Irradiation increases expression of GM-CSF in human fibroblasts by transcriptional and post-transcriptional regulation.
Fibroblasts produce a variety of cytokines including granulocyte/macrophage colony-stimulating factor (GM-CSF). GM-CSF is pivotal for proliferation and function of myeloid cells. In this report, we describe the regulation of GM-CSF gene by irradiation in human fibroblasts. We found that fibroblasts constitutively produced GM-CSF; irradiation markedly increased the production of GM-CSF. The increase in GM-CSF transcripts by irradiation was both time- and dose-dependent. Moreover, irradiation increased GM-CSF mRNA in cells with prolonged exposure to 12-O-tetradecanoyl-phorbol-13-acetate (TPA). WI38 fibroblasts constitutively produce low levels of IL-1. Induction of GM-CSF mRNA by irradiation was partially blocked by anti-IL-1 antibodies. On the other hand, inhibition of prostaglandin synthesis did not affect induction of GM-CSF RNA. Transcriptional run-on analysis showed that irradiation increased the rate of GM-CSF transcription. Stability studies of GM-CSF mRNA in these cells showed that half-life (t1/2) increased from < 20 min in unirradiated cells to > 100 min in irradiated cells. These findings suggest that the increase in GM-CSF mRNA observed after irradiation is regulated by transcriptional and post-transcriptional mechanisms. Our results indicate that induction of GM-CSF gene by irradiation requires de novo protein synthesis and increased levels of GM-CSF transcripts also occur through a pathway distinct from protein kinase C activation.
Hachiya
M
M
Division of Radiation Health, National Institute of Radiological Sciences, Chiba, Japan.
Suzuki
G
G
Koeffler
H P
HP
Akashi
M
M
D004307:Dose-Response Relationship, Radiation; D004789:Enzyme Activation; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D005720:Gamma Rays; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007375:Interleukin-1 / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000032:analysis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic
D007375:Interleukin-1; D012333:RNA, Messenger; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D007213:Indomethacin