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Faivre A, de Seigneux S. The role of hypoxia in chronic kidney disease: a nuanced perspective. Curr Opin Nephrol Hypertens 2024; 33:414-419. [PMID: 38597413 PMCID: PMC11139247 DOI: 10.1097/mnh.0000000000000989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
PURPOSE OF REVIEW This review critically examines the role of hypoxia in chronic kidney disease (CKD). While traditionally viewed as detrimental, recent insights suggest a more nuanced understanding of hypoxia's role during renal disease. RECENT FINDINGS Emerging evidence challenges the traditional view that hypoxia is universally harmful in CKD context. We review here the recent evidence about hypoxia and HIF activation in CKD. We also discuss the effect of hypoxia on the renal tissue, and the relative inhibition of different HIF isoforms. Recent advancements in therapies, such as HIF prolyl hydroxylase inhibitors (HIF-PHIs) and sodium-glucose cotransporter 2 (SGLT2) inhibitors seem to target the HIF pathway. These drugs impact anemia associated with CKDbut also renoprotection, hinting at a more complex interplay between hypoxia, HIF activation, and renal health. SUMMARY A certain level of hypoxia and specific HIF pathway activation, especially HIF-α, can be beneficial in CKD progression. Therapeutic strategies targeting HIF stabilization, such as with HIF-PHIs and SGLT2 inhibitors, offer promising avenues for enhancing renal protection. Future investigations should aim at better understanding the precise effects on HIF pathway and optimize their clinical application to improve outcomes for CKD patients.
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Affiliation(s)
- Anna Faivre
- Service de néphrologie, Département des Spécialités de Médecine Interne, Hôpitaux Universitaires de Genève
- Département de Physiologie Cellulaire et Métabolisme, Université de Genève, Genève, Suisse
| | - Sophie de Seigneux
- Service de néphrologie, Département des Spécialités de Médecine Interne, Hôpitaux Universitaires de Genève
- Département de Physiologie Cellulaire et Métabolisme, Université de Genève, Genève, Suisse
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Chae SY, Kim Y, Park CW. Oxidative Stress Induced by Lipotoxicity and Renal Hypoxia in Diabetic Kidney Disease and Possible Therapeutic Interventions: Targeting the Lipid Metabolism and Hypoxia. Antioxidants (Basel) 2023; 12:2083. [PMID: 38136203 PMCID: PMC10740440 DOI: 10.3390/antiox12122083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 11/26/2023] [Accepted: 12/01/2023] [Indexed: 12/24/2023] Open
Abstract
Oxidative stress, a hallmark pathophysiological feature in diabetic kidney disease (DKD), arises from the intricate interplay between pro-oxidants and anti-oxidants. While hyperglycemia has been well established as a key contributor, lipotoxicity emerges as a significant instigator of oxidative stress. Lipotoxicity encompasses the accumulation of lipid intermediates, culminating in cellular dysfunction and cell death. However, the mechanisms underlying lipotoxic kidney injury in DKD still require further investigation. The key role of cell metabolism in the maintenance of cell viability and integrity in the kidney is of paramount importance to maintain proper renal function. Recently, dysfunction in energy metabolism, resulting from an imbalance in oxygen levels in the diabetic condition, may be the primary pathophysiologic pathway driving DKD. Therefore, we aim to shed light on the pivotal role of oxidative stress related to lipotoxicity and renal hypoxia in the initiation and progression of DKD. Multifaceted mechanisms underlying lipotoxicity, including oxidative stress with mitochondrial dysfunction, endoplasmic reticulum stress activated by the unfolded protein response pathway, pro-inflammation, and impaired autophagy, are delineated here. Also, we explore potential therapeutic interventions for DKD, targeting lipotoxicity- and hypoxia-induced oxidative stress. These interventions focus on ameliorating the molecular pathways of lipid accumulation within the kidney and enhancing renal metabolism in the face of lipid overload or ameliorating subsequent oxidative stress. This review highlights the significance of lipotoxicity, renal hypoxia-induced oxidative stress, and its potential for therapeutic intervention in DKD.
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Affiliation(s)
- Seung Yun Chae
- Division of Nephrology, Department of Internal Medicine, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea; (S.Y.C.); (Y.K.)
| | - Yaeni Kim
- Division of Nephrology, Department of Internal Medicine, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea; (S.Y.C.); (Y.K.)
| | - Cheol Whee Park
- Division of Nephrology, Department of Internal Medicine, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea; (S.Y.C.); (Y.K.)
- Institute for Aging and Metabolic Disease, Seoul St. Mary’s Hospital, The College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul 06591, Republic of Korea
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Shen Z, Cui T, Liu Y, Wu S, Han C, Li J. Astragalus membranaceus and Salvia miltiorrhiza ameliorate diabetic kidney disease via the "gut-kidney axis". PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2023; 121:155129. [PMID: 37804821 DOI: 10.1016/j.phymed.2023.155129] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 08/02/2023] [Accepted: 09/28/2023] [Indexed: 10/09/2023]
Abstract
BACKGROUND The combination of Astragalus membranaceus and Salvia miltiorrhiza (AS) is an effective prescription for treating diabetic kidney disease (DKD) in traditional Chinese medicine. Its efficacy in treating DKD has been confirmed, but the potential regulatory mechanism has not yet been fully clarified. PURPOSE To explore the mechanism by which AS regulates the "gut-metabolism-transcription" coexpression network under the action of the "gut-kidney axis" to ameliorate DKD. METHODS SD rats were used to establish the DKD model by injecting STZ. After AS intervention, the structure and function of the kidney and colon were observed. We sequenced the gut microbiota utilizing 16S rDNA, identified serum differential metabolites using LC‒MS/MS, and observed renal mRNA expression by RNA seq. The "gut-metabolism-transcription" coexpression network was further constructed, and the target bacteria, target metabolites, and target genes of AS were ultimately screened and validated. RESULTS AS improved renal pathology and functional damage and increased the abundance of Akkermansia, Akkermansia_muciniphila, Lactobacillus and Lactobacillus_murinus. Fourteen target metabolites of AS were identified, which were mainly concentrated in 19 KEGG pathways, including sphingolipid metabolism and glycerophospholipid metabolism. Sixty-three target mRNAs of AS were identified. The top 20 pathways were closely related to glycolipid metabolism, and 14 differential mRNAs were expressed in these pathways. Correlation analysis showed that Akkermansia, Akkermansia muciniphila, Lactobacillus and Lactobacillus murinus were closely associated with sphingolipid metabolism, glycerophospholipid metabolism, arachidonic acid metabolism, ascorbate and aldarate metabolism and galactose metabolism. Moreover, the target metabolites and target mRNAs of AS were also enriched in five identical pathways of sphingolipid metabolism, glycerophospholipid metabolism, arachidonic acid metabolism, ascorbate and aldarate metabolism and galactose metabolism, including 8 different metabolites, such as sphingosine, and 5 different genes, such as Kng1. The 8 metabolites had high AUC prediction values, and the validation of the 5 genes was consistent with the sequencing results. CONCLUSION Our research showed that AS can improve DKD via the "gut-kidney axis". Akkermansia muciniphila and Lactobacillus murinus were the main driving bacteria, and five pathways related to glycolipid metabolism, especially sphingolipid metabolism and glycerophospholipid metabolism, may be important follow-up reactions and regulatory mechanisms.
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Affiliation(s)
- Zhen Shen
- Shandong University of Traditional Chinese Medicine, No.4655 Daxue Road, Jinan 250014, China
| | - Tao Cui
- Jinan Zhangqiu District Hospital of Traditional Chinese Medicine, Jinan 250200, China
| | - Yao Liu
- Shandong University of Traditional Chinese Medicine, No.4655 Daxue Road, Jinan 250014, China
| | - Shuai Wu
- Nephropathy Department, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, No.16369 Jingshi Road, Jinan 250014, China
| | - Cong Han
- Nephropathy Department, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, No.16369 Jingshi Road, Jinan 250014, China.
| | - Jie Li
- Shandong University of Traditional Chinese Medicine, No.4655 Daxue Road, Jinan 250014, China.
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André C, Bodeau S, Kamel S, Bennis Y, Caillard P. The AKI-to-CKD Transition: The Role of Uremic Toxins. Int J Mol Sci 2023; 24:16152. [PMID: 38003343 PMCID: PMC10671582 DOI: 10.3390/ijms242216152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/31/2023] [Accepted: 11/06/2023] [Indexed: 11/26/2023] Open
Abstract
After acute kidney injury (AKI), renal function continues to deteriorate in some patients. In a pro-inflammatory and profibrotic environment, the proximal tubules are subject to maladaptive repair. In the AKI-to-CKD transition, impaired recovery from AKI reduces tubular and glomerular filtration and leads to chronic kidney disease (CKD). Reduced kidney secretion capacity is characterized by the plasma accumulation of biologically active molecules, referred to as uremic toxins (UTs). These toxins have a role in the development of neurological, cardiovascular, bone, and renal complications of CKD. However, UTs might also cause CKD as well as be the consequence. Recent studies have shown that these molecules accumulate early in AKI and contribute to the establishment of this pro-inflammatory and profibrotic environment in the kidney. The objective of the present work was to review the mechanisms of UT toxicity that potentially contribute to the AKI-to-CKD transition in each renal compartment.
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Affiliation(s)
- Camille André
- Department of Clinical Pharmacology, Amiens Medical Center, 80000 Amiens, France; (S.B.); (Y.B.)
- GRAP Laboratory, INSERM UMR 1247, University of Picardy Jules Verne, 80000 Amiens, France
| | - Sandra Bodeau
- Department of Clinical Pharmacology, Amiens Medical Center, 80000 Amiens, France; (S.B.); (Y.B.)
- MP3CV Laboratory, UR UPJV 7517, University of Picardy Jules Verne, 80000 Amiens, France; (S.K.); (P.C.)
| | - Saïd Kamel
- MP3CV Laboratory, UR UPJV 7517, University of Picardy Jules Verne, 80000 Amiens, France; (S.K.); (P.C.)
- Department of Clinical Biochemistry, Amiens Medical Center, 80000 Amiens, France
| | - Youssef Bennis
- Department of Clinical Pharmacology, Amiens Medical Center, 80000 Amiens, France; (S.B.); (Y.B.)
- MP3CV Laboratory, UR UPJV 7517, University of Picardy Jules Verne, 80000 Amiens, France; (S.K.); (P.C.)
| | - Pauline Caillard
- MP3CV Laboratory, UR UPJV 7517, University of Picardy Jules Verne, 80000 Amiens, France; (S.K.); (P.C.)
- Department of Nephrology, Dialysis and Transplantation, Amiens Medical Center, 80000 Amiens, France
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Ahmed S, de Vries JC, Lu J, Stuart MHV, Mihăilă SM, Vernooij RWM, Masereeuw R, Gerritsen KGF. Animal Models for Studying Protein-Bound Uremic Toxin Removal-A Systematic Review. Int J Mol Sci 2023; 24:13197. [PMID: 37686004 PMCID: PMC10487432 DOI: 10.3390/ijms241713197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 08/18/2023] [Accepted: 08/23/2023] [Indexed: 09/10/2023] Open
Abstract
Protein-bound uremic toxins (PBUTs) are associated with the progression of chronic kidney disease (CKD) and its associated morbidity and mortality. The conventional dialysis techniques are unable to efficiently remove PBUTs due to their plasma protein binding. Therefore, novel approaches are being developed, but these require validation in animals before clinical trials can begin. We conducted a systematic review to document PBUT concentrations in various models and species. The search strategy returned 1163 results for which abstracts were screened, resulting in 65 full-text papers for data extraction (rats (n = 41), mice (n = 17), dogs (n = 3), cats (n = 4), goats (n = 1), and pigs (n = 1)). We performed descriptive and comparative analyses on indoxyl sulfate (IS) concentrations in rats and mice. The data on large animals and on other PBUTs were too heterogeneous for pooled analysis. Most rodent studies reported mean uremic concentrations of plasma IS close to or within the range of those during kidney failure in humans, with the highest in tubular injury models in rats. Compared to nephron loss models in rats, a greater rise in plasma IS compared to creatinine was found in tubular injury models, suggesting tubular secretion was more affected than glomerular filtration. In summary, tubular injury rat models may be most relevant for the in vivo validation of novel PBUT-lowering strategies for kidney failure in humans.
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Affiliation(s)
- Sabbir Ahmed
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (S.A.); (J.L.); (S.M.M.); (R.M.)
| | - Joost C. de Vries
- Department of Nephrology and Hypertension, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands; (J.C.d.V.); (M.H.V.S.); (R.W.M.V.)
| | - Jingyi Lu
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (S.A.); (J.L.); (S.M.M.); (R.M.)
| | - Milan H. Verrijn Stuart
- Department of Nephrology and Hypertension, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands; (J.C.d.V.); (M.H.V.S.); (R.W.M.V.)
| | - Silvia M. Mihăilă
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (S.A.); (J.L.); (S.M.M.); (R.M.)
| | - Robin W. M. Vernooij
- Department of Nephrology and Hypertension, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands; (J.C.d.V.); (M.H.V.S.); (R.W.M.V.)
- Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands
| | - Rosalinde Masereeuw
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands; (S.A.); (J.L.); (S.M.M.); (R.M.)
| | - Karin G. F. Gerritsen
- Department of Nephrology and Hypertension, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands; (J.C.d.V.); (M.H.V.S.); (R.W.M.V.)
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Sivertsson E, Ceder S, Nangaku M, Hansell P, Nordquist L, Palm F. AST-120 to Target Protein-Bound Uremic Toxins Improves Cardiac Output and Kidney Oxygenation in Experimental Chronic Kidney Disease. Kidney Blood Press Res 2023; 48:114-123. [PMID: 36791683 DOI: 10.1159/000529272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 01/11/2023] [Indexed: 02/17/2023] Open
Abstract
INTRODUCTION Chronic kidney disease (CKD) is a global health problem with increasing incidence which is closely associated with cardiac dysfunction. In CKD, uremic toxins accumulate as kidney function declines. Additionally, high salt intake is a growing health issue worldwide which can exacerbate kidney disease. In this study, we investigated the effect of reducing plasma levels of protein-bound uremic toxins in a rat model of CKD, challenged with high salt intake and compared the effects to those of conventional treatment using an angiotensin-converting enzyme inhibitor (ACEI). METHODS In rats, the right kidney and 2/3 of the left kidney were surgically removed (5/6 nephrectomy). Animals were fed a normal-salt diet and randomized to either no treatment (control) or chronic treatment with either the oral absorbent AST-120 to reduce plasma levels of protein-bound uremic toxins or the ACEI enalapril to inhibit angiotensin II signaling for 5 weeks. Following treatment, kidney function was measured before and after a week of high salt intake. Cardiac output and markers of oxidative stress were measured at the end of the study period. RESULTS Treatment with AST-120 resulted in decreased levels of the uremic toxin indoxyl sulfate, improved cardiac output (mL/min: AST-120 44.9 ± 5.4 compared to control 26.6 ± 2.0; p < 0.05), and decreased urinary oxidative stress. ACEI reduced oxidative stress in kidney tissue and improved the glomerular filtration rate in response to high salt intake (mL/min: ACEI 1.5 ± 0.1; compared to control 1.1 ± 0.1; p < 0.05). Both interventions improved intrarenal oxygen availability (mm Hg: AST-120 42.8 ± 0.8; ACEI 43.2 ± 1.9; compared to control 33.4 ± 1.3; p < 0.05). CONCLUSION AST-120 administered to reduce plasma levels of uremic toxins, such as indoxyl sulfate, has potential beneficial effects on both cardiac and kidney function. Targeting uremic toxins and angiotensin II signaling simultaneously could be an efficient strategy to target both cardiac and kidney dysfunction in CKD, to further slow progression of disease in patients with CKD.
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Affiliation(s)
- Ebba Sivertsson
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sara Ceder
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Masaomi Nangaku
- Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan
| | - Peter Hansell
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Lina Nordquist
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Fredrik Palm
- Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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Ebert T, Neytchev O, Witasp A, Kublickiene K, Stenvinkel P, Shiels PG. Inflammation and Oxidative Stress in Chronic Kidney Disease and Dialysis Patients. Antioxid Redox Signal 2021; 35:1426-1448. [PMID: 34006115 DOI: 10.1089/ars.2020.8184] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Significance: Chronic kidney disease (CKD) can be regarded as a burden of lifestyle disease that shares common underpinning features and risk factors with the aging process; it is a complex constituted by several adverse components, including chronic inflammation, oxidative stress, early vascular aging, and cellular senescence. Recent Advances: A systemic approach to tackle CKD, based on mitigating the associated inflammatory, cell stress, and damage processes, has the potential to attenuate the effects of CKD, but it also preempts the development and progression of associated morbidities. In effect, this will enhance health span and compress the period of morbidity. Pharmacological, nutritional, and potentially lifestyle-based interventions are promising therapeutic avenues to achieve such a goal. Critical Issues: In the present review, currents concepts of inflammation and oxidative damage as key patho-mechanisms in CKD are addressed. In particular, potential beneficial but also adverse effects of different systemic interventions in patients with CKD are discussed. Future Directions: Senotherapeutics, the nuclear factor erythroid 2-related factor 2-kelch-like ECH-associated protein 1 (NRF2-KEAP1) signaling pathway, the endocrine klotho axis, inhibitors of the sodium-glucose cotransporter 2 (SGLT2), and live bio-therapeutics have the potential to reduce the burden of CKD and improve quality of life, as well as morbidity and mortality, in this fragile high-risk patient group. Antioxid. Redox Signal. 35, 1426-1448.
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Affiliation(s)
- Thomas Ebert
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Ognian Neytchev
- Institute of Cancer Sciences, College of Medical, Veterinary & Life Sciences, Wolfson Wohl Cancer Research Centre, University of Glasgow, Glasgow, United Kingdom
| | - Anna Witasp
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Karolina Kublickiene
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Peter Stenvinkel
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Paul G Shiels
- Institute of Cancer Sciences, College of Medical, Veterinary & Life Sciences, Wolfson Wohl Cancer Research Centre, University of Glasgow, Glasgow, United Kingdom
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Sakashita M, Tanaka T, Inagi R. Metabolic Changes and Oxidative Stress in Diabetic Kidney Disease. Antioxidants (Basel) 2021; 10:1143. [PMID: 34356375 PMCID: PMC8301131 DOI: 10.3390/antiox10071143] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/12/2021] [Accepted: 07/14/2021] [Indexed: 12/15/2022] Open
Abstract
Diabetic kidney disease (DKD) is a major cause of end-stage kidney disease, and it is crucial to understand the pathophysiology of DKD. The control of blood glucose levels by various glucose-lowering drugs, the common use of inhibitors of the renin-angiotensin system, and the aging of patients with diabetes can alter the disease course of DKD. Moreover, metabolic changes and associated atherosclerosis play a major role in the etiology of DKD. The pathophysiology of DKD is largely attributed to the disruption of various cellular stress responses due to metabolic changes, especially an increase in oxidative stress. Therefore, many antioxidants have been studied as therapeutic agents. Recently, it has been found that NRF2, a master regulator of oxidative stress, plays a major role in the pathogenesis of DKD and bardoxolone methyl, an activator of NRF2, has attracted attention as a drug that increases the estimated glomerular filtration rate in patients with DKD. This review outlines the altered stress responses of cellular organelles in DKD, their involvement in the pathogenesis of DKD, and discusses strategies for developing therapeutic agents, especially bardoxolone methyl.
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Affiliation(s)
- Midori Sakashita
- Division of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan;
| | - Tetsuhiro Tanaka
- Division of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan;
| | - Reiko Inagi
- Division of CKD Pathophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan;
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Dinc B, Yilmaz VT, Aycan İO, Kisaoglu A, Dandin O, Aydinli B, Hadimioglu N, Ertug Z. Effect of post-perfusion hyperoxemia on early graft function in renal transplant recipients: a retrospective observational cohort study. Ir J Med Sci 2021; 190:1539-1545. [PMID: 33398714 DOI: 10.1007/s11845-020-02499-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 12/25/2020] [Indexed: 11/25/2022]
Abstract
BACKGROUND The effects of hyperoxemia on the transplanted grafts arouse interest nowadays, particularly intraoperative hyperoxemia, on transplant kidney function and survival in the 1-year post-operative period. AIMS We aimed to investigate the effect of post-perfusion (5 min after perfusion) hyperoxemia on early graft function and survival in renal transplant recipients. METHODS Two hundred forty-seven living donor kidney transplant recipients were included in the study. Patients were divided into the three groups according to their partial arterial oxygen pressure in post-perfusion blood gas samples: group 1: normoxia (n = 52, PaO2 pressure: < 120 mmHg, 103 ± 13); group 2: moderate hyperoxemia (n = 121, PaO2: 120-200 mmHg, 169 ± 21); group 3: severe hyperoxemia (n = 74, PaO2: > 200 mmHg, 233 ± 25). Graft functions (serum creatinine levels, estimated-glomerular filtration rate values, spot urine protein/creatinine ratio), survival rates, and groups' clinical outcomes were compared in the first year after transplantation. RESULTS Graft survival rates were similar in the groups and the rate of BK virus viremia was the lowest in the group 3 (groups 1, 2, and 3: 15.4% (n = 8), 6.6% (n = 8), 1.4% (n = 1), respectively, P: 0.009). Serum creatinine and proteinuria levels were lower, and estimated-glomerular filtration rate values were higher in group 3. A negative correlation between partial arterial oxygen pressure and serum creatinine levels and a positive correlation with estimated-glomerular filtration rate value were noted. These results were confirmed by univariate and multivariate analyses. CONCLUSIONS We demonstrated that the kidney transplant recipients with post-perfusion hyperoxemia have better early graft functions and lower BK virus viremia rates. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT04420897.
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Affiliation(s)
- Bora Dinc
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
| | - Vural T Yilmaz
- Division of Nephrology, Department of Internal Medicine, Akdeniz University Medical School, Antalya, Turkey.
| | - İlker O Aycan
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
| | - Abdullah Kisaoglu
- Department of General Surgery, Akdeniz University Medical School, Antalya, Turkey
| | - Ozgur Dandin
- Department of General Surgery, Akdeniz University Medical School, Antalya, Turkey
| | - Bulent Aydinli
- Department of General Surgery, Akdeniz University Medical School, Antalya, Turkey
| | - Necmiye Hadimioglu
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
| | - Zeki Ertug
- Department of Anaesthesiology and Reanimation, Akdeniz University Medical School, Antalya, Turkey
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Faivre A, Scholz CC, de Seigneux S. Hypoxia in chronic kidney disease: towards a paradigm shift? Nephrol Dial Transplant 2020; 36:1782-1790. [PMID: 33895835 DOI: 10.1093/ndt/gfaa091] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Indexed: 11/15/2022] Open
Abstract
Chronic kidney disease (CKD) is defined as an alteration of kidney structure and/or function lasting for >3 months [1]. CKD affects 10% of the general adult population and is responsible for large healthcare costs [2]. Since the end of the last century, the role of hypoxia in CKD progression has controversially been discussed. To date, there is evidence of the presence of hypoxia in late-stage renal disease, but we lack time-course evidence, stage correlation and also spatial co-localization with fibrotic lesions to ensure its causative role. The classical view of hypoxia in CKD progression is that it is caused by peritubular capillary alterations, renal anaemia and increased oxygen consumption regardless of the primary injury. In this classical view, hypoxia is assumed to further induce pro-fibrotic and pro-inflammatory responses, as well as oxidative stress, leading to CKD worsening as part of a vicious circle. However, recent investigations tend to question this paradigm, and both the presence of hypoxia and its role in CKD progression are still not clearly demonstrated. Hypoxia-inducible factor (HIF) is the main transcriptional regulator of the hypoxia response. Genetic HIF modulation leads to variable effects on CKD progression in different murine models. In contrast, pharmacological modulation of the HIF pathway [i.e. by HIF hydroxylase inhibitors (HIs)] appears to be generally protective against fibrosis progression experimentally. We here review the existing literature on the role of hypoxia, the HIF pathway and HIF HIs in CKD progression and summarize the evidence that supports or rejects the hypoxia hypothesis, respectively.
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Affiliation(s)
- Anna Faivre
- Department of Cell physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Carsten C Scholz
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Centre of Competence in Research "Kidney.CH", Zurich, Switzerland
| | - Sophie de Seigneux
- Department of Cell physiology and Metabolism, University of Geneva, Geneva, Switzerland.,National Centre of Competence in Research "Kidney.CH", Zurich, Switzerland.,Department of Medicine, Service of Nephrology, Geneva University Hospitals, Geneva, Switzerland
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Sun Z, Zheng W, Teng J, Fang Z, Lin C. Resveratrol Reduces Kidney Injury in a Rat Model of Uremia and is Associated with Increased Expression of Heat Shock Protein 70 (Hsp70). Med Sci Monit 2020; 26:e919086. [PMID: 32040471 PMCID: PMC7032531 DOI: 10.12659/msm.919086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND This study aimed to investigate the effects of resveratrol on kidney function in a rat model of uremia and the expression of heat shock proteins. MATERIAL AND METHODS The rat model of uremia was developed by 5/6 nephrectomy of Sprague-Dawley rats. The Hsp70 inhibitor MKT-077, a rhodacyanine dye, was used. The study groups included rats with sham surgery (the sham group), the rat model of uremia (the model group), the solvent-treated control group (the control group), the rat model treated with resveratrol group (the resveratrol group), the rat model treated with MKT-077 (the MKT-077 group), and the resveratrol+MKT-077 group. Kidney tissues were studied histologically. Renal cell apoptosis was detected by the TUNEL method. Expression of p53, Bax, and Bcl-2 mRNA and protein were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemistry, respectively. RESULTS Compared with the sham group, the expression levels of heat shock proteins Hsp70, Hsp90, Hsp27, Hsp25, Hsp40, and Hsp60 in the kidney of the rat model group increased to different degrees. Compared with the model group, the Hsp70 levels in the resveratrol group were significantly increased (p<0.05). Compared with the model group, treatment with MKT-077 reduced the survival rate of rats, which was increased following resveratrol treatment. Compared with the resveratrol group, renal function in the resveratrol+MKT-077 group was significantly reduced (p<0.05). CONCLUSIONS In a rat model of uremia, resveratrol reduced renal injury and improved both renal function and survival, which were associated with increased expression of Hsp70.
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Affiliation(s)
- Zhihong Sun
- Hemodialysis Room, Yantaishan Hospital, Yantai, Shandong, China (mainland)
| | - Weilei Zheng
- Department of Anesthesiology, Qingdao Central Hospital, Qingdao, Shandong, China (mainland)
| | - Jian Teng
- Department of Nephrology, Yantaishan Hospital, Yantai, Shandong, China (mainland)
| | - Zhan Fang
- Department of Nephrology, Yantaishan Hospital, Yantai, Shandong, China (mainland)
| | - Chongting Lin
- Hemodialysis Room, Yantaishan Hospital, Yantai, Shandong, China (mainland)
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12
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Charcoal for the management of pruritus and uremic toxins in patients with chronic kidney disease. Curr Opin Nephrol Hypertens 2020; 29:71-79. [DOI: 10.1097/mnh.0000000000000567] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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13
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Honda T, Hirakawa Y, Nangaku M. The role of oxidative stress and hypoxia in renal disease. Kidney Res Clin Pract 2019; 38:414-426. [PMID: 31558011 PMCID: PMC6913586 DOI: 10.23876/j.krcp.19.063] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/16/2019] [Accepted: 07/22/2019] [Indexed: 12/12/2022] Open
Abstract
Oxygen is required to sustain aerobic organisms. Reactive oxygen species (ROS) are constantly released during mitochondrial oxygen consumption for energy production. Any imbalance between ROS production and its scavenger system induces oxidative stress. Oxidative stress, a critical contributor to tissue damage, is well-known to be associated with various diseases. The kidney is susceptible to hypoxia, and renal hypoxia is a common final pathway to end stage kidney disease, regardless of the underlying cause. Renal hypoxia aggravates oxidative stress, and elevated oxidative stress, in turn, exacerbates renal hypoxia. Oxidative stress is also enhanced in chronic kidney disease, especially diabetic kidney disease, through various mechanisms. Thus, the vicious cycle between oxidative stress and renal hypoxia critically contributes to the progression of renal injury. This review examines recent evidence connecting chronic hypoxia and oxidative stress in renal disease and subsequently describes several promising therapeutic approaches against oxidative stress.
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Affiliation(s)
- Tomoko Honda
- Division of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yosuke Hirakawa
- Division of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Masaomi Nangaku
- Division of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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14
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Singh G, Krishan P. Dietary restriction regimens for fighting kidney disease: Insights from rodent studies. Exp Gerontol 2019; 128:110738. [PMID: 31593758 DOI: 10.1016/j.exger.2019.110738] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Revised: 09/12/2019] [Accepted: 09/13/2019] [Indexed: 01/11/2023]
Abstract
This review critically discusses the research findings on the effects of various dietary restriction regimens in rodent models of kidney disease. Long-term caloric restriction executed at both early and progressive stages of kidney disease was found to exert beneficial effects in rodents. Moreover, some studies have also demonstrated the efficacy of short-term caloric restriction in treating the kidney disease of variable aetiologies possibly by improving mitochondrial dysfunction, autophagy process and suppression of inflammation. However, the mechanisms underlying these short-term caloric restriction mediated protective effects in rodent models of kidney disease are not completely understood. Importantly, few available evidences have also suggested that carbohydrate restriction can exert beneficial effects in aging and experimentally induced renal injury models, but the mechanisms are not explored yet. Interestingly, the benefits of low protein diet in kidney disease models are extensively reported in literature. However, in most of these studies implementation of the low protein dietary regimen was found to associated with increased high carbohydrate and caloric intake (non-isocaloric). Thus, testing the effects of low protein diet under isocaloric conditions might further help to particularly understand the role of dietary protein content in pathology of kidney disease. Moreover, the direct evidences comparing the efficacy of various dietary restriction regimens in rodent models of kidney diseases are also scarce at present.
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Affiliation(s)
| | - Pawan Krishan
- Department of Pharmaceutical Sciences and Drug Research, Punjabi University, Patiala, India
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15
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Snelson M, Kellow NJ, Coughlan MT. Modulation of the Gut Microbiota by Resistant Starch as a Treatment of Chronic Kidney Diseases: Evidence of Efficacy and Mechanistic Insights. Adv Nutr 2019; 10:303-320. [PMID: 30668615 PMCID: PMC6416045 DOI: 10.1093/advances/nmy068] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 07/17/2018] [Accepted: 08/12/2018] [Indexed: 12/14/2022] Open
Abstract
Chronic kidney disease (CKD) has been associated with changes in gut microbial ecology, or "dysbiosis," which may contribute to disease progression. Recent studies have focused on dietary approaches to favorably alter the composition of the gut microbial communities as a treatment method in CKD. Resistant starch (RS), a prebiotic that promotes proliferation of gut bacteria such as Bifidobacteria and Lactobacilli, increases the production of metabolites including short-chain fatty acids, which confer a number of health-promoting benefits. However, there is a lack of mechanistic insight into how these metabolites can positively influence renal health. Emerging evidence shows that microbiota-derived metabolites can regulate the incretin axis and mitigate inflammation via expansion of regulatory T cells. Studies from animal models and patients with CKD show that RS supplementation attenuates the concentrations of uremic retention solutes, including indoxyl sulfate and p-cresyl sulfate. Here, we present the current state of knowledge linking the microbiome to CKD, we explore the efficacy of RS in animal models of CKD and in humans with the condition, and we discuss how RS supplementation could be a promising dietary approach for slowing CKD progression.
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Affiliation(s)
- Matthew Snelson
- Department of Diabetes, Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Nicole J Kellow
- Be Active Sleep & Eat (BASE) Facility, Department of Nutrition, Dietetics, and Food, Monash University, Notting Hill, Victoria, Australia
| | - Melinda T Coughlan
- Department of Diabetes, Central Clinical School, Monash University, Melbourne, Victoria, Australia
- Baker Heart Research Institute, Melbourne, Victoria, Australia
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16
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Veldeman L, Vanmassenhove J, Van Biesen W, Massy ZA, Liabeuf S, Glorieux G, Vanholder R. Evolution of protein-bound uremic toxins indoxyl sulphate and p-cresyl sulphate in acute kidney injury. Int Urol Nephrol 2019; 51:293-302. [PMID: 30604232 DOI: 10.1007/s11255-018-2056-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 12/10/2018] [Indexed: 01/05/2023]
Abstract
BACKGROUND There is a gradual increase in serum concentrations of protein-bound colon-derived uremic toxins indoxyl sulphate (IxS) and p-cresyl sulphate (pCS) as chronic kidney disease (CKD) progresses. In acute kidney injury (AKI), up till now, the retention pattern has not been studied. METHODS In this study, 194 adult patients admitted with sepsis to the intensive care unit were included. IxS, pCS and serum creatinine (sCrea) were quantified at inclusion (D0) and at day 4, unless follow-up ended earlier (Dend). RESULTS Serum levels of sCrea (P < 0.001), IxS (P < 0.001) and pCS (P < 0.05) were higher in patients with AKI according to RIFLE classification at D0. In contrast with sCrea, IxS and pCS levels only increased from stage I (IxS) and F (pCS) on. When grouped according to evolution in RIFLE class from D0 to Dend, all solute concentrations were higher (P < 0.001) in the group with unfavourable evolution. In this group, there was a marked rise in sCrea (P < 0.001), a moderate one for pCS (P < 0.05), but no change for IxS (P = 0.112). There was a decrease (P < 0.001) of all solute concentrations in the group with favourable evolution. Comparing AKI with CKD patients matched for sCrea, total levels of both IxS and pCS were higher (P < 0.01) in patients with CKD. CONCLUSIONS Although concentrations of IxS and pCS both tend to rise in sepsis patients with AKI, their evolution does not conform with that of sCrea. For the same level of sCrea, IxS and pCS concentrations are lower in AKI compared with CKD.
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Affiliation(s)
- Laurens Veldeman
- Nephrology Division, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium.
| | - Jill Vanmassenhove
- Nephrology Division, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Wim Van Biesen
- Nephrology Division, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Ziad A Massy
- Nephrology Division, Ambroise Paré Hospital, APHP, and Paris Ile de France West (UVSQ) University, Boulogne Billancourt, France.,Inserm U1018 Team5, UVSQ, University Paris, Saclay Villejuif, France
| | - Sophie Liabeuf
- Division of Clinical Pharmacology, Amiens University Hospital, Amiens, France
| | - Griet Glorieux
- Nephrology Division, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Raymond Vanholder
- Nephrology Division, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
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17
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Wu PJ, Chen JB, Lee WC, Ng HY, Lien SC, Tsai PY, Wu CH, Lee CT, Chiou TTY. Oxidative Stress and Nonalcoholic Fatty Liver Disease in Hemodialysis Patients. BIOMED RESEARCH INTERNATIONAL 2018; 2018:3961748. [PMID: 30515395 PMCID: PMC6236669 DOI: 10.1155/2018/3961748] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 10/14/2018] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Nonalcoholic fatty liver disease (NAFLD) is becoming more common around the world and it may progress to cirrhosis and liver failure, increasing mortality risk. In hemodialysis (HD) patients, NAFLD may be a novel risk factor for their high cardiovascular mortality. Heightened oxidative stress is highly prevalent in HD patients. However, the relationship between oxidative stress and NAFLD in HD patients is not well defined. METHODS We studied seventy-one stable nondiabetic HD patients. Nineteen patients had the diagnosis of NAFLD by ultrasonography. Blood levels of oxidative stress markers were measured in each patient, including thiobarbituric acid reactive substances (TBARS), free thiols, superoxide dismutase (SOD) activities, and glutathione peroxidase (GPx) activity. The copy numbers of mitochondrial DNA (mtDNA) in peripheral leukocytes were also determined. Demographic, biochemistry, and hemogram data were recorded. The two groups of patients were compared in order to determine the factors associated with NAFLD in HD patients. FINDINGS Compared to those without NAFLD, nondiabetic HD patients with NAFLD had significantly higher mtDNA copy number and GPx levels. The two groups did not differ significantly in dialysis adequacy, hemoglobin, serum calcium, phosphorus, albumin, liver function tests, or lipid profiles. Regression analysis confirmed mtDNA copy numbers and GPx levels as two independent factors associated with NAFLD. Compared to those with polysulfone, patients dialyzed with cellulose membrane have significantly higher levels of TBARS. However, patients with or without NAFLD did not differ in their use of either dialysis membrane. DISCUSSION Oxidative stress (represented by antioxidant defense, GPx) and mitochondrial DNA copy numbers are independently associated with fatty liver disease in nondiabetic HD patients. The diagnostic and therapeutic implications of this key observation warrant further exploration.
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Affiliation(s)
- Po-Jung Wu
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Jin-Bor Chen
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Wen-Chin Lee
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Hwee-Yeong Ng
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Shu-Ching Lien
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Pei-Ying Tsai
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Chien-Hsing Wu
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Chien-Te Lee
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
| | - Terry Ting-Yu Chiou
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine and Chung Shan Medical University School of Medicine, Taiwan
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18
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Ji C, Luo Y, Zou C, Huang L, Tian R, Lu Z. Effect of astragaloside IV on indoxyl sulfate-induced kidney injury in mice via attenuation of oxidative stress. BMC Pharmacol Toxicol 2018; 19:53. [PMID: 30176914 PMCID: PMC6122638 DOI: 10.1186/s40360-018-0241-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 08/08/2018] [Indexed: 01/16/2023] Open
Abstract
Background Astragalus membranaceus, a traditional Chinese medicine (TCM), has been widely used in the treatment of chronic kidney disease (CKD) in China. Astragaloside IV is one of the major compounds of Astragalus membranaceus. Recent research has shown that astragaloside IV demonstrates pharmacological effects, such as anti-inflammatory, anti-fibrotic and anti-oxidative stress activities. Our aim was to investigate the effects of astragaloside IV on indoxyl sulfate (IS)-induced kidney injury in vivo, and to study the underlying mechanism. Methods Forty C57BL/6 mice with ½ nephrectomy were divided into four groups: control group (n = 10), IS group (n = 10), IS plus 10 mg/kg of astragaloside IV group (n = 10) and IS plus 20 mg/kg of astragaloside IV group (n = 10). IS intraperitoneal injection and astragaloside IV treatment were administered continuously for 1 month. Next, the blood urea nitrogen (BUN) level, serum IS level, tubulointerstitial injury, renal oxidative stress and inflammatory injury were assessed. Results The IS intraperitoneal injection mouse group showed increasing levels of serum IS, BUN, tubulointerstitial injury, renal oxidative stress and inflammatory injury. Astragaloside IV treatment couldn’t reduce the serum IS level or renal nuclear factor-κB and interleukin-1β levels. However, 20 mg/kg astragaloside IV treatment reduced the BUN level and significantly attenuated IS-induced tubulointerstitial injury. Renal oxidative stress was decreased by the administration of astragaloside IV. Conclusions These results suggest that astragaloside IV prevents IS-induced tubulointerstitial injury by ameliorating oxidative stress and may be a promising agent for the treatment of uremia toxin-induced injury. Electronic supplementary material The online version of this article (10.1186/s40360-018-0241-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Chunlan Ji
- National Key Unit of Clinical Research of TCM on Chronic Kidney Diseases, Key Unit of Kidney Diseases, Guangdong Provincial Hospital of Chinese Medicine, The Second Clinical College of Guangzhou University of Chinese Medicine, 111th Dade Road, Guangzhou, 510120, People's Republic of China
| | - Yueming Luo
- National Key Unit of Clinical Research of TCM on Chronic Kidney Diseases, Key Unit of Kidney Diseases, Guangdong Provincial Hospital of Chinese Medicine, The Second Clinical College of Guangzhou University of Chinese Medicine, 111th Dade Road, Guangzhou, 510120, People's Republic of China
| | - Chuan Zou
- National Key Unit of Clinical Research of TCM on Chronic Kidney Diseases, Key Unit of Kidney Diseases, Guangdong Provincial Hospital of Chinese Medicine, The Second Clinical College of Guangzhou University of Chinese Medicine, 111th Dade Road, Guangzhou, 510120, People's Republic of China
| | - Lihua Huang
- National Key Unit of Clinical Research of TCM on Chronic Kidney Diseases, Key Unit of Kidney Diseases, Guangdong Provincial Hospital of Chinese Medicine, The Second Clinical College of Guangzhou University of Chinese Medicine, 111th Dade Road, Guangzhou, 510120, People's Republic of China
| | - Ruimin Tian
- National Key Unit of Clinical Research of TCM on Chronic Kidney Diseases, Key Unit of Kidney Diseases, Guangdong Provincial Hospital of Chinese Medicine, The Second Clinical College of Guangzhou University of Chinese Medicine, 111th Dade Road, Guangzhou, 510120, People's Republic of China
| | - Zhaoyu Lu
- National Key Unit of Clinical Research of TCM on Chronic Kidney Diseases, Key Unit of Kidney Diseases, Guangdong Provincial Hospital of Chinese Medicine, The Second Clinical College of Guangzhou University of Chinese Medicine, 111th Dade Road, Guangzhou, 510120, People's Republic of China.
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19
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Ow CPC, Ngo JP, Ullah MM, Hilliard LM, Evans RG. Renal hypoxia in kidney disease: Cause or consequence? Acta Physiol (Oxf) 2018; 222:e12999. [PMID: 29159875 DOI: 10.1111/apha.12999] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 11/10/2017] [Accepted: 11/15/2017] [Indexed: 02/06/2023]
Abstract
Tissue hypoxia has been proposed as an important factor in the pathophysiology of both chronic kidney disease (CKD) and acute kidney injury (AKI), initiating and propagating a vicious cycle of tubular injury, vascular rarefaction, and fibrosis and thus exacerbation of hypoxia. Here, we critically evaluate this proposition by systematically reviewing the literature relevant to the following six questions: (i) Is kidney disease always associated with tissue hypoxia? (ii) Does tissue hypoxia drive signalling cascades that lead to tissue damage and dysfunction? (iii) Does tissue hypoxia per se lead to kidney disease? (iv) Does tissue hypoxia precede pathology? (v) Does tissue hypoxia colocalize with pathology? (vi) Does prevention of tissue hypoxia prevent kidney disease? We conclude that tissue hypoxia is a common feature of both AKI and CKD. Furthermore, at least under in vitro conditions, renal tissue hypoxia drives signalling cascades that lead to tissue damage and dysfunction. Tissue hypoxia itself can lead to renal pathology, independent of other known risk factors for kidney disease. There is also some evidence that tissue hypoxia precedes renal pathology, at least in some forms of kidney disease. However, we have made relatively little progress in determining the spatial relationships between tissue hypoxia and pathological processes (i.e. colocalization) or whether therapies targeted to reduce tissue hypoxia can prevent or delay the progression of renal disease. Thus, the hypothesis that tissue hypoxia is a "common pathway" to both AKI and CKD still remains to be adequately tested.
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Affiliation(s)
- C. P. C. Ow
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Vic. Australia
| | - J. P. Ngo
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Vic. Australia
| | - M. M. Ullah
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Vic. Australia
| | - L. M. Hilliard
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Vic. Australia
| | - R. G. Evans
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Vic. Australia
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20
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Wu CJ, Chen CY, Lai TS, Wu PC, Chuang CK, Sun FJ, Liu HL, Chen HH, Yeh HI, Lin CS, Lin CJ. The role of indoxyl sulfate in renal anemia in patients with chronic kidney disease. Oncotarget 2017; 8:83030-83037. [PMID: 29137321 PMCID: PMC5669947 DOI: 10.18632/oncotarget.18789] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 05/29/2017] [Indexed: 12/23/2022] Open
Abstract
Renal anemia is a common complication in patients with advanced chronic kidney disease. In vitro studies have shown that indoxyl sulfate decreases erythropoietin production. Whether this effect is seen in vivo remains unclear. Our goal was to explore the role of indoxyl sulfate in renal anemia. We found serum indoxyl sulfate levels are significantly and negatively associated with erythropoietin levels in human. A multiple stepwise linear regression analyses after adjustment for other independent parameters revealed that free indoxyl sulfate, and total indoxyl sulfate were significantly associated with erythropoietin levels. In animal studies, erythropoietin gene and protein expression were markedly inhibited in rats with chronic kidney disease; however, this effect was significantly reversed by lowering serum indoxyl sulfate with AST-120. Indoxyl sulfate may also inhibit erythropoietin expression in animal models with chronic kidney disease. These findings further support the role of indoxyl sulfate in the development of renal anemia.
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Affiliation(s)
- Chih-Jen Wu
- Division of Nephrology, Department of Internal Medicine, Mackay Memorial Hospital, Mackay Medical College ,Taipei, Taiwan.,Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan.,Graduate Institute of Medical Sciences and Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Cheng-Yi Chen
- Division of Nephrology, Department of Internal Medicine, Mackay Memorial Hospital, Mackay Medical College ,Taipei, Taiwan.,Mackay Junior College of Medicine, Nursing and Management, Taipei, Taiwan.,Department of Biological Science and Technology, National Chaio Tung University, Hsinchu, Taiwan
| | - Thung-S Lai
- Graduate Institute of Biomedical Science, Mackay Medical College, New Taipei City, Taiwan
| | - Pei-Chen Wu
- Division of Nephrology, Department of Internal Medicine, Mackay Memorial Hospital, Mackay Medical College ,Taipei, Taiwan
| | - Chih-Kuang Chuang
- Institute of Biotechnology, National Taipei University of Technology, Taipei, Taiwan.,Division of Genetics and Metabolism, Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan.,College of Medicine, Fu-Jen Catholic University, Taipei, Taiwan
| | - Fang-Ju Sun
- Mackay Junior College of Medicine, Nursing and Management, Taipei, Taiwan.,Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan
| | - Hsuan-Liang Liu
- Institute of Biotechnology, National Taipei University of Technology, Taipei, Taiwan
| | - Han-Hsiang Chen
- Division of Nephrology, Department of Internal Medicine, Mackay Memorial Hospital, Mackay Medical College ,Taipei, Taiwan.,Mackay Junior College of Medicine, Nursing and Management, Taipei, Taiwan
| | - Hung-I Yeh
- Department of Medicine, Mackay Medical College, New Taipei City, Taiwan
| | - Chih-Sheng Lin
- Department of Biological Science and Technology, National Chaio Tung University, Hsinchu, Taiwan
| | - Cheng-Jui Lin
- Division of Nephrology, Department of Internal Medicine, Mackay Memorial Hospital, Mackay Medical College ,Taipei, Taiwan.,Institute of Biotechnology, National Taipei University of Technology, Taipei, Taiwan.,Mackay Junior College of Medicine, Nursing and Management, Taipei, Taiwan
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21
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Hansen ESS, Stewart NJ, Wild JM, Stødkilde-Jørgensen H, Laustsen C. Hyperpolarized 13 C, 15 N 2 -Urea MRI for assessment of the urea gradient in the porcine kidney. Magn Reson Med 2016; 76:1895-1899. [PMID: 27670826 DOI: 10.1002/mrm.26483] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 08/10/2016] [Accepted: 09/07/2016] [Indexed: 12/24/2022]
Abstract
PURPOSE A decline in cortico-medullary osmolality gradient of the kidney may serve as an early indicator of pathological disruption of the tubular reabsorption process. The purpose of this study was to investigate the feasibility of hyperpolarized 13 C,15 N2 -urea MRI as a biomarker of renal function in healthy porcine kidneys resembling the human physiology. METHODS Five healthy female Danish domestic pigs (weight 30 kg) were scanned at 3 Tesla (T) using a 13 C 3D balanced steady-state MR pulse sequence following injection of hyperpolarized 13 C,15 N2 -urea via a femoral vein catheter. Images were acquired at different time points after urea injection, and following treatment with furosemide. RESULTS A gradient in cortico-medullary urea was observed with an intramedullary accumulation 75 s after injection of hyperpolarized 13 C,15 N2 -urea, whereas images acquired at earlier time points postinjection were dominated by cortical perfusion. Furosemide treatment resulted in an increased urea accumulation in the cortical space, leading to a reduction of the medullary-to-cortical signal ratio of 49%. CONCLUSION This study demonstrates that hyperpolarized 13 C,15 N2 -urea MRI is capable of identifying the intrarenal accumulation of urea and can differentiate acute renal functional states in multipapillary kidneys, highlighting the potential for human translation. Magn Reson Med 76:1895-1899, 2016. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Esben S S Hansen
- MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Danish Diabetes Academy, Odense, Denmark
| | - Neil J Stewart
- Academic Unit of Radiology, University of Sheffield, Sheffield, UK
| | - Jim M Wild
- Academic Unit of Radiology, University of Sheffield, Sheffield, UK
| | | | - Christoffer Laustsen
- MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
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22
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Chen J, Zhang X, Zhang H, Liu T, Zhang H, Teng J, Ji J, Ding X. Indoxyl Sulfate Enhance the Hypermethylation of Klotho and Promote the Process of Vascular Calcification in Chronic Kidney Disease. Int J Biol Sci 2016; 12:1236-1246. [PMID: 27766038 PMCID: PMC5069445 DOI: 10.7150/ijbs.15195] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 07/29/2016] [Indexed: 12/16/2022] Open
Abstract
Chronic kidney disease (CKD) is a state of Klotho deficiency. The Klotho expression may be suppressed due to DNA hypermethylation in cancer cells so we have investigated the effects and possible mechanisms by which Klotho expression is regulated in human aortic smooth muscle cells (HASMCs). The vascular Klotho hypermethylation in radial arteries of patients with end-stage renal disease was described. Cultured HASMCs and 5/6-nephrectomized Sprague Dawley (SD) rats treated with indoxyl sulfate (IS) were used as in vitro and in vivo models, respectively. IS increased CpG hypermethylation of the Klotho gene and decreased Klotho expression in HASMCs, and potentiated HASMCs calcification. The expression of DNA methyltransferase (DNMT) 1 and 3a in HASMCs treated with IS was significantly increased and specific inhibition of DNA methyltransferase 1 by 5-aza-2'-deoxycytidine(5Aza-2dc) caused demethylation of the Klotho gene and increased Klotho expression. In rats, injection of IS potentiated vascular calcification, increased CpG hypermethylation of the Klotho gene and decreased Klotho expression in the aortic medial layer and all of these changes could be reverted by 5Aza-2dc treatment. Transcriptional suppression of vascular Klotho gene expression by IS and epigenetic modification of Klotho by IS may be an important pathological mechanism of vascular calcification in CKD.
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Affiliation(s)
- Jing Chen
- Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.; Kidney and Dialysis Institute of Shanghai, Shanghai, China.; Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China
| | - Xiaoyan Zhang
- Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.; Kidney and Dialysis Institute of Shanghai, Shanghai, China.; Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China
| | - Han Zhang
- Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Tongqiang Liu
- Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Hui Zhang
- Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Jie Teng
- Kidney and Dialysis Institute of Shanghai, Shanghai, China
| | - Jun Ji
- Kidney and Dialysis Institute of Shanghai, Shanghai, China
| | - Xiaoqiang Ding
- Department of Nephrology, Zhongshan Hospital, Fudan University, Shanghai, China.; Kidney and Dialysis Institute of Shanghai, Shanghai, China.; Kidney and Blood Purification Laboratory of Shanghai, Shanghai, China
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23
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Tanaka T. A mechanistic link between renal ischemia and fibrosis. Med Mol Morphol 2016; 50:1-8. [PMID: 27438710 DOI: 10.1007/s00795-016-0146-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 07/14/2016] [Indexed: 01/11/2023]
Abstract
Renal fibrosis is characterized by tubular cell atrophy and accumulation of extracellular matrix. Fibroblast activation becomes evident in areas surrounding atrophic tubules, with rarefaction of peritubular capillaries. Tubulointerstitial hypoxia is the final common pathway in progressive kidney disease. Hypoxia suppresses tubular epithelial growth and leads to failure of remodeling by facilitating dedifferentiation and apoptosis. Profibrotic factors such as transforming growth factor-β (TGF-β) mediate fibroblast activation, and recruited leukocytes, which appear in hypoxic areas, contribute to fibrosis. While resident renal cells adapt to the hypoxic environment via upregulation of relevant genes by hypoxia-inducible factor (HIF) family members, hypoxic adaptation via HIF may not be sufficient in chronic kidney disease (CKD) due to multiple factors. Thus, restoration of HIF-mediated responses may contribute to amelioration of CKD pathology. Studies to date have reported that HIF activation reduces inflammation and oxidative stress and ameliorates injury by decreasing tubular cell apoptosis and restoring peritubular capillary network. Prolyl hydroxylase domain (PHD) inhibitors that specifically activate HIF are currently evaluated for the treatment of renal anemia and may be effective for the treatment of CKD.
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Affiliation(s)
- Tetsuhiro Tanaka
- Division of Nephrology and Endocrinology, The University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
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Tanaka S, Tanaka T, Nangaku M. Hypoxia and hypoxia-inducible factors in chronic kidney disease. RENAL REPLACEMENT THERAPY 2016. [DOI: 10.1186/s41100-016-0038-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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25
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Shi H, Hu L, Chen S, Bao W, Yang S, Zhao X, Sun C. Metabolomics analysis of urine from rats administered with long-term, low-dose acrylamide by ultra-performance liquid chromatography-mass spectrometry. Xenobiotica 2016; 47:439-449. [DOI: 10.1080/00498254.2016.1196509] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Haidan Shi
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang, China
| | - Liyan Hu
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang, China
| | - Shuai Chen
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang, China
| | - Wei Bao
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang, China
| | - Shuang Yang
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang, China
| | - Xiujuan Zhao
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang, China
| | - Changhao Sun
- Department of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang, China
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26
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Expanding roles of the hypoxia-response network in chronic kidney disease. Clin Exp Nephrol 2016; 20:835-844. [PMID: 26857707 DOI: 10.1007/s10157-016-1241-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 01/26/2016] [Indexed: 12/19/2022]
Abstract
Studies over the last two decades have established tubulointerstitial hypoxia as a final common pathway leading to end-stage kidney disease (ESKD). Chronic kidney disease (CKD) is frequently associated with various degrees of hypoxic injury in distinct tubular segments, depending on the etiology and pathological stages, which constitutes an intricate link among inflammation, oxidative stress and fibrosis. Resident cells in the kidney are equipped with mechanisms through which they cope with hypoxia. Here, transcription of genes by hypoxia-inducible factors (HIFs) plays a central role. In the ischemic kidney, HIF-1 is expressed in tubular and glomerular epithelial cells and in papillary interstitial cells, whereas HIF-2 is expressed in endothelial cells and interstitial fibroblasts. There is ample evidence that HIF protects the kidney from acute ischemic damage. In CKD, studies suggest that the function of HIF may be suppressed because of factors, such as oxidative stress and uremia, which may underlie the pathogenesis of both CKD and co-existing problems, such as renal anemia. Based on these observations, efforts are in progress to test whether restoration and activation of HIF might protect the kidney from CKD. Initial studies using non-specific or supraphysiological HIF activation suggested that the role of HIF may be multifactorial and depend on pathological context. On the other hand, specific HIF stabilizers, such as prolyl hydroxylase (PHD) inhibitors, are being developed for the treatment of renal anemia. Application of these compounds in experimental CKD may override those previous findings and provide deeper insight into the roles of hypoxia and oxygen-sensing pathways.
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27
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Laustsen C, Stokholm Nørlinger T, Christoffer Hansen D, Qi H, Mose Nielsen P, Bonde Bertelsen L, Henrik Ardenkjaer-Larsen J, Stødkilde Jørgensen H. Hyperpolarized 13C urea relaxation mechanism reveals renal changes in diabetic nephropathy. Magn Reson Med 2015; 75:515-8. [PMID: 26584247 PMCID: PMC4738460 DOI: 10.1002/mrm.26036] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/01/2015] [Accepted: 10/15/2015] [Indexed: 01/01/2023]
Abstract
PURPOSE Our aim was to assess a novel (13) C radial fast spin echo golden ratio single shot method for interrogating early renal changes in the diabetic kidney, using hyperpolarized (HP) [(13) C,(15) N2 ]urea as a T2 relaxation based contrast bio-probe. METHODS A novel HP (13) C MR contrast experiment was conducted in a group of streptozotocin type-1 diabetic rat model and age matched controls. RESULTS A significantly different relaxation time (P = 0.004) was found in the diabetic kidney (0.49 ± 0.03 s) compared with the controls (0.64 ± 0.02 s) and secondly, a strong correlation between the blood oxygen saturation level and the relaxation times were observed in the healthy controls. CONCLUSION HP [(13) C,(15) N2 ]urea apparent T2 mapping may be a useful for interrogating local renal pO2 status and renal tissue alterations. Magn Reson Med, 2015. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
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Affiliation(s)
- Christoffer Laustsen
- MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | | | | | - Haiyun Qi
- MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Per Mose Nielsen
- MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Lotte Bonde Bertelsen
- MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Jan Henrik Ardenkjaer-Larsen
- GE Healthcare, Broendby, Denmark.,Department of Electrical Engineering, Technical University of Denmark, Kgs Lyngby, Denmark
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Enhanced NADPH oxidases and reactive oxygen species in the mechanism of methanol-initiated protein oxidation and embryopathies in vivo and in embryo culture. Arch Toxicol 2015; 90:717-30. [DOI: 10.1007/s00204-015-1482-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 02/12/2015] [Indexed: 01/01/2023]
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Nangaku M, Mimura I, Yamaguchi J, Higashijima Y, Wada T, Tanaka T. Role of uremic toxins in erythropoiesis-stimulating agent resistance in chronic kidney disease and dialysis patients. J Ren Nutr 2014; 25:160-3. [PMID: 25556149 DOI: 10.1053/j.jrn.2014.10.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 10/29/2014] [Indexed: 11/11/2022] Open
Abstract
Patients with advanced chronic kidney disease are exposed to uremic toxins. In addition to causing uremic symptoms, uremic toxins accelerate the progression of renal failure. Indoxyl sulfate (IS) increases oxygen consumption in tubules, aggravating hypoxia of the kidney, and progression of the kidney disease. IS also induces endoplasmic reticulum stress and thereby contributes the progression of cellular damages in tubular epithelial cells. Hypoxia-inducible factor (HIF) is a master transcriptional regulator of adaptive responses against hypoxia and regulates expression of erythropoietin (EPO). IS suppresses EPO expression via HIF-dependent and HIF-independent manner. IS impedes the recruitment of transcriptional coactivators to HIF via upregulation of Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 through a mechanism of posttranscriptional messenger RNA stabilization. Furthermore, IS induces activating transcription factor 4 via endoplasmic reticulum stress, decreasing EPO expression. Although erythropoiesis-stimulating agent (ESA) resistance is generally defined as lack of responses to exogenous ESA administration, suppression of endogenous production of EPO under uremic conditions may aggravate ESA resistance. Uremia is associated with increased formation of advanced glycation end products (AGE). Studies of transgenic rats overexpressing glyoxalse 1 (GLO1), which detoxifies precursors of advanced glycation end products, demonstrated that glycative stress causes renal senescence and vascular endothelial dysfunction. Glycative stress also suppresses HIF activation making the kidney susceptible to hypoxia as a final common pathway to end-stage kidney disease.
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Affiliation(s)
- Masaomi Nangaku
- Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan.
| | - Imari Mimura
- Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan
| | - Junna Yamaguchi
- Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan
| | - Yoshiki Higashijima
- Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan
| | - Takehiko Wada
- Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan
| | - Tetsuhiro Tanaka
- Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, Tokyo, Japan
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30
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Chao CT, Chiang CK. Uremic toxins, oxidative stress, and renal fibrosis: an interwined complex. J Ren Nutr 2014; 25:155-9. [PMID: 25511523 DOI: 10.1053/j.jrn.2014.10.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 10/29/2014] [Indexed: 11/11/2022] Open
Abstract
The prevalence of end-stage renal diseases is currently on the rise globally, and finding the way to curb this tide is urgently needed. Tubulointerstitial fibrosis is a common pathway for essentially all the nephropathy categories known to date, and the manifestations of renal fibrosis include excessive deposition of extracellular matrix with distortion of renal microstructures and functional deterioration. Uremic toxins have been gradually found to play an important role in the development of progressive renal fibrosis, with protein-bound indoxyl sulfate, p-cresol, and p-cresyl sulfate receiving the most attention. However, the contribution of oxidative stress among the pathogenesis of uremic toxins and renal fibrosis has not been evaluated much until recently. In this review, we will discuss about the nature and sources of oxidative stress in the kidney and how uremic toxins use oxidative stress to orchestrate the processes of renal fibrosis.
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Affiliation(s)
- Chia-Ter Chao
- Renal Division, Department of Internal Medicine, National Taiwan University Hospital Jin-Shan Branch, New Taipei City, Taiwan; Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan; Graduate Institute of Toxicology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Chih-Kang Chiang
- Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan; Graduate Institute of Toxicology, National Taiwan University College of Medicine, Taipei, Taiwan; Department of Integrative Diagnostics and Therapeutics, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan.
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31
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Schulz AM, Terne C, Jankowski V, Cohen G, Schaefer M, Boehringer F, Tepel M, Kunkel D, Zidek W, Jankowski J. Modulation of NADPH oxidase activity by known uraemic retention solutes. Eur J Clin Invest 2014; 44:802-11. [PMID: 25041433 DOI: 10.1111/eci.12297] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2013] [Accepted: 06/24/2014] [Indexed: 12/18/2022]
Abstract
BACKGROUND Uraemia and cardiovascular disease appear to be associated with an increased oxidative burden. One of the key players in the genesis of reactive oxygen species (ROS) is nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Based on initial experiments demonstrating a decreased inhibitory effect on NADPH oxidase activity in the presence of plasma from patients with CKD-5D after dialysis compared with before dialysis, we investigated the effect of 48 known and commercially available uraemic retention solutes on the enzymatic activity of NADPH oxidase. METHODS Mononuclear leucocytes isolated from buffy coats of healthy volunteers were isolated, lysed and incubated with NADH in the presence of plasma from healthy controls and patients with CKD-5D. Furthermore, the leucocytes were lysed and incubated in the presence of uraemic retention solute of interest and diphenyleneiodonium chloride (DPI), an inhibitor of NADPH oxidase. The effect on enzymatic activity of NADPH oxidase was quantified within an incubation time of 120 min. RESULTS Thirty-nine of the 48 uraemic retention solutes tested had a significant decreasing effect on NADPH oxidase activity. Oxalate has been characterized as the strongest inhibitor of NADPH oxidase (90% of DPI inhibition). Surprisingly, none of the uraemic retention solutes we investigated was found to increase NADPH oxidase activity. Furthermore, plasma from patients with CKD-5D before dialysis caused significantly higher inhibitory effect on NADPH oxidase activity compared with plasma from healthy subjects. However, this effect was significantly decreased in plasma from patients with CKD-5D after dialysis. CONCLUSIONS The results of this study show that uraemic retention solutes modulated the activity of the NADPH oxidase. The results of this study might be the basis for the development of inhibitors applicable as drug in the situation of increased oxidative stress.
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Affiliation(s)
- Anna Marta Schulz
- Charité-Universitätsmedizin Berlin (CBF), Medizinische Klinik IV, Berlin, Germany
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32
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Furuse SU, Ohse T, Jo-Watanabe A, Shigehisa A, Kawakami K, Matsuki T, Chonan O, Nangaku M. Galacto-oligosaccharides attenuate renal injury with microbiota modification. Physiol Rep 2014; 2:2/7/e12029. [PMID: 24994892 PMCID: PMC4187549 DOI: 10.14814/phy2.12029] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Tubulointerstitial injury is central to the progression of end‐stage renal disease. Recent studies have revealed that one of the most investigated uremic toxins, indoxyl sulfate (IS), caused tubulointerstitial injury through oxidative stress and endoplasmic reticulum (ER) stress. Because indole, the precursor of IS, is synthesized from dietary tryptophan by the gut microbiota, we hypothesized that the intervention targeting the gut microbiota in kidney disease with galacto‐oligosaccharides (GOS) would attenuate renal injury. After 2 weeks of GOS administration for 5/6 nephrectomized (Nx) or sham‐operated (Sham) rats, cecal indole and serum IS were measured, renal injury was evaluated, and the effects of GOS on the gut microbiota were examined using pyrosequencing methods. Cecal indole and serum IS were significantly decreased and renal injury was improved with decreased infiltrating macrophages in GOS‐treated Nx rats. The expression levels of ER stress markers and apoptosis were significantly increased in the Nx rats and decreased with GOS. The microbiota analysis indicated that GOS significantly increased three bacterial families and decreased five families in the Nx rats. In addition, the analysis also revealed that the bacterial family Clostridiaceae was significantly increased in the Nx rats compared with the Sham rats and decreased with GOS. Taken altogether, our data show that GOS decreased cecal indole and serum IS, attenuated renal injury, and modified the gut microbiota in the Nx rats, and that the gut microbiota were altered in kidney disease. GOS could be a novel therapeutic agent to protect against renal injury. GOS ameliorated the renal injury with lower indoxyl sulfate. GOS could be a novel therapeutic agent to protect against kidney disease.
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Affiliation(s)
- Satoshi U Furuse
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan Division of Nephrology, Mitsui Memorial Hospital, Tokyo, Japan
| | - Takamoto Ohse
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
| | - Airi Jo-Watanabe
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
| | - Akira Shigehisa
- Yakult Central Institute for Microbiological Research, Kunitachi, Japan
| | - Koji Kawakami
- Yakult Central Institute for Microbiological Research, Kunitachi, Japan
| | - Takahiro Matsuki
- Yakult Central Institute for Microbiological Research, Kunitachi, Japan
| | - Osamu Chonan
- Yakult Central Institute for Microbiological Research, Kunitachi, Japan
| | - Masaomi Nangaku
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
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Holmar J, Uhlin F, Ferenets R, Lauri K, Tanner R, Arund J, Luman M, Fridolin I. Estimation of removed uremic toxin indoxyl sulphate during hemodialysis by using optical data of the spent dialysate. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2014; 2013:6707-10. [PMID: 24111282 DOI: 10.1109/embc.2013.6611095] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The aim of this study was to explore the possibility to determine the amount of total removed Indoxyl Sulphate (TR_IS) during dialysis session, an optical method utilizing absorbance and fluorescence spectral data of the spent dialysate was used. Eight uremic patients from Linköping, Sweden and 10 from Tallinn, Estonia, were studied during dialysis treatments. Dialysate samples were taken during each treatment and analyzed at a laboratory. Fluorescence and absorbance spectra of the spent dialysate were measured with spectrofluorophotometer and spectrophotometer. The spectral values were transformed into IS concentration using multiple linear regression model from the total material noted as optical method (Opt). IS concentration was estimated using high-performance liquid chromatography (HPLC) method as a reference. TR_IS values were calculated. Achieved results were compared regarding mean values and SD and collated with the amount of total removed urea value (TR_Urea) for the same dialysis procedures. Mean TR value ± SD (mg) for urea was 28 947 ± 9 241; TR for IS was 151.4 ± 87.3 estimated by HPLC and 149.4 ± 84.9 estimated by Opt. The TR_IS values were not significantly different (p ≤ 0.05). This study indicates, that it is possible to estimate TR_IS using only spectral values of the spent dialysate and the parameter can be used for quantifying the elimination of protein bound uremic toxins during the dialysis procedure.
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Franzén S, Friederich-Persson M, Fasching A, Hansell P, Nangaku M, Palm F. Differences in susceptibility to develop parameters of diabetic nephropathy in four mouse strains with type 1 diabetes. Am J Physiol Renal Physiol 2014; 306:F1171-8. [DOI: 10.1152/ajprenal.00595.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
One-third of diabetes mellitus patients develop diabetic nephropathy, and with underlying mechanisms unknown it is imperative that diabetic animal models resemble human disease. The present study investigated the susceptibility to develop diabetic nephropathy in four commonly used and commercially available mouse strains with type 1 diabetes to determine the suitability of each strain. Type 1 diabetes was induced in C57Bl/6, NMRI, BALB/c, and 129Sv mice by alloxan, and conscious glomerular filtration rate, proteinuria, and oxidative stress levels were measured in control and diabetic animals at baseline and after 5 and 10 wk. Histological alterations were analyzed using periodic acid-Schiff staining. Diabetic C57Bl/6 displayed increased glomerular filtration rate, i.e., hyperfiltration, whereas all other parameters remained unchanged. Diabetic NMRI developed the most pronounced hyperfiltration as well as increased oxidative stress and proteinuria but without glomerular damage. Diabetic BALB/c did not develop hyperfiltration but presented with pronounced proteinuria, increased oxidative stress, and glomerular damage. Diabetic 129Sv displayed proteinuria and increased oxidative stress without glomerular hyperfiltration or damage. However, all strains displayed intrastrain correlation between oxidative stress and proteinuria. In conclusion, diabetic C57Bl/6 and NMRI both developed glomerular hyperfiltration but neither presented with histological damage, although NMRI developed low-degree proteinuria. Thus these strains may be suitable when investigating the mechanism causing hyperfiltration. Neither BALB/c nor 129Sv developed hyperfiltration although both developed pronounced proteinuria. However, only BALB/c developed detectable histological damage. Thus BALB/c may be suitable when studying the roles of proteinuria and histological alterations for the progression of diabetic nephropathy.
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Affiliation(s)
- Stephanie Franzén
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden
| | | | - Angelica Fasching
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and
| | - Peter Hansell
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and
| | - Masaomi Nangaku
- Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan
| | - Fredrik Palm
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization, Linköping University, Linköping, Sweden
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and
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35
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Ng HY, Yisireyili M, Saito S, Lee CT, Adelibieke Y, Nishijima F, Niwa T. Indoxyl sulfate downregulates expression of Mas receptor via OAT3/AhR/Stat3 pathway in proximal tubular cells. PLoS One 2014; 9:e91517. [PMID: 24614509 PMCID: PMC3948887 DOI: 10.1371/journal.pone.0091517] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 02/10/2014] [Indexed: 01/09/2023] Open
Abstract
Renin-angiotensin system (RAS) plays a pivotal role in chronic kidney disease (CKD). Angiotensin converting enzyme-related carboxypeptidase 2 (ACE2)/angiotensin (Ang)-(1–7)/Mas receptor axis counteracts the deleterious actions of Ang II. ACE2 exerts its actions by cleaving Ang II into Ang-(1–7) which activates Mas receptor. This study aimed to determine if the expression of Mas receptor is altered in the kidneys of CKD rats, and if indoxyl sulfate (IS), a uremic toxin, affects the expression of Mas receptor in rat kidneys and cultured human proximal tubular cells (HK-2 cells). The expression of Mas receptor was examined in the kidneys of CKD and AST-120-treated CKD rats using immunohistochemistry. Further, the effects of IS on Mas receptor expression in the kidneys of normotensive and hypertensive rats were examined. The effects of IS on the expression of Mas receptor and phosphorylation of endothelial nitric oxide synthase (eNOS) in HK-2 cells were examined using immunoblotting. CKD rats showed reduced renal expression of Mas receptor, while AST-120 restored its expression. Administration of IS downregulated Mas receptor expression in the kidneys of normotensive and hypertensive rats. IS downregulated Mas receptor expression in HK-2 cells in a time- and dose-dependent manner. Knockdown of organic anion transporter 3 (OAT3), aryl hydrocarbon receptor (AhR), and signal transducer and activator of transcription 3 (Stat3) inhibited IS-induced downregulation of Mas receptor and phosphorylated eNOS. N-acetylcysteine, an antioxidant, also inhibited IS-induced downregulation of Mas receptor and phosphorylated eNOS. Ang-(1–7) attenuated IS-induced transforming growth factor-β1 (TGF-β1) expression. Conclusion Mas receptor expression is reduced in the kidneys of CKD rats. IS downregulates renal expression of Mas receptor via OAT3/AhR/Stat3 pathway in proximal tubular cells. IS-induced downregulation of Mas receptor might be involved in upregulation of TGF-β1 in proximal tubular cells.
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MESH Headings
- Acetylcysteine/pharmacology
- Angiotensins/pharmacology
- Animals
- Down-Regulation/drug effects
- Humans
- Immunohistochemistry
- Indican/administration & dosage
- Indican/pharmacology
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Male
- Models, Biological
- Nitric Oxide Synthase Type III/metabolism
- Organic Anion Transporters, Sodium-Independent/metabolism
- Phosphorylation/drug effects
- Proto-Oncogene Mas
- Proto-Oncogene Proteins/metabolism
- RNA, Small Interfering/metabolism
- Rats, Inbred Dahl
- Rats, Sprague-Dawley
- Reactive Oxygen Species/metabolism
- Receptors, Aryl Hydrocarbon/metabolism
- Receptors, G-Protein-Coupled/metabolism
- Renal Insufficiency, Chronic/metabolism
- STAT3 Transcription Factor/metabolism
- Signal Transduction/drug effects
- Time Factors
- Transforming Growth Factor beta1/metabolism
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Affiliation(s)
- Hwee-Yeong Ng
- Department of Advanced Medicine for Uremia, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Maimaiti Yisireyili
- Department of Advanced Medicine for Uremia, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shinichi Saito
- Department of Advanced Medicine for Uremia, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Chien-Te Lee
- Division of Nephrology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan
| | - Yelixiati Adelibieke
- Department of Advanced Medicine for Uremia, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | | | - Toshimitsu Niwa
- Department of Advanced Medicine for Uremia, Nagoya University Graduate School of Medicine, Nagoya, Japan
- * E-mail:
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Sirich TL, Meyer TW, Gondouin B, Brunet P, Niwa T. Protein-bound molecules: a large family with a bad character. Semin Nephrol 2014; 34:106-17. [PMID: 24780467 DOI: 10.1016/j.semnephrol.2014.02.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Many small solutes excreted by the kidney are bound to plasma proteins, chiefly albumin, in the circulation. The combination of protein binding and tubular secretion allows the kidney to reduce the free, unbound concentrations of such solutes to lower levels than could be obtained by tubular secretion alone. Protein-bound solutes accumulate in the plasma when the kidneys fail, and the free, unbound levels of these solutes increase more than their total plasma levels owing to competition for binding sites on plasma proteins. Given the efficiency by which the kidney can clear protein-bound solutes, it is tempting to speculate that some compounds in this class are important uremic toxins. Studies to date have focused largely on two specific protein-bound solutes: indoxyl sulfate and p-cresyl sulfate. The largest body of evidence suggests that both of these compounds contribute to cardiovascular disease, and that indoxyl sulfate contributes to the progression of chronic kidney disease. Other protein-bound solutes have been investigated to a much lesser extent, and could in the future prove to be even more important uremic toxins.
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Affiliation(s)
- Tammy L Sirich
- Department of Medicine, VA Palo Alto Healthcare System and Stanford University, Palo Alto, CA
| | - Timothy W Meyer
- Department of Medicine, VA Palo Alto Healthcare System and Stanford University, Palo Alto, CA.
| | - Bertrand Gondouin
- Aix-Marseille University, INSERM UMR_S 1076, Marseille, France; Centre de Nephrologie et Transplantation Renale, Assistance-Publique Hopitaux de Marseille, Marseille, France
| | - Philippe Brunet
- Aix-Marseille University, INSERM UMR_S 1076, Marseille, France; Centre de Nephrologie et Transplantation Renale, Assistance-Publique Hopitaux de Marseille, Marseille, France
| | - Toshimitsu Niwa
- Department of Advanced Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Oxidative and Endoplasmic Reticulum (ER) Stress in Tissue Fibrosis. CURRENT PATHOBIOLOGY REPORTS 2013. [DOI: 10.1007/s40139-013-0029-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Hansell P, Welch WJ, Blantz RC, Palm F. Determinants of kidney oxygen consumption and their relationship to tissue oxygen tension in diabetes and hypertension. Clin Exp Pharmacol Physiol 2013. [PMID: 23181475 DOI: 10.1111/1440-1681.12034] [Citation(s) in RCA: 212] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The high renal oxygen (O(2) ) demand is associated primarily with tubular O(2) consumption (Qo(2) ) necessary for solute reabsorption. Increasing O(2) delivery relative to demand via increased blood flow results in augmented tubular electrolyte load following elevated glomerular filtration, which, in turn, increases metabolic demand. Consequently, elevated kidney metabolism results in decreased tissue oxygen tension. The metabolic efficiency for solute transport (Qo(2) /T(Na) ) varies not only between different nephron sites, but also under different conditions of fluid homeostasis and disease. Contributing mechanisms include the presence of different Na(+) transporters, different levels of oxidative stress and segmental tubular dysfunction. Sustained hyperglycaemia results in increased kidney Qo(2) , partly due to mitochondrial dysfunction and reduced electrolyte transport efficiency. This results in intrarenal tissue hypoxia because the increased Qo(2) is not matched by a similar increase in O(2) delivery. Hypertension leads to renal hypoxia, mediated by increased angiotensin receptor tonus and oxidative stress. Reduced uptake in the proximal tubule increases load to the thick ascending limb. There, the increased load is reabsorbed, but at greater O(2) cost. The combination of hypertension, angiotensin II and oxidative stress initiates events leading to renal damage and reduced function. Tissue hypoxia is now recognized as a unifying pathway to chronic kidney disease. We have gained good knowledge about major changes in O(2) metabolism occurring in diabetic and hypertensive kidneys. However, further efforts are needed to elucidate how these alterations can be prevented or reversed before translation into clinical practice.
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Affiliation(s)
- Peter Hansell
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
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Nangaku M. Energy policy of the kidney: launch of AMPK as a novel therapeutic target. Am J Physiol Renal Physiol 2013; 305:F977-8. [DOI: 10.1152/ajprenal.00385.2013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Masaomi Nangaku
- Division of Nephrology and Endocrinology, The University of Tokyo School of Medicine, Tokyo, Japan
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40
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Yamaguchi S, Inada C, Tamura M, Sato N, Yamada M, Itaba S, Okazaki S, Matsuura H, Fujii S, Matsuda F, Goto Y, Mochizuki H, Kurumatani H, Miyamoto M. Beraprost sodium improves survival rates in anti-glomerular basement membrane glomerulonephritis and 5/6 nephrectomized chronic kidney disease rats. Eur J Pharmacol 2013; 714:325-31. [PMID: 23911885 DOI: 10.1016/j.ejphar.2013.07.032] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 07/05/2013] [Accepted: 07/16/2013] [Indexed: 11/16/2022]
Abstract
Beraprost sodium, a stable prostacyclin analog, was showed to improve survival rates in two different rat models, anti-glomerular basement membrane (GBM) glomerulonephritis (GN) and 5/6 nephrectomized (Nx) chronic kidney disease (CKD) rats. In the anti-GBM rat, beraprost sodium (0.2 and 0.6 mg/kg/day) improved survival rate (hazard ratio for beraprost sodium 0.6 mg/kg/day group, 0.10; 95% confidence interval, 0.01 to 0.68). Subsequently, in the 5/6 Nx CKD rat, beraprost sodium (0.6 mg/kg/day) improved survival rate (hazard ratio for beraprost sodium, 0.46; 95% confidence interval, 0.23 to 0.92), serum creatinine doubling time and the slope of the reciprocal of serum creatinine. In the anti-GBM GN rats, beraprost sodium suppressed the serum accumulation of representative uremic toxins such as indoxyl sulfate. Furthermore, beraprost sodium inhibited human aortic endothelial cell (HAEC) injury induced by indoxyl sulfate, indicating that beraprost sodium might have a protective effect against cardiovascular damage due to CKD. These results show that beraprost sodium can improve the survival rates in two rat models of anti-GBM GN and 5/6 Nx CKD rats by protecting endothelial cells and thereby ameliorating decreased renal function. Therefore, clinical studies are needed in patients with chronic kidney failure to determine whether beraprost sodium will become a useful medication in CKD.
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Affiliation(s)
- Shinichi Yamaguchi
- Pharmacology Laboratory, Pharmaceutical Research Laboratories, Toray Industries, Inc., Kanagawa 248 8555, Japan.
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Tanaka T, Yamaguchi J, Higashijima Y, Nangaku M. Indoxyl sulfate signals for rapid mRNA stabilization of Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) and suppresses the expression of hypoxia-inducible genes in experimental CKD and uremia. FASEB J 2013; 27:4059-75. [PMID: 23792300 DOI: 10.1096/fj.13-231837] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Chronic hypoxia in the tubulointerstitium serves as a final common pathway in progressive renal disease. Circumstantial evidence suggests that hypoxia-inducible factor (HIF)-1 in the ischemic tubules may be functionally inhibited in a chronic kidney disease (CKD) milieu. In this study, we hypothesized that indoxyl sulfate (IS), a uremic toxin, impairs the cellular hypoxic response. In human kidney (HK-2) proximal tubular cells, IS reduced the hypoxic induction of HIF-1 target genes. This effect was not associated with quantitative changes in the HIF-1α protein, but with functional impairment of the HIF-1α C-terminal transactivation domain (CTAD). Among factors that impeded the recruitment of transcriptional coactivators to the HIF-1αCTAD, IS markedly up-regulated Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) through a mechanism of post-transcriptional mRNA stabilization involving the extracellular signal-regulated kinase (ERK) 1/2 pathway. In vivo, disproportionate expression of HIF target genes was demonstrated in several CKD models, which was offset by an oral adsorbent, AST-120. Furthermore, administration of indole reduced the induction of angiogenic, hypoxia-inducible genes in rats with experimental heart failure. Results of these studies reveal a novel role of IS in modulating the transcriptional response of HIF-1 and provide insight into molecular mechanisms underlying progressive nephropathies as well as cardiovascular complications.
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Affiliation(s)
- Tetsuhiro Tanaka
- 1Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo-ku, 113-8655 Tokyo, Japan. T.T.,
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Ito S, Higuchi Y, Yagi Y, Nishijima F, Yamato H, Ishii H, Osaka M, Yoshida M. Reduction of indoxyl sulfate by AST-120 attenuates monocyte inflammation related to chronic kidney disease. J Leukoc Biol 2013; 93:837-45. [DOI: 10.1189/jlb.0112023] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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43
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Verzola D, Famà A, Villaggio B, Di Rocco M, Simonato A, D'Amato E, Gianiorio F, Garibotto G. Lysine triggers apoptosis through a NADPH oxidase-dependent mechanism in human renal tubular cells. J Inherit Metab Dis 2012; 35:1011-9. [PMID: 22403019 DOI: 10.1007/s10545-012-9468-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 02/06/2012] [Accepted: 02/13/2012] [Indexed: 10/28/2022]
Abstract
Progressive chronic kidney disease (CKD) is common in lysinuric protein intolerance (LPI), a primary inherited aminoaciduria characterized by massive Lysine excretion in urine. However, by which mechanisms Lysine may cause kidney damage to tubule cells is still not understood. This study determined whether Lysine overloading of human proximal tubular cells (HK-2) in culture enhances apoptotic cell loss and its associated mechanisms. Overloading HK-2 with Lysine levels reproducing those observed in urine of patients affected by LPI (10 mM) increased apoptosis (+30%; p < 0.01 vs.C), as well as Bax and Apaf-1 expressions (+30-50% p < 0.05), while downregulated Bcl-2 (-40% p < 0.05). Apoptosis induced by high Lysine was no longer observed after addition of caspase-9 and caspase-3 inhibitors while caspase-8 inhibitor had no protective effect. High Lysine induced elevations in ROS generation and NADPH oxidase subunits mRNAs (p22 (phox) +106 ± 23%, p67 (phox) +108 ± 22% and gp91 (phox) +75 ± 4% p < 0.05-0.01). In addition, the NADPH oxidase inhibitor DPI prevented both ROS production and apoptosis. Treating HK-2 with antioxidants, such as Cysteine and its analog, N-acetyl-L-cysteine (NAC), rescued the HK-2 from apoptosis induced by Lysine. In summary, our data show that high Lysine in vitro increases the permissiveness of proximal tubule kidney cells to apoptosis by triggering a pathway involving NADPH oxidase signaling. This event may represent a key cellular effect in the increasing the susceptibility of human tubular cells to apoptosis when the tubules cope with a high Lysine load. This effect is instrumental to renal damage and disease progression in patients with LPI.
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MESH Headings
- Amino Acid Metabolism, Inborn Errors/complications
- Amino Acid Metabolism, Inborn Errors/etiology
- Amino Acid Metabolism, Inborn Errors/metabolism
- Amino Acid Metabolism, Inborn Errors/pathology
- Antioxidants/pharmacology
- Apoptosis/drug effects
- Apoptosis/physiology
- Caspase Inhibitors/pharmacology
- Cell Line
- Disease Progression
- Gene Expression/drug effects
- Humans
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Kidney Tubules, Proximal/pathology
- Lysine/metabolism
- Lysine/toxicity
- Membrane Potential, Mitochondrial/drug effects
- NADPH Oxidases/chemistry
- NADPH Oxidases/genetics
- NADPH Oxidases/metabolism
- Protein Subunits
- Reactive Oxygen Species/metabolism
- Renal Insufficiency, Chronic/etiology
- Renal Insufficiency, Chronic/metabolism
- Renal Insufficiency, Chronic/pathology
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Affiliation(s)
- Daniela Verzola
- Department of Internal Medicine, Nephrology Division, Genoa University, IRCSS Azienda Ospedaliera Universitaria San Martino - IST, Viale Benedetto XV,6, 16132, Genoa, Italy
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44
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Miyamoto Y, Iwao Y, Mera K, Watanabe H, Kadowaki D, Ishima Y, Chuang VTG, Sato K, Otagiri M, Maruyama T. A uremic toxin, 3-carboxy-4-methyl-5-propyl-2-furanpropionate induces cell damage to proximal tubular cells via the generation of a radical intermediate. Biochem Pharmacol 2012; 84:1207-14. [PMID: 22898098 DOI: 10.1016/j.bcp.2012.07.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 07/28/2012] [Accepted: 07/30/2012] [Indexed: 10/28/2022]
Abstract
3-Carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF), a furan fatty acid uremic toxin (UT) and a substrate for organic ion transporters, contributes to the accumulation of CMPF in renal tubular cells. Although oxidative stress induced by UTs has been proposed as a mechanism of its toxicity in chronic kidney disease, little information is available regarding the redox property of CMPF and its relation to renal cell damage. The findings herein show that CMPF enhances the production of reactive oxygen species (ROS) in HK-2 cells in the presence of angiotensin II (A-II), an inducer of O(2)(·-). When iron is also present, CMPF and A-II induce the Fenton reaction, resulting in a further increase in ROS production. Such CMPF-induced oxidative stress increases TGF-β1 secretion in HK-2 cells, and a positive correlation between CMPF-induced ROS production and the secretion of active TGF-β1 was observed. CMPF caused a reduction in cell viability which was negatively correlated with intracellular ROS production. These negative effects of CMPF in HK-2 cells were completely suppressed by probenecid, an inhibitor of organic anion transport. Interestingly, in vitro ROS assays indicate that CMPF directly interacts with superoxide anion radicals (O(2)(·-)) and peroxy radicals (LOO) to produce CMPF radicals. The subsequent interaction of CMPF radicals with dissolved oxygen leads to the overproduction of O(2)(·-). Based on these findings, we conclude that CMPF, which accumulates in the renal cells, appears to play a prominent role as a pro-oxidant which subsequently leads to renal cellular damage via the overproduction of O(2)(·-).
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Affiliation(s)
- Yohei Miyamoto
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1, Oe-honmachi, Kumamoto 862-0973, Japan
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45
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Sun CY, Hsu HH, Wu MS. p-Cresol sulfate and indoxyl sulfate induce similar cellular inflammatory gene expressions in cultured proximal renal tubular cells. Nephrol Dial Transplant 2012; 28:70-8. [PMID: 22610984 DOI: 10.1093/ndt/gfs133] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND p-Cresol sulfate (PCS) and indoxyl sulfate (IS) have important roles in the kidney injury. The aim of this study was to determine the inflammatory response to PCS and IS. METHODS Cultured mouse proximal renal tubular cells were treated with PCS or IS and analyzed by polymerase chain reaction array with an inflammation and immune panel. Gene annotation enrichment and functional annotation clustering were analyzed with the Database for Annotation, Visualization, and Integrated Discovery (DAVID). Functional networks of the target genes were analyzed with the algorithm GeneMANIA. RESULTS PCS and IS increased the expression of inflammation associated genes. Sixteen upregulated gene clusters of cells treated with PCS or IS were found. The major cytokines in the functional networks generated by PCS or IS treatment were Tgfb1, Fasl, Il6/15, Il15, Csf1/3 and Cxcl10. The major intracellular signal triggered by PCS or IS included Stats, Smads, Nfkb2, Ikbkb, Bcl2 and Bax. In both PCS- and IS-treated cells, Col4a5, Cxc10, Fasl, Stat1 and Ikbkb were the target genes in the predicted molecular functional networks connected to Tgfb1. CONCLUSIONS PCS and IS stimulate significant cellular inflammation. Similar immune and cellular inflammatory responses were induced by PCS or IS on cultured proximal renal tubular cells.
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Affiliation(s)
- Chiao-Yin Sun
- School of Medicine, Chang Gung University, Taoyuan, Taiwan
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46
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Chiang CK, Tanaka T, Nangaku M. Dysregulated oxygen metabolism of the kidney by uremic toxins: review. J Ren Nutr 2012; 22:77-80. [PMID: 22200419 DOI: 10.1053/j.jrn.2011.10.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 10/13/2011] [Indexed: 11/11/2022] Open
Abstract
Because kidneys consume a large amount of oxygen and are relatively inefficient in oxygen uptake, they are susceptible to hypoxia, especially in patients with advanced chronic kidney disease accompanied by loss of peritubular capillaries. Accumulating evidence suggests that chronic tubulointerstitial hypoxia acts as a final common pathway leading to end-stage renal disease. Some biologically active uremic retention molecules, considered as uremic toxins, accumulate as the renal function declines, and at this moment, more than 90 bioactive uremic toxins have been identified. Uremic toxins per se have been proven to accelerate the progression of renal failure. However, the causal relationship between uremic toxin and tubulointerstitial hypoxia remains unclear. Our studies provided direct evidence that uremic toxin dysregulates oxygen metabolism in the kidney. Indoxyl sulfate (IS), a representative protein-bound uremic toxin, increased oxygen consumption in proximal renal tubules, decreased renal oxygenation, and consequently aggravated hypoxia in the remnant rat kidneys. The increase in tubular oxygen consumption by IS was dependent on sodium-potassium adenosine triphosphatase and oxidative stress. Our work also indicated a possible connection between IS and the desensitization of the oxygen-sensing mechanism in erythropoietin-producing cells, which may partly explain inadequate erythropoietin production in hypoxic kidneys of end-stage renal disease patients. Studies of uremic toxins will open a new avenue in development of novel therapeutic approaches of kidney disease.
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Affiliation(s)
- Chih-Kang Chiang
- Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Bunkyo-ku, Tokyo, Japan
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47
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Lai EY, Luo Z, Onozato ML, Rudolph EH, Solis G, Jose PA, Wellstein A, Aslam S, Quinn MT, Griendling K, Le T, Li P, Palm F, Welch WJ, Wilcox CS. Effects of the antioxidant drug tempol on renal oxygenation in mice with reduced renal mass. Am J Physiol Renal Physiol 2012; 303:F64-74. [PMID: 22492941 DOI: 10.1152/ajprenal.00005.2012] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We tested the hypothesis that reactive oxygen species (ROS) contributed to renal hypoxia in C57BL/6 mice with ⅚ surgical reduction of renal mass (RRM). ROS can activate the mitochondrial uncoupling protein 2 (UCP-2) and increase O(2) usage. However, UCP-2 can be inactivated by glutathionylation. Mice were fed normal (NS)- or high-salt (HS) diets, and HS mice received the antioxidant drug tempol or vehicle for 3 mo. Since salt intake did not affect the tubular Na(+) transport per O(2) consumed (T(Na/)Q(O2)), further studies were confined to HS mice. RRM mice had increased excretion of 8-isoprostane F(2α) and H(2)O(2), renal expression of UCP-2 and renal O(2) extraction, and reduced T(Na/)Q(O2) (sham: 20 ± 2 vs. RRM: 10 ± 1 μmol/μmol; P < 0.05) and cortical Po(2) (sham: 43 ± 2, RRM: 29 ± 2 mmHg; P < 0.02). Tempol normalized all these parameters while further increasing compensatory renal growth and glomerular volume. RRM mice had preserved blood pressure, glomeruli, and patchy tubulointerstitial fibrosis. The patterns of protein expression in the renal cortex suggested that RRM kidneys had increased ROS from upregulated p22(phox), NOX-2, and -4 and that ROS-dependent increases in UCP-2 led to hypoxia that activated transforming growth factor-β whereas erythroid-related factor 2 (Nrf-2), glutathione peroxidase-1, and glutathione-S-transferase mu-1 were upregulated independently of ROS. We conclude that RRM activated distinct processes: a ROS-dependent activation of UCP-2 leading to inefficient renal O(2) usage and cortical hypoxia that was offset by Nrf-2-dependent glutathionylation. Thus hypoxia in RRM may be the outcome of NADPH oxidase-initiated ROS generation, leading to mitochondrial uncoupling counteracted by defense pathways coordinated by Nrf-2.
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Affiliation(s)
- En Yin Lai
- Division of Nephrology and Hypertension, Center for Hypertension, Kidney and Vascular Research, Georgetown University, Washington, DC, USA
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Kim SH, Yu MA, Ryu ES, Jang YH, Kang DH. Indoxyl sulfate-induced epithelial-to-mesenchymal transition and apoptosis of renal tubular cells as novel mechanisms of progression of renal disease. J Transl Med 2012; 92:488-98. [PMID: 22231736 DOI: 10.1038/labinvest.2011.194] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Indoxyl sulfate (IS), one of the uremic toxins, is regarded to have a substantial role in the progression of chronic kidney disease (CKD). Epithelial-to-mesenchymal transition (EMT) and apoptosis of renal tubular cells are known to be the critical mechanisms of the development and aggravation of CKD. We investigated the effect of IS on EMT and apoptosis in renal proximal tubular cells, NRK-52E cells. IS significantly inhibited cell proliferation and induced cell migration with a morphological transition from cuboidal epithelial cells to spindle-shaped scattered fibroblast-like cells. IS downregulated the expressions of zonula occluden-1 and E-cadherin, whereas upregulated α-SMA expression at 48 h, which was blocked by a pretreatment of the organic anion transporter, probenecid. IS also induced apoptosis of NRK cells from a concentration of 25 μg/ml with an activation of ERK1/2 and p38 MAP kinase (MAPK). Pretreatment of ERK1/2 or p38 MAPK inhibitors, PD98059 or SB203580, resulted in no significant effect on IS-induced EMT, whereas it ameliorated IS-induced apoptosis of NRK cells. These findings suggested phenotypic transition and apoptosis as potential mechanisms of IS-induced renal damage and the differential role of MAPK activation in IS-induced EMT and apoptosis of renal tubular cells.
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Affiliation(s)
- Su Hyun Kim
- Division of Nephrology, Department of Internal Medicine, Chung-Ang University, Seoul, Korea
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Sun CY, Chang SC, Wu MS. Uremic toxins induce kidney fibrosis by activating intrarenal renin-angiotensin-aldosterone system associated epithelial-to-mesenchymal transition. PLoS One 2012; 7:e34026. [PMID: 22479508 PMCID: PMC3316590 DOI: 10.1371/journal.pone.0034026] [Citation(s) in RCA: 178] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2011] [Accepted: 02/20/2012] [Indexed: 01/11/2023] Open
Abstract
Background Uremic toxins are considered to have a determinant pathological role in the progression of chronic kidney disease. The aim of this study was to define the putative pathological roles of the renal renin–angiotensin–aldosterone system (RAAS) and renal tubular epithelial-to-mesenchymal transition (EMT) in kidney fibrosis induced by (indoxyl sulfate) IS and (p-cresol sulfate) PCS. Methods Mouse proximal renal tubular cells (PKSV-PRs) treated with IS or PCS were used. Half-nephrectomized B-6 mice were treated with IS or PCS for 4 weeks. In the losartan treatment study, the study animal was administrated with IS+losartan or PCS+losartan for 4 weeks. Results IS and PCS significantly activated the intrarenal RAAS by increasing renin, angiotensinogen, and angiotensin 1 (AT1) receptor expression, and decreasing AT2 receptor expression in vitro and in vivo. IS and PCS significantly increased transforming growth factor-β1 (TGF-β1) expression and activated the TGF-β pathway by increasing Smad2/Smad2-P, Smad3/Smad3-P, and Smad4 expression. The expression of the EMT-associated transcription factor Snail was increased by IS and PCS treatment. IS and PCS induced the phenotype of EMT-like transition in renal tubules by increasing the expression of fibronectin and α-smooth muscle actin and decreasing the expression of E-cadherin. Losartan significantly attenuated the expression of TGF-β1 and Snail, and decreased kidney fibrosis induced by IS and PCS in vivo. Conclusion Activating the renal RAAS/TGF-β pathway has an important pathological role in chronic kidney injury caused by IS and PCS. IS and PCS may increase Snail expression and induce EMT-like transition.
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Affiliation(s)
- Chiao-Yin Sun
- School of Medicine, Chang Gung University, Taoyuan, Taiwan
- Division of Nephrology, Chang Gung Memorial Hospital, Keelung, Taiwan
| | - Shih-Chung Chang
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Mai-Szu Wu
- School of Medicine, Chang Gung University, Taoyuan, Taiwan
- Division of Nephrology, Chang Gung Memorial Hospital, Keelung, Taiwan
- * E-mail:
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50
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Suppression of Klotho expression by protein-bound uremic toxins is associated with increased DNA methyltransferase expression and DNA hypermethylation. Kidney Int 2012; 81:640-50. [PMID: 22237753 PMCID: PMC3306006 DOI: 10.1038/ki.2011.445] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The expression of the renoprotective antiaging gene Klotho is decreased in uremia. Recent studies suggest that Klotho may be a tumor suppressor, and its expression may be repressed by DNA hypermethylation in cancer cells. Here we investigated the effects and possible mechanisms by which Klotho expression is regulated during uremia in uninephrectomized B-6 mice given the uremic toxins indoxyl sulfate or p-cresyl sulfate. Cultured human renal tubular HK2 cells treated with these toxins were used as an in vitro model. Injections of indoxyl sulfate or p-cresyl sulfate increased their serum concentrations, kidney fibrosis, CpG hypermethylation of the Klotho gene, and decreased Klotho expression in renal tubules of these mice. The expression of DNA methyltransferases 1, 3a, and 3b isoforms in HK2 cells treated with indoxyl sulfate or p-cresyl sulfate was significantly increased. Specific inhibition of DNA methyltransferase isoform 1 by 5-aza-2′-deoxycytidine caused demethylation of the Klotho gene and increased Klotho expression in vitro. Thus, inhibition of Klotho gene expression by uremic toxins correlates with gene hypermethylation, suggesting that epigenetic modification of specific genes by uremic toxins may be an important pathological mechanism of disease.
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