WR-151327 increases resistance to Klebsiella pneumoniae infection in mixed-field- and gamma-photon-irradiated mice.

PURPOSE: To determine the efficacy of WR-151327 (WR) [S-3-(3-methylaminopropylamino) propylphosphorothioic acid; (CH3-HN-(CH2)3-NH-(CH2)3-S-PO3H2)] in increasing resistance to bacterial infection after a sublethal dose of gamma-photons or mixed-field neutrons plus gamma-photons. MATERIALS AND METHODS: B6D2F1/J female mice received 200 mg/kg WR i.p. or saline vehicle 20-30 min before or after sham (0 Gy) or 7.0 Gy 60Co gamma-photon irradiation. WR or saline vehicle was given only before 3.5 Gy TRIGA-reactor-produced mixed-field [n/(n+y) = 0.67] irradiation. Four days after drug treatment or drug treatment and irradiation, graded doses of Klebsiella pneumoniae were injected s.c. into mice, and 30-day survival was recorded. To assess haemopoietic changes other unirradiated and irradiated mice not injected with bacteria were given WR or saline. Peripheral blood (PB) and femoral bone marrow (BM) cells were measured 1, 3 or 4, 7, 10 and 14 or 15 days later. RESULTS: WR pretreatment increased resistance to infection in irradiated but not in unirradiated mice. Bacterial CFU-LD50/30 values for 0 Gy saline-treated mice were 1.20x10(6); for 0 Gy WR-treated mice 1.16x10(6); for gamma-photon-irradiated saline-treated mice 3.02x10(1); for gamma-photon-irradiated WR-treated mice 1.24x10(4); for mixed-field-irradiated saline-treated mice 1.94x10(2); and for mixed-field-irradiated WR-treated mice 6.13x10(3). WR-induced resistance to infection paralleled increased numbers of PB white cells, neutrophils, platelets, femoral BM cells and granulocyte macrophage colony-forming cells (GM-CFC) in irradiated mice not given bacteria. CONCLUSIONS: These studies quantify the resistance to bacterial infection in mice treated with WR before sublethal irradiation. The findings suggest that WR treatment increases resistance to infection in immunocompromised hosts.

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.

Mixed-field neutrons and gamma photons induce different changes in ileal bacteria and correlated sepsis in mice.

High doses of radiation induce septicaemia, from bacterial translocation, and death in animals. Mice were exposed to either comparable lethal (LD90/30) or sublethal (LD0/30) doses of mixed-field [n/(n + y) = 0.67] or pure 60Co gamma-photon radiation. The relative biological effectiveness of these comparable doses of radiation was 1.82, determined by probit analysis. Mice given a lethal dose of mixed-field radiation developed a significant (p < 0.01), 10(9)-fold increase in Gram-negative facultative bacteria in their ilea over values in control mice. In contrast, mice given a lethal dose of gamma-photon radiation developed a significant (p < 0.01) increase in only Gram-positive bacteria in their ilea, while the number of Gram-negative bacteria remained near values in control mice. Data correlated with bacteria that were isolated and identified from the livers of mice that were given comparable lethal doses (LD99/30) of mixed-field or gamma-photon radiation. In sublethally irradiated mice, fluctuation in the total number of bacteria was detected in their ilea during the first week following irradiation, after which the number approximated the value in control mice. This difference in the predominant facultative bacteria in ilea resulting from different qualities of radiation has important implications for the treatment of septicaemic-irradiated hosts.

Survival of irradiated mice treated with WR-151327, synthetic trehalose dicorynomycolate, or ofloxacin.

Spaceflight personnel need treatment options that would enhance survival from radiation and would not disrupt task performance. Doses of prophylactic or therapeutic agents known to induce significant short-term (30-day) survival with minimal behavioral (locomotor) changes were used for 180-day survival studies. In protection studies, groups of mice were treated with the phosphorothioate WR-151327 (200 mg/kg, 25% of the LD(10)) or the immunomodulator, synthetic trehalose dicorynomycolate (S-TDCM; 8 mg/kg), before lethal irradiation with reactor-generated fission neutrons and gamma-rays (n/gamma=1) or 60Co gamma-rays. In therapy studies, groups of mice received either S-TDCM, the antimicrobial ofloxacin, or S-TDCM plus ofloxacin after irradiation. For WR-151327 treated-mice, survival at 180 days for n/gamma=1 and gamma-irradiated mice was 90% and 92%, respectively; for S-TDCM (protection), 57% and 78%, respectively; for S-TDCM (therapy), 20% and 25%, respectively; for ofloxacin, 38% and 5%, respectively; for S-TDCM combined with ofloxacin, 30% and 30%, respectively; and for saline, 8% and 5%, respectively. Ofloxacin or combined ofloxacin and S-TDCM increased survival from the gram-negative bacterial sepsis that predominated in n/gamma=1 irradiated mice. The efficacies of the treatments depended on radiation quality, treatment agent and its mode of use, and microflora of the host.

Acquisition of iron from citrate by Pseudomonas aeruginosa.

Transport of [14C]citrate, ferric [14C]citrate and [55Fe]ferric citrate into Pseudomonas aeruginosa grown in synthetic media containing citrate, succinate, or succinate and citrate as carbon and energy sources was measured. Cells grown in citrate-containing medium transported radiolabelled citrate and iron, whereas the succinate-grown cells transported iron but not citrate. Binding studies revealed that isolated outer and inner membranes of citrate-grown cells contain a citrate receptor, absent from membranes of succinate-grown cells. [55Fe]Ferric citrate bound to the isolated outer membranes of each cell type. The failure of citrate to compete with this binding suggests the presence of a ferric citrate receptor on the outer membranes of each cell type. Citrate induced the synthesis of two outer-membrane proteins of 41 and 19 kDa. A third protein of 17 kDa was more dominant in citrate-grown cells than in succinate-grown cells.