DNA excision repair and double-strand break repair gene polymorphisms and the level of chromosome aberration in children with long-term exposure to radon

Residential exposure to radon and levels of histone γH2AX and DNA damage in peripheral blood lymphocytes of residents of Kowary city regions (Poland)

INTRODUCTION

Radon-induced biological effects have been studied mainly through epidemiological investigations, and well-controlled in vitro and in vivo experiments. To provide data explaining radon exposure-induced harmful effects in natural environment, exposure assessment under these conditions is needed. The objective of the study was to examine the level of genetic damage assessed with biomarkers of DNA single- and double-strand breaks (SSBs and DSBs) in peripheral blood mononuclear cells obtained from individuals continuously exposed to Rn in homes. Naturally elevated Rn concentrations in homes can be found in the South of Poland, in Kowary city.

METHODS

Measurements of expression of phosphorylated histone γH2AX was used as a marker of DNA double strand breaks. To detect DNA single and double-strand breaks and alkali labile sites, the alkaline comet assay was used. Oxidative damage of DNA was evaluated by formamidopyrimidyne (FPG)-modified comet assay. The blood was collected from 94 volunteers living in Kowary. Subjects were grouped according to their status of living in radon concentration ≥100 Bq/m³ (n = 67), and <100 Bq/m³ (n = 27).

RESULTS

The statistically significant differences in levels of DNA damage in peripheral lymphocytes assessed with comet assay were found to be associated with levels of radon exposure in indoor air (p = 0.034). DNA damage in the comet assay was significantly correlated with DNA damage assessed with γH2AX staining.

CONCLUSIONS

Results of the present study indicate the suitability of alkaline comet assay for the detection of DNA damage in peripheral blood lymphocytes of people environmentally exposed to radon.

Residential exposure to radon and DNA methylation across the lifecourse: an exploratory study in the ALSPAC birth cohort

Background: Radon (and its decay products) is a known human carcinogen and the leading cause of lung cancer in never-smokers and the second in ever-smokers. The carcinogenic mechanism from radiation is a combination of genetic and epigenetic processes, but compared to the genetic mechanisms, epigenetic processes remain understudied in humans. This study aimed to explore associations between residential radon exposure and DNA methylation in the general population. Methods: Potential residential radon exposure for 75-metre area buffers was linked to genome-wide DNA methylation measured in peripheral blood from children and mothers of the Accessible Resource for Integrated Epigenomic Studies subsample of the ALSPAC birth cohort. Associations with DNA methylation were tested at over 450,000 CpG sites at ages 0, 7 and 17 years (children) and antenatally and during middle-age (mothers). Analyses were adjusted for potential residential and lifestyle confounding factors and were determined for participants with complete data (n = 786 to 980). Results: Average potential exposure to radon was associated in an exposure-dependent manner with methylation at cg25422346 in mothers during pregnancy, with no associations at middle age. For children, radon potential exposure was associated in an exposure-dependent manner with methylation of cg16451995 at birth, cg01864468 at age 7, and cg04912984, cg16105117, cg23988964, cg04945076, cg08601898, cg16260355 and cg26056703 in adolescence. Conclusions: Residential radon exposure was associated with DNA methylation in an exposure-dependent manner. Although chance and residual confounding cannot be excluded, the identified associations may show biological mechanisms involved in early biological effects from radon exposure.

Residential exposure to radon and DNA methylation across the lifecourse: an exploratory study in the ALSPAC birth cohort

Background: Radon (and its decay products) is a known human carcinogen and the leading cause of lung cancer in never-smokers and the second in ever-smokers. The carcinogenic mechanism from radiation is a combination of genetic and epigenetic processes, but compared to the genetic mechanisms, epigenetic processes remain understudied in humans. This study aimed to explore associations between residential radon exposure and DNA methylation in the general population. Methods: Potential residential radon exposure for 75-metre area buffers was linked to genome-wide DNA methylation measured in peripheral blood from children and mothers of the Accessible Resource for Integrated Epigenomic Studies subsample of the ALSPAC birth cohort. Associations with DNA methylation were tested at over 450,000 CpG sites at ages 0, 7 and 17 years (children) and antenatally and during middle-age (mothers). Analyses were adjusted for potential residential and lifestyle confounding factors and were determined for participants with complete data (n = 786-980). Results: Average potential exposure to radon was associated in an exposure-dependent manner with methylation at cg25422346 in mothers during pregnancy, with no associations at middle age. For children, radon potential exposure was associated in an exposure-dependent manner with methylation of cg16451995 at birth, cg01864468 at age 7, and cg04912984, cg16105117, cg23988964, cg04945076, cg08601898, cg16260355 and cg26056703 in adolescence. Conclusions: Residential radon exposure was associated with DNA methylation in an exposure-dependent manner. Although residual confounding cannot be excluded, the identified associations may show biological mechanisms involved in early biological effects from radon exposure.

DNA Repair Molecular Beacon assay: a platform for real-time functional analysis of cellular DNA repair capacity

Numerous studies have shown that select DNA repair enzyme activities impact response and/or toxicity of genotoxins, suggesting a requirement for enzyme functional analyses to bolster precision medicine or prevention. To address this need, we developed a DNA Repair Molecular Beacon (DRMB) platform that rapidly measures DNA repair enzyme activity in real-time. The DRMB assay is applicable for discovery of DNA repair enzyme inhibitors, for the quantification of enzyme rates and is sufficiently sensitive to differentiate cellular enzymatic activity that stems from variation in expression or effects of amino acid substitutions. We show activity measures of several different base excision repair (BER) enzymes, including proteins with tumor-identified point mutations, revealing lesion-, lesion-context- and cell-type-specific repair dependence; suggesting application for DNA repair capacity analysis of tumors. DRMB measurements using lysates from isogenic control and APE1-deficient human cells suggests the major mechanism of base lesion removal by most DNA glycosylases may be mono-functional base hydrolysis. In addition, development of a microbead-conjugated DRMB assay amenable to flow cytometric analysis further advances its application. Our studies establish an analytical platform capable of evaluating the enzyme activity of select DNA repair proteins in an effort to design and guide inhibitor development and precision cancer therapy options.