Inflammatory reaction and changes in expression of coagulation proteins on lung endothelial cells after total-body irradiation in mice

Inflammatory reaction is a classical feature of radiation exposure, and pneumonitis is a dose-limiting complication in the handling of hematological disorders treated with total-body irradiation. In the present study, we first evaluated the inflammatory response in C57BL6/J mice exposed to lethal doses of gamma rays treated with antibiotics or not. Both interleukin 6 and KC (also known as Gro1) were increased in the plasma 10 to 18 days after radiation exposure, independent of bacterial infection, whereas fibrinogen release was linked to a bacterial infection. Furthermore, both Il6 and KC were increased in the lungs of irradiated mice. Our second objective was to characterize the endothelial cell changes in the lungs of total-body-irradiated mice. For this purpose, a quantitative RT-PCR was used to determine the expression of genes involved in inflammatory and coagulation processes. We found that the adhesion molecules P-selectin and platelet endothelial cell adhesion molecule 1 were up-regulated, whereas E-selectin remained unchanged. Tissue factor expression was up-regulated as well, and thrombomodulin gene expression was down-regulated. The investigation by immunohistochemistry of adhesion molecules confirmed the increase in the basal expression of both P-selectin and platelet endothelial cell adhesion molecule 1 on pulmonary endothelial cells. All together, our results suggest the involvement of endothelial cells in the development of radiation-induced inflammatory and thrombotic processes.