Cyclooxygenase-2-mediated DNA damage

J Biol Chem. 2005 Aug 5;280(31):28337-46. doi: 10.1074/jbc.M504178200. Epub 2005 Jun 17.


Rat intestinal epithelial cells that express the cyclooxygenase-2 (COX-2) gene permanently (RIES cells) were used as a model of in vivo oxidative stress. A targeted lipidomics approach showed that 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) was the major hydroxylated non-esterified lipid formed in unstimulated intact cells. The corresponding hydroperoxide, 15(S)-hydroperoxyeicosatetraenoic acid (15(S)-HPETE) undergoes homolytic decomposition to the DNA-reactive bifunctional electrophile 4-oxo-2(E)-nonenal, a precursor of heptanone-etheno-2'-deoxyguanosine. This etheno adduct was identified in the DNA of RIES cells. A dose-dependent increase in adduct levels was observed in the presence of vitamin C. This suggested that vitamin C increased lipid hydroperoxide-mediated 4-oxo-2(E)-nonenal formation in the cells. The selective COX-2 inhibitor NS-398 was protective against cellular DNA damage but was less effective if vitamin C was present. Prostaglandin E(2) and 15(S)-HETE biosynthesis were completely inhibited by 110 mum NS-398 in the intact RIES cells. No inhibition of COX-1 was detected in the wild-type RIE cells at this concentration of NS-398. Arachidonic acid treatment of RIES cell lysates and ionophore stimulation of intact RIES cells produced significantly more 15(R)-HETE than the untreated intact cells. These preparations also both produced 11(R)-HETE, which was not detected in the intact cells. Aspirin treatment of the intact unstimulated RIES cells resulted in the exclusive formation of 15(R)-HETE in amounts that were slightly higher than the original 15(S)-HETE observed in the absence of aspirin, implying that significant amounts of 15(R)-HPETE had also been formed. 15(R)-HPETE should give exactly the same amount of heptanone-etheno-2'-deoxyguanosine as its 15(S)-enantiomer. However, no increase in heptanone-etheno adduct formation occurred in the aspirin-treated cells. The present study suggests a potential mechanism of tumorigenesis that involves DNA adduct formation from COX-2-mediated lipid peroxidation rather than prostaglandin formation. Therefore, inhibition of COX-2-mediated lipid hydroperoxide formation offers a potential therapeutic alternative to COX-2 inhibitors in chemoprevention strategies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Arachidonate 15-Lipoxygenase / metabolism
  • Base Sequence
  • Calcimycin / pharmacology
  • Cells, Cultured
  • Cyclooxygenase 2
  • Cyclooxygenase 2 Inhibitors
  • Cyclooxygenase Inhibitors / pharmacology
  • DNA Damage*
  • DNA Primers
  • Intestinal Mucosa / drug effects
  • Intestinal Mucosa / physiology*
  • Lipid Peroxidation
  • Nitrobenzenes / pharmacology
  • Prostaglandin-Endoperoxide Synthases / genetics
  • Prostaglandin-Endoperoxide Synthases / metabolism*
  • Rats
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sulfonamides / pharmacology


  • Cyclooxygenase 2 Inhibitors
  • Cyclooxygenase Inhibitors
  • DNA Primers
  • Nitrobenzenes
  • Sulfonamides
  • N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide
  • Calcimycin
  • Arachidonate 15-Lipoxygenase
  • Cyclooxygenase 2
  • Prostaglandin-Endoperoxide Synthases