Indirect macrophage responses to ionizing radiation: implications for genotype-dependent bystander signaling

PJ Coates, JK Rundle, SA Lorimore, EG Wright - Cancer research, 2008 - AACR
PJ Coates, JK Rundle, SA Lorimore, EG Wright
Cancer research, 2008AACR
In addition to the directly mutagenic effects of energy deposition in DNA, ionizing radiation is
associated with a variety of untargeted and delayed effects that result in ongoing bone
marrow damage. Delayed effects are genotype dependent with CBA/Ca mice, but not
C57BL/6 mice, susceptible to the induction of damage and also radiation-induced acute
myeloid leukemia. Because macrophages are a potential source of ongoing damaging
signals, we have determined their gene expression profiles and we show that bone marrow …
Abstract
In addition to the directly mutagenic effects of energy deposition in DNA, ionizing radiation is associated with a variety of untargeted and delayed effects that result in ongoing bone marrow damage. Delayed effects are genotype dependent with CBA/Ca mice, but not C57BL/6 mice, susceptible to the induction of damage and also radiation-induced acute myeloid leukemia. Because macrophages are a potential source of ongoing damaging signals, we have determined their gene expression profiles and we show that bone marrow–derived macrophages show widely different intrinsic expression patterns. The profiles classify macrophages derived from CBA/Ca mice as M1-like (pro-inflammatory) and those from C57BL/6 mice as M2-like (anti-inflammatory); measurements of NOS2 and arginase activity in normal bone marrow macrophages confirm these findings. After irradiation in vivo, but not in vitro, C57BL/6 macrophages show a reduction in NOS2 and an increase in arginase activities, indicating a further M2 response, whereas CBA/Ca macrophages retain an M1 phenotype. Activation of specific signal transducer and activator of transcription signaling pathways in irradiated hemopoietic tissues supports these observations. The data indicate that macrophage activation is not a direct effect of radiation but a tissue response, secondary to the initial radiation exposure, and have important implications for understanding genotype-dependent responses and the mechanisms of the hemotoxic and leukemogenic consequences of radiation exposure. [Cancer Res 2008;68(2):450–6]
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