Screening of Pesticides with the Potential of Inducing DSB and Successive Recombinational Repair

Abstract

A study was realized to ascertain whether eight selected pesticides would induce double strand breaks (DSB) in lymphocyte cultures and whether this damage would induce greater levels of proteins Rad51 participating in homologous recombination or of p-Ku80 participating in nonhomologous end joining. Only five pesticides were found to induce DSB of which only glyphosate and paraoxon induced a significant increase of p-Ku80 protein, indicating that nonhomologous end joining recombinational DNA repair system would be activated. The type of gamma-H2AX foci observed was comparable to that induced by etoposide at similar concentrations. These results are of importance since these effects occurred at low concentrations in the micromolar range, in acute treatments to the cells. Effects over longer exposures in actual environmental settings are expected to produce cumulative damage if repeated events of recombination take place over time.

Figure 1

Graph: p-Ku80 protein increased due to treatments with glyphosate in a dose-dependent manner (linear regression, p < 0.05). Individual concentrations were analyzed by Kruskal-Wallis and Dunn's multiple comparison test; the asterisk shows that 5 microM was significantly different from the negative control. The bottom part shows a representative membrane: lane 1, negative control; lanes 2–4, pentachlorophenol (0.2, 1.0, and 5 microM); lanes 5–7, glyphosate (1.25, 2.5, and 5 microM, see graph); lane 8, etoposide (10 microM).

Figure 2

Increase in the amount of p-Ku80 protein in cells treated with paraoxon: lane 1, negative control; lanes 2–4, paraoxon (1, 5, and 25 microM); lane 5, etoposide (10 microM). Rad51 did not show significant variation among treatments as is shown in the graph.  ^∗Significantly different dose; Kruskal-Wallis; Dunn's post hoc test, p < 0.05.

Figure 3

Percentage of cells with more than 10 gamma-H2AX foci induced by treatments with etoposide, glyphosate, and paraoxon. The three compounds induced an increase related to the dose; see Results for statistical values of linear regression analyses.