Microwave exposure of neuronal cells in vitro:: Study of apoptosis

Purpose: The aim of this study was to investigate microwave ( MW) effects on neuronal apoptosis in vitro. Materials and methods: Human neuroblastoma cells SH-SY5Y were exposed to a 900 MHz global system for mobile communication (GSM) or continuous-wave (CW) radiofrequency fields for 24 h in a wire-patch cell. The specific absorption rates (SAR) used were 2 W/kg for CW and 0.25 W/kg average for GSM. During CW exposure, an increase of 2 degrees C was measured, and controls with cells exposed to 39 degrees C were then performed. Apoptosis rate was assessed immediately or 24 h after exposure using three methods: (i) 40,6-diamino-2-phenylindole (DAPI) staining; (ii) flow cytometry using double staining with TdT-mediated dUTP nick-end labeling (TUNEL) and propidium iodide (PI); and (iii) measurement of caspase-3 activity by fluorimetry. Results: No statistically significant difference in the apoptosis rate was observed between sham and 24 h MW-exposed cells, either GSM-900 at an average SAR of 0.25 W/kg, or CW 900 MHz at a SAR of 2 W/kg, either 0 h or 24 h post-exposure. Furthermore, for CW-exposure, apoptosis rates were comparable between sham-, CW-, 37 degrees C- and 39 degrees C-exposed cells. All three methods used to assess apoptosis were concordant. Conclusion: These results showed that, under the conditions of the present experiment, MW-exposure (either CW or GSM-900) does not significantly increase the apoptosis rate in the human neuroblastoma cell line SH-SY5Y.