Study of Electrical Stimulation with Different Electric-Field Intensities in the Regulation of the Differentiation of PC12 Cells.

The strategy of using electrical stimulation (ES) to promote the neural differentiation and regeneration of injured nerves is proven feasible. Study of the possible molecular mechanisms in relation to this ES promotion effect should be helpful for understanding the phenomenon. In this study, it was identified that the neuronal differentiation of PC12 cells was enhanced when the electric field intensity was in the range of 30-80 mV/mm, and a lower or higher electric-field intensity displayed inferior effects. Under ES, however, levels of intracellular reactive oxygen species (ROS), intracellular Ca2+ dynamics, and expression of TREK-1 were measured as being gradually increasing alongside higher electric-field intensity. In trying to understand the relationship between the ES enhancement on differentiation and these variations in cell activities, parallel experiments were conducted by introducing exogeneous H2O2 into culture systems at different concentrations. Similarly, the effects of H2O2 concentration on the neuronal differentiation of PC12 cells, intracellular ROS and Ca2+ levels, and TREK-1 expression were systematically characterized. In comparative studies, it was found in two cases that ES of 50 mV/mm for 2 h/day and H2O2 of 5 μM in culture medium shared comparable results for intracellular ROS and Ca2+ levels and TREK-1 expression. Higher H2O2 concentrations (e.g., 10 and 20 μM) demonstrated adverse effects on cell differentiation and caused DNA damage. A stronger ES (e.g., 100 mV/mm), being associated with a higher intracellular ROS level, also resulted in weaker enhancement of the neuronal differentiation of PC12 cells. These facts suggested that the intracellular ROS generated under ES might be an intermediate signal transducer involved in cascade reactions relative to cell differentiation.