Abstract
Even if the two neonicotinoids nitenpyram and imidacloprid have been considered safe for humans, their potential genotoxicity still remains a matter of discussion. The DNA-damaging effects of these two compounds were therefore evaluated in a lymphoma cell line of human origin (U-937) using the comet assay after 3-h exposure to up to 50 μM, with or without metabolic activation using S9 from human liver. The comet data were analysed using a traditional one-way ANOVA after pooling the data on cellular level, and a new alternative approach we have called Uppsala Comet Data Analysis Strategy (UCDAS). UCDAS is a proportional odds model tailored to continuous outcomes, taking the number of pooled cultures, slides and cells into consideration in the same analysis. To the best of our knowledge, the UCDAS approach when analysing comet data has never been presented before. Without metabolic activation, no increase in DNA damage was observed in the neonicotinoide-exposed cells. Nitenpyram was also without DNA-damaging effects when S9 was added. However, in the presence of S9, imidacloprid was found to increase the level of DNA damage. Whereas the ANOVA showed an increase (P < 0.001) both at 5 and 50 μM, UCDAS showed an increase only at the lowest concentration (P < 0.001). Based on these findings, the two neonicotinoids seem to be of little concern when it comes to their potential genotoxicity. However, since the U-937 cells were rather resistant to our positive controls, they may not be the best cells to use when evaluating potential genotoxicity of chemicals.
Highlights
Neonicotinoids are nicotine derivates used as insecticides and in veterinary parasite remedies (Calderon-Segura et al 2012; Schenker et al 2003)
When the cells were exposed for 3 h in the presence of human S9, imidacloprid increased the level of DNA damage both at 5 and 50 μM according to the ANOVA analysis, but only at 5 μM according to the Uppsala Comet Data Analysis Strategy (UCDAS) analysis (Table 2)
The potential DNA-damaging effects of the two neonicotinoids imidacloprid and nitenpyram were evaluated in human U-937 lymphoma cells after 3-h exposure to up to 50 μM, with or without a metabolic activation system based on S9 from human liver
Summary
Neonicotinoids are nicotine derivates used as insecticides and in veterinary parasite remedies (Calderon-Segura et al 2012; Schenker et al 2003). The use of neonicotinoids in insecticides has grown rapidly since their introduction in 1991 (Calderon-Segura et al 2012). Imidacloprid had the highest sale value of all insecticides in 2009 but has since been banned in the European Union (EU) due to its toxic effects in honeybees (Jeschke et al 2011). As recent as in April 2018, the member states of EU decided to accept the recommendation proposed by the European Commission to expand the previous ban on neonicotinoide use (Union 2018). The extended ban restricts and prohibits the use of the three most commonly used neonicotinoids: imidacloprid, clothianidin and thiamethoxam within open field agricultural
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