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Yuan M, Chen X, Ou R, Luo R, Fan W, Wang X, Guo Z. Renal anemia: from relative insufficiency of EPO to imbalance of erythropoiesis and eryptosis. Int Urol Nephrol 2024:10.1007/s11255-024-04146-x. [PMID: 38982020 DOI: 10.1007/s11255-024-04146-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Accepted: 07/03/2024] [Indexed: 07/11/2024]
Abstract
Chronic kidney disease has emerged as a major health issue both in China and worldwide. Renal anemia frequently occurs in patients with chronic kidney disease, and its severity and incidence rate increase as the disease progresses. Over the last 30 years, the administration of exogenous EPO and EPO stimulants has been employed to alleviate renal anemia, suggesting that a relative deficiency in EPO may be a primary cause. However, this approach has overshadowed other contributing factors, particularly eryptosis, which results from the reduced lifespan of red blood cells. Numerous studies reveal that there are nephrogenic and extrarenal EPO secretion indicating that an absolute deficiency of EPO is not always present in patients. Therefore, this paper speculates that renal anemia may arise when EPO-driven erythropoiesis fails to adequately compensate for aggravating eryptosis. Other factors including iron metabolism disorder, uremic toxin accumulation, inflammatory state, oxidative stress, and secondary hyperparathyroidism affect EPO reactivity bone marrow hematopoiesis and eryptosis, leading to an imbalance between red blood cell production and destruction, and cause anemia ultimately. More further studies on the pathogenesis and treatment of renal anemia would be expected to provide evidence to support our opinion.
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Affiliation(s)
- Mengxue Yuan
- Department of Nephrology, Affiliated Hospital of Shandong Second Medical University, 2428 Yuhe Road, Weifang, 261031, Shandong, China
| | - Xinping Chen
- Department of Nephrology, Affiliated Hospital of Shandong Second Medical University, 2428 Yuhe Road, Weifang, 261031, Shandong, China
| | - Ruilin Ou
- Department of Nephrology, Affiliated Hospital of Shandong Second Medical University, 2428 Yuhe Road, Weifang, 261031, Shandong, China
| | - Ruiling Luo
- Department of Nephrology, Affiliated Hospital of Shandong Second Medical University, 2428 Yuhe Road, Weifang, 261031, Shandong, China
| | - Wenwen Fan
- Department of Clinical Laboratory, Affiliated Hospital of Shandong Second Medical University, 2428 Yuhe Road, Weifang, 261031, Shandong, China
| | - Xiangming Wang
- Department of Nephrology, Affiliated Hospital of Shandong Second Medical University, 2428 Yuhe Road, Weifang, 261031, Shandong, China.
| | - Zhentao Guo
- Department of Nephrology, Affiliated Hospital of Shandong Second Medical University, 2428 Yuhe Road, Weifang, 261031, Shandong, China.
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2
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Westphal A. Current insights into the Pathophysiology of kidney diseases. Acta Physiol (Oxf) 2024; 240:e14158. [PMID: 38695204 DOI: 10.1111/apha.14158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 04/23/2024] [Indexed: 06/09/2024]
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3
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Burgraff NJ. Keeping breathing in balance through hormonal modulation in respiratory control. Acta Physiol (Oxf) 2024; 240:e14094. [PMID: 38235961 DOI: 10.1111/apha.14094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Accepted: 10/04/2023] [Indexed: 01/19/2024]
Affiliation(s)
- Nicholas J Burgraff
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, USA
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4
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Liu D, Wang L, Ha W, Li K, Shen R, Wang D. HIF-1α: A potential therapeutic opportunity in renal fibrosis. Chem Biol Interact 2024; 387:110808. [PMID: 37980973 DOI: 10.1016/j.cbi.2023.110808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 11/04/2023] [Accepted: 11/14/2023] [Indexed: 11/21/2023]
Abstract
Renal fibrosis is a common outcome of various renal injuries, leading to structural destruction and functional decline of the kidney, and is also a critical prognostic indicator and determinant in renal diseases therapy. Hypoxia is induced in different stress and injuries in kidney, and the hypoxia inducible factors (HIFs) are activated in the context of hypoxia in response and regulation the hypoxia in time. Under stress and hypoxia conditions, HIF-1α increases rapidly and regulates intracellular energy metabolism, cell proliferation, apoptosis, and inflammation. Through reprogramming cellular metabolism, HIF-1α can directly or indirectly induce abnormal accumulation of metabolites, changes in cellular epigenetic modifications, and activation of fibrotic signals. HIF-1α protein expression and activity are regulated by various posttranslational modifications. The drugs targeting HIF-1α can regulate the downstream cascade signals by inhibiting HIF-1α activity or promoting its degradation. As the renal fibrosis is affected by renal diseases, different diseases may trigger different mechanisms which will affect the therapy effect. Therefore, comprehensive analysis of the role and contribution of HIF-1α in occurrence and progression of renal fibrosis, and determination the appropriate intervention time of HIF-1α in the process of renal fibrosis are important ideas to explore effective treatment strategies. This study reviews the regulation of HIF-1α and its mediated complex cascade reactions in renal fibrosis, and lists some drugs targeting HIF-1α that used in preclinical studies, to provide new insight for the study of the renal fibrosis mechanism.
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Affiliation(s)
- Disheng Liu
- The First Hospital of Lanzhou University, Lanzhou University, Gansu, 730000, China
| | - Lu Wang
- The First Hospital of Lanzhou University, Lanzhou University, Gansu, 730000, China
| | - Wuhua Ha
- The First Hospital of Lanzhou University, Lanzhou University, Gansu, 730000, China
| | - Kan Li
- The First Hospital of Lanzhou University, Lanzhou University, Gansu, 730000, China
| | - Rong Shen
- School of Basic Medical Sciences, Lanzhou University, Gansu, 730000, China.
| | - Degui Wang
- School of Basic Medical Sciences, Lanzhou University, Gansu, 730000, China.
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5
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Rodrigues AF, Bader M. The contribution of the AT1 receptor to erythropoiesis. Biochem Pharmacol 2023; 217:115805. [PMID: 37714274 DOI: 10.1016/j.bcp.2023.115805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 09/09/2023] [Accepted: 09/12/2023] [Indexed: 09/17/2023]
Abstract
The renin-angiotensin system (RAS) comprises a broad set of functional peptides and receptors that play a role in cardiovascular homeostasis and contribute to cardiovascular pathologies. Angiotensin II (Ang II) is the most potent peptide hormone produced by the RAS due to its high abundance and its strong and pleiotropic impact on the cardiovascular system. Formation of Ang II takes place in the bloodstream and additionally in tissues in the so-called local RAS. Of the two Ang II receptors (AT1 and AT2) that Ang II binds to, AT1 is the most expressed throughout the mammalian body. AT1 expression is not restricted to cells of the cardiovascular system but in fact AT1 protein is found in nearly all organs, hence, Ang II takes part in several modulatory physiological processes one of which is erythropoiesis. In this review, we present multiple evidence supporting that Ang II modulates physiological and pathological erythropoiesis processes trough the AT1 receptor. Cumulative evidence indicates that Ang II by three distinct mechanisms influences erythropoiesis: 1) stimulation of renal erythropoietin synthesis; 2) direct action on bone marrow precursor cells; and 3) modulation of sympathetic nerve activity to the bone marrow. The text highlights clinical and preclinical evidence focusing on mechanistic studies using rodent models.
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Affiliation(s)
- André F Rodrigues
- Max Delbrück Center (MDC), Berlin, Germany; German Center for Cardiovascular Research (DZHK), Partner Site Berlin, Germany.
| | - Michael Bader
- Max Delbrück Center (MDC), Berlin, Germany; German Center for Cardiovascular Research (DZHK), Partner Site Berlin, Germany; Charité Universitätsmedizin Berlin, Berlin, Germany; Institute for Biology, University of Lübeck, Lübeck, Germany.
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6
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Locatelli F, Del Vecchio L, Elliott S. The anaemia treatment journey of CKD patients: from epoetins to hypoxia-inducible factor-prolyl hydroxylase inhibitors. Clin Kidney J 2023; 16:1563-1579. [PMID: 37779852 PMCID: PMC10539216 DOI: 10.1093/ckj/sfad105] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Indexed: 10/03/2023] Open
Abstract
The discovery and development of erythropoiesis-stimulating agents was a journey lasting more than a century, leading to the cloning and approval of recombinant human erythropoietin (rHuEpo). This was an impressive clinical advance, providing the possibility of correcting the symptoms associated with anaemia in chronic kidney disease. Associated iron use was needed to produce new haemoglobin-containing blood red cells. Partial anaemia correction became the standard of care since trials aiming for near-normal haemoglobin levels showed a higher risk of adverse cardiovascular events. Hoping to reduce the cardiovascular risks, a new category of drugs was developed and tested. Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) are small molecules than can be formulated into orally active pills. They simulate reduced tissue oxygen pressure, thus stimulating the production of endogenous erythropoietin (Epo) by the kidneys and liver. Clinical trials with these compounds demonstrated that HIF-PHIs are at least as effective as rHuEpo in treating or correcting anaemia in non-dialysis and dialysis patients. Trials with HIF-PHIs did not demonstrate superiority in safety outcomes and in some trials, outcomes were worse. There was also a focus on oral delivery, a possible beneficial iron-sparing effect and the ability to overcome Epo resistance in inflamed patients. A negative effect is possible iron depletion, which may explain adverse outcomes.
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Affiliation(s)
- Francesco Locatelli
- Department of Nephrology and Dialysis, Alessandro Manzoni Hospital, Lecco, Italy
| | - Lucia Del Vecchio
- Department of Nephrology and Dialysis, Sant’ Anna Hospital, ASST Lariana, Como, Italy
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7
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Kragesteen BK, Giladi A, David E, Halevi S, Geirsdóttir L, Lempke OM, Li B, Bapst AM, Xie K, Katzenelenbogen Y, Dahl SL, Sheban F, Gurevich-Shapiro A, Zada M, Phan TS, Avellino R, Wang SY, Barboy O, Shlomi-Loubaton S, Winning S, Markwerth PP, Dekalo S, Keren-Shaul H, Kedmi M, Sikora M, Fandrey J, Korneliussen TS, Prchal JT, Rosenzweig B, Yutkin V, Racimo F, Willerslev E, Gur C, Wenger RH, Amit I. The transcriptional and regulatory identity of erythropoietin producing cells. Nat Med 2023; 29:1191-1200. [PMID: 37106166 DOI: 10.1038/s41591-023-02314-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 03/17/2023] [Indexed: 04/29/2023]
Abstract
Erythropoietin (Epo) is the master regulator of erythropoiesis and oxygen homeostasis. Despite its physiological importance, the molecular and genomic contexts of the cells responsible for renal Epo production remain unclear, limiting more-effective therapies for anemia. Here, we performed single-cell RNA and transposase-accessible chromatin (ATAC) sequencing of an Epo reporter mouse to molecularly identify Epo-producing cells under hypoxic conditions. Our data indicate that a distinct population of kidney stroma, which we term Norn cells, is the major source of endocrine Epo production in mice. We use these datasets to identify the markers, signaling pathways and transcriptional circuits characteristic of Norn cells. Using single-cell RNA sequencing and RNA in situ hybridization in human kidney tissues, we further provide evidence that this cell population is conserved in humans. These preliminary findings open new avenues to functionally dissect EPO gene regulation in health and disease and may serve as groundwork to improve erythropoiesis-stimulating therapies.
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Affiliation(s)
- Bjørt K Kragesteen
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel.
| | - Amir Giladi
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, Utrecht, the Netherlands
- Oncode Institute, Utrecht, the Netherlands
| | - Eyal David
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Shahar Halevi
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Laufey Geirsdóttir
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Olga M Lempke
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Baoguo Li
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Andreas M Bapst
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Ken Xie
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | | | - Sophie L Dahl
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Fadi Sheban
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Anna Gurevich-Shapiro
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
- Division of Haematology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Mor Zada
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Truong San Phan
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Roberto Avellino
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Shuang-Yin Wang
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Oren Barboy
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Shir Shlomi-Loubaton
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Sandra Winning
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany
| | | | - Snir Dekalo
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Urology Department, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
| | - Hadas Keren-Shaul
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Merav Kedmi
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Martin Sikora
- GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Joachim Fandrey
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany
| | | | - Josef T Prchal
- Department of Medicine, University of Utah, Salt Lake City, UT, USA
| | - Barak Rosenzweig
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Department of Urology, Sheba Medical Center, Ramat Gan, Israel
| | - Vladimir Yutkin
- Department of Urology, Hadassah Medical Center, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Fernando Racimo
- GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Eske Willerslev
- GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Chamutal Gur
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel
- Department of Medicine, Hadassah Medical Center, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Roland H Wenger
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- National Centre of Competence in Research 'Kidney.CH', University of Zurich, Zurich, Switzerland
| | - Ido Amit
- Department of Systems Immunology, Weizmann Institute of Science, Rehovot, Israel.
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8
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Labes R, Roegner K. Prolyl hydroxylase inhibitors, polydrug use, and the phosphoproteome. Acta Physiol (Oxf) 2023; 237:e13898. [PMID: 36251506 DOI: 10.1111/apha.13898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 10/14/2022] [Indexed: 01/03/2023]
Affiliation(s)
- Robert Labes
- Institute of Translational Physiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Kameliya Roegner
- Institute of Translational Physiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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9
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Locatelli F, Del Vecchio L. Hypoxia-Inducible Factor-Prolyl Hydroxyl Domain Inhibitors: From Theoretical Superiority to Clinical Noninferiority Compared with Current ESAs? J Am Soc Nephrol 2022; 33:1966-1979. [PMID: 36041790 PMCID: PMC9678041 DOI: 10.1681/asn.2022040413] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Anemia is a common complication of chronic kidney disease; it is mainly treated with erythropoiesis-stimulating agents (ESAs) and iron. Experimental studies extensively investigated the mechanisms involved in the body's response to hypoxia and led to the discovery of the hypoxia-inducible factor (HIF) pathway and the enzymes regulating its function. HIF-prolyl-hydroxyl domain (PHD) inhibitors are a new class of oral drugs developed to treat anemia in chronic kidney disease. By inhibiting the function of PHD enzymes, they mimic the exposure to moderate hypoxia and stimulate the production of endogenous erythropoietin and very likely increase iron availability. Some data also suggest that their efficacy and, consequently, dose needs are less influenced by inflammation than ESAs. Overall, data from phases 2 and 3 clinical development showed efficacy in anemia correction and maintenance for all of the class molecules compared with placebo (superiority) or erythropoiesis-stimulating agents (noninferiority). Three molecules, roxadustat, vadadustat, and daprodustat, underwent extensive clinical investigation to assess their safety on hard cardiovascular end points, mortality, and special interest events (including cancer and thrombosis). Aside from vadadustat in the nondialysis population, at the prespecified primary analyses, all three molecules met the noninferiority margin for the risk of major cardiovascular events compared with erythropoiesis-stimulating agents or placebo. The reason for this discrepancy is difficult to explain. Other safety signals came from secondary analyses of some of the other randomized clinical trials, including a higher incidence of thrombosis. A more extensive clinical experience with post-marketing data on hard safety issues is needed to define better when and how to use HIF-PHD inhibitors compared with already available ESAs.
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Affiliation(s)
- Francesco Locatelli
- Department of Nephrology and Dialysis, Alessandro Manzoni Hospital (past Director) ASST Lecco, Lecco, Italy
| | - Lucia Del Vecchio
- Department of Nephrology and Dialysis, Sant’Anna Hospital, ASST Lariana, Como, Italy
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10
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Fuchs MAA, Kurtz A. The fate of erythropoietin-producing cells: another piece of the puzzle. Kidney Int 2022; 102:230-233. [PMID: 35870811 DOI: 10.1016/j.kint.2022.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 05/18/2022] [Accepted: 05/19/2022] [Indexed: 10/17/2022]
Abstract
In this issue, Kaneko et al. reported the generation of a mouse line that allows for the labeling of cells under control of the erythropoietin (Epo) gene promotor. The authors show that Epo-producing cells become proliferating, profibrotic cells after kidney injury and lose their ability to produce Epo. Furthermore, they show that the fluorescent-labeled cells can recover their Epo synthesis capability subsequently to a recovery period.
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Affiliation(s)
| | - Armin Kurtz
- Institute of Physiology, University of Regensburg, Regensburg, Germany
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11
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Schley G, Hartner A. The Prolyl hydroxylase inhibitor molidustat fails to restore erythropoietin production in the fibrotic kidney. Acta Physiol (Oxf) 2022; 235:e13858. [PMID: 35768895 DOI: 10.1111/apha.13858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 06/27/2022] [Accepted: 06/27/2022] [Indexed: 11/29/2022]
Affiliation(s)
- Gunnar Schley
- Departments of Nephrology and Hypertension , Friedrich-Alexander University Erlangen-Nürnberg (FAU) and University Hospital Erlangen, Erlangen, Germany
| | - Andrea Hartner
- Pediatrics and Adolescent Medicine, Friedrich-Alexander University Erlangen-Nürnberg (FAU) and University Hospital Erlangen, Erlangen, Germany
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12
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Fount, fate, features, and function of renal erythropoietin-producing cells. Pflugers Arch 2022; 474:783-797. [PMID: 35750861 PMCID: PMC9338912 DOI: 10.1007/s00424-022-02714-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 05/18/2022] [Accepted: 05/27/2022] [Indexed: 12/19/2022]
Abstract
Renal erythropoietin (Epo)-producing (REP) cells represent a rare and incompletely understood cell type. REP cells are fibroblast-like cells located in close proximity to blood vessels and tubules of the corticomedullary border region. Epo mRNA in REP cells is produced in a pronounced “on–off” mode, showing transient transcriptional bursts upon exposure to hypoxia. In contrast to “ordinary” fibroblasts, REP cells do not proliferate ex vivo, cease to produce Epo, and lose their identity following immortalization and prolonged in vitro culture, consistent with the loss of Epo production following REP cell proliferation during tissue remodelling in chronic kidney disease. Because Epo protein is usually not detectable in kidney tissue, and Epo mRNA is only transiently induced under hypoxic conditions, transgenic mouse models have been developed to permanently label REP cell precursors, active Epo producers, and inactive descendants. Future single-cell analyses of the renal stromal compartment will identify novel characteristic markers of tagged REP cells, which will provide novel insights into the regulation of Epo expression in this unique cell type.
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Abstract
Cellular hypoxia occurs when the demand for sufficient molecular oxygen needed to produce the levels of ATP required to perform physiological functions exceeds the vascular supply, thereby leading to a state of oxygen depletion with the associated risk of bioenergetic crisis. To protect against the threat of hypoxia, eukaryotic cells have evolved the capacity to elicit oxygen-sensitive adaptive transcriptional responses driven primarily (although not exclusively) by the hypoxia-inducible factor (HIF) pathway. In addition to the canonical regulation of HIF by oxygen-dependent hydroxylases, multiple other input signals, including gasotransmitters, non-coding RNAs, histone modifiers and post-translational modifications, modulate the nature of the HIF response in discreet cell types and contexts. Activation of HIF induces various effector pathways that mitigate the effects of hypoxia, including metabolic reprogramming and the production of erythropoietin. Drugs that target the HIF pathway to induce erythropoietin production are now approved for the treatment of chronic kidney disease-related anaemia. However, HIF-dependent changes in cell metabolism also have profound implications for functional responses in innate and adaptive immune cells, and thereby heavily influence immunity and the inflammatory response. Preclinical studies indicate a potential use of HIF therapeutics to treat inflammatory diseases, such as inflammatory bowel disease. Understanding the links between HIF, cellular metabolism and immunity is key to unlocking the full therapeutic potential of drugs that target the HIF pathway. Hypoxia-dependent changes in cellular metabolism have important implications for the effective functioning of multiple immune cell subtypes. This Review describes the inputs that shape the hypoxic response in individual cell types and contexts, and the implications of this response for cellular metabolism and associated alterations in immune cell function. Hypoxia is a common feature of particular microenvironments and at sites of immunity and inflammation, resulting in increased activity of the hypoxia-inducible factor (HIF). In addition to hypoxia, multiple inputs modulate the activity of the HIF pathway, allowing nuanced downstream responses in discreet cell types and contexts. HIF-dependent changes in cellular metabolism mitigate the effects of hypoxia and ensure that energy needs are met under conditions in which oxidative phosphorylation is reduced. HIF-dependent changes in metabolism also profoundly affect the phenotype and function of immune cells. The immunometabolic effects of HIF have important implications for targeting the HIF pathway in inflammatory disease.
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Affiliation(s)
- Cormac T Taylor
- School of Medicine, The Conway Institute & Systems Biology Ireland, University College Dublin, Belfield, Dublin, Ireland.
| | - Carsten C Scholz
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,Institute of Physiology, University Medicine Greifswald, Greifswald, Germany
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14
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Kobayashi H, Davidoff O, Pujari‐Palmer S, Drevin M, Haase VH. EPO synthesis induced by HIF-PHD inhibition is dependent on myofibroblast transdifferentiation and colocalizes with non-injured nephron segments in murine kidney fibrosis. Acta Physiol (Oxf) 2022; 235:e13826. [PMID: 35491502 PMCID: PMC9329237 DOI: 10.1111/apha.13826] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/14/2022] [Accepted: 04/28/2022] [Indexed: 12/22/2022]
Abstract
AIM Erythropoietin (EPO) is regulated by hypoxia-inducible factor (HIF)-2. In the kidney, it is produced by cortico-medullary perivascular interstitial cells, which transdifferentiate into collagen-producing myofibroblasts in response to injury. Inhibitors of prolyl hydroxylase domain (PHD) dioxygenases (HIF-PHIs) activate HIF-2 and stimulate kidney and liver EPO synthesis in patients with anemia of chronic kidney disease (CKD). We examined whether HIF-PHIs can reactivate EPO synthesis in interstitial cells that have undergone myofibroblast transdifferentiation in established kidney fibrosis. METHODS We investigated Epo transcription in myofibroblasts and characterized the histological distribution of kidney Epo transcripts by RNA in situ hybridization combined with immunofluorescence in mice with adenine nephropathy (AN) treated with HIF-PHI molidustat. Lectin absorption chromatography was used to assess liver-derived EPO. In addition, we examined kidney Epo transcription in Phd2 knockout mice with obstructive nephropathy. RESULTS In AN, molidustat-induced Epo transcripts were not found in areas of fibrosis and did not colocalize with interstitial cells that expressed α-smooth muscle actin, a marker of myofibroblast transdifferentiation. Epo transcription was associated with megalin-expressing, kidney injury molecule 1-negative nephron segments and contingent on residual renal function. Liver-derived EPO did not contribute to serum EPO in molidustat-treated mice. Epo transcription was not associated with myofibroblasts in Phd2 knockout mice with obstructive nephropathy. CONCLUSIONS Our studies suggest that HIF-PHIs do not reactivate Epo transcription in interstitial myofibroblasts and that their efficacy in inducing kidney EPO in CKD is dependent on the degree of myofibroblast formation, the preservation of renal parenchyma and the level of residual renal function.
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Affiliation(s)
- Hanako Kobayashi
- Department of Medicine Vanderbilt University Medical Center and Vanderbilt University School of Medicine Nashville Tennessee USA
- Medical and Research Services Department of Veterans Affairs Hospital Tennessee Valley Healthcare System Nashville Tennessee USA
| | - Olena Davidoff
- Department of Medicine Vanderbilt University Medical Center and Vanderbilt University School of Medicine Nashville Tennessee USA
- Medical and Research Services Department of Veterans Affairs Hospital Tennessee Valley Healthcare System Nashville Tennessee USA
| | | | | | - Volker H. Haase
- Department of Medicine Vanderbilt University Medical Center and Vanderbilt University School of Medicine Nashville Tennessee USA
- Medical and Research Services Department of Veterans Affairs Hospital Tennessee Valley Healthcare System Nashville Tennessee USA
- Department of Molecular Physiology & Biophysics and Program in Cancer Biology Vanderbilt University School of Medicine Nashville Tennessee USA
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15
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Bapst AM, Knöpfel T, Nolan KA, Imeri F, Schuh CD, Hall AM, Guo J, Katschinski DM, Wenger RH. Neurogenic and pericytic plasticity of conditionally immortalized cells derived from renal erythropoietin-producing cells. J Cell Physiol 2022; 237:2420-2433. [PMID: 35014036 PMCID: PMC9303970 DOI: 10.1002/jcp.30677] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 12/17/2021] [Accepted: 12/22/2021] [Indexed: 12/19/2022]
Abstract
In adult mammals, the kidney is the main source of circulating erythropoietin (Epo), the master regulator of erythropoiesis. In vivo data in mice demonstrated multiple subtypes of interstitial renal Epo‐producing (REP) cells. To analyze the differentiation plasticity of fibroblastoid REP cells, we used a transgenic REP cell reporter mouse model to generate conditionally immortalized REP‐derived (REPD) cell lines. Under nonpermissive conditions, REPD cells ceased from proliferation and acquired a stem cell‐like state, with strongly enhanced hypoxia‐inducible factor 2 (HIF‐2α), stem cell antigen 1 (SCA‐1), and CD133 expression, but also enhanced alpha‐smooth muscle actin (αSMA) expression, indicating myofibroblastic signaling. These cells maintained the “on‐off” nature of Epo expression observed in REP cells in vivo, whereas other HIF target genes showed a more permanent regulation. Like REP cells in vivo, REPD cells cultured in vitro generated long tunneling nanotubes (TNTs) that aligned with endothelial vascular structures, were densely packed with mitochondria and became more numerous under hypoxic conditions. Although inhibition of mitochondrial oxygen consumption blunted HIF signaling, removal of the TNTs did not affect or even enhance the expression of HIF target genes. Apart from pericytes, REPD cells readily differentiated into neuroglia but not adipogenic, chondrogenic, or osteogenic lineages, consistent with a neuronal origin of at least a subpopulation of REP cells. In summary, these results suggest an unprecedented combination of differentiation features of this unique cell type.
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Affiliation(s)
- Andreas M Bapst
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Thomas Knöpfel
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Karen A Nolan
- Institute of Physiology, University of Zürich, Zürich, Switzerland.,National Centre of Competence in Research "Kidney.CH", University of Zürich, Zürich, Switzerland
| | - Faik Imeri
- Institute of Physiology, University of Zürich, Zürich, Switzerland.,National Centre of Competence in Research "Kidney.CH", University of Zürich, Zürich, Switzerland
| | - Claus D Schuh
- National Centre of Competence in Research "Kidney.CH", University of Zürich, Zürich, Switzerland.,Institute of Anatomy, University of Zürich, Zürich, Switzerland
| | - Andrew M Hall
- National Centre of Competence in Research "Kidney.CH", University of Zürich, Zürich, Switzerland.,Institute of Anatomy, University of Zürich, Zürich, Switzerland
| | - Jia Guo
- Institute for Cardiovascular Physiology, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - Dörthe M Katschinski
- Institute for Cardiovascular Physiology, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - Roland H Wenger
- Institute of Physiology, University of Zürich, Zürich, Switzerland.,National Centre of Competence in Research "Kidney.CH", University of Zürich, Zürich, Switzerland
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