Beta androstenediol mitigates the damage of 1 GeV/n Fe ion particle radiation to the hematopoietic system

Abstract

Space exploration is associated with exposure to 1-3 Gy solar particle radiation and galactic cosmic radiation that could increase cancer rates. Effective nontoxic countermeasures to high linear energy transfer (LET) radiation exposure are highly desirable but currently not available. The aim was to determine whether a single subcutaneous injection of androstenediol (Δ(5) androsten-3β, 17β-diol [AED]) could mitigate and restore the mouse hematopoetic system from the radiation-mediated injury of 3 Gy whole-body high LET (56)Fe(26+) exposure. The findings show that postradiation AED treatment has an overall positive and significant beneficial effect to restore the levels of hematopoeitic elements (p<0.001). Androstenediol treatment significantly increased monocyte levels at days 4, 7, and 14 and, similarly, increased red blood cell, hemoglobin, and platelet counts. Flow cytometry analysis 14 days after radiation and AED treatment demonstrated an increase (p<0.05) in bone marrow cells counts. Ex vivo osteoclastogenesis studies show that AED treatment is necessary and advantageous for the development and restoration of osteoclastogenesis after radiation exposure. These findings clearly show that androstenediol functions as a countermeasure to remedy hematopoeitic injury mediated by high LET iron ion radiation. Presently, no other agent has been shown to have such properties.

FIG. 1.

The effects of irradiation with 1 GeV/nucleon ⁵⁶Fe²⁶⁺ particles on peripheral WBC counts are illustrated. Data are average value±SE. Radiation reduced WBC levels by 86.26% (p<0.001), lymphocyte levels by 74.72% (p<0.01), monocytes by 77.78% (p<0.05), and granulocytes by 91.79% (p<0.01). l, liter; WBC, white blood cell.

FIG. 2.

The effects of a single subcutaneous injection of AED (8.0 mg/25 g mouse) after whole-body radiation exposure to a dose of 3 Gy of high LET iron ions on total WBC, granulocyte, and lymphocyte counts. During the test period a positive effect of AED treatment on peripheral blood cell counts as compared to vehicle is evident (p<0.001). AED, Δ⁵ androsten-3β, 17β-diol; l, liter; LET, linear energy transfer.

FIG. 3.

The effects of a single subcutaneous dose of AED (8.0 mg/25 g mouse) after whole-body radiation exposure to a dose of 3 Gy of high LET iron ions on monocytes levels. Monocyte average±SE levels of AED-treated animals as compared to vehicle-treated animals are significantly higher at days 4, 7, and 14, p<0.05 and 0.01, respectively. l, liter.

FIG. 4.

The effects of a single subcutaneous injection of AED (8.0 mg/25 g mouse) after whole-body radiation exposure to a dose of 3 Gy of high LET iron ions on RBC levels and hemoglobin (HGB) levels 7 days after treatment. The increase in RBC and HBG levels is statistically significant (p<0.01 and 0.01, respectively). l, liter; RBC, red blood cell.

FIG. 5.

The effects of a single subcutaneous injection of AED (8.0 mg/25 g mouse) after whole-body radiation exposure to a dose of 3 Gy of high LET iron ions on platelets levels. Platelet levels (average±SE) of AED-treated animals as compared to vehicle-treated animals are significantly higher at day 14. l, liter.

FIG. 6.

(A, B) Trap staining of multinucleated osteoclasts. Bone marrow macrophages (BMM) were harvested and cultured from mouse femurs at 7 days postirradiaton. Conversion of BMM within the osteoclast lineage occurred in the presence of continuous incubation of m-CSF (25 ng/mL) and recombinant human RANKL (100 ng/mL) for 10 days. Thin arrows indicate red tartrate resistant acid phosphatase (TRAP) staining of multinucleated osteoclasts. The large arrow heads reveal remnant osteoclasts, where previously formed osteclasts underwent a process of cell death. A representative image from irradiated, vehicle-treated animals (A) and from irradiated, AED-treated animals (B) is shown. (C, D) Osteoclastogenesis was random, impaired, and incomplete using BMM from vehicle-treated whole-body irradiated mice. (C) Osteoclastogenesis of BMM harvested from mice treated with AED after whole-body irradiation was characterized by enlarged but mostly stable multinucleated cell structures, (D). Magnification for each panel is 200×.