Article

5-AED enhances survival of irradiated mice in a G-CSF-dependent manner, stimulates innate immune cell function, reduces radiation-induced DNA damage and induces genes that modulate cell cycle progression and apoptosis

Radiation Countermeasures Program, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, 8901 Wisconsin Ave, Bethesda, MD 20889-5603, USA.
Journal of Radiation Research (Impact Factor: 1.69). 07/2012; 53(6). DOI: 10.1093/jrr/rrs060
Source: PubMed

ABSTRACT The steroid androst-5-ene-3ß,17ß-diol (5-androstenediol, 5-AED) elevates circulating granulocytes and platelets in animals and humans, and enhances survival during the acute radiation syndrome (ARS) in mice and non-human primates. 5-AED promotes survival of irradiated human hematopoietic progenitors in vitro through induction of Nuclear Factor-κB (NFκB)-dependent Granulocyte Colony-Stimulating Factor (G-CSF) expression, and causes elevations of circulating G-CSF and interleukin-6 (IL-6). However, the in vivo cellular and molecular effects of 5-AED are not well understood. The aim of this study was to investigate the mechanisms of action of 5-AED administered subcutaneously (s.c.) to mice 24 h before total body γ- or X-irradiation (TBI). We used neutralizing antibodies, flow cytometric functional assays of circulating innate immune cells, analysis of expression of genes related to cell cycle progression, DNA repair and apoptosis, and assessment of DNA strand breaks with halo-comet assays. Neutralization experiments indicated endogenous G-CSF but not IL-6 was involved in survival enhancement by 5-AED. In keeping with known effects of G-CSF on the innate immune system, s.c. 5-AED stimulated phagocytosis in circulating granulocytes and oxidative burst in monocytes. 5-AED induced expression of both bax and bcl-2 in irradiated animals. Cdkn1a and ddb1, but not gadd45a expression, were upregulated by 5-AED in irradiated mice. S.c. 5-AED administration caused decreased DNA strand breaks in splenocytes from irradiated mice. Our results suggest 5-AED survival enhancement is G-CSF-dependent, and that it stimulates innate immune cell function and reduces radiation-induced DNA damage via induction of genes that modulate cell cycle progression and apoptosis.

Download full-text

Full-text

Available from: Vijay K Singh, Feb 25, 2015
0 Followers
 · 
183 Views
  • Source
    • "We also have reported that radiation exposure induces elevation of circulating G-CSF and that administering a neutralizing antibody to G-CSF exacerbates the deleterious effects of radiation exposure, suggesting that G-CSF induced in response to irradiation plays an important protective role in recovery (Singh et al., 2012d). Recently, we have demonstrated that the use of the G-CSF antibody abrogates the radioprotective efficacy of few radiation countermeasures (Singh et al., 2010; Kulkarni et al., 2013; Krivokrysenko et al., 2012; Grace et al., 2012). Our current study demonstrates that DT3 is a potent stimulator of several cytokines including G-CSF, and that the radioprotective efficacy of DT3 is mediated through G-CSF. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this study was to determine the cytokine induction by delta tocotrienol (DT3, a promising radiation countermeasure) and to investigate the role of granulocyte colony-stimulating factor (G-CSF) in its radioprotective efficacy against ionizing radiation in mice. Multiplex Luminex was used to analyze DT3- and other tocols (gamma-tocotrienol and tocopherol succinate)-induced cytokines in CD2F1 mice. Mice were injected with an optimal dose of DT3 and a G-CSF antibody, and their 30-day survival against cobalt-60 gamma-irradiation was monitored. Neutralization of G-CSF by administration of a G-CSF-specific antibody in DT3-injected mice was investigated by multiplex Luminex. Our data demonstrate that DT3 induced high levels of various cytokines comparable to other tocols being developed as radiation countermeasures. DT3 significantly protected mice against ionizing radiation, and administration of a G-CSF neutralizing antibody to DT3-treated animals resulted in complete abrogation of DT3's radioprotective efficacy and neutralization of G-CSF in peripheral blood. Our study findings suggest that G-CSF induced by DT3 mediates its radioprotective efficacy against ionizing radiation in mice.
    Life sciences 01/2014; 98(2). DOI:10.1016/j.lfs.2014.01.065 · 2.30 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This study aimed to determine the role of granulocyte colony-stimulating factor (G-CSF), induced by a promising radiation countermeasure, gamma tocotrienol (GT3), in protecting mice from lethal doses of ionizing radiation. CD2F1 mice were injected with an optimal dose of GT3 and a G-CSF antibody, and their 30-d survival was monitored. An appropriate antibody isotype was used as a control. Multiplex Luminex was used to analyze GT3-induced cytokines. G-CSF neutralization by exogenous administration of a G-CSF antibody was confirmed by analyzing serum cytokine levels. Our results demonstrate that GT3 significantly protected mice against ionizing radiation, and induced high levels of G-CSF in peripheral blood 24h after administration. Injection of a G-CSF neutralizing antibody to the GT3-treated mice resulted in complete neutralization of G-CSF and abrogation of its protective efficacy. Administration of a G-CSF antibody did not affect levels of other cytokines induced by GT3. Histopathology of bone marrow from GT3-treated and -irradiated mice demonstrated protection of the hematopoietic tissue, and also that such protection was abrogated by administering a G-CSF antibody. Our results suggest that induction of high levels of G-CSF by GT3 administration is responsible for its protective efficacy against radiation injury.
    Cytokine 04/2013; 62(2). DOI:10.1016/j.cyto.2013.03.009 · 2.87 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Journal of Radiation Research 05/2013; 54(6). DOI:10.1093/jrr/rrt048 · 1.69 Impact Factor
Show more