Cytokinesis-blocked micronucleus cytome and comet assays in peripheral blood lymphocytes of workers exposed to lead considering folate and vitamin B12 status

Abstract

In human biomonitoring, factors such as age, gender, smoking habit and alcohol consumption are usually considered and identified as agents that exert an impact on genotoxicity biomarkers. However, as a rule, factors like micronutrient status are not considered in biomonitoring studies. This paper reports on genotoxic damage in Pb-exposed workers using data obtained from the cytokinesis-block micronucleus (CBMN) cytome assay and alkaline comet assay with silver staining, considering folate and vitamin B12 nutritional status. Analysis of the results showed that the Pb-exposed group presented a 24-fold higher Pb content in the blood compared to controls. The Pb-exposed workers presented significantly greater micronuclei (MNi) counts (Z=7.9583; p<0.0001) and DNA damage, assessed by the comet assay (DF: Z=7.7056; p<0.0001 and DI: Z=7.4749; p<0.0001), but no correlation with Pb blood concentrations were detected. These two groups did not differ significantly concerning folate and vitamin B12 levels. Regarding folate, it is possible that this similarity is associated with folic acid flour-enrichment, introduced in Brazil in 2004 to prevent neural tube defects. The mean folate level obtained in the Pb-exposed group was 6.18ng/ml. The subgroup of individuals with serum folate levels equal to or higher than the mean presented significantly higher MNi (Z=2.3776; p=0.017) and nucleoplasmic bridge (NPB) frequencies (Z=1.9850; p=0.047) in peripheral blood lymphocytes. A significant positive correlation was observed between the age of Pb-exposed workers and MNi frequencies (Γ=0.3328; p<0.001), NPBs (Γ=0.1832; p<0.042) and DNA damage assessed by the comet assay (DF: Γ=0.1764; p=0.035 and DI: Γ=0.11852; p=0.028). These findings suggest that high folate levels alone do not guarantee protection against genotoxic damage. Moreover, folic acid supplementation should be studied using more efficient approaches to determine safe amounts and potential deleterious effects.