A tool for rapid screening of direct DNA agents using reaction rates and relative interaction potency: towards screening environmental contaminants for hazard

Abstract

DNA damage represents a potential biomarker for determining the exposure risk to chemicals and may provide early warning data for identifying chemical hazards to human health. Here, we have demonstrated a simple chromatography-based method that can be used to rapidly screen for the presence of chemical hazards as well as to determine parameters relevant to hazard assessment. In this proof-of-principle study, a simple in vitro system was used to determine the interaction of pollutants and probable carcinogens, phenyl glycidyl ether (PGE), tetrachlorohydroquinone (Cl₄HQ), methylmethane sulfonate (MMS), styrene-7,8-oxide (SO), and benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), a metabolite of benzo[a]pyrene (B[a]P), with single- and double-stranded DNA probes. Differences in potency and reaction kinetics were studied for chemical and DNA type. A relative interaction potency equivalency (PEQ) of a chemical was determined by ratio of interaction potency of a chemical to BPDE as the reference chemical in the reaction with single- and double-stranded oligodeoxynucleotides. PEQs were found to be BPDE > PGE > SO > MMS > Cl₄HQ for single-stranded oligodeoxynucleotides while they were found to be BPDE > PGE > Cl₄HQ > MMS > SO for double-stranded oligodeoxynucleotides. Kinetics evaluation revealed that BPDE reacted with both DNA probes at a significantly faster rate, as compared to the remaining test chemicals. Equilibrium was reached within an hour for BPDE, but required a minimum of 48 h for the remaining chemicals. First-order rate constants were (1.61 ± 0.2) × 10⁻³s⁻¹ and (3.18 ± 0.4) × 10⁻⁴ s⁻¹ for reaction of BPDE with double- and single-stranded DNA, respectively. The remaining chemicals possessed rate constants from 2 to 13 × 10⁻⁶s⁻¹ with a relative kinetic order for reaction with DNA of BPDE ≫ MMS > SO > PGE > Cl₄HQ for ds-DNA and BPDE ≫ SO ≈ Cl₄HQ ≈ MMS > PGE for ss-DNA. We further found that the reaction potency, defined by dose–response between chemical pollutants and DNA, depends on the form of DNA present for reaction. Noteworthy, we found that relative PEQ did not follow the same kinetic trends. However, our preliminary findings suggest that reaction kinetics, in combination with relative interaction potency, may be a significant parameter that can be used to evaluate the hazard level of environmental pollutants.