Thomas M. Seed

Androstenediol stimulates myelopoiesis and enhances resistance to infection in gamma-irradiated mice.

The ionizing radiation-induced hemopoietic syndrome is characterized by defects in immune function and increased mortality due to infections and hemorrhage. Since the steroid 5-androstene-3beta, 17beta-diol (5-androstenediol, AED) modulates cytokine expression and increases resistance to bacterial and viral infections in rodents, we tested its ability to promote survival after whole-body ionizing radiation in mice. In unirradiated female B6D2F1 mice, sc AED elevated numbers of circulating neutrophils and platelets and induced proliferation of neutrophil progenitors in bone marrow. In mice exposed to whole-body (60)Co gamma-radiation (3 Gy), AED injected 1 h later ameliorated radiation-induced decreases in circulating neutrophils and platelets and marrow granulocyte-macrophage colony-forming cells, but had no effect on total numbers of circulating lymphocytes or erythrocytes. In mice irradiated (0, 1 or 3 Gy) and inoculated four days later with Klebsiella pneumoniae, AED injected 2 h after irradiation enhanced 30-d survival. Injecting AED 24 h before irradiation or 2 h after irradiation increased survival to approximately the same extent. In K. pneumoniae-inoculated mice (irradiated at 3-7 Gy) and uninoculated mice (irradiated at 8-12 Gy), AED (160 mg/kg) injected 24 h before irradiation significantly promoted survival with dose reduction factors (DRFs) of 1.18 and 1.26, respectively. 5-Androstene-3beta-ol-17-one (dehydroepiandrosterone, DHEA) was markedly less efficacious than AED in augmenting survival, indicating specificity. These results demonstrate for the first time that a DHEA-related steroid stimulates myelopoiesis, and ameliorates neutropenia and thrombocytopenia and enhances resistance to infection after exposure of animals to ionizing radiation.

RADIOPROTECTIVE EFFICACY AND ACUTE TOXICITY OF 5-ANDROSTENEDIOL AFTER SUBCUTANEOUS OR ORAL ADMINISTRATION IN MICE

ABSTRACT We previously showed that one subcutaneous (sc) injection of 5-androstene-3beta,17beta-diol (AED) stimulated the innate immune system in mice and prevented mortality due to hemopoietic suppression after whole-body ionizing irradiation with gamma rays. In the present study, we tested whether there was any significant toxicity in mice that might hinder development of this steroid for human use. There were no indications of toxicity in chemical analyses of serum after sc doses as high as 4000 mg/kg. At this dose, 2 of 54 mice died when given AED alone. When 4800 mg/kg was given orally, no deaths resulted. The only adverse findings attributed to AED administration were 1) a moderate elevation of granulocytes in abdominal organs and fat after sc injections of 320 mg/kg; and 2) occasional wasting of skin over the injection site in female B6D2F1 but not male C3H/HeN mice. Significant weight loss (6%) was observed after sc injections of 320 mg/kg but not 160 or 80 mg/kg. When male C3H/HeN mice were injected sc with AED at doses of 0–200 mg/kg 24 h before whole body gamma-irradiation (9 Gy), a significant improvement in survival was observed at doses as low as 5 mg/kg. Oral administration of AED produced significant survival enhancement at a dose of 1600 mg/kg. We conclude that the radioprotective efficacy of AED is accompanied by low toxicity.Androst-5-ene-3 beta, 17 beta-diol; Ionizing radiation; Experimental radiation injuries; Toxicity; Clinical chemistry; Histopathology

Radioprotection, pharmacokinetic and behavioural studies in mouse implanted with biodegradable drug (amifostine) pellets.

Purpose : We evaluated the use of a subcutaneously (s.c.) implantable, biodegradable pellet as a drug delivery system for the radioprotector amifostine. Materials and methods : Mice were implanted s.c. with either the custom-made biodegradable amifostine drug pellet or the placebo pellet without amifostine, exposed to cobalt-60 γ-radiation (bilateral, 1 Gy min -1, 7-16 Gy), and the 30-day survival rate was monitored. The non-irradiated mouse was used for pharmacokinetic and behavioural tests. Results : Significant radioprotection (85-95% survival) at 10 Gy was observed in the three-amifostine pellet implanted group 3-5 h after implantation. LD 50/30 was 7.97, 8.74 and 16.64 Gy for the control, three-placebo pellet (dose reduction factor, DRF=1.10, p <0.01), and three-amifostine pellet (DRF=1.79, p <0.01) groups respectively in mouse exposed to radiation 2h after implantation. Radioprotection at 12 Gy was observed up to 4h after s.c. amifostine administration and up to 3h after implantation. Pharmacokinetic data revealed that the three-amifostine pellet group had sustained blood WR-1065 levels at 2 h after implantation, in contrast to the reported sharp peak at 30 min for s.c. administration. Although locomotor activity was significantly reduced (p <0.01) in the amifostine pellet group, the onset of the locomotor decrement was delayed as compared with groups that received 400 and 750 mg kg -1 s.c. amifostine. Conclusions : Amifostine in biodegradable implant was effective. The radioprotection observed was comparable between conventional s.c. administration of the drug and implantation. Pharmacokinetic data and locomotor activity suggest that the implantation was beneficial though radioprotection data warrants formulation improvements in implants.

Amelioration of radiation-induced hematopoietic and gastrointestinal damage by Ex-RAD® in mice

The aim of the present study was to assess recovery from hematopoietic and gastrointestinal damage by Ex-RAD®, also known as ON01210.Na (4-carboxystyryl-4-chlorobenzylsulfone, sodium salt), after total body radiation. In our previous study, we reported that Ex-RAD, a small-molecule radioprotectant, enhances survival of mice exposed to gamma radiation, and prevents radiation-induced apoptosis as measured by the inhibition of radiation-induced protein 53 (p53) expression in cultured cells. We have expanded this study to determine best effective dose, dose-reduction factor (DRF), hematological and gastrointestinal protection, and in vivo inhibition of p53 signaling. A total of 500 mg/kg of Ex-RAD administered at 24 h and 15 min before radiation resulted in a DRF of 1.16. Ex-RAD ameliorated radiation-induced hematopoietic damage as monitored by the accelerated recovery of peripheral blood cells, and protection of granulocyte macrophage colony-forming units (GM-CFU) in bone marrow. Western blot analysis on spleen indicated that Ex-RAD treatment inhibited p53 phosphorylation. Ex-RAD treatment reduces terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay (TUNEL)-positive cells in jejunum compared with vehicle-treated mice after radiation injury. Finally, Ex-RAD preserved intestinal crypt cells compared with the vehicle control at 13 and 14 Gy. The results demonstrated that Ex-RAD ameliorates radiation-induced peripheral blood cell depletion, promotes bone marrow recovery, reduces p53 signaling in spleen and protects intestine from radiation injury.

Molecular Specificity of 5-Androstenediol as a Systemic Radioprotectant in Mice

We compared in vivo radioprotective efficacy of 5-androstenediol (5-AED) to that of ten other steroids: 17α-androstenediol, dehydroepiandrosterone, 5-androstenetriol (AET), 4-androstenedione (AND), testosterone, estradiol, fluasterone, 16α-bromoepiandrosterone, 16α-fluoro-androst-5-en-17α-ol (α-fluorohydrin, AFH), and 16α-fluoro-androst-5-en-17β-ol (β-fluorohydrin). Steroids were administered 24 or 48 hr before, or 1 hr after, whole-body γ-irradiation. Two days after irradiation at 3 Gy, blood elements were counted. In addition, after irradiation at 9–12.5 Gy, survival was recorded for 30 days. The results showed radioprotective efficacy was specific for 5-AED. One other steroid, AFH, demonstrated appreciable survival effects but was less efficacious than 5-AED. AND and AET produced slight enhancement of survival in some experiments. This is the first demonstration that the prophylactic window for survival enhancement by 1 subcutaneous (sc) injection of 5-AED is as long as 48 hr in mice. Moreover, the results indicate that 1 sc injection of 5-AED 1 hr after irradiation is much less effective than 1 injection 24–48 hr before irradiation. Comparing the molecular features of steroids with radioprotective efficacy leads to the following conclusions: 1) these effects are due to interaction with specific receptors, since sc injection of extremely similar molecules with the same physicochemical properties as 5-AED were not radioprotective; 2) the17-hydroxyl group is essential; 3) this group must be in the β configuration in the absence of nearby side groups; 4) a halogen atom at 16 changes the 17-hydroxyl specificity to α; 5) the 3β-hydroxyl group is not essential; 6) addition of a 7β-hydroxyl group is deleterious; and 7) the effects are not due to activation of sex steroid receptors.

Preclinical development of a bridging therapy for radiation casualties

OBJECTIVE Victims of a terrorist attack presenting with the hematopoietic syndrome resulting from exposure to excessive levels of ionizing radiation will succumb to sepsis if not adequately treated. The probability of survival is increased substantially if the victims immune system is allowed to recover before sepsis sets in. We report here preclinical development of a new bridging therapy that will allow the victims immune system to recover from damage caused by ionizing radiation. MATERIALS AND METHODS The hematopoietic progenitor cells in blood from tocopherol succinate (TS)-injected mice were analyzed quantitatively by standard in vitro soft matrix colony procedures. CD2F1 mice were irradiated with lethal, whole-body doses (9.2 Gy) of (60)Co gamma-rays and then transfused intravenously (periorbital sinus, venous plexus behind the eye) with whole blood, peripheral blood mononuclear cells, or plasma from TS-injected mice 2 and 24 hours postirradiation. Survival was monitored for 30 days after transfusion of whole blood, peripheral blood mononuclear cells, or plasma. RESULTS Progenitor cell analyses revealed that hematopoietic progenitors were mobilized into the peripheral blood of TS-injected mice. Our results demonstrated that infusions of whole blood or peripheral blood mononuclear cells from TS-injected mice greatly improved chances of extended survival of lethally irradiated mice. CONCLUSION TS-stimulated granulocyte colony-stimulating factor mobilizes high numbers of progenitors into the peripheral circulation; in turn, this blood-these progenitors-can be used upon subsequent transfusion to effectively mitigate and repair primary acute radiation injury. The transfused cells act secondarily as a bridging therapy for irradiated mice while their own immune system recovers from the radiation-induced damage.

Hematopoietic responses under protracted exposures to low daily dose gamma irradiation

In attempting to evaluate the possible health consequences of chronic ionizing radiation exposure during extended space travel (e.g., Mars Mission), ground-based experimental studies of the clinical and pathological responses of canines under low daily doses of 60Co gamma irradiation (0.3-26.3 cGy d-1) have been examined. Specific reference was given to responses of the blood forming system. Results suggest that the daily dose rate of 7.5 cGy d-1 represents a threshold below which the hematopoietic system can retain either partial or full trilineal cell-producing capacity (erythropoiesis, myelopoiesis, and megakaryopoiesis) for extended periods of exposure (>1 yr). Trilineal capacity was fully retained for several years of exposure at the lowest dose-rate tested (0.3 cGy d-1) but was completely lost within several hundred days at the highest dose-rate (26.3 cGy d-1). Retention of hematopoietic capacity under chronic exposure has been demonstrated to be mediated by hematopoietic progenitors with acquired radioresistance and repair functions, altered cytogenetics, and cell-cycle characteristics. Radiological, biological, and temporal parameters responsible for these vital acquisitions by hematopoietic progenitors have been partially characterized. These parameters, along with threshold responses, are described and discussed in relation to potential health risks of the space traveler under chronic stress of low-dose irradiation.

Mobilized progenitor cells as a bridging therapy for radiation casualties: A brief review of tocopherol succinate-based approaches

Nuclear detonation through either military or terrorist action would most likely lead to a mass-casualty scenario involving victims with varying degrees of exposure to ionizing radiation. As a result of radiation injury to the hematopoietic system, victims would suffer from a lack of red blood cells that deliver oxygen, immune cells that detect and eliminate infectious agents, and blood platelets that promote blood clot formation. In part, these symptoms are generally referred to as acute radiation syndrome (ARS). While some victims of moderate to high levels of radiation will be beyond saving, most will have received enough radiation to injure but not kill their bone marrow cells completely. Such people will recover from their injuries but face a 30-60day period during which they cannot fully fight infections and are prone to uncontrolled bleeding and anemia. To keep them alive until their hematopoietic system recovers, they must receive supportive care. Recently, using experimental animal models of ARS, transfusion of myeloid progenitor cells have been tried as a bridging therapy for radiation-exposed animals. Such cells have been shown to be effective in protecting animals exposed to lethal doses of radiation. These myeloid progenitors (along with of other hematopoietic progenitor cell types) can be mobilized out of the bone marrow into the blood for the reconstitution of hematopoiesis. This review discusses various approaches to the mobilization of progenitors using different mobilizing agents, and their utility as a bridging therapy for radiation casualties. We suggest that α-tocopherol succinate (TS) is an optimal mobilizing agent for progenitors. The extent of progenitor mobilization TS elicits in experimental mice is comparable to clinically used drugs such as recombinant granulocyte-colony stimulating factor rhG-CSF/Neupogen® and the bicyclam AMD3100 (plerixafor/Mozobil); therefore, we propose that TS be considered for further translational development and, ultimately for use in humans.

Progenitors mobilized by gamma-tocotrienol as an effective radiation countermeasure.

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.

Caspase-Dependent and -Independent Panc-1 Cell Death Due to Actinomycin D and MK 886 are Additive but Increase Clonogenic Survival

In human panc-1 pancreatic cancer cells, actinomycin D (act D) induces a type 1 (apoptotic, extrinsic, death domain, receptor-dependent, and caspase-positive) form of programmed cell death (PCD) and MK 886, a 5-Iipoxygenase inhibitor serving among other functions as a surrogate for increasing oxidative stress, a type 2 form, defined as an intrinsic, mitochondria-dependent, autophagic form of cellular suicide. Using both agents simultaneously should allow for examination of their interaction in cells able to express either form of PCD. Activation of both forms might result in synergistic, additive, null, or inhibitory effects on the reduction in proliferation, PCD, and clonogenicity of surviving cells. Co-culture of panc-1 cells with act D and MK 886, which both inhibit their proliferation, had an additive effect on increasing the development of these forms of PCD, as determined by morphology, a nucleosome assay, and flow cytometry. Initially, laddering on agarose detected with propidium iodide, present in act D, and act D plus MK 886-treated cells was partially obscured by randomly degraded DNA. With the use of the more sensitive SYBR green dye and reduced exposure of detached cells to 37°C, a limited laddering of DNA from MK 886-treated cells was also detected. Caspase activity was present in act-D-cultured cells but was absent in cells cultured with MK 886. Combined culture reduced caspase activity in act D-treated cells, consistent with interference from type 2 of type 1 PCD. Removal after 48 hr of act D or MK 886 allowed regrowth of residual cells, the latter agent to a greater extent than the former. In combination, the number of clones was increased compared with act D alone. These features distinguish two forms of PCD. In therapeutic settings in which the modes of cell death have not been identified, unintentional activation of several cellular suicide pathways with “crosstalk” between them occurs. Their intentional simultaneous activation and responses, as modulated by the history of cells in or out of cycle, could reduce the intended therapeutic outcome with survival of additional clonogenic cells due to various forms of mutual interference.