Effects of chlorpyrifos on transglutaminase activity in differentiating rat C6 glioma cells

The organophosphorothioate compound chlorpyrifos (CPF) is a widely used pesticide, which is known to inhibit the differentiation of mouse N2a neuroblastoma and rat C6 glioma cells. This study in focused on the possible effects of CPF in the activity and expression of tissue transglutaminase (TGase 2) in differentiating C6 cells. Cells exposed for 24 h to 10 μM CPF, which had no effect on cell viability, exhibited a significant increase in cytosolic TGase 2 activity. Western blotting analysis indicated that there was no change in the cytosolic TGase 2 protein levels, suggesting that the enzyme was activated under these conditions. When commercially available TGase 2 was incubated with CPF in vitro, an increase in activity was also observed, suggesting that CPF might interact directly with TGase 2.