Computational modeling of the variation of the transmembrane potential of the endothelial cells of the blood-brain-barrier subject to an external electric field

The electromechanical properties of the membrane of endothelial cells forming the blood-brain barrier play a vital role in the function of this barrier. The mechanical effect exerted by external electric fields on the membrane could change its electrical properties. In this study the effect of extremely low frequency (ELF) external electric fields on the electrical activity of these cells has been studied by considering the mechanical effect of these fields on the capacitance of the membrane. The effect of time-dependent capacitance of the membrane is incorporated in the current components of the parallel conductance model for the electrical activity of the cells. The results show that the application of ELF electric fields induces hyperpolarization, having an indirect effect on the release of nitric oxide from the endothelial cell and the polymerization of actin filaments. Accordingly, this could play an important role in the permeability of the barrier. Our finding can have possible consequences in the field of drug delivery into the central nervous system.

Terahertz Wave Enhances Permeability of the Voltage-Gated Calcium Channel

A deficiency of Ca²⁺ fluxes arising from dysfunctional voltage-gated calcium channels has been associated with a list of calcium channelopathies such as epilepsy, hypokalemic periodic paralysis, episodic ataxia, etc. Apart from analyzing the pathogenic channel mutations, understanding how the channel regulates the ion conduction would be instructive to the treatment as well. In the present work, in relating the free energetics of Ca²⁺ transport to the calcium channel, we demonstrate the importance of bridging Ca²⁺ hydration waters, which form hydrogen bonds with channel -COO^- and -C═O groups and enable a long-distance effect on the Ca²⁺ permeation. By firing a terahertz wave which resonates with the stretching mode of either the -COO^- or the -C═O group, we obtain significantly enhanced selectivity and conductance of Ca²⁺. The Ca²⁺ free energy negatively grows nearly 5-fold. The direct evidence is the reinforced hydrogen bonds. In addition, thanks to forced vibrations, -COO^- contributes to raised permeation as well even under a field in resonance with -C═O, and vice versa. Since the resonant terahertz field could manipulate the conduction of calcium channels, it has potential applications in therapeutic intervention such as rectifying a Ca²⁺ deficiency in degraded calcium channels, inducing apoptosis of tumor cells with overloaded calcium etc.