H. Sajedi, R. | Search bioRxiv

bioRxiv2026

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 ({Delta}{Psi}m) were monitored. Exposure likely led to rapid ROS elevation and a decrease in {Delta}{Psi}m, 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 IPL-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.

cell biology↗

bioRxiv2020

Stress-Dependent Conformational Changes of Artemin: Effects of Heat and Oxidant

Artemin is an abundant thermostable protein in Artemia embryos and considered as a highly efficient molecular chaperone against extreme environmental stress conditions. The dynamic conformational properties of artemin appear to play a critical role in its biological activities. In this study, we have investigated the conformational transitions and functional changes of artemin under heat and oxidative stress to find some evidence of the relationship between the structure and function of artemin. The tertiary and quaternary structures of artemin have been evaluated by fluorescence measurements, protein cross-linking analysis, and dynamic light scattering. Based on the structural analysis, artemin showed irreversible substantial conformational lability in response to heat and oxidant which mainly mediated through the hydrophobic interactions and dimerization of the chaperone. In addition, the chaperone-like activity of the heated and oxidized artemin was examined using lysozyme refolding assay and the experiments showed that although both factors, i.e. heat and oxidant, at specific levels improved artemin potency, simultaneous incubation with both stressors significantly triggered the activation of artemin. Moreover, the heat-induced dimerization of artemin was found to be the most critical factor for its activation. It was suggested that oxidation presumably acts through stabilizing the dimer structures of artemin through formation of disulfide bridges between the subunits and strengthens its chaperoning efficacy. Accordingly, it was proposed that artemin probably exists in a monomer-oligomer equilibrium in Artemia cysts and environmental stresses and intracellular portion of protein substrates may shift the equilibrium towards the active dimer forms of the chaperone. STATEMENT OF SIGNIFICANCEThere are a number of reports in which the chaperone-like activity of artemin, as a stress protein, has been confirmed in vivo and in vitro. Nonetheless, the details of structural changes of the protein have not been fully discovered yet. In the present work, we focused on conformational properties of artemin from A. urmiana upon exposing to heat and oxidation, by using various structural and functional analysis in order to predict the mechanisms of artemins activation. Notably, this is the first document on reporting the structural transitions of the chaperone in stress conditions.

biochemistry↗