title: Effects of lipopolysaccharide on the response of C57BL/6J mice to whole thorax irradiation.
abstract: OBJECTIVE
  Inflammatory and fibrogenic processes play a crucial role in the radiation-induced injury in the lung. The aim of the present study was to examine whether additive LPS exposure in the lung (to simulate respiratory infection) would affect pneumonitis or fibrosis associated with lung irradiation.
  
  
  METHODS
  Wildtype C57Bl/6J (WT-C57) and TNFα, TNFR1 and TNFR2 knockout ((-/-)) mice, in C57Bl/6J background, were given whole thorax irradiation (10 Gy) with or without post-irradiation intratracheal administration of LPS (50μg/mice). Functional deficit was examined by measuring breathing rate at various times after treatment. Real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and immunohistochemistry were used to analyze the protein expression and m-RNA of Interleukin-1 alpha (IL-1α), Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), Tumour Necrosis Factor alpha (TNFα) and Transforming Growth Factor beta (TGFβ) in the lung at various times after treatment. Inflammatory cells were detected by Mac-3 (macrophages) and Toluidine Blue (mast cells) staining. Collagen content was estimated by hydroxyproline (total collagen) and Sircol assay (soluble collagen). Levels of oxidative damage were assessed by 8-hydroxy-2-deoxyguanosine (8-OHdG) staining.
  
  
  RESULTS
  LPS exposure significantly attenuated the breathing rate increases following irradiation of WT-C57, TNFR1(-/-) and TNFR2(-/-)mice and to a lesser extent in TNFα(-/-) mice. Collagen content was significantly reduced after LPS treatment in WT-C57, TNFR1(-/-) and TNFα(-/-) mice and there was a trend in TNFR2(-/-) mice. Similarly there were lower levels of inflammatory cells and cytokines in the LPS treated mice.
  
  
  CONCLUSIONS
  This study reveals a mitigating effect of early exposure to LPS on injury caused by irradiation on lungs of C57Bl mice. The results suggest that immediate infection post irradiation may not impact lung response negatively in radiation-accident victims, however, further studies are required in different animal models, and with specific infectious agents, to confirm and extend our findings.
authors.affiliation: Ontario Cancer Institute, Toronto, Ontario, Canada.
authors.forename: Asif
authors.initials: A
authors.lastname: Zaidi
authors.forename: Salomeh
authors.initials: S
authors.lastname: Jelveh
authors.forename: Javed
authors.initials: J
authors.lastname: Mahmood
authors.forename: Richard P
authors.initials: RP
authors.lastname: Hill
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D005260:Female; D053582:Interleukin-1alpha / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D016014:Linear Models; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000378:metabolism; D011833:Radiation Injuries, Experimental; D017564:Radiation Pneumonitis / Q000378:metabolism / Q000517:prevention & control*; D011837:Radiation-Protective Agents / Q000008:administration & dosage / Q000494:pharmacology*; D056152:Respiratory Rate; D013909:Thorax / Q000528:radiation effects*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015415:Biomarkers; D053582:Interleukin-1alpha; D053583:Interleukin-1beta; D015850:Interleukin-6; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D011837:Radiation-Protective Agents; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D003094:Collagen