Cyanide, Peroxide and Nitric Oxide Formation in Solutions of Hydroxyurea Causes Cellular Toxicity and May Contribute to Its Therapeutic Potency

Kawai J. Kuong, Andrei Kuzminov

Research output: Contribution to journalArticlepeer-review

Abstract

Hydroxyurea (HU) is a potent remedy against a variety of ailments and an efficient inhibitor of DNA synthesis, yet its pharmacology is unclear. HU acts in Escherichia coli by the same mechanism as it does in eukaryotes, via inhibition of ribonucleotide reductase. When examining a controversy about concentrations of HU that prevent thymineless death in E. coli, we found instability in HU solutions that avoided prior detection due to its peculiar nature. In contrast to freshly dissolved HU, which did not affect respiration and was bacteriostatic, 1-day-old HU solutions inhibited respiration and were immediately bactericidal. Respiration was inhibited by two gases, hydrogen cyanide (HCN) and nitric oxide (NO), whose appearance we detected in "aged" HU stocks by gas chromatography-mass spectrometry; however, neither gas was bactericidal. While determining the cause of toxicity, we found that HU damages DNA directly. We also demonstrated accumulation of peroxides in HU solutions by enzymatic assays, which explains the toxicity, as both NO and HCN are known to kill bacteria when combined with hydrogen peroxide. Remarkably, we found that bactericidal effects of NO + H2O2 and HCN + H2O2 mixtures were further synergistic. Accumulation of decomposition products in solutions of HU may explain the broad therapeutic effects of this drug.

Original languageEnglish (US)
Pages (from-to)845-862
Number of pages18
JournalJournal of Molecular Biology
Volume390
Issue number5
DOIs
StatePublished - Jul 31 2009

Keywords

  • hydrogen cyanide
  • hydrogen peroxide
  • hydroxyurea
  • nitric oxide
  • thymineless death

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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