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Vitamin E Analogs as Radiation Response Modifiers. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2015; 2015:741301. [PMID: 26366184 PMCID: PMC4558447 DOI: 10.1155/2015/741301] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 05/06/2015] [Accepted: 07/22/2015] [Indexed: 02/07/2023]
Abstract
The potentially life-threatening effects of total body ionizing radiation exposure have been known for more than a century. Despite considerable advances in our understanding of the effects of radiation over the past six decades, efforts to identify effective radiation countermeasures for use in case of a radiological/nuclear emergency have been largely unsuccessful. Vitamin E is known to have antioxidant properties capable of scavenging free radicals, which have critical roles in radiation injuries. Tocopherols and tocotrienols, vitamin E analogs together known as tocols, have shown promise as radioprotectors. Although the pivotal mechanisms of action of tocols have long been thought to be their antioxidant properties and free radical scavenging activities, other alternative mechanisms have been proposed to drive their activity as radioprotectors. Here we provide a brief overview of the effects of ionizing radiation, the mechanistic mediators of radiation-induced damage, and the need for radiation countermeasures. We further outline the role for, efficacy of, and mechanisms of action of tocols as radioprotectors, and we compare and contrast their efficacy and mode of action with that of another well-studied chemical radioprotector, amifostine.
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Singh VK, Romaine PLP, Newman VL, Seed TM. Tocols induce G-CSF and mobilise progenitors that mitigate radiation injury. RADIATION PROTECTION DOSIMETRY 2014; 162:83-87. [PMID: 24993008 PMCID: PMC4434803 DOI: 10.1093/rpd/ncu223] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Tocols induce high levels of granulocyte-colony-stimulating factor (G-CSF). G-CSF mobilises progenitors that allow mice that have been severely immunocompromised by exposure to acute, high-dose ionising irradiation to recover and to survive. The neutralisation of G-CSF abrogates the radioprotective efficacy of tocols. This article reviews studies in which CD2F1 mice were irradiated with sufficiently high doses to cause acute radiation syndrome symptoms and then administered (iv) progenitor-enriched whole blood or peripheral blood mononuclear cells from tocol- and AMD3100-injected donor mice (AMD3100 is a chemokine receptor antagonist used to improve the yield of mobilised progenitors). In some experiments, G-CSF was neutralised completely. Irradiated recipient mice were observed for 30 d post-irradiation for survival, a primary endpoint used for determining therapeutic effectiveness. Additionally, potential tocol-induced biomarkers (cytokines, chemokines and growth factors) were quantified. The authors suggest that tocols are highly effective agents for mobilising progenitors with significant therapeutic potential.
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Affiliation(s)
- Vijay K Singh
- Armed Forces Radiobiology Research Institute, Bethesda, MD, USA
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Singh VK, Wise SY, Fatanmi OO, Beattie LA, Seed TM. Preclinical development of a bridging therapy for radiation casualties: appropriate for high risk personnel. HEALTH PHYSICS 2014; 106:689-698. [PMID: 24776901 DOI: 10.1097/hp.0000000000000089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The authors demonstrate the efficacy of a bridging therapy in a preclinical animal model that allows the lymphohematopoietic system of severely immunocompromised individuals exposed to acute, high-dose ionizing irradiation to recover and to survive. CD2F1 mice were irradiated acutely with high doses causing severe, potentially fatal hematopoietic or gastrointestinal injuries and then transfused intravenously with progenitor-enriched, whole blood, or peripheral blood mononuclear cells from mice injected with tocopherol succinate- and AMD3100- (a chemokine receptor anatogonist used to improve the yield of mobilized progenitors). Survival of these mice over a 30-d period was used as the primary measured endpoint of therapeutic effectiveness. The authors demonstrate that tocopherol succinate and AMD3100 mobilize progenitors into peripheral circulation and that the infusion of mobilized progenitor enriched blood or mononuclear cells acts as a bridging therapy for lymphohematopoietic system recovery in mice exposed to whole-body ionizing irradiation. The results demonstrate that infusion of whole blood or blood mononuclear cells from tocopherol succinate (TS)- and AMD3100-injected mice improved the survival of mice receiving high radiation doses significantly. The efficacy of TS-injected donor mice blood or mononuclear cells was comparable to that of blood or cells obtained from mice injected with granulocyte colony-stimulating factor. Donor origin-mobilized progenitors were found to localize in various tissues. The authors suggest that tocopherol succinate is an optimal agent for mobilizing progenitors with significant therapeutic potential. The extent of progenitor mobilization that tocopherol succinate elicits in experimental mice is comparable quantitatively to clinically used drugs such as granulocyte-colony stimulating factor and AMD3100. Therefore, it is proposed that tocopherol succinate be considered for further translational development and ultimately for use in humans.
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Affiliation(s)
- Vijay K Singh
- *Armed Forces Radiobiology Research Institute, Bethesda, MD; †Department of Radiation Biology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD; ‡Tech Micro Services, 4417 Maple Avenue, Bethesda, MD
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Singh VK, Wise SY, Fatanmi OO, Beattie LA, Ducey EJ, Seed TM. Alpha-tocopherol succinate- and AMD3100-mobilized progenitors mitigate radiation combined injury in mice. JOURNAL OF RADIATION RESEARCH 2014; 55:41-53. [PMID: 23814114 PMCID: PMC3885121 DOI: 10.1093/jrr/rrt088] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 05/23/2013] [Accepted: 05/27/2013] [Indexed: 05/28/2023]
Abstract
The purpose of this study was to elucidate the role of alpha-tocopherol succinate (TS)- and AMD3100-mobilized progenitors in mitigating combined injury associated with acute radiation exposure in combination with secondary physical wounding. CD2F1 mice were exposed to high doses of cobalt-60 gamma-radiation and then transfused intravenously with 5 million peripheral blood mononuclear cells (PBMCs) from TS- and AMD3100-injected mice after irradiation. Within 1 h after irradiation, mice were exposed to secondary wounding. Mice were observed for 30 d after irradiation and cytokine analysis was conducted by multiplex Luminex assay at various time-points after irradiation and wounding. Our results initially demonstrated that transfusion of TS-mobilized progenitors from normal mice enhanced survival of acutely irradiated mice exposed 24 h prior to transfusion to supralethal doses (11.5-12.5 Gy) of (60)Co gamma-radiation. Subsequently, comparable transfusions of TS-mobilized progenitors were shown to significantly mitigate severe combined injuries in acutely irradiated mice. TS administered 24 h before irradiation was able to protect mice against combined injury as well. Cytokine results demonstrated that wounding modulates irradiation-induced cytokines. This study further supports the conclusion that the infusion of TS-mobilized progenitor-containing PBMCs acts as a bridging therapy in radiation-combined-injury mice. We suggest that this novel bridging therapeutic approach involving the infusion of TS-mobilized hematopoietic progenitors following acute radiation exposure or combined injury might be applicable to humans.
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Affiliation(s)
- Vijay K. Singh
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA
- Department of Radiation Biology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4417 Maple Avenue, Bethesda, MD, USA
| | - Stephen Y. Wise
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA
| | - Oluseyi O. Fatanmi
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA
| | - Lindsay A. Beattie
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA
| | - Elizabeth J. Ducey
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA
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Singh VK, Beattie LA, Seed TM. Vitamin E: tocopherols and tocotrienols as potential radiation countermeasures. JOURNAL OF RADIATION RESEARCH 2013; 54:973-88. [PMID: 23658414 PMCID: PMC3823775 DOI: 10.1093/jrr/rrt048] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Despite the potential devastating health consequences of intense total-body irradiation, and the decades of research, there still remains a dearth of safe and effective radiation countermeasures for emergency, radiological/nuclear contingencies that have been fully approved and sanctioned for use by the US FDA. Vitamin E is a well-known antioxidant, effective in scavenging free radicals generated by radiation exposure. Vitamin E analogs, collectively known as tocols, have been subject to active investigation for a long time as radioprotectors in patients undergoing radiotherapy and in the context of possible radiation accidents or terrorism scenarios. Eight major isoforms comprise the tocol group: four tocopherols and four tocotrienols. A number of these agents and their derivatives are being investigated actively as radiation countermeasures using animal models, and several appear promising. Although the tocols are well recognized as potent antioxidants and are generally thought to mediate radioprotection through 'free radical quenching', recent studies have suggested several alternative mechanisms: most notably, an 'indirect effect' of tocols in eliciting specific species of radioprotective growth factors/cytokines such as granulocyte colony-stimulating factor (G-CSF). The radioprotective efficacy of at least two tocols has been abrogated using a neutralizing antibody of G-CSF. Based on encouraging results of radioprotective efficacy, laboratory testing of γ-tocotrienol has moved from a small rodent model to a large nonhuman primate model for preclinical evaluation. In this brief review we identify and discuss selected tocols and their derivatives currently under development as radiation countermeasures, and attempt to describe in some detail their in vivo efficacy.
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Affiliation(s)
- Vijay K. Singh
- Radiation Countermeasures Program, Scientific Research Department, Armed Forces Radiobiology Research Institute, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA
- Department of Radiation Biology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
- Corresponding author. Radiation Countermeasures Program, Armed Forces Radiobiology Research Institute, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA. Tel: +1-301-295-2347; Fax: +1-301-295-6503;
| | - Lindsay A. Beattie
- Radiation Countermeasures Program, Scientific Research Department, Armed Forces Radiobiology Research Institute, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA
| | - Thomas M. Seed
- Tech Micro Services, 4417 Maple Avenue, Bethesda, MD, USA
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Singh VK, Wise SY, Singh PK, Posarac A, Fatanmi OO, Ducey EJ, Bolduc DL, Elliott TB, Seed TM. Alpha-tocopherol succinate-mobilized progenitors improve intestinal integrity after whole body irradiation. Int J Radiat Biol 2013; 89:334-45. [PMID: 23270472 DOI: 10.3109/09553002.2013.762137] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE The objective of this study was to elucidate the action of α-tocopherol succinate (TS)- and AMD3100-mobilized progenitors in mitigating radiation-induced injuries. MATERIAL AND METHODS CD2F1 mice were exposed to a high dose of radiation and then transfused intravenously with 5 million peripheral blood mononuclear cells (PBMC) from TS- and AMD3100-injected mice after irradiation. Intestinal and splenic tissues were harvested after irradiation and cells of those tissues were analyzed for markers of apoptosis and mitosis. Bacterial translocation from gut to heart, spleen, and liver in TS-treated and irradiated mice was evaluated by bacterial culture. RESULTS We observed that the infusion of PBMC from TS- and AMD3100-injected mice significantly inhibited apoptosis, increased cell proliferation in the analyzed tissues of recipient mice, and inhibited bacterial translocation to various organs compared to mice receiving cells from vehicle-mobilized cells. This study further supports our contention that the infusion of TS-mobilized progenitor-containing PBMC acts as a bridging therapy by inhibiting radiation-induced apoptosis, enhancing cell proliferation, and inhibiting bacterial translocation in irradiated mice. CONCLUSIONS We suggest that this novel bridging therapeutic approach that involves the infusion of TS-mobilized hematopoietic progenitors following acute radiation injury might be applicable to humans as well.
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Affiliation(s)
- Vijay K Singh
- Armed Forces Radiobiology Research Institute, Bethesda, MD 20889-5603, USA.
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Singh VK, Fatanmi OO, Singh PK, Whitnall MH. Role of radiation-induced granulocyte colony-stimulating factor in recovery from whole body gamma-irradiation. Cytokine 2012; 58:406-14. [PMID: 22487481 DOI: 10.1016/j.cyto.2012.03.011] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 01/31/2012] [Accepted: 03/16/2012] [Indexed: 01/13/2023]
Abstract
The purpose of this study was to further elucidate the radioprotective role of granulocyte colony-stimulating factor (G-CSF) induced in response to irradiation. The induction of G-CSF and interleukin-6 (IL-6) in response to radiation exposure was evaluated in mice. The level of cytokine in serum was determined by multiplex Luminex. The role of G-CSF on survival and tissue injury after total body gamma-irradiation was evaluated by administration of neutralizing antibody to G-CSF before radiation exposure. An isotype control was used for comparison and survival was monitored for 30 d after irradiation. Jejunum samples were used for immunohistochemistry. Ionizing radiation exposure induced significant levels of the hematopoietic cytokines G-CSF and IL-6, in mice receiving 9.2 Gy radiation. Maximal levels of G-CSF were observed in peripheral blood of mice 8h after irradiation. IL-6 levels were maximum at 12h after irradiation. Administration of G-CSF antibody significantly enhanced mortality in irradiated mice. G-CSF antibody-treated mice had higher numbers of CD68(+) cells and apoptotic cells in intestinal villi. Our results confirm that radiation exposure induces elevations of circulating G-CSF and IL-6. Neutralizing antibody to G-CSF exacerbates the deleterious effects of radiation, indicating that G-CSF induced in response to irradiation plays an important role in recovery.
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Affiliation(s)
- Vijay K Singh
- Radiation Countermeasures Program, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
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Cerezo L, Macià I Garau M. Acute radiation syndrome and Fukushima: A watershed moment? Rep Pract Oncol Radiother 2012; 17:1-3. [PMID: 24376998 DOI: 10.1016/j.rpor.2012.01.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Laura Cerezo
- Department of Radiation Oncology, Instituto de Investigación Sanitaria, Hospital Universitario de la Princesa, Madrid, Spain
| | - Miquel Macià I Garau
- Radiation Oncology Department, Institut Català d'Oncologia, Hospital Duran i Reynals, L'Hospitalet de Llobregat, Barcelona, Spain
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Singh VK, Wise SY, Singh PK, Ducey EJ, Fatanmi OO, Seed TM. α-Tocopherol succinate- and AMD3100-mobilized progenitors mitigate radiation-induced gastrointestinal injury in mice. Exp Hematol 2012; 40:407-17. [PMID: 22240608 DOI: 10.1016/j.exphem.2012.01.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/05/2011] [Accepted: 01/04/2012] [Indexed: 11/17/2022]
Abstract
The goal of this study was to elucidate the role of α-tocopherol succinate (TS)- and AMD3100-mobilized progenitors in mitigating the ionizing-radiation-induced gastrointestinal syndrome in mice. We demonstrate the efficacy of a bridging therapy that will allow the lymphohematopoietic system of severely immunocompromised victims exposed to ionizing radiation to recover from high doses of radiation. CD2F1 mice were irradiated with a high dose of radiation causing gastrointestinal syndrome (11 Gy, cobalt-60 γ-radiation) and then transfused intravenously (retro-orbital sinus) with whole blood or peripheral blood mononuclear cells (PBMC) from TS- and AMD3100-injected mice 2, 24, or 48 hours post irradiation and monitored for 30-day survival. Jejunum sections were analyzed for tissue area, surviving crypts, villi, mitotic figures, and basal lamina enterocytes. Our results demonstrate that infusion of whole blood or PBMC from TS- and AMD3100-injected mice significantly improved survival of mice receiving a high dose of radiation. Histopathology and immunostaining of jejunum from irradiated and TS- and AMD3100-mobilized PBMC-transfused mice reveal significant protection of gastrointestinal tissue from radiation injury. We demonstrate that TS and AMD3100 mobilize progenitors into peripheral circulation and that the infusion of mobilized progenitor-containing blood or PBMC acts as a bridging therapy for immune-system recovery in mice exposed to high, potentially fatal, doses of ionizing radiation.
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Affiliation(s)
- Vijay K Singh
- Radiation Countermeasures Program, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, MD 20889-5603, USA.
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Singh VK, Ducey EJ, Fatanmi OO, Singh PK, Brown DS, Purmal A, Shakhova VV, Gudkov AV, Feinstein E, Shakhov A. CBLB613: a TLR 2/6 agonist, natural lipopeptide of Mycoplasma arginini , as a novel radiation countermeasure. Radiat Res 2011; 177:628-42. [PMID: 22175300 DOI: 10.1667/rr2657.1] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
To date, there are no safe and effective drugs available for protection against ionizing radiation damage. Therefore, a great need exists to identify and develop non-toxic agents that will be useful as radioprotectors or postirradiation therapies under a variety of operational scenarios. We have developed a new pharmacological agent, CBLB613 (a naturally occurring Mycoplasma-derived lipopeptide ligand for Toll-like receptor 2/6), as a novel radiation countermeasure. Using CD2F1 mice, we investigated CBLB613 for toxicity, immunogenicity, radioprotection, radiomitigation and pharmacokinetics. We also evaluated CBLB613 for its effects on cytokine induction and radiation-induced cytopenia in unirradiated and irradiated mice. The no-observable-adverse-effect level of CBLB613 was 1.79 mg/kg and 1 mg/kg for single and repeated doses, respectively. CBLB613 significantly protected mice against a lethal dose of (60)Co γ radiation. The dose reduction factor of CBLB613 as a radioprotector was 1.25. CBLB613 also mitigated the effects of (60)Co γ radiation on survival in mice. In both irradiated and unirradiated mice, the drug stimulated induction of interleukin-1β (IL-1β), IL-6, IL-10, IL-12, keratinocyte-derived chemokine, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-1α. CBLB613 also reduced radiation-induced cytopenia and increased bone marrow cellularity in irradiated mice. Our immunogenicity study demonstrated that CBLB613 is not immunogenic in mice, indicating that it could be developed as a radioprotector and radiomitigator for humans against the potentially lethal effects of radiation exposure.
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Affiliation(s)
- Vijay K Singh
- Radiation Countermeasures Program, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20889-5603, USA.
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Singh PK, Wise SY, Ducey EJ, Brown DS, Singh VK. Radioprotective efficacy of tocopherol succinate is mediated through granulocyte-colony stimulating factor. Cytokine 2011; 56:411-21. [DOI: 10.1016/j.cyto.2011.08.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Revised: 07/14/2011] [Accepted: 08/05/2011] [Indexed: 12/17/2022]
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