Parkinson's disease can be caused by genetic as well as environmental factors, like the MPP+ toxin. MPP+ (1-methyl-4-phenylpyridinium) creates oxidative stress in dopaminergic neurons in the brain leading to apoptosis and neuronal loss. Extremely low frequency magnetic fields could be a potential (synergistic) environmental factor.
Neuroblastoma cells were either differentiated into a dopaminergic phenotype 24 hours prior to the exposure or kept in an undifferentiated state. They were then exposed to the magnetic field for 6 h, 12 h, 24 h, 48 h or 72 h with or without the addition of acetylcysteine or reduced glutathione ethyl ester (both antioxidants). In the MPP+ tests, MPP+ was added after 24 hours of exposure (concentrations in medium of 0.1 - 5 mM) and then the cells were incubated for 6 h or 24 h without exposure. To investigate recovery effects, MPP+ was removed after 24 h in one approach and cells were investigated after further 24 hours of incubation without exposure. For each exposure condition, a separate sham exposure was conducted.
Exposure duration: continuous for 6, 12, 24, 48 oder 72 hours
Exposure duration: continuous for 24 hours
|Exposure duration||continuous for 6, 12, 24, 48 oder 72 hours|
|Chamber||60 mm petri dishes in incubator|
|Setup||two Helmholtz coils (side length of 38 cm, placed 12 cm apart, coil section was square with a side of 2 cm and composed of 25 cable turns, each cable was made of copper with two wires with a diameter of 2.5 mm) provided a homogeneous magnetic field; temperature in samples was maintained at 37 ± 0.2°C; applied current of coils was 3.4 A; petri dishes were positioned in two stacks of five dishes each (4 ml sample per dish), placed with their bottom layer parallel to the magnetic field direction|
|Sham exposure||A sham exposure was conducted.|
|Additional info||coil double wire configuration was used for sham exposure, to obtain a zero B-field, using currents flowing in opposite directions; temperature in sham exposure samples was maintained at 37 ± 0.2°C|
|Exposure duration||continuous for 24 hours|
|Additional info||MPP+ tests|
Exposure to the magnetic field alone had no significant effect on cell viability, proliferation, morphology or apoptosis in comparison to the sham exposure. However, the amount of reactive oxygen species and carbonyl proteins was significantly increased and the amount of thiols significantly reduced in exposed cells compared to sham exposed cells.
Even in low concentrations, the toxicity of MPP+ was enhanced by exposure to the magnetic field. A significantly decreased viability and proliferation and a significantly increased amount of reactive oxygen species and carbonyl proteins as well as significantly more apoptotic cells were found in exposed cells treated with MPP+ compared to sham exposed cells with MPP+. No recovery effects were observed.
Addition of the antioxidants acetylcysteine and glutathione ethyl ester significantly reduced the amount of reactive oxygen species and apoptosis in exposed cells with MPP+ compared to exposed cells with MPP+ without these antioxidants.
The authors conclude that exposure of human neuroblastoma cells to a 50 Hz magnetic field might induce oxidative stress and thus enhance the potency of the pro-Parkinson's disease toxin MPP+.