Chlorpyrifos organophosphorous pesticide differentially alters redox metabolism in estrogen-dependent and estrogen-independent breast cancer cells.

C VENTURA; M NUÑEZ; D MARTIEL LAMAS; N MOHAMAD; C A PONTILLO; A RANDI; E RIVERA; A VENTURINO; C COCCA

Lisboa

Congreso; International Congress on Environmental Health 2012; 2012

Escola Superior de Tecnología da Saúde de Lisboa. Instituto politécnico de Lisboa.

Chlorpyrifos (CPF) is a broad spectrum organophosphorous pesticide (OPs) that is widely used throughout the world in agriculture and non-agriculture applications. Oxidative stress has been described in acute, chronic, and developmental exposure to OPs, in both animals and humans, as well as in some in vitro studies. Although reactive oxygen species (ROS) modulate various biological processes, they can cause severe damage to DNA, protein and lipids. It has been reported that moderate increase of ROS may stimulate cell proliferation and estrogens may induce oxidative stress in MCF-7 cells. Previously, we have studied the effect of CPF on cell proliferation in estrogen-dependent (MCF-7) and in estrogen-independent (MDA-MB-231) breast cancer cell lines. We observed that CPF 50 µM inhibits clonogenicity, increases the doubling time and induces apoptosis in both lines. The cell cycle analysis showed that MCF-7 and MDA-MB-231 cells are arrested at S and G2/M phases, respectively, when they were treated with CPF 50 µM. On the other hand, CPF at 5.10-2 µM stimulated cell proliferation of MCF-7 cells and the phosphorylation of a tyrosin residue in position 537 in the estrogen receptor alpha which resulted implicated in pesticide action. In contrast, CPF did not affect MDA-MB-231 cells proliferation at any dose assayed. To understand the mechanisms implicated in cell proliferation modulation by CPF exposure, we analyzed the effect of the pesticide on redox metabolism. Concentrations ranging from 5.10-2 to 50 µM were tested. We studied ROS content by flow citometry by staining cells with DCF-2DA. The activity enzymes implicated in redox balance such as catalase, superoxide dismutase (SOD) and glutation transferase (GST) were measured by spectrometry. Our results demonstrated that CPF 50 µM produces an increment of the ROS content in both lines (32% over control in MCF-7, 108% over control in MDA-MB-231, p lower than 0.001). This action was reverted by addition of catalase 30 IU/mL in MCF-7 cell line but had not affect MDA-MB-231 cells response. Furthermore, catalase activity resulted increased in both lines exposed to CPF 50 and 5 µM (78% over control in MCF-7, p lower than 0.05; 98% over control in MDA-MB-231, p lower than 0.05). CPF 50 µM decreased SOD activity in MCF-7 cell line (60% vs. control, p lower than 0.05) but CPF 5.10-1 and 5.10-2 µM induced this enzyme activity (115 and 92% vs. control respectively, p lower than 0.001). In MDA-MB-231 cells, SOD activity was not modified at any concentration assayed. Finally, CPF 50 µM increased GST activity (226% over control, p lower than 0.001) and CPF 5.10-2 µM decreased the activity of this enzyme (60% vs. control, p lower than 0.05) in MCF-7 cells. No changes were observed in MDA-MB-231 cells exposed to CPF at any dose assayed. In summary, CPF differently affects the oxidant-antioxidant balance in MCF-7 and MDA-MB-231 cells. These alterations may conduce to the inhibition of cell proliferation observed in estrogen dependent and independent breast cancer cells exposed to CPF 50 μM. Conversely, CPF 5.10-2 μM only affected redox metabolism in MCF-7 cells which could be related to the xenoestrogenic action of the pesticide at this dose on this cell line.