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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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2
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Kishimoto S, Devasahayam N, Chandramouli GVR, Murugesan R, Otowa Y, Yamashita K, Yamamoto K, Brender JR, Krishna MC. Evaluation of a deuterated triarylmethyl spin probe for in vivo R 2 ∗-based EPR oximetric imaging with enhanced dynamic range. Magn Reson Med 2024; 91:413-423. [PMID: 37676121 PMCID: PMC10841161 DOI: 10.1002/mrm.29811] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/03/2023] [Accepted: 07/11/2023] [Indexed: 09/08/2023]
Abstract
PURPOSE In this study, we compared two triarylmethyl (TAM) spin probes, Ox071 and Ox063 for their efficacy in measuring tissue oxygen levels under hypoxic and normoxic conditions by R2 *-based EPR oximetry. METHODS The R2 * dependencies on the spin probe concentration and oxygen level were calibrated using deoxygenated 1, 2, 5, and 10 mM standard solutions and 2 mM solutions saturated at 0%, 2%, 5%, 10%, and 21% of oxygen. For the hypoxic model, in vivo imaging of a MIA PaCa-2 tumor implanted in the hind leg of a mouse was performed on successive days by R2 *-based EPR oximetry using either Ox071 or Ox063. For the normoxic model, renal imaging of healthy athymic mice was performed using both spin probes. The 3D images were reconstructed by single point imaging and multi-gradient technique was used to determine R2 * maps. RESULTS The signal intensities of Ox071 were approximately three times greater than that of Ox063 in the entire partial pressure of oxygen (pO2 ) range investigated. The histograms of the tumor pO2 images were skewed for both spin probes, and Ox071 showed more frequency counts at pO2 > 32 mm Hg. In the normoxic kidney model, there was a clear delineation between the high pO2 cortex and the low pO2 medulla regions. The histogram of high-resolution kidney oximetry image using Ox071 was nearly symmetrical and frequency counts were seen up to 55 mm Hg, which were missed in Ox063 imaging. CONCLUSION As an oximetric probe, Ox071 has clear advantages over Ox063 in terms of sensitivity and the pO2 dynamic range.
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Affiliation(s)
- Shun Kishimoto
- Radiation Biology Branch, Center for Cancer Research, NCI, Bethesda, Maryland, USA
- Urologic Oncology Branch, Center for Cancer Research, NCI, Bethesda, Maryland, USA
| | | | | | - Ramachandran Murugesan
- Karpaga Vinayaga Institute of Medical Sciences and Research Center, Chengalpattu, Tamil Nadu, India
| | - Yasunori Otowa
- Radiation Biology Branch, Center for Cancer Research, NCI, Bethesda, Maryland, USA
| | - Kota Yamashita
- Radiation Biology Branch, Center for Cancer Research, NCI, Bethesda, Maryland, USA
| | - Kazutoshi Yamamoto
- Radiation Biology Branch, Center for Cancer Research, NCI, Bethesda, Maryland, USA
| | - Jeffrey R Brender
- Radiation Biology Branch, Center for Cancer Research, NCI, Bethesda, Maryland, USA
| | - Murali C Krishna
- Radiation Biology Branch, Center for Cancer Research, NCI, Bethesda, Maryland, USA
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3
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Habas E, Al Adab A, Arryes M, Alfitori G, Farfar K, Habas AM, Akbar RA, Rayani A, Habas E, Elzouki A. Anemia and Hypoxia Impact on Chronic Kidney Disease Onset and Progression: Review and Updates. Cureus 2023; 15:e46737. [PMID: 38022248 PMCID: PMC10631488 DOI: 10.7759/cureus.46737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/09/2023] [Indexed: 12/01/2023] Open
Abstract
Chronic kidney disease (CKD) is caused by hypoxia in the renal tissue, leading to inflammation and increased migration of pathogenic cells. Studies showed that leukocytes directly sense hypoxia and respond by initiating gene transcription, encoding the 2-integrin adhesion molecules. Moreover, other mechanisms participate in hypoxia, including anemia. CKD-associated anemia is common, which induces and worsens hypoxia, contributing to CKD progression. Anemia correction can slow CKD progression, but it should be cautiously approached. In this comprehensive review, the underlying pathophysiology mechanisms and the impact of renal tissue hypoxia and anemia in CKD onset and progression will be reviewed and discussed in detail. Searching for the latest updates in PubMed Central, Medline, PubMed database, Google Scholar, and Google search engines were conducted for original studies, including cross-sectional studies, cohort studies, clinical trials, and review articles using different keywords, phrases, and texts such as "CKD progression, anemia in CKD, CKD, anemia effect on CKD progression, anemia effect on CKD progression, and hypoxia and CKD progression". Kidney tissue hypoxia and anemia have an impact on CKD onset and progression. Hypoxia causes nephron cell death, enhancing fibrosis by increasing interstitium protein deposition, inflammatory cell activation, and apoptosis. Severe anemia correction improves life quality and may delay CKD progression. Detection and avoidance of the risk factors of hypoxia prevent recurrent acute kidney injury (AKI) and reduce the CKD rate. A better understanding of kidney hypoxia would prevent AKI and CKD and lead to new therapeutic strategies.
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Affiliation(s)
| | - Aisha Al Adab
- Internal Medicine, Hamad General Hospital, Doha, QAT
| | - Mehdi Arryes
- Internal Medicine, Hamad General Hospital, Doha, QAT
| | | | | | - Ala M Habas
- Internal Medicine, Tripoli University, Tripoli, LBY
| | - Raza A Akbar
- Internal Medicine, Hamad General Hospital, Doha, QAT
| | - Amnna Rayani
- Hemat-oncology Department, Pediatric Tripoli Hospital, Tripoli University, Tripoli, LBY
| | - Eshrak Habas
- Internal Medicine, Tripoli University, Tripoli, LBY
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4
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Osawa EA, Cutuli SL, Yanase F, Iguchi N, Bitker L, Maciel AT, Lankadeva YR, May CN, Evans RG, Eastwood GM, Bellomo R. Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements. Intensive Care Med Exp 2022; 10:52. [PMID: 36504004 PMCID: PMC9742069 DOI: 10.1186/s40635-022-00479-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 11/15/2022] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Continuous measurement of urinary PO2 (PuO2) is being applied to indirectly monitor renal medullary PO2. However, when applied to critically ill patients with shock, its measurement may be affected by changes in FiO2 and PaO2 and potential associated O2 diffusion between urine and ureteric or bladder tissue. We aimed to investigate PuO2 measurements in septic shock patients with a fiberoptic luminescence optode inserted into the urinary catheter lumen in relation to episodes of FiO2 change. We also evaluated medullary and urinary oxygen tension values in Merino ewes at two different FiO2 levels. RESULTS In 10 human patients, there were 32 FiO2 decreases and 31 increases in FiO2. Median pre-decrease FiO2 was 0.36 [0.30, 0.39] and median post-decrease FiO2 was 0.30 [0.23, 0.30], p = 0.006. PaO2 levels decreased from 83 mmHg [77, 94] to 72 [62, 80] mmHg, p = 0.009. However, PuO2 was 23.2 mmHg [20.5, 29.0] before and 24.2 mmHg [20.6, 26.3] after the intervention (p = 0.56). The median pre-increase FiO2 was 0.30 [0.21, 0.30] and median post-increase FiO2 was 0.35 [0.30, 0.40], p = 0.008. PaO2 levels increased from 64 mmHg [58, 72 mmHg] to 71 mmHg [70, 100], p = 0.04. However, PuO2 was 25.0 mmHg [IQR: 20.7, 26.8] before and 24.3 mmHg [IQR: 20.7, 26.3] after the intervention (p = 0.65). A mixed linear regression model showed a weak correlation between the variation in PaO2 and the variation in PuO2 values. In 9 Merino ewes, when comparing oxygen tension levels between FiO2 of 0.21 and 0.40, medullary values did not differ (25.1 ± 13.4 mmHg vs. 27.9 ± 15.4 mmHg, respectively, p = 0.6766) and this was similar to urinary oxygen values (27.1 ± 6.17 mmHg vs. 29.7 ± 4.41 mmHg, respectively, p = 0.3192). CONCLUSIONS Changes in FiO2 and PaO2 within the context of usual care did not affect PuO2. Our findings were supported by experimental data and suggest that PuO2 can be used as biomarker of medullary oxygenation irrespective of FiO2.
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Affiliation(s)
- Eduardo A. Osawa
- Imed Group Research Department, Sao Paulo, Brazil ,grid.477346.5Intensive Care Unit, Hospital Sao Camilo, Unidade Pompeia, Sao Paulo, Brazil ,grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia
| | - Salvatore L. Cutuli
- grid.414603.4Dipartimento di Scienze dell’Emergenza, Anestesiologiche e della Rianimazione, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy ,grid.8142.f0000 0001 0941 3192Università Cattolica del Sacro Cuore, Rome, Italy
| | - Fumitaka Yanase
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.1002.30000 0004 1936 7857Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia
| | - Naoya Iguchi
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.136593.b0000 0004 0373 3971Department of Anaesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka University, Suita, Japan ,grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia
| | - Laurent Bitker
- grid.413306.30000 0004 4685 6736Service de Médecine Intensive – Réanimation, Hôpital de La Croix Rousse, Hospices Civils de Lyon, Lyon, France
| | - Alexandre T. Maciel
- Imed Group Research Department, Sao Paulo, Brazil ,grid.477346.5Intensive Care Unit, Hospital Sao Camilo, Unidade Pompeia, Sao Paulo, Brazil
| | - Yugeesh R. Lankadeva
- grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia ,grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC Australia
| | - Clive N. May
- grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia ,grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC Australia
| | - Roger G. Evans
- grid.418025.a0000 0004 0606 5526Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC Australia ,grid.1002.30000 0004 1936 7857Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Australia
| | - Glenn M. Eastwood
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.1002.30000 0004 1936 7857Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia
| | - Rinaldo Bellomo
- grid.414094.c0000 0001 0162 7225Department of Intensive Care, Austin Hospital, Melbourne, VIC 3084 Australia ,grid.1002.30000 0004 1936 7857Australian and New Zealand Intensive Care Research Centre, Monash University, Melbourne, Australia ,grid.1008.90000 0001 2179 088XDepartment of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, VIC Australia
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Della Rocca Y, Fonticoli L, Rajan TS, Trubiani O, Caputi S, Diomede F, Pizzicannella J, Marconi GD. Hypoxia: molecular pathophysiological mechanisms in human diseases. J Physiol Biochem 2022; 78:739-752. [PMID: 35870078 PMCID: PMC9684243 DOI: 10.1007/s13105-022-00912-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 07/14/2022] [Indexed: 12/01/2022]
Abstract
Abstract
Hypoxia, a low O2 tension, is a fundamental feature that occurs in physiological events as well as pathophysiological conditions, especially mentioned for its role in the mechanism of angiogenesis, glucose metabolism, and cell proliferation/survival. The hypoxic state through the activation of specific mechanisms is an aggravating circumstance commonly noticed in multiple sclerosis, cancer, heart disease, kidney disease, liver disease, lung disease, and in inflammatory bowel disease. On the other hand, hypoxia could play a key role in tissue regeneration and repair of damaged tissues, especially by acting on specific tissue stem cells, but their features may result as a disadvantage when it is concerned for neoplastic stem cells. Furthermore, hypoxia could also have a potential role in tissue engineering and regenerative medicine due to its capacity to improve the performance of biomaterials. The current review aims to highlight the hypoxic molecular mechanisms reported in different pathological conditions to provide an overview of hypoxia as a therapeutic agent in regenerative and molecular therapy.
Graphical abstract
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Affiliation(s)
- Ylenia Della Rocca
- Department of Innovative Technologies in Medicine & Dentistry, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy
| | - Luigia Fonticoli
- Department of Innovative Technologies in Medicine & Dentistry, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy
| | | | - Oriana Trubiani
- Department of Innovative Technologies in Medicine & Dentistry, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy
| | - Sergio Caputi
- Department of Innovative Technologies in Medicine & Dentistry, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy
| | - Francesca Diomede
- Department of Innovative Technologies in Medicine & Dentistry, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy.
| | - Jacopo Pizzicannella
- Cardiology Intensive Care Unit, "Ss. Annunziata" Hospital, ASL02 Lanciano-Vasto-Chieti, Chieti, Italy
| | - Guya Diletta Marconi
- Department of Medical, Oral and Biotechnological Sciences, University "G. d'Annunzio" Chieti-Pescara, Chieti, Italy
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6
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Edwards A, Kurtcuoglu V. Renal blood flow and oxygenation. Pflugers Arch 2022; 474:759-770. [PMID: 35438336 PMCID: PMC9338895 DOI: 10.1007/s00424-022-02690-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/19/2022] [Accepted: 03/21/2022] [Indexed: 02/07/2023]
Abstract
Our kidneys receive about one-fifth of the cardiac output at rest and have a low oxygen extraction ratio, but may sustain, under some conditions, hypoxic injuries that might lead to chronic kidney disease. This is due to large regional variations in renal blood flow and oxygenation, which are the prerequisite for some and the consequence of other kidney functions. The concurrent operation of these functions is reliant on a multitude of neuro-hormonal signaling cascades and feedback loops that also include the regulation of renal blood flow and tissue oxygenation. Starting with open questions on regulatory processes and disease mechanisms, we review herein the literature on renal blood flow and oxygenation. We assess the current understanding of renal blood flow regulation, reasons for disparities in oxygen delivery and consumption, and the consequences of disbalance between O2 delivery, consumption, and removal. We further consider methods for measuring and computing blood velocity, flow rate, oxygen partial pressure, and related parameters and point out how limitations of these methods constitute important hurdles in this area of research. We conclude that to obtain an integrated understanding of the relation between renal function and renal blood flow and oxygenation, combined experimental and computational modeling studies will be needed.
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Affiliation(s)
- Aurelie Edwards
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA, 02215, USA
| | - Vartan Kurtcuoglu
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. .,National Center of Competence in Research, Kidney.CH, University of Zurich, Zurich, Switzerland. .,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
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7
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Wang B, Li ZL, Zhang YL, Wen Y, Gao YM, Liu BC. Hypoxia and chronic kidney disease. EBioMedicine 2022; 77:103942. [PMID: 35290825 PMCID: PMC8921539 DOI: 10.1016/j.ebiom.2022.103942] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 02/22/2022] [Accepted: 03/01/2022] [Indexed: 12/12/2022] Open
Abstract
Hypoxia is an inherent pathophysiological characteristic of chronic kidney disease (CKD), which is closely associated with the development of renal inflammation and fibrosis, as well as CKD-related complications such as anaemia, cardiovascular events, and sarcopenia. This review outlined the characteristics of oxygen supply in the kidney, changes in oxygen metabolism and factors leading to hypoxia in CKD. Mechanistically, we discussed how hypoxia contributes to renal injury as well as complications associated with CKD. Furthermore, we also discussed the potential therapeutic approaches that target chronic hypoxia, as well as the challenges in the study of oxygen homeostasis imbalance in CKD.
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Affiliation(s)
- Bin Wang
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, Jiangsu, China
| | - Zuo-Lin Li
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, Jiangsu, China
| | - Yi-Lin Zhang
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, Jiangsu, China
| | - Yi Wen
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, Jiangsu, China
| | - Yue-Ming Gao
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, Jiangsu, China
| | - Bi-Cheng Liu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, Jiangsu, China.
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8
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Weng X, Li J, Guan Q, Zhao H, Wang Z, Gleave ME, Nguan CY, Du C. The functions of clusterin in renal mesenchymal stromal cells: Promotion of cell growth and regulation of macrophage activation. Exp Cell Res 2022; 413:113081. [PMID: 35218723 DOI: 10.1016/j.yexcr.2022.113081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 01/31/2022] [Accepted: 02/15/2022] [Indexed: 12/24/2022]
Abstract
Clusterin (CLU) increases resistance to renal ischemia-reperfusion injury and promotes renal tissue repair. However, the mechanisms underlying of the renal protection of CLU remain unknown. Mesenchymal stromal cells (MSCs) may contribute to kidney cell turnover and injury repair. This study investigated the in vitro functions of CLU in kidney mesenchymal stromal cells (KMSCs). KMSCs were grown in plastic culture plates. Cell surface markers, apoptosis and phagocytosis were determined by flow cytometry, and CLU protein by Western blot. There were no differences in the expression of MSC markers (positive: CD133, Sca-1, CD44, CD117 and NG2, and negative: CD34, CD45, CD163, CD41, CD276, CD138, CD79a, CD146 and CD140b) and in the trilineage differentiation to chondrocytes, adipocytes and osteocytes between wild type (WT) and CLU knockout (KO) KMSCs. CLU was expressed intracellularly and secreted by WT KMSCs, and it was up-regulated by hypoxia. CLU did not prevent hypoxia-induced cell apoptosis but promoted cell growth in KMSC cultures. Furthermore, incubation with CLU-containing culture medium from WT KMSCs increased CD206 expression and phagocytic capacity of macrophages. In conclusion, our data for the first time demonstrate the function of CLU in the promotion of KMSCs proliferation, and it may be required for KMSCs-regulated macrophage M2 polarization and phagocytic activity.
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Affiliation(s)
- Xiaodong Weng
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, 430060, Hubei, China; Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jing Li
- Department of Ophthamology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430060, China
| | - Qiunong Guan
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Haimei Zhao
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada; College of Traditional Chinese Medicine, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004, Jiangxi Province, China
| | - Zihuan Wang
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada; First Clinical Medical School, Southern Medical University, Guangzhou, 510000, China
| | - Martin E Gleave
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Christopher Yc Nguan
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Caigan Du
- Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada.
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9
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Kidney Microcirculation as a Target for Innovative Therapies in AKI. J Clin Med 2021; 10:jcm10184041. [PMID: 34575154 PMCID: PMC8471583 DOI: 10.3390/jcm10184041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/29/2021] [Accepted: 09/02/2021] [Indexed: 12/19/2022] Open
Abstract
Acute kidney injury (AKI) is a serious multifactorial conditions accompanied by the loss of function and damage. The renal microcirculation plays a crucial role in maintaining the kidney’s functional and structural integrity for oxygen and nutrient supply and waste product removal. However, alterations in microcirculation and oxygenation due to renal perfusion defects, hypoxia, renal tubular, and endothelial damage can result in AKI and the loss of renal function regardless of systemic hemodynamic changes. The unique structural organization of the renal microvasculature and the presence of autoregulation make it difficult to understand the mechanisms and the occurrence of AKI following disorders such as septic, hemorrhagic, or cardiogenic shock; ischemia/reperfusion; chronic heart failure; cardiorenal syndrome; and hemodilution. In this review, we describe the organization of microcirculation, autoregulation, and pathophysiological alterations leading to AKI. We then suggest innovative therapies focused on the protection of the renal microcirculation and oxygenation to prevent AKI.
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10
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Franzén S, Näslund E, Wang H, Frithiof R. Prevention of hemorrhage-induced renal vasoconstriction and hypoxia by angiotensin II type 1 receptor antagonism in pigs. Am J Physiol Regul Integr Comp Physiol 2021; 321:R12-R20. [PMID: 34009032 DOI: 10.1152/ajpregu.00073.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Angiotensin II (ANG II) is a potent vasoconstrictor and may reduce renal blood flow (RBF), causing renal hypoxia. Hypotensive hemorrhage elevates plasma ANG II levels and is associated with increased risk of acute kidney injury. We hypothesized that ANG II antagonism prevents renal vasoconstriction and hypoxia caused by hemorrhage. Pigs were anaesthetized, surgically prepared, and randomized to intravenous losartan (1.5 mg·kg-1·h-1, n = 8) or an equal volume of intravenous Ringer acetate (vehicle-treated, n = 8). Hemorrhage was induced by continuous aspiration of blood to reach and sustain mean arterial pressure of <50 mmHg for 30 min. Plasma ANG II levels, hemodynamics and oxygenation were assessed 60 min prehemorrhage, 30-min after the start of hemorrhage, and 60 min posthemorrhage. Erythropoietin mRNA was analyzed in cortical and medullary tissue sampled at the end of the experiment. Hypotensive hemorrhage increased plasma ANG II levels and decreased RBF and oxygen delivery in both groups. Losartan-treated animals recovered in RBF and oxygen delivery, whereas vehicle-treated animals had persistently reduced RBF and oxygen delivery. In accordance, renal vascular resistance increased over time post hemorrhage in vehicle-treated animals but was unchanged in losartan-treated animals. Renal oxygen extraction rate and cortical erythropoietin mRNA levels increased in the vehicle group but not in the losartan group. In conclusion, ANG II antagonism alleviates prolonged renal vasoconstriction and renal hypoxia in a large animal model of hypotensive hemorrhage.
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Affiliation(s)
- Stephanie Franzén
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden
| | - Erik Näslund
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden.,Centre for Research and Development, Uppsala University/Region Gävleborg, Gavle, Sweden
| | - Helen Wang
- Department of Medical Biochemistry and Microbiology, Infections and Defenses, Uppsala University, Uppsala, Sweden
| | - Robert Frithiof
- Department of Surgical Sciences, Anesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden
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11
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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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12
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Gardiner BS, Smith DW, Lee C, Ngo JP, Evans RG. Renal oxygenation: From data to insight. Acta Physiol (Oxf) 2020; 228:e13450. [PMID: 32012449 DOI: 10.1111/apha.13450] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 01/14/2020] [Accepted: 01/30/2020] [Indexed: 12/14/2022]
Abstract
Computational models have made a major contribution to the field of physiology. As the complexity of our understanding of biological systems expands, the need for computational methods only increases. But collaboration between experimental physiologists and computational modellers (ie theoretical physiologists) is not easy. One of the major challenges is to break down the barriers created by differences in vocabulary and approach between the two disciplines. In this review, we have two major aims. Firstly, we wish to contribute to the effort to break down these barriers and so encourage more interdisciplinary collaboration. So, we begin with a "primer" on the ways in which computational models can help us understand physiology and pathophysiology. Second, we aim to provide an update of recent efforts in one specific area of physiology, renal oxygenation. This work is shedding new light on the causes and consequences of renal hypoxia. But as importantly, computational modelling is providing direction for experimental physiologists working in the field of renal oxygenation by: (a) generating new hypotheses that can be tested in experimental studies, (b) allowing experiments that are technically unfeasible to be simulated in silico, or variables that cannot be measured experimentally to be estimated, and (c) providing a means by which the quality of experimental data can be assessed. Critically, based on our experience, we strongly believe that experimental and theoretical physiology should not be seen as separate exercises. Rather, they should be integrated to permit an iterative process between modelling and experimentation.
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Affiliation(s)
- Bruce S. Gardiner
- College of Science Health, Engineering and Education Murdoch University Perth Australia
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - David W. Smith
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - Chang‐Joon Lee
- College of Science Health, Engineering and Education Murdoch University Perth Australia
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Australia
| | - Jennifer P. Ngo
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Australia
- Department of Cardiac Physiology National Cerebral and Cardiovascular Research Center Osaka Japan
| | - Roger G. Evans
- Cardiovascular Disease Program Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Australia
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13
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Cardiogenic Shock: Reflections at the Crossroad Between Perfusion, Tissue Hypoxia, and Mitochondrial Function. Can J Cardiol 2020; 36:184-196. [PMID: 32036863 DOI: 10.1016/j.cjca.2019.11.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 11/19/2019] [Accepted: 11/19/2019] [Indexed: 02/06/2023] Open
Abstract
Cardiogenic shock is classically defined by systemic hypotension with evidence of hypoperfusion and end organ dysfunction. In modern practice, however, these metrics often incompletely describe cardiogenic shock because patients present with more advanced cardiovascular disease and greater degrees of multiorgan dysfunction. Understanding how perfusion, congestion, and end organ dysfunction contribute to hypoxia at the cellular level are central to the diagnosis and management of cardiogenic shock. Although, in clinical practice, increased lactate level is often equated with hypoxia, several other factors might contribute to an elevated lactate level including mitochondrial dysfunction, impaired hepatic and renal clearance, as well as epinephrine use. To this end, we present the evidence underlying the value of lactate to pyruvate ratio as a potential discriminator of cellular hypoxia. We will then discuss the physiological implications of hypoxia and congestion on hepatic, intestinal, and renal physiology. Organ-specific susceptibility to hypoxia is presented in the context of their functional architecture. We discuss how the concepts of contractile reserve, fluid responsiveness, tissue oxygenation, and cardiopulmonary interactions can help personalize the management of cardiogenic shock. Finally, we highlight the limitations of using lactate for tailoring therapy in cardiogenic shock.
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14
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Aubert V, Kaminski J, Guillaud F, Hauet T, Hannaert P. A Computer Model of Oxygen Dynamics in the Cortex of the Rat Kidney at the Cell-Tissue Level. Int J Mol Sci 2019; 20:E6246. [PMID: 31835730 PMCID: PMC6941061 DOI: 10.3390/ijms20246246] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 12/02/2019] [Accepted: 12/05/2019] [Indexed: 02/06/2023] Open
Abstract
The renal cortex drives renal function. Hypoxia/reoxygenation are primary factors in ischemia-reperfusion (IR) injuries, but renal oxygenation per se is complex and awaits full elucidation. Few mathematical models address this issue: none captures cortical tissue heterogeneity. Using agent-based modeling, we develop the first model of cortical oxygenation at the cell-tissue level (RCM), based on first principles and careful bibliographical analysis. Entirely parameterized with Rat data, RCM is a morphometrically equivalent 2D-slice of cortical tissue, featuring peritubular capillaries (PTC), tubules and interstitium. It implements hemoglobin/O2 binding-release, oxygen diffusion, and consumption, as well as capillary and tubular flows. Inputs are renal blood flow RBF and PO2 feeds; output is average tissue PO2 (tPO2). After verification and sensitivity analysis, RCM was validated at steady-state (tPO2 37.7 ± 2.2 vs. 36.9 ± 6 mmHg) and under transients (ischemic oxygen half-time: 4.5 ± 2.5 vs. 2.3 ± 0.5 s in situ). Simulations confirm that PO2 is largely independent of RBF, except at low values. They suggest that, at least in the proximal tubule, the luminal flow dominantly contributes to oxygen delivery, while the contribution of capillaries increases under partial ischemia. Before addressing IR-induced injuries, upcoming developments include ATP production, adaptation to minutes-hours scale, and segmental and regional specification.
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Affiliation(s)
| | | | | | | | - Patrick Hannaert
- INSERM U1082-IRTOMIT, 86000 Poitiers, France; (V.A.); (J.K.); (F.G.); (T.H.)
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15
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Ogbadu J, Singh G, Aggarwal D. Factors affecting the transition of acute kidney injury to chronic kidney disease: Potential mechanisms and future perspectives. Eur J Pharmacol 2019; 865:172711. [DOI: 10.1016/j.ejphar.2019.172711] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 09/22/2019] [Accepted: 09/30/2019] [Indexed: 12/12/2022]
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16
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Thomas SR. Mathematical models for kidney function focusing on clinical interest. Morphologie 2019; 103:161-168. [PMID: 31722814 DOI: 10.1016/j.morpho.2019.10.043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 10/11/2019] [Indexed: 01/22/2023]
Abstract
We give an overview of mathematical models of renal physiology and anatomy with the clinician in mind. Beyond the past focus on issues of local transport mechanisms along the nephron and the urine concentrating mechanism, recent models have brought insight into difficult problems such as renal ischemia (oxygen and CO2 diffusion in the medulla) or calcium and potassium homeostasis. They have also provided revealing 3D reconstructions of the full trajectories of families of nephrons and collecting ducts through cortex and medulla. The recent appearance of sophisticated whole-kidney models representing nephrons and their associated renal vasculature promises more realistic simulation of renal pathologies and pharmacological treatments in the foreseeable future.
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Affiliation(s)
- S Randall Thomas
- Inserm, LTSI - UMR 1099, Université Rennes, 35000 Rennes, France.
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17
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Evans RG, Smith DW, Lee C, Ngo JP, Gardiner BS. What Makes the Kidney Susceptible to Hypoxia? Anat Rec (Hoboken) 2019; 303:2544-2552. [DOI: 10.1002/ar.24260] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 04/24/2019] [Accepted: 05/13/2019] [Indexed: 12/19/2022]
Affiliation(s)
- Roger G. Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Victoria Australia
| | - David W. Smith
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Western Australia Australia
| | - Chang‐Joon Lee
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Western Australia Australia
- College of Science, Health, Engineering and Education Murdoch University Perth Western Australia Australia
| | - Jennifer P. Ngo
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology Monash University Melbourne Victoria Australia
| | - Bruce S. Gardiner
- Faculty of Engineering and Mathematical Sciences The University of Western Australia Perth Western Australia Australia
- College of Science, Health, Engineering and Education Murdoch University Perth Western Australia Australia
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18
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Sun J, Yu S, Chen J, Xing Z, Zha T, Fan M, Zeng D, Xing W. Assessment of delayed graft function using susceptibility-weighted imaging in the early period after kidney transplantation: a feasibility study. Abdom Radiol (NY) 2019; 44:218-226. [PMID: 30054685 DOI: 10.1007/s00261-018-1709-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
PURPOSE This study aimed to explore the feasibility of susceptibility-weighted imaging (SWI) for evaluating delayed graft function (DGF) during the early posttransplantation period. METHODS Sixty-nine recipients who accepted allograft renal transplantation underwent SWI during the second posttransplantation week. Renal allograft function was estimated via the glomerular filtration rate. Recipients with and without DGF were identified. For each transplanted kidney, the presence of abnormal signal intensity lesions (ASILs), excluding benign lesions, on SWI was assessed. Renal allograft function was compared between the recipients with and without ASILs. The correlation between ASILs and renal allograft function was tested by Spearman's rank correlation analysis. RESULTS Thirty-four recipients were diagnosed with DGF, while 35 recipients showed no DGF. In the DGF group, 16 recipients had low-intensity ASILs, primarily at the corticomedullary junction of transplanted kidneys on SWI, and no ASILs were found in 18 recipients. In the non-DGF group, none of the recipients showed ASILs on SWI. In the DGF group, the renal allograft function among the 16 recipients with low-intensity ASILs was significantly lower than that among the other 18 recipients (8.5 ± 4.2 vs. 19.7 ± 9.7 mL/min, P < 0.001). The presence of low-intensity ASILs on SWI showed a moderate negative correlation with renal allograft function in recipients with DGF (r = - 0.553, P = 0.001). CONCLUSION SWI can be used to evaluate DGF in the early post-kidney transplantation period.
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19
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Commereuc M, Schortgen F. Néphrotoxicité des produits de remplissage. Nephrol Ther 2018; 14:555-563. [DOI: 10.1016/j.nephro.2018.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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20
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Lee CJ, Gardiner BS, Evans RG, Smith DW. A model of oxygen transport in the rat renal medulla. Am J Physiol Renal Physiol 2018; 315:F1787-F1811. [DOI: 10.1152/ajprenal.00363.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The renal medulla is prone to hypoxia. Medullary hypoxia is postulated to be a leading cause of acute kidney injury, so there is considerable interest in predicting the oxygen tension in the medulla. Therefore we have developed a computational model for blood and oxygen transport within a physiologically normal rat renal medulla, using a multilevel modeling approach. For the top-level model we use the theory of porous media and advection-dispersion transport through a realistic three-dimensional representation of the medulla’s gross anatomy to describe blood flow and oxygen transport throughout the renal medulla. For the lower-level models, we employ two-dimensional reaction-diffusion models describing the distribution of oxygen through tissue surrounding the vasculature. Steady-state model predictions at the two levels are satisfied simultaneously, through iteration between the levels. The computational model was validated by simulating eight sets of experimental data regarding renal oxygenation in rats (using 4 sets of control groups and 4 sets of treatment groups, described in 4 independent publications). Predicted medullary tissue oxygen tension or microvascular oxygen tension for control groups and for treatment groups that underwent moderate perturbation in hemodynamic and renal functions is within ±2 SE values observed experimentally. Diffusive shunting between descending and ascending vasa recta is predicted to be only 3% of the oxygen delivered. The validation tests confirm that the computational model is robust and capable of capturing the behavior of renal medullary oxygenation in both normal and early-stage pathological states in the rat.
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Affiliation(s)
- Chang-Joon Lee
- School of Engineering and Information Technology, Murdoch University, Perth, Western Australia, Australia
- Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Bruce S. Gardiner
- School of Engineering and Information Technology, Murdoch University, Perth, Western Australia, Australia
- Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Roger G. Evans
- Cardiovascular Disease Program, Biomedicine Discovery Institute, and Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - David W. Smith
- Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Perth, Western Australia, Australia
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21
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Güven Bağla A, Içkin Gülen M, Ercan F, Aşgün F, Ercan E, Bakar C. Changes in kidney tissue and effects of erythropoietin after acute heart failure. Biotech Histochem 2018; 93:340-353. [PMID: 29671622 DOI: 10.1080/10520295.2018.1443347] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
Abstract
Impairment of cardiac function causes renal damage. Renal failure after heart failure is attributed to hemodynamic derangement including reduced renal perfusion and increased venous pressure. One mechanism involves apoptosis and is defined as cardiorenal syndrome type 1. Erythropoietin (EPO) is a cytokine that induces erythropoiesis under hypoxic conditions. Hypoxia inducible factor 1 alpha (HIF-1α) plays a regulatory role in cellular response to hypoxia. Protective effects of EPO on heart, kidney and nervous system are unrelated to red blood cell production. We investigated early changes in and effects of EPO on renal tissues of rats with myocardial infarction by morphology and immunohistochemistry. Coronary artery ligation was used to induce myocardial infarction in Wistar rats. Group 1 comprised sham operated rats; groups 2, 3 and 4 included rats after coronary artery ligation that were sacrificed 6 h after ligation and that were treated with saline, 5,000 U/kg EPO or 10,000 U/kg EPO, respectively; group 5 included rats sacrificed 1 h after ligation. Group 2 showed increased renal tubule damage. Significantly less tubule damage was observed in EPO treated groups. EPO and EPO receptor (EPO-R) immunostaining intensities increased slightly for group 5 and became more intense for group 2. EPO and EPO-R immunostaining was observed in the interstitial area, glomerular cells and tubule epithelial cells of EPO treated groups. HIF-1α immunostaining was observed in collecting tubules in the medulla only in group 2. Caspase-3 immunostaining is an indicator of apoptosis. Caspase-3 staining intensity decreased in renal medulla of EPO treated groups. EPO treatment may exert a protective effect on the renal tissues of patients with cardiorenal syndrome.
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Affiliation(s)
- A Güven Bağla
- a Çanakkale Onsekiz Mart University , School of Medicine, Department of Histology and Embryology , Çanakkale
| | - M Içkin Gülen
- a Çanakkale Onsekiz Mart University , School of Medicine, Department of Histology and Embryology , Çanakkale
| | - F Ercan
- b Marmara University , School of Medicine, Department of Histology and Embryology , Istanbul
| | - F Aşgün
- c Çanakkale Onsekiz Mart University , School of Medicine, Department of Cardiovascular Surgery , Çanakkale
| | - E Ercan
- d Department of Cardiology , Medical Park Hospital , Izmir
| | - C Bakar
- e Çanakkale Onsekiz Mart University , School of Medicine, Department of Public Health , Çanakkale , Turkey
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22
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Guerci P, Ergin B, Ince C. The macro- and microcirculation of the kidney. Best Pract Res Clin Anaesthesiol 2017; 31:315-329. [PMID: 29248139 DOI: 10.1016/j.bpa.2017.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 10/25/2017] [Indexed: 01/22/2023]
Abstract
Acute kidney injury (AKI) remains one of the main causes of morbidity and mortality in the intensive care medicine today. Its pathophysiology and progress to chronic kidney disease is still under investigation. In addition, the lack of techniques to adequately monitor renal function and microcirculation at the bedside makes its therapeutic resolution challenging. In this article, we review current concepts related to renal hemodynamics compromise as being the event underlying AKI. In doing so, we discuss the physiology of the renal circulation and the effects of alterations in systemic hemodynamics that lead to renal injury specifically in the context of reperfusion injury and sepsis. The ultimate key culprit of AKI leading to failure is the dysfunction of the renal microcirculation. The cellular and subcellular components of the renal microcirculation are discussed and how their injury contributes to AKI is described.
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Affiliation(s)
- Philippe Guerci
- Department of Anesthesiology and Critical Care Medicine, University Hospital of Nancy, France; INSERM U1116, University of Lorraine, Vandoeuvre-Les-Nancy, France; Department of Translational Physiology, Academic Medical Centre, Amsterdam, The Netherlands
| | - Bulent Ergin
- Department of Translational Physiology, Academic Medical Centre, Amsterdam, The Netherlands; Department of Intensive Care Medicine, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands
| | - Can Ince
- Department of Translational Physiology, Academic Medical Centre, Amsterdam, The Netherlands; Department of Intensive Care Medicine, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands.
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23
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Patinha D, Pijacka W, Paton JFR, Koeners MP. Cooperative Oxygen Sensing by the Kidney and Carotid Body in Blood Pressure Control. Front Physiol 2017; 8:752. [PMID: 29046642 PMCID: PMC5632678 DOI: 10.3389/fphys.2017.00752] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 09/15/2017] [Indexed: 12/13/2022] Open
Abstract
Oxygen sensing mechanisms are vital for homeostasis and survival. When oxygen levels are too low (hypoxia), blood flow has to be increased, metabolism reduced, or a combination of both, to counteract tissue damage. These adjustments are regulated by local, humoral, or neural reflex mechanisms. The kidney and the carotid body are both directly sensitive to falls in the partial pressure of oxygen and trigger reflex adjustments and thus act as oxygen sensors. We hypothesize a cooperative oxygen sensing function by both the kidney and carotid body to ensure maintenance of whole body blood flow and tissue oxygen homeostasis. Under pathological conditions of severe or prolonged tissue hypoxia, these sensors may become continuously excessively activated and increase perfusion pressure chronically. Consequently, persistence of their activity could become a driver for the development of hypertension and cardiovascular disease. Hypoxia-mediated renal and carotid body afferent signaling triggers unrestrained activation of the renin angiotensin-aldosterone system (RAAS). Renal and carotid body mediated responses in arterial pressure appear to be synergistic as interruption of either afferent source has a summative effect of reducing blood pressure in renovascular hypertension. We discuss that this cooperative oxygen sensing system can activate/sensitize their own afferent transduction mechanisms via interactions between the RAAS, hypoxia inducible factor and erythropoiesis pathways. This joint mechanism supports our view point that the development of cardiovascular disease involves afferent nerve activation.
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Affiliation(s)
- Daniela Patinha
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University of Bristol, Bristol, United Kingdom.,Institute of Biomedical and Clinical Science, University of Exeter Medical School, University of Exeter, Exeter, United Kingdom
| | - Wioletta Pijacka
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University of Bristol, Bristol, United Kingdom
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University of Bristol, Bristol, United Kingdom
| | - Maarten P Koeners
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University of Bristol, Bristol, United Kingdom.,Institute of Biomedical and Clinical Science, University of Exeter Medical School, University of Exeter, Exeter, United Kingdom
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24
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Ostermann M, Liu K. Pathophysiology of AKI. Best Pract Res Clin Anaesthesiol 2017; 31:305-314. [PMID: 29248138 DOI: 10.1016/j.bpa.2017.09.001] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 09/18/2017] [Indexed: 12/12/2022]
Abstract
Acute kidney injury (AKI) is common in the perioperative and intensive care setting. Although AKI is usually multifactorial, haemodynamic instability, sepsis and drug toxicity are commonly implicated. Independent of the exact aetiology, several different pathophysiologic processes occur simultaneously and in sequence, including endothelial dysfunction, alteration of the microcirculation, tubular injury, venous congestion and intrarenal inflammation. A multitude of different immune cells from within the kidney and the systemic circulation play a role in the development, maintenance and recovery phase of AKI. In this review, we describe the common processes involved in AKI and their connections, with particular emphasis on the perioperative and critical care setting.
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Affiliation(s)
- Marlies Ostermann
- Department of Critical Care & Nephrology, King's College London, Guy's & St Thomas' Hospital, London, SE1 7EH, UK.
| | - Kathleen Liu
- Division of Nephrology and Critical Care, Department of Medicine, University of California, San Francisco, CA, USA
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25
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Chae MS, Lee N, Park DH, Lee J, Jung HS, Park CS, Lee J, Choi JH, Hong SH. Influence of oxygen content immediately after graft reperfusion on occurrence of postoperative acute kidney injury in living donor liver transplantation. Medicine (Baltimore) 2017; 96:e7626. [PMID: 28767577 PMCID: PMC5626131 DOI: 10.1097/md.0000000000007626] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Acute kidney injury (AKI) is a common complication after living donor liver transplantation (LDLT). In this study, we investigated perioperative factors, including oxygen content, related to the postoperative development of AKI after LDLT. The perioperative data of 334 patients were reviewed retrospectively. We identified the postoperative development of AKI based on the Acute Kidney Injury Network criteria. Perioperative variables, including oxygen content, were compared between patients with and without AKI. Potentially significant variables in a univariate analysis were evaluated by multivariate analysis. Postoperative AKI developed in 76 patients (22.7%). Univariate analysis revealed that preoperative factors (body mass index [BMI], diabetes mellitus, C-reactive protein) and intraoperative factors (severe postreperfusion syndrome, packed red blood cell transfusion, furosemide, and oxygen content at the anhepatic phase, 5 minutes and 1 hour after graft reperfusion, and at peritoneal closure) of recipients were significant. The multivariate analysis showed that oxygen content 5 minutes after graft reperfusion, BMI, and furosemide administration were independently associated with postoperative AKI. In conclusion, postoperative AKI was independently associated with oxygen content 5 minutes after graft reperfusion, BMI, and furosemide administration. Meticulous ventilator care and transfusion should be required to maintain sufficient oxygen content immediately after graft reperfusion in patients who undergo LDLT.
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26
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27
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Chen Y, Sullivan JC, Edwards A, Layton AT. Sex-specific computational models of the spontaneously hypertensive rat kidneys: factors affecting nitric oxide bioavailability. Am J Physiol Renal Physiol 2017; 313:F174-F183. [PMID: 28356289 DOI: 10.1152/ajprenal.00482.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 03/22/2017] [Accepted: 03/23/2017] [Indexed: 12/31/2022] Open
Abstract
The goals of this study were to 1) develop a computational model of solute transport and oxygenation in the kidney of the female spontaneously hypertensive rat (SHR), and 2) apply that model to investigate sex differences in nitric oxide (NO) levels in SHR and their effects on medullary oxygenation and oxidative stress. To accomplish these goals, we first measured NO synthase (NOS) 1 and NOS3 protein expression levels in total renal microvessels of male and female SHR. We found that the expression of both NOS1 and NOS3 is higher in the renal vasculature of females compared with males. To predict the implications of that finding on medullary oxygenation and oxidative stress levels, we developed a detailed computational model of the female SHR kidney. The model was based on a published male kidney model and represents solute transport and the biochemical reactions among O2, NO, and superoxide ([Formula: see text]) in the renal medulla. Model simulations conducted using both male and female SHR kidney models predicted significant radial gradients in interstitial fluid oxygen tension (Po2) and NO and [Formula: see text] concentration in the outer medulla and upper inner medulla. The models also predicted that increases in endothelial NO-generating capacity, even when limited to specific vascular segments, may substantially raise medullary NO and Po2 levels. Other potential sex differences in SHR, including [Formula: see text] production rate, are predicted to significantly impact oxidative stress levels, but effects on NO concentration and Po2 are limited.
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Affiliation(s)
- Ying Chen
- Department of Mathematics, Duke University, Durham, North Carolina
| | | | - Aurélie Edwards
- Sorbonne Universités, UPMC University Paris 06, Université Paris Descartes, Sorbonne Paris, France.,INSERM UMRS 1138, CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France; and.,Department of Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina;
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28
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Ngo JP, Ow CP, Gardiner BS, Kar S, Pearson JT, Smith DW, Evans RG. Diffusive shunting of gases and other molecules in the renal vasculature: physiological and evolutionary significance. Am J Physiol Regul Integr Comp Physiol 2016; 311:R797-R810. [DOI: 10.1152/ajpregu.00246.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 07/27/2016] [Indexed: 01/22/2023]
Abstract
Countercurrent systems have evolved in a variety of biological systems that allow transfer of heat, gases, and solutes. For example, in the renal medulla, the countercurrent arrangement of vascular and tubular elements facilitates the trapping of urea and other solutes in the inner medulla, which in turn enables the formation of concentrated urine. Arteries and veins in the cortex are also arranged in a countercurrent fashion, as are descending and ascending vasa recta in the medulla. For countercurrent diffusion to occur, barriers to diffusion must be small. This appears to be characteristic of larger vessels in the renal cortex. There must also be gradients in the concentration of molecules between afferent and efferent vessels, with the transport of molecules possible in either direction. Such gradients exist for oxygen in both the cortex and medulla, but there is little evidence that large gradients exist for other molecules such as carbon dioxide, nitric oxide, superoxide, hydrogen sulfide, and ammonia. There is some experimental evidence for arterial-to-venous (AV) oxygen shunting. Mathematical models also provide evidence for oxygen shunting in both the cortex and medulla. However, the quantitative significance of AV oxygen shunting remains a matter of controversy. Thus, whereas the countercurrent arrangement of vasa recta in the medulla appears to have evolved as a consequence of the evolution of Henle’s loop, the evolutionary significance of the intimate countercurrent arrangement of blood vessels in the renal cortex remains an enigma.
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Affiliation(s)
- Jennifer P. Ngo
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
| | - Connie P.C. Ow
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
| | - Bruce S. Gardiner
- School of Engineering and Information Technology, Murdoch University, Perth, Western Australia
| | - Saptarshi Kar
- School of Computer Science and Software Engineering, The University of Western Australia, Perth, Australia; and
| | - James T. Pearson
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
- Monash Biomedical Imaging Facility, Monash University, Melbourne, Australia
- Department of Cardiac Physiology, National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan
| | - David W. Smith
- School of Computer Science and Software Engineering, The University of Western Australia, Perth, Australia; and
| | - Roger G. Evans
- Cardiovascular Disease Program, Biosciences Discovery Institute and Department of Physiology and
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Fu Q, Colgan SP, Shelley CS. Hypoxia: The Force that Drives Chronic Kidney Disease. Clin Med Res 2016; 14:15-39. [PMID: 26847481 PMCID: PMC4851450 DOI: 10.3121/cmr.2015.1282] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 09/30/2015] [Indexed: 12/15/2022]
Abstract
In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy.
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Affiliation(s)
- Qiangwei Fu
- Kabara Cancer Research Institute, La Crosse, WI
| | - Sean P Colgan
- Mucosal Inflammation Program and University of Colorado School of Medicine, Aurora, CO
| | - Carl Simon Shelley
- University of Wisconsin School of Medicine and Public Health, Madison, WI
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Farías JG, Herrera EA, Carrasco-Pozo C, Sotomayor-Zárate R, Cruz G, Morales P, Castillo RL. Pharmacological models and approaches for pathophysiological conditions associated with hypoxia and oxidative stress. Pharmacol Ther 2015; 158:1-23. [PMID: 26617218 DOI: 10.1016/j.pharmthera.2015.11.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hypoxia is the failure of oxygenation at the tissue level, where the reduced oxygen delivered is not enough to satisfy tissue demands. Metabolic depression is the physiological adaptation associated with reduced oxygen consumption, which evidently does not cause any harm to organs that are exposed to acute and short hypoxic insults. Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability of endogenous antioxidant systems to scavenge ROS, where ROS overwhelms the antioxidant capacity. Oxidative stress plays a crucial role in the pathogenesis of diseases related to hypoxia during intrauterine development and postnatal life. Thus, excessive ROS are implicated in the irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Here, we describe several pathophysiological conditions and in vivo and ex vivo models developed for the study of hypoxic and oxidative stress injury. We reviewed existing literature on the responses to hypoxia and oxidative stress of the cardiovascular, renal, reproductive, and central nervous systems, and discussed paradigms of chronic and intermittent hypobaric hypoxia. This systematic review is a critical analysis of the advantages in the application of some experimental strategies and their contributions leading to novel pharmacological therapies.
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Affiliation(s)
- Jorge G Farías
- Facultad de Ingeniería y Ciencias, Departamento de Ingeniería Química, Universidad de la Frontera, Casilla 54-D, Temuco, Chile
| | - Emilio A Herrera
- Programa de Fisiopatología, ICBM, Facultad de Medicina, Universidad de Chile, Chile; International Center for Andean Studies (INCAS), Universidad de Chile, Chile
| | | | - Ramón Sotomayor-Zárate
- Centro de Neurobiología y Plasticidad Cerebral (CNPC), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Chile
| | - Gonzalo Cruz
- Centro de Neurobiología y Plasticidad Cerebral (CNPC), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Chile
| | - Paola Morales
- Programa de Farmacología Molecular y Clínica, ICBM, Facultad de Medicina, Universidad de Chile, Chile
| | - Rodrigo L Castillo
- Programa de Fisiopatología, ICBM, Facultad de Medicina, Universidad de Chile, Chile.
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31
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Ding J, Xing W, Wu D, Chen J, Pan L, Sun J, Xing S, Dai Y. Evaluation of Renal Oxygenation Level Changes after Water Loading Using Susceptibility-Weighted Imaging and T2* Mapping. Korean J Radiol 2015; 16:827-34. [PMID: 26175582 PMCID: PMC4499547 DOI: 10.3348/kjr.2015.16.4.827] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 04/08/2015] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVE To assess the feasibility of susceptibility-weighted imaging (SWI) while monitoring changes in renal oxygenation level after water loading. MATERIALS AND METHODS Thirty-two volunteers (age, 28.0 ± 2.2 years) were enrolled in this study. SWI and multi-echo gradient echo sequence-based T2(*) mapping were used to cover the kidney before and after water loading. Cortical and medullary parameters were measured using small regions of interest, and their relative changes due to water loading were calculated based on baseline and post-water loading data. An intraclass correlation coefficient analysis was used to assess inter-observer reliability of each parameter. A receiver operating characteristic curve analysis was conducted to compare the performance of the two methods for detecting renal oxygenation changes due to water loading. RESULTS Both medullary phase and medullary T2(*) values increased after water loading (p < 0.001), although poor correlations were found between the phase changes and the T2(*) changes (p > 0.05). Interobserver reliability was excellent for the T2(*) values, good for SWI cortical phase values, and moderate for the SWI medullary phase values. The area under receiver operating characteristic curve of the SWI medullary phase values was 0.85 and was not different from the medullary T2(*) value (0.84). CONCLUSION Susceptibility-weighted imaging enabled monitoring changes in the oxygenation level in the medulla after water loading, and may allow comparable feasibility to detect renal oxygenation level changes due to water loading compared with that of T2(*) mapping.
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Affiliation(s)
- Jiule Ding
- Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China
| | - Wei Xing
- Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China
| | - Dongmei Wu
- Shanghai Key Laboratory of Magnetic Resonance Imaging, East China Normal University, Shanghai 200241, China
| | - Jie Chen
- Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China
| | - Liang Pan
- Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China
| | - Jun Sun
- Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China
| | - Shijun Xing
- Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China
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Olgac U, Kurtcuoglu V. Renal oxygenation: preglomerular vasculature is an unlikely contributor to renal oxygen shunting. Am J Physiol Renal Physiol 2015; 308:F671-88. [DOI: 10.1152/ajprenal.00551.2014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/04/2014] [Indexed: 11/22/2022] Open
Abstract
The primary aim of this study was to assess the plausibility of preglomerular arterial-to-venous oxygen shunting in the kidney. To this end, we have developed a segment-wise three-dimensional computational model that takes into account transport processes in arteries, veins, cortical tissue, and capillaries. Our model suggests that the amount of preglomerular oxygen shunting is negligible. Consequently, it is improbable that preglomerular shunting contributes to the hypothesized regulation of renal oxygenation. Cortical tissue oxygenation is more likely determined by the interplay between oxygen supply, either from the preglomerular vasculature or from capillaries, and oxygen consumption. We show that reported differences in permeability to oxygen between perfused and unperfused tissue may be explained by what we refer to as advection-facilitated diffusion. We further show that the preglomerular vasculature is the primary source of oxygen for the tissue when cortical consumption is high or renal arterial blood is highly oxygenated, i.e., under hyperoxemic conditions. Conversely, when oxygen demand in the tissue is decreased, or under hypoxemic conditions, oxygen is supplied predominantly by capillaries.
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Affiliation(s)
- Ufuk Olgac
- The Interface Group, Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Vartan Kurtcuoglu
- The Interface Group, Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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33
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Pannabecker TL, Layton AT. Targeted delivery of solutes and oxygen in the renal medulla: role of microvessel architecture. Am J Physiol Renal Physiol 2014; 307:F649-55. [PMID: 25056344 DOI: 10.1152/ajprenal.00276.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Renal medullary function is characterized by corticopapillary concentration gradients of various molecules. One example is the generally decreasing axial gradient in oxygen tension (Po2). Another example, found in animals in the antidiuretic state, is a generally increasing axial solute gradient, consisting mostly of NaCl and urea. This osmolality gradient, which plays a principal role in the urine concentrating mechanism, is generally considered to involve countercurrent multiplication and countercurrent exchange, although the underlying mechanism is not fully understood. Radial oxygen and solute gradients in the transverse dimension of the medullary parenchyma have been hypothesized to occur, although strong experimental evidence in support of these gradients remains lacking. This review considers anatomic features of the renal medulla that may impact the formation and maintenance of oxygen and solute gradients. A better understanding of medullary architecture is essential for more clearly defining the compartment-to-compartment flows taken by fluid and molecules that are important in producing axial and radial gradients. Preferential interactions between nephron and vascular segments provide clues as to how tubular and interstitial oxygen flows contribute to safeguarding active transport pathways in renal function in health and disease.
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Affiliation(s)
- Thomas L Pannabecker
- Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona; and
| | - Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina
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34
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Mechanisms of contrast-induced nephropathy reduction for saline (NaCl) and sodium bicarbonate (NaHCO3). BIOMED RESEARCH INTERNATIONAL 2014; 2014:510385. [PMID: 24826379 PMCID: PMC4009105 DOI: 10.1155/2014/510385] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Revised: 02/28/2014] [Accepted: 03/19/2014] [Indexed: 11/17/2022]
Abstract
Nephropathy following contrast media (CM) exposure is reduced by administration before, during, and after the contrast procedure of either isotonic sodium chloride solution (Saline) or isotonic sodium bicarbonate solution (IsoBicarb). The reasons for this reduction are not well established for either sodium salt; probable mechanisms are discussed in this paper. For Saline, the mechanism for the decrease in CIN is likely related primarily to the increased tubular flow rates produced by volume expansion and therefore a decreased concentration of the filtered CM during transit through the kidney tubules. Furthermore, increased tubular flow rates produce a slight increase in tubular pH resulting from a fixed acid excretion in an increased tubular volume. The mechanism for the decreased CIN associated with sodium bicarbonate includes the same mechanisms listed for Saline in addition to a renal pH effect. Increased filtered bicarbonate anion raises both tubular pH and tubular bicarbonate anion levels toward blood physiologic levels, thus providing increased buffer for reactive oxygen species (ROS) formed in the tubules as a result of exposure to CM in renal tubular fluid.
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35
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Zhang JL, Morrell G, Rusinek H, Warner L, Vivier PH, Cheung AK, Lerman LO, Lee VS. Measurement of renal tissue oxygenation with blood oxygen level-dependent MRI and oxygen transit modeling. Am J Physiol Renal Physiol 2014; 306:F579-87. [PMID: 24452640 DOI: 10.1152/ajprenal.00575.2013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Blood oxygen level-dependent (BOLD) MRI data of kidney, while indicative of tissue oxygenation level (Po2), is in fact influenced by multiple confounding factors, such as R2, perfusion, oxygen permeability, and hematocrit. We aim to explore the feasibility of extracting tissue Po2 from renal BOLD data. A method of two steps was proposed: first, a Monte Carlo simulation to estimate blood oxygen saturation (SHb) from BOLD signals, and second, an oxygen transit model to convert SHb to tissue Po2. The proposed method was calibrated and validated with 20 pigs (12 before and after furosemide injection) in which BOLD-derived tissue Po2 was compared with microprobe-measured values. The method was then applied to nine healthy human subjects (age: 25.7 ± 3.0 yr) in whom BOLD was performed before and after furosemide. For the 12 pigs before furosemide injection, the proposed model estimated renal tissue Po2 with errors of 2.3 ± 5.2 mmHg (5.8 ± 13.4%) in cortex and -0.1 ± 4.5 mmHg (1.7 ± 18.1%) in medulla, compared with microprobe measurements. After injection of furosemide, the estimation errors were 6.9 ± 3.9 mmHg (14.2 ± 8.4%) for cortex and 2.6 ± 4.0 mmHg (7.7 ± 11.5%) for medulla. In the human subjects, BOLD-derived medullary Po2 increased from 16.0 ± 4.9 mmHg (SHb: 31 ± 11%) at baseline to 26.2 ± 3.1 mmHg (SHb: 53 ± 6%) at 5 min after furosemide injection, while cortical Po2 did not change significantly at ∼58 mmHg (SHb: 92 ± 1%). Our proposed method, validated with a porcine model, appears promising for estimating tissue Po2 from renal BOLD MRI data in human subjects.
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36
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Layton AT. Mathematical modeling of kidney transport. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2013; 5:557-73. [PMID: 23852667 DOI: 10.1002/wsbm.1232] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 05/16/2013] [Accepted: 05/20/2013] [Indexed: 11/08/2022]
Abstract
In addition to metabolic waste and toxin excretion, the kidney also plays an indispensable role in regulating the balance of water, electrolytes, nitrogen, and acid-base. In this review, we describe representative mathematical models that have been developed to better understand kidney physiology and pathophysiology, including the regulation of glomerular filtration, the regulation of renal blood flow by means of the tubuloglomerular feedback mechanisms and of the myogenic mechanism, the urine concentrating mechanism, epithelial transport, and regulation of renal oxygen transport. We discuss the extent to which these modeling efforts have expanded our understanding of renal function in both health and disease.
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Affiliation(s)
- Anita T Layton
- Department of Mathematics, Duke University, Durham, NC, USA
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37
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Darby PJ, Kim N, Hare GMT, Tsui A, Wang Z, Harrington A, Mazer CD. Anemia increases the risk of renal cortical and medullary hypoxia during cardiopulmonary bypass. Perfusion 2013; 28:504-11. [DOI: 10.1177/0267659113490219] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Introduction: Anemia is an independent predictor of acute kidney injury (AKI) following cardiopulmonary bypass (CPB), possibly due to inadequate renal oxygen delivery. The objective of this study was to investigate the effects of CPB and anemia on tissue oxygen tension (pO2) and blood flow in the renal cortex and medulla. Methods: Rats (n=6/group) underwent 1hr of normothermic cardiopulmonary bypass (CPB), with target hemoglobin concentrations (Hb) of 10g/dL (CPB) or 6.5g/dL (anemia-CPB). Renal blood flow (RBF) and tissue PO2 were measured before, during and after 1hr of CPB. To confirm the observed differences in renal cortical and medullary PO2, HIF-1α (ODD) luciferase mice were exposed to 8% O2 (hypoxia) and HIF-1α dependent luminescence was measured in the renal cortex and medulla (n=5). Results: Renal tissue PO2 values decreased initially and returned towards baseline, however, values at the end of CPB. Anemia-CPB resulted in a significant increase in both renal cortical and medullary blood flow, PO2 remained significantly reduced throughout anemia-CPB. Renal medullary HIF-1α-dependent luminescence confirmed a greater degree of hypoxia in the renal medulla. Discussion: During CPB, renal O2 delivery was transiently jeopardized, but recovered after 1hr. Anemia-CPB resulted in a dramatic and sustained reduction in renal cortical and medullary PO2, which suggests an increased risk of renal hypoxic injury with anemia. Conclusion: The clear difference in the degree of hypoxia in the renal cortex and medulla may be useful in understanding the progress of medullary hypoxia during CPB with anemia and the potential development of AKI. Further studies should aim at identifying early markers of medullary hypoxia and potential agents that may decrease the work and O2 consumption in the renal medulla to reduce the risk of hypoxic damage during CPB and anemia.
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Affiliation(s)
- PJ Darby
- Department of Anesthesia, Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - N Kim
- Department of Anesthesia, Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
- Departments of Anesthesia & Physiology, University of Toronto, Toronto, Ontario, Canada
| | - GMT Hare
- Department of Anesthesia, Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
- Departments of Anesthesia & Physiology, University of Toronto, Toronto, Ontario, Canada
| | - A Tsui
- Department of Anesthesia, Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - Z Wang
- Department of Anesthesia, Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - A Harrington
- Department of Anesthesia, Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - CD Mazer
- Department of Anesthesia, Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
- Departments of Anesthesia & Physiology, University of Toronto, Toronto, Ontario, Canada
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38
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Evans RG, Ince C, Joles JA, Smith DW, May CN, O'Connor PM, Gardiner BS. Haemodynamic influences on kidney oxygenation: Clinical implications of integrative physiology. Clin Exp Pharmacol Physiol 2013; 40:106-22. [DOI: 10.1111/1440-1681.12031] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 10/21/2012] [Accepted: 11/15/2012] [Indexed: 01/08/2023]
Affiliation(s)
- Roger G Evans
- Department of Physiology; Monash University; Melbourne; Victoria; Australia
| | - Can Ince
- Department of Translational Physiology; Academic Medical Center; University of Amsterdam; Amsterdam; The Netherlands
| | - Jaap A Joles
- Department of Nephrology and Hypertension; University Medical Center; Utrecht; The Netherlands
| | - David W Smith
- School of Computer Science and Software Engineering; The University of Western Australia; Perth; Western Australia; Australia
| | - Clive N May
- Florey Institute of Neuroscience and Mental Health; University of Melbourne; Melbourne; Victoria; Australia
| | - Paul M O'Connor
- Department of Physiology; Georgia Health Sciences University; Augusta; GA; USA
| | - Bruce S Gardiner
- School of Computer Science and Software Engineering; The University of Western Australia; Perth; Western Australia; Australia
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39
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Abstract
The kidney plays an indispensable role in the regulation of whole-organism water balance, electrolyte balance, and acid-base balance, and in the excretion of metabolic wastes and toxins. In this paper, we review representative mathematical models that have been developed to better understand kidney physiology and pathophysiology, including the regulation of glomerular filtration, the regulation of renal blood flow by means of the tubuloglomerular feedback mechanisms and of the myogenic mechanism, the urine concentrating mechanism, and regulation of renal oxygen transport. We discuss how such modeling efforts have significantly expanded our understanding of renal function in both health and disease.
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Affiliation(s)
- Anita T Layton
- Department of Mathematics, Duke University, P.O. Box 90320, Durham, NC 27708-0320, USA
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40
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41
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Deshmukh AB, Patel JK, Prajapati AR, Shah S. Perspective in Chronic Kidney Disease: Targeting Hypoxia-Inducible Factor (HIF) as Potential Therapeutic Approach. Ren Fail 2012; 34:521-32. [DOI: 10.3109/0886022x.2011.653754] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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42
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Evans RG, Goddard D, Eppel GA, O'Connor PM. Stability of tissue PO2 in the face of altered perfusion: a phenomenon specific to the renal cortex and independent of resting renal oxygen consumption. Clin Exp Pharmacol Physiol 2011; 38:247-54. [PMID: 21306412 DOI: 10.1111/j.1440-1681.2011.05494.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
1. Oxygen tension (PO(2)) in renal cortical tissue can remain relatively constant when renal blood flow changes in the physiological range, even when changes in renal oxygen delivery (DO(2)) and oxygen consumption (VO(2)) are mismatched. In the current study, we examined whether this also occurs in the renal medulla and skeletal muscle, or if it is an unusual property of the renal cortex. We also examined the potential for dysfunction of the mechanisms underlying this phenomenon to contribute to kidney hypoxia in disease states associated with increased renal VO(2) . 2. In both the kidney and hindlimb of pentobarbitone anaesthetized rabbits, whole organ blood flow was reduced by intra-arterial infusion of angiotensin-II and increased by acetylcholine infusion. In the kidney, this was carried out before and during renal arterial infusion of the mitochondrial uncoupler, 2,4-dinitrophenol (DNP), or its vehicle. 3. Angiotensin-II reduced renal (-34%) and hindlimb (-25%) DO(2) , whereas acetylcholine increased renal (+38%) and hindlimb (+66%) DO(2) . However, neither renal nor hindlimb VO(2) were altered. Tissue PO(2) varied with local perfusion in the renal medulla and biceps femoris, but not the renal cortex. DNP increased renal VO(2) (+38%) and reduced cortical tissue PO(2) (-44%), but both still remained stable during subsequent infusion of angiotensin-II and acetylcholine. 4. We conclude that maintenance of tissue PO(2) in the face of mismatched changes in local perfusion and VO(2) is an unusual property of the renal cortex. The underlying mechanisms remain unknown, but our current findings suggest they are not compromised when resting renal VO(2) is increased.
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Affiliation(s)
- Roger G Evans
- Department of Physiology, Monash University, Melbourne, Victoria, Australia.
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43
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Gardiner BS, Smith DW, O'Connor PM, Evans RG. A mathematical model of diffusional shunting of oxygen from arteries to veins in the kidney. Am J Physiol Renal Physiol 2011; 300:F1339-52. [DOI: 10.1152/ajprenal.00544.2010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To understand how arterial-to-venous (AV) oxygen shunting influences kidney oxygenation, a mathematical model of oxygen transport in the renal cortex was created. The model consists of a multiscale hierarchy of 11 countercurrent systems representing the various branch levels of the cortical vasculature. At each level, equations describing the reactive-advection-diffusion of oxygen are solved. Factors critical in renal oxygen transport incorporated into the model include the parallel geometry of arteries and veins and their respective sizes, variation in blood velocity in each vessel, oxygen transport (along the vessels, between the vessels and between vessel and parenchyma), nonlinear binding of oxygen to hemoglobin, and the consumption of oxygen by renal tissue. The model is calibrated using published measurements of cortical vascular geometry and microvascular Po2. The model predicts that AV oxygen shunting is quantitatively significant and estimates how much kidney V̇o2 must change, in the face of altered renal blood flow, to maintain cortical tissue Po2 at a stable level. It is demonstrated that oxygen shunting increases as renal V̇o2 or arterial Po2 increases. Oxygen shunting also increases as renal blood flow is reduced within the physiological range or during mild hemodilution. In severe ischemia or anemia, or when kidney V̇o2 increases, AV oxygen shunting in proximal vascular elements may reduce the oxygen content of blood destined for the medullary circulation, thereby exacerbating the development of tissue hypoxia. That is, cortical ischemia could cause medullary hypoxia even when medullary perfusion is maintained. Cortical AV oxygen shunting limits the change in oxygen delivery to cortical tissue and stabilizes tissue Po2 when arterial Po2 changes, but renders the cortex and perhaps also the medulla susceptible to hypoxia when oxygen delivery falls or consumption increases.
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Affiliation(s)
- Bruce S. Gardiner
- School of Computer Science and Software Engineering, The University of Western Australia, Perth
| | - David W. Smith
- School of Computer Science and Software Engineering, The University of Western Australia, Perth
| | - Paul M. O'Connor
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; and
| | - Roger G. Evans
- Department of Physiology, Monash University, Melbourne, Australia
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44
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Evans RG, Goddard D, Eppel GA, O'Connor PM. Factors that render the kidney susceptible to tissue hypoxia in hypoxemia. Am J Physiol Regul Integr Comp Physiol 2011; 300:R931-40. [DOI: 10.1152/ajpregu.00552.2010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To better understand what makes the kidney susceptible to tissue hypoxia, we compared, in the rabbit kidney and hindlimb, the ability of feedback mechanisms governing oxygen consumption (V̇o2) and oxygen delivery (Do2) to attenuate tissue hypoxia during hypoxemia. In the kidney (cortex and medulla) and hindlimb (biceps femoris muscle), we determined responses of whole organ blood flow and V̇o2, and local perfusion and tissue Po2, to reductions in Do2 mediated by graded systemic hypoxemia. Progressive hypoxemia reduced tissue Po2 similarly in the renal cortex, renal medulla, and biceps femoris. Falls in tissue Po2 could be detected when arterial oxygen content was reduced by as little as 4–8%. V̇o2 remained stable during progressive hypoxemia, only tending to fall once arterial oxygen content was reduced by 55% for the kidney or 42% for the hindlimb. Even then, the fall in renal V̇o2 could be accounted for by reduced oxygen demand for sodium transport rather than limited oxygen availability. Hindlimb blood flow and local biceps femoris perfusion increased progressively during graded hypoxia. In contrast, neither total renal blood flow nor cortical or medullary perfusion was altered by hypoxemia. Our data suggest that the absence in the kidney of hyperemic responses to hypoxia, and the insensitivity of renal V̇o2 to limited oxygen availability, contribute to kidney hypoxia during hypoxemia. The susceptibility of the kidney to tissue hypoxia, even in relatively mild hypoxemia, may have important implications for the progression of kidney disease, particularly in patients at high altitude or with chronic obstructive pulmonary disease.
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Affiliation(s)
- Roger G. Evans
- Department of Physiology, Monash University, Melbourne, Australia; and
| | - Duncan Goddard
- Department of Physiology, Monash University, Melbourne, Australia; and
| | - Gabriela A. Eppel
- Department of Physiology, Monash University, Melbourne, Australia; and
| | - Paul M. O'Connor
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
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45
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Edwards A. Modeling transport in the kidney: investigating function and dysfunction. Am J Physiol Renal Physiol 2009; 298:F475-84. [PMID: 19889951 DOI: 10.1152/ajprenal.00501.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Mathematical models of water and solute transport in the kidney have significantly expanded our understanding of renal function in both health and disease. This review describes recent theoretical developments and emphasizes the relevance of model findings to major unresolved questions and controversies. These include the fundamental processes by which urine is concentrated in the inner medulla, the ultrastructural basis of proteinuria, irregular flow oscillation patterns in spontaneously hypertensive rats, and the mechanisms underlying the hypotensive effects of thiazides. Macroscopic models of water, NaCl, and urea transport in populations of nephrons have served to test, confirm, or refute a number of hypotheses related to the urine concentrating mechanism. Other macroscopic models focus on the mechanisms, role, and irregularities of renal hemodynamic control and on the regulation of renal oxygenation. At the mesoscale, models of glomerular filtration have yielded significant insight into the ultrastructural basis underlying a number of disorders. At the cellular scale, models of epithelial solute transport and pericyte Ca2+ signaling are being used to elucidate transport pathways and the effects of hormones and drugs. Areas where further theoretical progress is conditional on experimental advances are also identified.
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Affiliation(s)
- Aurélie Edwards
- Department of Chemical and Biological Engineering, Tufts University, Medford, Massachusetts 02155, USA.
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46
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Jaschinski U, Lichtwarck-Aschoff M. [Acute perioperative disturbances of renal function. Strategies for prevention and therapy]. Anaesthesist 2009; 58:829-47; quiz 848-9. [PMID: 19669104 DOI: 10.1007/s00101-009-1592-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The increasing life expectancy in industrial nations leads to an increase in the number of elderly and aged persons treated in hospital. Increasingly more complex operations are being carried out on this group of patients. Renal dysfunction in the preoperative situation increases morbidity and mortality. Acute kidney injury (AKI) is nearly always part of a multi-organ dysfunction syndrome in critically ill patients. The treatment strategy of the AKI should be oriented to the degree of organ dysfunction. However, the stage of organ dysfunction is mostly unknown so that the therapeutically exploitable interval is often missed. The same therapy is practically always used for all patients: administration of fluids and diuretics often under the premise of "the kidneys must be rinsed". A unified classification of the continuation of kidney function disorders using the RIFLE criteria (risk, injury, failure, loss, endstage kidney disease) can assist recognition of early stages of kidney failure in order to react correspondingly with therapeutic measures and to critically question or optimize the use of conservative treatment strategies.
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Affiliation(s)
- U Jaschinski
- Klinik für Anästhesiologie und Operative Intensivmedizin, Klinikum Augsburg, Augsburg.
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Randall Thomas S. Kidney modeling and systems physiology. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2009; 1:172-190. [DOI: 10.1002/wsbm.14] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- S. Randall Thomas
- IBISC CNRS FRE 3190 and University of Evry, Tour Evry 2, 91000 Evry, France
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Oliver JA, Klinakis A, Cheema FH, Friedlander J, Sampogna RV, Martens TP, Liu C, Efstratiadis A, Al-Awqati Q. Proliferation and migration of label-retaining cells of the kidney papilla. J Am Soc Nephrol 2009; 20:2315-27. [PMID: 19762493 DOI: 10.1681/asn.2008111203] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The kidney papilla contains a population of cells with several characteristics of adult stem cells, including the retention of proliferation markers during long chase periods (i.e., they are label-retaining cells [LRCs]). To determine whether the papillary LRCs generate new cells in the normal adult kidney, we examined cell proliferation throughout the kidney and found that the upper papilla is a site of enhanced cell cycling. Using genetically modified mice that conditionally expressed green fluorescence protein fused to histone 2B, we observed that the LRCs of the papilla proliferated only in its upper part, where they associate with "chains" of cycling cells. The papillary LRCs decreased in number with age, suggesting that the cells migrated to the upper papilla before entering the cell cycle. To test this directly, we marked papillary cells with vital dyes in vivo and found that some cells in the kidney papilla, including LRCs, migrated toward other parts of the kidney. Acute kidney injury enhanced both cell migration and proliferation. These results suggest that during normal homeostasis, LRCs of the kidney papilla (or their immediate progeny) migrate to the upper papilla and form a compartment of rapidly proliferating cells, which may play a role in repair after ischemic injury.
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Affiliation(s)
- Juan A Oliver
- Department of Medicine, Columbia University, New York, NY 10032, USA.
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Evans RG, Gardiner BS, Smith DW, O'Connor PM. Methods for studying the physiology of kidney oxygenation. Clin Exp Pharmacol Physiol 2009; 35:1405-12. [PMID: 18983577 DOI: 10.1111/j.1440-1681.2008.05063.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
1. An improved understanding of the regulation of kidney oxygenation has the potential to advance preventative, diagnostic and therapeutic strategies for kidney disease. Here, we review the strengths and limitations of available and emerging methods for studying kidney oxygen status. 2. To fully characterize kidney oxygen handling, we must quantify multiple parameters, including renal oxygen delivery (DO2) and consumption (VO2), as well as oxygen tension (Po2). Ideally, these parameters should be quantified both at the whole-organ level and within specific vascular, tubular and interstitial compartments. 3. Much of our current knowledge of kidney oxygen physiology comes from established techniques that allow measurement of global kidney DO2 and VO2, or local tissue Po2. When used in tandem, these techniques can help us understand oxygen mass balance in the kidney. Po2 can be resolved to specific tissue compartments in the superficial cortex, but not deep below the kidney surface. We have limited ability to measure local kidney tissue DO2 and VO2. 4. Mathematical modelling has the potential to provide new insights into the physiology of kidney oxygenation, but is limited by the quality of the information such models are based on. 5. Various imaging techniques and other emerging technologies have the potential to allow Po2 mapping throughout the kidney and/or spatial resolution of Po2 in specific renal tissues, even in humans. All currently available methods have serious limitations, but with further refinement should provide a pathway through which data obtained from experimental animal models can be related to humans in the clinical setting.
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Affiliation(s)
- Roger G Evans
- Department of Physiology, Monash University, Victoria, Australia.
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Chen J, Layton AT, Edwards A. A mathematical model of O2 transport in the rat outer medulla. I. Model formulation and baseline results. Am J Physiol Renal Physiol 2009; 297:F517-36. [PMID: 19403646 DOI: 10.1152/ajprenal.90496.2008] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mammalian kidney is particularly vulnerable to hypoperfusion, because the O(2) supply to the renal medulla barely exceeds its O(2) requirements. In this study, we examined the impact of the complex structural organization of the rat outer medulla (OM) on O(2) distribution. We extended the region-based mathematical model of the rat OM developed by Layton and Layton (Am J Physiol Renal Physiol 289: F1346-F1366, 2005) to incorporate the transport of RBCs, Hb, and O(2). We considered basal cellular O(2) consumption and O(2) consumption for active transport of NaCl across medullary thick ascending limb epithelia. Our model predicts that the structural organization of the OM results in significant Po(2) gradients in the axial and radial directions. The segregation of descending vasa recta, the main supply of O(2), at the center and immediate periphery of the vascular bundles gives rise to large radial differences in Po(2) between regions, limits O(2) reabsorption from long descending vasa recta, and helps preserve O(2) delivery to the inner medulla. Under baseline conditions, significantly more O(2) is transferred radially between regions by capillary flow, i.e., advection, than by diffusion. In agreement with experimental observations, our results suggest that 79% of the O(2) supplied to the medulla is consumed in the OM and that medullary thick ascending limbs operate on the brink of hypoxia.
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Affiliation(s)
- Jing Chen
- Department of Chemical and Biological Engineering, Tufts University, Medford, Massachusetts 02155, UAS
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