Electrophysiological effects of silver species in U251 human cell line

The electrophysiological effects of silver species was largely investigated in aquatic organism, but scanty datas are present in mammalians. By using patch clamp technique, we studied the electrophysiological effects of silver cation, Ag(+), and metal silver nanoparticles (AgNPs) application on U251 cell line. In whole cell perforated configuration, batch application of 10 M Ag(+) activated an inward current at 0 mV. Extracellular sodium ion substitution with choline, reduce silver activated current (IAg) demonstrating its cation nature. Calcium imaging experiments by using Fura-2, indicate that IAg current, was permeable to calcium ion since an intracellular calcium increase was observed following Ag+ application. The IAg was prevented by co-application of cysteine (20 M) and catalase (1500 catalytic units/ml) suggesting a role of thiol groups and hydroperoxide ROS specie in the activation pathway of IAg by silver ion. IAg current was also inhibited by the aspecific chloride current blocker DIDS (4,4'-Diisothiocyano-2,2'-stilbenedisulfonic acid), whereas it was insensible to DCPIB (4-(2-Butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid), a selective inhibitor of swelling activated chloride current. Batch application of AgNPs activated a cationic current that displays similar biophysical and pharmacological profile of IAg. These data, indicate that the Ag(+), present in physiological medium in equilibrium with AgNPs, may represents the silver specie responsible of electrophysiological effects displayed by silver nanoparticles.