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Abstract
The discovery of vitamin E (α-tocopherol) began in 1922 as a vital component required in reproduction. Today, there are eight naturally occurring vitamin E isoforms, namely α-, β-, γ- and δ-tocopherol and α-, β-, γ- and δ-tocotrienol. Vitamin E is potent antioxidants, capable of neutralizing free radicals directly by donating hydrogen from its chromanol ring. α-Tocopherol is regarded the dominant form in vitamin E as the α-tocopherol transfer protein in the liver binds mainly α-tocopherol, thus preventing its degradation. That contributed to the oversight of tocotrienols and resulted in less than 3% of all vitamin E publications studying tocotrienols. Nevertheless, tocotrienols have been shown to possess superior antioxidant and anti-inflammatory properties over α-tocopherol. In particular, inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase to lower cholesterol, attenuating inflammation via downregulation of transcription factor NF-κB activation, and potent radioprotectant against radiation damage are some properties unique to tocotrienols, not tocopherols. Aside from cancer, vitamin E has also been shown protective in bone, cardiovascular, eye, nephrological and neurological diseases. In light of the different pharmacological properties of tocopherols and tocotrienols, it becomes critical to specify which vitamin E isoform(s) are being studied in any future vitamin E publications. This review provides an update on vitamin E therapeutic potentials, protective effects and modes of action beyond cancer, with comparison of tocopherols against tocotrienols. With the concerted efforts in synthesizing novel vitamin E analogs and clinical pharmacology of vitamin E, it is likely that certain vitamin E isoform(s) will be therapeutic agents against human diseases besides cancer.
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Affiliation(s)
- Hong Yong Peh
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University Health System, Singapore
| | - W S Daniel Tan
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University Health System, Singapore
| | - Wupeng Liao
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University Health System, Singapore
| | - W S Fred Wong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University Health System, Singapore; Immunology Program, Life Science Institute, National University of Singapore, Singapore.
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Singh VK, Newman VL, Romaine PL, Hauer-Jensen M, Pollard HB. Use of biomarkers for assessing radiation injury and efficacy of countermeasures. Expert Rev Mol Diagn 2015; 16:65-81. [PMID: 26568096 PMCID: PMC4732464 DOI: 10.1586/14737159.2016.1121102] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Several candidate drugs for acute radiation syndrome (ARS) have been identified that have low toxicity and significant radioprotective and radiomitigative efficacy. Inasmuch as exposing healthy human volunteers to injurious levels of radiation is unethical, development and approval of new radiation countermeasures for ARS are therefore presently based on animal studies and Phase I safety study in healthy volunteers. The Animal Efficacy Rule, which underlies the Food and Drug Administration approval pathway, requires a sound understanding of the mechanisms of injury, drug efficacy, and efficacy biomarkers. In this context, it is important to identify biomarkers for radiation injury and drug efficacy that can extrapolate animal efficacy results, and can be used to convert drug doses deduced from animal studies to those that can be efficacious when used in humans. Here, we summarize the progress of studies to identify candidate biomarkers for the extent of radiation injury and for evaluation of countermeasure efficacy.
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Affiliation(s)
- Vijay K Singh
- a F. Edward Hébert School of Medicine 'America's Medical School' , Uniformed Services University of the Health Sciences , Bethesda , MD , USA.,b Armed Forces Radiobiology Research Institute , Uniformed Services University of the Health Sciences , Bethesda , MD , USA
| | - Victoria L Newman
- a F. Edward Hébert School of Medicine 'America's Medical School' , Uniformed Services University of the Health Sciences , Bethesda , MD , USA.,b Armed Forces Radiobiology Research Institute , Uniformed Services University of the Health Sciences , Bethesda , MD , USA
| | - Patricia Lp Romaine
- a F. Edward Hébert School of Medicine 'America's Medical School' , Uniformed Services University of the Health Sciences , Bethesda , MD , USA.,b Armed Forces Radiobiology Research Institute , Uniformed Services University of the Health Sciences , Bethesda , MD , USA
| | - Martin Hauer-Jensen
- c Departments of Pharmaceutical Sciences, Surgery, and Pathology , University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare Systems , Little Rock , AR , USA
| | - Harvey B Pollard
- a F. Edward Hébert School of Medicine 'America's Medical School' , Uniformed Services University of the Health Sciences , Bethesda , MD , USA
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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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Elliott TB, Bolduc DL, Ledney GD, Kiang JG, Fatanmi OO, Wise SY, Romaine PLP, Newman VL, Singh VK. Combined immunomodulator and antimicrobial therapy eliminates polymicrobial sepsis and modulates cytokine production in combined injured mice. Int J Radiat Biol 2015; 91:690-702. [PMID: 25994812 PMCID: PMC4673550 DOI: 10.3109/09553002.2015.1054526] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Purpose: A combination therapy for combined injury (CI) using a non-specific immunomodulator, synthetic trehalose dicorynomycolate and monophosphoryl lipid A (STDCM-MPL), was evaluated to augment oral antimicrobial agents, levofloxacin (LVX) and amoxicillin (AMX), to eliminate endogenous sepsis and modulate cytokine production. Materials and methods: Female B6D2F1/J mice received 9.75 Gy cobalt-60 gamma-radiation and wound. Bacteria were isolated and identified in three tissues. Incidence of bacteria and cytokines were compared between treatment groups. Results: Results demonstrated that the lethal dose for 50% at 30 days (LD50/30) of B6D2F1/J mice was 9.42 Gy. Antimicrobial therapy increased survival in radiation-injured (RI) mice. Combination therapy increased survival after RI and extended survival time but did not increase survival after CI. Sepsis began five days earlier in CI mice than RI mice with Gram-negative species predominating early and Gram-positive species increasing later. LVX plus AMX eliminated sepsis in CI and RI mice. STDCM-MPL eliminated Gram-positive bacteria in CI and most RI mice but not Gram-negative. Treatments significantly modulated 12 cytokines tested, which pertain to wound healing or elimination of infection. Conclusions: Combination therapy eliminates infection and prolongs survival time but does not assure CI mouse survival, suggesting that additional treatment for proliferative-cell recovery is required.
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Affiliation(s)
- Thomas B Elliott
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA
| | - David L Bolduc
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA
| | - G David Ledney
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA
| | - Juliann G Kiang
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA.,b Department of Radiation Biology , F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences , Bethesda , MD , USA.,c Department of Medicine , F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences , Bethesda , MD , USA
| | - Oluseyi O Fatanmi
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA
| | - Stephen Y Wise
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA
| | | | - Victoria L Newman
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA
| | - Vijay K Singh
- a Armed Forces Radiobiology Research Institute , Bethesda , MD , USA.,b Department of Radiation Biology , F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences , Bethesda , MD , USA
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Singh VK, Romaine PL, Seed TM. Medical Countermeasures for Radiation Exposure and Related Injuries: Characterization of Medicines, FDA-Approval Status and Inclusion into the Strategic National Stockpile. HEALTH PHYSICS 2015; 108:607-630. [PMID: 25905522 PMCID: PMC4418776 DOI: 10.1097/hp.0000000000000279] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/05/2015] [Indexed: 05/28/2023]
Abstract
World events over the past decade have highlighted the threat of nuclear terrorism as well as an urgent need to develop radiation countermeasures for acute radiation exposures and subsequent bodily injuries. An increased probability of radiological or nuclear incidents due to detonation of nuclear weapons by terrorists, sabotage of nuclear facilities, dispersal and exposure to radioactive materials, and accidents provides the basis for such enhanced radiation exposure risks for civilian populations. Although the search for suitable radiation countermeasures for radiation-associated injuries was initiated more than half a century ago, no safe and effective radiation countermeasure for the most severe of these injuries, namely acute radiation syndrome (ARS), has been approved by the United States Food and Drug Administration (FDA). The dearth of FDA-approved radiation countermeasures has prompted intensified research for a new generation of radiation countermeasures. In this communication, the authors have listed and reviewed the status of radiation countermeasures that are currently available for use, or those that might be used for exceptional nuclear/radiological contingencies, plus a limited few medicines that show early promise but still remain experimental in nature and unauthorized for human use by the FDA.
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Affiliation(s)
- Vijay K. Singh
- *Radiation Countermeasures Program, 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, Bethesda, MD
| | - Patricia L.P. Romaine
- *Radiation Countermeasures Program, 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, Bethesda, MD
| | - Thomas M. Seed
- *Radiation Countermeasures Program, 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, Bethesda, MD
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Pathak R, Shao L, Ghosh SP, Zhou D, Boerma M, Weiler H, Hauer-Jensen M. Thrombomodulin contributes to gamma tocotrienol-mediated lethality protection and hematopoietic cell recovery in irradiated mice. PLoS One 2015; 10:e0122511. [PMID: 25860286 PMCID: PMC4393275 DOI: 10.1371/journal.pone.0122511] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 02/12/2015] [Indexed: 01/09/2023] Open
Abstract
Systemic administration of recombinant thrombomodulin (TM) confers radiation protection partly by accelerating hematopoietic recovery. The uniquely potent radioprotector gamma tocotrienol (GT3), in addition to being a strong antioxidant, inhibits the enzyme hydroxy-methyl-glutaryl-coenzyme A reductase (HMGCR) and thereby likely modulates the expression of TM. We hypothesized that the mechanism underlying the exceptional radioprotective properties of GT3 partly depends on the presence of endothelial TM. In vitro studies confirmed that ionizing radiation suppresses endothelial TM (about 40% at 4 hr after 5 Gy γ-irradiation) and that GT3 induces TM expression (about 2 fold at the mRNA level after 5 μM GT3 treatment for 4 hr). In vivo survival studies showed that GT3 was significantly more effective as a radioprotector in TM wild type (TM+/+) mice than in mice with low TM function (TMPro/-). After exposure to 9 Gy TBI, GT3 pre-treatment conferred 85% survival in TM+/+ mice compared to only 50% in TMPro/-. Thus, GT3-mediated radiation lethality protection is partly dependent on endothelial TM. Significant post-TBI recovery of hematopoietic cells, particularly leukocytes, was observed in TM+/+ mice (p = 0.003), but not in TMPro/- mice, despite the fact that GT3 induced higher levels of granulocyte colony stimulating factor (G-CSF) in TMPro/- mice (p = 0.0001). These data demonstrate a critical, G-CSF-independent, role for endothelial TM in GT3-mediated lethality protection and hematopoietic recovery after exposure to TBI and may point to new strategies to enhance the efficacy of current medical countermeasures in radiological/nuclear emergencies.
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Affiliation(s)
- Rupak Pathak
- Division of Radiation Health, Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
- * E-mail:
| | - Lijian Shao
- Division of Radiation Health, Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
| | - Sanchita P. Ghosh
- Armed Forces Radiobiology Research Institute, USUHS, Bethesda, MD, United States of America
| | - Daohong Zhou
- Division of Radiation Health, Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
| | - Marjan Boerma
- Division of Radiation Health, Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
| | - Hartmut Weiler
- Blood Research Institute, Blood Center of Wisconsin and the Medical College of Wisconsin, Milwaukee, WI, United States of America
| | - Martin Hauer-Jensen
- Division of Radiation Health, Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
- Surgical Service, Central Arkansas Veterans Healthcare System, Little Rock, AR, United States of America
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Rosen EM, Day R, Singh VK. New approaches to radiation protection. Front Oncol 2015; 4:381. [PMID: 25653923 PMCID: PMC4299410 DOI: 10.3389/fonc.2014.00381] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 12/19/2014] [Indexed: 12/16/2022] Open
Abstract
Radioprotectors are compounds that protect against radiation injury when given prior to radiation exposure. Mitigators can protect against radiation injury when given after exposure but before symptoms appear. Radioprotectors and mitigators can potentially improve the outcomes of radiotherapy for cancer treatment by allowing higher doses of radiation and/or reduced damage to normal tissues. Such compounds can also potentially counteract the effects of accidental exposure to radiation or deliberate exposure (e.g., nuclear reactor meltdown, dirty bomb, or nuclear bomb explosion); hence they are called radiation countermeasures. Here, we will review the general principles of radiation injury and protection and describe selected examples of radioprotectors/mitigators ranging from small-molecules to proteins to cell-based treatments. We will emphasize agents that are in more advanced stages of development.
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Affiliation(s)
- Eliot M Rosen
- Departments of Oncology, Biochemistry and Molecular & Cellular Biology, and Radiation Medicine, Lombardi Comprehensive Cancer Center, Georgetown University School of Medicine , Washington, DC , USA
| | - Regina Day
- Department of Pharmacology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences , Bethesda, MD , USA
| | - Vijay K Singh
- Department of Radiation Biology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences , Bethesda, MD , USA ; Radiation Countermeasures Program, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences , Bethesda, MD , USA
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Singh VK, Wise SY, Fatanmi OO, Scott J, Romaine PLP, Newman VL, Verma A, Elliott TB, Seed TM. Progenitors mobilized by gamma-tocotrienol as an effective radiation countermeasure. PLoS One 2014; 9:e114078. [PMID: 25423021 PMCID: PMC4244184 DOI: 10.1371/journal.pone.0114078] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 11/03/2014] [Indexed: 11/18/2022] Open
Abstract
The purpose of this study was to elucidate the role of gamma-tocotrienol (GT3)-mobilized progenitors in mitigating damage to mice exposed to a supralethal dose of cobalt-60 gamma-radiation. CD2F1 mice were transfused 24 h post-irradiation with whole blood or isolated peripheral blood mononuclear cells (PBMC) from donors that had received GT3 72 h prior to blood collection and recipient mice were monitored for 30 days. To understand the role of GT3-induced granulocyte colony-stimulating factor (G-CSF) in mobilizing progenitors, donor mice were administered a neutralizing antibody specific to G-CSF or its isotype before blood collection. Bacterial translocation from gut to heart, spleen and liver of irradiated recipient mice was evaluated by bacterial culture on enriched and selective agar media. Endotoxin in serum samples also was measured. We also analyzed the colony-forming units in the spleens of irradiated mice. Our results demonstrate that whole blood or PBMC from GT3-administered mice mitigated radiation injury when administered 24 h post-irradiation. Furthermore, administration of a G-CSF antibody to GT3-injected mice abrogated the efficacy of blood or PBMC obtained from such donors. Additionally, GT3-mobilized PBMC inhibited the translocation of intestinal bacteria to the heart, spleen, and liver, and increased colony forming unit-spleen (CFU-S) numbers in irradiated mice. Our data suggests that GT3 induces G-CSF, which mobilizes progenitors and these progenitors mitigate radiation injury in recipient mice. This approach using mobilized progenitor cells from GT3-injected donors could be a potential treatment for humans exposed to high doses of radiation.
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Affiliation(s)
- Vijay K. Singh
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
- Department of Radiation Biology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
- * E-mail:
| | - Stephen Y. Wise
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
| | - Oluseyi O. Fatanmi
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
| | - Jessica Scott
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
| | - Patricia L. P. Romaine
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
| | - Victoria L. Newman
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
| | - Amit Verma
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
| | - Thomas B. Elliott
- Armed Forces Radiobiology Research Institute, Bethesda, Maryland, United States of America
| | - Thomas M. Seed
- Tech Micro Services, Bethesda, Maryland, United States of America
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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, Newman VL, Romaine PLP, Wise SY, Seed TM. Radiation countermeasure agents: an update (2011-2014). Expert Opin Ther Pat 2014; 24:1229-55. [PMID: 25315070 PMCID: PMC4438421 DOI: 10.1517/13543776.2014.964684] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
INTRODUCTION Despite significant scientific advances over the past 60 years towards the development of a safe, nontoxic and effective radiation countermeasure for the acute radiation syndrome (ARS), no drug has been approved by the US FDA. A radiation countermeasure to protect the population at large from the effects of lethal radiation exposure remains a significant unmet medical need of the US citizenry and, thus, has been recognized as a high priority area by the government. AREA COVERED This article reviews relevant publications and patents for recent developments and progress for potential ARS treatments in the area of radiation countermeasures. Emphasis is placed on the advanced development of existing agents since 2011 and new agents identified as radiation countermeasure for ARS during this period. EXPERT OPINION A number of promising radiation countermeasures are currently under development, seven of which have received US FDA investigational new drug status for clinical investigation. Four of these agents, CBLB502, Ex-RAD, HemaMax and OrbeShield, are progressing with large animal studies and clinical trials. G-CSF has high potential and well-documented therapeutic effects in countering myelosuppression and may receive full licensing approval by the US FDA in the future.
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Affiliation(s)
- Vijay K Singh
- Armed Forces Radiobiology Research Institute , 8901 Wisconsin Ave, Bethesda, MD 20889-5603 , USA +1 301 295 2347 ; +1 301 295 6503 ;
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Kim JH, Jenrow KA, Brown SL. Mechanisms of radiation-induced normal tissue toxicity and implications for future clinical trials. Radiat Oncol J 2014; 32:103-15. [PMID: 25324981 PMCID: PMC4194292 DOI: 10.3857/roj.2014.32.3.103] [Citation(s) in RCA: 196] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 08/18/2014] [Indexed: 01/10/2023] Open
Abstract
To summarize current knowledge regarding mechanisms of radiation-induced normal tissue injury and medical countermeasures available to reduce its severity. Advances in radiation delivery using megavoltage and intensity-modulated radiation therapy have permitted delivery of higher doses of radiation to well-defined tumor target tissues. Injury to critical normal tissues and organs, however, poses substantial risks in the curative treatment of cancers, especially when radiation is administered in combination with chemotherapy. The principal pathogenesis is initiated by depletion of tissue stem cells and progenitor cells and damage to vascular endothelial microvessels. Emerging concepts of radiation-induced normal tissue toxicity suggest that the recovery and repopulation of stromal stem cells remain chronically impaired by long-lived free radicals, reactive oxygen species, and pro-inflammatory cytokines/chemokines resulting in progressive damage after radiation exposure. Better understanding the mechanisms mediating interactions among excessive generation of reactive oxygen species, production of pro-inflammatory cytokines and activated macrophages, and role of bone marrow-derived progenitor and stem cells may provide novel insight on the pathogenesis of radiation-induced injury of tissues. Further understanding the molecular signaling pathways of cytokines and chemokines would reveal novel targets for protecting or mitigating radiation injury of tissues and organs.
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Affiliation(s)
- Jae Ho Kim
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, USA
| | - Kenneth A. Jenrow
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, USA
| | - Stephen L. Brown
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, 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, Scott JR, Romaine PL, Newman VL, Fatanmi OO. Radioprotective efficacy of delta-tocotrienol, a vitamin E isoform, is mediated through granulocyte colony-stimulating factor. Life Sci 2014; 98:113-22. [DOI: 10.1016/j.lfs.2014.01.065] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 11/29/2013] [Accepted: 01/16/2014] [Indexed: 12/31/2022]
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Bioavailability of tocotrienols: evidence in human studies. Nutr Metab (Lond) 2014; 11:5. [PMID: 24410975 PMCID: PMC3895660 DOI: 10.1186/1743-7075-11-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 01/08/2014] [Indexed: 01/07/2023] Open
Abstract
As a minor component of vitamin E, tocotrienols were evident in exhibiting biological activities such as neuroprotection, radio-protection, anti-cancer, anti-inflammatory and lipid lowering properties which are not shared by tocopherols. However, available data on the therapeutic window of tocotrienols remains controversial. It is important to understand the absorption and bioavailability mechanisms before conducting in-depth investigations into the therapeutic efficacy of tocotrienols in humans. In this review, we updated current evidence on the bioavailability of tocotrienols from human studies. Available data from five studies suggested that tocotrienols may reach its target destination through an alternative pathway despite its low affinity for α-tocopherol transfer protein. This was evident when studies reported considerable amount of tocotrienols detected in HDL particles and adipose tissues after oral consumption. Besides, plasma concentrations of tocotrienols were shown to be higher when administered with food while self-emulsifying preparation of tocotrienols was shown to enhance the absorption of tocotrienols. Nevertheless, mixed results were observed based on the outcome from 24 clinical studies, focusing on the dosages, study populations and formulations used. This may be due to the variation of compositions and dosages of tocotrienols used, suggesting a need to understand the formulation of tocotrienols in the study design. Essentially, implementation of a control diet such as AHA Step 1 diet may influence the study outcomes, especially in hypercholesterolemic subjects when lipid profile might be modified due to synergistic interaction between tocotrienols and control diet. We also found that the bioavailability of tocotrienols were inconsistent in different target populations, from healthy subjects to smokers and diseased patients. In this review, the effect of dosage, composition and formulation of tocotrienols as well as study populations on the bioavailability of tocotrienols will be discussed.
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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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Kulkarni S, Chakraborty K, Kumar KS, Kao TC, Hauer-Jensen M, Ghosh SP. Synergistic radioprotection by gamma-tocotrienol and pentoxifylline: role of cAMP signaling. ISRN RADIOLOGY 2013; 2013:390379. [PMID: 24959559 PMCID: PMC4045513 DOI: 10.5402/2013/390379] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 05/30/2013] [Indexed: 11/23/2022]
Abstract
Purpose. This study was designed to determine the efficacy and mechanisms of radioprotection by the combination of gamma-tocotrienol (GT3) and pentoxifylline (PTX) against acute radiation injury. Materials and Methods. Post-irradiation survival was monitored to determine the most efficacious dose and time of administration of PTX. Dose reduction factor (DRF) was calculated to compare the radioprotective efficacy of the combination. To determine the mechanism of synergistic radioprotection by the combination, mevalonate or calmodulin were coadministered with the GT3-PTX combination. Mevalonate was used to reverse the inhibitory effect of GT3 on 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR), and calmodulin was used to reverse the inhibition of phosphodiesterase (PDE) by PTX. Results. The combination was most effective when 200 mg/kg of PTX was administered 15 min before irradiation along with 200 mg/kg of GT3 (-24 h) and resulted in a DRF of 1.5. White blood cells and neutrophil counts showed accelerated recovery in GT3-PTX-treated groups compared to GT3. Mevalonate had no effect on the radioprotection of GT3-PTX; calmodulin abrogated the synergistic radioprotection by GT3-PTX. Conclusion. The mechanism of radioprotection by GT3-PTX may involve PDE inhibition.
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Affiliation(s)
- Shilpa Kulkarni
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Scientific Research Department, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA
| | - Kushal Chakraborty
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Scientific Research Department, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA
| | - K. Sree Kumar
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Scientific Research Department, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA
| | - Tzu-Cheg Kao
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Scientific Research Department, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA
| | - Martin Hauer-Jensen
- University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, USA
| | - Sanchita P. Ghosh
- Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Scientific Research Department, 8901 Wisconsin Avenue, Bethesda, MD 20889, USA
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