment, we examined the impact of high AGE exposure in rats following bile duct ligation (BDL). RESULTS In normal rats, chronic AGE-rat serum albumin administration induced significant increases in α-smooth muscle actin gene and protein expression but did not induce fibrosis or biochemical evidence of liver injury. However, in BDL animals, AGE-bovine serum albumin administration significantly increased hepatic fibrosis as evidenced by increased collagen content and α-smooth muscle actin expression, compared with BDL alone. Furthermore, AGEs increased hepatic oxidative stress and receptor for advanced glycation end products gene expression. CONCLUSIONS These findings suggest that AGEs may contribute to the pathogenesis of chronic liver injury and fibrosis.
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Affiliation(s)
- Michelle Goodwin
- Department of Medicine, The University of Melbourne, Melbourne, Victoria, Australia.
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11
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Nicousamide blocks the effects of advanced glycation end products on renal cells. Eur J Pharmacol 2012; 674:455-9. [PMID: 21763303 DOI: 10.1016/j.ejphar.2011.06.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 06/20/2011] [Accepted: 06/27/2011] [Indexed: 12/22/2022]
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12
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Lipid-induced peroxidation in the intestine is involved in glucose homeostasis imbalance in mice. PLoS One 2011; 6:e21184. [PMID: 21698161 PMCID: PMC3116876 DOI: 10.1371/journal.pone.0021184] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 05/22/2011] [Indexed: 12/03/2022] Open
Abstract
Background Daily variations in lipid concentrations in both gut lumen and blood are detected by specific sensors located in the gastrointestinal tract and in specialized central areas. Deregulation of the lipid sensors could be partly involved in the dysfunction of glucose homeostasis. The study aimed at comparing the effect of Medialipid (ML) overload on insulin secretion and sensitivity when administered either through the intestine or the carotid artery in mice. Methodology/Principal Findings An indwelling intragastric or intracarotid catheter was installed in mice and ML or an isocaloric solution was infused over 24 hours. Glucose and insulin tolerance and vagus nerve activity were assessed. Some mice were treated daily for one week with the anti-lipid peroxidation agent aminoguanidine prior to the infusions and tests. The intestinal but not the intracarotid infusion of ML led to glucose and insulin intolerance when compared with controls. The intestinal ML overload induced lipid accumulation and increased lipid peroxidation as assessed by increased malondialdehyde production within both jejunum and duodenum. These effects were associated with the concomitant deregulation of vagus nerve. Administration of aminoguanidine protected against the effects of lipid overload and normalized glucose homeostasis and vagus nerve activity. Conclusions/Significance Lipid overload within the intestine led to deregulation of gastrointestinal lipid sensing that in turn impaired glucose homeostasis through changes in autonomic nervous system activity.
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Bocci V, Zanardi I, Huijberts MSP, Travagli V. Diabetes and chronic oxidative stress. A perspective based on the possible usefulness of ozone therapy. Diabetes Metab Syndr 2011; 5:45-49. [PMID: 22814842 DOI: 10.1016/j.dsx.2010.05.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
It is now well established that hyperglycemia, present in both type 1 and type 2 diabetes, causes a variety of biochemical derangements leading to a diffused vascular damage responsible for several pathologic manifestations. Although preclinical and clinical studies have been performed by an unreliable administration route, the correct approach of oxygen-ozonetherapy may break a vicious circle. Messengers, released by a precise interaction ex vivo of the patient's blood with an equivalent calculated dose of ozone (0.42-0.84 mM), react with a variety of cells after blood infusion and restore a number of functions went astray. This paper aims to open a debate on this new therapy for improving the prognosis of diabetes.
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Affiliation(s)
- Velio Bocci
- Department of Physiology, University of Siena, Via A. Moro 2, 53100 Siena, Italy.
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14
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Motta AB. Dehydroepiandrosterone to induce murine models for the study of polycystic ovary syndrome. J Steroid Biochem Mol Biol 2010; 119:105-11. [PMID: 20188831 DOI: 10.1016/j.jsbmb.2010.02.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 02/05/2010] [Accepted: 02/16/2010] [Indexed: 12/25/2022]
Abstract
During the last decade a battery of animal models used for the study of polycystic ovary syndrome (PCOS) have allowed a focus on different aspects of the pathology. Since dehydroepiandrosterone (DHEA) was found to be one of the most abundant circulating androgens in women with PCOS, a rodent model showing the salient features found in women with PCOS was developed by the injection of DHEA. Although insulin-sensitizing agents, such as biguanides, are clinically used in the treatment of diabetes and PCOS, the complete understanding of their mechanisms of action remains unknown. The present review discusses the molecular mechanisms involved in the development of PCOS by using the DHEA-PCOS murine model and analyzes the role of the biguanide metformin as treatment.
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Affiliation(s)
- A B Motta
- Laboratorio de Fisio-patología Ovárica, Centro de Estudios Farmacológicos y Botánicos (CEFYBO), Facultad de Medicina, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Paraguay 2155, 1121 Buenos Aires, Argentina.
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15
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Li H, Zheng X, Wang H, Zhang Y, Xin H, Chen X. XLF-III-43, a novel coumarin-aspirin compound, prevents diabetic nephropathy in rats via inhibiting advanced glycation end products. Eur J Pharmacol 2009; 627:340-7. [PMID: 19895808 DOI: 10.1016/j.ejphar.2009.10.065] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 09/28/2009] [Accepted: 10/14/2009] [Indexed: 11/25/2022]
Abstract
Advanced glycation end products (AGE) have been implicated in the pathogenesis of diabetic complications. The purpose of this study was to examine the novel coumarin-aspirin compound XLF-III-43 in the inhibition of AGE formation in diabetic nephropathy. In vitro analysis showed XLF-III-43 in a dose-dependent manner decreased glucose induced formation of glycation adducts on albumin and inhibited AGE-lysozyme crosslinking. The streptozotocin-induced diabetic rats were used to investigate the beneficial effects of XLF-III-43 treatment on diabetic nephropathy. Administration of XLF-III-43 significantly decreased (P<0.05) blood urea nitrogen and urinary albumin excretion. Moreover, XLF-III-43 ameliorated kidney hypertrophy, mesangial expansion and glomerulosclerosis in diabetic rats relative to untreated model group. These data correlated with decreased both AGE and downstream markers of AGE stress (TGF-beta1, CTGF, fibronectin and collagen IV fibrolysis) in kidneys of diabetic rats. These data support further development of XLF-III-43 for prevention of nephropathy via inhibition of AGE formation consequent to chronic hyperglycemia.
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Affiliation(s)
- Hongyan Li
- Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, China.
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16
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Kelly DJ, Allen TJ, Cooper ME. Experimental diabetic nephropathy: Is it relevant to the human disease. Nephrology (Carlton) 2008. [DOI: 10.1046/j.1440-1797.2000.00003.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Darren J Kelly
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Center (Repatriation Campus), Heidelberg West, Victoria, Australia
| | - Terri J Allen
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Center (Repatriation Campus), Heidelberg West, Victoria, Australia
| | - Mark E Cooper
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Center (Repatriation Campus), Heidelberg West, Victoria, Australia
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17
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Williams ME, Bolton WK, Khalifah RG, Degenhardt TP, Schotzinger RJ, McGill JB. Effects of pyridoxamine in combined phase 2 studies of patients with type 1 and type 2 diabetes and overt nephropathy. Am J Nephrol 2007; 27:605-14. [PMID: 17823506 DOI: 10.1159/000108104] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 07/26/2007] [Indexed: 01/05/2023]
Abstract
BACKGROUND/AIMS Treatments of diabetic nephropathy (DN) delay the onset of end-stage renal disease. We report the results of safety/tolerability studies in patients with overt nephropathy and type 1/type 2 diabetes treated with pyridoxamine, a broad inhibitor of advanced glycation. METHODS The two 24-week studies were multicenter Phase 2 trials in patients under standard-of-care. In PYR-206, patients were randomized 1:1 and had baseline serum creatinine (bSCr) <or=2.0 mg/dl. In PYR-205/207, randomization was 2:1 and bSCr was <or=2.0 for PYR-205 and >or=2.0 but <or=3.5 mg/dl for PYR-207. Treated patients (122 active, 90 placebo) received 50 mg pyridoxamine twice daily in PYR-206; PYR-205/207 patients were escalated to 250 mg twice daily. RESULTS Adverse events were balanced between the groups (p = NS). Slight imbalances, mainly in the PYR-205/207 groups, were noted in deaths (from diverse causes, p = NS) and serious adverse events (p = 0.05) that were attributed to pre-existing conditions. In a merged data set, pyridoxamine significantly reduced the change from baseline in serum creatinine (p < 0.03). In patients similar to the RENAAL/IDNT studies (bSCr >or=1.3 mg/dl, type 2 diabetes), a treatment effect was observed on the rise in serum creatinine (p = 0.007). No differences in urinary albumin excretion were seen. Urinary TGF-beta1 also tended to decrease with pyridoxamine (p = 0.049) as did the CML and CEL AGEs. CONCLUSION These data provide a foundation for further evaluation of this AGE inhibitor in DN.
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Affiliation(s)
- Mark E Williams
- Harvard Medical School, Joslin Diabetes Center, Boston, MA 02215, USA.
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18
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Tang SCW, Leung JCK, Chan LYY, Tsang AWL, Lai KN. Activation of tubular epithelial cells in diabetic nephropathy and the role of the peroxisome proliferator-activated receptor-gamma agonist. J Am Soc Nephrol 2006; 17:1633-43. [PMID: 16687627 DOI: 10.1681/asn.2005101113] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The effects of advanced glycation end products (AGE) in the form of glycated albumin (GA) on the proinflammatory phenotype of cultured renal proximal tubular epithelial cells (PTEC) and the therapeutic potential of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist were studied. Human PTEC were exposed to medium alone or supplemented with albumin or GA with or without previous addition of rosiglitazone (0.1 to 0.5 microM). Exposure to GA (up to 0.5 mg/ml) but not the equivalent dose of neat albumin significantly upregulated both mRNA and protein expression of IL-8 and soluble intercellular adhesion molecule-1 (sICAM-1) in a dose- and time-dependent manner. Using immunohistochemistry, ICAM-1 signals were detected in the tubular epithelia and peritubular capillaries in association with AGE deposition and leukocyte infiltration, whereas IL-8 staining was localized in the tubular epithelia of human diabetic kidney biopsies. Also in a dose-dependent manner, GA (0.5 mg/ml) but not albumin caused nuclear translocation of NF-kappaB and activation of mitogen-activated protein kinase (MAPK) p44/p42 and signal transducer and activator of transcription (STAT-1). Inhibition of these pathways with pyrrolidine dithiocarbamate, PD 98059, and fludarabine, respectively, attenuated GA-induced IL-8 secretion. Rosiglitazone dose-dependently attenuated GA-induced IL-8 and ICAM-1 signals in PTEC and completely abolished GA-induced STAT-1 signals but had no effect on NF-kappaB and MAPK activation. These findings suggest that AGE stimulate renal tubular expression of adhesion molecule and chemokine that together may account for the transmigration of inflammatory cells into the interstitial space during diabetic tubulopathy. Such proinflammatory phenotype may be partially modified by PPAR-gamma ligation through STAT-1 inhibition independent of NF-kappaB transcriptional activity and MAPK signaling.
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Affiliation(s)
- Sydney C W Tang
- Division of Nephrology, Department of Medicine, University of Hong Kong, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong
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19
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Bach LA, Gallicchio MA, McRobert EA, Tikoo A, Cooper ME. Effects of Advanced Glycation End Products on Ezrin-Dependent Functions in LLC-PK1 Proximal Tubule Cells. Ann N Y Acad Sci 2006; 1043:609-16. [PMID: 16037284 DOI: 10.1196/annals.1338.069] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have recently shown that advanced glycation products (AGEs) bind to the ERM (ezrin, radixin, moesin) family of proteins. ERM proteins act as cross-linkers between cell membrane proteins and the actin cytoskeleton. They are also involved in signal transduction pathways. They therefore have a critical role in normal cell processes, including modulation of cell shape, adhesion, and motility. We postulate that AGEs may contribute to diabetic complications by disrupting ERM function. In support of this hypothesis, AGEs inhibit ezrin-dependent tubulogenesis of proximal tubule cells. Phosphorylation is an important activating mechanism for ERM proteins, and AGEs inhibit ezrin phosphorylation mediated by the epidermal growth factor receptor.
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Affiliation(s)
- Leon A Bach
- University of Melbourne, Department of Medicine, Austin Hospital, Heidelberg, Vic 3084 Australia.
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20
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McRobert EA, Tikoo A, Gallicchio MA, Cooper ME, Bach LA. Localization of the Ezrin Binding Epitope for Glycated Proteins. Ann N Y Acad Sci 2006; 1043:617-24. [PMID: 16037285 DOI: 10.1196/annals.1333.070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
ERM proteins (ezrin, radixin, and moesin) have recently been identified as a new class of AGE-binding proteins. ERM proteins link the plasma membrane with the actin cytoskeleton and regulate cell shape, motility, adhesion, and signal transduction. ERM proteins have three structural domains: the N-terminal domain, a coiled midregion, and the C-terminal domain. The N-terminal domain binds to a number of plasma membrane ligands and is involved in signal transduction, while the C-domain binds to actin filaments. Binding studies with isolated structural domains showed that glycated proteins bind to an epitope within the N-terminal domain of ezrin (aa 1-324). It is postulated that some of the cellular effects of AGEs leading to diabetic complications may be mediated by binding to this region of ezrin, thereby interrupting the cross-linking between the plasma membrane and actin cytoskeleton and downstream signaling pathways. Indeed, changes in actin arrangement, cell shape, and adhesion have been described in diabetes, and AGE-BSA inhibits ezrin-dependent tubulogenesis of LLC-PK1 proximal tubular cells. For future development of antagonists, further identification of the ezrin-binding epitope for glycated proteins is required.
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Affiliation(s)
- E Anne McRobert
- Present address and address for correspondence: E. Anne McRobert, Central and Eastern Clinical School, Department of Medicine, Monash University, AMREP, Alfred Hospital, Prahran, Vic 3181, Australia.
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21
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Abstract
Despite the worldwide epidemic of chronic kidney disease complicating diabetes mellitus, current therapies directed against nephroprogression are limited to angiotensin conversion or receptor blockade. Nonetheless, additional therapeutic possibilities are slowly emerging. The diversity of therapies currently in development reflects the pathogenic complexity of diabetic nephropathy. The three most important candidate drugs currently in development include a glycosaminoglycan, a protein kinase C (PKC) inhibitor and an inhibitor of advanced glycation. In targeting primary mechanisms by which hyperglycaemia contributes to diabetic complications, these drugs could provide risk reduction complementary to the partial reduction proven for ACE inhibitors and angiotensin II receptor antagonists (angiotensin receptor blockers). Glycosaminoglycans act to restore glycoproteins present in reduced amounts in the glomerular basement membrane and mesangium of diabetic animal models. Components of the drug sulodexide prevent pathological changes and proteinuria in diabetic rats. Reductions in albuminuria, a hallmark of early diabetic kidney disease, have been reported in initial human trials. In the US, a multicentre phase II study has been completed, with an interim analysis indicating reduction in urinary albumin losses. Pivotal phase II trials have begun in patients with type 2 diabetes. A second metabolic pathway of diabetic complications is overexpression of PKC. Several activators of this family of intracellular kinases have been identified and PKC activation may result in tissue damage through a variety of mechanisms. In animal models, the inhibitor ruboxistaurin reduces albuminuria, diabetic histological changes and kidney injury. Like sulodexide, drug development of ruboxistaurin has reached completion of a phase II evaluation with mixed results. The third metabolic target is the nonenzymatic formulation of advanced glycation end-products (AGEs) through well described biochemical pathways. Multiple pathways lead to AGE accumulation in tissues in diabetes and diverse AGE products are formed. AGE deposition has been implicated in animal models of diabetic nephropathy. The leading AGE inhibitor currently in development is pyridoxamine, which has multiple actions that inhibit glycation. Pyridoxamine is an efficient AGE inhibitor in experimental diabetes. A phase II study in diabetic patients with nephropathy reported mixed efficacy results and a favourable safety profile. Phase III evaluation of pyridoxamine has not begun. These three classes of potential therapies, if successfully developed, will confirm that diabetic kidney disease has entered the era of biochemical treatments.
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Affiliation(s)
- Mark E Williams
- Renal Unit, The Joslin Diabetes Center, Boston, Massachusetts 02215, USA.
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22
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Bohlender JM, Franke S, Stein G, Wolf G. Advanced glycation end products and the kidney. Am J Physiol Renal Physiol 2005; 289:F645-59. [PMID: 16159899 DOI: 10.1152/ajprenal.00398.2004] [Citation(s) in RCA: 272] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Advanced glycation end products (AGEs) are a heterogeneous group of protein and lipids to which sugar residues are covalently bound. AGE formation is increased in situations with hyperglycemia (e.g., diabetes mellitus) and is also stimulated by oxidative stress, for example in uremia. It appears that activation of the renin-angiotensin system may contribute to AGE formation through various mechanisms. Although AGEs could nonspecifically bind to basement membranes and modify their properties, they also induce specific cellular responses including the release of profibrogenic and proinflammatory cytokines by interacting with the receptor for AGE (RAGE). However, additional receptors could bind AGEs, adding to the complexity of this system. The kidney is both: culprit and target of AGEs. A decrease in renal function increases circulating AGE concentrations by reduced clearance as well as increased formation. On the other hand, AGEs are involved in the structural changes of progressive nephropathies such as glomerulosclerosis, interstitial fibrosis, and tubular atrophy. These effects are most prominent in diabetic nephropathy, but they also contribute to renal pathophysiology in other nondiabetic renal diseases. Interference with AGE formation has therapeutic potential for preventing the progression of chronic renal diseases, as shown from data of animal experiments and, more recently, the first clinical trials.
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Affiliation(s)
- Jürgen M Bohlender
- Klinik für Innere Medizin III, Universitätsklinik Jena, Erlanger Allee 101, Jena, Germany.
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23
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Thomas MC, Forbes JM, MacIsaac R, Jerums G, Cooper ME. Low-molecular weight advanced glycation end products: markers of tissue AGE accumulation and more? Ann N Y Acad Sci 2005; 1043:644-54. [PMID: 16037288 DOI: 10.1196/annals.1333.073] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Incomplete digestion of advanced glycation end product (AGE)-modified protein results in the formation of low-molecular weight degradation products incorporating AGE modifications (LMW-AGEs). In addition to being biomarkers of AGE modification, LMW-AGEs may have a high toxic potential, being free to interact with AGE receptors at distant sites via the circulation. Several free AGEs have been identified, including pentosidine, N(epsilon)-(carboxymethyl)lysine (CML), and free-imidazole AGEs. In addition, fluorescence (370 nm [excitation]/440 nm [emission]) in the LMW phase of serum correlates with tissue fluorescence, an established marker for AGE modification. In experimental diabetes, LMW fluorescence increases with duration of disease and is normalized with the AGE inhibitor aminoguanidine. LMW fluorescence is also higher in patients with diabetes, in whom it is associated with glomerular filtration rate and hemoglobin. Patients with hyperfiltration have lower LMW fluorescence than those with normal renal function, which may protect them from AGE accumulation in the short term. These findings provide clinical support for the association between AGEs and progressive renal injury in diabetes.
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Affiliation(s)
- Merlin C Thomas
- The Baker Heart Research Institute, P.O. Box 6492, St. Kilda Rd. Central, Melbourne, Victoria, Australia.
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24
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Williams ME, Tuttle KR. The next generation of diabetic nephropathy therapies: an update. Adv Chronic Kidney Dis 2005; 12:212-22. [PMID: 15822057 DOI: 10.1053/j.ackd.2005.01.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Although treatments for diabetic kidney disease are available, many patients still have progressive disease. More effective therapies are urgently needed. Novel agents currently under evaluation in clinical trials are described in this review. Sulodexide, a mixture of three glycosaminoglycans, appears to prevent diabetic nephropathy in experimental models by ameliorating abnormalities in the glomerular basement membrane and mesangial matrix. Pyridoxamine is an inhibitor of advanced glycation end-product (AGE) formation derived from vitamin B(6). Alagebrium is an AGE cross-link breaker. AGEs injure the kidneys and other vascular targets by mechanisms such as oxidative stress, inflammation, and protein cross-linking, among others. By inhibiting AGE formation or breaking AGE cross-links, experimental models have demonstrated kidney protection. Ruboxistaurin is an inhibitor of protein kinase C beta (PKC-beta), a mediator of signal transduction that leads to cell growth, fibrosis, and tissue injury. In diabetes, PKC-beta is up-regulated and activated in the kidney. Ruboxistaurin prevents diabetic kidney disease in animal models. These agents have appeared promising (by reduction of albuminuria and preservation of kidney function) in phase II studies. To determine whether clinical outcomes (mortality, renal, and cardiovascular events) are improved beyond the current standard of care, phase III trials are planned.
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25
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Susztak K, Ciccone E, McCue P, Sharma K, Böttinger EP. Multiple metabolic hits converge on CD36 as novel mediator of tubular epithelial apoptosis in diabetic nephropathy. PLoS Med 2005; 2:e45. [PMID: 15737001 PMCID: PMC549593 DOI: 10.1371/journal.pmed.0020045] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Accepted: 12/21/2004] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Diabetic nephropathy (DNP) is a common complication of type 1 and type 2 diabetes mellitus and the most common cause of kidney failure. While DNP manifests with albuminuria and diabetic glomerulopathy, its progression correlates best with tubular epithelial degeneration (TED) and interstitial fibrosis. However, mechanisms leading to TED in DNP remain poorly understood. METHODS AND FINDINGS We found that expression of scavenger receptor CD36 coincided with proximal tubular epithelial cell (PTEC) apoptosis and TED specifically in human DNP. High glucose stimulated cell surface expression of CD36 in PTECs. CD36 expression was necessary and sufficient to mediate PTEC apoptosis induced by glycated albumins (AGE-BSA and CML-BSA) and free fatty acid palmitate through sequential activation of src kinase, and proapoptotic p38 MAPK and caspase 3. In contrast, paucity of expression of CD36 in PTECs in diabetic mice with diabetic glomerulopathy was associated with normal tubular epithelium and the absence of tubular apoptosis. Mouse PTECs lacked CD36 and were resistant to AGE-BSA-induced apoptosis. Recombinant expression of CD36 in mouse PTECs conferred susceptibility to AGE-BSA-induced apoptosis. CONCLUSION Our findings suggest a novel role for CD36 as an essential mediator of proximal tubular apoptosis in human DNP. Because CD36 expression was induced by glucose in PTECs, and because increased CD36 mediated AGE-BSA-, CML-BSA-, and palmitate-induced PTEC apoptosis, we propose a two-step metabolic hit model for TED, a hallmark of progression in DNP.
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Affiliation(s)
- Katalin Susztak
- 1Division of Nephrology, Department of MedicineMount Sinai School of Medicine, New York, New YorkUnited States of America
- 2Division of Nephrology, Department of MedicineAlbert Einstein College of Medicine, Bronx, New YorkUnited States of America
| | - Emilio Ciccone
- 3Dorrance Hamilton Research Laboratories, Division of NephrologyDepartment of Medicine, Thomas Jefferson University, Philadelphia, PennsylvaniaUnited States of America
| | - Peter McCue
- 4Department of Pathology, Anatomyand Cell Biology, Thomas Jefferson University, Philadelphia, PennsylvaniaUnited States of America
| | - Kumar Sharma
- 3Dorrance Hamilton Research Laboratories, Division of NephrologyDepartment of Medicine, Thomas Jefferson University, Philadelphia, PennsylvaniaUnited States of America
- *To whom correspondence should be addressed. E-mail: , E-mail:
| | - Erwin P Böttinger
- 1Division of Nephrology, Department of MedicineMount Sinai School of Medicine, New York, New YorkUnited States of America
- *To whom correspondence should be addressed. E-mail: , E-mail:
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26
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Abstract
Current treatment of the nephropathy complication of diabetes mellitus is suboptimal in halting the progression of the complex disease. Among the irreversible effects of sustained hyperglycemia is the heightened formation of advanced glycation end products (AGEs). The role of AGEs in diabetic nephropathy has been established by years of basic research. This article reports progression through human studies of the few AGE inhibitors that have reached clinical development, including pimagedine, pyridoxamine, and alagebrium.
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Affiliation(s)
- Mark E Williams
- Joslin Diabetes Center, Harvard Medical School, 1 Joslin Place, Boston, MA 02215, USA.
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27
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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: 12.1] [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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Menè P, Festuccia F, Pugliese F. Clinical potential of advanced glycation end-product inhibitors in diabetes mellitus. Am J Cardiovasc Drugs 2004; 3:315-20. [PMID: 14728065 DOI: 10.2165/00129784-200303050-00002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Non-enzymatic accumulation of advanced glycation end-products (AGE) is to some extent a physiologic consequence of tissue aging. On the other hand, circulating AGE and tissue deposits mark the course of diabetes mellitus as well as a variety of other vascular or degenerative diseases. AGE generation is paralleled by oxidative damage and lipid peroxidation within target tissue, with features of inflammation through the involvement of monocytes/macrophages expressing receptors for glycated macromolecules. Over the past 15 years, a wealth of data concerning the pharmacology of AGE have been gathered through animal and human investigations, targeting their likely contribution to the progression of diabetic and non-diabetic vascular damage. Several agents have been shown to interfere with the formation of AGE or AGE precursors, bind to tissue receptors, or promote breakdown of deposits. The first and most studied inhibitor, aminoguanidine, has shown extensive beneficial effects in experimental models of diabetic vascular damage, recently entering phase I-III clinical investigation. Newer anti-AGE agents include pyridoxamine and the so-called 'amadorins', cross-link breakers, AGE binders and receptor antagonists.
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Affiliation(s)
- Paolo Menè
- Department of Clinical Sciences, Division of Nephrology, University of Rome La Sapienza, Rome, Italy.
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29
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Osicka TM, Forbes JM, Thallas V, Brammar GC, Jerums G, Comper WD. Ramipril prevents microtubular changes in proximal tubules from streptozotocin diabetic rats. Nephrology (Carlton) 2004; 8:205-11. [PMID: 15012722 DOI: 10.1046/j.1440-1797.2003.00159.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This study has investigated the microtubular cytoskeleton in rat glomerular and proximal tubule cells in experimental diabetes. The effect of treatment with ramipril on the relationship between microtubule organization and albuminuria in diabetes has also been examined. Diabetes was induced in male Sprague-Dawley rats by administration of streptozotocin (50 mg/kg, i.v.). Rats were treated with or without ramipril in their drinking water for 12 weeks. Diabetes was characterized by an increase in blood glucose level, glomerular filtration rate, and albumin excretion rate. Treatment of diabetic rats with ramipril did not affect glycaemic control, but reduced systolic blood pressure and prevented the rise in albuminuria and glomerular filtration rate. Immunohistochemistry was performed by using the ARK Peroxidase method with alpha-tubulin antibody. The regular, grainy staining pattern of the microtubules present in the renal proximal tubules from control kidneys was altered in diabetic animals, and appeared fragmented and striated. This was prevented by treatment with ramipril. Quantitative morphometric analysis revealed an increase in the percent proportional staining for alpha-tubulin in the proximal tubules of untreated diabetic rats (33.3 +/- 3.3%, n = 8, P < 0.05 vs control) compared with control rats (11.7 +/- 1.7%, n = 6), which was reduced by ramipril treatment (26.7 +/- 2.1%, n = 6, P < 0.05 vs untreated diabetic). Staining for alpha-tubulin in glomerular cells was unchanged in all groups. There was no significant difference in renal alpha-tubulin expression among all groups, as determined by real-time reverse transcription-polymerase chain reaction. These results raise the possibility that diabetes-induced changes in microtubules in the renal proximal tubules may contribute, in part, to the increase in albuminuria observed in diabetes.
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Affiliation(s)
- Tanya M Osicka
- Endocrine Unit, Department of Medicine, University of Melbourne, Austin & Repatriation Medical Centre, Heidelberg, Victoria, Australia.
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30
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Flyvbjerg A, Denner L, Schrijvers BF, Tilton RG, Mogensen TH, Paludan SR, Rasch R. Long-term renal effects of a neutralizing RAGE antibody in obese type 2 diabetic mice. Diabetes 2004; 53:166-72. [PMID: 14693711 DOI: 10.2337/diabetes.53.1.166] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Advanced glycation end products (AGEs) have been implicated in the pathogenesis of diabetic kidney disease. The actions of AGEs are mediated both through a non-receptor-mediated pathway and through specific receptors for AGE (RAGEs). To explore a specific role for RAGE in renal changes in type 2 diabetes, we examined the renal effects of a neutralizing murine RAGE antibody in db/db mice, a model of obese type 2 diabetes. One group of db/db mice was treated for 2 months with the RAGE antibody, and another db/db group was treated for the same period with an irrelevant IgG. Two groups of nondiabetic db/+ mice were treated with either RAGE antibody or isotype-matched IgG for 2 months. Placebo-treated db/db mice showed a pronounced increase in kidney weight, glomerular volume, basement membrane thickness (BMT), total mesangial volume, urinary albumin excretion (UAE), and creatinine clearance compared with nondiabetic controls. In RAGE antibody-treated db/db mice, the increase in kidney weight, glomerular volume, mesangial volume, and UAE was reduced, whereas the increase in creatinine clearance and BMT was fully normalized. Notably, these effects in db/db mice were seen without impact on body weight, blood glucose, insulin levels, or food consumption. In conclusion, RAGE is an important pathogenetic factor in the renal changes in an animal model of type 2 diabetes.
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Affiliation(s)
- Allan Flyvbjerg
- Medical Department M and Medical Research Laboratories, Institute of Experimental Clinical Research, Aarhus University Hospital, Aarhus, Denmark.
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31
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Osicka TM, Russo LM, Qiu ML, Brammar GC, Thallas V, Forbes JM, Comper WD, Jerums G. Additive effects of hypertension and diabetes on renal cortical expression of PKC-?? and -??? and ??-tubulin but not PKC-??1 and -??2. J Hypertens 2003; 21:2399-407. [PMID: 14654761 DOI: 10.1097/00004872-200312000-00029] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE This study examined the separate and combined effects of hypertension and diabetes on renal cortical expression of protein kinase C (PKC) isoforms -beta 1, -beta 2, -alpha and -epsilon, to determine whether albuminuria is the result of an increase in the expression of one or a combination of PKC isoforms. Corresponding changes in renal microtubules were also assessed. METHODS Diabetes (D) was induced in Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) by streptozotocin. After 24 weeks, PKC expression was determined by Western blot and microtubules were assessed by immunohistochemistry for alpha-tubulin protein. RESULTS Diabetes was characterized by significant increases in glycated haemoglobin (HbA1c) as compared to controls (C). There was a significant increase of three- to four-fold in PKC protein content for all four isoforms in renal cortex from SHR-C and WKY-D, and similar and significant levels of albuminuria (approximately 10 mg/24 h) observed in these groups in comparison to WKY-C (approximately 1 mg/24 h). Interestingly, PKC-alpha and -epsilon but not PKC-beta 1 and -beta 2 protein content was doubled in SHR-D, and albuminuria increased tenfold (approximately 100 mg/24 h) in comparison to SHR-C and WKY-D. These changes were paralleled by a significant decrease in alpha-tubulin protein content of approximately 50% in SHR-C and approximately 33% in WKY-D compared to WKY-C, with a further decrease of approximately 67% in SHR-D compared to WKY-C. CONCLUSION These findings indicate that PKC expression can be increased by either diabetes or hypertension, and that there are further specific increases in the expression of PKC isoforms -alpha and -epsilon in the model of combined diabetes and hypertension. In addition, the degree of disruption in microtubular cytoskeleton appears to be correlated with PKC activation and levels of albuminuria.
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Affiliation(s)
- Tanya M Osicka
- Endocrine Unit, Department of Medicine, University of Melbourne, Austin and Repatriation Medical Centre, Heidelberg, Victoria, Australia.
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Jerums G, Panagiotopoulos S, Forbes J, Osicka T, Cooper M. Evolving concepts in advanced glycation, diabetic nephropathy, and diabetic vascular disease. Arch Biochem Biophys 2003; 419:55-62. [PMID: 14568009 DOI: 10.1016/j.abb.2003.08.017] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Advanced glycation endproducts (AGEs) have been postulated to play a role in the development of both nephropathy and large vessel disease in diabetes. However, it is still not clear which AGE subtypes play a pathogenetic role and which of several AGE receptors mediate AGE effects on cells. This review summarises the renoprotective effect of inhibitors of AGE formation, including aminoguanidine, and of cross-link breakers, including ALT-711, on experimental diabetic nephropathy and on mesenteric vascular hypertrophy. It also demonstrates similar effects of aminoguanidine and ramipril (an angiotensin converting enzyme inhibitor) on fluorescent and immunoassayable AGE levels, renal protein kinase C activity, nitrotyrosine expression, lysosomal function, and protein handling in experimental diabetes. These findings indicate that inhibition of the renin angiotensin system blocks both upstream and downstream pathways leading to tissue injury. We postulate that the chemical pathways leading to advanced glycation endproduct formation and the renin angiotensin systems may interact through the generation of free radicals, induced both by glucose and angiotensin II. There is also evidence to suggest that AGE-dependent pathways may play a role in the development of tubulointerstitial fibrosis in the diabetic kidney. This effect is mediated through RAGE and is TGF-beta and CTGF-dependent.
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Affiliation(s)
- George Jerums
- Endocrine Unit, Austin Health, University of Melbourne, Studley Road, 3084 Heidelberg, Australia.
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Forbes JM, Thallas V, Thomas MC, Founds HW, Burns WC, Jerums G, Cooper ME. The breakdown of preexisting advanced glycation end products is associated with reduced renal fibrosis in experimental diabetes. FASEB J 2003; 17:1762-4. [PMID: 12958202 DOI: 10.1096/fj.02-1102fje] [Citation(s) in RCA: 199] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Renal accumulation of advanced glycation end products (AGEs) has been linked to the progression of diabetic nephropathy. Cleavage of pre-formed AGEs within the kidney by a cross-link breaker, such as ALT-711, may confer renoprotection in diabetes. STZ diabetic rats were randomized into a) no treatment (D); b) treatment with the AGE cross-link breaker, ALT-711, weeks 16-32 (DALT early); and c) ALT-711, weeks 24-32 (DALT late). Treatment with ALT-711 resulted in a significant reduction in diabetes-induced serum and renal AGE peptide fluorescence, associated with decreases in renal carboxymethyllysine and RAGE immunostaining. Cross-linking of tail tendon collagen seen in diabetic groups was attenuated only by 16 weeks of ALT-711 treatment. ALT-711, independent of treatment duration, retarded albumin excretion rate (AER), reduced blood pressure, and renal hypertrophy. It also reduced diabetes-induced increases in gene expression of transforming growth factor beta1 (TGF-beta1), connective tissue growth factor (CTGF), and collagen IV. However, glomerulosclerotic index, tubulointerstitial area, total renal collagen, nitrotyrosine, protein expression of collagen IV, and TGF-beta1 only showed improvement with early ALT treatment alone. This study demonstrates the utility of a cross-link breaker as a treatment for diabetic nephropathy and describes effects not only on renal AGEs but on putative mediators of renal injury, such as prosclerotic cytokines and oxidative stress.
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Affiliation(s)
- Josephine M Forbes
- Division of Diabetic Complications, Baker Medical Research Institute, Melbourne, Australia.
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McRobert EA, Gallicchio M, Jerums G, Cooper ME, Bach LA. The amino-terminal domains of the ezrin, radixin, and moesin (ERM) proteins bind advanced glycation end products, an interaction that may play a role in the development of diabetic complications. J Biol Chem 2003; 278:25783-9. [PMID: 12734202 DOI: 10.1074/jbc.m210433200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The presence of advanced glycation end products (AGEs) formed because of hyperglycemia in diabetic patients has been strongly linked to the development of diabetic complications and disturbances in cellular function. In this report, we describe the isolation and identification of novel AGE-binding proteins from diabetic rat kidneys. The proteins were purified by cation exchange and AGE-modified bovine serum albumin (AGE-BSA) affinity chromatography. NH2-terminal and internal sequencing identified the proteins as the NH2-terminal domains of ezrin, radixin, and moesin (ERM proteins). Using BIAcore biosensor analysis, human N-ezrin-(1-324) bound to immobilized AGE-BSA with a KD of 5.3 +/- 2.1 x 10 -7 m, whereas full-length ezrin-(1-586) and C-ezrin-(323-586) did not bind. Other glycated proteins such as AGE-RNase, N in -carboxymethyllysine (CML)-BSA, and glycated human serum albumin isolated from hyperglycemic diabetic sera competed with the immobilized AGE-BSA for binding to N-ezrin, but non-glycated BSA and RNase did not. Thus N-ezrin binds to AGEs in a glycation- and concentration-dependent manner. Phosphorylated ezrin plays a crucial role in cell shape changes, cell attachment, and cell adhesion. The effect of AGE-BSA on ezrin function was studied in a tubulogenesis model in which LLC-PK1 cell tubule formation is dependent on phosphorylated ezrin. Addition of AGE-BSA completely inhibited the ability of the cells to produce tubules. Furthermore, in vitro tyrosine phosphorylation of N-ezrin and ezrin was also inhibited by AGE-BSA. These proteins represent a novel family of intracellular binding molecules for glycated proteins and provide a potential new target for therapeutic intervention in the prevention or treatment of diabetic complications.
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Affiliation(s)
- E Anne McRobert
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Centre, Heidelberg, 3084 Victoria, Australia
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Bonnefont-Rousselot D, Raji B, Walrand S, Gardès-Albert M, Jore D, Legrand A, Peynet J, Vasson MP. An intracellular modulation of free radical production could contribute to the beneficial effects of metformin towards oxidative stress. Metabolism 2003; 52:586-9. [PMID: 12759888 DOI: 10.1053/meta.2003.50093] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Metformin (dimethylbiguanide) is an antihyperglycemic agent used in type 2 diabetes. Beyond its action on glycemic control, metformin exhibits other intrinsic effects that could play a role in prevention against diabetes complications. Some studies thus reported an improvement in the antioxidant status in patients treated with metformin. This might be in part related to its property to limit formation of advanced glycation end products (AGEs) and to decrease the overproduction of free radicals in diabetic subjects. The aim of this study was to investigate the in vitro ability of metformin to modulate the action of reactive oxygen species (ROS) generated either by water gamma radiolysis or by stimulated human leukocytes. Our results showed that metformin at pharmacologically relevant concentrations was in vitro able to scavenge hydroxyl ((.)OH) but not superoxide (O(.-)(2)) free radicals and that hydrogen peroxide did not react with metformin. Nevertheless, when polymorphonuclear cells (PMN) are stimulated by phorbol myristate acetate (PMA), or above all by formyl methionine leucyl phenylalanine (fMLP), a systematic (although nonsignificant) decrease of the ROS-induced chimiluminescence (CL) was observed. These results suggest that metformin could directly scavenge ROS or indirectly act by modulating the intracellular production of superoxide anion, of which NADPH oxidase constitutes the major source. This could contribute to the additional benefits of metformin, especially those related to the improvement in the cardiovascular outcomes in diabetes.
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Affiliation(s)
- D Bonnefont-Rousselot
- Laboratoire de Biochimie Métabolique et Clinique (EA 3617), Faculté de Pharmacie, Paris, France
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Williams ME. New therapies for advanced glycation end product nephrotoxicity: current challenges. Am J Kidney Dis 2003; 41:S42-7. [PMID: 12612951 DOI: 10.1053/ajkd.2003.50083] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND The role of advanced glycation end products (AGEs) in diabetic nephropathy has been developed during several years of research and increasingly complex AGE biochemistry. However, the structural diversity of AGE chemistry has created new challenges in the search for AGE-based inhibition therapies. RESULTS The challenges include the need to standardize measurements of serum and tissue AGE levels, identifying nephrotoxic AGE compounds, understanding the cell biological state of AGEs in the diabetic kidney, determining the mechanism of action of selective inhibition of the glycation cascade, and forming complementary therapies. CONCLUSION Current challenges in the development of new therapies for AGE nephrotoxicity are reviewed.
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Affiliation(s)
- Mark E Williams
- Joslin Diabetes Center and Harvard Medical School, Boston, MA, USA.
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Morcos M, Sayed AAR, Bierhaus A, Yard B, Waldherr R, Merz W, Kloeting I, Schleicher E, Mentz S, Abd el Baki RF, Tritschler H, Kasper M, Schwenger V, Hamann A, Dugi KA, Schmidt AM, Stern D, Ziegler R, Haering HU, Andrassy M, van der Woude F, Nawroth PP. Activation of tubular epithelial cells in diabetic nephropathy. Diabetes 2002; 51:3532-44. [PMID: 12453911 DOI: 10.2337/diabetes.51.12.3532] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Previous studies have shown that renal function in type 2 diabetes correlates better with tubular changes than with glomerular pathology. Since advanced glycation end products (AGEs; AGE-albumin) and in particular carboxymethyllysine (CML) are known to play a central role in diabetic nephropathy, we studied the activation of nuclear factor kappaB (NF-kappaB) in tubular epithelial cells in vivo and in vitro by AGE-albumin and CML. Urine samples from healthy control subjects (n = 50) and type 2 diabetic patients (n = 100) were collected and tested for excretion of CML and the presence of proximal tubular epithelial cells (pTECs). CML excretion was significantly higher in diabetic patients than in healthy control subjects (P < 0.0001) and correlated with the degree of albuminuria (r = 0.7, P < 0.0001), while there was no correlation between CML excretion and HbA(1c) (r = 0.03, P = 0.76). Urine sediments from 20 of 100 patients contained pTECs, evidenced by cytokeratin 18 positivity, while healthy control subjects (n = 50) showed none (P < 0.0001). Activated NF-kappaB could be detected in the nuclear region of excreted pTECs in 8 of 20 patients with pTECs in the urine sediment (40%). Five of eight NF-kappaBp65 antigen-positive cells stained positive for interleukin-6 (IL-6) antigen (62%), while only one of the NF-kappaB-negative cells showed IL-6 positivity. pTECs in the urine sediment correlated positively with albuminuria (r = 0.57, P < 0.0001) and CML excretion (r = 0.55, P < 0.0001). Immunohistochemistry in diabetic rat kidneys and a human diabetic kidney confirmed strong expression of NF-kappaB in tubular cells. To further prove an AGE/CML-induced NF-kappaB activation in pTECs, NF-kappaB activation was studied in cultured human pTECs by electrophoretic mobility shift assays (EMSAs) and Western blot. Stimulation of NF-kappaB binding activity was dose dependent and was one-half maximal at 250 nmol/l AGE-albumin or CML and time dependent at a maximum of activation after 4 days. Functional relevance of the observed NF-kappaB activation was demonstrated in pTECs transfected with a NF-kappaB-driven luciferase reporter plasmid and was associated with an increased release of IL-6 into the supernatant. The AGE- and CML-dependent activation of NF-kappaBp65 and NF-kappaB-dependent IL-6 expression could be inhibited using the soluble form of the receptor for AGEs (RAGE) (soluble RAGE [sRAGE]), RAGE-specific antibody, or the antioxidant thioctic acid. In addition transcriptional activity and IL-6 release from transfected cells could be inhibited by overexpression of the NF-kappaB-specific inhibitor kappaBalpha. The findings that excreted pTECs demonstrate activated NF-kappaB and IL-6 antigen and that AGE-albumin and CML lead to a perpetuated activation of NF-kappaB in vitro infer that a perpetuated increase in proinflammtory gene products, such as IL-6, plays a role in damaging the renal tubule.
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Affiliation(s)
- Michael Morcos
- Department of Internal Medicine 1, University of Heidelberg, Bergheimerstrasse 58, 69115 Heidelberg, Germany.
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Forbes JM, Cooper ME, Thallas V, Burns WC, Thomas MC, Brammar GC, Lee F, Grant SL, Burrell LM, Burrell LA, Jerums G, Osicka TM. Reduction of the accumulation of advanced glycation end products by ACE inhibition in experimental diabetic nephropathy. Diabetes 2002; 51:3274-82. [PMID: 12401719 DOI: 10.2337/diabetes.51.11.3274] [Citation(s) in RCA: 211] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The effect of ACE inhibition on the formation of advanced glycation end products (AGEs) and oxidative stress was explored. Streptozocin-induced diabetic animals were randomized to no treatment, the ACE inhibitor ramipril (3 mg/l), or the AGE formation inhibitor aminoguanidine (1 g/l) and followed for 12 weeks. Control groups were followed concurrently. Renal AGE accumulation, as determined by immunohistochemistry and both serum and renal fluorescence, were increased in diabetic animals. This was attenuated by both ramipril and aminoguanidine to a similar degree. Nitrotyrosine, a marker of protein oxidation, also followed a similar pattern. The receptor for AGEs, gene expression of the membrane-bound NADPH oxidase subunit gp91phox, and nuclear transcription factor-kappaB were all increased by diabetes but remained unaffected by either treatment regimen. Two other AGE receptors, AGE R2 and AGE R3, remained unchanged for the duration of the study. The present study has identified a relationship between the renin-angiotensin system and the accumulation of AGEs in experimental diabetic nephropathy that may be linked through oxidative stress
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Affiliation(s)
- Josephine M Forbes
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Centre, West Heidelberg, Australia.
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Abstract
Hyperglycaemia is directly involved in causing long-term diabetic complications. The non-enzymatic glycation of proteins, yielding irreversible advanced glycation end products and advanced glycation end products-derived protein crosslinking, participates in the development of diabetic complications, such as diabetic nephropathy. Diabetic nephropathy is becoming a major medical problem with increasing numbers of these patients progressing to end stage renal disease, thus requiring renal replacement therapy. While several interventions may slow the development and progression of diabetic nephropathy, there is no effective treatment to prevent or reverse the disease. Pimagedine (aminoguanidine HCl) has been shown to be an effective agent in reducing the severity of the structural and functional alterations associated with experimental diabetic nephropathy. Preliminary studies suggest a beneficial effect of pimagedine in treating patients with diabetic nephropathy. In summary, these observations support a role for advanced glycation end products inhibitors, like pimagedine, in the management of diabetic nephropathy, either alone or in combination with other therapies.
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Affiliation(s)
- Emaad Abdel-Rahman
- Division of Nephrology, University of Virginia, Charlottesville 22908-0133, USA.
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40
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Oldfield MD, Bach LA, Forbes JM, Nikolic-Paterson D, McRobert A, Thallas V, Atkins RC, Osicka T, Jerums G, Cooper ME. Advanced glycation end products cause epithelial-myofibroblast transdifferentiation via the receptor for advanced glycation end products (RAGE). J Clin Invest 2002. [PMID: 11748269 DOI: 10.1172/jci200111951] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Tubulointerstitial disease, a prominent phenomenon in diabetic nephropathy, correlates with decline in renal function. The underlying pathogenic link between chronic hyperglycemia and the development of tubulointerstitial injury has not been fully elucidated, but myofibroblast formation represents a key step in the development of tubulointerstitial fibrosis. RAGE, the receptor for advanced glycation end products (AGEs), induces the expression of TGF-beta and other cytokines that are proposed to mediate the transdifferentiation of epithelial cells to form myofibroblasts. Here we report specific binding of (125)I-AGE-BSA to cell membranes prepared from a rat proximal tubule cell line and show that the binding site was RAGE. AGE exposure induced dose-dependent epithelial-myofibroblast transdifferentiation determined by morphological changes, de novo alpha smooth-muscle actin expression, and loss of epithelial E-cadherin staining. These effects could be blocked with neutralizing Ab's to RAGE or to TGF-beta. Transdifferentiation was also apparent in the proximal tubules of diabetic rats and in a renal biopsy from a patient with type 1 diabetes. The AGE cross-link breaker, phenyl-4,5-dimethylthiazolium bromide (ALT 711) reduced transdifferentiation in diabetic rats in association with reduced tubular AGE and TGF-beta expression. This study provides a novel mechanism to explain the development of tubulointerstitial disease in diabetic nephropathy and provides a new treatment target.
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Affiliation(s)
- M D Oldfield
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Centre, Heidelberg, Australia
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41
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Oldfield MD, Bach LA, Forbes JM, Nikolic-Paterson D, McRobert A, Thallas V, Atkins RC, Osicka T, Jerums G, Cooper ME. Advanced glycation end products cause epithelial-myofibroblast transdifferentiation via the receptor for advanced glycation end products (RAGE). J Clin Invest 2001; 108:1853-63. [PMID: 11748269 PMCID: PMC209461 DOI: 10.1172/jci11951] [Citation(s) in RCA: 317] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Tubulointerstitial disease, a prominent phenomenon in diabetic nephropathy, correlates with decline in renal function. The underlying pathogenic link between chronic hyperglycemia and the development of tubulointerstitial injury has not been fully elucidated, but myofibroblast formation represents a key step in the development of tubulointerstitial fibrosis. RAGE, the receptor for advanced glycation end products (AGEs), induces the expression of TGF-beta and other cytokines that are proposed to mediate the transdifferentiation of epithelial cells to form myofibroblasts. Here we report specific binding of (125)I-AGE-BSA to cell membranes prepared from a rat proximal tubule cell line and show that the binding site was RAGE. AGE exposure induced dose-dependent epithelial-myofibroblast transdifferentiation determined by morphological changes, de novo alpha smooth-muscle actin expression, and loss of epithelial E-cadherin staining. These effects could be blocked with neutralizing Ab's to RAGE or to TGF-beta. Transdifferentiation was also apparent in the proximal tubules of diabetic rats and in a renal biopsy from a patient with type 1 diabetes. The AGE cross-link breaker, phenyl-4,5-dimethylthiazolium bromide (ALT 711) reduced transdifferentiation in diabetic rats in association with reduced tubular AGE and TGF-beta expression. This study provides a novel mechanism to explain the development of tubulointerstitial disease in diabetic nephropathy and provides a new treatment target.
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Affiliation(s)
- M D Oldfield
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Centre, Heidelberg, Australia
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Kelly DJ, Gilbert RE, Cox AJ, Soulis T, Jerums G, Cooper ME. Aminoguanidine ameliorates overexpression of prosclerotic growth factors and collagen deposition in experimental diabetic nephropathy. J Am Soc Nephrol 2001; 12:2098-2107. [PMID: 11562408 DOI: 10.1681/asn.v12102098] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Profibrotic cytokines and the formation of advanced-glycation end products (AGE) have both been implicated in the pathogenesis of glomerulosclerosis in diabetic kidney disease. However, tubulointerstitial pathology is also an important determinant of progressive renal dysfunction in diabetic nephropathy. This study sought to investigate the expression of profibrotic growth factors and matrix deposition in the glomerulus and the tubulointerstitium and to examine the effect of blocking AGE formation in experimental diabetic nephropathy. Thirty-six male Sprague-Dawley rats were randomized into control and diabetic groups. Diabetes was induced in 24 rats by streptozotocin. Twelve diabetic rats were further randomized to receive the inhibitor of AGE formation, aminoguanidine (1 g/l drinking water). At 6 mo, experimental diabetes was associated with a three-fold increase in expression of transforming growth factor (TGF)-beta1 (P < 0.01 versus control) and five-fold increase in platelet-derived growth factor (PDGF)-B gene expression (P < 0.01 versus control) in the tubulointerstitium. In situ hybridization demonstrated a diffuse increase in both TGF-beta1 and PDGF-B mRNA in renal tubules. Aminoguanidine attenuated not only the overexpression of TGF-beta1 and PDGF-B but also reduced type IV collagen deposition in diabetic rats (P < 0.05). TGF-beta1 and PDGF mRNA within glomeruli were also similarly increased with diabetes and attenuated with aminoguanidine. The observed beneficial effects of aminoguanidine on the tubulointerstitium in experimental diabetes suggest that AGE-mediated expression of profibrotic cytokines may contribute to tubulointerstitial injury and the pathogenesis of diabetic nephropathy.
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Affiliation(s)
- Darren J Kelly
- University of Melbourne, Department of Medicine, St. Vincent's Hospital, Victoria, Australia
| | - Richard E Gilbert
- University of Melbourne, Department of Medicine, St. Vincent's Hospital, Victoria, Australia
| | - Alison J Cox
- University of Melbourne, Department of Medicine, St. Vincent's Hospital, Victoria, Australia
| | - Tina Soulis
- Department of Medicine, Austin and Repatriation Medical Centre, Victoria, Australia
| | - George Jerums
- Department of Medicine, Austin and Repatriation Medical Centre, Victoria, Australia
| | - Mark E Cooper
- Department of Medicine, Austin and Repatriation Medical Centre, Victoria, Australia
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Xiang G, Schinzel R, Simm A, Münch G, Sebekova K, Kasper M, Niwa T, Schmitz C, Heidland A. Advanced glycation end products (AGEs)-induced expression of TGF-beta 1 is suppressed by a protease in the tubule cell line LLC-PK1. Nephrol Dial Transplant 2001; 16:1562-9. [PMID: 11477156 DOI: 10.1093/ndt/16.8.1562] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Advanced glycation end products (AGEs) are assumed to play a key role in diabetic nephropathy (DN). Since little is known about their action in tubule cells, we investigated in LLC-PK1 cells: (i) whether AGE-bovine serum albumin (AGE-BSA) affects cell proliferation and expression of transforming growth factor-beta (TGF-beta 1); and (ii) whether the AGE-induced effects can be modulated by trypsin due to interference with its binding proteins at the cell surface. METHODS Arrested cells were exposed to vehicle (control), AGE-BSA (19--76 microM) and BSA (38 microM) in the presence or absence of trypsin (0.625--5.0 microg/ml) (2.5 microg/ml) for 24 h. We evaluated cell proliferation by cell count and by [(3)H]thymidine incorporation, TGF-beta 1 expression by reverse transcription-polymerase chain reaction (RT-PCR), and TGF-beta 1 protein by ELISA. In addition, cell accumulation of AGEs was studied by immunohistochemical staining of the AGE imidazolone. RESULTS AGE-BSA inhibited [(3)H]thymidine incorporation, lowered cell number and increased cell protein content as well as TGF-beta 1 mRNA and protein as compared with control and BSA. Immunohistochemical staining revealed a marked intracellular accumulation of the AGE imidazolone. Co-incubation of AGE-BSA with trypsin ameliorated the impaired thymidine incorporation, the decreased cell count and the enhanced cell protein content. TGF-beta 1 overexpression was normalized, while TGF-beta 1 protein declined insignificantly. Intracellular imidazolone accumulation was strikingly suppressed. CONCLUSIONS In the tubule cell line LLC-PK1, AGE-BSA exerts an antiproliferative effect, most probably due to TGF-beta 1 overproduction. The co-administration of trypsin abrogated this alteration, very likely as a result of an interaction with AGE-binding protein(s), which is supported by the decreased intracellular AGE accumulation. These findings may be the starting point for the development of specific proteolytic enzymes to interfere with the interaction between AGEs and their receptors/binding proteins.
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Affiliation(s)
- G Xiang
- Department of Internal Medicine and Institute of Physiological Chemistry, University of Würzburg, Germany
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Kim YS, Kim BC, Song CY, Hong HK, Moon KC, Lee HS. Advanced glycosylation end products stimulate collagen mRNA synthesis in mesangial cells mediated by protein kinase C and transforming growth factor-beta. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 2001; 138:59-68. [PMID: 11433229 DOI: 10.1067/mlc.2001.115494] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Advanced glycosylation end products (AGE) seem to be implicated in the pathogenesis of diabetic nephropathy. The present study has examined the effects of AGE on protein kinase C (PKC) activity and transforming growth factor-beta1 (TGF-beta1) in relation to collagen gene regulation in cultured human mesangial cells (HMCs). Quiescent HMCs were exposed to serum-free media containing bovine serum albumin (BSA), AGE-modified BSA (AGE-BSA), or glycated BSA in which AGE formation was prevented by the use of aminoguanidine (BSA-AM). AGE-BSA (200 microg/mL) induced a peak membrane-associated PKC activity, particularly PKC-a, at 4 hours. AGE-BSA stimulated alpha1(I) and alpha1(IV) collagen mRNA expression after 24-hour incubation with HMCs, which remained elevated until hour 60. HMCs incubated with AGE-BSA induced a significant inhibition of cell proliferation compared with cells incubated with BSA. AGE-BSA stimulated TGF-beta mRNA and protein expression in HMCs. The TGF-beta secreted by HMCs was shown by CCL-64 mink lung cell assay to be bioactive. In contrast, BSA-AM did not affect either collagen or TGF-beta mRNA or protein expression in HMCs. The stimulatory effects of AGE-BSA on collagen gene regulation in HMCs could be negated by the pretreatment of HMCs with GF 109203X for 30 minutes or with phorbol myristate acetate for 24 hours before AGE-BSA administration. Neutralizing antibody to TGF-beta inhibited increased collagen mRNA expression by HMCs exposed to AGE-BSA. These results suggest that AGE-BSA stimulates collagen mRNA expression by activating PKC and the transcriptional upregulation of TGF-beta1 in HMCs. Thus, PKC and TGF-beta may function as key signaling intermediaries in the AGE-up-regulated collagen gene expression pathway in HMCs.
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Affiliation(s)
- Y S Kim
- Department of Pathology, Seoul National University College of Medicine, Chongno-gu, Yongon-dong 28, Seoul 110-799, Korea
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Xiang G, Schinzel R, Simm A, Sebekova K, Heidland A. Advanced glycation end products impair protein turnover in LLC-PK1: amelioration by trypsin. KIDNEY INTERNATIONAL. SUPPLEMENT 2001; 78:S53-7. [PMID: 11168983 DOI: 10.1046/j.1523-1755.2001.59780053.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Advanced glycation end products (AGEs) are assumed to play a key role in the pathogenesis of diabetic nephropathy (DN) and other diabetic complications. While AGEs have been shown to exert marked effects on mesangial and endothelial cells as well as on monocytes/macrophages, little is known about their effects on tubule cells. Therefore, we addressed the questions of (1) whether AGE-bovine serum albumin (AGE-BSA) impairs the protein metabolism in the tubule cells, and if so, (2) whether the AGE-induced effects are mediated via a protease sensitive mechanism. METHODS Arrested LLC-PK1 cells were exposed to a medium containing the vehicle (control, serum free), AGE-BSA (38 micromol/L), or BSA (38 micromol/L) in the presence or absence of trypsin (2.5 microg/mL) for 24 hours. We evaluated cell number, cell size, and cell protein content, as well as protein synthesis and protein degradation. RESULTS After an incubation period of 24 hours, AGE-BSA decreased the cell number to 84.5 +/- 5.5% of control and 82.5 +/- 5.6% of BSA-treated cells (P < 0.05). [3H]-thymidine incorporation declined to 66% of control (P < 0.05), while BSA was without any effect. The same AGE-BSA dose reduced protein degradation (P < 0.05) and stimulated total protein synthesis slightly, as determined by L-[14C]Phe incorporation into acidic-insoluble proteins. These effects resulted in a rise in cell protein content (AGE-BSA vs. control, 21.9 +/- 6.7%; AGE-BSA vs. BSA, 11.1 +/- 6.0%, P < 0.05) and cell volume (AGE-BSA vs. control 9.4 +/- 3.2%, AGE-BSA vs. BSA 18.4 +/- 3.7%, P < 0.05). Coincubation with AGE-BSA and trypsin was associated with an amelioration of all investigated parameters concerning cell number, cell proliferation, raised cell protein content, decreased protein degradation, and enhanced protein synthesis. CONCLUSION These data indicate that AGE-BSA impairs cell proliferation and protein turnover in LLC-PK1 cells with a consequent rise in cell protein. Since these alterations were abrogated by coincubation with trypsin, an interference of this serine protease with the AGE-binding proteins on cell surfaces is assumed.
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Affiliation(s)
- G Xiang
- Department of Internal Medicine, Institute of Physiological Chemistry, University of Würzburg, Würzburg, Germany
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Abstract
The objective of this review is to discuss recent experimental and clinical data concerning the effectiveness of antihypertensive drugs in preventing or delaying renal changes caused by diabetes mellitus and hypertension and to examine possible future developments. A brief description of the mechanisms involved in the development of renal failure in diabetes and hypertension is included. Evidence is presented to show that in addition to renoprotection offered by reduction in arterial pressure, some antihypertensive agents may give more nephroprotection. This added renoprotective potential of antihypertensive agents, which are either already in use or are being developed, is discussed. The nephroprotective action of conventional antihypertensive drugs, such as beta-blockers, calcium antagonists and angiotensin-converting enzyme inhibitors is briefly reviewed. It is noted that several studies indicate that angiotensin-converting enzyme inhibitors may be more effective in preventing or retarding renal failure than other conventional drugs. The renoprotective potential of newly developed agents, such as angiotensin II Type 1 receptor antagonists, vasopeptidase inhibitors and endothelin receptor antagonists is also examined. Emphasis is placed on a possible superior renoprotective effect of combination therapy over monotherapy.
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Affiliation(s)
- D Susic
- Hypertension Research Laboratory, Division of Research, Alton Ochsner Medical Foundation, 1520 Jefferson Highway, New Orleans, LA 70121, USA.
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Raj DS, Choudhury D, Welbourne TC, Levi M. Advanced glycation end products: a Nephrologist's perspective. Am J Kidney Dis 2000; 35:365-80. [PMID: 10692262 DOI: 10.1016/s0272-6386(00)70189-2] [Citation(s) in RCA: 227] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Advanced glycation end products (AGEs) are a heterogeneous group of molecules that accumulate in plasma and tissues with advancing age, diabetes, and renal failure. There is emerging evidence that AGEs are potential uremic toxins and may have a role in the pathogenesis of vascular and renal complications associated with diabetes and aging. AGEs are formed when a carbonyl of a reducing sugar condenses with a reactive amino group in target protein. These toxic molecules interact with specific receptors and elicit pleiotropic responses. AGEs accelerate atherosclerosis through cross-linking of proteins, modification of matrix components, platelet aggregation, defective vascular relaxation, and abnormal lipoprotein metabolism. In vivo and in vitro studies indicate that AGEs have a vital role in the pathogenesis of diabetic nephropathy and the progression of renal failure. The complications of normal aging, such as loss of renal function, Alzheimer's disease, skin changes, and cataracts, may also be mediated by progressive glycation of long-lived proteins. AGEs accumulate in renal failure as a result of decreased excretion and increased generation resulting from oxidative and carbonyl stress of uremia. AGE-modified beta(2)-microglobulin is the principal pathogenic component of dialysis-related amyloidosis in patients undergoing dialysis. Available dialytic modalities are not capable of normalizing AGE levels in patients with end-stage renal disease. A number of reports indicated that restoration of euglycemia with islet-cell transplantation normalized and prevented further glycosylation of proteins. Aminoguanidine (AGN), a nucleophilic compound, not only decreases the formation of AGEs but also inhibits their action. A number of studies have shown that treatment with AGN improves neuropathy and delays the onset of retinopathy and nephropathy. N-Phenacylthiazolium bromide is a prototype AGE cross-link breaker that reacts with and can cleave covalent AGE-derived protein cross-links. Thus, there is an exciting possibility that the complications of diabetes, uremia, and aging may be prevented with these novel agents.
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Affiliation(s)
- D S Raj
- Department of Medicine, Lousiana State University Medical Center, Shreveport, LA,USA
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Bach LA, Dean R, Youssef S, Cooper ME. Aminoguanidine ameliorates changes in the IGF system in experimental diabetic nephropathy. Nephrol Dial Transplant 2000; 15:347-54. [PMID: 10692520 DOI: 10.1093/ndt/15.3.347] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Formation of advanced glycation end-products (AGEs) has been implicated in the development of diabetic complications. As well as causing changes in structural proteins, AGEs may also alter gene expression of growth factors in vitro. The insulin-like growth factor (IGF) system, including IGF-I and modulatory IGF binding proteins (IGFBPs), is dysregulated during the development of diabetic nephropathy. METHODS Quantitative in situ hybridization histochemistry and immunohistochemistry were used to determine the effects of aminoguanidine, an inhibitor of AGE formation, on gene expression of IGF-I and IGFBPs in kidneys of long-term (8 months duration) streptozotocin-diabetic rats. RESULTS Diabetes was associated with increased renal expression of IGFBP-1 mRNA (diabetes 824+/-236 vs control 264+/-76 arbitrary units, P<0.01) and decreased expression of mRNAs for IGF-I (diabetes 39+/-7 vs control 185+/-23 arbitrary units, P<0.001) and IGFBP-4 (diabetes 139+/-25 vs control 383+/-54 arbitrary units, P<0.001). Aminoguanidine treatment inhibited the effects of diabetes on renal expression of mRNA for IGF-I, IGFBP-1 and IGFBP-4. The changes in IGF-I and IGFBP-1 mRNA levels were reflected in altered peptide levels. In diabetic kidneys, IGFBP-5 mRNA levels were slightly decreased to 75% of control levels (P<0.01); aminoguanidine had no effect on IGFBP-5 mRNA levels. CONCLUSIONS These results suggest that amelioration of changes in the renal IGF system by aminoguanidine may contribute to the renoprotective effects of the latter, which have been previously shown to inhibit structural and functional aspects of diabetic nephropathy in the rat.
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Affiliation(s)
- L A Bach
- University of Melbourne, Department of Medicine, Austin and Repatriation Medical Centre, Heidelberg, Victoria, Australia
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Gilbert RE, Cooper ME. The tubulointerstitium in progressive diabetic kidney disease: more than an aftermath of glomerular injury? Kidney Int 1999; 56:1627-37. [PMID: 10571771 DOI: 10.1046/j.1523-1755.1999.00721.x] [Citation(s) in RCA: 480] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Although the glomerulus, particularly the mesangium, has been the focus of intense investigation in diabetes, tubulointerstitial injury is also a major feature of diabetic nephropathy and an important predictor of renal dysfunction. The renal tubule in diabetes is subject to both direct and indirect pathogenetic influences as a consequence of its position in the nephron and its resorptive function. On exposure to glucose, proximal tubular cells elaborate vasoactive hormones, including angiotensin II and injurious cytokines such as transforming growth factor-beta (TGF-beta), as well as extracellular matrix proteins. In turn, angiotensin II may further increase TGF-beta expression in both proximal tubular and interstitial cells, thus amplifying the stimulus to fibrogenesis in the renal tubulointerstitium. In addition to these mostly direct influences, the renal tubule, particularly its proximal segment, is exposed to glomerular effluent. In the diabetic state, this includes large quantities of advanced glycation end products and glucose and, at later stages in the evolution of diabetic nephropathy, protein, all of which are factors that may induce TGF-beta expression and fibrosis. Diabetic nephropathy should therefore be viewed as a disease affecting the entire nephron. Continued exploration into tubulointerstitial disease in addition to glomerular injury in diabetes may help provide further insights into the pathogenesis of diabetic nephropathy and additional targets for therapeutic intervention.
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Affiliation(s)
- R E Gilbert
- University of Melbourne, Department of Medicine, West Heidelberg, Victoria, 3081, Australia.
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Pugliese G, Pricci F, Romeo G, Leto G, Amadio L, Iacobini C, Di Mario U. Autocrine and paracrine mechanisms in the early stages of diabetic nephropathy. J Endocrinol Invest 1999; 22:708-35. [PMID: 10595837 DOI: 10.1007/bf03343635] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- G Pugliese
- Dipartimento di Scienze Cliniche, Endocrinologia III, La Sapienza University, Rome, Italy.
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