Spatiotemporal magnetic fields enhance cytosolic Ca2+ levels and induce actin polymerization via activation of voltage-gated sodium channels in skeletal muscle cells

• Published in: Biomaterials 2018-05, Vol.163, p.174-184
• Main Authors: Rubio Ayala, Mónica, Syrovets, Tatiana, Hafner, Susanne, Zablotskii, Vitalii, Dejneka, Alexandr, Simmet, Thomas
• Format: Article
• Language: English
• Subjects: Alternating magnetic field; Cytosolic calcium; Eddy current; Modeling; Skeletal muscle; Voltage-gated sodium channels
• ISSN: 0142-9612; 1878-5905
• DOI: 10.1016/j.biomaterials.2018.02.031

Cellular function is modulated by the electric membrane potential controlling intracellular physiology and signal propagation from a motor neuron to a muscle fiber resulting in muscle contraction. Unlike electric fields, magnetic fields are not attenuated by biological materials and penetrate deep into the tissue. We used complex spatiotemporal magnetic fields (17–70 mT) to control intracellular signaling in skeletal muscle cells. By changing different parameters of the alternating magnetic field (amplitude, inversion time, rotation frequency), we induced transient depolarization of cellular membranes leading to i) Na+ influx through voltage-gated sodium channels (VGSC), ii) cytosolic calcium increase, and iii) VGSC- and ryanodine receptor-dependent increase of actin polymerization. The ion fluxes occurred only, when the field was applied and returned to baseline after the field was turned off. The 30-s-activation-cycle could be repeated without any loss of signal intensity. By contrast, static magnetic fields of the same strength exhibited no effect on myotube Ca2+ levels. Mathematical modeling suggested a role for the alternating magnetic field-induced eddy current, which mediates a local change in the membrane potential triggering the activation of VGSC. These findings might pave the way for the use of complex magnetic fields to improve function of skeletal muscles in myopathies. [Display omitted] •Spatiotemporal magnetic fields increase Ca2+i and actin polymerization in skeletal muscle cells.•Eddy-current-induced changes of the cell membrane potential trigger activation of VGSC.•A theoretical model for inhomogeneous alternating magnetic fields was developed.