Endogenous production of TNFalpha is a potent trigger of NFkappaB activation by irradiation in human monocytic cells THP-1.
Irradiation causes DNA damage and induces neoplastic transformation. In response to irradiation, cells induce genes or activate proteins that protect themselves from the external insult. Nuclear factor kappaB (NFkappaB) activates transcription of target genes and plays important roles in inflammation. We studied the mechanism(s) for activation of NFkappaB by irradiation in human monocytic cells THP-1. Gel mobility shift assays showed that irradiation stimulated the NFkappaB-DNA binding activity of nuclear extracts from these cells. Western blot analysis using polyclonal antibody against phosphorylated IkappaB protein showed that irradiation increased the levels of phosphorylated IkappaB. The production of tumor necrosis factor alpha (TNFalpha) was stimulated by irradiation in these cells. Treatment with exogenously added TNFalpha also stimulated the NFkappaB binding activity with concomitant degradation of IkappaB. Further study found that the activation of NFkappaB by irradiation was inhibited by a neutralizing anti-TNFalpha antibody. Macrophages from TNFalpha-deficient mice were also defective in the irradiation-induced activation of NFkappaB. These results indicate that endogenous production of TNFalpha in macrophages/monocytes is required for NFkappaB activation by irradiation. Our data also suggest that TNFalpha in monocytes/macrophages exposed to irradiation is involved in signal transduction network initiation.
Hachiya
Misao
M
Department of Radiation Emergency Medicine, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba-city, Chiba 263-8555, Japan.
Takada
Masuhiro
M
Sekikawa
Kenji
K
Akashi
Makoto
M
D000818:Animals; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism; D053938:DNA Fragmentation / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000528:radiation effects*; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009000:Monocytes / Q000378:metabolism* / Q000528:radiation effects*; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000172:deficiency / Q000378:metabolism
D020672:I-kappa B Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D004247:DNA