Effects of minocycline on hematopoietic recovery after whole-body irradiation

Background/Aim: We previously found that minocycline enhanced the levels of several leukocyte populations and had the capacity to induce secretion of certain cytokines early after irradiation. In the current study we further determined the drug's effect on hematopoietic recovery. Materials and Methods: Minocycline was injected intraperitoneally into C57BL/6 mice for 5 days, beginning immediately before exposure to ⁶⁰Co γ-rays (1, 2, 3 Gy). Thirty-two days post-irradiation, spleen and blood were collected to quantify cell populations, cytokines in splenic T-cell supernatants after anti-CD3 activation, and chromosomic status based on spectral karyotyping. Results: While radiation resulted in significantly lower B-cell counts at 3 Gy in both blood and spleen, minocycline treatment increased the counts and/or percentages of splenic B-cells at 2 Gy and 3 Gy. In spleen supernatants, the drug-alone increased the levels of cytokines, including interleukin-1α (IL-1α) and IL-6 that are radioprotective, as well as granulocyte- macrophage colony-stimulating factor (GM-CSF) and G-CSF that accelerate neutrophil recovery. In addition, minocycline suppressed the production of interferon-γ that can prevent hematopoiesis. Dose-dependent radiation-induced chromosomic abnormalities were present in splenic leukocytes. Conclusion: The data indicate that minocycline exerts a relatively long-term effect on parameters that influence hematopoietic recovery. Further testing of this drug as a countermeasure for acute radiation syndrome, is necessary to determine its full potential.