Background: Low-dose irradiation (LDI) is employed to extend the irradiation area in vascular brachytherapy to minimize the edge effect. Stimulation of adhesion molecule 1 (ICAM-1) is one of many mechanisms important in the early stages of atherosclerosis and restenosis. This study investigates the effect of γ-irradiation on mRNA expression of ICAM-1 in human coronary vascular cells.
Material/Methods: Human coronary endothelial cells (HCAECs), human umbilical endothelial cells (HUVECs), and human coronary smooth muscle cells (HCMSMCs) were cultured and identifi ed. Twenty-four hours after seeding, γ-irradiation at doses of 0.5 Gy, 1 Gy, 10 Gy, 20 Gy, and 30 Gy (Linac Philips FL 75/20) was carried out. Twenty hours after irradiation, ICAM-1 expression was stimulated for 6 h with TNF-α (20 ng/ml). In Northern blot assays, 10 μg of RNA were used. The relative band density of ICAM-1 mRNA of irradiated and stimulated cells were compared with that of non-irradiated
cells after TNF-a stimulus only.
Results: In HCAECs and HCMSMCs, stimulation of ICAM-1 mRNA was detected after irradiation, no matter which dose was applied. After low-dose irradiation (0.5 Gy and 1 Gy) the stimulating effect was pronounced, signifi cant differences being found in HCAECs after irradiation with 1 Gy.
Conclusions: Stimulation of ICAM-1 mRNA expression after LDI of human coronary vascular cells may be one of the many mechanisms that trigger the edge effect in vivo. If these results are confi rmed by further studies and if anti-infl ammatory treatment strategies cannot inhibit the stimulatory effects, a
major problem exists for the future of vascular brachytherapy.

Keywords: Endothelial Cells - radiation effects, Gamma Rays, Heart - anatomy & histology, Intercellular Adhesion Molecule-1 - metabolism, Myocardium - cytology, Myocytes, Smooth Muscle - radiation effects, RNA, Messenger - metabolism, Tumor Necrosis Factor-alpha - metabolism