title: Ionizing radiation-induced oxidative stress alters miRNA expression.
abstract: BACKGROUND
  MicroRNAs (miRNAs) are small, highly conserved, non-coding RNA that alter protein expression and regulate multiple intracellular processes, including those involved in the response to cellular stress. Alterations in miRNA expression may occur following exposure to several stress-inducing anticancer agents including ionizing radiation, etoposide, and hydrogen peroxide (H(2)O(2)).
  
  
  RESULTS
  Normal human fibroblasts were exposed to radiation, H(2)O(2), or etoposide at doses determined by clonogenic cell survival curves. Total RNA was extracted and miRNA expression was determined by microarray. Time course and radiation dose responses were determined using RT-PCR for individual miRNA species. Changes in miRNA expression were observed for 17 miRNA species following exposure to radiation, 23 after H(2)O(2) treatment, and 45 after etoposide treatment. Substantial overlap between the miRNA expression changes between agents was observed suggesting a signature miRNA response to cell stress. Changes in the expression of selected miRNA species varied in response to radiation dose and time. Finally, production of reactive oxygen species (ROS) increased with increasing doses of radiation and pre-treatment with the thiol antioxidant cysteine decreased both ROS production and the miRNA response to radiation.
  
  
  CONCLUSIONS
  These results demonstrate a common miRNA expression signature in response to exogenous genotoxic agents including radiation, H(2)O(2), and etoposide. Additionally, pre-treatment with cysteine prevented radiation-induced alterations in miRNA expression which suggests that miRNAs are responsive to oxidative stress. Taken together, these results imply that miRNAs play a role in cellular defense against exogenous stress and are involved in the generalized cellular response to genotoxic oxidative stress.
authors.affiliation: Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, USA. simonen@mail.nih.gov
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Simone
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Soule
authors.forename: David
authors.initials: D
authors.lastname: Ly
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Saleh
authors.forename: Jason E
authors.initials: JE
authors.lastname: Savage
authors.forename: William
authors.initials: W
authors.lastname: Degraff
authors.forename: John
authors.initials: J
authors.lastname: Cook
authors.forename: Curtis C
authors.initials: CC
authors.lastname: Harris
authors.forename: David
authors.initials: D
authors.lastname: Gius
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
mesh_terms: D002478:Cells, Cultured; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D018384:Oxidative Stress; D011839:Radiation, Ionizing; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D035683:MicroRNAs