Exposure to Insecticides Modifies Gene Expression and DNA Methylation in Hematopoietic Tissues In Vitro

Abstract

The evidence supporting the biological plausibility of the association of permethrin and malathion with hematological cancer is limited and contradictory; thus, further studies are needed. This study aimed to investigate whether in vitro exposure to 0.1 μM permethrin and malathion at 0, 24, 48 and 72 h after cell culture initiation induced changes in the gene expression and DNA methylation in mononuclear cells from bone marrow and peripheral blood (BMMCs, PBMCs). Both pesticides induced several gene expression modifications in both tissues. Through gene ontology analysis, we found that permethrin deregulates ion channels in PBMCs and BMMCs and that malathion alters genes coding proteins with nucleic acid binding capacity, which was also observed in PBMCs exposed to permethrin. Additionally, we found that both insecticides deregulate genes coding proteins with chemotaxis functions, ion channels, and cytokines. Several genes deregulated in this study are potentially associated with cancer onset and development, and some of them have been reported to be deregulated in hematological cancer. We found that permethrin does not induce DNA hypermethylation but can induce hypomethylation, and that malathion generated both types of events. Our results suggest that these pesticides have the potential to modify gene expression through changes in promoter DNA methylation and potentially through other mechanisms that should be investigated.

Keywords: gene expression; malathion; permethrin.

Figure 1

Distribution of genes with low expression (upside down triangles) and with overexpression (triangles looking up) on each microarray. Gene expression was analyzed in PBMCs and BMMCs exposed in vitro to permethrin or malathion. Each colored rhombus belongs to a specific treatment condition.

Figure 2

Summary of over-representation test results of genes with altered expression in BMMCs and PBMCs exposed to malathion. Green section shows cellular functions associated with genes with underexpression, and red section with genes with overexpression. The upper part displays results of BMMCs and lower part shows results of PBMCs.

Figure 3

Summary of over-representation test results of genes with altered expression in BMMCs and PBMCs exposed to permethrin. The green section shows cellular functions associated with genes with underexpression and the red section with genes with overexpression. The upper part displays the results of BMMCs and the lower part shows the results of PBMCs.

Figure 4

Common cellular functions altered by modification in gene expression in BMMCs and PBMCs exposed to insecticides. Results derived from over-representation test analyzing the total of genes with gene expression changes determined by Panther Pathways program.

Figure 5

Pathway ontology analysis in BMMCs exposed to malathion.

Figure 6

Pathway ontology analysis in PBMCs exposed to malathion.

Figure 7

Pathway ontology analysis in BMMCs exposed to permethrin.

Figure 8

Pathway ontology analyisis in PBMCs exposed to permethrin.

Figure 9

Genes with altered expression in more than one treatment condition and tissue. Results derived from the analysis of the top and bottom 100 genes over or underexpressed in BMMCs and PBMCs, exposed to malathion or permethrin. Figure shows genes that where concordant between two different assays.

Figure 10

GeneMANIA tool interaction analysis of overexpressed genes in BMMCs exposed to permethrin.

Figure 11

GeneMANIA tool interaction analysis of overexpressed genes in BMMCs exposed to malathion.

Figure 12

qPCR validation of changes in gene expression in cells exposed to insecticides. Gene expression alterations were assessed on independent PBMCs and BMMCs exposed to malathion and permethrin (0.1 μM, 72 h) * p < 0.05, t test.