Power Frequency Magnetic Fields Induced Reactive Oxygen Specieses-Related Autophagy In Mouse Embryonic Fibroblasts

BACKGROUND:50/60Hz power frequency magnetic fields (PFMF) belong to extremely low frequency magnetic fields(0-300Hz), which are generated by alternating current supplied by, for instance, power lines and domestic appliances. PFMF were reported to alter the homeostasis of Ca2+in neural tissues, increase reactive oxygen species (ROS) in different cell lines, disturb cellular or organismal homeostasis, and then cause different cellular function alterations. Autophagy is now recognized as indispensable for the homeostasis of cells, tissues and organisms. Autophagy is a process in which cytosol and damaged organelles are sequestered within double-membrane vesicles that deliver the contents to the lysosome for degradation and recycling of the resulting macromolecules. It is an important cellular defense and protection mechanism. It is unclear that whether PFMF exposure will induce cellular autophagy to regulate cellular metabolic disturbance.AIMS:In this study, we aimed to investigate the effect of PFMF on autophagy in mouse embryonic fibroblasts cells (MEF).METHODS:MEF were exposed to2mT PFMF for0.5h,2h,6h,12h and24h, and then subjected to western blotting. After finding a timepoint that the autophagic marker increased signifitantly in exposed group, we used confocal microscope to observe GFP-LC3puncta and electron microscope to observe autophagosome formation in MEF. Chloroquine was used to monitor autophagic flux. Intracellular ROS levels were measured using a Reactive Oxygen Species Assay Kit. Apoptosis were further explored with flow cytometry and TUNEL assays.RESULTS:Under the experimental conditions, we observed a significant increase of autophagic markers at6h, including (i) higher microtubule-associated protein1light chain3-II (LC3-II),(ii) increased formation of GFP-LC3puncta, and (iii) increased numbers of autophagic vacuoles under transmission electron microscope. What’s more, we provided convincing evidence that the increase of autophagic markers was the result of enhanced autophagic flux, not due to suppression of lysosomal function by using chloroquine. In search of the molecular mechanisms underlying PFMF-mediated autophagy, we found that the autophagic process might be related with ROS and independent of mammalian target of rapamycin (mTOR) signaling pathway. PFMF exposure of6h had no effects on apoptosis in MEF.Conlusions:Under current experiment conditions, PFMF induced ROS-related auotphagy in MEF.