title: Partial volume rat lung irradiation: temporal fluctuations of in-field and out-of-field DNA damage and inflammatory cytokines following irradiation.
abstract: OBJECTIVE
  The current study investigated the early activation of inflammatory cytokines and macrophages in different regions of the lung following partial volume irradiation. We examined temporal fluctuations in DNA damage, cytokine expression and macrophage activation during 16 weeks post-irradiation.
  
  
  METHODS
  We irradiated the lower lung of Sprague-Dawley rats with 10 Gy. A micronucleus assay was used to examine DNA damage. Real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was used to analyse the RNA expression of Interleukin-1 alpha (IL-1a), Interleukin-1 beta (IL-1ss), Interleukin-6 (IL-6), Tumour Necrosis Factor alpha (TNF-a) and Transforming Growth Factor beta (TGF-ss) relative to Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH). The activation of macrophages was determined using the antibody ED-1 for immunohistochemical analysis.
  
  
  RESULTS
  The expression of DNA damage, the activation of macrophages and the expression of inflammatory cytokines all fluctuated in a cyclic pattern. The initial induction of cytokine expression and the activation of macrophages occurred at very early times (1 h) following irradiation. Waves of cytokine expression and macrophage activation were also seen at later times (up to 16 weeks) following irradiation. DNA damage also occurred in a cyclic pattern though this was less pronounced out-of-field. The levels of cytokines and activated macrophages were elevated to a similar degree both in- and out-of-field, whereas there was a greater micronuclei yield in-field than out-of-field.
  
  
  CONCLUSIONS
  An inflammatory response triggered by the partial volume irradiation occurs in the whole rat lung at very early times following irradiation and is maintained in a cyclic pattern to later times when the onset of functional symptoms is expected. We hypothesize that Reactive Oxygen Species (ROS) induced by this response play an important role in the induction of both in-field and out-of-field DNA damage.
authors.affiliation: Research Division, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Canada.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Calveley
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Khan
authors.forename: Ivan W T
authors.initials: IW
authors.lastname: Yeung
authors.forename: Jake
authors.initials: J
authors.lastname: Vandyk
authors.forename: Richard P
authors.initials: RP
authors.lastname: Hill
mesh_terms: D000818:Animals; D016207:Cytokines / Q000096:biosynthesis*; D004249:DNA Damage / Q000528:radiation effects*; D005260:Female; D007249:Inflammation; D008168:Lung / Q000528:radiation effects*; D008262:Macrophage Activation / Q000528:radiation effects*; D016676:Macrophages, Alveolar / Q000528:radiation effects; D015162:Micronucleus Tests; D011832:Radiation Injuries / Q000235:genetics / Q000276:immunology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species
chemical_list: D016207:Cytokines; D017382:Reactive Oxygen Species