Di (2-ethylhexyl) phthalate (DEHP) is used as an industrial plasticizer in, e.g. plastic bags, food packaging, children’s toys, and widely distributed in air, dust, water, and sediment soil. DEHP is an known endocrine disruptor. Studies have reported that both DEHP and magnetic fields could promote cell proliferation which may be related with adverse bioeffects.
Cells were treated with DEHP at different concentrations (0.01-100 µM). Cells were (1) sham exposed, (2) exposed to DEHP, (3) exposed to the magnetic field (0.2 mT and 0.4 mT) and (4) co-exposed to DEHP and the magnetic field.
To investigate the signal pathway in more detail, different inhibitors were used (SphK specific inhibitor, Akt phosphorylation inhibitor, ERK phosphorylation inhibitor).
|Exposure duration||1 h or 24 h|
|Chamber||each chamber consisted of a set of square Helmholtz coils (20×20 cm2) which was placed inside a 25×25×25 cm3 metal box; chambers could be set randomly as “magnetic field exposure” and “sham exposure”; cell plates or dishes were put in the center of the coils|
|Setup||the exposure system was composed of two exposure chambers which were put in a CO2 incubator, and a set of control devices outside the incubator; to remove heat produced by the current in the coils from the exposure chambers, an air cooling system based on two fans has been installed per coil; a fan on the metal wall ensured that the air and temperature were uniform inside the chamber and incubator; the temperature of the magnetic field and sham exposure groups was recorded real time and difference between them did not exceed 0.1 °C during the experiment|
|Sham exposure||A sham exposure was conducted.|
The data showed that a 50 Hz, 0.4 mT magnetic field exposure (1 h and 24 h) could promote the cell proliferation, whereas a 0.2 mT magnetic field exposure did not influence cell proliferation. When FL cells were co-exposed to a 0.2 mT magnetic field and 0.1 μM DEHP for 1 h or 24 h, cell proliferation rate was significantly higher (15% and 9%) than in the separate DEHP and magnetic field exposure groups.
Additionally, co-exposure to under-threshold (i.e. no effect was found for the separate exposures) magnetic field and DEHP could synergistically activate protein kinase B (Akt), sphingosine kinase 1 (SphK1) and extracellular signal-regulated kinase (ERK) in a cascade manner, and finally mediate cell proliferation.
In conclusion, the findings indicated that the co-exposure to under-threshold magnetic field and DEHP could jointly promote cell proliferation through activating proliferation-related signal pathway. The authors highlight that it requires a comprehensive consideration for evaluating the health effects of environmental contaminants at under-threshold levels.