title: Nuclear factor-kappaB and manganese superoxide dismutase mediate adaptive radioresistance in low-dose irradiated mouse skin epithelial cells.
abstract: Mechanisms governing inducible resistance to ionizing radiation in untransformed epithelial cells pre-exposed to low-dose ionizing radiation (LDIR; </=10 cGy) are not well understood. The present study provides evidence that pre-exposure to 10 cGy X-rays increases clonogenic survival of mouse skin JB6P+ epithelial cells subsequently exposed to 2 Gy doses of gamma-rays. To elucidate the molecular pathways of LDIR-induced adaptive radioresistance, the transcription factor nuclear factor-kappaB (NF-kappaB) and a group of NF-kappaB-related proteins [i.e., p65, manganese superoxide dismutase (MnSOD), phosphorylated extracellular signal-regulated kinase, cyclin B1, and 14-3-3zeta] were identified to be activated as early as 15 min after LDIR. Further analysis revealed that a substantial amount of both 14-3-3zeta and cyclin B1 accumulated in the cytoplasm at 4 to 8 h when cell survival was enhanced. The nuclear 14-3-3zeta and cyclin B1 were reduced and increased at 4 and 24 h, respectively, after LDIR. Using YFP-fusion gene expression vectors, interaction between 14-3-3zeta and cyclin B1 was visualized in living cells, and LDIR enhanced the nuclear translocation of the 14-3-3zeta/cyclin B1 complex. Treatment of JB6P+ cells with the NF-kappaB inhibitor IMD-0354 suppressed LDIR-induced expression of MnSOD, 14-3-3zeta, and cyclin B1 and diminished the adaptive radioresistance. In addition, treatment with small interfering RNA against mouse MnSOD was shown to inhibit the development of LDIR-induced radioresistance. Together, these results show that NF-kappaB, MnSOD, 14-3-3zeta, and cyclin B1 contribute to LDIR-induced adaptive radioresistance in mouse skin epithelial cells.
authors.affiliation: Division of Molecular Radiobiology, School of Health Sciences and Purdue Cancer Center, Purdue University, West Lafayette, Indiana, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Fan
authors.forename: Kazi Mokim
authors.initials: KM
authors.lastname: Ahmed
authors.forename: Mitchell C
authors.initials: MC
authors.lastname: Coleman
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Spitz
authors.forename: Jian Jian
authors.initials: JJ
authors.lastname: Li
mesh_terms: D048948:14-3-3 Proteins / Q000096:biosynthesis / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D004307:Dose-Response Relationship, Radiation; D004847:Epithelial Cells / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance / Q000502:physiology*; D012867:Skin / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects*; D013482:Superoxide Dismutase / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*
chemical_list: D048948:14-3-3 Proteins; C534700:Ccnb1 protein, mouse; D019926:Cyclin B; D056744:Cyclin B1; D016328:NF-kappa B; D034741:RNA, Small Interfering; D013482:Superoxide Dismutase