Arecoline inhibits intermediate-conductance calcium-activated potassium channels in human glioblastoma cell lines

Arecoline (ARE) is an alkaloid type natural product from areca nut. This compound has numerous pharmacological and toxicological effects. Whether this agent interacts with ion channels to perturb functional activity of cells remains unknown. The effects of ARE on ionic currents were studied in glioma cell lines (U373 and 1387MG) using patch clamp technique. Like TRAM-34(1-[(2-chlorophenyl)-diphenylmethyl]pyrazole), ARE suppressed the amplitude of whole cell voltage gated K+ currents in 13373 cells elicited by a ramp voltage clamp. In cell attached configuration, ARE did not modify the single channel conductance of iniermediaLe-conducLance Ca2+-activated K+ (IKCa) channels; however, it did reduce channel activity. Its inhibition of IKCa channels was accompanied by a significant lengthening in the slow component of mean closed time of lKo channels. Based on minimal kinetic scheme, the dissociation constant (K-D) required for ARE mediated prolongation of mean closed time was 11.2 mu M ARE-induced inhibition of IKCa channels was voltage-dependent. Inability (A ARE to perturb the activity of large-conductance Ca2+-activated K+ (BKCa) channels was seen. Under current-clamp recordings, ARE depolarized the membrane of U373 cells and DCEBIO reversed ARE-induced depolarization. Similarly, ARE suppressed IKCa-channel activities in oral keratinocytes. This study provides the evidence that ARE block lK(Ca) channels in a concentration, voltage and state-dependent manner. ARE-induced block of lK(Ca) channels is unrelated to the binding of muscarinic receptors. The effects of ARE on these channels may partially be responsible for the underlying cellular mechanisms by which it influences the functional activities of glioma cells or oral keratinocytes, if similar findings occur in vivo. (C) 2015 Elsevier B.V. All rights reserved,