IONIZING-RADIATION INDUCES HUMAN INTERCELLULAR-ADHESION MOLECULE-1 IN-VITRO

Intercellular adhesion molecule-1 (ICAM-1) plays a central role in var ious inflammatory reactions and its expression is readily induced by i nflammatory stimuli such as cytokines or ultraviolet irradiation. We h ave investigated the effect of ionizing radiation (IR) on human ICAM-1 expression in human cell Lines and skin cultures. ICAM-1 mRNA levels in HL60, HaCaT, and HeLa cells were elevated at 3-6 h after irradiatio n and increased with doses from 10-40 Gy. The rapid induction of ICAM- 1 occurred at the level of transcription, was independent of de novo p rotein synthesis, and did not involve autocrine stimuli including tumo r necrosis factor-alpha and interleukin-1. IR also induced ICAM-1 cell surface expression within 24 h. Immunohistologic analysis of cultured human split skin revealed ICAM-1. upregulation on epidermal keratinoc ytes and dermal microvascular endothelial cells 24 h after exposure to 6 Gy. In conclusion, we propose ICAM-1 as an important radiation-indu ced enhancer of immunologic cell adhesion, which contributes to inflam matory reactions after local and total body irradiation.