title: Protracted low-dose radiation priming and response of liver to acute gamma and proton radiation.
abstract: This study evaluated liver from C57BL/6 mice irradiated with low-dose/low-dose-rate (LDR) γ-rays (0.01 Gy, 0.03 cGy/h), with and without subsequent exposure to acute 2 Gy gamma or proton radiation. Analyses were performed on day 56 post-exposure. Expression patterns of apoptosis-related genes were strikingly different among irradiated groups compared with 0 Gy (p < 0.05). Two genes were affected in the Gamma group, whereas 10 were modified in the LDR + Gamma group. In Proton and LDR + Proton groups, there were six and 12 affected genes, respectively. Expression of genes in the Gamma (Traf3) and Proton (Bak1, Birc2, Birc3, Mcl1) groups was no longer different from 0 Gy control group when mice were pre-exposed to LDR γ-rays. When each combined regimen was compared with the corresponding group that received acute radiation alone, two genes in the LDR + Gamma group and 17 genes in the LDR + Proton group were modified; greatest effect was on Birc2 and Nol3 (> 5-fold up-regulated by LDR + Protons). Oxygen radical production in livers from the LDR + Proton group was higher in LDR, Gamma, and LDR + Gamma groups (p < 0.05 vs. 0 Gy), but there were no differences in phagocytosis of E. coli. Sections stained with hematoxylin and eosin (H&E) suggested more inflammation, with and without necrosis, in some irradiated groups. The data demonstrate that response to acute radiation is dependent on radiation quality and regimen and that some LDR γ-ray-induced modifications in liver response were still evident nearly 2 months after exposure.
authors.affiliation: Division of Radiation Research, Department of Basic Sciences, Loma Linda University and Medical Center , Loma Linda, CA , USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Gridley
authors.forename: X W
authors.initials: XW
authors.lastname: Mao
authors.forename: J D
authors.initials: JD
authors.lastname: Cao
authors.forename: E J M
authors.initials: EJ
authors.lastname: Bayeta
authors.forename: M J
authors.initials: MJ
authors.lastname: Pecaut
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D015870:Gene Expression / Q000528:radiation effects; D008099:Liver / Q000378:metabolism / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D011522:Protons; D017382:Reactive Oxygen Species / Q000378:metabolism; D016897:Respiratory Burst / Q000528:radiation effects
chemical_list: D011522:Protons; D017382:Reactive Oxygen Species