Cell Cycle Regulation by Ca2+-Activated K+ (BK) Channels Modulators in SH-SY5Y Neuroblastoma Cells

The effects of Ca2+-activated K+ (BK) channel modulation by Paxilline (PAX) (10(-7)-10(-4) M), Iberiotoxin (IbTX) (0.1-1 x 10(-6) M) and Resveratrol (RESV) (1-2 x 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 x 10(-7) M), PAX (5 x 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 x 10(-4) M) (IC50 = 1.50 x 10(-4) M), -65 +/- 6% for IbTX (10(-6) M) (IC50 = 5 x 10(-7) M), -97 +/- 6% for PAX (1 x 10(-4) M) (IC50 = 1.06 x 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.