The in vitro exposure to cypermethrin does not inhibit the proliferative response of peripheral blood mononuclear cells.

This study evaluated the effect of in vitro exposure to cypermethrin on peripheral blood mononuclear cells proliferative response, considering reduced peripheral blood mononuclear cells proliferative response observed in individuals occupationally exposed to pyrethroids. Peripheral blood mononuclear cells were obtained from 21 healthy subjects (28.0 ± 9.0 years old). The effect of cypermethrin (at 0.5, 1.0 and 5.0 mg/ml) on cell viability was evaluated by flow cytometry using an apoptosis detection kit. Cell proliferation (PI) was evaluated by 5-(and 6)-carboxyfluorescein diacetate succinimidyl ester (CFSE) fluorescence decay using flow cytometry. Cells labeled with CFSE were exposed, in vitro, to cypermethrin (0.5, 1.0, 2.0, 2.5 and 4 μg/ml) and stimulated with phytohemagglutinin (PHA 1.0 or 5.0 μg/ml) for 5 d (37 °C, 5% CO2). The in vitro treatment of peripheral blood mononuclear cells with cypermethrin did not induce apoptosis or necrosis after 5 d in culture. Stimulation by PHA induced cell proliferation (PI = 1.29 ± 1.09 and 2.01 ± 0.62, PHA at 1.0 and 5.0 μg/ml, respectively, mean ± SD) and in vitro exposure to cypermethrin did not alter cellular proliferative response to PHA (PI = 1.80 ± 0.50, 2.60 ± 0.05 and 2.10 ± 1.20 for cypermethrin at 1.0, 2.0 and 4.0 μg/ml, respectively, and PHA at 5.0 μg/ml). In vitro treatment of peripheral blood mononuclear cells with cypermethrin, at the doses tested, does not affect cell viability or proliferation. These findings suggest that the reduction of proliferation observed on lymphocytes derived from individuals occupationally exposed to pesticides may be related to other mechanisms than direct action of cypermethrin on lymphocytes.