Cell Cycle Regulation by Ca(2+)-Activated K(+) (BK) Channels Modulators in SH-SY5Y Neuroblastoma Cells

The effects of Ca(2+)-activated K(+) (BK) channel modulation by Paxilline (PAX) (10(−7)–10(−4) M), Iberiotoxin (IbTX) (0.1–1 × 10(−6) M) and Resveratrol (RESV) (1–2 × 10(−4) M) on cell cycle and proliferation, AKT1p(Ser473) phosphorylation, cell diameter, and BK currents were investigated in SH-SY5Y cells using Operetta-high-content-Imaging-System, ELISA-assay, impedentiometric counting method and patch-clamp technique, respectively. IbTX (4 × 10(−7) M), PAX (5 × 10(−5) M) and RESV (10(−4) M) caused a maximal decrease of the outward K(+) current at +30 mV (Vm) of −38.3 ± 10%, −31.9 ± 9% and −43 ± 8%, respectively, which was not reversible following washout and cell depolarization. After 6h of incubation, the drugs concentration dependently reduced proliferation. A maximal reduction of cell proliferation, respectively of −60 ± 8% for RESV (2 × 10(−4) M) (IC50 = 1.50 × 10(−4) M), −65 ± 6% for IbTX (10(−6) M) (IC50 = 5 × 10(−7) M), −97 ± 6% for PAX (1 × 10(−4) M) (IC50 = 1.06 × 10(−5) M) and AKT1p(ser473) dephosphorylation was observed. PAX induced a G1/G2 accumulation and contraction of the S-phase, reducing the nuclear area and cell diameter. IbTX induced G1 contraction and G2 accumulation reducing diameter. RESV induced G2 accumulation and S contraction reducing diameter. These drugs share common actions leading to a block of the surface membrane BK channels with cell depolarization and calcium influx, AKT1p(ser473) dephosphorylation by calcium-dependent phosphatase, accumulation in the G2 phase, and a reduction of diameter and proliferation. In addition, the PAX action against nuclear membrane BK channels potentiates its antiproliferative effects with early apoptosis.