Department of Pharmacy-Drug-Science, University of Bari, Bari, Italy.
PLoS One. 2013 Jul 16;8(7):e69551. doi: 10.1371/journal.pone.0069551. Print 2013.
Emerging evidences suggest that Ca(2+)activated-K(+)-(BK) channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L) or hypokalemia (0.55 mEq/L) conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293) in the presence or absence of BK channel modulators. The BK channel openers(10(-11)-10(-3)M) were: acetazolamide(ACTZ), Dichlorphenamide(DCP), methazolamide(MTZ), bendroflumethiazide(BFT), ethoxzolamide(ETX), hydrochlorthiazide(HCT), quercetin(QUERC), resveratrol(RESV) and NS1619; and the BK channel blockers(2 x 10(-7)M-5 x 10(-3)M) were: tetraethylammonium(TEA), iberiotoxin(IbTx) and charybdotoxin(ChTX). Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm) was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing the cell proliferation induced by hyperkalemia. These findings may have relevance in disorders associated with abnormal K(+) ion homeostasis including periodic paralysis and myotonia.
研究发现钙激活钾通道（BK）参与细胞活力的调节。本文旨在探讨 BK 通道调节剂对高钾（15 mEq/L）和低钾（0.55 mEq/L）条件下 HEK293 细胞（表达 hslo 亚基）活力变化的影响。BK 通道开放剂（10（-11）-10（-3）M）有乙酰唑胺（ACTZ）、二氯苯甲酰胺（DCP）、甲唑胺（MTZ）、苯氟噻嗪（BFT）、依他唑胺（ETX）、氢氯噻嗪（HCT）、槲皮素（QUERC）、白藜芦醇（RESV）和 NS1619；BK 通道阻滞剂（2×10（-7）M-5×10（-3）M）有四乙铵（TEA）、iberiotoxin（IbTx）和芋螺毒素（ChTX）。采用细胞计数试剂盒-8 和膜片钳技术分别进行细胞活力和通道电流实验。BK 通道开放剂在 hslo-HEK293 中以不同的效力和效率增强 hslo 全细胞电流。在 -60 mV（Vm）时，开放剂的效价排序为 BFT>ACTZ>DCP≥RESV≥ETX>NS1619>MTZ≥QUERC；HCT 无效。在 hslo-HEK293 细胞和 HEK293 细胞中，高钾孵育 24 小时后细胞活力分别增强 82+6%和 33+7%。IbTx、ChTX 和 TEA 增强 hslo-HEK293 细胞活力。BK 通道开放剂可防止高钾或 IbTx 诱导的 hslo-HEK293 细胞活力增强，其疗效与作为 BK 通道开放剂观察到的疗效相当。BK 通道调节剂在 hslo 亚基缺失的情况下，不能影响高钾条件下的细胞电流和活力。相比之下，在低钾条件下，hslo-HEK293 和 HEK293 细胞的细胞活力分别降低了 -22+4%和 -23+6%；BK 通道调节剂不能影响这些细胞的这一参数。结论：BK 通道调节高钾条件下的细胞活力，但不调节低钾条件下的细胞活力。BFT 和 ACTZ 是激活 BK 电流和防止高钾诱导细胞增殖最有效的药物。这些发现可能与异常钾离子稳态相关的疾病有关，包括周期性瘫痪和肌强直。
