Dietary Isoflavone-Dependent and Estradiol Replacement Effects on Body Weight in the Ovariectomized (OVX) Rat.

17ß-Estradiol is known to regulate energy metabolism and body weight. Ovariectomy results in body weight gain while estradiol administration results in a reversal of weight gain. Isoflavones, found in rodent chow, can mimic estrogenic effects making it crucial to understand the role of these compounds on metabolic regulation. The goal of this study is to examine the effect of dietary isoflavones on body weight regulation in the ovariectomized rat. This study will examine how dietary isoflavones can interact with estradiol treatment to affect body weight. Consistent with previous findings, animals fed an isoflavone-rich diet had decreased body weight (p<0.05), abdominal fat (p<0.05), and serum leptin levels (p<0.05) compared to animals fed an isoflavone-free diet. Estradiol replacement resulted in decreased body weight (p<0.05), abdominal fat (p<0.05), and serum leptin (p<0.05). Current literature suggests the involvement of cytokines in the inflammatory response of body weight gain. We screened a host of cytokines and chemokines that may be altered by dietary isoflavones or estradiol replacement. Serum cytokine analysis revealed significant (p<0.05) diet-dependent increases in inflammatory cytokines (keratinocyte-derived chemokine). The isoflavone-free diet in OVX rats resulted in the regulation of the following cytokines and chemokines: interleukin-10, interleukin-18, serum regulated on activation, normal T cell expressed and secreted, and monocyte chemoattractant protein-1 (p<0.05). Overall, these results reveal that estradiol treatment can have differential effects on energy metabolism and body weight regulation depending on the presence of isoflavones in rodent chow.

History and development of radiation-protective agents.

PURPOSE: The search for ideal protective agents for use in a variety of radiation scenarios has continued for more than six decades. This review evaluates agents and procedures that have the potential to protect against acute and late effects of ionising radiation when administered either before or after radiation exposure. CONCLUSION: Over the years, extensive experimental studies of radiation-protective agents have enhanced our knowledge of radiation physics, chemistry, and biology. However, translation of agents from animal testing to use in various scenarios, such as prophylactic adjuncts in radiotherapy or post-exposure treatments for potential victims of radiation accidents/incidents, has been slow. Nevertheless, a number of compounds are now available for use in a variety of radiation situations. These include agents approved by the U.S. Food and Drug Administration for use in reducing exposure to internal radionuclides (Prussian blue, calcium diethylenetriamene pentaacetate (DTPA) and zinc DTPA, potassium iodide) and amifostine for alleviating xerostomia associated with radiotherapy. Consensus groups have also recommended other therapies such as granulocyte colony-stimulating factor for radiation-induced neutropenia. The variety of prophylactic and therapeutic agents in the research pipeline includes those that are naturally-occurring with low toxicity, provide a long window of protection, protect normal tissue while sensitising tumours, or act via receptors and modulate biological processes such as induction of genes responsible for radioresistance. The search for agents that protect against acute and late effects of ionising radiation injury will undoubtedly continue into the future and influence other areas of radiation research.

Mechanism and therapeutic window of a genistein nanosuspension to protect against hematopoietic-acute radiation syndrome.

There are no FDA-approved drugs that can be administered prior to ionizing radiation exposure to prevent hematopoietic-acute radiation syndrome (H-ARS). A suspension of synthetic genistein nanoparticles was previously shown to be an effective radioprotectant against H-ARS when administered prior to exposure to a lethal dose of total body radiation. Here we aimed to determine the time to protection and the duration of protection when the genistein nanosuspension was administered by intramuscular injection, and we also investigated the drug's mechanism of action. A single intramuscular injection of the genistein nanosuspension was an effective radioprotectant when given prophylactically 48 h to 12 h before irradiation, with maximum effectiveness occurring when administered 24 h before. No survival advantage was observed in animals administered only a single dose of drug after irradiation. The dose reduction factor of the genistein nanosuspension was determined by comparing the survival of treated and untreated animals following different doses of total body irradiation. As genistein is a selective estrogen receptor beta agonist, we also explored whether this was a central component of its radioprotective mechanism of action. Mice that received an intramuscular injection of an estrogen receptor antagonist (ICI 182,780) prior to administration of the genistein nanosuspension had significantly lower survival following total body irradiation compared with animals only receiving the nanosuspension (P < 0.01). These data define the time to and duration of radioprotection following a single intramuscular injection of the genistein nanosuspension and identify its likely mechanism of action.

Genistein induces radioprotection by hematopoietic stem cell quiescence.

PURPOSE: In this study we addressed whether genistein-induced radioprotection in mice is associated with alterations of the cell cycle of hematopoietic stem and progenitor cells. MATERIALS AND METHODS: C57BL/6J female mice received a single subcutaneous injection of genistein (200 mg/kg) 24 h prior to a lethal dose (7.75 Gy, (60)Co) of total body irradiation. Proliferation-associated Ki-67 protein/7-aminoactinomycin-D (Ki67/7AAD) cell cycle staining was used to differentiate between G(0), G(1), and S/G(2)/M in bone marrow cell populations negative for expression of mature hematopoietic lineage marker cells but positive for expression of stem cell antigen-1 and tyrosine kinase receptor for stem cell factor (Lin(-)Sca-1(+)cKit(+), LSK(+)). Quantitative real-time polymerase chain reaction (qRT-PCR) microarrays were utilized to examine cell cycle specific genes. RESULTS: At 24 h following radiation exposure, a greater percentage of LSK(+) in genistein-treated mice accumulated in the G(0) phase of the cell cycle, whereas a large percentage of LSK(+) bone marrow cells from untreated and vehicle (PEG-400)-treated mice progressed into the G(1) and S/G(2)/M phases. Moreover, the absolute number of marrow total LSK(+), long-term LSK(+), and short-term LSK(+) increased 2.8, 12.1, and 4.2-fold, respectively, at 7 days post-irradiation in genistein-treated vs. untreated irradiated mice. Lin(-) cells from genistein-treated mice expressed fewer DNA damage responsive and cell cycle checkpoint genes than LSK(+) from untreated or vehicle-treated mice. CONCLUSION: Pretreatment with genistein provides in vivo protection from acute myelotoxicity through extended quiescence followed by reduced senescence of marrow repopulating LSK(+).

Genistein protects against biomarkers of delayed lung sequelae in mice surviving high-dose total body irradiation.

The effects of genistein on 30-day survival and delayed lung injury were examined in C57BL/6J female mice. A single subcutaneous injection of vehicle (PEG-400) or genistein (200 mg/kg) was administered 24 h before total body irradiation (7.75 Gy (60)Co, 0.6 Gy/min). Experimental groups were: No treatment + Sham (NC), Vehicle + Sham (VC), Genistein + Sham (GC), Radiation only (NR), Vehicle + Radiation (VR), Genistein + Radiation (GR). Thirty-day survivals after 7.75 Gy were: NR 23%, VR 53%, and GR 92%, indicating significant protection from acute radiation injury by genistein. Genistein also mitigated radiation-induced weight loss on days 13-28 postirradiation. First generation lung fibroblasts were analyzed for micronuclei 24 h postirradiation. Fibroblasts from the lungs of GR-treated mice had significantly reduced micronuclei compared with NR mice. Collagen deposition was examined by histochemical staining. At 90 days postirradiation one half of the untreated and vehicle irradiated mice had focal distributions of small collagen-rich plaques in the lungs, whereas all of the genistein-treated animals had morphologically normal lungs. Radiation reduced the expression of COX-2, transforming growth factor-beta receptor (TGFbetaR) I and II at 90 days after irradiation. Genistein prevented the reduction in TGFbetaRI. However, by 180 days postirradiation, these proteins normalized in all groups. These results demonstrate that genistein protects against acute radiation-induced mortality in female mice and that GR-treated mice have reduced lung damage compared to NR or VR. These data suggest that genistein is protective against a range of radiation injuries.

Subcutaneous administration of genistein prior to lethal irradiation supports multilineage, hematopoietic progenitor cell recovery and survival.

PURPOSE: Genistein, a non-toxic isoflavone from soybeans, has immunomodulating and radioprotective properties. In this study we investigated the mechanism for genistein-induced radioprotection by evaluating the recovery of bone marrow cells and peripheral blood hematology in lethally irradiated mice. MATERIALS AND METHODS: CD2F1 male mice received a single subcutaneous injection of genistein (200 mg/kg) 24 h prior to a lethal, total body irradiation dose (8.75 Gy) of cobalt-60 gamma radiation. Survival and hematopoietic reconstitution were evaluated over nine weeks post-irradiation. Hematopoietic progenitor colony-forming cell assays were used to assess the reconstitution of bone marrow after radiation-induced myelosuppression. RESULTS: A total of 97% of genistein-treated mice survived after 30 days while 31% of vehicle-treated and 0% of untreated mice survived. The improvement in survival was related to accelerated neutrophil and platelet recovery, resulting from earlier and more pronounced multilineage, hematopoietic progenitor cell reconstitution in the femoral marrow compartment. Myeloid and erythroid progenitor cell numbers at day 15 post-irradiation were 6-fold to 20-fold higher in genistein-treated animals than in control animals. CONCLUSIONS: These results demonstrate that a single subcutaneous administration of genistein 24 h before irradiation provides significant radioprotection to the hematopoietic progenitor cell compartment.

The interaction of dietary isoflavones and estradiol replacement on behavior and brain-derived neurotrophic factor in the ovariectomized rat.

Phytoestrogens are plant derived, non-steroidal compounds naturally found in rodent chows that potentially have endocrine-disrupting effects. Isoflavones, the most common phytoestrogens, have a similar structure and molecular weight to 17ß-estradiol (E2) and have the ability to bind and activate both isoforms of the estrogen receptor (ER). Most isoflavones have a higher affinity for ERß, which is involved in sexually dimorphic behavioral regulation. The goal of this study was to examine the interaction of isoflavones and E2 presence in the OVX rat on anxiety- and depressive- like behavior and the related BDNF pathophysiology. E2 administration resulted in anxiogenic behaviors when isoflavones were present in the diet (p<0.05), but anxiolytic behaviors when isoflavones were not present (p<0.05). E2 resulted in antidepressive-like behaviors in animals fed an isoflavone-rich diet (p<0.05), with no effect when isoflavones were removed. Increased hippocampal BDNF expression was observed in animals fed an isoflavone-rich diet after E2 administration (p<0.05). BDNF expression in the amygdala and hypothalamus was increased after E2 treatment in animals fed an isoflavone-rich diet. Overall, these results demonstrate that the presence of dietary isoflavones can differentially regulate the effect of E2 replacement on behavior and BDNF expression.

Accelerated senescence in skin in a murine model of radiation-induced multi-organ injury.

Accidental high-dose radiation exposures can lead to multi-organ injuries, including radiation dermatitis. The types of cellular damage leading to radiation dermatitis are not completely understood. To identify the cellular mechanisms that underlie radiation-induced skin injury in vivo, we evaluated the time-course of cellular effects of radiation (14, 16 or 17 Gy X-rays; 0.5 Gy/min) in the skin of C57BL/6 mice. Irradiation of 14 Gy induced mild inflammation, observed histologically, but no visible hair loss or erythema. However, 16 or 17 Gy radiation induced dry desquamation, erythema and mild ulceration, detectable within 14 days post-irradiation. Histological evaluation revealed inflammation with mast cell infiltration within 14 days. Fibrosis occurred 80 days following 17 Gy irradiation, with collagen deposition, admixed with neutrophilic dermatitis, and necrotic debris. We found that in cultures of normal human keratinocytes, exposure to 17.9 Gy irradiation caused the upregulation of p21/waf1, a marker of senescence. Using western blot analysis of 17.9 Gy-irradiated mice skin samples, we also detected a marker of accelerated senescence (p21/waf1) 7 days post-irradiation, and a marker of cellular apoptosis (activated caspase-3) at 30 days, both preceding histological evidence of inflammatory infiltrates. Immunohistochemistry revealed reduced epithelial stem cells from hair follicles 14-30 days post-irradiation. Furthermore, p21/waf1 expression was increased in the region of the hair follicle stem cells at 14 days post 17 Gy irradiation. These data indicate that radiation induces accelerated cellular senescence in the region of the stem cell population of the skin.

Delta-tocotrienol suppresses radiation-induced microRNA-30 and protects mice and human CD34+ cells from radiation injury.

We reported that microRNA-30c (miR-30c) plays a key role in radiation-induced human cell damage through an apoptotic pathway. Herein we further evaluated radiation-induced miR-30 expression and mechanisms of delta-tocotrienol (DT3), a radiation countermeasure candidate, for regulating miR-30 in a mouse model and human hematopoietic CD34+ cells. CD2F1 mice were exposed to 0 (control) or 7-12.5 Gy total-body gamma-radiation, and CD34+ cells were irradiated with 0, 2 or 4 Gy of radiation. Single doses of DT3 (75 mg/kg, subcutaneous injection for mice or 2 µM for CD34+ cell culture) were administrated 24 h before irradiation and animal survival was monitored for 30 days. Mouse bone marrow (BM), jejunum, kidney, liver and serum as well as CD34+ cells were collected at 1, 4, 8, 24, 48 or 72 h after irradiation to determine apoptotic markers, pro-inflammatory cytokines interleukin (IL)-1ß and IL-6, miR-30, and stress response protein expression. Our results showed that radiation-induced IL-1ß release and cell damage are pathological states that lead to an early expression and secretion of miR-30b and miR-30c in mouse tissues and serum and in human CD34+ cells. DT3 suppressed IL-1ß and miR-30 expression, protected against radiation-induced apoptosis in mouse and human cells, and increased survival of irradiated mice. Furthermore, an anti-IL-1ß antibody downregulated radiation-induced NFκBp65 phosphorylation, inhibited miR-30 expression and protected CD34+ cells from radiation exposure. Knockdown of NFκBp65 by small interfering RNA (siRNA) significantly suppressed radiation-induced miR-30 expression in CD34+ cells. Our data suggest that DT3 protects human and mouse cells from radiation damage may through suppression of IL-1ß-induced NFκB/miR-30 signaling.

Protein Oxidation in the Lungs of C57BL/6J Mice Following X-Irradiation.

Damage to normal lung tissue is a limiting factor when ionizing radiation is used in clinical applications. In addition, radiation pneumonitis and fibrosis are a major cause of mortality following accidental radiation exposure in humans. Although clinical symptoms may not develop for months after radiation exposure, immediate events induced by radiation are believed to generate molecular and cellular cascades that proceed during a clinical latent period. Oxidative damage to DNA is considered a primary cause of radiation injury to cells. DNA can be repaired by highly efficient mechanisms while repair of oxidized proteins is limited. Oxidized proteins are often destined for degradation. We examined protein oxidation following 17 Gy (0.6 Gy/min) thoracic X-irradiation in C57BL/6J mice. Seventeen Gy thoracic irradiation resulted in 100% mortality of mice within 127-189 days postirradiation. Necropsy findings indicated that pneumonitis and pulmonary fibrosis were the leading cause of mortality. We investigated the oxidation of lung proteins at 24 h postirradiation following 17 Gy thoracic irradiation using 2-D gel electrophoresis and OxyBlot for the detection of protein carbonylation. Seven carbonylated proteins were identified using mass spectrometry: serum albumin, selenium binding protein-1, alpha antitrypsin, cytoplasmic actin-1, carbonic anhydrase-2, peroxiredoxin-6, and apolipoprotein A1. The carbonylation status of carbonic anhydrase-2, selenium binding protein, and peroxiredoxin-6 was higher in control lung tissue. Apolipoprotein A1 and serum albumin carbonylation were increased following X-irradiation, as confirmed by OxyBlot immunoprecipitation and Western blotting. Our findings indicate that the profile of specific protein oxidation in the lung is altered following radiation exposure.

Protection against ionizing radiation by antioxidant nutrients and phytochemicals.

The potential of antioxidants to reduce the cellular damage induced by ionizing radiation has been studied in animal models for more than 50 years. The application of antioxidant radioprotectors to various human exposure situations has not been extensive although it is generally accepted that endogenous antioxidants, such as cellular non-protein thiols and antioxidant enzymes, provide some degree of protection. This review focuses on the radioprotective efficacy of naturally occurring antioxidants, specifically antioxidant nutrients and phytochemicals, and how they might influence various endpoints of radiation damage. Results from animal experiments indicate that antioxidant nutrients, such as vitamin E and selenium compounds, are protective against lethality and other radiation effects but to a lesser degree than most synthetic protectors. Some antioxidant nutrients and phytochemicals have the advantage of low toxicity although they are generally protective when administered at pharmacological doses. Naturally occurring antioxidants also may provide an extended window of protection against low-dose, low-dose-rate irradiation, including therapeutic potential when administered after irradiation. A number of phytochemicals, including caffeine, genistein, and melatonin, have multiple physiological effects, as well as antioxidant activity, which result in radioprotection in vivo. Many antioxidant nutrients and phytochemicals have antimutagenic properties, and their modulation of long-term radiation effects, such as cancer, needs further examination. In addition, further studies are required to determine the potential value of specific antioxidant nutrients and phytochemicals during radiotherapy for cancer.

Radiation-induced performance decrement.

This article is a brief review of performance decrement expected after low-level radiation doses (0.70 Gy or less) and after higher radiation doses. Examples are presented from both animal and human data. The data indicate that low-level radiation doses in humans are not expected to degrade performance on the battlefield. Doses higher than 1.25 Gy are likely to degrade performance. Transient performance deficits known as early transient incapacitation observed in animals and humans after large, rapidly delivered doses of ionizing radiation are discussed.

Psychological consequences of military operations in low-level radiation environments.

Military operations have produced neuropsychiatric (NP) casualties throughout history. The same is true for radiation accidents. Although we have not carried out military operations in nuclear environments, related experience suggests that operations performed under low-level radiation conditions could serve to compound the factors that are known to produce NP casualties. Historically, military NP casualty rates have varied widely depending on a complex array of factors, ranging from the actual conditions of the operation and experiences of the soldiers to the perception of the conflict by both the soldiers and the people back home. History has also shown that lack of preparation contributes to NP casualties. The number and severity of NP casualties can be minimized by ensuring that the equipment, training, and leadership are in place to instill in our soldiers the confidence that they can cope with the types of threats that are part of modern-day missions.

Protection against gamma-irradiation with 5-androstenediol.

We showed previously that treatment of gamma-irradiated female B6D2F1 mice with 5-androstenediol (AED) enhanced survival, stimulated myelopoiesis, and ameliorated radiation-induced decreases in circulating neutrophils and platelets. We have now tested survival in male CD2F1 mice, and we have investigated molecular and functional effects on neutrophils and bone marrow stromal cells and screened for toxicity in female B6D2F1 mice. AED (160 mg/kg, subcutaneously, 24 hours before irradiation) enhanced survival in male CD2F1 mice with a dose-reduction factor of 1.23, similar to the dose-reduction factor of 1.26 found previously for female B6D2F1 mice. Expression of CD11b, a developmental marker, was reduced on circulating neutrophils after either in vivo AED administration or whole-body gamma-irradiation (3 Gy), but neutrophil peroxidase activity was unchanged. Stromal cell progenitors (fibroblastoid colony-forming units) were reduced in marrow 5 days after AED injection in nonirradiated mice. Clinical chemistry, histopathology, and behavioral assays showed no evidence of toxicity. We conclude that AED and related steroids are attractive candidates to explore as countermeasures to high- and low-level ionizing radiation.

Health effects of embedded depleted uranium.

The health effects of embedded fragments of depleted uranium (DU) are being investigated to determine whether current surgical fragment-removal policies are appropriate for this metal. The authors studied rodents implanted with DU pellets as well as cultured human cells exposed to DU compounds. Results indicate that uranium from implanted DU fragments distributes to tissues distant from implantation sites, including bone, kidney, muscle, and liver. Despite levels of uranium in kidney that would be nephrotoxic after acute exposure, no histological or functional kidney toxicity was observed with embedded DU, indicating that the kidney adapts when exposed chronically. Nonetheless, further studies of the long-term health impact are needed. DU is mutagenic and transforms human osteoblastic cells into a tumorigenic phenotype. It alters neurophysiological parameters in rat hippocampus, crosses the placental barrier, and enters fetal tissue. Preliminary data also indicate decreased rodent litter size when animals are bred 6 months or longer after DU implantation.

Nuclear, biological, and chemical combined injuries and countermeasures on the battlefield.

The Armed Forces Radiobiological Research Institute (AFRRI) has developed a research program to determine the major health risks from exposure to ionizing radiation in combination with biological and chemical warfare agents and to assess the extent to which exposure to ionizing radiation compromises the effectiveness of protective drugs, vaccines, and other biological and chemical warfare prophylactic and treatment strategies. AFRRI's Defense Technology Objective MD22 supports the development of treatment modalities and studies to assess the mortality rates for combined injuries from exposure to ionizing radiation and Bacillus anthracis, and research to provide data for casualty prediction models that assess the health consequences of combined exposures. In conjunction with the Defense Threat Reduction Agency, our research data are contributing to the development of casualty prediction models that estimate mortality and incapacitation in an environment of radiation exposure plus other weapons of mass destruction. Specifically, the AFFRI research program assesses the effects of ionizing radiation exposure in combination with B. anthracis, Venezuelan equine encephalomyelitis virus, Shigella sonnei, nerve agents, and mustard as well as their associated treatments and vaccines. In addition, the long-term psychological effects of radiation combined with nuclear, biological, and chemical (NBC) injuries are being evaluated. We are also assessing the effectiveness of gamma photons and high-speed neutrons and electrons for neutralizing biological and chemical warfare agents. New protocols based on our NBC bioeffects experiments will enable U.S. armed forces to accomplish military operations in NBC environments while optimizing both survival and military performance. Preserving combatants' health in an NBC environment will improve warfighting operations and mission capabilities.

Genistein nanoparticles protect mouse hematopoietic system and prevent proinflammatory factors after gamma irradiation.

Previous studies demonstrated that genistein protects mice from radiation-induced bone marrow failure. To overcome genistein's extremely low water solubility, a nanoparticle suspension of genistein has been formulated for more rapid dissolution. In the current study, we evaluated the radioprotective effects of a nanoparticle formulation of genistein on survival and hematopoietic recovery in mice exposed to total-body gamma irradiation. A single intramuscular injection of a saline-based genistein nanosuspension (150 mg/kg) administered to CD2F1 mice 24 h before 9.25 Gy (60)Co radiation exposure resulted in a 30-day survival rate of 95% compared to 25% in vehicle-treated animals. In mice irradiated at 7 Gy, the genistein nanosuspension increased mouse bone marrow cellularity from approximately 2.9% (vehicle treated) to 28.3% on day 7 postirradiation. Flow cytometry analysis demonstrated decreased radiation-induced hematopoietic stem and progenitor cell (HSPC, Lineage(-)/cKit(+)) death from 77.0% (vehicle) to 43.9% (genistein nanosuspension) with a significant recovery of clonogenicity 7 days after irradiation. The genistein nanosuspension also attenuated the radiation-induced elevation of proinflammatory factors interleukin 1 beta (IL-1ß), IL-6 and cyclooxygenase-2 (COX-2) in mouse bone marrow and spleen, which may contribute to protecting HSPCs.

Delta-tocotrienol protects mice from radiation-induced gastrointestinal injury.

We recently demonstrated that natural delta-tocotrienol (DT3) significantly enhanced survival in total-body irradiated (TBI) mice, and protected mouse bone marrow cells from radiation-induced damage through Erk activation-associated mTOR survival pathways. Here, we further evaluated the effects and mechanisms of DT3 on survival of radiation-induced mouse acute gastrointestinal syndrome. DT3 (75-100 mg/kg) or vehicle was administered as a single subcutaneous injection to CD2F1 mice 24 h before 10-12 Gy (60)Co total-body irradiation at a dose rate of 0.6 Gy/min and survival was monitored. In a separate group of mice, jejunum sections were stained with hematoxylin and eosin and the surviving crypts in irradiated mice were counted. Apoptosis in intestinal epithelial cells was measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining and bacterial translocation from gut to heart, spleen and liver in irradiated mice were evaluated. DT3 (75 mg/kg) significantly enhanced survival in mice that received 10, 10.5, 11 or 12 Gy TBI. Administration of DT3 protected intestinal tissue, decreased apoptotic cells in jejunum and inhibited gut bacterial translocation in irradiated mice. Furthermore, DT3 significantly inhibited radiation-induced production of pro-inflammatory factors interleukin-1ß and -6 and suppressed expression of protein tyrosine kinase 6 (PTK6), a stress-induced kinase that promotes apoptosis in mouse intestinal cells. Our data demonstrate that administration of DT3 protected mice from radiation-induced gastrointestinal system damage.

Captopril modulates hypoxia-inducible factors and erythropoietin responses in a murine model of total body irradiation.

OBJECTIVE: Our laboratory reported that the angiotensin converting enzyme inhibitor captopril improves erythroid recovery from total body irradiation (TBI) in mice when administered after irradiation. However, captopril administered before TBI attenuates erythroid recovery. Here we investigate captopril and radiation regulation of erythropoietin (EPO) and thrombopoietin (TPO), key effectors of erythroid progenitor proliferation and differentiation. MATERIALS AND METHODS: C57BL/6 mice, nonirradiated or exposed to 7.5 Gy TBI ((60)Co, 0.6 Gy/min) were untreated or administered captopril. Plasma EPO and TPO levels were measured by enzyme-linked immunosorbent assay. Gene expression of EPO was determined by quantitative reverse transcription polymerase chain reaction. The hypoxia-inducible factors (HIF)-1α and -2α were measured by immunoblotting. RESULTS: In nonirradiated mice, continuous captopril administration in the water transiently reduced reticulocytes and red blood cells after 7 and 10 days, respectively. EPO plasma levels and gene expression were reduced below detectable limits after 2 days of captopril treatment, but recovered within 7 days. HIF-1α and HIF-2α were activated preceding reticulocyte and red blood cell recovery. TBI, which ablates early and late-stage erythroid progenitors, activated both HIFs and increased EPO and TPO. Captopril treatment postirradiation suppressed radiation-induced HIF activation and EPO expression. In contrast, captopril administration for 7 days before TBI resulted in earlier EPO induction and activation. Captopril treatment lowered TPO levels in nonirradiated mice, but had minimal effects on radiation-induced TPO. CONCLUSIONS: In nonirradiated mice, captopril biphasically regulates EPO via HIF activation. TBI ablates erythroid progenitors, resulting in hypoxia, HIF activation, and increased EPO expression that are modulated by captopril treatment. These data suggest that short-term suppression of radiation-induced EPO immediately after TBI is favorable for erythroid recovery.

Evaluation of hydration and nutritional gels as supportive care after total-body irradiation in mice (Mus musculus).

Concern regarding the potential for radiation exposure from accidents or nuclear and radiologic terrorism is increasing. The purpose of this study was to determine whether the addition of minimal supportive care consisting of hydration or nutritional gels could be used to reduce mortality in mice exposed to (60)Co gamma-radiation. Male CD2F1 mice received 0, 8.50, or 9.25 Gy (60)Co at a dose rate of 0.6 Gy/min. These groups were further divided into 3 treatment groups that-in addition to pelleted food and water-received no supportive care, hydration gel, or nutritional gel. Overall survival, mean survival time, consumption of pelleted food and gel, and body weight were recorded for 30 d. Radiation caused dose-dependent decreases in overall survival, consumption of pelleted food and supplemental gel, and body weight. However, at each radiation dose (0, 8.50, 9.25 Gy), the type of supportive care did not modify overall survival, mean survival time, or changes in body weight. These results demonstrate that hydration and nutritional gels were not effective methods of supportive care after high-dose total body irradiation in mice.