Nuclear accumulation and activation of nuclear factor kappaB after split-dose irradiation in LS174T cells.
Although radiation-induced gene expression has been extensively studied, most of the studies to date have focused on that after single-dose irradiation. As split-dose irradiation, rather than single-dose irradiation, is usual in clinical situations, we investigated the effects of split-dose irradiation on nuclear factor kappaB (NF-kappaB) in the human rectum carcinoma cell line, LS174T. After either single- or split-dose irradiation with a different interval, nuclear localization of NF-kappaB was examined by Western blot and immunofluorescence and its DNA-binding activity was measured by ELISA-based assay. Irradiation-induced NF-kappaB nuclear accumulation and DNA binding activity increased in a dose-dependent manner. The peak of NF-kappaB nuclear accumulation and DNA binding activity was seen 2 to 6 hours after a single dose of 4 Gy irradiation and returned to control levels after 12 hours. In split-dose irradiation, NF-kappaB activity was similar after the first and second doses of 4 Gy irradiation separated by 12 hours. In addition, NF-kappaB activity was decreased by lengthening the interval between irradiation. The cell survival, which was assessed by colony formation assay, showed inverse correlation to this: the surviving fraction was higher after split-dose irradiation than after single-dose irradiation of the same total dose and it increased as the interval between irradiation was lengthened. Thus the present results showed a correlation between NF-kappaB activation and the repair of sublethal damage in split-dose irradiation.
Liu
Yong
Y
Department of Radiology, School of Medicine, Hirosaki University, Japan.
Nakahara
Takehisa
T
Miyakoshi
Junji
J
Hu
Dong-Liang
DL
Nakane
Akio
A
Abe
Yoshinao
Y
D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism* / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects*; D004273:DNA, Neoplasm / Q000528:radiation effects*; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D004789:Enzyme Activation / Q000528:radiation effects; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D011829:Radiation Dosage; D012004:Rectal Neoplasms / Q000201:enzymology* / Q000473:pathology
D004273:DNA, Neoplasm; D016328:NF-kappa B