Crosstalk Between Calcium Dynamics and ROS Levels in U87 Glioblastoma Cells Exposed to Extremely Low Frequency Pulsed Electromagnetic Fields

Extremely low-frequency pulsed electromagnetic fields (ELF PEMFs) have been proposed to modulate intracellular signaling in cancer cells, however, the primary mediators and their temporal sequence remain incompletely understood. In this study, U87 glioblastoma cells were exposed to ELF PEMF at varying frequencies and amplitudes, and intracellular calcium (Ca2+) dynamics, reactive oxygen species (ROS) levels, and mitochondrial membrane potential (DeltaPsim) were monitored. Exposure likely led to rapid ROS elevation and a decrease in DeltaPsim, indicating early mitochondrial involvement in ELF PEMF responses. Fast Fourier transform (FFT) analysis of Ca2+ oscillations suggested that low-frequency exposures produced higher spectral power and amplitude compared with controls, consistent with enhanced Ca2+ signaling activity. Parallel pharmacological experiments demonstrated that ROS elevation may occur independently of IP-dependent endoplasmic reticulum (ER) Ca2+ release, as 2-Aminoethoxydiphenyl borate (2 APB) inhibition did not prevent ROS increase. In contrast, treatment with the antioxidant N-acetylcysteine (NAC) effectively suppressed ROS without significantly altering basal cytosolic Ca2+ levels. These observations indicate that ROS likely acts as an early mediator of cellular responses to ELF PEMF exposure, with downstream modulation of calcium signaling pathways. The magnitude of ROS elevation and Ca2+ modulation was strongly dependent on field frequency and amplitude, consistent with a frequency-dependent biological window. Overall, ROS likely acts as a primary mediator of ELF PEMF bioeffects, highlighting its potential relevance for glioblastoma therapy, and future studies are warranted to assess other glioma lines to confirm generalizability.