Effects of multiple doses of ionizing radiation on cytokine expression in rat and human cells

Purpose : To determine the effect of daily fractionated irradiation on the expression of growth factors and cytokines in different cardiac and vascular cell types. Materials and methods : Cell cultures of rat cardiac myocytes, fibroblasts, a rat cardiac microvascular endothelial cell line and human artery endothelial cells were irradiated with doses of 2 Gy, given daily during 5 consecutive days. Twenty-four hours after each fraction, gene expression was determined by competitive or semiquantitative polymerase chain reaction. Protein secretion into culture media was determined by enzyme-linked immunoabsorbant assay. Results : Of all investigated mRNA levels, transforming growth factor (TGF)-ss1 and fibroblast growth factor (FGF)-2 were slightly upregulated in the rat cardiac endothelial cell line after irradiation. TGF-ss1 protein secretion by these cells was slightly, but non-significantly, elevated. Interleukin 1ss protein levels in myocyte culture media were decreased in control cultures at days 3 and 4 compared with day 2. No significant changes were observed in expression of FGF-2 in either of the four cell types. Moreover, no changes were observed in gene expression of platelet-derived growth factors A, B and interleukin 8 in the human artery endothelial cells. Conclusions : Fractionated irradiation leads to minor changes in the expression of specific cytokines in cardiac myocytes, fibroblasts and endothelial cells.