Assessment of DNA damage in a group of professional dancers during a 10-month dancing season

Occupational exposure to wildland firefighting and its effects on systemic DNA damage

BACKGROUND

Portugal is among the European Union countries more devastated by forest fires. Wildland firefighters are at the forefront of this battle, facing exposure to a wide range of harmful pollutants. Epidemiological studies have highlighted a potential link between occupational firefighting exposure and several diseases, including cancer. To date, very few studies have explored the biological mechanisms associated with such exposure. The present longitudinal study aims to assess changes in early effect biomarkers following wildland firefighters' occupational exposure to a real wildfire event.

METHODS

Paired blood samples from 59 healthy Portuguese wildland firefighters were collected at two different time points: before wildfire season and after a fire event during wildfire season. Sociodemographic variables (e.g., age, sex) and work-related factors (e.g., years of service) were assessed via a self-reported questionnaire. Levels of early effect biomarkers, such as primary DNA damage and oxidative DNA damage (oxidised purines) were assessed via comet assay. DNA double-strand breaks (DSBs) were evaluated by phosphorylated H2AX (γH2AX). Moreover, hydroxylated polycyclic aromatic hydrocarbon metabolites (OHPAHs) and metal(loid)s were quantified in urine samples. The influence of urinary OHPAHs, urinary metal(loid)s, and other exposure-related factors (e.g., firefighting duration) on changes (Δ) in early effect biomarkers (post-vs. baseline levels) was investigated.

RESULTS

Firefighting activities led to a significant increase in both primary DNA damage and oxidative DNA damage by 22 % (95 % CI: 1.11-1.35; p < 0.05) and 23 % (95 % CI: 1.04-1.45; p < 0.05), respectively. Results from linear regression revealed that per each unit increase of urinary 2-hydroxyfluorene (2-OHFlu) (μmol/mol creatinine), the risk of ⧍ oxidative DNA damage increased by 20 % [FR: 1.20 (1.09-1.32); p < 0.01]. Additionally, each unit increase in urinary cesium (Cs) (μg/L) resulted in a significant 4 % increase in Δ primary DNA damage [FR: 1.04 (1.01-1.06); p < 0.05] and a 3 % increase in Δ oxidative DNA damage [FR: 1.03 (1.01-1.05); p < 0.05]. Post-exposure levels of γH2AX were significantly correlated with urinary 2-OHFlu levels assessed after firefighting (r = 0.30; p < 0.05). Furthermore, exposure duration and reported breathing difficulties during firefighting were significantly associated with increased levels of primary DNA damage.

CONCLUSION

Results obtained provide insights into the potential human health effects of wildland firefighting occupational exposure at the genetic and molecular levels, offering new and important mechanistic data. These findings are crucial for implementing health and safety measures, recommendations, and best practices to mitigate occupational risks and protect the health of wildland firefighters.

Application of the comet assay in human biomonitoring: An hCOMET perspective

The comet assay is a well-accepted biomonitoring tool to examine the effect of dietary, lifestyle, environmental and occupational exposure on levels of DNA damage in human cells. With such a wide range of determinants for DNA damage levels, it becomes challenging to deal with confounding and certain factors are inter-related (e.g. poor nutritional intake may correlate with smoking status). This review describes the effect of intrinsic (i.e. sex, age, tobacco smoking, occupational exposure and obesity) and extrinsic (season, environmental exposures, diet, physical activity and alcohol consumption) factors on the level of DNA damage measured by the standard or enzyme-modified comet assay. Although each factor influences at least one comet assay endpoint, the collective evidence does not indicate single factors have a large impact. Thus, controlling for confounding may be necessary in a biomonitoring study, but none of the factors is strong enough to be regarded a priori as a confounder. Controlling for confounding in the comet assay requires a case-by-case approach. Inter-laboratory variation in levels of DNA damage and to some extent also reproducibility in biomonitoring studies are issues that have haunted the users of the comet assay for years. Procedures to collect specimens, and their storage, are not standardized. Likewise, statistical issues related to both sample-size calculation (before sampling of specimens) and statistical analysis of the results vary between studies. This review gives guidance to statistical analysis of the typically complex exposure, co-variate, and effect relationships in human biomonitoring studies.

Traditional Indian sports - A case-control study on Kho Kho players investigating genomic instability and oxidative stress as a function of metabolic genotypes

The beneficial effects of physical exercise regularly for overall well being, or for recreational or professional purposes are widely accepted in clinical practice and have from time immemorial been the reasons for performing traditional sports. On the contrary, there is also evidence implying increased oxidative stress and genetic damage from intensive exercising. Depending on the intensity, time, frequency and characteristics of exercises, there can be differential induction of oxidative stress and provocation of oxidation of cellular macromolecules (including DNA) and cellular dysfunction which can likely accumulate with age, physical attributes and increase the susceptibility to disease on one hand, while stimulating cell signalling pathways leading to cell adaptation and improved resistance to stress, on the other. In order to observe if continuous sports activities as in Kho Kho increase oxidation capacity, which can also provoke oxidation of cellular macromolecules, the effects on oxidative/antioxidant changes and DNA damage in professional Kho Kho players modulated by individual genetic differences were assessed. Kho Kho, a traditional Indian game of ‘Tag’, is an all-time favourite which requires endurance, agility and strength. Healthy Kho Kho players (20.27 ± 0.28 y; sports age 6.78 ± 0.52 y) and controls (20.90 ± 0.45 y) were matched for age, gender, BMI, VO₂ max (maximal oxygen uptake), frequency of GSTT1 (present/null), M1 (present/null), SOD2 (C199T) polymorphisms but differed for variant allele frequencies of GSTP1 (A313G) and SOD2 (C47T). Players compared to controls had significantly increased levels of DNA damage (1.8x, 44.66 ± 1.68 vs. 23.85 ± 1.79 μm, p = 0.000), lipid (MDA) peroxidation (2x, 1.72 ± 0.06 vs. 0.83 ± 0.16 μmol/l, p = 0.000) and total antioxidant capacity (1.09x, 1.69 ± 0.06 vs. 1.11 ± 0.03 mmol Trolox equivalent/l, p = 0.000) but with no differences for SOD activity (94.99 ± 2.42 vs. 93.36 ± 2.54 U/ml, p = 0.935). These results suggest that the players have increased genetic damage and oxidative stress probably from the intense physical activity in the absence of other exposure(s) as other attributes were comparable in the study group. The players may therefore be at increased risk for susceptibility to cancer, various diseases and precocious age-related changes and should be sensitized to health risks related to regular intensive physical exercise.