Effects of Ibandronate Sodium, a Nitrogen-Containing Bisphosphonate, on Intermediate-Conductance Calcium-Activated Potassium Channels in Osteoclast Precursor Cells (RAW 264.7)

Abstract

Ibanonate sodium (Iban), a nitrogen-containing bisphosphonate, is recognized to reduce skeletal complications through an inhibition of osteoclast-mediated bone resorption. However, how this drug interacts with ion channels in osteoclasts and creates anti-osteoclastic activity remains largely unclear. In this study, we investigated the possible effects of Iban and other related compounds on ionic currents in the osteoclast precursor RAW 264.7 cells. Iban suppressed the amplitude of whole-cell K(+) currents (I K) in a concentration-dependent manner with an IC50 value of 28.9 μM. The I K amplitude was sensitive to block by TRAM-34 and Iban-mediated inhibition of I K was reversed by further addition of DCEBIO, an activator of intermediate-conductance Ca(2+)-activated K(+) (IKCa) channels. Intracellular dialysis with Iban diminished I K amplitude and further addition of ionomycin reversed its inhibition. In 17β-estradiol-treated cells, Iban-mediated inhibition of I K remained effective. In cell-attached current recordings, Iban applied to bath did not modify single-channel conductance of IKCa channels; however, it did reduce channel activity. Iban-induced inhibition of IKCa channels was voltage-dependent. As IKCa-channel activity was suppressed by KN-93, subsequent addition of Iban did not further decrease the channel open probability. Iban could not exert any effect on inwardly rectifying K(+) current in RAW 264.7 cells. Under current-clamp recordings, Iban depolarized the membrane of RAW 264.7 cells and DCEBIO reversed Iban-induced depolarization. Iban also suppressed lipopolysaccharide-stimulated migration of RAW 264.7 cells in a concentration-dependent manner. Therefore, the inhibition by Iban of IKCa channels would be an important mechanism underlying its actions on the functional activity of osteoclasts occurring in vivo.

The Inhibition by Oxaliplatin, a Platinum-Based Anti-Neoplastic Agent, of the Activity of Intermediate-Conductance Ca2+-Activated K+ Channels in Human Glioma Cells

“…DCEBIO is an activator of IK Ca channels, while ionomycin is a Ca 2+ ionophore [22,30,32]. These results led us to suggest that the component of K + currents suppressed by OXAL in 13-06-MG cells should be linked to the activity of IK Ca channels [14,30]. Table 1.…”

“…The channel open probabilities were measured in the control and during cell exposure to different concentrations (3 µM-1 mM) of OXAL, and they were then compared with those measured after subsequent addition of TRAM-34 (3 µM). TRAM-34 is known to be a selective blocker of IK Ca channels [22,29,30]. The concentration required to suppress 50% of channel activity was determined by means of a Hill function [28]:…”

Actions of FTY720 (Fingolimod), a Sphingosine-1-Phosphate Receptor Modulator, on Delayed-Rectifier K+ Current and Intermediate-Conductance Ca2+-Activated K+ Channel in Jurkat T-Lymphocytes

“…As illustrated in Figure 1 , FTY720 suppressed I K(DR) amplitude in a concentration-dependent manner. By virtue of a non-linear least-squares fit to the data [ 26 , 27 , 28 ], the IC 50 value required for the inhibitory effect of FTY720 on I K(DR) in Jurkat T-lymphocytes was calculated to be 1.51 μM. These results reflect that FTY is capable of exerting a depressant action on I K(DR) in these cells.…”

Inhibitory actions by ibandronate sodium, a nitrogen-containing bisphosphonate, on calcium-activated potassium channels in Madin–Darby canine kidney cells

“…It has been demonstrated that intermittent treatment with ibandronate (Iban) or zoledronate, which is known to be a potent nitrogen-containing bisphosphonate, caused hypertrophy and hyperplasia of distal tubules and collecting ducts in the rats [29] . Alternatively, previous observations at our laboratory showed that iban was able to decrease the activity of IK Ca channels in RAW 264.7 osteoclast precursor cells and that its block of these channels appeared to have a causal link to the inhibition of cell migration [45] . In contrast, another noteworthy study by Ma et al [20] has demonstrated that zoledronate could activate the activity of BK Ca channels in breast cancer cells and that such effect appeared to be responsible for the apoptotic change caused by this compound.…”

“…An anti-vibration air table was used to enhance stability during electrophysiological experiments. Patch clamp recordings were obtained in cell-attached, inside-out or whole-cell configuration using an RK-400 (Bio-Logic, Claix, France) or Axopatch 200B (Molecular Devices, Sunnyvale, CA) amplifier [45] . The junctional potentials between the pipette solution and extracellular medium were corrected immediately before seal formation was made.…”