Phenotype and functional alterations of human NK cells by organophosphate pesticides

Abstract

Chlorpyrifos (CPF) and Glyphosate (GLY) are organophosphate pesticides widely used in agriculture. Several evidences suggest that CPF- and GLY-based pesticides are genotoxic and their use has been linked to the increased frequency of malignancies observed in highly fumigated rural areas. However, their effect on the immune system, including cells involved in immunosurveillance of tumor cells, has been poorly explored. Here, we investigated the effects of two commercial formulations containing CPF (Clorpi48) and GLY (Roundup Plus) as well as their isolated active principles on the phenotype and function of human NK cells. First, we identified sub-apoptotic doses of these substances by flow cytometry performing a dose-response curve with human peripheral blood mononuclear cells (PMBC). Next, using such sub-apoptotic doses, we analyzed the phenotype of pesticide-treated NK cells. We observed a pesticide dose-dependent reduction in the expression of CD16 and CD62L on NK cells after a 24 h of culture with CPF, GLY, Roundup and Clorpi48. Moreover, a diminished frequency of IFN--producing NK cells was observed upon exposure of cytokine-stimulated NK cells to 5 mM GLY, 0.05 mM Roundup, 0.01 mM Clorpi48 but not to 0.02 mM CPF (p<0.05). Moreover, NK cell-mediated cytotoxicity against K562 cells was also affected by pesticide treatment. After 0.05 mM Roundup and 0.01 mM Clorpi48 treatment, cytotoxicity was reduced by 27% (p<0.01) and 29% (p<0.001), respectively. In accordance with previous scientific evidence, final formulations of pesticides (which include additional compounds such as polyethoxylated alkylamines surfactants that facilitate their absorption by cells and tissues) showed a more potent effect on phenotype and function of NK cells than the isolated compounds. Therefore, we conclude that GLY- and CPF-based pesticides affect NK phenotype and function, which might impact on their ability to detect and eliminate nascent tumor cells.