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Hypochlorous acid-induced base modifications in isolated calf thymus DNA
M Whiteman1, A Jenner, B Halliwell
1International Antioxidant Research Centre, University of London, Kings College, England. MATT.WHITEMAN@kcl.ac.uk
Chemical Research in Toxicology
|December 24, 1997
Summary
Hypochlorous acid (HOCl) causes significant DNA damage, primarily oxidizing pyrimidines and forming novel chlorinated bases like 5-chlorouracil. This unique damage pattern may serve as a fingerprint for HOCl-induced DNA modification.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- DNA is susceptible to oxidative damage from reactive oxygen species.
- Hypochlorous acid (HOCl) is a reactive molecule produced during inflammation.
- Understanding HOCl's DNA modification mechanisms is crucial for assessing its biological impact.
Purpose of the Study:
- To investigate the specific DNA base modifications induced by hypochlorous acid (HOCl) at physiological pH.
- To determine if HOCl preferentially targets pyrimidines or purines.
- To explore the potential of HOCl-induced DNA damage as a biomarker.
Main Methods:
- Incubation of calf thymus DNA with varying concentrations of HOCl at pH 7.4.
- Analysis of DNA base modifications using chromatographic and mass spectrometric techniques.
- Investigating the effect of HOCl on pre-existing .OH-induced DNA damage.
Main Results:
- HOCl induced significant concentration-dependent increases in pyrimidine oxidation products (thymine glycol, 5-hydroxycytosine, 5-hydroxyuracil, 5-hydroxyhydantoin).
- No significant increase in purine oxidation products was observed.
- A novel chlorinated base, 5-chlorouracil, was detected in large amounts.
- HOCl exposure led to a loss of existing purine oxidation products and 5-hydroxycytosine in pre-damaged DNA.
Conclusions:
- HOCl primarily modifies DNA pyrimidine bases through oxidation.
- The formation of 5-chlorouracil is a distinctive hallmark of HOCl-induced DNA damage.
- The unique damage profile suggests HOCl-induced DNA modifications could serve as a specific biomarker.