Background and purpose: We previously showed that mice with reduced levels of the transforming growth factor-beta (TGF-β) co-receptor endoglin (Eng(+/-) mice) develop less fibrosis and vascular damage after kidney irradiation than their wild type (Eng(+/+) mice) littermates; however, the underlying mechanism was unclear. Results from current studies suggest that this occurs via modulation of the radiation-induced inflammatory response.
Materials and methods: Kidneys of Eng(+/+) and Eng(+/-) mice were irradiated with 16Gy. Mice were sacrificed at 20weeks after irradiation and gene expression and protein levels were analyzed.
Results: Kidney irradiation triggered the infiltration of macrophages in both Eng(+/+) and Eng(+/-) mice, however, levels of macrophage-produced cytokines interleukin 1 beta (Il1b) and interleukin 6 (Il6) were reduced in irradiated Eng(+/-) compared to Eng(+/+) mice. Double immuno-stainings confirmed that IL-6 was produced by macrophages, whereas IL-1β was mainly detected in other cell types. Accordingly, inflammatory cell precursors derived from the bone marrow of Eng(+/-) mice showed impaired ability to express Il1b and Il6 compared to wild type mice.
Conclusions: Endoglin promotes kidney inflammation after irradiation by regulating macrophage infiltration and interleukin production, thereby promoting pathogenic changes after radiation exposure.
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