title: Expression of genes involved in mouse lung cell differentiation/regulation after acute exposure to photons and protons with or without low-dose preirradiation.
abstract: The goal of this study was to compare the effects of acute 2 Gy irradiation with photons (0.8 Gy/min) or protons (0.9 Gy/min), both with and without pre-exposure to low-dose/low-dose-rate γ rays (0.01 Gy at 0.03 cGy/h), on 84 genes involved in stem cell differentiation or regulation in mouse lungs on days 21 and 56. Genes with a ≥1.5-fold difference in expression and P < 0.05 compared to 0 Gy controls are emphasized. Two proteins specific for lung stem cells/progenitors responsible for local tissue repair were also compared. Overall, striking differences were present between protons and photons in modulating the genes. More genes were affected by protons than by photons (22 compared to 2 and 6 compared to 2 on day 21 and day 56, respectively) compared to 0 Gy. Preirradiation with low-dose-rate γ rays enhanced the acute photon-induced gene modulation on day 21 (11 compared to 2), and all 11 genes were significantly downregulated on day 56. On day 21, seven genes (aldh2, bmp2, cdc2a, col1a1, dll1, foxa2 and notch1) were upregulated in response to most of the radiation regimens. Immunoreactivity of Clara cell secretory protein was enhanced by all radiation regimens. The number of alveolar type 2 cells positive for prosurfactant protein C in irradiated groups was higher on day 56 (12.4-14.6 cells/100) than on day 21 (8.5-11.2 cells/100) (P < 0.05). Taken together, these results showed that acute photons and protons induced different gene expression profiles in the lungs and that pre-exposure to low-dose-rate γ rays sometimes had modulatory effects. In addition, proteins associated with lung-specific stem cells/progenitors were highly sensitive to radiation.
authors.affiliation: Department of Radiation Medicine, Radiation Research Laboratories, Loma Linda University, Loma Linda, California 92354, USA. jtian@dominion.llumc.edu
authors.forename: Jian
authors.initials: J
authors.lastname: Tian
authors.forename: WeiLing
authors.initials: W
authors.lastname: Zhao
authors.forename: Sisi
authors.initials: S
authors.lastname: Tian
authors.forename: James M
authors.initials: JM
authors.lastname: Slater
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Deng
authors.forename: Daila S
authors.initials: DS
authors.lastname: Gridley
mesh_terms: D053687:Adult Stem Cells / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D008168:Lung / Q000166:cytology* / Q000378:metabolism* / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009928:Organ Specificity; D017785:Photons / Q000009:adverse effects*; D011522:Protons / Q000009:adverse effects*; D013997:Time Factors; D059467:Transcriptome / Q000528:radiation effects*
chemical_list: D015415:Biomarkers; D011522:Protons