RT Journal Article
SR Electronic
T1 Oxidative Stress-Induced Homologous Recombination As a Novel Mechanism for Phenytoin-Initiated Toxicity
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 523
OP 527
DO 10.1124/jpet.103.052639
VO 306
IS 2
A1 Louise M. Winn
A1 Perry M. Kim
A1 Jac A. Nickoloff
YR 2003
UL http://jpet.aspetjournals.org/content/306/2/523.abstract
AB Although the mechanism(s) of phenytoin-initiated toxicity is unknown, phenytoin can be enzymatically bioactivated to a reactive intermediate leading to increased formation of reactive oxygen species, which can damage essential macromolecules, including DNA. The oxidation of DNA can induce DNA double-strand breaks (DSBs), which may be repaired through homologous recombination. Increased levels of DSBs may induce hyper-recombination, leading to deleterious genetic changes. We hypothesize that these genetic changes mediate phenytoin-initiated toxicity. To investigate this hypothesis we used a Chinese hamster ovary cell line containing a neo direct repeat recombination substrate to determine whether phenytoin-initiated DNA oxidation increases homologous recombination. Cells were treated with 0 to 800 μM phenytoin for 5 or 24 h, and homologous recombination frequencies and recombinant product structures were determined. Phenytoin-initiated DNA oxidation was determined by measuring the formation of 8-hydroxy-2′-deoxyguanosine. We demonstrate that phenytoin increases both DNA oxidation and homologous recombination in a concentration- and time-dependent manner. All recombination products analyzed arose via gene conversion without associated crossover. Our data demonstrate that phenytoin-initiated DNA damage can induce homologous recombination, which may be a novel mechanism mediating phenytoin-initiated toxicity. The American Society for Pharmacology and Experimental Therapeutics