Cytokine expression induced by ionizing radiation

It has been reported that several genes are induced by radiation. These genes can be categorized either as 'early-response genes (ERG)' which are inducible just after irradiation or as 'late-response genes (LRG)' which are inducible several hours after irradiation. After irradiation, the ERGs such as protooncogene c-jun are induced via activation of protein kinase C. The gene products stimulate the transcription of the LRGs. The LRG products probably acts for the recovery of damages by radiation. Genes of several cytokines which can be used for the therapy of the damages have been characterized as the LRG. We show that one of the cytokines, interleukin (IL)-1β, was expressed immediately after ionizing radiation both in myeloid leukemic cells and in normal blood cells which are freshly isolated from mice. When radiation was given twice to the cells, the duration of the expression after the second dose was longer than that after the first dose. In this paper, this finding and current studies of the ERGs are summarized and discussed. (author)