Characterization of Direct Cyclodextrin Effects on Voltage-Gated Potassium Channels

Abstract

Cyclodextrins (CDs) are cyclic oligosaccharides consisting of six, seven or eight alpha-D-glucopyranoside units. Due to their truncated cone structure they can form complexes with various drugs and lipid molecules. CDs are widely used as inert carriers and in research to selectively deplete cholesterol levels in biological membranes. The direct effects of CDs on ion channels have not been studied yet. Since voltage-gated potassium (Kv) channels regulate a great variety of biological processes, direct effects of CDs on these channels can contribute to the known side effects (such as immunosuppression via Kv1.3) of numerous drugs. Our aim was to characterize direct, ligand-like effects of CDs with different sizes and side chain substitutions on various Kv channels and to demonstrate that these are independent from their effects on membrane cholesterol depletion. We carried out patch-clamp measurements to characterize the direct effects of CDs on Kv channels. Most of the tested CDs at concentrations of 1 and 5 mM partially reversibly inhibited Kv1.3 currents within 15 seconds, while some of them had no such effect. To examine the potential membrane biophysical and cholesterol depleting effects of CDs, after 1 hour incubation we measured membrane fluidity, hydration, lipid order and the extent of cholesterol depletion. We also performed a cell viability assay on Jurkat cells using flow cytometry, where in parallel with direct inhibitory effects on Kv1.3 and independent from cholesterol depletion we detected cell death after 24-hour-long CD treatments.Based on our results we can conclude that CDs exert previously unknown direct inhibitory effects on Kv ion channels independent from cholesterol depletion, which can play an important role in side effects of drugs containing CDs., Supported by the ÚNKP-19-3-III-DE-92 New National Excellence Program of the Ministry for Innovation and Technology”