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Rassol N, Andersson C, Pettersson D, Al-Awar A, Shubbar E, Kovács A, Åkerström B, Gram M, Helou K, Forssell-Aronsson E. Co-administration with A1M does not influence apoptotic response of 177Lu-octreotate in GOT1 neuroendocrine tumors. Sci Rep 2023; 13:6417. [PMID: 37076494 PMCID: PMC10115890 DOI: 10.1038/s41598-023-32091-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 03/22/2023] [Indexed: 04/21/2023] Open
Abstract
Recombinant α1-microglobulin (A1M) is a proposed radioprotector during 177Lu-octreotate therapy of neuroendocrine tumors (NETs). To ensure a maintained therapeutic effect, we previously demonstrated that A1M does not affect the 177Lu-octreotate induced decrease in GOT1 tumor volume. However, the underlying biological events of these findings are still unknown. The aim of this work was to examine the regulation of apoptosis-related genes in GOT1 tumors short-time after i.v. administration of 177Lu-octreotate with and without A1M or A1M alone. Human GOT1 tumor-bearing mice received 30 MBq 177Lu-octreotate or 5 mg/kg A1M or co-treatment with both. Animals were sacrificed after 1 or 7 days. Gene expression analysis of apoptosis-related genes in GOT1 tissue was performed with RT-PCR. In general, similar expression patterns of pro- and anti-apoptotic genes were found after 177Lu-octreotate exposure with or without co-administration of A1M. The highest regulated genes in both irradiated groups compared to untreated controls were FAS and TNFSFRS10B. Administration of A1M alone only resulted in significantly regulated genes after 7 days. Co-administration of A1M did not negatively affect the transcriptional apoptotic response of 177Lu-octreotate in GOT1 tumors.
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Affiliation(s)
- Nishte Rassol
- Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
- Sahlgrenska Center for Cancer Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
| | - Charlotte Andersson
- Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Sahlgrenska Center for Cancer Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Daniella Pettersson
- Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Sahlgrenska Center for Cancer Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Amin Al-Awar
- Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Sahlgrenska Center for Cancer Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Emman Shubbar
- Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Sahlgrenska Center for Cancer Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Anikó Kovács
- Department of Clinical Pathology, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Bo Åkerström
- Department of Clinical Sciences, Infection Medicine, Lund University, Lund, Sweden
| | - Magnus Gram
- Neonatology Unit, Department of Clinical Sciences, Pediatrics, Lund University, Lund, Sweden
| | - Khalil Helou
- Sahlgrenska Center for Cancer Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Oncology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Eva Forssell-Aronsson
- Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Sahlgrenska Center for Cancer Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden
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Bergwik J, Kristiansson A, Larsson J, Ekström S, Åkerström B, Allhorn M. Binding of the human antioxidation protein α 1-microglobulin (A1M) to heparin and heparan sulfate. Mapping of binding site, molecular and functional characterization, and co-localization in vivo and in vitro. Redox Biol 2021; 41:101892. [PMID: 33607500 PMCID: PMC7900767 DOI: 10.1016/j.redox.2021.101892] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/03/2021] [Accepted: 02/04/2021] [Indexed: 12/27/2022] Open
Abstract
Heparin and heparan sulfate (HS) are linear sulfated disaccharide polymers. Heparin is found mainly in mast cells, while heparan sulfate is found in connective tissue, extracellular matrix and on cell membranes in most tissues. α1-microglobulin (A1M) is a ubiquitous protein with thiol-dependent antioxidant properties, protecting cells and matrix against oxidative damage due to its reductase activities and radical- and heme-binding properties. In this work, it was shown that A1M binds to heparin and HS and can be purified from human plasma by heparin affinity chromatography and size exclusion chromatography. The binding strength is inversely dependent of salt concentration and proportional to the degree of sulfation of heparin and HS. Potential heparin binding sites, located on the outside of the barrel-shaped A1M molecule, were determined using hydrogen deuterium exchange mass spectrometry (HDX-MS). Immunostaining of endothelial cells revealed pericellular co-localization of A1M and HS and the staining of A1M was almost completely abolished after treatment with heparinase. A1M and HS were also found to be co-localized in vivo in the lungs, aorta, kidneys and skin of mice. The redox-active thiol group of A1M was unaffected by the binding to HS, and the cell protection and heme-binding abilities of A1M were slightly affected. The discovery of the binding of A1M to heparin and HS provides new insights into the biological role of A1M and represents the basis for a novel method for purification of A1M from plasma.
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Affiliation(s)
- Jesper Bergwik
- Section for Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden.
| | - Amanda Kristiansson
- Section for Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Jörgen Larsson
- Section for Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Simon Ekström
- Swedish National Infrastructure for Biological Mass Spectrometry (BioMS), Lund University, Lund, Sweden
| | - Bo Åkerström
- Section for Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Maria Allhorn
- Section for Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
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Strategies Towards Improving Clinical Outcomes of Peptide Receptor Radionuclide Therapy. Curr Oncol Rep 2021; 23:46. [PMID: 33721105 PMCID: PMC7960621 DOI: 10.1007/s11912-021-01037-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/26/2021] [Indexed: 02/07/2023]
Abstract
Purpose of Review Peptide receptor radionuclide therapy (PRRT) with [177Lu-DOTA0,Tyr3] octreotate is an effective and safe second- or third-line treatment option for patients with low-grade advanced gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN). In this review, we will focus on possible extensions of the current use of PRRT and on new approaches which could further improve its treatment efficacy and safety. Recent Findings Promising results were published regarding PRRT in other NENs, including lung NENs or high-grade NENs, and applying PRRT as neoadjuvant or salvage therapy. Furthermore, a diversity of strategic approaches, including dosimetry, somatostatin receptor antagonists, somatostatin receptor upregulation, radiosensitization, different radionuclides, albumin binding, alternative renal protection, and liver-directed therapy in combination with PRRT, have the potential to improve the outcome of PRRT. Also, novel biomarkers are presented that could predict response to PRRT. Summary Multiple preclinical and early clinical studies have shown encouraging potential to advance the clinical outcome of PRRT in NEN patients. However, at this moment, most of these strategies have not yet reached the clinical setting of randomized phase III trials.
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177Lu-PSMA-617 Therapy in Mice, with or without the Antioxidant α 1-Microglobulin (A1M), Including Kidney Damage Assessment Using 99mTc-MAG3 Imaging. Biomolecules 2021; 11:biom11020263. [PMID: 33579037 PMCID: PMC7916794 DOI: 10.3390/biom11020263] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 02/05/2021] [Accepted: 02/06/2021] [Indexed: 12/31/2022] Open
Abstract
Anti-prostate specific membrane antigen (PSMA) radioligand therapy is promising but not curative in castration resistant prostate cancer. One way to broaden the therapeutic index could be to administer higher doses in combination with radioprotectors, since administered radioactivity is kept low today in order to avoid side-effects from a high absorbed dose to healthy tissue. Here, we investigated the human radical scavenger α1-microglobulin (A1M) together with 177-Lutetium (177Lu) labeled PSMA-617 in preclinical models with respect to therapeutic efficacy and kidney toxicity. Nude mice with subcutaneous LNCaP xenografts were injected with 50 or 100 MBq of [177Lu]Lu-PSMA-617, with or without injections of recombinant A1M (rA1M) (at T = 0 and T = 24 h). Kidney absorbed dose was calculated to 7.36 Gy at 4 days post a 100 MBq injection. Activity distribution was imaged with Single-Photon Emission Computed Tomography (SPECT) at 24 h. Tumor volumes were measured continuously, and kidneys and blood were collected at termination (3–4 days and 3–4 weeks after injections). In a parallel set of experiments, mice were given [177Lu]Lu-PSMA-617 and rA1M as above and dynamic technetium-99m mercaptoacetyltriglycine ([99mTc]Tc-MAG3) SPECT imaging was performed prior to injection, and 3- and 6-months post injection. Blood and urine were continuously sampled. At termination (6 months) the kidneys were resected. Biomarkers of kidney function, expression of stress genes and kidney histopathology were analyzed. [177Lu]Lu-PSMA-617 uptake, in tumors and kidneys, as well as treatment efficacy did not differ between rA1M and vehicle groups. In mice given rA1M, [99mTc]Tc-MAG3 imaging revealed a significantly higher slope of initial uptake at three months compared to mice co-injected with [177Lu]Lu-PSMA-617 and vehicle. Little or no change compared to control was seen in urine albumin, serum/plasma urea levels, RT-qPCR analysis of stress response genes and in the kidney histopathological evaluation. In conclusion, [99mTc]Tc-MAG3 imaging presented itself as a sensitive tool to detect changes in kidney function revealing that administration of rA1M has a potentially positive effect on kidney perfusion and tubular function when combined with [177Lu]Lu-PSMA-617 therapy. Furthermore, we could show that rA1M did not affect anti-PSMA radioligand therapy efficacy.
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Pregnant alpha-1-microglobulin (A1M) knockout mice exhibit features of kidney and placental damage, hemodynamic changes and intrauterine growth restriction. Sci Rep 2020; 10:20625. [PMID: 33244052 PMCID: PMC7691512 DOI: 10.1038/s41598-020-77561-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 11/11/2020] [Indexed: 11/09/2022] Open
Abstract
Alpha-1-microglobulin (A1M) is an antioxidant previously shown to be elevated in maternal blood during pregnancies complicated by preeclampsia and suggested to be important in the endogenous defense against oxidative stress. A knockout mouse model of A1M (A1Mko) was used in the present study to assess the importance of A1M during pregnancy in relation to the kidney, heart and placenta function. Systolic blood pressure (SBP) and heart rate (HR) were determined before and throughout gestation. The morphology of the organs was assessed by both light and electron microscopy. Gene expression profiles relating to vascular tone and oxidative stress were analyzed using RT-qPCR with validation of selected gene expression relating to vascular tone and oxidative stress response. Pregnant age-matched wild type mice were used as controls. In the A1Mko mice there was a significantly higher SBP before pregnancy that during pregnancy was significantly reduced compared to the control. In addition, the HR was higher both before and during pregnancy compared to the controls. Renal morphological abnormalities were more frequent in the A1Mko mice, and the gene expression profiles in the kidney and the heart showed downregulation of transcripts associated with vasodilation. Simultaneously, an upregulation of vasoconstrictors, blood pressure regulators, and genes for osmotic stress response, ion transport and reactive oxygen species (ROS) metabolism occurred. Fetal weight was lower in the A1Mko mice at E17.5. The vessels in the labyrinth zone of the placentas and the endoplasmic reticulum in the spongiotrophoblasts were collapsed. The gene profiles in the placenta showed downregulation of antioxidants, ROS metabolism and oxidative stress response genes. In conclusion, intact A1M expression is necessary for the maintenance of normal kidney, heart as well as placental structure and function for a normal pregnancy adaptation.
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Andersson CK, Shubbar E, Schüler E, Åkerström B, Gram M, Forssell-Aronsson EB. Recombinant α 1-Microglobulin Is a Potential Kidney Protector in 177Lu-Octreotate Treatment of Neuroendocrine Tumors. J Nucl Med 2019; 60:1600-1604. [PMID: 30926650 DOI: 10.2967/jnumed.118.225243] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/19/2019] [Indexed: 12/30/2022] Open
Abstract
Treatment of neuroendocrine tumors with 177Lu-octreotate results in prolonged survival and improved quality of life for the patient. However, the treatment is today limited by side effects on kidney and bone marrow, and complete tumor remission is rarely seen. A possible way to minimize dose-limiting toxicity and to optimize this treatment method is to use radioprotectors in conjunction with radiotherapy. A recombinant form of α1-microglobulin (rA1M) was recently shown to preserve kidney structure and function after 177Lu-octreotate injection in mice and was suggested as a radioprotector in peptide receptor radionuclide therapy. The aims of this work were to investigate the influence of rA1M on the in vivo biokinetics of 177Lu-octreotate, with a focus on tumor tissue, and to study the impact of rA1M on the therapeutic response in tumor tissue subjected to 177Lu-octreotate treatment. Methods: The biodistribution of 177Lu-octreotate was examined in BALB/c nude mice with GOT2 tumors 1-168 h after injection with either 177Lu-octreotate or coadministration of 177Lu-octreotate and rA1M. The effects of rA1M on the tumor response after 177Lu-octreotate treatment were studied in BALB/c nude mice with GOT1 tumors. Three groups of mice were administered rA1M, 177Lu-octreotate, or both. Another group served as untreated controls. Tumor volume was measured to follow the treatment effects. Results: No statistically significant difference in biodistribution of 177Lu was observed between the groups receiving 177Lu-octreotate or coinjection of 177Lu-octreotate and rA1M. The therapy study showed a decrease in mean tumor volume during the first 2 wk for both the 177Lu-octreotate group and the coadministration group, followed by tumor regrowth. No statistically significant difference between the groups was found. Conclusion: rA1M did not negatively impact absorbed dose to tumor or therapeutic response in combination with 177Lu-octreotate and may be a promising kidney protector during 177Lu-octreotate treatment of patients with neuroendocrine tumors.
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Affiliation(s)
- Charlotte K Andersson
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Cancer Center, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Emman Shubbar
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Cancer Center, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Emil Schüler
- Department of Radiation Oncology, Stanford School of Medicine, Stanford University, Stanford, California
| | - Bo Åkerström
- Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden; and
| | - Magnus Gram
- Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden; and.,A1M Pharma AB, Lund, Sweden
| | - Eva B Forssell-Aronsson
- Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Cancer Center, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
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Chen H, Lin H, Xu M, Xu G, Fang X, He L, Chen Z, Wu Z, Geng H. Quantitative Urinary Proteome Reveals Potential Biomarkers for Ureteropelvic Junction Obstruction. Proteomics Clin Appl 2018; 13:e1800101. [PMID: 30471240 DOI: 10.1002/prca.201800101] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Revised: 11/08/2018] [Indexed: 01/07/2023]
Affiliation(s)
- Honghao Chen
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
| | - Houwei Lin
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
| | - Maosheng Xu
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
| | - Guofeng Xu
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
| | - Xiaoliang Fang
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
| | - Lei He
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
| | - Zhoutong Chen
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
| | - Zhixiang Wu
- Department of Pediatric SurgeryXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Hongquan Geng
- Department of Pediatric UrologyXinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine 200092 Shanghai China
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Larsson S, Åkerström B, Gram M, Lohmander LS, Struglics A. α1-Microglobulin Protects Against Bleeding-Induced Oxidative Damage in Knee Arthropathies. Front Physiol 2018; 9:1596. [PMID: 30505280 PMCID: PMC6250851 DOI: 10.3389/fphys.2018.01596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 10/24/2018] [Indexed: 11/13/2022] Open
Abstract
Knee injury increases the risk of developing knee osteoarthritis (OA). Recent evidence suggests involvement of oxidative stress induced by inflammation and bleeding in the joint. This study investigates the role in this process of α1-microglobulin (A1M), a plasma and tissue antioxidant protein with reducing function, and heme- and radical-binding properties. We studied matched knee synovial fluid (sf) and serum (s) samples from 122 subjects (mean age 40 years, 31% females): 10 were knee healthy references, 13 had acute inflammatory arthritis (AIA), 79 knee injury 0–10 years prior to sampling, and 20 knee OA. Using immunoassays, we measured sf-A1M and s-A1M, sf-hemoglobin (sf-Hb), sf-total free heme (sf-Heme), and sf-carbonyl groups (sf-Carbonyl). We explored associations by partial correlation, or linear regression models with adjustments for age, sex and diagnosis, and evaluated diagnostic capacity by area under the receiver operator characteristics curve (AUC). The AIA group had 1.2- to 1.7-fold higher sf-A1M and s-A1M concentrations compared to the other diagnostic groups; other biomarkers showed no between-group differences. sf-A1M and s-A1M were with AUC of 0.76 and 0.78, respectively, diagnostic for AIA. In the injury group, the amount of bleeding in the joint was inversely correlated to time after injury when measured as sf-Heme (r = -0.41, p < 0.001), but not when measured as sf-Hb (r = -0.19, p = 0.098). A similar inverse association with time after injury was noted for sf-A1M (r = -0.30, p = 0.007), but not for s-A1M and sf-Carbonyl. Linear regression models showed that sf-Heme was more strongly associated with sf-A1M and sf-Carbonyl than sf-Hb. Independent of diagnosis, sf-Heme explained 5.7% of the variability in sf-A1M and 3.0% in the variability in sf-Carbonyl, but appeared unrelated to s-A1M. High sf-A1M and low sf-Heme or sf-Hb were independently associated with low sf-Carbonyl. In conclusion, our results demonstrate that independent of disease, Hb and heme within a knee joint correlates with an increased sf-A1M concentration that appears to be protective of oxidative damage, i.e., a reduction in carbonyl groups. High concentrations of A1M in synovial fluid and serum was further diagnostic for AIA.
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Affiliation(s)
- Staffan Larsson
- Department of Clinical Sciences Lund, Orthopaedics, Faculty of Medicine, Lund University, Lund, Sweden
- *Correspondence: Staffan Larsson,
| | - Bo Åkerström
- Department of Clinical Sciences Lund, Infection Medicine, Faculty of Medicine, Lund University, Lund, Sweden
| | - Magnus Gram
- Department of Clinical Sciences Lund, Infection Medicine, Faculty of Medicine, Lund University, Lund, Sweden
| | - L. Stefan Lohmander
- Department of Clinical Sciences Lund, Orthopaedics, Faculty of Medicine, Lund University, Lund, Sweden
| | - André Struglics
- Department of Clinical Sciences Lund, Orthopaedics, Faculty of Medicine, Lund University, Lund, Sweden
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Abstract
Alpha 1 microglobulin is a low molecular weight heme binding antioxidant protein with interesting, and potentially important, clinical applications. However, much remains to be learned about its in vivo effects. This invited review raises a number of physiologic issues regarding this compound as it pertains to clinical use.
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Affiliation(s)
- Richard A Zager
- Department of Medicine, University of Washington, Seattle, WA, USA
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Zager RA, Johnson ACM, Frostad K. An evaluation of the antioxidant protein α1-microglobulin as a renal tubular cytoprotectant. Am J Physiol Renal Physiol 2016; 311:F640-51. [DOI: 10.1152/ajprenal.00264.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 05/04/2016] [Indexed: 11/22/2022] Open
Abstract
α1-Microglobulin (A1M) is a low-molecular-weight heme-binding antioxidant protein that is readily filtered by the glomerulus and reabsorbed by proximal tubules. Given these properties, recombinant A1M (rA1M) has been proposed as a renal antioxidant and therapeutic agent. However, little direct evidence to support this hypothesis exists. Hence, we have sought “proof of concept” in this regard. Cultured proximal tubule (HK-2) cells or isolated mouse proximal tubule segments were challenged with a variety of prooxidant insults: 1) hemin, 2) myoglobin; 3) “catalytic” iron, 4) H2O2/Fenton reagents, 5) a Ca2+ ionophore, 6) antimycin A, or 7) hypoxia (with or without rA1M treatment). HK-2 injury was gauged by the percent lactate dehydrogenase release and 4,5-(dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide uptake. In vivo protection was sought in rA1M-treated mice subjected to 1) graded myohemoglobinura (2, 4, 8, or 9 ml/kg glycerol injection), 2) purified myoglobinemia/uria, or 3) endotoxemia. In vivo injury was assessed by blood urea nitrogen, creatinine, and the expression of redox-sensitive genes (heme oxygenase-1, neutrophil gelatinase-associated lipocalin, and monocyte chemoattractant protein-1 mRNAs). Although rA1M totally blocked in vitro hemin toxicity, equimolar albumin (another heme binder) or 10% serum induced equal protection. rA1M failed to mitigate any nonhemin forms of either in vitro or in vivo injury. A1M appeared to be rapidly degraded within proximal tubules (by Western blot analysis). Surprisingly, rA1M exerted select injury-promoting effects (increased in vitro catalytic iron/antimycin toxicities and increased in vivo monocyte chemoattractant protein-1/neutrophil gelatinase-associated lipocalin mRNA expression after glycerol or endotoxin injection). We conclude that rA1M has questionable utility as a renal antioxidant/cytoprotective agent, particularly in the presence of larger amounts of competitive free heme (e.g., albumin) binders.
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Affiliation(s)
- Richard A. Zager
- Fred Hutchinson Cancer Center, Seattle, Washington; and
- University of Washington, Seattle Washington
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