Key result
Novel high-throughput screening demonstrates acacetin and citalopram non-selectively block both Kv1.3 and Kv1.5 channels.
Why the study?
A simple, accurate, and cost-effective screening system for selective blockers of voltage-gated Kv1.3 and Kv1.5 channels was needed.
A new cell-based screening system using recombinant cell lines dying upon single action potential provides a simple and accurate method for high-throughput screening of Kv1.3 and Kv1.5 channel blockers.
May warrant caution with citalopram due to Kv blockade; hypothesis-generating for selective inhibitors in arrhythmia or autoimmunity.
To develop a simple screening system for blockers of voltage-gated Kv1.3 and Kv1.5 channels, new cell lines co-expressing mutated Nav1.5 (IFM/Q3), Kir2.1 (Kir), and Kv1.3 or Kv1.5 were introduced as IFM/Q3+Kir+Kv1.3 and IFM/Q3+Kir+Kv1.5, respectively. Electrical stimulation (ES) of a cell line, IFM/Q3+Kir, induced prolonged action potentials due to the slow inactivation of IFM/Q3 and subsequent cell death. Additional co-expression of Kv1.3 or Kv1.5 to IFM/Q3+Kir shortened the evoked action potentials and prevented cell death. In the presence of margatoxin, a selective Kv1.3-blocker, ES induced cell death in IFM/Q3+Kir+Kv1.3, but not in IFM/Q3+Kir+Kv1.5. In the presence of 4-aminopyridine, a non-selective Kv-channel blocker, ES application elicited cell death in both cell lines. The IC50s of acacetin, a Kv1.5-blocker, was 10.2 μM in IFM/Q3+Kir+Kv1.3 and almost identical to that in IFM/Q3+Kir+Kv1.5 (7.6 μM). The IC50s of citalopram, a 5-HT uptake-inhibitor, were 1.8 μM in IFM/Q3+Kir+Kv1.3 and 1.5 μM in IFM/Q3+Kir+Kv1.5, respectively. These IC50s were comparable to those determined electrophysiologically. In conclusion, acacetin and citalopram block both Kv1.3 and Kv1.5 without selectivity. The Kv1.3 or Kv1.5 channel inhibition assay using these new cell lines may be applicable to high-throughput screening because of its simplicity, accuracy, and high cost-performance.
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Fujii et al. (2013) studied this question. Kv1.3 and Kv1.5 channel blockers (acacetin, citalopram, margatoxin, 4-AP) vs. Control (no drug) was evaluated on IC50 for channel blockade measured by post-electrical stimulation cell viability. A novel high-throughput screening system using recombinant cell lines successfully quantified the blocking potencies of acacetin and citalopram, demonstrating they block both Kv1.3 and Kv1.5 channels without selectivity.
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